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Sample records for actin flap dynamics

  1. Actin dynamics and the elasticity of cytoskeletal networks

    Directory of Open Access Journals (Sweden)

    2009-09-01

    Full Text Available The structural integrity of a cell depends on its cytoskeleton, which includes an actin network. This network is transient and depends upon the continual polymerization and depolymerization of actin. The degradation of an actin network, and a corresponding reduction in cell stiffness, can indicate the presence of disease. Numerical simulations will be invaluable for understanding the physics of these systems and the correlation between actin dynamics and elasticity. Here we develop a model that is capable of generating actin network structures. In particular, we develop a model of actin dynamics which considers the polymerization, depolymerization, nucleation, severing, and capping of actin filaments. The structures obtained are then fed directly into a mechanical model. This allows us to qualitatively assess the effects of changing various parameters associated with actin dynamics on the elasticity of the material.

  2. Apatite-mediated actin dynamics in resorbing osteoclasts.

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    Saltel, Frédéric; Destaing, Olivier; Bard, Frédéric; Eichert, Diane; Jurdic, Pierre

    2004-12-01

    The actin cytoskeleton is essential for osteoclasts main function, bone resorption. Two different organizations of actin have been described in osteoclasts, the podosomes belt corresponding to numerous F-actin columns arranged at the cell periphery, and the sealing zone defined as a unique large band of actin. To compare the role of these two different actin organizations, we imaged osteoclasts on various substrata: glass, dentin, and apatite. Using primary osteoclasts expressing GFP-actin, we found that podosome belts and sealing zones, both very dynamic actin structures, were present in mature osteoclasts; podosome belts were observed only in spread osteoclasts adhering onto glass, whereas sealing zone were seen in apico-basal polarized osteoclasts adherent on mineralized matrix. Dynamic observations of several resorption cycles of osteoclasts seeded on apatite revealed that 1) podosomes do not fuse together to form the sealing zone; 2) osteoclasts alternate successive stationary polarized resorption phases with a sealing zone and migration, nonresorption phases without any specific actin structure; and 3) apatite itself promotes sealing zone formation though c-src and Rho signaling. Finally, our work suggests that apatite-mediated sealing zone formation is dependent on both c-src and Rho whereas apico-basal polarization requires only Rho.

  3. Dynamic Flaps Electronic Scan Antenna

    National Research Council Canada - National Science Library

    Gonzalez, Daniel

    2000-01-01

    A dynamic FLAPS(TM) electronic scan antenna was the focus of this research. The novelty S of this SBIR resides in the use of plasma as the main component of this dynamic X-Band phased S array antenna...

  4. Stochastic Severing of Actin Filaments by Actin Depolymerizing Factor/Cofilin Controls the Emergence of a Steady Dynamical Regime

    Science.gov (United States)

    Roland, Jeremy; Berro, Julien; Michelot, Alphée; Blanchoin, Laurent; Martiel, Jean-Louis

    2008-01-01

    Actin dynamics (i.e., polymerization/depolymerization) powers a large number of cellular processes. However, a great deal remains to be learned to explain the rapid actin filament turnover observed in vivo. Here, we developed a minimal kinetic model that describes key details of actin filament dynamics in the presence of actin depolymerizing factor (ADF)/cofilin. We limited the molecular mechanism to 1), the spontaneous growth of filaments by polymerization of actin monomers, 2), the ageing of actin subunits in filaments, 3), the cooperative binding of ADF/cofilin to actin filament subunits, and 4), filament severing by ADF/cofilin. First, from numerical simulations and mathematical analysis, we found that the average filament length, 〈L〉, is controlled by the concentration of actin monomers (power law: 5/6) and ADF/cofilin (power law: −2/3). We also showed that the average subunit residence time inside the filament, 〈T〉, depends on the actin monomer (power law: −1/6) and ADF/cofilin (power law: −2/3) concentrations. In addition, filament length fluctuations are ∼20% of the average filament length. Moreover, ADF/cofilin fragmentation while modulating filament length keeps filaments in a high molar ratio of ATP- or ADP-Pi versus ADP-bound subunits. This latter property has a protective effect against a too high severing activity of ADF/cofilin. We propose that the activity of ADF/cofilin in vivo is under the control of an affinity gradient that builds up dynamically along growing actin filaments. Our analysis shows that ADF/cofilin regulation maintains actin filaments in a highly dynamical state compatible with the cytoskeleton dynamics observed in vivo. PMID:18065447

  5. Hypertrophic stimulation increases beta-actin dynamics in adult feline cardiomyocytes.

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    Sundaravadivel Balasubramanian

    2010-07-01

    Full Text Available The myocardium responds to hemodynamic stress through cellular growth and organ hypertrophy. The impact of cytoskeletal elements on this process, however, is not fully understood. While alpha-actin in cardiomyocytes governs muscle contraction in combination with the myosin motor, the exact role of beta-actin has not been established. We hypothesized that in adult cardiomyocytes, as in non-myocytes, beta-actin can facilitate cytoskeletal rearrangement within cytoskeletal structures such as Z-discs. Using a feline right ventricular pressure overload (RVPO model, we measured the level and distribution of beta-actin in normal and pressure overloaded myocardium. Resulting data demonstrated enriched levels of beta-actin and enhanced translocation to the Triton-insoluble cytoskeletal and membrane skeletal complexes. In addition, RVPO in vivo and in vitro hypertrophic stimulation with endothelin (ET or insulin in isolated adult cardiomyocytes enhanced the content of polymerized fraction (F-actin of beta-actin. To determine the localization and dynamics of beta-actin, we adenovirally expressed GFP-tagged beta-actin in isolated adult cardiomyocytes. The ectopically expressed beta-actin-GFP localized to the Z-discs, costameres, and cell termini. Fluorescence recovery after photobleaching (FRAP measurements of beta-actin dynamics revealed that beta-actin at the Z-discs is constantly being exchanged with beta-actin from cytoplasmic pools and that this exchange is faster upon hypertrophic stimulation with ET or insulin. In addition, in electrically stimulated isolated adult cardiomyocytes, while beta-actin overexpression improved cardiomyocyte contractility, immunoneutralization of beta-actin resulted in a reduced contractility suggesting that beta-actin could be important for the contractile function of adult cardiomyocytes. These studies demonstrate the presence and dynamics of beta-actin in the adult cardiomyocyte and reinforce its usefulness in measuring

  6. Initiation of DNA replication requires actin dynamics and formin activity.

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    Parisis, Nikolaos; Krasinska, Liliana; Harker, Bethany; Urbach, Serge; Rossignol, Michel; Camasses, Alain; Dewar, James; Morin, Nathalie; Fisher, Daniel

    2017-11-02

    Nuclear actin regulates transcriptional programmes in a manner dependent on its levels and polymerisation state. This dynamics is determined by the balance of nucleocytoplasmic shuttling, formin- and redox-dependent filament polymerisation. Here, using Xenopus egg extracts and human somatic cells, we show that actin dynamics and formins are essential for DNA replication. In proliferating cells, formin inhibition abolishes nuclear transport and initiation of DNA replication, as well as general transcription. In replicating nuclei from transcriptionally silent Xenopus egg extracts, we identified numerous actin regulators, and disruption of actin dynamics abrogates nuclear transport, preventing NLS (nuclear localisation signal)-cargo release from RanGTP-importin complexes. Nuclear formin activity is further required to promote loading of cyclin-dependent kinase (CDK) and proliferating cell nuclear antigen (PCNA) onto chromatin, as well as initiation and elongation of DNA replication. Therefore, actin dynamics and formins control DNA replication by multiple direct and indirect mechanisms. © 2017 The Authors.

  7. Coordination of membrane and actin cytoskeleton dynamics during filopodia protrusion.

    Directory of Open Access Journals (Sweden)

    Changsong Yang

    2009-05-01

    Full Text Available Leading edge protrusion of migrating cells involves tightly coordinated changes in the plasma membrane and actin cytoskeleton. It remains unclear whether polymerizing actin filaments push and deform the membrane, or membrane deformation occurs independently and is subsequently stabilized by actin filaments. To address this question, we employed an ability of the membrane-binding I-BAR domain of IRSp53 to uncouple the membrane and actin dynamics and to induce filopodia in expressing cells. Using time-lapse imaging and electron microscopy of IRSp53-I-BAR-expressing B16F1 melanoma cells, we demonstrate that cells are not able to protrude or maintain durable long extensions without actin filaments in their interior, but I-BAR-dependent membrane deformation can create a small and transient space at filopodial tips that is subsequently filled with actin filaments. Moreover, the expressed I-BAR domain forms a submembranous coat that may structurally support these transient actin-free protrusions until they are further stabilized by the actin cytoskeleton. Actin filaments in the I-BAR-induced filopodia, in contrast to normal filopodia, do not have a uniform length, are less abundant, poorly bundled, and display erratic dynamics. Such unconventional structural organization and dynamics of actin in I-BAR-induced filopodia suggests that a typical bundle of parallel actin filaments is not necessary for generation and mechanical support of the highly asymmetric filopodial geometry. Together, our data suggest that actin filaments may not directly drive the protrusion, but only stabilize the space generated by the membrane deformation; yet, such stabilization is necessary for efficient protrusion.

  8. Dynamics of actin cables in polarized growth of the filamentous fungus Aspergillus nidulans

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    Anna eBergs

    2016-05-01

    Full Text Available Highly polarized growth of filamentous fungi requires a continuous supply of proteins and lipids to the hyphal tip. This transport is managed by vesicle trafficking via the actin and microtubule cytoskeletons and their associated motor proteins. Particularly, actin cables originating from the hyphal tip are essential for hyphal growth. Although specific marker proteins to visualize actin cables have been developed in filamentous fungi, the exact organization and dynamics of actin cables has remained elusive. Here we visualized actin cables using tropomyosin (TpmA and Lifeact fused to fluorescent proteins in Aspergillus nidulans and studied the dynamics and regulation. GFP tagged TpmA visualized dynamic actin cables formed from the hyphal tip with cycles of elongation and shrinkage. The elongation and shrinkage rates of actin cables were similar and approximately 0.6 μm/s. Comparison of actin markers revealed that high concentrations of Lifeact reduced actin dynamics. Simultaneous visualization of actin cables and microtubules suggests temporally and spatially coordinated polymerization and depolymerization between the two cytoskeletons. Our results provide new insights into the molecular mechanism of ordered polarized growth regulated by actin cables and microtubules.

  9. Changes in actin dynamics are involved in salicylic acid signaling pathway.

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    Matoušková, Jindřiška; Janda, Martin; Fišer, Radovan; Sašek, Vladimír; Kocourková, Daniela; Burketová, Lenka; Dušková, Jiřina; Martinec, Jan; Valentová, Olga

    2014-06-01

    Changes in actin cytoskeleton dynamics are one of the crucial players in many physiological as well as non-physiological processes in plant cells. Positioning of actin filament arrays is necessary for successful establishment of primary lines of defense toward pathogen attack, depolymerization leads very often to the enhanced susceptibility to the invading pathogen. On the other hand it was also shown that the disruption of actin cytoskeleton leads to the induction of defense response leading to the expression of PATHOGENESIS RELATED proteins (PR). In this study we show that pharmacological actin depolymerization leads to the specific induction of genes in salicylic acid pathway but not that involved in jasmonic acid signaling. Life imaging of leafs of Arabidopsis thaliana with GFP-tagged fimbrin (GFP-fABD2) treated with 1 mM salicylic acid revealed rapid disruption of actin filaments resembling the pattern viewed after treatment with 200 nM latrunculin B. The effect of salicylic acid on actin filament fragmentation was prevented by exogenous addition of phosphatidic acid, which binds to the capping protein and thus promotes actin polymerization. The quantitative evaluation of actin filament dynamics is also presented. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  10. Investigating sub-spine actin dynamics in rat hippocampal neurons with super-resolution optical imaging.

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    Vedakumar Tatavarty

    Full Text Available Morphological changes in dendritic spines represent an important mechanism for synaptic plasticity which is postulated to underlie the vital cognitive phenomena of learning and memory. These morphological changes are driven by the dynamic actin cytoskeleton that is present in dendritic spines. The study of actin dynamics in these spines traditionally has been hindered by the small size of the spine. In this study, we utilize a photo-activation localization microscopy (PALM-based single-molecule tracking technique to analyze F-actin movements with approximately 30-nm resolution in cultured hippocampal neurons. We were able to observe the kinematic (physical motion of actin filaments, i.e., retrograde flow and kinetic (F-actin turn-over dynamics of F-actin at the single-filament level in dendritic spines. We found that F-actin in dendritic spines exhibits highly heterogeneous kinematic dynamics at the individual filament level, with simultaneous actin flows in both retrograde and anterograde directions. At the ensemble level, movements of filaments integrate into a net retrograde flow of approximately 138 nm/min. These results suggest a weakly polarized F-actin network that consists of mostly short filaments in dendritic spines.

  11. Investigating sub-spine actin dynamics in rat hippocampal neurons with super-resolution optical imaging.

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    Tatavarty, Vedakumar; Kim, Eun-Ji; Rodionov, Vladimir; Yu, Ji

    2009-11-09

    Morphological changes in dendritic spines represent an important mechanism for synaptic plasticity which is postulated to underlie the vital cognitive phenomena of learning and memory. These morphological changes are driven by the dynamic actin cytoskeleton that is present in dendritic spines. The study of actin dynamics in these spines traditionally has been hindered by the small size of the spine. In this study, we utilize a photo-activation localization microscopy (PALM)-based single-molecule tracking technique to analyze F-actin movements with approximately 30-nm resolution in cultured hippocampal neurons. We were able to observe the kinematic (physical motion of actin filaments, i.e., retrograde flow) and kinetic (F-actin turn-over) dynamics of F-actin at the single-filament level in dendritic spines. We found that F-actin in dendritic spines exhibits highly heterogeneous kinematic dynamics at the individual filament level, with simultaneous actin flows in both retrograde and anterograde directions. At the ensemble level, movements of filaments integrate into a net retrograde flow of approximately 138 nm/min. These results suggest a weakly polarized F-actin network that consists of mostly short filaments in dendritic spines.

  12. Water Tunnel Studies of Dynamic Wing Flap Effects

    Science.gov (United States)

    2016-06-01

    NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS Approved for public release; distribution is unlimited WATER TUNNEL...Master’s Thesis 4. TITLE AND SUBTITLE WATER TUNNEL STUDIES OF DYNAMIC WING FLAP EFFECTS 5. FUNDING NUMBERS 6. AUTHOR(S) Edgar E. González 7. PERFORMING...ABSTRACT (maximum 200 words ) The flow features developing over a two-element NACA 0012 airfoil, with the rear portion serving as a trailing edge flap

  13. Dynamic properties of blood flow and leukocyte mobilization in infected flaps

    International Nuclear Information System (INIS)

    Feng, L.J.; Price, D.C.; Mathes, S.J.; Hohn, D.

    1990-01-01

    Two aspects of the inflammatory response to infection--blood flow alteration and leukocyte mobilization--are investigated in the canine model. The elevation of paired musculocutaneous (MC) and random pattern (RP) flaps allowed comparison of healing flaps with significant differences in blood flow (lower in random pattern flaps) and resistance to infection (greater in musculocutaneous flaps). Blood flow changes as determined by radioactive xenon washout were compared in normal skin and distal flap skin both after elevation and following bacterial inoculation. Simultaneous use of In-111 labeled leukocytes allowed determination of leukocyte mobilization and subsequent localization in response to flap infection. Blood flow significantly improved in the musculocutaneous flap in response to infection. Although total leukocyte mobilization in the random pattern flap was greater, the leukocytes in the musculocutaneous flap were localized around the site of bacterial inoculation within the dermis. Differences in the dynamic blood flow and leukocyte mobilization may, in part, explain the greater reliability of musculocutaneous flaps when transposed in the presence of infection

  14. The cell wall of Arabidopsis thaliana influences actin network dynamics.

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    Tolmie, Frances; Poulet, Axel; McKenna, Joseph; Sassmann, Stefan; Graumann, Katja; Deeks, Michael; Runions, John

    2017-07-20

    In plant cells, molecular connections link the cell wall-plasma membrane-actin cytoskeleton to form a continuum. It is hypothesized that the cell wall provides stable anchor points around which the actin cytoskeleton remodels. Here we use live cell imaging of fluorescently labelled marker proteins to quantify the organization and dynamics of the actin cytoskeleton and to determine the impact of disrupting connections within the continuum. Labelling of the actin cytoskeleton with green fluorescent protein (GFP)-fimbrin actin-binding domain 2 (FABD2) resulted in a network composed of fine filaments and thicker bundles that appeared as a highly dynamic remodelling meshwork. This differed substantially from the GFP-Lifeact-labelled network that appeared much more sparse with thick bundles that underwent 'simple movement', in which the bundles slightly change position, but in such a manner that the structure of the network was not substantially altered during the time of observation. Label-dependent differences in actin network morphology and remodelling necessitated development of two new image analysis techniques. The first of these, 'pairwise image subtraction', was applied to measurement of the more rapidly remodelling actin network labelled with GFP-FABD2, while the second, 'cumulative fluorescence intensity', was used to measure bulk remodelling of the actin cytoskeleton when labelled with GFP-Lifeact. In each case, these analysis techniques show that the actin cytoskeleton has a decreased rate of bulk remodelling when the cell wall-plasma membrane-actin continuum is disrupted either by plasmolysis or with isoxaben, a drug that specifically inhibits cellulose deposition. Changes in the rate of actin remodelling also affect its functionality, as observed by alteration in Golgi body motility. © The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

  15. Bacterial subversion of host actin dynamics at the plasma membrane.

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    Carabeo, Rey

    2011-10-01

    Invasion of non-phagocytic cells by a number of bacterial pathogens involves the subversion of the actin cytoskeletal remodelling machinery to produce actin-rich cell surface projections designed to engulf the bacteria. The signalling that occurs to induce these actin-rich structures has considerable overlap among a diverse group of bacteria. The molecular organization within these structures act in concert to internalize the invading pathogen. This dynamic process could be subdivided into three acts - actin recruitment, engulfment, and finally, actin disassembly/internalization. This review will present the current state of knowledge of the molecular processes involved in each stage of bacterial invasion, and provide a perspective that highlights the temporal and spatial control of actin remodelling that occurs during bacterial invasion. © 2011 Blackwell Publishing Ltd.

  16. Organization and dynamics of the actin cytoskeleton during dendritic spine morphological remodeling.

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    Chazeau, Anaël; Giannone, Grégory

    2016-08-01

    In the central nervous system, most excitatory post-synapses are small subcellular structures called dendritic spines. Their structure and morphological remodeling are tightly coupled to changes in synaptic transmission. The F-actin cytoskeleton is the main driving force of dendritic spine remodeling and sustains synaptic plasticity. It is therefore essential to understand how changes in synaptic transmission can regulate the organization and dynamics of actin binding proteins (ABPs). In this review, we will provide a detailed description of the organization and dynamics of F-actin and ABPs in dendritic spines and will discuss the current models explaining how the actin cytoskeleton sustains both structural and functional synaptic plasticity.

  17. Self-assembly of actin monomers into long filaments: Brownian Dynamics simulations

    DEFF Research Database (Denmark)

    Shillcock, Julian C.

    2009-01-01

    Brownian dynamics simulations are used to study the dynamical process of self-assembly of actin monomers into long filaments containing up to 1000 actin protomers. In order to overcome the large separation of time scales between the diffusive motion of the freemonomers and the relatively slow....../detachment events. When a single filament is allowed to grow in a bath of constant concentration of free ADP-actin monomers, its growth rate increases linearly with the free monomer concentration in quantitative agreement with in vitro experiments. Theresults also show that the waiting time is governed by...

  18. The ADF/Cofilin-Pathway and Actin Dynamics in Podocyte Injury

    Directory of Open Access Journals (Sweden)

    Beina Teng

    2012-01-01

    Full Text Available ADF/cofilins are the major regulators of actin dynamics in mammalian cells. The activation of ADF/cofilins is controlled by a variety of regulatory mechanisms. Dysregulation of ADF/cofilin may result in loss of a precisely organized actin cytoskeletal architecture and can reduce podocyte migration and motility. Recent studies suggest that cofilin-1 can be regulated through several extracellular signals and slit diaphragm proteins. Cofilin knockdown and knockout animal models show dysfunction of glomerular barrier and filtration with foot process effacement and loss of secondary foot processes. This indicates that cofilin-1 is necessary for modulating actin dynamics in podocytes. Podocyte alterations in actin architecture may initiate or aid the progression of a large variety of glomerular diseases, and cofilin activity is required for reorganization of an intact filtration barrier. Since almost all proteinuric diseases result from a similar phenotype with effacement of the foot processes, we propose that cofilin-1 is at the centre stage of the development of proteinuria and thus may be an attractive drug target for antiproteinuric treatment strategies.

  19. Wnt Signalling Promotes Actin Dynamics during Axon Remodelling through the Actin-Binding Protein Eps8.

    Directory of Open Access Journals (Sweden)

    Eleanna Stamatakou

    Full Text Available Upon arrival at their synaptic targets, axons slow down their growth and extensively remodel before the assembly of presynaptic boutons. Wnt proteins are target-derived secreted factors that promote axonal remodelling and synaptic assembly. In the developing spinal cord, Wnts secreted by motor neurons promote axonal remodelling of NT-3 responsive dorsal root ganglia neurons. Axon remodelling induced by Wnts is characterised by growth cone pausing and enlargement, processes that depend on the re-organisation of microtubules. However, the contribution of the actin cytoskeleton has remained unexplored. Here, we demonstrate that Wnt3a regulates the actin cytoskeleton by rapidly inducing F-actin accumulation in growth cones from rodent DRG neurons through the scaffold protein Dishevelled-1 (Dvl1 and the serine-threonine kinase Gsk3β. Importantly, these changes in actin cytoskeleton occurs before enlargement of the growth cones is evident. Time-lapse imaging shows that Wnt3a increases lamellar protrusion and filopodia velocity. In addition, pharmacological inhibition of actin assembly demonstrates that Wnt3a increases actin dynamics. Through a yeast-two hybrid screen, we identified the actin-binding protein Eps8 as a direct interactor of Dvl1, a scaffold protein crucial for the Wnt signalling pathway. Gain of function of Eps8 mimics Wnt-mediated axon remodelling, whereas Eps8 silencing blocks the axon remodelling activity of Wnt3a. Importantly, blockade of the Dvl1-Eps8 interaction completely abolishes Wnt3a-mediated axonal remodelling. These findings demonstrate a novel role for Wnt-Dvl1 signalling through Eps8 in the regulation of axonal remodeling.

  20. The atypical Rho GTPase RhoD is a regulator of actin cytoskeleton dynamics and directed cell migration

    Energy Technology Data Exchange (ETDEWEB)

    Blom, Magdalena; Reis, Katarina [Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77 Stockholm (Sweden); Heldin, Johan [Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala SE-751 22 Uppsala (Sweden); Kreuger, Johan [Department of Medical Cell Biology, Science for Life Laboratory, Uppsala University, SE-751 23 Uppsala (Sweden); Aspenström, Pontus, E-mail: pontus.aspenstrom@ki.se [Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, SE-171 77 Stockholm (Sweden)

    2017-03-15

    RhoD belongs to the Rho GTPases, a protein family responsible for the regulation and organization of the actin cytoskeleton, and, consequently, many cellular processes like cell migration, cell division and vesicle trafficking. Here, we demonstrate that the actin cytoskeleton is dynamically regulated by increased or decreased protein levels of RhoD. Ectopic expression of RhoD has previously been shown to give an intertwined weave of actin filaments. We show that this RhoD-dependent effect is detected in several cell types and results in a less dynamic actin filament system. In contrast, RhoD depletion leads to increased actin filament-containing structures, such as cortical actin, stress fibers and edge ruffles. Moreover, vital cellular functions such as cell migration and proliferation are defective when RhoD is silenced. Taken together, we present data suggesting that RhoD is an important component in the control of actin dynamics and directed cell migration. - Highlights: • Increased RhoD expression leads to loss of actin structures, e.g. stress fibers and gives rise to decreased actin dynamics. • RhoD knockdown induces various actin-containing structures such as edge ruffles, stress fibers and cortical actin, in a cell-type specific manner. • RhoD induces specific actin rearrangements depending on its subcellular localization. • RhoD knockdown has effects on cellular processes, such as directed cell migration and proliferation.

  1. The atypical Rho GTPase RhoD is a regulator of actin cytoskeleton dynamics and directed cell migration

    International Nuclear Information System (INIS)

    Blom, Magdalena; Reis, Katarina; Heldin, Johan; Kreuger, Johan; Aspenström, Pontus

    2017-01-01

    RhoD belongs to the Rho GTPases, a protein family responsible for the regulation and organization of the actin cytoskeleton, and, consequently, many cellular processes like cell migration, cell division and vesicle trafficking. Here, we demonstrate that the actin cytoskeleton is dynamically regulated by increased or decreased protein levels of RhoD. Ectopic expression of RhoD has previously been shown to give an intertwined weave of actin filaments. We show that this RhoD-dependent effect is detected in several cell types and results in a less dynamic actin filament system. In contrast, RhoD depletion leads to increased actin filament-containing structures, such as cortical actin, stress fibers and edge ruffles. Moreover, vital cellular functions such as cell migration and proliferation are defective when RhoD is silenced. Taken together, we present data suggesting that RhoD is an important component in the control of actin dynamics and directed cell migration. - Highlights: • Increased RhoD expression leads to loss of actin structures, e.g. stress fibers and gives rise to decreased actin dynamics. • RhoD knockdown induces various actin-containing structures such as edge ruffles, stress fibers and cortical actin, in a cell-type specific manner. • RhoD induces specific actin rearrangements depending on its subcellular localization. • RhoD knockdown has effects on cellular processes, such as directed cell migration and proliferation.

  2. Rapid and dynamic arginylation of the leading edge β-actin is required for cell migration.

    Science.gov (United States)

    Pavlyk, Iuliia; Leu, Nicolae A; Vedula, Pavan; Kurosaka, Satoshi; Kashina, Anna

    2018-04-01

    β-actin plays key roles in cell migration. Our previous work demonstrated that β-actin in migratory non-muscle cells is N-terminally arginylated and that this arginylation is required for normal lamellipodia extension. Here, we examined the function of β-actin arginylation in cell migration. We found that arginylated β-actin is concentrated at the leading edge of lamellipodia and that this enrichment is abolished after serum starvation as well as in contact-inhibited cells in confluent cultures, suggesting that arginylated β-actin at the cell leading edge is coupled to active migration. Arginylated actin levels exhibit dynamic changes in response to cell stimuli, lowered after serum starvation and dramatically elevating within minutes after cell stimulation by readdition of serum or lysophosphatidic acid. These dynamic changes require active translation and are not seen in confluent contact-inhibited cell cultures. Microinjection of arginylated actin antibodies into cells severely and specifically inhibits their migration rates. Together, these data strongly suggest that arginylation of β-actin is a tightly regulated dynamic process that occurs at the leading edge of locomoting cells in response to stimuli and is integral to the signaling network that regulates cell migration. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  3. Live cell imaging of actin dynamics in dexamethasone-treated porcine trabecular meshwork cells.

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    Fujimoto, Tomokazu; Inoue, Toshihiro; Inoue-Mochita, Miyuki; Tanihara, Hidenobu

    2016-04-01

    The regulation of the actin cytoskeleton in trabecular meshwork (TM) cells is important for controlling outflow of the aqueous humor. In some reports, dexamethasone (DEX) increased the aqueous humor outflow resistance and induced unusual actin structures, such as cross-linked actin networks (CLAN), in TM cells. However, the functions and dynamics of CLAN in TM cells are not completely known, partly because actin stress fibers have been observed only in fixed cells. We conducted live-cell imaging of the actin dynamics in TM cells with or without DEX treatment. An actin-green fluorescent protein (GFP) fusion construct with a modified insect virus was transfected into porcine TM cells. Time-lapse imaging of live TM cells treated with 25 μM Y-27632 and 100 nM DEX was performed using an inverted fluorescence microscope. Fluorescent images were recorded every 15 s for 30 min after Y-27632 treatment or every 30 min for 72 h after DEX treatment. The GFP-actin was expressed in 22.7 ± 10.9% of the transfected TM cells. In live TM cells, many actin stress fibers were observed before the Y-27632 treatment. Y-27632 changed the cell shape and decreased stress fibers in a time-dependent manner. In fixed cells, CLAN-like structures were seen in 26.5 ± 1.7% of the actin-GFP expressed PTM cells treated with DEX for 72 h. In live imaging, there was 28% CLAN-like structure formation at 72 h after DEX treatment, and the lifetime of CLAN-like structures increased after DEX treatment. The DEX-treated cells with CLAN-like structures showed less migration than DEX-treated cells without CLAN-like structures. Furthermore, the control cells (without DEX treatment) with CLAN-like structures also showed less migration than the control cells without CLAN-like structures. These results suggested that CLAN-like structure formation was correlated with cell migration in TM cells. Live cell imaging of the actin cytoskeleton provides valuable information on the actin dynamics in TM

  4. TWISTED DWARF1 Mediates the Action of Auxin Transport Inhibitors on Actin Cytoskeleton Dynamics

    Science.gov (United States)

    Bailly, Aurelien; Zwiewka, Marta; Sovero, Valpuri; Ge, Pei; Aryal, Bibek; Hao, Pengchao; Linnert, Miriam; Burgardt, Noelia Inés; Lücke, Christian; Weiwad, Matthias; Michel, Max; Weiergräber, Oliver H.; Pollmann, Stephan; Azzarello, Elisa; Fukao, Yoichiro; Hoffmann, Céline; Wedlich-Söldner, Roland

    2016-01-01

    Plant growth and architecture is regulated by the polar distribution of the hormone auxin. Polarity and flexibility of this process is provided by constant cycling of auxin transporter vesicles along actin filaments, coordinated by a positive auxin-actin feedback loop. Both polar auxin transport and vesicle cycling are inhibited by synthetic auxin transport inhibitors, such as 1-N-naphthylphthalamic acid (NPA), counteracting the effect of auxin; however, underlying targets and mechanisms are unclear. Using NMR, we map the NPA binding surface on the Arabidopsis thaliana ABCB chaperone TWISTED DWARF1 (TWD1). We identify ACTIN7 as a relevant, although likely indirect, TWD1 interactor, and show TWD1-dependent regulation of actin filament organization and dynamics and that TWD1 is required for NPA-mediated actin cytoskeleton remodeling. The TWD1-ACTIN7 axis controls plasma membrane presence of efflux transporters, and as a consequence act7 and twd1 share developmental and physiological phenotypes indicative of defects in auxin transport. These can be phenocopied by NPA treatment or by chemical actin (de)stabilization. We provide evidence that TWD1 determines downstream locations of auxin efflux transporters by adjusting actin filament debundling and dynamizing processes and mediating NPA action on the latter. This function appears to be evolutionary conserved since TWD1 expression in budding yeast alters actin polarization and cell polarity and provides NPA sensitivity. PMID:27053424

  5. Effects of F/G-actin ratio and actin turn-over rate on NADPH oxidase activity in microglia

    DEFF Research Database (Denmark)

    Rasmussen, Izabela; Pedersen, Line Hjortshøj; Byg, Luise

    2010-01-01

    Most in vivo studies that have addressed the role of actin dynamics in NADPH oxidase function in phagocytes have used toxins to modulate the polymerization state of actin and mostly effects on actin has been evaluated by end point measurements of filamentous actin, which says little about actin d...... dynamics, and without consideration for the subcellular distribution of the perturbed actin cytoskeleton....

  6. Actin filaments as tension sensors.

    Science.gov (United States)

    Galkin, Vitold E; Orlova, Albina; Egelman, Edward H

    2012-02-07

    The field of mechanobiology has witnessed an explosive growth over the past several years as interest has greatly increased in understanding how mechanical forces are transduced by cells and how cells migrate, adhere and generate traction. Actin, a highly abundant and anomalously conserved protein, plays a large role in forming the dynamic cytoskeleton that is so essential for cell form, motility and mechanosensitivity. While the actin filament (F-actin) has been viewed as dynamic in terms of polymerization and depolymerization, new results suggest that F-actin itself may function as a highly dynamic tension sensor. This property may help explain the unusual conservation of actin's sequence, as well as shed further light on actin's essential role in structures from sarcomeres to stress fibers. Copyright © 2012 Elsevier Ltd. All rights reserved.

  7. Flapping dynamics of a thin liquid sheet

    Science.gov (United States)

    Vadivukkarasan, M.; Kumaran, Dhivyaraja; Panchagnula, Mahesh; Multi-phase flow physics Group Team

    2017-11-01

    We attempt to delineate and describe the complete evolution of a thin soap film when air is blown through a nozzle in the normal direction. The sequence of events and its intrinsic dynamics are captured using high speed imaging. By careful observation, it was observed that multiple mechanisms occur in the same system and each event is triggered by an independent mechanism. The events include (a) flapping of a liquid sheet and pinching of the bubble, (b) onset of rupture on the liquid sheet, (c) formation of ligaments and (d) ejection of drops. From this study, it is shown that these events are predominantly governed by Kelvin-Helmholtz instability, Taylor - Culick law, Rayleigh-Taylor instability and capillary instability, respectively. The present experiments can be considered as an extension to the previous studies on soap films as well as thin flapping sheets which has direct relevance to coaxial atomizers used in aircraft applications.

  8. Dynamics of actin-based movement by Rickettsia rickettsii in vero cells.

    Science.gov (United States)

    Heinzen, R A; Grieshaber, S S; Van Kirk, L S; Devin, C J

    1999-08-01

    Actin-based motility (ABM) is a virulence mechanism exploited by invasive bacterial pathogens in the genera Listeria, Shigella, and Rickettsia. Due to experimental constraints imposed by the lack of genetic tools and their obligate intracellular nature, little is known about rickettsial ABM relative to Listeria and Shigella ABM systems. In this study, we directly compared the dynamics and behavior of ABM of Rickettsia rickettsii and Listeria monocytogenes. A time-lapse video of moving intracellular bacteria was obtained by laser-scanning confocal microscopy of infected Vero cells synthesizing beta-actin coupled to green fluorescent protein (GFP). Analysis of time-lapse images demonstrated that R. rickettsii organisms move through the cell cytoplasm at an average rate of 4.8 +/- 0.6 micrometer/min (mean +/- standard deviation). This speed was 2.5 times slower than that of L. monocytogenes, which moved at an average rate of 12.0 +/- 3.1 micrometers/min. Although rickettsiae moved more slowly, the actin filaments comprising the actin comet tail were significantly more stable, with an average half-life approximately three times that of L. monocytogenes (100.6 +/- 19.2 s versus 33.0 +/- 7.6 s, respectively). The actin tail associated with intracytoplasmic rickettsiae remained stationary in the cytoplasm as the organism moved forward. In contrast, actin tails of rickettsiae trapped within the nucleus displayed dramatic movements. The observed phenotypic differences between the ABM of Listeria and Rickettsia may indicate fundamental differences in the mechanisms of actin recruitment and polymerization.

  9. The Stationary-Phase Cells of Saccharomyces cerevisiae Display Dynamic Actin Filaments Required for Processes Extending Chronological Life Span.

    Science.gov (United States)

    Vasicova, Pavla; Lejskova, Renata; Malcova, Ivana; Hasek, Jiri

    2015-11-01

    Stationary-growth-phase Saccharomyces cerevisiae yeast cultures consist of nondividing cells that undergo chronological aging. For their successful survival, the turnover of proteins and organelles, ensured by autophagy and the activation of mitochondria, is performed. Some of these processes are engaged in by the actin cytoskeleton. In S. cerevisiae stationary-phase cells, F actin has been shown to form static aggregates named actin bodies, subsequently cited to be markers of quiescence. Our in vivo analyses revealed that stationary-phase cultures contain cells with dynamic actin filaments, besides the cells with static actin bodies. The cells with dynamic actin displayed active endocytosis and autophagy and well-developed mitochondrial networks. Even more, stationary-phase cell cultures grown under calorie restriction predominantly contained cells with actin cables, confirming that the presence of actin cables is linked to successful adaptation to stationary phase. Cells with actin bodies were inactive in endocytosis and autophagy and displayed aberrations in mitochondrial networks. Notably, cells of the respiratory activity-deficient cox4Δ strain displayed the same mitochondrial aberrations and actin bodies only. Additionally, our results indicate that mitochondrial dysfunction precedes the formation of actin bodies and the appearance of actin bodies corresponds to decreased cell fitness. We conclude that the F-actin status reflects the extent of damage that arises from exponential growth. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  10. Myosin isoform determines the conformational dynamics and cooperativity of actin filaments in the strongly bound actomyosin complex

    Science.gov (United States)

    Prochniewicz, Ewa; Chin, Harvey F.; Henn, Arnon; Hannemann, Diane E.; Olivares, Adrian O.; Thomas, David D.; De La Cruz, Enrique M.

    2010-01-01

    SUMMARY We have used transient phosphorescence anisotropy (TPA) to detect the microsecond rotational dynamics of erythrosin iodoacetamide (ErIA)-labeled actin strongly bound to single-headed fragments of muscle myosin (muscle S1) and non-muscle myosin V (MV). The conformational dynamics of actin filaments in solution are markedly influenced by the isoform of bound myosin. Both myosins increase the final anisotropy of actin at sub-stoichiometric binding densities, indicating long-range, non-nearest neighbor cooperative restriction of filament rotational dynamics amplitude, but the cooperative unit is larger with MV than muscle S1. Both myosin isoforms also cooperatively affect the actin filament rotational correlation time, but with opposite effects; muscle S1 decreases rates of intrafilament torsional motion, while binding of MV increases the rates of motion. The cooperative effects on the rates of intrafilament motions correlate with the kinetics of myosin binding to actin filaments such that MV binds more rapidly, and muscle myosin more slowly, to partially decorated filaments than to bare filaments. The two isoforms also differ in their effects on the phosphorescence lifetime of the actin-bound ErIA; while muscle S1 increases the lifetime, suggesting decreased aqueous exposure of the probe, MV does not induce a significant change. We conclude that the dynamics and structure of actin in the strongly bound actomyosin complex is determined by the isoform of the bound myosin, in a manner likely to accommodate the diverse functional roles of actomyosin in muscle and non-muscle cells. PMID:19962990

  11. Separation of actin-dependent and actin-independent lipid rafts

    NARCIS (Netherlands)

    Klappe, Karin; Hummel, Ina; Kok, Jan Willem

    2013-01-01

    Lipid rafts have been isolated on the basis of their resistance to various detergents and more recently by using detergent-free procedures. The actin cytoskeleton is now recognized as a dynamic regulator of lipid raft stability. We carefully analyzed the effects of the cortical actin-disrupting

  12. The value of dynamic infrared thermography (DIRT) in perforatorselection and planning of free DIEP flaps.

    Science.gov (United States)

    de Weerd, Louis; Weum, Sven; Mercer, James B

    2009-09-01

    The aim of this paper is to evaluate dynamic infrared thermography (DIRT) as a technique to assist in preoperative perforator selection and planning of free deep inferior epigastric perforator (DIEP) flaps. Twenty-seven patients, scheduled for secondary autologous breast reconstruction with either a free DIEP flap or superficial inferior epigastric artery flap, were included in this prospective clinical study. Preoperative mapping of perforators was performed with a hand-held Doppler and DIRT. A multidetector computer tomography scan was additionally carried out in the last 8 patients. In 23 patients a DIEP flap was used. The perforator as selected from DIRT was a suitable perforator in all DIEP flaps. The location and quality of the selected perforator from DIRT corresponded well with the multidetector computer tomography scan results. Preoperative perforator selection and planning of DIEP flaps is facilitated with the use of DIRT. The technique is noninvasive and easy to use.

  13. Pdlim7 Regulates Arf6-Dependent Actin Dynamics and Is Required for Platelet-Mediated Thrombosis in Mice.

    Directory of Open Access Journals (Sweden)

    Alexander E Urban

    Full Text Available Upon vessel injury, platelets become activated and rapidly reorganize their actin cytoskeleton to adhere to the site of endothelial damage, triggering the formation of a fibrin-rich plug to prevent further blood loss. Inactivation of Pdlim7 provides the new perspective that regulation of actin cytoskeletal changes in platelets is dependent on the encoded PDZ-LIM protein. Loss-of-function of Pdlim7 triggers hypercoagulopathy and causes significant perinatal lethality in mice. Our in vivo and in vitro studies reveal that Pdlim7 is dynamically distributed along actin fibers, and lack of Pdlim7 leads to a marked inability to rearrange the actin cytoskeleton. Specifically, the absence of Pdlim7 prevents platelets from bundling actin fibers into a concentric ring that defines the round spread shape of activated platelets. Similarly, in mouse embryonic fibroblasts, loss of Pdlim7 abolishes the formation of stress fibers needed to adopt the typical elongated fibroblast shape. In addition to revealing a fundamental cell biological role in actin cytoskeletal organization, we also demonstrate a function of Pdlim7 in regulating the cycling between the GTP/GDP-bound states of Arf6. The small GTPase Arf6 is an essential factor required for actin dynamics, cytoskeletal rearrangements, and platelet activation. Consistent with our findings of significantly elevated initial F-actin ratios and subsequent morphological aberrations, loss of Pdlim7 causes a shift in balance towards an increased Arf6-GTP level in resting platelets. These findings identify a new Pdlim7-Arf6 axis controlling actin dynamics and implicate Pdlim7 as a primary endogenous regulator of platelet-dependent hemostasis.

  14. Computational Study of the Binding Mechanism of Actin-Depolymerizing Factor 1 with Actin in Arabidopsis thaliana.

    Directory of Open Access Journals (Sweden)

    Juan Du

    Full Text Available Actin is a highly conserved protein. It plays important roles in cellular function and exists either in the monomeric (G-actin or polymeric form (F-actin. Members of the actin-depolymerizing factor (ADF/cofilin protein family bind to both G-actin and F-actin and play vital roles in actin dynamics by manipulating the rates of filament polymerization and depolymerization. It has been reported that the S6D and R98A/K100A mutants of actin-depolymerizing factor 1 (ADF1 in Arabidopsis thaliana decreased the binding affinity of ADF for the actin monomer. To investigate the binding mechanism and dynamic behavior of the ADF1-actin complex, we constructed a homology model of the AtADF1-actin complex based on the crystal structure of AtADF1 and the twinfilin C-terminal ADF-H domain in a complex with a mouse actin monomer. The model was then refined for subsequent molecular dynamics simulations. Increased binding energy of the mutated system was observed using the Molecular Mechanics Generalized Born Surface Area and Poisson-Boltzmann Surface Area (MM-GB/PBSA methods. To determine the residues that make decisive contributions to the ADF1 actin-binding affinity, per-residue decomposition and computational alanine scanning analyses were performed, which provided more detailed information on the binding mechanism. Root-mean-square fluctuation and principal component analyses confirmed that the S6D and R98A/K100A mutants induced an increased conformational flexibility. The comprehensive molecular insight gained from this study is of great importance for understanding the binding mechanism of ADF1 and G-actin.

  15. Actin-interacting Protein 1 Promotes Disassembly of Actin-depolymerizing Factor/Cofilin-bound Actin Filaments in a pH-dependent Manner.

    Science.gov (United States)

    Nomura, Kazumi; Hayakawa, Kimihide; Tatsumi, Hitoshi; Ono, Shoichiro

    2016-03-04

    Actin-interacting protein 1 (AIP1) is a conserved WD repeat protein that promotes disassembly of actin filaments when actin-depolymerizing factor (ADF)/cofilin is present. Although AIP1 is known to be essential for a number of cellular events involving dynamic rearrangement of the actin cytoskeleton, the regulatory mechanism of the function of AIP1 is unknown. In this study, we report that two AIP1 isoforms from the nematode Caenorhabditis elegans, known as UNC-78 and AIPL-1, are pH-sensitive in enhancement of actin filament disassembly. Both AIP1 isoforms only weakly enhance disassembly of ADF/cofilin-bound actin filaments at an acidic pH but show stronger disassembly activity at neutral and basic pH values. However, a severing-defective mutant of UNC-78 shows pH-insensitive binding to ADF/cofilin-decorated actin filaments, suggesting that the process of filament severing or disassembly, but not filament binding, is pH-dependent. His-60 of AIP1 is located near the predicted binding surface for the ADF/cofilin-actin complex, and an H60K mutation of AIP1 partially impairs its pH sensitivity, suggesting that His-60 is involved in the pH sensor for AIP1. These biochemical results suggest that pH-dependent changes in AIP1 activity might be a novel regulatory mechanism of actin filament dynamics. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  16. Geometrical Determinants of Neuronal Actin Waves

    OpenAIRE

    Tomba, Caterina; Bra?ni, C?line; Bugnicourt, Ghislain; Cohen, Floriane; Friedrich, Benjamin M.; Gov, Nir S.; Villard, Catherine

    2017-01-01

    Hippocampal neurons produce in their early stages of growth propagative, actin-rich dynamical structures called actin waves. The directional motion of actin waves from the soma to the tip of neuronal extensions has been associated with net forward growth, and ultimately with the specification of neurites into axon and dendrites. Here, geometrical cues are used to control actin wave dynamics by constraining neurons on adhesive stripes of various widths. A key observable, the average time betwe...

  17. Cytoskeletal actin dynamics shape a ramifying actin network underpinning immunological synapse formation

    DEFF Research Database (Denmark)

    Fritzsche, Marco; Fernandes, Ricardo A.; Chang, Veronica T.

    2017-01-01

    optical microscopes to analyze resting and activated T cells, we show that, following contact formation with activating surfaces, these cells sequentially rearrange their cortical actin across the entire cell, creating a previously unreported ramifying actin network above the immunological synapse...

  18. Dynamics of the actin cytoskeleton mediates receptor cross talk: An emerging concept in tuning receptor signaling

    Science.gov (United States)

    Mattila, Pieta K.; Batista, Facundo D.

    2016-01-01

    Recent evidence implicates the actin cytoskeleton in the control of receptor signaling. This may be of particular importance in the context of immune receptors, such as the B cell receptor, where dysregulated signaling can result in autoimmunity and malignancy. Here, we discuss the role of the actin cytoskeleton in controlling receptor compartmentalization, dynamics, and clustering as a means to regulate receptor signaling through controlling the interactions with protein partners. We propose that the actin cytoskeleton is a point of integration for receptor cross talk through modulation of protein dynamics and clustering. We discuss the implication of this cross talk via the cytoskeleton for both ligand-induced and low-level constitutive (tonic) signaling necessary for immune cell survival. PMID:26833785

  19. How does the antagonism between capping and anti-capping proteins affect actin network dynamics?

    International Nuclear Information System (INIS)

    Hu Longhua; Papoian, Garegin A

    2011-01-01

    Actin-based cell motility is essential to many biological processes. We built a simplified, three-dimensional computational model and subsequently performed stochastic simulations to study the growth dynamics of lamellipodia-like branched networks. In this work, we shed light on the antagonism between capping and anti-capping proteins in regulating actin dynamics in the filamentous network. We discuss detailed mechanisms by which capping and anti-capping proteins affect the protrusion speed of the actin network and the rate of nucleation of filaments. We computed a phase diagram showing the regimes of motility enhancement and inhibition by these proteins. Our work shows that the effects of capping and anti-capping proteins are mainly transmitted by modulation of the filamentous network density and local availability of monomeric actin. We discovered that the combination of the capping/anti-capping regulatory network with nucleation-promoting proteins introduces robustness and redundancy in cell motility machinery, allowing the cell to easily achieve maximal protrusion speeds under a broader set of conditions. Finally, we discuss distributions of filament lengths under various conditions and speculate on their potential implication for the emergence of filopodia from the lamellipodial network.

  20. Cortical actin nodes: Their dynamics and recruitment of podosomal proteins as revealed by super-resolution and single-molecule microscopy

    Science.gov (United States)

    Shirai, Yuki M.; Tsunoyama, Taka A.; Hiramoto-Yamaki, Nao; Hirosawa, Koichiro M.; Shibata, Akihiro C. E.; Kondo, Kenichi; Tsurumune, Atsushi; Ishidate, Fumiyoshi; Kusumi, Akihiro

    2017-01-01

    Electron tomography of the plasma membrane (PM) identified several layers of cortical actin meshwork running parallel to the PM cytoplasmic surface throughout the PM. Here, cortical actin structures and dynamics were examined in living cells, using super-resolution microscopy, with (x,y)- and z-resolutions of ~140 and ~400 nm, respectively, and single-molecule imaging. The super-resolution microscopy identified sub-micron-sized actin clusters that appeared identical by both phalloidin post-fixation staining and Lifeact-mGFP expression followed by fixation, and therefore, these actin clusters were named “actin-pl-clusters”. In live cells, the actin-pl-clusters visualized by Lifeact-mGFP linked two or more actin filaments in the fine actin meshwork, acting as a node of the meshwork, and dynamically moved on/along the meshwork in a myosin II-dependent manner. Their formation depended on the Arp2/3 activities, suggesting that the movements could involve both the myosin motor activity and actin polymerization-depolymerization. The actin-pl-clusters differ from the actin nodes/asters found previously after latrunculin treatments, since myosin II and filamin A were not colocalized with the actin-pl-clusters, and the actin-pl-clusters were much smaller than the previously reported nodes/asters. The Lifeact linked to a fluorescently-labeled transmembrane peptide from syntaxin4 (Lifeact-TM) expressed in the PM exhibited temporary immobilization in the PM regions on which actin-pl-clusters and stress fibers were projected, showing that ≥66% of actin-pl-clusters and 89% of stress fibers were located in close proximity (within 3.5 nm) to the PM cytoplasmic surface. Podosome-associated cytoplasmic proteins, Tks4, Tks5, cortactin, and N-WASP, were transiently recruited to actin-pl-clusters, and thus, we propose that actin-pl-clusters also represent “actin podosome-like clusters”. PMID:29190677

  1. Changes in actin dynamics are involved in salicylic acid signaling pathway

    Czech Academy of Sciences Publication Activity Database

    Matoušková, J.; Janda, M.; Fišer, R.; Šašek, Vladimír; Kocourková, Daniela; Burketová, Lenka; Dušková, J.; Martinec, Jan; Valentová, O.

    2014-01-01

    Roč. 223, JUN 2014 (2014), s. 36-44 ISSN 0168-9452 R&D Projects: GA ČR(CZ) GAP501/11/1654 Institutional support: RVO:61389030 Keywords : Actin dynamics * Salicylic acid * PR genes Subject RIV: CE - Biochemistry Impact factor: 3.607, year: 2014

  2. Dynamic Regulation of Sarcomeric Actin Filaments in Striated Muscle

    OpenAIRE

    Ono, Shoichiro

    2010-01-01

    In striated muscle, the actin cytoskeleton is differentiated into myofibrils. Actin and myosin filaments are organized in sarcomeres and specialized for producing contractile forces. Regular arrangement of actin filaments with uniform length and polarity is critical for the contractile function. However, the mechanisms of assembly and maintenance of sarcomeric actin filaments in striated muscle are not completely understood. Live imaging of actin in striated muscle has revealed that actin sub...

  3. Probing friction in actin-based motility

    International Nuclear Information System (INIS)

    Marcy, Yann; Joanny, Jean-Francois; Prost, Jacques; Sykes, Cecile

    2007-01-01

    Actin dynamics are responsible for cell protrusion and certain intracellular movements. The transient attachment of the actin filaments to a moving surface generates a friction force that resists the movement. We probe here the dynamics of these attachments by inducing a stick-slip behavior via micromanipulation of a growing actin comet. We show that general principles of adhesion and friction can explain our observations

  4. Consequences of Molecular-Scale Non-Equilibrium Activity on the Dynamics and Mechanics of Self-Assembled Actin-Based Structures and Materials

    Science.gov (United States)

    Marshall Mccall, Patrick

    Living cells are hierarchically self-organized forms of active soft matter: molecules on the nanometer scale form functional structures and organelles on the micron scale, which then compose cells on the scale of 10s of microns. While the biological functions of intracellular organelles are defined by the composition and properties of the structures themselves, how those bulk properties emerge from the properties and interactions of individual molecules remains poorly understood. Actin, a globular protein which self-assembles into dynamic semi-flexible polymers, is the basic structural material of cells and the major component of many functional organelles. In this thesis, I have used purified actin as a model system to explore the interplay between molecular-scale dynamics and organelle-scale functionality, with particular focus on the role of molecular-scale non-equilibrium activity. One of the most canonical forms of molecular-scale non-equilibrium activity is that of mechanoenzymes, also called motor proteins. These proteins utilized the free energy liberated by hydrolysis of ATP to perform mechanical work, thereby introducing non-equilibrium "active" stresses on the molecular scale. Combining experiments with mathematical modeling, we demonstrate in this thesis that non-equilibrium motor activity is sufficient to drive self-organization and pattern formation of the multimeric actin-binding motor protein Myosin II on 1D reconstituted actomyosin bundles. Like myosin, actin is itself an ATPase. However, nono-equilibrium ATP hydrolysis on actin is known to regulate the stability and assembly kinetics of actin filaments rather than generate active stresses per se. At the level of single actin filaments, the inhomogeneous nucleotide composition generated along the filament length by hydrolysis directs binding of regulatory proteins like cofilin, which mediate filament disassembly and thereby accelerate actin filament turnover. The concequences of this non

  5. The F-Actin Binding Protein Cortactin Regulates the Dynamics of the Exocytotic Fusion Pore through its SH3 Domain

    Science.gov (United States)

    González-Jamett, Arlek M.; Guerra, María J.; Olivares, María J.; Haro-Acuña, Valentina; Baéz-Matus, Ximena; Vásquez-Navarrete, Jacqueline; Momboisse, Fanny; Martinez-Quiles, Narcisa; Cárdenas, Ana M.

    2017-01-01

    Upon cell stimulation, the network of cortical actin filaments is rearranged to facilitate the neurosecretory process. This actin rearrangement includes both disruption of the preexisting actin network and de novo actin polymerization. However, the mechanism by which a Ca2+ signal elicits the formation of new actin filaments remains uncertain. Cortactin, an actin-binding protein that promotes actin polymerization in synergy with the nucleation promoting factor N-WASP, could play a key role in this mechanism. We addressed this hypothesis by analyzing de novo actin polymerization and exocytosis in bovine adrenal chromaffin cells expressing different cortactin or N-WASP domains, or cortactin mutants that fail to interact with proline-rich domain (PRD)-containing proteins, including N-WASP, or to be phosphorylated by Ca2+-dependent kinases, such as ERK1/2 and Src. Our results show that the activation of nicotinic receptors in chromaffin cells promotes cortactin translocation to the cell cortex, where it colocalizes with actin filaments. We further found that, in association with PRD-containing proteins, cortactin contributes to the Ca2+-dependent formation of F-actin, and regulates fusion pore dynamics and the number of exocytotic events induced by activation of nicotinic receptors. However, whereas the actions of cortactin on the fusion pore dynamics seems to depend on the availability of monomeric actin and its phosphorylation by ERK1/2 and Src kinases, cortactin regulates the extent of exocytosis by a mechanism independent of actin polymerization. Together our findings point out a role for cortactin as a critical modulator of actin filament formation and exocytosis in neuroendocrine cells. PMID:28522963

  6. Self-Propulsion of a Flapping Airfoil Using Cyber-Physical Fluid Dynamics

    Science.gov (United States)

    Young, Jay; Asselin, Daniel; Williamson, C. H. K.

    2017-11-01

    The fluid dynamics of biologically-inspired flapping propulsion provides a fertile testing ground for the field of unsteady aerodynamics, serving as important groundwork for the design and development of underwater vehicles and micro air vehicles (MAVs). These technologies can provide low cost, compact, and maneuverable means for terrain mapping, search and rescue operations, and reconnaissance. However, most laboratory experiments and simulations have been conducted using tethered airfoils with an imposed freestream velocity, which does not necessarily reflect the conditions under which an airfoil employed as a propulsor would operate. Using a closed-loop force-feedback control system, defined as Cyber-Physical Fluid Dynamics, or CPFD (Mackowski & Williamson 2011, 2015, & 2016), we allow a flapping airfoil to fly forward freely, achieving an equilibrium velocity at which thrust and drag are balanced. We study a combination of actively and passively controlled pitching and heaving dynamics in order to find motions that minimize the energy expended per distance traveled by the propulsion system. This work was supported by the National Science Foundation and the Air Force Office of Scientific Research Grant No. FA9550-15-1-0243, monitored by Dr. Douglas Smith.

  7. On the Connection Between Flap Side-Edge Noise and Tip Vortex Dynamics

    Science.gov (United States)

    Casalino, D.; Hazir, A.; Fares, E.; Duda, B.; Khorrami, M. R.

    2015-01-01

    The goal of the present work is to investigate how the dynamics of the vortical flow about the flap side edge of an aircraft determine the acoustic radiation. A validated lattice- Boltzmann CFD solution of the unsteady flow about a detailed business jet configuration in approach conditions is used for the present analysis. Evidence of the connection between the noise generated by several segments of the inboard flap tip and the aerodynamic forces acting on the same segments is given, proving that the noise generation mechanism has a spatially coherent and acoustically compact character on the scale of the flap chord, and that the edge-scattering effects are of secondary importance. Subsequently, evidence of the connection between the kinematics of the tip vortex system and the aerodynamic force is provided. The kinematics of the dual vortex system are investigated via a core detection technique. Emphasis is placed on the mutual induction effects between the two main vortices rolling up from the pressure and suction sides of the flap edge. A simple heuristic formula that relates the far-field noise spectrum and the cross-spectrum of the unsteady vortical positions is developed.

  8. Actin dynamics at focal adhesions: a common endpoint and putative therapeutic target for proteinuric kidney diseases.

    Science.gov (United States)

    Sever, Sanja; Schiffer, Mario

    2018-06-01

    Proteinuria encompasses diverse causes including both genetic diseases and acquired forms such as diabetic and hypertensive nephropathy. The basis of proteinuria is a disturbance in size selectivity of the glomerular filtration barrier, which largely depends on the podocyte: a terminally differentiated epithelial cell type covering the outer surface of the glomerulus. Compromised podocyte structure is one of the earliest signs of glomerular injury. The phenotype of diverse animal models and podocyte cell culture firmly established the essential role of the actin cytoskeleton in maintaining functional podocyte structure. Podocyte foot processes, actin-based membrane extensions, contain 2 molecularly distinct "hubs" that control actin dynamics: a slit diaphragm and focal adhesions. Although loss of foot processes encompasses disassembly of slit diaphragm multiprotein complexes, as long as cells are attached to the glomerular basement membrane, focal adhesions will be the sites in which stress due to filtration flow is counteracted by forces generated by the actin network in foot processes. Numerous studies within last 20 years have identified actin binding and regulatory proteins as well as integrins as essential components of signaling and actin dynamics at focal adhesions in podocytes, suggesting that some of them may become novel, druggable targets for proteinuric kidney diseases. Here we review evidence supporting the idea that current treatments for chronic kidney diseases beneficially and directly target the podocyte actin cytoskeleton associated with focal adhesions and suggest that therapeutic reagents that target the focal adhesion-regulated actin cytoskeleton in foot processes have potential to modernize treatments for chronic kidney diseases. Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.

  9. ATEFlap aerodynamic model, a dynamic stall model including the effects of trailing edge flap deflection

    Energy Technology Data Exchange (ETDEWEB)

    Bergami, L.; Gaunaa, M.

    2012-02-15

    The report presents the ATEFlap aerodynamic model, which computes the unsteady lift, drag and moment on a 2D airfoil section equipped with Adaptive Trailing Edge Flap. The model captures the unsteady response related to the effects of the vorticity shed into the wake, and the dynamics of flow separation a thin-airfoil potential flow model is merged with a dynamic stall model of the Beddoes-Leishmann type. The inputs required by the model are steady data for lift, drag, and moment coefficients as function of angle of attack and flap deflection. Further steady data used by the Beddoes- Leishmann dynamic stall model are computed in an external preprocessor application, which gives the user the possibility to verify, and eventually correct, the steady data passed to the aerodynamic model. The ATEFlap aerodynamic model is integrated in the aeroelastic simulation tool HAWC2, thus al- lowing to simulate the response of a wind turbine with trailing edge flaps on the rotor. The algorithms used by the preprocessor, and by aerodynamic model are presented, and modifications to previous implementations of the aerodynamic model are briefly discussed. The performance and the validity of the model are verified by comparing the dynamic response computed by the ATEFlap with solutions from CFD simulations. (Author)

  10. Bundling Actin Filaments From Membranes: Some Novel Players

    Directory of Open Access Journals (Sweden)

    Clément eThomas

    2012-08-01

    Full Text Available Progress in live-cell imaging of the cytoskeleton has significantly extended our knowledge about the organization and dynamics of actin filaments near the plasma membrane of plant cells. Noticeably, two populations of filamentous structures can be distinguished. On the one hand, fine actin filaments which exhibit an extremely dynamic behavior basically characterized by fast polymerization and prolific severing events, a process referred to as actin stochastic dynamics. On the other hand, thick actin bundles which are composed of several filaments and which are comparatively more stable although they constantly remodel as well. There is evidence that the actin cytoskeleton plays critical roles in trafficking and signaling at both the cell cortex and organelle periphery but the exact contribution of actin bundles remains unclear. A common view is that actin bundles provide the long-distance tracks used by myosin motors to deliver their cargo to growing regions and accordingly play a particularly important role in cell polarization. However, several studies support that actin bundles are more than simple passive highways and display multiple and dynamic roles in the regulation of many processes, such as cell elongation, polar auxin transport, stomatal and chloroplast movement, and defense against pathogens. The list of identified plant actin-bundling proteins is ever expanding, supporting that plant cells shape structurally and functionally different actin bundles. Here I review the most recently characterized actin-bundling proteins, with a particular focus on those potentially relevant to membrane trafficking and/or signaling.

  11. Geometrical Determinants of Neuronal Actin Waves.

    Science.gov (United States)

    Tomba, Caterina; Braïni, Céline; Bugnicourt, Ghislain; Cohen, Floriane; Friedrich, Benjamin M; Gov, Nir S; Villard, Catherine

    2017-01-01

    Hippocampal neurons produce in their early stages of growth propagative, actin-rich dynamical structures called actin waves. The directional motion of actin waves from the soma to the tip of neuronal extensions has been associated with net forward growth, and ultimately with the specification of neurites into axon and dendrites. Here, geometrical cues are used to control actin wave dynamics by constraining neurons on adhesive stripes of various widths. A key observable, the average time between the production of consecutive actin waves, or mean inter-wave interval (IWI), was identified. It scales with the neurite width, and more precisely with the width of the proximal segment close to the soma. In addition, the IWI is independent of the total number of neurites. These two results suggest a mechanistic model of actin wave production, by which the material conveyed by actin waves is assembled in the soma until it reaches the threshold leading to the initiation and propagation of a new actin wave. Based on these observations, we formulate a predictive theoretical description of actin wave-driven neuronal growth and polarization, which consistently accounts for different sets of experiments.

  12. Effects of polymerization and nucleotide identity on the conformational dynamics of the bacterial actin homolog MreB.

    Science.gov (United States)

    Colavin, Alexandre; Hsin, Jen; Huang, Kerwyn Casey

    2014-03-04

    The assembly of protein filaments drives many cellular processes, from nucleoid segregation, growth, and division in single cells to muscle contraction in animals. In eukaryotes, shape and motility are regulated through cycles of polymerization and depolymerization of actin cytoskeletal networks. In bacteria, the actin homolog MreB forms filaments that coordinate the cell-wall synthesis machinery to regulate rod-shaped growth and contribute to cellular stiffness through unknown mechanisms. Like actin, MreB is an ATPase and requires ATP to polymerize, and polymerization promotes nucleotide hydrolysis. However, it is unclear whether other similarities exist between MreB and actin because the two proteins share low sequence identity and have distinct cellular roles. Here, we use all-atom molecular dynamics simulations to reveal surprising parallels between MreB and actin structural dynamics. We observe that MreB exhibits actin-like polymerization-dependent structural changes, wherein polymerization induces flattening of MreB subunits, which restructures the nucleotide-binding pocket to favor hydrolysis. MreB filaments exhibited nucleotide-dependent intersubunit bending, with hydrolyzed polymers favoring a straighter conformation. We use steered simulations to demonstrate a coupling between intersubunit bending and the degree of flattening of each subunit, suggesting cooperative bending along a filament. Taken together, our results provide molecular-scale insight into the diversity of structural states of MreB and the relationships among polymerization, hydrolysis, and filament properties, which may be applicable to other members of the broad actin family.

  13. Actin filaments – a target for redox regulation

    Science.gov (United States)

    Wilson, Carlos; Terman, Jonathan R.; González-Billault, Christian; Ahmed, Giasuddin

    2016-01-01

    Actin and its ability to polymerize into dynamic filaments is critical for the form and function of cells throughout the body. While multiple proteins have been characterized as affecting actin dynamics through non-covalent means, actin and its protein regulators are also susceptible to covalent modifications of their amino acid residues. In this regard, oxidation-reduction (Redox) intermediates have emerged as key modulators of the actin cytoskeleton with multiple different effects on cellular form and function. Here, we review work implicating Redox intermediates in post-translationally altering actin and discuss what is known regarding how these alterations affect the properties of actin. We also focus on two of the best characterized enzymatic sources of these Redox intermediates – the NADPH oxidase NOX and the flavoprotein monooxygenase MICAL – and detail how they have both been identified as altering actin, but share little similarity and employ different means to regulate actin dynamics. Finally, we discuss the role of these enzymes and redox signaling in regulating the actin cytoskeleton in vivo and highlight their importance for neuronal form and function in health and disease. PMID:27309342

  14. Dynamics of a pneumatic artificial muscle actuation system driving a trailing edge flap

    Science.gov (United States)

    Woods, Benjamin K. S.; Kothera, Curt S.; Wang, Gang; Wereley, Norman M.

    2014-09-01

    This study presents a time domain dynamic model of an antagonistic pneumatic artificial muscle (PAM) driven trailing edge flap (TEF) system for next generation active helicopter rotors. Active rotor concepts are currently being widely researched in the rotorcraft community as a means to provide a significant leap forward in performance through primary aircraft control, vibration mitigation and noise reduction. Recent work has shown PAMs to be a promising candidate for active rotor actuation due to their combination of high force, large stroke, light weight, and suitable bandwidth. When arranged into biologically inspired agonist/antagonist muscle pairs they can produce bidirectional torques for effectively driving a TEF. However, there are no analytical dynamic models in the literature that can accurately capture the behavior of such systems across the broad range of frequencies required for this demanding application. This work combines mechanical, pneumatic, and aerodynamic component models into a global flap system model developed for the Bell 407 rotor system. This model can accurately predict pressure, force, and flap angle response to pneumatic control valve inputs over a range of operating frequencies from 7 to 35 Hz (1/rev to 5/rev for the Bell 407) and operating pressures from 30 to 90 psi.

  15. Dynamics of a pneumatic artificial muscle actuation system driving a trailing edge flap

    International Nuclear Information System (INIS)

    Woods, Benjamin K S; Kothera, Curt S; Wang, Gang; Wereley, Norman M

    2014-01-01

    This study presents a time domain dynamic model of an antagonistic pneumatic artificial muscle (PAM) driven trailing edge flap (TEF) system for next generation active helicopter rotors. Active rotor concepts are currently being widely researched in the rotorcraft community as a means to provide a significant leap forward in performance through primary aircraft control, vibration mitigation and noise reduction. Recent work has shown PAMs to be a promising candidate for active rotor actuation due to their combination of high force, large stroke, light weight, and suitable bandwidth. When arranged into biologically inspired agonist/antagonist muscle pairs they can produce bidirectional torques for effectively driving a TEF. However, there are no analytical dynamic models in the literature that can accurately capture the behavior of such systems across the broad range of frequencies required for this demanding application. This work combines mechanical, pneumatic, and aerodynamic component models into a global flap system model developed for the Bell 407 rotor system. This model can accurately predict pressure, force, and flap angle response to pneumatic control valve inputs over a range of operating frequencies from 7 to 35 Hz (1/rev to 5/rev for the Bell 407) and operating pressures from 30 to 90 psi. (paper)

  16. Modulation of actin dynamics as potential macrophage subtype-targeting anti-tumour strategy.

    Science.gov (United States)

    Pergola, Carlo; Schubert, Katrin; Pace, Simona; Ziereisen, Jana; Nikels, Felix; Scherer, Olga; Hüttel, Stephan; Zahler, Stefan; Vollmar, Angelika M; Weinigel, Christina; Rummler, Silke; Müller, Rolf; Raasch, Martin; Mosig, Alexander; Koeberle, Andreas; Werz, Oliver

    2017-01-30

    Tumour-associated macrophages mainly comprise immunosuppressive M2 phenotypes that promote tumour progression besides anti-tumoural M1 subsets. Selective depletion or reprogramming of M2 may represent an innovative anti-cancer strategy. The actin cytoskeleton is central for cellular homeostasis and is targeted for anti-cancer chemotherapy. Here, we show that targeting G-actin nucleation using chondramide A (ChA) predominantly depletes human M2 while promoting the tumour-suppressive M1 phenotype. ChA reduced the viability of M2, with minor effects on M1, but increased tumour necrosis factor (TNF)α release from M1. Interestingly, ChA caused rapid disruption of dynamic F-actin filaments and polymerization of G-actin, followed by reduction of cell size, binucleation and cell division, without cellular collapse. In M1, but not in M2, ChA caused marked activation of SAPK/JNK and NFκB, with slight or no effects on Akt, STAT-1/-3, ERK-1/2, and p38 MAPK, seemingly accounting for the better survival of M1 and TNFα secretion. In a microfluidically-supported human tumour biochip model, circulating ChA-treated M1 markedly reduced tumour cell viability through enhanced release of TNFα. Together, ChA may cause an anti-tumoural microenvironment by depletion of M2 and activation of M1, suggesting induction of G-actin nucleation as potential strategy to target tumour-associated macrophages in addition to neoplastic cells.

  17. Dendritic Actin Cytoskeleton: Structure, Functions, and Regulations

    Directory of Open Access Journals (Sweden)

    Anja Konietzny

    2017-05-01

    Full Text Available Actin is a versatile and ubiquitous cytoskeletal protein that plays a major role in both the establishment and the maintenance of neuronal polarity. For a long time, the most prominent roles that were attributed to actin in neurons were the movement of growth cones, polarized cargo sorting at the axon initial segment, and the dynamic plasticity of dendritic spines, since those compartments contain large accumulations of actin filaments (F-actin that can be readily visualized using electron- and fluorescence microscopy. With the development of super-resolution microscopy in the past few years, previously unknown structures of the actin cytoskeleton have been uncovered: a periodic lattice consisting of actin and spectrin seems to pervade not only the whole axon, but also dendrites and even the necks of dendritic spines. Apart from that striking feature, patches of F-actin and deep actin filament bundles have been described along the lengths of neurites. So far, research has been focused on the specific roles of actin in the axon, while it is becoming more and more apparent that in the dendrite, actin is not only confined to dendritic spines, but serves many additional and important functions. In this review, we focus on recent developments regarding the role of actin in dendrite morphology, the regulation of actin dynamics by internal and external factors, and the role of F-actin in dendritic protein trafficking.

  18. Actin dynamics, architecture, and mechanics in cell motility.

    Science.gov (United States)

    Blanchoin, Laurent; Boujemaa-Paterski, Rajaa; Sykes, Cécile; Plastino, Julie

    2014-01-01

    Tight coupling between biochemical and mechanical properties of the actin cytoskeleton drives a large range of cellular processes including polarity establishment, morphogenesis, and motility. This is possible because actin filaments are semi-flexible polymers that, in conjunction with the molecular motor myosin, can act as biological active springs or "dashpots" (in laymen's terms, shock absorbers or fluidizers) able to exert or resist against force in a cellular environment. To modulate their mechanical properties, actin filaments can organize into a variety of architectures generating a diversity of cellular organizations including branched or crosslinked networks in the lamellipodium, parallel bundles in filopodia, and antiparallel structures in contractile fibers. In this review we describe the feedback loop between biochemical and mechanical properties of actin organization at the molecular level in vitro, then we integrate this knowledge into our current understanding of cellular actin organization and its physiological roles.

  19. Letrozole regulates actin cytoskeleton polymerization dynamics in a SRC-1 dependent manner in the hippocampus of mice.

    Science.gov (United States)

    Zhao, Yangang; Yu, Yanlan; Zhang, Yuanyuan; He, Li; Qiu, Linli; Zhao, Jikai; Liu, Mengying; Zhang, Jiqiang

    2017-03-01

    In the hippocampus, local estrogens (E 2 ) derived from testosterone that is catalyzed by aromatase play important roles in the regulation of hippocampal neural plasticity, but the underlying mechanisms remain unclear. The actin cytoskeleton contributes greatly to hippocampal synaptic plasticity; however, whether it is regulated by local E 2 and the related mechanisms remain to be elucidated. In this study, we first examined the postnatal developmental profiles of hippocampal aromatase and specific proteins responsible for actin cytoskeleton dynamics. Then we used aromatase inhibitor letrozole (LET) to block local E 2 synthesis and examined the changes of these proteins and steroid receptor coactivator-1 (SRC-1), the predominant coactivator for steroid nuclear receptors. Finally, SRC-1 specific RNA interference was used to examine the effects of SRC-1 on the expression of these actin remodeling proteins. The results showed a V-type profile for aromatase and increased profiles for actin cytoskeleton proteins in both male and female hippocampus without obvious sex differences. LET treatment dramatically decreased the F-actin/G-actin ratio, the expression of Rictor, phospho-AKT (ser473), Profilin-1, phospho-Cofilin (Ser3), and SRC-1 in a dose-dependent manner. In vitro studies demonstrated that LET induced downregulation of these proteins could be reversed by E 2 , and E 2 induced increase of these proteins were significantly suppressed by SRC-1 shRNA interference. These results for the first time clearly demonstrated that local E 2 inhibition could induce aberrant actin polymerization; they also showed an important role of SRC-1 in the mediation of local E 2 action on hippocampal synaptic plasticity by regulation of actin cytoskeleton dynamics. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Neonatal isolation augments social dominance by altering actin dynamics in the medial prefrontal cortex.

    Science.gov (United States)

    Tada, Hirobumi; Miyazaki, Tomoyuki; Takemoto, Kiwamu; Takase, Kenkichi; Jitsuki, Susumu; Nakajima, Waki; Koide, Mayu; Yamamoto, Naoko; Komiya, Kasane; Suyama, Kumiko; Sano, Akane; Taguchi, Akiko; Takahashi, Takuya

    2016-10-25

    Social separation early in life can lead to the development of impaired interpersonal relationships and profound social disorders. However, the underlying cellular and molecular mechanisms involved are largely unknown. Here, we found that isolation of neonatal rats induced glucocorticoid-dependent social dominance over nonisolated control rats in juveniles from the same litter. Furthermore, neonatal isolation inactivated the actin-depolymerizing factor (ADF)/cofilin in the juvenile medial prefrontal cortex (mPFC). Isolation-induced inactivation of ADF/cofilin increased stable actin fractions at dendritic spines in the juvenile mPFC, decreasing glutamate synaptic AMPA receptors. Expression of constitutively active ADF/cofilin in the mPFC rescued the effect of isolation on social dominance. Thus, neonatal isolation affects spines in the mPFC by reducing actin dynamics, leading to altered social behavior later in life.

  1. Neonatal isolation augments social dominance by altering actin dynamics in the medial prefrontal cortex

    Science.gov (United States)

    Tada, Hirobumi; Miyazaki, Tomoyuki; Takemoto, Kiwamu; Takase, Kenkichi; Jitsuki, Susumu; Nakajima, Waki; Koide, Mayu; Yamamoto, Naoko; Komiya, Kasane; Suyama, Kumiko; Sano, Akane; Taguchi, Akiko; Takahashi, Takuya

    2016-01-01

    Social separation early in life can lead to the development of impaired interpersonal relationships and profound social disorders. However, the underlying cellular and molecular mechanisms involved are largely unknown. Here, we found that isolation of neonatal rats induced glucocorticoid-dependent social dominance over nonisolated control rats in juveniles from the same litter. Furthermore, neonatal isolation inactivated the actin-depolymerizing factor (ADF)/cofilin in the juvenile medial prefrontal cortex (mPFC). Isolation-induced inactivation of ADF/cofilin increased stable actin fractions at dendritic spines in the juvenile mPFC, decreasing glutamate synaptic AMPA receptors. Expression of constitutively active ADF/cofilin in the mPFC rescued the effect of isolation on social dominance. Thus, neonatal isolation affects spines in the mPFC by reducing actin dynamics, leading to altered social behavior later in life. PMID:27791080

  2. Spontaneous actin dynamics in contractile rings

    Science.gov (United States)

    Kruse, Karsten; Wollrab, Viktoria; Thiagarajan, Raghavan; Wald, Anne; Riveline, Daniel

    Networks of polymerizing actin filaments are known to be capable to self-organize into a variety of structures. For example, spontaneous actin polymerization waves have been observed in living cells in a number of circumstances, notably, in crawling neutrophils and slime molds. During later stages of cell division, they can also spontaneously form a contractile ring that will eventually cleave the cell into two daughter cells. We present a framework for describing networks of polymerizing actin filaments, where assembly is regulated by various proteins. It can also include the effects of molecular motors. We show that the molecular processes driven by these proteins can generate various structures that have been observed in contractile rings of fission yeast and mammalian cells. We discuss a possible functional role of each of these patterns. The work was supported by Agence Nationale de la Recherche, France, (ANR-10-LABX-0030-INRT) and by Deutsche Forschungsgemeinschaft through SFB1027.

  3. Structural dynamics and aerodynamics measurements of biologically inspired flexible flapping wings

    International Nuclear Information System (INIS)

    Wu, P; Stanford, B K; Ifju, P G; Saellstroem, E; Ukeiley, L

    2011-01-01

    Flapping wing flight as seen in hummingbirds and insects poses an interesting unsteady aerodynamic problem: coupling of wing kinematics, structural dynamics and aerodynamics. There have been numerous studies on the kinematics and aerodynamics in both experimental and computational cases with both natural and artificial wings. These studies tend to ignore wing flexibility; however, observation in nature affirms that passive wing deformation is predominant and may be crucial to the aerodynamic performance. This paper presents a multidisciplinary experimental endeavor in correlating a flapping micro air vehicle wing's aeroelasticity and thrust production, by quantifying and comparing overall thrust, structural deformation and airflow of six pairs of hummingbird-shaped membrane wings of different properties. The results show that for a specific spatial distribution of flexibility, there is an effective frequency range in thrust production. The wing deformation at the thrust-productive frequencies indicates the importance of flexibility: both bending and twisting motion can interact with aerodynamic loads to enhance wing performance under certain conditions, such as the deformation phase and amplitude. By measuring structural deformations under the same aerodynamic conditions, beneficial effects of passive wing deformation can be observed from the visualized airflow and averaged thrust. The measurements and their presentation enable observation and understanding of the required structural properties for a thrust effective flapping wing. The intended passive responses of the different wings follow a particular pattern in correlation to their aerodynamic performance. Consequently, both the experimental technique and data analysis method can lead to further studies to determine the design principles for micro air vehicle flapping wings.

  4. Structural dynamics and aerodynamics measurements of biologically inspired flexible flapping wings

    Energy Technology Data Exchange (ETDEWEB)

    Wu, P; Stanford, B K; Ifju, P G [Department of Mechanical and Aerospace Engineering, MAE-A 231, University of Florida, Gainesville, FL 32611 (United States); Saellstroem, E; Ukeiley, L, E-mail: diccidwp@ufl.edu [Department of Mechanical and Aerospace Engineering, University of Florida, Shalimar, FL 32579 (United States)

    2011-03-15

    Flapping wing flight as seen in hummingbirds and insects poses an interesting unsteady aerodynamic problem: coupling of wing kinematics, structural dynamics and aerodynamics. There have been numerous studies on the kinematics and aerodynamics in both experimental and computational cases with both natural and artificial wings. These studies tend to ignore wing flexibility; however, observation in nature affirms that passive wing deformation is predominant and may be crucial to the aerodynamic performance. This paper presents a multidisciplinary experimental endeavor in correlating a flapping micro air vehicle wing's aeroelasticity and thrust production, by quantifying and comparing overall thrust, structural deformation and airflow of six pairs of hummingbird-shaped membrane wings of different properties. The results show that for a specific spatial distribution of flexibility, there is an effective frequency range in thrust production. The wing deformation at the thrust-productive frequencies indicates the importance of flexibility: both bending and twisting motion can interact with aerodynamic loads to enhance wing performance under certain conditions, such as the deformation phase and amplitude. By measuring structural deformations under the same aerodynamic conditions, beneficial effects of passive wing deformation can be observed from the visualized airflow and averaged thrust. The measurements and their presentation enable observation and understanding of the required structural properties for a thrust effective flapping wing. The intended passive responses of the different wings follow a particular pattern in correlation to their aerodynamic performance. Consequently, both the experimental technique and data analysis method can lead to further studies to determine the design principles for micro air vehicle flapping wings.

  5. Azadirachtin(A) distinctively modulates subdomain 2 of actin - novel mechanism to induce depolymerization revealed by molecular dynamics study.

    Science.gov (United States)

    Pravin Kumar, R; Roopa, L; Sudheer Mohammed, M M; Kulkarni, Naveen

    2016-12-01

    Azadirachtin(A) (AZA), a potential insecticide from neem, binds to actin and induces depolymerization in Drosophila. AZA binds to the pocket same as that of Latrunculin A (LAT), but LAT inhibits actin polymerization by stiffening the actin structure and affects the ADP-ATP exchange. The mechanism by which AZA induces actin depolymerization is not clearly understood. Therefore, different computational experiments were conducted to delineate the precise mechanism of AZA-induced actin depolymerization. Molecular dynamics studies showed that AZA strongly interacted with subdomain 2 and destabilized the interactions between subdomain 2 of one actin and subdomains 1 and 4 of the adjacent actin, causing the separation of actin subunits. The separation was observed between subdomain 3 of subunit n and subdomain 4 of subunit n + 2. However, the specific triggering point for the separation of the subunits was the destabilization of direct interactions between subdomain 2 of subunit n (Arg39, Val45, Gly46 and Arg62) and subdomain 4 of subunit n + 2 (Asp286, Ile287, Asp288, Ile289, Asp244 and Lys291). These results reveal a unique mechanism of an actin filament modulator that induces depolymerization. This mechanism of AZA can be used to design similar molecules against mammalian actins for cancer therapy.

  6. Networks Models of Actin Dynamics during Spermatozoa Postejaculatory Life: A Comparison among Human-Made and Text Mining-Based Models

    Directory of Open Access Journals (Sweden)

    Nicola Bernabò

    2016-01-01

    Full Text Available Here we realized a networks-based model representing the process of actin remodelling that occurs during the acquisition of fertilizing ability of human spermatozoa (HumanMade_ActinSpermNetwork, HM_ASN. Then, we compared it with the networks provided by two different text mining tools: Agilent Literature Search (ALS and PESCADOR. As a reference, we used the data from the online repository Kyoto Encyclopaedia of Genes and Genomes (KEGG, referred to the actin dynamics in a more general biological context. We found that HM_ALS and the networks from KEGG data shared the same scale-free topology following the Barabasi-Albert model, thus suggesting that the information is spread within the network quickly and efficiently. On the contrary, the networks obtained by ALS and PESCADOR have a scale-free hierarchical architecture, which implies a different pattern of information transmission. Also, the hubs identified within the networks are different: HM_ALS and KEGG networks contain as hubs several molecules known to be involved in actin signalling; ALS was unable to find other hubs than “actin,” whereas PESCADOR gave some nonspecific result. This seems to suggest that the human-made information retrieval in the case of a specific event, such as actin dynamics in human spermatozoa, could be a reliable strategy.

  7. Dynamics of an Active-Site Flap Contributes to Catalysis in a JAMM Family Metallo Deubiquitinase.

    Science.gov (United States)

    Bueno, Amy N; Shrestha, Rashmi K; Ronau, Judith A; Babar, Aditya; Sheedlo, Michael J; Fuchs, Julian E; Paul, Lake N; Das, Chittaranjan

    2015-10-06

    The endosome-associated deubiquitinase (DUB) AMSH is a member of the JAMM family of zinc-dependent metallo isopeptidases with high selectivity for Lys63-linked polyubiquitin chains, which play a key role in endosomal-lysosomal sorting of activated cell surface receptors. The catalytic domain of the enzyme features a flexible flap near the active site that opens and closes during its catalytic cycle. Structural analysis of its homologues, AMSH-LP (AMSH-like protein) and the fission yeast counterpart, Sst2, suggests that a conserved Phe residue in the flap may be critical for substrate binding and/or catalysis. To gain insight into the contribution of this flap in substrate recognition and catalysis, we generated mutants of Sst2 and characterized them using a combination of enzyme kinetics, X-ray crystallography, molecular dynamics simulations, and isothermal titration calorimetry (ITC). Our analysis shows that the Phe residue in the flap contributes key interactions during the rate-limiting step but not to substrate binding, since mutants of Phe403 exhibit a defect only in kcat but not in KM. Moreover, ITC studies show Phe403 mutants have similar KD for ubiquitin compared to the wild-type enzyme. The X-ray structures of both Phe403Ala and the Phe403Trp, in both the free and ubiquitin bound form, reveal no appreciable structural change that might impair substrate or alter product binding. We observed that the side chain of the Trp residue is oriented identically with respect to the isopeptide moiety of the substrate as the Phe residue in the wild-type enzyme, so the loss of activity seen in this mutant cannot be explained by the absence of a group with the ability to provide van der Waals interactions that facilitate the hyrdolysis of the Lys63-linked diubiquitin. Molecular dynamics simulations indicate that the flap in the Trp mutant is quite flexible, allowing almost free rotation of the indole side chain. Therefore, it is possible that these different dynamic

  8. Xenopus egg cytoplasm with intact actin.

    Science.gov (United States)

    Field, Christine M; Nguyen, Phuong A; Ishihara, Keisuke; Groen, Aaron C; Mitchison, Timothy J

    2014-01-01

    We report optimized methods for preparing Xenopus egg extracts without cytochalasin D, that we term "actin-intact egg extract." These are undiluted egg cytoplasm that contains abundant organelles, and glycogen which supplies energy, and represents the least perturbed cell-free cytoplasm preparation we know of. We used this system to probe cell cycle regulation of actin and myosin-II dynamics (Field et al., 2011), and to reconstitute the large, interphase asters that organize early Xenopus embryos (Mitchison et al., 2012; Wühr, Tan, Parker, Detrich, & Mitchison, 2010). Actin-intact Xenopus egg extracts are useful for analysis of actin dynamics, and interaction of actin with other cytoplasmic systems, in a cell-free system that closely mimics egg physiology, and more generally for probing the biochemistry and biophysics of the egg, zygote, and early embryo. Detailed protocols are provided along with assays used to check cell cycle state and tips for handling and storing undiluted egg extracts. © 2014 Elsevier Inc. All rights reserved.

  9. Recruitment Kinetics of Tropomyosin Tpm3.1 to Actin Filament Bundles in the Cytoskeleton Is Independent of Actin Filament Kinetics.

    Science.gov (United States)

    Appaduray, Mark A; Masedunskas, Andrius; Bryce, Nicole S; Lucas, Christine A; Warren, Sean C; Timpson, Paul; Stear, Jeffrey H; Gunning, Peter W; Hardeman, Edna C

    2016-01-01

    The actin cytoskeleton is a dynamic network of filaments that is involved in virtually every cellular process. Most actin filaments in metazoa exist as a co-polymer of actin and tropomyosin (Tpm) and the function of an actin filament is primarily defined by the specific Tpm isoform associated with it. However, there is little information on the interdependence of these co-polymers during filament assembly and disassembly. We addressed this by investigating the recovery kinetics of fluorescently tagged isoform Tpm3.1 into actin filament bundles using FRAP analysis in cell culture and in vivo in rats using intracellular intravital microscopy, in the presence or absence of the actin-targeting drug jasplakinolide. The mobile fraction of Tpm3.1 is between 50% and 70% depending on whether the tag is at the C- or N-terminus and whether the analysis is in vivo or in cultured cells. We find that the continuous dynamic exchange of Tpm3.1 is not significantly impacted by jasplakinolide, unlike tagged actin. We conclude that tagged Tpm3.1 may be able to undergo exchange in actin filament bundles largely independent of the assembly and turnover of actin.

  10. Concerning the dynamic instability of actin homolog ParM

    International Nuclear Information System (INIS)

    Popp, David; Yamamoto, Akihiro; Iwasa, Mitsusada; Narita, Akihiro; Maeda, Kayo; Maeda, Yuichiro

    2007-01-01

    Using in vitro TIRF- and electron-microscopy, we reinvestigated the dynamics of native ParM, a prokaryotic DNA segregation protein and actin homolog. In contrast to a previous study, which used a cysteine ParM mutant, we find that the polymerization process of wild type ATP-ParM filaments consists of a polymerization phase and a subsequent steady state phase, which is dynamically unstable, like that of microtubules. We find that the apparent bidirectional polymerization of ParM, is not due to the intrinsic nature of this filament, but results from ParM forming randomly oriented bundles in the presence of crowding agents. Our results imply, that in the bacterium, ParM filaments spontaneously form bipolar bundles. Due to their intrinsic dynamic instability, ParM bundles can efficiently 'search' the cytoplasmic lumen for DNA, bind it equally well at the bipolar ends and segregate it approximately symmetrically, by the insertion of ParM subunits at either end

  11. Toward the Structure of Dynamic Membrane-Anchored Actin Networks

    Science.gov (United States)

    Weber, Igor

    2007-01-01

    In the cortex of a motile cell, membrane-anchored actin filaments assemble into structures of varying shape and function. Filopodia are distinguished by a core of bundled actin filaments within finger-like extensions of the membrane. In a recent paper by Medalia et al1 cryo-electron tomography has been used to reconstruct, from filopodia of Dictyostelium cells, the 3-dimensional organization of actin filaments in connection with the plasma membrane. A special arrangement of short filaments converging toward the filopod's tip has been called a “terminal cone”. In this region force is applied for protrusion of the membrane. Here we discuss actin organization in the filopodia of Dictyostelium in the light of current views on forces that are generated by polymerizing actin filaments, and on the resistance of membranes against deformation that counteracts these forces. PMID:19262130

  12. The actinome of Dictyostelium discoideum in comparison to actins and actin-related proteins from other organisms.

    Directory of Open Access Journals (Sweden)

    Jayabalan M Joseph

    Full Text Available Actin belongs to the most abundant proteins in eukaryotic cells which harbor usually many conventional actin isoforms as well as actin-related proteins (Arps. To get an overview over the sometimes confusing multitude of actins and Arps, we analyzed the Dictyostelium discoideum actinome in detail and compared it with the genomes from other model organisms. The D. discoideum actinome comprises 41 actins and actin-related proteins. The genome contains 17 actin genes which most likely arose from consecutive gene duplications, are all active, in some cases developmentally regulated and coding for identical proteins (Act8-group. According to published data, the actin fraction in a D. discoideum cell consists of more than 95% of these Act8-type proteins. The other 16 actin isoforms contain a conventional actin motif profile as well but differ in their protein sequences. Seven actin genes are potential pseudogenes. A homology search of the human genome using the most typical D. discoideum actin (Act8 as query sequence finds the major actin isoforms such as cytoplasmic beta-actin as best hit. This suggests that the Act8-group represents a nearly perfect actin throughout evolution. Interestingly, limited data from D. fasciculatum, a more ancient member among the social amoebae, show different relationships between conventional actins. The Act8-type isoform is most conserved throughout evolution. Modeling of the putative structures suggests that the majority of the actin-related proteins is functionally unrelated to canonical actin. The data suggest that the other actin variants are not necessary for the cytoskeleton itself but rather regulators of its dynamical features or subunits in larger protein complexes.

  13. Electrostatics Control Actin Filament Nucleation and Elongation Kinetics*

    Science.gov (United States)

    Crevenna, Alvaro H.; Naredi-Rainer, Nikolaus; Schönichen, André; Dzubiella, Joachim; Barber, Diane L.; Lamb, Don C.; Wedlich-Söldner, Roland

    2013-01-01

    The actin cytoskeleton is a central mediator of cellular morphogenesis, and rapid actin reorganization drives essential processes such as cell migration and cell division. Whereas several actin-binding proteins are known to be regulated by changes in intracellular pH, detailed information regarding the effect of pH on the actin dynamics itself is still lacking. Here, we combine bulk assays, total internal reflection fluorescence microscopy, fluorescence fluctuation spectroscopy techniques, and theory to comprehensively characterize the effect of pH on actin polymerization. We show that both nucleation and elongation are strongly enhanced at acidic pH, with a maximum close to the pI of actin. Monomer association rates are similarly affected by pH at both ends, although dissociation rates are differentially affected. This indicates that electrostatics control the diffusional encounter but not the dissociation rate, which is critical for the establishment of actin filament asymmetry. A generic model of protein-protein interaction, including electrostatics, explains the observed pH sensitivity as a consequence of charge repulsion. The observed pH effect on actin in vitro agrees with measurements of Listeria propulsion in pH-controlled cells. pH regulation should therefore be considered as a modulator of actin dynamics in a cellular environment. PMID:23486468

  14. Electrostatics control actin filament nucleation and elongation kinetics.

    Science.gov (United States)

    Crevenna, Alvaro H; Naredi-Rainer, Nikolaus; Schönichen, André; Dzubiella, Joachim; Barber, Diane L; Lamb, Don C; Wedlich-Söldner, Roland

    2013-04-26

    The actin cytoskeleton is a central mediator of cellular morphogenesis, and rapid actin reorganization drives essential processes such as cell migration and cell division. Whereas several actin-binding proteins are known to be regulated by changes in intracellular pH, detailed information regarding the effect of pH on the actin dynamics itself is still lacking. Here, we combine bulk assays, total internal reflection fluorescence microscopy, fluorescence fluctuation spectroscopy techniques, and theory to comprehensively characterize the effect of pH on actin polymerization. We show that both nucleation and elongation are strongly enhanced at acidic pH, with a maximum close to the pI of actin. Monomer association rates are similarly affected by pH at both ends, although dissociation rates are differentially affected. This indicates that electrostatics control the diffusional encounter but not the dissociation rate, which is critical for the establishment of actin filament asymmetry. A generic model of protein-protein interaction, including electrostatics, explains the observed pH sensitivity as a consequence of charge repulsion. The observed pH effect on actin in vitro agrees with measurements of Listeria propulsion in pH-controlled cells. pH regulation should therefore be considered as a modulator of actin dynamics in a cellular environment.

  15. Regulation of the actin cytoskeleton-plasma membrane interplay by phosphoinositides.

    Science.gov (United States)

    Saarikangas, Juha; Zhao, Hongxia; Lappalainen, Pekka

    2010-01-01

    The plasma membrane and the underlying cortical actin cytoskeleton undergo continuous dynamic interplay that is responsible for many essential aspects of cell physiology. Polymerization of actin filaments against cellular membranes provides the force for a number of cellular processes such as migration, morphogenesis, and endocytosis. Plasma membrane phosphoinositides (especially phosphatidylinositol bis- and trisphosphates) play a central role in regulating the organization and dynamics of the actin cytoskeleton by acting as platforms for protein recruitment, by triggering signaling cascades, and by directly regulating the activities of actin-binding proteins. Furthermore, a number of actin-associated proteins, such as BAR domain proteins, are capable of directly deforming phosphoinositide-rich membranes to induce plasma membrane protrusions or invaginations. Recent studies have also provided evidence that the actin cytoskeleton-plasma membrane interactions are misregulated in a number of pathological conditions such as cancer and during pathogen invasion. Here, we summarize the wealth of knowledge on how the cortical actin cytoskeleton is regulated by phosphoinositides during various cell biological processes. We also discuss the mechanisms by which interplay between actin dynamics and certain membrane deforming proteins regulate the morphology of the plasma membrane.

  16. Actin, actin-binding proteins, and actin-related proteins in the nucleus.

    Science.gov (United States)

    Kristó, Ildikó; Bajusz, Izabella; Bajusz, Csaba; Borkúti, Péter; Vilmos, Péter

    2016-04-01

    Extensive research in the past decade has significantly broadened our view about the role actin plays in the life of the cell and added novel aspects to actin research. One of these new aspects is the discovery of the existence of nuclear actin which became evident only recently. Nuclear activities including transcriptional activation in the case of all three RNA polymerases, editing and nuclear export of mRNAs, and chromatin remodeling all depend on actin. It also became clear that there is a fine-tuned equilibrium between cytoplasmic and nuclear actin pools and that this balance is ensured by an export-import system dedicated to actin. After over half a century of research on conventional actin and its organizing partners in the cytoplasm, it was also an unexpected finding that the nucleus contains more than 30 actin-binding proteins and new classes of actin-related proteins which are not able to form filaments but had evolved nuclear-specific functions. The actin-binding and actin-related proteins in the nucleus have been linked to RNA transcription and processing, nuclear transport, and chromatin remodeling. In this paper, we attempt to provide an overview of the wide range of information that is now available about actin, actin-binding, and actin-related proteins in the nucleus.

  17. Dynamic localization and interaction with other Bacillus subtilis actin-like proteins are important for the function of MreB.

    Science.gov (United States)

    Defeu Soufo, Hervé Joël; Graumann, Peter L

    2006-12-01

    Bacterial actin-like proteins play a key role in cell morphology and in chromosome segregation. Many bacteria, like Bacillus subtilis, contain three genes encoding actin-like proteins, called mreB, mbl and mreBH in B. subtilis. We show that MreB and Mbl colocalize extensively within live cells, and that all three B. subtilis actin paralogues interact with each other underneath the cell membrane. A mutation in the phosphate 2 motif of MreB had a dominant negative effect on cell morphology and on chromosome segregation. Expression of this mutant allele of MreB interfered with the dynamic localization of Mbl. These experiments show that the interaction between MreB and Mbl has physiological significance. An mreB deletion strain can grow under special media conditions, however, depletion of Mbl in this mutant background abolished growth, indicating that actin paralogues can partially complement each other. The membrane protein MreC was found to interact with Mbl, but not with MreB, revealing a clear distinction between the function of the two paralogues. The phosphate 2 mutant MreB protein allowed for filament formation of mutant or wild-type MreB, but abolished the dynamic reorganization of the filaments. The latter mutation led to a strong reduction, but not complete loss, of function of MreB, both in terms of chromosome segregation and of cell morphology. Our work shows that that the dynamic localization of MreB is essential for the proper activity of the actin-like protein and that the interactions between MreB paralogues have important physiological significance.

  18. Filopodial retraction force is generated by cortical actin dynamics and controlled by reversible tethering at the tip

    DEFF Research Database (Denmark)

    Bornschlögl, Thomas; Romero, Stéphane; Vestergaard, Christian L.

    2013-01-01

    Filopodia are dynamic, finger-like plasma membrane protrusions that sense the mechanical and chemical surroundings of the cell. Here, we show in epithelial cells that the dynamics of filopodial extension and retraction are determined by the difference between the actin polymerization rate at the ...

  19. Integrins in cell migration – the actin connection

    OpenAIRE

    Vicente-Manzanares, Miguel; Choi, Colin Kiwon; Horwitz, Alan Rick

    2008-01-01

    The connection between integrins and actin is driving the field of cell migration in new directions. Integrins and actin are coupled through a physical linkage, which provides traction for migration. Recent studies show the importance of this linkage in regulating adhesion organization and development. Actin polymerization orchestrates adhesion assembly near the leading edge of a migrating cell, and the dynamic cross-linking of actin filaments promotes adhesion maturat...

  20. Actin is an essential component of plant gravitropic signaling pathways

    Science.gov (United States)

    Braun, Markus; Hauslage, Jens; Limbach, Christoph

    2003-08-01

    A role of the actin cytoskeleton in the different phases of gravitropism in higher plant organs seems obvious, but experimental evidence is still inconclusive and contradictory. In gravitropically tip-growing rhizoids and protonemata, however, it is well documented that actin is an essential component of the tip-growth machinery and is involved either in the cellular mechanisms that lead to gravity sensing and in the processes of the graviresponses that result in the reorientation of the growth direction. All these processes depend on a complexly organized and highly dynamic organization of actin filaments whose diverse functions are coordinated by numerous associated proteins. Actin filaments and myosins mediate the transport of secretory vehicles to the growing tip and precisely control the delivery of cell wall material. In addition, both cell types use a very efficient actomyosin-based system to control and correct the position of their statoliths and to direct sedimenting statoliths to confined graviperception sites at the plasma membrane. The studies presented in this paper provide evidence for the essential role of actin in plant gravity sensing and the gravitropic responses. A unique actin-organizing center exists in the tip of characean rhizoids and protonemata which is associated with and dynamically regulated by a specific set of actin-dynamizing proteins. It is concluded that this highly dynamic apical actin array is an essential prerequisite for gravity sensing and gravity-oriented tip growth.

  1. Morphodynamics of the Actin-Rich Cytoskeleton in Entamoeba histolytica

    Directory of Open Access Journals (Sweden)

    Maria Manich

    2018-05-01

    Full Text Available Entamoeba histolytica is the anaerobic protozoan parasite responsible for human amoebiasis, the third most deadly parasitic disease worldwide. This highly motile eukaryotic cell invades human tissues and constitutes an excellent experimental model of cell motility and cell shape deformation. The absence of extranuclear microtubules in Entamoeba histolytica means that the actin-rich cytoskeleton takes on a crucial role in not only amoebic motility but also other processes sustaining pathogenesis, such as the phagocytosis of human cells and the parasite's resistance of host immune responses. Actin is highly conserved among eukaryotes, although diverse isoforms exist in almost all organisms studied to date. However, E. histolytica has a single actin protein, the structure of which differs significantly from those of its human homologs. Here, we studied the expression, structure and dynamics of actin in E. histolytica. We used molecular and cellular approaches to evaluate actin gene expression during intestinal invasion by E. histolytica trophozoites. Based on a three-dimensional structural bioinformatics analysis, we characterized protein domains differences between amoebic actin and human actin. Fine-tuned molecular dynamics simulations enabled us to examine protein motion and refine the three-dimensional structures of both actins, including elements potentially accounting for differences changes in the affinity properties of amoebic actin and deoxyribonuclease I. The dynamic, multifunctional nature of the amoebic cytoskeleton prompted us to examine the pleiotropic forms of actin structures within live E. histolytica cells; we observed the cortical cytoskeleton, stress fibers, “dot-like” structures, adhesion plates, and macropinosomes. In line with these data, a proteomics study of actin-binding proteins highlighted the Arp2/3 protein complex as a crucial element for the development of macropinosomes and adhesion plaques.

  2. Addition of Passive Dynamics to a Flapping Airfoil to Improve Performance

    Science.gov (United States)

    Asselin, Daniel; Young, Jay; Williamson, C. H. K.

    2017-11-01

    Animals which fly or swim typically employ flapping motions of their wings and fins in order to produce thrust and to maneuver. Small, unmanned vehicles might also exploit such motions and are of considerable interest for the purposes of surveillance, environmental monitoring, and search and rescue. Flapping refers to a combination of pitch and heave and has been shown to provide good thrust and efficiency (Read, et al. 2003) when both axes are independently controlled (an Active-Active system). In this study, we examine the performance of an airfoil actuated only in the heave direction but allowed to pitch passively under the control of a torsion spring (an Active-Passive system). The presence of the spring is simulated in software using a force-feedback control system called Cyber-Physical Fluid Dynamics, or CPFD (Mackowski & Williamson 2011, 2015, 2016). Adding passive pitch to active heave provides significantly improved thrust and efficiency compared with heaving alone, especially when the torsion spring stiffness is selected so that the system operates near resonance (in an Active-Passive system). In many cases, values of thrust and efficiency are comparable to or better than those obtained with two actively controlled degrees of freedom. By using carefully-designed passive dynamics in the pitch direction, we can eliminate one of the two actuators, saving cost, complexity, and weight, while maintaining performance. This work was supported by the Air Force Office of Scientific Research Grant No. FA9550-15-1-0243, monitored by Dr. Douglas Smith.

  3. CFD based aerodynamic modeling to study flight dynamics of a flapping wing micro air vehicle

    Science.gov (United States)

    Rege, Alok Ashok

    The demand for small unmanned air vehicles, commonly termed micro air vehicles or MAV's, is rapidly increasing. Driven by applications ranging from civil search-and-rescue missions to military surveillance missions, there is a rising level of interest and investment in better vehicle designs, and miniaturized components are enabling many rapid advances. The need to better understand fundamental aspects of flight for small vehicles has spawned a surge in high quality research in the area of micro air vehicles. These aircraft have a set of constraints which are, in many ways, considerably different from that of traditional aircraft and are often best addressed by a multidisciplinary approach. Fast-response non-linear controls, nano-structures, integrated propulsion and lift mechanisms, highly flexible structures, and low Reynolds aerodynamics are just a few of the important considerations which may be combined in the execution of MAV research. The main objective of this thesis is to derive a consistent nonlinear dynamic model to study the flight dynamics of micro air vehicles with a reasonably accurate representation of aerodynamic forces and moments. The research is divided into two sections. In the first section, derivation of the nonlinear dynamics of flapping wing micro air vehicles is presented. The flapping wing micro air vehicle (MAV) used in this research is modeled as a system of three rigid bodies: a body and two wings. The design is based on an insect called Drosophila Melanogaster, commonly known as fruit-fly. The mass and inertial effects of the wing on the body are neglected for the present work. The nonlinear dynamics is simulated with the aerodynamic data published in the open literature. The flapping frequency is used as the control input. Simulations are run for different cases of wing positions and the chosen parameters are studied for boundedness. Results show a qualitative inconsistency in boundedness for some cases, and demand a better

  4. The Bacterial Actin MamK

    Science.gov (United States)

    Ozyamak, Ertan; Kollman, Justin; Agard, David A.; Komeili, Arash

    2013-01-01

    It is now recognized that actin-like proteins are widespread in bacteria and, in contrast to eukaryotic actins, are highly diverse in sequence and function. The bacterial actin, MamK, represents a clade, primarily found in magnetotactic bacteria, that is involved in the proper organization of subcellular organelles, termed magnetosomes. We have previously shown that MamK from Magnetospirillum magneticum AMB-1 (AMB-1) forms dynamic filaments in vivo. To gain further insights into the molecular mechanisms that underlie MamK dynamics and function, we have now studied the in vitro properties of MamK. We demonstrate that MamK is an ATPase that, in the presence of ATP, assembles rapidly into filaments that disassemble once ATP is depleted. The mutation of a conserved active site residue (E143A) abolishes ATPase activity of MamK but not its ability to form filaments. Filament disassembly depends on both ATPase activity and potassium levels, the latter of which results in the organization of MamK filaments into bundles. These data are consistent with observations indicating that accessory factors are required to promote filament disassembly and for spatial organization of filaments in vivo. We also used cryo-electron microscopy to obtain a high resolution structure of MamK filaments. MamK adopts a two-stranded helical filament architecture, but unlike eukaryotic actin and other actin-like filaments, subunits in MamK strands are unstaggered giving rise to a unique filament architecture. Beyond extending our knowledge of the properties and function of MamK in magnetotactic bacteria, this study emphasizes the functional and structural diversity of bacterial actins in general. PMID:23204522

  5. Cytoplasmic Actin: Purification and Single Molecule Assembly Assays

    Science.gov (United States)

    Hansen, Scott D.; Zuchero, J. Bradley; Mullins, R. Dyche

    2014-01-01

    The actin cytoskeleton is essential to all eukaryotic cells. In addition to playing important structural roles, assembly of actin into filaments powers diverse cellular processes, including cell motility, cytokinesis, and endocytosis. Actin polymerization is tightly regulated by its numerous cofactors, which control spatial and temporal assembly of actin as well as the physical properties of these filaments. Development of an in vitro model of actin polymerization from purified components has allowed for great advances in determining the effects of these proteins on the actin cytoskeleton. Here we describe how to use the pyrene actin assembly assay to determine the effect of a protein on the kinetics of actin assembly, either directly or as mediated by proteins such as nucleation or capping factors. Secondly, we show how fluorescently labeled phalloidin can be used to visualize the filaments that are created in vitro to give insight into how proteins regulate actin filament structure. Finally, we describe a method for visualizing dynamic assembly and disassembly of single actin filaments and fluorescently labeled actin binding proteins using total internal reflection fluorescence (TIRF) microscopy. PMID:23868587

  6. Topography on a subcellular scale modulates cellular adhesions and actin stress fiber dynamics in tumor associated fibroblasts

    Science.gov (United States)

    Azatov, Mikheil; Sun, Xiaoyu; Suberi, Alexandra; Fourkas, John T.; Upadhyaya, Arpita

    2017-12-01

    Cells can sense and adapt to mechanical properties of their environment. The local geometry of the extracellular matrix, such as its topography, has been shown to modulate cell morphology, migration, and proliferation. Here we investigate the effect of micro/nanotopography on the morphology and cytoskeletal dynamics of human pancreatic tumor-associated fibroblast cells (TAFs). We use arrays of parallel nanoridges with variable spacings on a subcellular scale to investigate the response of TAFs to the topography of their environment. We find that cell shape and stress fiber organization both align along the direction of the nanoridges. Our analysis reveals a strong bimodal relationship between the degree of alignment and the spacing of the nanoridges. Furthermore, focal adhesions align along ridges and form preferentially on top of the ridges. Tracking actin stress fiber movement reveals enhanced dynamics of stress fibers on topographically patterned surfaces. We find that components of the actin cytoskeleton move preferentially along the ridges with a significantly higher velocity along the ridges than on a flat surface. Our results suggest that a complex interplay between the actin cytoskeleton and focal adhesions coordinates the cellular response to micro/nanotopography.

  7. Formin' actin in the nucleus.

    Science.gov (United States)

    Baarlink, Christian; Grosse, Robert

    2014-01-01

    Many if not most proteins can, under certain conditions, change cellular compartments, such as, for example, shuttling from the cytoplasm to the nucleus. Thus, many proteins may exert functions in various and very different subcellular locations, depending on the signaling context. A large amount of actin regulatory proteins has been detected in the mammalian cell nucleus, although their potential roles are much debated and are just beginning to emerge. Recently, members of the formin family of actin nucleators were also reported to dynamically localize to the nuclear environment. Here we discuss our findings that specific diaphanous-related formins can promote nuclear actin assembly in a signal-dependent manner.

  8. Regimes of wave type patterning driven by refractory actin feedback: transition from static polarization to dynamic wave behaviour

    International Nuclear Information System (INIS)

    Holmes, W R; Edelstein-Keshet, L; Carlsson, A E

    2012-01-01

    Patterns of waves, patches, and peaks of actin are observed experimentally in many living cells. Models of this phenomenon have been based on the interplay between filamentous actin (F-actin) and its nucleation promoting factors (NPFs) that activate the Arp2/3 complex. Here we present an alternative biologically-motivated model for F-actin-NPF interaction based on properties of GTPases acting as NPFs. GTPases (such as Cdc42, Rac) are known to promote actin nucleation, and to have active membrane-bound and inactive cytosolic forms. The model is a natural extension of a previous mathematical mini-model of small GTPases that generates static cell polarization. Like other modellers, we assume that F-actin negative feedback shapes the observed patterns by suppressing the trailing edge of NPF-generated wave-fronts, hence localizing the activity spatially. We find that our NPF-actin model generates a rich set of behaviours, spanning a transition from static polarization to single pulses, reflecting waves, wave trains, and oscillations localized at the cell edge. The model is developed with simplicity in mind to investigate the interaction between nucleation promoting factor kinetics and negative feedback. It explains distinct types of pattern initiation mechanisms, and identifies parameter regimes corresponding to distinct behaviours. We show that weak actin feedback yields static patterning, moderate feedback yields dynamical behaviour such as travelling waves, and strong feedback can lead to wave trains or total suppression of patterning. We use a recently introduced nonlinear bifurcation analysis to explore the parameter space of this model and predict its behaviour with simulations validating those results. (paper)

  9. A single charge in the actin binding domain of fascin can independently tune the linear and non-linear response of an actin bundle network.

    Science.gov (United States)

    Maier, M; Müller, K W; Heussinger, C; Köhler, S; Wall, W A; Bausch, A R; Lieleg, O

    2015-05-01

    Actin binding proteins (ABPs) not only set the structure of actin filament assemblies but also mediate the frequency-dependent viscoelastic moduli of cross-linked and bundled actin networks. Point mutations in the actin binding domain of those ABPs can tune the association and dissociation dynamics of the actin/ABP bond and thus modulate the network mechanics both in the linear and non-linear response regime. We here demonstrate how the exchange of a single charged amino acid in the actin binding domain of the ABP fascin triggers such a modulation of the network rheology. Whereas the overall structure of the bundle networks is conserved, the transition point from strain-hardening to strain-weakening sensitively depends on the cross-linker off-rate and the applied shear rate. Our experimental results are consistent both with numerical simulations of a cross-linked bundle network and a theoretical description of the bundle network mechanics which is based on non-affine bending deformations and force-dependent cross-link dynamics.

  10. Probing GFP-actin diffusion in living cells using fluorescence correlation spectroscopy

    International Nuclear Information System (INIS)

    Engelke, Hanna; Heinrich, Doris; Rädler, Joachim O.

    2010-01-01

    The cytoskeleton of eukaryotic cells is continuously remodeled by polymerization and depolymerization of actin. Consequently, the relative content of polymerized filamentous actin (F-actin) and monomeric globular actin (G-actin) is subject to temporal and spatial fluctuations. Since fluorescence correlation spectroscopy (FCS) can measure the diffusion of fluorescently labeled actin it seems likely that FCS allows us to determine the dynamics and hence indirectly the structural properties of the cytoskeleton components with high spatial resolution. To this end we investigate the FCS signal of GFP-actin in living Dictyostelium discoideum cells and explore the inherent spatial and temporal signatures of the actin cytoskeleton. Using the free green fluorescent protein (GFP) as a reference, we find that actin diffusion inside cells is dominated by G-actin and slower than diffusion in diluted cell extract. The FCS signal in the dense cortical F-actin network near the cell membrane is probed using the cytoskeleton protein LIM and is found to be slower than cytosolic G-actin diffusion. Furthermore, we show that polymerization of the cytoskeleton induced by Jasplakinolide leads to a substantial decrease of G-actin diffusion. Pronounced fluctuations in the distribution of the FCS correlation curves can be induced by latrunculin, which is known to induce actin waves. Our work suggests that the FCS signal of GFP-actin in combination with scanning or spatial correlation techniques yield valuable information about the local dynamics and concomitant cytoskeletal properties

  11. Antiepileptic teratogen valproic acid (VPA) modulates organisation and dynamics of the actin cytoskeleton

    DEFF Research Database (Denmark)

    Walmod, P S; Skladchikova, G; Kawa, A

    1999-01-01

    for the VPA mediated inhibition of motility. In addition it is shown that the actomyosin cytoskeleton of VPA-treated cells was capable of contraction upon exposure to ATP, indicating that the reduced motility of VPA-treated cells was not caused by an inhibition of actomyosin contraction. On the other hand...... state. These findings indicate that VPA affects cell morphology and motility through interference with the dynamics of the actin cytoskeleton....

  12. Axon initial segment cytoskeleton comprises a multiprotein submembranous coat containing sparse actin filaments

    Science.gov (United States)

    Jones, Steven L.; Korobova, Farida

    2014-01-01

    The axon initial segment (AIS) of differentiated neurons regulates action potential initiation and axon–dendritic polarity. The latter function depends on actin dynamics, but actin structure and functions at the AIS remain unclear. Using platinum replica electron microscopy (PREM), we have characterized the architecture of the AIS cytoskeleton in mature and developing hippocampal neurons. The AIS cytoskeleton assembly begins with bundling of microtubules and culminates in formation of a dense, fibrillar–globular coat over microtubule bundles. Immunogold PREM revealed that the coat contains a network of known AIS proteins, including ankyrin G, spectrin βIV, neurofascin, neuronal cell adhesion molecule, voltage-gated sodium channels, and actin filaments. Contrary to existing models, we find neither polarized actin arrays, nor dense actin meshworks in the AIS. Instead, the AIS contains two populations of sparse actin filaments: short, stable filaments and slightly longer dynamic filaments. We propose that stable actin filaments play a structural role for formation of the AIS diffusion barrier, whereas dynamic actin may promote AIS coat remodeling. PMID:24711503

  13. Folding in and out: passive morphing in flapping wings.

    Science.gov (United States)

    Stowers, Amanda K; Lentink, David

    2015-03-25

    We present a new mechanism for passive wing morphing of flapping wings inspired by bat and bird wing morphology. The mechanism consists of an unactuated hand wing connected to the arm wing with a wrist joint. Flapping motion generates centrifugal accelerations in the hand wing, forcing it to unfold passively. Using a robotic model in hover, we made kinematic measurements of unfolding kinematics as functions of the non-dimensional wingspan fold ratio (2-2.5) and flapping frequency (5-17 Hz) using stereo high-speed cameras. We find that the wings unfold passively within one to two flaps and remain unfolded with only small amplitude oscillations. To better understand the passive dynamics, we constructed a computer model of the unfolding process based on rigid body dynamics, contact models, and aerodynamic correlations. This model predicts the measured passive unfolding within about one flap and shows that unfolding is driven by centrifugal acceleration induced by flapping. The simulations also predict that relative unfolding time only weakly depends on flapping frequency and can be reduced to less than half a wingbeat by increasing flapping amplitude. Subsequent dimensional analysis shows that the time required to unfold passively is of the same order of magnitude as the flapping period. This suggests that centrifugal acceleration can drive passive unfolding within approximately one wingbeat in small and large wings. Finally, we show experimentally that passive unfolding wings can withstand impact with a branch, by first folding and then unfolding passively. This mechanism enables flapping robots to squeeze through clutter without sophisticated control. Passive unfolding also provides a new avenue in morphing wing design that makes future flapping morphing wings possibly more energy efficient and light-weight. Simultaneously these results point to possible inertia driven, and therefore metabolically efficient, control strategies in bats and birds to morph or recover

  14. Functional and Histological Evaluation following Canine Vocal Fold Reconstruction Using Composite Thyroid Ala Perichondrium Flaps.

    Science.gov (United States)

    Hoffman, Matthew R; Glab, Rachel; Gunderson, McLean; Maytag, Allison L; Yang, David T; Jiang, Jack J; Dailey, Seth H

    2015-07-01

    We evaluated the effects of vocal fold reconstruction using a composite thyroid ala perichondrium flap (CTAP) after unilateral vocal fold stripping in beagles. We hypothesized that CTAP would improve glottic closure, decrease phonation threshold pressure, and decrease perturbation. In addition, vocal folds with CTAP would exhibit neovascularization and fat with increased von Willebrand factor (vWF) and smooth muscle actin (SMA), reflecting neoangiogenesis and flap viability. Randomized controlled trial using beagles. University laboratory. Ten beagles underwent unilateral vocal fold stripping. Dogs in the scar-only group (n = 5) were sacrificed at 1 month. Dogs in the CTAP group (n = 5) underwent ipsilateral reconstruction with CTAP at 1 month and were sacrificed at 2 months. Excised larynx experiments evaluated vocal fold vibration using aerodynamic, acoustic, and mucosal wave measurements. Qualitative evaluation of vocal fold morphology and quantitative analysis of elastin, collagen, glycosaminoglycans, vWF, SMA, and hyaluronic acid were performed. Phonation threshold pressure (P = .005), percent jitter (P = .010), percent shimmer (P = .007), and open quotient (P = .007) were lower in the CTAP group. Neovascularization (P = .0079) and fat (P = .1667) occurred more with CTAP, although the difference in fat was not significant. von Willebrand factor was higher with CTAP vs contralateral normal fold (P = .110), although not statistically significant. Smooth muscle actin was higher with CTAP vs contralateral normal fold (P = .038) and scarred vocal folds (P = .022). Composite thyroid ala perichondrium flap restored glottic closure and vibratory periodicity following vocal fold scarring. Additional investigation on biologic response is warranted. Composite thyroid ala perichondrium flap offers an autologous, vascularized implant that can improve both vocal fold structure and function. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2015.

  15. The nature of the globular- to fibrous-actin transition.

    Science.gov (United States)

    Oda, Toshiro; Iwasa, Mitsusada; Aihara, Tomoki; Maéda, Yuichiro; Narita, Akihiro

    2009-01-22

    Actin plays crucial parts in cell motility through a dynamic process driven by polymerization and depolymerization, that is, the globular (G) to fibrous (F) actin transition. Although our knowledge about the actin-based cellular functions and the molecules that regulate the G- to F-actin transition is growing, the structural aspects of the transition remain enigmatic. We created a model of F-actin using X-ray fibre diffraction intensities obtained from well oriented sols of rabbit skeletal muscle F-actin to 3.3 A in the radial direction and 5.6 A along the equator. Here we show that the G- to F-actin conformational transition is a simple relative rotation of the two major domains by about 20 degrees. As a result of the domain rotation, the actin molecule in the filament is flat. The flat form is essential for the formation of stable, helical F-actin. Our F-actin structure model provides the basis for understanding actin polymerization as well as its molecular interactions with actin-binding proteins.

  16. Exploring the Possible Role of Lysine Acetylation on Entamoeba histolytica Virulence: A Focus on the Dynamics of the Actin Cytoskeleton

    Directory of Open Access Journals (Sweden)

    L. López-Contreras

    2013-01-01

    Full Text Available Cytoskeleton remodeling can be regulated, among other mechanisms, by lysine acetylation. The role of acetylation on cytoskeletal and other proteins of Entamoeba histolytica has been poorly studied. Dynamic rearrangements of the actin cytoskeleton are crucial for amebic motility and capping formation, processes that may be effective means of evading the host immune response. Here we report the possible effect of acetylation on the actin cytoskeleton dynamics and in vivo virulence of E. histolytica. Using western blot, immunoprecipitation, microscopy assays, and in silico analysis, we show results that strongly suggest that the increase in Aspirin-induced cytoplasm proteins acetylation reduced cell movement and capping formation, likely as a consequence of alterations in the structuration of the actin cytoskeleton. Additionally, intrahepatic inoculation of Aspirin-treated trophozoites in hamsters resulted in severe impairment of the amebic virulence. Taken together, these results suggest an important role for lysine acetylation in amebic invasiveness and virulence.

  17. Spinoculation Triggers Dynamic Actin and Cofilin Activity That Facilitates HIV-1 Infection of Transformed and Resting CD4 T Cells▿

    Science.gov (United States)

    Guo, Jia; Wang, Weifeng; Yu, Dongyang; Wu, Yuntao

    2011-01-01

    Centrifugal inoculation, or spinoculation, is widely used in virology research to enhance viral infection. However, the mechanism remained obscure. Using HIV-1 infection of human T cells as a model, we demonstrate that spinoculation triggers dynamic actin and cofilin activity, probably resulting from cellular responses to centrifugal stress. This actin activity also leads to the upregulation of the HIV-1 receptor and coreceptor, CD4 and CXCR4, enhancing viral binding and entry. We also demonstrate that an actin inhibitor, jasplakinolide, diminishes spin-mediated enhancement. In addition, small interfering RNA (siRNA) knockdown of LIMK1, a cofilin kinase, decreases the enhancement. These results suggest that spin-mediated enhancement cannot be explained simply by a virus-concentrating effect; rather, it is coupled with spin-induced cytoskeletal dynamics that promote receptor mobilization, viral entry, and postentry processes. Our results highlight the importance of cofilin and a dynamic cytoskeleton for the initiation of viral infection. Our results also indicate that caution needs to be taken in data interpretation when cells are spinoculated; some of the spin-induced cellular permissiveness may be beyond the natural capacity of an infecting virus. PMID:21795326

  18. Dynamics of F-actin prefigure the structure of butterfly wing scales.

    Science.gov (United States)

    Dinwiddie, April; Null, Ryan; Pizzano, Maria; Chuong, Lisa; Leigh Krup, Alexis; Ee Tan, Hwei; Patel, Nipam H

    2014-08-15

    The wings of butterflies and moths consist of dorsal and ventral epidermal surfaces that give rise to overlapping layers of scales and hairs (Lepidoptera, "scale wing"). Wing scales (average length ~200 µm) are homologous to insect bristles (macrochaetes), and their colors create the patterns that characterize lepidopteran wings. The topology and surface sculpture of wing scales vary widely, and this architectural complexity arises from variations in the developmental program of the individual scale cells of the wing epithelium. One of the more striking features of lepidopteran wing scales are the longitudinal ridges that run the length of the mature (dead) cell, gathering the cuticularized scale cell surface into pleats on the sides of each scale. While also present around the periphery of other insect bristles and hairs, longitudinal ridges in lepidopteran wing scales gain new significance for their creation of iridescent color through microribs and lamellae. Here we show the dynamics of the highly organized F-actin filaments during scale cell development, and present experimental manipulations of actin polymerization that reveal the essential role of this cytoskeletal component in wing scale elongation and the positioning of longitudinal ribs. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Bacterial Actins.

    Science.gov (United States)

    Izoré, Thierry; van den Ent, Fusinita

    2017-01-01

    A diverse set of protein polymers, structurally related to actin filaments contributes to the organization of bacterial cells as cytomotive or cytoskeletal filaments. This chapter describes actin homologs encoded by bacterial chromosomes. MamK filaments, unique to magnetotactic bacteria, help establishing magnetic biological compasses by interacting with magnetosomes. Magnetosomes are intracellular membrane invaginations containing biomineralized crystals of iron oxide that are positioned by MamK along the long-axis of the cell. FtsA is widespread across bacteria and it is one of the earliest components of the divisome to arrive at midcell, where it anchors the cell division machinery to the membrane. FtsA binds directly to FtsZ filaments and to the membrane through its C-terminus. FtsA shows altered domain architecture when compared to the canonical actin fold. FtsA's subdomain 1C replaces subdomain 1B of other members of the actin family and is located on the opposite side of the molecule. Nevertheless, when FtsA assembles into protofilaments, the protofilament structure is preserved, as subdomain 1C replaces subdomain IB of the following subunit in a canonical actin filament. MreB has an essential role in shape-maintenance of most rod-shaped bacteria. Unusually, MreB filaments assemble from two protofilaments in a flat and antiparallel arrangement. This non-polar architecture implies that both MreB filament ends are structurally identical. MreB filaments bind directly to membranes where they interact with both cytosolic and membrane proteins, thereby forming a key component of the elongasome. MreB filaments in cells are short and dynamic, moving around the long axis of rod-shaped cells, sensing curvature of the membrane and being implicated in peptidoglycan synthesis.

  20. The F-actin modifier villin regulates insulin granule dynamics and exocytosis downstream of islet cell autoantigen 512

    Directory of Open Access Journals (Sweden)

    Hassan Mziaut

    2016-08-01

    Full Text Available Objective: Insulin release from pancreatic islet β cells should be tightly controlled to avoid hypoglycemia and insulin resistance. The cortical actin cytoskeleton is a gate for regulated exocytosis of insulin secretory granules (SGs by restricting their mobility and access to the plasma membrane. Prior studies suggest that SGs interact with F-actin through their transmembrane cargo islet cell autoantigen 512 (Ica512 (also known as islet antigen 2/Ptprn. Here we investigated how Ica512 modulates SG trafficking and exocytosis. Methods: Transcriptomic changes in Ica512−/− mouse islets were analyzed. Imaging as well as biophysical and biochemical methods were used to validate if and how the Ica512-regulated gene villin modulates insulin secretion in mouse islets and insulinoma cells. Results: The F-actin modifier villin was consistently downregulated in Ica512−/− mouse islets and in Ica512-depleted insulinoma cells. Villin was enriched at the cell cortex of β cells and dispersed villin−/− islet cells were less round and less deformable. Basal mobility of SGs in villin-depleted cells was enhanced. Moreover, in cells depleted either of villin or Ica512 F-actin cages restraining cortical SGs were enlarged, basal secretion was increased while glucose-stimulated insulin release was blunted. The latter changes were reverted by overexpressing villin in Ica512-depleted cells, but not vice versa. Conclusion: Our findings show that villin controls the size of the F-actin cages restricting SGs and, thus, regulates their dynamics and availability for exocytosis. Evidence that villin acts downstream of Ica512 also indicates that SGs directly influence the remodeling properties of the cortical actin cytoskeleton for tight control of insulin secretion. Keywords: F-actin, Granules, Ica512, Insulin, Secretion, Villin

  1. Histones bundle F-actin filaments and affect actin structure.

    Science.gov (United States)

    Blotnick, Edna; Sol, Asaf; Muhlrad, Andras

    2017-01-01

    Histones are small polycationic proteins complexed with DNA located in the cell nucleus. Upon apoptosis they are secreted from the cells and react with extracellular polyanionic compounds. Actin which is a polyanionic protein, is also secreted from necrotic cells and interacts with histones. We showed that both histone mixture (histone type III) and the recombinant H2A histone bundles F-actin, increases the viscosity of the F-actin containing solution and polymerizes G-actin. The histone-actin bundles are relatively insensitive to increase of ionic strength, unlike other polycation, histatin, lysozyme, spermine and LL-37 induced F-actin bundles. The histone-actin bundles dissociate completely only in the presence of 300-400 mM NaCl. DNA, which competes with F-actin for histones, disassembles histone induced actin bundles. DNase1, which depolymerizes F- to G-actin, actively unbundles the H2A histone induced but slightly affects the histone mixture induced actin bundles. Cofilin decreases the amount of F-actin sedimented by low speed centrifugation, increases light scattering and viscosity of F-actin-histone mixture containing solutions and forms star like superstructures by copolymerizing G-actin with H2A histone. The results indicate that histones are tightly attached to F-actin by strong electrostatic and hydrophobic forces. Since both histones and F-actin are present in the sputum of patients with cystic fibrosis, therefore, the formation of the stable histone-actin bundles can contribute to the pathology of this disease by increasing the viscosity of the sputum. The actin-histone interaction in the nucleus might affect gene expression.

  2. Unconventional actin conformations localize on intermediate filaments in mitosis

    International Nuclear Information System (INIS)

    Hubert, Thomas; Vandekerckhove, Joel; Gettemans, Jan

    2011-01-01

    Research highlights: → Unconventional actin conformations colocalize with vimentin on a cage-like structure in metaphase HEK 293T cells. → These conformations are detected with the anti-actin antibodies 1C7 ('lower dimer') and 2G2 ('nuclear actin'), but not C4 (monomeric actin). → Mitotic unconventional actin cables are independent of filamentous actin or microtubules. → Unconventional actin colocalizes with vimentin on a nocodazole-induced perinuclear dense mass of cables. -- Abstract: Different structural conformations of actin have been identified in cells and shown to reside in distinct subcellular locations of cells. In this report, we describe the localization of actin on a cage-like structure in metaphase HEK 293T cells. Actin was detected with the anti-actin antibodies 1C7 and 2G2, but not with the anti-actin antibody C4. Actin contained in this structure is independent of microtubules and actin filaments, and colocalizes with vimentin. Taking advantage of intermediate filament collapse into a perinuclear dense mass of cables when microtubules are depolymerized, we were able to relocalize actin to such structures. We hypothesize that phosphorylation of intermediate filaments at mitosis entry triggers the recruitment of different actin conformations to mitotic intermediate filaments. Storage and partition of the nuclear actin and antiparallel 'lower dimer' actin conformations between daughter cells possibly contribute to gene transcription and transient actin filament dynamics at G1 entry.

  3. Fine-tuning of actin dynamics by the HSPB8-BAG3 chaperone complex facilitates cytokinesis and contributes to its impact on cell division.

    Science.gov (United States)

    Varlet, Alice Anaïs; Fuchs, Margit; Luthold, Carole; Lambert, Herman; Landry, Jacques; Lavoie, Josée N

    2017-07-01

    The small heat shock protein HSPB8 and its co-chaperone BAG3 are proposed to regulate cytoskeletal proteostasis in response to mechanical signaling in muscle cells. Here, we show that in dividing cells, the HSPB8-BAG3 complex is instrumental to the accurate disassembly of the actin-based contractile ring during cytokinesis, a process required to allow abscission of daughter cells. Silencing of HSPB8 markedly decreased the mitotic levels of BAG3 in HeLa cells, supporting its crucial role in BAG3 mitotic functions. Cells depleted of HSPB8 were delayed in cytokinesis, remained connected via a disorganized intercellular bridge, and exhibited increased incidence of nuclear abnormalities that result from failed cytokinesis (i.e., bi- and multi-nucleation). Such phenotypes were associated with abnormal accumulation of F-actin at the intercellular bridge of daughter cells at telophase. Remarkably, the actin sequestering drug latrunculin A, like the inhibitor of branched actin polymerization CK666, normalized F-actin during cytokinesis and restored proper cell division in HSPB8-depleted cells, implicating deregulated actin dynamics as a cause of abscission failure. Moreover, this HSPB8-dependent phenotype could be corrected by rapamycin, an autophagy-promoting drug, whereas it was mimicked by drugs impairing lysosomal function. Together, the results further support a role for the HSPB8-BAG3 chaperone complex in quality control of actin-based structure dynamics that are put under high tension, notably during cell cytokinesis. They expand a so-far under-appreciated connection between selective autophagy and cellular morphodynamics that guide cell division.

  4. Hippocampal Dendritic Spines Are Segregated Depending on Their Actin Polymerization.

    Science.gov (United States)

    Domínguez-Iturza, Nuria; Calvo, María; Benoist, Marion; Esteban, José Antonio; Morales, Miguel

    2016-01-01

    Dendritic spines are mushroom-shaped protrusions of the postsynaptic membrane. Spines receive the majority of glutamatergic synaptic inputs. Their morphology, dynamics, and density have been related to synaptic plasticity and learning. The main determinant of spine shape is filamentous actin. Using FRAP, we have reexamined the actin dynamics of individual spines from pyramidal hippocampal neurons, both in cultures and in hippocampal organotypic slices. Our results indicate that, in cultures, the actin mobile fraction is independently regulated at the individual spine level, and mobile fraction values do not correlate with either age or distance from the soma. The most significant factor regulating actin mobile fraction was the presence of astrocytes in the culture substrate. Spines from neurons growing in the virtual absence of astrocytes have a more stable actin cytoskeleton, while spines from neurons growing in close contact with astrocytes show a more dynamic cytoskeleton. According to their recovery time, spines were distributed into two populations with slower and faster recovery times, while spines from slice cultures were grouped into one population. Finally, employing fast lineal acquisition protocols, we confirmed the existence of loci with high polymerization rates within the spine.

  5. Histones bundle F-actin filaments and affect actin structure.

    Directory of Open Access Journals (Sweden)

    Edna Blotnick

    Full Text Available Histones are small polycationic proteins complexed with DNA located in the cell nucleus. Upon apoptosis they are secreted from the cells and react with extracellular polyanionic compounds. Actin which is a polyanionic protein, is also secreted from necrotic cells and interacts with histones. We showed that both histone mixture (histone type III and the recombinant H2A histone bundles F-actin, increases the viscosity of the F-actin containing solution and polymerizes G-actin. The histone-actin bundles are relatively insensitive to increase of ionic strength, unlike other polycation, histatin, lysozyme, spermine and LL-37 induced F-actin bundles. The histone-actin bundles dissociate completely only in the presence of 300-400 mM NaCl. DNA, which competes with F-actin for histones, disassembles histone induced actin bundles. DNase1, which depolymerizes F- to G-actin, actively unbundles the H2A histone induced but slightly affects the histone mixture induced actin bundles. Cofilin decreases the amount of F-actin sedimented by low speed centrifugation, increases light scattering and viscosity of F-actin-histone mixture containing solutions and forms star like superstructures by copolymerizing G-actin with H2A histone. The results indicate that histones are tightly attached to F-actin by strong electrostatic and hydrophobic forces. Since both histones and F-actin are present in the sputum of patients with cystic fibrosis, therefore, the formation of the stable histone-actin bundles can contribute to the pathology of this disease by increasing the viscosity of the sputum. The actin-histone interaction in the nucleus might affect gene expression.

  6. Monoubiquitination Inhibits the Actin Bundling Activity of Fascin.

    Science.gov (United States)

    Lin, Shengchen; Lu, Shuang; Mulaj, Mentor; Fang, Bin; Keeley, Tyler; Wan, Lixin; Hao, Jihui; Muschol, Martin; Sun, Jianwei; Yang, Shengyu

    2016-12-30

    Fascin is an actin bundling protein that cross-links individual actin filaments into straight, compact, and stiff bundles, which are crucial for the formation of filopodia, stereocillia, and other finger-like membrane protrusions. The dysregulation of fascin has been implicated in cancer metastasis, hearing loss, and blindness. Here we identified monoubiquitination as a novel mechanism that regulates fascin bundling activity and dynamics. The monoubiquitination sites were identified to be Lys 247 and Lys 250 , two residues located in a positive charge patch at the actin binding site 2 of fascin. Using a chemical ubiquitination method, we synthesized chemically monoubiquitinated fascin and determined the effects of monoubiquitination on fascin bundling activity and dynamics. Our data demonstrated that monoubiquitination decreased the fascin bundling EC 50 , delayed the initiation of bundle assembly, and accelerated the disassembly of existing bundles. By analyzing the electrostatic properties on the solvent-accessible surface of fascin, we proposed that monoubiquitination introduced steric hindrance to interfere with the interaction between actin filaments and the positively charged patch at actin binding site 2. We also identified Smurf1 as a E3 ligase regulating the monoubiquitination of fascin. Our findings revealed a previously unidentified regulatory mechanism for fascin, which will have important implications for the understanding of actin bundle regulation under physiological and pathological conditions. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  7. Monoubiquitination Inhibits the Actin Bundling Activity of Fascin*

    Science.gov (United States)

    Lin, Shengchen; Lu, Shuang; Mulaj, Mentor; Fang, Bin; Keeley, Tyler; Wan, Lixin; Hao, Jihui; Muschol, Martin; Sun, Jianwei; Yang, Shengyu

    2016-01-01

    Fascin is an actin bundling protein that cross-links individual actin filaments into straight, compact, and stiff bundles, which are crucial for the formation of filopodia, stereocillia, and other finger-like membrane protrusions. The dysregulation of fascin has been implicated in cancer metastasis, hearing loss, and blindness. Here we identified monoubiquitination as a novel mechanism that regulates fascin bundling activity and dynamics. The monoubiquitination sites were identified to be Lys247 and Lys250, two residues located in a positive charge patch at the actin binding site 2 of fascin. Using a chemical ubiquitination method, we synthesized chemically monoubiquitinated fascin and determined the effects of monoubiquitination on fascin bundling activity and dynamics. Our data demonstrated that monoubiquitination decreased the fascin bundling EC50, delayed the initiation of bundle assembly, and accelerated the disassembly of existing bundles. By analyzing the electrostatic properties on the solvent-accessible surface of fascin, we proposed that monoubiquitination introduced steric hindrance to interfere with the interaction between actin filaments and the positively charged patch at actin binding site 2. We also identified Smurf1 as a E3 ligase regulating the monoubiquitination of fascin. Our findings revealed a previously unidentified regulatory mechanism for fascin, which will have important implications for the understanding of actin bundle regulation under physiological and pathological conditions. PMID:27879315

  8. Ornithine decarboxylase and extracellular polyamines regulate microvascular sprouting and actin cytoskeleton dynamics in endothelial cells

    International Nuclear Information System (INIS)

    Kucharzewska, Paulina; Welch, Johanna E.; Svensson, Katrin J.; Belting, Mattias

    2010-01-01

    The polyamines are essential for cancer cell proliferation during tumorigenesis. Targeted inhibition of ornithine decarboxylase (ODC), i.e. a key enzyme of polyamine biosynthesis, by α-difluoromethylornithine (DFMO) has shown anti-neoplastic activity in various experimental models. This activity has mainly been attributed to the anti-proliferative effect of DFMO in cancer cells. Here, we provide evidence that unperturbed ODC activity is a requirement for proper microvessel sprouting ex vivo as well as the migration of primary human endothelial cells. DFMO-mediated ODC inhibition was reversed by extracellular polyamine supplementation, showing that anti-angiogenic effects of DFMO were specifically related to polyamine levels. ODC inhibition was associated with an abnormal morphology of the actin cytoskeleton during cell spreading and migration. Moreover, our data suggest that de-regulated actin cytoskeleton dynamics in DFMO treated endothelial cells may be related to constitutive activation of the small GTPase CDC42, i.e. a well-known regulator of cell motility and actin cytoskeleton remodeling. These insights into the potential role of polyamines in angiogenesis should stimulate further studies testing the combined anti-tumor effect of polyamine inhibition and established anti-angiogenic therapies in vivo.

  9. Mutations in actin used for structural studies partially disrupt β-thymosin/WH2 domains interaction.

    Science.gov (United States)

    Deville, Célia; Girard-Blanc, Christine; Assrir, Nadine; Nhiri, Naïma; Jacquet, Eric; Bontems, François; Renault, Louis; Petres, Stéphane; van Heijenoort, Carine

    2016-10-01

    Understanding the structural basis of actin cytoskeleton remodeling requires stabilization of actin monomers, oligomers, and filaments in complex with partner proteins, using various biochemical strategies. Here, we report a dramatic destabilization of the dynamic interaction with a model β-thymosin/WH2 domain induced by mutations in actin. This result underlines that mutant actins should be used with prudence to characterize interactions with intrinsically disordered partners as destabilization of dynamic interactions, although identifiable by NMR, may be invisible to other structural techniques. It also highlights how both β-thymosin/WH2 domains and actin tune local structure and dynamics in regulatory processes involving intrinsically disordered domains. © 2016 Federation of European Biochemical Societies.

  10. Investigation of aeroacoustics and flow dynamics of a NACA 0015 airfoil with a Gurney flap using TR-PIV

    NARCIS (Netherlands)

    Shah, J.; Sciacchitano, A.; Pröbsting, S.

    The present study employs simultaneous planar TR-PIV and microphone measurements to obtain the flow dynamics and aeroacoustic causality correlation associated with a Gurney flap of various sizes in case of low Mach and high Reynolds number flows. The objectives are to investigate the secondary

  11. Free-style puzzle flap: the concept of recycling a perforator flap.

    Science.gov (United States)

    Feng, Kuan-Ming; Hsieh, Ching-Hua; Jeng, Seng-Feng

    2013-02-01

    Theoretically, a flap can be supplied by any perforator based on the angiosome theory. In this study, the technique of free-style perforator flap dissection was used to harvest a pedicled or free skin flap from a previous free flap for a second difficult reconstruction. The authors call this a free-style puzzle flap. For the past 3 years, the authors treated 13 patients in whom 12 pedicled free-style puzzle flaps were harvested from previous redundant free flaps and recycled to reconstruct soft-tissue defects at various anatomical locations. One free-style free puzzle flap was harvested from a previous anterolateral thigh flap for buccal cancer to reconstruct a foot defect. Total flap survival was attained in 12 of 13 flaps. One transferred flap failed completely. This patient had received postoperative radiotherapy after the initial cancer ablation and free anterolateral thigh flap reconstruction. Another free flap was used to close and reconstruct the wound. All the donor sites could be closed primarily. The free-style puzzle flap, harvested from a previous redundant free flap and used as a perforator flap to reconstruct a new defect, has proven to be versatile and reliable. When indicated, it is an alternative donor site for further reconstruction of soft-tissue defects.

  12. Comparisons of actin filament disruptors and Rho kinase inhibitors as potential antiglaucoma medications

    OpenAIRE

    Tian, Baohe; Kaufman, Paul L

    2012-01-01

    Dynamics of the actin cytoskeleton in the trabecular meshwork play a crucial role in the regulation of trabecular outflow resistance. The actin filament disruptors and Rho kinase inhibitors affect the dynamics of the actomyosin system by either disrupting the actin filaments or inhibiting the Rho kinase-activated cellular contractility. Both approaches induce similar morphological changes and resistance decreases in the trabecular outflow pathway, and thus both have potential as antiglaucoma ...

  13. Role of cyclic nucleotide-dependent actin cytoskeletal dynamics:Ca(2+](i and force suppression in forskolin-pretreated porcine coronary arteries.

    Directory of Open Access Journals (Sweden)

    Kyle M Hocking

    Full Text Available Initiation of force generation during vascular smooth muscle contraction involves a rise in intracellular calcium ([Ca(2+]i and phosphorylation of myosin light chains (MLC. However, reversal of these two processes alone does not account for the force inhibition that occurs during relaxation or inhibition of contraction, implicating that other mechanisms, such as actin cytoskeletal rearrangement, play a role in the suppression of force. In this study, we hypothesize that forskolin-induced force suppression is dependent upon changes in actin cytoskeletal dynamics. To focus on the actin cytoskeletal changes, a physiological model was developed in which forskolin treatment of intact porcine coronary arteries (PCA prior to treatment with a contractile agonist resulted in complete suppression of force. Pretreatment of PCA with forskolin suppressed histamine-induced force generation but did not abolish [Ca(2+]i rise or MLC phosphorylation. Additionally, forskolin pretreatment reduced filamentous actin in histamine-treated tissues, and prevented histamine-induced changes in the phosphorylation of the actin-regulatory proteins HSP20, VASP, cofilin, and paxillin. Taken together, these results suggest that forskolin-induced complete force suppression is dependent upon the actin cytoskeletal regulation initiated by the phosphorylation changes of the actin regulatory proteins and not on the MLC dephosphorylation. This model of complete force suppression can be employed to further elucidate the mechanisms responsible for smooth muscle tone, and may offer cues to pathological situations, such as hypertension and vasospasm.

  14. Every day I'm rufflin': Calcium sensing and actin dynamics in the growth factor-independent membrane ruffling of professional phagocytes.

    Science.gov (United States)

    Schlam, Daniel; Canton, Johnathan

    2017-04-03

    Professional phagocytes continuously extend dynamic, actin-driven membrane protrusions. These protrusions, often referred to as membrane ruffles, serve a critical role in the essential phagocyte processes of macropinocytosis and phagocytosis. Small GTPases, such as RAC1/2, spatially and temporally regulate membrane ruffle formation. We have recently shown that extracellular calcium regulates the elaboration of membrane ruffles primarily through the synthesis of phosphatidic acid (PtdOH) at the plasma membrane. RAC1/2 guanine nucleotide exchange factors harbouring polybasic stretches are recruited by PtdOH to sites of ruffle formation. Here we discuss our findings and offer perspectives on how the regulation of dynamic actin structures at the plasma membrane by small GTPases is a critical component of phagocyte function.

  15. PIV study of flow around unsteady airfoil with dynamic trailing-edge flap deflection

    Energy Technology Data Exchange (ETDEWEB)

    Gerontakos, P.; Lee, T. [McGill University, Department of Mechanical Engineering, Montreal, Quebec (Canada)

    2008-12-15

    The flow around an oscillating NACA 0015 airfoil with prescheduled trailing-edge flap motion control was investigated by using particle image velocimetry (PIV). Aerodynamic load coefficients, obtained via surface pressure measurements, were also acquired to supplement the PIV results. The results demonstrate that upward flap deflections led to an improved negative peak pitching moment coefficient C{sub m,peak}, mainly as a consequence of the increased suction pressure on the lower surface of the flap. The behavior of the leading-edge vortex (LEV) was largely unaffected. Its strength was, however, reduced slightly compared to that of the uncontrolled airfoil. No trailing-edge vortex was observed. For downward flap deflection, the strength of the LEV was found to be slightly increased. A favorable increase in C{sub l,max}, as a consequence of downward flap-induced positive camber effects, accompanied by a detrimental increase in the nose-down C{sub m,peak}, due to the large pressure increase on the lower surface of the flap, was also observed. (orig.)

  16. A nucleator arms race: cellular control of actin assembly.

    Science.gov (United States)

    Campellone, Kenneth G; Welch, Matthew D

    2010-04-01

    For over a decade, the actin-related protein 2/3 (ARP2/3) complex, a handful of nucleation-promoting factors and formins were the only molecules known to directly nucleate actin filament formation de novo. However, the past several years have seen a surge in the discovery of mammalian proteins with roles in actin nucleation and dynamics. Newly recognized nucleation-promoting factors, such as WASP and SCAR homologue (WASH), WASP homologue associated with actin, membranes and microtubules (WHAMM), and junction-mediating regulatory protein (JMY), stimulate ARP2/3 activity at distinct cellular locations. Formin nucleators with additional biochemical and cellular activities have also been uncovered. Finally, the Spire, cordon-bleu and leiomodin nucleators have revealed new ways of overcoming the kinetic barriers to actin polymerization.

  17. The ubiquitin C-terminal hydrolase UCH-L1 promotes bacterial invasion by altering the dynamics of the actin cytoskeleton

    DEFF Research Database (Denmark)

    Basseres, Eugene; Coppotelli, Giuseppe; Pfirrmann, Thorsten

    2010-01-01

    Invasion of eukaryotic target cells by pathogenic bacteria requires extensive remodelling of the membrane and actin cytoskeleton. Here we show that the remodelling process is regulated by the ubiquitin C-terminal hydrolase UCH-L1 that promotes the invasion of epithelial cells by Listeria monocyto......Invasion of eukaryotic target cells by pathogenic bacteria requires extensive remodelling of the membrane and actin cytoskeleton. Here we show that the remodelling process is regulated by the ubiquitin C-terminal hydrolase UCH-L1 that promotes the invasion of epithelial cells by Listeria...... of downstream ERK1/2- and AKT-dependent signalling in response to the natural ligand Hepatocyte Growth Factor (HGF). The regulation of cytoskeleton dynamics was further confirmed by the induction of actin stress fibres in HeLa expressing the active enzyme but not the catalytic mutant UCH-L1(C90S...

  18. Profilin-Dependent Nucleation and Assembly of Actin Filaments Controls Cell Elongation in Arabidopsis1[OPEN

    Science.gov (United States)

    Cao, Lingyan; Blanchoin, Laurent; Staiger, Christopher J.

    2016-01-01

    Actin filaments in plant cells are incredibly dynamic; they undergo incessant remodeling and assembly or disassembly within seconds. These dynamic events are choreographed by a plethora of actin-binding proteins, but the exact mechanisms are poorly understood. Here, we dissect the contribution of Arabidopsis (Arabidopsis thaliana) PROFILIN1 (PRF1), a conserved actin monomer-binding protein, to actin organization and single filament dynamics during axial cell expansion of living epidermal cells. We found that reduced PRF1 levels enhanced cell and organ growth. Surprisingly, we observed that the overall frequency of nucleation events in prf1 mutants was dramatically decreased and that a subpopulation of actin filaments that assemble at high rates was reduced. To test whether profilin cooperates with plant formin proteins to execute actin nucleation and rapid filament elongation in cells, we used a pharmacological approach. Here, we used Small Molecule Inhibitor of Formin FH2 (SMIFH2), after validating its mode of action on a plant formin in vitro, and observed a reduced nucleation frequency of actin filaments in live cells. Treatment of wild-type epidermal cells with SMIFH2 mimicked the phenotype of prf1 mutants, and the nucleation frequency in prf1-2 mutant was completely insensitive to these treatments. Our data provide compelling evidence that PRF1 coordinates the stochastic dynamic properties of actin filaments by modulating formin-mediated actin nucleation and assembly during plant cell expansion. PMID:26574597

  19. Vault-poly-ADP-ribose polymerase in the Octopus vulgaris brain: a regulatory factor of actin polymerization dynamic.

    Science.gov (United States)

    De Maio, Anna; Natale, Emiliana; Rotondo, Sergio; Di Cosmo, Anna; Faraone-Mennella, Maria Rosaria

    2013-09-01

    Our previous behavioural, biochemical and immunohistochemical analyses conducted in selected regions (supra/sub oesophageal masses) of the Octopus vulgaris brain detected a cytoplasmic poly-ADP-ribose polymerase (more than 90% of total enzyme activity). The protein was identified as the vault-free form of vault-poly-ADP-ribose polymerase. The present research extends and integrates the biochemical characterization of poly-ADP-ribosylation system, namely, reaction product, i.e., poly-ADP-ribose, and acceptor proteins, in the O. vulgaris brain. Immunochemical analyses evidenced that the sole poly-ADP-ribose acceptor was the octopus cytoskeleton 50-kDa actin. It was present in both free, endogenously poly-ADP-ribosylated form (70kDa) and in complex with V-poly-ADP-ribose polymerase and poly-ADP-ribose (260kDa). The components of this complex, alkali and high salt sensitive, were purified and characterized. The kind and the length of poly-ADP-ribose corresponded to linear chains of 30-35 ADP-ribose units, in accordance with the features of the polymer synthesized by the known vault-poly-ADP-ribose polymerase. In vitro experiments showed that V-poly-ADP-ribose polymerase activity of brain cytoplasmic fraction containing endogenous actin increased upon the addition of commercial actin and was highly reduced by ATP. Anti-actin immunoblot of the mixture in the presence and absence of ATP showed that the poly-ADP-ribosylation of octopus actin is a dynamic process balanced by the ATP-dependent polymerization of the cytoskeleton protein, a fundamental mechanism for synaptic plasticity. © 2013 Elsevier Inc. All rights reserved.

  20. An efficient fluid–structure interaction model for optimizing twistable flapping wings

    NARCIS (Netherlands)

    Wang, Q.; Goosen, J.F.L.; van Keulen, A.

    2017-01-01

    Spanwise twist can dominate the deformation of flapping wings and alters the aerodynamic performance and power efficiency of flapping wings by changing the local angle of attack. Traditional Fluid–Structure Interaction (FSI) models, based on Computational Structural Dynamics (CSD) and

  1. The RhoGAP Stard13 controls insulin secretion through F-actin remodeling

    Directory of Open Access Journals (Sweden)

    Heike Naumann

    2018-02-01

    Full Text Available Objective: Actin cytoskeleton remodeling is necessary for glucose-stimulated insulin secretion in pancreatic β-cells. A mechanistic understanding of actin dynamics in the islet is paramount to a better comprehension of β-cell dysfunction in diabetes. Here, we investigate the Rho GTPase regulator Stard13 and its role in F-actin cytoskeleton organization and islet function in adult mice. Methods: We used Lifeact-EGFP transgenic animals to visualize actin cytoskeleton organization and dynamics in vivo in the mouse islets. Furthermore, we applied this model to study actin cytoskeleton and insulin secretion in mutant mice deleted for Stard13 selectively in pancreatic cells. We isolated transgenic islets for 3D-imaging and perifusion studies to measure insulin secretion dynamics. In parallel, we performed histological and morphometric analyses of the pancreas and used in vivo approaches to study glucose metabolism in the mouse. Results: In this study, we provide the first genetic evidence that Stard13 regulates insulin secretion in response to glucose. Postnatally, Stard13 expression became restricted to the mouse pancreatic islets. We showed that Stard13 deletion results in a marked increase in actin polymerization in islet cells, which is accompanied by severe reduction of insulin secretion in perifusion experiments. Consistently, Stard13-deleted mice displayed impaired glucose tolerance and reduced glucose-stimulated insulin secretion. Conclusions: Taken together, our results suggest a previously unappreciated role for the RhoGAP protein Stard13 in the interplay between actin cytoskeletal remodeling and insulin secretion. Keywords: F-actin, Insulin secretion, Islet, Pancreas, Lifeact, Stard13

  2. Flapping inertia for selected rotor blades

    Science.gov (United States)

    Berry, John D.; May, Matthew J.

    1991-01-01

    Aerodynamics of helicopter rotor systems cannot be investigated without consideration for the dynamics of the rotor. One of the principal properties of the rotor which affects the rotor dynamics is the inertia of the rotor blade about its root attachment. Previous aerodynamic investigation have been performed on rotor blades with a variety of planforms to determine the performance differences due to blade planform. The blades tested for this investigation have been tested on the U.S. Army 2 meter rotor test system (2MRTS) in the NASA Langley 14 by 22 foot subsonic tunnel for hover performance. This investigation was intended to provide fundamental information on the flapping inertia of five rotor blades with differing planforms. The inertia of the bare cuff and the cuff with a blade extension were also measured for comparison with the inertia of the blades. Inertia was determined using a swing testing technique, using the period of oscillation to determine the effective flapping inertia. The effect of damping in the swing test was measured and described. A comparison of the flapping inertials for rectangular and tapered planform blades of approximately the same mass showed the tapered blades to have a lower inertia, as expected.

  3. Flapping wing flight can save aerodynamic power compared to steady flight.

    Science.gov (United States)

    Pesavento, Umberto; Wang, Z Jane

    2009-09-11

    Flapping flight is more maneuverable than steady flight. It is debated whether this advantage is necessarily accompanied by a trade-off in the flight efficiency. Here we ask if any flapping motion exists that is aerodynamically more efficient than the optimal steady motion. We solve the Navier-Stokes equation governing the fluid dynamics around a 2D flapping wing, and determine the minimal aerodynamic power needed to support a specified weight. While most flapping wing motions are more costly than the optimal steady wing motion, we find that optimized flapping wing motions can save up to 27% of the aerodynamic power required by the optimal steady flight. We explain the cause of this energetic advantage.

  4. Actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations

    Science.gov (United States)

    Westendorf, Christian; Negrete, Jose; Bae, Albert J.; Sandmann, Rabea; Bodenschatz, Eberhard; Beta, Carsten

    2013-01-01

    The rapid reorganization of the actin cytoskeleton in response to external stimuli is an essential property of many motile eukaryotic cells. Here, we report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. When averaging the actin response of many cells to a short pulse of the chemoattractant cAMP, we observed a transient accumulation of cortical actin reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. To substantiate that an oscillatory mechanism governs the actin dynamics in these cells, we systematically exposed a large number of cells to periodic pulse trains of different frequencies. Our results indicate a resonance peak at a stimulation period of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the regulatory network of the actin system. To test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and actin-interacting protein 1, as well as knockout mutants that lack Coronin and actin-interacting protein 1. These actin-binding proteins enhance the disassembly of actin filaments and thus allow us to estimate the delay time in the regulatory feedback loop. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed in our periodic stimulation experiments. PMID:23431176

  5. In vivo microvascular imaging of cutaneous actinic keratosis, Bowen's disease and squamous cell carcinoma using dynamic optical coherence tomography

    DEFF Research Database (Denmark)

    Themstrup, L; Pellacani, G; Welzel, J

    2017-01-01

    BACKGROUND: A clear distinction between actinic keratosis (AK), Bowen's disease (BD) and squamous cell carcinoma (SCC) cannot reliably be made by clinical and dermoscopic evaluation alone. Dynamic optical coherence tomography (D-OCT) is a novel angiographic variant of OCT that allows for non...

  6. Amphidinolide H, a novel type of actin-stabilizing agent isolated from dinoflagellate

    International Nuclear Information System (INIS)

    Saito, Shin-ya; Feng Jue; Kira, Atsushi; Kobayashi, Jun'ichi; Ohizumi, Yasushi

    2004-01-01

    The effect of novel cytotoxic marine macrolide, amphidinolide H (Amp-H), on actin dynamics was investigated in vitro. Amp-H attenuated actin depolymerization induced by diluting F-actin. This effect remained after washing out of unbound Amp-H by filtration. In the presence of either Amp-H or phalloidin, lag phase, which is the rate-limiting step of actin polymerization, was shortened. Phalloidin decreased the polymerization-rate whereas Amp-H did not. Meanwhile, the effects of both compounds were the same when barbed end of actin was capped by cytochalasin D. Quartz crystal microbalance system revealed interaction of Amp-H with G-actin and F-actin. Amp-H also enhanced the binding of phalloidin to F-actin. We concluded that Amp-H stabilizes actin in a different manner from that of phalloidin and serves as a novel pharmacological tool for analyzing actin-mediated cell function

  7. Distinct functional interactions between actin isoforms and nonsarcomeric myosins.

    Directory of Open Access Journals (Sweden)

    Mirco Müller

    Full Text Available Despite their near sequence identity, actin isoforms cannot completely replace each other in vivo and show marked differences in their tissue-specific and subcellular localization. Little is known about isoform-specific differences in their interactions with myosin motors and other actin-binding proteins. Mammalian cytoplasmic β- and γ-actin interact with nonsarcomeric conventional myosins such as the members of the nonmuscle myosin-2 family and myosin-7A. These interactions support a wide range of cellular processes including cytokinesis, maintenance of cell polarity, cell adhesion, migration, and mechano-electrical transduction. To elucidate differences in the ability of isoactins to bind and stimulate the enzymatic activity of individual myosin isoforms, we characterized the interactions of human skeletal muscle α-actin, cytoplasmic β-actin, and cytoplasmic γ-actin with human myosin-7A and nonmuscle myosins-2A, -2B and -2C1. In the case of nonmuscle myosins-2A and -2B, the interaction with either cytoplasmic actin isoform results in 4-fold greater stimulation of myosin ATPase activity than was observed in the presence of α-skeletal muscle actin. Nonmuscle myosin-2C1 is most potently activated by β-actin and myosin-7A by γ-actin. Our results indicate that β- and γ-actin isoforms contribute to the modulation of nonmuscle myosin-2 and myosin-7A activity and thereby to the spatial and temporal regulation of cytoskeletal dynamics. FRET-based analyses show efficient copolymerization abilities for the actin isoforms in vitro. Experiments with hybrid actin filaments show that the extent of actomyosin coupling efficiency can be regulated by the isoform composition of actin filaments.

  8. Actinic keratosis

    Science.gov (United States)

    Solar keratosis; Sun-induced skin changes - keratosis; Keratosis - actinic (solar); Skin lesion - actinic keratosis ... Actinic keratosis is caused by exposure to sunlight. You are more likely to develop it if you: Have fair ...

  9. Keystone flaps in coloured skin: Flap technology for the masses?

    Directory of Open Access Journals (Sweden)

    Satish P Bhat

    2013-01-01

    Full Text Available Introduction: Viscoelastic properties of skin in coloured ethnic groups are less favourable compared to Caucasians for executing Keystone flaps. Keystone flaps have so far been evaluated and reported only in Caucasians. The potential of Keystone flaps in a coloured ethnic group is yet unknown. Aim: This article reviews the experience to reconstruct skin defects presenting in a coloured ethnic group, by using Keystone flaps, with a review of existing literature. Design: Uncontrolled case series. Materials and Methods: This retrospective review involves 55 consecutive Keystone flaps used from 2009 to 2012, for skin defects in various locations. Patient demographic data, medical history, co-morbidity, surgical indication, defect features, complications, and clinical outcomes are evaluated and presented. Results: In this population group with Fitzpatrick type 4 and 5 skin, the average patient age was 35.73. Though 60% of flaps (33/55 in the series involved specific risk factors, only two flaps failed. Though seven flaps had complications, sound healing was achieved by suitable intervention giving a success rate of 96.36%. Skin grafts were needed in only four cases. Conclusions: Keystone flaps achieve primary wound healing for a wide spectrum of defects with an acceptable success rate in a coloured skin population with unfavorable biophysical properties. By avoiding conventional local flaps and at times even microsurgical flaps, good aesthetic outcome is achieved without additional skin grafts or extensive operative time. All advantages seen in previous studies were verified. These benefits can be most appreciated in coloured populations, with limited resources and higher proportion of younger patients and unfavorable defects.

  10. NKCC1 Regulates Migration Ability of Glioblastoma Cells by Modulation of Actin Dynamics and Interacting with Cofilin

    Directory of Open Access Journals (Sweden)

    Paula Schiapparelli

    2017-07-01

    Full Text Available Glioblastoma (GBM is the most aggressive primary brain tumor in adults. The mechanisms that confer GBM cells their invasive behavior are poorly understood. The electroneutral Na+-K+-2Cl− co-transporter 1 (NKCC1 is an important cell volume regulator that participates in cell migration. We have shown that inhibition of NKCC1 in GBM cells leads to decreased cell migration, in vitro and in vivo. We now report on the role of NKCC1 on cytoskeletal dynamics. We show that GBM cells display a significant decrease in F-actin content upon NKCC1 knockdown (NKCC1-KD. To determine the potential actin-regulatory mechanisms affected by NKCC1 inhibition, we studied NKCC1 protein interactions. We found that NKCC1 interacts with the actin-regulating protein Cofilin-1 and can regulate its membrane localization. Finally, we analyzed whether NKCC1 could regulate the activity of the small Rho-GTPases RhoA and Rac1. We observed that the active forms of RhoA and Rac1 were decreased in NKCC1-KD cells. In summary, we report that NKCC1 regulates GBM cell migration by modulating the cytoskeleton through multiple targets including F-actin regulation through Cofilin-1 and RhoGTPase activity. Due to its essential role in cell migration NKCC1 may serve as a specific therapeutic target to decrease cell invasion in patients with primary brain cancer.

  11. Structural Studies of a Rationally Selected Multi-Drug Resistant HIV-1 Protease Reveal Synergistic Effect of Distal Mutations on Flap Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Agniswamy, Johnson; Louis, John M.; Roche, Julien; Harrison, Robert W.; Weber, Irene T. (GSU); (NIH); (Iowa State)

    2016-12-16

    We report structural analysis of HIV protease variant PRS17 which was rationally selected by machine learning to represent wide classes of highly drug-resistant variants. Crystal structures were solved of PRS17 in the inhibitor-free form and in complex with antiviral inhibitor, darunavir. Despite its 17 mutations, PRS17 has only one mutation (V82S) in the inhibitor/substrate binding cavity, yet exhibits high resistance to all clinical inhibitors. PRS17 has none of the major mutations (I47V, I50V, I54ML, L76V and I84V) associated with darunavir resistance, but has 10,000-fold weaker binding affinity relative to the wild type PR. Comparable binding affinity of 8000-fold weaker than PR is seen for drug resistant mutant PR20, which bears 3 mutations associated with major resistance to darunavir (I47V, I54L and I84V). Inhibitor-free PRS17 shows an open flap conformation with a curled tip correlating with G48V flap mutation. NMR studies on inactive PRS17 D25N unambiguously confirm that the flaps adopt mainly an open conformation in solution very similar to that in the inhibitor-free crystal structure. In PRS17, the hinge loop cluster of mutations, E35D, M36I and S37D, contributes to the altered flap dynamics by a mechanism similar to that of PR20. An additional K20R mutation anchors an altered conformation of the hinge loop. Flap mutations M46L and G48V in PRS17/DRV complex alter the Phe53 conformation by steric hindrance between the side chains. Unlike the L10F mutation in PR20, L10I in PRS17 does not break the inter-subunit ion pair or diminish the dimer stability, consistent with a very low dimer dissociation constant comparable to that of wild type PR. Distal mutations A71V, L90M and I93L propagate alterations to the catalytic site of PRS17. PRS17 exhibits a molecular mechanism whereby mutations act synergistically to alter the flap dynamics resulting in significantly weaker binding yet maintaining active site contacts with darunavir.

  12. Actin filaments regulate the adhesion between the plasma membrane and the cell wall of tobacco guard cells.

    Science.gov (United States)

    Yu, Qin; Ren, Jing-Jing; Kong, Lan-Jing; Wang, Xiu-Ling

    2018-01-01

    During the opening and closing of stomata, guard cells undergo rapid and reversible changes in their volume and shape, which affects the adhesion of the plasma membrane (PM) to the cell wall (CW). The dynamics of actin filaments in guard cells are involved in stomatal movement by regulating structural changes and intracellular signaling. However, it is unclear whether actin dynamics regulate the adhesion of the PM to the CW. In this study, we investigated the relationship between actin dynamics and PM-CW adhesion by the hyperosmotic-induced plasmolysis of tobacco guard cells. We found that actin filaments in guard cells were depolymerized during mannitol-induced plasmolysis. The inhibition of actin dynamics by treatment with latrunculin B or jasplakinolide and the disruption of the adhesion between the PM and the CW by treatment with RGDS peptide (Arg-Gly-Asp-Ser) enhanced guard cell plasmolysis. However, treatment with latrunculin B alleviated the RGDS peptide-induced plasmolysis and endocytosis. Our results reveal that the actin depolymerization is involved in the regulation of the PW-CW adhesion during hyperosmotic-induced plasmolysis in tobacco guard cells.

  13. Optimization of morphing flaps based on fluid structure interaction modeling

    DEFF Research Database (Denmark)

    Barlas, Athanasios; Akay, Busra

    2018-01-01

    This article describes the design optimization of morphing trailing edge flaps for wind turbines with ‘smart blades’. A high fidelity Fluid Structure Interaction (FSI) simulation framework is utilized, comprised of 2D Finite Element Analysis (FEA) and Computational Fluid Dynamics (CFD) models....... A coupled aero-structural simulation of a 10% chordwise length morphing trailing edge flap for a 4 MW wind turbine rotor is carried out and response surfaces are produced with respect to the flap internal geometry design parameters for the design conditions. Surrogate model based optimization is applied...

  14. Pedicled perforator flaps

    DEFF Research Database (Denmark)

    Demirtas, Yener; Ozturk, Nuray; Kelahmetoglu, Osman

    2009-01-01

    Described in this study is a surgical concept that supports the "consider and use a pedicled perforator flap whenever possible and indicated" approach to reconstruct a particular skin defect. The operation is entirely free-style; the only principle is to obtain a pedicled perforator flap...... to reconstruct the defect. The perforators are marked with a hand-held Doppler probe and multiple flaps are designed. The appropriate flap is elevated after identifying the perforator(s). Dissection of the perforator(s) or complete incision of the flap margins are not mandatory if the flap is mobilized...... adequately to cover the defect. Defects measuring 3 x 3 cm up to 20 x 20 cm at diverse locations were successfully reconstructed in 20 of 21 patients with 26 flaps. Pedicled perforator flaps offer us reliable and satisfactory results of reconstruction at different anatomic territories of the body. It sounds...

  15. Profilin connects actin assembly with microtubule dynamics

    Czech Academy of Sciences Publication Activity Database

    Nejedla, M.; Sadi, S.; Sulimenko, Vadym; de Almeida, F.N.; Blom, H.; Dráber, Pavel; Aspenstrom, P.; Karlsson, R.

    2016-01-01

    Roč. 27, č. 15 (2016), s. 2381-2393 ISSN 1059-1524 R&D Projects: GA ČR GA16-25159S Institutional support: RVO:68378050 Keywords : cross-linked profilin * arp2/3 complex * f-actin * microfilament system * migrating cells * focal adhesions * cultured-cells * messenger-rna * living cells * protein Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.685, year: 2016

  16. IFT88 influences chondrocyte actin organization and biomechanics.

    Science.gov (United States)

    Wang, Z; Wann, A K T; Thompson, C L; Hassen, A; Wang, W; Knight, M M

    2016-03-01

    Primary cilia are microtubule based organelles which control a variety of signalling pathways important in cartilage development, health and disease. This study examines the role of the intraflagellar transport (IFT) protein, IFT88, in regulating fundamental actin organisation and mechanics in articular chondrocytes. The study used an established chondrocyte cell line with and without hypomorphic mutation of IFT88 (IFT88(orpk)). Confocal microscopy was used to quantify F-actin and myosin IIB organisation. Viscoelastic cell and actin cortex mechanics were determined using micropipette aspiration with actin dynamics visualised in live cells transfected with LifeACT-GFP. IFT88(orpk) cells exhibited a significant increase in acto-myosin stress fibre organisation relative to wild-type (WT) cells in monolayer and an altered response to cytochalasin D. Rounded IFT88(orpk) cells cultured in suspension exhibited reduced cortical actin expression with reduced cellular equilibrium modulus. Micropipette aspiration resulted in reduced membrane bleb formation in IFT88(orpk) cells. Following membrane blebbing, IFT88(orpk) cells exhibited slower reformation of the actin cortex. IFT88(orpk) cells showed increased actin deformability and reduced cortical tension confirming that IFT regulates actin cortex mechanics. The reduced cortical tension is also consistent with the reduced bleb formation. This study demonstrates for the first time that the ciliary protein IFT88 regulates fundamental actin organisation and the stiffness of the actin cortex leading to alterations in cell deformation, mechanical properties and blebbing in an IFT88 chondrocyte cell line. This adds to the growing understanding of the role of primary cilia and IFT in regulating cartilage biology. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  17. Actin-myosin network is required for proper assembly of influenza virus particles

    Energy Technology Data Exchange (ETDEWEB)

    Kumakura, Michiko; Kawaguchi, Atsushi, E-mail: ats-kawaguchi@md.tsukuba.ac.jp; Nagata, Kyosuke, E-mail: knagata@md.tsukuba.ac.jp

    2015-02-15

    Actin filaments are known to play a central role in cellular dynamics. After polymerization of actin, various actin-crosslinking proteins including non-muscle myosin II facilitate the formation of spatially organized actin filament networks. The actin-myosin network is highly expanded beneath plasma membrane. The genome of influenza virus (vRNA) replicates in the cell nucleus. Then, newly synthesized vRNAs are nuclear-exported to the cytoplasm as ribonucleoprotein complexes (vRNPs), followed by transport to the beneath plasma membrane where virus particles assemble. Here, we found that, by inhibiting actin-myosin network formation, the virus titer tends to be reduced and HA viral spike protein is aggregated on the plasma membrane. These results indicate that the actin-myosin network plays an important role in the virus formation. - Highlights: • Actin-myosin network is important for the influenza virus production. • HA forms aggregations at the plasma membrane in the presence of blebbistatin. • M1 is recruited to the budding site through the actin-myosin network.

  18. Actin-myosin network is required for proper assembly of influenza virus particles

    International Nuclear Information System (INIS)

    Kumakura, Michiko; Kawaguchi, Atsushi; Nagata, Kyosuke

    2015-01-01

    Actin filaments are known to play a central role in cellular dynamics. After polymerization of actin, various actin-crosslinking proteins including non-muscle myosin II facilitate the formation of spatially organized actin filament networks. The actin-myosin network is highly expanded beneath plasma membrane. The genome of influenza virus (vRNA) replicates in the cell nucleus. Then, newly synthesized vRNAs are nuclear-exported to the cytoplasm as ribonucleoprotein complexes (vRNPs), followed by transport to the beneath plasma membrane where virus particles assemble. Here, we found that, by inhibiting actin-myosin network formation, the virus titer tends to be reduced and HA viral spike protein is aggregated on the plasma membrane. These results indicate that the actin-myosin network plays an important role in the virus formation. - Highlights: • Actin-myosin network is important for the influenza virus production. • HA forms aggregations at the plasma membrane in the presence of blebbistatin. • M1 is recruited to the budding site through the actin-myosin network

  19. Functional characterisation of filamentous actin probe expression in neuronal cells.

    Directory of Open Access Journals (Sweden)

    Shrujna Patel

    Full Text Available Genetically encoded filamentous actin probes, Lifeact, Utrophin and F-tractin, are used as tools to label the actin cytoskeleton. Recent evidence in several different cell types indicates that these probes can cause changes in filamentous actin dynamics, altering cell morphology and function. Although these probes are commonly used to visualise actin dynamics in neurons, their effects on axonal and dendritic morphology has not been systematically characterised. In this study, we quantitatively analysed the effect of Lifeact, Utrophin and F-tractin on neuronal morphogenesis in primary hippocampal neurons. Our data show that the expression of actin-tracking probes significantly impacts on axonal and dendrite growth these neurons. Lifeact-GFP expression, under the control of a pBABE promoter, caused a significant decrease in total axon length, while another Lifeact-GFP expression, under the control of a CAG promoter, decreased the length and complexity of dendritic trees. Utr261-EGFP resulted in increased dendritic branching but Utr230-EGFP only accumulated in cell soma, without labelling any neurites. Lifeact-7-mEGFP and F-tractin-EGFP in a pEGFP-C1 vector, under the control of a CMV promoter, caused only minor changes in neuronal morphology as detected by Sholl analysis. The results of this study demonstrate the effects that filamentous actin tracking probes can have on the axonal and dendritic compartments of neuronal cells and emphasise the care that must be taken when interpreting data from experiments using these probes.

  20. LL-37 induces polymerization and bundling of actin and affects actin structure.

    Directory of Open Access Journals (Sweden)

    Asaf Sol

    Full Text Available Actin exists as a monomer (G-actin which can be polymerized to filaments F-actin that under the influence of actin-binding proteins and polycations bundle and contribute to the formation of the cytoskeleton. Bundled actin from lysed cells increases the viscosity of sputum in lungs of cystic fibrosis patients. The human host defense peptide LL-37 was previously shown to induce actin bundling and was thus hypothesized to contribute to the pathogenicity of this disease. In this work, interactions between actin and the cationic LL-37 were studied by optical, proteolytic and surface plasmon resonance methods and compared to those obtained with scrambled LL-37 and with the cationic protein lysozyme. We show that LL-37 binds strongly to CaATP-G-actin while scrambled LL-37 does not. While LL-37, at superstoichiometric LL-37/actin concentrations polymerizes MgATP-G-actin, at lower non-polymerizing concentrations LL-37 inhibits actin polymerization by MgCl(2 or NaCl. LL-37 bundles Mg-F-actin filaments both at low and physiological ionic strength when in equimolar or higher concentrations than those of actin. The LL-37 induced bundles are significantly less sensitive to increase in ionic strength than those induced by scrambled LL-37 and lysozyme. LL-37 in concentrations lower than those needed for actin polymerization or bundling, accelerates cleavage of both monomer and polymer actin by subtilisin. Our results indicate that the LL-37-actin interaction is partially electrostatic and partially hydrophobic and that a specific actin binding sequence in the peptide is responsible for the hydrophobic interaction. LL-37-induced bundles, which may contribute to the accumulation of sputum in cystic fibrosis, are dissociated very efficiently by DNase-1 and also by cofilin.

  1. Prokaryotic DNA segregation by an actin-like filament

    DEFF Research Database (Denmark)

    Møller-Jensen, Jakob; Bugge Jensen, Rasmus; Löwe, Jan

    2002-01-01

    The mechanisms responsible for prokaryotic DNA segregation are largely unknown. The partitioning locus (par) encoded by the Escherichia coli plasmid R1 actively segregates its replicon to daughter cells. We show here that the ParM ATPase encoded by par forms dynamic actin-like filaments with prop...... point for ParM polymerization. Hence, we provide evidence for a simple prokaryotic analogue of the eukaryotic mitotic spindle apparatus.......The mechanisms responsible for prokaryotic DNA segregation are largely unknown. The partitioning locus (par) encoded by the Escherichia coli plasmid R1 actively segregates its replicon to daughter cells. We show here that the ParM ATPase encoded by par forms dynamic actin-like filaments...

  2. Head and neck reconstruction with pedicled flaps in the free flap era.

    Science.gov (United States)

    Mahieu, R; Colletti, G; Bonomo, P; Parrinello, G; Iavarone, A; Dolivet, G; Livi, L; Deganello, A

    2016-12-01

    Nowadays, the transposition of microvascular free flaps is the most popular method for management of head and neck defects. However, not all patients are suitable candidates for free flap reconstruction. In addition, not every defect requires a free flap transfer to achieve good functional results. The aim of this study was to assess whether pedicled flap reconstruction of head and neck defects is inferior to microvascular free flap reconstruction in terms of complications, functionality and prognosis. The records of consecutive patients who underwent free flap or pedicled flap reconstruction after head and neck cancer ablation from 2006 to 2015, from a single surgeon, in the AOUC Hospital, Florence Italy were analysed. A total of 93 patients, the majority with oral cancer (n = 59), were included, of which 64 were pedicled flap reconstructions (69%). The results showed no significant differences in terms of functional outcome, flap necrosis and complications in each type of reconstruction. Multivariate regression analysis of flap necrosis and functional impairments showed no associated factors. Multivariate regression analysis of complicated flap healing showed that only comorbidities remained an explaining factor (p = 0.019). Survival analysis and proportional hazard regression analysis regarding cancer relapse or distant metastasis, showed no significant differences in prognosis of patients concerning both types of reconstruction. In this retrospective, non-randomised study cohort, pedicled flaps were not significantly inferior to free flaps for reconstruction of head and neck defects, considering functionality, complications and prognosis. © Copyright by Società Italiana di Otorinolaringologia e Chirurgia Cervico-Facciale, Rome, Italy.

  3. Actin depolymerization enhances adipogenic differentiation in human stromal stem cells

    DEFF Research Database (Denmark)

    Chen, Li; Hu, Huimin; Qiu, Weimin

    2018-01-01

    Human stromal stem cells (hMSCs) differentiate into adipocytes that play a role in skeletal tissue homeostasis and whole body energy metabolism. During adipocyte differentiation, hMSCs exhibit significant changes in cell morphology suggesting changes in cytoskeletal organization. Here, we examined...... the effect of direct modulation of actin microfilament dynamics on adipocyte differentiation. Stabilizing actin filaments in hMSCs by siRNA-mediated knock down of the two main actin depolymerizing factors (ADFs): Cofilin 1 (CFL1) and Destrin (DSTN) or treating the cells by Phalloidin reduced adipocyte...

  4. Dipteran wing motor-inspired flapping flight versatility and effectiveness enhancement.

    Science.gov (United States)

    Harne, R L; Wang, K W

    2015-03-06

    Insects are a prime source of inspiration towards the development of small-scale, engineered, flapping wing flight systems. To help interpret the possible energy transformation strategies observed in Diptera as inspiration for mechanical flapping flight systems, we revisit the perspective of the dipteran wing motor as a bistable click mechanism and take a new, and more flexible, outlook to the architectural composition previously considered. Using a representative structural model alongside biological insights and cues from nonlinear dynamics, our analyses and experimental results reveal that a flight mechanism able to adjust motor axial support stiffness and compression characteristics may dramatically modulate the amplitude range and type of wing stroke dynamics achievable. This corresponds to significantly more versatile aerodynamic force generation without otherwise changing flapping frequency or driving force amplitude. Whether monostable or bistable, the axial stiffness is key to enhance compressed motor load bearing ability and aerodynamic efficiency, particularly compared with uncompressed linear motors. These findings provide new foundation to guide future development of bioinspired, flapping wing mechanisms for micro air vehicle applications, and may be used to provide insight to the dipteran muscle-to-wing interface. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  5. The Actin-Binding Protein α-Adducin Is Required for Maintaining Axon Diameter

    Directory of Open Access Journals (Sweden)

    Sérgio Carvalho Leite

    2016-04-01

    Full Text Available The actin-binding protein adducin was recently identified as a component of the neuronal subcortical cytoskeleton. Here, we analyzed mice lacking adducin to uncover the function of this protein in actin rings. α-adducin knockout mice presented progressive axon enlargement in the spinal cord and optic and sciatic nerves, followed by axon degeneration and loss. Using stimulated emission depletion super-resolution microscopy, we show that a periodic subcortical actin cytoskeleton is assembled in every neuron type inspected including retinal ganglion cells and dorsal root ganglia neurons. In neurons devoid of adducin, the actin ring diameter increased, although the inter-ring periodicity was maintained. In vitro, the actin ring diameter adjusted as axons grew, suggesting the lattice is dynamic. Our data support a model in which adducin activity is not essential for actin ring assembly and periodicity but is necessary to control the diameter of both actin rings and axons and actin filament growth within rings.

  6. The Actin-Binding Protein α-Adducin Is Required for Maintaining Axon Diameter.

    Science.gov (United States)

    Leite, Sérgio Carvalho; Sampaio, Paula; Sousa, Vera Filipe; Nogueira-Rodrigues, Joana; Pinto-Costa, Rita; Peters, Luanne Laurel; Brites, Pedro; Sousa, Mónica Mendes

    2016-04-19

    The actin-binding protein adducin was recently identified as a component of the neuronal subcortical cytoskeleton. Here, we analyzed mice lacking adducin to uncover the function of this protein in actin rings. α-adducin knockout mice presented progressive axon enlargement in the spinal cord and optic and sciatic nerves, followed by axon degeneration and loss. Using stimulated emission depletion super-resolution microscopy, we show that a periodic subcortical actin cytoskeleton is assembled in every neuron type inspected including retinal ganglion cells and dorsal root ganglia neurons. In neurons devoid of adducin, the actin ring diameter increased, although the inter-ring periodicity was maintained. In vitro, the actin ring diameter adjusted as axons grew, suggesting the lattice is dynamic. Our data support a model in which adducin activity is not essential for actin ring assembly and periodicity but is necessary to control the diameter of both actin rings and axons and actin filament growth within rings. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  7. Phase-resolved fluid dynamic forces of a flapping foil energy harvester based on PIV measurements

    Science.gov (United States)

    Liburdy, James

    2017-11-01

    Two-dimensional particle image velocimetry measurements are performed in a wind tunnel to evaluate the spatial and temporal fluid dynamic forces acting on a flapping foil operating in the energy harvesting regime. Experiments are conducted at reduced frequencies (k = fc/U) of 0.05 - 0.2, pitching angle of, and heaving amplitude of A / c = 0.6. The phase-averaged pressure field is obtained by integrating the pressure Poisson equation. Fluid dynamic forces are then obtained through the integral momentum equation. Results are compared with a simple force model based on the concept of flow impulse. These results help to show the detailed force distributions, their transient nature and aide in understanding the impact of the fluid flow structures that contribute to the power production.

  8. Cdc42/N-WASP signaling links actin dynamics to pancreatic β cell delamination and differentiation

    Science.gov (United States)

    Kesavan, Gokul; Lieven, Oliver; Mamidi, Anant; Öhlin, Zarah Löf; Johansson, Jenny Kristina; Li, Wan-Chun; Lommel, Silvia; Greiner, Thomas Uwe; Semb, Henrik

    2014-01-01

    Delamination plays a pivotal role during normal development and cancer. Previous work has demonstrated that delamination and epithelial cell movement within the plane of an epithelium are associated with a change in cellular phenotype. However, how this positional change is linked to differentiation remains unknown. Using the developing mouse pancreas as a model system, we show that β cell delamination and differentiation are two independent events, which are controlled by Cdc42/N-WASP signaling. Specifically, we show that expression of constitutively active Cdc42 in β cells inhibits β cell delamination and differentiation. These processes are normally associated with junctional actin and cell-cell junction disassembly and the expression of fate-determining transcription factors, such as Isl1 and MafA. Mechanistically, we demonstrate that genetic ablation of N-WASP in β cells expressing constitutively active Cdc42 partially restores both delamination and β cell differentiation. These findings elucidate how junctional actin dynamics via Cdc42/N-WASP signaling cell-autonomously control not only epithelial delamination but also cell differentiation during mammalian organogenesis. PMID:24449844

  9. Modeling of Airfoil Trailing Edge Flap with Immersed Boundary Method

    DEFF Research Database (Denmark)

    Zhu, Wei Jun; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2011-01-01

    The present work considers incompressible flow over a 2D airfoil with a deformable trailing edge. The aerodynamic characteristics of an airfoil with a trailing edge flap is numerically investigated using computational fluid dynamics. A novel hybrid immersed boundary (IB) technique is applied...... to simulate the moving part of the trailing edge. Over the main fixed part of the airfoil the Navier-Stokes (NS) equations are solved using a standard body-fitted finite volume technique whereas the moving trailing edge flap is simulated with the immersed boundary method on a curvilinear mesh. The obtained...... results show that the hybrid approach is an efficient and accurate method for solving turbulent flows past airfoils with a trailing edge flap and flow control using trailing edge flap is an efficient way to regulate the aerodynamic loading on airfoils....

  10. An investigation of unsteady 3-D effects on trailing edge flaps

    Directory of Open Access Journals (Sweden)

    E. Jost

    2017-05-01

    Full Text Available The present study investigates the impact of unsteady 3-D aerodynamic effects on a wind turbine blade with trailing edge flap by means of computational fluid dynamics (CFD. Harmonic oscillations are simulated on the DTU 10 MW rotor with a morphing flap of 10 % chord extent ranging from 70 to 80 % blade radius. The deflection frequency is varied in the range between 1 and 6 p. To quantify 3-D effects, rotor simulations are compared to 2-D airfoil computations and the 2-D theory by Theodorsen. It was found that the deflection of the flap on the 3-D rotor causes a complex wake development and induction which influences the loads over large parts of the blade. In particular, the rotor near wake with its trailing and shed vortex structures revealed a great impact. Trailing vorticity, a 3-D phenomenon, is caused by the gradient of bound circulation along the blade span. Shed vorticity originates from the temporal bound circulation gradient and is thus also apparent in 2-D. Both lead to an amplitude reduction and shed vorticity additionally to a hysteresis of the lift response with regard to the deflection signal in the flap section. A greater amplitude reduction and a less pronounced hysteresis is observed on the 3-D rotor compared to the 2-D airfoil case. Blade sections neighboring the flap experience, however, an opposing impact and hence partly compensate for the negative effect of trailing vortices in the flap section with respect to integral loads. Comparisons to steady flap deflections at the 3-D rotor revealed the high influence of dynamic inflow effects.

  11. [Saphenous perforator flap].

    Science.gov (United States)

    Winkel, R; Tajsic, N; Husum, H; Schlageter, M; Hanebuth, G; Hoffmann, R

    2013-04-01

    Replacement of full thickness soft tissue defects in the lower leg and ankle, appropriate to the defect and following the course of blood vessels feeding the skin of a distally hinged fasciocutaneous flap most reliably based on the individual anatomy of distal perforators of the posterior tibial artery. Full thickness soft tissue defects, up to 12 cm in length and up to 8 cm in width. Sufficient vascularization of the foot required, in osteomyelitis, and when joints, fractures, implants and tendons are exposed and when a split skin graft, a local flap, a suralis perforator flap or a free flap is not indicated. For patients, in whom a 1-2 h operation is not possible; necessity of angioplasty; decollement or scars around the distal perforators of the posterior tibial artery; local infection or necrosis of soft tissues and/or bone, which cannot be totally excised. Radical debridement; flap dissection without tourniquet; microdissection; design of the flap on the skin: pivot point ~ 10 cm (6-14 cm) proximal of the tip of the medial malleolus; base ~ 5 cm in width, between the course of the saphenous nerve and of the great saphenous vein and the Achilles tendon; adipofascial pedicle up to 15 cm in length sited over the septum between soleus and flexor digitorum muscles, following the course of the saphenous nerve, with a central skin stripe, which expands into a proximal skin island; skin island is outlined similar to the defect, but larger by 1 to 2 cm, surrounded by an adipofascial border: adjustment of the planning as well as of the elevation of these flaps according to the individual position and the caliber of perforators requires in each case the search for a perforator at the estimated pivot point. Delay of transposition, if the division of more than one perforator proximal to the pivot point obviously diminishes circulation. No "tunnelling "of the pedicle; defects of skin due to the elevation of the flap are replaced by split and meshed skin grafts or temporary

  12. Region-Specific Involvement of Actin Rearrangement-Related Synaptic Structure Alterations in Conditioned Taste Aversion Memory

    Science.gov (United States)

    Bi, Ai-Ling; Wang, Yue; Li, Bo-Qin; Wang, Qian-Qian; Ma, Ling; Yu, Hui; Zhao, Ling; Chen, Zhe-Yu

    2010-01-01

    Actin rearrangement plays an essential role in learning and memory; however, the spatial and temporal regulation of actin dynamics in different phases of associative memory has not been fully understood. Here, using the conditioned taste aversion (CTA) paradigm, we investigated the region-specific involvement of actin rearrangement-related…

  13. Management of Vortices Trailing Flapped Wings via Separation Control

    Science.gov (United States)

    Greenblatt, David

    2005-01-01

    A pilot study was conducted on a flapped semi-span model to investigate the concept and viability of near-wake vortex management via separation control. Passive control was achieved by means of a simple fairing and active control was achieved via zero mass-flux blowing slots. Vortex sheet strength, estimated by integrating surface pressure ports, was used to predict vortex characteristics by means of inviscid rollup relations. Furthermore, vortices trailing the flaps were mapped using a seven-hole probe. Separation control was found to have a marked effect on vortex location, strength, tangential velocity, axial velocity and size over a wide range of angles of attack and control conditions. In general, the vortex trends were well predicted by the inviscid rollup relations. Manipulation of the separated flow near the flap edges exerted significant control over both outboard and inboard edge vortices while producing negligible lift excursions. Dynamic separation and attachment control was found to be an effective means for dynamically perturbing the vortex from arbitrarily long wavelengths down to wavelengths less than a typical wingspan. In summary, separation control has the potential for application to time-independent or time-dependent wake alleviation schemes, where the latter can be deployed to minimize adverse effects on ride-quality and dynamic structural loading.

  14. Comparison of heaving buoy and oscillating flap wave energy converters

    Science.gov (United States)

    Abu Bakar, Mohd Aftar; Green, David A.; Metcalfe, Andrew V.; Najafian, G.

    2013-04-01

    Waves offer an attractive source of renewable energy, with relatively low environmental impact, for communities reasonably close to the sea. Two types of simple wave energy converters (WEC), the heaving buoy WEC and the oscillating flap WEC, are studied. Both WECs are considered as simple energy converters because they can be modelled, to a first approximation, as single degree of freedom linear dynamic systems. In this study, we estimate the response of both WECs to typical wave inputs; wave height for the buoy and corresponding wave surge for the flap, using spectral methods. A nonlinear model of the oscillating flap WEC that includes the drag force, modelled by the Morison equation is also considered. The response to a surge input is estimated by discrete time simulation (DTS), using central difference approximations to derivatives. This is compared with the response of the linear model obtained by DTS and also validated using the spectral method. Bendat's nonlinear system identification (BNLSI) technique was used to analyze the nonlinear dynamic system since the spectral analysis was only suitable for linear dynamic system. The effects of including the nonlinear term are quantified.

  15. Exploring the A22-Bacterial Actin MreB Interaction through Molecular Dynamics Simulations.

    Science.gov (United States)

    Awuni, Yaw; Jiang, Shimin; Robinson, Robert C; Mu, Yuguang

    2016-09-22

    MreB is an actin-like cytoskeleton protein that plays a vital role in the maintenance of the rod-shaped morphology of many bacteria. S-(3,4-Dichlorobenzyl) isothiourea (A22) is an antibiotic-like small molecule that perturbs the rod cell shape and has been suggested to inhibit MreB by targeting ATP hydrolysis. However, without the elucidation of the structure of the ATP-bound state of MreB in the presence of A22, the mechanism of A22 inhibition is still not clear. Here we apply conventional molecular dynamics simulations to explore the dynamics of the active site of MreB in complex with A22 and different nucleotides. We observe that hydrogen bonding between A22 and the catalytic Glu140 residue is not favored in the ATP-A22-bound state of MreB. Water dynamics analysis in the MreB active site reveals that in the presence of A22 water molecules are able to occupy positions suitable for ATP hydrolysis. Overall, our results are consistent with a mechanism in which A22 affects MreB polymerization/depolymerization dynamics in part through slowing phosphate release rather than by inhibiting ATP hydrolysis. These data can be incorporated in the design/development of the next generation of MreB inhibitors.

  16. Fluid dynamics of flapping aquatic flight in the bird wrasse: three-dimensional unsteady computations with fin deformation.

    Science.gov (United States)

    Ramamurti, Ravi; Sandberg, William C; Löhner, Rainald; Walker, Jeffrey A; Westneat, Mark W

    2002-10-01

    Many fishes that swim with the paired pectoral fins use fin-stroke parameters that produce thrust force from lift in a mechanism of underwater flight. These locomotor mechanisms are of interest to behavioral biologists, biomechanics researchers and engineers. In the present study, we performed the first three-dimensional unsteady computations of fish swimming with oscillating and deforming fins. The objective of these computations was to investigate the fluid dynamics of force production associated with the flapping aquatic flight of the bird wrasse Gomphosus varius. For this computational work, we used the geometry of the wrasse and its pectoral fin, and previously measured fin kinematics, as the starting points for computational investigation of three-dimensional (3-D) unsteady fluid dynamics. We performed a 3-D steady computation and a complete set of 3-D quasisteady computations for a range of pectoral fin positions and surface velocities. An unstructured, grid-based, unsteady Navier-Stokes solver with automatic adaptive remeshing was then used to compute the unsteady flow about the wrasse through several complete cycles of pectoral fin oscillation. The shape deformation of the pectoral fin throughout the oscillation was taken from the experimental kinematics. The pressure distribution on the body of the bird wrasse and its pectoral fins was computed and integrated to give body and fin forces which were decomposed into lift and thrust. The velocity field variation on the surface of the wrasse body, on the pectoral fins and in the near-wake was computed throughout the swimming cycle. We compared our computational results for the steady, quasi-steady and unsteady cases with the experimental data on axial and vertical acceleration obtained from the pectoral fin kinematics experiments. These comparisons show that steady state computations are incapable of describing the fluid dynamics of flapping fins. Quasi-steady state computations, with correct incorporation of

  17. An innovative method of planning and displaying flap volume in DIEP flap breast reconstructions.

    Science.gov (United States)

    Hummelink, S; Verhulst, Arico C; Maal, Thomas J J; Hoogeveen, Yvonne L; Schultze Kool, Leo J; Ulrich, Dietmar J O

    2017-07-01

    Determining the ideal volume of the harvested flap to achieve symmetry in deep inferior epigastric artery perforator (DIEP) flap breast reconstructions is complex. With preoperative imaging techniques such as 3D stereophotogrammetry and computed tomography angiography (CTA) available nowadays, we can combine information to preoperatively plan the optimal flap volume to be harvested. In this proof-of-concept, we investigated whether projection of a virtual flap planning onto the patient's abdomen using a projection method could result in harvesting the correct flap volume. In six patients (n = 9 breasts), 3D stereophotogrammetry and CTA data were combined from which a virtual flap planning was created comprising perforator locations, blood vessel trajectory and flap size. All projected perforators were verified with Doppler ultrasound. Intraoperative flap measurements were collected to validate the determined flap delineation volume. The measured breast volume using 3D stereophotogrammetry was 578 ± 127 cc; on CTA images, 527 ± 106 cc flap volumes were planned. The nine harvested flaps weighed 533 ± 109 g resulting in a planned versus harvested flap mean difference of 5 ± 27 g (flap density 1.0 g/ml). In 41 out of 42 projected perforator locations, a Doppler signal was audible. This proof-of-concept shows in small numbers that flap volumes can be included into a virtual DIEP flap planning, and transferring the virtual planning to the patient through a projection method results in harvesting approximately the same volume during surgery. In our opinion, this innovative approach is the first step in consequently achieving symmetric breast volumes in DIEP flap breast reconstructions. Copyright © 2017 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

  18. Blowing Flap Experiment: PIV Measurements

    Science.gov (United States)

    Hutcheson, Florence V.; Stead, Daniel J.; Bremmer, David M.

    2004-01-01

    PIV measurements of the flow in the region of a flap side edge are presented for several flap configurations. The test model is a NACA 63(sub 2)-215 Hicks Mod-B main element airfoil with a half-span Fowler flap. Air is blown from small slots located along the flap side edge on either the top, bottom or side surfaces. The test set up is described and flow measurements for a baseline and three blowing flap configurations are presented. The effects that the flap tip jets have on the structure of the flap side edge flow are discussed for each of the flap configurations tested. The results indicate that blowing air from a slot located along the top surface of the flap greatly weakened the top vortex system and pushed it further off the top surface. Blowing from the bottom flap surface kept the strong side vortex further outboard while blowing from the side surface only strengthened the flap vortex system. It is concluded that blowing from the top or bottom surfaces of the flap may lead to a reduction of flap side edge noise.

  19. HIV infection of T cells: actin-in and actin-out.

    Science.gov (United States)

    Liu, Yin; Belkina, Natalya V; Shaw, Stephen

    2009-04-14

    Three studies shed light on the decade-old observation that the actin cytoskeleton is hijacked to facilitate entry of HIV into its target cells. Polymerization of actin is required to assemble high concentrations of CD4 and CXCR4 at the plasma membrane, which promote viral binding and entry in both the simple model of infection by free virus and the more physiologically relevant route of infection through the virological synapse. Three types of actin-interacting proteins-filamin, ezrin/radixin/moesin (ERM), and cofilin-are now shown to play critical roles in this process. Filamin binds to both CD4 and CXCR4 in a manner promoted by signaling of the HIV gp120 glycoprotein. ERM proteins attach actin filaments to the membrane and may promote polymerization of actin. Early in the process of viral entry, cofilin is inactivated, which is proposed to facilitate the early assembly of actin filaments, but cofilin is reported to be activated soon thereafter to facilitate postentry events. This complex role of cofilin may help to reconcile the paradox that actin polymerization promotes initial binding and fusion steps but inhibits some subsequent early postentry events.

  20. Experimental Study of Wake / Flap Interaction Noise and the Reduction of Flap Side Edge Noise

    Science.gov (United States)

    Hutcheson, Florence V.; Stead, Daniel J.; Plassman, Gerald E.

    2016-01-01

    The effects of the interaction of a wake with a half-span flap on radiated noise are examined. The incident wake is generated by bars of various widths and lengths or by a simplified landing gear model. Single microphone and phased array measurements are used to isolate the effects of the wake interaction on the noise radiating from the flap side edge and flap cove regions. The effects on noise of the wake generator's geometry and relative placement with respect to the flap are assessed. Placement of the wake generators upstream of the flap side edge is shown to lead to the reduction of flap side edge noise by introducing a velocity deficit and likely altering the instabilities in the flap side edge vortex system. Significant reduction in flap side edge noise is achieved with a bar positioned directly upstream of the flap side edge. The noise reduction benefit is seen to improve with increased bar width, length and proximity to the flap edge. Positioning of the landing gear model upstream of the flap side edge also leads to decreased flap side edge noise. In addition, flap cove noise levels are significantly lower than when the landing gear is positioned upstream of the flap mid-span. The impact of the local flow velocity on the noise radiating directly from the landing gear is discussed. The effects of the landing gear side-braces on flap side edge, flap cove and landing gear noise are shown.

  1. Machine Learning for Flapping Wing Flight Control

    NARCIS (Netherlands)

    Goedhart, Menno; van Kampen, E.; Armanini, S.F.; de Visser, C.C.; Chu, Q.

    2018-01-01

    Flight control of Flapping Wing Micro Air Vehicles is challenging, because of their complex dynamics and variability due to manufacturing inconsistencies. Machine Learning algorithms can be used to tackle these challenges. A Policy Gradient algorithm is used to tune the gains of a

  2. Sensory role of actin in auxin-dependent responses of tobacco BY-2.

    Science.gov (United States)

    Huang, Xiang; Maisch, Jan; Nick, Peter

    2017-11-01

    Polar auxin transport depends on the polar localization of auxin-efflux carriers. The cycling of these carriers between cell interior and plasma membrane depends on actin. The dynamic of actin not only affects auxin transport, but also changes the auxin-responsiveness. To study the potential link between auxin responsiveness and actin dynamics, we investigated developmental responses of the non-transformed BY-2 (Nicotiana tabacum L. cv Bright Yellow 2) cell line and the transgenic BY-2 strain GF11 (stably transformed BY-2 cells with a GFP-fimbrin actin-binding domain 2 construct). The developmental process was divided into three distinct stages: cell cycling, cell elongation and file disintegration. Several phenotypes were measured to monitor the cellular responses to different concentrations of exogenous natural auxin (Indole-3-acetic acid, IAA). We found that auxin stimulated and prolonged the mitotic activity, and delayed the exit from the proliferation phase. However, both responses were suppressed in the GF11 line. At the stationary phase of the cultivation cycle, auxin strongly accelerated the cell file disintegration. Interestingly, it was not suppressed but progressed to a more complete disintegration in the GF11 line. During the cultivation cycle, we also followed the organization of actin in the GF11 line and did not detect any significant difference in actin organization from untreated control or exogenous IAA treatment. Therefore, our findings indicate that the specific differences observed in the GF11 line must be linked with a function of actin that is not structural. It means that there is a sensory role of actin for auxin signaling. Copyright © 2017 Elsevier GmbH. All rights reserved.

  3. Parametric study of fluid flow manipulation with piezoelectric macrofiber composite flaps

    Science.gov (United States)

    Sadeghi, O.; Tarazaga, P.; Stremler, M.; Shahab, S.

    2017-04-01

    Active Fluid Flow Control (AFFC) has received great research attention due to its significant potential in engineering applications. It is known that drag reduction, turbulence management, flow separation delay and noise suppression through active control can result in significantly increased efficiency of future commercial transport vehicles and gas turbine engines. In microfluidics systems, AFFC has mainly been used to manipulate fluid passing through the microfluidic device. We put forward a conceptual approach for fluid flow manipulation by coupling multiple vibrating structures through flow interactions in an otherwise quiescent fluid. Previous investigations of piezoelectric flaps interacting with a fluid have focused on a single flap. In this work, arrays of closely-spaced, free-standing piezoelectric flaps are attached perpendicular to the bottom surface of a tank. The coupling of vibrating flaps due to their interacting with the surrounding fluid is investigated in air (for calibration) and under water. Actuated flaps are driven with a harmonic input voltage, which results in bending vibration of the flaps that can work with or against the flow-induced bending. The size and spatial distribution of the attached flaps, and the phase and frequency of the input actuation voltage are the key parameters to be investigated in this work. Our analysis will characterize the electrohydroelastic dynamics of active, interacting flaps and the fluid motion induced by the system.

  4. New compliant strain gauges for self-sensing dynamic deformation of flapping wings on miniature air vehicles

    Science.gov (United States)

    Wissman, James; Perez-Rosado, Ariel; Edgerton, Alex; Levi, Benjamin M.; Karakas, Zeynep N.; Kujawski, Mark; Philipps, Alyssa; Papavizas, Nicholas; Fallon, Danielle; Bruck, Hugh A.; Smela, Elisabeth

    2013-08-01

    Over the past several years there has been an increasing interest in the development of miniature air vehicles (MAVs) with flapping wings. To allow these MAVs to adjust to changes in wind direction and to maximize their efficiency, it is desirable to monitor the deformation of the wing during flight. This paper presents a step in this direction, demonstrating the measurement of strain on the surface of the wing using minimally invasive compliant piezoresistive sensors. The strain gauges consisted of latex mixed with electrically conducting exfoliated graphite, and they were applied by spray coating. To calibrate the gauges, both static and dynamic testing up to 10 Hz were performed using cantilever structures. In tension the static sensitivity was a linear 0.4 Ω μɛ-1 and the gauge factor was 28; in compression, the gauge factor was -5. Although sensitivities in tension and compression differed by a factor of almost six, this was not reflected in the dynamic data, which followed the strain reversibly with little distortion. There was no attenuation with frequency, indicating a sufficiently small time constant for this application. The gauges were thin, compliant, and light enough to measure, without interference, deformations due to shape changes of the flexible wing associated with generating lift and thrust. During flapping the resistance closely tracked the generated thrust, measured on a test stand, with both signals tracing figure-8 loops as a function of wing position throughout each cycle.

  5. New compliant strain gauges for self-sensing dynamic deformation of flapping wings on miniature air vehicles

    International Nuclear Information System (INIS)

    Wissman, James; Perez-Rosado, Ariel; Edgerton, Alex; Levi, Benjamin M; Karakas, Zeynep N; Kujawski, Mark; Philipps, Alyssa; Papavizas, Nicholas; Fallon, Danielle; Bruck, Hugh A; Smela, Elisabeth

    2013-01-01

    Over the past several years there has been an increasing interest in the development of miniature air vehicles (MAVs) with flapping wings. To allow these MAVs to adjust to changes in wind direction and to maximize their efficiency, it is desirable to monitor the deformation of the wing during flight. This paper presents a step in this direction, demonstrating the measurement of strain on the surface of the wing using minimally invasive compliant piezoresistive sensors. The strain gauges consisted of latex mixed with electrically conducting exfoliated graphite, and they were applied by spray coating. To calibrate the gauges, both static and dynamic testing up to 10 Hz were performed using cantilever structures. In tension the static sensitivity was a linear 0.4 Ω με −1 and the gauge factor was 28; in compression, the gauge factor was −5. Although sensitivities in tension and compression differed by a factor of almost six, this was not reflected in the dynamic data, which followed the strain reversibly with little distortion. There was no attenuation with frequency, indicating a sufficiently small time constant for this application. The gauges were thin, compliant, and light enough to measure, without interference, deformations due to shape changes of the flexible wing associated with generating lift and thrust. During flapping the resistance closely tracked the generated thrust, measured on a test stand, with both signals tracing figure-8 loops as a function of wing position throughout each cycle. (paper)

  6. Actin Filaments and Myosin I Alpha Cooperate with Microtubules for the Movement of LysosomesV⃞

    OpenAIRE

    Cordonnier, Marie-Neige; Dauzonne, Daniel; Louvard, Daniel; Coudrier, Evelyne

    2001-01-01

    An earlier report suggested that actin and myosin I alpha (MMIα), a myosin associated with endosomes and lysosomes, were involved in the delivery of internalized molecules to lysosomes. To determine whether actin and MMIα were involved in the movement of lysosomes, we analyzed by time-lapse video microscopy the dynamic of lysosomes in living mouse hepatoma cells (BWTG3 cells), producing green fluorescent protein actin or a nonfunctional domain of MMIα. In GFP-actin cells, lysosomes displayed ...

  7. Actin-Dependent Alterations of Dendritic Spine Morphology in Shankopathies

    Directory of Open Access Journals (Sweden)

    Tasnuva Sarowar

    2016-01-01

    Full Text Available Shank proteins (Shank1, Shank2, and Shank3 act as scaffolding molecules in the postsynaptic density of many excitatory neurons. Mutations in SHANK genes, in particular SHANK2 and SHANK3, lead to autism spectrum disorders (ASD in both human and mouse models. Shank3 proteins are made of several domains—the Shank/ProSAP N-terminal (SPN domain, ankyrin repeats, SH3 domain, PDZ domain, a proline-rich region, and the sterile alpha motif (SAM domain. Via various binding partners of these domains, Shank3 is able to bind and interact with a wide range of proteins including modulators of small GTPases such as RICH2, a RhoGAP protein, and βPIX, a RhoGEF protein for Rac1 and Cdc42, actin binding proteins and actin modulators. Dysregulation of all isoforms of Shank proteins, but especially Shank3, leads to alterations in spine morphogenesis, shape, and activity of the synapse via altering actin dynamics. Therefore, here, we highlight the role of Shank proteins as modulators of small GTPases and, ultimately, actin dynamics, as found in multiple in vitro and in vivo models. The failure to mediate this regulatory role might present a shared mechanism in the pathophysiology of autism-associated mutations, which leads to dysregulation of spine morphogenesis and synaptic signaling.

  8. Src kinases regulate de novo actin polymerization during exocytosis in neuroendocrine chromaffin cells.

    Directory of Open Access Journals (Sweden)

    María José Olivares

    Full Text Available The cortical actin network is dynamically rearranged during secretory processes. Nevertheless, it is unclear how de novo actin polymerization and the disruption of the preexisting actin network control transmitter release. Here we show that in bovine adrenal chromaffin cells, both formation of new actin filaments and disruption of the preexisting cortical actin network are induced by Ca2+ concentrations that trigger exocytosis. These two processes appear to regulate different stages of exocytosis; whereas the inhibition of actin polymerization with the N-WASP inhibitor wiskostatin restricts fusion pore expansion, thus limiting the release of transmitters, the disruption of the cortical actin network with cytochalasin D increases the amount of transmitter released per event. Further, the Src kinase inhibitor PP2, and cSrc SH2 and SH3 domains also suppress Ca2+-dependent actin polymerization, and slow down fusion pore expansion without disturbing the cortical F-actin organization. Finally, the isolated SH3 domain of c-Src prevents both the disruption of the actin network and the increase in the quantal release induced by cytochalasin D. These findings support a model where a rise in the cytosolic Ca2+ triggers actin polymerization through a mechanism that involves Src kinases. The newly formed actin filaments would speed up the expansion of the initial fusion pore, whereas the preexisting actin network might control a different step of the exocytosis process.

  9. Structure and Function of an Actin-Based Filter in the Proximal Axon

    Directory of Open Access Journals (Sweden)

    Varuzhan Balasanyan

    2017-12-01

    Full Text Available Summary: The essential organization of microtubules within neurons has been described; however, less is known about how neuronal actin is arranged and the functional implications of its arrangement. Here, we describe, in live cells, an actin-based structure in the proximal axon that selectively prevents some proteins from entering the axon while allowing the passage of others. Concentrated patches of actin in proximal axons are present shortly after axonal specification in rat and zebrafish neurons imaged live, and they mark positions where anterogradely traveling vesicles carrying dendritic proteins halt and reverse. Patches colocalize with the ARP2/3 complex, and when ARP2/3-mediated nucleation is blocked, a dendritic protein mislocalizes to the axon. Patches are highly dynamic, with few persisting longer than 30 min. In neurons in culture and in vivo, actin appears to form a contiguous, semipermeable barrier, despite its apparently sparse distribution, preventing axonal localization of constitutively active myosin Va but not myosin VI. : Balasanyan et al. find dynamic patches of actin in proximal axons of live neurons, mature and newly differentiated, in culture and in vivo. Patches contribute to a filter that sequesters some proteins within the somatodendritic domain while allowing others to pass into the axon, leading to polarized localization of proteins.

  10. The transverse musculocutaneous gracilis flap for breast reconstruction: guidelines for flap and patient selection.

    Science.gov (United States)

    Schoeller, Thomas; Huemer, Georg M; Wechselberger, Gottfried

    2008-07-01

    The transverse musculocutaneous gracilis (TMG) flap has received little attention in the literature as a valuable alternative source of donor tissue in the setting of breast reconstruction. The authors give an in-depth review of their experience with breast reconstruction using the TMG flap. A retrospective review of 111 patients treated with a TMG flap for breast reconstruction in an immediate or a delayed setting between August of 2002 and July of 2007 was undertaken. Of these, 26 patients underwent bilateral reconstruction and 68 underwent unilateral reconstruction, and 17 patients underwent reconstruction unilaterally with a double TMG flap. Patient age ranged between 24 and 65 years (mean, 37 years). Twelve patients had to be taken back to the operating room because of flap-related problems and nine patients underwent successful revision microsurgically, resulting in three complete flap losses in a series of 111 patients with 154 transplanted TMG flaps. Partial flap loss was encountered in two patients, whereas fat tissue necrosis was managed conservatively in six patients. Donor-site morbidity was an advantage of this flap, with a concealed scar and minimal contour irregularities of the thigh, even in unilateral harvest. Complications included delayed wound healing (n = 10), hematoma (n = 5), and transient sensory deficit over the posterior thigh (n = 49). The TMG flap is more than an alternative to the deep inferior epigastric perforator (DIEP) flap in microsurgical breast reconstruction in selected patients. In certain indications, such as bilateral reconstructions, it possibly surpasses the DIEP flap because of a better concealed donor scar and easier harvest.

  11. Actin grips: circular actin-rich cytoskeletal structures that mediate the wrapping of polymeric microfibers by endothelial cells.

    Science.gov (United States)

    Jones, Desiree; Park, DoYoung; Anghelina, Mirela; Pécot, Thierry; Machiraju, Raghu; Xue, Ruipeng; Lannutti, John J; Thomas, Jessica; Cole, Sara L; Moldovan, Leni; Moldovan, Nicanor I

    2015-06-01

    Interaction of endothelial-lineage cells with three-dimensional substrates was much less studied than that with flat culture surfaces. We investigated the in vitro attachment of both mature endothelial cells (ECs) and of less differentiated EC colony-forming cells to poly-ε-capro-lactone (PCL) fibers with diameters in 5-20 μm range ('scaffold microfibers', SMFs). We found that notwithstanding the poor intrinsic adhesiveness to PCL, both cell types completely wrapped the SMFs after long-term cultivation, thus attaining a cylindrical morphology. In this system, both EC types grew vigorously for more than a week and became increasingly more differentiated, as shown by multiplexed gene expression. Three-dimensional reconstructions from multiphoton confocal microscopy images using custom software showed that the filamentous (F) actin bundles took a conspicuous ring-like organization around the SMFs. Unlike the classical F-actin-containing stress fibers, these rings were not associated with either focal adhesions or intermediate filaments. We also demonstrated that plasma membrane boundaries adjacent to these circular cytoskeletal structures were tightly yet dynamically apposed to the SMFs, for which reason we suggest to call them 'actin grips'. In conclusion, we describe a particular form of F-actin assembly with relevance for cytoskeletal organization in response to biomaterials, for endothelial-specific cell behavior in vitro and in vivo, and for tissue engineering. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. Inhibiting actin depolymerization enhances osteoblast differentiation and bone formation in human stromal stem cells

    DEFF Research Database (Denmark)

    Chen, Li; Shi, Kaikai; Frary, Charles

    2015-01-01

    Remodeling of the actin cytoskeleton through actin dynamics is involved in a number of biological processes, but its role in human stromal (skeletal) stem cells (hMSCs) differentiation is poorly understood. In the present study, we demonstrated that stabilizing actin filaments by inhibiting gene...... expression of the two main actin depolymerizing factors (ADFs): Cofilin 1 (CFL1) and Destrin (DSTN) in hMSCs, enhanced cell viability and differentiation into osteoblastic cells (OB) in vitro, as well as heterotopic bone formation in vivo. Similarly, treating hMSC with Phalloidin, which is known to stabilize...... polymerized actin filaments, increased hMSCs viability and OB differentiation. Conversely, Cytocholasin D, an inhibitor of actin polymerization, reduced cell viability and inhibited OB differentiation of hMSC. At a molecular level, preventing Cofilin phosphorylation through inhibition of LIM domain kinase 1...

  13. When fat is not bad: the regulation of actin dynamics by phospholipid signaling molecules

    Czech Academy of Sciences Publication Activity Database

    Pleskot, Roman; Pejchar, Přemysl; Staiger, Ch. J.; Potocký, Martin

    2014-01-01

    Roč. 5, JAN 2014 (2014) ISSN 1664-462X R&D Projects: GA ČR GA13-19073S Institutional support: RVO:61389030 Keywords : actin * actin-binding proteins * capping protein Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.948, year: 2014

  14. Actin-based gravity-sensing mechanisms in unicellular plant model systems

    Science.gov (United States)

    Braun, Markus; Limbach, Christoph

    2005-08-01

    Considerable progress has been made in the understanding of the molecular and cellular mechanisms underlying gravity sensing and gravity-oriented polarized growth in single-celled rhizoids and protonemata of the characean algae. It is well known that the actin cytoskeleton plays a key role in these processes. Numerous actin-binding proteins control apical actin polymerization and the dynamic remodeling of the actin arrangement. An actomyosin-based system mediates the delivery and incorporation of secretory vesicles at the growing tip and coordinates the tip-high gradient of cytoplasmic free calcium which is required for local exocytosis. Additionally, the actomyosin system precisely controls the position of statoliths and, upon a change in orientation relative to the gravity vector, directs sedimenting statoliths to the confined graviperception sites of the plasma membrane where gravitropic signalling is initiated. The upward growth response of protonemata is preceded by an actin-dependent relocalization of the Ca2+-gradient to the upper flank. The downward growth response of rhizoids, however, is caused by differential growth of the opposite flankes due to a local reduction of cytoplasmic free calcium limited to the plasma membrane area where statoliths are sedimented. Thus, constant actin polymerization in the growing tip and the spatiotemporal control of actin remodeling are essential for gravity sensing and gravity-oriented polarized growth of characean rhizoids and protonemata.

  15. Curative effect observation of n-flap and off-flap EPi-LASIK in ametropia

    Directory of Open Access Journals (Sweden)

    Chao Liu

    2015-11-01

    Full Text Available AIM:To observe the clinical effect of on-flap and off-flap epipolis laser in situ keratomileusis(EPi-LASIKin ametropia.METHODS: Sixty-eight myopia patients(136 eyesreceiving surgical treatment were selected and divided into research group and control group according to different therapies. The patients in research group adopted off-flap EPi-LASIK and those in control group adopted on-flap EPi-LASIK. The index like uncorrected visual acuity, diopter and Haze of two groups before surgery, 1wk, 1 and 4mo after surgery was observed. RESULTS: One month after surgery, the uncorrected visual acuity of research group was 1.33±0.22 while that of control group was 1.22±0.19(PPPCONCLUSION:On-flap and off-flap EPi-LASIK are safe and effective surgery approaches in the clinical treatment of ametropia. The presence of corneal epithelial flap has a certain effect in the postoperative clinical outcome at early stage. The impact will be gradually reduced over time.

  16. Pedicled Temporalis Muscle Flap for Craniofacial Reconstruction: A 35-Year Clinical Experience with 366 Flaps.

    Science.gov (United States)

    Spanio di Spilimbergo, Stefano; Nordera, Paolo; Mardini, Samir; Castiglione, Giusy; Chim, Harvey; Pinna, Vittore; Brunello, Massimo; Cusino, Claudio; Roberto, Squaquara; Baciliero, Ugo

    2017-02-01

    In the past 130 years, the temporalis muscle flap has been used for a variety of different indications. In this age of microsurgery and perforator flaps, the temporalis muscle flap still has many useful applications for craniofacial reconstruction. Three hundred sixty-six temporalis muscle flaps were performed in a single center between 1978 and 2012. The authors divided the cases into two series-before and after 1994-because, after 1994, they started to perform free flap reconstructions, and indications for reconstruction with a temporalis muscle flap were changed RESULTS:: In the series after 1994, flaps were most commonly used for reconstruction of defects in the maxilla, mandible, and oropharynx, in addition to facial reanimation and filling of orbital defects. Complications included total flap necrosis (1.6 percent) and partial flap necrosis (10.7 percent). The rate of material extrusion at the donor site decreased after porous polyethylene was uniformly used for reconstruction from 17.1 to 7.9 percent. The pedicled temporalis muscle flap continues to have many applications in craniofacial reconstruction. With increasing use of free flaps, the authors' indications for the pedicled temporalis muscle flap are now restricted to (1) orbital filling for congenital or acquired anophthalmia; (2) filling of unilateral maxillectomy defects; and (3) facial reanimation in selected cases of facial nerve palsy. Therapeutic, IV.

  17. Strategies for the stabilization of longitudinal forward flapping flight revealed using a dynamically-scaled robotic fly

    International Nuclear Information System (INIS)

    Elzinga, Michael J; Van Breugel, Floris; Dickinson, Michael H

    2014-01-01

    The ability to regulate forward speed is an essential requirement for flying animals. Here, we use a dynamically-scaled robot to study how flapping insects adjust their wing kinematics to regulate and stabilize forward flight. The results suggest that the steady-state lift and thrust requirements at different speeds may be accomplished with quite subtle changes in hovering kinematics, and that these adjustments act primarily by altering the pitch moment. This finding is consistent with prior hypotheses regarding the relationship between body pitch and flight speed in fruit flies. Adjusting the mean stroke position of the wings is a likely mechanism for trimming the pitch moment at all speeds, whereas changes in the mean angle of attack may be required at higher speeds. To ensure stability, the flapping system requires additional pitch damping that increases in magnitude with flight speed. A compensatory reflex driven by fast feedback of pitch rate from the halteres could provide such damping, and would automatically exhibit gain scheduling with flight speed if pitch torque was regulated via changes in stroke deviation. Such a control scheme would provide an elegant solution for stabilization across a wide range of forward flight speeds. (paper)

  18. Head and neck reconstruction with pedicled flaps in the free flap era

    NARCIS (Netherlands)

    Mahieu, R.; Colletti, G.; Bonomo, P.; Parrinello, G.; Iavarone, A.; Dolivet, G.; Livi, L.; Deganello, A.

    2016-01-01

    Nowadays, the transposition of microvascular free flaps is the most popular method for management of head and neck defects. However, not all patients are suitable candidates for free flap reconstruction. In addition, not every defect requires a free flap transfer to achieve good functional results.

  19. Aerodynamics power consumption for mechanical flapping wings undergoing flapping and pitching motion

    Science.gov (United States)

    Razak, N. A.; Dimitriadis, G.; Razaami, A. F.

    2017-07-01

    Lately, due to the growing interest in Micro Aerial Vehicles (MAV), interest in flapping flight has been rekindled. The reason lies in the improved performance of flapping wing flight at low Reynolds number regime. Many studies involving flapping wing flight focused on the generation of unsteady aerodynamic forces such as lift and thrust. There is one aspect of flapping wing flight that received less attention. The aspect is aerodynamic power consumption. Since most mechanical flapping wing aircraft ever designed are battery powered, power consumption is fundamental in improving flight endurance. This paper reports the results of experiments carried out on mechanical wings under going active root flapping and pitching in the wind tunnel. The objective of the work is to investigate the effect of the pitch angle oscillations and wing profile on the power consumption of flapping wings via generation of unsteady aerodynamic forces. The experiments were repeated for different airspeeds, flapping and pitching kinematics, geometric angle of attack and wing sections with symmetric and cambered airfoils. A specially designed mechanical flapper modelled on large migrating birds was used. It will be shown that, under pitch leading conditions, less power is required to overcome the unsteady aerodnamics forces. The study finds less power requirement for downstroke compared to upstroke motion. Overall results demonstrate power consumption depends directly on the unsteady lift force.

  20. Mechanical coupling between transsynaptic N-cadherin adhesions and actin flow stabilizes dendritic spines

    Science.gov (United States)

    Chazeau, Anaël; Garcia, Mikael; Czöndör, Katalin; Perrais, David; Tessier, Béatrice; Giannone, Grégory; Thoumine, Olivier

    2015-01-01

    The morphology of neuronal dendritic spines is a critical indicator of synaptic function. It is regulated by several factors, including the intracellular actin/myosin cytoskeleton and transcellular N-cadherin adhesions. To examine the mechanical relationship between these molecular components, we performed quantitative live-imaging experiments in primary hippocampal neurons. We found that actin turnover and structural motility were lower in dendritic spines than in immature filopodia and increased upon expression of a nonadhesive N-cadherin mutant, resulting in an inverse relationship between spine motility and actin enrichment. Furthermore, the pharmacological stimulation of myosin II induced the rearward motion of actin structures in spines, showing that myosin II exerts tension on the actin network. Strikingly, the formation of stable, spine-like structures enriched in actin was induced at contacts between dendritic filopodia and N-cadherin–coated beads or micropatterns. Finally, computer simulations of actin dynamics mimicked various experimental conditions, pointing to the actin flow rate as an important parameter controlling actin enrichment in dendritic spines. Together these data demonstrate that a clutch-like mechanism between N-cadherin adhesions and the actin flow underlies the stabilization of dendritic filopodia into mature spines, a mechanism that may have important implications in synapse initiation, maturation, and plasticity in the developing brain. PMID:25568337

  1. Profilin as a regulator of the membrane-actin cytoskeleton interface in plant cells

    Directory of Open Access Journals (Sweden)

    Tiantian eSun

    2013-12-01

    Full Text Available Membrane structures and cytoskeleton dynamics are intimately inter-connected in the eukaryotic cell. Recently, the molecular mechanisms operating at this interface have been progressively addressed. Many experiments have revealed that the actin cytoskeleton can interact with membranes through various discrete membrane domains. The actin-binding protein, profilin has been proven to inhibit actin polymerization and to promote F-actin elongation. This is dependent on many factors, such as the profilin/G-actin ratio and the ionic environment of the cell. Additionally, profilin has specific domains that interact with phosphoinositides and poly-L-proline rich proteins; theoretically, this gives profilin the opportunity to interact with membranes, and a large number of experiments have confirmed this possibility. In this article, we summarize recent findings in plant cells, and discuss the evidence of the connections among actin cytoskeleton, profilin and biomembranes through direct or indirect relationships.

  2. Numerical and experimental investigations on unsteady aerodynamics of flapping wings

    Science.gov (United States)

    Yu, Meilin

    The development of a dynamic unstructured grid high-order accurate spectral difference (SD) method for the three dimensional compressible Navier-Stokes (N-S) equations and its applications in flapping-wing aerodynamics are carried out in this work. Grid deformation is achieved via an algebraic blending strategy to save computational cost. The Geometric Conservation Law (GCL) is imposed to ensure that grid deformation will not contaminate the flow physics. A low Mach number preconditioning procedure is conducted in the developed solver to handle the bio-inspired flow. The capability of the low Mach number preconditioned SD solver is demonstrated by a series of two dimensional (2D) and three dimensional (3D) simulations of the unsteady vortex dominated flow. Several topics in the flapping wing aerodynamics are numerically and experimentally investigated in this work. These topics cover some of the cutting-edge issues in flapping wing aerodynamics, including the wake structure analysis, airfoil thickness and kinematics effects on the aerodynamic performances, vortex structure analysis around 3D flapping wings and the kinematics optimization. Wake structures behind a sinusoidally pitching NACA0012 airfoil are studied with both experimental and numerical approaches. The experiments are carried out with Particle Image Velocimetry (PIV) and two types of wake transition processes, namely the transition from a drag-indicative wake to a thrust-indicative wake and that from the symmetric wake to the asymmetric wake are distinguished. The numerical results from the developed SD solver agree well with the experimental results. It is numerically found that the deflective direction of the asymmetric wake is determined by the initial conditions, e.g. initial phase angle. As most insects use thin wings (i. e., wing thickness is only a few percent of the chord length) in flapping flight, the effects of airfoil thickness on thrust generation are numerically investigated by simulating

  3. Tight coupling between nucleus and cell migration through the perinuclear actin cap

    Science.gov (United States)

    Kim, Dong-Hwee; Cho, Sangkyun; Wirtz, Denis

    2014-01-01

    ABSTRACT Although eukaryotic cells are known to alternate between ‘advancing’ episodes of fast and persistent movement and ‘hesitation’ episodes of low speed and low persistence, the molecular mechanism that controls the dynamic changes in morphology, speed and persistence of eukaryotic migratory cells remains unclear. Here, we show that the movement of the interphase nucleus during random cell migration switches intermittently between two distinct modes – rotation and translocation – that follow with high fidelity the sequential rounded and elongated morphologies of the nucleus and cell body, respectively. Nuclear rotation and translocation mediate the stop-and-go motion of the cell through the dynamic formation and dissolution, respectively, of the contractile perinuclear actin cap, which is dynamically coupled to the nuclear lamina and the nuclear envelope through LINC complexes. A persistent cell movement and nuclear translocation driven by the actin cap are halted following the disruption of the actin cap, which in turn allows the cell to repolarize for its next persistent move owing to nuclear rotation mediated by cytoplasmic dynein light intermediate chain 2. PMID:24639463

  4. PIV Measurements on a Blowing Flap

    Science.gov (United States)

    Hutcheson, Florence V.; Stead, Daniel J.

    2004-01-01

    PIV measurements of the flow in the region of a flap side edge are presented for several blowing flap configurations. The test model is a NACA 63(sub 2)-215 Hicks Mod-B main-element airfoil with a half-span Fowler flap. Air is blown from small slots located along the flap side edge on either the top, bottom or side surfaces. The test set up is described and flow measurements for a baseline and three blowing flap configurations are presented. The effects that the flap tip jets have on the structure of the flap side edge flow are discussed for each of the flap configurations tested. The results indicate that blowing air from a slot located along the top surface of the flap greatly weakened the top vortex system and pushed it further off the top surface. Blowing from the bottom flap surface kept the strong side vortex further outboard while blowing from the side surface only strengthened the vortex system or accelerated the merging of the side vortex to the flap top surface. It is concluded that blowing from the top or bottom surfaces of the flap may lead to a reduction of flap side edge noise.

  5. Characterization of the activities of actin-affecting drugs on tumor cell migration

    International Nuclear Information System (INIS)

    Hayot, Caroline; Debeir, Olivier; Ham, Philippe van; Damme, Marc van; Kiss, Robert; Decaestecker, Christine

    2006-01-01

    Metastases kill 90% of cancer patients. It is thus a major challenge in cancer therapy to inhibit the spreading of tumor cells from primary tumor sites to those particular organs where metastases are likely to occur. Whereas the actin cytoskeleton is a key component involved in cell migration, agents targeting actin dynamics have been relatively poorly investigated. Consequently, valuable in vitro pharmacological tools are needed to selectively identify this type of agent. In response to the absence of any standardized process, the present work aims to develop a multi-assay strategy for screening actin-affecting drugs with anti-migratory potentials. To validate our approach, we used two cancer cell lines (MCF7 and A549) and three actin-affecting drugs (cytochalasin D, latrunculin A, and jasplakinolide). We quantified the effects of these drugs on the kinetics of actin polymerization in tubes (by means of spectrofluorimetry) and on the dynamics of actin cytoskeletons within whole cells (by means of fluorescence microscopy). Using quantitative videomicroscopy, we investigated the actual effects of the drugs on cell motility. Finally, the combined drug effects on cell motility and cell growth were evaluated by means of a scratch-wound assay. While our results showed concordant drug-induced effects on actin polymerization occurring in vitro in test tubes and within whole cells, the whole cell assay appeared more sensitive than the tube assay. The inhibition of actin polymerization induced by cytochalasin D was paralleled by a decrease in cell motility for both cell types. In the case of jasplakinolide, which induces actin polymerization, while it significantly enhanced the locomotion of the A549 cells, it significantly inhibited that of the MCF-7 ones. All these effects were confirmed by means of the scratch-wound assay except of the jasplakinolide-induced effects on MCF-7 cell motility. These later seemed compensated by an additional effect occurring during wound

  6. Spatiotemporal dynamics of actin remodeling and endomembrane trafficking in alveolar epithelial type I cell wound healing.

    Science.gov (United States)

    Godin, Lindsay M; Vergen, Jorge; Prakash, Y S; Pagano, Richard E; Hubmayr, Rolf D

    2011-04-01

    Alveolar epithelial type I cell (ATI) wounding is prevalent in ventilator-injured lungs and likely contributes to pathogenesis of "barotrauma" and "biotrauma." In experimental models most wounded alveolar cells repair plasma membrane (PM) defects and survive insults. Considering the force balance between edge energy at the PM wound margins and adhesive interactions of the lipid bilayer with the underlying cytoskeleton (CSK), we tested the hypothesis that subcortical actin depolymerization is a key facilitator of PM repair. Using real-time fluorescence imaging of primary rat ATI transfected with a live cell actin-green fluorescent protein construct (Lifeact-GFP) and loaded with N-rhodamine phosphatidylethanolamine (PE), we examined the spatial and temporal coordination between cytoskeletal remodeling and PM repair following micropuncture. Membrane integrity was inferred from the fluorescence intensity profiles of the cytosolic label calcein AM. Wounding led to rapid depolymerization of the actin CSK near the wound site, concurrent with accumulation of endomembrane-derived N-rhodamine PE. Both responses were sustained until PM integrity was reestablished, which typically occurs between ∼10 and 40 s after micropuncture. Only thereafter did the actin CSK near the wound begin to repolymerize, while the rate of endomembrane lipid accumulation decreased. Between 60 and 90 s after successful PM repair, after translocation of the actin nucleation factor cortactin, a dense actin fiber network formed. In cells that did not survive micropuncture injury, actin remodeling did not occur. These novel results highlight the importance of actin remodeling in ATI cell repair and suggest molecular targets for modulating the repair process.

  7. Rescue of Primary Incomplete Microkeratome Flap with Secondary Femtosecond Laser Flap in LASIK

    Directory of Open Access Journals (Sweden)

    E. A. Razgulyaeva

    2014-01-01

    Full Text Available For laser-assisted in situ keratomileusis (LASIK retreatments with a previous unsuccessful mechanical microkeratome-assisted surgery, some surgical protocols have been described as feasible, such as relifting of the flap or the creation of a new flap and even the change to a surface ablation procedure (photorefractive keratectomy (PRK. This case shows the use of femtosecond technology for the creation of a secondary flap to perform LASIK in a cornea with a primary incomplete flap obtained with a mechanical microkeratome. As we were unable to characterize the interface of the first partial lamellar cut, a thick flap was planned and created using a femtosecond laser platform. As the primary cut was very thick in the nasal quadrant, a piece of loose corneal tissue appeared during flap lifting which was fitted in its position and not removed. Despite this condition and considering the regularity of the new femtosecond laser cut, the treatment was uneventful. This case report shows the relevance of a detailed corneal analysis with an advanced imaging technique before performing a secondary flap in a cornea with a primary incomplete flap. The femtosecond laser technology seems to be an excellent tool to manage such cases successfully.

  8. Innovation in the planning of V-Y rotation advancement flaps: A template for flap design

    Directory of Open Access Journals (Sweden)

    Utku Can Dölen

    2018-01-01

    Full Text Available Local flaps exhibit excellent color matching that no other type of flap can compete with. Moreover, surgery using a local flap is easier and faster than surgery using a distant or free flap. However, local flaps can be much more difficult to design. We designed 2 templates to plan a V-Y rotation advancement flap. The template for a unilateral V-Y rotation advancement flap was used on the face (n=5, anterior tibia (n=1, posterior axilla (n=1, ischium (n=1, and trochanter (n=2. The template for a bilateral flap was used on the sacrum (n=8, arm (n=1, and anterior tibia (n=1. The causes of the defects were meningocele (n=3, a decubitus ulcer (n=5, pilonidal sinus (n=3, and skin tumor excision (n=10. The meningocele patients were younger than 8 days. The mean age of the adult patients was 50.4 years (range, 19–80 years. All the donor areas of the flaps were closed primarily. None of the patients experienced wound dehiscence or partial/total flap necrosis. The templates guided surgeons regarding the length and the placement of the incision for a V-Y rotation advancement flap according to the size of the wound. In addition, they could be used for the training of residents.

  9. Navier-Stokes Computations of a Wing-Flap Model With Blowing Normal to the Flap Surface

    Science.gov (United States)

    Boyd, D. Douglas, Jr.

    2005-01-01

    A computational study of a generic wing with a half span flap shows the mean flow effects of several blown flap configurations. The effort compares and contrasts the thin-layer, Reynolds averaged, Navier-Stokes solutions of a baseline wing-flap configuration with configurations that have blowing normal to the flap surface through small slits near the flap side edge. Vorticity contours reveal a dual vortex structure at the flap side edge for all cases. The dual vortex merges into a single vortex at approximately the mid-flap chord location. Upper surface blowing reduces the strength of the merged vortex and moves the vortex away from the upper edge. Lower surface blowing thickens the lower shear layer and weakens the merged vortex, but not as much as upper surface blowing. Side surface blowing forces the lower surface vortex farther outboard of the flap edge by effectively increasing the aerodynamic span of the flap. It is seen that there is no global aerodynamic penalty or benefit from the particular blowing configurations examined.

  10. RIT1 controls actin dynamics via complex formation with RAC1/CDC42 and PAK1.

    Directory of Open Access Journals (Sweden)

    Uta Meyer Zum Büschenfelde

    2018-05-01

    Full Text Available RIT1 belongs to the RAS family of small GTPases. Germline and somatic RIT1 mutations have been identified in Noonan syndrome (NS and cancer, respectively. By using heterologous expression systems and purified recombinant proteins, we identified the p21-activated kinase 1 (PAK1 as novel direct effector of RIT1. We found RIT1 also to directly interact with the RHO GTPases CDC42 and RAC1, both of which are crucial regulators of actin dynamics upstream of PAK1. These interactions are independent of the guanine nucleotide bound to RIT1. Disease-causing RIT1 mutations enhance protein-protein interaction between RIT1 and PAK1, CDC42 or RAC1 and uncouple complex formation from serum and growth factors. We show that the RIT1-PAK1 complex regulates cytoskeletal rearrangements as expression of wild-type RIT1 and its mutant forms resulted in dissolution of stress fibers and reduction of mature paxillin-containing focal adhesions in COS7 cells. This effect was prevented by co-expression of RIT1 with dominant-negative CDC42 or RAC1 and kinase-dead PAK1. By using a transwell migration assay, we show that RIT1 wildtype and the disease-associated variants enhance cell motility. Our work demonstrates a new function for RIT1 in controlling actin dynamics via acting in a signaling module containing PAK1 and RAC1/CDC42, and highlights defects in cell adhesion and migration as possible disease mechanism underlying NS.

  11. RIT1 controls actin dynamics via complex formation with RAC1/CDC42 and PAK1.

    Science.gov (United States)

    Meyer Zum Büschenfelde, Uta; Brandenstein, Laura Isabel; von Elsner, Leonie; Flato, Kristina; Holling, Tess; Zenker, Martin; Rosenberger, Georg; Kutsche, Kerstin

    2018-05-01

    RIT1 belongs to the RAS family of small GTPases. Germline and somatic RIT1 mutations have been identified in Noonan syndrome (NS) and cancer, respectively. By using heterologous expression systems and purified recombinant proteins, we identified the p21-activated kinase 1 (PAK1) as novel direct effector of RIT1. We found RIT1 also to directly interact with the RHO GTPases CDC42 and RAC1, both of which are crucial regulators of actin dynamics upstream of PAK1. These interactions are independent of the guanine nucleotide bound to RIT1. Disease-causing RIT1 mutations enhance protein-protein interaction between RIT1 and PAK1, CDC42 or RAC1 and uncouple complex formation from serum and growth factors. We show that the RIT1-PAK1 complex regulates cytoskeletal rearrangements as expression of wild-type RIT1 and its mutant forms resulted in dissolution of stress fibers and reduction of mature paxillin-containing focal adhesions in COS7 cells. This effect was prevented by co-expression of RIT1 with dominant-negative CDC42 or RAC1 and kinase-dead PAK1. By using a transwell migration assay, we show that RIT1 wildtype and the disease-associated variants enhance cell motility. Our work demonstrates a new function for RIT1 in controlling actin dynamics via acting in a signaling module containing PAK1 and RAC1/CDC42, and highlights defects in cell adhesion and migration as possible disease mechanism underlying NS.

  12. The Versatile Modiolus Perforator Flap

    DEFF Research Database (Denmark)

    Gunnarsson, Gudjon Leifur; Thomsen, Jorn Bo

    2016-01-01

    BACKGROUND: Perforator flaps are well established, and their usefulness as freestyle island flaps is recognized. The whereabouts of vascular perforators and classification of perforator flaps in the face are a debated subject, despite several anatomical studies showing similar consistency. In our...... experience using freestyle facial perforator flaps, we have located areas where perforators are consistently found. This study is focused on a particular perforator lateral to the angle of the mouth; the modiolus and the versatile modiolus perforator flap. METHODS: A cohort case series of 14 modiolus...... perforator flap reconstructions in 14 patients and a color Doppler ultrasonography localization of the modiolus perforator in 10 volunteers. RESULTS: All 14 flaps were successfully used to reconstruct the defects involved, and the location of the perforator was at the level of the modiolus as predicted...

  13. Decidable and undecidable arithmetic functions in actin filament networks

    Science.gov (United States)

    Schumann, Andrew

    2018-01-01

    The plasmodium of Physarum polycephalum is very sensitive to its environment, and reacts to stimuli with appropriate motions. Both the sensory and motor stages of these reactions are explained by hydrodynamic processes, based on fluid dynamics, with the participation of actin filament networks. This paper is devoted to actin filament networks as a computational medium. The point is that actin filaments, with contributions from many other proteins like myosin, are sensitive to extracellular stimuli (attractants as well as repellents), and appear and disappear at different places in the cell to change aspects of the cell structure—e.g. its shape. By assembling and disassembling actin filaments, some unicellular organisms, like Amoeba proteus, can move in response to various stimuli. As a result, these organisms can be considered a simple reversible logic gate—extracellular signals being its inputs and motions its outputs. In this way, we can implement various logic gates on amoeboid behaviours. These networks can embody arithmetic functions within p-adic valued logic. Furthermore, within these networks we can define the so-called diagonalization for deducing undecidable arithmetic functions.

  14. Venous coupler use for free-flap breast reconstructions: specific analyses of TMG and DIEP flaps.

    Science.gov (United States)

    Bodin, Frédéric; Brunetti, Stefania; Dissaux, Caroline; Erik, A Sauleau; Facca, Sybille; Bruant-Rodier, Catherine; Liverneaux, Philippe

    2015-05-01

    The purpose of this report was to present the results of comparisons of anastomotic data and flap complications in the use of venous coupler in breast reconstruction with the transverse musculocutaneous gracilis (TMG) flap and the deep inferior epigastric perforator (DIEP) flap. Over a three-year period, 95 patients suffering from breast cancer were treated with mastectomy and breast reconstruction using free flaps. We performed 121 mechanical venous anastomoses for 105 flap procedures (80 DIEP and 25 TMG). The coupler size, anastomotic duration, number of anastomoses and postoperative complications were assessed for the entire series. The coupling device was perfectly suitable for all end-to-end anastomoses between the vein(s) of the flap and the internal mammary vein(s). No venous thrombosis occurred. The mean anastomotic time did not significantly differ between the DIEP (330 seconds) and TMG flap procedures (352 seconds) (P = 0.069). Additionally, there were no differences in coupling time observed following a comparison of seven coupler sizes (P = 0.066). The mean coupler size used during the TMG flap procedure was smaller than that used with the DIEP (2.4 mm versus 2.8 mm) (P TMG flap (28%) than with the DIEP flap (11%). The coupler size used was smaller for the TMG procedure and when double venous anastomosis was performed. Additionally, anastomotic time was not affected by the flap type or coupler size used or by anastomosis number. © 2014 Wiley Periodicals, Inc.

  15. Face resurfacing using a cervicothoracic skin flap prefabricated by lateral thigh fascial flap and tissue expander.

    Science.gov (United States)

    Li, Qingfeng; Zan, Tao; Gu, Bin; Liu, Kai; Shen, Guoxiong; Xie, Yun; Weng, Rui

    2009-01-01

    Resurfacing of facial massive soft tissue defect is a formidable challenge because of the unique character of the region and the limitation of well-matched donor site. In this report, we introduce a technique for using the prefabricated cervicothoracic skin flap for facial resurfacing, in an attempt to meet the principle of flap selection in face reconstructive surgery for matching the color and texture, large dimension, and thinner thickness (MLT) of the recipient. Eleven patients with massive facial scars underwent resurfacing procedures with prefabricated cervicothoracic flaps. The vasculature of the lateral thigh fascial flap, including the descending branch of the lateral femoral circumflex vessels and the surrounding muscle fascia, was used as the vascular carrier, and the pedicles of the fascial flap were anastomosed to either the superior thyroid or facial vessels in flap prefabrication. A tissue expander was placed beneath the fascial flap to enlarge the size and reduce the thickness of the flap. The average size of the harvested fascia flap was 6.5 x 11.7 cm. After a mean interval of 21.5 weeks, the expanders were filled to a mean volume of 1,685 ml. The sizes of the prefabricated skin flaps ranged from 12 x 15 cm to 15 x 32 cm. The prefabricated skin flaps were then transferred to the recipient site as pedicled flaps for facial resurfacing. All facial soft tissue defects were successfully covered by the flaps. The donor sites were primarily closed and healed without complications. Although varied degrees of venous congestion were developed after flap transfers, the marginal necrosis only occurred in two cases. The results in follow-up showed most resurfaced faces restored natural contour and regained emotional expression. MLT is the principle for flap selection in resurfacing of the massive facial soft tissue defect. Our experience in this series of patients demonstrated that the prefabricated cervicothoracic skin flap could be a reliable alternative

  16. Comparison of gluteal perforator flaps and gluteal fasciocutaneous rotation flaps for reconstruction of sacral pressure sores.

    Science.gov (United States)

    Chen, Yen-Chou; Huang, Eng-Yen; Lin, Pao-Yuan

    2014-03-01

    The gluteus maximus myocutaneous flap was considered the workhorse that reconstructed sacral pressure sores, but was gradually replaced by fasciocutaneous flap because of several disadvantages. With the advent of the perforator flap technique, gluteal perforator (GP) flap has gained popularity nowadays. The aim of this study was to compare the complications and outcomes between GP flaps and gluteal fasciocutaneous rotation (FR) flaps in the treatment of sacral pressure sores. Between April 2007 and June 2012, 63 patients underwent sacral pressure sore reconstructions, with a GP flap used in 31 cases and an FR flap used in 32 cases. Data collected on the patients included patient age, gender, co-morbidity for being bedridden and follow-up time. Surgical details collected included the defect size, operative time and estimated blood loss. Complications recorded included re-operation, dehiscence, flap necrosis, wound infection, sinus formation, donor-site morbidity and recurrence. The complications and clinical outcomes were compared between these two groups. We found that there was no significant difference in patient demographics, surgical complications and recurrence between these two groups. In gluteal FR flap group, all recurrent cases (five) were treated by reuse of previous flaps. Both methods are comparable, good and safe in treating sacral pressure sores. Gluteal FR flap can be performed without microsurgical dissection, and re-rotation is feasible in recurrent cases. The authors suggest using gluteal FR flaps in patients with a high risk of sore recurrence. Copyright © 2013 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

  17. Pneumatic artificial muscles for trailing edge flap actuation: a feasibility study

    Science.gov (United States)

    Woods, Benjamin K. S.; Kothera, Curt S.; Sirohi, Jayant; Wereley, Norman M.

    2011-10-01

    In this study a novel aircraft trailing edge flap actuation system was developed and tested. Pneumatic artificial muscles (PAMs) were used as the driving elements of this system to demonstrate their feasibility and utility as an alternative aerospace actuation technology. A prototype flap/actuator system was integrated into a model wing section and tested on the bench-top under simulated airloads for flight at 100 m s-1 (M = 0.3) and in an open-jet wind tunnel at free stream velocities ranging up to 45 m s-1 (M = 0.13). Testing was performed for actuator pressures ranging from 0.069 to 0.62 MPa (10-90 psi) and actuation frequencies from 0.1 to 31 Hz. Results show that the PAM-driven trailing edge flap system can generate substantial and sustainable dynamic deflections, thereby proving the feasibility of using pneumatic artificial muscle actuators in a trailing edge flap system. Key issues limiting system performance are identified, that should be resolved in future research.

  18. Lift and Power Required for Flapping Wing Hovering Flight on Mars

    Science.gov (United States)

    Pohly, Jeremy; Sridhar, Madhu; Bluman, James; Kang, Chang-Kwon; Landrum, D. Brian; Fahimi, Farbod; Aono, Hikaru; Liu, Hao

    2017-11-01

    Achieving flight on Mars is challenging due to the ultra-low density atmosphere. Bio-inspired flapping motion can generate sufficient lift if bumblebee-inspired wings are scaled up between 2 and 4 times their nominal size. However, due to this scaling, the inertial power required to sustain hover increases and dominates over the aerodynamic power. Our results show that a torsional spring placed at the wing root can reduce the flapping power required for hover by efficiently storing and releasing energy while operating at its resonance frequency. The spring assisted reduction in flapping power is demonstrated with a well-validated, coupled Navier-Stokes and flight dynamics solver. The total power is reduced by 79%, whereas the flapping power is reduced by 98%. Such a reduction in power paves the way for an efficient, realizable micro air vehicle capable of vertical takeoff and landing as well as sustained flight on Mars. Alabama Space Grant Consortium Fellowship.

  19. Cell stress promotes the association of phosphorylated HspB1 with F-actin.

    Directory of Open Access Journals (Sweden)

    Joseph P Clarke

    Full Text Available Previous studies have suggested that the small heat shock protein, HspB1, has a direct influence on the dynamics of cytoskeletal elements, in particular, filamentous actin (F-actin polymerization. In this study we have assessed the influence of HspB1 phosphorylation on its interaction(s with F-actin. We first determined the distribution of endogenous non-phosphorylated HspB1, phosphorylated HspB1 and F-actin in neuroendocrine PC12 cells by immunocytochemistry and confocal microscopy. We then investigated a potential direct interaction between HspB1 with F-actin by precipitating F-actin directly with biotinylated phalloidin followed by Western analyses; the reverse immunoprecipitation of HspB1 was also carried out. The phosphorylation influence of HspB1 in this interaction was investigated by using pharmacologic inhibition of p38 MAPK. In control cells, HspB1 interacts with F-actin as a predominantly non-phosphorylated protein, but subsequent to stress there is a redistribution of HspB1 to the cytoskeletal fraction and a significantly increased association of pHspB1 with F-actin. Our data demonstrate HspB1 is found in a complex with F-actin both in phosphorylated and non-phosphorylated forms, with an increased association of pHspB1 with F-actin after heat stress. Overall, our study combines both cellular and biochemical approaches to show cellular localization and direct demonstration of an interaction between endogenous HspB1 and F-actin using methodolgy that specifically isolates F-actin.

  20. Thrust augmentation in tandem flapping foils by foil-wake interaction

    Science.gov (United States)

    Anderson, Erik; Lauder, George

    2006-11-01

    Propulsion by pitching and heaving airfoils and hydrofoils has been a focus of much research in the field of biologically inspired propulsion. Organisms that use this sort of propulsion are self-propelled, so it is difficult to use standard experimental metrics such as thrust and drag to characterize performance. We have constructed a flapping foil robot mounted in a flume on air-bearings that allows for the determination of self-propelled speed as a metric of performance. We have used a pair of these robots to examine the impact of an upstream flapping foil on a downstream flapping foil as might apply to tandem fins of a swimming organism or in-line swimming of schooling organisms. Self-propelled speed and a force transducer confirmed significant thrust augmentation for particular foil-to-foil spacings, phase differences, and flapping frequencies. Flow visualization shows the mechanism to be related to the effective angle of attack of the downstream foil due to the structure of the wake of the upstream foil. This confirms recent computational work and the hypotheses by early investigators of fish fluid dynamics.

  1. Plant villin, lily P-135-ABP, possesses G-actin binding activity and accelerates the polymerization and depolymerization of actin in a Ca2+-sensitive manner.

    Science.gov (United States)

    Yokota, Etsuo; Tominaga, Motoki; Mabuchi, Issei; Tsuji, Yasunori; Staiger, Christopher J; Oiwa, Kazuhiro; Shimmen, Teruo

    2005-10-01

    From germinating pollen of lily, two types of villins, P-115-ABP and P-135-ABP, have been identified biochemically. Ca(2+)-CaM-dependent actin-filament binding and bundling activities have been demonstrated for both villins previously. Here, we examined the effects of lily villins on the polymerization and depolymerization of actin. P-115-ABP and P-135-ABP present in a crude protein extract prepared from germinating pollen bound to a DNase I affinity column in a Ca(2+)-dependent manner. Purified P-135-ABP reduced the lag period that precedes actin filament polymerization from monomers in the presence of either Ca(2+) or Ca(2+)-CaM. These results indicated that P-135-ABP can form a complex with G-actin in the presence of Ca(2+) and this complex acts as a nucleus for polymerization of actin filaments. However, the nucleation activity of P-135-ABP is probably not relevant in vivo because the assembly of G-actin saturated with profilin, a situation that mimics conditions found in pollen, was not accelerated in the presence of P-135-ABP. P-135-ABP also enhanced the depolymerization of actin filaments during dilution-mediated disassembly. Growth from filament barbed ends in the presence of Ca(2+)-CaM was also prevented, consistent with filament capping activity. These results suggested that lily villin is involved not only in the arrangement of actin filaments into bundles in the basal and shank region of the pollen tube, but also in regulating and modulating actin dynamics through its capping and depolymerization (or fragmentation) activities in the apical region of the pollen tube, where there is a relatively high concentration of Ca(2+).

  2. Hydrodynamic schooling of flapping swimmers

    International Nuclear Information System (INIS)

    Becker, Alexander D.; Masoud, Hassan; Newbolt, Joel W.; Shelley, Michael; Ristroph, Leif

    2015-01-01

    Fish schools and bird flocks are fascinating examples of collective behaviours in which many individuals generate and interact with complex flows. Motivated by animal groups on the move, here we explore how the locomotion of many bodies emerges from their flow-mediated interactions. Through experiments and simulations of arrays of flapping wings that propel within a collective wake, we discover distinct modes characterized by the group swimming speed and the spatial phase shift between trajectories of neighbouring wings. For identical flapping motions, slow and fast modes coexist and correspond to constructive and destructive wing-wake interactions. Simulations show that swimming in a group can enhance speed and save power, and we capture the key phenomena in a mathematical model based on memory or the storage and recollection of information in the flow field. Lastly, these results also show that fluid dynamic interactions alone are sufficient to generate coherent collective locomotion, and thus might suggest new ways to characterize the role of flows in animal groups

  3. Hydrodynamic schooling of flapping swimmers

    Science.gov (United States)

    Becker, Alexander D.; Masoud, Hassan; Newbolt, Joel W.; Shelley, Michael; Ristroph, Leif

    2015-10-01

    Fish schools and bird flocks are fascinating examples of collective behaviours in which many individuals generate and interact with complex flows. Motivated by animal groups on the move, here we explore how the locomotion of many bodies emerges from their flow-mediated interactions. Through experiments and simulations of arrays of flapping wings that propel within a collective wake, we discover distinct modes characterized by the group swimming speed and the spatial phase shift between trajectories of neighbouring wings. For identical flapping motions, slow and fast modes coexist and correspond to constructive and destructive wing-wake interactions. Simulations show that swimming in a group can enhance speed and save power, and we capture the key phenomena in a mathematical model based on memory or the storage and recollection of information in the flow field. These results also show that fluid dynamic interactions alone are sufficient to generate coherent collective locomotion, and thus might suggest new ways to characterize the role of flows in animal groups.

  4. Phosphorylation of actin-binding protein (ABP-280; filamin) by tyrosine kinase p56lck modulates actin filament cross-linking.

    Science.gov (United States)

    Pal Sharma, C; Goldmann, Wolfgang H

    2004-01-01

    Actin-binding protein (ABP-280; filamin) is a phosphoprotein present in the periphery of the cytoplasm where it can cross-link actin filaments, associate with lipid membranes, and bind to membrane surface receptors. Given its function and localization in the cell, we decided to investigate the possibility of whether it serves as substrate for p56lck, a lymphocyte-specific member of the src family of protein tyrosine kinases associated with cell surface glycoproteins. The interaction of p56lck with membrane glycoproteins is important for cell development and functional activation. Here, we show that purified p56lck interacts and catalyzes in vitro kinase reactions. Tyrosine phosphorylation by p56lck is restricted to a single peptide of labeled ABP-280 shown by protease digest. The addition of phorbol ester to cells results in the inhibition of phosphorylation of ABP-280 by p56lck. These results show a decrease in phosphorylation suggesting conformationally induced regulation. Dynamic light scattering confirmed increased actin filament cross-linking due to phosphorylation of ABP-280 by p56lck.

  5. Triptolide disrupts the actin-based Sertoli-germ cells adherens junctions by inhibiting Rho GTPases expression

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xiang; Zhao, Fang [Jiangsu Key Laboratory of Drug Screening, China Pharmaceutical University, Nanjing 210009 (China); Lv, Zhong-ming; Shi, Wei-qin [Jiangsu Provincial Center for Disease Control and Prevention, Nanjing (China); Zhang, Lu-yong, E-mail: lyzhang@cpu.edu.cn [Jiangsu Key Laboratory of Drug Screening, China Pharmaceutical University, Nanjing 210009 (China); Key Laboratory of Drug Quality Control and Pharmacovigilance, China Pharmaceutical University, Nanjing (China); State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing 210009 (China); Yan, Ming, E-mail: brookming@cpu.edu.cn [Jiangsu Key Laboratory of Drug Screening, China Pharmaceutical University, Nanjing 210009 (China)

    2016-11-01

    Triptolide (TP), derived from the medicinal plant Triterygium wilfordii Hook. f. (TWHF), is a diterpene triepoxide with variety biological and pharmacological activities. However, TP has been restricted in clinical application due to its narrow therapeutic window especially in reproductive system. During spermatogenesis, Sertoli cell cytoskeleton plays an essential role in facilitating germ cell movement and cell-cell actin-based adherens junctions (AJ). At Sertoli cell-spermatid interface, the anchoring device is a kind of AJ, known as ectoplasmic specializations (ES). In this study, we demonstrate that β-actin, an important component of cytoskeleton, has been significantly down-regulated after TP treatment. TP can inhibit the expression of Rho GTPase such as, RhoA, RhoB, Cdc42 and Rac1. Downstream of Rho GTPase, Rho-associated protein kinase (ROCKs) gene expressions were also suppressed by TP. F-actin immunofluorescence proved that TP disrupts Sertoli cells cytoskeleton network. As a result of β-actin down-regulation, TP treatment increased expression of testin, which indicating ES has been disassembled. In summary, this report illustrates that TP induces cytoskeleton dysfunction and disrupts cell-cell adherens junctions via inhibition of Rho GTPases. - Highlights: • Triptolide induced the disruption of Sertoli-germ cell adherens junction. • Rho GTPases expression and actin dynamics have been suppressed by triptolide. • Actin-based adherens junction is a potential antifertility target of triptolide. • Rho-Rock is involved in the regulation of actin dynamics.

  6. Triptolide disrupts the actin-based Sertoli-germ cells adherens junctions by inhibiting Rho GTPases expression

    International Nuclear Information System (INIS)

    Wang, Xiang; Zhao, Fang; Lv, Zhong-ming; Shi, Wei-qin; Zhang, Lu-yong; Yan, Ming

    2016-01-01

    Triptolide (TP), derived from the medicinal plant Triterygium wilfordii Hook. f. (TWHF), is a diterpene triepoxide with variety biological and pharmacological activities. However, TP has been restricted in clinical application due to its narrow therapeutic window especially in reproductive system. During spermatogenesis, Sertoli cell cytoskeleton plays an essential role in facilitating germ cell movement and cell-cell actin-based adherens junctions (AJ). At Sertoli cell-spermatid interface, the anchoring device is a kind of AJ, known as ectoplasmic specializations (ES). In this study, we demonstrate that β-actin, an important component of cytoskeleton, has been significantly down-regulated after TP treatment. TP can inhibit the expression of Rho GTPase such as, RhoA, RhoB, Cdc42 and Rac1. Downstream of Rho GTPase, Rho-associated protein kinase (ROCKs) gene expressions were also suppressed by TP. F-actin immunofluorescence proved that TP disrupts Sertoli cells cytoskeleton network. As a result of β-actin down-regulation, TP treatment increased expression of testin, which indicating ES has been disassembled. In summary, this report illustrates that TP induces cytoskeleton dysfunction and disrupts cell-cell adherens junctions via inhibition of Rho GTPases. - Highlights: • Triptolide induced the disruption of Sertoli-germ cell adherens junction. • Rho GTPases expression and actin dynamics have been suppressed by triptolide. • Actin-based adherens junction is a potential antifertility target of triptolide. • Rho-Rock is involved in the regulation of actin dynamics.

  7. Actin Cytoskeleton Manipulation by Effector Proteins Secreted by Diarrheagenic Escherichia coli Pathotypes

    Directory of Open Access Journals (Sweden)

    Fernando Navarro-Garcia

    2013-01-01

    Full Text Available The actin cytoskeleton is a dynamic structure necessary for cell and tissue organization, including the maintenance of epithelial barriers. Disruption of the epithelial barrier coincides with alterations of the actin cytoskeleton in several disease states. These disruptions primarily affect the paracellular space, which is normally regulated by tight junctions. Thereby, the actin cytoskeleton is a common and recurring target of bacterial virulence factors. In order to manipulate the actin cytoskeleton, bacteria secrete and inject toxins and effectors to hijack the host cell machinery, which interferes with host-cell pathways and with a number of actin binding proteins. An interesting model to study actin manipulation by bacterial effectors is Escherichia coli since due to its genome plasticity it has acquired diverse genetic mobile elements, which allow having different E. coli varieties in one bacterial species. These E. coli pathotypes, including intracellular and extracellular bacteria, interact with epithelial cells, and their interactions depend on a specific combination of virulence factors. In this paper we focus on E. coli effectors that mimic host cell proteins to manipulate the actin cytoskeleton. The study of bacterial effector-cytoskeleton interaction will contribute not only to the comprehension of the molecular causes of infectious diseases but also to increase our knowledge of cell biology.

  8. Feedback Interactions of Polymerized Actin with the Cell Membrane: Waves, Pulses, and Oscillations

    Science.gov (United States)

    Carlsson, Anders

    Polymerized filaments of the protein actin have crucial functions in cell migration, and in bending the cell membrane to drive endocytosis or the formation of protrusions. The nucleation and polymerization of actin filaments are controlled by upstream agents in the cell membrane, including nucleation-promoting factors (NPFs) that activate the Arp2/3 complex to form new branches on pre-existing filaments. But polymerized actin (F-actin) also feeds back on the assembly of NPFs. We explore the effects of the resulting feedback loop of F-actin and NPFs on two phenomena: actin pulses that drive endocytosis in yeast, and actin waves traveling along the membrane of several cell types. In our model of endocytosis in yeast, the actin network is grown explicitly in three dimensions, exerts a negative feedback interaction on localized patch of NPFs in the membrane, and bends the membrane by exerting a distribution of forces. This model explains observed actin and NPF pulse dynamics, and the effects of several interventions including i) NPF mutations, ii) inhibition of actin polymerization, and iii) deletion of a protein that allows F-actin to bend the cell membrane. The model predicts that mutation of the active region of an NPF will enhance the accumulation of that NPF, and we confirm this prediction by quantitative fluorescence microscopy. For actin waves, we treat a similar model, with NPFs distributed over a larger region of the cell membrane. This model naturally generates actin waves, and predicts a transition from wave behavior to spatially localized oscillations when NPFs are confined to a small region. We also predict a transition from waves to static polarization as the negative-feedback coupling between F-actin and the NPFs is reduced. Supported by NIGMS Grant R01 GM107667.

  9. The Pedicled LICAP Flap Combined with a Free Abdominal Flap In Autologous Breast Reconstructions

    Directory of Open Access Journals (Sweden)

    Thomas Sjøberg, MD

    2018-01-01

    Conclusion:. In selected patients with insufficient abdominal flap tissue, a combination of a free abdominal flap and a pedicled LICAP flap is a valuable option to increase breast size and cosmetic outcome. Additional symmetrizing surgery might still be necessary.

  10. NHERF1 regulates actin cytoskeleton organization through modulation of α-actinin-4 stability.

    Science.gov (United States)

    Sun, Licui; Zheng, Junfang; Wang, Qiqi; Song, Ran; Liu, Hua; Meng, Ran; Tao, Tao; Si, Yang; Jiang, Wenguo; He, Junqi

    2016-02-01

    The actin cytoskeleton is composed of a highly dynamic network of filamentous proteins, yet the molecular mechanism that regulates its organization and remodeling remains elusive. In this study, Na(+)/H(+) exchanger regulatory factor (NHERF)-1 loss-of-function and gain-of-function experiments reveal that polymerized actin cytoskeleton (F-actin) in HeLa cells is disorganized by NHERF1, whereas actin protein expression levels exhibit no detectable change. To elucidate the molecular mechanism underlying actin cytoskeleton disorganization by NHERF1, a combined 2-dimensional electrophoresis-matrix-assisted laser desorption/ionization-time of flight mass spectrometry approach was used to screen for proteins regulated by NHERF1 in HeLa cells. α-Actinin-4, an actin cross-linking protein, was identified. Glutathione S-transferase pull-down and coimmunoprecipitation studies showed the α-actinin-4 carboxyl-terminal region specifically interacted with the NHERF1 postsynaptic density 95/disc-large/zona occludens-1 domain. The NHERF1/α-actinin-4 interaction increased α-actinin-4 ubiquitination and decreased its expression levels, resulting in actin cytoskeleton disassembly. Our study identified α-actinin-4 as a novel NHERF1 interaction partner and provided new insights into the regulatory mechanism of the actin cytoskeleton by NHERF1. © FASEB.

  11. Comparison of Dorsal Intercostal Artery Perforator Propeller Flaps and Bilateral Rotation Flaps in Reconstruction of Myelomeningocele Defects.

    Science.gov (United States)

    Tenekeci, Goktekin; Basterzi, Yavuz; Unal, Sakir; Sari, Alper; Demir, Yavuz; Bagdatoglu, Celal; Tasdelen, Bahar

    2018-04-09

    Bilateral rotation flaps are considered the workhorse flaps in reconstruction of myelomeningocele defects. Since the introduction of perforator flaps in the field of reconstructive surgery, perforator flaps have been used increasingly in the reconstruction of various soft tissue defects all over the body because of their appreciated advantages. The aim of this study was to compare the complications and surgical outcomes between bilateral rotation flaps and dorsal intercostal artery perforator (DICAP) flaps in the soft tissue reconstruction of myelomeningocele defects. Between January 2005-February 2017, we studied 47 patients who underwent reconstruction of myelomeningocele defects. Patient demographics, operative data, and postoperative data were reviewed retrospectively and are included in the study. We found no statistically significant differences in patient demographics and surgical complications between these two groups; this may be due to small sample size. With regard to complications-partial flap necrosis, cerebrospinal fluid (CSF) leakage, necessity for reoperation, and wound infection-DICAP propeller flaps were clinically superior to rotation flaps. Partial flap necrosis was associated with CSF leakage and wound infection, and CSF leakage was associated with wound dehiscence. Although surgical outcomes obtained with DICAP propeller flaps were clinically superior to those obtained with rotation flaps, there was no statistically significant difference between the two patient groups. A well-designed comparative study with adequate sample size is needed. Nonetheless, we suggest using DICAP propeller flaps for reconstruction of large myelomeningocele defects.

  12. Total endoscopic free flap harvest of a serratus anterior fascia flap for microsurgical lower leg reconstruction

    Directory of Open Access Journals (Sweden)

    Erdmann, Alfons

    2014-04-01

    Full Text Available [english] Background: A tremendous number of free flaps have been developed in the past. As the surgical result depends not only on a successful flap transfer but also on the harvest, this paper details the procedures for undertaking the first total endoscopic harvest of a serratus fascia flap for free flap transplantation to the lower leg. Patient and methods: In September 2012 we performed the first total endoscopic serratus anterior fascia free flap harvest. The incision of 2.5 cm length was made 10 cm in front of anterior muscle border of the latissimus dorsi at level with the midthorax. After insertion of a flexible laparoscopic single port system we started CO gas insufflation. We used this setting to meticulously prepare a neo cavity between atissimus dorsi and M. serratus anterior. The vessels were dissected and the thoraco-dorsal nerve was separated. With a second auxiliary incision we used a clamp to support the raising of the fascia flap from the underlying muscle. Finally we clipped the vessels to the latissimus dorsi muscle and the flap vessels at the Arteria and Vena axillaris. The flap was extracted via the 2.5 cm incision.Results: We were able to perform a total endoscopic harvest of a serratus fascia flap for free flap reconstruction of soft tissues. With this new operative technique we were able to avoid a long skin incision, which in our view lowers the morbidity at the harvest area.Conclusion: We describe a new method for the total endoscopic harvest of the serratus fascia flap for free flap transfer. The flap was harvested within reasonable time and following surgery leaves the patient with minimal donor site morbidity compared to the open technique.

  13. Actin depolymerization enhances adipogenic differentiation in human stromal stem cells

    Directory of Open Access Journals (Sweden)

    Li Chen

    2018-05-01

    Full Text Available Human stromal stem cells (hMSCs differentiate into adipocytes that play a role in skeletal tissue homeostasis and whole body energy metabolism. During adipocyte differentiation, hMSCs exhibit significant changes in cell morphology suggesting changes in cytoskeletal organization. Here, we examined the effect of direct modulation of actin microfilament dynamics on adipocyte differentiation. Stabilizing actin filaments in hMSCs by siRNA-mediated knock down of the two main actin depolymerizing factors (ADFs: Cofilin 1 (CFL1 and Destrin (DSTN or treating the cells by Phalloidin reduced adipocyte differentiation as evidenced by decreased number of mature adipocytes and decreased adipocyte specific gene expression (ADIPOQ, LPL, PPARG, FABP4. In contrast, disruption of actin cytoskeleton by Cytochalasin D enhanced adipocyte differentiation. Follow up studies revealed that the effects of CFL1 on adipocyte differentiation depended on the activity of LIM domain kinase 1 (LIMK1 which is the major upstream kinase of CFL1. Inhibiting LIMK by its specific chemical inhibitor LIMKi inhibited the phosphorylation of CFL1 and actin polymerization, and enhanced the adipocyte differentiation. Moreover, treating hMSCs by Cytochalasin D inhibited ERK and Smad2 signaling and this was associated with enhanced adipocyte differentiation. On the other hand, Phalloidin enhanced ERK and Smad2 signaling, but inhibited adipocyte differentiation which was rescued by ERK specific chemical inhibitor U0126. Our data provide a link between restructuring of hMSCs cytoskeleton and hMSCs lineage commitment and differentiation. Keywords: Actin cytoskeleton, Actin depolymerizing factors, Adipocyte differentiation, Human stromal stem cells

  14. Propeller Flaps: A Literature Review.

    Science.gov (United States)

    Sisti, Andrea; D'Aniello, Carlo; Fortezza, Leonardo; Tassinari, Juri; Cuomo, Roberto; Grimaldi, Luca; Nisi, Giuseppe

    2016-01-01

    Since their introduction in 1991, propeller flaps are increasingly used as a surgical approach to loss of substance. The aim of this study was to evaluate the indications and to verify the outcomes and the complication rates using this reconstructing technique through a literature review. A search on PubMed was performed using "propeller flap", "fasciocutaneous flap", "local flap" or "pedicled flap" as key words. We selected clinical studies using propeller flaps as a reconstructing technique. We found 119 studies from 1991 to 2015. Overall, 1,315 propeller flaps were reported in 1,242 patients. Most frequent indications included loss of substance following tumor excision, repair of trauma-induced injuries, burn scar contractures, pressure sores and chronic infections. Complications were observed in 281/1242 patients (22.6%) occurring more frequently in the lower limbs (31.8%). Partial flap necrosis and venous congestion were the most frequent complications. The complications' rate was significantly higher in infants (70 years old) but there was not a significant difference between the sexes. Trend of complication rate has not improved during the last years. Propeller flaps showed a great success rate with low morbidity, quick recovery, good aesthetic outcomes and reduced cost. The quality and volume of the transferred soft tissue, the scar orientation and the possibility of direct donor site closure should be considered in order to avoid complications. Indications for propeller flaps are small- or medium-sized defects located in a well-vascularized area with healthy surrounding tissues. Copyright © 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

  15. T lymphocyte migration: an action movie starring the actin and associated actors

    Directory of Open Access Journals (Sweden)

    Loïc eDupré

    2015-11-01

    Full Text Available The actin cytoskeleton is composed of a dynamic filament meshwork that builds the architecture of the cell to sustain its fundamental properties. This physical structure is characterized by a continuous remodeling, which allows cells to accomplish complex motility steps such as directed migration, crossing of biological barriers and interaction with other cells. T lymphocytes excel in these motility steps to ensure their immune surveillance duties. In particular, actin cytoskeleton remodeling is key to facilitate the journey of T lymphocytes through distinct tissue environments and to tune their stop and go behavior during the scanning of antigen-presenting cells. The molecular mechanisms controlling actin cytoskeleton remodeling during T lymphocyte motility have been only partially unraveled, since the function of many actin regulators has not yet been assessed in these cells. Our review aims to integrate the current knowledge into a comprehensive picture of how the actin cytoskeleton drives T lymphocyte migration. We will present the molecular actors that control actin cytoskeleton remodeling, as well as their role in the different T lymphocyte motile steps. We will also highlight which challenges remain to be addressed experimentally and which approaches appear promising to tackle them.

  16. T Lymphocyte Migration: An Action Movie Starring the Actin and Associated Actors.

    Science.gov (United States)

    Dupré, Loïc; Houmadi, Raïssa; Tang, Catherine; Rey-Barroso, Javier

    2015-01-01

    The actin cytoskeleton is composed of a dynamic filament meshwork that builds the architecture of the cell to sustain its fundamental properties. This physical structure is characterized by a continuous remodeling, which allows cells to accomplish complex motility steps such as directed migration, crossing of biological barriers, and interaction with other cells. T lymphocytes excel in these motility steps to ensure their immune surveillance duties. In particular, actin cytoskeleton remodeling is a key to facilitate the journey of T lymphocytes through distinct tissue environments and to tune their stop and go behavior during the scanning of antigen-presenting cells. The molecular mechanisms controlling actin cytoskeleton remodeling during T lymphocyte motility have been only partially unraveled, since the function of many actin regulators has not yet been assessed in these cells. Our review aims to integrate the current knowledge into a comprehensive picture of how the actin cytoskeleton drives T lymphocyte migration. We will present the molecular actors that control actin cytoskeleton remodeling, as well as their role in the different T lymphocyte motile steps. We will also highlight which challenges remain to be addressed experimentally and which approaches appear promising to tackle them.

  17. An analytical model and scaling of chordwise flexible flapping wings in forward flight.

    Science.gov (United States)

    Kodali, Deepa; Kang, Chang-Kwon

    2016-12-13

    Aerodynamic performance of biological flight characterized by the fluid structure interaction of a flapping wing and the surrounding fluid is affected by the wing flexibility. One of the main challenges to predict aerodynamic forces is that the wing shape and motion are a priori unknown. In this study, we derive an analytical fluid-structure interaction model for a chordwise flexible flapping two-dimensional airfoil in forward flight. A plunge motion is imposed on the rigid leading-edge (LE) of teardrop shape and the flexible tail dynamically deforms. The resulting unsteady aeroelasticity is modeled with the Euler-Bernoulli-Theodorsen equation under a small deformation assumption. The two-way coupling is realized by considering the trailing-edge deformation relative to the LE as passive pitch, affecting the unsteady aerodynamics. The resulting wing deformation and the aerodynamic performance including lift and thrust agree well with high-fidelity numerical results. Under the dynamic balance, the aeroelastic stiffness decreases, whereas the aeroelastic stiffness increases with the reduced frequency. A novel aeroelastic frequency ratio is derived, which scales with the wing deformation, lift, and thrust. Finally, the dynamic similarity between flapping in water and air is established.

  18. The freestyle pedicle perforator flap

    DEFF Research Database (Denmark)

    Gunnarsson, Gudjon Leifur; Jackson, Ian T; Westvik, Tormod S

    2015-01-01

    BACKGROUND: Perforating vessels are a consistent anatomical finding and well described in the current literature. Any skin flap can be raised on a subcutaneous pedicle as long as it contains at least one supplying perforator. Perforator flaps have been interlinked with microsurgery and generally...... not widely performed by the general plastic surgeons. The aim of this paper is to present the simplicity of pedicled perforator flap reconstruction of moderate-sized defects of the extremities and torso. METHODS: We retrospectively reviewed the charts of 34 patients reconstructed using 34 freestyle pedicled...... perforator flaps for moderate-sized defects of the truncus and extremities. We registered indications, flap size and localization, success rate, and complications. Most importantly, we describe a simple approach to the design of freestyle pedicled perforator flaps and elaborate on technical aspects...

  19. Gamma interferon-induced guanylate binding protein 1 is a novel actin cytoskeleton remodeling factor.

    Science.gov (United States)

    Ostler, Nicole; Britzen-Laurent, Nathalie; Liebl, Andrea; Naschberger, Elisabeth; Lochnit, Günter; Ostler, Markus; Forster, Florian; Kunzelmann, Peter; Ince, Semra; Supper, Verena; Praefcke, Gerrit J K; Schubert, Dirk W; Stockinger, Hannes; Herrmann, Christian; Stürzl, Michael

    2014-01-01

    Gamma interferon (IFN-γ) regulates immune defenses against viruses, intracellular pathogens, and tumors by modulating cell proliferation, migration, invasion, and vesicle trafficking processes. The large GTPase guanylate binding protein 1 (GBP-1) is among the cellular proteins that is the most abundantly induced by IFN-γ and mediates its cell biologic effects. As yet, the molecular mechanisms of action of GBP-1 remain unknown. Applying an interaction proteomics approach, we identified actin as a strong and specific binding partner of GBP-1. Furthermore, GBP-1 colocalized with actin at the subcellular level and was both necessary and sufficient for the extensive remodeling of the fibrous actin structure observed in IFN-γ-exposed cells. These effects were dependent on the oligomerization and the GTPase activity of GBP-1. Purified GBP-1 and actin bound to each other, and this interaction was sufficient to impair the formation of actin filaments in vitro, as demonstrated by atomic force microscopy, dynamic light scattering, and fluorescence-monitored polymerization. Cosedimentation and band shift analyses demonstrated that GBP-1 binds robustly to globular actin and slightly to filamentous actin. This indicated that GBP-1 may induce actin remodeling via globular actin sequestering and/or filament capping. These results establish GBP-1 as a novel member within the family of actin-remodeling proteins specifically mediating IFN-γ-dependent defense strategies.

  20. A new F-actin structure in fungi: actin ring formation around the cell nucleus of Cryptococcus neoformans.

    Science.gov (United States)

    Kopecká, Marie; Kawamoto, Susumu; Yamaguchi, Masashi

    2013-04-01

    The F-actin cytoskeleton of Cryptococcus neoformans is known to comprise actin cables, cortical patches and cytokinetic ring. Here, we describe a new F-actin structure in fungi, a perinuclear F-actin collar ring around the cell nucleus, by fluorescent microscopic imaging of rhodamine phalloidin-stained F-actin. Perinuclear F-actin rings form in Cryptococcus neoformans treated with the microtubule inhibitor Nocodazole or with the drug solvent dimethyl sulfoxide (DMSO) or grown in yeast extract peptone dextrose (YEPD) medium, but they are absent in cells treated with Latrunculin A. Perinuclear F-actin rings may function as 'funicular cabin' for the cell nucleus, and actin cables as intracellular 'funicular' suspending nucleus in the central position in the cell and moving nucleus along the polarity axis along actin cables.

  1. Optimal propulsive flapping in Stokes flows.

    Science.gov (United States)

    Was, Loïc; Lauga, Eric

    2014-03-01

    Swimming fish and flying insects use the flapping of fins and wings to generate thrust. In contrast, microscopic organisms typically deform their appendages in a wavelike fashion. Since a flapping motion with two degrees of freedom is able, in theory, to produce net forces from a time-periodic actuation at all Reynolds numbers, we compute in this paper the optimal flapping kinematics of a rigid spheroid in a Stokes flow. The hydrodynamics for the force generation and energetics of the flapping motion is solved exactly. We then compute analytically the gradient of a flapping efficiency in the space of all flapping gaits and employ it to derive numerically the optimal flapping kinematics as a function of the shape of the flapper and the amplitude of the motion. The kinematics of optimal flapping are observed to depend weakly on the flapper shape and are very similar to the figure-eight motion observed in the motion of insect wings. Our results suggest that flapping could be a exploited experimentally as a propulsion mechanism valid across the whole range of Reynolds numbers.

  2. Optimal propulsive flapping in Stokes flows

    International Nuclear Information System (INIS)

    Was, Loïc; Lauga, Eric

    2014-01-01

    Swimming fish and flying insects use the flapping of fins and wings to generate thrust. In contrast, microscopic organisms typically deform their appendages in a wavelike fashion. Since a flapping motion with two degrees of freedom is able, in theory, to produce net forces from a time-periodic actuation at all Reynolds numbers, we compute in this paper the optimal flapping kinematics of a rigid spheroid in a Stokes flow. The hydrodynamics for the force generation and energetics of the flapping motion is solved exactly. We then compute analytically the gradient of a flapping efficiency in the space of all flapping gaits and employ it to derive numerically the optimal flapping kinematics as a function of the shape of the flapper and the amplitude of the motion. The kinematics of optimal flapping are observed to depend weakly on the flapper shape and are very similar to the figure-eight motion observed in the motion of insect wings. Our results suggest that flapping could be a exploited experimentally as a propulsion mechanism valid across the whole range of Reynolds numbers. (paper)

  3. Modelling phagosomal lipid networks that regulate actin assembly

    Directory of Open Access Journals (Sweden)

    Schwarz Roland

    2008-12-01

    Full Text Available Abstract Background When purified phagosomes are incubated in the presence of actin under appropriate conditions, microfilaments start growing from the membrane in a process that is affected by ATP and the lipid composition of the membrane. Isolated phagosomes are metabolically active organelles that contain enzymes and metabolites necessary for lipid interconversion. Hence, addition of ATP, lipids, and actin to the system alter the steady-state composition of the phagosomal membrane at the same time that the actin nucleation is initiated. Our aim was to model all these processes in parallel. Results We compiled detailed experimental data on the effects of different lipids and ATP on actin nucleation and we investigated experimentally lipid interconversion and ATP metabolism in phagosomes by using suitable radioactive compounds. In a first step, a complex lipid network interconnected by chemical reactions catalyzed by known enzymes was modelled in COPASI (Complex Pathway Simulator. However, several lines of experimental evidence indicated that only the phosphatidylinositol branch of the network was active, an observation that dramatically reduced the number of parameters in the model. The results also indicated that a lipid network-independent ATP-consuming activity should be included in the model. When this activity was introduced, the set of differential equations satisfactorily reproduced the experimental data. On the other hand, a molecular mechanism connecting membrane lipids, ATP, and the actin nucleation process is still missing. We therefore adopted a phenomenological (black-box approach to represent the empirical observations. We proposed that lipids and ATP influence the dynamic interconversion between active and inactive actin nucleation sites. With this simple model, all the experimental data were satisfactorily fitted with a single positive parameter per lipid and ATP. Conclusion By establishing an active 'dialogue' between an

  4. [A variant of island flaps for the covering of pressure sores: the hatchet flap. Apropos of 31 cases].

    Science.gov (United States)

    Quillot, M; Lodde, J P; Pegorier, O; Reynaud, J P; Cormerais, A

    1994-08-01

    The authors propose a modification of the classical design of island flaps for cover of pressure sores, applied to gluteus maximus and tensor fascia lata muscles: the hatchet flap. 31 flaps have been used including 13 gluteus maximus superior flaps for sacral pressure sores, 9 gluteal inferior flaps for ischial pressure sores and 9 tensor fascia lata flaps for trochanteric pressure sores. A small partial necrosis and two cases of sepsis were observed in this series, but did not require surgical revision. The authors emphasize the value of this modification of the classical flap design, which preserves an even better musculocutaneous capital in these patients, who are often already multi-operated. The very rapid recovery of patients supports the authors' application of hatchet flaps to the surgery of pressure sores, and suggests the extension to other musculocutaneous flaps in the future.

  5. Comprehensive modeling and control of flexible flapping wing micro air vehicles

    Science.gov (United States)

    Nogar, Stephen Michael

    Flapping wing micro air vehicles hold significant promise due to the potential for improved aerodynamic efficiency, enhanced maneuverability and hover capability compared to fixed and rotary configurations. However, significant technical challenges exist to due the lightweight, highly integrated nature of the vehicle and coupling between the actuators, flexible wings and control system. Experimental and high fidelity analysis has demonstrated that aeroelastic effects can change the effective kinematics of the wing, reducing vehicle stability. However, many control studies for flapping wing vehicles do not consider these effects, and instead validate the control strategy with simple assumptions, including rigid wings, quasi-steady aerodynamics and no consideration of actuator dynamics. A control evaluation model that includes aeroelastic effects and actuator dynamics is developed. The structural model accounts for geometrically nonlinear behavior using an implicit condensation technique and the aerodynamic loads are found using a time accurate approach that includes quasi-steady, rotational, added mass and unsteady effects. Empirically based parameters in the model are fit using data obtained from a higher fidelity solver. The aeroelastic model and its ingredients are compared to experiments and computations using models of higher fidelity, and indicate reasonable agreement. The developed control evaluation model is implemented in a previously published, baseline controller that maintains stability using an asymmetric wingbeat, known as split-cycle, along with changing the flapping frequency and wing bias. The model-based controller determines the control inputs using a cycle-averaged, linear control design model, which assumes a rigid wing and no actuator dynamics. The introduction of unaccounted for dynamics significantly degrades the ability of the controller to track a reference trajectory, and in some cases destabilizes the vehicle. This demonstrates the

  6. Bilateral simultaneous breast reconstruction with SGAP flaps.

    Science.gov (United States)

    Flores, Jaime I; Magarakis, Michael; Venkat, Raghunandan; Shridharani, Sachin M; Rosson, Gedge D

    2012-07-01

    Two work-horse approaches to postmastectomy breast reconstruction are the deep inferior epigastric perforator flap and the superior gluteal artery perforator (SGAP) flap [and its variation, the lateral septocutaneous superior gluteal artery perforator flap]. Our purpose was fourfold: 1) to analyze our experience with the SGAP flaps for simultaneous bilateral breast reconstruction; 2) to analyze our experience with lateral septocutaneous superior gluteal artery perforator flaps for that procedure; 3) to compare our results with those in the literature; and 4) to highlight the importance of preoperative three-dimensional computed tomographic angiography. A retrospective chart review was completed for 23 patients who underwent breast reconstruction between December 2005 and January 2010 via an SGAP flap (46 flaps). We reviewed flap weight, ischemia time, length of stay, overall flap survival, fat necrosis development, and emergency re-exploration. Mean weights were 571.2 ± 222.0 g (range 186-1,117 g) and 568.0 ± 237.5 g (range 209-1,115 g) for the left and right buttock flap, respectively. Mean ischemia time was 129.1 ± 15.7 and 177.7 ± 24.7 minutes for the first and second flap, respectively. Mean hospital stay was 5.3 ± 2.5 days. All flaps survived. Fat necrosis developed in five flaps (10.8%), and emergency re-exploration was required in three patients (three flaps). When harvesting abdominal tissue is a poor option, the SGAP flap is an efficacious procedure for patients desiring autologous breast reconstruction, and bilateral procedures can be performed simultaneously. Copyright © 2012 Wiley Periodicals, Inc.

  7. Pneumatic artificial muscles for trailing edge flap actuation: a feasibility study

    International Nuclear Information System (INIS)

    Woods, Benjamin K S; Wereley, Norman M; Kothera, Curt S; Sirohi, Jayant

    2011-01-01

    In this study a novel aircraft trailing edge flap actuation system was developed and tested. Pneumatic artificial muscles (PAMs) were used as the driving elements of this system to demonstrate their feasibility and utility as an alternative aerospace actuation technology. A prototype flap/actuator system was integrated into a model wing section and tested on the bench-top under simulated airloads for flight at 100 m s −1 (M = 0.3) and in an open-jet wind tunnel at free stream velocities ranging up to 45 m s −1 (M = 0.13). Testing was performed for actuator pressures ranging from 0.069 to 0.62 MPa (10–90 psi) and actuation frequencies from 0.1 to 31 Hz. Results show that the PAM-driven trailing edge flap system can generate substantial and sustainable dynamic deflections, thereby proving the feasibility of using pneumatic artificial muscle actuators in a trailing edge flap system. Key issues limiting system performance are identified, that should be resolved in future research

  8. Power performance optimization and loads alleviation with active flaps using individual flap control

    DEFF Research Database (Denmark)

    Pettas, Vasilis; Barlas, Athanasios; Gertz, Drew Patrick

    2016-01-01

    the sensor inputs. The AEP is increased due to the upscaling but also further due to the flap system while the fatigue loads in components of interest (blade, tower, nacelle and main bearing) are reduced close to the level of the original turbine. The aim of this study is to demonstrate a simple....... In an industrial-oriented manner the baseline rotor is upscaled by 5% and the ATEFs are implemented in the outer 30% of the blades. The flap system is kept simple and robust with a single flap section and control with wind speed, rotor azimuth, root bending moments and angle of attack in flap's mid-section being...

  9. Kinematic control of aerodynamic forces on an inclined flapping wing with asymmetric strokes

    International Nuclear Information System (INIS)

    Park, Hyungmin; Choi, Haecheon

    2012-01-01

    In the present study, we conduct an experiment using a one-paired dynamically scaled model of an insect wing, to investigate how asymmetric strokes with different wing kinematic parameters are used to control the aerodynamics of a dragonfly-like inclined flapping wing in still fluid. The kinematic parameters considered are the angles of attack during the mid-downstroke (α md ) and mid-upstroke (α mu ), and the duration (Δτ) and time of initiation (τ p ) of the pitching rotation. The present dragonfly-like inclined flapping wing has the aerodynamic mechanism of unsteady force generation similar to those of other insect wings in a horizontal stroke plane, but the detailed effect of the wing kinematics on the force control is different due to the asymmetric use of the angle of attack during the up- and downstrokes. For example, high α md and low α mu produces larger vertical force with less aerodynamic power, and low α md and high α mu is recommended for horizontal force (thrust) production. The pitching rotation also affects the aerodynamics of a flapping wing, but its dynamic rotational effect is much weaker than the effect from the kinematic change in the angle of attack caused by the pitching rotation. Thus, the influences of the duration and timing of pitching rotation for the present inclined flapping wing are found to be very different from those for a horizontal flapping wing. That is, for the inclined flapping motion, the advanced and delayed rotations produce smaller vertical forces than the symmetric one and the effect of pitching duration is very small. On the other hand, for a specific range of pitching rotation timing, delayed rotation requires less aerodynamic power than the symmetric rotation. As for the horizontal force, delayed rotation with low α md and high α mu is recommended for long-duration flight owing to its high efficiency, and advanced rotation should be employed for hovering flight for nearly zero horizontal force. The present

  10. Dynamic Filament Formation by a Divergent Bacterial Actin-Like ParM Protein.

    Directory of Open Access Journals (Sweden)

    Anthony J Brzoska

    Full Text Available Actin-like proteins (Alps are a diverse family of proteins whose genes are abundant in the chromosomes and mobile genetic elements of many bacteria. The low-copy-number staphylococcal multiresistance plasmid pSK41 encodes ParM, an Alp involved in efficient plasmid partitioning. pSK41 ParM has previously been shown to form filaments in vitro that are structurally dissimilar to those formed by other bacterial Alps. The mechanistic implications of these differences are not known. In order to gain insights into the properties and behavior of the pSK41 ParM Alp in vivo, we reconstituted the parMRC system in the ectopic rod-shaped host, E. coli, which is larger and more genetically amenable than the native host, Staphylococcus aureus. Fluorescence microscopy showed a functional fusion protein, ParM-YFP, formed straight filaments in vivo when expressed in isolation. Strikingly, however, in the presence of ParR and parC, ParM-YFP adopted a dramatically different structure, instead forming axial curved filaments. Time-lapse imaging and selective photobleaching experiments revealed that, in the presence of all components of the parMRC system, ParM-YFP filaments were dynamic in nature. Finally, molecular dissection of the parMRC operon revealed that all components of the system are essential for the generation of dynamic filaments.

  11. Cofilin is a pH sensor for actin free barbed end formation: role of phosphoinositide binding.

    Science.gov (United States)

    Frantz, Christian; Barreiro, Gabriela; Dominguez, Laura; Chen, Xiaoming; Eddy, Robert; Condeelis, John; Kelly, Mark J S; Jacobson, Matthew P; Barber, Diane L

    2008-12-01

    Newly generated actin free barbed ends at the front of motile cells provide sites for actin filament assembly driving membrane protrusion. Growth factors induce a rapid biphasic increase in actin free barbed ends, and we found both phases absent in fibroblasts lacking H(+) efflux by the Na-H exchanger NHE1. The first phase is restored by expression of mutant cofilin-H133A but not unphosphorylated cofilin-S3A. Constant pH molecular dynamics simulations and nuclear magnetic resonance (NMR) reveal pH-sensitive structural changes in the cofilin C-terminal filamentous actin binding site dependent on His133. However, cofilin-H133A retains pH-sensitive changes in NMR spectra and severing activity in vitro, which suggests that it has a more complex behavior in cells. Cofilin activity is inhibited by phosphoinositide binding, and we found that phosphoinositide binding is pH-dependent for wild-type cofilin, with decreased binding at a higher pH. In contrast, phosphoinositide binding by cofilin-H133A is attenuated and pH insensitive. These data suggest a molecular mechanism whereby cofilin acts as a pH sensor to mediate a pH-dependent actin filament dynamics.

  12. [Aesthetic effect of wound repair with flaps].

    Science.gov (United States)

    Tan, Qian; Zhou, Hong-Reng; Wang, Shu-Qin; Zheng, Dong-Feng; Xu, Peng; Wu, Jie; Ge, Hua-Qiang; Lin, Yue; Yan, Xin

    2012-08-01

    To investigate the aesthetic effect of wound repair with flaps. One thousand nine hundred and ninety-six patients with 2082 wounds hospitalized from January 2004 to December 2011. These wounds included 503 deep burn wounds, 268 pressure sores, 392 soft tissue defects caused by trauma, 479 soft tissue defects due to resection of skin cancer and mole removal, 314 soft tissue defects caused by scar excision, and 126 other wounds. Wound area ranged from 1.5 cm x 1.0 cm to 30.0 cm x 22.0 cm. Sliding flaps, expanded flaps, pedicle flaps, and free flaps were used to repair the wounds in accordance with the principle and timing of wound repair with flaps. Five flaps showed venous congestion within 48 hours post-operation, 2 flaps of them improved after local massage. One flap survived after local heparin wet packing and venous bloodletting. One flap survived after emergency surgical embolectomy and bridging with saphenous vein graft. One flap showed partial necrosis and healed after skin grafting. The other flaps survived well. One thousand three hundred and twenty-one patients were followed up for 3 months to 2 years, and flaps of them were satisfactory in shape, color, and elasticity, similar to that of normal skin. Some patients underwent scar revision later with good results. Application of suitable flaps in wound repair will result in quick wound healing, good function recovery, and satisfactory aesthetic effect.

  13. Laser resurfacing of skin flaps: an experimental comparison

    Directory of Open Access Journals (Sweden)

    Srdan Babovic

    2011-05-01

    Full Text Available Objective. The influence of Coherent Ultrapulse, TruPulse and Erbium: YAG laser skin resurfacing on survival of the skin flaps when performed simultaneously was evaluated. Material and methods. We used twelve female Yucatan minipigs in the study. Skin flaps including paniculus carnosus were raised on the animals’ back. The flaps were sutured into the defect under tension. We designed 4 experimental groups: Control-Flaps only, Group 2-Flaps + 4 immediate TruPulse laser passes, Group 3-Flaps + 2 immediate Coherent UltraPulse laser passes, Group 4-Flaps – immediate 50J/cm2 total fluence with Erbium: YAG laser. Results. Flap survival in Control group was 98.8%. There was no flap in Group 2 with complete survival. Survival of the flaps in Group 2 (Tru-Pulse ranged from 75-90%, with average flap survival area of 85.2%. In Group 3 (UltraPulse all 24 flaps had some area of necrosis. Flap survival in Group 3 ranged from 75-95%, with an average of 85.6%. In Group 4 (Erbium: YAG flap survival area ranged from 70-95%, with all 24 flaps with some area of necrosis, with average flap survival area of 87.3%. There is a significant statistical difference in flap survival area between groups 2, 3 and 4 versus Control (p<0.001. Conclusion. The results of our study suggest that laser resurfacing of skin flaps sutured under tension in the same operative session is detrimental for skin flap survival. We also found no significant difference in flap survival area between TruPulse, Coherent UltraPulse and Erbium: YAG laser treated flaps.

  14. Cryptococcus neoformans Is Internalized by Receptor-Mediated or ‘Triggered’ Phagocytosis, Dependent on Actin Recruitment

    Science.gov (United States)

    Guerra, Caroline Rezende; Seabra, Sergio Henrique; de Souza, Wanderley; Rozental, Sonia

    2014-01-01

    Cryptococcosis by the encapsulated yeast Cryptococcus neoformans affects mostly immunocompromised individuals and is a frequent neurological complication in AIDS patients. Recent studies support the idea that intracellular survival of Cryptococcus yeast cells is important for the pathogenesis of cryptococcosis. However, the initial steps of Cryptococcus internalization by host cells remain poorly understood. Here, we investigate the mechanism of Cryptococcus neoformans phagocytosis by peritoneal macrophages using confocal and electron microscopy techniques, as well as flow cytometry quantification, evaluating the importance of fungal capsule production and of host cell cytoskeletal elements for fungal phagocytosis. Electron microscopy analyses revealed that capsular and acapsular strains of C. neoformans are internalized by macrophages via both ‘zipper’ (receptor-mediated) and ‘trigger’ (membrane ruffle-dependent) phagocytosis mechanisms. Actin filaments surrounded phagosomes of capsular and acapsular yeasts, and the actin depolymerizing drugs cytochalasin D and latrunculin B inhibited yeast internalization and actin recruitment to the phagosome area. In contrast, nocodazole and paclitaxel, inhibitors of microtubule dynamics decreased internalization but did not prevent actin recruitment to the site of phagocytosis. Our results show that different uptake mechanisms, dependent on both actin and tubulin dynamics occur during yeast internalization by macrophages, and that capsule production does not affect the mode of Cryptococcus uptake by host cells. PMID:24586631

  15. Myosin-1 inhibition by PClP affects membrane shape, cortical actin distribution and lipid droplet dynamics in early Zebrafish embryos.

    Directory of Open Access Journals (Sweden)

    Prabuddha Gupta

    Full Text Available Myosin-1 (Myo1 represents a mechanical link between the membrane and actin-cytoskeleton in animal cells. We have studied the effect of Myo1 inhibitor PClP in 1-8 cell Zebrafish embryos. Our results indicate a unique involvement of Myo1 in early development of Zebrafish embryos. Inhibition of Myo1 (by PClP and Myo2 (by Blebbistatin lead to arrest in cell division. While Myo1 isoforms appears to be important for both the formation and the maintenance of cleavage furrows, Myo2 is required only for the formation of furrows. We found that the blastodisc of the embryo, which contains a thick actin cortex (~13 μm, is loaded with cortical Myo1. Myo1 appears to be crucial for maintaining the blastodisc morphology and the actin cortex thickness. In addition to cell division and furrow formation, inhibition of Myo1 has a drastic effect on the dynamics and distribution of lipid droplets (LDs in the blastodisc near the cleavage furrow. All these results above are effects of Myo1 inhibition exclusively; Myo2 inhibition by blebbistatin does not show such phenotypes. Therefore, our results demonstrate a potential role for Myo1 in the maintenance and formation of furrow, blastodisc morphology, cell-division and LD organization within the blastodisc during early embryogenesis.

  16. Propeller TAP flap

    DEFF Research Database (Denmark)

    Thomsen, Jørn Bo; Bille, Camilla; Wamberg, Peter

    2013-01-01

    major complications needing additional surgery. One flap was lost due to a vascular problem. Breast reconstruction can be performed by a propeller TAP flap without cutting the descending branch of the thoracodorsal vessels. However, the authors would recommend that a small cuff of muscle is left around...

  17. Actinic keratosis

    DEFF Research Database (Denmark)

    Erlendsson, Andrés M; Egekvist, Henrik; Lorentzen, Henrik F.

    2016-01-01

    Objectives: The incidence of actinic keratosis (AK) is increasing, and several treatment options are available. The aim of this study was to describe clinical characteristics and treatment patterns in patients with AK treated by Danish dermatologists. Methods: A multicenter, non-interventional, c......Objectives: The incidence of actinic keratosis (AK) is increasing, and several treatment options are available. The aim of this study was to describe clinical characteristics and treatment patterns in patients with AK treated by Danish dermatologists. Methods: A multicenter, non...... and currently suspected in 9.4% of AK-affected anatomical regions. Lesions of AK were located primarily on the face (38.6%), scalp (12.8%), and hands (11.2%). Actinic keratosis commonly presented with multiple AK lesions (38.6%) and field cancerization (38.5%). The treatments used most frequently were...

  18. Active Control of Long Bridges Using Flaps

    DEFF Research Database (Denmark)

    Hansen, H. I.; Thoft-Christensen, Palle

    The main problem in designing ultra-long span suspension bridges is flutter. A solution to this problem might be to introduce an active flap control system to increase the flutter wind velocity. The investigated flap control system consists of flaps integrated in the bridge girder so each flap...... is the streamlined part of the edge of the girder. Additional aerodynamic derivatives are shown for the flaps and it is shown how methods already developed can be used to estimate the flutter wind velocity for a bridge section with flaps. As an example, the flutter wind velocity is calculated for different flap...... configurations for a bridge section model by using aerodynamic derivatives for a flat plate. The example shows that different flap configurations can either increase or decrease the flutter wind velocity. for optimal flap configurations flutter will not occur....

  19. Treatment of ischial pressure sores with both profunda femoris artery perforator flaps and muscle flaps.

    Science.gov (United States)

    Kim, Chae Min; Yun, In Sik; Lee, Dong Won; Lew, Dae Hyun; Rah, Dong Kyun; Lee, Won Jai

    2014-07-01

    Reconstruction of ischial pressure sore defects is challenging due to extensive bursas and high recurrence rates. In this study, we simultaneously applied a muscle flap that covered the exposed ischium and large bursa with sufficient muscular volume and a profunda femoris artery perforator fasciocutaneous flap for the management of ischial pressure sores. We retrospectively analyzed data from 14 patients (16 ischial sores) whose ischial defects had been reconstructed using both a profunda femoris artery perforator flap and a muscle flap between January 2006 and February 2014. We compared patient characteristics, operative procedure, and clinical course. All flaps survived the entire follow-up period. Seven patients (50%) had a history of surgery at the site of the ischial pressure sore. The mean age of the patients included was 52.8 years (range, 18-85 years). The mean follow-up period was 27.9 months (range, 3-57 months). In two patients, a biceps femoris muscle flap was used, while a gracilis muscle flap was used in the remaining patients. In four cases (25%), wound dehiscence occurred, but healed without further complication after resuturing. Additionally, congestion occurred in one case (6%), but resolved with conservative treatment. Among 16 cases, there was only one (6%) recurrence at 34 months. The combination of a profunda femoris artery perforator fasciocutaneous flap and muscle flap for the treatment of ischial pressure sores provided pliability, adequate bulkiness and few long-term complications. Therefore, this may be used as an alternative treatment method for ischial pressure sores.

  20. Treatment of Ischial Pressure Sores with Both Profunda Femoris Artery Perforator Flaps and Muscle Flaps

    Directory of Open Access Journals (Sweden)

    Chae Min Kim

    2014-07-01

    Full Text Available Background Reconstruction of ischial pressure sore defects is challenging due to extensive bursas and high recurrence rates. In this study, we simultaneously applied a muscle flap that covered the exposed ischium and large bursa with sufficient muscular volume and a profunda femoris artery perforator fasciocutaneous flap for the management of ischial pressure sores. Methods We retrospectively analyzed data from 14 patients (16 ischial sores whose ischial defects had been reconstructed using both a profunda femoris artery perforator flap and a muscle flap between January 2006 and February 2014. We compared patient characteristics, operative procedure, and clinical course. Results All flaps survived the entire follow-up period. Seven patients (50% had a history of surgery at the site of the ischial pressure sore. The mean age of the patients included was 52.8 years (range, 18-85 years. The mean follow-up period was 27.9 months (range, 3-57 months. In two patients, a biceps femoris muscle flap was used, while a gracilis muscle flap was used in the remaining patients. In four cases (25%, wound dehiscence occurred, but healed without further complication after resuturing. Additionally, congestion occurred in one case (6%, but resolved with conservative treatment. Among 16 cases, there was only one (6% recurrence at 34 months. Conclusions The combination of a profunda femoris artery perforator fasciocutaneous flap and muscle flap for the treatment of ischial pressure sores provided pliability, adequate bulkiness and few long-term complications. Therefore, this may be used as an alternative treatment method for ischial pressure sores.

  1. A PM7 dynamic residue-ligand interactions energy landscape of the BACE1 inhibitory pathway by hydroxyethylamine compounds. Part I: The flap closure process.

    Science.gov (United States)

    Gueto-Tettay, Carlos; Martinez-Consuegra, Alejandro; Zuchniarz, Joshua; Gueto-Tettay, Luis Roberto; Drosos-Ramírez, Juan Carlos

    2017-09-01

    BACE1 is an enzyme of scientific interest because it participates in the progression of Alzheimer's disease. Hydroxyethylamines (HEAs) are a family of compounds which exhibit inhibitory activity toward BACE1 at a nanomolar level, favorable pharmacokinetic properties and oral bioavailability. The first step in the inhibition of BACE1 by HEAs consists of their entrance into the protease active site and the resultant conformational change in the protein, from Apo to closed form. These two conformations differ in the position of an antiparallel loop (called the flap) which covers the entrance to the catalytic site. For BACE1, closure of this flap is vital to its catalytic activity and to inhibition of the enzyme due to the new interactions thereby formed with the ligand. In the present study a dynamic energy landscape of residue-ligand interaction energies (ReLIE) measured for 112 amino acids in the BACE1 active site and its immediate vicinity during the closure of the flap induced by 8 HEAs of different inhibitory power is presented. A total of 6.272 million ReLIE calculations, based on the PM7 semiempirical method, provided a deep and quantitative view of the first step in the inhibition of the aspartyl protease. The information suggests that residues Asp93, Asp289, Thr292, Thr293, Asn294 and Arg296 are anchor points for the ligand, accounting for approximately 45% of the total protein-ligand interaction. Additionally, flap closure improved the BACE1-HEA interaction by around 25%. Furthermore, the inhibitory activity of HEAs could be related to the capacity of these ligands to form said anchor point interactions and maintain them over time: the lack of some of these anchor interactions delayed flap closure or impeded it completely, or even caused the flap to reopen. The methodology employed here could be used as a tool to evaluate future structural modifications which lead to improvements in the favorability and stability of BACE1-HEA ReLIEs, aiding in the design of

  2. WHAMM links actin assembly via the Arp2/3 complex to autophagy.

    Science.gov (United States)

    Kast, David J; Dominguez, Roberto

    2015-01-01

    Macroautophagy (hereafter autophagy) is the process by which cytosolic material destined for degradation is enclosed inside a double-membrane cisterna known as the autophagosome and processed for secretion and/or recycling. This process requires a large collection of proteins that converge on certain sites of the ER membrane to generate the autophagosome membrane. Recently, it was shown that actin accumulates around autophagosome precursors and could play a role in this process, but the mechanism and role of actin polymerization in autophagy were unknown. Here, we discuss our recent finding that the nucleation-promoting factor (NPF) WHAMM recruits and activates the Arp2/3 complex for actin assembly at sites of autophagosome formation on the ER. Using high-resolution, live-cell imaging, we showed that WHAMM forms dynamic puncta on the ER that comigrate with several autophagy markers, and propels the spiral movement of these puncta by an Arp2/3 complex-dependent actin comet tail mechanism. In starved cells, WHAMM accumulates at the interface between neighboring autophagosomes, whose number and size increases with WHAMM expression. Conversely, knocking down WHAMM, inhibiting the Arp2/3 complex or interfering with actin polymerization reduces the size and number of autophagosomes. These findings establish a link between Arp2/3 complex-mediated actin assembly and autophagy.

  3. Multiple roles for the actin cytoskeleton during regulated exocytosis

    Science.gov (United States)

    Porat-Shliom, Natalie; Milberg, Oleg; Masedunskas, Andrius; Weigert, Roberto

    2014-01-01

    Regulated exocytosis is the main mechanism utilized by specialized secretory cells to deliver molecules to the cell surface by virtue of membranous containers (i.e. secretory vesicles). The process involves a series of highly coordinated and sequential steps, which include the biogenesis of the vesicles, their delivery to the cell periphery, their fusion with the plasma membrane and the release of their content into the extracellular space. Each of these steps is regulated by the actin cytoskeleton. In this review, we summarize the current knowledge regarding the involvement of actin and its associated molecules during each of the exocytic steps in vertebrates, and suggest that the overall role of the actin cytoskeleton during regulated exocytosis is linked to the architecture and the physiology of the secretory cells under examination. Specifically, in neurons, neuroendocrine, endocrine, and hematopoietic cells, which contain small secretory vesicles that undergo rapid exocytosis (on the order of milliseconds), the actin cytoskeleton plays a role in pre-fusion events, where it acts primarily as a functional barrier and facilitates docking. In exocrine and other secretory cells, which contain large secretory vesicles that undergo slow exocytosis (seconds to minutes), the actin cytoskeleton plays a role in post-fusion events, where it regulates the dynamics of the fusion pore, facilitates the integration of the vesicles into the plasma membrane, provides structural support, and promotes the expulsion of large cargo molecules. PMID:22986507

  4. Performance of flapping airfoil propulsion with LBM method and DMD analysis

    Science.gov (United States)

    Li, Bing-Hua; Huang, Xian-Wen; Zheng, Yao; Xie, Fang-Fang; Wang, Jing; Zou, Jian-Feng

    2018-05-01

    In this work, the performance of flapping airfoil propulsion at low Reynolds number of Re = 100-400 is studied numerically with the lattice Boltzmann method (LBM). Combined with immersed boundary method (IBM), the LBM has been widely used to simulate moving boundary problems. The influences of the reduced frequency on the plunging and pitching airfoil are explored. It is found that the leading-edge vertex separation and inverted wake structures are two main coherent structures, which dominate the flapping airfoil propulsion. However, the two structures play different roles in the flow and the combination effects on the propulsion need to be clarified. To do so, we adopt the dynamic mode decomposition (DMD) algorithm to reveal the underlying physics. The DMD has been proven to be very suitable for analyzing the complex transient systems like the vortex structure of flapping flight.

  5. Free Boomerang-shaped Extended Rectus Abdominis Myocutaneous flap: The longest possible skin/myocutaneous free flap for soft tissue reconstruction of extremities.

    Science.gov (United States)

    Koul, Ashok R; Nahar, Sushil; Prabhu, Jagdish; Kale, Subhash M; Kumar, Praveen H P

    2011-09-01

    A soft tissue defect requiring flap cover which is longer than that provided by the conventional "long" free flaps like latissimus dorsi (LD) and anterolateral thigh (ALT) flap is a challenging problem. Often, in such a situation, a combination of flaps is required. Over the last 3 years, we have managed nine such defects successfully with a free "Boomerang-shaped" Extended Rectus Abdominis Myocutaneous (BERAM) flap. This flap is the slightly modified and "free" version of a similar flap described by Ian Taylor in 1983. This is a retrospective study of patients who underwent free BERAM flap reconstruction of soft tissue defects of extremity over the last 3 years. We also did a clinical study on 30 volunteers to compare the length of flap available using our design of BERAM flap with the maximum available flap length of LD and ALT flaps, using standard markings. Our clinical experience of nine cases combined with the results of our clinical study has confirmed that our design of BERAM flap consistently provides a flap length which is 32.6% longer than the standard LD flap and 42.2% longer than the standard ALT flap in adults. The difference is even more marked in children. The BERAM flap is consistently reliable as long as the distal end is not extended beyond the mid-axillary line. BERAM flap is simple in design, easy to harvest, reliable and provides the longest possible free skin/myocutaneous flap in the body. It is a useful new alternative for covering long soft tissue defects in the limbs.

  6. Altered Cell Mechanics from the Inside: Dispersed Single Wall Carbon Nanotubes Integrate with and Restructure Actin

    Directory of Open Access Journals (Sweden)

    Mohammad F. Islam

    2012-05-01

    Full Text Available With a range of desirable mechanical and optical properties, single wall carbon nanotubes (SWCNTs are a promising material for nanobiotechnologies. SWCNTs also have potential as biomaterials for modulation of cellular structures. Previously, we showed that highly purified, dispersed SWCNTs grossly alter F-actin inside cells. F-actin plays critical roles in the maintenance of cell structure, force transduction, transport and cytokinesis. Thus, quantification of SWCNT-actin interactions ranging from molecular, sub-cellular and cellular levels with both structure and function is critical for developing SWCNT-based biotechnologies. Further, this interaction can be exploited, using SWCNTs as a unique actin-altering material. Here, we utilized molecular dynamics simulations to explore the interactions of SWCNTs with actin filaments. Fluorescence lifetime imaging microscopy confirmed that SWCNTs were located within ~5 nm of F-actin in cells but did not interact with G-actin. SWCNTs did not alter myosin II sub-cellular localization, and SWCNT treatment in cells led to significantly shorter actin filaments. Functionally, cells with internalized SWCNTs had greatly reduced cell traction force. Combined, these results demonstrate direct, specific SWCNT alteration of F-actin structures which can be exploited for SWCNT-based biotechnologies and utilized as a new method to probe fundamental actin-related cellular processes and biophysics.

  7. Chimeric superficial temporal artery based skin and temporal fascia flap plus temporalis muscle flap - An alternative to free flap for suprastructure maxillectomy with external skin defect

    Directory of Open Access Journals (Sweden)

    Dushyant Jaiswal

    2011-01-01

    Full Text Available Flaps from temporal region have been used for mid face, orbital and peri-orbital reconstruction. The knowledge of the vascular anatomy of the region helps to dissect and harvest the muscle/fascia/skin/combined tissue flaps from that region depending upon the requirement. Suprastructure maxillectomy defects are usually covered with free flaps to fill the cavity. Here we report an innovative idea in which a patient with a supra structure maxillectomy with external skin defect was covered with chimeric flap based on the parietal and frontal branches of superficial temporal artery and the temporalis muscle flap based on deep temporal artery.

  8. Free Boomerang-shaped Extended Rectus Abdominis Myocutaneous flap: The longest possible skin/myocutaneous free flap for soft tissue reconstruction of extremities

    Directory of Open Access Journals (Sweden)

    Ashok R Koul

    2011-01-01

    Full Text Available Background: A soft tissue defect requiring flap cover which is longer than that provided by the conventional "long" free flaps like latissimus dorsi (LD and anterolateral thigh (ALT flap is a challenging problem. Often, in such a situation, a combination of flaps is required. Over the last 3 years, we have managed nine such defects successfully with a free "Boomerang-shaped" Extended Rectus Abdominis Myocutaneous (BERAM flap. This flap is the slightly modified and "free" version of a similar flap described by Ian Taylor in 1983. Materials and Methods: This is a retrospective study of patients who underwent free BERAM flap reconstruction of soft tissue defects of extremity over the last 3 years. We also did a clinical study on 30 volunteers to compare the length of flap available using our design of BERAM flap with the maximum available flap length of LD and ALT flaps, using standard markings. Results: Our clinical experience of nine cases combined with the results of our clinical study has confirmed that our design of BERAM flap consistently provides a flap length which is 32.6% longer than the standard LD flap and 42.2% longer than the standard ALT flap in adults. The difference is even more marked in children. The BERAM flap is consistently reliable as long as the distal end is not extended beyond the mid-axillary line. Conclusion: BERAM flap is simple in design, easy to harvest, reliable and provides the longest possible free skin/myocutaneous flap in the body. It is a useful new alternative for covering long soft tissue defects in the limbs.

  9. Polycation induced actin bundles

    OpenAIRE

    Muhlrad, Andras; Grintsevich, Elena E.; Reisler, Emil

    2011-01-01

    Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations an...

  10. Cell Adhesions: Actin-Based Modules that Mediate Cell-Extracellular Matrix and Cell-Cell Interactions

    Science.gov (United States)

    Bachir, Alexia; Horwitz, Alan Rick; Nelson, W. James; Bianchini, Julie M.

    2018-01-01

    Cell adhesions link cells to the extracellular matrix (ECM) and to each other, and depend on interactions with the actin cytoskeleton. Both cell-ECM and cell-cell adhesion sites contain discrete, yet overlapping functional modules. These modules establish physical association with the actin cytoskeleton, locally modulate actin organization and dynamics, and trigger intracellular signaling pathways. Interplay between these modules generates distinct actin architectures that underlie different stages, types, and functions of cell-ECM and cell-cell adhesions. Actomyosin contractility is required to generate mature, stable adhesions, as well as sense and translate the mechanical properties of the cellular environment to changes in cell organization and behavior. In this chapter we discuss the organization and function of different adhesion modules and how they interact with the actin cytoskeleton. We highlight the molecular mechanisms of mechanotransduction in adhesions, and how adhesion molecules mediate crosstalk between cell-ECM and cell-cell adhesion sites. PMID:28679638

  11. Cost-effectiveness of monitoring free flaps.

    Science.gov (United States)

    Subramaniam, Shiva; Sharp, David; Jardim, Christopher; Batstone, Martin D

    2016-06-01

    Methods of free flap monitoring have become more sophisticated and expensive. This study aims to determine the cost of free flap monitoring and examine its cost effectiveness. We examined a group of patients who had had free flaps to the head and neck over a two-year period, and combined these results with costs obtained from business managers and staff. There were 132 free flaps with a success rate of 99%. The cost of monitoring was Aus $193/flap. Clinical monitoring during this time period cost Aus$25 476 and did not lead to the salvage of any free flaps. Cost equivalence is reached between monitoring and not monitoring only at a failure rate of 15.8%. This is to our knowledge the first study to calculate the cost of clinical monitoring of free flaps, and to examine its cost-effectiveness. Copyright © 2016 The British Association of Oral and Maxillofacial Surgeons. All rights reserved.

  12. Tailor-made ezrin actin binding domain to probe its interaction with actin in-vitro.

    Directory of Open Access Journals (Sweden)

    Rohini Shrivastava

    Full Text Available Ezrin, a member of the ERM (Ezrin/Radixin/Moesin protein family, is an Actin-plasma membrane linker protein mediating cellular integrity and function. In-vivo study of such interactions is a complex task due to the presence of a large number of endogenous binding partners for both Ezrin and Actin. Further, C-terminal actin binding capacity of the full length Ezrin is naturally shielded by its N-terminal, and only rendered active in the presence of Phosphatidylinositol bisphosphate (PIP2 or phosphorylation at the C-terminal threonine. Here, we demonstrate a strategy for the design, expression and purification of constructs, combining the Ezrin C-terminal actin binding domain, with functional elements such as fusion tags and fluorescence tags to facilitate purification and fluorescence microscopy based studies. For the first time, internal His tag was employed for purification of Ezrin actin binding domain based on in-silico modeling. The functionality (Ezrin-actin interaction of these constructs was successfully demonstrated by using Total Internal Reflection Fluorescence Microscopy. This design can be extended to other members of the ERM family as well.

  13. Adhesive F-actin Waves: A Novel Integrin-Mediated Adhesion Complex Coupled to Ventral Actin Polymerization

    OpenAIRE

    Case, Lindsay B.; Waterman, Clare M.

    2011-01-01

    At the leading lamellipodium of migrating cells, protrusion of an Arp2/3-nucleated actin network is coupled to formation of integrin-based adhesions, suggesting that Arp2/3-mediated actin polymerization and integrin-dependent adhesion may be mechanistically linked. Arp2/3 also mediates actin polymerization in structures distinct from the lamellipodium, in "ventral F-actin waves" that propagate as spots and wavefronts along the ventral plasma membrane. Here we show that integrins engage the ex...

  14. Actinic keratosis among seafarers.

    Science.gov (United States)

    Oldenburg, M; Kuechmeister, B; Ohnemus, U; Baur, X; Moll, I

    2013-11-01

    The aim of this study was to assess the prevalence of UV-induced actinic keratosis and further skin lesions. A newly developed questionnaire about lifetime UV radiation exposure was completed by 514 seafarers. An experienced dermatologist inspected the whole-body skin status of all participants. The questionnaire revealed a pre-employment UV radiation exposure in 104 seafarers, sunbed use in 26 subjects and a median work-related UV radiation exposure at sea of 20 years. The diagnosis of actinic keratoses was made in 94 seafarers and the clinical diagnosis of skin cancers in 48 seafarers (28 basal cell carcinoma, 11 squamous cell carcinoma, 9 malignant melanoma). After age standardisation according to a European reference population, the male European seafarers in this study had a 1.80-fold increased risk of actinic keratosis. Actinic keratoses [OR 1.03 (1.01-1.05)] and squamous cell carcinoma [OR 1.07 (1.01-1.13)] were related to the duration of seafaring time in years. A significant association was also found between actinic keratosis/squamous cell carcinoma and sunlight exposure during home leave [OR 1.67 (1.03-2.81) and OR 6.19 (1.18-32.40)]. Furthermore, the engine room personnel-especially the technical officers-were at higher risk of developing actinic keratosis. Due to the high prevalence of actinic keratosis especially among older seafarers with fair skin, with longer duration of seafaring employment at sea and with higher UV exposure during home leave, more intensive advice should be given on sun protection both at sea and ashore.

  15. Shape optimisation and performance analysis of flapping wings

    KAUST Repository

    Ghommem, Mehdi

    2012-09-04

    In this paper, shape optimisation of flapping wings in forward flight is considered. This analysis is performed by combining a local gradient-based optimizer with the unsteady vortex lattice method (UVLM). Although the UVLM applies only to incompressible, inviscid flows where the separation lines are known a priori, Persson et al. [1] showed through a detailed comparison between UVLM and higher-fidelity computational fluid dynamics methods for flapping flight that the UVLM schemes produce accurate results for attached flow cases and even remain trend-relevant in the presence of flow separation. As such, they recommended the use of an aerodynamic model based on UVLM to perform preliminary design studies of flapping wing vehicles Unlike standard computational fluid dynamics schemes, this method requires meshing of the wing surface only and not of the whole flow domain [2]. From the design or optimisation perspective taken in our work, it is fairly common (and sometimes entirely necessary, as a result of the excessive computational cost of the highest fidelity tools such as Navier-Stokes solvers) to rely upon such a moderate level of modelling fidelity to traverse the design space in an economical manner. The objective of the work, described in this paper, is to identify a set of optimised shapes that maximise the propulsive efficiency, defined as the ratio of the propulsive power over the aerodynamic power, under lift, thrust, and area constraints. The shape of the wings is modelled using B-splines, a technology used in the computer-aided design (CAD) field for decades. This basis can be used to smoothly discretize wing shapes with few degrees of freedom, referred to as control points. The locations of the control points constitute the design variables. The results suggest that changing the shape yields significant improvement in the performance of the flapping wings. The optimisation pushes the design to "bird-like" shapes with substantial increase in the time

  16. Green fluorescent protein-mtalin causes defects in actin organization and cell expansion in Arabidopsis and inhibits actin depolymerizing factor's actin depolymerizing activity in vitro

    NARCIS (Netherlands)

    Ketelaar, T.; Anthony, R.G.; Hussey, P.J.

    2004-01-01

    Expression of green fluorescent protein (GFP) linked to an actin binding domain is a commonly used method for live cell imaging of the actin cytoskeleton. One of these chimeric proteins is GFP-mTalin (GFP fused to the actin binding domain of mouse talin). Although it has been demonstrated that

  17. SYP73 Anchors the ER to the Actin Cytoskeleton for Maintenance of ER Integrity and Streaming in Arabidopsis.

    Science.gov (United States)

    Cao, Pengfei; Renna, Luciana; Stefano, Giovanni; Brandizzi, Federica

    2016-12-05

    The endoplasmic reticulum (ER) is an essential organelle that spreads throughout the cytoplasm as one interconnected network of narrow tubules and dilated cisternae that enclose a single lumen. The ER network undergoes extensive remodeling, which critically depends on membrane-cytoskeleton interactions [1]. In plants, the ER is also highly mobile, and its streaming contributes significantly to the movement of other organelles [2, 3]. The remodeling and motility of the plant ER rely mainly on actin [4] and to a minor extent on microtubules [5]. Although a three-way interaction between the ER, cytosolic myosin-XI, and F-actin mediates the plant ER streaming [6], the mechanisms underlying stable interaction of the ER membrane with actin are unknown. Early electron microscopy studies suggested a direct attachment of the plant ER with actin filaments [7, 8], but it is plausible that yet-unknown proteins facilitate anchoring of the ER membrane with the cytoskeleton. We demonstrate here that SYP73, a member of the plant Syp7 subgroup of SNARE proteins [9] containing actin-binding domains, is a novel ER membrane-associated actin-binding protein. We show that overexpression of SYP73 causes a striking rearrangement of the ER over actin and that, similar to mutations of myosin-XI [4, 10, 11], loss of SYP73 reduces ER streaming and affects overall ER network morphology and plant growth. We propose a model for plant ER remodeling whereby the dynamic rearrangement and streaming of the ER network depend on the propelling action of myosin-XI over actin coupled with a SYP73-mediated bridging, which dynamically anchors the ER membrane with actin filaments. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. Model for adhesion clutch explains biphasic relationship between actin flow and traction at the cell leading edge

    Science.gov (United States)

    Craig, Erin M.; Stricker, Jonathan; Gardel, Margaret L.; Mogilner, Alex

    2015-01-01

    Cell motility relies on the continuous reorganization of a dynamic actin-myosin-adhesion network at the leading edge of the cell, in order to generate protrusion at the leading edge and traction between the cell and its external environment. We analyze experimentally measured spatial distributions of actin flow, traction force, myosin density, and adhesion density in control and pharmacologically perturbed epithelial cells in order to develop a mechanical model of the actin-adhesion-myosin self-organization at the leading edge. A model in which the F-actin network is treated as a viscous gel, and adhesion clutch engagement is strengthened by myosin but weakened by actin flow, can explain the measured molecular distributions and correctly predict the spatial distributions of the actin flow and traction stress. We test the model by comparing its predictions with measurements of the actin flow and traction stress in cells with fast and slow actin polymerization rates. The model predicts how the location of the lamellipodium-lamellum boundary depends on the actin viscosity and adhesion strength. The model further predicts that the location of the lamellipodium-lamellum boundary is not very sensitive to the level of myosin contraction. PMID:25969948

  19. Effects of irradiation of skin flaps

    International Nuclear Information System (INIS)

    Sumi, Y.; Ueda, M.; Oka, T.; Torii, S.

    1984-01-01

    The reaction of skin flaps to irradiation and the optimum postoperative time for irradiation was studied in the rat. Flaps showed different reactions depending on the time of irradiation. There was a correlation between the radiosensitivity and the vascularity of the flap. Those flaps in the marginal hypovascular stage of revascularization showed reactions similar to normal skin. However, severe adverse reactions were observed in the marginal hypervascular stage

  20. Flap Lymphedema after Successful Reconstruction of the Chronic Inguinal Wound with a Vertical Rectus Abdominis Flap (VRAM

    Directory of Open Access Journals (Sweden)

    Yalcin Kulahci

    2012-07-01

    Full Text Available The reconstruction of extensive and complex wounds represents a challenging problem for reconstructive surgeon. The reconstructive options to provide cover-age following debridment of these complicated wounds are local, distant flaps, or freetissue transfer. Vertical rectus abdominis flaps have been used succes-sully to repair defects in the groin, hip, perineal, trunk, and breast regions. We encountered flap lymphedema after successful reconstruction of the chronic in-guinal wound with a vertical rectus abdominis (VRAM flap. As far as were able to ascertain, there is no report in the literature related to flap lymphedema.

  1. Mechanical Response of Single Filamin A (ABP-280) Molecules and Its Role in the Actin/Filamin A Gel

    Science.gov (United States)

    Sano, Ryoko; Furuike, Shou; Ito, Tadanao; Ohashi, Kazuyo; Yamazaki, Masahito

    2004-04-01

    Actin/filamin A gel plays important roles in mechanical response of cells. We found a force (50 to 220 pN)-induced unfolding of single filamin A molecules using AFM, and have proposed a hypothesis on the role of single filamin A in the novel property of viscoelasticity of actin/filamin A gel. We also investigated structure and its dynamics of actin/filamin A gel formed in a giant liposome using fluorescence microscopy.

  2. Donor-site morbidity of the radial forearm free flap versus the ulnar forearm free flap.

    Science.gov (United States)

    Hekner, Dominique D; Abbink, Jan H; van Es, Robert J; Rosenberg, Antoine; Koole, Ronald; Van Cann, Ellen M

    2013-08-01

    Donor-site morbidity following harvest of the radial forearm free flap was compared with that following harvest of the ulnar forearm free flap. Twenty-eight radial forearm and 27 ulnar forearm flaps were harvested in 55 patients with head and neck defects. Pressure perception was measured with Semmes-Weinstein monofilaments. Cold perception was tested with chloroethyl. Donor-site healing was evaluated. Patients were interviewed about grip and pinch strength and donor-site appearance. In the radial forearm free flap group, pressure perception and cold perception were reduced in the donor hand, whereas in the ulnar group, no differences were observed between the donor and unoperated hands. In the radial forearm group, 15 percent of patients experienced reduced strength in the donor hand, whereas in the ulnar forearm group, none of the patients reported reduced strength in the donor hand. In the radial forearm group, 14 percent had partial or complete loss of the skin graft, whereas in the ulnar forearm group, 4 percent had partial loss of the skin graft. In the radial forearm group, 18 percent of patients were dissatisfied with the appearance of the donor site, and no complaints were reported in the ulnar forearm group. The authors' study shows less donor site-morbidity following harvest of the ulnar forearm free flap than following harvest of the radial forearm free flap. These results emphasize that the ulnar forearm free flap should be considered as an alternative for the radial forearm free flap for reconstruction of soft-tissue defects. Therapeutic, III.

  3. Development of a morphing flap using shape memory alloy actuators: the aerodynamic characteristics of a morphing flap

    International Nuclear Information System (INIS)

    Ko, Seung-Hee; Bae, Jae-Sung; Rho, Jin-Ho

    2014-01-01

    The discontinuous contour of a wing with conventional flaps diminishes the aerodynamic performance of an aircraft. A wing with a continuous contour does not experience extreme flow stream fluctuations during flight, and consequently has good aerodynamic characteristics. In this study, a morphing flap using shape memory alloy actuators is proposed, designed and fabricated, and its aerodynamic characteristics are investigated using aerodynamic analyses and wind tunnel tests. The ribs of the morphing flap are designed and fabricated with multiple elements joined together in a way that allows relative rotations of adjacent elements and forms a smooth contour of the morphing flap. The aerodynamic analyses of this multiple-element morphing-flap wing are performed using XFLR pro; its aerodynamic performance is compared with that of a mechanical-flap wing, and is measured through wind-tunnel tests. (papers)

  4. Median forehead flap - beyond classic indication

    Directory of Open Access Journals (Sweden)

    Cristian R. Jecan

    2016-11-01

    Full Text Available Introduction. The paramedian forehead flap is one of the best options for reconstruction of the median upper two-thirds of the face due to its vascularity, color, texture match and ability to resurface all or part of the reconstructed area. The forehead flap is the gold standard for nasal soft tissue reconstruction and the flap of choice for larger cutaneous nasal defects having a robust pedicle and large amount of tissue. Materials and Methods. We are reporting a clinical series of cutaneous tumors involving the nose, medial canthus, upper and lower eyelid through a retrospective review of 6 patients who underwent surgical excision of the lesion and primary reconstruction using a paramedian forehead flap. Results. The forehead flap was used for total nose reconstruction, eyelids and medial canthal reconstruction. All flaps survived completely and no tumor recurrence was seen in any of the patients. Cosmetic and functional results were favorable. Conclusions. The forehead flap continues to be one of the best options for nose reconstruction and for closure of surgical defects of the nose larger than 2 cm. Even though is not a gold standard, median forehead flap can be an advantageous technique in periorbital defects reconstruction.

  5. The pathogen-actin connection: A platform for defense signaling in plants

    Energy Technology Data Exchange (ETDEWEB)

    Day, B; Henty, Jessica L; Porter, K J; Staiger, Chris J

    2011-09-08

    The cytoskeleton, a dynamic network of cytoplasmic polymers, plays a central role in numerous fundamental processes, such as development, reproduction, and cellular responses to biotic and abiotic stimuli. As a platform for innate immune responses in mammalian cells, the actin cytoskeleton is a central component in the organization and activation of host defenses, including signaling and cellular repair. In plants, our understanding of the genetic and biochemical responses in both pathogen and host that are required for virulence and resistance has grown enormously. Additional advances in live-cell imaging of cytoskeletal dynamics have markedly altered our view of actin turnover in plants. In this review, we outline current knowledge of host resistance following pathogen perception, both in terms of the genetic interactions that mediate defense signaling, as well as the biochemical and cellular processes that are required for defense signaling.

  6. Mesoscopic model of actin-based propulsion.

    Directory of Open Access Journals (Sweden)

    Jie Zhu

    Full Text Available Two theoretical models dominate current understanding of actin-based propulsion: microscopic polymerization ratchet model predicts that growing and writhing actin filaments generate forces and movements, while macroscopic elastic propulsion model suggests that deformation and stress of growing actin gel are responsible for the propulsion. We examine both experimentally and computationally the 2D movement of ellipsoidal beads propelled by actin tails and show that neither of the two models can explain the observed bistability of the orientation of the beads. To explain the data, we develop a 2D hybrid mesoscopic model by reconciling these two models such that individual actin filaments undergoing nucleation, elongation, attachment, detachment and capping are embedded into the boundary of a node-spring viscoelastic network representing the macroscopic actin gel. Stochastic simulations of this 'in silico' actin network show that the combined effects of the macroscopic elastic deformation and microscopic ratchets can explain the observed bistable orientation of the actin-propelled ellipsoidal beads. To test the theory further, we analyze observed distribution of the curvatures of the trajectories and show that the hybrid model's predictions fit the data. Finally, we demonstrate that the model can explain both concave-up and concave-down force-velocity relations for growing actin networks depending on the characteristic time scale and network recoil. To summarize, we propose that both microscopic polymerization ratchets and macroscopic stresses of the deformable actin network are responsible for the force and movement generation.

  7. Polycation induced actin bundles.

    Science.gov (United States)

    Muhlrad, Andras; Grintsevich, Elena E; Reisler, Emil

    2011-04-01

    Three polycations, polylysine, the polyamine spermine and the polycationic protein lysozyme were used to study the formation, structure, ionic strength sensitivity and dissociation of polycation-induced actin bundles. Bundles form fast, simultaneously with the polymerization of MgATP-G-actins, upon the addition of polycations to solutions of actins at low ionic strength conditions. This indicates that nuclei and/or nascent filaments bundle due to attractive, electrostatic effect of polycations and the neutralization of repulsive interactions of negative charges on actin. The attractive forces between the filaments are strong, as shown by the low (in nanomolar range) critical concentration of their bundling at low ionic strength. These bundles are sensitive to ionic strength and disassemble partially in 100 mM NaCl, but both the dissociation and ionic strength sensitivity can be countered by higher polycation concentrations. Cys374 residues of actin monomers residing on neighboring filaments in the bundles can be cross-linked by the short span (5.4Å) MTS-1 (1,1-methanedyl bismethanethiosulfonate) cross-linker, which indicates a tight packing of filaments in the bundles. The interfilament cross-links, which connect monomers located on oppositely oriented filaments, prevent disassembly of bundles at high ionic strength. Cofilin and the polysaccharide polyanion heparin disassemble lysozyme induced actin bundles more effectively than the polylysine-induced bundles. The actin-lysozyme bundles are pathologically significant as both proteins are found in the pulmonary airways of cystic fibrosis patients. Their bundles contribute to the formation of viscous mucus, which is the main cause of breathing difficulties and eventual death in this disorder. Copyright © 2011 Elsevier B.V. All rights reserved.

  8. The actin multigene family of Paramecium tetraurelia

    Directory of Open Access Journals (Sweden)

    Wagner Erika

    2007-03-01

    Full Text Available Abstract Background A Paramecium tetraurelia pilot genome project, the subsequent sequencing of a Megabase chromosome as well as the Paramecium genome project aimed at gaining insight into the genome of Paramecium. These cells display a most elaborate membrane trafficking system, with distinct, predictable pathways in which actin could participate. Previously we had localized actin in Paramecium; however, none of the efforts so far could proof the occurrence of actin in the cleavage furrow of a dividing cell, despite the fact that actin is unequivocally involved in cell division. This gave a first hint that Paramecium may possess actin isoforms with unusual characteristics. The genome project gave us the chance to search the whole Paramecium genome, and, thus, to identify and characterize probably all actin isoforms in Paramecium. Results The ciliated protozoan, P. tetraurelia, contains an actin multigene family with at least 30 members encoding actin, actin-related and actin-like proteins. They group into twelve subfamilies; a large subfamily with 10 genes, seven pairs and one trio with > 82% amino acid identity, as well as three single genes. The different subfamilies are very distinct from each other. In comparison to actins in other organisms, P. tetraurelia actins are highly divergent, with identities topping 80% and falling to 30%. We analyzed their structure on nucleotide level regarding the number and position of introns. On amino acid level, we scanned the sequences for the presence of actin consensus regions, for amino acids of the intermonomer interface in filaments, for residues contributing to ATP binding, and for known binding sites for myosin and actin-specific drugs. Several of those characteristics are lacking in several subfamilies. The divergence of P. tetraurelia actins and actin-related proteins between different P. tetraurelia subfamilies as well as with sequences of other organisms is well represented in a phylogenetic

  9. Hyperbaric oxygen therapy and surgical delay improve flap survival of reverse pedicle flaps for lower third leg and foot reconstruction

    Directory of Open Access Journals (Sweden)

    Pradeoth Mukundan Korambayil

    2015-06-01

    Full Text Available Aim: The purpose of the study is to present a management protocol for various types of soft tissue defects of the distal third region of leg and foot treated with pedicle flaps, by including hyperbaric oxygen (HBO therapy in the treatment regimen with flap delay. Methods: We present a prospective study of 23 patients with various types of soft tissue defects of the foot, and lower third of leg managed in our institution from December 2012 to December 2013. All soft tissue defects were treated by a reverse pedicle flap. Twelve patients were managed with flap delay with HBO therapy and 11 patients with immediate flaps without HBO therapy. The postoperative period, hospital course, and follow-up were documented. Results: Of 12 patients with flap delay and HBO, 10 patients did not suffer any complications secondary to flap transfer. One patient had discoloration of the tip of the flap, which settled without the intervention, and 1 patient had recurrent abscess formation, which required debridement and closure. Of 11 patients with direct transfer, 6 patients presented with complications including flap congestion, partial flap loss, and tip necrosis, which required secondary intervention. Conclusion: HBO therapy is a useful adjunct in flap delay of the reverse pedicle flap for soft tissue reconstruction of the lower third of the leg and foot regions.

  10. Influence of inflow angle on flexible flap aerodynamic performance

    International Nuclear Information System (INIS)

    Zhao, H Y; Ye, Z; Li, Z M; Li, C

    2013-01-01

    Large scale wind turbines have larger blade lengths and weights, which creates new challenges for blade design. This paper selects NREL S809 airfoil, and uses the parameterized technology to realize the flexible trailing edge deformation, researches the dynamic aerodynamic characteristics in the process of continuous flexible deformation, analyses the influence of inflow angle on flexible flap aerodynamic performance, in order to further realize the flexible wind turbine blade design and provides some references for the active control scheme. The results show that compared with the original airfoil, proper trailing edge deformation can improve the lift coefficient, reduce the drag coefficient, and thereby more efficiently realize flow field active control. With inflow angle increases, dynamic lift-drag coefficient hysteresis loop shape deviation occurs, even turns into different shapes. Appropriate swing angle can improve the flap lift coefficient, but may cause early separation of flow. To improve the overall performance of wind turbine blades, different angular control should be used at different cross sections, in order to achieve the best performance

  11. Diclofenac Topical (actinic keratosis)

    Science.gov (United States)

    ... topical gel (Solaraze) is used to treat actinic keratosis (flat, scaly growths on the skin caused by ... The way diclofenac gel works to treat actinic keratosis is not known.Diclofenac is also available as ...

  12. The Temporalis Muscle Flap in Maxillofacial Reconstruction

    International Nuclear Information System (INIS)

    ElSheikh, M; Zeitoun, I; ElMassry, M A K

    1991-01-01

    The temporalis muscle flap is a very versatile and valuable axial flap, which could be used in various reconstructive procedures in and around the oro-maxillofacial region. The surgical anatomy, vascular pattern and technique of elevation of the flap are described, together with our experience in different reconstructive situations. The advantages and disadvantages of the use of this flap are thoroughly discussed taking into consideration the potentiality of cancer recurrence under cover of the flap. (author)

  13. Leading tip drives soma translocation via forward F-actin flow during neuronal migration.

    Science.gov (United States)

    He, Min; Zhang, Zheng-hong; Guan, Chen-bing; Xia, Di; Yuan, Xiao-bing

    2010-08-11

    Neuronal migration involves coordinated extension of the leading process and translocation of the soma, but the relative contribution of different subcellular regions, including the leading process and cell rear, in driving soma translocation remains unclear. By local manipulation of cytoskeletal components in restricted regions of cultured neurons, we examined the molecular machinery underlying the generation of traction force for soma translocation during neuronal migration. In actively migrating cerebellar granule cells in culture, a growth cone (GC)-like structure at the leading tip exhibits high dynamics, and severing the tip or disrupting its dynamics suppressed soma translocation within minutes. Soma translocation was also suppressed by local disruption of F-actin along the leading process but not at the soma, whereas disrupting microtubules along the leading process or at the soma accelerated soma translocation. Fluorescent speckle microscopy using GFP-alpha-actinin showed that a forward F-actin flow along the leading process correlated with and was required for soma translocation, and such F-actin flow depended on myosin II activity. In migrating neurons, myosin II activity was high at the leading tip but low at the soma, and increasing or decreasing this front-to-rear difference accelerated or impeded soma advance. Thus, the tip of the leading process actively pulls the soma forward during neuronal migration through a myosin II-dependent forward F-actin flow along the leading process.

  14. Tensor fascia lata flap versus tensor fascia lata perforator-based island flap for the coverage of extensive trochanteric pressure sores.

    Science.gov (United States)

    Kim, Youn Hwan; Kim, Sang Wha; Kim, Jeong Tae; Kim, Chang Yeon

    2013-06-01

    Tensor fascia lata (TFL) musculocutaneous flaps often require a donor site graft when harvesting a large flap. However, a major drawback is that it also sacrifices the muscle. To overcome this disadvantage, we designed a TFL perforator-based island flap that was harvested from a site near the defect and involved transposition within 90 degrees without full isolation of the pedicles. We performed procedures on 17 musculocutaneous flaps and 23 perforator-based island flaps, and compared the outcomes of these surgeries. The overall complication rate was 27.5% (11 regions). There were 7 complications related to the musculocutaneous flaps and 4 complications related to the perforator flaps. Although there were no statistical differences between those groups, lower complication rates were associated with procedures involving perforator flaps. The TFL perforator procedure is a simple and fast operation that avoids sacrificing muscle. This decreases complication rates compared to true perforator flap techniques that require dissection around the perforator or pedicle.

  15. Rate-determining Step of Flap Endonuclease 1 (FEN1) Reflects a Kinetic Bias against Long Flaps and Trinucleotide Repeat Sequences.

    Science.gov (United States)

    Tarantino, Mary E; Bilotti, Katharina; Huang, Ji; Delaney, Sarah

    2015-08-21

    Flap endonuclease 1 (FEN1) is a structure-specific nuclease responsible for removing 5'-flaps formed during Okazaki fragment maturation and long patch base excision repair. In this work, we use rapid quench flow techniques to examine the rates of 5'-flap removal on DNA substrates of varying length and sequence. Of particular interest are flaps containing trinucleotide repeats (TNR), which have been proposed to affect FEN1 activity and cause genetic instability. We report that FEN1 processes substrates containing flaps of 30 nucleotides or fewer at comparable single-turnover rates. However, for flaps longer than 30 nucleotides, FEN1 kinetically discriminates substrates based on flap length and flap sequence. In particular, FEN1 removes flaps containing TNR sequences at a rate slower than mixed sequence flaps of the same length. Furthermore, multiple-turnover kinetic analysis reveals that the rate-determining step of FEN1 switches as a function of flap length from product release to chemistry (or a step prior to chemistry). These results provide a kinetic perspective on the role of FEN1 in DNA replication and repair and contribute to our understanding of FEN1 in mediating genetic instability of TNR sequences. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

  16. Tubularized Penile-Flap Urethroplasty Using a Fasciocutaneous Random Pedicled Flap for Recurrent Anterior Urethral Stricture

    Directory of Open Access Journals (Sweden)

    Yong Jig Lee

    2012-05-01

    Full Text Available This report describes the use of a tubularized random flap for the curative treatment of recurrent anterior urethral stricture. Under the condition of pendulous lithotomy and suprapubic cystostomy, the urethral stricture was removed via a midline ventral penile incision followed by elevation of the flap and insertion of an 18-Fr catheter. Subcutaneous buried interrupted sutures were used to reapproximate the waterproof tubularized neourethra and to coapt with the neourethra and each stump of the urethra, first proximally and then distally. The defect of the penile shaft was covered by advancement of the surrounding scrotal flap. The indwelling catheter was maintained for 21 days. A 9 month postoperative cystoscopy showed no flap necrosis, no mechanical stricture, and no hair growth on the lumen of the neourethra. The patient showed no voiding discomfort 6 months after the operation. The advantages of this procedure are the lack of need for microsurgery, shortening of admission, the use of only spinal anesthesia (no general anesthesia, and a relatively short operative time. The tubularized unilateral penile fasciocutaneous flap should be considered an option for initial flap urethroplasty as a curative technique.

  17. Cellular prion protein is required for neuritogenesis: fine-tuning of multiple signaling pathways involved in focal adhesions and actin cytoskeleton dynamics

    Directory of Open Access Journals (Sweden)

    Alleaume-Butaux A

    2013-07-01

    Full Text Available Aurélie Alleaume-Butaux,1,2 Caroline Dakowski,1,2 Mathéa Pietri,1,2 Sophie Mouillet-Richard,1,2 Jean-Marie Launay,3,4 Odile Kellermann,1,2 Benoit Schneider1,2 1INSERM, UMR-S 747, 2Paris Descartes University, Sorbonne Paris Cité, UMR-S 747, 3Public Hospital of Paris, Department of Biochemistry, INSERM UMR-S 942, Lariboisière Hospital, Paris, France; 4Pharma Research Department, Hoffmann La Roche Ltd, Basel, Switzerland Abstract: Neuritogenesis is a dynamic phenomenon associated with neuronal differentiation that allows a rather spherical neuronal stem cell to develop dendrites and axon, a prerequisite for the integration and transmission of signals. The acquisition of neuronal polarity occurs in three steps: (1 neurite sprouting, which consists of the formation of buds emerging from the postmitotic neuronal soma; (2 neurite outgrowth, which represents the conversion of buds into neurites, their elongation and evolution into axon or dendrites; and (3 the stability and plasticity of neuronal polarity. In neuronal stem cells, remodeling and activation of focal adhesions (FAs associated with deep modifications of the actin cytoskeleton is a prerequisite for neurite sprouting and subsequent neurite outgrowth. A multiple set of growth factors and interactors located in the extracellular matrix and the plasma membrane orchestrate neuritogenesis by acting on intracellular signaling effectors, notably small G proteins such as RhoA, Rac, and Cdc42, which are involved in actin turnover and the dynamics of FAs. The cellular prion protein (PrPC, a glycosylphosphatidylinositol (GPI-anchored membrane protein mainly known for its role in a group of fatal neurodegenerative diseases, has emerged as a central player in neuritogenesis. Here, we review the contribution of PrPC to neuronal polarization and detail the current knowledge on the signaling pathways fine-tuned by PrPC to promote neurite sprouting, outgrowth, and maintenance. We emphasize that Pr

  18. Reconstruction of the Lower Extremity Using Free Flaps

    Directory of Open Access Journals (Sweden)

    Min Jo Kang

    2013-09-01

    Full Text Available Background The aim of lower-extremity reconstruction has focused on wound coverage andfunctional recovery. However, there are limitations in the use of a local flap in cases of extensivedefects of the lower-extremities. Therefore, free flap is a useful option in lower-extremityreconstruction.Methods We performed a retrospective review of 49 patients (52 cases who underwentlower-extremity reconstruction at our institution during a 10-year period. In these patients,we evaluated causes and sites of defects, types of flaps, recipient vessels, types of anastomosis,survival rate, and complications.Results There were 42 men and 10 women with a mean age of 32.7 years (range, 3-72years. The sites of defects included the dorsum of the foot (19, pretibial area (17, ankle(7, heel (5 and other sites (4. The types of free flap included latissimus dorsi muscle flap(10, scapular fascial flap (6, anterolateral thigh flap (6, and other flaps (30. There werefour cases of vascular complications, out of which two flaps survived after intervention. Theoverall survival of the flaps was 96.2% (50/52. There were 19 cases of other complications atrecipient sites such as partial graft loss (8, partial flap necrosis (6 and infection (5. However,these complications were not notable and were resolved with skin grafts.Conclusions The free flap is an effective method of lower-extremity reconstruction. Goodoutcomes can be achieved with complete debridement and the selection of appropriaterecipient vessels and flaps according to the recipient site.

  19. Free flap reconstruction for diabetic foot limb salvage.

    Science.gov (United States)

    Sato, Tomoya; Yana, Yuichiro; Ichioka, Shigeru

    2017-12-01

    Although free flap is gaining popularity for the reconstruction of diabetic foot ulcers, it is unclear whether free flap reconstruction increases the chances of postoperative independent ambulation. The aim of this study is to evaluate the relationship between free flap success and postoperative ambulation. This study reviewed 23 cases of free flap reconstruction for diabetic foot ulcers between January 2007 and March 2014. Free rectus abdominis, latissimus dorsi, and anterolateral thigh flaps were used in ten, eight, and five patients, respectively. A comparison was made between free flap success and postoperative independent ambulation using Fisher's exact test. Two patients developed congestive heart failure with fatal consequences within 14 days postoperatively, resulting in an in-hospital mortality rate of 8.7%. Five patients lost their flaps (21.7%). Of the 16 patients who had flap success, 12 achieved independent ambulation. Five patients with flap loss did not achieve independent ambulation, except one patient who underwent secondary flap reconstruction using a distally based sural flap. Fisher's exact test revealed that independent ambulation was associated with free flap success (p = 0.047). The present study indicates that free flap reconstruction may increase the possibility of independent ambulation for patients with extensive tissue defects due to diabetic ulcers. Intermediate limb salvage rates and independent ambulation rates were favourable in patients with successful reconstruction. The use of foot orthoses and a team approach with pedorthists were effective to prevent recurrence.

  20. Use if a soecuak sokubt ub reverse syrak artery flap to reduce venous congestion and flap necrosis

    International Nuclear Information System (INIS)

    Masood, T.; Ahmed, R.; Obaidullah, M.

    2016-01-01

    Background: Distally based sural fascio-cutaneous flap is a commonly performed plastic surgery procedure for the coverage of distal third of leg, ankle and foot defects. However congestion is the main complication of this flap which results into partial or complete loss of the flap. We devised a special splint to reduce this complication and retrospectively reviewed its effect on this complication between two groups. Methods: This retrospective study was carried out at Northwest General hospital between 1995 and 2012. Group-A included 30 patients who were managed without the splint between 1995 and 2005 and group B comprised of 35 patients were treated with the splint between 2006 and 2012. Complications like venous congestion, epidermolysis, and partial and complete flap failure were documented. Data were analyzed by SPSS.16.5 software. Chi- square test was used for data analysis. P value less than 0.05 was considered as the level of significance. Results: Total 65 patients were operated. Age of the patients ranged from 7 to 60 years. Road traffic accident and spoke wheel injury was the main cause of soft tissue loss in our patients. In group A 12 patients suffered from venous congestion. Out of 12, three patients had epidermolysis while partial flap necrosis occurred in 9 patients. Only 3 patients had venous congestion in group B. Two patients suffered from epidermolysis and one had partial flap necrosis. None of patient suffered from complete flap loss in both groups. Conclusion: Reverse sural artery flap continues to be a versatile flap for distal lower extremity reconstruction. By using a special splint to reduce pressure on the pedicle site as a modification, flap complication rate can be decreased significantly. (author)

  1. Non-Straub type actin from molluscan catch muscle

    Energy Technology Data Exchange (ETDEWEB)

    Shelud' ko, Nikolay S., E-mail: sheludko@stl.ru; Girich, Ulyana V.; Lazarev, Stanislav S.; Vyatchin, Ilya G.

    2016-05-27

    We have developed a method of obtaining natural actin from smooth muscles of the bivalves on the example of the Crenomytilus grayanus catch muscle. The muscles were previously rigorized to prevent a loss of thin filaments during homogenization and washings. Thin filaments were isolated with a low ionic strength solution in the presence of ATP and sodium pyrophosphate. Surface proteins of thin filaments-tropomyosin, troponin, calponin and some minor actin-binding proteins-were dissociated from actin filaments by increasing the ionic strength to 0.6 M KCL. Natural fibrillar actin obtained in that way depolymerizes easily in low ionic strength solutions commonly used for the extraction of Straub-type actin from acetone powder. Purification of natural actin was carried out by the polymerization–depolymerization cycle. The content of inactivated actin remaining in the supernatant is much less than at a similar purification of Straub-type actin. A comparative investigation was performed between the natural mussel actin and the Straub-type rabbit skeletal actin in terms of the key properties of actin: polymerization, activation of Mg-ATPase activity of myosin, and the electron-microscopic structure of actin polymers. -- Highlights: •We developed method of repolymerizable invertebrate smooth muscle actin obtaining. •Our method does not involve use of denaturating agents, which could modify proteins. •Viscosity and polymerization rate of actin, gained that way, is similar to Straub one. •Electron microscopy showed that repolymerized mussel actin is similar to Straub one. •Repolymerized mussel actin has greater ATPase activating capacity, than Straub actin.

  2. Use of the Anterolateral Thigh and Vertical Rectus Abdominis Musculocutaneous Flaps as Utility Flaps in Reconstructing Large Groin Defects

    Directory of Open Access Journals (Sweden)

    Edwin Jonathan Aslim

    2014-09-01

    Full Text Available BackgroundGroin dissections result in large wounds with exposed femoral vessels requiring soft tissue coverage, and the reconstructive options are diverse. In this study we reviewed our experience with the use of the pedicled anterolateral thigh and vertical rectus abdominis musculocutaneous flaps in the reconstruction of large groin wounds.MethodsGroin reconstructions performed over a period of 10 years were evaluated, with a mean follow up of two years. We included all cases with large or complex (involving perineum defects, which were reconstructed with the pedicled anterolateral thigh musculocutaneous or the vertical rectus abdominis musculocutaneous (VRAM flaps. Smaller wounds which were covered with skin grafts, locally based flaps and pedicled muscle flaps were excluded.ResultsTwenty-three reconstructions were performed for large or complex groin defects, utilising the anterolateral thigh (n=10 and the vertical rectus abdominis (n=13 pedicled musculocutaneous flaps. Femoral vein reconstruction with a prosthetic graft was required in one patient, and a combination flap (VRAM and gracilis muscle flap was performed in another. Satisfactory coverage was achieved in all cases without major complications. No free flaps were used in our series.ConclusionsThe anterolateral thigh and vertical rectus abdominis pedicled musculocutaneous flaps yielded consistent results with little morbidity in the reconstruction of large and complex groin defects. A combination of flaps can be used in cases requiring extensive cover.

  3. Identification of Flap Motion Parameters for Vibration Reduction in Helicopter Rotors with Multiple Active Trailing Edge Flaps

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    Uğbreve;ur Dalli

    2011-01-01

    Full Text Available An active control method utilizing the multiple trailing edge flap configuration for rotorcraft vibration suppression and blade loads control is presented. A comprehensive model for rotor blade with active trailing edge flaps is used to calculate the vibration characteristics, natural frequencies and mode shapes of any complex composite helicopter rotor blade. A computer program is developed to calculate the system response, rotor blade root forces and moments under aerodynamic forcing conditions. Rotor blade system response is calculated using the proposed solution method and the developed program depending on any structural and aerodynamic properties of rotor blades, structural properties of trailing edge flaps and properties of trailing edge flap actuator inputs. Rotor blade loads are determined first on a nominal rotor blade without multiple active trailing edge flaps and then the effects of the active flap motions on the existing rotor blade loads are investigated. Multiple active trailing edge flaps are controlled by using open loop controllers to identify the effects of the actuator signal output properties such as frequency, amplitude and phase on the system response. Effects of using multiple trailing edge flaps on controlling rotor blade vibrations are investigated and some design criteria are determined for the design of trailing edge flap controller that will provide actuator signal outputs to minimize the rotor blade root loads. It is calculated that using the developed active trailing edge rotor blade model, helicopter rotor blade vibrations can be reduced up to 36% of the nominal rotor blade vibrations.

  4. The actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations

    Science.gov (United States)

    Westendorf, Christian; Negrete, Jose, Jr.; Bae, Albert; Sandmann, Rabea; Bodenschatz, Eberhard; Beta, Carsten

    2013-03-01

    We report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. The averaged F-actin response of many cells to a short-time pulse of cAMP is reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. We systematically exposed a large number of cells to periodic pulse trains. The results indicate a resonance peak at periodic inputs of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the actin regulatory network. To quantitatively test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and Aip1. These served as markers of the F-actin disassembly process and thus allow us to estimate the delay time. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed experimentally. Financial support by the Max-Planck Society and the DFG (SFB 937).

  5. Flapping modes of three filaments placed side by side in a free stream

    Science.gov (United States)

    Tian, Fang-Bao; Luo, Haoxiang; Zhu, Luoding; Lu, Xi-Yun

    2010-11-01

    Flexible filaments flapping in a surrounding flow are useful models for understanding the flow-induced vibration and mimicking the schooling behavior of fish. In the present work, the coupled modes of three identical filaments in a side-by- side arrangement are studied using the linear stability analysis and also an immersed boundary--lattice Boltzmann method for low Reynolds numbers (Re on order of 100). The numerical simulations show that the system dynamics exhibits several patterns that depend on the spacing between the filaments. Among these patterns, three can be predicted by the linear analysis and have been reported before. These modes are: (1) the three filaments all flap in phase; (2) the two outer filaments are out of phase while the middle one is stable; (3) the two outer filaments are in phase while the middle one is out of phase. The simulations also identified two additional modes: (1) the outer two filaments are out of phase while the middle one flaps at a frequency reduced by half; (2) the outer two filaments are out of phase while the middle one flaps at a slightly different frequency. In addition to the vibratory modes, the drag force and the flapping amplitude are also computed, and the implication of the result will be discussed.

  6. Formation of vortex pairs with hinged rigid flaps at the nozzle exit

    Science.gov (United States)

    Das, Prashant; Govardhan, Raghuraman; Arakeri, Jaywant

    2013-11-01

    Biological flows related to aquatic propulsion using pulsed jets, or flow through the valves in a human heart, have received considerable attention in the last two decades. Both these flows are associated with starting jets that occur through biological tissue/membranes that are flexible. Motivated by these flows, we explore in the present work, the effect of passive flexibility of the nozzle exit on vortex generation from a starting jet. The starting jet is generated using a two-dimensional piston cylinder mechanism, the cross-section of the cylinder being rectangular with large aspect ratio. The fluid is pushed out of this cylinder or channel using a computer controlled piston. We introduce flexibility at the channel exit by hinging rigid flaps, which are initially parallel to the channel. The hinge used is such that it provides negligible stiffness or damping, thus allowing for the maximum opening of the flaps due to fluid forces. Using this system, we study both the flap kinematics and the vorticity dynamics downstream of the channel exit. Visualizations show large flap motions as the piston starts and this dramatically changes the vorticity distribution downstream of the flaps, with the formation of up to three different kinds of vortex pairs. This idealized configuration opens new opportunities to look at the effect of flexibility in such biological flows.

  7. Regulation of the actin cytoskeleton in Helicobacter pylori-induced migration and invasive growth of gastric epithelial cells

    Directory of Open Access Journals (Sweden)

    Rieder Gabriele

    2011-11-01

    Full Text Available Abstract Dynamic rearrangement of the actin cytoskeleton is a significant hallmark of Helicobacter pylori (H. pylori infected gastric epithelial cells leading to cell migration and invasive growth. Considering the cellular mechanisms, the type IV secretion system (T4SS and the effector protein cytotoxin-associated gene A (CagA of H. pylori are well-studied initiators of distinct signal transduction pathways in host cells targeting kinases, adaptor proteins, GTPases, actin binding and other proteins involved in the regulation of the actin lattice. In this review, we summarize recent findings of how H. pylori functionally interacts with the complex signaling network that controls the actin cytoskeleton of motile and invasive gastric epithelial cells.

  8. Energy management - The delayed flap approach

    Science.gov (United States)

    Bull, J. S.

    1976-01-01

    Flight test evaluation of a Delayed Flap approach procedure intended to provide reductions in noise and fuel consumption is underway using the NASA CV-990 test aircraft. Approach is initiated at a high airspeed (240 kt) and in a drag configuration that allows for low thrust. The aircraft is flown along the conventional ILS glide slope. A Fast/Slow message display signals the pilot when to extend approach flaps, landing gear, and land flaps. Implementation of the procedure in commercial service may require the addition of a DME navigation aid co-located with the ILS glide slope transmitter. The Delayed Flap approach saves 250 lb of fuel over the Reduced Flap approach, with a 95 EPNdB noise contour only 43% as large.

  9. Single molecules of the bacterial actin MreB undergo directed treadmilling motion in Caulobacter crescentus.

    Science.gov (United States)

    Kim, So Yeon; Gitai, Zemer; Kinkhabwala, Anika; Shapiro, Lucy; Moerner, W E

    2006-07-18

    The actin cytoskeleton represents a key regulator of multiple essential cellular functions in both eukaryotes and prokaryotes. In eukaryotes, these functions depend on the orchestrated dynamics of actin filament assembly and disassembly. However, the dynamics of the bacterial actin homolog MreB have yet to be examined in vivo. In this study, we observed the motion of single fluorescent MreB-yellow fluorescent protein fusions in living Caulobacter cells in a background of unlabeled MreB. With time-lapse imaging, polymerized MreB [filamentous MreB (fMreB)] and unpolymerized MreB [globular MreB (gMreB)] monomers could be distinguished: gMreB showed fast motion that was characteristic of Brownian diffusion, whereas the labeled molecules in fMreB displayed slow, directed motion. This directional movement of labeled MreB in the growing polymer provides an indication that, like actin, MreB monomers treadmill through MreB filaments by preferential polymerization at one filament end and depolymerization at the other filament end. From these data, we extract several characteristics of single MreB filaments, including that they are, on average, much shorter than the cell length and that the direction of their polarized assembly seems to be independent of the overall cellular polarity. Thus, MreB, like actin, exhibits treadmilling behavior in vivo, and the long MreB structures that have been visualized in multiple bacterial species seem to represent bundles of short filaments that lack a uniform global polarity.

  10. Effect of flexibility on flapping wing characteristics under forward flight

    International Nuclear Information System (INIS)

    Zhu, Jianyang; Jiang, Lin; Zhou, Chaoying; Wang, Chao

    2014-01-01

    Through two-dimensional numerical simulation and by solving the unsteady incompressible Navier–Stokes (NS) equations, coupled with the structural dynamic equation for the motion of the wing, the effect of flexibility on flapping wing characteristics during forward flight is systematically studied. The flapping wing is considered as a cantilever, which performs the translational and rotational motion at its leading edge, and the other part is passively deformed by the aerodynamic force. The frequency ratio ω* and mass ratio m* are defined and used to characterize the flexibility of the flapping wing. It has been found that an optimal range of the frequency ratio exists in which the flexible wing possesses both a larger propulsive efficiency and lifting efficiency than their rigid counterpart. Also, the flexible wing with the smaller mass ratio may be of benefit to generate thrust, while the larger mass ratio may be of benefit to generate lift. In addition, a stronger leading edge vortex and reattachment vortex are observed around the appropriate flexibility wing’s surface, which therefore leads to better aerodynamic characteristics. (paper)

  11. Bistable flapping of flexible flyers in oscillatory flow

    Science.gov (United States)

    Huang, Yangyang; Kanso, Eva

    2016-11-01

    Biological and bio-inspired flyers move by shape actuation. The direct control of shape variables for locomotory purposes is well studied. Less is known about indirect shape actuation via the fluid medium. Here, we consider a flexible Λ-flyer in oscillatory flow that is free to flap and rotate around its fixed apex. We study its motion in the context of the inviscid vortex sheet model. We first analyze symmetric flapping about the vertical axis of gravity. We find that there is a finite value of the flexibility that maximizes both the flapping amplitude and elastic energy storage. Our results show that rather than resonance, the flyer relies on fluidic effects to optimize these two quantities. We then perturb the flyer away from the vertical and analyze its stability. Four distinct types of rolling behavior are identified: mono-stable, bistable, bistable oscillatory rotations and chaotic dynamics. We categorize these types of behavior in terms of the flyer's and flow parameters. In particular, the transition from mono-stable to bistable behavior occurs at a constant value of the product of the flow amplitude and acceleration. This product can be interpreted as the ratio of fluidic drag to gravity, confirming the fluid role in this transition.

  12. All-Ceramic Body Flap Qualified for Space Flight on X38

    Science.gov (United States)

    Pfeiffer, H.; Peetz, K.

    2002-01-01

    Ceramic matrix composite (CMC) materials allow design of high-temperature resistant, light and robust structures. CMC materials with silicon-carbide matrix reinforced by carbon fibers (C/SiC) show constant strength and damage-tolerant behavior up to very high temperatures. CMC thermal protection systems and hot structures have been developed in Europe over many years. MAN Technologie developed the necessary technologies to create the technological basis for CMC structures for future, more economical and reusable launch vehicles. Within the German space technology program TETRA (Technologies for Future Space Transportation Systems) body flaps were developed for X-38 by MAN Technologie. Key technologies like high strength oxidation protected CMC materials, manufacturing processes for large and complex structures, advanced high temperature lubricant coating combinations for bearings, joining with ceramic fasteners, metal-to-ceramic interfaces as well as dynamic seals are required for hot structures like control surfaces for re-entry vehicles. Because of the high heat and mechanical loads of a lifting body together with the low mass requirements the body flaps for NASA's X-38 re-entry vehicle V-201were selected to demonstrate as a first flight maturity of a large and complex ceramic structure. The flaps are designed as an all-ceramic, load-carrying hot structure, which needs no heavy metallic primary structure and no additional thermal protection tiles and subsequently offers considerable mass and volume savings. The X-38 body flaps are conceived as a revolutionary step forward. The twin flaps, each with the size of 1.6 m x 1.4 m (5.25 ft x 4.6 ft) and the low weight of 68 kg (150 lb) are all made of C/SiC material to operate up to temperatures of 1800 C (3.270 F) in oxidizing atmosphere while they are deflectable under high mechanical loads up to 50 kN (11.260 lbf) at the same time. The flaps are deflected about the hinge axis on two ceramic bearings and moved by an

  13. Reconstruction of the Lower Extremity Using Free Flaps

    Directory of Open Access Journals (Sweden)

    Min Jo Kang

    2013-09-01

    Full Text Available BackgroundThe aim of lower-extremity reconstruction has focused on wound coverage and functional recovery. However, there are limitations in the use of a local flap in cases of extensive defects of the lower-extremities. Therefore, free flap is a useful option in lower-extremity reconstruction.MethodsWe performed a retrospective review of 49 patients (52 cases who underwent lower-extremity reconstruction at our institution during a 10-year period. In these patients, we evaluated causes and sites of defects, types of flaps, recipient vessels, types of anastomosis, survival rate, and complications.ResultsThere were 42 men and 10 women with a mean age of 32.7 years (range, 3-72 years. The sites of defects included the dorsum of the foot (19, pretibial area (17, ankle (7, heel (5 and other sites (4. The types of free flap included latissimus dorsi muscle flap (10, scapular fascial flap (6, anterolateral thigh flap (6, and other flaps (30. There were four cases of vascular complications, out of which two flaps survived after intervention. The overall survival of the flaps was 96.2% (50/52. There were 19 cases of other complications at recipient sites such as partial graft loss (8, partial flap necrosis (6 and infection (5. However, these complications were not notable and were resolved with skin grafts.ConclusionsThe free flap is an effective method of lower-extremity reconstruction. Good outcomes can be achieved with complete debridement and the selection of appropriate recipient vessels and flaps according to the recipient site.

  14. [COMPARISON OF REPAIR EFFECT BETWEEN CHIMERIC ANTEROLATERAL THIGH FLAP AND SERIES-WOUND FLAPS FOR DEFECT AFTER RESECTION OF ORAL AND MAXILLOFACIAL CANCER].

    Science.gov (United States)

    Yang, Heping; Zhang, Hongwu; Chen, Haidi; Yang, Shuxiong; Wang, Jun; Hu, Dawang

    2016-04-01

    To compare the effectiveness of complex defects repair between using chimeric anterolateral thigh flap and series-wound flaps after resection of oral and maxillofacial cancer. After resection of oral and maxillofacial cancer, defect was repaired with chimeric anterolateral thigh flap in 39 patients between January 2011 and July 2014 (chimeric anterolateral thigh flap group); and defect was repaired with series-wound flaps in 35 patients between January 2009 and December 2010 (series-wound flaps group). There was no significant difference in gender, age, duration of disease, tumor type, tumor staging, defect location, and defect area between 2 groups (P > 0.05). The operation time, flap harvesting and microvascular anastomosis time, stomach tube extraction time, and oral feeding time were recorded and compared between 2 groups, and postoperative complications were observed; the effectiveness was evaluated according to clinical efficacy evaluation table of bone and soft tissue defects reconstruction surgery in oral and maxillofacial region. Vascular crisis occurred in 2 cases of chimeric anterolateral thigh flap group, and 4 cases of series-wound flaps group. Partial necrosis appeared at distal end of a series-wound flaps, and oral fistula and infection developed in 3 series-wound flaps. The other flaps and the grafted skin at donor site survived; wounds at recipient site healed by first intention. The operation time, stomach tube extraction time, and oral feeding time of chimeric anterolateral thigh flap group were significantly shorter than those of series-wound flaps group (P oral closure function, chew, language performance, and swallowing scores of the chimeric anterolateral thigh-flap group were significantly better than those of the series-wound flaps group (P oral cavity holding water test, and occlusion scores between the 2 groups (P > 0.05). Using chimeric anterolateral thigh flap for defect repair after resection of oral and maxillofacial cancer can

  15. Innervated boomerang flap for finger pulp reconstruction.

    Science.gov (United States)

    Chen, Shao-Liang; Chiou, Tai-Fung

    2007-11-01

    The boomerang flap originates from the dorsolateral aspect of the proximal phalanx of an adjacent digit and is supplied by the retrograde blood flow through the vascular arcades between the dorsal and palmar digital arteries. To provide sensation of the boomerang flap for finger pulp reconstruction, the dorsal sensory branch of the proper digital nerve and the superficial sensory branch of the corresponding radial or ulnar nerve are included within the skin flap. After transfer of the flap to the injured site, epineural neurorrhaphies are done between the digital nerves of the pulp and the sensory branches of the flap. We used this sensory flap in five patients, with more than 1 year follow-up, and all patients achieved measurable two-points discrimination. The boomerang flap not only preserves the proper palmar digital artery but also provides an extended and innervated skin paddle. It seems to be an alternative choice for one-stage reconstruction of major pulp defect.

  16. Reconstruction of Facial Defect Using Deltopectoral Flap.

    Science.gov (United States)

    Aldelaimi, Tahrir N; Khalil, Afrah A

    2015-11-01

    Reconstruction of the head and neck is a challenge for otolarygology surgeons, maxillofacial surgeons as well as plastic surgeons. Defects caused by the resection and/or trauma should be closed with flaps which match in color, texture and hair bearing characteristics with the face. Deltopectoral flap is a one such flap from chest and neck skin mainly used to cover the facial defects. This study report a patient presenting with tragic Road Traffic Accident (RTA) admitted to maxillofacial surgery department at Ramadi Teaching Hospital, Anbar province, Iraq. An incision, medially based, was done and deltopectoral fascio-cutaneous flap was used for surgical exposure and closure of defects after RTA. There was no major complication. Good aesthetic and functional results were achieved. Deltopectoral flap is an excellent alternative for the reconstruction of head and neck. Harvesting and application of the flap is rapid and safe. Only a single incision is sufficient for dissection and flap elevation.

  17. Filament formation of the Escherichia coli actin-related protein, MreB, in fission yeast.

    Science.gov (United States)

    Srinivasan, Ramanujam; Mishra, Mithilesh; Murata-Hori, Maki; Balasubramanian, Mohan K

    2007-02-06

    Proteins structurally related to eukaryotic actins have recently been identified in several prokaryotic organisms. These actin-like proteins (MreB and ParM) and the deviant Walker A ATPase (SopA) play a key role in DNA segregation and assemble into polymers in vitro and in vivo. MreB also plays a role in cellular morphogenesis. Whereas the dynamic properties of eukaryotic actins have been extensively characterized, those of bacterial actins are only beginning to emerge. We have established the fission yeast Schizosaccharomyces pombe as a cellular model for the functional analysis of the Escherichia coli actin-related protein MreB. We show that MreB organizes into linear bundles that grow in a symmetrically bidirectional manner at 0.46 +/- 0.03 microm/min, with new monomers and/or oligomers being added along the entire length of the bundle. Organization of linear arrays was dependent on the ATPase activity of MreB, and their alignment along the cellular long axis was achieved by sliding along the cortex of the cylindrical part of the cell. The cell ends appeared to provide a physical barrier for bundle elongation. These experiments provide new insights into the mechanism of assembly and organization of the bacterial actin cytoskeleton.

  18. Refining the intrinsic chimera flap: a review.

    Science.gov (United States)

    Agarwal, Jayant P; Agarwal, Shailesh; Adler, Neta; Gottlieb, Lawrence J

    2009-10-01

    Reconstruction of complex tissue deficiencies in which each missing component is in a different spatial relationship to each other can be particularly challenging, especially in patients with limited recipient vessels. The chimera flap design is uniquely suited to reconstruct these deformities. Chimera flaps have been previously defined in many ways with 2 main categories: prefabricated or intrinsic. Herein we attempt to clarify the definition of a true intrinsic chimeric flap and provide examples of how these constructs provide a method for reconstruction of complex defects. The versatility of the intrinsic chimera flap and its procurement from 7 different vascular systems is described. A clarification of the definition of a true intrinsic chimera flap is described. In addition, construction of flaps from the lateral femoral circumflex, deep circumflex iliac, inferior gluteal, peroneal, subscapular, thoracodorsal, and radial arterial systems is described to showcase the versatility of these chimera flaps. A true intrinsic chimera flap must consist of more than a single tissue type. Each of the tissue components receives its blood flow from separate vascular branches or perforators that are connected to a single vascular source. These vascular branches must be of appropriate length to allow for insetting with 3-dimensional spatial freedom. There are a multitude of sites from which true intrinsic chimera flaps may be harvested.

  19. The role of postoperative hematoma on free flap compromise.

    Science.gov (United States)

    Ahmad, Faisal I; Gerecci, Deniz; Gonzalez, Javier D; Peck, Jessica J; Wax, Mark K

    2015-08-01

    Hematomas may develop in the postoperative setting after free tissue transfer. When hematomas occur, they can exert pressure on surrounding tissues. Their effect on the vascular pedicle of a free flap is unknown. We describe our incidence of hematoma in free flaps and outcomes when the flap is compromised. Retrospective chart review of 1,883 free flaps performed between July 1998 and June 2014 at a tertiary referral center. Patients with free flap compromise due to hematoma were identified. Etiology, demographic data, and outcomes were evaluated. Eighty-eight (4.7%) patients developed hematomas. Twenty (22.7%) of those had flap compromise. Twelve compromises (60%) showed evidence of pedicle thrombosis. The salvage rate was 75% versus 54% in 79 flaps with compromise from other causes (P = .12). Mean time to detection of the hematoma was 35.3 hours in salvaged flaps compared to 91.6 hours in unsalvageable flaps (P = .057). Time to operating room (OR) from detection was 2.8 hours in salvageable flaps compared to 12.4 hours in nonsalvageable flaps (P = .053). The salvage rate for flaps that returned to the OR in hematomas developed rarely. When they did, 23% went on to develop flap compromise. Prompt recognition and re-exploration allowed for a high salvage rate. Vessel thrombosis predicted inability to salvage the flap. 4 © 2015 The American Laryngological, Rhinological and Otological Society, Inc.

  20. Achieving bioinspired flapping wing hovering flight solutions on Mars via wing scaling.

    Science.gov (United States)

    Bluman, James E; Pohly, Jeremy; Sridhar, Madhu; Kang, Chang-Kwon; Landrum, David Brian; Fahimi, Farbod; Aono, Hikaru

    2018-05-29

    Achieving atmospheric flight on Mars is challenging due to the low density of the Martian atmosphere. Aerodynamic forces are proportional to the atmospheric density, which limits the use of conventional aircraft designs on Mars. Here, we show using numerical simulations that a flapping wing robot can fly on Mars via bioinspired dynamic scaling. Trimmed, hovering flight is possible in a simulated Martian environment when dynamic similarity with insects on earth is achieved by preserving the relevant dimensionless parameters while scaling up the wings three to four times its normal size. The analysis is performed using a well-validated two-dimensional Navier-Stokes equation solver, coupled to a three-dimensional flight dynamics model to simulate free flight. The majority of power required is due to the inertia of the wing because of the ultra-low density. The inertial flap power can be substantially reduced through the use of a torsional spring. The minimum total power consumption is 188 W/kg when the torsional spring is driven at its natural frequency. © 2018 IOP Publishing Ltd.

  1. Actin depolymerization enhances adipogenic differentiation in human stromal stem cells.

    Science.gov (United States)

    Chen, Li; Hu, Huimin; Qiu, Weimin; Shi, Kaikai; Kassem, Moustapha

    2018-05-01

    Human stromal stem cells (hMSCs) differentiate into adipocytes that play a role in skeletal tissue homeostasis and whole body energy metabolism. During adipocyte differentiation, hMSCs exhibit significant changes in cell morphology suggesting changes in cytoskeletal organization. Here, we examined the effect of direct modulation of actin microfilament dynamics on adipocyte differentiation. Stabilizing actin filaments in hMSCs by siRNA-mediated knock down of the two main actin depolymerizing factors (ADFs): Cofilin 1 (CFL1) and Destrin (DSTN) or treating the cells by Phalloidin reduced adipocyte differentiation as evidenced by decreased number of mature adipocytes and decreased adipocyte specific gene expression (ADIPOQ, LPL, PPARG, FABP4). In contrast, disruption of actin cytoskeleton by Cytochalasin D enhanced adipocyte differentiation. Follow up studies revealed that the effects of CFL1 on adipocyte differentiation depended on the activity of LIM domain kinase 1 (LIMK1) which is the major upstream kinase of CFL1. Inhibiting LIMK by its specific chemical inhibitor LIMKi inhibited the phosphorylation of CFL1 and actin polymerization, and enhanced the adipocyte differentiation. Moreover, treating hMSCs by Cytochalasin D inhibited ERK and Smad2 signaling and this was associated with enhanced adipocyte differentiation. On the other hand, Phalloidin enhanced ERK and Smad2 signaling, but inhibited adipocyte differentiation which was rescued by ERK specific chemical inhibitor U0126. Our data provide a link between restructuring of hMSCs cytoskeleton and hMSCs lineage commitment and differentiation. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. An innovative method of planning and displaying flap volume in DIEP flap breast reconstructions

    NARCIS (Netherlands)

    Hummelink, S.L.; Verhulst, A.C.; Maal, T.J.J.; Hoogeveen, Y.L.; Schultze Kool, L.J.; Ulrich, D.J.O.

    2017-01-01

    BACKGROUND: Determining the ideal volume of the harvested flap to achieve symmetry in deep inferior epigastric artery perforator (DIEP) flap breast reconstructions is complex. With preoperative imaging techniques such as 3D stereophotogrammetry and computed tomography angiography (CTA) available

  3. Elbow Reconstruction Using Island Flap for Burn Patients

    Directory of Open Access Journals (Sweden)

    Gi Yeun Hur

    2012-11-01

    Full Text Available BackgroundDeep burns of the elbow lead to soft tissue necrosis and infection, with exposure of deep structures. Adequate wound coverage of this area requires thin, pliable, and durable tissue, while optimal functional recovery requires early coverage and functional rehabilitation. We have found 3 types of island flaps that provide reliable coverage for the elbow.MethodsA retrospective study was performed on all patients who underwent flap coverage of an elbow defect at our hospital. The patients' data including age, sex, cause of injury, wound dimensions, timing of flap coverage, postoperative elbow motion, and complications were investigated.ResultsBetween 2001 and 2012, 16 patients were treated at our hospital. The mean age was 53.3 years. Three kinds of flaps were performed: 9 latissimus dorsi flaps, 4 lateral arm flaps, and 4 radial forearm flaps. The average defect size was 183.5 cm2 (range, 28 to 670 cm2. Wound coverage was performed at mean duration of 45.9 days (range, 14 to 91 days. The mean postoperative active elbow flexion was 98° (range, 85° to 115°. Partial flap failure occurred in 1 latissimus dorsi flap. Minor complications included partial flap loss (11.8%, hematoma (23.5%, seroma (35.3%, and wound infection (5.9%.ConclusionsFlap selection for elbow reconstruction is determined by the defect size and the extent of the adjacent tissue injury. Elbow reconstruction using an island flap is a single-staged, reliable, and relatively simple procedure that permits initiation of early rehabilitation, thereby improving a patient's functional outcome.

  4. Aerodynamic response of an airfoil section undergoing pitch motion and trailing edge flap deflection: a comparison of simulation methods

    DEFF Research Database (Denmark)

    Bergami, Leonardo; Riziotis, Vasilis A.; Gaunaa, Mac

    2015-01-01

    The study presents and compares aerodynamic simulations for an airfoil section with an adaptive trailing edge flap, which deflects following a smooth deformation shape. The simulations are carried out with three substantially different methods: a Reynolds-averaged Navier–Stokes solver, a viscous–inviscid...... to separated conditions and accounting for the effects of flap deflection; the steady results from the Navier–Stokes solver and the viscous–inviscid interaction method are used as input data for the simpler dynamic stall model. The paper characterizes then the dynamics of the unsteady forces and moments...

  5. Retention of a reconstructed nipple using a C-V flap with different layer thicknesses in the C-flap.

    Science.gov (United States)

    Sowa, Yoshihiro; Itsukage, Sizu; Sakaguchi, Kouichi; Taguchi, Tetsuya; Numajiri, Toshiaki

    2018-04-01

    The C-V flap for nipple reconstruction is now one of standard surgical techniques. But decreased projection is still a problem. In recent years, it has been suggested that projection can be more easily maintained when raising of the C-flap is performed with a split thickness dermis. In this study, we examined whether decrease of projection can be prevented by raising of a C-flap with a split dermis rather than with full dermis. A total of 49 consecutive patients who underwent reconstruction of a nipple using the C-V flap technique were enrolled. The patients included 22 who underwent surgery using a C-flap with a full thickness dermis (Group F), and 27 who underwent surgery with raising of a flap with a split thickness dermis (Group S). The size of the reconstructed nipple was measured at 2 weeks, 6 months and 1 year postoperatively for comparison between Groups F and S. Partial necrosis of the C-flap end occurred in 4 subjects in only Group S. The decrease in projection after 1 year postoperatively in Group S was significantly lower than that in Group F. In contrast, the teat base size in Group F tended to be greater than that in Group S, suggesting a tendency for an expanded base using a flap with a full dermis. Our results indicated that it is recommended to use a C-flap with a split dermis for cases with high projection of the nipple on the contralateral side.

  6. Parasacral Perforator Flaps for Reconstruction of Sacral Pressure Sores.

    Science.gov (United States)

    Lin, Chin-Ta; Chen, Shih-Yi; Chen, Shyi-Gen; Tzeng, Yuan-Sheng; Chang, Shun-Cheng

    2015-07-01

    Despite advances in reconstruction techniques, pressure sores continue to present a challenge to the plastic surgeon. The parasacral perforator flap is a reliable flap that preserves the entire contralateral side as a future donor site. On the ipsilateral side, the gluteal muscle itself is preserved and all flaps based on the inferior gluteal artery are still possible. We present our experience of using parasacral perforator flaps in reconstructing sacral defects. Between August 2004 and January 2013, 19 patients with sacral defects were included in this study. All the patients had undergone surgical reconstruction of sacral defects with a parasacral perforator flap. The patients' sex, age, cause of sacral defect, flap size, flap type, numbers of perforators used, rotation angle, postoperative complications, and hospital stay were recorded. There were 19 parasacral perforator flaps in this series. All flaps survived uneventfully except for 1 parasacral perforator flap, which failed because of methicillin-resistant Staphylococcus aureus infection. The overall flap survival rate was 95% (18/19). The mean follow-up period was 17.3 months (range, 2-24 months). The average length of hospital stay was 20.7 days (range, 9-48 days). No flap surgery-related mortality was found. Also, there was no recurrence of sacral pressure sores or infected pilonidal cysts during the follow-up period. Perforator-based flaps have become popular in modern reconstructive surgery because of low donor-site morbidity and good preservation of muscle. Parasacral perforator flaps are durable and reliable in reconstructing sacral defects. We recommend the parasacral perforator flap as a good choice for reconstructing sacral defects.

  7. Boolean gates on actin filaments

    International Nuclear Information System (INIS)

    Siccardi, Stefano; Tuszynski, Jack A.; Adamatzky, Andrew

    2016-01-01

    Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications. - Highlights: • We simulate interaction between voltage pulses using on actin filaments. • We use a coupled nonlinear transmission line model. • We design Boolean logical gates via interactions between the voltage pulses. • We construct one-bit half-adder with interacting voltage pulses.

  8. Boolean gates on actin filaments

    Energy Technology Data Exchange (ETDEWEB)

    Siccardi, Stefano, E-mail: ssiccardi@2ssas.it [The Unconventional Computing Centre, University of the West of England, Bristol (United Kingdom); Tuszynski, Jack A., E-mail: jackt@ualberta.ca [Department of Oncology, University of Alberta, Edmonton, Alberta (Canada); Adamatzky, Andrew, E-mail: andrew.adamatzky@uwe.ac.uk [The Unconventional Computing Centre, University of the West of England, Bristol (United Kingdom)

    2016-01-08

    Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications. - Highlights: • We simulate interaction between voltage pulses using on actin filaments. • We use a coupled nonlinear transmission line model. • We design Boolean logical gates via interactions between the voltage pulses. • We construct one-bit half-adder with interacting voltage pulses.

  9. Modified cup flap for volar oblique fingertip amputations

    Directory of Open Access Journals (Sweden)

    Ahmadli, A.

    2016-02-01

    Full Text Available We describe a modified volar “V-Y cup” flap for volar fingertip defects that do not exceed more than half of the distal phalanx for better aesthetic and functional outcome. In seven cases out of eight, the flap was elevated with a subdermal pedicle, whereas in one case, the flap was elevated as an island on the bilateral neurovascular bundle. The fingertips have been evaluated for sensibility using standard tests, hook nail deformity and patient satisfaction. Seven flaps have survived completely. The flap with skeletonized bilateral digital neurovascular bundle has shown signs of venous insufficiency on the 5 postoperative day with consecutive necrosis. Suturing the distal edges of the flap in a “cupping” fashion provided a normal pulp contour. The modified flap can be used for defects as mentioned above. Subdermally dissected pedicle-based flap is safe and easy to elevate. The aesthetic and functional outcomes have been reported to be satisfactory.

  10. Flapping Wings of an Inclined Stroke Angle: Experiments and Reduced-Order Models in Dual Aerial/Aquatic Flight

    Science.gov (United States)

    Izraelevitz, Jacob; Triantafyllou, Michael

    2016-11-01

    Flapping wings in nature demonstrate a large force actuation envelope, with capabilities beyond the limits of static airfoil section coefficients. Puffins, guillemots, and other auks particularly showcase this mechanism, as they are able to both generate both enough thrust to swim and lift to fly, using the same wing, by changing the wing motion trajectory. The wing trajectory is therefore an additional design criterion to be optimized along with traditional aircraft parameters, and could possibly enable dual aerial/aquatic flight. We showcase finite aspect-ratio flapping wing experiments, dynamic similarity arguments, and reduced-order models for predicting the performance of flapping wings that carry out complex motion trajectories.

  11. Design and evaluation of Actichip, a thematic microarray for the study of the actin cytoskeleton

    Science.gov (United States)

    Muller, Jean; Mehlen, André; Vetter, Guillaume; Yatskou, Mikalai; Muller, Arnaud; Chalmel, Frédéric; Poch, Olivier; Friederich, Evelyne; Vallar, Laurent

    2007-01-01

    Background The actin cytoskeleton plays a crucial role in supporting and regulating numerous cellular processes. Mutations or alterations in the expression levels affecting the actin cytoskeleton system or related regulatory mechanisms are often associated with complex diseases such as cancer. Understanding how qualitative or quantitative changes in expression of the set of actin cytoskeleton genes are integrated to control actin dynamics and organisation is currently a challenge and should provide insights in identifying potential targets for drug discovery. Here we report the development of a dedicated microarray, the Actichip, containing 60-mer oligonucleotide probes for 327 genes selected for transcriptome analysis of the human actin cytoskeleton. Results Genomic data and sequence analysis features were retrieved from GenBank and stored in an integrative database called Actinome. From these data, probes were designed using a home-made program (CADO4MI) allowing sequence refinement and improved probe specificity by combining the complementary information recovered from the UniGene and RefSeq databases. Actichip performance was analysed by hybridisation with RNAs extracted from epithelial MCF-7 cells and human skeletal muscle. Using thoroughly standardised procedures, we obtained microarray images with excellent quality resulting in high data reproducibility. Actichip displayed a large dynamic range extending over three logs with a limit of sensitivity between one and ten copies of transcript per cell. The array allowed accurate detection of small changes in gene expression and reliable classification of samples based on the expression profiles of tissue-specific genes. When compared to two other oligonucleotide microarray platforms, Actichip showed similar sensitivity and concordant expression ratios. Moreover, Actichip was able to discriminate the highly similar actin isoforms whereas the two other platforms did not. Conclusion Our data demonstrate that

  12. "The Practical Perforator Flap": the sural artery flap for lower extremity soft tissue reconstruction in wounds of war

    NARCIS (Netherlands)

    O.J.F. van Waes (Oscar); J.A. Halm (Jens); J. Vermeulen (Jefrey); S. Ashford (Sofie)

    2012-01-01

    textabstractBackground: Sural artery perforator flaps have been described for use as both local flaps and in free tissue transfer. We present the use of this flap for compound soft tissue defects of the lower limb in civilian casualties of armed conflict in Afghanistan. Methods/results: Detailed

  13. An F-actin-depleted zone is present at the hyphal tip of invasive hyphae of Neurospora crassa.

    Science.gov (United States)

    Suei, S; Garrill, A

    2008-01-01

    The distribution of filamentous actin (F-actin) in invasive and noninvasive hyphae of the ascomycete Neurospora crassa was investigated. Eighty six percent of noninvasive hyphae had F-actin in the tip region compared to only 9% of invasive hyphae. The remaining 91% of the invasive hyphae had no obvious tip high concentration of F-actin staining; instead they had an F-actin-depleted zone in this region, although some F-actin, possibly associated with the Spitzenkörper, remained at the tip. The size of the F-actin-depleted zone in invasive hyphae increased with an increase in agar concentration. The membrane stain FM 4-64 reveals a slightly larger accumulation of vesicles at the tips of invasive hyphae relative to noninvasive hyphae, although this difference is unlikely to be sufficient to account for the exclusion of F-actin from the depleted zone. Antibodies raised against the actin filament-severing protein cofilin from both yeast and human cells localize to the tips of invasive hyphae. The human cofilin antibody shows a more random distribution in noninvasive hyphae locating primarily at the hyphal periphery but with some diffuse cytoplasmic staining. This antibody also identifies a single band at 21 kDa in immunoblots of whole hyphal fractions. These data suggest that a protein with epitopic similarity to cofilin may function in F-actin dynamics that underlie invasive growth. The F-actin-depleted zone may play a role in the regulation of tip yielding to turgor pressure, thus increasing the protrusive force necessary for invasive growth.

  14. Bulkiness or aromatic nature of tyrosine-143 of actin is important for the weak binding between F-actin and myosin-ADP-phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Gomibuchi, Yuki [Graduate School of Science and Engineering, Teikyo University, Toyosatodai 1-1, Utsunomiya 320-8551 (Japan); Uyeda, Taro Q.P. [Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, AIST Tsukuba Central 4, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Wakabayashi, Takeyuki, E-mail: tw007@nasu.bio.teikyo-u.ac.jp [Graduate School of Science and Engineering, Teikyo University, Toyosatodai 1-1, Utsunomiya 320-8551 (Japan); Department of Judo Therapy, Faculty of Medical Technology, Teikyo University, Toyosatodai 1-1, Utsunomiya 320-8551 (Japan)

    2013-11-29

    Highlights: •The effect of mutation of Tyr143 that becomes more exposed on assembly was examined. •Mutation of tyrosine-143 of Dictyostelium actin changed actin polymerizability. •The bulkiness or aromatic nature of Tyr143 is important for the weak binding. •The weak interaction between myosin and actin strengthened by Tyr143Trp mutation. -- Abstract: Actin filaments (F-actin) interact with myosin and activate its ATPase to support force generation. By comparing crystal structures of G-actin and the quasi-atomic model of F-actin based on high-resolution cryo-electron microscopy, the tyrosine-143 was found to be exposed more than 60 Å{sup 2} to the solvent in F-actin. Because tyrosine-143 flanks the hydrophobic cleft near the hydrophobic helix that binds to myosin, the mutant actins, of which the tyrosine-143 was replaced with tryptophan, phenylalanine, or isoleucine, were generated using the Dictyostelium expression system. It polymerized significantly poorly when induced by NaCl, but almost normally by KCl. In the presence of phalloidin and KCl, the extents of the polymerization of all the mutant actins were comparable to that of the wild-type actin so that the actin-activated myosin ATPase activity could be reliably compared. The affinity of skeletal heavy meromyosin to F-actin and the maximum ATPase activity (V{sub max}) were estimated by a double reciprocal plot. The Tyr143Trp-actin showed the higher affinity (smaller K{sub app}) than that of the wild-type actin, with the V{sub max} being almost unchanged. The K{sub app} and V{sub max} of the Tyr143Phe-actin were similar to those of the wild-type actin. However, the activation by Tyr143Ile-actin was much smaller than the wild-type actin and the accurate determination of K{sub app} was difficult. Comparison of the myosin ATPase activated by the various mutant actins at the same concentration of F-actin showed that the extent of activation correlates well with the solvent-accessible surface areas (ASA

  15. Gust alleviation for a STOL transport by using elevator, spoilers, and flaps

    Science.gov (United States)

    Lallman, F. J.

    1974-01-01

    Control laws were developed to investigate methods of alleviating the response of a STOL transport to gusty air. The transport considered in the study had triple-slotted, externally blown jet flaps and a large T-tail. The control devices used were the elevator, spoilers, and flaps. A hybrid computing system was used to simulate linearized longitudinal dynamics of the aircraft and to implement a conjugate gradient optimal search algorithm. The aircraft was simulated in the low-speed approach condition only. Feedback control matrices were found which minimized the average of a quadratic functional involving passenger compartment accelerations, pitch angle and rate, flight path angle and speed variations. The optimization was performed for artificially designed gust inputs in the form of predetermined rectangular waveforms. Results were obtained for elevator, spoilers, and flaps acting singly and in combination. Additional results were obtained for unit sinusoidal gust inputs by using the gain matrices computed for the artificial test gusts. Various sensor configurations were also investigated.

  16. [Pedicled versus free TRAM flap for breast reconstruction].

    Science.gov (United States)

    Galla, T J; Lukas, B; Feller, A M

    1999-03-01

    In breast reconstruction, the free TRAM-flap offers many advantages over the pedicled TRAM-flap. Due to its superior perfusion, the free flap rarely develops necrosis. Shaping of the flap is easier due to the lack of the thick muscle pedicle. Because the rectus muscle is spared, there is minimal donor site morbidity. However, the necessary microvascular anastomoses reduced the acceptance of the free TRAM-flap. During a 13-months period, 51 breast reconstructions were performed in 41 patients, 31 unilateral and ten bilateral. 45 flaps served for delayed reconstruction and six flaps for immediate reconstruction. The operations were performed by two teams working simultaneously. The average operating time was 3.9 hours for unilateral and 6.9 hours for bilateral delayed reconstruction. For immediate reconstruction, 6.2 and 6.3 hours were required for uni- and bilateral procedures, respectively. In 38 flaps, the thoracodorsal vessels served as recipient vessels; 13 flaps were anastomosed to the internal mammary artery and vein. Postoperative complications were observed in 13 patients. Three vessel anastomoses had to be revised. In one flap, a partial necrosis occurred; in two flaps hematoma evacuation was necessary. Two patients suffered from fat necroses at the abdomen and one umbilicus was lost. Skin irritations and seromas at the abdomen occurred in five patients. Pulmonary embolism was diagnosed in one patient three weeks postoperatively. Abdominal hernias or bulging in the epigastric area were not observed up to 15 months after reconstruction. These results reveal a low complication rate for breast reconstruction with the free TRAM-flap. The advantages of this technique as compared to the pedicled technique are discussed.

  17. Release of hand burn contracture: comparing the ALT perforator flap with the gracilis free flap with split skin graft.

    Science.gov (United States)

    Misani, M; Zirak, C; Hau, Lê Thua Trung; De Mey, A; Boeckx, W

    2013-08-01

    The use of microsurgery in the management of burn sequelae is not a new idea. According to the properties of various types of free flaps different goals can be achieved or various additional procedures have to be combined. We report the comparison of two different free flaps on a single patient for reconstruction of both upper extremities for burn sequelae. A 1-year-old child sustained severe burns on both hands, arms and thorax and was initially only treated conservatively. This resulted in severe contractures. At the age of 4-years a free gracilis flap was selected for reconstruction of his left hand and a free anterolateral thigh flap for the right hand. We noticed a better functional and esthetic result for the gracilis flap associated with a shorter operative time and a minor donor site morbidity. The intraoperative technique and time, postoperative complications, functional and esthetic results and donor site morbidities were studied in the two types of flaps chosen. A review of literature was also performed. Our experience reported a better success of the gracilis muscle flap covered with a split skin graft compared to the anterolateral thigh flap in the reconstruction of hand function after severe burn sequelae. Copyright © 2013 Elsevier Ltd and ISBI. All rights reserved.

  18. Enhancement of radiosensitivity in H1299 cancer cells by actin-associated protein cofilin

    International Nuclear Information System (INIS)

    Lee, Y.-J.; Sheu, T.-J.; Keng, Peter C.

    2005-01-01

    Cofilin is an actin-associated protein that belongs to the actin depolymerization factor/cofilin family and is important for regulation of actin dynamics. Cofilin can import actin monomers into the nucleus under certain stress conditions, however the biological effects of nuclear transport are unclear. In this study, we found that over-expression of cofilin led to increased radiation sensitivity in human non-small lung cancer H1299 cells. Cell survival as determined by colony forming assay showed that cells over-expressing cofilin were more sensitive to ionizing radiation (IR) than normal cells. To determine whether the DNA repair capacity was altered in cofilin over-expressing cells, comet assays were performed on irradiated cells. Repair of DNA damage caused by ionizing radiation was detected in cofilin over-expressing cells after 24 h of recovery. Consistent with this observation, the key components for repair of DNA double-strand breaks, including Rad51, Rad52, and Ku70/Ku80, were down-regulated in cofilin over-expressing cells after IR exposure. These findings suggest that cofilin can influence radiosensitivity by altering DNA repair capacity

  19. Cations Stiffen Actin Filaments by Adhering a Key Structural Element to Adjacent Subunits

    Science.gov (United States)

    2016-01-01

    Ions regulate the assembly and mechanical properties of actin filaments. Recent work using structural bioinformatics and site-specific mutagenesis favors the existence of two discrete and specific divalent cation binding sites on actin filaments, positioned in the long axis between actin subunits. Cation binding at one site drives polymerization, while the other modulates filament stiffness and plays a role in filament severing by the regulatory protein, cofilin. Existing structural methods have not been able to resolve filament-associated cations, and so in this work we turn to molecular dynamics simulations to suggest a candidate binding pocket geometry for each site and to elucidate the mechanism by which occupancy of the “stiffness site” affects filament mechanical properties. Incorporating a magnesium ion in the “polymerization site” does not seem to require any large-scale change to an actin subunit’s conformation. Binding of a magnesium ion in the “stiffness site” adheres the actin DNase-binding loop (D-loop) to its long-axis neighbor, which increases the filament torsional stiffness and bending persistence length. Our analysis shows that bound D-loops occupy a smaller region of accessible conformational space. Cation occupancy buries key conserved residues of the D-loop, restricting accessibility to regulatory proteins and enzymes that target these amino acids. PMID:27146246

  20. Dorsal hand coverage with free serratus fascia flap

    DEFF Research Database (Denmark)

    Fotopoulos, Peter; Holmer, Per; Leicht, Pernille

    2003-01-01

    in the flap, leaving the long thoracic nerve intact on the serratus muscle. Coverage of the flap with split-thickness skin graft is done immediately. The free serratus fascia flap is an ideal flap for dorsal hand coverage when the extensor tendons are exposed, especially because of low donor-site morbidity....

  1. Design and Performance of Insect-Scale Flapping-Wing Vehicles

    Science.gov (United States)

    Whitney, John Peter

    Micro-air vehicles (MAVs)---small versions of full-scale aircraft---are the product of a continued path of miniaturization which extends across many fields of engineering. Increasingly, MAVs approach the scale of small birds, and most recently, their sizes have dipped into the realm of hummingbirds and flying insects. However, these non-traditional biologically-inspired designs are without well-established design methods, and manufacturing complex devices at these tiny scales is not feasible using conventional manufacturing methods. This thesis presents a comprehensive investigation of new MAV design and manufacturing methods, as applicable to insect-scale hovering flight. New design methods combine an energy-based accounting of propulsion and aerodynamics with a one degree-of-freedom dynamic flapping model. Important results include analytical expressions for maximum flight endurance and range, and predictions for maximum feasible wing size and body mass. To meet manufacturing constraints, the use of passive wing dynamics to simplify vehicle design and control was investigated; supporting tests included the first synchronized measurements of real-time forces and three-dimensional kinematics generated by insect-scale flapping wings. These experimental methods were then expanded to study optimal wing shapes and high-efficiency flapping kinematics. To support the development of high-fidelity test devices and fully-functional flight hardware, a new class of manufacturing methods was developed, combining elements of rigid-flex printed circuit board fabrication with "pop-up book" folding mechanisms. In addition to their current and future support of insect-scale MAV development, these new manufacturing techniques are likely to prove an essential element to future advances in micro-optomechanics, micro-surgery, and many other fields.

  2. Dermatosurgery Rounds - The Island SKIN Infraorbital Flap

    Directory of Open Access Journals (Sweden)

    Georgi Tchernev

    2017-07-01

    Full Text Available The main objective in dermatologic surgery is complete excision of the tumour while achieving the best possible functional and cosmetic outcome. Also we must take into account age, sex, and tumour size and site. We should also consider the patient's expectations, the preservation of the different cosmetic units, and the final cosmetic outcome. Various reconstructive methods ranging from secondary healing to free flap applications are usedfor the reconstruction of perinasal or facial defects caused by trauma or tumour surgery. Herein, we describe the nasal infraorbital island skin flap for the reconstruction in a patient with basal cell carcinoma. No complications were observed in operation field. The infraorbital island skin flap which we describe for the perinasal area reconstruction is a safe, easily performed and versatile flap. The multidimensional use of this flap together with a relatively easy reconstruction plan and surgical procedure would be effective in flap choice.

  3. Elbow Reconstruction Using Island Flap for Burn Patients

    Directory of Open Access Journals (Sweden)

    Gi Yeun Hur

    2012-11-01

    Full Text Available Background Deep burns of the elbow lead to soft tissue necrosis and infection, with exposureof deep structures. Adequate wound coverage of this area requires thin, pliable, and durabletissue, while optimal functional recovery requires early coverage and functional rehabilitation.We have found 3 types of island flaps that provide reliable coverage for the elbow.Methods A retrospective study was performed on all patients who underwent flap coverageof an elbow defect at our hospital. The patients’ data including age, sex, cause of injury, wounddimensions, timing of flap coverage, postoperative elbow motion, and complications wereinvestigated.Results Between 2001 and 2012, 16 patients were treated at our hospital. The mean agewas 53.3 years. Three kinds of flaps were performed: 9 latissimus dorsi flaps, 4 lateral armflaps, and 4 radial forearm flaps. The average defect size was 183.5 cm2 (range, 28 to 670cm2. Wound coverage was performed at mean duration of 45.9 days (range, 14 to 91 days.The mean postoperative active elbow flexion was 98° (range, 85° to 115°. Partial flap failureoccurred in 1 latissimus dorsi flap. Minor complications included partial flap loss (11.8%,hematoma (23.5%, seroma (35.3%, and wound infection (5.9%.Conclusions Flap selection for elbow reconstruction is determined by the defect size andthe extent of the adjacent tissue injury. Elbow reconstruction using an island flap is a singlestaged,reliable, and relatively simple procedure that permits initiation of early rehabilitation,thereby improving a patient’s functional outcome.

  4. Actin expression in some Platyhelminthe species.

    Science.gov (United States)

    Fagotti, A; Panara, F; Di Rosa, I; Simoncelli, F; Gabbiani, G; Pascolini, R

    1994-10-01

    Actin expression in some Platyhelminthe species was demonstrated by western-blotting and immunocytochemical analysis using two distinct anti-actin antibodies: the anti-total actin that reacts against all actin isoforms of higher vertebrates and the anti-alpha SM-1 that recognizes the alpha-smooth muscle (alpha SM) isotype of endothermic vertebrates (Skalli et al., 1986). Western-blotting experiments showed that all species tested, including some free-living Platyhelminthes (Tricladida and Rhabdocoela) and the parasitic Fasciola hepatica, were stained by anti-total actin antibody while only Dugesidae and Dendrocoelidae showed a positive immunoreactivity against anti-alpha SM-1. These results were confirmed by cytochemical immunolocalization using both avidin biotin conjugated peroxidase reaction on paraffin sections, and immunogold staining on Lowicryl 4KM embedded specimens. Our findings may contribute to the understanding of Platyhelminthes phylogeny.

  5. Adaptive Trailing Edge Flaps for Active Load Alleviation in a Smart Rotor Configuration

    DEFF Research Database (Denmark)

    Bergami, Leonardo

    to withstand. The investigation focuses on a specific actuator type: the Adaptive Trailing Edge Flap (ATEF), which introduces a continuous deformation of the aft part of the airfoil camber-line. An aerodynamic model that accounts for the steady and unsteady effects of the flap deflection on a 2D airfoil...... section is developed, and, considering both attached and separated flow conditions, is validated by comparison against Computational Fluid Dynamic solutions and a panel code method. The aerodynamic model is integrated in the BEM-based aeroelastic simulation code HAWC2, thus providing a tool able...... with flaps laid out on the outer 20 % of the blade span, from 77 % to 97% of the blade length. The configuration is first tested with a simplified cyclic control approach, which gives a preliminary indication of the load alleviation potential, and also reveals the possibility to enhance the rotor energy...

  6. Simulation Study of Flap Effects on a Commercial Transport Airplane in Upset Conditions

    Science.gov (United States)

    Cunningham, Kevin; Foster, John V.; Shah, Gautam H.; Stewart, Eric C.; Ventura, Robin N.; Rivers, Robert A.; Wilborn, James E.; Gato, William

    2005-01-01

    As part of NASA's Aviation Safety and Security Program, a simulation study of a twinjet transport airplane crew training simulation was conducted to address fidelity for upset or loss of control conditions and to study the effect of flap configuration in those regimes. Piloted and desktop simulations were used to compare the baseline crew training simulation model with an enhanced aerodynamic model that was developed for high-angle-of-attack conditions. These studies were conducted with various flap configurations and addressed the approach-to-stall, stall, and post-stall flight regimes. The enhanced simulation model showed that flap configuration had a significant effect on the character of departures that occurred during post-stall flight. Preliminary comparisons with flight test data indicate that the enhanced model is a significant improvement over the baseline. Some of the unrepresentative characteristics that are predicted by the baseline crew training simulation for flight in the post-stall regime have been identified. This paper presents preliminary results of this simulation study and discusses key issues regarding predicted flight dynamics characteristics during extreme upset and loss-of-control flight conditions with different flap configurations.

  7. Prospective evaluation of outcome measures in free-flap surgery.

    LENUS (Irish Health Repository)

    Kelly, John L

    2004-08-01

    Free-flap failure is usually caused by venous or arterial thrombosis. In many cases, lack of experience and surgical delay also contribute to flap loss. The authors prospectively analyzed the outcome of 57 free flaps over a 28-month period (January, 1999 to April, 2001). The setting was a university hospital tertiary referral center. Anastomotic technique, ischemia time, choice of anticoagulant, and the grade of surgeon were recorded. The type of flap, medications, and co-morbidities, including preoperative radiotherapy, were also documented. Ten flaps were re-explored (17 percent). There were four cases of complete flap failure (6.7 percent) and five cases of partial failure (8.5 percent). In patients who received perioperative systemic heparin or dextran, there was no evidence of flap failure (p = .08). The mean ischemia time was similar in flaps that failed (95 +\\/- 29 min) and in those that survived (92 +\\/- 34 min). Also, the number of anastomoses performed by trainees in flaps that failed (22 percent), was similar to the number in flaps that survived (28 percent). Nine patients received preoperative radiotherapy, and there was complete flap survival in each case. This study reveals that closely supervised anastomoses performed by trainees may have a similar outcome to those performed by more senior surgeons. There was no adverse effect from radiotherapy or increased ischemia time on flap survival.

  8. Efficient flapping flight of pterosaurs

    Science.gov (United States)

    Strang, Karl Axel

    In the late eighteenth century, humans discovered the first pterosaur fossil remains and have been fascinated by their existence ever since. Pterosaurs exploited their membrane wings in a sophisticated manner for flight control and propulsion, and were likely the most efficient and effective flyers ever to inhabit our planet. The flapping gait is a complex combination of motions that sustains and propels an animal in the air. Because pterosaurs were so large with wingspans up to eleven meters, if they could have sustained flapping flight, they would have had to achieve high propulsive efficiencies. Identifying the wing motions that contribute the most to propulsive efficiency is key to understanding pterosaur flight, and therefore to shedding light on flapping flight in general and the design of efficient ornithopters. This study is based on published results for a very well-preserved specimen of Coloborhynchus robustus, for which the joints are well-known and thoroughly described in the literature. Simplifying assumptions are made to estimate the characteristics that can not be inferred directly from the fossil remains. For a given animal, maximizing efficiency is equivalent to minimizing power at a given thrust and speed. We therefore aim at finding the flapping gait, that is the joint motions, that minimize the required flapping power. The power is computed from the aerodynamic forces created during a given wing motion. We develop an unsteady three-dimensional code based on the vortex-lattice method, which correlates well with published results for unsteady motions of rectangular wings. In the aerodynamic model, the rigid pterosaur wing is defined by the position of the bones. In the aeroelastic model, we add the flexibility of the bones and of the wing membrane. The nonlinear structural behavior of the membrane is reduced to a linear modal decomposition, assuming small deflections about the reference wing geometry. The reference wing geometry is computed for

  9. Cannula-Assisted Flap Elevation (CAFE): a novel technique for developing flaps during skin-sparing mastectomies.

    Science.gov (United States)

    Grant, Michael D

    2015-02-01

    One of the most challenging procedures in breast surgery is the skin-sparing mastectomy (SSM). Various techniques and incisions have evolved that characterize this procedure; however, what is common in all of them is the smaller the incision, the more difficult it is to develop the skin flaps. A procedure was developed that incorporates the use of liposuction cannulas (without suction) to create the skin flaps. The technique and results are described in this manuscript. From October of 2012 to April 2014, 289 mastectomies (171 patients) were performed using the CAFE procedure on women of all shapes and sizes. Postoperatively, no problems were experienced with flap viability using this technique. The main difference in side effects between the CAFE technique and other standard techniques for developing flaps in SSMs was more bruising than normal, but this resolved rapidly. The results for use of this technique were consistently impressive. The learning curve for this procedure is very short, especially for those who perform SSMs using sharp technique (scissors). Residents and fellows became proficient with the CAFE technique in a relatively short amount of time. Plastic surgeons were pleased with the cosmetic outcomes of their reconstructions that follow this type of mastectomy. Patients were extremely satisfied with their reconstructions as well. Incorporating the use of liposuction cannulas (without suction) makes the creation of flaps for SSM a relatively simple and rapid method. It is especially useful to assist in developing skin flaps with even the smallest of skin incisions.

  10. The prepuce free flap in 10 patients : modifications in flap design and surgical technique

    NARCIS (Netherlands)

    Werker, Paul M N

    The prepuce free flap was used in 10 oral and oropharyngeal reconstructions. During the course of this study, various modifications took place. Residual penile skin necrosis and skin island necrosis early in the series led to modification of flap design. This solved the donor-site problem by placing

  11. Espins are multifunctional actin cytoskeletal regulatory proteins in the microvilli of chemosensory and mechanosensory cells

    Science.gov (United States)

    Sekerková, Gabriella; Zheng, Lili; Loomis, Patricia A.; Changyaleket, Benjarat; Whitlon, Donna S.; Mugnaini, Enrico; Bartles, James R.

    2010-01-01

    Espins are associated with the parallel actin bundles of hair cell stereocilia and are the target of mutations that cause deafness and vestibular dysfunction in mice and humans. Here, we report that espins are also concentrated in the microvilli of a number of other sensory cells: vomeronasal organ sensory neurons, solitary chemoreceptor cells, taste cells and Merkel cells. Moreover, we show that hair cells and these other sensory cells contain novel espin isoforms that arise from a different transcriptional start site and differ significantly from other espin isoforms in their complement of ligand-binding activities and their effects on actin polymerization. The novel espin isoforms of sensory cells bundled actin filaments with high affinity in a Ca2+-resistant fashion, bound actin monomer via a WASP homology 2 domain, bound profilin via a single proline-rich peptide, and caused a dramatic elongation of microvillus-type parallel actin bundles in transfected epithelial cells. In addition, the novel espin isoforms of sensory cells differed from other espin isoforms in that they potently inhibited actin polymerization in vitro, did not bind the Src homology 3 domain of the adapter protein insulin receptor substrate p53 and did not bind the acidic, signaling phospholipid phosphatidylinositol 4,5- bisphosphate. Thus, the espins constitute a family of multifunctional actin cytoskeletal regulatory proteins with the potential to differentially influence the organization, dimensions, dynamics and signaling capabilities of the actin filament-rich, microvillus-type specializations that mediate sensory transduction in a variety of mechanosensory and chemosensory cells. PMID:15190118

  12. Fibroblast-mediated contraction in actinically exposed and actinically protected aging skin

    International Nuclear Information System (INIS)

    Marks, M.W.; Morykwas, M.J.; Wheatley, M.J.

    1990-01-01

    The changes in skin morphology over time are a consequence of both chronologic aging and the accumulation of environmental exposure. Through observation, we know that actinic radiation intensifies the apparent aging of skin. We have investigated the effects of aging and actinic radiation on the ability of fibroblasts to contract collagen-fibroblast lattices. Preauricular and postauricular skin samples were obtained from eight patients aged 49 to 74 undergoing rhytidectomy. The samples were kept separate, and the fibroblasts were grown in culture. Lattices constructed with preauricular fibroblasts consistently contracted more than lattices containing postauricular fibroblasts. The difference in amount of contraction in 7 days between sites was greatest for the younger patients and decreased linearly as donor age increased (r = -0.96). This difference may be due to preauricular fibroblasts losing their ability to contract a lattice as aging skin is exposed to more actinic radiation

  13. Nonlinear dynamics of biomimetic micro air vehicles

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Y; Kong, J [College of Mechanical Automation, Wuhan University of Science and Technology, Wuhan, 430081 (China)], E-mail: fly_houyu@163.com.cn

    2008-02-15

    Flapping-wing micro air vehicles (FMAV) are new conceptual air vehicles that mimic the flying modes of birds and insects. They surpass the research fields of traditional airplane design and aerodynamics on application technologies, and initiate the applications of MEMS technologies on aviation fields. This paper studies a micro flapping mechanism that based upon insect thorax and actuated by electrostatic force. Because there are strong nonlinear coupling between the two physical domains, electrical and mechanical, the static and dynamic characteristics of this system are very complicated. Firstly, the nonlinear dynamic model of the electromechanical coupling system is set up according to the physical model of the flapping mechanism. The dynamic response of the system in constant voltage is studied by numerical method. Then the effect of damping and initial condition on dynamic characteristics of the system is analyzed in phase space. In addition, the dynamic responses of the system in sine voltage excitation are discussed. The results of research are helpful to the design, fabrication and application of the micro flapping mechanism of FMAV, and also to other micro electromechanical system that actuated by electrostatic force.

  14. Dual omental flap in obliterating post-pneumonectomy ...

    African Journals Online (AJOL)

    Background: Post-pneumonectomy bronchopleural fistulae is associated with high mortality and morbidity. The omental flap has been widely used to manage this condition either through laparoscopic or open surgery with varied degrees of success. We present a modification of the omental flap by using two flaps of the ...

  15. Vascularized Fibula Flaps for Mandibular Reconstruction: An ...

    African Journals Online (AJOL)

    For decades, osseous vascularised flaps have been used for reconstruction of the mandible with the vascularised fibula flap (VFF) remaining the commonly used osseous free flap, reasons ranging from its adequate bone and pedicle length to its receptive dental implant placement quality. This report considers a modest use ...

  16. Managing actinic keratosis in primary care.

    Science.gov (United States)

    Salmon, Nicola; Tidman, Michael J

    2016-10-01

    Actinic, or solar, keratosis is caused by chronic ultraviolet-induced damage to the epidermis. In the UK, 15-23% of individuals have actinic keratosis lesions. Risk factors include: advanced age; male gender; cumulative sun exposure or phototherapy; Fitzpatrick skin phototypes I-II; long-term immuno-suppression and genetic syndromes e.g. xeroderma pigmentosum and albinism. Actinic keratoses are regarded by some authorities as premalignant lesions that may transform into invasive squamous cell carcinoma (SCC) and by others as in situ SCC that may progress to an invasive stage. The risk of malignant change appears low; up to 0.5% per lesion per year. Up to 20-30% of lesions may spontaneously regress but in the absence of any reliable prognostic clinical indicators regarding malignant potential active treatment is considered appropriate. Actinic keratosis lesions may present as discrete hyperkeratotic papules, cutaneous horns, or more subtle flat lesions on sun-exposed areas of skin. The single most helpful diagnostic sign is an irregularly roughened surface texture: a sandpaper-like feel almost always indicates actinic damage. Dermatoscopy can be helpful in excluding signs of basal cell carcinoma when actinic keratosis is non-keratotic. It is always important to consider the possibility of SCC. The principal indication for referral to secondary care is the possibility of cutaneous malignancy. However, widespread and severe actinic damage in patients who are immunosuppressed is also a reason for referral.

  17. Reconstruction of pressure sores with perforator-based propeller flaps.

    Science.gov (United States)

    Jakubietz, Rafael G; Jakubietz, Danni F; Zahn, Robert; Schmidt, Karsten; Meffert, Rainer H; Jakubietz, Michael G

    2011-03-01

    Perforator flaps have been successfully used for reconstruction of pressure sores. Although V-Y advancement flaps approximate debrided wound edges, perforator-based propeller flaps allow rotation of healthy tissue into the defect. Perforator-based propeller flaps were planned in 13 patients. Seven pressure sores were over the sacrum, five over the ischial tuberosity, and one on the tip of the scapula. Three patients were paraplegic, six were bedridden, and five were ambulatory. In three patients, no perforators were found. In 10 patients, propeller flaps were transferred. In two patients, total flap necrosis occurred, which was reconstructed with local advancement flaps. In two cases, a wound dehiscence occurred and had to be revised. One hematoma required evacuation. No further complications were noted. No recurrence at the flap site occurred. Local perforator flaps allow closure of pressure sores without harvesting muscle. The propeller version has the added benefit of transferring tissue from a distant site, avoiding reapproximation of original wound edges. Twisting of the pedicle may cause torsion and venous obstruction. This can be avoided by dissecting a pedicle of at least 3 cm. Propeller flaps are a safe option for soft tissue reconstruction of pressure sores. © Thieme Medical Publishers.

  18. Flow control over a NACA 0012 airfoil using dielectric-barrier-discharge plasma actuator with a Gurney flap

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Li-Hao [Beijing University of Aeronautics and Astronautics, Fluid Mechanics Key Laboratory of Education Ministry, Beijing (China); University of Nottingham, University Park, Faculty of Engineering, Nottingham (United Kingdom); Jukes, Timothy N. [University of Nottingham, University Park, Faculty of Engineering, Nottingham (United Kingdom); AIST, Research Centre for New Fuels and Vehicle Technology, Tsukuba (Japan); Choi, Kwing-So [University of Nottingham, University Park, Faculty of Engineering, Nottingham (United Kingdom); Wang, Jin-Jun [Beijing University of Aeronautics and Astronautics, Fluid Mechanics Key Laboratory of Education Ministry, Beijing (China)

    2012-06-15

    Flow control study of a NACA 0012 airfoil with a Gurney flap was carried out in a wind tunnel, where it was demonstrated that a dielectric-barrier-discharge (DBD) plasma actuator attached to the flap could increase the lift further, but with a small drag penalty. Time-resolved PIV measurements of the near-wake region indicated that the plasma forcing shifted the wake downwards, reducing its recirculation length. Analysis of wake vortex dynamics suggested that the plasma actuator initially amplified the lower wake shear layer by adding momentum along the downstream surface of the Gurney flap. This enhanced mutual entrainment between the upper and lower wake vortices, leading to an increase in lift on the airfoil. (orig.)

  19. F-actin-based Ca signaling-a critical comparison with the current concept of Ca signaling.

    Science.gov (United States)

    Lange, Klaus; Gartzke, Joachim

    2006-11-01

    A short comparative survey on the current idea of Ca signaling and the alternative concept of F-actin-based Ca signaling is given. The two hypotheses differ in one central aspect, the mechanism of Ca storage. The current theory rests on the assumption of Ca-accumulating endoplasmic/sarcoplasmic reticulum-derived vesicles equipped with an ATP-dependent Ca pump and IP3- or ryanodine-sensitive channel-receptors for Ca-release. The alternative hypothesis proceeds from the idea of Ca storage at the high-affinity binding sites of actin filaments. Cellular sites of F-actin-based Ca storage are microvilli and the submembrane cytoskeleton. Several specific features of Ca signaling such as store-channel coupling, quantal Ca release, spiking and oscillations, biphasic and "phasic" uptake kinetics, and Ca-induced Ca release (CICR), which are not adequately described by the current concept, are inherent properties of the F-actin system and its dynamic state of treadmilling. Copyright 2006 Wiley-Liss, Inc.

  20. Bioinformatics study of the mangrove actin genes

    Science.gov (United States)

    Basyuni, M.; Wasilah, M.; Sumardi

    2017-01-01

    This study describes the bioinformatics methods to analyze eight actin genes from mangrove plants on DDBJ/EMBL/GenBank as well as predicted the structure, composition, subcellular localization, similarity, and phylogenetic. The physical and chemical properties of eight mangroves showed variation among the genes. The percentage of the secondary structure of eight mangrove actin genes followed the order of a helix > random coil > extended chain structure for BgActl, KcActl, RsActl, and A. corniculatum Act. In contrast to this observation, the remaining actin genes were random coil > extended chain structure > a helix. This study, therefore, shown the prediction of secondary structure was performed for necessary structural information. The values of chloroplast or signal peptide or mitochondrial target were too small, indicated that no chloroplast or mitochondrial transit peptide or signal peptide of secretion pathway in mangrove actin genes. These results suggested the importance of understanding the diversity and functional of properties of the different amino acids in mangrove actin genes. To clarify the relationship among the mangrove actin gene, a phylogenetic tree was constructed. Three groups of mangrove actin genes were formed, the first group contains B. gymnorrhiza BgAct and R. stylosa RsActl. The second cluster which consists of 5 actin genes the largest group, and the last branch consist of one gene, B. sexagula Act. The present study, therefore, supported the previous results that plant actin genes form distinct clusters in the tree.

  1. Colgajo perforante tóracodorsal Toracodorsal perforator flap

    Directory of Open Access Journals (Sweden)

    C. Angrigiani

    2006-12-01

    Full Text Available La espalda es una excelente zona dadora de colgajos. El colgajo perforante tóracodorsal basado en ramas cutáneas de la arteria y vena tóracodorsales que perforan el músculo dorsal ancho, es una modifica ción del tradicional colgajo musculocutáneo de dorsal ancho que permite lograr una mayor flexibilidad en su traslado y una disminución de su volumen. Puede emplearse como colgajo libre o en isla. Presentamos su anatomía, disección e indicaciones.Back is an excellent donor site for flaps. The tora codorsal perforator flap, based on cutaneous vessels from toracodorsal artery and vein that pass through Latissimus Dorsi muscle, is a modified conventional musculocutaneous Latissimus Dorsi flap that allows easier movility and a volume reduction. This flap can be used both, free flap or island flap. We present the anatomy, dissection and applica tions of this flap.

  2. Lift production through asymmetric flapping

    Science.gov (United States)

    Jalikop, Shreyas; Sreenivas, K. R.

    2009-11-01

    At present, there is a strong interest in developing Micro Air Vehicles (MAV) for applications like disaster management and aerial surveys. At these small length scales, the flight of insects and small birds suggests that unsteady aerodynamics of flapping wings can offer many advantages over fixed wing flight, such as hovering-flight, high maneuverability and high lift at large angles of attack. Various lift generating mechanims such as delayed stall, wake capture and wing rotation contribute towards our understanding of insect flight. We address the effect of asymmetric flapping of wings on lift production. By visualising the flow around a pair of rectangular wings flapping in a water tank and numerically computing the flow using a discrete vortex method, we demonstrate that net lift can be produced by introducing an asymmetry in the upstroke-to-downstroke velocity profile of the flapping wings. The competition between generation of upstroke and downstroke tip vortices appears to hold the key to understanding this lift generation mechanism.

  3. Versatality of Nasolabial Flap in Orofacial Reconstruction

    Directory of Open Access Journals (Sweden)

    Nandesh Shetty

    2015-01-01

    Materials and Methods: A total of 10 patients were selected based on the size of surgical defect. Nasolabial flap was used to reconstruct defects of small to moderate size in the oro-facial region and post-operative follow up was done. Results: All of the patients underwent inferiorly based Transposition Island flap for reconstruction of different oro-facial defects. Few complications like bulky size of the flap, slight donor site distortion (scar formation and intra-oral hair growth were seen in six patients. Two incidences of infection in the transferred flap were seen. Conclusion: It is a safe minor procedure done under general anesthesia with good reconstructive results over small or moderately sized maxillofacial defects. Proper attention to flap design, operative technique and post - operative management are useful in reducing the incidence of complications.

  4. Robot-Assisted Free Flap in Head and Neck Reconstruction

    Directory of Open Access Journals (Sweden)

    Han Gyeol Song

    2013-07-01

    Full Text Available BackgroundRobots have allowed head and neck surgeons to extirpate oropharyngeal tumors safely without the need for lip-split incision or mandibulotomy. Using robots in oropharyngeal reconstruction is new but essential for oropharyngeal defects that result from robotic tumor excision. We report our experience with robotic free-flap reconstruction of head and neck defects to exemplify the necessity for robotic reconstruction.MethodsWe investigated head and neck cancer patients who underwent ablation surgery and free-flap reconstruction by robot. Between July 1, 2011 and March 31, 2012, 5 cases were performed and patient demographics, location of tumor, pathologic stage, reconstruction methods, flap size, recipient vessel, necessary pedicle length, and operation time were investigated.ResultsAmong five free-flap reconstructions, four were radial forearm free flaps and one was an anterolateral thigh free-flap. Four flaps used the superior thyroid artery and one flap used a facial artery as the recipient vessel. The average pedicle length was 8.8 cm. Flap insetting and microanastomosis were achieved using a specially manufactured robotic instrument. The total operation time was 1,041.0 minutes (range, 814 to 1,132 minutes, and complications including flap necrosis, hematoma, and wound dehiscence did not occur.ConclusionsThis study demonstrates the clinically applicable use of robots in oropharyngeal reconstruction, especially using a free flap. A robot can assist the operator in insetting the flap at a deep portion of the oropharynx without the need to perform a traditional mandibulotomy. Robot-assisted reconstruction may substitute for existing surgical methods and is accepted as the most up-to-date method.

  5. Flow field of flexible flapping wings

    Science.gov (United States)

    Sallstrom, Erik

    The agility and maneuverability of natural fliers would be desirable to incorporate into engineered micro air vehicles (MAVs). However, there is still much for engineers to learn about flapping flight in order to understand how such vehicles can be built for efficient flying. The goal of this study is to develop a methodology for capturing high quality flow field data around flexible flapping wings in a hover environment and to interpret it to gain a better understanding of how aerodynamic forces are generated. The flow field data was captured using particle image velocimetry (PIV) and required that measurements be taken around a repeatable flapping motion to obtain phase-averaged data that could be studied throughout the flapping cycle. Therefore, the study includes the development of flapping devices with a simple repeatable single degree of freedom flapping motion. The acquired flow field data has been examined qualitatively and quantitatively to investigate the mechanisms behind force production in hovering flight and to relate it to observations in previous research. Specifically, the flow fields have been investigated around a rigid wing and several carbon fiber reinforced flexible membrane wings. Throughout the whole study the wings were actuated with either a sinusoidal or a semi-linear flapping motion. The semi-linear flapping motion holds the commanded angular velocity nearly constant through half of each half-stroke while the sinusoidal motion is always either accelerating or decelerating. The flow fields were investigated by examining vorticity and vortex structures, using the Q criterion as the definition for the latter, in two and three dimensions. The measurements were combined with wing deflection measurements to demonstrate some of the key links in how the fluid-structure interactions generated aerodynamic forces. The flow fields were also used to calculate the forces generated by the flapping wings using momentum balance methods which yielded

  6. Neuroinspired control strategies with applications to flapping flight

    Science.gov (United States)

    Dorothy, Michael Ray

    This dissertation is centered on a theoretical, simulation, and experimental study of control strategies which are inspired by biological systems. Biological systems, along with sufficiently complicated engineered systems, often have many interacting degrees of freedom and need to excite large-displacement oscillations in order to locomote. Combining these factors can make high-level control design difficult. This thesis revolves around three different levels of abstraction, providing tools for analysis and design. First, we consider central pattern generators (CPGs) to control flapping-flight dynamics. The key idea here is dimensional reduction - we want to convert complicated interactions of many degrees of freedom into a handful of parameters which have intuitive connections to the overall system behavior, leaving the control designer unconcerned with the details of particular motions. A rigorous mathematical and control theoretic framework to design complex three-dimensional wing motions is presented based on phase synchronization of nonlinear oscillators. In particular, we show that flapping-flying dynamics without a tail or traditional aerodynamic control surfaces can be effectively controlled by a reduced set of central pattern generator parameters that generate phase-synchronized or symmetry-breaking oscillatory motions of two main wings. Furthermore, by using a Hopf bifurcation, we show that tailless aircraft (inspired by bats) alternating between flapping and gliding can be effectively stabilized by smooth wing motions driven by the central pattern generator network. Results of numerical simulation with a full six-degree-of-freedom flight dynamic model validate the effectiveness of the proposed neurobiologically inspired control approach. Further, we present experimental micro aerial vehicle (MAV) research with low-frequency flapping and articulated wing gliding. The importance of phase difference control via an abstract mathematical model of central

  7. Perforator anatomy of the radial forearm free flap versus the ulnar forearm free flap for head and neck reconstruction

    NARCIS (Netherlands)

    Hekner, D.D.; Roeling, TAP; van Cann, EM

    The aim of this study was to investigate the vascular anatomy of the distal forearm in order to optimize the choice between the radial forearm free flap and the ulnar forearm free flap and to select the best site to harvest the flap. The radial and ulnar arteries of seven fresh cadavers were

  8. Characterizing interaction forces between actin and proteins of the tropomodulin family reveals the presence of the N-terminal actin-binding site in leiomodin.

    Science.gov (United States)

    Arslan, Baran; Colpan, Mert; Gray, Kevin T; Abu-Lail, Nehal I; Kostyukova, Alla S

    2018-01-15

    Tropomodulin family of proteins includes several isoforms of tropomodulins (Tmod) and leiomodins (Lmod). These proteins can sequester actin monomers or nucleate actin polymerization. Although it is known that their actin-binding properties are isoform-dependent, knowledge on how they vary in strengths of interactions with G-actin is missing. While it is confirmed in many studies that Tmods have two actin-binding sites, information on number and location of actin-binding sites in Lmod2 is controversial. We used atomic force microscopy to study interactions between G-actin and proteins of the tropomodulin family. Unbinding forces between G-actin and Tmod1, Tmod2, Tmod3, or Lmod2 were quantified. Our results indicated that Tmod1 and Tmod3 had unimodal force distributions, Tmod2 had a bimodal distribution and Lmod2 had a trimodal distribution. The number of force distributions correlates with the proteins' abilities to sequester actin or to nucleate actin polymerization. We assigned specific unbinding forces to the individual actin-binding sites of Tmod2 and Lmod2 using mutations that destroy actin-binding sites of Tmod2 and truncated Lmod2. Our results confirm the existence of the N-terminal actin-binding site in Lmod2. Altogether, our data demonstrate how the differences between the number and the strength of actin-binding sites of Tmod or Lmod translate to their functional abilities. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Flow structures around a flapping wing considering ground effect

    Science.gov (United States)

    Van Truong, Tien; Kim, Jihoon; Kim, Min Jun; Park, Hoon Cheol; Yoon, Kwang Joon; Byun, Doyoung

    2013-07-01

    Over the past several decades, there has been great interest in understanding the aerodynamics of flapping flight, namely the two flight modes of hovering and forward flight. However, there has been little focus on the aerodynamic characteristics during takeoff of insects. In a previous study we found that the Rhinoceros Beetle ( Trypoxylusdichotomus) takes off without jumping, which is uncommon for other insects. In this study we built a scaled-up electromechanical model of a flapping wing and investigated fluid flow around the beetle's wing model. In particular, the present dynamically scaled mechanical model has the wing kinematics pattern achieved from the real beetle's wing kinematics during takeoff. In addition, we could systematically change the three-dimensional inclined motion of the flapping model through each stroke. We used digital particle image velocimetry with high spatial resolution, and were able to qualitatively and quantitatively study the flow field around the wing at a Reynolds number of approximately 10,000. The present results provide insight into the aerodynamics and the evolution of vortical structures, as well as the ground effect experienced by a beetle's wing during takeoff. The main unsteady mechanisms of beetles have been identified and intensively analyzed as the stability of the leading edge vortex (LEV) during strokes, the delayed stall during upstroke, the rotational circulation in pronation periods, and wake capture in supination periods. Due to the ground effect, the LEV was enhanced during half downstroke, and the lift force could thus be increased to lift the beetle during takeoff. This is useful for researchers in developing a micro air vehicle that has a beetle-like flapping wing motion.

  10. Perforator plus flaps: Optimizing results while preserving function and esthesis

    Directory of Open Access Journals (Sweden)

    Mehrotra Sandeep

    2010-01-01

    Full Text Available Background: The tenuous blood supply of traditional flaps for wound cover combined with collateral damage by sacrifice of functional muscle, truncal vessels, or nerves has been the bane of reconstructive procedures. The concept of perforator plus flaps employs dual vascular supply to flaps. By safeguarding perforators along with supply from its base, robust flaps can be raised in diverse situations. This is achieved while limiting collateral damage and preserving nerves, vessels, and functioning muscle with better function and aesthesis. Materials and Methods: The perforator plus concept was applied in seven different clinical situations. Functional muscle and fasciocutaneous flaps were employed in five and adipofascial flaps in two cases, primarily involving lower extremity defects and back. Adipofascial perforator plus flaps were employed to provide cover for tibial fracture in one patients and chronic venous ulcer in another. Results: All flaps survived without any loss and provided long-term stable cover, both over soft tissue and bone. Functional preservation was achieved in all cases where muscle flaps were employed with no clinical evidence of loss of power. There was no sensory loss or significant oedema in or distal to the flap in both cases where neurovascular continuity was preserved during flap elevation. Fracture union and consolidation were satisfactory. One patient had minimal graft loss over fascia which required application of stored grafts with subsequent take. No patient required re-operation. Conclusions: Perforator plus concept is holistic and applicable to most flap types in varied situations. It permits the exercise of many locoregional flap options while limiting collateral functional damage. Aesthetic considerations are also addressed while raising adipofascial flaps because of no appreciable donor defects. With quick operating times and low failure risk, these flaps can be a better substitute to traditional flaps and at

  11. Locomotion Dynamics for Bio-inspired Robots with Soft Appendages: Application to Flapping Flight and Passive Swimming

    Science.gov (United States)

    Boyer, Frédéric; Porez, Mathieu; Morsli, Ferhat; Morel, Yannick

    2017-08-01

    In animal locomotion, either in fish or flying insects, the use of flexible terminal organs or appendages greatly improves the performance of locomotion (thrust and lift). In this article, we propose a general unified framework for modeling and simulating the (bio-inspired) locomotion of robots using soft organs. The proposed approach is based on the model of Mobile Multibody Systems (MMS). The distributed flexibilities are modeled according to two major approaches: the Floating Frame Approach (FFA) and the Geometrically Exact Approach (GEA). Encompassing these two approaches in the Newton-Euler modeling formalism of robotics, this article proposes a unique modeling framework suited to the fast numerical integration of the dynamics of a MMS in both the FFA and the GEA. This general framework is applied on two illustrative examples drawn from bio-inspired locomotion: the passive swimming in von Karman Vortex Street, and the hovering flight with flexible flapping wings.

  12. A Simple Strategy in Avulsion Flap Injury: Prediction of Flap Viability Using Wood's Lamp Illumination and Resurfacing with a Full-thickness Skin Graft.

    Science.gov (United States)

    Lim, Hyoseob; Han, Dae Hee; Lee, Il Jae; Park, Myong Chul

    2014-03-01

    Extensive degloving injuries of the extremities usually result in necrosis of the flap, necessitating comprehensive skin grafting. Provided there is a sufficient tool to evaluate flap viability, full-thickness skin can be used from a nonviable avulsed flap. We used a Wood's lamp to determine the viability of avulsed flaps in the operation field after intravenous injection of fluorescein dye. We experienced 13 cases during 16 months. Fifteen minutes after the intravenous injection of fluorescein dye, the avulsed skin flaps were examined and non-fluorescent areas were marked under Wood's lamp illumination. The marked area was defatted for full-thickness skin grafting. The fluorescent areas were sutured directly without tension. The non-fluorescent areas were covered by defatted skin. Several days later, there was soft tissue necrosis within the flap area. We measured necrotic area and revised the flap. Among all the cases, necrotic area was 21.3% of the total avulsed area. However, if we exclude three cases, one of a carelessly managed patient and two cases of the flaps were inappropriately applied, good results were obtained, with a necrotic area of only 8.4%. Eight patients needed split-thickness skin grafts, and heel pad reconstruction was performed with free flap. A full-thickness skin graft from an avulsed flap is a good method for addressing aesthetic concerns without producing donor site morbidity. Fluorescein dye is a useful, simple, and cost-effective tool for evaluating flap viability. Avulsed flap injuries can be managed well with Wood's lamp illumination and a full-thickness skin graft.

  13. A Simple Strategy in Avulsion Flap Injury: Prediction of Flap Viability Using Wood's Lamp Illumination and Resurfacing with a Full-thickness Skin Graft

    Directory of Open Access Journals (Sweden)

    Hyoseob Lim

    2014-03-01

    Full Text Available Background Extensive degloving injuries of the extremities usually result in necrosis of the flap, necessitating comprehensive skin grafting. Provided there is a sufficient tool to evaluate flap viability, full-thickness skin can be used from a nonviable avulsed flap. We used a Wood's lamp to determine the viability of avulsed flaps in the operation field after intravenous injection of fluorescein dye. Methods We experienced 13 cases during 16 months. Fifteen minutes after the intravenous injection of fluorescein dye, the avulsed skin flaps were examined and non-fluorescent areas were marked under Wood's lamp illumination. The marked area was defatted for full-thickness skin grafting. The fluorescent areas were sutured directly without tension. The non-fluorescent areas were covered by defatted skin. Several days later, there was soft tissue necrosis within the flap area. We measured necrotic area and revised the flap. Results Among all the cases, necrotic area was 21.3% of the total avulsed area. However, if we exclude three cases, one of a carelessly managed patient and two cases of the flaps were inappropriately applied, good results were obtained, with a necrotic area of only 8.4%. Eight patients needed split-thickness skin grafts, and heel pad reconstruction was performed with free flap. Conclusions A full-thickness skin graft from an avulsed flap is a good method for addressing aesthetic concerns without producing donor site morbidity. Fluorescein dye is a useful, simple, and cost-effective tool for evaluating flap viability. Avulsed flap injuries can be managed well with Wood's lamp illumination and a full-thickness skin graft.

  14. Repair of nostril stenosis using a triple flap combination: boomerang, nasolabial, and vestibular rotation flaps.

    Science.gov (United States)

    Bozkurt, Mehmet; Kapi, Emin; Kuvat, Samet Vasfi; Selçuk, Caferi Tayyar

    2012-11-01

    Tissue losses within the nose due to various reasons result in the loss of normal anatomy and function. The external nasal valve area is one of the most important functional components of the nose. The columella, lobule, nostril, and alar region are among the components forming the external nasal valve area. Deformities of the nostrils are among the most frequently observed features that interfere with the functional anatomy of the nose. Malformations of the nostrils often emerge subsequent to cleft lip repairs. Stenoses are a common type of pathology among nostril deformities. In cases where a stenosis has formed, breathing problems and developmental anomalies may occur. In the patient with nostril stenosis presented in this report, there was a serious alar collapse and contracture subsequent to a cleft lip repair. In order to repair the nostril stenosis, a "boomerang flap" was chosen. This boomerang flap was used in combination with a nasolabial flap, a vestibular rotation flap, and a conchal cartilage graft to achieve a satisfactory repair.

  15. Positioning the 5'-flap junction in the active site controls the rate of flap endonuclease-1-catalyzed DNA cleavage

    KAUST Repository

    Song, Bo

    2018-02-09

    Flap endonucleases catalyze cleavage of single-stranded DNA flaps formed during replication, repair and recombination, and are therefore essential for genome processing and stability. Recent crystal structures of DNA-bound human flap endonuclease (hFEN1) offer new insights into how conformational changes in the DNA and hFEN1 may facilitate the reaction mechanism. For example, previous biochemical studies of DNA conformation performed under non-catalytic conditions with Ca2+ have suggested that base unpairing at the 5\\'-flap:template junction is an important step in the reaction, but the new structural data suggest otherwise. To clarify the role of DNA changes in the kinetic mechanism, we measured a series of transient steps - from substrate binding to product release - during the hFEN1-catalyzed reaction in the presence of Mg2+. We found that while hFEN1 binds and bends DNA at a fast, diffusion-limited rate, much slower Mg2+-dependent conformational changes in DNA around the active site are subsequently necessary and rate-limiting for 5\\'-flap cleavage. These changes are reported overall by fluorescence of 2-aminopurine at the 5\\'-flap:template junction, indicating that local DNA distortion (e.g., disruption of base stacking observed in structures), associated with positioning the 5\\'-flap scissile phosphodiester bond in the hFEN1 active site, controls catalysis. hFEN1 residues with distinct roles in the catalytic mechanism, including those binding metal ions (Asp-34, Asp-181), steering the 5\\'-flap through the active site and binding the scissile phosphate (Lys-93, Arg-100), and stacking against the base 5\\' to the scissile phosphate (Tyr-40), all contribute to these rate-limiting conformational changes, ensuring efficient and specific cleavage of 5\\'-flaps.

  16. Positioning the 5'-flap junction in the active site controls the rate of flap endonuclease-1-catalyzed DNA cleavage

    KAUST Repository

    Song, Bo; Hamdan, Samir; Hingorani, Manju M

    2018-01-01

    Flap endonucleases catalyze cleavage of single-stranded DNA flaps formed during replication, repair and recombination, and are therefore essential for genome processing and stability. Recent crystal structures of DNA-bound human flap endonuclease (hFEN1) offer new insights into how conformational changes in the DNA and hFEN1 may facilitate the reaction mechanism. For example, previous biochemical studies of DNA conformation performed under non-catalytic conditions with Ca2+ have suggested that base unpairing at the 5'-flap:template junction is an important step in the reaction, but the new structural data suggest otherwise. To clarify the role of DNA changes in the kinetic mechanism, we measured a series of transient steps - from substrate binding to product release - during the hFEN1-catalyzed reaction in the presence of Mg2+. We found that while hFEN1 binds and bends DNA at a fast, diffusion-limited rate, much slower Mg2+-dependent conformational changes in DNA around the active site are subsequently necessary and rate-limiting for 5'-flap cleavage. These changes are reported overall by fluorescence of 2-aminopurine at the 5'-flap:template junction, indicating that local DNA distortion (e.g., disruption of base stacking observed in structures), associated with positioning the 5'-flap scissile phosphodiester bond in the hFEN1 active site, controls catalysis. hFEN1 residues with distinct roles in the catalytic mechanism, including those binding metal ions (Asp-34, Asp-181), steering the 5'-flap through the active site and binding the scissile phosphate (Lys-93, Arg-100), and stacking against the base 5' to the scissile phosphate (Tyr-40), all contribute to these rate-limiting conformational changes, ensuring efficient and specific cleavage of 5'-flaps.

  17. Plasmin enzymatic activity in the presence of actin

    Directory of Open Access Journals (Sweden)

    Yusova E. I.

    2015-10-01

    Full Text Available Aim. To study the changes in the plasmin activity towards substrates with high and low molecular mass in the presence of actin. Methods. The proteins used for this investigation were obtained by affinity chromatography and gel-filtration. The plasmin enzymatic activity was determined by a turbidimetric assay and a chromogenic substrate-based assay. The enzyme linked immunosorbent assay and biotin-avidin-phosphatase system were used to study the interaction of plasminogen and its fragments with actin. Results. It was shown that G-actin causes 1.5-fold decrease in the rate of polymeric fibrin hydrolysis by plasmin and Glu-plasminogen activated by the tissue plasminogen activator. However, actin did not impede plasmin autolysis and had no influence on its amidase activity. We have studied an interaction of biotinylated Glu-plasminogen and its fragments (kringle 1-3, kringle 4 and mini-plasminogen with immobilized G-actin. Glu-plasminogen and kringle 4 had a high affinity towards actin (C50 is 113 and 117 nM correspondingly. Mini-plasminogen and kringe 4 did not bind to actin. A similar affinity of Glu-plasminogen and kringle 1-3 towards actin proves the involvement of the kringle 1-3 lysine-binding sites of the native plasminogen form in the actin interaction. Conclusions. Actin can modulate plasmin specificity towards high molecular mass substrates through its interaction with lysine-binding sites of the enzyme kringle domains. Actin inhibition of the fibrinolytic activity of plasmin is due to its competition with fibrin for thelysine binding sites of plasminogen/plasmin.

  18. An Adjoint-Based Approach to Study a Flexible Flapping Wing in Pitching-Rolling Motion

    Science.gov (United States)

    Jia, Kun; Wei, Mingjun; Xu, Min; Li, Chengyu; Dong, Haibo

    2017-11-01

    Flapping-wing aerodynamics, with advantages in agility, efficiency, and hovering capability, has been the choice of many flyers in nature. However, the study of bio-inspired flapping-wing propulsion is often hindered by the problem's large control space with different wing kinematics and deformation. The adjoint-based approach reduces largely the computational cost to a feasible level by solving an inverse problem. Facing the complication from moving boundaries, non-cylindrical calculus provides an easy extension of traditional adjoint-based approach to handle the optimization involving moving boundaries. The improved adjoint method with non-cylindrical calculus for boundary treatment is first applied on a rigid pitching-rolling plate, then extended to a flexible one with active deformation to further increase its propulsion efficiency. The comparison of flow dynamics with the initial and optimal kinematics and deformation provides a unique opportunity to understand the flapping-wing mechanism. Supported by AFOSR and ARL.

  19. Triple flap technique for vulvar reconstruction.

    Science.gov (United States)

    Mercut, R; Sinna, R; Vaucher, R; Giroux, P A; Assaf, N; Lari, A; Dast, S

    2018-04-09

    Perineal defects are encountered ever more frequently, in the treatment of vulvar cancers or abdominoperineal resection. The surgical treatment of vulvar cancer leads to significant skin defect. The aim of the reconstruction is not to provide volume but rather to resurface perineum. We propose a new solution to cover the extensive skin defect remaining after excision. We report 3 patients who underwent large excision for vulvar cancer, with lymph node dissection. For reconstruction, we performed 3 advancement flaps. Two V-Y flaps cantered on the infra-gluteal folds and based on pudendal perforator arteries were used to cover the postero-lateral parts of the defect. The third advancement flap from the superior aspect of the defect was a Y-V Mons pubis flap. The defects were successfully covered by the 3 flap technique. The first patient suffered a non-union that slowly healed by secondary intention. For the other cases, we used the same technique, but applied negative pressure wound therapy on the sutures, with excellent results. The 3 flap technique is a simple and reliable method and the donor site morbidity is minimal. It can be realised without changing the position of the patient after tumour excision, and does not require delicate perforator dissection. This surgical option can be easily applied, allowing better management of these cases. Copyright © 2018 Elsevier Masson SAS. All rights reserved.

  20. "Internet of Things" Real-Time Free Flap Monitoring.

    Science.gov (United States)

    Kim, Sang Hun; Shin, Ho Seong; Lee, Sang Hwan

    2018-01-01

    Free flaps are a common treatment option for head and neck reconstruction in plastic reconstructive surgery, and monitoring of the free flap is the most important factor for flap survival. In this study, the authors performed real-time free flap monitoring based on an implanted Doppler system and "internet of things" (IoT)/wireless Wi-Fi, which is a convenient, accurate, and efficient approach for surgeons to monitor a free flap. Implanted Doppler signals were checked continuously until the patient was discharged by the surgeon and residents using their own cellular phone or personal computer. If the surgeon decided that a revision procedure or exploration was required, the authors checked the consumed time (positive signal-to-operating room time) from the first notification when the flap's status was questioned to the determination for revision surgery according to a chart review. To compare the efficacy of real-time monitoring, the authors paired the same number of free flaps performed by the same surgeon and monitored the flaps using conventional methods such as a physical examination. The total survival rate was greater in the real-time monitoring group (94.7% versus 89.5%). The average time for the real-time monitoring group was shorter than that for the conventional group (65 minutes versus 86 minutes). Based on this study, real-time free flap monitoring using IoT technology is a method that surgeon and reconstruction team can monitor simultaneously at any time in any situation.

  1. Perforator anatomy of the radial forearm free flap versus the ulnar forearm free flap for head and neck reconstruction.

    Science.gov (United States)

    Hekner, D D; Roeling, T A P; Van Cann, E M

    2016-08-01

    The aim of this study was to investigate the vascular anatomy of the distal forearm in order to optimize the choice between the radial forearm free flap and the ulnar forearm free flap and to select the best site to harvest the flap. The radial and ulnar arteries of seven fresh cadavers were injected with epoxy resin (Araldite) and the perforating arteries were dissected. The number of clinically relevant perforators from the radial and ulnar arteries was not significantly different in the distal forearm. Most perforators were located in the proximal half of the distal one third, making this part probably the safest location for flap harvest. Close to the wrist, i.e. most distally, there were more perforators on the ulnar side than on the radial side. The ulnar artery stained 77% of the skin surface area of the forearm, showing the ulnar forearm free flap to be more suitable than the radial forearm free flap for the restoration of large defects. Copyright © 2016 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.

  2. EXTENDED REVERSE SURAL FLAP FOR LOWER LIMB COVERAGE

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    Biswajit Mishra

    2018-12-01

    Full Text Available BACKGROUND The reverse sural artery flap has been a workhorse for the reconstruction of distal third of leg, ankle, sole and foot. Major limitation of reverse sural flap has been venous congestion particularly when harvested from proximal third of the leg. Objective- To evaluate the efficacy, safety of the extended reverse sural flap from proximal third of the leg. MATERIALS AND METHODS A prospective study was conducted at the department of plastic surgery on twenty patients who needed soft tissue reconstruction in the distal third of the leg, ankle, heel, forefoot and midfoot due to various cause. In all cases flap was extended proximally to the upper third of the calf and neurovenoadipo fascial pedicled sural fasciocutaneous flap was harvested. RESULTS There were only two cases of marginal necrosis. None of the patients had complete necrosis. Two patients developed hypertrophy of the flap margin. CONCLUSION Distally based neuroveno adipofascial pedicled sural fasciocutaneous flap can be safely extended to proximal third of the leg and is a reliable option for reconstruction of the defects in the foot, ankle and sole.

  3. Flap Edge Noise Reduction Fins

    Science.gov (United States)

    Khorrami, Mehdi R. (Inventor); Choudhan, Meelan M. (Inventor)

    2015-01-01

    A flap of the type that is movably connected to an aircraft wing to provide control of an aircraft in flight includes opposite ends, wherein at least a first opposite end includes a plurality of substantially rigid, laterally extending protrusions that are spaced apart to form a plurality of fluidly interconnected passageways. The passageways have openings adjacent to upper and lower sides of the flap, and the passageways include a plurality of bends such that high pressure fluid flows from a high pressure region to a low pressure region to provide a boundary condition that inhibits noise resulting from airflow around the end of the flap.

  4. Intrinsic, Functional, and Structural Properties of β-Thymosins and β-Thymosin/WH2 Domains in the Regulation and Coordination of Actin Self-Assembly Dynamics and Cytoskeleton Remodeling.

    Science.gov (United States)

    Renault, L

    2016-01-01

    β-Thymosins are a family of heat-stable multifunctional polypeptides that are expressed as small proteins of about 5kDa (~45 amino acids) almost exclusively in multicellular animals. They were first isolated from the thymus. As full-length or truncated polypeptides, they appear to stimulate a broad range of extracellular activities in various signaling pathways, including tissue repair and regeneration, inflammation, cell migration, and immune defense. However, their cell surface receptors and structural mechanisms of regulations in these multiple pathways remain still poorly understood. Besides their extracellular activities, they belong to a larger family of small, intrinsically disordered actin-binding domains called WH2/β-thymosin domains that have been identified in more than 1800 multidomain proteins found in different taxonomic domains of life and involved in various actin-based motile processes including cell morphogenesis, motility, adhesions, tissue development, intracellular trafficking, or pathogen infections. This review briefly surveys the main recent findings to understand how these small, intrinsically disordered but functional domains can interact with many unrelated partners and can thus integrate and coordinate various intracellular activities in actin self-assembly dynamics and cell signaling pathways linked to their cytoskeleton remodeling. © 2016 Elsevier Inc. All rights reserved.

  5. Characterization of f-actin tryptophan phosphorescence in the presence and absence of tryptophan-free myosin motor domain.

    Science.gov (United States)

    Bódis, Emöke; Strambini, Giovanni B; Gonnelli, Margherita; Málnási-Csizmadia, András; Somogyi, Béla

    2004-08-01

    The effect of binding the Trp-free motor domain mutant of Dictyostelium discoideum, rabbit skeletal muscle myosin S1, and tropomyosin on the dynamics and conformation of actin filaments was characterized by an analysis of steady-state tryptophan phosphorescence spectra and phosphorescence decay kinetics over a temperature range of 140-293 K. The binding of the Trp-free motor domain mutant of D. discoideum to actin caused red shifts in the phosphorescence spectrum of two internal Trp residues of actin and affected the intrinsic lifetime of each emitter, decreasing by roughly twofold the short phosphorescence lifetime components (tau(1) and tau(2)) and increasing by approximately 20% the longest component (tau(3)). The alteration of actin phosphorescence by the motor protein suggests that i), structural changes occur deep down in the core of actin and that ii), subtle changes in conformation appear also on the surface but in regions distant from the motor domain binding site. When actin formed complexes with skeletal S1, an extra phosphorescence lifetime component appeared (tau(4), twice as long as tau(3)) in the phosphorescence decay that is absent in the isolated proteins. The lack of this extra component in the analogous actin-Trp-free motor domain mutant of D. discoideum complex suggests that it should be assigned to Trps in S1 that in the complex attain a more compact local structure. Our data indicated that the binding of tropomyosin to actin filaments had no effect on the structure or flexibility of actin observable by this technique.

  6. Mechanics model for actin-based motility.

    Science.gov (United States)

    Lin, Yuan

    2009-02-01

    We present here a mechanics model for the force generation by actin polymerization. The possible adhesions between the actin filaments and the load surface, as well as the nucleation and capping of filament tips, are included in this model on top of the well-known elastic Brownian ratchet formulation. A closed form solution is provided from which the force-velocity relationship, summarizing the mechanics of polymerization, can be drawn. Model predictions on the velocity of moving beads driven by actin polymerization are consistent with experiment observations. This model also seems capable of explaining the enhanced actin-based motility of Listeria monocytogenes and beads by the presence of Vasodilator-stimulated phosphoprotein, as observed in recent experiments.

  7. Phosphate steering by Flap Endonuclease 1 promotes 5′-flap specificity and incision to prevent genome instability

    KAUST Repository

    Tsutakawa, Susan E.

    2017-06-27

    DNA replication and repair enzyme Flap Endonuclease 1 (FEN1) is vital for genome integrity, and FEN1 mutations arise in multiple cancers. FEN1 precisely cleaves single-stranded (ss) 5\\'-flaps one nucleotide into duplex (ds) DNA. Yet, how FEN1 selects for but does not incise the ss 5\\'-flap was enigmatic. Here we combine crystallographic, biochemical and genetic analyses to show that two dsDNA binding sites set the 5\\'polarity and to reveal unexpected control of the DNA phosphodiester backbone by electrostatic interactions. Via phosphate steering\\', basic residues energetically steer an inverted ss 5\\'-flap through a gateway over FEN1\\'s active site and shift dsDNA for catalysis. Mutations of these residues cause an 18,000-fold reduction in catalytic rate in vitro and large-scale trinucleotide (GAA) repeat expansions in vivo, implying failed phosphate-steering promotes an unanticipated lagging-strand template-switch mechanism during replication. Thus, phosphate steering is an unappreciated FEN1 function that enforces 5\\'-flap specificity and catalysis, preventing genomic instability.

  8. Reconstructive Surgery for Severe Penile Inadequacy: Phalloplasty with a Free Radial Forearm Flap or a Pedicled Anterolateral Thigh Flap

    Directory of Open Access Journals (Sweden)

    N. Lumen

    2008-01-01

    Full Text Available Objectives. Severe penile inadequacy in adolescents is rare. Phallic reconstruction to treat this devastating condition is a major challenge to the reconstructive surgeon. Phallic reconstruction using the free radial forearm flap (RFF or the pedicled anterolateral thigh flap (ALTF has been routinely used in female-to-male transsexuals. Recently we started to use these techniques in the treatment of severe penile inadequacy. Methods. Eleven males (age 15 to 42 years were treated with a phallic reconstruction. The RFF is our method of choice; the ALTF is an alternative when a free flap is contraindicated or less desired by the patient. The RFF was used in 7 patients, the ALTF in 4 patients. Mean followup was 25 months (range: 4–49 months. Aesthetic and functional results were evaluated. Results. There were no complications related to the flap. Aesthetic results were judged as “good” in 9 patients and “moderate” in 2 patients. Sensitivity in the RFF was superior compared to the ALTF. Four patients developed urinary complications (stricture and/or fistula. Six patients underwent erectile implant surgery. In 2 patients the erectile implant had to be removed due to infection or erosion. Conclusion. In case of severe penile inadequacy due to whatever condition, a phalloplasty is the preferred treatment nowadays. The free radial forearm flap is still the method of choice. The anterolateral thigh flap can be a good alternative, especially when free flaps are contraindicated, but sensitivity is markedly inferior in these flaps.

  9. A Review Of Pectoralis Major Musculocutaneous Island Flap In ...

    African Journals Online (AJOL)

    Like microvascular free flaps, pectoralis major flaps can be transferred in a single stage and have largely replaced deltepectoral (Bakanjiam) flap in head and neck reconstruction. This retrospective study was carried out to highlight the usefulness of this flap in different situations. Ten patients, aged six to 55 years operated ...

  10. Titin-Actin Interaction: PEVK-Actin-Based Viscosity in a Large Animal

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    Charles S. Chung

    2011-01-01

    Full Text Available Titin exhibits an interaction between its PEVK segment and the actin filament resulting in viscosity, a speed dependent resistive force, which significantly influences diastolic filling in mice. While diastolic disease is clinically pervasive, humans express a more compliant titin (N2BA:N2B ratio ~0.5–1.0 than mice (N2BA:N2B ratio ~0.2. To examine PEVK-actin based viscosity in compliant titin-tissues, we used pig cardiac tissue that expresses titin isoforms similar to that in humans. Stretch-hold experiments were performed at speeds from 0.1 to 10 lengths/s from slack sarcomere lengths (SL to SL of 2.15 μm. Viscosity was calculated from the slope of stress-relaxation vs stretch speed. Recombinant PEVK was added to compete off native interactions and this found to reduce the slope by 35%, suggesting that PEVK-actin interactions are a strong contributor of viscosity. Frequency sweeps were performed at frequencies of 0.1–400 Hz and recombinant protein reduced viscous moduli by 40% at 2.15 μm and by 50% at 2.25 μm, suggesting a SL-dependent nature of viscosity that might prevent SL ``overshoot’’ at long diastolic SLs. This study is the first to show that viscosity is present at physiologic speeds in the pig and supports the physiologic relevance of PEVK-actin interactions in humans in both health and disease.

  11. Robot-Assisted Free Flap in Head and Neck Reconstruction

    Directory of Open Access Journals (Sweden)

    Han Gyeol Song

    2013-07-01

    Full Text Available Background  Robots have allowed head and neck surgeons to extirpate oropharyngealtumors safely without the need for lip-split incision or mandibulotomy. Using robots inoropharyngealreconstruction is newbut essentialfor oropharyngeal defectsthatresultfromrobotic tumor excision. We report our experience with robotic free-flap reconstruction ofhead and neck defectsto exemplify the necessity forrobotic reconstruction.Methods  We investigated head and neck cancer patients who underwent ablation surgeryand free-flap reconstruction by robot. Between July 1, 2011 andMarch 31, 2012, 5 caseswereperformed and patient demographics, location of tumor, pathologic stage, reconstructionmethods, flap size, recipient vessel, necessary pedicle length, and operation time wereinvestigated.Results  Among five free-flap reconstructions, four were radial forearm free flaps and onewas an anterolateral thigh free-flap. Four flaps used the superior thyroid artery and oneflap used a facial artery as the recipient vessel. The average pedicle length was 8.8 cm. Flapinsetting and microanastomosis were achieved using a specially manufactured roboticinstrument. The total operation timewas 1,041.0 minutes(range, 814 to 1,132 minutes, andcomplicationsincluding flap necrosis, hematoma, andwound dehiscence did not occur.Conclusions  Thisstudy demonstratesthe clinically applicable use ofrobotsin oropharyngealreconstruction, especially using a free flap. A robot can assist the operator in insettingthe flap at a deep portion of the oropharynx without the need to perform a traditionalmandibulotomy. Robot-assisted reconstruction may substitute for existing surgical methodsand is accepted asthemost up-to-datemethod.

  12. Control of Electrostatic Interactions Between F-Actin And Genetically Modified Lysozyme in Aqueous Media

    International Nuclear Information System (INIS)

    Sanders, L.K.; Xian, W.; Guaqueta, C.; Strohman, M.; Vrasich, C.R.; Luijten, E.; Wong, G.C.L.

    2009-01-01

    The aim for deterministic control of the interactions between macroions in aqueous media has motivated widespread experimental and theoretical work. Although it has been well established that like-charged macromolecules can aggregate under the influence of oppositely charged condensing agents, the specific conditions for the stability of such aggregates can only be determined empirically. We examine these conditions, which involve an interplay of electrostatic and osmotic effects, by using a well defined model system composed of F-actin, an anionic rod-like polyelectrolyte, and lysozyme, a cationic globular protein with a charge that can be genetically modified. The structure and stability of actin-lysozyme complexes for different lysozyme charge mutants and salt concentrations are examined by using synchrotron x-ray scattering and molecular dynamics simulations. We provide evidence that supports a structural transition from columnar arrangements of F-actin held together by arrays of lysozyme at the threefold interstitial sites of the actin sublattice to marginally stable complexes in which lysozyme resides at twofold bridging sites between actin. The reduced stability arises from strongly reduced partitioning of salt between the complex and the surrounding solution. Changes in the stability of actin-lysozyme complexes are of biomedical interest because their formation has been reported to contribute to the persistence of airway infections in cystic fibrosis by sequestering antimicrobials such as lysozyme. We present x-ray microscopy results that argue for the existence of actin-lysozyme complexes in cystic fibrosis sputum and demonstrate that, for a wide range of salt conditions, charge-reduced lysozyme is not sequestered in ordered complexes while retaining its bacterial killing activity.

  13. Aerodynamics of a bio-inspired flexible flapping-wing micro air vehicle

    International Nuclear Information System (INIS)

    Nakata, T; Liu, H; Nishihashi, N; Wang, X; Sato, A; Tanaka, Y

    2011-01-01

    MAVs (micro air vehicles) with a maximal dimension of 15 cm and nominal flight speeds of around 10 m s −1 , operate in a Reynolds number regime of 10 5 or lower, in which most natural flyers including insects, bats and birds fly. Furthermore, due to their light weight and low flight speed, the MAVs' flight characteristics are substantially affected by environmental factors such as wind gust. Like natural flyers, the wing structures of MAVs are often flexible and tend to deform during flight. Consequently, the aero/fluid and structural dynamics of these flyers are closely linked to each other, making the entire flight vehicle difficult to analyze. We have recently developed a hummingbird-inspired, flapping flexible wing MAV with a weight of 2.4–3.0 g and a wingspan of 10–12 cm. In this study, we carry out an integrated study of the flexible wing aerodynamics of this flapping MAV by combining an in-house computational fluid dynamic (CFD) method and wind tunnel experiments. A CFD model that has a realistic wing planform and can mimic realistic flexible wing kinematics is established, which provides a quantitative prediction of unsteady aerodynamics of the four-winged MAV in terms of vortex and wake structures and their relationship with aerodynamic force generation. Wind tunnel experiments further confirm the effectiveness of the clap and fling mechanism employed in this bio-inspired MAV as well as the importance of the wing flexibility in designing small flapping-wing MAVs.

  14. Revisit of Nasolabial flap in the reconstruction of defects involving ...

    African Journals Online (AJOL)

    Conclusion: Data from this study suggest that NL flap is a reliable option for reconstruction of the oral floor, in form as well as function, without esthetic compromise and has a major role even in this era of free flaps. Keywords: Floor of mouth defects, local flaps, nasolabail flap, oral cavity defects, reconstruction, regional flaps ...

  15. The N-terminal tropomyosin- and actin-binding sites are important for leiomodin 2's function.

    Science.gov (United States)

    Ly, Thu; Moroz, Natalia; Pappas, Christopher T; Novak, Stefanie M; Tolkatchev, Dmitri; Wooldridge, Dayton; Mayfield, Rachel M; Helms, Gregory; Gregorio, Carol C; Kostyukova, Alla S

    2016-08-15

    Leiomodin is a potent actin nucleator related to tropomodulin, a capping protein localized at the pointed end of the thin filaments. Mutations in leiomodin-3 are associated with lethal nemaline myopathy in humans, and leiomodin-2-knockout mice present with dilated cardiomyopathy. The arrangement of the N-terminal actin- and tropomyosin-binding sites in leiomodin is contradictory and functionally not well understood. Using one-dimensional nuclear magnetic resonance and the pointed-end actin polymerization assay, we find that leiomodin-2, a major cardiac isoform, has an N-terminal actin-binding site located within residues 43-90. Moreover, for the first time, we obtain evidence that there are additional interactions with actin within residues 124-201. Here we establish that leiomodin interacts with only one tropomyosin molecule, and this is the only site of interaction between leiomodin and tropomyosin. Introduction of mutations in both actin- and tropomyosin-binding sites of leiomodin affected its localization at the pointed ends of the thin filaments in cardiomyocytes. On the basis of our new findings, we propose a model in which leiomodin regulates actin poly-merization dynamics in myocytes by acting as a leaky cap at thin filament pointed ends. © 2016 Ly, Moroz, et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  16. Noisy Oscillations in the Actin Cytoskeleton of Chemotactic Amoeba

    Science.gov (United States)

    Negrete, Jose; Pumir, Alain; Hsu, Hsin-Fang; Westendorf, Christian; Tarantola, Marco; Beta, Carsten; Bodenschatz, Eberhard

    2016-09-01

    Biological systems with their complex biochemical networks are known to be intrinsically noisy. Here we investigate the dynamics of actin polymerization of amoeboid cells, which are close to the onset of oscillations. We show that the large phenotypic variability in the polymerization dynamics can be accurately captured by a generic nonlinear oscillator model in the presence of noise. We determine the relative role of the noise with a single dimensionless, experimentally accessible parameter, thus providing a quantitative description of the variability in a population of cells. Our approach, which rests on a generic description of a system close to a Hopf bifurcation and includes the effect of noise, can characterize the dynamics of a large class of noisy systems close to an oscillatory instability.

  17. Incorporation of mammalian actin into microfilaments in plant cell nucleus

    Directory of Open Access Journals (Sweden)

    Paves Heiti

    2004-04-01

    Full Text Available Abstract Background Actin is an ancient molecule that shows more than 90% amino acid homology between mammalian and plant actins. The regions of the actin molecule that are involved in F-actin assembly are largely conserved, and it is likely that mammalian actin is able to incorporate into microfilaments in plant cells but there is no experimental evidence until now. Results Visualization of microfilaments in onion bulb scale epidermis cells by different techniques revealed that rhodamine-phalloidin stained F-actin besides cytoplasm also in the nuclei whereas GFP-mouse talin hybrid protein did not enter the nuclei. Microinjection of fluorescently labeled actin was applied to study the presence of nuclear microfilaments in plant cells. Ratio imaging of injected fluorescent rabbit skeletal muscle actin and phalloidin staining of the microinjected cells showed that mammalian actin was able to incorporate into plant F-actin. The incorporation occurred preferentially in the nucleus and in the perinuclear region of plant cells whereas part of plant microfilaments, mostly in the periphery of cytoplasm, did not incorporate mammalian actin. Conclusions Microinjected mammalian actin is able to enter plant cell's nucleus, whereas incorporation of mammalian actin into plant F-actin occurs preferentially in the nucleus and perinuclear area.

  18. Temporalis myo-osseous flap: an experimental study

    International Nuclear Information System (INIS)

    Antonyshyn, O.; Colcleugh, R.G.; Hurst, L.N.; Anderson, C.

    1986-01-01

    The present paper investigates the anatomy and vascularization of the temporalis myo-osseous flap. This is a calvarial bone flap that employs temporalis muscle and its distal pericranial extension as a pedicle. In six human cadavers the flap was raised as an island on the anterior deep temporal artery after transecting the zygomatic arch and coronoid process. Maximal mobilization was thus obtained, allowing rotation of the flap into the mouth for intraoral reconstruction. The arc of rotation and potential surgical applications were noted. A comparative study of the temporalis myo-osseous flap and free calvarial bone graft was then conducted in a rabbit model. Vascularization of the calvarial bone flap was confirmed by technetium scintigraphy performed on the first postoperative day. The uptake of fluorochrome labels immediately after transfer verified the adequacy of the periosteal circulation in maintaining viability and new osteoid formation throughout the full thickness of calvarial bone. The transplantation of free calvarial bone grafts was followed by necrosis of most cellular elements. This was demonstrated by an absence of fluorochrome uptake up to 19 days postoperatively and a predominance of empty lacunae and nonviable marrow

  19. External stimulation strength controls actin response dynamics in Dictyostelium cells

    Science.gov (United States)

    Hsu, Hsin-Fang; Westendorf, Christian; Tarantola, Marco; Zykov, Vladimir; Bodenschatz, Eberhard; Beta, Carsten

    2015-03-01

    Self-sustained oscillation and the resonance frequency of the cytoskeletal actin polymerization/depolymerization have recently been observed in Dictyostelium, a model system for studying chemotaxis. Here we report that the resonance frequency is not constant but rather varies with the strength of external stimuli. To understand the underlying mechanism, we analyzed the polymerization and depolymerization time at different levels of external stimulation. We found that polymerization time is independent of external stimuli but the depolymerization time is prolonged as the stimulation increases. These observations can be successfully reproduced in the frame work of our time delayed differential equation model.

  20. Adipofascial Anterolateral Thigh Flap Safety: Applications and Complications

    Directory of Open Access Journals (Sweden)

    Tommaso Agostini

    2013-03-01

    Full Text Available BackgroundA thinned anterolateral thigh (ALT flap is often harvested to achieve optimal skin resurfacing. Several techniques have been described to thin an ALT flap including an adipocutaneous flap, an adipofascial flap and delayed debulking.MethodsBy systematically reviewing all of the available literature in English and French, the present manuscript attempts to identify the common surgical indications, complications and donor site morbidity of the adipofascial variant of the ALT flap. The studies were identified by performing a systematic search on Medline, Ovid, EMBASE, the Cochrane Database of Systematic Reviews, Current Contents, PubMed, Google, and Google Scholar.ResultsThe study selection process was adapted from the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement, and 15 articles were identified using the study inclusion criteria. These articles were then reviewed for author name(s, year of publication, flap dimensions and thickness following defatting, perforator type, type of transfer, complications, thinning technique, number of cases with a particular area of application and donor site morbidity.ConclusionsThe adipofascial variant of the ALT flap provides tissue to fill large defects and improve pliability. Its strong and safe blood supply permits adequate immediate or delayed debulking without vascular complications. The presence of the deep fascia makes it possible to prevent sagging by suspending and fixing the flap for functional reconstructive purposes (e.g., the intraoral cavity. Donor site morbidity is minimal, and thigh deformities can be reduced through immediate direct closure or liposuction and direct closure. A safe blood supply was confirmed by the rate of secondary flap debulking.

  1. Reconstruction of eyelids with Washio flap in anophthalmia.

    Science.gov (United States)

    Tvrdek, M; Kozák, J

    2014-01-01

    The authors present a case report of a patient with anophthalmia in whom retroauriculo-temporal flap (Washio flap) was used for reconstruction of eyelids. This flap, which is mostly used for reconstructions of nasal defects, was not used in this way according to available literature.

  2. Cdc42-dependent actin dynamics controls maturation and secretory activity of dendritic cells

    DEFF Research Database (Denmark)

    Schulz, Anna M; Stutte, Susanne; Hogl, Sebastian

    2015-01-01

    Cell division cycle 42 (Cdc42) is a member of the Rho guanosine triphosphatase family and has pivotal functions in actin organization, cell migration, and proliferation. To further study the molecular mechanisms of dendritic cell (DC) regulation by Cdc42, we used Cdc42-deficient DCs. Cdc42 defici...

  3. Influence of hinge point on flexible flap aerodynamic performance

    International Nuclear Information System (INIS)

    Zhao, H Y; Ye, Z; Wu, P; Li, C

    2013-01-01

    Large scale wind turbines lead to increasing blade lengths and weights, which presents new challenges for blade design. This paper selects NREL S809 airfoil, uses the parameterized technology to realize the flexible trailing edge deformation, researches the static aerodynamic characteristics of wind turbine blade airfoil with flexible deformation, and the dynamic aerodynamic characteristics in the process of continuous deformation, analyses the influence of hinge point position on flexible flap aerodynamic performance, in order to further realize the flexible wind turbine blade design and provides some references for the active control scheme. The results show that compared with the original airfoil, proper trailing edge deformation can improve the lift coefficient, reduce the drag coefficient, and thereby more efficiently realize flow field active control. With hinge point moving forward, total aerodynamic performance of flexible flap improves. Positive swing angle can push the transition point backward, thus postpones the occurrence of the transition phenomenon

  4. Reconstruction of cica-contracture on the face and neck with skin flap and expanded skin flap pedicled by anterior branch of transverse cervical artery.

    Science.gov (United States)

    Chen, Baoguo; Song, Huifeng; Xu, Minghuo; Gao, Quanwen

    2016-09-01

    A high-quality flap is necessary for repairing faciocervical scar contractures. The supraclavicular region and chest wall are the preferred choices for reconstruction. The supraclavicular island flap (SIF) pedicled by the transverse cervical artery (TCA) has been reported. Compared to the traditional SIF flap, another type of flap pedicled by the anterior perforator of transverse cervical artery (ap-TCA) is more convenient for transfer to the faciocervical area. In this article, we use this type of perforator flap and expanded perforator flap to repair the faciocervical contracture. In this study, 10 cases (deformity caused by burn or trauma to the face and neck sites) with an average age of 32 years-old, were treated by ap-TCA flap and this type of expanded flap. In between, the flap was pre-expanded for approximately 3 months prior to transfer in 6 patients. Another 4 cases did not want the expander because of the long duration required for saline filling and potential complications of the expander. Bilateral prefabricated flaps were designed in two female cases. All 12 flaps in 10 patients were transferred tension-free to the defects and no flap was lost. The size of the flap ranged from 12 cm × 8 cm to 15 cm × 20 cm. All 12 flaps survived completely. The donor sites were closed directly in the above 6 patients where an expander had been used and reconstructed by split skin graft in 4 patients where no expander had been employed. Through a mean time of 6 months' follow-up, only one female patient was disappointed with the cicatrix that presented on the upper polar skin of both breasts, the other 9 patients were satisfied with both recipient function and appearance. The color and the texture matched well with the recipient area. The ap-TCA flap and expanded ap-TCA flap can be considered reliable options for faciocervical deformities as it can be easily elevated and it matches well with faciocervical area in color. With regards to the expanded flap, we

  5. Flexible wings in flapping flight

    Science.gov (United States)

    Moret, Lionel; Thiria, Benjamin; Zhang, Jun

    2007-11-01

    We study the effect of passive pitching and flexible deflection of wings on the forward flapping flight. The wings are flapped vertically in water and are allowed to move freely horizontally. The forward speed is chosen by the flapping wing itself by balance of drag and thrust. We show, that by allowing the wing to passively pitch or by adding a flexible extension at its trailing edge, the forward speed is significantly increased. Detailed measurements of wing deflection and passive pitching, together with flow visualization, are used to explain our observations. The advantage of having a wing with finite rigidity/flexibility is discussed as we compare the current results with our biological inspirations such as birds and fish.

  6. Comparison of 5468 retreatments after laser in situ keratomileusis by lifting the flap or performing photorefractive keratectomy on the flap.

    Science.gov (United States)

    Ortega-Usobiaga, J; Llovet-Osuna, F; Katz, T; Djodeyre, M R; Druchkiv, V; Bilbao-Calabuig, R; Baviera, J

    2018-02-01

    To assess visual outcomes of retreatment after laser in situ keratomileusis (LASIK) by lifting the flap or performing photorefractive keratectomy (PRK) on the flap, as well as to establish whether there was an increased risk of epithelial ingrowth (EIG) when LASIK and lifting of the flap are separated by a long time interval and to determine the incidence of corneal haze after PRK. Retrospective study of 4077 patients (5468 eyes) who underwent LASIK and subsequent retreatment were reviewed in order to study their visual results and identify cases of EIG and corneal haze. Enhancements included 5196 eyes from 3876 patients that were retreated by lifting the flap, and 272 eyes from 201 patients that were retreated by PRK on the flap. No statistically significant differences were found between the retreatments in terms of predictability, efficacy, and safety. A total of 704 cases of EIG were found after lifting the flap, for which surgical cleansing was necessary in 70. Surgical cleansing decreased the efficacy index when compared with patients with EIG who did not need cleansing (P=.01). Differences in terms of safety and predictability were not statistically significant. The incidence of corneal haze after ablation of the surface of the previous flap was 14.34%, although none of these cases were clinically relevant. Visual outcomes were similar between patients who were retreated by lifting the flap and those who underwent PRK. The incidence of EIG when the flap was lifted was 13.55%. The incidence of EIG increases with the time elapsed between the primary procedure and retreatment. Copyright © 2017 Sociedad Española de Oftalmología. Publicado por Elsevier España, S.L.U. All rights reserved.

  7. Measurement and Analysis of in vitro Actin Polymerization

    Science.gov (United States)

    Doolittle, Lynda K.; Rosen, Michael K.; Padrick, Shae B.

    2014-01-01

    Summary The polymerization of actin underlies force generation in numerous cellular processes. While actin polymerization can occur spontaneously, cells maintain control over this important process by preventing actin filament nucleation and then allowing stimulated polymerization and elongation by several regulated factors. Actin polymerization, regulated nucleation and controlled elongation activities can be reconstituted in vitro, and used to probe the signaling cascades cells use to control when and where actin polymerization occurs. Introducing a pyrene fluorophore allows detection of filament formation by an increase in pyrene fluorescence. This method has been used for many years and continues to be broadly used, owing to its simplicity and flexibility. Here we describe how to perform and analyze these in vitro actin polymerization assays, with an emphasis on extracting useful descriptive parameters from kinetic data. PMID:23868594

  8. Actin polymerisation at the cytoplasmic face of eukaryotic nuclei

    Directory of Open Access Journals (Sweden)

    David-Watine Brigitte

    2006-05-01

    Full Text Available Abstract Background There exists abundant molecular and ultra-structural evidence to suggest that cytoplasmic actin can physically interact with the nuclear envelope (NE membrane system. However, this interaction has yet to be characterised in living interphase cells. Results Using a fluorescent conjugate of the actin binding drug cytochalasin D (CD-BODIPY we provide evidence that polymerising actin accumulates in vicinity to the NE. In addition, both transiently expressed fluorescent actin and cytoplasmic micro-injection of fluorescent actin resulted in accumulation of actin at the NE-membrane. Consistent with the idea that the cytoplasmic phase of NE-membranes can support this novel pool of perinuclear actin polymerisation we show that isolated, intact, differentiated primary hepatocyte nuclei support actin polymerisation in vitro. Further this phenomenon was inhibited by treatments hindering steric access to outer-nuclear-membrane proteins (e.g. wheat germ agglutinin, anti-nesprin and anti-nucleoporin antibodies. Conclusion We conclude that actin polymerisation occurs around interphase nuclei of living cells at the cytoplasmic phase of NE-membranes.

  9. Actin-interacting protein 1 controls assembly and permeability of intestinal epithelial apical junctions.

    Science.gov (United States)

    Lechuga, Susana; Baranwal, Somesh; Ivanov, Andrei I

    2015-05-01

    Adherens junctions (AJs) and tight junctions (TJs) are crucial regulators of the integrity and restitution of the intestinal epithelial barrier. The structure and function of epithelial junctions depend on their association with the cortical actin cytoskeleton that, in polarized epithelial cells, is represented by a prominent perijunctional actomyosin belt. The assembly and stability of the perijunctional cytoskeleton is controlled by constant turnover (disassembly and reassembly) of actin filaments. Actin-interacting protein (Aip) 1 is an emerging regulator of the actin cytoskeleton, playing a critical role in filament disassembly. In this study, we examined the roles of Aip1 in regulating the structure and remodeling of AJs and TJs in human intestinal epithelium. Aip1 was enriched at apical junctions in polarized human intestinal epithelial cells and normal mouse colonic mucosa. Knockdown of Aip1 by RNA interference increased the paracellular permeability of epithelial cell monolayers, decreased recruitment of AJ/TJ proteins to steady-state intercellular contacts, and attenuated junctional reassembly in a calcium-switch model. The observed defects of AJ/TJ structure and functions were accompanied by abnormal organization and dynamics of the perijunctional F-actin cytoskeleton. Moreover, loss of Aip1 impaired the apico-basal polarity of intestinal epithelial cell monolayers and inhibited formation of polarized epithelial cysts in 3-D Matrigel. Our findings demonstrate a previously unanticipated role of Aip1 in regulating the structure and remodeling of intestinal epithelial junctions and early steps of epithelial morphogenesis. Copyright © 2015 the American Physiological Society.

  10. Soft Palate Reconstruction Using Bilateral Palatal Mucomuscular Flap and Pharyngeal Flap after Resection of Squamous Cell Carcinoma

    Directory of Open Access Journals (Sweden)

    Jun Sik Kim

    2012-11-01

    Full Text Available Squamous cell carcinoma infrequently occurs at the soft palate. Although various methodscan be used for reconstruction of soft palate defects that occur after resecting squamous cellcarcinoma, it is difficult to obtain satisfactory results from the perspective of the functionalrestoration of the soft palate. A combination of bilateral palatal mucomuscular flap for theoral side and superiorly based posterior pharyngeal flap for the nasal side were performed ontwo patients who were diagnosed with squamous cell carcinoma of the soft palate in orderto reconstruct the soft palate defects after surgical resection. After surgery, the patients werefollowed-up for a mean period of 11 months. The flaps were well maintained in both patients.The donor site defects were epithelialized and completely recovered. Additionally, no recurrenceof the primary sites was shown. Slight hyponasality was observed in the voice assessmentsthat were conducted 6 months after surgery. No food regurgitation or aspiration was observedin the swallowing tests. We used a combination of bilateral palatal mucomuscular flap andsuperiorly based posterior pharyngeal flap to reconstruct the soft palate defects that occurredafter resecting the squamous cell carcinomas. We reduced the donor site complications andachieved functionally satisfactory outcomes.

  11. Defining the Role of Free Flaps in Partial Breast Reconstruction.

    Science.gov (United States)

    Smith, Mark L; Molina, Bianca J; Dayan, Erez; Jablonka, Eric M; Okwali, Michelle; Kim, Julie N; Dayan, Joseph H

    2018-03-01

     Free flaps have a well-established role in breast reconstruction after mastectomy; however, their role in partial breast reconstruction remains poorly defined. We reviewed our experience with partial breast reconstruction to better understand indications for free tissue transfer.  A retrospective review was performed of all patients undergoing partial breast reconstruction at our center between February 2009 and October 2015. We evaluated the characteristics of patients who underwent volume displacement procedures versus volume replacement procedures and free versus pedicled flap reconstruction.  There were 78 partial breast reconstructions, with 52 reductions/tissue rearrangements (displacement group) and 26 flaps (replacement group). Bra cup size and body mass index (BMI) were significantly smaller in the replacement group. Fifteen pedicled and 11 free flaps were performed. Most pedicled flaps (80.0%) were used for lateral or upper pole defects. Most free flaps (72.7%) were used for medial and inferior defects or when there was inadequate donor tissue for a pedicled flap. Complications included hematoma, cellulitis, and one aborted pedicled flap.  Free and pedicled flaps are useful for partial breast reconstruction, particularly in breast cancer patients with small breasts undergoing breast-conserving treatment (BCT). Flap selection depends on defect size, location, and donor tissue availability. Medial defects are difficult to reconstruct using pedicled flaps due to arc of rotation and intervening breast tissue. Free tissue transfer can overcome these obstacles. Confirming negative margins before flap reconstruction ensures harvest of adequate volume and avoids later re-operation. Judicious use of free flaps for oncoplastic reconstruction expands the possibility for breast conservation. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  12. Medial canthal reconstruction with multiple local flaps

    Directory of Open Access Journals (Sweden)

    Akihiro Ogino

    2018-03-01

    Conclusion: This method is somewhat complicated compared to reconstruction with a single flap, but it is a combination of standard local flaps and is a simple reconstructive procedure. By adding additional resection, the suture line is consistent with the border of the facial unit, so postoperative scarring is inconspicuous. This technique is aesthetically useful because of the continuity of colour and texture resulting from the use of adjacent flaps.

  13. Increased actin polymerization and stabilization interferes with neuronal function and survival in the AMPKγ mutant Loechrig.

    Directory of Open Access Journals (Sweden)

    Mandy Cook

    Full Text Available loechrig (loe mutant flies are characterized by progressive neuronal degeneration, behavioral deficits, and early death. The mutation is due to a P-element insertion in the gene for the γ-subunit of the trimeric AMP-activated protein kinase (AMPK complex, whereby the insertion affects only one of several alternative transcripts encoding a unique neuronal isoform. AMPK is a cellular energy sensor that regulates a plethora of signaling pathways, including cholesterol and isoprenoid synthesis via its downstream target hydroxy-methylglutaryl (HMG-CoA reductase. We recently showed that loe interferes with isoprenoid synthesis and increases the prenylation and thereby activation of RhoA. During development, RhoA plays an important role in neuronal outgrowth by activating a signaling cascade that regulates actin dynamics. Here we show that the effect of loe/AMPKγ on RhoA prenylation leads to a hyperactivation of this signaling pathway, causing increased phosphorylation of the actin depolymerizating factor cofilin and accumulation of filamentous actin. Furthermore, our results show that the resulting cytoskeletal changes in loe interfere with neuronal growth and disrupt axonal integrity. Surprisingly, these phenotypes were enhanced by expressing the Slingshot (SSH phosphatase, which during development promotes actin depolymerization by dephosphorylating cofilin. However, our studies suggest that in the adult SSH promotes actin polymerization, supporting in vitro studies using human SSH1 that suggested that SSH can also stabilize and bundle filamentous actin. Together with the observed increase in SSH levels in the loe mutant, our experiments suggest that in mature neurons SSH may function as a stabilization factor for filamentous actin instead of promoting actin depolymerization.

  14. Accuracy of Visual Estimation of LASIK Flap Thickness.

    Science.gov (United States)

    Brenner, Jason E; Fadlallah, Ali; Hatch, Kathryn M; Choi, Catherine; Sayegh, Rony R; Kouyoumjian, Paul; Wu, Simon; Frangieh, George T; Melki, Samir A

    2017-11-01

    To assess the accuracy of surgeons' visual estimation of LASIK flap thickness when created by a femtosecond laser by comparing it to ultrasound measurements. Surgeons were asked to visually estimate the thickness of a femtosecond flap during the procedure. Total corneal thickness was measured by ultrasound pachymetry prior to the procedure and the stromal bed was similarly measured after flap lifting. The estimates from three experienced surgeons (cornea fellowship trained and more than 5 years in practice) were compared to those of three cornea fellows, with each surgeon evaluating 20 eyes (120 total). Surgeons were not told the thickness of the flaps unless required for safety reasons. The average difference between visual and ultrasonic estimation of LASIK flap thickness was 15.20 μm. The flap was 10 μm thicker than estimated in 37% of eyes, 20 μm thicker in 17% of eyes, and 30 μm thicker in 10% of eyes. The largest deviation was 53 μm. There was no statistically significant difference between the accuracy of experienced surgeons and fellows (P = .51). There are significant differences between surgeons' visual estimates and ultrasonic measurements of LASIK flap thickness. Relying on these visual estimates may lead to deeper excimer laser ablation than intended. This could lead to thinner residual stromal beds and higher percent tissue altered than planned. The authors recommend that surgeons measure flaps intraoperatively to maximize accuracy and safety. [J Refract Surg. 2017;33(11):765-767.]. Copyright 2017, SLACK Incorporated.

  15. Plant actin cytoskeleton re-modeling by plant parasitic nematodes.

    Science.gov (United States)

    Engler, Janice de Almeida; Rodiuc, Natalia; Smertenko, Andrei; Abad, Pierre

    2010-03-01

    The cytoskeleton is an important component of the plant's defense mechanism against the attack of pathogenic organisms. Plants however, are defenseless against parasitic root-knot and cyst nematodes and respond to the invasion by the development of a special feeding site that supplies the parasite with nutrients required for the completion of its life cycle. Recent studies of nematode invasion under treatment with cytoskeletal drugs and in mutant plants where normal functions of the cytoskeleton have been affected, demonstrate the importance of the cytoskeleton in the establishment of a feeding site and successful nematode reproduction. It appears that in the case of microfilaments, nematodes hijack the intracellular machinery that regulates actin dynamics and modulate the organization and properties of the actin filament network. Intervening with this process reduces the nematode infection efficiency and inhibits its life cycle. This discovery uncovers a new pathway that can be exploited for the protection of plants against nematodes.

  16. Extracellular Actin Is a Receptor for Mycoplasma hyopneumoniae

    Directory of Open Access Journals (Sweden)

    Benjamin B. A. Raymond

    2018-02-01

    Full Text Available Mycoplasma hyopneumoniae, an agriculturally important porcine pathogen, disrupts the mucociliary escalator causing ciliostasis, loss of cilial function, and epithelial cell death within the porcine lung. Losses to swine production due to growth rate retardation and reduced feed conversion efficiency are severe, and antibiotics are used heavily to control mycoplasmal pneumonia. Notably, little is known about the repertoire of host receptors that M. hyopneumoniae targets to facilitate colonization. Here we show, for the first time, that actin exists extracellularly on porcine epithelial monolayers (PK-15 using surface biotinylation and 3D-Structured Illumination Microscopy (3D-SIM, and that M. hyopneumoniae binds to the extracellular β-actin exposed on the surface of these cells. Consistent with this hypothesis we show: (i monoclonal antibodies that target β-actin significantly block the ability of M. hyopneumoniae to adhere and colonize PK-15 cells; (ii microtiter plate binding assays show that M. hyopneumoniae cells bind to monomeric G-actin in a dose dependent manner; (iii more than 100 M. hyopneumoniae proteins were recovered from affinity-chromatography experiments using immobilized actin as bait; and (iv biotinylated monomeric actin binds directly to M. hyopneumoniae proteins in ligand blotting studies. Specifically, we show that the P97 cilium adhesin possesses at least two distinct actin-binding regions, and binds monomeric actin with nanomolar affinity. Taken together, these observations suggest that actin may be an important receptor for M. hyopneumoniae within the swine lung and will aid in the future development of intervention strategies against this devastating pathogen. Furthermore, our observations have wider implications for extracellular actin as an important bacterial receptor.

  17. Extracellular Actin Is a Receptor for Mycoplasma hyopneumoniae.

    Science.gov (United States)

    Raymond, Benjamin B A; Madhkoor, Ranya; Schleicher, Ina; Uphoff, Cord C; Turnbull, Lynne; Whitchurch, Cynthia B; Rohde, Manfred; Padula, Matthew P; Djordjevic, Steven P

    2018-01-01

    Mycoplasma hyopneumoniae , an agriculturally important porcine pathogen, disrupts the mucociliary escalator causing ciliostasis, loss of cilial function, and epithelial cell death within the porcine lung. Losses to swine production due to growth rate retardation and reduced feed conversion efficiency are severe, and antibiotics are used heavily to control mycoplasmal pneumonia. Notably, little is known about the repertoire of host receptors that M. hyopneumoniae targets to facilitate colonization. Here we show, for the first time, that actin exists extracellularly on porcine epithelial monolayers (PK-15) using surface biotinylation and 3D-Structured Illumination Microscopy (3D-SIM), and that M. hyopneumoniae binds to the extracellular β-actin exposed on the surface of these cells. Consistent with this hypothesis we show: (i) monoclonal antibodies that target β-actin significantly block the ability of M. hyopneumoniae to adhere and colonize PK-15 cells; (ii) microtiter plate binding assays show that M. hyopneumoniae cells bind to monomeric G-actin in a dose dependent manner; (iii) more than 100 M. hyopneumoniae proteins were recovered from affinity-chromatography experiments using immobilized actin as bait; and (iv) biotinylated monomeric actin binds directly to M. hyopneumoniae proteins in ligand blotting studies. Specifically, we show that the P97 cilium adhesin possesses at least two distinct actin-binding regions, and binds monomeric actin with nanomolar affinity. Taken together, these observations suggest that actin may be an important receptor for M. hyopneumoniae within the swine lung and will aid in the future development of intervention strategies against this devastating pathogen. Furthermore, our observations have wider implications for extracellular actin as an important bacterial receptor.

  18. Biphasic interactions between a cationic dendrimer and actin.

    Science.gov (United States)

    Ruenraroengsak, Pakatip; Florence, Alexander T

    2010-12-01

    Gene delivery systems face the problem not only of the route toward the cell and tissues in question, but also of the molecularly crowded environment of both the cytoplasm and the nucleus itself. One of the physical barriers in the cytoplasm for diffusing nanoparticles is an actin network. Here, we describe the finding that a self-fluorescent sixth generation cationic dendrimer (6 nm in diameter) interacts reversibly and possibly electrostatically with actin filaments in vitro. Not only does this interaction slow the diffusion of the dendrimer but it also affects actin polymerization in a biphasic manner. At low concentrations the dendrimer behaves like a G-binding actin protein, retarding actin polymerization, whereas at high concentrations the dendrimer acts as a nucleating protein accelerating the polymerization. Thus in vivo the diffusion of a dendrimer carrier such as this has both physical and chemical elements: by decreasing polymerization it might accelerate its own transport, and by enhancing actin polymerization retard it. This finding suggests that such a dendrimer may have a role as an anticancer agent through its inhibitory effect on actin polymerization.

  19. Investigating chaotic wake dynamics past a flapping airfoil and the role of vortex interactions behind the chaotic transition

    Science.gov (United States)

    Bose, Chandan; Sarkar, Sunetra

    2018-04-01

    The present study investigates the complex vortex interactions in two-dimensional flow-field behind a symmetric NACA0012 airfoil undergoing a prescribed periodic pitching-plunging motion in low Reynolds number regime. The flow-field transitions from periodic to chaotic through a quasi-periodic route as the plunge amplitude is gradually increased. This study unravels the role of the complex interactions that take place among the main vortex structures in making the unsteady flow-field transition from periodicity to chaos. The leading-edge separation plays a key role in providing the very first trigger for aperiodicity. Subsequent mechanisms like shredding, merging, splitting, and collision of vortices in the near-field that propagate and sustain the disturbance have also been followed and presented. These fundamental mechanisms are seen to give rise to spontaneous and irregular formation of new vortex couples at arbitrary locations, which are the primary agencies for sustaining chaos in the flow-field. The interactions have been studied for each dynamical state to understand the course of transition in the flow-field. The qualitative changes observed in the flow-field are manifestation of changes in the underlying dynamical system. The overall dynamics are established in the present study by means of robust quantitative measures derived from classical and non-classical tools from the dynamical system theory. As the present analysis involves a high fidelity multi-unknown system, non-classical dynamical tools such as recurrence-based time series methods are seen to be very efficient. Moreover, their application is novel in the context of pitch-plunge flapping flight.

  20. Smart Rotor Modeling: Aero-Servo-Elastic Modeling of a Smart Rotor with Adaptive Trailing Edge Flaps

    DEFF Research Database (Denmark)

    Bergami, Leonardo

    the trailing edge flap deflection to actively reduce the fatigue loads on the structure. The performance of the smart rotor configuration and its control algorithms are finally quantified by aero-servo-elastic simulations of the smart rotor turbine operating in a standard turbulent wind field.......This book presents the formulation of an aero-servo-elastic model for a wind turbine rotor equipped with Adaptive Trailing Edge Flaps (ATEF), a smart rotor configuration. As the name suggests, an aero-servo-elastic model consists of three main components: an aerodynamic model, a structural model......, and a control model. The book first presents an engineering type of aerodynamic model that accounts for the dynamic effects of flap deflection. The aerodynamic model is implemented in a Blade Element Momentum framework, and coupled with a multi-body structural model in the aero-servoelastic simulation code HAWC...

  1. Actin genes and their expression in pacific white shrimp, Litopenaeus vannamei.

    Science.gov (United States)

    Zhang, Xiaoxi; Zhang, Xiaojun; Yuan, Jianbo; Du, Jiangli; Li, Fuhua; Xiang, Jianhai

    2018-04-01

    Actin is a multi-functional gene family that can be divided into muscle-type actins and non-muscle-type actins. In this study, 37 unigenes encoding actins were identified from RNA-Seq data of Pacific white shrimp, Litopenaeus vannamei. According to phylogenetic analysis, four and three cDNAs belong to cytoplasmic- and heart-type actins and were named LvActinCT and LvActinHT, respectively. 10 cDNAs belong to the slow-type skeletal muscle actins, and 18 belong to the fast-type skeletal muscle actins; they were designated LvActinSSK and LvActinFSK, respectively. Some muscle actin genes formed gene clusters in the genome. Multiple alternative transcription starts sites (ATSSs) were found for LvActinCT1. Based on the early developmental expression profile, almost all LvActins were highly expressed between the early limb bud and post-larval stages. Using LvActinSSK5 as probes, slow-type muscle was localized in pleopod muscle and superficial ventral muscle. We also found three actin genes that were down-regulated in the hemocytes of white spot syndrome virus (WSSV)- and Vibrio parahaemolyticus-infected L. vannamei. This study provides valuable information on the actin gene structure of shrimp, furthers our understanding of the shrimp muscle system and helps us develop strategies for disease control and sustainable shrimp farming.

  2. Bacterial Actins? An Evolutionary Perspective

    Science.gov (United States)

    Doolittle, Russell F.; York, Amanda L.

    2003-01-01

    According to the conventional wisdom, the existence of a cytoskeleton in eukaryotes and its absence in prokaryotes constitute a fundamental divide between the two domains of life. An integral part of the dogma is that a cytoskeleton enabled an early eukaryote to feed upon prokaryotes, a consequence of which was the occasional endosymbiosis and the eventual evolution of organelles. Two recent papers present compelling evidence that actin, one of the principal components of a cytoskeleton, has a homolog in Bacteria that behaves in many ways like eukaryotic actin. Sequence comparisons reveml that eukaryotic actin and the bacterial homolog (mreB protein), unlike many other proteins common to eukaryotes and Bacteria, have very different and more highly extended evolutionary histories.

  3. Differential nuclear shape dynamics of invasive andnon-invasive breast cancer cells are associated with actin cytoskeleton organization and stability.

    Science.gov (United States)

    Chiotaki, Rena; Polioudaki, Hara; Theodoropoulos, Panayiotis A

    2014-08-01

    Cancer cells often exhibit characteristic aberrations in their nuclear architecture, which are indicative of their malignant potential. In this study, we have examined the nuclear and cytoskeletal composition, attachment configuration dynamics, and osmotic or drug treatment response of invasive (Hs578T and MDA-MB-231) and non-invasive (MCF-10A and MCF-7) breast cancer cell lines. Unlike MCF-10A and MCF-7, Hs578T and MDA-MB-231 cells showed extensive nuclear elasticity and deformability and displayed distinct kinetic profiles during substrate attachment. The nuclear shape of MCF-10A and MCF-7 cells remained almost unaffected upon detachment, hyperosmotic shock, or cytoskeleton depolymerization, while Hs578T and MDA-MB-231 revealed dramatic nuclear contour malformations following actin reorganization.

  4. Boomerang flap reconstruction for the breast.

    Science.gov (United States)

    Baumholtz, Michael A; Al-Shunnar, Buthainah M; Dabb, Richard W

    2002-07-01

    The boomerang-shaped latissimus dorsi musculocutaneous flap for breast reconstruction offers a stable platform for breast reconstruction. It allows for maximal aesthetic results with minimal complications. The authors describe a skin paddle to obtain a larger volume than either the traditional elliptical skin paddle or the extended latissimus flap. There are three specific advantages to the boomerang design: large volume, conical shape (often lacking in the traditional skin paddle), and an acceptable donor scar. Thirty-eight flaps were performed. No reconstruction interfered with patient's ongoing oncological regimen. The most common complication was seroma, which is consistent with other latissimus reconstructions.

  5. Actin retrograde flow controls natural killer cell response by regulating the conformation state of SHP-1.

    Science.gov (United States)

    Matalon, Omri; Ben-Shmuel, Aviad; Kivelevitz, Jessica; Sabag, Batel; Fried, Sophia; Joseph, Noah; Noy, Elad; Biber, Guy; Barda-Saad, Mira

    2018-03-01

    Natural killer (NK) cells are a powerful weapon against viral infections and tumor growth. Although the actin-myosin (actomyosin) cytoskeleton is crucial for a variety of cellular processes, the role of mechanotransduction, the conversion of actomyosin mechanical forces into signaling cascades, was never explored in NK cells. Here, we demonstrate that actomyosin retrograde flow (ARF) controls the immune response of primary human NK cells through a novel interaction between β-actin and the SH2-domain-containing protein tyrosine phosphatase-1 (SHP-1), converting its conformation state, and thereby regulating NK cell cytotoxicity. Our results identify ARF as a master regulator of the NK cell immune response. Since actin dynamics occur in multiple cellular processes, this mechanism might also regulate the activity of SHP-1 in additional cellular systems. © 2018 The Authors.

  6. Wavefront aberrometry and refractive outcomes of flap amputation after LASIK

    NARCIS (Netherlands)

    Al Saady, Rana L.; van der Meulen, Ivanka J.; Nieuwendaal, Carla P.; Engelbrecht, Leonore A.; Mourits, Maarten P.; Lapid-Gortzak, Ruth

    2014-01-01

    Laser in situ keratomileusis flap amputation was performed in 3 eyes of 2 patients because of flap melt and surface irregularity. In the first patient, a 34-year-old man, flaps were excised after a photorefractive keratectomy retreatment procedure on a previous LASIK flap had been done, secondary to

  7. RNase L Interacts with Filamin A To Regulate Actin Dynamics and Barrier Function for Viral Entry

    Science.gov (United States)

    Siddiqui, Mohammad Adnan; Dayal, Shubham; Naji, Merna; Ezelle, Heather J.; Zeng, Chun; Zhou, Aimin; Hassel, Bret A.

    2014-01-01

    ABSTRACT The actin cytoskeleton and its network of associated proteins constitute a physical barrier that viruses must circumvent to gain entry into cells for productive infection. The mechanisms by which the physical signals of infection are sensed by the host to activate an innate immune response are not well understood. The antiviral endoribonuclease RNase L is ubiquitously expressed in a latent form and activated upon binding 2-5A, a unique oligoadenylate produced during viral infections. We provide evidence that RNase L in its inactive form interacts with the actin-binding protein Filamin A to modulate the actin cytoskeleton and inhibit virus entry. Cells lacking either RNase L or Filamin A displayed increased virus entry which was exacerbated in cells lacking both proteins. RNase L deletion mutants that reduced Filamin A interaction displayed a compromised ability to restrict virus entry, supporting the idea of an important role for the RNase L-Filamin A complex in barrier function. Remarkably, both the wild type and a catalytically inactive RNase L mutant were competent to reduce virus entry when transfected into RNase L-deficient cells, indicating that this novel function of RNase L is independent of its enzymatic activity. Virus infection and RNase L activation disrupt its association with Filamin A and release RNase L to mediate its canonical nuclease-dependent antiviral activities. The dual functions of RNase L as a constitutive component of the actin cytoskeleton and as an induced mediator of antiviral signaling and effector functions provide insights into its mechanisms of antiviral activity and opportunities for the development of novel antiviral agents. PMID:25352621

  8. Stress generation by myosin minifilaments in actin bundles

    International Nuclear Information System (INIS)

    Dasanayake, Nilushi L; Carlsson, Anders E

    2013-01-01

    Forces and stresses generated by the action of myosin minifilaments are analyzed in idealized computer-generated actin bundles, and compared to results for isotropic actin networks. The bundles are generated as random collections of actin filaments in two dimensions with constrained orientations, crosslinked and attached to two fixed walls. Myosin minifilaments are placed on actin filament pairs and allowed to move and deform the network so that it exerts forces on the walls. The vast majority of simulation runs end with contractile minifilament stress, because minifilaments rotate into energetically stable contractile configurations. This process is aided by the bending and stretching of actin filaments, which accomodate minifilament rotation. Stresses for bundles are greater than those for isotropic networks, and antiparallel filaments generate more tension than parallel filaments. The forces transmitted by the actin network to the walls of the simulation cell often exceed the tension in the minifilament itself. (paper)

  9. The Internal Pudendal Artery Perforator Thigh Flap: A New Freestyle Pedicle Flap for the Ischial Region

    Directory of Open Access Journals (Sweden)

    Ichiro Hashimoto, MD

    2014-05-01

    Conclusions: The perforator vessels of the internal pudendal artery are very close to the ischial tuberosity. Blood flow to the flap is reliable when careful debridement of the pressure sore is performed. The iPap thigh flap is a new option for soft-tissue defects in the ischial region, including ischial pressure sores.

  10. Falling, flapping, flying, swimming,...: High-Re fluid-solid interactions with vortex shedding

    Science.gov (United States)

    Michelin, Sebastien Honore Roland

    The coupling between the motion of a solid body and the dynamics of the surrounding flow is essential to the understanding of a large number of engineering and physical problems, from the stability of a slender structure exposed to the wind to the locomotion of insects, birds and fishes. Because of the strong coupling on a moving boundary of the equations for the solid and fluid, the simulation of such problems is computationally challenging and expensive. This justifies the development of simplified models for the fluid-solid interactions to study their physical properties and behavior. This dissertation proposes a reduced-order model for the interaction of a sharp-edged solid body with a strongly unsteady high Reynolds number flow. In such a case, viscous forces in the fluid are often negligible compared to the fluid inertia or the pressure forces, and the thin boundary layers separate from the solid at the edges, leading to the shedding of large and persistent vortices in the solid's wake. A general two-dimensional framework is presented based on complex potential flow theory. The formation of the solid's vortical wake is accounted for by the shedding of point vortices with unsteady intensity from the solid's sharp edges, and the fluid-solid problem is reformulated exclusively as a solid-vortex interaction problem. In the case of a rigid solid body, the coupled problem is shown to reduce to a set of non-linear ordinary differential equations. This model is used to study the effect of vortex shedding on the stability of falling objects. The solid-vortex model is then generalized to study the fluttering instability and non-linear flapping dynamics of flexible plates or flags. The uttering instability and resulting flapping motion result from the competing effects of the fluid forcing and of the solid's flexural rigidity and inertia. Finally, the solid-vortex model is applied to the study of the fundamental effect of bending rigidity on the flapping performance of

  11. Freestyle-Like V-Y Flaps of the Eyebrow: A New Outlook and Indication of an Historical Technique

    Directory of Open Access Journals (Sweden)

    Angelo Alberto Leto Barone

    2013-01-01

    Full Text Available The eyebrow region is of utmost importance for facial movement, symmetry, and the overall cosmetic appearance of the face. Trauma or tumor resection often leave scars that may dislocate the eyebrow producing an alteration both in static symmetry of the face and in the dynamic expressivity. The authors present a technique for eyebrow’s defects repair using the remaining eyebrow advancement by means of a “freestyle-like” V-Y flap. In the past two years a total of eight consecutive patients underwent excision of skin lesions in the superciliary region and immediate reconstruction with this technique. On histology, six patients were affected from basal cell carcinomas, one from squamous cell carcinoma, and one from congenital intradermal melanocytic nevus. The pedicle of the flap included perforators from the supratrochlear, supraorbital, or superficial temporalis artery. Advancement of the entire aesthetic subunit that includes the eyebrow using a V-Y perforator flap was performed successfully in all cases achieving full, tension-free closure of defects up to 3.0 cm. “Freestyle-like” V-Y flaps should be considered as a first-line choice for partial defects of the eyebrow. The greater mobility compared to random subcutaneous flaps allows to reconstruct large defects providing an excellent cosmetic result.

  12. Developmental expression of the alpha-skeletal actin gene

    Directory of Open Access Journals (Sweden)

    Vonk Freek J

    2008-06-01

    Full Text Available Abstract Background Actin is a cytoskeletal protein which exerts a broad range of functions in almost all eukaryotic cells. In higher vertebrates, six primary actin isoforms can be distinguished: alpha-skeletal, alpha-cardiac, alpha-smooth muscle, gamma-smooth muscle, beta-cytoplasmic and gamma-cytoplasmic isoactin. Expression of these actin isoforms during vertebrate development is highly regulated in a temporal and tissue-specific manner, but the mechanisms and the specific differences are currently not well understood. All members of the actin multigene family are highly conserved, suggesting that there is a high selective pressure on these proteins. Results We present here a model for the evolution of the genomic organization of alpha-skeletal actin and by molecular modeling, illustrate the structural differences of actin proteins of different phyla. We further describe and compare alpha-skeletal actin expression in two developmental stages of five vertebrate species (mouse, chicken, snake, salamander and fish. Our findings confirm that alpha-skeletal actin is expressed in skeletal muscle and in the heart of all five species. In addition, we identify many novel non-muscular expression domains including several in the central nervous system. Conclusion Our results show that the high sequence homology of alpha-skeletal actins is reflected by similarities of their 3 dimensional protein structures, as well as by conserved gene expression patterns during vertebrate development. Nonetheless, we find here important differences in 3D structures, in gene architectures and identify novel expression domains for this structural and functional important gene.

  13. The Versatile Extended Thoracodorsal Artery Perforator Flap for Breast Reconstruction

    DEFF Research Database (Denmark)

    Jacobs, Jordan; Børsen-Koch, Mikkel; Gunnarsson, Gudjon L.

    2016-01-01

    complications occurred in 10 of 106 (10%) cases and included hematoma (1/108), venous congestion (2/108), and partial flap necrosis (7/108). The reconstructive goal was achieved in 103 of 106 (97%) flaps. CONCLUSIONS: The TAP flap is a pedicled, fasciocutaneous flap that can be used for total breast...

  14. Unique ζ-chain motifs mediate a direct TCR-actin linkage critical for immunological synapse formation and T-cell activation.

    Science.gov (United States)

    Klieger, Yair; Almogi-Hazan, Osnat; Ish-Shalom, Eliran; Pato, Aviad; Pauker, Maor H; Barda-Saad, Mira; Wang, Lynn; Baniyash, Michal

    2014-01-01

    TCR-mediated activation induces receptor microclusters that evolve to a defined immune synapse (IS). Many studies showed that actin polymerization and remodeling, which create a scaffold critical to IS formation and stabilization, are TCR mediated. However, the mechanisms controlling simultaneous TCR and actin dynamic rearrangement in the IS are yet not fully understood. Herein, we identify two novel TCR ζ-chain motifs, mediating the TCR's direct interaction with actin and inducing actin bundling. While T cells expressing the ζ-chain mutated in these motifs lack cytoskeleton (actin) associated (cska)-TCRs, they express normal levels of non-cska and surface TCRs as cells expressing wild-type ζ-chain. However, such mutant cells are unable to display activation-dependent TCR clustering, IS formation, expression of CD25/CD69 activation markers, or produce/secrete cytokine, effects also seen in the corresponding APCs. We are the first to show a direct TCR-actin linkage, providing the missing gap linking between TCR-mediated Ag recognition, specific cytoskeleton orientation toward the T-cell-APC interacting pole and long-lived IS maintenance. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Suspension Bridge Flutter for Girder with Separate Control Flaps

    DEFF Research Database (Denmark)

    Huynh, T.; Thoft-Christensen, Palle

    Active vibration control of long span suspension bridge flutter using separated control flaps (SFSC) has shown to increase effectively the critical wind speed of bridges. In this paper, an SFSC calculation based on modal equations of the vertical and torsional motions of the bridge girder including...... the flaps is presented. The length of the flaps attached to the girder, the flap configuration and the flap rotational angles are parameters used to increase the critical wind speed of the bridge. To illustrate the theory a numerical example is shown for a suspension bridge of 1000m+2500m+1000m span based...... on the Great Belt Bridge streamlined girder....

  16. Reconstruction of radionecrotic ulcer using a myocutaneous flap

    International Nuclear Information System (INIS)

    Takahashi, Hiroyuki; Okano, Shinji; Iwasaki, Yasumasa; Mori, Tamotsu; Miyamoto, Yoshihiro; Shigeki, Sadayuki

    1990-01-01

    Problems in the surgical treatment of radionecrotic ulcers, using a myocutaneous flap, have been reviewed in 21 patients. These problems included poor wound healing, radiation damage to important nerves and vessels there by making dissection difficult, malignant changes, infections, continuing necrosis of the tissue, and bleeding during surgery and secondary hemorrhaging. The use of a myocutaneous flap has many advantages when compared with conventional flaps and free skin grafts in the reconstruction of radionecrotic ulcers. Flap survival was good, but an incomplete excision of the ulcer delayed primary wound healing. Therefore, complete excision of the radionecrotic ulcer is imperative. (author)

  17. Island Latissimus Dorsi Muscle Flap and a Perforator Flap in Repairing Post-Gunshot Thoracic Spine CSF Fistula: Case Presentation

    Directory of Open Access Journals (Sweden)

    Nangole F. Wanjala

    2015-01-01

    Full Text Available Persistent posttraumatic CSF fluid leakage may present a challenge to manage. Failure to address the leakage may result in complications such as meningitis, septicemia, radiculopathy, muscle weakness, and back pains. While the majority of the leakages may be managed conservatively, large dura defects as a result of gunshot wounds or motor vehicle accidents are best managed by surgical interventions. This may range from primary closure of the defect to fascial grafts, adhesive glues, and flaps. We present our experience with the use of flaps in a patient who had sustained such wounds in the thoracic spine. An island latissimus dorsal flap and a perforator fasciocutaneous flap were used to close the defect. Postoperatively the patient recovered well and the wounds healed without any complications.

  18. [Repair of pressure sores over ischial tuberosity with long head of biceps femoris muscle flap combined with semi-V posterior thigh fasciocutaneous flap].

    Science.gov (United States)

    Hai, Heng-lin; Shen, Chuan-an; Chai, Jia-ke; Li, Hua-tao

    2012-02-01

    To explore the clinical effect of transplantation of the long head of biceps femoris muscle flap in combination with semi-V posterior thigh fasciocutaneous flap for repair of pressure sores over ischial tuberosity. Eight patients with 10 deep pressure sores over ischial tuberosity were admitted to the First Affiliated Hospital to the PLA General Hospital and the 98th Hospital of PLA from April 2004 to June 2010. The wounds measured from 2 cm × 2 cm to 6 cm × 4 cm were covered with the long head of biceps femoris muscle flap and semi-V posterior thigh fasciocutaneous flap (ranged from 10 cm × 6 cm to 13 cm × 8 cm). The condition of flaps was observed and followed up for a long time. All flaps survived. Nine wounds healed by first intention. Subcutaneous accumulation of fluids occurred in one wound with formation of a sinus at drainage site, and it healed after dressing change for 25 days. Patients were followed up for 7 to 34 months. Sore recurred in one patient 9 months after surgery, and it was successfully repaired with the same flap for the second time. Flaps in the other 7 patients appeared satisfactory with soft texture and without ulceration. This combined flap is easy in formation and transfer, and it causes little side injury with good resistance against pressure. It is a new method for repair of pressure sore over sacral region.

  19. Internal Mammary Vessels’ Impact on Abdominal Skin Perfusion in Free Abdominal Flap Breast Reconstruction

    Directory of Open Access Journals (Sweden)

    Solveig Nergård, MD

    2017-12-01

    Conclusions:. Using the IMV in free abdominal flap breast reconstruction had a significant effect on abdominal skin perfusion and may contribute to abdominal wound healing problems. The reperfusion of the abdominal skin was a dynamic process showing an increase in perfusion in the affected areas during the postoperative days.

  20. Changes in Actin Organization During the Cytotoxic Process

    NARCIS (Netherlands)

    Radosevic, K.; Radosevic, Katarina; van Leeuwen, Anne Marie T.; Segers-Nolten, Gezina M.J.; Figdor, Carl; de Grooth, B.G.; Greve, Jan

    1994-01-01

    Changes in organization of F-actin during the cytotoxic process between NK and K562 cells have been observed and studied using confpcal laser scanning microscopy and quantitative fluorescence microscopy. An increase in F-actin content and orientation of F-actin towards the target cell have been

  1. Antibodies to actin in autoimmune haemolytic anaemia

    Directory of Open Access Journals (Sweden)

    Ritzmann Mathias

    2010-03-01

    Full Text Available Abstract Background In autoimmune haemolytic anaemia (AIHA, autoreactive antibodies directed against red blood cells are up-regulated, leading to erythrocyte death. Mycoplasma suis infections in pigs induce AIHA of both the warm and cold types. The aim of this study was to identify the target autoantigens of warm autoreactive IgG antibodies. Sera from experimentally M. suis-infected pigs were screened for autoreactivity. Results Actin-reactive antibodies were found in the sera of 95% of all animals tested. The reactivity was species-specific, i.e. reactivity with porcine actin was significantly higher than with rabbit actin. Sera of animals previously immunised with the M. suis adhesion protein MSG1 showed reactivity with actin prior to infection with M. suis indicating that molecular mimicry is involved in the specific autoreactive mechanism. A potentially cross-reactive epitope was detected. Conclusions This is the first report of autoreactive anti-actin antibodies involved in the pathogenesis of autoimmune haemolytic anaemia.

  2. Structural Basis of Actin Filament Nucleation by Tandem W Domains

    Science.gov (United States)

    Chen, Xiaorui; Ni, Fengyun; Tian, Xia; Kondrashkina, Elena; Wang, Qinghua; Ma, Jianpeng

    2013-01-01

    SUMMARY Spontaneous nucleation of actin is very inefficient in cells. To overcome this barrier, cells have evolved a set of actin filament nucleators to promote rapid nucleation and polymerization in response to specific stimuli. However, the molecular mechanism of actin nucleation remains poorly understood. This is hindered largely by the fact that actin nucleus, once formed, rapidly polymerizes into filament, thus making it impossible to capture stable multisubunit actin nucleus. Here, we report an effective double-mutant strategy to stabilize actin nucleus by preventing further polymerization. Employing this strategy, we solved the crystal structure of AMPPNP-actin in complex with the first two tandem W domains of Cordon-bleu (Cobl), a potent actin filament nucleator. Further sequence comparison and functional studies suggest that the nucleation mechanism of Cobl is probably shared by the p53 cofactor JMY, but not Spire. Moreover, the double-mutant strategy opens the way for atomic mechanistic study of actin nucleation and polymerization. PMID:23727244

  3. Traumatic corneal flap displacement after laser in situ keratomileusis (LASIK).

    Science.gov (United States)

    Tsai, Tsung-Han; Peng, Kai-Ling; Lin, Chien-Jen

    2017-01-01

    Laser in situ keratomileusis (LASIK) is the most common and popular procedure performed for the correction of refractive errors in the last two decades. We report a case of traumatic flap displacement with flap folding which occurred 3 years after LASIK was performed. Previous literature suggests that vision prognosis would be closely related to proper and prompt management of traumatic flap displacement with flap folding 3 years after LASIK. A 23-year-old female presented to our hospital who had undergone uneventful LASIK in both eyes 3 years prior. Unfortunately, she had suffered a blunt trauma in her right eye in a car accident. A late onset of corneal flap displacement was found with upper and lower portion of the flap being folded inside the corneal bed. Surgical intervention for debridement with subsequent reposition of corneal flap was performed as soon as possible in the operating room. A bandage contact lens was placed, and topical antibiotic and corticosteroids were given postoperatively. Two days after the operation, the displaced corneal flap was found to be well attached smoothly on the corneal bed without folds. The best-corrected visual acuity was 6/6 with refraction of -0.75 D to 1.0 D ×175° in her right eye 1 month later. We reviewed a total of 19 published cases of late-onset traumatic flap dislocations or displacements after LASIK with complete data from 2000 to 2014. Traumatic displacement of corneal flaps after LASIK may occur after blunt injury with specific direction of force to the flap margin, especially tangential one. According to the previous literature, late-onset traumatic flap displacement may happen at any time after LASIK and be caused by various types of injuries. Fortunately, good visual function could mostly be restored with immediate and proper management.

  4. An Elongated Leading Edge Facilitates Rotation Flap Closure: In Vivo Demonstration.

    Science.gov (United States)

    Lichon, Vanessa; Barbosa, Naiara; Gomez, Doug; Goldman, Glenn

    2016-01-01

    Variation in the design of a rotation flap may affect wound closure tension. Lengthening the leading edge of a rotation flap has been a method of reducing the tension of closure in the primary motion. An in vitro study negating this tenant has been published. The authors set out to design an in vivo experiment to determine if lengthening the leading edge of a rotation flap has the effect of reducing closure tension in the primary motion of the repair. An animal study approved by Institutional Animal Care and Use Committee was undertaken in a pig model. A tension-measuring apparatus was designed using Teflon-coated wires and digital tensiometers. Rotation flaps of a standard design and with elongated leading edges were incised on the flanks of pigs under general anesthesia. Flap closure tensions were measured at points along the leading edge of the flap and in the secondary motion. Elongating the leading edge of a flap led to a statistically significant reduction in closure tension in the primary motion of the flap and at the flap tip. The secondary motion closure tensions were essentially unaffected. The authors confirm that elongating the leading edge of a standard rotation flap will reduce closure tension in the primary flap motion.

  5. The effect of atorvastatin on survival of rat ischemic flap

    Directory of Open Access Journals (Sweden)

    Jian-Xun Chen

    2013-04-01

    Full Text Available Management of skin avulsion with tissue exposure is a challenge for plastic surgeons. Clinical observations have suggested that longer survival of skin flap prevents further contamination and infection. Less well known is the role of atorvastatin in avulsion skin flap. Therefore, we attempted to determine whether atorvastatin could alleviate avulsion skin flap in a rat model. Twenty male Sprague–Dawley rats were randomized into two groups: the atorvastatin group and the control. Before operation, each rat received an initial blood perfusion scan as baseline data. Then, each rat received an operation of skin flap incision, elevation, and resuturing to the original position under general anesthesia. Another blood perfusion scan was performed on each rat 30 minutes, 4 days, and 7 days postoperatively. On the 7th postoperative day, the necrotic area of skin flap was measured as the skin flap viability. The skin flap tissues at 2.5 and 5 cm distal to the skin flap base were collected for histopathological analysis, as well as measurement of vascular endothelial growth factor (VEGF mRNA expression, and vascular density. Compared with 30 minutes postoperation, there was a significant increase in the ratio of skin flap blood perfusion on the 4th and 7th days postoperation in both control and atorvastatin groups (p<0.05. Compared with the control group, there was a significant decrease in necrotic area, significant increase in ratio of skin flap blood perfusion on postoperation days 4 and 7, and significant increase in vascular density under high field at 2.5 cm distal to the base of skin flap in the atorvastatin group (p<0.05. The VEGF121 and VEGF165 mRNA expression at 2.5 cm distal to the base of skin flap differed significantly between the two groups (p<0.05. Compared with the control group, atorvastatin treatment improved skin flap blood perfusion, vascular density, and necrotic area dependent on VEGF mRNA expression.

  6. Postirradiation flap infection about the oral cavity

    International Nuclear Information System (INIS)

    Cabbabe, E.B.; Herbold, D.R.; Sunwoo, Y.C.; Baroudi, I.F.

    1983-01-01

    Postirradiation alteration of oral flora is well documented in the literature. Infection as a complication leading to partial or complete loss of a flap used to reconstruct a defect in the oral cavity is a worrisome outcome. We describe how a flap that was judged clinically to be viable became overwhelmingly infected with the Klebsiella oxytoca, an oral cavity pathogen encountered in this patient following irradiation. Local and systemic changes led to detachment of the flap. This complication may be explained, in view of the absence of venous congestion or arterial ischemia both clinically and pathologically, by the proven contamination of the flap by the Klebsiella pathogen. Local factors resulted in lower resistance and subsequent overwhelming infection. Discussion of the case, review of pertinent literature, and proposed solutions are presented

  7. Traumatic corneal flap displacement after laser in situ keratomileusis (LASIK

    Directory of Open Access Journals (Sweden)

    Tsai TH

    2017-04-01

    Full Text Available Tsung-Han Tsai,1 Kai-Ling Peng,1 Chien-Jen Lin2 1Department of Ophthalmology, 2Department of Radiology, Chi Mei Medical Center, Tainan, Taiwan Background: Laser in situ keratomileusis (LASIK is the most common and popular procedure performed for the correction of refractive errors in the last two decades. We report a case of traumatic flap displacement with flap folding which occurred 3 years after LASIK was performed. Previous literature suggests that vision prognosis would be closely related to proper and prompt management of traumatic flap displacement with flap folding 3 years after LASIK.Case presentation: A 23-year-old female presented to our hospital who had undergone uneventful LASIK in both eyes 3 years prior. Unfortunately, she had suffered a blunt trauma in her right eye in a car accident. A late onset of corneal flap displacement was found with upper and lower portion of the flap being folded inside the corneal bed. Surgical intervention for debridement with subsequent reposition of corneal flap was performed as soon as possible in the operating room. A bandage contact lens was placed, and topical antibiotic and corticosteroids were given postoperatively. Two days after the operation, the displaced corneal flap was found to be well attached smoothly on the corneal bed without folds. The best-corrected visual acuity was 6/6 with refraction of −0.75 D to 1.0 D ×175° in her right eye 1 month later.Literature review: We reviewed a total of 19 published cases of late-onset traumatic flap dislocations or displacements after LASIK with complete data from 2000 to 2014.Conclusion: Traumatic displacement of corneal flaps after LASIK may occur after blunt injury with specific direction of force to the flap margin, especially tangential one. According to the previous literature, late-onset traumatic flap displacement may happen at any time after LASIK and be caused by various types of injuries. Fortunately, good visual function could

  8. A Single Amino Acid Difference between Mouse and Human 5-Lipoxygenase Activating Protein (FLAP) Explains the Speciation and Differential Pharmacology of Novel FLAP Inhibitors.

    Science.gov (United States)

    Blevitt, Jonathan M; Hack, Michael D; Herman, Krystal; Chang, Leon; Keith, John M; Mirzadegan, Tara; Rao, Navin L; Lebsack, Alec D; Milla, Marcos E

    2016-06-10

    5-Lipoxygenase activating protein (FLAP) plays a critical role in the metabolism of arachidonic acid to leukotriene A4, the precursor to the potent pro-inflammatory mediators leukotriene B4 and leukotriene C4 Studies with small molecule inhibitors of FLAP have led to the discovery of a drug binding pocket on the protein surface, and several pharmaceutical companies have developed compounds and performed clinical trials. Crystallographic studies and mutational analyses have contributed to a general understanding of compound binding modes. During our own efforts, we identified two unique chemical series. One series demonstrated strong inhibition of human FLAP but differential pharmacology across species and was completely inactive in assays with mouse or rat FLAP. The other series was active across rodent FLAP, as well as human and dog FLAP. Comparison of rodent and human FLAP amino acid sequences together with an analysis of a published crystal structure led to the identification of amino acid residue 24 in the floor of the putative binding pocket as a likely candidate for the observed speciation. On that basis, we tested compounds for binding to human G24A and mouse A24G FLAP mutant variants and compared the data to that generated for wild type human and mouse FLAP. These studies confirmed that a single amino acid mutation was sufficient to reverse the speciation observed in wild type FLAP. In addition, a PK/PD method was established in canines to enable preclinical profiling of mouse-inactive compounds. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

  9. Blood Perfusion in Human Eyelid Skin Flaps Examined by Laser Speckle Contrast Imaging-Importance of Flap Length and the Use of Diathermy.

    Science.gov (United States)

    Nguyen, Cu Dinh; Hult, Jenny; Sheikh, Rafi; Tenland, Kajsa; Dahlstrand, Ulf; Lindstedt, Sandra; Malmsjö, Malin

    2017-10-11

    It is well known that blood perfusion is important for the survival of skin flaps. As no study has been conducted to investigate how the blood perfusion in human eyelid skin flaps is affected by the flap length and diathermy, the present study was carried out to investigate these in patients. Fifteen upper eyelids were dissected as part of a blepharoplastic procedure, releasing a 30-mm long piece of skin, while allowing the 5 mm wide distal part of the skin to remain attached, to mimic a skin flap (hereafter called a "skin flap"). Blood perfusion was measured before and after repeated diathermy, using laser speckle contrast imaging. Blood perfusion decreased from the base to the tip of the flap: 5 mm from the base, the perfusion was 69%, at 10 mm it was 40%, at 15 mm it was 20%, and at 20 mm it was only 13% of baseline values. Diathermy further decreased blood perfusion (measured 15 mm from the base) to 13% after applying diathermy for the first time, to 6% after the second and to 4% after the third applications of diathermy. Blood perfusion falls rapidly with distance from the base of skin flaps on the human eyelid, and diathermy reduces blood perfusion even further. Clinically, it may be advised that flaps with a width of 5 mm be no longer than 15 mm (i.e., a width:length ratio of 1:3), and that the use of diathermy should be carefully considered.

  10. "Apron" flap and re-creation of the inframammary fold following TRAM flap breast reconstruction.

    Science.gov (United States)

    Amir, A; Silfen, R; Hauben, D J

    2000-03-01

    To the best of our knowledge, the recreation of an inframammary fold after TRAM flap breast reconstruction has not yet been described. This article offers a technique for the creation of an inframammary fold as a secondary procedure. The technique has been performed thus far in two patients with good aesthetic outcomes and no postoperative complications. It may also be suitable for adding bulk to the TRAM flap, especially in bilateral breast reconstruction, and for other minor chest deformities.

  11. Contralateral lumbo-umbilical flap: A versatile technique for volar finger coverage

    Directory of Open Access Journals (Sweden)

    Akram Hussain Bijli

    2017-01-01

    Full Text Available Background: While contemplating any difficult soft tissue reconstruction, patient comfort and compliance is of paramount importance. Reconstruction of the volar aspect of fingers and hand by the ipsilateral pedicled flaps (groin flap, abdominal flaps is demanding as the flap inset is difficult for the surgeon and very uncomfortable for the patient. This often leads to flap complications. For the comfort of the patient, better compliance and ease of complete inset, we planned to manage soft tissue defects of the volar aspect of fingers and hand by a new contralateral pedicled lumbo-umbilical flap. This flap is based on the paraumbilical perforators of deep inferior epigastric artery. Materials and Methods: The contralateral pedicled lumbo-umbilical flap was used in eight patients with high-tension electrical burn injuries involving the volar aspect of fingers and hand. The patients were closely observed for first 6 weeks for any flap or donor site complications and then followed monthly to assess donor and recipient site characteristics for 6 months to 2 years. Results and Conclusion: Large flaps up to 8 cm × 16 cm were raised. All but one flaps survived completely. All patients were mobilised within 48 h and five were discharged in less than a week after initial inset. The flap is reliable, easy to harvest and easy to inset on the volar aspect of fingers. The arm is positioned in a very comfortable position. The main disadvantage, however, is a conspicuous abdominal scar.

  12. A standardized model for predicting flap failure using indocyanine green dye

    Science.gov (United States)

    Zimmermann, Terence M.; Moore, Lindsay S.; Warram, Jason M.; Greene, Benjamin J.; Nakhmani, Arie; Korb, Melissa L.; Rosenthal, Eben L.

    2016-03-01

    Techniques that provide a non-invasive method for evaluation of intraoperative skin flap perfusion are currently available but underutilized. We hypothesize that intraoperative vascular imaging can be used to reliably assess skin flap perfusion and elucidate areas of future necrosis by means of a standardized critical perfusion threshold. Five animal groups (negative controls, n=4; positive controls, n=5; chemotherapy group, n=5; radiation group, n=5; chemoradiation group, n=5) underwent pre-flap treatments two weeks prior to undergoing random pattern dorsal fasciocutaneous flaps with a length to width ratio of 2:1 (3 x 1.5 cm). Flap perfusion was assessed via laser-assisted indocyanine green dye angiography and compared to standard clinical assessment for predictive accuracy of flap necrosis. For estimating flap-failure, clinical prediction achieved a sensitivity of 79.3% and a specificity of 90.5%. When average flap perfusion was more than three standard deviations below the average flap perfusion for the negative control group at the time of the flap procedure (144.3+/-17.05 absolute perfusion units), laser-assisted indocyanine green dye angiography achieved a sensitivity of 81.1% and a specificity of 97.3%. When absolute perfusion units were seven standard deviations below the average flap perfusion for the negative control group, specificity of necrosis prediction was 100%. Quantitative absolute perfusion units can improve specificity for intraoperative prediction of viable tissue. Using this strategy, a positive predictive threshold of flap failure can be standardized for clinical use.

  13. Chronic Actinic Dermatitis

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    Bengü Çevirgen Cemil

    2017-06-01

    Full Text Available Chronic actinic dermatitis (CAD is characterized by persistent eczema-like lesions, mainly on sun-exposed sites, induced by ultraviolet B, sometimes ultraviolet A, and occasionally visible light. CAD is a rare photodermatitis. It is often associated with contact allergens including airborne allergens such as fragrances, plant antigens and topical medications. A 62 year old farmer is applied with eczematous lesions restricted to sun-exposed areas. Clinical findings and histopathologic features were consistent with the diagnosis of chronic actinic dermatitis. The patient also had contact allergy to multiple allergens. We present this case to emphasize the significance of patch test on CAD treatment and the success of topical tacrolimus and azathioprine.

  14. Actinic Granuloma with Focal Segmental Glomerulosclerosis

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    Ruedee Phasukthaworn

    2016-02-01

    Full Text Available Actinic granuloma is an uncommon granulomatous disease, characterized by annular erythematous plaque with central clearing predominately located on sun-damaged skin. The pathogenesis is not well understood, ultraviolet radiation is recognized as precipitating factor. We report a case of a 52-year-old woman who presented with asymptomatic annular erythematous plaques on the forehead and both cheeks persisting for 2 years. The clinical presentation and histopathologic findings support the diagnosis of actinic granuloma. During that period of time, she also developed focal segmental glomerulosclerosis. The association between actinic granuloma and focal segmental glomerulosclerosis needs to be clarified by further studies.

  15. Clinical application of scrotal flap on penis lengthening.

    Science.gov (United States)

    Zhuo, Qinqiang; Li, Shirong; Wu, Julong; Wang, Zhenxiang; Yang, Dongyun; Tao, Ling

    2009-03-01

    To investigate the clinical application of the scrotal flap on penis lengthening. One hundred and fifty-two patients were operated using the scrotal flap from July 1998 to January 2008 at the Department of Plastic and Aesthetic, Surgery Southwest Hospital, Chongqing, China. The procedure consisted of designing a positive sign shaped incision 1.5cm above the root of the penis, dissect and release the superficial suspensory ligament and part of the deep suspensory ligament, then cover the elongated cavernosum with proper scrotal flap. Six-month to 5-year follow-up showed that all patients were satisfied with the good contour and function of the penis. The operation was successful. The method of using scrotal flap on penis lengthening has the following advantages: simple operation, reliable blood supply of the flap, one-stage operation, and satisfactory postoperative results. It is a preferable operation technique for penis lengthening.

  16. Ring closure in actin polymers

    Energy Technology Data Exchange (ETDEWEB)

    Sinha, Supurna, E-mail: supurna@rri.res.in [Raman Research Institute, Bangalore 560080 (India); Chattopadhyay, Sebanti [Doon University, Dehradun 248001 (India)

    2017-03-18

    We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers. - Highlights: • Ring closure of biopolymers. • Worm like chain model. • Predictions for experiments.

  17. p95-APP1 links membrane transport to Rac-mediated reorganization of actin

    DEFF Research Database (Denmark)

    Di Cesare, A; Paris, S; Albertinazzi, C

    2000-01-01

    Motility requires protrusive activity at the cellular edge, where Rho family members regulate actin dynamics. Here we show that p95-APP1 (ArfGAP-putative, Pix-interacting, paxillin-interacting protein 1), a member of the GIT1/PKL family, is part of a complex that interacts with Rac. Wild-type and...

  18. The evolution of compositionally and functionally distinct actin filaments.

    Science.gov (United States)

    Gunning, Peter W; Ghoshdastider, Umesh; Whitaker, Shane; Popp, David; Robinson, Robert C

    2015-06-01

    The actin filament is astonishingly well conserved across a diverse set of eukaryotic species. It has essentially remained unchanged in the billion years that separate yeast, Arabidopsis and man. In contrast, bacterial actin-like proteins have diverged to the extreme, and many of them are not readily identified from sequence-based homology searches. Here, we present phylogenetic analyses that point to an evolutionary drive to diversify actin filament composition across kingdoms. Bacteria use a one-filament-one-function system to create distinct filament systems within a single cell. In contrast, eukaryotic actin is a universal force provider in a wide range of processes. In plants, there has been an expansion of the number of closely related actin genes, whereas in fungi and metazoa diversification in tropomyosins has increased the compositional variety in actin filament systems. Both mechanisms dictate the subset of actin-binding proteins that interact with each filament type, leading to specialization in function. In this Hypothesis, we thus propose that different mechanisms were selected in bacteria, plants and metazoa, which achieved actin filament compositional variation leading to the expansion of their functional diversity. © 2015. Published by The Company of Biologists Ltd.

  19. Digital artery perforator (DAP) flaps: modifications for fingertip and finger stump reconstruction.

    Science.gov (United States)

    Mitsunaga, Narushima; Mihara, Makoto; Koshima, Isao; Gonda, Koichi; Takuya, Iida; Kato, Harunosuke; Araki, Jun; Yamamoto, Yushuke; Yuhei, Otaki; Todokoro, Takeshi; Ishikawa, Shoichi; Eri, Uehara; Mundinger, Gerhard S

    2010-08-01

    Various fingertip reconstructions have been reported for situations where microsurgical finger replantation is impossible. One method is the digital artery perforator (DAP) flap. Herein we report 13 DAP flaps for fingertip and finger stump reconstruction following traumatic finger amputations, highlighting modifications to the originally described DAP flap. From October 1998 to December 2007, a total of 13 fingers (11 patients) underwent fingertip and finger stump reconstruction with modified DAP flaps following traumatic finger amputations. We performed six adipocutaneous flaps, three adipose-only flaps, two supercharged flaps and two extended flaps. Flap size ranged from 1.44 to 8 cm(2) (average 3.25 cm(2)). All flaps survived completely with the exception of partial skin necrosis in two cases. One of these cases required debridement and skin grafting. Our initial three cases used donor-site skin grafting. The donor site was closed primarily in the 10 subsequent cases. No patients showed postoperative hypersensitivity of repaired fingertips. Semmes-Weinstein (SW) test result for flaps including a digital nerve branch did not differ from those without (average 4.07 vs. 3.92). Modified DAP flaps allow for preservation of digital length, volume and finger function. They can be raised as adiposal-only flaps or extended flaps and supercharged through perforator-to-perforator anastomoses. The donor defect on the lateral pulp can be closed primarily or by skin grafting. For traumatic fingertip and finger stump reconstructions, DAP flaps deliver consistent aesthetic and functional results. Copyright 2009 British Association of Plastic, Reconstructive and Aesthetic Surgeons. Published by Elsevier Ltd. All rights reserved.

  20. Biomechanical corneal changes induced by different flap thickness created by femtosecond laser

    Directory of Open Access Journals (Sweden)

    Fabricio W. Medeiros

    2011-01-01

    Full Text Available OBJECTIVE: To evaluate the impact of the creation of corneal flaps at different thicknesses on the biomechanical properties of swine corneas. METHOD: Twelve swine eyes were obtained to form two groups: 100 μm flap thickness and 300 μm flap thickness. Each eye was submitted to the following examinations: raster topography to investigate corneal curvature alterations, ocular response analyzer to investigate corneal hysteresis change, optical coherence tomography to measure central corneal and flap thickness and sonic wave propagation velocity as a measure of stiffness, before and immediately after flap creation. After flap amputation, surface wave velocity measurements were repeated. RESULTS: Measured flap thicknesses were statistically different for thin and thick flap groups, with an average of 108.5 + 6.9 and 307.8 + 11.5 μm respectively. Hysteresis and corneal resistance factor did not change significantly after flap creation in the thin flap group. With thicker flaps, both parameters decreased significantly from 8.0 +1.0 to 5.1 +1.5 mmHg and from 8.2 + 1.6 to 4.1 +2.5 mmHg respectively. Simulated keratometry values increased in the thick flap group (from 39.5 + 1 D to 45.9+1.2 D after flap creation but not in the thin flap group (from 40.6 + 0.6 D to 41.4+ 1.0 D. Regarding surface wave velocity analysis, the surgical procedures induced statistically lower results in some positions. CONCLUSION: In the experimental conditions established by this model, thicker flaps presented a greater biomechanical impact on the cornea.

  1. Ornithopter Type Flapping Wings for Autonomous Micro Air Vehicles

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    Sutthiphong Srigrarom

    2015-05-01

    Full Text Available In this paper, an ornithopter prototype that mimics the flapping motion of bird flight is developed, and the lift and thrust generation characteristics of different wing designs are evaluated. This project focused on the spar arrangement and material used for the wings that could achieves improved performance. Various lift and thrust measurement techniques are explored and evaluated. Various wings of insects and birds were evaluated to understand how these natural flyers with flapping wings are able to produce sufficient lift to fly. The differences in the flapping aerodynamics were also detailed. Experiments on different wing designs and materials were conducted and a paramount wing was built for a test flight. The first prototype has a length of 46.5 cm, wing span of 88 cm, and weighs 161 g. A mechanism which produced a flapping motion was fabricated and designed to create flapping flight. The flapping flight was produced by using a single motor and a flexible and light wing structure. A force balance made of load cell was then designed to measure the thrust and lift force of the ornithopter. Three sets of wings varying flexibility were fabricated, therefore lift and thrust measurements were acquired from each different set of wings. The lift will be measured in ten cycles computing the average lift and frequency in three different speeds or frequencies (slow, medium and fast. The thrust measurement was measure likewise but in two cycles only. Several observations were made regarding the behavior of flexible flapping wings that should aid in the design of future flexible flapping wing vehicles. The wings angle or phase characteristic were analyze too and studied. The final ornithopter prototype weighs only 160 g, has a wing span of 88.5 cm, that could flap at a maximum flapping frequency of 3.869 Hz, and produce a maximum thrust and lift of about 0.719 and 0.264 N respectively. Next, we proposed resonance type flapping wing utilizes the near

  2. AtFH1 formin mutation affects actin filament and microtubule dynamics in Arabidopsis thaliana

    Czech Academy of Sciences Publication Activity Database

    Rosero, A.; Žárský, Viktor; Cvrčková, F.

    2013-01-01

    Roč. 64, č. 2 (2013), s. 585-597 ISSN 0022-0957 R&D Projects: GA ČR GAP305/10/0433 Institutional research plan: CEZ:AV0Z50380511 Keywords : Actin * Arabidopsis * At5g25500 Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.794, year: 2013

  3. Rho Kinase (ROCK) collaborates with Pak to Regulate Actin Polymerization and Contraction in Airway Smooth Muscle.

    Science.gov (United States)

    Zhang, Wenwu; Bhetwal, Bhupal P; Gunst, Susan J

    2018-05-10

    The mechanisms by which Rho kinase (ROCK) regulates airway smooth muscle contraction were determined in tracheal smooth muscle tissues. ROCK may mediate smooth muscle contraction by inhibiting myosin regulatory light chain (RLC) phosphatase. ROCK can also regulate F-actin dynamics during cell migration, and actin polymerization is critical for airway smooth muscle contraction. Our results show that ROCK does not regulate airway smooth muscle contraction by inhibiting myosin RLC phosphatase or by stimulating myosin RLC phosphorylation. We find that ROCK regulates airway smooth muscle contraction by activating the serine-threonine kinase Pak, which mediates the activation of Cdc42 and Neuronal-Wiskott-Aldrich Syndrome protein (N-WASp). N-WASP transmits signals from cdc42 to the Arp2/3 complex for the nucleation of actin filaments. These results demonstrate a novel molecular function for ROCK in the regulation of Pak and cdc42 activation that is critical for the processes of actin polymerization and contractility in airway smooth muscle. Rho kinase (ROCK), a RhoA GTPase effector, can regulate the contraction of airway and other smooth muscle tissues. In some tissues, ROCK can inhibit myosin regulatory light chain (RLC) phosphatase, which increases the phosphorylation of myosin RLC and promotes smooth muscle contraction. ROCK can also regulate cell motility and migration by affecting F-actin dynamics. Actin polymerization is stimulated by contractile agonists in airway smooth muscle tissues and is required for contractile tension development in addition to myosin RLC phosphorylation. We investigated the mechanisms by which ROCK regulates the contractility of tracheal smooth muscle tissues by expressing a kinase inactive mutant of ROCK, ROCK-K121G, in the tissues or by treating them with the ROCK inhibitor, H-1152P. Our results show no role for ROCK in the regulation of non-muscle or smooth muscle myosin RLC phosphorylation during contractile stimulation in this tissue

  4. Droplet ejection and sliding on a flapping film

    Directory of Open Access Journals (Sweden)

    Xi Chen

    2017-03-01

    Full Text Available Water recovery and subsequent reuse are required for human consumption as well as industrial, and agriculture applications. Moist air streams, such as cooling tower plumes and fog, represent opportunities for water harvesting. In this work, we investigate a flapping mechanism to increase droplet shedding on thin, hydrophobic films for two vibrational cases (e.g., ± 9 mm and 11 Hz; ± 2 mm and 100 Hz. Two main mechanisms removed water droplets from the flapping film: vibrational-induced coalescence/sliding and droplet ejection from the surface. Vibrations mobilized droplets on the flapping film, increasing the probability of coalescence with neighboring droplets leading to faster droplet growth. Droplet departure sizes of 1–2 mm were observed for flapping films, compared to 3–4 mm on stationary films, which solely relied on gravity for droplet removal. Additionally, flapping films exhibited lower percentage area coverage by water after a few seconds. The second removal mechanism, droplet ejection was analyzed with respect to surface wave formation and inertia. Smaller droplets (e.g., 1-mm diameter were ejected at a higher frequency which is associated with a higher acceleration. Kinetic energy of the water was the largest contributor to energy required to flap the film, and low energy inputs (i.e., 3.3 W/m2 were possible. Additionally, self-flapping films could enable novel water collection and condensation with minimal energy input.

  5. The Versatile Naso-Labial Flaps in Facial Reconstruction

    International Nuclear Information System (INIS)

    El-Marakby, H.H.

    2005-01-01

    Surgical excision of tumors from the face may create a defect that is difficult to restore. Skin grafts can only cover superficial defects and has a natural tendency to contract and may not take properly. Also, because of the colour mismatch, it is not cosmetically identical to the face. The use of regional flaps such as the median forehead flaps are usually bulky, can not cover a wide range of facial reconstruction and usually require the donor area to be grafted. The naso-labial flaps are very useful and versatile local flaps, with robust vascularity that can be readily elevated without a delay. The flap can be superiorly based to reconstruct defects on the cheek, side wall or the dorsum of the nose, alae, collumula and the lower eye lid. Inferiorly based flaps can be used to reconstruct defects in the upper lip, anterior floor of the mouth and the lower lip. The flap can be turned over and used as a lining of the nose and the lip. Aim of the Study: In the current study we present our experience with utilization of the nasolabial flaps in facial reconstruction. We evaluated the indications, flap designs, technique, and complications. We will also assess the final functional and aesthetic results. Material and Methods: The study included 20 patients (12 males and 8 females) presented at the surgical department, National Cancer Institute (NCl) Cairo University with skin cancer at different areas of the face. Preoperative assessment includes. Assessment of the stage of the disease, the flap design and patient general condition. The mean age of the patients was 56.3±6 years (range ]6-62 years). Fifteen patients presented with basal cell carcinoma, 2 squamous cell carcinoma, one malignant melanoma, one keratoacanthoma, and one xeroderma pigmentosa. Nasal defects constituted 75% of cases, the rest were lower eye lid (2), one upper lip and one oral commisure beside a case of cheek reconstruction. There was no major complication; only one patient suffered a reactionary

  6. Edaravone enhances the viability of ischemia/reperfusion flaps.

    Science.gov (United States)

    Zhang, Dong-Yi; Kang, Shen-Song; Zhang, Zheng-Wen; Wu, Rui

    2017-02-01

    The purpose of the experiment was to study the efficacy of edaravone in enhancing flap viability after ischemia/reperfusion (IR) and its mechanism. Forty-eight adult male SD rats were randomly divided into 3 groups: control group (n=16), IR group (n=16), and edaravone-treated IR group (n=16). An island flap at left lower abdomen (6.0 cm×3.0 cm in size), fed by the superficial epigastric artery and vein, was created in each rat of all the three groups. The arterial blood flow of flaps in IR group and edaravone-treated IR group was blocked for 10 h, and then the blood perfusion was restored. From 15 min before reperfusion, rats in the edaravone-treated IR group were intraperitoneally injected with edaravone (10 mg/kg), once every 12 h, for 3 days. Rats in the IR group and control group were intraperitoneally injected with saline, with the same method and frequency as the rats in the edaravone-treated IR group. In IR group and edaravone-treated IR group, samples of flaps were harvested after reperfusion of the flaps for 24 h. In the control group, samples of flaps were harvested 34 h after creation of the flaps. The content of malondialdehyde (MDA) and activity of superoxide dismutase (SOD) were determined, and changes in organizational structure and infiltration of inflammatory cells were observed by hematoxylin-eosin (HE) staining, apoptotic cells of vascular wall were marked by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, and the apoptotic rate of cells in vascular wall was calculated. The ultrastructural changes of vascular endothelial cells were observed by transmission electron microscopy (TEM). Seven days after the operation, we calculated the flap viability of each group, and marked vessels of flaps by immunohistochemical staining for calculating the average number of subcutaneous vessels. The results showed that the content of MDA, the number of multicore inflammatory cells and apoptotic rate of cells in vascular wall

  7. Scrotal reconstruction with superomedial fasciocutaneous thigh flap

    Directory of Open Access Journals (Sweden)

    DANIEL FRANCISCO MELLO

    2018-02-01

    Full Text Available ABSTRACT Objective: to describe the use of a superomedial fasciocutaneous thigh flap for scrotal reconstruction in open areas secondary to the surgical treatment of perineal necrotizing fasciitis (Fournier’s gangrene. Methods: retrospective analysis of cases treated at the Plastic Surgery Service of Santa Casa de Misericórdia, São Paulo, from 2009 to 2015. Results: fifteen patients underwent scrotal reconstruction using the proposed flap. The mean age was 48.9 years (28 to 66. Skin loss estimates in the scrotal region ranged from 60 to 100%. Definitive reconstruction was performed on average 30.6 days (22 to 44 after the initial surgical treatment. The mean surgical time was 76 minutes (65 to 90 to obtain the flaps, bilateral in all cases. Flap size ranged from 10cm to 13cm in the longitudinal direction and 8cm to 10cm in the cross-sectional direction. The complication rate was 26.6% (four cases, related to the occurrence of segmental and partial dehiscence. Conclusion: the superomedial fasciocutaneous flap of thigh is a reliable and versatile option for the reconstruction of open areas in the scrotal region, showing adequate esthetic and functional results.

  8. Diffusion of lipids and GPI-anchored proteins in actin-free plasma membrane vesicles measured by STED-FCS

    DEFF Research Database (Denmark)

    Schneider, Falk; Waithe, Dominic; Clausen, Mathias P

    2017-01-01

    (STED-FCS) to access and compare the diffusion characteristics of fluorescent lipid analogues and GPI-anchored proteins (GPI-APs) in the live cell plasma membrane and in actin cytoskeleton-free cell-derived giant plasma membrane vesicles (GPMVs). Hindered diffusion of phospholipids and sphingolipids......Diffusion and interaction dynamics of molecules at the plasma membrane play an important role in cellular signalling, and they are suggested to be strongly associated with the actin cytoskeleton. Here, we utilise super-resolution STED microscopy combined with fluorescence correlation spectroscopy...... forming immobile clusters, both of which disappear in GPMVs. Our data underline the crucial role of the actin cortex in maintaining hindered diffusion modes of many but not all of the membrane molecules, and highlight a powerful experimental approach to decipher specific influences on molecular plasma...

  9. Effects of structural flexibility of wings in flapping flight of butterfly.

    Science.gov (United States)

    Senda, Kei; Obara, Takuya; Kitamura, Masahiko; Yokoyama, Naoto; Hirai, Norio; Iima, Makoto

    2012-06-01

    The objective of this paper is to clarify the effects of structural flexibility of wings of a butterfly in flapping flight. For this purpose, a dynamics model of a butterfly is derived by Lagrange's method, where the butterfly is considered as a rigid multi-body system. The panel method is employed to simulate the flow field and the aerodynamic forces acting on the wings. The mathematical model is validated by the agreement of the numerical result with the experimentally measured data. Then, periodic orbits of flapping-of-wings flights are parametrically searched in order to fly the butterfly models. Almost periodic orbits are found, but they are unstable. Deformation of the wings is modeled in two ways. One is bending and its effect on the aerodynamic forces is discussed. The other is passive wing torsion caused by structural flexibility. Numerical simulations demonstrate that flexible torsion reduces the flight instability.

  10. Effects of structural flexibility of wings in flapping flight of butterfly

    International Nuclear Information System (INIS)

    Senda, Kei; Yokoyama, Naoto; Obara, Takuya; Kitamura, Masahiko; Hirai, Norio; Iima, Makoto

    2012-01-01

    The objective of this paper is to clarify the effects of structural flexibility of wings of a butterfly in flapping flight. For this purpose, a dynamics model of a butterfly is derived by Lagrange’s method, where the butterfly is considered as a rigid multi-body system. The panel method is employed to simulate the flow field and the aerodynamic forces acting on the wings. The mathematical model is validated by the agreement of the numerical result with the experimentally measured data. Then, periodic orbits of flapping-of-wings flights are parametrically searched in order to fly the butterfly models. Almost periodic orbits are found, but they are unstable. Deformation of the wings is modeled in two ways. One is bending and its effect on the aerodynamic forces is discussed. The other is passive wing torsion caused by structural flexibility. Numerical simulations demonstrate that flexible torsion reduces the flight instability. (paper)

  11. Building bridges: formin1 of Arabidopsis forms a connection between the cell wall and the actin cytoskeleton.

    Science.gov (United States)

    Martinière, Alexandre; Gayral, Philippe; Hawes, Chris; Runions, John

    2011-04-01

    Actin microfilament (MF) organization and remodelling is critical to cell function. The formin family of actin binding proteins are involved in nucleating MFs in Arabidopsis thaliana. They all contain formin homology domains in the intracellular, C-terminal half of the protein that interacts with MFs. Formins in class I are usually targeted to the plasma membrane and this is true of Formin1 (AtFH1) of A. thaliana. In this study, we have investigated the extracellular domain of AtFH1 and we demonstrate that AtFH1 forms a bridge from the actin cytoskeleton, across the plasma membrane and is anchored within the cell wall. AtFH1 has a large, extracellular domain that is maintained by purifying selection and that contains four conserved regions, one of which is responsible for immobilising the protein. Protein anchoring within the cell wall is reduced in constructs that express truncations of the extracellular domain and in experiments in protoplasts without primary cell walls. The 18 amino acid proline-rich extracellular domain that is responsible for AtFH1 anchoring has homology with cell-wall extensins. We also have shown that anchoring of AtFH1 in the cell wall promotes actin bundling within the cell and that overexpression of AtFH1 has an inhibitory effect on organelle actin-dependant dynamics. Thus, the AtFH1 bridge provides stable anchor points for the actin cytoskeleton and is probably a crucial component of the signalling response and actin-remodelling mechanisms. © 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd.

  12. Optimal pitching axis location of flapping wings for efficient hovering flight.

    Science.gov (United States)

    Wang, Q; Goosen, J F L; van Keulen, F

    2017-09-01

    Flapping wings can pitch passively about their pitching axes due to their flexibility, inertia, and aerodynamic loads. A shift in the pitching axis location can dynamically alter the aerodynamic loads, which in turn changes the passive pitching motion and the flight efficiency. Therefore, it is of great interest to investigate the optimal pitching axis for flapping wings to maximize the power efficiency during hovering flight. In this study, flapping wings are modeled as rigid plates with non-uniform mass distribution. The wing flexibility is represented by a linearly torsional spring at the wing root. A predictive quasi-steady aerodynamic model is used to evaluate the lift generated by such wings. Two extreme power consumption scenarios are modeled for hovering flight, i.e. the power consumed by a drive system with and without the capacity of kinetic energy recovery. For wings with different shapes, the optimal pitching axis location is found such that the cycle-averaged power consumption during hovering flight is minimized. Optimization results show that the optimal pitching axis is located between the leading edge and the mid-chord line, which shows close resemblance to insect wings. An optimal pitching axis can save up to 33% of power during hovering flight when compared to traditional wings used by most of flapping wing micro air vehicles (FWMAVs). Traditional wings typically use the straight leading edge as the pitching axis. With the optimized pitching axis, flapping wings show higher pitching amplitudes and start the pitching reversals in advance of the sweeping reversals. These phenomena lead to higher lift-to-drag ratios and, thus, explain the lower power consumption. In addition, the optimized pitching axis provides the drive system higher potential to recycle energy during the deceleration phases as compared to their counterparts. This observation underlines the particular importance of the wing pitching axis location for energy-efficient FWMAVs when

  13. Distally based sural neuro-fasciocutaneous perforator flap for foot and ankle reconstruction: Surgical modifications for flap pedicle and donor site closure without skin graft.

    Science.gov (United States)

    Chi, Zhenglin; Chen, Yiheng; Chu, Tinggang; Gao, Weiyang; Li, Zhijie; Yan, Hede; Song, Yonghuan

    2018-02-01

    The conventional procedure of the sural neuro-fasciocutaneous flap enables the supply of blood and venous drainage by increasing the width of the adipofascial tissue and preserving tiny venous return routes. Moreover, skin graft is a common method for donor site closure, which may lead to some complications and influence the aesthetic appearance. We report modifications for a distally based sural neuro-fasciocutaneous perforator flap and a relaying flap for donor site closure without skin graft. Twelve patients undergoing the modified flap for foot and ankle reconstruction were included in this study between 2014 and 2016. A peroneal-based perforator, a superficial vein, and the vascular axis of the sural nerve were included in the pedicle. A Z-shape skin incision was performed to explore the perforator vessels and a relaying island perforator flap was used to close the donor site. All flaps survived completely without necrosis. The area of the flaps ranged from 16 × 8 cm to 30 × 15 cm. The diameter width of the pedicle ranged from 1.0 to 2.0 cm. A relaying perforator island flap was used in 10 cases for donor site closure and no skin graft was performed. There were no serious donor site complications. All patients were satisfied with the aesthetic outcome postoperatively at the final follow-up. The distally based sural neuro-fasciocutaneous perforator flap is considered a reliable method for foot and ankle reconstruction. The modification for flap pedicle and donor site closure method without skin graft should be recommended. Copyright © 2017. Published by Elsevier Ltd.

  14. Novel method for measuring a dense 3D strain map of robotic flapping wings

    Science.gov (United States)

    Li, Beiwen; Zhang, Song

    2018-04-01

    Measuring dense 3D strain maps of the inextensible membranous flapping wings of robots is of vital importance to the field of bio-inspired engineering. Conventional high-speed 3D videography methods typically reconstruct the wing geometries through measuring sparse points with fiducial markers, and thus cannot obtain the full-field mechanics of the wings in detail. In this research, we propose a novel system to measure a dense strain map of inextensible membranous flapping wings by developing a superfast 3D imaging system and a computational framework for strain analysis. Specifically, first we developed a 5000 Hz 3D imaging system based on the digital fringe projection technique using the defocused binary patterns to precisely measure the dynamic 3D geometries of rapidly flapping wings. Then, we developed a geometry-based algorithm to perform point tracking on the precisely measured 3D surface data. Finally, we developed a dense strain computational method using the Kirchhoff-Love shell theory. Experiments demonstrate that our method can effectively perform point tracking and measure a highly dense strain map of the wings without many fiducial markers.

  15. The conserved Tarp actin binding domain is important for chlamydial invasion.

    Directory of Open Access Journals (Sweden)

    Travis J Jewett

    2010-07-01

    Full Text Available The translocated actin recruiting phosphoprotein (Tarp is conserved among all pathogenic chlamydial species. Previous reports identified single C. trachomatis Tarp actin binding and proline rich domains required for Tarp mediated actin nucleation. A peptide antiserum specific for the Tarp actin binding domain was generated and inhibited actin polymerization in vitro and C. trachomatis entry in vivo, indicating an essential role for Tarp in chlamydial pathogenesis. Sequence analysis of Tarp orthologs from additional chlamydial species and C. trachomatis serovars indicated multiple putative actin binding sites. In order to determine whether the identified actin binding domains are functionally conserved, GST-Tarp fusions from multiple chlamydial species were examined for their ability to bind and nucleate actin. Chlamydial Tarps harbored variable numbers of actin binding sites and promoted actin nucleation as determined by in vitro polymerization assays. Our findings indicate that Tarp mediated actin binding and nucleation is a conserved feature among diverse chlamydial species and this function plays a critical role in bacterial invasion of host cells.

  16. The Reliability of Pectorals Major Myocutaneous Flap in Head and Neck Reconstruction

    International Nuclear Information System (INIS)

    El-Marakby, H.H.

    2006-01-01

    Background: The pectorals major myocutaneous pedicle flap (PMMPF) has been considered to be the workhorse of pedicled flaps in head and neck reconstruction. Several series of PMMPF procedures in head and neck reconstruction have been reported in the literature. Even with the worldwide use of free flaps, the flap is still considered the mainstay head and neck reconstructive procedures in many centers. However, the flap is usually associated with a high incidence of complications in addition 10 its large bulk compared with the free fasciocutaneous flaps. Also the final functional and the aesthetic results are not comparable to free flaps head and neck reconstruction. Aim of the Study: The aim of the study is to evaluate the reliability of such flap in selected cases of head and neck reconstruction. The indications, technique, complications and the functional as well as the aesthetic results of the flap utilization were evaluated. Patients and Methods: Between May 2002 and May 2005 a 26 consecutive head and neck reconstruction procedures using the PMMPF were carried out on 25 patients at the Department of Surgery, National Cancer Institute, Cairo University. The indications for the flap use were defects due to resection of stage II-IV cancer in the head and neck region. The site, stage of the disease and the presence or absence of distant metastasis were assessed. Also preoperative assessment included the fitness of patients for such an extensive procedure. The total operative time, the need for blood transfusion, the postoperative complications, were all documented. The length of hospital stay, the follow-up of patients as well as the incidence of local recurrence underneath the flap were all evaluated. Results: Pectorals major myocutaneous pedicled flap reconstructions were used to reconstruct defects in the following sites: oral cavity (LO patients); oropharynx/hypopharynx, (5 patients); and neck or face (10 patients). Of the 26 PMMPF reconstructions. 22 flaps were

  17. Desferrioxamine: a practical method for improving neovascularization of prefabricated flaps.

    Science.gov (United States)

    Li, Bin; Li, Hua; Jin, Rui; Cheng, Chen; Wang, Jing; Zhu, Hainan; Zan, Tao; Li, Qingfeng; Hao, Lijun

    2015-02-01

    Prefabricated flaps are an ideal alternative to repair massive and complex tissue defects. Nevertheless, the risk of necrosis due to unpredictable blood supplies is a major obstacle to the application of prefabricated flaps. The survival of a prefabricated flap depends on the neovascularization between the vascular carrier and the donor tissue. Here, we proposed that the iron chelator, desferrioxamine (DFX), owned therapeutic effects that promoted the neovascularization of prefabricated flaps. An abdominal prefabricated flap model was created in rats via a 2-stage operation. The rats were allocated into 4 groups as follows: 2 groups of rats received DFX treatments during the first or the second stage of the operation, respectively; 1 group of rats received a delay procedure 1 week before the second operation; and the final group was used as a blank control. Flap survival rates and capillary densities were evaluated between groups. The influence of DFX on the dermal fibroblasts was also studied in vitro. Desferrioxamine treatment during the first stage of the operation greatly increased flap survival rate compared to the blank control. The results were similar to those produced by the delay treatment. The vessel count results were consistent with the flap survival rate findings. In vitro, DFX treatment up-regulated the expression levels of several angiogenic factors in the dermal fibroblasts. Nevertheless, DFX treatment during the second stage of the operation was therapeutically detrimental. The application of DFX around the time of vascular carrier implantation greatly promoted neovascularization of prefabricated flaps, but was therapeutically detrimental after the flaps had been elevated.

  18. Effects of hyperbaric oxygen and irradiation on experimental skin flaps in rats

    International Nuclear Information System (INIS)

    Nemiroff, P.M.; Merwin, G.E.; Brant, T.; Cassisi, N.J.

    1985-01-01

    This study investigated the effects of hyperbaric oxygen (HBO) and irradiation (RT) on experimental skin flaps in rats under varying conditions. Animals were assigned at random to 1 of 15 groups that represented all possible ordering effects of HBO, RT, and flap, as well as controls that included flap-only, RT-only, and HBO-only groups. Cranially based skin flaps measuring 3 x 9 cm were elevated on the dorsum. The surviving length was evaluated with fluorescein dye 7 days after the operation. Depending on the treatment condition, HBO was given either 48 hours or 24 hours before flap elevation, or within 4 hours or 48 hours after flap elevation. Rats receiving RT ( 60 Co) were given a single dose of 1000 rads to the dorsum. Results showed that all groups receiving HBO within 4 hours after flap elevation had significantly greater flap survival length, with as much as a 22% greater length of surviving flap. HBO given 48 hours before flap elevation also significantly improved flap survival over controls. RT appeared to have no immediate significant effect on flap survival. However, rats receiving RT, regardless of other factors, gained significantly less weight than did controls. Findings clearly indicate that, to be effective, HBO needs to be given as soon after surgery as possible

  19. In vitro contraction of cytokinetic ring depends on myosin II but not on actin dynamics.

    Science.gov (United States)

    Mishra, Mithilesh; Kashiwazaki, Jun; Takagi, Tomoko; Srinivasan, Ramanujam; Huang, Yinyi; Balasubramanian, Mohan K; Mabuchi, Issei

    2013-07-01

    Cytokinesis in many eukaryotes involves the contraction of an actomyosin-based contractile ring. However, the detailed mechanism of contractile ring contraction is not fully understood. Here, we establish an experimental system to study contraction of the ring to completion in vitro. We show that the contractile ring of permeabilized fission yeast cells undergoes rapid contraction in an ATP- and myosin-II-dependent manner in the absence of other cytoplasmic constituents. Surprisingly, neither actin polymerization nor its disassembly is required for contraction of the contractile ring, although addition of exogenous actin-crosslinking proteins blocks ring contraction. Using contractile rings generated from fission yeast cytokinesis mutants, we show that not all proteins required for assembly of the ring are required for its contraction in vitro. Our work provides the beginnings of the definition of a minimal contraction-competent cytokinetic ring apparatus.

  20. Activation of moesin, a protein that links actin cytoskeleton to the plasma membrane, occurs by phosphatidylinositol 4,5-bisphosphate (PIP2) binding sequentially to two sites and releasing an autoinhibitory linker.

    Science.gov (United States)

    Ben-Aissa, Khadija; Patino-Lopez, Genaro; Belkina, Natalya V; Maniti, Ofelia; Rosales, Tilman; Hao, Jian-Jiang; Kruhlak, Michael J; Knutson, Jay R; Picart, Catherine; Shaw, Stephen

    2012-05-11

    Many cellular processes depend on ERM (ezrin, moesin, and radixin) proteins mediating regulated linkage between plasma membrane and actin cytoskeleton. Although conformational activation of the ERM protein is mediated by the membrane PIP2, the known properties of the two described PIP2-binding sites do not explain activation. To elucidate the structural basis of possible mechanisms, we generated informative moesin mutations and tested three attributes: membrane localization of the expressed moesin, moesin binding to PIP2, and PIP2-induced release of moesin autoinhibition. The results demonstrate for the first time that the POCKET containing inositol 1,4,5-trisphosphate on crystal structure (the "POCKET" Lys-63, Lys-278 residues) mediates all three functions. Furthermore the second described PIP2-binding site (the "PATCH," Lys-253/Lys-254, Lys-262/Lys-263) is also essential for all three functions. In native autoinhibited ERM proteins, the POCKET is a cavity masked by an acidic linker, which we designate the "FLAP." Analysis of three mutant moesin constructs predicted to influence FLAP function demonstrated that the FLAP is a functional autoinhibitory region. Moreover, analysis of the cooperativity and stoichiometry demonstrate that the PATCH and POCKET do not bind PIP2 simultaneously. Based on our data and supporting published data, we propose a model of progressive activation of autoinhibited moesin by a single PIP2 molecule in the membrane. Initial transient binding of PIP2 to the PATCH initiates release of the FLAP, which enables transition of the same PIP2 molecule into the newly exposed POCKET where it binds stably and completes the conformational activation.

  1. Mena/VASP and αII-Spectrin complexes regulate cytoplasmic actin networks in cardiomyocytes and protect from conduction abnormalities and dilated cardiomyopathy.

    Science.gov (United States)

    Benz, Peter M; Merkel, Carla J; Offner, Kristin; Abeßer, Marco; Ullrich, Melanie; Fischer, Tobias; Bayer, Barbara; Wagner, Helga; Gambaryan, Stepan; Ursitti, Jeanine A; Adham, Ibrahim M; Linke, Wolfgang A; Feller, Stephan M; Fleming, Ingrid; Renné, Thomas; Frantz, Stefan; Unger, Andreas; Schuh, Kai

    2013-08-12

    In the heart, cytoplasmic actin networks are thought to have important roles in mechanical support, myofibrillogenesis, and ion channel function. However, subcellular localization of cytoplasmic actin isoforms and proteins involved in the modulation of the cytoplasmic actin networks are elusive. Mena and VASP are important regulators of actin dynamics. Due to the lethal phenotype of mice with combined deficiency in Mena and VASP, however, distinct cardiac roles of the proteins remain speculative. In the present study, we analyzed the physiological functions of Mena and VASP in the heart and also investigated the role of the proteins in the organization of cytoplasmic actin networks. We generated a mouse model, which simultaneously lacks Mena and VASP in the heart. Mena/VASP double-deficiency induced dilated cardiomyopathy and conduction abnormalities. In wild-type mice, Mena and VASP specifically interacted with a distinct αII-Spectrin splice variant (SH3i), which is in cardiomyocytes exclusively localized at Z- and intercalated discs. At Z- and intercalated discs, Mena and β-actin localized to the edges of the sarcomeres, where the thin filaments are anchored. In Mena/VASP double-deficient mice, β-actin networks were disrupted and the integrity of Z- and intercalated discs was markedly impaired. Together, our data suggest that Mena, VASP, and αII-Spectrin assemble cardiac multi-protein complexes, which regulate cytoplasmic actin networks. Conversely, Mena/VASP deficiency results in disrupted β-actin assembly, Z- and intercalated disc malformation, and induces dilated cardiomyopathy and conduction abnormalities.

  2. Design of flapping wings for application to single active degree of freedom micro air vehicles

    Science.gov (United States)

    Chang, Kelvin Thomas

    This dissertation covers an experimental program to understand how wing compliance influences the performance of flapping micro air vehicle wings. The focus is the design of a membraned flapping wing for a single active degree of freedom mechanism, looking to maximize thrust performance in hover conditions. The optimization approach is unique in that experiments were the chosen engine as opposed to a computation model; this is because of the complexity involved in hover-mode flapping aerodynamics. The flapping mechanism and manufacturing process for fabricating the wings were carefully developed. The uncertainty in the thrust measurement was identified and reduced by implementing precision machining and repeatable techniques for fabrication. This resulted in a reduction of the manufacturing coefficient of variation from 16.8% to 2.6%. Optimization was then conducted for a single objective (Maximize thrust), using a three parameter design space, finding the highest thrust performance in wings with high aspect ratio; then, a multi-objective optimization was conducted with two objectives (Thrust and Power) and a four parameter space. The research then shifted focus to identifying the stiffness and deformation characteristics of high performance wing designs. Static stiffness measurements with a simple line load suggested that high chordwise stiffness or lower spanwise stiffness would be favorable for aerodynamic performance. To explore more components of the deformation, a full-field imaging technique was used and a uniform load was substituted to engage with the membrane. It was found that there is a range of torsional compliance where the wing is most efficient especially at higher flapping frequencies. The final component of the study was the dynamic deformation measurement. The two system, four camera digital image correlation setup uses stroboscopic measurement to capture the wing deformation. The phase shift between the twist and stroke, and the tip deflection

  3. Treatment of ischial pressure sores with double adipofascial turnover flaps.

    Science.gov (United States)

    Lin, Haodong; Hou, Chunlin; Xu, Zhen; Chen, Aiming

    2010-01-01

    Despite a variety of flap reconstruction options, the ischium remains the most difficult pressure sore site to treat. This article describes the authors' successful surgical procedure for coverage of ischial ulcers using double adipofascial turnover flaps.After debridement, the adipofascial flaps are harvested both cephalad and caudal to the defect. The flaps are then turned over to cover the exposed bone in a manner so as to overlap the 2 flaps. The skin is then closed with sutures in 2 layers. A total of 15 patients with ischial sores were treated using this surgical procedure.The follow-up period ranged from 11 to 159 months, with a mean of 93.6 months. Overall, 86.7% of the flaps (13 of 15) healed primarily. One patient had a recurrent grade II ischial pressure sore again 11 months after the operation. The other 14 patients did not have a recurrence.Treatment of ischial pressure sores with adipofascial turnover flaps provides an easy, minimally invasive procedure, with preservation of future flap options, and a soft-tissue supply sufficient for covering the bony prominence and filling dead space. This technique is a reliable and safe reconstructive modality for the management of minor ischial pressure sores.

  4. Development of an Extracorporeal Perfusion Device for Small Animal Free Flaps.

    Directory of Open Access Journals (Sweden)

    Andreas M Fichter

    Full Text Available Extracorporeal perfusion (ECP might prolong the vital storage capabilities of composite free flaps, potentially opening a wide range of clinical applications. Aim of the study was the development a validated low-cost extracorporeal perfusion model for further research in small animal free flaps.After establishing optimal perfusion settings, a specially designed extracorporeal perfusion system was evaluated during 8-hour perfusion of rat epigastric flaps followed by microvascular free flap transfer. Controls comprised sham-operation, ischemia and in vivo perfusion. Flaps and perfusate (diluted blood were closely monitored by blood gas analysis, combined laser Doppler flowmetry and remission spectroscopy and Indocyanine-Green angiography. Evaluations were complemented by assessment of necrotic area and light microscopy at day 7.ECP was established and maintained for 8 hours with constant potassium and pH levels. Subsequent flap transfer was successful. Notably, the rate of necrosis of extracorporeally perfused flaps (27% was even lower than after in vivo perfusion (49%, although not statistically significant (P = 0,083. After sham-operation, only 6% of the total flap area became necrotic, while 8-hour ischemia led to total flap loss (98%. Angiographic and histological findings confirmed these observations.Vital storage capabilities of microvascular flaps can be prolonged by temporary ECP. Our study provides important insights on the pathophysiological processes during extracorporeal tissue perfusion and provides a validated small animal perfusion model for further studies.

  5. A lining vomer flap for palate pushback in unilateral cleft palate repair.

    Science.gov (United States)

    Clavin, H D; Owsley, J Q

    1978-01-01

    A combinaation vomer mucoperiosteal flap and nasal floor mucoperiosteal flap is described which is used to achieve nasal coverage in unilateral cleft palate patients requiring pushbacks. A posteriorly based readily accessible vomer flap is raised on the cleft side and used as nasal lining for the palatal mucoperiosteal flap on the non-cleft side. On the cleft side, a symmetrically sized nasal floor flap is easily elevated under direct vision and used to cover the nasal aspect of the corresponding mucoperiosteal palatal flap.

  6. Freestyle multiple propeller flap reconstruction (jigsaw puzzle approach) for complicated back defects.

    Science.gov (United States)

    Park, Sung Woo; Oh, Tae Suk; Eom, Jin Sup; Sun, Yoon Chi; Suh, Hyun Suk; Hong, Joon Pio

    2015-05-01

    The reconstruction of the posterior trunk remains to be a challenge as defects can be extensive, with deep dead space, and fixation devices exposed. Our goal was to achieve a tension-free closure for complex defects on the posterior trunk. From August 2006 to May 2013, 18 cases were reconstructed with multiple flaps combining perforator(s) and local skin flaps. The reconstructions were performed using freestyle approach. Starting with propeller flap(s) in single or multilobed design and sequentially in conjunction with adjacent random pattern flaps such as fitting puzzle. All defects achieved tensionless primary closure. The final appearance resembled a jigsaw puzzle-like appearance. The average size of defect was 139.6 cm(2) (range, 36-345 cm(2)). A total of 26 perforator flaps were used in addition to 19 random pattern flaps for 18 cases. In all cases, a single perforator was used for each propeller flap. The defect and the donor site all achieved tension-free closure. The reconstruction was 100% successful without flap loss. One case of late infection was noted at 12 months after surgery. Using multiple lobe designed propeller flaps in conjunction with random pattern flaps in a freestyle approach, resembling putting a jigsaw puzzle together, we can achieve a tension-free closure by distributing the tension to multiple flaps, supplying sufficient volume to obliterate dead space, and have reliable vascularity as the flaps do not need to be oversized. This can be a viable approach to reconstruct extensive defects on the posterior trunk. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  7. Experience with Perforator Based Flaps for Wound Cover of the Leg ...

    African Journals Online (AJOL)

    Background: Open fractures of the distal third of the tibia and fibular offer a challenge to the orthopedic surgeon because of skin coverage. The reconstructive surgeon's help is often required in trying to achieve this. There are several options: - local flap, free flap or a cross leg flap. Local flaps have always had limitations ...

  8. Unsteady bio-fluid dynamics in flying and swimming

    Science.gov (United States)

    Liu, Hao; Kolomenskiy, Dmitry; Nakata, Toshiyuki; Li, Gen

    2017-08-01

    Flying and swimming in nature present sophisticated and exciting ventures in biomimetics, which seeks sustainable solutions and solves practical problems by emulating nature's time-tested patterns, functions, and strategies. Bio-fluids in insect and bird flight, as well as in fish swimming are highly dynamic and unsteady; however, they have been studied mostly with a focus on the phenomena associated with a body or wings moving in a steady flow. Characterized by unsteady wing flapping and body undulation, fluid-structure interactions, flexible wings and bodies, turbulent environments, and complex maneuver, bio-fluid dynamics normally have challenges associated with low Reynolds number regime and high unsteadiness in modeling and analysis of flow physics. In this article, we review and highlight recent advances in unsteady bio-fluid dynamics in terms of leading-edge vortices, passive mechanisms in flexible wings and hinges, flapping flight in unsteady environments, and micro-structured aerodynamics in flapping flight, as well as undulatory swimming, flapping-fin hydrodynamics, body-fin interaction, C-start and maneuvering, swimming in turbulence, collective swimming, and micro-structured hydrodynamics in swimming. We further give a perspective outlook on future challenges and tasks of several key issues of the field.

  9. Actin-cytoskeleton rearrangement modulates proton-induced uptake

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Dov, Nadav [Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, 69978 Tel-Aviv (Israel); Korenstein, Rafi, E-mail: korens@post.tau.ac.il [Department of Physiology and Pharmacology, Faculty of Medicine, Tel-Aviv University, 69978 Tel-Aviv (Israel)

    2013-04-15

    Recently it has been shown that elevating proton concentration at the cell surface stimulates the formation of membrane invaginations and vesicles accompanied by an enhanced uptake of macromolecules. While the initial induction of inward membrane curvature was rationalized in terms of proton-based increase of charge asymmetry across the membrane, the mechanisms underlying vesicle formation and its scission are still unknown. In light of the critical role of actin in vesicle formation during endocytosis, the present study addresses the involvement of cytoskeletal actin in proton-induced uptake (PIU). The uptake of dextran-FITC is used as a measure for the factual fraction of inward invaginations that undergo scission from the cell's plasma membrane. Our findings show that the rate of PIU in suspended cells is constant, whereas the rate of PIU in adherent cells is gradually increased in time, saturating at the level possessed by suspended cells. This is consistent with pH induced gradual degradation of stress-fibers in adherent cells. Wortmannin and calyculin-A are able to elevate PIU by 25% in adherent cells but not in suspended cells, while cytochalasin-D, rapamycin and latrunculin-A elevate PIU both in adherent and suspended cells. However, extensive actin depolymerization by high concentrations of latrunculin-A is able to inhibit PIU. We conclude that proton-induced membrane vesiculation is restricted by the actin structural resistance to the plasma membrane bending. Nevertheless, a certain degree of cortical actin restructuring is required for the completion of the scission process. - Highlights: ► Acidification of cells' exterior enhances uptake of macromolecules by the cells. ► Disruption of actin stress fibers leads to enhancement of proton induced uptake. ► Extensive depolymerization of cellular actin attenuates proton-induced uptake.

  10. Reconstruction of trochanteric pressure sores with pedicled anterolateral thigh myocutaneous flaps.

    Science.gov (United States)

    Wang, Chih-Hsin; Chen, Shih-Yi; Fu, Ju-Peng; Dai, Niann-Tzyy; Chen, Shao-Liang; Chen, Tim-Mo; Chen, Shyi-Gen

    2011-05-01

    To provide an alternative choice for covering trochanteric pressure sores, we report on a modified pedicle anterolateral thigh (ALT) myocutaneous flap based on the descending branch of the lateral circumflex femoral artery. From August 2007 to January 2010, 20 consecutive patients (10 men and 10 women) underwent 21 pedicled ALT myocutaneous flaps for reconstruction of trochanteric pressure sores. The flap was designed and elevated, resembling the ALT perforator flap including part of the vastus lateralis muscle but without skeletonisation of the perforators. The mean age of patients was 79.4 years (range: 46-103). The mean follow-up period was 13.9 months (range: 3-32). The flaps were 8-21 cm long and 5-11 cm wide. All flaps healed without major complications. All donor sites were closed primarily without skin grafting and showed good aesthetic results. No recurrence was observed. This modified design of pedicled ALT myocutaneous flap without skeletonisation of perforators is a reliable and easily harvested flap for reconstruction of trochanteric pressure sores with limited morbidity. Crown Copyright © 2010. Published by Elsevier Ltd. All rights reserved.

  11. Actin and Arp2/3 localize at the centrosome of interphase cells

    Energy Technology Data Exchange (ETDEWEB)

    Hubert, Thomas; Vandekerckhove, Joel; Gettemans, Jan, E-mail: jan.gettemans@vib-ugent.be

    2011-01-07

    Research highlights: {yields} Actin was detected at the centrosome with the anti-actin antibody 1C7 that recognizes antiparallel ('lower dimer') actin dimers. {yields} Centrosomal actin was found in interphase but not mitotic MDA-MB-231 cells. {yields} Neither the anti-actin antibody C4 that binds to globular, monomer actin, nor the anti-actin antibody 2G2 that recognizes the nuclear conformation of actin detect actin at the centrosome. {yields} The Arp2/3 complex transiently localizes at the pericentriolar matrix but not at the centrioles of interphase HEK 293T cells. -- Abstract: Although many actin binding proteins such as cortactin and the Arp2/3 activator WASH localize at the centrosome, the presence and conformation of actin at the centrosome has remained elusive. Here, we report the localization of actin at the centrosome in interphase but not in mitotic MDA-MB-231 cells. Centrosomal actin was detected with the anti-actin antibody 1C7 that recognizes antiparallel ('lower dimer') actin dimers. In addition, we report the transient presence of the Arp2/3 complex at the pericentriolar matrix but not at the centrioles of interphase HEK 293T cells. Overexpression of an Arp2/3 component resulted in expansion of the pericentriolar matrix and selective accumulation of the Arp2/3 component in the pericentriolar matrix. Altogether, we hypothesize that the centrosome transiently recruits Arp2/3 to perform processes such as centrosome separation prior to mitotic entry, whereas the observed constitutive centrosomal actin staining in interphase cells reinforces the current model of actin-based centrosome reorientation toward the leading edge in migrating cells.

  12. Actin and Arp2/3 localize at the centrosome of interphase cells

    International Nuclear Information System (INIS)

    Hubert, Thomas; Vandekerckhove, Joel; Gettemans, Jan

    2011-01-01

    Research highlights: → Actin was detected at the centrosome with the anti-actin antibody 1C7 that recognizes antiparallel ('lower dimer') actin dimers. → Centrosomal actin was found in interphase but not mitotic MDA-MB-231 cells. → Neither the anti-actin antibody C4 that binds to globular, monomer actin, nor the anti-actin antibody 2G2 that recognizes the nuclear conformation of actin detect actin at the centrosome. → The Arp2/3 complex transiently localizes at the pericentriolar matrix but not at the centrioles of interphase HEK 293T cells. -- Abstract: Although many actin binding proteins such as cortactin and the Arp2/3 activator WASH localize at the centrosome, the presence and conformation of actin at the centrosome has remained elusive. Here, we report the localization of actin at the centrosome in interphase but not in mitotic MDA-MB-231 cells. Centrosomal actin was detected with the anti-actin antibody 1C7 that recognizes antiparallel ('lower dimer') actin dimers. In addition, we report the transient presence of the Arp2/3 complex at the pericentriolar matrix but not at the centrioles of interphase HEK 293T cells. Overexpression of an Arp2/3 component resulted in expansion of the pericentriolar matrix and selective accumulation of the Arp2/3 component in the pericentriolar matrix. Altogether, we hypothesize that the centrosome transiently recruits Arp2/3 to perform processes such as centrosome separation prior to mitotic entry, whereas the observed constitutive centrosomal actin staining in interphase cells reinforces the current model of actin-based centrosome reorientation toward the leading edge in migrating cells.

  13. Coupled Vortex-Lattice Flight Dynamic Model with Aeroelastic Finite-Element Model of Flexible Wing Transport Aircraft with Variable Camber Continuous Trailing Edge Flap for Drag Reduction

    Science.gov (United States)

    Nguyen, Nhan; Ting, Eric; Nguyen, Daniel; Dao, Tung; Trinh, Khanh

    2013-01-01

    This paper presents a coupled vortex-lattice flight dynamic model with an aeroelastic finite-element model to predict dynamic characteristics of a flexible wing transport aircraft. The aircraft model is based on NASA Generic Transport Model (GTM) with representative mass and stiffness properties to achieve a wing tip deflection about twice that of a conventional transport aircraft (10% versus 5%). This flexible wing transport aircraft is referred to as an Elastically Shaped Aircraft Concept (ESAC) which is equipped with a Variable Camber Continuous Trailing Edge Flap (VCCTEF) system for active wing shaping control for drag reduction. A vortex-lattice aerodynamic model of the ESAC is developed and is coupled with an aeroelastic finite-element model via an automated geometry modeler. This coupled model is used to compute static and dynamic aeroelastic solutions. The deflection information from the finite-element model and the vortex-lattice model is used to compute unsteady contributions to the aerodynamic force and moment coefficients. A coupled aeroelastic-longitudinal flight dynamic model is developed by coupling the finite-element model with the rigid-body flight dynamic model of the GTM.

  14. The 5’cap of Tobacco Mosaic Virus (TMV) is required for virion attachment to the actin/ER network during early infection

    DEFF Research Database (Denmark)

    Christensen, Nynne Meyn; Tilsner, Jens; Bell, Karen

    to the motile cortical actin/ER network within minutes of injection. Granule movement on actin/ER was arrested by actin inhibitors indicating actindependent RNA movement. The 5’ methylguanosine TMV cap was shown to be required for vRNA anchoring to the ER. TMV vRNA lacking the 5’cap failed to form granules...... the fluorescent vRNA pool nor co-injected GFP left the injected trichome, indicating that the synthesis of unlabelled progeny viral (v)RNA is required to initiate cell-cell movement, and that virus movement is not accompanied by passive plasmodesmatal gating. Cy3-vRNA formed granules that became anchored...... on the same ER-bound granules, indicating that TMV virions may become attached to the ER prior to uncoating of the viral genome....

  15. Unsteady Aerodynamics of Flapping Wing of a Bird

    Directory of Open Access Journals (Sweden)

    M. Agoes Moelyadi

    2013-04-01

    Full Text Available The unsteady flow behavior and time-dependent aerodynamic characteristics of the flapping motion of a bird’s wing were investigated using a computational method. During flapping, aerodynamic interactions between bird wing surfaces and surrounding flow may occur, generating local time-dependent flow changes in the flow field and aerodynamic load of birds. To study the effect of flapping speed on unsteady aerodynamic load, two kinds of computational simulations were carried out, namely a quasi-steady and an unsteady simulation. To mimic the movement of the down-stroke and the upstroke of a bird, the flapping path accorded to a sinus function, with the wing attitude changing in dihedral angle and time. The computations of time-dependent viscous flow were based on the solution of the Reynolds Averaged Navier-Stokes equations by applying the k-e turbulence model. In addition, the discretization for the computational domain around the model used multi-block structured grid to provide more accuracy in capturing viscous flow, especially in the vicinity of the wing and body surfaces, to obtain a proper wing-body geometry model. For this research, the seagull bird was chosen, which has high aspect ratio wings with pointed wing-tips and a high camber wing section. The results include mesh movement, velocity contours as well as aerodynamic coefficients of the flapping motion of the bird at various flapping frequencies.

  16. The forked flap repair for hypospadias

    Directory of Open Access Journals (Sweden)

    Anil Chadha

    2012-01-01

    Full Text Available Context: Despite the abundance of techniques for the repair of Hypospadias, its problems still persist and a satisfactory design to correct the penile curvature with the formation of neourethra from the native urethral tissue or genital or extragenital tissues, with minimal postoperative complications has yet to evolve. Aim: Persisting with such an endeavor, a new technique for the repair of distal and midpenile hypospadias is described. Materials and Methods: The study has been done in 70 cases over the past 11 years. The "Forked-Flap" repair is a single stage method for the repair of such Hypospadias with chordee. It takes advantage of the rich vascular communication at the corona and capitalizes on the established reliability of the meatal based flip-flap. The repair achieves straightening of the curvature of the penis by complete excision of chordee tissue from the ventral surface of the penis beneath the urethral plate. The urethra is reconstructed using the native plate with forked flap extensions and genital tissue relying on the concept of meatal based flaps. Water proofing by dartos tissue and reinforcement by Nesbit′s prepucial tissue transfer completes the one stage procedure. Statistical Analysis: An analysis of 70 cases of this single stage technique of repair of penile hypospadias with chordee, operated at 3 to 5 years of age over the past 11 years is presented. Results and Conclusion: The Forked Flap gives comparable and replicable results; except for a urethrocutaneous fistula rate of 4% no other complications were observed.

  17. Incorporation of β-actin loading control into zymography.

    Science.gov (United States)

    Govindasamy, Natasha; Yan, MengJie; Jurasz, Paul

    2016-11-01

    Gelatin zymography and immunoblot are widely used gel electrophoresis techniques to study matrix metalloproteinases-2 and -9. Each method has its advantages and disadvantages. Zymography is exquisitely sensitive but offers no loading control to ensure equal sample loading. Immunoblot is a 100-1000-fold less sensitive, but allows for the probing of a sample loading control such as β-actin to ensure accurate protein loading. In this report, we describe two simple protocols that combine gelatin zymography to study MMP-2 and -9 levels with an in-gel β-actin immunoblot loading control, thus combining sensitivity and accuracy in a single assay. The protocols incorporate the loading of molecular weight markers to demarcate MMP-2/-9 from the β-actin. The first protocol utilizes the overlay of a 10% zymography gel over a 5% Tris-Glycine separating gel from which the β-actin is transferred. The second protocol involves the direct transfer of the β-actin from a single 10% zymography gel.

  18. Free radial forearm adiposo-fascial flap for inferior maxillectomy defect reconstruction

    Science.gov (United States)

    Thankappan, Krishnakumar; Trivedi, Nirav P.; Sharma, Mohit; Kuriakose, Moni A.; Iyer, Subramania

    2009-01-01

    A free radial forearm fascial flap has been described for intraoral reconstruction. Adiposo-fascial flap harvesting involves few technical modifications from the conventional radial forearm fascio-cutaneous free flap harvesting. We report a case of inferior maxillectomy defect reconstruction in a 42-year-old male with a free radial forearm adiposo-fascial flap with good aesthetic and functional outcome with minimal primary and donor site morbidity. The technique of raising the flap and closing the donor site needs to be meticulous in order to achieve good cosmetic and functional outcome. PMID:19881028

  19. Free radial forearm adiposo-fascial flap for inferior maxillectomy defect reconstruction

    Directory of Open Access Journals (Sweden)

    Thankappan Krishnakumar

    2009-01-01

    Full Text Available A free radial forearm fascial flap has been described for intraoral reconstruction. Adiposo-fascial flap harvesting involves few technical modifications from the conventional radial forearm fascio-cutaneous free flap harvesting. We report a case of inferior maxillectomy defect reconstruction in a 42-year-old male with a free radial forearm adiposo-fascial flap with good aesthetic and functional outcome with minimal primary and donor site morbidity. The technique of raising the flap and closing the donor site needs to be meticulous in order to achieve good cosmetic and functional outcome.

  20. Quasi-3d aerodynamic code for analyzing dynamic flap response

    DEFF Research Database (Denmark)

    Ramos García, Néstor

    A computational model for predicting the aerodynamic behavior of wind turbine airfoil profiles subjected to steady and unsteady motions has been developed. The model is based on a viscous-inviscid interaction technique using strong coupling between the viscous and inviscid parts. The inviscid part...... transition model. Validation of the steady two dimensional version of the code has been carried out against experiments for different airfoil geometries and Reynolds numbers. The unsteady version of the code has been benchmarked against experiments for different airfoil geometries at various reduced...... frequencies and oscillation amplitudes, and generally a good agreement is obtained. The capability of the code to simulate a trailing edge flap under steady or unsteady flow conditions has been proven. A parametric study on rotational effects induced by Coriolis and centrifugal forces in the boundary layer...

  1. Development of a Wind Turbine Test Rig and Rotor for Trailing Edge Flap Investigation: Static Flap Angles Case

    International Nuclear Information System (INIS)

    Abdelrahman, Ahmed; Johnson, David A

    2014-01-01

    One of the strategies used to improve performance and increase the life-span of wind turbines is active flow control. It involves the modification of the aerodynamic characteristics of a wind turbine blade by means of moveable aerodynamic control surfaces. Trailing edge flaps are relatively small moveable control surfaces placed at the trailing edge of a blade's airfoil that modify the lift of a blade or airfoil section. An instrumented wind turbine test rig and rotor were specifically developed to enable a wide-range of experiments to investigate the potential of trailing edge flaps as an active control technique. A modular blade based on the S833 airfoil was designed to allow accurate instrumentation and customizable settings. The blade is 1.7 meters long, had a constant 178mm chord and a 6° pitch. The modular aerodynamic parts were 3D printed using plastic PC-ABS material. The blade design point was within the range of wind velocities in the available large test facility. The wind facility is a large open jet wind tunnel with a maximum velocity of 11m/s in the test area. The capability of the developed system was demonstrated through an initial study of the effect of stationary trailing edge flaps on blade load and performance. The investigation focused on measuring the changes in flapwise bending moment and power production for different trailing edge flap spanwise locations and deflection angles. The relationship between the load reduction and deflection angle was linear as expected from theory and the highest reduction was caused by the flap furthest from the rotor center. Overall, the experimental setup proved to be effective in measuring small changes in flapwise bending moment within the wind turbine blade and will provide insight when (active) flap control is targeted

  2. 50 CFR Figure 16 to Part 223 - Escape Opening and Flap Dimensions for the Double Cover Flap TED

    Science.gov (United States)

    2010-10-01

    ... 50 Wildlife and Fisheries 7 2010-10-01 2010-10-01 false Escape Opening and Flap Dimensions for the Double Cover Flap TED 16 Figure 16 to Part 223 Wildlife and Fisheries NATIONAL MARINE FISHERIES SERVICE, NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION, DEPARTMENT OF COMMERCE MARINE MAMMALS THREATENED MARINE AND ANADROMOUS SPECIES Pt. 223, Fig. 1...

  3. [The vola stress change of patients after operation of wrop-around flap for thumb reconstruction].

    Science.gov (United States)

    Chen, Zhao-Jun; Pan, Yong-Wei; Wang, Zheng-Yi; Lin, Shun-Fu; Zhu, Xian-Long; Jiang, Jun; Zeng, Yan-Feng

    2009-11-01

    To analyse the vola stress change after operation of wrop-around flap for thumb reconstruction,to know the influence of vola pressure change after operation of wrop-around flap. From 1996 to 2004, 23 patients after the operation of wrop-around flap for thumb reconstruction were measured the entire footprint, the vola stress of single foot and double feet on static state and walking status. There were 16 males and 7 females,with a mean age of 23.7 years (17 to 42 years). The time from operation to measuring was 1.6 to 6 years (meana 3.8 years). The results of measuring were analyzed. Whether static footprint analysis or dynamic mechanical analysis, the plantar pressure distribution of donated foot were obviously different with those of the opposite site. The weight bearing of heel and the fourth and fifth metatarsal heads were nearly consistent with normal foot. But the former feet were obviously different. The weight bearing of the first metatarsal head was obviously lower than normal foot. And the weight bearing of the second and third metatarsal heads were obviously higher than normal foot. The operation of wrop-around flap for thumb reconstruction has advantage of the cosmesis and function of the reconstructed thumbs nearly consistent with normal thumbs. But the operation influences the postoperative foot pressure.

  4. Medial circumflex femoral artery flap for ischial pressure sore

    Directory of Open Access Journals (Sweden)

    Palanivelu S

    2009-01-01

    Full Text Available A new axial pattern flap based on the terminal branches of the medial circumflex femoral artery is described for coverage of ischial pressure sore. Based on the terminal branches of the transverse branch of medial circumflex femoral artery, which exit through the gap between the quadratus femoris muscle above and the upper border of adductor magnus muscle below, this fascio cutaneous flap is much smaller than the posterior thigh flap but extremely useful to cover ischeal pressure sores. The skin redundancy below the gluteal fold allows a primary closure of the donor defect. It can also be used in combination with biceps femoris muscle flap.

  5. Aerodynamic optimization and mechanism design of flexible variable camber trailing-edge flap

    Directory of Open Access Journals (Sweden)

    Weishuang LU

    2017-06-01

    Full Text Available Trailing-edge flap is traditionally used to improve the takeoff and landing aerodynamic performance of aircraft. In order to improve flight efficiency during takeoff, cruise and landing states, the flexible variable camber trailing-edge flap is introduced, capable of changing its shape smoothly from 50% flap chord to the rear of the flap. Using a numerical simulation method for the case of the GA (W-2 airfoil, the multi-objective optimization of the overlap, gap, deflection angle, and bending angle of the flap under takeoff and landing configurations is studied. The optimization results show that under takeoff configuration, the variable camber trailing-edge flap can increase lift coefficient by about 8% and lift-to-drag ratio by about 7% compared with the traditional flap at a takeoff angle of 8°. Under landing configuration, the flap can improve the lift coefficient at a stall angle of attack about 1.3%. Under cruise state, the flap helps to improve the lift-to-drag ratio over a wide range of lift coefficients, and the maximum increment is about 30%. Finally, a corrugated structure–eccentric beam combination bending mechanism is introduced in this paper to bend the flap by rotating the eccentric beam.

  6. Surfing pathogens and the lessons learned for actin polymerization.

    Science.gov (United States)

    Frischknecht, F; Way, M

    2001-01-01

    A number of unrelated bacterial species as well as vaccinia virus (ab)use the process of actin polymerization to facilitate and enhance their infection cycle. Studies into the mechanism by which these pathogens hijack and control the actin cytoskeleton have provided many interesting insights into the regulation of actin polymerization in migrating cells. This review focuses on what we have learnt from the actin-based motilities of Listeria, Shigella and vaccinia and discusses what we would still like to learn from our nasty friends, including enteropathogenic Escherichia coli and Rickettsia

  7. Biochemical and Cellular Assessment of Acetabular Chondral Flaps Identified During Hip Arthroscopy.

    Science.gov (United States)

    Hariri, Sanaz; Truntzer, Jeremy; Smith, Robert Lane; Safran, Marc R

    2015-06-01

    To analyze chondral flaps debrided during hip arthroscopy to determine their biochemical and cellular composition. Thirty-one full-thickness acetabular chondral flaps were collected during hip arthroscopy. Biochemical analysis was undertaken in 21 flaps from 20 patients, and cellular viability was determined in 10 flaps from 10 patients. Biochemical analysis included concentrations of (1) DNA (an indicator of chondrocyte content), (2) hydroxyproline (an indicator of collagen content), and (3) glycosaminoglycan (an indicator of chondrocyte biosynthesis). Higher values for these parameters indicated more healthy tissue. The flaps were examined to determine the percentage of viable chondrocytes. The percentage of acetabular chondral flap specimens that had concentrations within 1 SD of the mean values reported in previous normal cartilage studies was 38% for DNA, 0% for glycosaminoglycan, and 43% for hydroxyproline. The average cellular viability of our acetabular chondral flap specimens was 39% (SD, 14%). Only 2 of the 10 specimens had more than half the cells still viable. There was no correlation between (1) the gross examination of the joint or knowledge of the patient's demographic characteristics and symptoms and (2) biochemical properties and cell viability of the flap, with one exception: a degenerative appearance of the surrounding cartilage correlated with a higher hydroxyproline concentration. Although full-thickness acetabular chondral flaps can appear normal grossly, the biochemical properties and percentage of live chondrocytes in full-thickness chondral flaps encountered in hip arthroscopy show that this tissue is not normal. There has been recent interest in repairing chondral flaps encountered during hip arthroscopy. These data suggest that acetabular chondral flaps are not biochemically and cellularly normal. Although these flaps may still be valuable mechanically and/or as a scaffold in some conductive or inductive capacity, further study is

  8. Study of Flapping Flight Using Discrete Vortex Method Based Simulations

    Science.gov (United States)

    Devranjan, S.; Jalikop, Shreyas V.; Sreenivas, K. R.

    2013-12-01

    In recent times, research in the area of flapping flight has attracted renewed interest with an endeavor to use this mechanism in Micro Air vehicles (MAVs). For a sustained and high-endurance flight, having larger payload carrying capacity we need to identify a simple and efficient flapping-kinematics. In this paper, we have used flow visualizations and Discrete Vortex Method (DVM) based simulations for the study of flapping flight. Our results highlight that simple flapping kinematics with down-stroke period (tD) shorter than the upstroke period (tU) would produce a sustained lift. We have identified optimal asymmetry ratio (Ar = tD/tU), for which flapping-wings will produce maximum lift and find that introducing optimal wing flexibility will further enhances the lift.

  9. LASIK flap buttonhole treated immediately by PRK with mitomycin C.

    Science.gov (United States)

    Kymionis, George D; Portaliou, Dimitra M; Karavitaki, Alexandra E; Krasia, Maria S; Kontadakis, Georgios A; Stratos, Aimilianos; Yoo, Sonia H

    2010-03-01

    To describe the visual outcomes of three patients who had LASIK flap buttonhole and were treated immediately with photorefractive keratectomy (PRK) and topical mitomycin C (MMC) 0.02%. Three patients underwent bilateral LASIK with the SCHWIND Carriazo-Pendula 90 microm head microkeratome. In all three cases, a buttonhole flap occurred in the left eye. The flap was repositioned and phototherapeutic keratectomy for 50 microm was used for epithelial removal while immediate PRK with MMC was performed to treat the buttonhole flap. Three months after the procedure, uncorrected distance visual acuity and corrected distance visual acuity were 20/20 with regular topographic findings. Using PRK with MCC immediately after the occurrence of the LASIK flap buttonhole may be an effective treatment.

  10. WICH, a member of WASP-interacting protein family, cross-links actin filaments

    International Nuclear Information System (INIS)

    Kato, Masayoshi; Takenawa, Tadaomi

    2005-01-01

    In yeast, Verprolin plays an important role in rearrangement of the actin cytoskeleton. There are three mammalian homologues of Verprolin, WIP, CR16, and WICH, and all of them bind actin and Wiskott-Aldrich syndrome protein (WASP) and/or neural-WASP. Here, we describe a novel function of WICH. In vitro co-sedimentation analysis revealed that WICH not only binds to actin filaments but also cross-links them. Fluorescence and electron microscopy detected that this cross-linking results in straight bundled actin filaments. Overexpression of WICH alone in cultured fibroblast caused the formation of thick actin fibers. This ability of WICH depended on its own actin cross-linking activity. Importantly, the actin cross-linking activity of WICH was modified through a direct association with N-WASP. Taken together, these data suggest that WICH induces a bundled form of actin filament with actin cross-linking activity and the association with N-WASP suppresses that activity. WICH thus appears to be a novel actin bundling protein

  11. Binding and assembly of actin filaments by plasma membranes from dictyostelium discoideum

    International Nuclear Information System (INIS)

    Schwartz, M.A.; Luna, E.J.

    1986-01-01

    The binding of native, 125 I-Bolton-Hunter-labeled actin to purified Dictyostelium discoideum plasma membranes was measured using a sedimentation assay. Binding was saturable only in the presence of the actin capping protein, gelsolin. The binding curves were sigmoidal, indicating positive cooperativity at low actin concentrations. This cooperativity appeared to be due to actin-actin associations during polymerization, since phalloidin converted the curve to a hyperbolic shape. This membrane-bound actin stained with rhodamine-phalloidin and was cross-linked by m-maleimidobenzoyl succinimide ester, a bifunctional cross-linker, into multimers with the same pattern observed for cross-linked F-actin. The authors conclude that D. discoideum plasma membranes bind actin specifically and saturably and that these membranes organize actin into filaments below the normal critical concentration for polymerization. This interaction probably occurs between multiple binding sites on the membrane and the side of the actin filament, and may be related to the clustering of membrane proteins

  12. Long-term Outcomes After Flap Reconstruction in Pediatric Pressure Ulcers.

    Science.gov (United States)

    Firriolo, Joseph M; Ganske, Ingrid M; Pike, Carolyn M; Caillouette, Catherine; Faulkner, Heather R; Upton, Joseph; Labow, Brian I

    2018-02-01

    Pressure ulcers refractory to nonoperative management may undergo flap reconstruction. This study aims to evaluate the long-term outcomes and recurrence rates of flap reconstruction for pediatric pressure ulcers. We reviewed the records of patients who underwent flap reconstruction for pressure ulcer(s) from 1995 to 2013. Twenty-four patients with 30 pressure ulcers, requiring 52 flaps were included. Ulcers were stages III and IV and mostly involved either the ischia (15/30) or sacrum (8/30). Flaps were followed for a median of 4.9 years. Twenty-three patients were wheelchair dependent, and 20 had sensory impairment at their ulcer site(s). Ten patients had a history of noncompliance with preoperative management, 8 of whom experienced ulcer recurrence. Twenty-one ulcers had underlying osteomyelitis, associated with increased admissions (P = 0.019) and cumulative length of stay (P = 0.031). Overall, there was a 42% recurrence rate in ulceration after flap reconstruction. Recurrence was associated with a preoperative history of noncompliance with nonoperative therapy (P = 0.030), but not with flap type or location, age, sex, body mass index, osteomyelitis, or urinary/fecal incontinence (P > 0.05, all). Flap reconstruction can be beneficial in the management of pediatric pressure ulcers. Although high rates of long-term success with this intervention have been reported in children, we found rates of ulcer recurrence similar to that seen in adults. Poor compliance with nonoperative care and failure to modify the biopsychosocial perpetuators of pressure ulcers will likely eventuate in postoperative recurrence. Despite the many comorbidities observed in our patient sample, compliance was the best indicator of long-term skin integrity and flap success.

  13. Ezrin is down-regulated in diabetic kidney glomeruli and regulates actin reorganization and glucose uptake via GLUT1 in cultured podocytes.

    Science.gov (United States)

    Wasik, Anita A; Koskelainen, Susanna; Hyvönen, Mervi E; Musante, Luca; Lehtonen, Eero; Koskenniemi, Kerttu; Tienari, Jukka; Vaheri, Antti; Kerjaschki, Dontscho; Szalay, Csaba; Révész, Csaba; Varmanen, Pekka; Nyman, Tuula A; Hamar, Peter; Holthöfer, Harry; Lehtonen, Sanna

    2014-06-01

    Diabetic nephropathy is a complication of diabetes and a major cause of end-stage renal disease. To characterize the early pathophysiological mechanisms leading to glomerular podocyte injury in diabetic nephropathy, we performed quantitative proteomic profiling of glomeruli isolated from rats with streptozotocin-induced diabetes and controls. Fluorescence-based two-dimensional difference gel electrophoresis, coupled with mass spectrometry, identified 29 differentially expressed spots, including actin-binding protein ezrin and its interaction partner, NHERF2, which were down-regulated in the streptozotocin group. Knockdown of ezrin by siRNA in cultured podocytes increased glucose uptake compared with control siRNA-transfected cells, apparently by increasing translocation of glucose transporter GLUT1 to the plasma membrane. Knockdown of ezrin also induced actin remodeling under basal conditions, but reduced insulin-stimulated actin reorganization. Ezrin-dependent actin remodeling involved cofilin-1 that is essential for the turnover and reorganization of actin filaments. Phosphorylated, inactive cofilin-1 was up-regulated in diabetic glomeruli, suggesting altered actin dynamics. Furthermore, IHC analysis revealed reduced expression of ezrin in the podocytes of patients with diabetes. Our findings suggest that ezrin may play a role in the development of the renal complication in diabetes by regulating transport of glucose and organization of the actin cytoskeleton in podocytes. Copyright © 2014 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.

  14. A peek into tropomyosin binding and unfolding on the actin filament.

    Directory of Open Access Journals (Sweden)

    Abhishek Singh

    Full Text Available BACKGROUND: Tropomyosin is a prototypical coiled coil along its length with subtle variations in structure that allow interactions with actin and other proteins. Actin binding globally stabilizes tropomyosin. Tropomyosin-actin interaction occurs periodically along the length of tropomyosin. However, it is not well understood how tropomyosin binds actin. PRINCIPAL FINDINGS: Tropomyosin's periodic binding sites make differential contributions to two components of actin binding, cooperativity and affinity, and can be classified as primary or secondary sites. We show through mutagenesis and analysis of recombinant striated muscle alpha-tropomyosins that primary actin binding sites have a destabilizing coiled-coil interface, typically alanine-rich, embedded within a non-interface recognition sequence. Introduction of an Ala cluster in place of the native, more stable interface in period 2 and/or period 3 sites (of seven increased the affinity or cooperativity of actin binding, analysed by cosedimentation and differential scanning calorimetry. Replacement of period 3 with period 5 sequence, an unstable region of known importance for cooperative actin binding, increased the cooperativity of binding. Introduction of the fluorescent probe, pyrene, near the mutation sites in periods 2 and 3 reported local instability, stabilization by actin binding, and local unfolding before or coincident with dissociation from actin (measured using light scattering, and chain dissociation (analyzed using circular dichroism. CONCLUSIONS: This, and previous work, suggests that regions of tropomyosin involved in binding actin have non-interface residues specific for interaction with actin and an unstable interface that is locally stabilized upon binding. The destabilized interface allows residues on the coiled-coil surface to obtain an optimal conformation for interaction with actin by increasing the number of local substates that the side chains can sample. We suggest

  15. Bidirectional Interplay between Vimentin Intermediate Filaments and Contractile Actin Stress Fibers

    Directory of Open Access Journals (Sweden)

    Yaming Jiu

    2015-06-01

    Full Text Available The actin cytoskeleton and cytoplasmic intermediate filaments contribute to cell migration and morphogenesis, but the interplay between these two central cytoskeletal elements has remained elusive. Here, we find that specific actin stress fiber structures, transverse arcs, interact with vimentin intermediate filaments and promote their retrograde flow. Consequently, myosin-II-containing arcs are important for perinuclear localization of the vimentin network in cells. The vimentin network reciprocally restricts retrograde movement of arcs and hence controls the width of flat lamellum at the leading edge of the cell. Depletion of plectin recapitulates the vimentin organization phenotype of arc-deficient cells without affecting the integrity of vimentin filaments or stress fibers, demonstrating that this cytoskeletal cross-linker is required for productive interactions between vimentin and arcs. Collectively, our results reveal that plectin-mediated interplay between contractile actomyosin arcs and vimentin intermediate filaments controls the localization and dynamics of these two cytoskeletal systems and is consequently important for cell morphogenesis.

  16. Effect of Frontal Gusts and Stroke Deviation in Forward Flapping Flight and Deconstructing the Aerodynamics of a Fruit Bat

    Science.gov (United States)

    Viswanath, Kamal

    This dissertation broadly seeks to understand the effect different kinematic parameters, external forces, and dynamic wing conformation have on the fluid dynamics of flapping flight. The primary motivation is to better grasp the fundamental fluid phenomena driving efficient flapping flight in the Reynolds number regime of birds, bats, and man made fliers of similar scale. The CFD solver (GenIDLEST) used is a Navier-Stokes solver in a finite volume formulation on non-staggered structured multiblock meshes. It has the capability for both body-fitted moving grid simulations and Immersed Boundary Method (IBM) for simulating complex bodies moving within a fluid. To that purpose we investigate the response of a rigid flapping thin surface planar wing in forward flight, at Re=10,000, subjected to frontal gusts. Gusts are a common ecological hazard for flapping fliers, especially in crowded environments. Among the various temporal and spatial scales of gust possible, we look at the phasing and duration of very large spatial scale gusts and their impact on the unsteady fluid dynamics of flapping within a single flapping cycle. The gust is characterized by a step function with time scale much smaller than the flapping time period. Having the advantage of prescribing the motion, as well as the timing and duration of the gust, this allowed the observation of the effect of angle of attack (AOA) and wing rotation on the evolution of the Leading Edge Vortex (LEV) and, hence the instantaneous lift and thrust profiles, by varying the parameters. During the downstroke, frontal gusts accelerated the flow development resulting in early separation of existing LEVs and formation of new ones on the wing surface which influenced the force generation by increasing the lift and thrust. These phenomena underscored the importance of the unsteady vortex structures as the primary force generators in flapping flight. The effect of the gust is observed to be diminished when it occurs during rapid

  17. Effect of topically applied minoxidil on the survival of rat dorsal skin flap.

    Science.gov (United States)

    Gümüş, Nazım; Odemiş, Yusuf; Yılmaz, Sarper; Tuncer, Ersin

    2012-12-01

    Flap necrosis still is a challenging problem in reconstructive surgery that results in irreversible tissue loss. This study evaluated the effect of topically applied minoxidil on angiogenesis and survival of a caudally based dorsal rat skin flap. For this study, 24 male Wistar rats were randomly divided into three groups of eight each. A caudally based dorsal skin flap with the dimensions of 9 × 3 cm was raised. After elevation of the flaps, they were sutured back into their initial positions. In group 1 (control group), 1 ml of isotonic saline was applied topically to the flaps of all the animals for 14 days. In group 2, minoxidil solution was spread uniformly over the flap surface for 7 days after the flap elevation. In group 3, minoxidil solution was applied topically to the flap surface during a 14-day period. On day 7 after the flap elevation, the rats were killed. The average area of flap survival was determined for each rat. Subdermal vascular architecture and angiogenesis were evaluated under a light microscope after two full-thickness skin biopsy specimens had been obtained from the midline of the flaps. The lowest flap survival rate was observed in group 1, and no difference was observed between groups 1 and 2. Compared with groups 1 and 2, group 3 had a significantly increased percentage of flap survival (P minoxidil is vasodilation and that prolonged use before flap elevation leads to angiogenesis, increasing flap viability. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

  18. Ipsilateral fasciocutaneous flaps for leg and foot defects

    Directory of Open Access Journals (Sweden)

    Bhattacharya V

    2003-01-01

    Full Text Available It was a revolutionary enhancement for lower limb reconstruction when fasciocutaneous flaps were first described and used in clinical practice in 1981. Subsequently persistent studies were made to emphasize and confirm the rich vascular network associated with deep fascia. Thereafter studies were directed to identify the various types of perforators supplying the deep fascia and the overlying subcutaneous tissue and skin. Accordingly the scientists classified these flaps keeping in mind their clinical applications. The authors of this article have also performed extensive research on various aspects. This has led to better understanding about the finer details of vascularity. Based on this various modifications have been made for safe application of reconstruction for defects extending from knee to sole. To avoid complications the clinician should be able to select the proper procedure as regards the donor site and the possible preoperative and postoperative technical faults. A well-designed and meticulously executed flap usually has smooth recovery. Both Colour Doppler and Audio Doppler are useful tools in planning a safe flap. Now these flaps have proved to be standard technique without requiring a special set up extensive training.

  19. Two Functionally Distinct Sources of Actin Monomers Supply the Leading Edge of Lamellipodia

    Science.gov (United States)

    Vitriol, Eric A.; McMillen, Laura M.; Kapustina, Maryna; Gomez, Shawn M.; Vavylonis, Dimitrios; Zheng, James Q.

    2015-01-01

    Summary Lamellipodia, the sheet-like protrusions of motile cells, consist of networks of actin filaments (F-actin) regulated by the ordered assembly from and disassembly into actin monomers (G-actin). Traditionally, G-actin is thought to exist as a homogeneous pool. Here, we show that there are two functionally and molecularly distinct sources of G-actin that supply lamellipodial actin networks. G-actin originating from the cytosolic pool requires the monomer binding protein thymosin β4 (Tβ4) for optimal leading edge localization, is targeted to formins, and is responsible for creating an elevated G/F-actin ratio that promotes membrane protrusion. The second source of G-actin comes from recycled lamellipodia F-actin. Recycling occurs independently of Tβ4 and appears to regulate lamellipodia homeostasis. Tβ4-bound G-actin specifically localizes to the leading edge because it doesn’t interact with Arp2/3-mediated polymerization sites found throughout the lamellipodia. These findings demonstrate that actin networks can be constructed from multiple sources of monomers with discrete spatiotemporal functions. PMID:25865895

  20. Surgeon-Based 3D Printing for Microvascular Bone Flaps.

    Science.gov (United States)

    Taylor, Erin M; Iorio, Matthew L

    2017-07-01

    Background  Three-dimensional (3D) printing has developed as a revolutionary technology with the capacity to design accurate physical models in preoperative planning. We present our experience in surgeon-based design of 3D models, using home 3D software and printing technology for use as an adjunct in vascularized bone transfer. Methods  Home 3D printing techniques were used in the design and execution of vascularized bone flap transfers to the upper extremity. Open source imaging software was used to convert preoperative computed tomography scans and create 3D models. These were printed in the surgeon's office as 3D models for the planned reconstruction. Vascularized bone flaps were designed intraoperatively based on the 3D printed models. Results  Three-dimensional models were created for intraoperative use in vascularized bone flaps, including (1) medial femoral trochlea (MFT) flap for scaphoid avascular necrosis and nonunion, (2) MFT flap for lunate avascular necrosis and nonunion, (3) medial femoral condyle (MFC) flap for wrist arthrodesis, and (4) free fibula osteocutaneous flap for distal radius septic nonunion. Templates based on the 3D models allowed for the precise and rapid contouring of well-vascularized bone flaps in situ, prior to ligating the donor pedicle. Conclusions  Surgeon-based 3D printing is a feasible, innovative technology that allows for the precise and rapid contouring of models that can be created in various configurations for pre- and intraoperative planning. The technology is easy to use, convenient, and highly economical as compared with traditional send-out manufacturing. Surgeon-based 3D printing is a useful adjunct in vascularized bone transfer. Level of Evidence  Level IV. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.