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Sample records for actin network growth

  1. 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...

  2. 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.

  3. Curvature and torsion in growing actin networks

    International Nuclear Information System (INIS)

    Shaevitz, Joshua W; Fletcher, Daniel A

    2008-01-01

    Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque

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

    Science.gov (United States)

    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.

  5. Formation of actin networks in microfluidic concentration gradients

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    Natalja eStrelnikova

    2016-05-01

    Full Text Available The physical properties of cytoskeletal networks are contributors in a number of mechanical responses of cells including cellular deformation and locomotion, and are crucial for the proper action of living cells. Local chemical gradients modulate cytoskeletal functionality including the interactions of the cytoskeleton with other cellular components. Actin is a major constituent of the cytoskeleton. Introducing a microfluidic-based platform, we explored the impact of concentration gradients on the formation and structural properties of actin networks. Microfluidics-controlled flow-free steady state experimental conditions allow for the generation of chemical gradients of different profiles, such as linear or step-like. We discovered specific features of actin networks emerging in defined gradients. In particular, we analyzed the effects of spatial conditions on network properties, bending rigidities of network links, and the network elasticity.

  6. Force Exertion and Transmission in Cross-Linked Actin Networks

    Science.gov (United States)

    Stam, Samantha

    Cells are responsive to external cues in their environment telling them to proliferate or migrate within their surrounding tissue. Sensing of cues that are mechanical in nature, such stiffness of a tissue or forces transmitted from other cells, is believed to involve the cytoskeleton of a cell. The cytoskeleton is a complex network of proteins consisting of polymers that provide structural support, motor proteins that remodel these structures, and many others. We do not yet have a complete understanding of how cytoskeletal components respond to either internal or external mechanical force and stiffness. Such an understanding should involve mechanisms by which constituent molecules, such as motor proteins, are responsive to mechanics. Additionally, physical models of how forces are transmitted through biopolymer networks are necessary. My research has focused on networks formed by the cytoskeletal filament actin and the molecular motor protein myosin II. Actin filaments form networks and bundles that form a structural framework of the cell, and myosin II slides actin filaments. In this thesis, we show that stiffness of an elastic load that opposes myosin-generated actin sliding has a very sharp effect on the myosin force output in simulations. Secondly, we show that the stiffness and connectivity of cytoskeletal filaments regulates the contractility and anisotropy of network deformations that transmit force on material length scales. Together, these results have implications for predicting and interpreting the deformations and forces in biopolymeric active materials.

  7. 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.

  8. 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.

  9. Modelling phagosomal lipid networks that regulate actin assembly

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    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

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

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    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.

  11. FIMBRIN1 is involved in lily pollen tube growth by stabilizing the actin fringe.

    Science.gov (United States)

    Su, Hui; Zhu, Jinsheng; Cai, Chao; Pei, Weike; Wang, Jiaojiao; Dong, Huaijian; Ren, Haiyun

    2012-11-01

    An actin fringe structure in the subapex plays an important role in pollen tube tip growth. However, the precise mechanism by which the actin fringe is generated and maintained remains largely unknown. Here, we cloned a 2606-bp full-length cDNA encoding a deduced 77-kD fimbrin-like protein from lily (Lilium longiflorum), named FIMBRIN1 (FIM1). Ll-FIM1 was preferentially expressed in pollen and concentrated at actin fringe in the subapical region, as well as in longitudinal actin-filament bundles in the shank of pollen tubes. Microinjection of Ll-FIM1 antibody into lily pollen tubes inhibited tip growth and disrupted the actin fringe. Furthermore, we verified the function of Ll-FIM1 in the fim5 mutant of its closest relative, Arabidopsis thaliana. Pollen tubes of fim5 mutants grew with a larger diameter in early stages but could recover into normal forms in later stages, despite significantly slower growth rates. The actin fringe of the fim5 mutants, however, was impaired during both early and late stages. Impressively, stable expression of fim5pro:GFP:Ll-FIM1 rescued the actin fringe and the growth rate of Arabidopsis fim5 pollen tubes. In vitro biochemical analysis showed that Ll-FIM1 could bundle actin filaments. Thus, our study has identified a fimbrin that may stabilize the actin fringe by cross-linking actin filaments into bundles, which is important for proper tip growth of lily pollen tubes.

  12. 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.

  13. Quantitative studies of subdiffusion in living cells and actin networks

    DEFF Research Database (Denmark)

    Munteanu, Emilia-Laura; Olsen, Anja Lea; Tolic-Nørrelykke, Iva Marija

    2006-01-01

    Optical tweezers are a versatile tool in biophysics and have matured from a tool of manipulation to a tool of precise measurements. We argue here that the data analysis with advantage can be developed to a level of sophistication that matches that of the instrument. We review methods of analysis...... of optical tweezers data, primarily baed on the power spectra of time series of postions for trapped spherical objects. The majority of precise studies in the literature are performed on in vitro systems, whereas in the present work, an example of an in vivo system is presented for which precise power...... spectral analysis is both useful and necessary. The biological system is the cytoplasm of fission yeast, S. pombe, in which we observe subdiffusion of lipid granuli. in a search for the cause of subdiffusion, we chemically disrupt the actin network in the cytoplasm and further consider in vitro networks...

  14. 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.

  15. 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

  16. 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

  17. Dual effect of pseudorabies virus growth factor (PRGF) displayed on actin cytoskeleton.

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    Urbancíková, M; Vozárová, G; Lesko, J; Golais, F

    1999-10-01

    Pseudorabies virus growth factor (PRGF) was shown to possess transforming activity as well as transformation repressing activity in in vitro systems. In order to better understand these phenomena we studied actin cytoskeleton and its alterations induced by PRGF using normal human fibroblasts VH-10 and transformed cell line HeLa. For specific detection of filamentous actin cells were stained with phalloidin conjugated with fluorescein isothiocyanate (FITC)-phalloidin. PRGF was applied to VH-10 cells for various length of time from 10 min up to 48 h. The effect was very fast and changes in actin filament composition could be detected already after 10 min. In comparison to untreated cells the staining of treated cells was more diffuse and a number of actin microfilaments in individual stress fibers became reduced. After 30 min thick short actin bundles appeared in the perinuclear region. A 24-h exposure resulted in a large reduction of actin bundles. After additional 24 h a partial restoration of actin cytoskeleton in cells was observed. In transformed HeLa cells PRGF induced opposite process than in normal cells: the number of filamentous actin structures increased. We hypothesise that PRGF may act as a transcription-like factor and may initiate changes in gene expression which consequently result in actin cytoskeleton alterations.

  18. Disruption of microtubule network rescues aberrant actin comets in dynamin2-depleted cells.

    Directory of Open Access Journals (Sweden)

    Yuji Henmi

    Full Text Available A large GTPase dynamin, which is required for endocytic vesicle formation, regulates the actin cytoskeleton through its interaction with cortactin. Dynamin2 mutants impair the formation of actin comets, which are induced by Listeria monocytogenes or phosphatidylinositol-4-phosphate 5-kinase. However, the role of dynamin2 in the regulation of the actin comet is still unclear. Here we show that aberrant actin comets in dynamin2-depleted cells were rescued by disrupting of microtubule networks. Depletion of dynamin2, but not cortactin, significantly reduced the length and the speed of actin comets induced by Listeria. This implies that dynamin2 may regulate the actin comet in a cortactin-independent manner. As dynamin regulates microtubules, we investigated whether perturbation of microtubules would rescue actin comet formation in dynamin2-depleted cells. Treatment with taxol or colchicine created a microtubule-free space in the cytoplasm, and made no difference between control and dynamin2 siRNA cells. This suggests that the alteration of microtubules by dynamin2 depletion reduced the length and the speed of the actin comet.

  19. 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.

  20. 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....

  1. FIMBRIN1 Is Involved in Lily Pollen Tube Growth by Stabilizing the Actin Fringe[C][W][OA

    Science.gov (United States)

    Su, Hui; Zhu, Jinsheng; Cai, Chao; Pei, Weike; Wang, Jiaojiao; Dong, Huaijian; Ren, Haiyun

    2012-01-01

    An actin fringe structure in the subapex plays an important role in pollen tube tip growth. However, the precise mechanism by which the actin fringe is generated and maintained remains largely unknown. Here, we cloned a 2606-bp full-length cDNA encoding a deduced 77-kD fimbrin-like protein from lily (Lilium longiflorum), named FIMBRIN1 (FIM1). Ll-FIM1 was preferentially expressed in pollen and concentrated at actin fringe in the subapical region, as well as in longitudinal actin-filament bundles in the shank of pollen tubes. Microinjection of Ll-FIM1 antibody into lily pollen tubes inhibited tip growth and disrupted the actin fringe. Furthermore, we verified the function of Ll-FIM1 in the fim5 mutant of its closest relative, Arabidopsis thaliana. Pollen tubes of fim5 mutants grew with a larger diameter in early stages but could recover into normal forms in later stages, despite significantly slower growth rates. The actin fringe of the fim5 mutants, however, was impaired during both early and late stages. Impressively, stable expression of fim5pro:GFP:Ll-FIM1 rescued the actin fringe and the growth rate of Arabidopsis fim5 pollen tubes. In vitro biochemical analysis showed that Ll-FIM1 could bundle actin filaments. Thus, our study has identified a fimbrin that may stabilize the actin fringe by cross-linking actin filaments into bundles, which is important for proper tip growth of lily pollen tubes. PMID:23150633

  2. Actin and microtubule networks contribute differently to cell response for small and large strains

    Science.gov (United States)

    Kubitschke, H.; Schnauss, J.; Nnetu, K. D.; Warmt, E.; Stange, R.; Kaes, J.

    2017-09-01

    Cytoskeletal filaments provide cells with mechanical stability and organization. The main key players are actin filaments and microtubules governing a cell’s response to mechanical stimuli. We investigated the specific influences of these crucial components by deforming MCF-7 epithelial cells at small (≤5% deformation) and large strains (>5% deformation). To understand specific contributions of actin filaments and microtubules, we systematically studied cellular responses after treatment with cytoskeleton influencing drugs. Quantification with the microfluidic optical stretcher allowed capturing the relative deformation and relaxation of cells under different conditions. We separated distinctive deformational and relaxational contributions to cell mechanics for actin and microtubule networks for two orders of magnitude of drug dosages. Disrupting actin filaments via latrunculin A, for instance, revealed a strain-independent softening. Stabilizing these filaments by treatment with jasplakinolide yielded cell softening for small strains but showed no significant change at large strains. In contrast, cells treated with nocodazole to disrupt microtubules displayed a softening at large strains but remained unchanged at small strains. Stabilizing microtubules within the cells via paclitaxel revealed no significant changes for deformations at small strains, but concentration-dependent impact at large strains. This suggests that for suspended cells, the actin cortex is probed at small strains, while at larger strains; the whole cell is probed with a significant contribution from the microtubules.

  3. The MARVEL domain protein Nce102 regulates actin organization and invasive growth of Candida albicans.

    Science.gov (United States)

    Douglas, Lois M; Wang, Hong X; Konopka, James B

    2013-11-26

    Invasive growth of the fungal pathogen Candida albicans into tissues promotes disseminated infections in humans. The plasma membrane is essential for pathogenesis because this important barrier mediates morphogenesis and invasive growth, as well as secretion of virulence factors, cell wall synthesis, nutrient import, and other processes. Previous studies showed that the Sur7 tetraspan protein that localizes to MCC (membrane compartment occupied by Can1)/eisosome subdomains of the plasma membrane regulates a broad range of key functions, including cell wall synthesis, morphogenesis, and resistance to copper. Therefore, a distinct tetraspan protein found in MCC/eisosomes, Nce102, was investigated. Nce102 belongs to the MARVEL domain protein family, which is implicated in regulating membrane structure and function. Deletion of NCE102 did not cause the broad defects seen in sur7Δ cells. Instead, the nce102Δ mutant displayed a unique phenotype in that it was defective in forming hyphae and invading low concentrations of agar but could invade well in higher agar concentrations. This phenotype was likely due to a defect in actin organization that was observed by phalloidin staining. In support of this, the invasive growth defect of a bni1Δ mutant that mislocalizes actin due to lack of the Bni1 formin was also reversed at high agar concentrations. This suggests that a denser matrix provides a signal that compensates for the actin defects. The nce102Δ mutant displayed decreased virulence and formed abnormal hyphae in mice. These studies identify novel ways that Nce102 and the physical environment surrounding C. albicans regulate morphogenesis and pathogenesis. The plasma membrane promotes virulence of the human fungal pathogen Candida albicans by acting as a protective barrier around the cell and mediating dynamic activities, such as morphogenesis, cell wall synthesis, secretion of virulence factors, and nutrient uptake. To better understand how the plasma membrane

  4. The apical actin fringe contributes to localized cell wall deposition and polarized growth in the lily pollen tube.

    Science.gov (United States)

    Rounds, Caleb M; Hepler, Peter K; Winship, Lawrence J

    2014-09-01

    In lily (Lilium formosanum) pollen tubes, pectin, a major component of the cell wall, is delivered through regulated exocytosis. The targeted transport and secretion of the pectin-containing vesicles may be controlled by the cortical actin fringe at the pollen tube apex. Here, we address the role of the actin fringe using three different inhibitors of growth: brefeldin A, latrunculin B, and potassium cyanide. Brefeldin A blocks membrane trafficking and inhibits exocytosis in pollen tubes; it also leads to the degradation of the actin fringe and the formation of an aggregate of filamentous actin at the base of the clear zone. Latrunculin B, which depolymerizes filamentous actin, markedly slows growth but allows focused pectin deposition to continue. Of note, the locus of deposition shifts frequently and correlates with changes in the direction of growth. Finally, potassium cyanide, an electron transport chain inhibitor, briefly stops growth while causing the actin fringe to completely disappear. Pectin deposition continues but lacks focus, instead being delivered in a wide arc across the pollen tube tip. These data support a model in which the actin fringe contributes to the focused secretion of pectin to the apical cell wall and, thus, to the polarized growth of the pollen tube. © 2014 American Society of Plant Biologists. All Rights Reserved.

  5. 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 ...

  6. How capping protein enhances actin filament growth and nucleation on biomimetic beads.

    Science.gov (United States)

    Wang, Ruizhe; Carlsson, Anders E

    2015-11-25

    Capping protein (CP), which caps the growing ends of actin filaments, accelerates actin-based motility. Recent experiments on biomimetic beads have shown that CP also enhances the rate of actin filament nucleation. Proposed explanations for these phenomena include (i) the actin funneling hypothesis (AFH), in which the presence of CP increases the free-actin concentration, and (ii) the monomer gating model, in which CP binding to actin filament barbed ends makes more monomers available for filament nucleation. To establish how CP increases the rates of filament elongation and nucleation on biomimetic beads, we perform a quantitative modeling analysis of actin polymerization, using rate equations that include actin filament nucleation, polymerization and capping, as modified by monomer depletion near the surface of the bead. With one adjustable parameter, our simulation results match previously measured time courses of polymerized actin and filament number. The results support a version of the AFH where CP increases the local actin monomer concentration at the bead surface, but leaves the global free-actin concentration nearly constant. Because the rate of filament nucleation increases with the monomer concentration, the increased local monomer concentration enhances actin filament nucleation. We derive a closed-form formula for the characteristic CP concentration where the local free-actin concentration reaches half the bulk value, and find it to be comparable to the global Arp2/3 complex concentration. We also propose an experimental protocol for distinguishing branching nucleation of filaments from spontaneous nucleation.

  7. Elastic coupling of nascent apCAM adhesions to flowing actin networks.

    Science.gov (United States)

    Mejean, Cecile O; Schaefer, Andrew W; Buck, Kenneth B; Kress, Holger; Shundrovsky, Alla; Merrill, Jason W; Dufresne, Eric R; Forscher, Paul

    2013-01-01

    Adhesions are multi-molecular complexes that transmit forces generated by a cell's acto-myosin networks to external substrates. While the physical properties of some of the individual components of adhesions have been carefully characterized, the mechanics of the coupling between the cytoskeleton and the adhesion site as a whole are just beginning to be revealed. We characterized the mechanics of nascent adhesions mediated by the immunoglobulin-family cell adhesion molecule apCAM, which is known to interact with actin filaments. Using simultaneous visualization of actin flow and quantification of forces transmitted to apCAM-coated beads restrained with an optical trap, we found that adhesions are dynamic structures capable of transmitting a wide range of forces. For forces in the picoNewton scale, the nascent adhesions' mechanical properties are dominated by an elastic structure which can be reversibly deformed by up to 1 µm. Large reversible deformations rule out an interface between substrate and cytoskeleton that is dominated by a number of stiff molecular springs in parallel, and favor a compliant cross-linked network. Such a compliant structure may increase the lifetime of a nascent adhesion, facilitating signaling and reinforcement.

  8. Elastic coupling of nascent apCAM adhesions to flowing actin networks.

    Directory of Open Access Journals (Sweden)

    Cecile O Mejean

    Full Text Available Adhesions are multi-molecular complexes that transmit forces generated by a cell's acto-myosin networks to external substrates. While the physical properties of some of the individual components of adhesions have been carefully characterized, the mechanics of the coupling between the cytoskeleton and the adhesion site as a whole are just beginning to be revealed. We characterized the mechanics of nascent adhesions mediated by the immunoglobulin-family cell adhesion molecule apCAM, which is known to interact with actin filaments. Using simultaneous visualization of actin flow and quantification of forces transmitted to apCAM-coated beads restrained with an optical trap, we found that adhesions are dynamic structures capable of transmitting a wide range of forces. For forces in the picoNewton scale, the nascent adhesions' mechanical properties are dominated by an elastic structure which can be reversibly deformed by up to 1 µm. Large reversible deformations rule out an interface between substrate and cytoskeleton that is dominated by a number of stiff molecular springs in parallel, and favor a compliant cross-linked network. Such a compliant structure may increase the lifetime of a nascent adhesion, facilitating signaling and reinforcement.

  9. Shortening actin filaments cause force generation in actomyosin network to change from contractile to extensile

    Science.gov (United States)

    Kumar, Nitin; Gardel, Margaret

    Motor proteins in conjunction with filamentous proteins convert biochemical energy into mechanical energy which serves a number of cellular processes including cell motility, force generation and intracellular cargo transport. In-vitro experiments suggest that the forces generated by kinesin motors on microtubule bundles are extensile in nature whereas myosin motors on actin filaments are contractile. It is not clear how qualitatively similar systems can show completely different behaviors in terms of the nature of force generation. In order to answer this question, we carry out in vitro experiments where we form quasi 2D filamentous actomyosin networks and vary the length of actin filaments by adding capping protein. We show that when filaments are much shorter than their typical persistence length (approximately 10 microns), the forces generated are extensile and we see active nematic defect propagation, as seen in the microtubule-kinesin system. Based on this observation, we claim that the rigidity of rods plays an important role in dictating the nature of force generation in such systems. In order to understand this transition, we selectively label individual filaments and find that longer filaments show considerable bending and buckling, making them difficult to slide and extend along their length.

  10. Ion Implantation Hampers Pollen Tube Growth and Disrupts Actin Cytoskeleton Organization in Pollen Tubes of Pinus thunbergii

    International Nuclear Information System (INIS)

    Li Guoping; Yang Lusheng; Huang Qunce; Qin Guangyong

    2008-01-01

    Pollen grains of Pinus thunbergii Parl. (Japanese black pine) were implanted with 30 keV nitrogen ion beams and the effects of nitrogen ion implantation on pollen tube growth in vitro and the organization of actin cytoskeleton in the pollen tube cell were investigated using a confocal laser scanning microscope after fluorescence labeling. Treatment with ion implantation significantly blocked pollen tube growth. Confocal microscopy showed that ion implantation disrupted actin filament cytoskeleton organization in the pollen tube. It was found that there was a distinct correlation between the inhibition of pollen tube growth and the disruption of actin cytoskeleton organization, indicating that an intact actin cytoskeleton is essential for continuous pollen tube elongation in Pinus thunbergii. Although the detailed mechanism for the ion-implantation-induced bioeffect still remains to be elucidated, the present study assumes that the cytoskeleton system in pollen grains may provide a key target in response to ion beam implantation and is involved in mediating certain subsequent cytological changes.

  11. 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.

  12. 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 ...

  13. The Apical Actin Fringe Contributes to Localized Cell Wall Deposition and Polarized Growth in the Lily Pollen Tube1[W][OPEN

    Science.gov (United States)

    Rounds, Caleb M.; Hepler, Peter K.; Winship, Lawrence J.

    2014-01-01

    In lily (Lilium formosanum) pollen tubes, pectin, a major component of the cell wall, is delivered through regulated exocytosis. The targeted transport and secretion of the pectin-containing vesicles may be controlled by the cortical actin fringe at the pollen tube apex. Here, we address the role of the actin fringe using three different inhibitors of growth: brefeldin A, latrunculin B, and potassium cyanide. Brefeldin A blocks membrane trafficking and inhibits exocytosis in pollen tubes; it also leads to the degradation of the actin fringe and the formation of an aggregate of filamentous actin at the base of the clear zone. Latrunculin B, which depolymerizes filamentous actin, markedly slows growth but allows focused pectin deposition to continue. Of note, the locus of deposition shifts frequently and correlates with changes in the direction of growth. Finally, potassium cyanide, an electron transport chain inhibitor, briefly stops growth while causing the actin fringe to completely disappear. Pectin deposition continues but lacks focus, instead being delivered in a wide arc across the pollen tube tip. These data support a model in which the actin fringe contributes to the focused secretion of pectin to the apical cell wall and, thus, to the polarized growth of the pollen tube. PMID:25037212

  14. Zinc and Copper Effects on Stability of Tubulin and Actin Networks in Dendrites and Spines of Hippocampal Neurons.

    Science.gov (United States)

    Perrin, Laura; Roudeau, Stéphane; Carmona, Asuncion; Domart, Florelle; Petersen, Jennifer D; Bohic, Sylvain; Yang, Yang; Cloetens, Peter; Ortega, Richard

    2017-07-19

    Zinc and copper ions can modulate the activity of glutamate receptors. However, labile zinc and copper ions likely represent only the tip of the iceberg and other neuronal functions are suspected for these metals in their bound state. We performed synchrotron X-ray fluorescence imaging with 30 nm resolution to image total biometals in dendrites and spines from hippocampal neurons. We found that zinc is distributed all along the dendrites while copper is mainly pinpointed within the spines. In spines, zinc content is higher within the spine head while copper is higher within the spine neck. Such specific distributions suggested metal interactions with cytoskeleton proteins. Zinc supplementation induced the increase of β-tubulin content in dendrites. Copper supplementation impaired the β-tubulin and F-actin networks. Copper chelation resulted in the decrease of F-actin content in dendrites, drastically reducing the number of F-actin protrusions. These results indicate that zinc is involved in microtubule stability whereas copper is essential for actin-dependent stability of dendritic spines, although copper excess can impair the dendritic cytoskeleton.

  15. 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.

  16. 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.

  17. Challenges of growth in a network company

    OpenAIRE

    Axani, Darrell Kirk

    2006-01-01

    Mark Engineering is a large network company facing challenges between growth and its small company feel. Small networks are rewarding for both individuals and companies. With growth, networks become cumbersome and costly to operate. Like effective teams, networks must remain small to be efficient. Growth tends to drive management to more traditional hierarchical structures, but such a move would undermine the value of a network organization. Strategy and market forces influence organizational...

  18. Cortactin involvement in the keratinocyte growth factor and fibroblast growth factor 10 promotion of migration and cortical actin assembly in human keratinocytes

    International Nuclear Information System (INIS)

    Ceccarelli, Simona; Cardinali, Giorgia; Aspite, Nicaela; Picardo, Mauro; Marchese, Cinzia; Torrisi, Maria Rosaria; Mancini, Patrizia

    2007-01-01

    Keratinocyte growth factor (KGF/FGF7) and fibroblast growth factor 10 (FGF10/KGF2) regulate keratinocyte proliferation and differentiation by binding to the tyrosine kinase KGF receptor (KGFR). KGF induces keratinocyte motility and cytoskeletal rearrangement, whereas a direct role of FGF10 on keratinocyte migration is not clearly established. Here we analyzed the motogenic activity of FGF10 and KGF on human keratinocytes. Migration assays and immunofluorescence of actin cytoskeleton revealed that FGF10 is less efficient than KGF in promoting migration and exerts a delayed effect in inducing lamellipodia and ruffles formation. Both growth factors promoted phosphorylation and subsequent membrane translocation of cortactin, an F-actin binding protein involved in cell migration; however, FGF10-induced cortactin phosphorylation was reduced, more transient and delayed with respect to that promoted by KGF. Cortactin phosphorylation induced by both growth factors was Src-dependent, while its membrane translocation and cell migration were blocked by either Src and PI3K inhibitors, suggesting that both pathways are involved in KGF- and FGF10-dependent motility. Furthermore, siRNA-mediated downregulation of cortactin inhibited KGF- and FGF10-induced migration. These results indicate that cortactin is involved in keratinocyte migration promoted by both KGF and FGF10

  19. Dorsal stress fibers, transverse actin arcs, and perinuclear actin fibers form an interconnected network that induces nuclear movement in polarizing fibroblasts

    Czech Academy of Sciences Publication Activity Database

    Maninová, Miloslava; Vomastek, Tomáš

    2016-01-01

    Roč. 283, č. 20 (2016), s. 3676-3693 ISSN 1742-464X R&D Projects: GA ČR GA13-06405S Institutional support: RVO:61388971 Keywords : actin dorsal fibers * cell polarity * nuclear reorientation Subject RIV: EE - Microbiology, Virology Impact factor: 3.902, year: 2016

  20. 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...

  1. 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.

  2. Growth Limits in Large Scale Networks

    DEFF Research Database (Denmark)

    Knudsen, Thomas Phillip

    limitations. The rising complexity of network management with the convergence of communications platforms is shown as problematic for both automatic management feasibility and for manpower resource management. In the fourth step the scope is extended to include the present society with the DDN project as its......The Subject of large scale networks is approached from the perspective of the network planner. An analysis of the long term planning problems is presented with the main focus on the changing requirements for large scale networks and the potential problems in meeting these requirements. The problems...... the fundamental technological resources in network technologies are analysed for scalability. Here several technological limits to continued growth are presented. The third step involves a survey of major problems in managing large scale networks given the growth of user requirements and the technological...

  3. Scaling of F-actin network rheology to probe single filament elasticity and dynamics.

    Science.gov (United States)

    Gardel, M L; Shin, J H; MacKintosh, F C; Mahadevan, L; Matsudaira, P A; Weitz, D A

    2004-10-29

    The linear and nonlinear viscoelastic response of networks of cross-linked and bundled cytoskeletal filaments demonstrates remarkable scaling with both frequency and applied prestress, which helps elucidate the origins of the viscoelasticity. The frequency dependence of the shear modulus reflects the underlying single-filament relaxation dynamics for 0.1-10 rad/sec. Moreover, the nonlinear strain stiffening of such networks exhibits a universal form as a function of prestress; this is quantitatively explained by the full force-extension relation of single semiflexible filaments.

  4. Actin polymerization in the endosomal pathway, but not on the Coxiella-containing vacuole, is essential for pathogen growth.

    Directory of Open Access Journals (Sweden)

    Heather E Miller

    2018-04-01

    Full Text Available Coxiella burnetii is an intracellular bacterium that replicates within an expansive phagolysosome-like vacuole. Fusion between the Coxiella-containing vacuole (CCV and late endosomes/multivesicular bodies requires Rab7, the HOPS tethering complex, and SNARE proteins, with actin also speculated to play a role. Here, we investigated the importance of actin in CCV fusion. Filamentous actin patches formed around the CCV membrane that were preferred sites of vesicular fusion. Accordingly, the mediators of endolysosomal fusion Rab7, VAMP7, and syntaxin 8 were concentrated in CCV actin patches. Generation of actin patches required C. burnetii type 4B secretion and host retromer function. Patches decorated with VPS29 and VPS35, components of the retromer, FAM21 and WASH, members of the WASH complex that engage the retromer, and Arp3, a component of the Arp2/3 complex that generates branched actin filaments. Depletion by siRNA of VPS35 or VPS29 reduced CCV actin patches and caused Rab7 to uniformly distribute in the CCV membrane. C. burnetii grew normally in VPS35 or VPS29 depleted cells, as well as WASH-knockout mouse embryo fibroblasts, where CCVs are devoid of actin patches. Endosome recycling to the plasma membrane and trans-Golgi of glucose transporter 1 (GLUT1 and cationic-independent mannose-6-phosphate receptor (CI-M6PR, respectively, was normal in infected cells. However, siRNA knockdown of retromer resulted in aberrant trafficking of GLUT1, but not CI-M6PR, suggesting canonical retrograde trafficking is unaffected by retromer disruption. Treatment with the specific Arp2/3 inhibitor CK-666 strongly inhibited CCV formation, an effect associated with altered endosomal trafficking of transferrin receptor. Collectively, our results show that CCV actin patches generated by retromer, WASH, and Arp2/3 are dispensable for CCV biogenesis and stability. However, Arp2/3-mediated production of actin filaments required for cargo transport within the

  5. Structure and growth of weighted networks

    Energy Technology Data Exchange (ETDEWEB)

    Riccaboni, Massimo [Department of Computer and Management Sciences, University of Trento, Trento (Italy); Schiavo, Stefano [Department of Economics, University of Trento, Trento (Italy)], E-mail: massimo.riccaboni@unitn.it, E-mail: stefano.schiavo@unitn.it

    2010-02-15

    We develop a simple theoretical framework for the evolution of weighted networks that is consistent with a number of stylized features of real-world data. In our framework, the Barabasi-Albert model of network evolution is extended by assuming that link weights evolve according to a geometric Brownian motion. Our model is verified by means of simulations and real-world trade data. We show that the model correctly predicts the intensity and growth distribution of links, the size-variance relationship of the growth of link weights, the relationship between the degree and strength of nodes, and the scale-free structure of the network.

  6. 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...

  7. Competitive cluster growth in complex networks.

    Science.gov (United States)

    Moreira, André A; Paula, Demétrius R; Costa Filho, Raimundo N; Andrade, José S

    2006-06-01

    In this work we propose an idealized model for competitive cluster growth in complex networks. Each cluster can be thought of as a fraction of a community that shares some common opinion. Our results show that the cluster size distribution depends on the particular choice for the topology of the network of contacts among the agents. As an application, we show that the cluster size distributions obtained when the growth process is performed on hierarchical networks, e.g., the Apollonian network, have a scaling form similar to what has been observed for the distribution of a number of votes in an electoral process. We suggest that this similarity may be due to the fact that social networks involved in the electoral process may also possess an underlining hierarchical structure.

  8. 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.

  9. 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.

  10. Disruption of the actin cytoskeleton results in the promotion of gravitropism in inflorescence stems and hypocotyls of Arabidopsis

    Science.gov (United States)

    Yamamoto, Kazuyoshi; Kiss, John Z.

    2002-01-01

    The actin cytoskeleton is hypothesized to play a major role in gravity perception and transduction mechanisms in roots of plants. To determine whether actin microfilaments (MFs) are involved in these processes in stem-like organs, we studied gravitropism in Arabidopsis inflorescence stems and hypocotyls. Localization studies using Alexa Fluor-phalloidin in conjugation with confocal microscopy demonstrated a longitudinally and transversely oriented actin MF network in endodermal cells of stems and hypocotyls. Latrunculin B (Lat-B) treatment of hypocotyls caused depolymerization of actin MFs in endodermal cells and a significant reduction of hypocotyl growth rates. Actin MFs in Lat-B-treated inflorescence stems also were disrupted, but growth rates were not affected. Despite disruption of the actin cytoskeleton in these two organs, Lat-B-treated stems and hypocotyls exhibited a promotion of gravitropic curvature in response to reorientation. In contrast, Lat-B reduced gravitropic curvature in roots but also reduced the growth rate. Thus, in contrast to prevailing hypotheses, our results suggest that actin MFs are not a necessary component of gravitropism in inflorescence stems and hypocotyls. Furthermore, this is the first study to demonstrate a prominent actin MF network in endodermal cells in the putative gravity-perceiving cells in stems.

  11. The actin-binding proteins eps8 and gelsolin have complementary roles in regulating the growth and stability of mechanosensory hair bundles of mammalian cochlear outer hair cells.

    Directory of Open Access Journals (Sweden)

    Jennifer Olt

    Full Text Available Sound transduction depends upon mechanosensitive channels localized on the hair-like bundles that project from the apical surface of cochlear hair cells. Hair bundles show a stair-case structure composed of rows of stereocilia, and each stereocilium contains a core of tightly-packed and uniformly-polarized actin filaments. The growth and maintenance of the stereociliary actin core are dynamically regulated. Recently, it was shown that the actin-binding protein gelsolin is expressed in the stereocilia of outer hair cells (OHCs and in its absence they become long and straggly. Gelsolin is part of a whirlin scaffolding protein complex at the stereocilia tip, which has been shown to interact with other actin regulatory molecules such as Eps8. Here we investigated the physiological effects associated with the absence of gelsolin and its possible overlapping role with Eps8. We found that, in contrast to Eps8, gelsolin does not affect mechanoelectrical transduction during immature stages of development. Moreover, OHCs from gelsolin knockout mice were able to mature into fully functional sensory receptors as judged by the normal resting membrane potential and basolateral membrane currents. Mechanoelectrical transducer current in gelsolin-Eps8 double knockout mice showed a profile similar to that observed in the single mutants for Eps8. We propose that gelsolin has a non-overlapping role with Eps8. While Eps8 is mainly involved in the initial growth of stereocilia in both inner hair cells (IHCs and OHCs, gelsolin is required for the maintenance of mature hair bundles of low-frequency OHCs after the onset of hearing.

  12. 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.

  13. Neural electrical activity and neural network growth.

    Science.gov (United States)

    Gafarov, F M

    2018-05-01

    The development of central and peripheral neural system depends in part on the emergence of the correct functional connectivity in its input and output pathways. Now it is generally accepted that molecular factors guide neurons to establish a primary scaffold that undergoes activity-dependent refinement for building a fully functional circuit. However, a number of experimental results obtained recently shows that the neuronal electrical activity plays an important role in the establishing of initial interneuronal connections. Nevertheless, these processes are rather difficult to study experimentally, due to the absence of theoretical description and quantitative parameters for estimation of the neuronal activity influence on growth in neural networks. In this work we propose a general framework for a theoretical description of the activity-dependent neural network growth. The theoretical description incorporates a closed-loop growth model in which the neural activity can affect neurite outgrowth, which in turn can affect neural activity. We carried out the detailed quantitative analysis of spatiotemporal activity patterns and studied the relationship between individual cells and the network as a whole to explore the relationship between developing connectivity and activity patterns. The model, developed in this work will allow us to develop new experimental techniques for studying and quantifying the influence of the neuronal activity on growth processes in neural networks and may lead to a novel techniques for constructing large-scale neural networks by self-organization. Copyright © 2018 Elsevier Ltd. All rights reserved.

  14. Innovation and growth in SME Networks

    DEFF Research Database (Denmark)

    Brink, Tove

    2015-01-01

    The aim of this paper is to reveal what organising can enable innovation and growth within entrepreneurial SME networks. The research is conducted in the Danish food industry with the participation of three food producing firm networks. The posed hypothesis are tested in a structural equation...... modeling (SEM) approach with data available from 55 SMEs. The findings show a significant positive impact from internal complementary preferences of behavior on innovation types. Furthermore, a significant positive impact is revealed from product-, process and systematic innovation types on growth...

  15. Networks: Innovation, Growth and Sustainable Development

    Directory of Open Access Journals (Sweden)

    Peter Johnston

    2013-05-01

    Full Text Available The emergence of the Internet as a measureable manifestation of our social and economic relationships changed the domination of networks in our lives. From about 2000, the internet has allowed us to study and understand the type of networks in which we live, and to model their behaviour. The Internet has fundamentally changed the distribution of wealth. The rich became richer simply because of the larger scale of the trading network and stretched national wealth distributions. Network effects are therefore likely to be responsible for much of the perceived increases in inequalities in the last 20-30 years, and policies to tackle poverty must therefore address the extent to which the poor can engage with society's networks of wealth creation. The greatest challenge to continued growth and prosperity, and therefore to peace and justice, is climate change. The potential cost of inaction on climate change could be as high. Our self-organising social networks have structured our societies and economies, and are now reflected in our technology networks. We can now replicate their evolution in computer simulations and can therefore better assess how to deal with the greatest challenges facing us in the next few decades.

  16. Agrobacterium-delivered virulence protein VirE2 is trafficked inside host cells via a myosin XI-K-powered ER/actin network.

    Science.gov (United States)

    Yang, Qinghua; Li, Xiaoyang; Tu, Haitao; Pan, Shen Q

    2017-03-14

    Agrobacterium tumefaciens causes crown gall tumors on various plants by delivering transferred DNA (T-DNA) and virulence proteins into host plant cells. Under laboratory conditions, the bacterium is widely used as a vector to genetically modify a wide range of organisms, including plants, yeasts, fungi, and algae. Various studies suggest that T-DNA is protected inside host cells by VirE2, one of the virulence proteins. However, it is not clear how Agrobacterium -delivered factors are trafficked through the cytoplasm. In this study, we monitored the movement of Agrobacterium -delivered VirE2 inside plant cells by using a split-GFP approach in real time. Agrobacterium -delivered VirE2 trafficked via the endoplasmic reticulum (ER) and F-actin network inside plant cells. During this process, VirE2 was aggregated as filamentous structures and was present on the cytosolic side of the ER. VirE2 movement was powered by myosin XI-K. Thus, exogenously produced and delivered VirE2 protein can use the endogenous host ER/actin network for movement inside host cells. The A. tumefaciens pathogen hijacks the conserved host infrastructure for virulence trafficking. Well-conserved infrastructure may be useful for Agrobacterium to target a wide range of recipient cells and achieve a high efficiency of transformation.

  17. Employment growth through labor flow networks.

    Science.gov (United States)

    Guerrero, Omar A; Axtell, Robert L

    2013-01-01

    It is conventional in labor economics to treat all workers who are seeking new jobs as belonging to a labor pool, and all firms that have job vacancies as an employer pool, and then match workers to jobs. Here we develop a new approach to study labor and firm dynamics. By combining the emerging science of networks with newly available employment micro-data, comprehensive at the level of whole countries, we are able to broadly characterize the process through which workers move between firms. Specifically, for each firm in an economy as a node in a graph, we draw edges between firms if a worker has migrated between them, possibly with a spell of unemployment in between. An economy's overall graph of firm-worker interactions is an object we call the labor flow network (LFN). This is the first study that characterizes a LFN for an entire economy. We explore the properties of this network, including its topology, its community structure, and its relationship to economic variables. It is shown that LFNs can be useful in identifying firms with high growth potential. We relate LFNs to other notions of high performance firms. Specifically, it is shown that fewer than 10% of firms account for nearly 90% of all employment growth. We conclude with a model in which empirically-salient LFNs emerge from the interaction of heterogeneous adaptive agents in a decentralized labor market.

  18. Employment growth through labor flow networks.

    Directory of Open Access Journals (Sweden)

    Omar A Guerrero

    Full Text Available It is conventional in labor economics to treat all workers who are seeking new jobs as belonging to a labor pool, and all firms that have job vacancies as an employer pool, and then match workers to jobs. Here we develop a new approach to study labor and firm dynamics. By combining the emerging science of networks with newly available employment micro-data, comprehensive at the level of whole countries, we are able to broadly characterize the process through which workers move between firms. Specifically, for each firm in an economy as a node in a graph, we draw edges between firms if a worker has migrated between them, possibly with a spell of unemployment in between. An economy's overall graph of firm-worker interactions is an object we call the labor flow network (LFN. This is the first study that characterizes a LFN for an entire economy. We explore the properties of this network, including its topology, its community structure, and its relationship to economic variables. It is shown that LFNs can be useful in identifying firms with high growth potential. We relate LFNs to other notions of high performance firms. Specifically, it is shown that fewer than 10% of firms account for nearly 90% of all employment growth. We conclude with a model in which empirically-salient LFNs emerge from the interaction of heterogeneous adaptive agents in a decentralized labor market.

  19. 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.

  20. 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.

  1. 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.

  2. Predicting economic growth with stock networks

    Science.gov (United States)

    Heiberger, Raphael H.

    2018-01-01

    Networks derived from stock prices are often used to model developments on financial markets and are tightly intertwined with crises. Yet, the influence of changing market topologies on the broader economy (i.e. GDP) is unclear. In this paper, we propose a Bayesian approach that utilizes individual-level network measures of companies as lagged probabilistic features to predict national economic growth. We use a comprehensive data set consisting of Standard and Poor's 500 corporations from January 1988 until October 2016. The final model forecasts correctly all major recession and prosperity phases of the U.S. economy up to one year ahead. By employing different network measures on the level of corporations, we can also identify which companies' stocks possess a key role in a changing economic environment and may be used as indication of critical (and prosperous) developments. More generally, the proposed approach allows to predict probabilities for different overall states of social entities by using local network positions and could be applied on various phenomena.

  3. Growth dominates choice in network percolation

    Science.gov (United States)

    Vijayaraghavan, Vikram S.; Noël, Pierre-André; Waagen, Alex; D'Souza, Raissa M.

    2013-09-01

    The onset of large-scale connectivity in a network (i.e., percolation) often has a major impact on the function of the system. Traditionally, graph percolation is analyzed by adding edges to a fixed set of initially isolated nodes. Several years ago, it was shown that adding nodes as well as edges to the graph can yield an infinite order transition, which is much smoother than the traditional second-order transition. More recently, it was shown that adding edges via a competitive process to a fixed set of initially isolated nodes can lead to a delayed, extremely abrupt percolation transition with a significant jump in large but finite systems. Here we analyze a process that combines both node arrival and edge competition. If started from a small collection of seed nodes, we show that the impact of node arrival dominates: although we can significantly delay percolation, the transition is of infinite order. Thus, node arrival can mitigate the trade-off between delay and abruptness that is characteristic of explosive percolation transitions. This realization may inspire new design rules where network growth can temper the effects of delay, creating opportunities for network intervention and control.

  4. 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.

  5. 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...

  6. 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.

  7. Growth of cortical neuronal network in vitro: Modeling and analysis

    International Nuclear Information System (INIS)

    Lai, P.-Y.; Jia, L. C.; Chan, C. K.

    2006-01-01

    We present a detailed analysis and theoretical growth models to account for recent experimental data on the growth of cortical neuronal networks in vitro [Phys. Rev. Lett. 93, 088101 (2004)]. The experimentally observed synchronized firing frequency of a well-connected neuronal network is shown to be proportional to the mean network connectivity. The growth of the network is consistent with the model of an early enhanced growth of connection, but followed by a retarded growth once the synchronized cluster is formed. Microscopic models with dominant excluded volume interactions are consistent with the observed exponential decay of the mean connection probability as a function of the mean network connectivity. The biological implications of the growth model are also discussed

  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. Analysis of Network Topologies Underlying Ethylene Growth Response Kinetics.

    Science.gov (United States)

    Prescott, Aaron M; McCollough, Forest W; Eldreth, Bryan L; Binder, Brad M; Abel, Steven M

    2016-01-01

    Most models for ethylene signaling involve a linear pathway. However, measurements of seedling growth kinetics when ethylene is applied and removed have resulted in more complex network models that include coherent feedforward, negative feedback, and positive feedback motifs. The dynamical responses of the proposed networks have not been explored in a quantitative manner. Here, we explore (i) whether any of the proposed models are capable of producing growth-response behaviors consistent with experimental observations and (ii) what mechanistic roles various parts of the network topologies play in ethylene signaling. To address this, we used computational methods to explore two general network topologies: The first contains a coherent feedforward loop that inhibits growth and a negative feedback from growth onto itself (CFF/NFB). In the second, ethylene promotes the cleavage of EIN2, with the product of the cleavage inhibiting growth and promoting the production of EIN2 through a positive feedback loop (PFB). Since few network parameters for ethylene signaling are known in detail, we used an evolutionary algorithm to explore sets of parameters that produce behaviors similar to experimental growth response kinetics of both wildtype and mutant seedlings. We generated a library of parameter sets by independently running the evolutionary algorithm many times. Both network topologies produce behavior consistent with experimental observations, and analysis of the parameter sets allows us to identify important network interactions and parameter constraints. We additionally screened these parameter sets for growth recovery in the presence of sub-saturating ethylene doses, which is an experimentally-observed property that emerges in some of the evolved parameter sets. Finally, we probed simplified networks maintaining key features of the CFF/NFB and PFB topologies. From this, we verified observations drawn from the larger networks about mechanisms underlying ethylene

  10. Analysis of Network Topologies Underlying Ethylene Growth Response Kinetics

    Directory of Open Access Journals (Sweden)

    Aaron M. Prescott

    2016-08-01

    Full Text Available Most models for ethylene signaling involve a linear pathway. However, measurements of seedling growth kinetics when ethylene is applied and removed have resulted in more complex network models that include coherent feedforward, negative feedback, and positive feedback motifs. However, the dynamical responses of the proposed networks have not been explored in a quantitative manner. Here, we explore (i whether any of the proposed models are capable of producing growth-response behaviors consistent with experimental observations and (ii what mechanistic roles various parts of the network topologies play in ethylene signaling. To address this, we used computational methods to explore two general network topologies: The first contains a coherent feedforward loop that inhibits growth and a negative feedback from growth onto itself (CFF/NFB. In the second, ethylene promotes the cleavage of EIN2, with the product of the cleavage inhibiting growth and promoting the production of EIN2 through a positive feedback loop (PFB. Since few network parameters for ethylene signaling are known in detail, we used an evolutionary algorithm to explore sets of parameters that produce behaviors similar to experimental growth response kinetics of both wildtype and mutant seedlings. We generated a library of parameter sets by independently running the evolutionary algorithm many times. Both network topologies produce behavior consistent with experimental observations and analysis of the parameter sets allows us to identify important network interactions and parameter constraints. We additionally screened these parameter sets for growth recovery in the presence of sub-saturating ethylene doses, which is an experimentally-observed property that emerges in some of the evolved parameter sets. Finally, we probed simplified networks maintaining key features of the CFF/NFB and PFB topologies. From this, we verified observations drawn from the larger networks about mechanisms

  11. Governance of innovation and growth in SME Networks

    DEFF Research Database (Denmark)

    Brink, Tove

    2016-01-01

    The aim of this article is to reveal what organizing of innovation and growth can be enabled in SME networks. This is especially interesting for the governance of loosely coupled networks. The research is conducted in the Danish food industry with three food-producing firm networks. The posed...... hypotheses are tested in a structural equation modelling (SEM) approach with the available data of 60 SMEs. The findings show that the governance of preferred behaviours of SMEs has a considerable significant positive impact on product and systematic innovation, which have a significant impact on growth....... Governance of network connections is also found to have a significant positive impact on growth. The findings contribute to an understanding of how both governance of preferred SME behaviour and network connections enable innovation. This study provides SMEs, SME network organizations and policy bodies...

  12. Model for the growth of the world airline network

    Science.gov (United States)

    Verma, T.; Araújo, N. A. M.; Nagler, J.; Andrade, J. S.; Herrmann, H. J.

    2016-06-01

    We propose a probabilistic growth model for transport networks which employs a balance between popularity of nodes and the physical distance between nodes. By comparing the degree of each node in the model network and the World Airline Network (WAN), we observe that the difference between the two is minimized for α≈2. Interestingly, this is the value obtained for the node-node correlation function in the WAN. This suggests that our model explains quite well the growth of airline networks.

  13. 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...

  14. 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.

  15. An evolving network model with modular growth

    International Nuclear Information System (INIS)

    Zou Zhi-Yun; Liu Peng; Lei Li; Gao Jian-Zhi

    2012-01-01

    In this paper, we propose an evolving network model growing fast in units of module, according to the analysis of the evolution characteristics in real complex networks. Each module is a small-world network containing several interconnected nodes and the nodes between the modules are linked by preferential attachment on degree of nodes. We study the modularity measure of the proposed model, which can be adjusted by changing the ratio of the number of inner-module edges and the number of inter-module edges. In view of the mean-field theory, we develop an analytical function of the degree distribution, which is verified by a numerical example and indicates that the degree distribution shows characteristics of the small-world network and the scale-free network distinctly at different segments. The clustering coefficient and the average path length of the network are simulated numerically, indicating that the network shows the small-world property and is affected little by the randomness of the new module. (interdisciplinary physics and related areas of science and technology)

  16. A network growth model based on the evolutionary ultimatum game

    International Nuclear Information System (INIS)

    Deng, L L; Zhou, G G; Cai, J H; Wang, C; Tang, W S

    2012-01-01

    In this paper, we provide a network growth model with incorporation into the ultimatum game dynamics. The network grows on the basis of the payoff-oriented preferential attachment mechanism, where a new node is added into the network and attached preferentially to nodes with higher payoffs. The interplay between the network growth and the game dynamics gives rise to quite interesting dynamical behaviors. Simulation results show the emergence of altruistic behaviors in the ultimatum game, which is affected by the growing network structure. Compared with the static counterpart case, the levels of altruistic behaviors are promoted. The corresponding strategy distributions and wealth distributions are also presented to further demonstrate the strategy evolutionary dynamics. Subsequently, we turn to the topological properties of the evolved network, by virtue of some statistics. The most studied characteristic path length and the clustering coefficient of the network are shown to indicate their small-world effect. Then the degree distributions are analyzed to clarify the interplay of structure and evolutionary dynamics. In particular, the difference between our growth network and the static counterpart is revealed. To explain clearly the evolved networks, the rich-club ordering and the assortative mixing coefficient are exploited to reveal the degree correlation. (paper)

  17. The effect of membrane-regulated actin polymerization on a two-phase flow model for cell motility

    KAUST Repository

    Kimpton, L. S.; Whiteley, J. P.; Waters, S. L.; Oliver, J. M.

    2014-01-01

    travelling-wave solutions with biologically plausible actin network profiles in two simple models that enforce polymerization or depolymerization of the actin network at the ends of the travelling, 1D strip of cytoplasm. © 2014 The authors 2014. Published

  18. Developmental time windows for axon growth influence neuronal network topology.

    Science.gov (United States)

    Lim, Sol; Kaiser, Marcus

    2015-04-01

    Early brain connectivity development consists of multiple stages: birth of neurons, their migration and the subsequent growth of axons and dendrites. Each stage occurs within a certain period of time depending on types of neurons and cortical layers. Forming synapses between neurons either by growing axons starting at similar times for all neurons (much-overlapped time windows) or at different time points (less-overlapped) may affect the topological and spatial properties of neuronal networks. Here, we explore the extreme cases of axon formation during early development, either starting at the same time for all neurons (parallel, i.e., maximally overlapped time windows) or occurring for each neuron separately one neuron after another (serial, i.e., no overlaps in time windows). For both cases, the number of potential and established synapses remained comparable. Topological and spatial properties, however, differed: Neurons that started axon growth early on in serial growth achieved higher out-degrees, higher local efficiency and longer axon lengths while neurons demonstrated more homogeneous connectivity patterns for parallel growth. Second, connection probability decreased more rapidly with distance between neurons for parallel growth than for serial growth. Third, bidirectional connections were more numerous for parallel growth. Finally, we tested our predictions with C. elegans data. Together, this indicates that time windows for axon growth influence the topological and spatial properties of neuronal networks opening up the possibility to a posteriori estimate developmental mechanisms based on network properties of a developed network.

  19. Growth and recruitment in the immune network

    NARCIS (Netherlands)

    Boer, R.J. de; Hogeweg, P.; Perelson, A.S.

    1992-01-01

    The development of the immune repertoire during neonatal life involves a strong selection process among different clones. We investigate the hypothetis that repertoire selection is carried out during early life by the immune network. There are at least two processes in repertoire selection: clonal

  20. Chemotaxis and Actin Oscillations

    Science.gov (United States)

    Bodenschatz, Eberhard; Hsu, Hsin-Fang; Negrete, Jose; Beta, Carsten; Pumir, Alain; Gholami, Azam; Tarantola, Marco; Westendorf, Christian; Zykov, Vladimir

    Recently, self-oscillations of the cytoskeletal actin have been observed in Dictyostelium, a model system for studying chemotaxis. Here we report experimental results on the self-oscillation mechanism and the role of regulatory proteins and myosin II. We stimulate cells rapidly and periodically by using photo un-caging of the chemoattractant in a micro-fluidic device and measured the cellular responses. We found that the response amplitude grows with stimulation strength only in a very narrow region of stimulation, after which the response amplitude reaches a plateau. Moreover, the frequency-response is not constant but rather varies with the strength of external stimuli. To understand the underlying mechanism, we analyzed the polymerization and de-polymerization time in the single cell level. Despite of the large cell-to-cell variability, we found that the polymerization time is independent of external stimuli and the de-polymerization time is prolonged as the stimulation strength increases. Our conclusions will be summarized and the role of noise in the signaling network will be discussed. German Science Foundation CRC 937.

  1. Complex Network Theory Applied to the Growth of Kuala Lumpur's Public Urban Rail Transit Network.

    Directory of Open Access Journals (Sweden)

    Rui Ding

    Full Text Available Recently, the number of studies involving complex network applications in transportation has increased steadily as scholars from various fields analyze traffic networks. Nonetheless, research on rail network growth is relatively rare. This research examines the evolution of the Public Urban Rail Transit Networks of Kuala Lumpur (PURTNoKL based on complex network theory and covers both the topological structure of the rail system and future trends in network growth. In addition, network performance when facing different attack strategies is also assessed. Three topological network characteristics are considered: connections, clustering and centrality. In PURTNoKL, we found that the total number of nodes and edges exhibit a linear relationship and that the average degree stays within the interval [2.0488, 2.6774] with heavy-tailed distributions. The evolutionary process shows that the cumulative probability distribution (CPD of degree and the average shortest path length show good fit with exponential distribution and normal distribution, respectively. Moreover, PURTNoKL exhibits clear cluster characteristics; most of the nodes have a 2-core value, and the CPDs of the centrality's closeness and betweenness follow a normal distribution function and an exponential distribution, respectively. Finally, we discuss four different types of network growth styles and the line extension process, which reveal that the rail network's growth is likely based on the nodes with the biggest lengths of the shortest path and that network protection should emphasize those nodes with the largest degrees and the highest betweenness values. This research may enhance the networkability of the rail system and better shape the future growth of public rail networks.

  2. Complex Network Theory Applied to the Growth of Kuala Lumpur's Public Urban Rail Transit Network.

    Science.gov (United States)

    Ding, Rui; Ujang, Norsidah; Hamid, Hussain Bin; Wu, Jianjun

    2015-01-01

    Recently, the number of studies involving complex network applications in transportation has increased steadily as scholars from various fields analyze traffic networks. Nonetheless, research on rail network growth is relatively rare. This research examines the evolution of the Public Urban Rail Transit Networks of Kuala Lumpur (PURTNoKL) based on complex network theory and covers both the topological structure of the rail system and future trends in network growth. In addition, network performance when facing different attack strategies is also assessed. Three topological network characteristics are considered: connections, clustering and centrality. In PURTNoKL, we found that the total number of nodes and edges exhibit a linear relationship and that the average degree stays within the interval [2.0488, 2.6774] with heavy-tailed distributions. The evolutionary process shows that the cumulative probability distribution (CPD) of degree and the average shortest path length show good fit with exponential distribution and normal distribution, respectively. Moreover, PURTNoKL exhibits clear cluster characteristics; most of the nodes have a 2-core value, and the CPDs of the centrality's closeness and betweenness follow a normal distribution function and an exponential distribution, respectively. Finally, we discuss four different types of network growth styles and the line extension process, which reveal that the rail network's growth is likely based on the nodes with the biggest lengths of the shortest path and that network protection should emphasize those nodes with the largest degrees and the highest betweenness values. This research may enhance the networkability of the rail system and better shape the future growth of public rail networks.

  3. 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.

  4. The impact of capacity growth in national telecommunications networks.

    Science.gov (United States)

    Lord, Andrew; Soppera, Andrea; Jacquet, Arnaud

    2016-03-06

    This paper discusses both UK-based and global Internet data bandwidth growth, beginning with historical data for the BT network. We examine the time variations in consumer behaviour and how this is statistically aggregated into larger traffic loads on national core fibre communications networks. The random nature of consumer Internet behaviour, where very few consumers require maximum bandwidth simultaneously, provides the opportunity for a significant statistical gain. The paper looks at predictions for how this growth might continue over the next 10-20 years, giving estimates for the amount of bandwidth that networks should support in the future. The paper then explains how national networks are designed to accommodate these traffic levels, and the various network roles, including access, metro and core, are described. The physical layer network is put into the context of how the packet and service layers are designed and the applications and location of content are also included in an overall network overview. The specific role of content servers in alleviating core network traffic loads is highlighted. The status of the relevant transmission technologies in the access, metro and core is given, showing that these technologies, with adequate research, should be sufficient to provide bandwidth for consumers in the next 10-20 years. © 2016 The Author(s).

  5. 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

  6. Weed Growth Stage Estimator Using Deep Convolutional Neural Networks

    DEFF Research Database (Denmark)

    Teimouri, Nima; Dyrmann, Mads; Nielsen, Per Rydahl

    2018-01-01

    conditions with regards to soil types, resolution and light settings. Then, 9649 of these images were used for training the computer, which automatically divided the weeds into nine growth classes. The performance of this proposed convolutional neural network approach was evaluated on a further set of 2516...... in estimating the number of leaves and 96% accuracy when accepting a deviation of two leaves. These results show that this new method of using deep convolutional neural networks has a relatively high ability to estimate early growth stages across a wide variety of weed species....

  7. 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

  8. Predicting company growth using logistic regression and neural networks

    Directory of Open Access Journals (Sweden)

    Marijana Zekić-Sušac

    2016-12-01

    Full Text Available The paper aims to establish an efficient model for predicting company growth by leveraging the strengths of logistic regression and neural networks. A real dataset of Croatian companies was used which described the relevant industry sector, financial ratios, income, and assets in the input space, with a dependent binomial variable indicating whether a company had high-growth if it had annualized growth in assets by more than 20% a year over a three-year period. Due to a large number of input variables, factor analysis was performed in the pre -processing stage in order to extract the most important input components. Building an efficient model with a high classification rate and explanatory ability required application of two data mining methods: logistic regression as a parametric and neural networks as a non -parametric method. The methods were tested on the models with and without variable reduction. The classification accuracy of the models was compared using statistical tests and ROC curves. The results showed that neural networks produce a significantly higher classification accuracy in the model when incorporating all available variables. The paper further discusses the advantages and disadvantages of both approaches, i.e. logistic regression and neural networks in modelling company growth. The suggested model is potentially of benefit to investors and economic policy makers as it provides support for recognizing companies with growth potential, especially during times of economic downturn.

  9. A Network Meta-Analysis of the Relative Efficacy of Treatments for Actinic Keratosis of the Face or Scalp in Europe

    Science.gov (United States)

    Vegter, Stefan; Tolley, Keith

    2014-01-01

    Background Several treatments are available for actinic keratosis (AK) on the face and scalp. Most treatment modalities were compared to placebo and therefore little is known on their relative efficacy. Objectives To compare the different treatments for mild to moderate AK on the face and scalp available in clinical practice in Europe. Methods A network meta-analysis (NMA) was performed on the outcome “complete patient clearance”. Ten treatment modalities were included: two 5-aminolaevulinic acid photodynamic therapies (ALA-PDT), applied as gel (BF-200 ALA) or patch; methyl-aminolevulinate photodynamic therapy (MAL-PDT); three modalities with imiquimod (IMI), applied as a 4-week or 16-week course with 5% imiquimod, or a 2–3 week course with 3.75% imiquimod; cryotherapy; diclofenac 3% in 2.5% hyaluronic acid; 0.5% 5-fluorouracil (5-FU); and ingenol mebutate (IMB). The only data available for 5% 5-FU was from one small study and was determined to be too limited to be reliably included in the analysis. For BF-200 ALA and MAL-PDT, data from illumination with narrow-band lights were selected as these are typically used in clinical practice. The NMA was performed with a random-effects Bayesian model. Results 25 trials on 5,562 patients were included in the NMA. All active treatments were significantly better than placebo. BF-200 ALA showed the highest efficacy compared to placebo to achieve total patient clearance. BF-200 ALA had the highest probability to be the best treatment and the highest SUCRA score (64.8% and 92.1%), followed by IMI 5% 4 weeks (10.1% and 74.2%) and 5-FU 0.5% (7.2% and 66.8%). Conclusions This NMA showed that BF-200 ALA, using narrow-band lights, was the most efficacious treatment for mild to moderate AK on the face and scalp. This analysis is relevant for clinical decision making and health technology assessment, assisting the improved management of AK. PMID:24892649

  10. A Network Meta-Analysis of the Relative Efficacy of Treatments for Actinic Keratosis of the Face or Scalp in Europe

    NARCIS (Netherlands)

    Vegter, Stefan; Tolley, Keith

    2014-01-01

    Background: Several treatments are available for actinic keratosis (AK) on the face and scalp. Most treatment modalities were compared to placebo and therefore little is known on their relative efficacy. Objectives: To compare the different treatments for mild to moderate AK on the face and scalp

  11. 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.

  12. Escherichia coli growth modeling using neural network | Shamsudin ...

    African Journals Online (AJOL)

    technique that has the ability to predict with efficient and good performance. Using NARX, a highly accurate model was developed to predict the growth of Escherichia coli (E. coli) based on pH water parameter. The multiparameter portable sensor and spectrophotometer data were used to build and train the neural network.

  13. Energy Saving: Scaling Network Energy Efficiency Faster than Traffic Growth

    NARCIS (Netherlands)

    Chen, Y.; Blume, O.; Gati, A.; Capone, A.; Wu, C.-E.; Barth, U.; Marzetta, T.; Zhang, H.; Xu, S.

    2013-01-01

    As the mobile traffic is expected to continue its exponential growth in the near future, energy efficiency has gradually become a must criterion for wireless network design. Three fundamental questions need to be answered before the detailed design could be carried out, namely what energy efficiency

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Weighted Scaling in Non-growth Random Networks

    International Nuclear Information System (INIS)

    Chen Guang; Yang Xuhua; Xu Xinli

    2012-01-01

    We propose a weighted model to explain the self-organizing formation of scale-free phenomenon in non-growth random networks. In this model, we use multiple-edges to represent the connections between vertices and define the weight of a multiple-edge as the total weights of all single-edges within it and the strength of a vertex as the sum of weights for those multiple-edges attached to it. The network evolves according to a vertex strength preferential selection mechanism. During the evolution process, the network always holds its total number of vertices and its total number of single-edges constantly. We show analytically and numerically that a network will form steady scale-free distributions with our model. The results show that a weighted non-growth random network can evolve into scale-free state. It is interesting that the network also obtains the character of an exponential edge weight distribution. Namely, coexistence of scale-free distribution and exponential distribution emerges.

  19. 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.

  20. 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.

  1. Fragmented Romanian sociology: growth and structure of the collaboration network.

    Science.gov (United States)

    Hâncean, Marian-Gabriel; Perc, Matjaž; Vlăsceanu, Lazăr

    2014-01-01

    Structural patterns in collaboration networks are essential for understanding how new ideas, research practices, innovation or cooperation circulate and develop within academic communities and between and within university departments. In our research, we explore and investigate the structure of the collaboration network formed by the academics working full-time within all the 17 sociology departments across Romania. We show that the collaboration network is sparse and fragmented, and that it constitutes an environment that does not promote the circulation of new ideas and innovation within the field. Although recent years have witnessed an increase in the productivity of Romanian sociologists, there is still ample room for improvement in terms of the interaction infrastructure that ought to link individuals together so that they could maximize their potentials. We also fail to discern evidence in favor of the Matthew effect governing the growth of the network, which suggests scientific success and productivity are not rewarded. Instead, the structural properties of the collaboration network are partly those of a core-periphery network, where the spread of innovation and change can be explained by structural equivalence rather than by interpersonal influence models. We also provide support for the idea that, within the observed network, collaboration is the product of homophily rather than prestige effects. Further research on the subject based on data from other countries in the region is needed to place our results in a comparative framework, in particular to discern whether the behavior of the Romanian sociologist community is unique or rather common.

  2. Drosophila growth cones: a genetically tractable platform for the analysis of axonal growth dynamics.

    Science.gov (United States)

    Sánchez-Soriano, Natalia; Gonçalves-Pimentel, Catarina; Beaven, Robin; Haessler, Ulrike; Ofner-Ziegenfuss, Lisa; Ballestrem, Christoph; Prokop, Andreas

    2010-01-01

    The formation of neuronal networks, during development and regeneration, requires outgrowth of axons along reproducible paths toward their appropriate postsynaptic target cells. Axonal extension occurs at growth cones (GCs) at the tips of axons. GC advance and navigation requires the activity of their cytoskeletal networks, comprising filamentous actin (F-actin) in lamellipodia and filopodia as well as dynamic microtubules (MTs) emanating from bundles of the axonal core. The molecular mechanisms governing these two cytoskeletal networks, their cross-talk, and their response to extracellular signaling cues are only partially understood, hindering our conceptual understanding of how regulated changes in GC behavior are controlled. Here, we introduce Drosophila GCs as a suitable model to address these mechanisms. Morphological and cytoskeletal readouts of Drosophila GCs are similar to those of other models, including mammals, as demonstrated here for MT and F-actin dynamics, axonal growth rates, filopodial structure and motility, organizational principles of MT networks, and subcellular marker localization. Therefore, we expect fundamental insights gained in Drosophila to be translatable into vertebrate biology. The advantage of the Drosophila model over others is its enormous amenability to combinatorial genetics as a powerful strategy to address the complexity of regulatory networks governing axonal growth. Thus, using pharmacological and genetic manipulations, we demonstrate a role of the actin cytoskeleton in a specific form of MT organization (loop formation), known to regulate GC pausing behavior. We demonstrate these events to be mediated by the actin-MT linking factor Short stop, thus identifying an essential molecular player in this context.

  3. Cell proliferation along vascular islands during microvascular network growth

    Directory of Open Access Journals (Sweden)

    Kelly-Goss Molly R

    2012-06-01

    Full Text Available Abstract Background Observations in our laboratory provide evidence of vascular islands, defined as disconnected endothelial cell segments, in the adult microcirculation. The objective of this study was to determine if vascular islands are involved in angiogenesis during microvascular network growth. Results Mesenteric tissues, which allow visualization of entire microvascular networks at a single cell level, were harvested from unstimulated adult male Wistar rats and Wistar rats 3 and 10 days post angiogenesis stimulation by mast cell degranulation with compound 48/80. Tissues were immunolabeled for PECAM and BRDU. Identification of vessel lumens via injection of FITC-dextran confirmed that endothelial cell segments were disconnected from nearby patent networks. Stimulated networks displayed increases in vascular area, length density, and capillary sprouting. On day 3, the percentage of islands with at least one BRDU-positive cell increased compared to the unstimulated level and was equal to the percentage of capillary sprouts with at least one BRDU-positive cell. At day 10, the number of vascular islands per vascular area dramatically decreased compared to unstimulated and day 3 levels. Conclusions These results show that vascular islands have the ability to proliferate and suggest that they are able to incorporate into the microcirculation during the initial stages of microvascular network growth.

  4. 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.

  5. Cortical actin networks induce spatio-temporal confinement of phospholipids in the plasma membrane--a minimally invasive investigation by STED-FCS.

    Science.gov (United States)

    Andrade, Débora M; Clausen, Mathias P; Keller, Jan; Mueller, Veronika; Wu, Congying; Bear, James E; Hell, Stefan W; Lagerholm, B Christoffer; Eggeling, Christian

    2015-06-29

    Important discoveries in the last decades have changed our view of the plasma membrane organisation. Specifically, the cortical cytoskeleton has emerged as a key modulator of the lateral diffusion of membrane proteins. Cytoskeleton-dependent compartmentalised lipid diffusion has been proposed, but this concept remains controversial because this phenomenon has thus far only been observed with artefact-prone probes in combination with a single technique: single particle tracking. In this paper, we report the first direct observation of compartmentalised phospholipid diffusion in the plasma membrane of living cells using a minimally invasive, fluorescent dye labelled lipid analogue. These observations were made using optical STED nanoscopy in combination with fluorescence correlation spectroscopy (STED-FCS), a technique which allows the study of membrane dynamics on a sub-millisecond time-scale and with a spatial resolution of down to 40 nm. Specifically, we find that compartmentalised phospholipid diffusion depends on the cortical actin cytoskeleton, and that this constrained diffusion is directly dependent on the F-actin branching nucleator Arp2/3. These findings provide solid evidence that the Arp2/3-dependent cortical actin cytoskeleton plays a pivotal role in the dynamic organisation of the plasma membrane, potentially regulating fundamental cellular processes.

  6. Weed Growth Stage Estimator Using Deep Convolutional Neural Networks

    DEFF Research Database (Denmark)

    Teimouri, Nima; Dyrmann, Mads; Nielsen, Per Rydahl

    2018-01-01

    This study outlines a new method of automatically estimating weed species and growth stages (from cotyledon until eight leaves are visible) of in situ images covering 18 weed species or families. Images of weeds growing within a variety of crops were gathered across variable environmental conditi...... in estimating the number of leaves and 96% accuracy when accepting a deviation of two leaves. These results show that this new method of using deep convolutional neural networks has a relatively high ability to estimate early growth stages across a wide variety of weed species....

  7. A synthetic mechano-growth factor E peptide promotes rat tenocyte migration by lessening cell stiffness and increasing F-actin formation via the FAK-ERK1/2 signaling pathway

    International Nuclear Information System (INIS)

    Zhang, Bingyu; Luo, Qing; Mao, Xinjian; Xu, Baiyao; Yang, Li; Ju, Yang; Song, Guanbin

    2014-01-01

    Tendon injuries are common in sports and are frequent reasons for orthopedic consultations. The management of damaged tendons is one of the most challenging problems in orthopedics. Mechano-growth factor (MGF), a recently discovered growth repair factor, plays positive roles in tissue repair through the improvement of cell proliferation and migration and the protection of cells against injury-induced apoptosis. However, it remains unclear whether MGF has the potential to accelerate tendon repair. We used a scratch wound assay in this study to demonstrate that MGF-C25E (a synthetic mechano-growth factor E peptide) promotes the migration of rat tenocytes and that this promotion is accompanied by an elevation in the expression of the following signaling molecules: focal adhesion kinase (FAK) and extracellular signal regulated kinase1/2 (ERK1/2). Inhibitors of the FAK and ERK1/2 pathways inhibited the MGF-C25E-induced tenocyte migration, indicating that MGF-C25E promotes tenocyte migration through the FAK-ERK1/2 signaling pathway. The analysis of the mechanical properties showed that the Young's modulus of tenocytes was decreased through treatment of MGF-C25E, and an obvious formation of pseudopodia and F-actin was observed in MGF-C25E-treated tenocytes. The inhibition of the FAK or ERK1/2 signals restored the decrease in Young's modulus and inhibited the formation of pseudopodia and F-actin. Overall, our study demonstrated that MGF-C25E promotes rat tenocyte migration by lessening cell stiffness and increasing pseudopodia formation via the FAK-ERK1/2 signaling pathway. - Highlights: • Mechano-growth factor E peptide (MGF-C25E) promotes migration of rat tenocytes. • MGF-C25E activates the FAK-ERK1/2 pathway in rat tenocytes. • MGF-C25E induces the actin remodeling and the formation of pseudopodia, and decreases the stiffness in rat tenocytes. • MGF-C25E promotes tenocyte migration via altering stiffness and forming pseudopodia by the activation of the

  8. A synthetic mechano-growth factor E peptide promotes rat tenocyte migration by lessening cell stiffness and increasing F-actin formation via the FAK-ERK1/2 signaling pathway

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Bingyu [Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400044 (China); Luo, Qing, E-mail: qing.luo@cqu.edu.cn [Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400044 (China); Mao, Xinjian [Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400044 (China); Xu, Baiyao [Department of Mechanical Science and Engineering, Nagoya University, Nagoya 464-8603 (Japan); Yang, Li [Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400044 (China); Ju, Yang [Department of Mechanical Science and Engineering, Nagoya University, Nagoya 464-8603 (Japan); Song, Guanbin, E-mail: song@cqu.edu.cn [Key Laboratory of Biorheological Science and Technology, Ministry of Education, College of Bioengineering, Chongqing University, Chongqing 400044 (China)

    2014-03-10

    Tendon injuries are common in sports and are frequent reasons for orthopedic consultations. The management of damaged tendons is one of the most challenging problems in orthopedics. Mechano-growth factor (MGF), a recently discovered growth repair factor, plays positive roles in tissue repair through the improvement of cell proliferation and migration and the protection of cells against injury-induced apoptosis. However, it remains unclear whether MGF has the potential to accelerate tendon repair. We used a scratch wound assay in this study to demonstrate that MGF-C25E (a synthetic mechano-growth factor E peptide) promotes the migration of rat tenocytes and that this promotion is accompanied by an elevation in the expression of the following signaling molecules: focal adhesion kinase (FAK) and extracellular signal regulated kinase1/2 (ERK1/2). Inhibitors of the FAK and ERK1/2 pathways inhibited the MGF-C25E-induced tenocyte migration, indicating that MGF-C25E promotes tenocyte migration through the FAK-ERK1/2 signaling pathway. The analysis of the mechanical properties showed that the Young's modulus of tenocytes was decreased through treatment of MGF-C25E, and an obvious formation of pseudopodia and F-actin was observed in MGF-C25E-treated tenocytes. The inhibition of the FAK or ERK1/2 signals restored the decrease in Young's modulus and inhibited the formation of pseudopodia and F-actin. Overall, our study demonstrated that MGF-C25E promotes rat tenocyte migration by lessening cell stiffness and increasing pseudopodia formation via the FAK-ERK1/2 signaling pathway. - Highlights: • Mechano-growth factor E peptide (MGF-C25E) promotes migration of rat tenocytes. • MGF-C25E activates the FAK-ERK1/2 pathway in rat tenocytes. • MGF-C25E induces the actin remodeling and the formation of pseudopodia, and decreases the stiffness in rat tenocytes. • MGF-C25E promotes tenocyte migration via altering stiffness and forming pseudopodia by the activation of the

  9. 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.

  10. Entrepreneurs’ growth-expectations: Enhanced by their networking and by national growth-policy

    DEFF Research Database (Denmark)

    Schøtt, Thomas; Ashourizadeh, Shayegheh

    or running the business. The entrepreneur’s expectation is shaped partly by individual behavior, including networking with others who give advice on the business. The entrepreneur’s expectation is also shaped by the societal context, including policies. Policy for growth-entrepreneurship is the societal...

  11. Horizontal and vertical growth of S. cerevisiae metabolic network.

    KAUST Repository

    Grassi, Luigi

    2011-10-14

    BACKGROUND: The growth and development of a biological organism is reflected by its metabolic network, the evolution of which relies on the essential gene duplication mechanism. There are two current views about the evolution of metabolic networks. The retrograde model hypothesizes that a pathway evolves by recruiting novel enzymes in a direction opposite to the metabolic flow. The patchwork model is instead based on the assumption that the evolution is based on the exploitation of broad-specificity enzymes capable of catalysing a variety of metabolic reactions. RESULTS: We analysed a well-studied unicellular eukaryotic organism, S. cerevisiae, and studied the effect of the removal of paralogous gene products on its metabolic network. Our results, obtained using different paralog and network definitions, show that, after an initial period when gene duplication was indeed instrumental in expanding the metabolic space, the latter reached an equilibrium and subsequent gene duplications were used as a source of more specialized enzymes rather than as a source of novel reactions. We also show that the switch between the two evolutionary strategies in S. cerevisiae can be dated to about 350 million years ago. CONCLUSIONS: Our data, obtained through a novel analysis methodology, strongly supports the hypothesis that the patchwork model better explains the more recent evolution of the S. cerevisiae metabolic network. Interestingly, the effects of a patchwork strategy acting before the Euascomycete-Hemiascomycete divergence are still detectable today.

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

    Directory of Open Access Journals (Sweden)

    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

  13. A Legionella Effector Disrupts Host Cytoskeletal Structure by Cleaving Actin.

    Directory of Open Access Journals (Sweden)

    Yao Liu

    2017-01-01

    Full Text Available Legionella pneumophila, the etiological agent of Legionnaires' disease, replicates intracellularly in protozoan and human hosts. Successful colonization and replication of this pathogen in host cells requires the Dot/Icm type IVB secretion system, which translocates approximately 300 effector proteins into the host cell to modulate various cellular processes. In this study, we identified RavK as a Dot/Icm substrate that targets the host cytoskeleton and reduces actin filament abundance in mammalian cells upon ectopic expression. RavK harbors an H95EXXH99 motif associated with diverse metalloproteases, which is essential for the inhibition of yeast growth and for the induction of cell rounding in HEK293T cells. We demonstrate that the actin protein itself is the cellular target of RavK and that this effector cleaves actin at a site between residues Thr351 and Phe352. Importantly, RavK-mediated actin cleavage also occurs during L. pneumophila infection. Cleavage by RavK abolishes the ability of actin to form polymers. Furthermore, an F352A mutation renders actin resistant to RavK-mediated cleavage; expression of the mutant in mammalian cells suppresses the cell rounding phenotype caused by RavK, further establishing that actin is the physiological substrate of RavK. Thus, L. pneumophila exploits components of the host cytoskeleton by multiple effectors with distinct mechanisms, highlighting the importance of modulating cellular processes governed by the actin cytoskeleton in the intracellular life cycle of this pathogen.

  14. 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

  15. Weed Growth Stage Estimator Using Deep Convolutional Neural Networks.

    Science.gov (United States)

    Teimouri, Nima; Dyrmann, Mads; Nielsen, Per Rydahl; Mathiassen, Solvejg Kopp; Somerville, Gayle J; Jørgensen, Rasmus Nyholm

    2018-05-16

    This study outlines a new method of automatically estimating weed species and growth stages (from cotyledon until eight leaves are visible) of in situ images covering 18 weed species or families. Images of weeds growing within a variety of crops were gathered across variable environmental conditions with regards to soil types, resolution and light settings. Then, 9649 of these images were used for training the computer, which automatically divided the weeds into nine growth classes. The performance of this proposed convolutional neural network approach was evaluated on a further set of 2516 images, which also varied in term of crop, soil type, image resolution and light conditions. The overall performance of this approach achieved a maximum accuracy of 78% for identifying Polygonum spp. and a minimum accuracy of 46% for blackgrass. In addition, it achieved an average 70% accuracy rate in estimating the number of leaves and 96% accuracy when accepting a deviation of two leaves. These results show that this new method of using deep convolutional neural networks has a relatively high ability to estimate early growth stages across a wide variety of weed species.

  16. Chronic Actinic Dermatitis

    Directory of Open Access Journals (Sweden)

    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.

  17. Actinic reticuloid. Diagnostics

    Directory of Open Access Journals (Sweden)

    E. V. Sokolovskiy

    2016-01-01

    Full Text Available This article is about the case of actinic reticuloid - the rare dermatosis which clinical presentation is similar to atopic dermatitis, T-cell lymphoma. Good treatment effect was obtained by long cycles (2 cycles for 3 months of hydroxychloroquine and sun protective therapy included sunscreens SPF 50, nicotinic acid, sun-safe clothes which blocked ultraviolet radiation without any glucocorticosteroid drugs and cytostatic treatment.

  18. Actin is closely associated with RNA polymerase II and involved in activation of gene transcription

    International Nuclear Information System (INIS)

    Zhu Xiaojuan; Zeng Xianlu; Huang Baiqu; Hao, Shui

    2004-01-01

    Biochemical and morphological studies have demonstrated the presence of actin in the nucleus of different eukaryotic cells, whereas its role remains unclear. In this work, we studied the interaction and the functional relationship between nuclear actin and RNA polymerase II (RNAP II). The immunofluorescence study demonstrated a clear co-localization of nuclear actin with RNAP II in HeLa cells. Meanwhile, actin can be immunoprecipitated by anti-RNAP II antibody, indicating that they could interact with each other. Treatment of cells with α-amanitin induced the formation of actin bundle network in the nucleoplasm. Blocking of the formation of filamentous actin (F-actin) by cytochalasin B modified the distribution of actin. Although the actin content remained unchanged in resting and concanavalinA stimulated mouse lymphocytes, the actin content in the nuclei showed a progressive increase after stimulation. Furthermore, the antibody against actin blocked RNA synthesis in a eukaryotic in vitro transcription system. These observations implicate that nuclear actin interacts with RNAP II and may have function on the RNAP II-mediated transcription

  19. Growth strategies and governance of horizontal business networks: the case of the biggest German cooperative food retail network

    Directory of Open Access Journals (Sweden)

    Douglas Wegner

    2011-08-01

    Full Text Available Several growth strategies may be adopted by cooperative retail networks, but these strategies create dilemmas about how to organize business networks with a large number of participants and the adjustments in the governance system that are necessary to facilitate growth. The article examines the relations between the growth strategies adopted by a horizontal business network and its governance system. We analyze the case of Edeka, a centennial cooperative network, leader in food retail in Germany, showing its growth strategies and implications for the network structure. The case study was based on various secondary data sources and focuses the whole network – and not the networked firms – as the unit of analysis. Results indicate that, in order to grow, the network changed its governance structure and the process of participation of members in decision making, creating a hierarchical structure with professional management. The paper contributes to the discussions on cooperative governance and demonstrates that governance systems are transient and adapt to the network strategies. From a management viewpoint, the results show the effects of the growth strategies adopted by business networks, regarding the role of network managers and entrepreneurs in network management.

  20. Capu and Spire Assemble a Cytoplasmic Actin~Mesh that Maintains Microtubule Organization in the Drosophila Oocyte

    DEFF Research Database (Denmark)

    Dahlgaard, K.; Raposo, A.A.S.F.; Niccoli, T.

    2007-01-01

    Mutants in the actin nucleators Cappuccino and Spire disrupt the polarized microtubule network in the Drosophila oocyte that defines the anterior-posterior axis, suggesting that microtubule organization depends on actin. Here, we show that Cappuccino and Spire organize an isotropic mesh of actin...

  1. 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.

  2. 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.

  3. The Growth of Transnational Corporate Networks: 1962-1998

    Directory of Open Access Journals (Sweden)

    Jeffrey Kentor

    2015-08-01

    Full Text Available This is a study of the growth of organizational power in the world-economy over the past forty years. It takes the position that transnational corporations (TNCs are increasingly significant actors in the world-economy, independent of the nation-states within which they are located. The goal of this work is to identify the expansion, spatial distribution, and concentration of this global power over time, and to consider its impact on the global economy. The TNC networks are identified by locating the headquarters and foreign subsidiaries of the world’s 100 largest manufacturing corporations in 1962, 1971, 1983, 1991 and 1998. The distribution of ownership and location of these foreign subsidiaries are examined, both globally and bilaterally. I find high levels of concentration in ownership of these global networks that decrease over time, in contrast to a high degree of dispersion in the location of these linkages. U.S. corporations are clearly the dominant actors from 1962 to 1971 but decline dramatically through 1998, while Japanese and Western European TNC control over transnational networks grows significantly over this period. An empirical measure of economic dominance in the global economy is also presented.

  4. Integrated healthcare networks' performance: a growth curve modeling approach.

    Science.gov (United States)

    Wan, Thomas T H; Wang, Bill B L

    2003-05-01

    This study examines the effects of integration on the performance ratings of the top 100 integrated healthcare networks (IHNs) in the United States. A strategic-contingency theory is used to identify the relationship of IHNs' performance to their structural and operational characteristics and integration strategies. To create a database for the panel study, the top 100 IHNs selected by the SMG Marketing Group in 1998 were followed up in 1999 and 2000. The data were merged with the Dorenfest data on information system integration. A growth curve model was developed and validated by the Mplus statistical program. Factors influencing the top 100 IHNs' performance in 1998 and their subsequent rankings in the consecutive years were analyzed. IHNs' initial performance scores were positively influenced by network size, number of affiliated physicians and profit margin, and were negatively associated with average length of stay and technical efficiency. The continuing high performance, judged by maintaining higher performance scores, tended to be enhanced by the use of more managerial or executive decision-support systems. Future studies should include time-varying operational indicators to serve as predictors of network performance.

  5. 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.

  6. A Gly65Val substitution in an actin, GhACT_LI1, disrupts cell polarity and membrane anchoring of F-actin resulting in dwarf, lintless Li1 cotton plants

    Science.gov (United States)

    Actin polymerizes to form the cytoskeleton and organize polar growth in all eukaryotic cells. Species with numerous actin genes are especially useful for the dissection of actin molecular function due to redundancy and neofunctionalization. Here, we investigated the role of a cotton (Gossypium hi...

  7. RhoA/Rho kinase signaling regulates transforming growth factor-β1-induced chondrogenesis and actin organization of synovium-derived mesenchymal stem cells through interaction with the Smad pathway.

    Science.gov (United States)

    Xu, Ting; Wu, Mengjie; Feng, Jianying; Lin, Xinping; Gu, Zhiyuan

    2012-11-01

    Recent studies have suggested that synovium-derived mesenchymal stem cells (SMSCs) may be promising candidates for tissue engineering and play an important role in cartilage regeneration. However, the mechanisms of SMSC chondrogenesis remain to be identified and characterized. The aim of this study was to evaluate the activation of the RhoA/Rho kinase (ROCK) pathway, as well as the manner by which it may contribute to chondrogenesis and the actin cytoskeletal organization of rat temporomandibular SMSCs in response to transforming growth factor-β1 (TGF-β1). Primary isolated SMSCs were treated with TGF-β1, and their actin organization was examined by fluorescein isothiocyanate-phalloidin staining. The specific biochemical inhibitors, C3 transferase, Y27632 and SB431542, were employed to evaluate the function of RhoA/ROCK and Smads. The effect of C3 transferase and Y27632 on the gene expression of chondrocyte-specific markers was evaluated by quantitative real-time polymerase chain reaction. To examine the effect of Y27632 on Smad2/3 phosphorylation induced by TGF-β1, western blot analysis was also performed. The stimulation of TGF-β1 in SMSCs resulted in the activation of the RhoA/ROCK pathway and concomitantly induced cytoskeletal reorganization, which was specifically blocked by C3 transferase and Y27632. The TGF-β-induced gene expression of Sox9, type I collagen, type II collagen and aggrecan was also inhibited by both C3 transferase and Y27632, at different levels. Y27632 treatment reduced the phosphorylation of Smad2/3 in a concentration-dependent manner. These results demonstrate the RhoA/ROCK activation regulates chondrocyte-specific gene transcription and cytoskeletal organization induced by TGF-β1 by interacting with the Smad pathway. This may have significant implications for the successful utilization of SMSCs as a cell source for articular cartilage tissue engineering.

  8. System-wide organization of actin cytoskeleton determines organelle transport in hypocotyl plant cells

    Science.gov (United States)

    Nowak, Jacqueline; Ivakov, Alexander; Somssich, Marc; Persson, Staffan; Nikoloski, Zoran

    2017-01-01

    The actin cytoskeleton is an essential intracellular filamentous structure that underpins cellular transport and cytoplasmic streaming in plant cells. However, the system-level properties of actin-based cellular trafficking remain tenuous, largely due to the inability to quantify key features of the actin cytoskeleton. Here, we developed an automated image-based, network-driven framework to accurately segment and quantify actin cytoskeletal structures and Golgi transport. We show that the actin cytoskeleton in both growing and elongated hypocotyl cells has structural properties facilitating efficient transport. Our findings suggest that the erratic movement of Golgi is a stable cellular phenomenon that might optimize distribution efficiency of cell material. Moreover, we demonstrate that Golgi transport in hypocotyl cells can be accurately predicted from the actin network topology alone. Thus, our framework provides quantitative evidence for system-wide coordination of cellular transport in plant cells and can be readily applied to investigate cytoskeletal organization and transport in other organisms. PMID:28655850

  9. 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.

  10. Roles of Asp179 and Glu270 in ADP-Ribosylation of Actin by Clostridium perfringens Iota Toxin.

    Directory of Open Access Journals (Sweden)

    Alexander Belyy

    Full Text Available Clostridium perfringens iota toxin is a binary toxin composed of the enzymatically active component Ia and receptor binding component Ib. Ia is an ADP-ribosyltransferase, which modifies Arg177 of actin. The previously determined crystal structure of the actin-Ia complex suggested involvement of Asp179 of actin in the ADP-ribosylation reaction. To gain more insights into the structural requirements of actin to serve as a substrate for toxin-catalyzed ADP-ribosylation, we engineered Saccharomyces cerevisiae strains, in which wild type actin was replaced by actin variants with substitutions in residues located on the Ia-actin interface. Expression of the actin mutant Arg177Lys resulted in complete resistance towards Ia. Actin mutation of Asp179 did not change Ia-induced ADP-ribosylation and growth inhibition of S. cerevisiae. By contrast, substitution of Glu270 of actin inhibited the toxic action of Ia and the ADP-ribosylation of actin. In vitro transcribed/translated human β-actin confirmed the crucial role of Glu270 in ADP-ribosylation of actin by Ia.

  11. 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.

  12. Interventions for actinic keratoses.

    Science.gov (United States)

    Gupta, Aditya K; Paquet, Maryse; Villanueva, Elmer; Brintnell, William

    2012-12-12

    Actinic keratoses are a skin disease caused by long-term sun exposure, and their lesions have the potential to develop into squamous cell carcinoma. Treatments for actinic keratoses are sought for cosmetic reasons, for the relief of associated symptoms, or for the prevention of skin cancer development. Detectable lesions are often associated with alteration of the surrounding skin (field) where subclinical lesions might be present. The interventions available for the treatment of actinic keratoses include individual lesion-based (e.g. cryotherapy) or field-directed (e.g. topical) treatments. These might vary in terms of efficacy, safety, and cosmetic outcomes. To assess the effects of topical, oral, mechanical, and chemical interventions for actinic keratosis. We searched the following databases up to March 2011: the Cochrane Skin Group Specialised Register, CENTRAL in The Cochrane Library, MEDLINE (from 2005), EMBASE (from 2010), and LILACS (from 1982). We also searched trials registers, conference proceedings, and grey literature sources. Randomised controlled trials (RCTs) comparing the treatment of actinic keratoses with either placebo, vehicle, or another active therapy. At least two authors independently abstracted data, which included adverse events, and assessed the quality of evidence. We performed meta-analysis to calculate a weighted treatment effect across trials, and we expressed the results as risk ratios (RR) and 95% confidence intervals (CI) for dichotomous outcomes (e.g. participant complete clearance rates), and mean difference (MD) and 95% CI for continuous outcomes (e.g. mean reduction in lesion counts). We included 83 RCTs in this review, with a total of 10,036 participants. The RCTs covered 18 topical treatments, 1 oral treatment, 2 mechanical interventions, and 3 chemical interventions, including photodynamic therapy (PDT). Most of the studies lacked descriptions of some methodological details, such as the generation of the randomisation

  13. 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.

  14. 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

  15. 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.

  16. Telecommunications energy and greenhouse gas emissions management for future network growth

    International Nuclear Information System (INIS)

    Chan, Chien Aun; Gygax, André F.; Leckie, Christopher; Wong, Elaine; Nirmalathas, Ampalavanapillai; Hinton, Kerry

    2016-01-01

    Highlights: • Model to evaluate key interdependencies of a fast growing telecommunications network. • Network growth analysis using real data and Monte Carlo simulation. • Importance of both operational and embodied energy efficiency improvements. • Embodied energy expected to dominate in the future under current energy efficiency trends. • Carbon footprint and energy management through optimum network replacement cycle. - Abstract: A key aspect of greener network deployment is how to achieve sustainable growth of a telecommunications network, both in terms of operational and embodied energy. Hence, in this paper we investigate how the overall energy consumption and greenhouse gas emissions of a fast growing telecommunications network can be minimized. Due to the complexities in modeling the embodied energy of networks, this aspect of energy consumption has received limited attention by network operators. Here, we present the first model to evaluate the interdependencies of the four main contributing factors in managing the sustainable growth of a telecommunications network: (i) the network’s operational energy consumption; (ii) the embodied energy of network equipment; (iii) network traffic growth; and (iv) the expected energy efficiency improvements in both the operational and embodied phases. Using Monte Carlo techniques with real network data, our results demonstrate that under the current trends in overall energy efficiency improvements the network embodied energy will account for over 40% of the total network energy in 2025 compared to 20% in 2015. Further, we find that the optimum equipment replacement cycle, which will result in the lowest total network life cycle energy, is directly dependent on the technological progress in energy efficiency improvements of both operational and embodied phases. Our model and analysis highlight the need for a comprehensive approach to better understand the interactions between network growth, technological

  17. 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.

  18. Growth of single walled carbon nanotubes networks using Al - Ni as catalyst

    International Nuclear Information System (INIS)

    Kotlar, M.; Vesely, M.; Redhammer, R.; Vretenar, V.

    2011-01-01

    The growth of SWCNTs networks on the SiO 2 chips was examined for different growth temperatures and annealing times. According to Raman spectroscopy the temperature is a significant parameter which affects quality of carbon nanotubes. For higher temperatures (850 - 900 deg C) the best quality was achieved. On the other hand, the different annealing times did not affect results of our experiments. SWCNTs network consists of large amount of intersecting carbon nanotubes. This network is electrically conductive over large distances. The SWCNTs networks can be used as transparent conductive layer or as sensitive layer of chemical sensors. (authors)

  19. Axonal regeneration and neuronal function are preserved in motor neurons lacking ß-actin in vivo.

    Directory of Open Access Journals (Sweden)

    Thomas R Cheever

    2011-03-01

    Full Text Available The proper localization of ß-actin mRNA and protein is essential for growth cone guidance and axon elongation in cultured neurons. In addition, decreased levels of ß-actin mRNA and protein have been identified in the growth cones of motor neurons cultured from a mouse model of Spinal Muscular Atrophy (SMA, suggesting that ß-actin loss-of-function at growth cones or pre-synaptic nerve terminals could contribute to the pathogenesis of this disease. However, the role of ß-actin in motor neurons in vivo and its potential relevance to disease has yet to be examined. We therefore generated motor neuron specific ß-actin knock-out mice (Actb-MNsKO to investigate the function of ß-actin in motor neurons in vivo. Surprisingly, ß-actin was not required for motor neuron viability or neuromuscular junction maintenance. Skeletal muscle from Actb-MNsKO mice showed no histological indication of denervation and did not significantly differ from controls in several measurements of physiologic function. Finally, motor axon regeneration was unimpaired in Actb-MNsKO mice, suggesting that ß-actin is not required for motor neuron function or regeneration in vivo.

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

    Directory of Open Access Journals (Sweden)

    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.

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

    Science.gov (United States)

    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.

  2. Growth and containment of a hierarchical criminal network

    Science.gov (United States)

    Marshak, Charles Z.; Rombach, M. Puck; Bertozzi, Andrea L.; D'Orsogna, Maria R.

    2016-02-01

    We model the hierarchical evolution of an organized criminal network via antagonistic recruitment and pursuit processes. Within the recruitment phase, a criminal kingpin enlists new members into the network, who in turn seek out other affiliates. New recruits are linked to established criminals according to a probability distribution that depends on the current network structure. At the same time, law enforcement agents attempt to dismantle the growing organization using pursuit strategies that initiate on the lower level nodes and that unfold as self-avoiding random walks. The global details of the organization are unknown to law enforcement, who must explore the hierarchy node by node. We halt the pursuit when certain local criteria of the network are uncovered, encoding if and when an arrest is made; the criminal network is assumed to be eradicated if the kingpin is arrested. We first analyze recruitment and study the large scale properties of the growing network; later we add pursuit and use numerical simulations to study the eradication probability in the case of three pursuit strategies, the time to first eradication, and related costs. Within the context of this model, we find that eradication becomes increasingly costly as the network increases in size and that the optimal way of arresting the kingpin is to intervene at the early stages of network formation. We discuss our results in the context of dark network disruption and their implications on possible law enforcement strategies.

  3. 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.

  4. All-Round Manipulation of the Actin Cytoskeleton by HIV.

    Science.gov (United States)

    Ospina Stella, Alberto; Turville, Stuart

    2018-02-05

    While significant progress has been made in terms of human immunodeficiency virus (HIV) therapy, treatment does not represent a cure and remains inaccessible to many people living with HIV. Continued mechanistic research into the viral life cycle and its intersection with many aspects of cellular biology are not only fundamental in the continued fight against HIV, but also provide many key observations of the workings of our immune system. Decades of HIV research have testified to the integral role of the actin cytoskeleton in both establishing and spreading the infection. Here, we review how the virus uses different strategies to manipulate cellular actin networks and increase the efficiency of various stages of its life cycle. While some HIV proteins seem able to bind to actin filaments directly, subversion of the cytoskeleton occurs indirectly by exploiting the power of actin regulatory proteins, which are corrupted at multiple levels. Furthermore, this manipulation is not restricted to a discrete class of proteins, but rather extends throughout all layers of the cytoskeleton. We discuss prominent examples of actin regulators that are exploited, neutralized or hijacked by the virus, and address how their coordinated deregulation can lead to changes in cellular behavior that promote viral spreading.

  5. 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

  6. 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

  7. 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.

  8. Noise suppress or express exponential growth for hybrid Hopfield neural networks

    International Nuclear Information System (INIS)

    Zhu Song; Shen Yi; Chen Guici

    2010-01-01

    In this Letter, we will show that noise can make the given hybrid Hopfield neural networks whose solution may grows exponentially become the new stochastic hybrid Hopfield neural networks whose solution will grows at most polynomially. On the other hand, we will also show that noise can make the given hybrid Hopfield neural networks whose solution grows at most polynomially become the new stochastic hybrid Hopfield neural networks whose solution will grows at exponentially. In other words, we will reveal that the noise can suppress or express exponential growth for hybrid Hopfield neural networks.

  9. F-actin distribution at nodes of Ranvier and Schmidt-Lanterman incisures in mammalian sciatic nerves.

    Science.gov (United States)

    Kun, Alejandra; Canclini, Lucía; Rosso, Gonzalo; Bresque, Mariana; Romeo, Carlos; Hanusz, Alicia; Cal, Karina; Calliari, Aldo; Sotelo Silveira, José; Sotelo, José R

    2012-07-01

    Very little is known about the function of the F-actin cytoskeleton in the regeneration and pathology of peripheral nerve fibers. The actin cytoskeleton has been associated with maintenance of tissue structure, transmission of traction and contraction forces, and an involvement in cell motility. Therefore, the state of the actin cytoskeleton strongly influences the mechanical properties of cells and intracellular transport therein. In this work, we analyze the distribution of F-actin at Schmidt-Lanterman Incisures (SLI) and nodes of Ranvier (NR) domains in normal, regenerating and pathologic Trembler J (TrJ/+) sciatic nerve fibers, of rats and mice. F-actin was quantified and it was found increased in TrJ/+, both in SLI and NR. However, SLI and NR of regenerating rat sciatic nerve did not show significant differences in F-actin, as compared with normal nerves. Cytochalasin-D and Latrunculin-A were used to disrupt the F-actin network in normal and regenerating rat sciatic nerve fibers. Both drugs disrupt F-actin, but in different ways. Cytochalasin-D did not disrupt Schwann cell (SC) F-actin at the NR. Latrunculin-A did not disrupt F-actin at the boundary region between SC and axon at the NR domain. We surmise that the rearrangement of F-actin in neurological disorders, as presented here, is an important feature of TrJ/+ pathology as a Charcot-Marie-Tooth (CMT) model. Copyright © 2012 Wiley Periodicals, Inc.

  10. Academic self-efficacy, growth mindsets, and university students' integration in academic and social support networks

    NARCIS (Netherlands)

    Zander, Lysann; Brouwer, Jasperina; Jansen, Ellen; Crayen, Claudia; Hannover, Bettina

    Combining complete social networks and structural equation modeling, we investigate how two learning-related cognitions, academic self-efficacy and growth mindsets, relate to integration in support networks of 580 university students in 30 seminar groups. We assessed integration as popularity in

  11. Growth of Railway Network in China (1988-2002

    Directory of Open Access Journals (Sweden)

    Serguei Tarkhov

    2003-05-01

    Full Text Available 20. 000 km of new railways were built in China in1988-2002. The railway network has increased its topologicalcomplexity from 75 to 112 circuits and the new 3nt topologicallayer appeared in 1993 and the 4'h will emerge in 2004 after the opening of the rail ferry Dalian - Yan-tai. The main features ofthe recent Chinese rail network are: 1 the predominance ofmeridional-ity, 2 the spatial disproportion between the easterncoastal area (with dense network and the empty western part,3 the low level of electrification (20% and the low share ofdouble-track sections (30%, 4 the land-lock orientation ofthe whole network and a small number of lines along the seacoasts. These disproportions are the main obstacles for a harmonicspatial devel-opment of the economic structure.

  12. Macroscopic Models of Clique Tree Growth for Bayesian Networks

    Data.gov (United States)

    National Aeronautics and Space Administration — In clique tree clustering, inference consists of propagation in a clique tree compiled from a Bayesian network. In this paper, we develop an analytical approach to...

  13. Fracture network growth for prediction of fracture characteristics and connectivity in tight reservoir rocks

    NARCIS (Netherlands)

    Barnhoorn, A.; Cox, S.F.

    2012-01-01

    Fracturing experiments on very low-porosity dolomite rocks shows a difference in growth of fracture networks by stress-driven fracturing and fluid-driven fracturing. Stress-driven fracture growth, in the absence of fluid pressure, initially forms fractures randomly throughout the rocks followed by

  14. Growth dynamics explain the development of spatiotemporal burst activity of young cultured neuronal networks in detail.

    Directory of Open Access Journals (Sweden)

    Taras A Gritsun

    Full Text Available A typical property of isolated cultured neuronal networks of dissociated rat cortical cells is synchronized spiking, called bursting, starting about one week after plating, when the dissociated cells have sufficiently sent out their neurites and formed enough synaptic connections. This paper is the third in a series of three on simulation models of cultured networks. Our two previous studies [26], [27] have shown that random recurrent network activity models generate intra- and inter-bursting patterns similar to experimental data. The networks were noise or pacemaker-driven and had Izhikevich-neuronal elements with only short-term plastic (STP synapses (so, no long-term potentiation, LTP, or depression, LTD, was included. However, elevated pre-phases (burst leaders and after-phases of burst main shapes, that usually arise during the development of the network, were not yet simulated in sufficient detail. This lack of detail may be due to the fact that the random models completely missed network topology .and a growth model. Therefore, the present paper adds, for the first time, a growth model to the activity model, to give the network a time dependent topology and to explain burst shapes in more detail. Again, without LTP or LTD mechanisms. The integrated growth-activity model yielded realistic bursting patterns. The automatic adjustment of various mutually interdependent network parameters is one of the major advantages of our current approach. Spatio-temporal bursting activity was validated against experiment. Depending on network size, wave reverberation mechanisms were seen along the network boundaries, which may explain the generation of phases of elevated firing before and after the main phase of the burst shape.In summary, the results show that adding topology and growth explain burst shapes in great detail and suggest that young networks still lack/do not need LTP or LTD mechanisms.

  15. Case for diagnosis. Actinic prurigo.

    Science.gov (United States)

    Daldon, Patricia Erica Christofoletti; Pascini, Mirella; Correa, Mariane

    2010-01-01

    A 13-year-old black boy had pruritic papular and nodular lesions on his forearms associated to edema of the lower lip, photophobia, conjunctivitis and pterygium. Skin biopsy of the lower lip revealed acanthosis, spongiosis with dermal perivascular mononuclear cell infiltration composed by lymphocytes, plasma cells and eosinophils consistent with actinic prurigo. Lesions improved considerably with the use of thalidomide 100mg/ day.

  16. 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

  17. Determining bank effects on economic growth: An artificial neural network analysis

    OpenAIRE

    Alex Senajon

    2016-01-01

    This study characterized the influence of the banking industry’s influence on the growth of the economy. A neural network using the Multilayer Perception was used to define functions of Universal Bank, Cooperative Bank, and Thrift Bank as predictors of Gross Domestic Product growth. Using data series from 2003- 2013, it was found that Universal banks have been growing tremendously taking huge shares of growth compared to the other two bank types. Meantime, the Gross Domestic Product was fo...

  18. 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

  19. A Method for Upper Bounding Long Term Growth of Network Access Speed

    Directory of Open Access Journals (Sweden)

    Thomas Phillip Knudsen

    2006-06-01

    Full Text Available The development in home Internet access speed has shown an exponential development with growth rates averaging 25% per year. For resource management in network provisioning it becomes an urgent question how long such growth can continue. This paper presents a method for calculating an upper bound to visual content driven growth, proceeding from datarate requirements for a full virtual environment. Scenarios and approaches for reducing datarate requirements are considered and discussed. The presented figures for an upper bound on network access speed are discussed and perspectives on further research presented.

  20. A Method for Upper Bounding Long Term Growth of Network Access Speed

    DEFF Research Database (Denmark)

    Knudsen, Thomas Phillip; Pedersen, Jens Myrup; Madsen, Ole Brun

    2004-01-01

    The development in home Internet access speed has shown an exponential development with growth rates averaging 25% per year. For resource management in network provisioning it becomes an urgent question how long such growth can continue. This paper presents a method for calculating an upper bound...... to visual content driven growth, proceeding from datarate requirements for a full virtual environment. Scenarios and approaches for reducing datarate requirements are considered and discussed. The presented figures for an upper bound on network access speed are discussed and perspectives on further research...

  1. Curation-Based Network Marketing: Strategies for Network Growth and Electronic Word-of-Mouth Diffusion

    Science.gov (United States)

    Church, Earnie Mitchell, Jr.

    2013-01-01

    In the last couple of years, a new aspect of online social networking has emerged, in which the strength of social network connections is based not on social ties but mutually shared interests. This dissertation studies these "curation-based" online social networks (CBN) and their suitability for the diffusion of electronic word-of-mouth…

  2. The transcriptional and gene regulatory network of Lactococcus lactis MG1363 during growth in milk.

    Directory of Open Access Journals (Sweden)

    Anne de Jong

    Full Text Available In the present study we examine the changes in the expression of genes of Lactococcus lactis subspecies cremoris MG1363 during growth in milk. To reveal which specific classes of genes (pathways, operons, regulons, COGs are important, we performed a transcriptome time series experiment. Global analysis of gene expression over time showed that L. lactis adapted quickly to the environmental changes. Using upstream sequences of genes with correlated gene expression profiles, we uncovered a substantial number of putative DNA binding motifs that may be relevant for L. lactis fermentative growth in milk. All available novel and literature-derived data were integrated into network reconstruction building blocks, which were used to reconstruct and visualize the L. lactis gene regulatory network. This network enables easy mining in the chrono-transcriptomics data. A freely available website at http://milkts.molgenrug.nl gives full access to all transcriptome data, to the reconstructed network and to the individual network building blocks.

  3. 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

  4. 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.

  5. 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.

  6. The growth of minicircle networks on regular lattices

    International Nuclear Information System (INIS)

    Diao, Y; Hinson, K; Arsuaga, J

    2012-01-01

    The mitochondrial DNA of trypanosomes is organized into a network of topologically linked minicircles. In order to investigate how key topological properties of the network change with minicircle density, the authors introduced, in an earlier study, a mathematical model in which randomly oriented minicircles were placed on the vertices of the simple square lattice. Using this model, the authors rigorously showed that when the density of minicircles increases, percolation clusters form. For higher densities, these percolation clusters are the backbones for networks of minicircles that saturate the entire lattice. An important relevant question is whether these findings are generally true. That is, whether these results are independent of the choice of the lattices on which the model is based. In this paper, we study two additional lattices (namely the honeycomb and the triangular lattices). These regular lattices are selected because they have been proposed for trypanosomes before and after replication. We compare our findings with our earlier results on the square lattice and show that the mathematical statements derived for the square lattice can be extended to these other lattices qualitatively. This finding suggests the universality of these properties. Furthermore, we performed a numerical study which provided data that are consistent with our theoretical analysis, and showed that the effect of the choice of lattices on the key network topological characteristics is rather small. (paper)

  7. 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....

  8. Simulating urban growth by emphasis on connective routes network (case study: Bojnourd city

    Directory of Open Access Journals (Sweden)

    Mehdi Saadat Novin

    2017-06-01

    Full Text Available Development of urban construction and ever-increasing growth of population lead to landuse changes especially in agricultural lands, which play an important role in providing human food. According to this issue, a proper landuse planning is required to protecting and preserving the valuable agricultural lands and environment, in today’s world. The prediction of urban growth can help in understanding the potential impacts on a region’s water resource, economy and people. One of the effective parameters in development of cities is connective routes network and their different types and qualities that play an important role in decreasing or increasing the growth of the city. On the other hand, the type of the connective routes network is an important factor for the speed and quality of development. In this paper, two different scenarios were used to simulate landuse changes and analyzing their results. In first scenario, modeling is based on the effective parameters in urban growth without classification of connective routes network. In the second scenario, effective parameters in urban growth were considered and connective routes were classified in 6 different classes with different weights in order to examine their effect on urban development. Simulation of landuse has been carried out for 2020–2050. The results clearly showed the effect of the connective routes network classification in output maps so that the effect of the first and second main routes network in development, is conspicuous.

  9. Allyl Isothiocyanate Inhibits Actin-Dependent Intracellular Transport in Arabidopsis thaliana

    Directory of Open Access Journals (Sweden)

    Bjørnar Sporsheim

    2015-12-01

    Full Text Available Volatile allyl isothiocyanate (AITC derives from the biodegradation of the glucosinolate sinigrin and has been associated with growth inhibition in several plants, including the model plant Arabidopsis thaliana. However, the underlying cellular mechanisms of this feature remain scarcely investigated in plants. In this study, we present evidence of an AITC-induced inhibition of actin-dependent intracellular transport in A. thaliana. A transgenic line of A. thaliana expressing yellow fluorescent protein (YFP-tagged actin filaments was used to show attenuation of actin filament movement by AITC. This appeared gradually in a time- and dose-dependent manner and resulted in actin filaments appearing close to static. Further, we employed four transgenic lines with YFP-fusion proteins labeling the Golgi apparatus, endoplasmic reticulum (ER, vacuoles and peroxisomes to demonstrate an AITC-induced inhibition of actin-dependent intracellular transport of or, in these structures, consistent with the decline in actin filament movement. Furthermore, the morphologies of actin filaments, ER and vacuoles appeared aberrant following AITC-exposure. However, AITC-treated seedlings of all transgenic lines tested displayed morphologies and intracellular movements similar to that of the corresponding untreated and control-treated plants, following overnight incubation in an AITC-absent environment, indicating that AITC-induced decline in actin-related movements is a reversible process. These findings provide novel insights into the cellular events in plant cells following exposure to AITC, which may further expose clues to the physiological significance of the glucosinolate-myrosinase system.

  10. 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.

  11. 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.

  12. A Model for the Growth of Network Service Providers

    Science.gov (United States)

    2011-12-01

    Service Provider O-D Origin-Destination POP Point of Presence UCG Unilateral Connection Game xiv THIS PAGE INTENTIONALLY LEFT BLANK xv EXECUTIVE...xvi We make use of the Abilene dataset as input to the network provisioning model and assume that the NSP is new to the market and is building an...has to decide on the connections to build and the markets to serve in order to maximize its profits. The NSP makes these decisions based on the market

  13. 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

  14. Growth hormone biases amygdala network activation after fear learning

    OpenAIRE

    Gisabella, Barbara; Farah, Shadia; Peng, Xiaoyu; Burgos-Robles, Anthony Noel; Lim, Seh Hong; Goosens, Ki Ann

    2016-01-01

    Prolonged stress exposure is a risk factor for developing posttraumatic stress disorder, a disorder characterized by the ?over-encoding' of a traumatic experience. A potential mechanism by which this occurs is through upregulation of growth hormone (GH) in the amygdala. Here we test the hypotheses that GH promotes the over-encoding of fearful memories by increasing the number of neurons activated during memory encoding and biasing the allocation of neuronal activation, one aspect of the proce...

  15. The impact on growth of outside-in and inside-out innovation in SME networks

    DEFF Research Database (Denmark)

    Brink, Tove

    2014-01-01

    The purpose of this paper is to reveal what impact the dual approaches of outside-in and inside-out innovation have on growth in turnover in small and medium sized enterprises (SMEs) working together in network context. This is illustrated through research in three informal, Danish food industry...... networks with 60 SMEs responding. The research employs structural equation modelling for statistical analyses. The findings reveal that both the outside-in and the inside-out approaches have a significant positive impact on innovation and growth. The findings shed light on the need for combined dual...... on innovation and growth. A contribution is also made to the SME-network for organising the loosely coupled system in a dual approach....

  16. Nerve growth factor stimulates axon outgrowth through negative regulation of growth cone actomyosin restraint of microtubule advance.

    Science.gov (United States)

    Turney, Stephen G; Ahmed, Mostafa; Chandrasekar, Indra; Wysolmerski, Robert B; Goeckeler, Zoe M; Rioux, Robert M; Whitesides, George M; Bridgman, Paul C

    2016-02-01

    Nerve growth factor (NGF) promotes growth, differentiation, and survival of sensory neurons in the mammalian nervous system. Little is known about how NGF elicits faster axon outgrowth or how growth cones integrate and transform signal input to motor output. Using cultured mouse dorsal root ganglion neurons, we found that myosin II (MII) is required for NGF to stimulate faster axon outgrowth. From experiments inducing loss or gain of function of MII, specific MII isoforms, and vinculin-dependent adhesion-cytoskeletal coupling, we determined that NGF causes decreased vinculin-dependent actomyosin restraint of microtubule advance. Inhibition of MII blocked NGF stimulation, indicating the central role of restraint in directed outgrowth. The restraint consists of myosin IIB- and IIA-dependent processes: retrograde actin network flow and transverse actin bundling, respectively. The processes differentially contribute on laminin-1 and fibronectin due to selective actin tethering to adhesions. On laminin-1, NGF induced greater vinculin-dependent adhesion-cytoskeletal coupling, which slowed retrograde actin network flow (i.e., it regulated the molecular clutch). On fibronectin, NGF caused inactivation of myosin IIA, which negatively regulated actin bundling. On both substrates, the result was the same: NGF-induced weakening of MII-dependent restraint led to dynamic microtubules entering the actin-rich periphery more frequently, giving rise to faster elongation. © 2016 Turney 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).

  17. 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+).

  18. 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

  19. 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...

  20. Ecological network analysis for economic systems: growth and development and implications for sustainable development.

    Science.gov (United States)

    Huang, Jiali; Ulanowicz, Robert E

    2014-01-01

    The quantification of growth and development is an important issue in economics, because these phenomena are closely related to sustainability. We address growth and development from a network perspective in which economic systems are represented as flow networks and analyzed using ecological network analysis (ENA). The Beijing economic system is used as a case study and 11 input-output (I-O) tables for 1985-2010 are converted into currency networks. ENA is used to calculate system-level indices to quantify the growth and development of Beijing. The contributions of each direct flow toward growth and development in 2010 are calculated and their implications for sustainable development are discussed. The results show that during 1985-2010, growth was the main attribute of the Beijing economic system. Although the system grew exponentially, its development fluctuated within only a small range. The results suggest that system ascendency should be increased in order to favor more sustainable development. Ascendency can be augmented in two ways: (1) strengthen those pathways with positive contributions to increasing ascendency and (2) weaken those with negative effects.

  1. 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.

  2. 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

  3. 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.

  4. Growth hormone biases amygdala network activation after fear learning.

    Science.gov (United States)

    Gisabella, B; Farah, S; Peng, X; Burgos-Robles, A; Lim, S H; Goosens, K A

    2016-11-29

    Prolonged stress exposure is a risk factor for developing posttraumatic stress disorder, a disorder characterized by the 'over-encoding' of a traumatic experience. A potential mechanism by which this occurs is through upregulation of growth hormone (GH) in the amygdala. Here we test the hypotheses that GH promotes the over-encoding of fearful memories by increasing the number of neurons activated during memory encoding and biasing the allocation of neuronal activation, one aspect of the process by which neurons compete to encode memories, to favor neurons that have stronger inputs. Viral overexpression of GH in the amygdala increased the number of amygdala cells activated by fear memory formation. GH-overexpressing cells were especially biased to express the immediate early gene c-Fos after fear conditioning, revealing strong autocrine actions of GH in the amygdala. In addition, we observed dramatically enhanced dendritic spine density in GH-overexpressing neurons. These data elucidate a previously unrecognized autocrine role for GH in the regulation of amygdala neuron function and identify specific mechanisms by which chronic stress, by enhancing GH in the amygdala, may predispose an individual to excessive fear memory formation.

  5. Pharmacological treatment of actinic keratosis

    Directory of Open Access Journals (Sweden)

    Ewa Zwierzyńska

    2016-09-01

    Full Text Available Actinic keratosis (AK is a disease characterized by hyperkeratotic lesions on skin damaged by ultraviolet. radiation. These lesions may progress to squamous cell or basal cell carcinoma. Currently pharmacotherapy and different surgical procedures are used in AK therapy. The most common treatment options are 5-fluorouracil, imiquimod, diclofenac, ingenol mebutate, and first and third generation retinoids (retinol, adapalene, tazarotene. Furthermore, research is being carried out in order to test new medications including nicotinamide, resiquimod, piroxicam, potassium dobesilate and oleogel based on a triterpene extract (betulin, betulinic acid. Recently, the preventive effect of acetylsalicylic acid and celecoxib has also been investigated.

  6. Action selection in growing state spaces: control of network structure growth

    International Nuclear Information System (INIS)

    Thalmeier, Dominik; Kappen, Hilbert J; Gómez, Vicenç

    2017-01-01

    The dynamical processes taking place on a network depend on its topology. Influencing the growth process of a network therefore has important implications on such dynamical processes. We formulate the problem of influencing the growth of a network as a stochastic optimal control problem in which a structural cost function penalizes undesired topologies. We approximate this control problem with a restricted class of control problems that can be solved using probabilistic inference methods. To deal with the increasing problem dimensionality, we introduce an adaptive importance sampling method for approximating the optimal control. We illustrate this methodology in the context of formation of information cascades, considering the task of influencing the structure of a growing conversation thread, as in Internet forums. Using a realistic model of growing trees, we show that our approach can yield conversation threads with better structural properties than the ones observed without control. (paper)

  7. Determining bank effects on economic growth: An artificial neural network analysis

    Directory of Open Access Journals (Sweden)

    Alex Senajon

    2016-01-01

    Full Text Available This study characterized the influence of the banking industry’s influence on the growth of the economy. A neural network using the Multilayer Perception was used to define functions of Universal Bank, Cooperative Bank, and Thrift Bank as predictors of Gross Domestic Product growth. Using data series from 2003- 2013, it was found that Universal banks have been growing tremendously taking huge shares of growth compared to the other two bank types. Meantime, the Gross Domestic Product was found to be steadily growing over the same period with a significant spike in 2004. In addition, neural network presents the contribution of the bank types on Gross Domestic Product, and found that the assets and capital of rural banks positively affect the Gross Domestic Product growth. As such, the sensitivity analysis of the Artificial Neural Network indicates Rural banks asset as the most important predictor of all the chosen variables followed by Universal bank capital. However, the capital of Thrift banks was found to show least contribution on the growth of the Gross Domestic Product.

  8. 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.

  9. Identification of cation-binding sites on actin that drive polymerization and modulate bending stiffness

    Science.gov (United States)

    Kang, Hyeran; Bradley, Michael J.; McCullough, Brannon R.; Pierre, Anaëlle; Grintsevich, Elena E.; Reisler, Emil; De La Cruz, Enrique M.

    2012-01-01

    The assembly of actin monomers into filaments and networks plays vital roles throughout eukaryotic biology, including intracellular transport, cell motility, cell division, determining cellular shape, and providing cells with mechanical strength. The regulation of actin assembly and modulation of filament mechanical properties are critical for proper actin function. It is well established that physiological salt concentrations promote actin assembly and alter the overall bending mechanics of assembled filaments and networks. However, the molecular origins of these salt-dependent effects, particularly if they involve nonspecific ionic strength effects or specific ion-binding interactions, are unknown. Here, we demonstrate that specific cation binding at two discrete sites situated between adjacent subunits along the long-pitch helix drive actin polymerization and determine the filament bending rigidity. We classify the two sites as “polymerization” and “stiffness” sites based on the effects that mutations at the sites have on salt-dependent filament assembly and bending mechanics, respectively. These results establish the existence and location of the cation-binding sites that confer salt dependence to the assembly and mechanics of actin filaments. PMID:23027950

  10. 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.

  11. 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.

  12. On a multistable competitive network model in the case of an inhomogeneous growth rate spectrum: With an application to priming

    International Nuclear Information System (INIS)

    Frank, T.D.

    2009-01-01

    A stability analysis of a network model proposed by Haken is carried out for the case of an inhomogeneous spectrum of growth rates. The degree of multistability as a function of the coupling strength between network units is determined. An application to priming shows that the network can reconstruct the fundamental phenomenon that primed items have shorter recall latencies than non-primed items when assuming that learning affects the inhomogeneity of the growth rate spectrum.

  13. Contribution to growth and increment analysis on the Italian CONECOFOR Level II Network

    Directory of Open Access Journals (Sweden)

    Emilio AMORINI

    2002-09-01

    Full Text Available The paper deals with the "Estimation of growth and yield" included in the National Programme on Intensive Monitoring of Forest Ecosystems CONECOFOR Aims of the paper are: i to outline the composition and design of Level II PMPs network, also examining the structural characteristics of forest stands; ii to describe the contents of mensurational surveys carried out in winter 1996/97 and 1999/00; iii to analyse the growth rates in progress at each PMP using selected descriptors. Stand origin (11 high forests and 13 stored coppices and transitory crops and the number of forest types tested are focused as the main discriminants of the PMPs network. This composition, together with irregular forestry practice, results in a number of consequences (prevailing age classes, tree densities and related stand structures, growth patterns which cause a high in-and-between variability of all growth parameters. For the purposes of this analysis, the network of the plots was divided into three main sets: broadleaved high forest (i.e. beech stands, 6 PMPs; coniferous forest (i.e. Norway spruce stands, 5 PMPs; coppice forest (i.e. deciduous and evergreen oaks, beech and hardbeam stands, 13 PMPs. The measurement of basic growth variables (dbh and tree height was used to describe the tree populations in each PMP; the calculation of basal area, mean and top dbh, mean and top height, provided the reference dataset at each inventory. The assessment of social class according to Kraft gave information on vertical stand structure and made it possible to analyse growth according to tree layers. Data comparison provided increments in the interval 1997-2000. The occurrence of natural mortality and ingrowth was also assessed to take into account their combined effect on tree population dynamics. No trend was found, due to limited data availability, but it was possible to have a detailed overview of the stand situation and growth rates in PMPs.

  14. Altered resting-state whole-brain functional networks of neonates with intrauterine growth restriction.

    Science.gov (United States)

    Batalle, Dafnis; Muñoz-Moreno, Emma; Tornador, Cristian; Bargallo, Nuria; Deco, Gustavo; Eixarch, Elisenda; Gratacos, Eduard

    2016-04-01

    The feasibility to use functional MRI (fMRI) during natural sleep to assess low-frequency basal brain activity fluctuations in human neonates has been demonstrated, although its potential to characterise pathologies of prenatal origin has not yet been exploited. In the present study, we used intrauterine growth restriction (IUGR) as a model of altered neurodevelopment due to prenatal condition to show the suitability of brain networks to characterise functional brain organisation at neonatal age. Particularly, we analysed resting-state fMRI signal of 20 neonates with IUGR and 13 controls, obtaining whole-brain functional networks based on correlations of blood oxygen level-dependent (BOLD) signal in 90 grey matter regions of an anatomical atlas (AAL). Characterisation of the networks obtained with graph theoretical features showed increased network infrastructure and raw efficiencies but reduced efficiency after normalisation, demonstrating hyper-connected but sub-optimally organised IUGR functional brain networks. Significant association of network features with neurobehavioral scores was also found. Further assessment of spatiotemporal dynamics displayed alterations into features associated to frontal, cingulate and lingual cortices. These findings show the capacity of functional brain networks to characterise brain reorganisation from an early age, and their potential to develop biomarkers of altered neurodevelopment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Tree growth-climate relationships in a forest-plot network on Mediterranean mountains.

    Science.gov (United States)

    Fyllas, Nikolaos M; Christopoulou, Anastasia; Galanidis, Alexandros; Michelaki, Chrysanthi Z; Dimitrakopoulos, Panayiotis G; Fulé, Peter Z; Arianoutsou, Margarita

    2017-11-15

    In this study we analysed a novel tree-growth dataset, inferred from annual ring-width measurements, of 7 forest tree species from 12 mountain regions in Greece, in order to identify tree growth - climate relationships. The tree species of interest were: Abies cephalonica, Abies borisii-regis, Picea abies, Pinus nigra, Pinus sylvestris, Fagus sylvatica and Quercus frainetto growing across a gradient of climate conditions with mean annual temperature ranging from 5.7 to 12.6°C and total annual precipitation from 500 to 950mm. In total, 344 tree cores (one per tree) were analysed across a network of 20 study sites. We found that water availability during the summer period (May-August) was a strong predictor of interannual variation in tree growth for all study species. Across species and sites, annual tree growth was positively related to summer season precipitation (P SP ). The responsiveness of annual growth to P SP was tightly related to species and site specific measurements of instantaneous photosynthetic water use efficiency (WUE), suggesting that the growth of species with efficient water use is more responsive to variations in precipitation during the dry months of the year. Our findings support the importance of water availability for the growth of mountainous Mediterranean tree species and highlight that future reductions in precipitation are likely to lead to reduced tree-growth under climate change conditions. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. The Continuing Growth of Global Cooperation Networks in Research: A Conundrum for National Governments.

    Directory of Open Access Journals (Sweden)

    Caroline S Wagner

    Full Text Available Global collaboration continues to grow as a share of all scientific cooperation, measured as coauthorships of peer-reviewed, published papers. The percent of all scientific papers that are internationally coauthored has more than doubled in 20 years, and they account for all the growth in output among the scientifically advanced countries. Emerging countries, particularly China, have increased their participation in global science, in part by doubling their spending on R&D; they are increasingly likely to appear as partners on internationally coauthored scientific papers. Given the growth of connections at the international level, it is helpful to examine the phenomenon as a communications network and to consider the network as a new organization on the world stage that adds to and complements national systems. When examined as interconnections across the globe over two decades, a global network has grown denser but not more clustered, meaning there are many more connections but they are not grouping into exclusive 'cliques'. This suggests that power relationships are not reproducing those of the political system. The network has features an open system, attracting productive scientists to participate in international projects. National governments could gain efficiencies and influence by developing policies and strategies designed to maximize network benefits-a model different from those designed for national systems.

  17. Spiking, Bursting, and Population Dynamics in a Network of Growth Transform Neurons.

    Science.gov (United States)

    Gangopadhyay, Ahana; Chakrabartty, Shantanu

    2017-04-27

    This paper investigates the dynamical properties of a network of neurons, each of which implements an asynchronous mapping based on polynomial growth transforms. In the first part of this paper, we present a geometric approach for visualizing the dynamics of the network where each of the neurons traverses a trajectory in a dual optimization space, whereas the network itself traverses a trajectory in an equivalent primal optimization space. We show that as the network learns to solve basic classification tasks, different choices of primal-dual mapping produce unique but interpretable neural dynamics like noise shaping, spiking, and bursting. While the proposed framework is general enough, in this paper, we demonstrate its use for designing support vector machines (SVMs) that exhibit noise-shaping properties similar to those of ΣΔ modulators, and for designing SVMs that learn to encode information using spikes and bursts. It is demonstrated that the emergent switching, spiking, and burst dynamics produced by each neuron encodes its respective margin of separation from a classification hyperplane whose parameters are encoded by the network population dynamics. We believe that the proposed growth transform neuron model and the underlying geometric framework could serve as an important tool to connect well-established machine learning algorithms like SVMs to neuromorphic principles like spiking, bursting, population encoding, and noise shaping.

  18. 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...

  19. Coronin 3 involvement in F-actin-dependent processes at the cell cortex

    International Nuclear Information System (INIS)

    Rosentreter, Andre; Hofmann, Andreas; Xavier, Charles-Peter; Stumpf, Maria; Noegel, Angelika A.; Clemen, Christoph S.

    2007-01-01

    The actin interaction of coronin 3 has been mainly documented by in vitro experiments. Here, we discuss coronin 3 properties in the light of new structural information and focus on assays that reflect in vivo roles of coronin 3 and its impact on F-actin-associated functions. Using GFP-tagged coronin 3 fusion proteins and RNAi silencing we show that coronin 3 has roles in wound healing, protrusion formation, cell proliferation, cytokinesis, endocytosis, axonal growth, and secretion. During formation of cell protrusions actin accumulation precedes the focal enrichment of coronin 3 suggesting a role for coronin 3 in events that follow the initial F-actin assembly. Moreover, we show that coronin 3 similar to other coronins interacts with the Arp2/3-complex and cofilin indicating that this family in general is involved in regulating Arp2/3-mediated events

  20. 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.

  1. Non-Contact Plant Growth Measurement Method and System Based on Ubiquitous Sensor Network Technologies

    Directory of Open Access Journals (Sweden)

    Intae Ryoo

    2011-04-01

    Full Text Available This paper proposes a non-contact plant growth measurement system using infrared sensors based on the ubiquitous sensor network (USN technology. The proposed system measures plant growth parameters such as the stem radius of plants using real-time non-contact methods, and generates diameter, cross-sectional area and thickening form of plant stems using this measured data. Non-contact sensors have been used not to cause any damage to plants during measurement of the growth parameters. Once the growth parameters are measured, they are transmitted to a remote server using the sensor network technology and analyzed in the application program server. The analyzed data are then provided for administrators and a group of interested users. The proposed plant growth measurement system has been designed and implemented using fixed-type and rotary-type infrared sensor based measurement methods and devices. Finally, the system performance is compared and verified with the measurement data that have been obtained by practical field experiments.

  2. Application of artificial neural network with extreme learning machine for economic growth estimation

    Science.gov (United States)

    Milačić, Ljubiša; Jović, Srđan; Vujović, Tanja; Miljković, Jovica

    2017-01-01

    The purpose of this research is to develop and apply the artificial neural network (ANN) with extreme learning machine (ELM) to forecast gross domestic product (GDP) growth rate. The economic growth forecasting was analyzed based on agriculture, manufacturing, industry and services value added in GDP. The results were compared with ANN with back propagation (BP) learning approach since BP could be considered as conventional learning methodology. The reliability of the computational models was accessed based on simulation results and using several statistical indicators. Based on results, it was shown that ANN with ELM learning methodology can be applied effectively in applications of GDP forecasting.

  3. Role of Strong versus Weak Networks in Small Business Growth in an Emerging Economy

    Directory of Open Access Journals (Sweden)

    M. Kamil Kozan

    2014-02-01

    Full Text Available The study tests whether strong rather than weak ties account for small business growth in Turkey. Data were collected by means of a questionnaire filled out by the owners of small firms operating in four cities. Growth is comprised of two main areas, production expansion and knowledge acquisition. Results show that strong ties are positively related to both types of growth. In contrast, loose ties have no effect on small business growth in either area. This finding is attributed to the influence of the collectivistic nature of the mainstream Turkish culture, where owners of small businesses are likely to rely on in-groups rather than out-groups for advice and for financial support. Implications of relative absence of weak ties for small business growth and innovation in emerging economies are discussed. The findings suggest that culture should be included as a contingency variable in future studies of network strength and growth relationship. The paper also discusses the possible moderating role of affective and cognition-based trust in the relation of strong and weak ties to small business growth.

  4. In silico reconstitution of actin-based symmetry breaking and motility.

    Directory of Open Access Journals (Sweden)

    Mark J Dayel

    2009-09-01

    Full Text Available Eukaryotic cells assemble viscoelastic networks of crosslinked actin filaments to control their shape, mechanical properties, and motility. One important class of actin network is nucleated by the Arp2/3 complex and drives both membrane protrusion at the leading edge of motile cells and intracellular motility of pathogens such as Listeria monocytogenes. These networks can be reconstituted in vitro from purified components to drive the motility of spherical micron-sized beads. An Elastic Gel model has been successful in explaining how these networks break symmetry, but how they produce directed motile force has been less clear. We have combined numerical simulations with in vitro experiments to reconstitute the behavior of these motile actin networks in silico using an Accumulative Particle-Spring (APS model that builds on the Elastic Gel model, and demonstrates simple intuitive mechanisms for both symmetry breaking and sustained motility. The APS model explains observed transitions between smooth and pulsatile motion as well as subtle variations in network architecture caused by differences in geometry and conditions. Our findings also explain sideways symmetry breaking and motility of elongated beads, and show that elastic recoil, though important for symmetry breaking and pulsatile motion, is not necessary for smooth directional motility. The APS model demonstrates how a small number of viscoelastic network parameters and construction rules suffice to recapture the complex behavior of motile actin networks. The fact that the model not only mirrors our in vitro observations, but also makes novel predictions that we confirm by experiment, suggests that the model captures much of the essence of actin-based motility in this system.

  5. PREDICTION OF BULLS’ SLAUGHTER VALUE FROM GROWTH DATA USING ARTIFICIAL NEURAL NETWORK

    Directory of Open Access Journals (Sweden)

    Krzysztof ADAMCZYK

    2006-02-01

    Full Text Available The objective of this research was to investigate the usefulness of artifi cial neural network (ANN in the prediction of slaughter value of young crossbred bulls based on growth data. The studies were carried out on 104 bulls fattened from 120 days of life until the weight of 500 kg. The bulls were group fed using mainly farm feeds. After slaughter the carcasses were dissected and meat was subjected to physico-chemical and organoleptic analyses. The obtained data were used for the development of an artifi cial neural network model of slaughter value prediction. It was found that some slaughter value traits (hot carcass, cold half-carcass, neck and round weights, bone content in dissected elements in half-carcass, meat pH, dry-matter and protein contents in meat and meat tenderness and juiciness can be predicted with a considerably high accuracy using the artifi cial neural network.

  6. 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.

  7. A Discrete Fracture Network Model with Stress-Driven Nucleation and Growth

    Science.gov (United States)

    Lavoine, E.; Darcel, C.; Munier, R.; Davy, P.

    2017-12-01

    The realism of Discrete Fracture Network (DFN) models, beyond the bulk statistical properties, relies on the spatial organization of fractures, which is not issued by purely stochastic DFN models. The realism can be improved by injecting prior information in DFN from a better knowledge of the geological fracturing processes. We first develop a model using simple kinematic rules for mimicking the growth of fractures from nucleation to arrest, in order to evaluate the consequences of the DFN structure on the network connectivity and flow properties. The model generates fracture networks with power-law scaling distributions and a percentage of T-intersections that are consistent with field observations. Nevertheless, a larger complexity relying on the spatial variability of natural fractures positions cannot be explained by the random nucleation process. We propose to introduce a stress-driven nucleation in the timewise process of this kinematic model to study the correlations between nucleation, growth and existing fracture patterns. The method uses the stress field generated by existing fractures and remote stress as an input for a Monte-Carlo sampling of nuclei centers at each time step. Networks so generated are found to have correlations over a large range of scales, with a correlation dimension that varies with time and with the function that relates the nucleation probability to stress. A sensibility analysis of input parameters has been performed in 3D to quantify the influence of fractures and remote stress field orientations.

  8. Cdc42 and phosphoinositide 3-kinase drive Rac-mediated actin polymerization downstream of c-Met in distinct and common pathways

    DEFF Research Database (Denmark)

    Bosse, Tanja; Ehinger, Julia; Czuchra, Aleksandra

    2007-01-01

    -WASP. Instead, actin polymerization was driven by Arp2/3 complex activation through the WAVE complex downstream of Rac. Together, our data establish an intricate signaling network comprising as key molecules Cdc42 and PI3-kinase, which converge on Rac-mediated actin reorganization essential for Listeria...

  9. 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.

  10. 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.

  11. Actinic Granuloma with Focal Segmental Glomerulosclerosis

    Directory of Open Access Journals (Sweden)

    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.

  12. Enhanced growth of neural networks on conductive cellulose-derived nanofibrous scaffolds

    International Nuclear Information System (INIS)

    Kuzmenko, Volodymyr; Kalogeropoulos, Theodoros; Thunberg, Johannes; Johannesson, Sara; Hägg, Daniel; Enoksson, Peter; Gatenholm, Paul

    2016-01-01

    The problem of recovery from neurodegeneration needs new effective solutions. Tissue engineering is viewed as a prospective approach for solving this problem since it can help to develop healthy neural tissue using supportive scaffolds. This study presents effective and sustainable tissue engineering methods for creating biomaterials from cellulose that can be used either as scaffolds for the growth of neural tissue in vitro or as drug screening models. To reach this goal, nanofibrous electrospun cellulose mats were made conductive via two different procedures: carbonization and addition of multi-walled carbon nanotubes. The resulting scaffolds were much more conductive than untreated cellulose material and were used to support growth and differentiation of SH-SY5Y neuroblastoma cells. The cells were evaluated by scanning electron microscopy and confocal microscopy methods over a period of 15 days at different time points. The results showed that the cellulose-derived conductive scaffolds can provide support for good cell attachment, growth and differentiation. The formation of a neural network occurred within 10 days of differentiation, which is a promising length of time for SH-SY5Y neuroblastoma cells. - Highlights: • The conductive scaffolds for neural tissue engineering are derived from cellulose. • The scaffolds are used to support growth and differentiation of SH-SY5Y cells. • Distinctive cell differentiation occurs within 10 days on conductive scaffolds. • Electrical conductivity and nanotopography improve neural network formation.

  13. Fibril growth kinetics link buffer conditions and topology of 3D collagen I networks.

    Science.gov (United States)

    Kalbitzer, Liv; Pompe, Tilo

    2018-02-01

    Three-dimensional fibrillar networks reconstituted from collagen I are widely used as biomimetic scaffolds for in vitro and in vivo cell studies. Various physicochemical parameters of buffer conditions for in vitro fibril formation are well known, including pH-value, ion concentrations and temperature. However, there is a lack of a detailed understanding of reconstituting well-defined 3D network topologies, which is required to mimic specific properties of the native extracellular matrix. We screened a wide range of relevant physicochemical buffer conditions and characterized the topology of the reconstituted 3D networks in terms of mean pore size and fibril diameter. A congruent analysis of fibril formation kinetics by turbidimetry revealed the adjustment of the lateral growth phase of fibrils by buffer conditions to be key in the determination of pore size and fibril diameter of the networks. Although the kinetics of nucleation and linear growth phase were affected by buffer conditions as well, network topology was independent of those two growth phases. Overall, the results of our study provide necessary insights into how to engineer 3D collagen matrices with an independent control over topology parameters, in order to mimic in vivo tissues in in vitro experiments and tissue engineering applications. The study reports a comprehensive analysis of physicochemical conditions of buffer solutions to reconstitute defined 3D collagen I matrices. By a combined analysis of network topology, i.e., pore size and fibril diameter, and the kinetics of fibril formation we can reveal the dependence of 3D network topology on buffer conditions, such as pH-value, phosphate concentration and sodium chloride content. With those results we are now able to provide engineering strategies to independently tune the topology parameters of widely used 3D collagen scaffolds based on the buffer conditions. By that, we enable the straightforward mimicking of extracellular matrices of in vivo

  14. Evolving spiking neural networks: a novel growth algorithm exhibits unintelligent design

    Science.gov (United States)

    Schaffer, J. David

    2015-06-01

    Spiking neural networks (SNNs) have drawn considerable excitement because of their computational properties, believed to be superior to conventional von Neumann machines, and sharing properties with living brains. Yet progress building these systems has been limited because we lack a design methodology. We present a gene-driven network growth algorithm that enables a genetic algorithm (evolutionary computation) to generate and test SNNs. The genome for this algorithm grows O(n) where n is the number of neurons; n is also evolved. The genome not only specifies the network topology, but all its parameters as well. Experiments show the algorithm producing SNNs that effectively produce a robust spike bursting behavior given tonic inputs, an application suitable for central pattern generators. Even though evolution did not include perturbations of the input spike trains, the evolved networks showed remarkable robustness to such perturbations. In addition, the output spike patterns retain evidence of the specific perturbation of the inputs, a feature that could be exploited by network additions that could use this information for refined decision making if required. On a second task, a sequence detector, a discriminating design was found that might be considered an example of "unintelligent design"; extra non-functional neurons were included that, while inefficient, did not hamper its proper functioning.

  15. The assembly of MreB, a prokaryotic homolog of actin.

    Science.gov (United States)

    Esue, Osigwe; Cordero, Maria; Wirtz, Denis; Tseng, Yiider

    2005-01-28

    MreB, a major component of the bacterial cytoskeleton, exhibits high structural homology to its eukaryotic counterpart actin. Live cell microscopy studies suggest that MreB molecules organize into large filamentous spirals that support the cell membrane and play a key shape-determining function. However, the basic properties of MreB filament assembly remain unknown. Here, we studied the assembly of Thermotoga maritima MreB triggered by ATP in vitro and compared it to the well-studied assembly of actin. These studies show that MreB filament ultrastructure and polymerization depend crucially on temperature as well as the ions present on solution. At the optimal growth temperature of T. maritima, MreB assembly proceeded much faster than that of actin, without nucleation (or nucleation is highly favorable and fast) and with little or no contribution from filament end-to-end annealing. MreB exhibited rates of ATP hydrolysis and phosphate release similar to that of F-actin, however, with a critical concentration of approximately 3 nm, which is approximately 100-fold lower than that of actin. Furthermore, MreB assembled into filamentous bundles that have the ability to spontaneously form ring-like structures without auxiliary proteins. These findings suggest that despite high structural homology, MreB and actin display significantly different assembly properties.

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

    Science.gov (United States)

    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

  17. Long-term reorganization of structural brain networks in a rabbit model of intrauterine growth restriction.

    Science.gov (United States)

    Batalle, Dafnis; Muñoz-Moreno, Emma; Arbat-Plana, Ariadna; Illa, Miriam; Figueras, Francesc; Eixarch, Elisenda; Gratacos, Eduard

    2014-10-15

    Characterization of brain changes produced by intrauterine growth restriction (IUGR) is among the main challenges of modern fetal medicine and pediatrics. This condition affects 5-10% of all pregnancies and is associated with a wide range of neurodevelopmental disorders. Better understanding of the brain reorganization produced by IUGR opens a window of opportunity to find potential imaging biomarkers in order to identify the infants with a high risk of having neurodevelopmental problems and apply therapies to improve their outcomes. Structural brain networks obtained from diffusion magnetic resonance imaging (MRI) is a promising tool to study brain reorganization and to be used as a biomarker of neurodevelopmental alterations. In the present study this technique is applied to a rabbit animal model of IUGR, which presents some advantages including a controlled environment and the possibility to obtain high quality MRI with long acquisition times. Using a Q-Ball diffusion model, and a previously published rabbit brain MRI atlas, structural brain networks of 15 IUGR and 14 control rabbits at 70 days of age (equivalent to pre-adolescence human age) were obtained. The analysis of graph theory features showed a decreased network infrastructure (degree and binary global efficiency) associated with IUGR condition and a set of generalized fractional anisotropy (GFA) weighted measures associated with abnormal neurobehavior. Interestingly, when assessing the brain network organization independently of network infrastructure by means of normalized networks, IUGR showed increased global and local efficiencies. We hypothesize that this effect could reflect a compensatory response to reduced infrastructure in IUGR. These results present new evidence on the long-term persistence of the brain reorganization produced by IUGR that could underlie behavioral and developmental alterations previously described. The described changes in network organization have the potential to be used

  18. Limited urban growth: London's street network dynamics since the 18th century.

    Directory of Open Access Journals (Sweden)

    A Paolo Masucci

    Full Text Available We investigate the growth dynamics of Greater London defined by the administrative boundary of the Greater London Authority, based on the evolution of its street network during the last two centuries. This is done by employing a unique dataset, consisting of the planar graph representation of nine time slices of Greater London's road network spanning 224 years, from 1786 to 2010. Within this time-frame, we address the concept of the metropolitan area or city in physical terms, in that urban evolution reveals observable transitions in the distribution of relevant geometrical properties. Given that London has a hard boundary enforced by its long standing green belt, we show that its street network dynamics can be described as a fractal space-filling phenomena up to a capacitated limit, whence its growth can be predicted with a striking level of accuracy. This observation is confirmed by the analytical calculation of key topological properties of the planar graph, such as the topological growth of the network and its average connectivity. This study thus represents an example of a strong violation of Gibrat's law. In particular, we are able to show analytically how London evolves from a more loop-like structure, typical of planned cities, toward a more tree-like structure, typical of self-organized cities. These observations are relevant to the discourse on sustainable urban planning with respect to the control of urban sprawl in many large cities which have developed under the conditions of spatial constraints imposed by green belts and hard urban boundaries.

  19. Limited urban growth: London's street network dynamics since the 18th century.

    Science.gov (United States)

    Masucci, A Paolo; Stanilov, Kiril; Batty, Michael

    2013-01-01

    We investigate the growth dynamics of Greater London defined by the administrative boundary of the Greater London Authority, based on the evolution of its street network during the last two centuries. This is done by employing a unique dataset, consisting of the planar graph representation of nine time slices of Greater London's road network spanning 224 years, from 1786 to 2010. Within this time-frame, we address the concept of the metropolitan area or city in physical terms, in that urban evolution reveals observable transitions in the distribution of relevant geometrical properties. Given that London has a hard boundary enforced by its long standing green belt, we show that its street network dynamics can be described as a fractal space-filling phenomena up to a capacitated limit, whence its growth can be predicted with a striking level of accuracy. This observation is confirmed by the analytical calculation of key topological properties of the planar graph, such as the topological growth of the network and its average connectivity. This study thus represents an example of a strong violation of Gibrat's law. In particular, we are able to show analytically how London evolves from a more loop-like structure, typical of planned cities, toward a more tree-like structure, typical of self-organized cities. These observations are relevant to the discourse on sustainable urban planning with respect to the control of urban sprawl in many large cities which have developed under the conditions of spatial constraints imposed by green belts and hard urban boundaries.

  20. 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.

  1. 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.

  2. Growth kinetics of borided layers: Artificial neural network and least square approaches

    Science.gov (United States)

    Campos, I.; Islas, M.; Ramírez, G.; VillaVelázquez, C.; Mota, C.

    2007-05-01

    The present study evaluates the growth kinetics of the boride layer Fe 2B in AISI 1045 steel, by means of neural networks and the least square techniques. The Fe 2B phase was formed at the material surface using the paste boriding process. The surface boron potential was modified considering different boron paste thicknesses, with exposure times of 2, 4 and 6 h, and treatment temperatures of 1193, 1223 and 1273 K. The neural network and the least square models were set by the layer thickness of Fe 2B phase, and assuming that the growth of the boride layer follows a parabolic law. The reliability of the techniques used is compared with a set of experiments at a temperature of 1223 K with 5 h of treatment time and boron potentials of 2, 3, 4 and 5 mm. The results of the Fe 2B layer thicknesses show a mean error of 5.31% for the neural network and 3.42% for the least square method.

  3. Effect of nickel on the organization of actin filaments in Arabidopsis thaliana primary root cells

    International Nuclear Information System (INIS)

    Goryunova, I.I.; Krasilenko, Yu.A.; Emets, A.I.; Blyum, Ya.B.

    2016-01-01

    The influence of one of the most toxic heavy metals - nickel (Ni 2+ ) - on the organization of actin filaments (microfilaments) of different types of Arabidopsis thaliana (L.) root cells is studied in living cells by the laser scanning microscopy. To visualize microfilaments, the A. thaliana line expressing chimeric gene gfp-fabd2 was used. Ni 2+ leads to a significant inhibition of the growth of the main root and disturbs its morphology, causing the swelling of epidermal cells and inducing a large number of abnormally long root hairs. For the first time, it has been shown that Ni 2+ disturbs the organization of actin filaments in cells, leading to morphological changes of a root as the main organ, being the first exposed to the intoxication by soil pollutants. It is found that the most sensitive to its action are actin filaments of epidermal cells of all growth zones of A. thaliana root

  4. Urban Growth Modeling Using AN Artificial Neural Network a Case Study of Sanandaj City, Iran

    Science.gov (United States)

    Mohammady, S.; Delavar, M. R.; Pahlavani, P.

    2014-10-01

    Land use activity is a major issue and challenge for town and country planners. Modelling and managing urban growth is a complex problem. Cities are now recognized as complex, non-linear and dynamic process systems. The design of a system that can handle these complexities is a challenging prospect. Local governments that implement urban growth models need to estimate the amount of urban land required in the future given anticipated growth of housing, business, recreation and other urban uses within the boundary. There are so many negative implications related with the type of inappropriate urban development such as increased traffic and demand for mobility, reduced landscape attractively, land use fragmentation, loss of biodiversity and alterations of the hydrological cycle. The aim of this study is to use the Artificial Neural Network (ANN) to make a powerful tool for simulating urban growth patterns. Our study area is Sanandaj city located in the west of Iran. Landsat imageries acquired at 2000 and 2006 are used. Dataset were used include distance to principle roads, distance to residential areas, elevation, slope, distance to green spaces and distance to region centers. In this study an appropriate methodology for urban growth modelling using satellite remotely sensed data is presented and evaluated. Percent Correct Match (PCM) and Figure of Merit were used to evaluate ANN results.

  5. URBAN GROWTH MODELING USING AN ARTIFICIAL NEURAL NETWORK A CASE STUDY OF SANANDAJ CITY, IRAN

    Directory of Open Access Journals (Sweden)

    S. Mohammady

    2014-10-01

    Full Text Available Land use activity is a major issue and challenge for town and country planners. Modelling and managing urban growth is a complex problem. Cities are now recognized as complex, non-linear and dynamic process systems. The design of a system that can handle these complexities is a challenging prospect. Local governments that implement urban growth models need to estimate the amount of urban land required in the future given anticipated growth of housing, business, recreation and other urban uses within the boundary. There are so many negative implications related with the type of inappropriate urban development such as increased traffic and demand for mobility, reduced landscape attractively, land use fragmentation, loss of biodiversity and alterations of the hydrological cycle. The aim of this study is to use the Artificial Neural Network (ANN to make a powerful tool for simulating urban growth patterns. Our study area is Sanandaj city located in the west of Iran. Landsat imageries acquired at 2000 and 2006 are used. Dataset were used include distance to principle roads, distance to residential areas, elevation, slope, distance to green spaces and distance to region centers. In this study an appropriate methodology for urban growth modelling using satellite remotely sensed data is presented and evaluated. Percent Correct Match (PCM and Figure of Merit were used to evaluate ANN results.

  6. 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

  7. Network analysis of epidermal growth factor signaling using integrated genomic, proteomic and phosphorylation data.

    Directory of Open Access Journals (Sweden)

    Katrina M Waters

    Full Text Available To understand how integration of multiple data types can help decipher cellular responses at the systems level, we analyzed the mitogenic response of human mammary epithelial cells to epidermal growth factor (EGF using whole genome microarrays, mass spectrometry-based proteomics and large-scale western blots with over 1000 antibodies. A time course analysis revealed significant differences in the expression of 3172 genes and 596 proteins, including protein phosphorylation changes measured by western blot. Integration of these disparate data types showed that each contributed qualitatively different components to the observed cell response to EGF and that varying degrees of concordance in gene expression and protein abundance measurements could be linked to specific biological processes. Networks inferred from individual data types were relatively limited, whereas networks derived from the integrated data recapitulated the known major cellular responses to EGF and exhibited more highly connected signaling nodes than networks derived from any individual dataset. While cell cycle regulatory pathways were altered as anticipated, we found the most robust response to mitogenic concentrations of EGF was induction of matrix metalloprotease cascades, highlighting the importance of the EGFR system as a regulator of the extracellular environment. These results demonstrate the value of integrating multiple levels of biological information to more accurately reconstruct networks of cellular response.

  8. Network Analysis of Epidermal Growth Factor Signaling using Integrated Genomic, Proteomic and Phosphorylation Data

    Energy Technology Data Exchange (ETDEWEB)

    Waters, Katrina M.; Liu, Tao; Quesenberry, Ryan D.; Willse, Alan R.; Bandyopadhyay, Somnath; Kathmann, Loel E.; Weber, Thomas J.; Smith, Richard D.; Wiley, H. S.; Thrall, Brian D.

    2012-03-29

    To understand how integration of multiple data types can help decipher cellular responses at the systems level, we analyzed the mitogenic response of human mammary epithelial cells to epidermal growth factor (EGF) using whole genome microarrays, mass spectrometry-based proteomics and large-scale western blots with over 1000 antibodies. A time course analysis revealed significant differences in the expression of 3172 genes and 596 proteins, including protein phosphorylation changes measured by western blot. Integration of these disparate data types showed that each contributed qualitatively different components to the observed cell response to EGF and that varying degrees of concordance in gene expression and protein abundance measurements could be linked to specific biological processes. Networks inferred from individual data types were relatively limited, whereas networks derived from the integrated data recapitulated the known major cellular responses to EGF and exhibited more highly connected signaling nodes than networks derived from any individual dataset. While cell cycle regulatory pathways were altered as anticipated, we found the most robust response to mitogenic concentrations of EGF was induction of matrix metalloprotease cascades, highlighting the importance of the EGFR system as a regulator of the extracellular environment. These results demonstrate the value of integrating multiple levels of biological information to more accurately reconstruct networks of cellular response.

  9. Modeling wormhole growth and wormhole networks in unconsolidated sand media using the BP CHOPS model

    Energy Technology Data Exchange (ETDEWEB)

    Vanderheyden, W.B. [BP America, Inc. Exploration and Production Technology Unconventional Oil Flagship (United States); Zhang, D. Z.; Jayaraman, B. [Los Alamos National Laboratory Theoretical Division Solid and Fluid Dynamics Group (United States)

    2011-07-01

    Cold Heavy Oil Production with Sand (CHOPS) is a recovery method used in unconsolidated sands to produce heavy oil. During the use of the CHOPS method, wormholes originating from production wells are generated. The aim of this paper is to present 2 modeling tools developed by BP in order to improve reservoir simulation of CHOPS operations with wormholes. The first tool developed is a CHOPS modeling framework representing wormhole networks through reservoir simulation and its wellbore model. The second one consists of the application of advanced fluid-structure interaction modeling into the simulation of wormhole and its network growth. Experiments were carried out and a qualitative agreement was achieved with the model. In addition the BP CHOPS model can predict probable oil production without calibration. This paper presented an improved model for reservoir simulation with wormholes but further work is required to predict wormhole shape in a more accurate manner.

  10. The transcriptional network that controls growth arrest and differentiation in a human myeloid leukemia cell line

    DEFF Research Database (Denmark)

    Suzuki, Harukazu; Forrest, Alistair R R; van Nimwegen, Erik

    2009-01-01

    , we identified the key transcription regulators, their time-dependent activities and target genes. Systematic siRNA knockdown of 52 transcription factors confirmed the roles of individual factors in the regulatory network. Our results indicate that cellular states are constrained by complex networks......Using deep sequencing (deepCAGE), the FANTOM4 study measured the genome-wide dynamics of transcription-start-site usage in the human monocytic cell line THP-1 throughout a time course of growth arrest and differentiation. Modeling the expression dynamics in terms of predicted cis-regulatory sites...... involving both positive and negative regulatory interactions among substantial numbers of transcription factors and that no single transcription factor is both necessary and sufficient to drive the differentiation process....

  11. Nucleation and growth of C60 overlayers on the Ag/Pt(111) dislocation network surface

    International Nuclear Information System (INIS)

    Ait-Mansour, K; Ruffieux, P; Xiao, W; Fasel, R; Groening, P; Groening, O

    2007-01-01

    We have investigated the room temperature growth of C 60 overlayers on the strainrelief dislocation network formed by two monolayers of Ag on Pt(111) by means of scanning tunneling microscopy. Extended domains of highly ordered dislocation networks with a typical superlattice parameter of 6.8 nm have been prepared, serving as templates for subsequent C 60 depositions. For low C 60 coverages, the molecules decorate the step-edges, where also the first islands nucleate. This indicates that at room temperature the C 60 molecules are sufficiently mobile to cross the dislocation lines and to diffuse to the step-edges. For C 60 coverages of 0.4 monolayer, besides the islands nucleated at the step-edges, C 60 islands also grow in the middle of terraces. The C 60 islands typically extend over several unit cells of the dislocation network and show an unusual orientation of the hexagonally close-packed C 60 lattice as compared to that found on the bare Ag(111) surface. Whereas C 60 grows preferentially in a (2 √3 x 2 √3) R30 0 structure on Ag(111), on the Ag/Pt(111) dislocation network the C 60 lattice adopts an orientation rotated by 30 0 , with the close-packed C 60 rows aligned along the dislocations which themselves are aligned along the Ag(1-10) directions. For higher coverages in the range of 1-2 monolayers, the growth of C 60 continues in a layer-by-layer fashion

  12. 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

  13. Molecular beam epitaxial growth of graphene and ridge-structure networks of graphene

    International Nuclear Information System (INIS)

    Maeda, Fumihiko; Hibino, Hiroki

    2011-01-01

    By gas-source molecular beam epitaxy (MBE) using cracked ethanol, we grew graphene at substrate temperatures between 600 and 915 °C on graphene formed on SiC(0 0 0 1) by thermal decomposition. To investigate the substrate temperature dependence of graphene growth we analysed the MBE-grown graphene by Raman spectroscopy and in situ x-ray photoelectron spectroscopy (XPS) and observed it by atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (TEM). Analyses using the G-band peak and the peak intensity ratio between D- and G-band peaks in the Raman spectra revealed that growth at higher temperatures improved the crystallinity and increased the domain size. Although the growth rate decreased at higher temperatures, as revealed by XPS, these results indicated that growth at a higher temperature is effective in obtaining graphene of higher quality. Furthermore, the AFM and TEM observations revealed a network of fin-like ridge structures of graphene sticking out from the surface. The presence of these 'graphene nanofins' indicated that two-dimensional islands of graphene are surrounded by the nanofins, and the island size was estimated to be 67 nm using the average distance between the nanofins.

  14. Product unit neural network models for predicting the growth limits of Listeria monocytogenes.

    Science.gov (United States)

    Valero, A; Hervás, C; García-Gimeno, R M; Zurera, G

    2007-08-01

    A new approach to predict the growth/no growth interface of Listeria monocytogenes as a function of storage temperature, pH, citric acid (CA) and ascorbic acid (AA) is presented. A linear logistic regression procedure was performed and a non-linear model was obtained by adding new variables by means of a Neural Network model based on Product Units (PUNN). The classification efficiency of the training data set and the generalization data of the new Logistic Regression PUNN model (LRPU) were compared with Linear Logistic Regression (LLR) and Polynomial Logistic Regression (PLR) models. 92% of the total cases from the LRPU model were correctly classified, an improvement on the percentage obtained using the PLR model (90%) and significantly higher than the results obtained with the LLR model, 80%. On the other hand predictions of LRPU were closer to data observed which permits to design proper formulations in minimally processed foods. This novel methodology can be applied to predictive microbiology for describing growth/no growth interface of food-borne microorganisms such as L. monocytogenes. The optimal balance is trying to find models with an acceptable interpretation capacity and with good ability to fit the data on the boundaries of variable range. The results obtained conclude that these kinds of models might well be very a valuable tool for mathematical modeling.

  15. Urban Growth Modelling with Artificial Neural Network and Logistic Regression. Case Study: Sanandaj City, Iran

    Directory of Open Access Journals (Sweden)

    SASSAN MOHAMMADY

    2013-01-01

    Full Text Available Cities have shown remarkable growth due to attraction, economic, social and facilities centralization in the past few decades. Population and urban expansion especially in developing countries, led to lack of resources, land use change from appropriate agricultural land to urban land use and marginalization. Under these circumstances, land use activity is a major issue and challenge for town and country planners. Different approaches have been attempted in urban expansion modelling. Artificial Neural network (ANN models are among knowledge-based models which have been used for urban growth modelling. ANNs are powerful tools that use a machine learning approach to quantify and model complex behaviour and patterns. In this research, ANN and logistic regression have been employed for interpreting urban growth modelling. Our case study is Sanandaj city and we used Landsat TM and ETM+ imageries acquired at 2000 and 2006. The dataset used includes distance to main roads, distance to the residence region, elevation, slope, and distance to green space. Percent Area Match (PAM obtained from modelling of these changes with ANN is equal to 90.47% and the accuracy achieved for urban growth modelling with Logistic Regression (LR is equal to 88.91%. Percent Correct Match (PCM and Figure of Merit for ANN method were 91.33% and 59.07% and then for LR were 90.84% and 57.07%, respectively.

  16. 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.

  17. 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.

  18. 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

  19. 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

  20. Incorporation of mammalian actin into microfilaments in plant cell nucleus

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    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.

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

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    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.

  2. 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.

  3. Antibodies to actin in autoimmune haemolytic anaemia

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    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.

  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. Actin restructuring during Salmonella typhimurium infection investigated by confocal and super-resolution microscopy

    Science.gov (United States)

    Han, Jason J.; Kunde, Yuliya A.; Hong-Geller, Elizabeth; Werner, James H.

    2014-01-01

    We have used super-resolution optical microscopy and confocal microscopy to visualize the cytoskeletal restructuring of HeLa cells that accompanies and enables Salmonella typhimurium internalization. Herein, we report the use of confocal microscopy to verify and explore infection conditions that would be compatible with super-resolution optical microscopy, using Alexa-488 labeled phalloidin to stain the actin cytoskeletal network. While it is well known that actin restructuring and cytoskeletal rearrangements often accompany and assist in bacterial infection, most studies have employed conventional diffraction-limited fluorescence microscopy to explore these changes. Here we show that the superior spatial resolution provided by single-molecule localization methods (such as direct stochastic optical reconstruction microscopy) enables more precise visualization of the nanoscale changes in the actin cytoskeleton that accompany bacterial infection. In particular, we found that a thin (100-nm) ring of actin often surrounds an invading bacteria 10 to 20 min postinfection, with this ring being transitory in nature. We estimate that a few hundred monofilaments of actin surround the S. typhimurium in this heretofore unreported bacterial internalization intermediate.

  6. Interaction of cytochalasin D with actin filaments in the presence of ADP and ATP.

    Science.gov (United States)

    Carlier, M F; Criquet, P; Pantaloni, D; Korn, E D

    1986-02-15

    Cytochalasin D strongly inhibits the faster components in the reactions of actin filament depolymerization and elongation in the presence of 10 mM Tris-Cl-, pH 7.8, 0.2 mM dithiothreitol, 1 mM MgCl2, 0.1 mM CaCl2, and 0.2 mM ATP or ADP. Assuming an exclusive and total capping of the barbed end by the drug, the kinetic parameters derived at saturation by cytochalasin D refer to the pointed end and are 10-15-fold lower than at the barbed end. In ATP, the critical concentration increases with cytochalasin D up to 12-fold its value when both ends are free; as a result of the lowering of the free energy of nucleation by cytochalasin D, short oligomers of F-actin exist just above and below the critical concentration. Cytochalasin D interacts strongly with the barbed ends independently of the ADP-G-actin concentration (K = 0.5 nM-1). In contrast, the affinity of cytochalasin D decreases cooperatively with increasing ATP-G-actin concentration. These data are equally well accounted for by two different models: either cytochalasin D binds very poorly to ATP-capped filament ends whose proportion increases with actin concentration, or cytochalasin D binds equally well to ATP-ends and ADP-ends and also binds to actin dimers in ATP but not in ADP. A linear actin concentration dependence of the rate of growth was found at the pointed end, consistent with the virtual absence of an ATP cap at that end.

  7. 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.

  8. The yeast Sks1p kinase signaling network regulates pseudohyphal growth and glucose response.

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    Cole Johnson

    2014-03-01

    Full Text Available The yeast Saccharomyces cerevisiae undergoes a dramatic growth transition from its unicellular form to a filamentous state, marked by the formation of pseudohyphal filaments of elongated and connected cells. Yeast pseudohyphal growth is regulated by signaling pathways responsive to reductions in the availability of nitrogen and glucose, but the molecular link between pseudohyphal filamentation and glucose signaling is not fully understood. Here, we identify the glucose-responsive Sks1p kinase as a signaling protein required for pseudohyphal growth induced by nitrogen limitation and coupled nitrogen/glucose limitation. To identify the Sks1p signaling network, we applied mass spectrometry-based quantitative phosphoproteomics, profiling over 900 phosphosites for phosphorylation changes dependent upon Sks1p kinase activity. From this analysis, we report a set of novel phosphorylation sites and highlight Sks1p-dependent phosphorylation in Bud6p, Itr1p, Lrg1p, Npr3p, and Pda1p. In particular, we analyzed the Y309 and S313 phosphosites in the pyruvate dehydrogenase subunit Pda1p; these residues are required for pseudohyphal growth, and Y309A mutants exhibit phenotypes indicative of impaired aerobic respiration and decreased mitochondrial number. Epistasis studies place SKS1 downstream of the G-protein coupled receptor GPR1 and the G-protein RAS2 but upstream of or at the level of cAMP-dependent PKA. The pseudohyphal growth and glucose signaling transcription factors Flo8p, Mss11p, and Rgt1p are required to achieve wild-type SKS1 transcript levels. SKS1 is conserved, and deletion of the SKS1 ortholog SHA3 in the pathogenic fungus Candida albicans results in abnormal colony morphology. Collectively, these results identify Sks1p as an important regulator of filamentation and glucose signaling, with additional relevance towards understanding stress-responsive signaling in C. albicans.

  9. Actinic Keratosis Pathogenesis Update and New Patents.

    Science.gov (United States)

    Cantisani, Carmen; Paolino, Giovanni; Melis, Marcello; Faina, Valentina; Romaniello, Federico; Didona, Dario; Cardone, Michele; Calvieri, Stefano

    2016-01-01

    Actinic keratosis is a common premalignant skin lesion. Because of its increasing incidence, several efforts have been made to earlier detectection and to improve knowledge on photocarcinogenic pathways of keratinocytes. As a consequence, recently new discoveries have been done in this field. Starting from our previous review on actinic keratosis, we reviewed the literature focusing on pathogenesis and new patents in order to highlight the most recent progresses in diagnosis and therapeutic approach. Although several efforts have been done in the field of photodamaged skin, new upgrades in diagnosis and therapy are needed to detect superficial actinic keratosis earlier, to improve the disease free survival of patient and to better treat the field cancerization.

  10. Myosin IIA interacts with the spectrin-actin membrane skeleton to control red blood cell membrane curvature and deformability.

    Science.gov (United States)

    Smith, Alyson S; Nowak, Roberta B; Zhou, Sitong; Giannetto, Michael; Gokhin, David S; Papoin, Julien; Ghiran, Ionita C; Blanc, Lionel; Wan, Jiandi; Fowler, Velia M

    2018-05-08

    The biconcave disk shape and deformability of mammalian RBCs rely on the membrane skeleton, a viscoelastic network of short, membrane-associated actin filaments (F-actin) cross-linked by long, flexible spectrin tetramers. Nonmuscle myosin II (NMII) motors exert force on diverse F-actin networks to control cell shapes, but a function for NMII contractility in the 2D spectrin-F-actin network of RBCs has not been tested. Here, we show that RBCs contain membrane skeleton-associated NMIIA puncta, identified as bipolar filaments by superresolution fluorescence microscopy. MgATP disrupts NMIIA association with the membrane skeleton, consistent with NMIIA motor domains binding to membrane skeleton F-actin and contributing to membrane mechanical properties. In addition, the phosphorylation of the RBC NMIIA heavy and light chains in vivo indicates active regulation of NMIIA motor activity and filament assembly, while reduced heavy chain phosphorylation of membrane skeleton-associated NMIIA indicates assembly of stable filaments at the membrane. Treatment of RBCs with blebbistatin, an inhibitor of NMII motor activity, decreases the number of NMIIA filaments associated with the membrane and enhances local, nanoscale membrane oscillations, suggesting decreased membrane tension. Blebbistatin-treated RBCs also exhibit elongated shapes, loss of membrane curvature, and enhanced deformability, indicating a role for NMIIA contractility in promoting membrane stiffness and maintaining RBC biconcave disk cell shape. As structures similar to the RBC membrane skeleton exist in many metazoan cell types, these data demonstrate a general function for NMII in controlling specialized membrane morphology and mechanical properties through contractile interactions with short F-actin in spectrin-F-actin networks.

  11. 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

  12. 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.

  13. Growth surveillance in the context of the Primary Public Healthcare Service Network in Brazil: literature review

    Directory of Open Access Journals (Sweden)

    Dixis Figueroa Pedraza

    2016-03-01

    Full Text Available Abstract Objectives: to identify and analyze the scientific literature on child growth monitoring in the context of the primary public healthcare service network in Brazil, focusing on the main problems detected in studies. Methods: the review was based on searches ofSciELO, Lilacs and PubMed databases to identify articles published between 2006 and 2014. The articles were categorized according to the analytical categories of structure (items needed to carry out primary activities or work processes (set of activities and procedures used in the management of resources. Results: of the 16 articles included in this review, only six dealt with structure and, in these, thetraining of professionals and availability of protocols were the most frequently identified problems. Processes, addressed in 15 articles, highlighted the underutilization of Child Health Handbook to record growth measurements and the adoption of guidelines on the basis of notes taken. Conclusions: the difficulties found demonstrate the everyday circumstances of the public health service which have a detrimental effect on growth surveillance.

  14. 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.

  15. 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.

  16. Actin cytoskeleton rearrangements in Arabidopsis roots under stress and during gravitropic response

    Science.gov (United States)

    Pozhvanov, Gregory; Medvedev, Sergei; Suslov, Dmitry; Demidchik, Vadim

    Among environmental factors, gravity vector is the only one which is constant in direction and accompanies the whole plant ontogenesis. That said, gravity vector can be considered as an essential factor for correct development of plants. Gravitropism is a plant growth response against changing its position relative to the gravity vector. It is well estableshed that gravitropism is directed by auxin redistribution across the gravistimulated organ. In addition to auxin, actin cytoskeleton was shown to be involved in gravitropism at different stages: gravity perception, signal transduction and gravitropic bending formation. However, the relationship between IAA and actin is still under discussion. In this work we studied rearrangements of actin cytoskeleton during root gravitropic response. Actin microfilaments were visualized in vivo in GFP-fABD2 transgenic Arabidopsis plants, and their angle distribution was acquired from MicroFilament Analyzer software. The curvature of actin microfilaments in root elongation zone was shown to be increased within 30-60 min of gravistimulation, the fraction of axially oriented microfilaments decreased with a concomitant increase in the fraction of oblique and transversally oriented microfilaments. In particular, the fraction of transversally oriented microfilaments (i.e. parallel to the gravity vector) increased 3-5 times. Under 10 min of sub-lethal salt stress impact, actin microfilament orientations widened from an initial axial orientation to a set of peaks at 15(°) , 45(°) and 90(°) . We conclude that the actin cytoskeleton rearrangements observed are associated with the regulation of basic mechanisms of cell extension growth by which the gravitropic bending is formed. Having common stress-related features, gravity-induced actin cytoskeleton rearrangement is slower but results in higher number of g-vector-parallel microfilaments when compared to salt stress-induced rearrangement. Also, differences in gravistimulated root

  17. Self-assembly of tetrapod-shaped CdS nanostructures into 3D networks by a transverse growth process

    International Nuclear Information System (INIS)

    Fu Xiuli; Li Dan; Zhang Lei; Xiao Jinghua; Li Jiangyan; Peng Zhijian; Fang Zheyu

    2011-01-01

    Spontaneous formation of 3D tetrapod-shaped CdS nanostructure networks has been achieved for the first time by vapor diffusion-deposition growth from CdS powders. The growth mechanism of the hexagonal and preferentially oriented CdS tetrapod-shaped nanostructures is a combination of the classic vapor-liquid-solid and vapor-solid processes, and the formation of a 3D network results from the spontaneous growths along the longitudinal and across the axial directions of the primarily formed CdS nanorods. Micro-photoluminescence measurements and near-field scanning optical microscopy investigations show that the synthesized CdS tetrapod networks have an excellent luminescence property and can be used as an optical waveguide cavities in which the guided light can be extremely confined.

  18. 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...

  19. Forecasting Financial Extremes: A Network Degree Measure of Super-Exponential Growth.

    Directory of Open Access Journals (Sweden)

    Wanfeng Yan

    Full Text Available Investors in stock market are usually greedy during bull markets and scared during bear markets. The greed or fear spreads across investors quickly. This is known as the herding effect, and often leads to a fast movement of stock prices. During such market regimes, stock prices change at a super-exponential rate and are normally followed by a trend reversal that corrects the previous overreaction. In this paper, we construct an indicator to measure the magnitude of the super-exponential growth of stock prices, by measuring the degree of the price network, generated from the price time series. Twelve major international stock indices have been investigated. Error diagram tests show that this new indicator has strong predictive power for financial extremes, both peaks and troughs. By varying the parameters used to construct the error diagram, we show the predictive power is very robust. The new indicator has a better performance than the LPPL pattern recognition indicator.

  20. Forecasting Financial Extremes: A Network Degree Measure of Super-Exponential Growth.

    Science.gov (United States)

    Yan, Wanfeng; van Tuyll van Serooskerken, Edgar

    2015-01-01

    Investors in stock market are usually greedy during bull markets and scared during bear markets. The greed or fear spreads across investors quickly. This is known as the herding effect, and often leads to a fast movement of stock prices. During such market regimes, stock prices change at a super-exponential rate and are normally followed by a trend reversal that corrects the previous overreaction. In this paper, we construct an indicator to measure the magnitude of the super-exponential growth of stock prices, by measuring the degree of the price network, generated from the price time series. Twelve major international stock indices have been investigated. Error diagram tests show that this new indicator has strong predictive power for financial extremes, both peaks and troughs. By varying the parameters used to construct the error diagram, we show the predictive power is very robust. The new indicator has a better performance than the LPPL pattern recognition indicator.

  1. 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.

  2. 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

  3. Distributions of positive correlations in sectoral value added growth in the global economic network*

    Science.gov (United States)

    Maluck, Julian; Donner, Reik V.

    2017-02-01

    International trade has grown considerably during the process of globalization. Complex supply chains for the production of goods have resulted in an increasingly connected International Trade Network (ITN). Traditionally, direct trade relations between industries have been regarded as mediators of supply and demand spillovers. With increasing network connectivity the question arises if higher-order relations become more important in explaining a national sector's susceptibility to supply and demand changes of its trading partner. In this study we address this question by investigating empirically to what extent the topological properties of the ITN provide information about positive correlations in the production of two industry sectors. We observe that although direct trade relations between industries serve as important indicators for correlations in the industries' value added growth, opportunities of substitution for required production inputs as well as second-order trade relations cannot be neglected. Our results contribute to a better understanding of the relation between trade and economic productivity and can serve as a basis for the improvement of crisis spreading models that evaluate contagion threats in the case of a node's failure in the ITN.

  4. Exponential growth for self-reproduction in a catalytic reaction network: relevance of a minority molecular species and crowdedness

    Science.gov (United States)

    Kamimura, Atsushi; Kaneko, Kunihiko

    2018-03-01

    Explanation of exponential growth in self-reproduction is an important step toward elucidation of the origins of life because optimization of the growth potential across rounds of selection is necessary for Darwinian evolution. To produce another copy with approximately the same composition, the exponential growth rates for all components have to be equal. How such balanced growth is achieved, however, is not a trivial question, because this kind of growth requires orchestrated replication of the components in stochastic and nonlinear catalytic reactions. By considering a mutually catalyzing reaction in two- and three-dimensional lattices, as represented by a cellular automaton model, we show that self-reproduction with exponential growth is possible only when the replication and degradation of one molecular species is much slower than those of the others, i.e., when there is a minority molecule. Here, the synergetic effect of molecular discreteness and crowding is necessary to produce the exponential growth. Otherwise, the growth curves show superexponential growth because of nonlinearity of the catalytic reactions or subexponential growth due to replication inhibition by overcrowding of molecules. Our study emphasizes that the minority molecular species in a catalytic reaction network is necessary for exponential growth at the primitive stage of life.

  5. A Wireless Sensor Network-Based Ubiquitous Paprika Growth Management System

    Directory of Open Access Journals (Sweden)

    Jeonghwan Hwang

    2010-12-01

    Full Text Available Wireless Sensor Network (WSN technology can facilitate advances in productivity, safety and human quality of life through its applications in various industries. In particular, the application of WSN technology to the agricultural area, which is labor-intensive compared to other industries, and in addition is typically lacking in IT technology applications, adds value and can increase the agricultural productivity. This study attempts to establish a ubiquitous agricultural environment and improve the productivity of farms that grow paprika by suggesting a ‘Ubiquitous Paprika Greenhouse Management System’ using WSN technology. The proposed system can collect and monitor information related to the growth environment of crops outside and inside paprika greenhouses by installing WSN sensors and monitoring images captured by CCTV cameras. In addition, the system provides a paprika greenhouse environment control facility for manual and automatic control from a distance, improves the convenience and productivity of users, and facilitates an optimized environment to grow paprika based on the growth environment data acquired by operating the system.

  6. A Wireless Sensor Network-Based Ubiquitous Paprika Growth Management System

    Science.gov (United States)

    Hwang, Jeonghwan; Shin, Changsun; Yoe, Hyun

    2010-01-01

    Wireless Sensor Network (WSN) technology can facilitate advances in productivity, safety and human quality of life through its applications in various industries. In particular, the application of WSN technology to the agricultural area, which is labor-intensive compared to other industries, and in addition is typically lacking in IT technology applications, adds value and can increase the agricultural productivity. This study attempts to establish a ubiquitous agricultural environment and improve the productivity of farms that grow paprika by suggesting a ‘Ubiquitous Paprika Greenhouse Management System’ using WSN technology. The proposed system can collect and monitor information related to the growth environment of crops outside and inside paprika greenhouses by installing WSN sensors and monitoring images captured by CCTV cameras. In addition, the system provides a paprika greenhouse environment control facility for manual and automatic control from a distance, improves the convenience and productivity of users, and facilitates an optimized environment to grow paprika based on the growth environment data acquired by operating the system. PMID:22163543

  7. Discovery of nitrate-CPK-NLP signalling in central nutrient-growth networks

    Science.gov (United States)

    Liu, Kun-hsiang; Niu, Yajie; Konishi, Mineko; Wu, Yue; Du, Hao; Sun Chung, Hoo; Li, Lei; Boudsocq, Marie; McCormack, Matthew; Maekawa, Shugo; Ishida, Tetsuya; Zhang, Chao; Shokat, Kevan; Yanagisawa, Shuichi; Sheen, Jen

    2018-01-01

    Nutrient signalling integrates and coordinates gene expression, metabolism and growth. However, its primary molecular mechanisms remain incompletely understood in plants and animals. Here we report novel Ca2+ signalling triggered by nitrate with live imaging of an ultrasensitive biosensor in Arabidopsis leaves and roots. A nitrate-sensitized and targeted functional genomic screen identifies subgroup III Ca2+-sensor protein kinases (CPKs) as master regulators orchestrating primary nitrate responses. A chemical switch with the engineered CPK10(M141G) kinase enables conditional analyses of cpk10,30,32 to define comprehensive nitrate-associated regulatory and developmental programs, circumventing embryo lethality. Nitrate-CPK signalling phosphorylates conserved NIN-LIKE PROTEIN (NLP) transcription factors (TFs) to specify reprogramming of gene sets for downstream TFs, transporters, N-assimilation, C/N-metabolism, redox, signalling, hormones, and proliferation. Conditional cpk10,30,32 and nlp7 similarly impair nitrate-stimulated system-wide shoot growth and root establishment. The nutrient-coupled Ca2+ signalling network integrates transcriptome and cellular metabolism with shoot-root coordination and developmental plasticity in shaping organ biomass and architecture. PMID:28489820

  8. 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.

  9. Chorein Sensitivity of Actin Polymerization, Cell Shape and Mechanical Stiffness of Vascular Endothelial Cells

    Directory of Open Access Journals (Sweden)

    Ioana Alesutan

    2013-09-01

    Full Text Available Background/Aims: Endothelial cell stiffness plays a key role in endothelium-dependent control of vascular tone and arterial blood pressure. Actin polymerization and distribution of microfilaments is essential for mechanical cell stiffness. Chorein, a protein encoded by the VPS13A gene, defective in chorea-acanthocytosis (ChAc, is involved in neuronal cell survival as well as cortical actin polymerization of erythrocytes and blood platelets. Chorein is expressed in a wide variety of further cells, yet nothing is known about the impact of chorein on cells other than neurons, erythrocytes and platelets. The present study explored whether chorein is expressed in human umbilical vein endothelial cells (HUVECs and addressed the putative role of chorein in the regulation of cytoskeletal architecture, stiffness and survival of those cells. Methods: In HUVECs with or without silencing of the VPS13A gene, VPS13A mRNA expression was determined utilizing quantitative RT-PCR, cytoskeletal organization visualized by confocal microscopy, G/F actin ratio and phosphorylation status of focal adhesion kinase quantified by western blotting, cell death determined by flow cytometry, mechanical properties studied by atomic force microscopy (AFM and cell morphology analysed by scanning ion conductance microscopy (SICM. Results: VPS13A mRNA expression was detectable in HUVECs. Silencing of the VPS13A gene attenuated the filamentous actin network, decreased the ratio of soluble G-actin over filamentous F-actin, reduced cell stiffness and changed cell morphology as compared to HUVECs silenced with negative control siRNA. These effects were paralleled by a significant decrease in FAK phosphorylation following VPS13A silencing. Moreover, silencing of the VPS13A gene increased caspase 3 activity and induced necrosis in HUVECs. Conclusions: Chorein is a novel regulator of cytoskeletal architecture, cell shape, mechanical stiffness and survival of vascular endothelial cells.

  10. 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.

  11. Stromal cell-derived factor 1 regulates the actin organization of chondrocytes and chondrocyte hypertrophy.

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    Koichi Murata

    Full Text Available Stromal cell-derived factor 1 (SDF-1/CXCL12/PBSF plays important roles in the biological and physiological functions of haematopoietic and mesenchymal stem cells. This chemokine regulates the formation of multiple organ systems during embryogenesis. However, its roles in skeletal development remain unclear. Here we investigated the roles of SDF-1 in chondrocyte differentiation. We demonstrated that SDF-1 protein was expressed at pre-hypertrophic and hypertrophic chondrocytes in the newly formed endochondral callus of rib fracture as well as in the growth plate of normal mouse tibia by immunohistochemical analysis. Using SDF-1(-/- mouse embryo, we histologically showed that the total length of the whole humeri of SDF-1(-/- mice was significantly shorter than that of wild-type mice, which was contributed mainly by shorter hypertrophic and calcified zones in SDF-1(-/- mice. Actin cytoskeleton of hypertrophic chondrocytes in SDF-1(-/- mouse humeri showed less F-actin and rounder shape than that of wild-type mice. Primary chondrocytes from SDF-1(-/- mice showed the enhanced formation of philopodia and loss of F-actin. The administration of SDF-1 to primary chondrocytes of wild-type mice and SDF-1(-/- mice promoted the formation of actin stress fibers. Organ culture of embryonic metatarsals from SDF-1(-/- mice showed the growth delay, which was recovered by an exogenous administration of SDF-1. mRNA expression of type X collagen in metatarsals and in primary chondrocytes of SDF-1(-/- mouse embryo was down-regulated while the administration of SDF-1 to metatarsals recovered. These data suggests that SDF-1 regulates the actin organization and stimulates bone growth by mediating chondrocyte hypertrophy.

  12. Stromal cell-derived factor 1 regulates the actin organization of chondrocytes and chondrocyte hypertrophy.

    Science.gov (United States)

    Murata, Koichi; Kitaori, Toshiyuki; Oishi, Shinya; Watanabe, Naoki; Yoshitomi, Hiroyuki; Tanida, Shimei; Ishikawa, Masahiro; Kasahara, Takashi; Shibuya, Hideyuki; Fujii, Nobutaka; Nagasawa, Takashi; Nakamura, Takashi; Ito, Hiromu

    2012-01-01

    Stromal cell-derived factor 1 (SDF-1/CXCL12/PBSF) plays important roles in the biological and physiological functions of haematopoietic and mesenchymal stem cells. This chemokine regulates the formation of multiple organ systems during embryogenesis. However, its roles in skeletal development remain unclear. Here we investigated the roles of SDF-1 in chondrocyte differentiation. We demonstrated that SDF-1 protein was expressed at pre-hypertrophic and hypertrophic chondrocytes in the newly formed endochondral callus of rib fracture as well as in the growth plate of normal mouse tibia by immunohistochemical analysis. Using SDF-1(-/-) mouse embryo, we histologically showed that the total length of the whole humeri of SDF-1(-/-) mice was significantly shorter than that of wild-type mice, which was contributed mainly by shorter hypertrophic and calcified zones in SDF-1(-/-) mice. Actin cytoskeleton of hypertrophic chondrocytes in SDF-1(-/-) mouse humeri showed less F-actin and rounder shape than that of wild-type mice. Primary chondrocytes from SDF-1(-/-) mice showed the enhanced formation of philopodia and loss of F-actin. The administration of SDF-1 to primary chondrocytes of wild-type mice and SDF-1(-/-) mice promoted the formation of actin stress fibers. Organ culture of embryonic metatarsals from SDF-1(-/-) mice showed the growth delay, which was recovered by an exogenous administration of SDF-1. mRNA expression of type X collagen in metatarsals and in primary chondrocytes of SDF-1(-/-) mouse embryo was down-regulated while the administration of SDF-1 to metatarsals recovered. These data suggests that SDF-1 regulates the actin organization and stimulates bone growth by mediating chondrocyte hypertrophy.

  13. Growth

    Science.gov (United States)

    John R. Jones; George A. Schier

    1985-01-01

    This chapter considers aspen growth as a process, and discusses some characteristics of the growth and development of trees and stands. For the most part, factors affecting growth are discussed elsewhere, particularly in the GENETICS AND VARIATION chapter and in chapters in PART 11. ECOLOGY. Aspen growth as it relates to wood production is examined in the WOOD RESOURCE...

  14. Global Business Networks and Cooperation within Supply Chain as a Strategy of High-Tech Companies’ Growth

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    Milena Ratajczak-Mrozek

    2012-01-01

    Full Text Available Abstract The specificity of the operation profile of high-tech companies, including the necessity of operating at the international scale may account for the fact that these companies may find in network relationships, business networks and cooperation an essential determinant for growth and competitiveness. Foreign entities should be especially interesting business partners for high- tech companies, as they are often seen as representing more advanced knowledge, resources and experience. The aim of the article is to point out to global business networks (i.e. including both local and foreign entities, and especially to cooperation within supply chain, as an important basis for a growth strategy of a high-tech company. The article adopts assumptions of the network approach as a concept of companies cooperation. An analysis of the author’s own as well as secondary empirical research, with the focus on high- tech companies located in Poland is presented. In particular, the data from own research of 62 high-tech companies in Poland conducted in the first half of 2011 is analysed. It shows that the high-tech companies placing great importance on cooperation within supply chain demonstrate a higher growth and level of competitiveness than the companies which do not ascribe such importance (bearing in mind that supply chain forms an important part of a business network.

  15. 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

  16. Bundling Actin Filaments From Membranes: Some Novel Players

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    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.

  17. Bidirectional Interplay between Vimentin Intermediate Filaments and Contractile Actin Stress Fibers

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    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.

  18. 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.

  19. Abscisic acid regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin.

    Science.gov (United States)

    Rowe, James H; Topping, Jennifer F; Liu, Junli; Lindsey, Keith

    2016-07-01

    Understanding the mechanisms regulating root development under drought conditions is an important question for plant biology and world agriculture. We examine the effect of osmotic stress on abscisic acid (ABA), cytokinin and ethylene responses and how they mediate auxin transport, distribution and root growth through effects on PIN proteins. We integrate experimental data to construct hormonal crosstalk networks to formulate a systems view of root growth regulation by multiple hormones. Experimental analysis shows: that ABA-dependent and ABA-independent stress responses increase under osmotic stress, but cytokinin responses are only slightly reduced; inhibition of root growth under osmotic stress does not require ethylene signalling, but auxin can rescue root growth and meristem size; osmotic stress modulates auxin transporter levels and localization, reducing root auxin concentrations; PIN1 levels are reduced under stress in an ABA-dependent manner, overriding ethylene effects; and the interplay among ABA, ethylene, cytokinin and auxin is tissue-specific, as evidenced by differential responses of PIN1 and PIN2 to osmotic stress. Combining experimental analysis with network construction reveals that ABA regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

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

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    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.

  1. Dynamics in steady state in vitro acto-myosin networks

    International Nuclear Information System (INIS)

    Sonn-Segev, Adar; Roichman, Yael; Bernheim-Groswasser, Anne

    2017-01-01

    It is well known that many biochemical processes in the cell such as gene regulation, growth signals and activation of ion channels, rely on mechanical stimuli. However, the mechanism by which mechanical signals propagate through cells is not as well understood. In this review we focus on stress propagation in a minimal model for cell elasticity, actomyosin networks, which are comprised of a sub-family of cytoskeleton proteins. After giving an overview of th actomyosin network components, structure and evolution we review stress propagation in these materials as measured through the correlated motion of tracer beads. We also discuss the possibility to extract structural features of these networks from the same experiments. We show that stress transmission through these networks has two pathways, a quickly dissipative one through the bulk, and a long ranged weakly dissipative one through the pre-stressed actin network. (topical review)

  2. 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

  3. Actin capping protein and its inhibitor CARMIL: how intrinsically disordered regions function

    International Nuclear Information System (INIS)

    Takeda, Shuichi; Maéda, Yuichiro; Koike, Ryotaro; Ota, Motonori; Nitanai, Yasushi; Minakata, Shiho

    2011-01-01

    The actin capping protein (CP) tightly binds to the barbed end of actin filaments to block further elongation. The β-tentacle in CP is an important region that ensures stable interaction with actin filaments. CARMIL inhibits the interaction of CP with actin filaments via the C-terminal portion containing the CP-binding motif, located in an intrinsically disordered region. We have proposed an allosteric inhibition model in which CARMIL suppresses CP by the population shift mechanism. Here, we solved a crystal structure of CP in complex with a CARMIL-derived peptide, CA32. The new structure clearly represents the α-helical form of the β-tentacle that was invisible in other CP/CARMIL peptide complex structures. In addition, we exhaustively performed a normal mode analysis with the elastic network model on all available crystal structures of the CP/CARMIL peptide complexes, including the new structure. We concluded that the CP-binding motif is necessary and sufficient for altering the fluctuation of CP, which is essential for attenuating the barbed-end-capping activity along the population shift mechanism. The roles and functions of the β-tentacle and the CP-binding motif are discussed in terms of their intrinsically disordered nature

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

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    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.

  5. 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

  6. 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.

  7. The usage of Internet social networking as a tool of linguist students' intercultural communication competence growth

    Directory of Open Access Journals (Sweden)

    Сергей Владимирович Сороколетов

    2009-06-01

    Full Text Available In work concepts «the intercultural communicative competence», «a social network», possibilities of use social the Internet of network FaceBook in training of students-linguists are described.

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

    Science.gov (United States)

    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.

  9. 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

  10. Nutrients interaction investigation to improve Monascus purpureus FTC5391 growth rate using Response Surface Methodology and Artificial Neural Network

    Directory of Open Access Journals (Sweden)

    Mohamad, R.

    2013-01-01

    Full Text Available Aims: Two vital factors, certain environmental conditions and nutrients as a source of energy are entailed for successful growth and reproduction of microorganisms. Manipulation of nutritional requirement is the simplest and most effectual strategy to stimulate and enhance the activity of microorganisms. Methodology and Results: In this study, response surface methodology (RSM and artificial neural network (ANN were employed to optimize the carbon and nitrogen sources in order to improve growth rate of Monascus purpureus FTC5391,a new local isolate. The best models for optimization of growth rate were a multilayer full feed-forward incremental back propagation network, and a modified response surface model using backward elimination. The optimum condition for cell mass production was: sucrose 2.5%, yeast extract 0.045%, casamino acid 0.275%, sodium nitrate 0.48%, potato starch 0.045%, dextrose 1%, potassium nitrate 0.57%. The experimental cell mass production using this optimal condition was 21 mg/plate/12days, which was 2.2-fold higher than the standard condition (sucrose 5%, yeast extract 0.15%, casamino acid 0.25%, sodium nitrate 0.3%, potato starch 0.2%, dextrose 1%, potassium nitrate 0.3%. Conclusion, significance and impact of study: The results of RSM and ANN showed that all carbon and nitrogen sources tested had significant effect on growth rate (P-value < 0.05. In addition the use of RSM and ANN alongside each other provided a proper growth prediction model.

  11. Inverse relationship between TCTP/RhoA and p53/ /cyclin A/actin expression in ovarian cancer cells Inverse relationship between TCTP/RhoA and p53/ /cyclin A/actin expression in ovarian cancer cells

    Directory of Open Access Journals (Sweden)

    Malgorzata Kloc

    2012-10-01

    Full Text Available The translationally controlled tumor protein (TCTP plays a role in cell growth, cell cycle and cancer
    progression. TCTP controls negatively the stability of the p53 tumor suppressor protein and interacts with the
    cellular cytoskeleton. The deregulation of the actin and cytokeratin cytoskeleton is responsible for the increased
    migratory activity of tumor cells and is linked with poor patient outcome. Recent studies indicate that cyclin A,
    a key regulator of cell cycle, controls actin organization and negatively regulates cell motility via regulation of RhoA
    expression. We studied the organization of actin and cytokeratin cytoskeleton and the expression of TCTP, p53,
    cyclin A, RhoA and actin in HIO180 non-transformed ovarian epithelial cells, and OVCAR3 and SKOV3 (expressing
    low level of inducible p53 ovarian epithelial cancer cells with different metastatic potential. Immunostaining
    and ultrastructural analyses illustrated a dramatic difference in the organization of the cytokeratin and actin
    filaments in non-transformed versus cancer cell lines. We also determined that there is an inverse relationship between
    the level of TCTP/RhoA and actin/p53/cyclin A expression in ovarian cancer cell lines. This previously unidentified
    negative relationship between TCTP/RhoA and actin/p53/cyclin A may suggest that this interaction is linked
    with the high aggressiveness of ovarian cancers.The translationally controlled tumor protein (TCTP plays a role in cell growth, cell cycle and cancer
    progression. TCTP controls negatively the stability of the p53 tumor suppressor protein and interacts with the
    cellular cytoskeleton. The deregulation of the actin and cytokeratin cytoskeleton is responsible for the increased
    migratory activity of tumor cells and is linked with poor patient outcome. Recent studies indicate that cyclin A,
    a key regulator of cell cycle, controls actin organization

  12. Protein Kinases Possibly Mediate Hypergravity-Induced Changes in F-Actin Expression by Endothelial Cells

    Science.gov (United States)

    Love, Felisha D.; Melhado, Caroline D.; Bosah, Francis N.; Harris-Hooker, Sandra A.; Sanford, Gary L.

    1998-01-01

    Basic cellular functions such as electrolyte concentration, cell growth rate, glucose utilization, bone formation, response to growth stimulation, and exocytosis are modified in microgravity. These studies indicate that microgravity affects a number of physiological systems and included in this are cell signaling mechanisms. Rijken and coworkers performed growth factor studies that showed PKC signaling and actin microfilament organization appears to be sensitive to microgravity, suggesting that the inhibition of signal transduction by microgravity may be related to alterations in actin microfilament organization. However, similar studies have not been done for vascular cells. Vascular endothelial cells play critical roles in providing nutrients to organ and tissues and in wound repair. The major deterrent to ground-based microgravity studies is that it is impossible to achieved true microgravity for longer than a few minutes on earth. Hence, it has not been possible to conduct prolonged microgravity studies except for two models that simulate certain aspects of microgravity. However, hypergravity is quite easily achieved. Several researchers have shown that hypergravity will increase the proliferation of several different cell lines while decreasing cell motility and slowing liver regeneration following partial hepatectomy, These studies indicate the hypergravity also alters the behavior of most cells. Several investigators have shown that hypergravity affects the activation of several protein kinases (PKs) in cells. In this study, we investigated whether hypergravity alters the expression of f-actin by bovine aortic endothelial cells (BAECs) and the role of PK's (calmodulin 11 dependent, PKA and PKC) as mediators of these effects.

  13. 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.

  14. WHAMM Directs the Arp2/3 Complex to the ER for Autophagosome Biogenesis through an Actin Comet Tail Mechanism.

    Science.gov (United States)

    Kast, David J; Zajac, Allison L; Holzbaur, Erika L F; Ostap, E Michael; Dominguez, Roberto

    2015-06-29

    Nucleation-promoting factors (NPFs) control the spatio-temporal activity of Arp2/3 complex in cells]. Thus, WASP and the WAVE complex direct the formation of branched actin networks at the leading edge during cell motility and endo/exocytosis, whereas the WASH complex is involved in endosomal transport. Less understood are WHAMM and JMY, two NPFs with similar domain architecture. JMY is found in the nucleus and the cytosol and is involved in transcriptional regulation, cell motility, and trans-Golgi transport. WHAMM was reported to bind microtubules and to be involved in ER to cis-Golgi transport. Here, we show that WHAMM directs the activity of Arp2/3 complex for autophagosome biogenesis through an actin-comet tail motility mechanism. Macroautophagy--the process by which cytosolic material is engulfed into autophagosomes for degradation and/or recycling--was recently shown to involve actin, but the mechanism is unknown. We found that WHAMM forms puncta that colocalize and comigrate with the autophagy markers LC3, DFCP1, and p62 through a WHAMM-dependent actin-comet tail mechanism. Under starvation, WHAMM and actin are observed at the interface between neighboring autophagosomes, whose number and size increase with WHAMM expression. Interfering with actin polymerization, inhibiting Arp2/3 complex, knocking down WHAMM, or blocking its interaction with Arp2/3 complex through mutagenesis all inhibit comet tail formation and reduce the size and number of autophagosomes. Finally, JMY shows similar localization to WHAMM and could be involved in similar processes. These results reveal a link between Arp2/3-complex-dependent actin assembly and autophagy. Copyright © 2015 Elsevier Ltd. All rights reserved.

  15. 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.

  16. 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

  17. 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.

  18. 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

  19. 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

  20. Growth-expectations among women entrepreneurs: embedded in networks and culture in Algeria, Morocco, Tunisia and in Belgium and France

    DEFF Research Database (Denmark)

    Cheraghi, Maryam; Setti, Zakia; Schøtt, Thomas

    2014-01-01

    Entrepreneurship Monitor, randomly sampling 39,336 women, including 2,306 entrepreneurs. Analyses show that women entrepreneurs have growth-expectations based on their background and increased by their competence and opportunity-motive, which also promote business networks around their firms. Formation......An entrepreneur usually has an expectation for the firm, expecting expansion, stability or contraction. Expectation is influenced by the entrepreneur's attributes, but expectation is also embedded in the micro-environment of networking and the macro-environment of culture. Traditional culture...... and secular-rational culture differ in roles for women, which influence women entrepreneurs' networking and expectations. The design compares cultures, with data from three traditional societies, Algeria, Morocco and Tunisia and two secular-rational societies, France and Belgium, surveyed in the Global...

  1. Transformation rules and degradation of CAHs by Fentonlike oxidation in growth ring of water distribution network-A review

    Science.gov (United States)

    Zhong, D.; Ma, W. C.; Jiang, X. Q.; Yuan, Y. X.; Yuan, Y.; Wang, Z. Q.; Fang, T. T.; Huang, W. Y.

    2017-08-01

    Chlorinated hydrocarbons are widely used as organic solvent and chemical raw materials. After treatment, water polluted with trichloroethylene (TCE)/tetrachloroethylene (PCE) can reach the water quality requirements, while water with trace amounts of TCE/PCE is still harmful to humans, which will cause cancers. Water distribution network is an extremely complicated system, in which adsorption, desorption, flocculation, movement, transformation and reduction will occur, leading to changes of TCE/PCE concentrations and products. Therefore, it is important to investigate the transformation rules of TCE/PCE in water distribution network. What’s more, growth-ring, including drinking water pipes deposits, can act as catalysts in Fenton-like reagent (H2O2). This review summarizes the status of transformation rules of CAHs in water distribution network. It also evaluates the effectiveness and fruit of CAHs degradation by Fenton-like reagent based on growth-ring. This review is important in solving the potential safety problems caused by TCE/PCE in water distribution network.

  2. 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.

  3. 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.

  4. 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.

  5. Distinct regimes of elastic response and deformation modes of cross-linked cytoskeletal and semiflexible polymer networks

    NARCIS (Netherlands)

    Head, D.A.; Levine, A.M.; Mac Kintosh, F.C.

    2003-01-01

    Semiflexible polymers such as filamentous actin (F-actin) play a vital role in the mechanical behavior of cells, yet the basic properties of cross-linked F-actin networks remain poorly understood. To address this issue, we have performed numerical studies of the linear response of homogeneous and

  6. Actin and Endocytosis in Budding Yeast

    Science.gov (United States)

    Goode, Bruce L.; Eskin, Julian A.; Wendland, Beverly

    2015-01-01

    Endocytosis, the process whereby the plasma membrane invaginates to form vesicles, is essential for bringing many substances into the cell and for membrane turnover. The mechanism driving clathrin-mediated endocytosis (CME) involves > 50 different protein components assembling at a single location on the plasma membrane in a temporally ordered and hierarchal pathway. These proteins perform precisely choreographed steps that promote receptor recognition and clustering, membrane remodeling, and force-generating actin-filament assembly and turnover to drive membrane invagination and vesicle scission. Many critical aspects of the CME mechanism are conserved from yeast to mammals and were first elucidated in yeast, demonstrating that it is a powerful system for studying endocytosis. In this review, we describe our current mechanistic understanding of each step in the process of yeast CME, and the essential roles played by actin polymerization at these sites, while providing a historical perspective of how the landscape has changed since the preceding version of the YeastBook was published 17 years ago (1997). Finally, we discuss the key unresolved issues and where future studies might be headed. PMID:25657349

  7. 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.

  8. A network model of correlated growth of tissue stiffening in pulmonary fibrosis

    International Nuclear Information System (INIS)

    Oliveira, Cláudio L N; Suki, Béla; Bates, Jason H T

    2014-01-01

    During the progression of pulmonary fibrosis, initially isolated regions of high stiffness form and grow in the lung tissue due to collagen deposition by fibroblast cells. We have previously shown that ongoing collagen deposition may not lead to significant increases in the bulk modulus of the lung until these local remodeled regions have become sufficiently numerous and extensive to percolate in a continuous path across the entire tissue (Bates et al 2007 Am. J. Respir. Crit. Care Med. 176 617). This model, however, did not include the possibility of spatially correlated deposition of collagen. In the present study, we investigate whether spatial correlations influence the bulk modulus in a two-dimensional elastic network model of lung tissue. Random collagen deposition at a single site is modeled by increasing the elastic constant of the spring at that site by a factor of 100. By contrast, correlated collagen deposition is represented by stiffening the springs encountered along a random walk starting from some initial spring, the rationale being that excess collagen deposition is more likely in the vicinity of an already stiff region. A combination of random and correlated deposition is modeled by performing random walks of length N from randomly selected initial sites, the balance between the two processes being determined by N. We found that the dependence of bulk modulus, B(N,c), on both N and the fraction of stiff springs, c, can be described by a strikingly simple set of empirical equations. For c<0.3, B(N,c) exhibits exponential growth from its initial value according to B(N,c)≈B 0 exp(2c)[1+c β ln(N a I )], where β=0.994± 0.024 and a I =0.54±0.026. For intermediate concentrations of stiffening, 0.3⩽c⩽0.8, another exponential rule describes the bulk modulus as B(N,c)=4B 0 exp[a II (c−c c )], where a II and c c are parameters that depend on N. For c>0.8, B(N,c) is linear in c and independent of N, such that B(N,c)=100 B 0 −100a III (1−c)B 0

  9. Apatite-mediated actin dynamics in resorbing osteoclasts.

    Science.gov (United States)

    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.

  10. 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.

  11. Looking for robust properties in the growth of an academic network: the case of the Uruguayan biological research community.

    Science.gov (United States)

    Cabana, Alvaro; Mizraji, Eduardo; Pomi, Andrés; Valle-Lisboa, Juan Carlos

    2008-04-01

    Graph-theoretical methods have recently been used to analyze certain properties of natural and social networks. In this work, we have investigated the early stages in the growth of a Uruguayan academic network, the Biology Area of the Programme for the Development of Basic Science (PEDECIBA). This transparent social network is a territory for the exploration of the reliability of clustering methods that can potentially be used when we are confronted with opaque natural systems that provide us with a limited spectrum of observables (happens in research on the relations between brain, thought and language). From our social net, we constructed two different graph representations based on the relationships among researchers revealed by their co-participation in Master's thesis committees. We studied these networks at different times and found that they achieve connectedness early in their evolution and exhibit the small-world property (i.e. high clustering with short path lengths). The data seem compatible with power law distributions of connectivity, clustering coefficients and betweenness centrality. Evidence of preferential attachment of new nodes and of new links between old nodes was also found in both representations. These results suggest that there are topological properties observed throughout the growth of the network that do not depend on the representations we have chosen but reflect intrinsic properties of the academic collective under study. Researchers in PEDECIBA are classified according to their specialties. We analysed the community structure detected by a standard algorithm in both representations. We found that much of the pre-specified structure is recovered and part of the mismatches can be attributed to convergent interests between scientists from different sub-disciplines. This result shows the potentiality of some clustering methods for the analysis of partially known natural systems.

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

    Science.gov (United States)

    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.

  13. 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.

  14. Clinical Response to Ingenol Mebutate in Patients With Actinic Keratoses.

    Science.gov (United States)

    Batalla, A; Flórez, Á; Feal, C; Peón, G; Abalde, M T; Salgado-Boquete, L; de la Torre, C

    2015-12-01

    Cryotherapy is the most common treatment for actinic keratosis, but its effect is limited to individual lesions. Several topical drugs, however, are available that, in addition to treating individual actinic keratoses, target field cancerization and thereby act on subclinical lesions. Examples are 5-fluorouracil, imiquimod, diclofenac, and ingenol mebutate. We report on 17 patients with actinic keratoses treated with ingenol mebutate and describe our findings on treatment effectiveness, adherence, and tolerance. Complete and partial response rates were 35% and 53%, respectively. Ninety-four percent of patients fully adhered to treatment and 18% developed severe local reactions. Ingenol mebutate is an effective treatment for actinic keratosis. Although it has a similar rate of local reactions to other treatments available for actinic keratosis, its short treatment regimen favors better adherence. Copyright © 2014 Elsevier España, S.L.U. y AEDV. All rights reserved.

  15. Beyond the functional matrix hypothesis: a network null model of human skull growth for the formation of bone articulations.

    Science.gov (United States)

    Esteve-Altava, Borja; Rasskin-Gutman, Diego

    2014-09-01

    Craniofacial sutures and synchondroses form the boundaries among bones in the human skull, providing functional, developmental and evolutionary information. Bone articulations in the skull arise due to interactions between genetic regulatory mechanisms and epigenetic factors such as functional matrices (soft tissues and cranial cavities), which mediate bone growth. These matrices are largely acknowledged for their influence on shaping the bones of the skull; however, it is not fully understood to what extent functional matrices mediate the formation of bone articulations. Aiming to identify whether or not functional matrices are key developmental factors guiding the formation of bone articulations, we have built a network null model of the skull that simulates unconstrained bone growth. This null model predicts bone articulations that arise due to a process of bone growth that is uniform in rate, direction and timing. By comparing predicted articulations with the actual bone articulations of the human skull, we have identified which boundaries specifically need the presence of functional matrices for their formation. We show that functional matrices are necessary to connect facial bones, whereas an unconstrained bone growth is sufficient to connect non-facial bones. This finding challenges the role of the brain in the formation of boundaries between bones in the braincase without neglecting its effect on skull shape. Ultimately, our null model suggests where to look for modified developmental mechanisms promoting changes in bone growth patterns that could affect the development and evolution of the head skeleton. © 2014 Anatomical Society.

  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. Genome-scale reconstruction of the Streptococcus pyogenes M49 metabolic network reveals growth requirements and indicates potential drug targets.

    Science.gov (United States)

    Levering, Jennifer; Fiedler, Tomas; Sieg, Antje; van Grinsven, Koen W A; Hering, Silvio; Veith, Nadine; Olivier, Brett G; Klett, Lara; Hugenholtz, Jeroen; Teusink, Bas; Kreikemeyer, Bernd; Kummer, Ursula

    2016-08-20

    Genome-scale metabolic models comprise stoichiometric relations between metabolites, as well as associations between genes and metabolic reactions and facilitate the analysis of metabolism. We computationally reconstructed the metabolic network of the lactic acid bacterium Streptococcus pyogenes M49. Initially, we based the reconstruction on genome annotations and already existing and curated metabolic networks of Bacillus subtilis, Escherichia coli, Lactobacillus plantarum and Lactococcus lactis. This initial draft was manually curated with the final reconstruction accounting for 480 genes associated with 576 reactions and 558 metabolites. In order to constrain the model further, we performed growth experiments of wild type and arcA deletion strains of S. pyogenes M49 in a chemically defined medium and calculated nutrient uptake and production fluxes. We additionally performed amino acid auxotrophy experiments to test the consistency of the model. The established genome-scale model can be used to understand the growth requirements of the human pathogen S. pyogenes and define optimal and suboptimal conditions, but also to describe differences and similarities between S. pyogenes and related lactic acid bacteria such as L. lactis in order to find strategies to reduce the growth of the pathogen and propose drug targets. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Network cohesion

    OpenAIRE

    Cavalcanti, Tiago Vanderlei; Giannitsarou, Chrysi; Johnson, CR

    2017-01-01

    We define a measure of network cohesion and show how it arises naturally in a broad class of dynamic models of endogenous perpetual growth with network externalities. Via a standard growth model, we show why network cohesion is crucial for conditional convergence and explain that as cohesion increases, convergence is faster. We prove properties of network cohesion and define a network aggregator that preserves network cohesion.

  19. [Actinic keratosis: New concept and therapeutic update].

    Science.gov (United States)

    Carmena-Ramón, Rafael; Mateu-Puchades, Almudena; Santos-Alarcón, Sergio; Lucas-Truyols, Sofía

    2017-10-01

    Actinic keratosis (AK) is a common reason for consultation in both Primary Care and Specialised Care. It is the third or fourth most common reason for consultation in dermatology, accounting for up to 5-6% of patients attended. It has also been observed that its prevalence has been increasing in the last 10years, compared to other dermatoses. This is also expected to continue to increase due to longer life expectancy, and by the changes in sun exposure habits since the middle of the last century. The aim of this article is to update the concepts of AK, cancerisation field and to present the currently available therapeutic tools. Copyright © 2017. Publicado por Elsevier España, S.L.U.

  20. Simulated juvenile salmon growth and phenology respond to altered thermal regimes and stream network shape

    Science.gov (United States)

    Context. Thermally diverse habitats may afford fish protection from climate change by providing opportunities to behaviorally optimize growing conditions. However, it is unclear what role the spatial properties of river networks will play in determining risk. Objectives. We hypot...

  1. Titin-Actin Interaction: PEVK-Actin-Based Viscosity in a Large Animal

    Directory of Open Access Journals (Sweden)

    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.

  2. Ultrastructural localization of actin and actin-binding proteins in the nucleus

    Czech Academy of Sciences Publication Activity Database

    Dingová, Hana; Fukalová, Jana; Maninová, Miloslava; Philimonenko, Vlada; Hozák, Pavel

    2009-01-01

    Roč. 131, č. 3 (2009), s. 425-434 ISSN 0948-6143 R&D Projects: GA MŠk LC545 Grant - others:MŠk(CZ) LC06063 Program:LC Institutional research plan: CEZ:AV0Z50520514 Keywords : nuclear actin * ultrastructure * actin–binding proteins Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.021, year: 2009

  3. Actinic Keratosis Clinical Practice Guidelines: An Appraisal of Quality

    Directory of Open Access Journals (Sweden)

    Joslyn S. Kirby

    2015-01-01

    Full Text Available Actinic keratosis (AK is a common precancerous skin lesion and many AK management guidelines exist, but there has been limited investigation into the quality of these documents. The objective of this study was to assess the strengths and weaknesses of guidelines that address AK management. A systematic search for guidelines with recommendations for AK was performed. The Appraisal of Guidelines for Research and Evaluation (AGREE II was used to appraise the quality of guidelines. Multiple raters independently reviewed each of the guidelines and applied the AGREE II tool and scores were calculated. Overall, 2,307 citations were identified and 7 fulfilled the study criteria. The Cancer Council of Australia/Australian Cancer Network guideline had the highest mean scores and was the only guideline to include a systematic review, include an evidence rating for recommendations, and report conflicts of interest and funding sources. High-quality, effective guidelines are evidence-based with recommendations that are concise and organized, so practical application is facilitated. Features such as concise tables, pictorial diagrams, and explicit links to evidence are helpful. However, the rigor and validity of some guidelines were weak. So, it is important for providers to be aware of the features that contribute to a high-quality, practical document.

  4. Urban Heat Island Growth Modeling Using Artificial Neural Networks and Support Vector Regression: A case study of Tehran, Iran

    Science.gov (United States)

    Sherafati, Sh. A.; Saradjian, M. R.; Niazmardi, S.

    2013-09-01

    Numerous investigations on Urban Heat Island (UHI) show that land cover change is the main factor of increasing Land Surface Temperature (LST) in urban areas. Therefore, to achieve a model which is able to simulate UHI growth, urban expansion should be concerned first. Considerable researches on urban expansion modeling have been done based on cellular automata. Accordingly the objective of this paper is to implement CA method for trend detection of Tehran UHI spatiotemporal growth based on urban sprawl parameters (such as Distance to nearest road, Digital Elevation Model (DEM), Slope and Aspect ratios). It should be mentioned that UHI growth modeling may have more complexities in comparison with urban expansion, since the amount of each pixel's temperature should be investigated instead of its state (urban and non-urban areas). The most challenging part of CA model is the definition of Transfer Rules. Here, two methods have used to find appropriate transfer Rules which are Artificial Neural Networks (ANN) and Support Vector Regression (SVR). The reason of choosing these approaches is that artificial neural networks and support vector regression have significant abilities to handle the complications of such a spatial analysis in comparison with other methods like Genetic or Swarm intelligence. In this paper, UHI change trend has discussed between 1984 and 2007. For this purpose, urban sprawl parameters in 1984 have calculated and added to the retrieved LST of this year. In order to achieve LST, Thematic Mapper (TM) and Enhanced Thematic Mapper (ETM+) night-time images have exploited. The reason of implementing night-time images is that UHI phenomenon is more obvious during night hours. After that multilayer feed-forward neural networks and support vector regression have used separately to find the relationship between this data and the retrieved LST in 2007. Since the transfer rules might not be the same in different regions, the satellite image of the city has

  5. Universal principles governing multiple random searchers on complex networks: The logarithmic growth pattern and the harmonic law

    Science.gov (United States)

    Weng, Tongfeng; Zhang, Jie; Small, Michael; Harandizadeh, Bahareh; Hui, Pan

    2018-03-01

    We propose a unified framework to evaluate and quantify the search time of multiple random searchers traversing independently and concurrently on complex networks. We find that the intriguing behaviors of multiple random searchers are governed by two basic principles—the logarithmic growth pattern and the harmonic law. Specifically, the logarithmic growth pattern characterizes how the search time increases with the number of targets, while the harmonic law explores how the search time of multiple random searchers varies relative to that needed by individual searchers. Numerical and theoretical results demonstrate these two universal principles established across a broad range of random search processes, including generic random walks, maximal entropy random walks, intermittent strategies, and persistent random walks. Our results reveal two fundamental principles governing the search time of multiple random searchers, which are expected to facilitate investigation of diverse dynamical processes like synchronization and spreading.

  6. Crosstalk between Rac1-mediated actin regulation and ROS production.

    Science.gov (United States)

    Acevedo, Alejandro; González-Billault, Christian

    2018-02-20

    The small RhoGTPase Rac1 is implicated in a variety of events related to actin cytoskeleton rearrangement. Remarkably, another event that is completely different from those related to actin regulation has the same relevance; the Rac1-mediated production of reactive oxygen species (ROS) through NADPH oxidases (NOX). Each outcome involves different Rac1 downstream effectors; on one hand, events related to the actin cytoskeleton require Rac1 to bind to WAVEs proteins and PAKs that ultimately promote actin branching and turnover, on the other, NOX-derived ROS production demands active Rac1 to be bound to a cytosolic activator of NOX. How Rac1-mediated signaling ends up promoting actin-related events, NOX-derived ROS, or both is poorly understood. Rac1 regulators, including scaffold proteins, are known to exert tight control over its functions. Hence, evidence of Rac1 regulatory events leading to both actin remodeling and NOX-mediated ROS generation are discussed. Moreover, cellular functions linked to physiological and pathological conditions that exhibit crosstalk between Rac1 outcomes are analyzed, while plausible roles in neuronal functions (and dysfunctions) are highlighted. Together, discussed evidence shed light on cellular mechanisms which requires Rac1 to direct either actin- and/or ROS-related events, helping to understand crucial roles of Rac1 dual functionality. Copyright © 2018 Elsevier Inc. All rights reserved.

  7. Placental determinants of fetal growth: identification of key factors in the insulin-like growth factor and cytokine systems using artificial neural networks

    Directory of Open Access Journals (Sweden)

    Faleschini Elena

    2008-06-01

    Full Text Available Abstract Background Changes and relationships of components of the cytokine and IGF systems have been shown in placenta and cord serum of fetal growth restricted (FGR compared with normal newborns (AGA. This study aimed to analyse a data set of clinical and biochemical data in FGR and AGA newborns to assess if a mathematical model existed and was capable of identifying these two different conditions in order to identify the variables which had a mathematically consistent biological relevance to fetal growth. Methods Whole villous tissue was collected at birth from FGR (N = 20 and AGA neonates (N = 28. Total RNA was extracted, reverse transcribed and then real-time quantitative (TaqMan RT-PCR was performed to quantify cDNA for IGF-I, IGF-II, IGFBP-1, IGFBP-2 and IL-6. The corresponding proteins with TNF-α in addition were assayed in placental lysates using specific kits. The data were analysed using Artificial Neural Networks (supervised networks, and principal component analysis and connectivity map. Results The IGF system and IL-6 allowed to predict FGR in approximately 92% of the cases and AGA in 85% of the cases with a low number of errors. IGF-II, IGFBP-2, and IL-6 content in the placental lysates were the most important factors connected with FGR. The condition of being FGR was connected mainly with the IGF-II placental content, and the latter with IL-6 and IGFBP-2 concentrations in placental lysates. Conclusion These results suggest that further research in humans should focus on these biochemical data. Furthermore, this study offered a critical revision of previous studies. The understanding of this system biology is relevant to the development of future therapeutical interventions possibly aiming at reducing IL-6 and IGFBP-2 concentrations preserving IGF bioactivity in both placenta and fetus.

  8. 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.

  9. Clarin-1, encoded by the Usher Syndrome III causative gene, forms a membranous microdomain: possible role of clarin-1 in organizing the actin cytoskeleton.

    Science.gov (United States)

    Tian, Guilian; Zhou, Yun; Hajkova, Dagmar; Miyagi, Masaru; Dinculescu, Astra; Hauswirth, William W; Palczewski, Krzysztof; Geng, Ruishuang; Alagramam, Kumar N; Isosomppi, Juha; Sankila, Eeva-Marja; Flannery, John G; Imanishi, Yoshikazu

    2009-07-10

    Clarin-1 is the protein product encoded by the gene mutated in Usher syndrome III. Although the molecular function of clarin-1 is unknown, its primary structure predicts four transmembrane domains similar to a large family of membrane proteins that include tetraspanins. Here we investigated the role of clarin-1 by using heterologous expression and in vivo model systems. When expressed in HEK293 cells, clarin-1 localized to the plasma membrane and concentrated in low density compartments distinct from lipid rafts. Clarin-1 reorganized actin filament structures and induced lamellipodia. This actin-reorganizing function was absent in the modified protein encoded by the most prevalent North American Usher syndrome III mutation, the N48K form of clarin-1 deficient in N-linked glycosylation. Proteomics analyses revealed a number of clarin-1-interacting proteins involved in cell-cell adhesion, focal adhesions, cell migration, tight junctions, and regulation of the actin cytoskeleton. Consistent with the hypothesized role of clarin-1 in actin organization, F-actin-enriched stereocilia of auditory hair cells evidenced structural disorganization in Clrn1(-/-) mice. These observations suggest a possible role for clarin-1 in the regulation and homeostasis of actin filaments, and link clarin-1 to the interactive network of Usher syndrome gene products.

  10. Leuconostoc mesenteroides growth in food products: prediction and sensitivity analysis by adaptive-network-based fuzzy inference systems.

    Directory of Open Access Journals (Sweden)

    Hue-Yu Wang

    Full Text Available BACKGROUND: An adaptive-network-based fuzzy inference system (ANFIS was compared with an artificial neural network (ANN in terms of accuracy in predicting the combined effects of temperature (10.5 to 24.5°C, pH level (5.5 to 7.5, sodium chloride level (0.25% to 6.25% and sodium nitrite level (0 to 200 ppm on the growth rate of Leuconostoc mesenteroides under aerobic and anaerobic conditions. METHODS: THE ANFIS AND ANN MODELS WERE COMPARED IN TERMS OF SIX STATISTICAL INDICES CALCULATED BY COMPARING THEIR PREDICTION RESULTS WITH ACTUAL DATA: mean absolute percentage error (MAPE, root mean square error (RMSE, standard error of prediction percentage (SEP, bias factor (Bf, accuracy factor (Af, and absolute fraction of variance (R (2. Graphical plots were also used for model comparison. CONCLUSIONS: The learning-based systems obtained encouraging prediction results. Sensitivity analyses of the four environmental factors showed that temperature and, to a lesser extent, NaCl had the most influence on accuracy in predicting the growth rate of Leuconostoc mesenteroides under aerobic and anaerobic conditions. The observed effectiveness of ANFIS for modeling microbial kinetic parameters confirms its potential use as a supplemental tool in predictive mycology. Comparisons between growth rates predicted by ANFIS and actual experimental data also confirmed the high accuracy of the Gaussian membership function in ANFIS. Comparisons of the six statistical indices under both aerobic and anaerobic conditions also showed that the ANFIS model was better than all ANN models in predicting the four kinetic parameters. Therefore, the ANFIS model is a valuable tool for quickly predicting the growth rate of Leuconostoc mesenteroides under aerobic and anaerobic conditions.

  11. 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

  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. Sequential growth in solution of NiFe Prussian blue coordination network nano-layers on Si(100) surfaces

    International Nuclear Information System (INIS)

    Tricard, Simon; Costa-Coquelard, Claire; Volatron, Florence; Fleury, Benoit; Huc, Vincent; Mallah, Talal; Albouy, Pierre-Antoine; David, Christophe; Miserque, Frederic; Jegou, Pascale; Palacin, Serge

    2012-01-01

    Controlling the elaboration of Coordination Networks (CoNet) on surfaces at the nano-scale remains a challenge. One suitable technique is the Sequential Growth in Solution (SGS), which has the advantage to be simple, cheap and fast. We addressed two issues in this article: i) the controlled synthesis of ultra thin films of CoNet (thickness lower than 10 nm), and ii) the investigation of the influence of the precursors' concentration on the growth process. Si(100) was used because it is possible to prepare atomically flat Si-H surfaces, which is necessary for the growth of ultrathin films. We used, as a model system, the sequential reactions of K 4 [Fe(II)(CN) 6 ] and [Ni(II)(H 2 O) 6 ]Cl 2 that occur by the substitution of the water molecules in the coordination sphere of Ni(II) by the nitrogen atoms of ferrocyanide. We demonstrated that the nature of the deposited film depends mainly on the relative concentration of the anchoring sites versus the precursors' solution. Attenuated Total Reflection Fourier Transformed Infra Red (ATR-FTIR), X-ray reflectivity, X-ray Photoelectron Spectroscopy (XPS) and Atomic Force Microscopy (AFM) were used to characterize the steps of the growth process. (authors)

  14. 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.

  15. How will e-commerce growth impact our transportation network? Final report.

    Science.gov (United States)

    2017-08-01

    The steady growth in online retailing continues to rattle long-established business models and the shopping patterns of consumers (who are also taxpayers, voters, and drivers). Those consumers are increasingly choosing shorter delivery cyclesoptin...

  16. Monitoring Coral Growth - the Dichotomy Between Underwater Photogrammetry and Geodetic Control Network

    Science.gov (United States)

    Neyer, F.; Nocerino, E.; Gruen, A.

    2018-05-01

    Creating 3-dimensional (3D) models of underwater scenes has become a common approach for monitoring coral reef changes and its structural complexity. Also in underwater archeology, 3D models are often created using underwater optical imagery. In this paper, we focus on the aspect of detecting small changes in the coral reef using a multi-temporal photogrammetric modelling approach, which requires a high quality control network. We show that the quality of a good geodetic network limits the direct change detection, i.e., without any further registration process. As the photogrammetric accuracy is expected to exceed the geodetic network accuracy by at least one order of magnitude, we suggest to do a fine registration based on a number of signalized points. This work is part of the Moorea Island Digital Ecosystem Avatar (IDEA) project that has been initiated in 2013 by a group of international researchers (https://mooreaidea.ethz.ch/).

  17. Analysis of the Yeast Kinome Reveals a Network of Regulated Protein Localization during Filamentous Growth

    OpenAIRE

    Bharucha, Nikë; Ma, Jun; Dobry, Craig J.; Lawson, Sarah K.; Yang, Zhifen; Kumar, Anuj

    2008-01-01

    The subcellular distribution of kinases and other signaling proteins is regulated in response to cellular cues; however, the extent of this regulation has not been investigated for any gene set in any organism. Here, we present a systematic analysis of protein kinases in the budding yeast, screening for differential localization during filamentous growth. Filamentous growth is an important stress response involving mitogen-activated protein kinase and cAMP-dependent protein kinase signaling m...

  18. 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...

  19. [At the plant side of formins--organizers of the actin cytoskeleton].

    Science.gov (United States)

    Maruniewicz, Michalina; Kasprowicz, Anna; Wojtaszek, Przemysław

    2009-01-01

    Rearrangements of actin cytoskeleton enable proper functioning of the cells under normal conditions, and also cellular adaptations to changes in the direct surroundings. Formins are actin binding proteins, responsible for actin nucleation and further elongation of microfilaments. The distinguishing feature of formins is the presence of conserved FH2 (formin homology domain 2) domain, as well as other domains typical for distinct formin classes. In animal cells formins are involved in cytokinesis and determination and maintenance of the cell shape and polarity, but also in the formation of filopodia, endocytosis and many other processes. The presence of proteins from the formin family in plant cells, and their involvement in the tip growth and cytokinesis, has been determined only recently. As the functional organization of plant and animal cells is different, one can assume that the range of putative functions of plant formins might also be diverse. One of such proposed functions for formins in plants is the role of linker protein within WMC continuum (cell wall-plasma membrane-cytoskeleton). Unfortunately, for that moment the state of knowledge about plant formins in comparison with animal or fungal ones is much poorer.

  20. Endophilin, Lamellipodin, and Mena cooperate to regulate F-actin-dependent EGF-receptor endocytosis.

    Science.gov (United States)

    Vehlow, Anne; Soong, Daniel; Vizcay-Barrena, Gema; Bodo, Cristian; Law, Ah-Lai; Perera, Upamali; Krause, Matthias

    2013-10-16

    The epidermal growth factor receptor (EGFR) plays an essential role during development and diseases including cancer. Lamellipodin (Lpd) is known to control lamellipodia protrusion by regulating actin filament elongation via Ena/VASP proteins. However, it is unknown whether this mechanism supports endocytosis of the EGFR. Here, we have identified a novel role for Lpd and Mena in clathrin-mediated endocytosis (CME) of the EGFR. We have discovered that endogenous Lpd is in a complex with the EGFR and Lpd and Mena knockdown impairs EGFR endocytosis. Conversely, overexpressing Lpd substantially increases the EGFR uptake in an F-actin-dependent manner, suggesting that F-actin polymerization is limiting for EGFR uptake. Furthermore, we found that Lpd directly interacts with endophilin, a BAR domain containing protein implicated in vesicle fission. We identified a role for endophilin in EGFR endocytosis, which is mediated by Lpd. Consistently, Lpd localizes to clathrin-coated pits (CCPs) just before vesicle scission and regulates vesicle scission. Our findings suggest a novel mechanism in which Lpd mediates EGFR endocytosis via Mena downstream of endophilin.

  1. The effect of membrane-regulated actin polymerization on a two-phase flow model for cell motility

    KAUST Repository

    Kimpton, L. S.

    2014-07-23

    Two-phase flow models have been widely used to model cell motility and we have previously demonstrated that even the simplest, stripped-down, 1D model displays many observed features of cell motility [Kimpton, L.S., Whiteley, J.P., Waters, S.L., King, J.R. & Oliver, J.M. (2013) Multiple travelling-wave solutions in a minimal model for cell motility. Math. Med. Biol. 30, 241 - 272]. In this paper, we address a limitation of the previous model.We show that the two-phase flow framework can exhibit travelling-wave solutions with biologically plausible actin network profiles in two simple models that enforce polymerization or depolymerization of the actin network at the ends of the travelling, 1D strip of cytoplasm. © 2014 The authors 2014. Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved.

  2. Growth anomalies in supramolecular networks: 4,4'-biphenyldicarboxylic acid on Cu(001)

    NARCIS (Netherlands)

    Schwarz, Daniel; van Gastel, Raoul; Zandvliet, Henricus J.W.; Poelsema, Bene

    2013-01-01

    We have used low energy electron microscopy to demonstrate how the interaction of 4,4 ′ -biphenyldicarboxylic acid (BDA) molecules with (steps on) the Cu(001) surface determines the structure of supramolecular BDA networks on a mesoscopic length scale. Our in situ real time observations reveal that

  3. Research on the co-movement between high-end talent and economic growth: A complex network approach

    Science.gov (United States)

    Zhang, Zhen; Wang, Minggang; Xu, Hua; Zhang, Wenbin; Tian, Lixin

    2018-02-01

    The major goal of this paper is to focus on the co-movement between high-end talent and economic growth by a complex network approach. Firstly, the national high-end talent development efficiency from 1990 to 2015 is taken as the quantitative index to measure the development of high-end talent. The added values of the primary industry, secondary industry, tertiary industry are selected as economic growth indexes, and all the selected sample data are standardized by the mean value processing method. Secondly, let seven months as the length of the sliding window, and one month as the sliding step, then the grey correlation degrees between systems are measured using the slope correlation degrees, and the grey correlation degree sequence is mapped into the symbol series composed by three symbols { Y , O , N } based on the coarse graining method. Let three characters as a mode, the nodes are obtained by the modes according to the time sequence. Let the transformation between the modal be the edge, and the times of the transformation be weight, then the co-movement networks between national high-end talent development efficiency and the added values of the primary industry, secondary industry, tertiary industry are built respectively. Finally, the dynamic characteristics of the networks are analysed by the node strength, strength distribution, weighted clustering coefficient, conversion cycle of the modes and the transition between the co-movement modes. The results indicate that there are mutual influence and promotion relations between the national high-end talent development efficiency and the added values of the primary, secondary and tertiary industry.

  4. Topical Imiquimod in the Treatment of Conjunctival Actinic Keratosis.

    Science.gov (United States)

    Rowlands, Megan A; Giacometti, Joseph N; Servat, Javier; Materin, Miguel A; Levin, Flora

    Conjunctival actinic keratosis is rare and difficult to treat, as recurrences are common. Imiquimod, an immune response modulator, is currently Food and Drug Administration-approved for cutaneous actinic keratosis and superficial basal cell carcinomas. Emerging reports have shown it to be effective in treating some periocular and conjunctival lesions. The authors present a case of a 68-year-old white man with recurrent actinic keratosis involving the pretarsal conjunctiva, which was successfully treated with 5% topical imiquimod following previous failure with cryotherapy and interferon α-2b. The patient had ocular irritation that resolved on cessation of treatment. To the authors' knowledge, this is the first report of conjunctival actinic keratosis being treated with and successfully eradicated by topical imiquimod.

  5. Nanosecond electric pulses trigger actin responses in plant cells

    International Nuclear Information System (INIS)

    Berghoefer, Thomas; Eing, Christian; Flickinger, Bianca; Hohenberger, Petra; Wegner, Lars H.; Frey, Wolfgang; Nick, Peter

    2009-01-01

    We have analyzed the cellular effects of nanosecond pulsed electrical fields on plant cells using fluorescently tagged marker lines in the tobacco cell line BY-2 and confocal laser scanning microscopy. We observe a disintegration of the cytoskeleton in the cell cortex, followed by contraction of actin filaments towards the nucleus, and disintegration of the nuclear envelope. These responses are accompanied by irreversible permeabilization of the plasma membrane manifest as uptake of Trypan Blue. By pretreatment with the actin-stabilizing drug phalloidin, the detachment of transvacuolar actin from the cell periphery can be suppressed, and this treatment can also suppress the irreversible perforation of the plasma membrane. We discuss these findings in terms of a model, where nanosecond pulsed electric fields trigger actin responses that are key events in the plant-specific form of programmed cell death.

  6. 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

    -equilibrium turnover on the steady-state properties of collections of filaments remained unclear. Here, I reconstituted tunable, non-equilibrium actin turnover dynamics in entangled solutions of actin filaments as a model of the actin cortex of living cells. We found that this non-equilibrium turnover decouples solution mechanics from microstructure, enabling structurally indistinguishable materials to behave effectively as either viscous fluids or elastic gels. Additionally, we employed computer simulations to identify the dynamical regime in which actin turnover controls the effective viscosity of 2D cross-linked actin networks in the presence of motors. Additionally, I examine in this thesis the localization and self-assembly of actin filaments in condensed liquid phases called polyelectrolyte coacervates as a model membrane-less organelle. We find that concentration of actin through spontaneous partitioning preferentially to the coacervate phase accelerates the assembly of filaments. These filaments then localize to the coacervate-bulk interface, generating particles with visco-elastic shells surrounding liquid cores. In this case, the properties of the condensed phase enable regulation of actin assembly dynamics.

  7. 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

  8. The role of antihistamines in chronic actinic dermatitis treatment

    Directory of Open Access Journals (Sweden)

    E. V. Orlov

    2016-01-01

    Full Text Available Inveterate actinic dermatitis is an immunologically mediated photodermatosis characterized by itchy eczematous dermhelminthiasis exposed to sunlight. The disease proceeds in the same way as the atopic eczema or atopic dermatitis. The treatment of patients with inveterate actinic dermatitis is similar to the treatment of patients with atopic dermatitis and eczema. Administration of the modern antihistaminic preparation desloratadine (Aerius in the treatment has a positive effect on the skin process relief and on some cellular and humoral immunity factors.

  9. Actinic prurigo in Scandinavian adolescent successfully treated with cyclosporine A

    Directory of Open Access Journals (Sweden)

    Jan C. Sitek

    2017-06-01

    Full Text Available Actinic prurigo is a pruritic sun-induced dermatosis classified among the immunologically mediated photodermatoses. The disease is a well-known entity among Native Americans and in Central and South America, however rare in Caucasians with only a few reports from Australia, Britain and France. We report the first case of actinic prurigo in a Scandinavian patient, responding favorably to systemic treatment with cyclosporine A.

  10. Actinic Prurigo in Scandinavian Adolescent Successfully Treated with Cyclosporine A.

    Science.gov (United States)

    Sitek, Jan C

    2017-03-13

    Actinic prurigo is a pruritic sun-induced dermatosis classified among the immunologically mediated photodermatoses. The disease is a well-known entity among Native Americans and in Central and South America, however rare in Caucasians with only a few reports from Australia, Britain and France. We report the first case of actinic prurigo in a Scandinavian patient, responding favorably to systemic treatment with cyclosporine A.

  11. 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

  12. The Transcriptional and Gene Regulatory Network of Lactococcus lactis MG1363 during Growth in Milk

    NARCIS (Netherlands)

    de Jong, Anne; Hansen, Morten E.; Kuipers, Oscar P.; Kilstrup, Mogens; Kok, Jan

    2013-01-01

    In the present study we examine the changes in the expression of genes of Lactococcus lactis subspecies cremoris MG1363 during growth in milk. To reveal which specific classes of genes (pathways, operons, regulons, COGs) are important, we performed a transcriptome time series experiment. Global

  13. Neural growth into a microchannel network: towards a regenerative neural interface

    NARCIS (Netherlands)

    Wieringa, P.A.; Wiertz, Remy; le Feber, Jakob; Rutten, Wim

    2009-01-01

    We propose and validated a design for a highly selective 'endcap' regenerative neural interface towards a neuroprosthesis. In vitro studies using rat cortical neurons determine if a branching microchannel structure can counter fasciculated growth and cause neurites to separte from one another,

  14. Networking

    OpenAIRE

    Rauno Lindholm, Daniel; Boisen Devantier, Lykke; Nyborg, Karoline Lykke; Høgsbro, Andreas; Fries, de; Skovlund, Louise

    2016-01-01

    The purpose of this project was to examine what influencing factor that has had an impact on the presumed increasement of the use of networking among academics on the labour market and how it is expressed. On the basis of the influence from globalization on the labour market it can be concluded that the globalization has transformed the labour market into a market based on the organization of networks. In this new organization there is a greater emphasis on employees having social qualificati...

  15. 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.

  16. 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

  17. Actin cytoskeleton modulates calcium signaling during maturation of starfish oocytes.

    Science.gov (United States)

    Kyozuka, Keiichiro; Chun, Jong T; Puppo, Agostina; Gragnaniello, Gianni; Garante, Ezio; Santella, Luigia

    2008-08-15

    Before successful fertilization can occur, oocytes must undergo meiotic maturation. In starfish, this can be achieved in vitro by applying 1-methyladenine (1-MA). The immediate response to 1-MA is the fast Ca2+ release in the cell cortex. Here, we show that this Ca2+ wave always initiates in the vegetal hemisphere and propagates through the cortex, which is the space immediately under the plasma membrane. We have observed that alteration of the cortical actin cytoskeleton by latrunculin-A and jasplakinolide can potently affect the Ca2+ waves triggered by 1-MA. This indicates that the cortical actin cytoskeleton modulates Ca2+ release during meiotic maturation. The Ca2+ wave was inhibited by the classical antagonists of the InsP(3)-linked Ca2+ signaling pathway, U73122 and heparin. To our surprise, however, these two inhibitors induced remarkable actin hyper-polymerization in the cell cortex, suggesting that their inhibitory effect on Ca2+ release may be attributed to the perturbation of the cortical actin cytoskeleton. In post-meiotic eggs, U73122 and jasplakinolide blocked the elevation of the vitelline layer by uncaged InsP(3), despite the massive release of Ca2+, implying that exocytosis of the cortical granules requires not only a Ca2+ rise, but also regulation of the cortical actin cytoskeleton. Our results suggest that the cortical actin cytoskeleton of starfish oocytes plays critical roles both in generating Ca2+ signals and in regulating cortical granule exocytosis.

  18. Prolactin promotes breast cancer cell migration through actin cytoskeleton remodeling

    Directory of Open Access Journals (Sweden)

    Priscilla Ludovico da Silva

    2015-12-01

    Full Text Available The role of prolactin on breast cancer development and progression is debated. Breast cancer progression largely depends on cell movement and on the ability to remodel the actin cytoskeleton. In this process, actin-binding proteins are requested to achieve fibrillar actin de-polymerization and relocation at the cell membrane. Kinases such as focal adhesion kinase (FAK are later required to form actin/vinculin-enriched structures called focal adhesion complexes, which mediate firm adhesion to the extracellular matrix. These controllers are regulated by c-Src, which forms multiprotein signaling complexes with membrane receptors and is regulated by a number of hormones, including prolactin. We here show that breast cancer cells exposed to prolactin display an elevated c-Src expression and phosphorylation. In parallel, increased moesin and FAK expression and phosphorylation are found. These molecular changes are associated to relocation to the plasma membrane of cytoskeletal actin fibers and to increased horizontal cell movement. In conclusion, prolactin regulates actin remodeling and enhances breast cancer cell movement. This finding broadens the understanding of prolactin actions on breast cancer cells, highlighting new pathways that may be relevant to on breast cancer progression.

  19. Bacillus subtilis actin-like protein MreB influences the positioning of the replication machinery and requires membrane proteins MreC/D and other actin-like proteins for proper localization

    OpenAIRE

    Defeu Soufo, Hervé Joël; Graumann, Peter L

    2005-01-01

    Abstract Background Bacterial actin-like proteins have been shown to perform essential functions in several aspects of cellular physiology. They affect cell growth, cell shape, chromosome segregation and polar localization of proteins, and localize as helical filaments underneath the cell membrane. Bacillus subtilis MreB and Mbl have been shown to perform dynamic motor like movements within cells, extending along helical tracks in a time scale of few seconds. Results In this work, we show tha...

  20. Nuclear actin filaments recruit cofilin and actin-related protein 3, and their formation is connected with a mitotic block

    Czech Academy of Sciences Publication Activity Database

    Kalendová, Alžběta; Kalasová, Ilona; Yamazaki, S.; Uličná, Lívia; Harata, M.; Hozák, Pavel

    2014-01-01

    Roč. 142, č. 2 (2014), s. 139-152 ISSN 0948-6143 R&D Projects: GA ČR GAP305/11/2232; GA MŠk LD12063; GA MŠk(CZ) ED1.1.00/02.0109 Institutional support: RVO:68378050 Keywords : nuclear actin * transcription * mitosis * actin-related protein 3 * cofilin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.927, year: 2013

  1. Beta adrenergic overstimulation impaired vascular contractility via actin-cytoskeleton disorganization in rabbit cerebral artery.

    Directory of Open Access Journals (Sweden)

    Hyoung Kyu Kim

    Full Text Available BACKGROUND AND PURPOSE: Beta adrenergic overstimulation may increase the vascular damage and stroke. However, the underlying mechanisms of beta adrenergic overstimulation in cerebrovascular dysfunctions are not well known. We investigated the possible cerebrovascular dysfunction response to isoproterenol induced beta-adrenergic overstimulation (ISO in rabbit cerebral arteries (CAs. METHODS: ISO was induced in six weeks aged male New Zealand white rabbit (0.8-1.0 kg by 7-days isoproterenol injection (300 μg/kg/day. We investigated the alteration of protein expression in ISO treated CAs using 2DE proteomics and western blot analysis. Systemic properties of 2DE proteomics result were analyzed using bioinformatics software. ROS generation and following DNA damage were assessed to evaluate deteriorative effect of ISO on CAs. Intracellular Ca(2+ level change and vascular contractile response to vasoactive drug, angiotensin II (Ang II, were assessed to evaluate functional alteration of ISO treated CAs. Ang II-induced ROS generation was assessed to evaluated involvement of ROS generation in CA contractility. RESULTS: Proteomic analysis revealed remarkably decreased expression of cytoskeleton organizing proteins (e.g. actin related protein 1A and 2, α-actin, capping protein Z beta, and vimentin and anti-oxidative stress proteins (e.g. heat shock protein 9A and stress-induced-phosphoprotein 1 in ISO-CAs. As a cause of dysregulation of actin-cytoskeleton organization, we found decreased level of RhoA and ROCK1, which are major regulators of actin-cytoskeleton organization. As functional consequences of proteomic alteration, we found the decreased transient Ca(2+ efflux and constriction response to angiotensin II and high K(+ in ISO-CAs. ISO also increased basal ROS generation and induced oxidative damage in CA; however, it decreased the Ang II-induced ROS generation rate. These results indicate that ISO disrupted actin cytoskeleton proteome network

  2. Estrogen and Resveratrol Regulate Rac and Cdc42 Signaling to the Actin Cytoskeleton of Metastatic Breast Cancer Cells

    Directory of Open Access Journals (Sweden)

    Nicolas G. Azios

    2007-02-01

    Full Text Available Estrogen and structurally related molecules play critical roles in breast cancer. We reported that resveratrol (50 µM, an estrogen-like phytosterol from grapes, acts in an antiestrogenic manner in breast cancer cells to reduce cell migration and to induce a global and sustained extension of actin structures called filopodia. Herein, we report that resveratrol-induced filopodia formation is time-dependent and concentration-dependent. In contrast to resveratrol at 50 µM, resveratrol at 5 µM acts in a manner similar to estrogen by increasing lamellipodia, as well as cell migration and invasion. Because Rho GTPases regulate the extension of actin structures, we investigated a role for Rac and Cdc42 in estrogen and resveratrol signaling. Our results demonstrate that 50 µM resveratrol decreases Rac and Cdc42 activity, whereas estrogen and 5 µM resveratrol increase Rac activity in breast cancer cells. MDA-MB-231 cells expressing dominant-negative Cdc42 or dominantnegative Rac retain filopodia response to 50 µM resveratrol. Lamellipodia response to 5 µM resveratrol, estrogen, or epidermal growth factor is inhibited in cells expressing dominant-negative Rac, indicating that Rac regulates estrogen and resveratrol (5 µM signaling to the actin cytoskeleton. These results indicate that signaling to the actin cytoskeleton by low and high concentrations of resveratrol may be differentially regulated by Rac and Cdc42.

  3. The alternatively-included 11a sequence modifies the effects of Mena on actin cytoskeletal organization and cell behavior.

    Science.gov (United States)

    Balsamo, Michele; Mondal, Chandrani; Carmona, Guillaume; McClain, Leslie M; Riquelme, Daisy N; Tadros, Jenny; Ma, Duan; Vasile, Eliza; Condeelis, John S; Lauffenburger, Douglas A; Gertler, Frank B

    2016-10-17

    During tumor progression, alternative splicing gives rise to different Mena protein isoforms. We analyzed how Mena11a, an isoform enriched in epithelia and epithelial-like cells, affects Mena-dependent regulation of actin dynamics and cell behavior. While other Mena isoforms promote actin polymerization and drive membrane protrusion, we find that Mena11a decreases actin polymerization and growth factor-stimulated membrane protrusion at lamellipodia. Ectopic Mena11a expression slows mesenchymal-like cell motility, while isoform-specific depletion of endogenous Mena11a in epithelial-like tumor cells perturbs cell:cell junctions and increases membrane protrusion and overall cell motility. Mena11a can dampen membrane protrusion and reduce actin polymerization in the absence of other Mena isoforms, indicating that it is not simply an inactive Mena isoform. We identify a phosphorylation site within 11a that is required for some Mena11a-specific functions. RNA-seq data analysis from patient cohorts demonstrates that the difference between mRNAs encoding constitutive Mena sequences and those containing the 11a exon correlates with metastasis in colorectal cancer, suggesting that 11a exon exclusion contributes to invasive phenotypes and leads to poor clinical outcomes.

  4. A Novel Actinic Keratosis Field Assessment Scale for Grading Actinic Keratosis Disease Severity.

    Science.gov (United States)

    Dréno, Brigitte; Cerio, Rino; Dirschka, Thomas; Nart, Ignasi Figueras; Lear, John T; Peris, Ketty; de Casas, Andrés Ruiz; Kaleci, Shaniko; Pellacani, Giovanni

    2017-10-02

    Actinic keratosis (AK) lesions are surrounded by field cancerization (areas of subclinical, non-visible sun damage). Existing AK grading tools rely on AK counts, which are not reproducible. An Actinic Keratosis Field Assessment Scale (AK-FAS) for grading the severity of AK/field was developed. Standardized photographs of patients representing the full range of AK severity were collected. Six investigators independently rated each photograph according to 3 criteria: AK area (total skin area affected by AK lesions), hyperkeratosis and sun damage. Inter-rater reproducibility was good for all 3 criteria. Validation of the AK-FAS showed good reproducibility for AK area and hyperkeratosis, even for dermatologists untrained on use of the scale. In conclusion, the AK-FAS is objective, easy to use and implement, and reproducible. It incorporates assessment of the entire field affected by AK instead of relying on lesion counts. Use of the AK-FAS may standardize AK diagnosis, making it relevant to routine clinical practice.

  5. Evolution of Transcriptional Regulatory Networks in Pseudomonas aeruginosa During Long Time Growth in Human Hosts

    DEFF Research Database (Denmark)

    Andresen, Eva Kammer

    extent these observations relate to natural microbial populations. The focus of this thesis has been to study how regulatory networks evolve in natural systems. By using a particular infectious disease scenario (human associated persistent airway infections caused by the bacterium Pseudomonas aeruginosa...... in global regulator genes facilitate the generation of novel phenotypes which again facilitate the shift in life-style of the bacterium from an environmental opportunistic pathogen to a human airway specific pathogen. These findings are not only applicable to P. aeruginosa specific studies, but suggest that...

  6. Heterogeneous network epidemics: real-time growth, variance and extinction of infection.

    Science.gov (United States)

    Ball, Frank; House, Thomas

    2017-09-01

    Recent years have seen a large amount of interest in epidemics on networks as a way of representing the complex structure of contacts capable of spreading infections through the modern human population. The configuration model is a popular choice in theoretical studies since it combines the ability to specify the distribution of the number of contacts (degree) with analytical tractability. Here we consider the early real-time behaviour of the Markovian SIR epidemic model on a configuration model network using a multitype branching process. We find closed-form analytic expressions for the mean and variance of the number of infectious individuals as a function of time and the degree of the initially infected individual(s), and write down a system of differential equations for the probability of extinction by time t that are numerically fast compared to Monte Carlo simulation. We show that these quantities are all sensitive to the degree distribution-in particular we confirm that the mean prevalence of infection depends on the first two moments of the degree distribution and the variance in prevalence depends on the first three moments of the degree distribution. In contrast to most existing analytic approaches, the accuracy of these results does not depend on having a large number of infectious individuals, meaning that in the large population limit they would be asymptotically exact even for one initial infectious individual.

  7. Bidirectional Interplay between Vimentin Intermediate Filaments and Contractile Actin Stress Fibers.

    Science.gov (United States)

    Jiu, Yaming; Lehtimäki, Jaakko; Tojkander, Sari; Cheng, Fang; Jäälinoja, Harri; Liu, Xiaonan; Varjosalo, Markku; Eriksson, John E; Lappalainen, Pekka

    2015-06-16

    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. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  8. 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

  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. Enhanced gravitropism of roots with a disrupted cap actin cytoskeleton

    Science.gov (United States)

    Hou, Guichuan; Mohamalawari, Deepti R.; Blancaflor, Elison B.

    2003-01-01

    The actin cytoskeleton has been proposed to be a major player in plant gravitropism. However, understanding the role of actin in this process is far from complete. To address this problem, we conducted an analysis of the effect of Latrunculin B (Lat B), a potent actin-disrupting drug, on root gravitropism using various parameters that included detailed curvature kinetics, estimation of gravitropic sensitivity, and monitoring of curvature development after extended clinorotation. Lat B treatment resulted in a promotion of root curvature after a 90 degrees reorientation in three plant species tested. More significantly, the sensitivity of maize (Zea mays) roots to gravity was enhanced after actin disruption, as determined from a comparison of presentation time of Lat B-treated versus untreated roots. A short 10-min gravistimulus followed by extended rotation on a 1-rpm clinostat resulted in extensive gravitropic responses, manifested as curvature that often exceeded 90 degrees. Application of Lat B to the cap or elongation zone of maize roots resulted in the disruption of the actin cytoskeleton, which was confined to the area of localized Lat B application. Only roots with Lat B applied to the cap displayed the strong curvature responses after extended clinorotation. Our study demonstrates that disrupting the actin cytoskeleton in the cap leads to the persistence of a signal established by a previous gravistimulus. Therefore, actin could function in root gravitropism by providing a mechanism to regulate the proliferation of a gravitropic signal originating from the cap to allow the root to attain its correct orientation or set point angle.

  11. A Wireless Sensor Network for Growth Environment Measurement and Multi-Band Optical Sensing to Diagnose Tree Vigor.

    Science.gov (United States)

    Kameoka, Shinichi; Isoda, Shuhei; Hashimoto, Atsushi; Ito, Ryoei; Miyamoto, Satoru; Wada, Genki; Watanabe, Naoki; Yamakami, Takashi; Suzuki, Ken; Kameoka, Takaharu

    2017-04-27

    We have tried to develop the guidance system for farmers to cultivate using various phenological indices. As the sensing part of this system, we deployed a new Wireless Sensor Network (WSN). This system uses the 920 MHz radio wave based on the Wireless Smart Utility Network that enables long-range wireless communication. In addition, the data acquired by the WSN were standardized for the advanced web service interoperability. By using these standardized data, we can create a web service that offers various kinds of phenological indices as secondary information to the farmers in the field. We have also established the field management system using thermal image, fluorescent and X-ray fluorescent methods, which enable the nondestructive, chemical-free, simple, and rapid measurement of fruits or trees. We can get the information about the transpiration of plants through a thermal image. The fluorescence sensor gives us information, such as nitrate balance index (NBI), that shows the nitrate balance inside the leaf, chlorophyll content, flavonol content and anthocyanin content. These methods allow one to quickly check the health of trees and find ways to improve the tree vigor of weak ones. Furthermore, the fluorescent x-ray sensor has the possibility to quantify the loss of minerals necessary for fruit growth.

  12. Synthetic dosage lethality in the human metabolic network is highly predictive of tumor growth and cancer patient survival.

    Science.gov (United States)

    Megchelenbrink, Wout; Katzir, Rotem; Lu, Xiaowen; Ruppin, Eytan; Notebaart, Richard A

    2015-09-29

    Synthetic dosage lethality (SDL) denotes a genetic interaction between two genes whereby the underexpression of gene A combined with the overexpression of gene B is lethal. SDLs offer a promising way to kill cancer cells by inhibiting the activity of SDL partners of activated oncogenes in tumors, which are often difficult to target directly. As experimental genome-wide SDL screens are still scarce, here we introduce a network-level computational modeling framework that quantitatively predicts human SDLs in metabolism. For each enzyme pair (A, B) we systematically knock out the flux through A combined with a stepwise flux increase through B and search for pairs that reduce cellular growth more than when either enzyme is perturbed individually. The predictive signal of the emerging network of 12,000 SDLs is demonstrated in five different ways. (i) It can be successfully used to predict gene essentiality in shRNA cancer cell line screens. Moving to clinical tumors, we show that (ii) SDLs are significantly underrepresented in tumors. Furthermore, breast cancer tumors with SDLs active (iii) have smaller sizes and (iv) result in increased patient survival, indicating that activation of SDLs increases cancer vulnerability. Finally, (v) patient survival improves when multiple SDLs are present, pointing to a cumulative effect. This study lays the basis for quantitative identification of cancer SDLs in a model-based mechanistic manner. The approach presented can be used to identify SDLs in species and cell types in which "omics" data necessary for data-driven identification are missing.

  13. A Wireless Sensor Network for Growth Environment Measurement and Multi-Band Optical Sensing to Diagnose Tree Vigor

    Directory of Open Access Journals (Sweden)

    Shinichi Kameoka

    2017-04-01

    Full Text Available We have tried to develop the guidance system for farmers to cultivate using various phenological indices. As the sensing part of this system, we deployed a new Wireless Sensor Network (WSN. This system uses the 920 MHz radio wave based on the Wireless Smart Utility Network that enables long-range wireless communication. In addition, the data acquired by the WSN were standardized for the advanced web service interoperability. By using these standardized data, we can create a web service that offers various kinds of phenological indices as secondary information to the farmers in the field. We have also established the field management system using thermal image, fluorescent and X-ray fluorescent methods, which enable the nondestructive, chemical-free, simple, and rapid measurement of fruits or trees. We can get the information about the transpiration of plants through a thermal image. The fluorescence sensor gives us information, such as nitrate balance index (NBI, that shows the nitrate balance inside the leaf, chlorophyll content, flavonol content and anthocyanin content. These methods allow one to quickly check the health of trees and find ways to improve the tree vigor of weak ones. Furthermore, the fluorescent x-ray sensor has the possibility to quantify the loss of minerals necessary for fruit growth.

  14. Combining affinity proteomics and network context to identify new phosphatase substrates and adapters in growth pathways.

    Directory of Open Access Journals (Sweden)

    Francesca eSacco

    2014-05-01

    Full Text Available Protein phosphorylation homoeostasis is tightly controlled and pathological conditions are caused by subtle alterations of the cell phosphorylation profile. Altered levels of kinase activities have already been associated to specific diseases. Less is known about the impact of phosphatases, the enzymes that down-regulate phosphorylation by removing the phosphate groups. This is partly due to our poor understanding of the phosphatase-substrate network. Much of phosphatase substrate specificity is not based on intrinsic enzyme specificity with the catalytic pocket recognizing the sequence/structure context of the phosphorylated residue. In addition many phosphatase catalytic subunits do not form a stable complex with their substrates. This makes the inference and validation of phosphatase substrates a non-trivial task. Here, we present a novel approach that builds on the observation that much of phosphatase substrate selection is based on the network of physical interactions linking the phosphatase to the substrate. We first used affinity proteomics coupled to quantitative mass spectrometry to saturate the interactome of eight phosphatases whose down regulations was shown to affect the activation of the RAS-PI#K pathway. By integrating information from functional siRNA with protein interaction information, we develop a strategy that aims at inferring phosphatase physiological substrates. Graph analysis is used to identify protein scaffolds that may link the catalytic subunits to their substrates. By this approach we rediscover several previously described phosphatase substrate interactions and characterize two new protein scaffolds that promote the dephosphorylation of PTPN11 and ERK by DUSP18 and DUSP26 respectively.

  15. Automated detection of actinic keratoses in clinical photographs.

    Science.gov (United States)

    Hames, Samuel C; Sinnya, Sudipta; Tan, Jean-Marie; Morze, Conrad; Sahebian, Azadeh; Soyer, H Peter; Prow, Tarl W

    2015-01-01

    Clinical diagnosis of actinic keratosis is known to have intra- and inter-observer variability, and there is currently no non-invasive and objective measure to diagnose these lesions. The aim of this pilot study was to determine if automatically detecting and circumscribing actinic keratoses in clinical photographs is feasible. Photographs of the face and dorsal forearms were acquired in 20 volunteers from two groups: the first with at least on actinic keratosis present on the face and each arm, the second with no actinic keratoses. The photographs were automatically analysed using colour space transforms and morphological features to detect erythema. The automated output was compared with a senior consultant dermatologist's assessment of the photographs, including the intra-observer variability. Performance was assessed by the correlation between total lesions detected by automated method and dermatologist, and whether the individual lesions detected were in the same location as the dermatologist identified lesions. Additionally, the ability to limit false positives was assessed by automatic assessment of the photographs from the no actinic keratosis group in comparison to the high actinic keratosis group. The correlation between the automatic and dermatologist counts was 0.62 on the face and 0.51 on the arms, compared to the dermatologist's intra-observer variation of 0.83 and 0.93 for the same. Sensitivity of automatic detection was 39.5% on the face, 53.1% on the arms. Positive predictive values were 13.9% on the face and 39.8% on the arms. Significantly more lesions (p<0.0001) were detected in the high actinic keratosis group compared to the no actinic keratosis group. The proposed method was inferior to assessment by the dermatologist in terms of sensitivity and positive predictive value. However, this pilot study used only a single simple feature and was still able to achieve sensitivity of detection of 53.1% on the arms.This suggests that image analysis is

  16. Small molecules CK-666 and CK-869 inhibit actin-related protein 2/3 complex by blocking an activating conformational change.

    Science.gov (United States)

    Hetrick, Byron; Han, Min Suk; Helgeson, Luke A; Nolen, Brad J

    2013-05-23

    Actin-related protein 2/3 (Arp2/3) complex is a seven-subunit assembly that nucleates branched actin filaments. Small molecule inhibitors CK-666 and CK-869 bind to Arp2/3 complex and inhibit nucleation, but their modes of action are unknown. Here, we use biochemical and structural methods to determine the mechanism of each inhibitor. Our data indicate that CK-666 stabilizes the inactive state of the complex, blocking movement of the Arp2 and Arp3 subunits into the activated filament-like (short pitch) conformation, while CK-869 binds to a serendipitous pocket on Arp3 and allosterically destabilizes the short pitch Arp3-Arp2 interface. These results provide key insights into the relationship between conformation and activity in Arp2/3 complex and will be critical for interpreting the influence of the inhibitors on actin filament networks in vivo. Copyright © 2013 Elsevier Ltd. All rights reserved.

  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. 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.

  19. 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.

  20. 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

  1. Addition of electrophilic lipids to actin alters filament structure

    International Nuclear Information System (INIS)

    Gayarre, Javier; Sanchez, David; Sanchez-Gomez, Francisco J.; Terron, Maria C.; Llorca, Oscar; Perez-Sala, Dolores

    2006-01-01

    Pathophysiological processes associated with oxidative stress lead to the generation of reactive lipid species. Among them, lipids bearing unsaturated aldehyde or ketone moieties can form covalent adducts with cysteine residues and modulate protein function. Through proteomic techniques we have identified actin as a target for the addition of biotinylated analogs of the cyclopentenone prostaglandins 15-deoxy-Δ 12,14 -PGJ 2 (15d-PGJ 2 ) and PGA 1 in NIH-3T3 fibroblasts. This modification could take place in vitro and mapped to the protein C-terminal end. Other electrophilic lipids, like the isoprostane 8-iso-PGA 1 and 4-hydroxy-2-nonenal, also bound to actin. The C-terminal region of actin is important for monomer-monomer interactions and polymerization. Electron microscopy showed that actin treated with 15d-PGJ 2 or 4-hydroxy-2-nonenal formed filaments which were less abundant and displayed shorter length and altered structure. Streptavidin-gold staining allowed mapping of biotinylated 15d-PGJ 2 at sites of filament disruption. These results shed light on the structural implications of actin modification by lipid electrophiles

  2. A network model of correlated growth of tissue stiffening in pulmonary fibrosis

    Science.gov (United States)

    Oliveira, Cláudio L. N.; Bates, Jason H. T.; Suki, Béla

    2014-06-01

    During the progression of pulmonary fibrosis, initially isolated regions of high stiffness form and grow in the lung tissue due to collagen deposition by fibroblast cells. We have previously shown that ongoing collagen deposition may not lead to significant increases in the bulk modulus of the lung until these local remodeled regions have become sufficiently numerous and extensive to percolate in a continuous path across the entire tissue (Bates et al 2007 Am. J. Respir. Crit. Care Med. 176 617). This model, however, did not include the possibility of spatially correlated deposition of collagen. In the present study, we investigate whether spatial correlations influence the bulk modulus in a two-dimensional elastic network model of lung tissue. Random collagen deposition at a single site is modeled by increasing the elastic constant of the spring at that site by a factor of 100. By contrast, correlated collagen deposition is represented by stiffening the springs encountered along a random walk starting from some initial spring, the rationale being that excess collagen deposition is more likely in the vicinity of an already stiff region. A combination of random and correlated deposition is modeled by performing random walks of length N from randomly selected initial sites, the balance between the two processes being determined by N. We found that the dependence of bulk modulus, B(N,c), on both N and the fraction of stiff springs, c, can be described by a strikingly simple set of empirical equations. For c0.8, B(N,c) is linear in c and independent of N, such that B(N,c)=100\\;{{B}_{0}}-100{{a}_{III}}(1-c){{B}_{0}}, where {{a}_{III}}=2.857. For small concentrations, the physiologically most relevant regime, the forces in the network springs are distributed according to a power law. When c = 0.3, the exponent of this power law increases from -4.5, when N = 1, and saturates to about -2, as N increases above 40. These results suggest that the spatial correlation of

  3. The C-terminus SH3-binding domain of Kv1.3 is required for the actin-mediated immobilization of the channel via cortactin

    Science.gov (United States)

    Hajdu, Peter; Martin, Geoffrey V.; Chimote, Ameet A.; Szilagyi, Orsolya; Takimoto, Koichi; Conforti, Laura

    2015-01-01

    Kv1.3 channels play a pivotal role in the activation and migration of T-lymphocytes. These functions are accompanied by the channels' polarization, which is essential for associated downstream events. However, the mechanisms that govern the membrane movement of Kv1.3 channels remain unclear. F-actin polymerization occurs concomitantly to channel polarization, implicating the actin cytoskeleton in this process. Here we show that cortactin, a factor initiating the actin network, controls the membrane mobilization of Kv1.3 channels. FRAP with EGFP-tagged Kv1.3 channels demonstrates that knocking down cortactin decreases the actin-based immobilization of the channels. Using various deletion and mutation constructs, we show that the SH3 motif of Kv1.3 mediates the channel immobilization. Proximity ligation assays indicate that deletion or mutation of the SH3 motif also disrupts interaction of the channel with cortactin. In T-lymphocytes, the interaction between HS1 (the cortactin homologue) and Kv1.3 occurs at the immune synapse and requires the channel's C-terminal domain. These results show that actin dynamics regulates the membrane motility of Kv1.3 channels. They also provide evidence that the SH3 motif of the channel and cortactin plays key roles in this process. PMID:25739456

  4. Spatially restricted actin-regulatory signaling contributes to synapse morphology

    Science.gov (United States)

    Nicholson, Daniel A.; Cahill, Michael E.; Tulisiak, Christopher T.; Geinisman, Yuri; Penzes, Peter

    2012-01-01

    The actin cytoskeleton in dendritic spines is organized into microdomains, but how signaling molecules that regulate actin are spatially governed is incompletely understood. Here we examine how the localization of the RacGEF kalirin-7, a well-characterized regulator of actin in spines, varies as a function of postsynaptic density (PSD) area and spine volume. Using serial section electron microscopy (EM), we find that extrasynaptic, but not synaptic, expression of kalirin-7 varies directly with synapse size and spine volume. Moreover, we find that overall expression levels of kalirin-7 differ in spines bearing perforated and non-perforated synapses, due primarily to extrasynaptic pools of kalirin-7 expression in the former. Overall, our findings indicate that kalirin-7 is differentially compartmentalized in spines as a function of both synapse morphology and spine size. PMID:22458534

  5. Fascin- and α-Actinin-Bundled Networks Contain Intrinsic Structural Features that Drive Protein Sorting.

    Science.gov (United States)

    Winkelman, Jonathan D; Suarez, Cristian; Hocky, Glen M; Harker, Alyssa J; Morganthaler, Alisha N; Christensen, Jenna R; Voth, Gregory A; Bartles, James R; Kovar, David R

    2016-10-24

    Cells assemble and maintain functionally distinct actin cytoskeleton networks with various actin filament organizations and dynamics through the coordinated action of different sets of actin-binding proteins. The biochemical and functional properties of diverse actin-binding proteins, both alone and in combination, have been increasingly well studied. Conversely, how different sets of actin-binding proteins properly sort to distinct actin filament networks in the first place is not nearly as well understood. Actin-binding protein sorting is critical for the self-organization of diverse dynamic actin cytoskeleton networks within a common cytoplasm. Using in vitro reconstitution techniques including biomimetic assays and single-molecule multi-color total internal reflection fluorescence microscopy, we discovered that sorting of the prominent actin-bundling proteins fascin and α-actinin to distinct networks is an intrinsic behavior, free of complicated cellular signaling cascades. When mixed, fascin and α-actinin mutually exclude each other by promoting their own recruitment and inhibiting recruitment of the other, resulting in the formation of distinct fascin- or α-actinin-bundled domains. Subdiffraction-resolution light microscopy and negative-staining electron microscopy revealed that fascin domains are densely packed, whereas α-actinin domains consist of widely spaced parallel actin filaments. Importantly, other actin-binding proteins such as fimbrin and espin show high specificity between these two bundle types within the same reaction. Here we directly observe that fascin and α-actinin intrinsically segregate to discrete bundled domains that are specifically recognized by other actin-binding proteins. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. 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...

  7. 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.

  8. 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.

  9. Photodynamic therapy for actinic keratosis in organ transplant patients

    DEFF Research Database (Denmark)

    Basset-Seguin, N; Baumann Conzett, K; Gerritsen, M J P

    2013-01-01

    Background The incidence of actinic keratoses (AK) and non-melanoma skin cancer (NMSC) in organ transplant recipients (OTRs) is significantly higher than in immunocompetent patients. Rates of progression and recurrence following treatment are higher too, in part due to the effects of the immunosu......Background The incidence of actinic keratoses (AK) and non-melanoma skin cancer (NMSC) in organ transplant recipients (OTRs) is significantly higher than in immunocompetent patients. Rates of progression and recurrence following treatment are higher too, in part due to the effects...... investigate induced immunosuppression with PDT in healthy volunteers....

  10. Real-world approach to actinic keratosis management

    DEFF Research Database (Denmark)

    Dirschka, Thomas; Gupta, Girish; Micali, Giuseppe

    2017-01-01

    Actinic keratosis (AK) is a chronic skin disease in which multiple clinical and subclinical lesions co-exist across large areas of sun-exposed skin, resulting in field cancerisation. Lesions require treatment because of their potential to transform into invasive squamous cell carcinoma. This arti......Actinic keratosis (AK) is a chronic skin disease in which multiple clinical and subclinical lesions co-exist across large areas of sun-exposed skin, resulting in field cancerisation. Lesions require treatment because of their potential to transform into invasive squamous cell carcinoma...

  11. The integrin-actin connection, an eternal love affair

    DEFF Research Database (Denmark)

    Brakebusch, Cord; Fässler, Reinhard

    2003-01-01

    Integrin receptors connect the extracellular matrix to the actin cytoskeleton. This interaction can be viewed as a cyclical liaison, which develops again and again at new adhesion sites only to cease at sites of de-adhesion. Recent work has demonstrated that multidomain proteins play crucial roles...... in the integrin-actin connection by providing a high degree of regulation adjusted to the needs of the cell. In this review we present several examples of this paradigm and with special emphasis on the ILK-PINCH-parvin complex, which amply demonstrates how structural and signalling functions are linked together....

  12. DNA repair deficiency in lymphocytes from patients with actinic keratosis

    International Nuclear Information System (INIS)

    Abo-Darub, J.M.; Mackie, R.; Pitts, J.D.

    1978-01-01

    DNA repair activity was measured in peripheral blood lymphocytes from 18 patients with Actinic Keratosis and 18 age-matched control subjects, by comparing the incorporation of 3 H-thymidine into cells after irradiation with ultraviolet light with that into unirradiated cells. The incorporation was followed autoradiographically or by measuring acid insoluble radioactivity in cells labelled in the presence of hydroxyurea. The repair activity in lymphocytes from Actinic keratosis patients was only 47.1% (+-6.5%) of that in cells from the control subjects

  13. Modeling the growth and interaction of stylolite networks, using the discrete element method for pressure solution

    Science.gov (United States)

    Makedonska, N.; Sparks, D. W.; Aharonov, E.

    2012-12-01

    heteregeneous, but stress-dependent dissolution tends to equalize them. We apply our model to the simulation of stylolite networks, particularly the interaction of stylolite tips. The stress concentrations from these tips are transmitted through the intervening rock, which can cause elastic strain, brittle damage and frictional sliding. Our model shows that grain rearrangement and compaction rate depend on the surface friction coefficient of grains. Simulation results show the development of shear zones between stylolites, and a high porosity process zone at the tips of stylolites. These features, which have been observed in field studies, are modeled and predicted for the first time. This modeling tool holds a promise to provide many new insights regarding the coupling between pressure solution and brittle deformation, i.e. between mechanical and chemical compaction.

  14. Fission yeast Sec3 and Exo70 are transported on actin cables and localize the exocyst complex to cell poles.

    Directory of Open Access Journals (Sweden)

    Felipe O Bendezú

    Full Text Available The exocyst complex is essential for many exocytic events, by tethering vesicles at the plasma membrane for fusion. In fission yeast, polarized exocytosis for growth relies on the combined action of the exocyst at cell poles and myosin-driven transport along actin cables. We report here the identification of fission yeast Schizosaccharomyces pombe Sec3 protein, which we identified through sequence homology of its PH-like domain. Like other exocyst subunits, sec3 is required for secretion and cell division. Cells deleted for sec3 are only conditionally lethal and can proliferate when osmotically stabilized. Sec3 is redundant with Exo70 for viability and for the localization of other exocyst subunits, suggesting these components act as exocyst tethers at the plasma membrane. Consistently, Sec3 localizes to zones of growth independently of other exocyst subunits but depends on PIP(2 and functional Cdc42. FRAP analysis shows that Sec3, like all other exocyst subunits, localizes to cell poles largely independently of the actin cytoskeleton. However, we show that Sec3, Exo70 and Sec5 are transported by the myosin V Myo52 along actin cables. These data suggest that the exocyst holocomplex, including Sec3 and Exo70, is present on exocytic vesicles, which can reach cell poles by either myosin-driven transport or random walk.

  15. The actin binding cytoskeletal protein Moesin is involved in nuclear mRNA export.

    Science.gov (United States)

    Kristó, Ildikó; Bajusz, Csaba; Borsos, Barbara N; Pankotai, Tibor; Dopie, Joseph; Jankovics, Ferenc; Vartiainen, Maria K; Erdélyi, Miklós; Vilmos, Péter

    2017-10-01

    Current models imply that the evolutionarily conserved, actin-binding Ezrin-Radixin-Moesin (ERM) proteins perform their activities at the plasma membrane by anchoring membrane proteins to the cortical actin network. Here we show that beside its cytoplasmic functions, the single ERM protein of Drosophila, Moesin, has a novel role in the nucleus. The activation of transcription by heat shock or hormonal treatment increases the amount of nuclear Moesin, indicating biological function for the protein in the nucleus. The distribution of Moesin in the nucleus suggests a function in transcription and the depletion of mRNA export factors Nup98 or its interacting partner, Rae1, leads to the nuclear accumulation of Moesin, suggesting that the nuclear function of the protein is linked to mRNA export. Moesin localizes to mRNP particles through the interaction with the mRNA export factor PCID2 and knock down of Moesin leads to the accumulation of mRNA in the nucleus. Based on our results we propose that, beyond its well-known, manifold functions in the cytoplasm, the ERM protein of Drosophila is a new, functional component of the nucleus where it participates in mRNA export. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. 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 ...

  17. A class of vertex-edge-growth small-world network models having scale-free, self-similar and hierarchical characters

    Science.gov (United States)

    Ma, Fei; Su, Jing; Hao, Yongxing; Yao, Bing; Yan, Guanghui

    2018-02-01

    The problem of uncovering the internal operating function of network models is intriguing, demanded and attractive in researches of complex networks. Notice that, in the past two decades, a great number of artificial models are built to try to answer the above mentioned task. Based on the different growth ways, these previous models can be divided into two categories, one type, possessing the preferential attachment, follows a power-law P(k) ∼k-γ, 2 motivated from a new attachment way, vertex-edge-growth network-operation, more precisely, the couple of both them. We report that this model is sparse, small world and hierarchical. And then, not only is scale-free feature in our model, but also lies the degree parameter γ(≈ 3 . 242) out the typical range. Note that, we suggest that the coexistence of multiple vertex growth ways will have a prominent effect on the power-law parameter γ, and the preferential attachment plays a dominate role on the development of networks over time. At the end of this paper, we obtain an exact analytical expression for the total number of spanning trees of models and also capture spanning trees entropy which we have compared with those of their corresponding component elements.

  18. Fragmentation of Human Erythrocyte Actin following Exposure to Hypoxia

    Czech Academy of Sciences Publication Activity Database

    Risso, A.; Santamaria, B.; Pistarino, E.; Cosulich, M. E.; Pompach, Petr; Bezouška, Karel; Antonutto, G.

    2010-01-01

    Roč. 123, č. 1 (2010), s. 6-13 ISSN 0001-5792 Institutional research plan: CEZ:AV0Z50200510 Keywords : beta-Actin * Erythrocytes * Hypoxia Subject RIV: EE - Microbiology, Virology Impact factor: 1.316, year: 2010

  19. The roles of the actin cytoskeleton in fear memory formation

    Directory of Open Access Journals (Sweden)

    Raphael eLamprecht

    2011-07-01

    Full Text Available The formation and storage of fear memory is needed to adapt behavior and avoid danger during subsequent fearful events. However, fear memory may also play a significant role in stress and anxiety disorders. When fear becomes disproportionate to that necessary to cope with a given stimulus, or begins to occur in inappropriate situations, a fear or anxiety disorder exists. Thus, the study of cellular and molecular mechanisms underpinning fear memory may shed light on the formation of memory and on anxiety and stress related disorders. Evidence indicates that fear learning leads to changes in neuronal synaptic transmission and morphology in brain areas underlying fear memory formation including the amygdala and hippocampus. The actin cytoskeleton has been shown to participate in these key neuronal processes. Recent findings show that the actin cytoskeleton is needed for fear memory formation and extinction. Moreover, the actin cytoskeleton is involved in synaptic plasticity and in neuronal morphogenesis in brain areas that mediate fear memory. The actin cytoskeleton may therefore mediate between synaptic transmission during fear learning and long-term cellular alterations mandatory for fear memory formation.

  20. Actinic cell effects after radiotherapy for cervical cancer

    International Nuclear Information System (INIS)

    Padilha, C.M.L.; Bergmann, A.; Chaves, C.B.P.; Thuler, L.C.S.; Araújo Junior, M.L.C.; Souza, S.A.L. de

    2017-01-01

    Introduction: It is very common for patients with cervical cancer to be referred to the radiotherapy when the disease is in advanced stages, this fact determines high rates of locoregional recurrence. Radiation treatment causes actinic morphological changes, not only in neoplastic epithelial cells, but also in normal cells. These changes induced by radiation, often make difficult the differential diagnosis of the residual lesion, resulting in a dilemma in cytopathological follow-up. Objective: To describe the actinic cytopathologic changes in patients submitted to radiotherapy for cervical cancer. Methodology: The re-evaluation of cytopathologic smears and description of actinic cytopathic effects were performed. This information was complemented by the cytopathological report of the smears, available in the archives of the Division of Pathology (DIPAT) / INCA. Results: The most frequent cytopathological changes observed were: nuclear activation, cytoplasmic enhancement, cytoplasmic vacuolisation, eosinophilia, polychromasia, multinucleated giant cells, binucleation, nuclear vacuolisation, prominent nucleoli, as well as presence of leukocyte exudate. Conclusion: The cytopathological diagnosis of tumor persistence or recurrence after radiotherapy is always a great challenge for the professional, even the experienced one. Studies and reports in the literature on actinic cytopathologic changes and radiotherapy are scarce

  1. Actinic Keratosis and Non-Invasive Diagnostic Techniques: An Update

    Science.gov (United States)

    Casari, Alice; Chester, Johanna; Pellacani, Giovanni

    2018-01-01

    Actinic keratosis represents the earliest manifestation of non-melanoma skin cancer. Because of their risk of progression to invasive squamous cell carcinoma, an earlier diagnosis and treatment are mandatory. Their diagnosis sometimes could represent a challenge even for expert dermatologists. Dermoscopy, confocal laser microscopy and optical coherence tomography could help clinicians in diagnosis. PMID:29316678

  2. Pharmacoeconomic Considerations in Treating Actinic Keratosis: An Update.

    Science.gov (United States)

    Vale, Spencer M; Hill, Dane; Feldman, Steven R

    2017-02-01

    Actinic keratosis is one of the most common dermatological diagnoses worldwide, especially among the elderly, fair-skinned, and immunocompromised, and is associated with a risk of transformation to skin cancer. With actinic keratosis and skin cancer prevalence increasing as the aged population expands in the US, optimizing treatment strategies may produce cost savings for the healthcare system. Since the time of our last review in 2008, investigation of the economic considerations in treating actinic keratosis has advanced. To provide an update of treatment cost effectiveness and to review factors relating to the costs of care, we conducted a systematic review of pharmacoeconomic publications since December 2008. We identified 11 pharmacoeconomic studies, with one cost-of-treatment, five cost-effectiveness, and five cost-utility analyses. Photodynamic therapy (PDT) was well tolerated and produced a favorable cosmetic outcome in most studies. Ingenol mebutate, the newest but most expensive topical field therapy, 5-fluorouracil, and PDT were the most cost-effective treatments in our review. Patient adherence to therapy and the management of adverse effects were significant contributors to treatment costs. In the US, treatment guidelines and formalized cost-effectiveness analyses for actinic keratosis are absent from the recent literature. Future pharmacoeconomic investigation will depend on up-to-date comparative efficacy data, as well as clarification of rates of, and management strategies for, adverse effects, therapeutic non-adherence, and lesion recurrence.

  3. Actin and myosin contribute to mammalian mitochondrial DNA maintenance

    Science.gov (United States)

    Reyes, A.; He, J.; Mao, C. C.; Bailey, L. J.; Di Re, M.; Sembongi, H.; Kazak, L.; Dzionek, K.; Holmes, J. B.; Cluett, T. J.; Harbour, M. E.; Fearnley, I. M.; Crouch, R. J.; Conti, M. A.; Adelstein, R. S.; Walker, J. E.; Holt, I. J.

    2011-01-01

    Mitochondrial DNA maintenance and segregation are dependent on the actin cytoskeleton in budding yeast. We found two cytoskeletal proteins among six proteins tightly associated with rat liver mitochondrial DNA: non-muscle myosin heavy chain IIA and β-actin. In human cells, transient gene silencing of MYH9 (encoding non-muscle myosin heavy chain IIA), or the closely related MYH10 gene (encoding non-muscle myosin heavy chain IIB), altered the topology and increased the copy number of mitochondrial DNA; and the latter effect was enhanced when both genes were targeted simultaneously. In contrast, genetic ablation of non-muscle myosin IIB was associated with a 60% decrease in mitochondrial DNA copy number in mouse embryonic fibroblasts, compared to control cells. Gene silencing of β-actin also affected mitochondrial DNA copy number and organization. Protease-protection experiments and iodixanol gradient analysis suggest some β-actin and non-muscle myosin heavy chain IIA reside within human mitochondria and confirm that they are associated with mitochondrial DNA. Collectively, these results strongly implicate the actomyosin cytoskeleton in mammalian mitochondrial DNA maintenance. PMID:21398640

  4. 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.

  5. Interconnection between actin cytoskeleton and plant defense signaling

    Czech Academy of Sciences Publication Activity Database

    Janda, Martin; Matoušková, J.; Burketová, Lenka; Valentová, O.

    2014-01-01

    Roč. 9, č. 11 (2014) ISSN 1559-2316 R&D Projects: GA ČR(CZ) GAP501/11/1654 Institutional support: RVO:61389030 Keywords : Actin * Cytoskeleton * Pathogen Subject RIV: ED - Physiology http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=MEDLINE&DestLinkType=FullRecord&UT=25482795

  6. Suspected Pulmonary Metastasis of Actinic Cutaneous Squamous Cell Carcinoma

    Directory of Open Access Journals (Sweden)

    Monet E. Meter

    2017-01-01

    Full Text Available Introduction. It is rare for actinic or squamous cell carcinoma (SCC in situ to metastasize. Case Presentation. A 67-year-old male had a significant medical history including severe psoriatic arthritis treated with UVB, methotrexate, and rapamycin. He had twenty-five different skin excisions of actinic keratosis four of which were invasive SCC. Our patient developed shortness of breath necessitating a visit to the emergency department. A CT scan of his chest revealed a mass in the right lower lung. A subsequent biopsy of the mass revealed well-differentiated SCC. He underwent thoracoscopic surgery with wedge resection of the lung lesion. Discussion. Actinic keratosis (AK is considered precancerous and associated with UV exposure. It exists as a continuum of progression with low potential for malignancy. The majority of invasive SCCs are associated with malignant progression of AK, but only 5–10% of AKs will progress to malignant potential. Conclusion. In this case, a new finding of lung SCC in the setting of multiple invasive actinic cutaneous SCC associated with a history of extensive UV light exposure and immunosuppression supports a metastatic explanation for lung cancer.

  7. Genomic instability in human actinic keratosis and squamous cell carcinoma

    Science.gov (United States)

    Cabral, Luciana Sanches; Neto, Cyro Festa; Sanches, José A; Ruiz, Itamar R G

    2011-01-01

    OBJECTIVE: To compare the repetitive DNA patterns of human actinic keratoses and squamous cell carcinomas to determine the genetic alterations that are associated with malignant transformation. INTRODUCTION: Cancer cells are prone to genomic instability, which is often due to DNA polymerase slippage during the replication of repetitive DNA and to mutations in the DNA repair genes. The progression of benign actinic keratoses to malignant squamous cell carcinomas has been proposed by several authors. MATERIAL AND METHODS: Eight actinic keratoses and 24 squamous cell carcinomas (SCC), which were pair-matched to adjacent skin tissues and/or leucocytes, were studied. The presence of microsatellite instability (MSI) and the loss of heterozygosity (LOH) in chromosomes 6 and 9 were investigated using nine PCR primer pairs. Random Amplified Polymorphic DNA patterns were also evaluated using eight primers. RESULTS: MSI was detected in two (D6S251, D9S50) of the eight actinic keratosis patients. Among the 8 patients who had squamous cell carcinoma-I and provided informative results, a single patient exhibited two LOH (D6S251, D9S287) and two instances of MSI (D9S180, D9S280). Two LOH and one example of MSI (D6S251) were detected in three out of the 10 patients with squamous cell carcinoma-II. Among the four patients with squamous cell carcinoma-III, one patient displayed three MSIs (D6S251, D6S252, and D9S180) and another patient exhibited an MSI (D9S280). The altered random amplified polymorphic DNA ranged from 70% actinic keratoses, 76% squamous cell carcinoma-I, and 90% squamous cell carcinoma-II, to 100% squamous cell carcinoma-III. DISCUSSION: The increased levels of alterations in the microsatellites, particularly in D6S251, and the random amplified polymorphic DNA fingerprints were statistically significant in squamous cell carcinomas, compared with actinic keratoses. CONCLUSION: The overall alterations that were observed in the repetitive DNA of actinic keratoses and

  8. Probing cytoplasmic organization and the actin cytoskeleton of plant cells with optical tweezers

    NARCIS (Netherlands)

    Ketelaar, T.; Honing, van der H.S.; Emons, A.M.C.

    2010-01-01

    In interphase plant cells, the actin cytoskeleton is essential for intracellular transport and organization. To fully understand how the actin cytoskeleton functions as the structural basis for cytoplasmic organization, both molecular and physical aspects of the actin organization have to be

  9. Multidrug Resistance-Related Protein 1 (MRP1) Function and Localization Depend on Cortical Actin

    NARCIS (Netherlands)

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

    MRP1 (ABCC1) is known to be localized in lipid rafts. Here we show in two different cell lines that localization of Mrp1/MRP1 (Abcc1/ABCC1) in lipid rafts and its function as an efflux pump are dependent on cortical actin. Latrunculin B disrupts both cortical actin and actin stress fibers. This

  10. The effect of pyrene labelling on the thermal stability of actin filaments

    International Nuclear Information System (INIS)

    Halasi, Szulamit; Papp, Gabor; Bugyi, Beata; Barko, Szilvia; Orban, Jozsef; Ujfalusi, Zoltan; Visegrady, Balazs

    2006-01-01

    The ability of actin to form filaments is fundamental to its biological function and often characterised by various methods in vitro. One of the most frequently used methods capitalises on the observation that the fluorescence emission of a pyrene label on the Cys-374 residue of actin is enhanced by a factor of ∼20 during polymerisation. This method inherently involves the chemical modification of actin monomers with pyrene. It was reported earlier that the pyrene labelling of actin monomers has only small effect on the polymerisation and depolymerisation rates of actin, indicating that the method is suitable to characterise the effect of actin-binding proteins or peptides on the polymerisation kinetics. In our present work we tested the effect of the pyrene labelling on the thermal denaturation of actin filaments by using the method of differential scanning calorimetry (DSC). By recording the heat denaturation profiles of unlabelled and pyrene labelled actin filaments we observed that pyrene labelling shifted the melting point (T m ) of actin filaments from 66 to 68 deg. C. A similar effect was detected in the presence of equimolar concentration of phalloidin where the T m shifted from 79 to 82 deg. C. We concluded that the observed pyrene labelling induced differences of the thermal denaturation of actin filaments were small. The DSC results, therefore, confirmed that the methods based on the measurements of pyrene intensity during actin polymerisation are suitable to characterise the polymerisation kinetics of actin under in vitro conditions

  11. An integrated enhancement and reconstruction strategy for the quantitative extraction of actin stress fibers from fluorescence micrographs.

    Science.gov (United States)

    Zhang, Zhen; Xia, Shumin; Kanchanawong, Pakorn

    2017-05-22

    The stress fibers are prominent organization of actin filaments that perform important functions in cellular processes such as migration, polarization, and traction force generation, and whose collective organization reflects the physiological and mechanical activities of the cells. Easily visualized by fluorescence microscopy, the stress fibers are widely used as qualitative descriptors of cell phenotypes. However, due to the complexity of the stress fibers and the presence of other actin-containing cellular features, images of stress fibers are relatively challenging to quantitatively analyze using previously developed approaches, requiring significant user intervention. This poses a challenge for the automation of their detection, segmentation, and quantitative analysis. Here we describe an open-source software package, SFEX (Stress Fiber Extractor), which is geared for efficient enhancement, segmentation, and analysis of actin stress fibers in adherent tissue culture cells. Our method made use of a carefully chosen image filtering technique to enhance filamentous structures, effectively facilitating the detection and segmentation of stress fibers by binary thresholding. We subdivided the skeletons of stress fiber traces into piecewise-linear fragments, and used a set of geometric criteria to reconstruct the stress fiber networks by pairing appropriate fiber fragments. Our strategy enables the trajectory of a majority of stress fibers within the cells to be comprehensively extracted. We also present a method for quantifying the dimensions of the stress fibers using an image gradient-based approach. We determine the optimal parameter space using sensitivity analysis, and demonstrate the utility of our approach by analyzing actin stress fibers in cells cultured on various micropattern substrates. We present an open-source graphically-interfaced computational tool for the extraction and quantification of stress fibers in adherent cells with minimal user input. This

  12. 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.

  13. Variation in the Cost of Managing Actinic Keratosis

    Science.gov (United States)

    Gregory, Tanner; Liu, Guodong; Leslie, Douglas L.; Miller, Jeffrey J.

    2017-01-01

    Importance Actinic keratosis (AK), a skin growth induced by ultraviolet light exposure, requires chronic management because a small proportion can progress into squamous cell skin cancer. Spending for AK management was more than $1 billion in 2004. Investigating geographic variation in AK spending presents an opportunity to decrease waste or recoup excess spending. Objective To evaluate geographic variation in health care cost for management of AKs and the association with patient-related and health-related factors. Design, Setting, and Participants This retrospective cohort study was performed using data from the MarketScan medical claims database of 488 324 continuously enrolled members with 2 or more claims for AK. Data from January 1, 2008, to December 31, 2012, was used. Main Outcomes and Measures Annual costs of care were calculated for outpatient visits, AK destruction, and medications for AKs, and the total of these components. Costs were adjusted for inflation to 2014 US dollars. To display cost variation, we calculated the ratio of mean cost in the highest quintile (Q5) relative to the mean in the lowest quintile (Q1), or the Q5:Q1 ratio; Q5:Q1 ratios were adjusted based on age, sex, history of nonmelanoma skin cancer, US geographic region, and population density (metropolitan statistical area). Results Overall, data from 488 324 continuously enrolled members (mean [SD] age, 53.1 [7.5] years; 243 662 women) with 2 or more claims for AK were included. Overall, patients had 1 085 985 claims related to AK, and dermatologists accounted for 71.0% of claims. The 2-year total cost was $111.5 million, with $52.4 million in 2011 and $59.1 million in 2012. The unadjusted Q5:Q1 ratios for total annual cost per patient ranged from 9.49 to 15.10. Adjusted ratios ranged from 1.72 to 1.80. Conclusions and Relevance There is variation in AK management cost within and between regions. This is not fully explained by differences in patient characteristics such as

  14. 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.

  15. Normalization of similarity-based individual brain networks from gray matter MRI and its association with neurodevelopment in infants with intrauterine growth restriction.

    Science.gov (United States)

    Batalle, Dafnis; Muñoz-Moreno, Emma; Figueras, Francesc; Bargallo, Nuria; Eixarch, Elisenda; Gratacos, Eduard

    2013-12-01

    Obtaining individual biomarkers for the prediction of altered neurological outcome is a challenge of modern medicine and neuroscience. Connectomics based on magnetic resonance imaging (MRI) stands as a good candidate to exhaustively extract information from MRI by integrating the information obtained in a few network features that can be used as individual biomarkers of neurological outcome. However, this approach typically requires the use of diffusion and/or functional MRI to extract individual brain networks, which require high acquisition times and present an extreme sensitivity to motion artifacts, critical problems when scanning fetuses and infants. Extraction of individual networks based on morphological similarity from gray matter is a new approach that benefits from the power of graph theory analysis to describe gray matter morphology as a large-scale morphological network from a typical clinical anatomic acquisition such as T1-weighted MRI. In the present paper we propose a methodology to normalize these large-scale morphological networks to a brain network with standardized size based on a parcellation scheme. The proposed methodology was applied to reconstruct individual brain networks of 63 one-year-old infants, 41 infants with intrauterine growth restriction (IUGR) and 22 controls, showing altered network features in the IUGR group, and their association with neurodevelopmental outcome at two years of age by means of ordinal regression analysis of the network features obtained with Bayley Scale for Infant and Toddler Development, third edition. Although it must be more widely assessed, this methodology stands as a good candidate for the development of biomarkers for altered neurodevelopment in the pediatric population. © 2013 Elsevier Inc. All rights reserved.

  16. Network cosmology.

    Science.gov (United States)

    Krioukov, Dmitri; Kitsak, Maksim; Sinkovits, Robert S; Rideout, David; Meyer, David; Boguñá, Marián

    2012-01-01

    Prediction and control of the dynamics of complex networks is a central problem in network science. Structural and dynamical similarities of different real networks suggest that some universal laws might accurately describe the dynamics of these networks, albeit the nature and common origin of such laws remain elusive. Here we show that the causal network representing the large-scale structure of spacetime in our accelerating universe is a power-law graph with strong clustering, similar to many complex networks such as the Internet, social, or biological networks. We prove that this structural similarity is a consequence of the asymptotic equivalence between the large-scale growth dynamics of complex networks and causal networks. This equivalence suggests that unexpectedly similar laws govern the dynamics of complex networks and spacetime in the universe, with implications to network science and cosmology.

  17. F-actin distribution and function during sexual differentiation in Schizosaccharomyces pombe

    DEFF Research Database (Denmark)

    Petersen, J; Nielsen, O; Egel, R

    1998-01-01

    Sexual differentiation in Schizosaccharomyces pombe is induced from the G1 phase of the cell cycle by nitrogen starvation and the presence of mating pheromones. We describe the distribution of F-actin during sexual differentiation. Cortical F-actin dots have previously been shown to be restricted...... to one end of the rod shaped cell during the G1 phase of the cell cycle. Within half an hour of nitrogen starvation the distribution of cortical F-actin dots switched from being monopolar to bipolar. This was then reversed as the F-actin cytoskeleton repolarized so that cortical F-actin dots accumulated...

  18. Effect of 0.4 mT power frequency magnetic field on F-actin assembly of CHL cells

    International Nuclear Information System (INIS)

    Chu Keping; Cai Zhiyin; Zhang Yukun; Xia Nuohong

    2007-01-01

    Objective: To investigate the effect of 0.4mT power frequency magnetic field on the microfilament (F- actin) assembly of Chinese hamster lung (CHL) cells. Methods: F-actin were marked with immunohistochemical method, then observed under a confocal microscope. The content of ECFRs in the preparation of the detergent-insoluble cytoskeleton was measured with Western-blotting. Results: The stress fiber's of CHL cells decreased after exposure to 0.4mT power frequency magnetic field for 30min, as well as after treatment with epidermal growth factor (ECF) of 50nM. Filopodias appeared at the periphery after exposure to magnetic field as well as treatment with EGF. The EGF receptor mass associated with the detergent-insoluble cytoskeleton increased after exposure to magnetic field as well as treatment with EGF. Conclusion: 0.4mT power frequency magnetic field induced assembly of F-actin in CHL cells. The change induced by magnetic field would be related to clustering of EGFR induced by magnetic field and passing the signal down. (authors)

  19. 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.

  20. 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...

  1. 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...... 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 h...

  2. Health related quality of life in patients with actinic keratosis

    DEFF Research Database (Denmark)

    Tennvall, Gunnel Ragnarson; Norlin, J M; Malmberg, I

    2015-01-01

    BACKGROUND: Actinic keratosis (AK) is a common skin condition that may progress to non-melanoma skin cancer (NMSC). The disease may influence Health Related Quality of Life (HRQoL), but studies of HRQoL in patients with AK are limited. The purpose of the study was to analyze HRQoL in patients......-center setting. Dermatologists assessed AK severity and patients completed: Actinic Keratosis Quality of Life Questionnaire (AKQoL), Dermatology Life Quality Index (DLQI), and EQ-5D-5 L including EQ-VAS. Differences between categorical subgroups were tested with Wilcoxon rank-sum test. The relationship between...... with different severity levels of AK treated in dermatology specialist care using generic and disease-specific HRQoL instruments and to analyze their relationship. METHODS: AK patients who visited dermatological clinics in Denmark were included in an observational, cross-sectional, study in a multi...

  3. Mapping of the Mouse Actin Capping Protein Beta Subunit Gene

    Directory of Open Access Journals (Sweden)

    Cooper John A

    2000-07-01

    Full Text Available Abstract Background Capping protein (CP, a heterodimer of α and β subunits, is found in all eukaryotes. CP binds to the barbed ends of actin filaments in vitro and controls actin assembly and cell motility in vivo. Vertebrates have three isoforms of CPβ produced by alternatively splicing from one gene; lower organisms have one gene and one isoform. Results We isolated genomic clones corresponding to the β subunit of mouse CP and identified its chromosomal location by interspecies backcross mapping. Conclusions The CPβ gene (Cappb1 mapped to Chromosome 4 between Cdc42 and D4Mit312. Three mouse mutations, snubnose, curly tail, and cribriform degeneration, map in the vicinity of the β gene.

  4. Osmosensation in vasopressin neurons: changing actin density to optimize function.

    Science.gov (United States)

    Prager-Khoutorsky, Masha; Bourque, Charles W

    2010-02-01

    The proportional relation between circulating vasopressin concentration and plasma osmolality is fundamental for body fluid homeostasis. Although changes in the sensitivity of this relation are associated with pathophysiological conditions, central mechanisms modulating osmoregulatory gain are unknown. Here, we review recent data that sheds important light on this process. The cell autonomous osmosensitivity of vasopressin neurons depends on cation channels comprising a variant of the transient receptor potential vanilloid 1 (TRPV1) channel. Hyperosmotic activation is mediated by a mechanical process where sensitivity increases in proportion with actin filament density. Moreover, angiotensin II amplifies osmotic activation by a rapid stimulation of actin polymerization, suggesting that neurotransmitter-induced changes in cytoskeletal organization in osmosensory neurons can mediate central changes in osmoregulatory gain. (c) 2009 Elsevier Ltd. All rights reserved.

  5. Actinic inspection of multilayer defects on EUV masks

    International Nuclear Information System (INIS)

    Barty, A; Liu, Y; Gullikson, E; Taylor, J S; Wood, O

    2005-01-01

    The production of defect-free mask blanks, and the development of techniques for inspecting and qualifying EUV mask blanks, remains a key challenge for EUV lithography. In order to ensure a reliable supply of defect-free mask blanks, it is necessary to develop techniques to reliably and accurately detect defects on un-patterned mask blanks. These inspection tools must be able to accurately detect all critical defects whilst simultaneously having the minimum possible false-positive detection rate. There continues to be improvement in high-speed non-actinic mask blank inspection tools, and it is anticipated that these tools can and will be used by industry to qualify EUV mask blanks. However, the outstanding question remains one of validating that non-actinic inspection techniques are capable of detecting all printable EUV defects. To qualify the performance of non-actinic inspection tools, a unique dual-mode EUV mask inspection system has been installed at the Advanced Light Source (ALS) synchrotron at Lawrence Berkeley National Laboratory. In high-speed inspection mode, whole mask blanks are scanned for defects using 13.5-nm wavelength light to identify and map all locations on the mask that scatter a significant amount of EUV light. In imaging, or defect review mode, a zone plate is placed in the reflected beam path to image a region of interest onto a CCD detector with an effective resolution on the mask of 100-nm or better. Combining the capabilities of the two inspection tools into one system provides the unique capability to determine the coordinates of native defects that can be used to compare actinic defect inspection with visible light defect inspection tools under commercial development, and to provide data for comparing scattering models for EUV mask defects

  6. Capture of microtubule plus-ends at the actin cortex promotes axophilic neuronal migration by enhancing microtubule tension in the leading process.

    Science.gov (United States)

    Hutchins, B Ian; Wray, Susan

    2014-01-01

    Microtubules are a critical part of neuronal polarity and leading process extension, thus microtubule movement plays an important role in neuronal migration. However, the dynamics of microtubules during the forward movement of the nucleus into the leading process (nucleokinesis) is unclear and may be dependent on the cell type and mode of migration used. In particular, little is known about cytoskeletal changes during axophilic migration, commonly used in anteroposterior neuronal migration. We recently showed that leading process actin flow in migrating GnRH neurons is controlled by a signaling cascade involving IP3 receptors, CaMKK, AMPK, and RhoA. In the present study, microtubule dynamics were examined in GnRH neurons. Failure of the migration of these cells leads to the neuroendocrine disorder Kallmann Syndrome. Microtubules translocated forward along the leading process shaft during migration, but reversed direction and moved toward the nucleus when migration stalled. Blocking calcium release through IP3 receptors halted migration and induced the same reversal of microtubule translocation, while blocking cortical actin flow prevented microtubules from translocating toward the distal leading process. Super-resolution imaging revealed that microtubule plus-end tips are captured at the actin cortex through calcium-dependent mechanisms. This work shows that cortical actin flow draws the microtubule network forward through calcium-dependent capture in order to promote nucleokinesis, revealing a novel mechanism engaged by migrating neurons to facilitate movement.

  7. Oral acetylsalicylic acid and prevalence of actinic keratosis.

    Science.gov (United States)

    Schmitt, Juliano; Miot, Hélio

    2014-01-01

    To investigate the influence of a regular oral use of acetylsalicylic acid in the prevalence of actinic keratosis. A case-control study with dermatologic outpatients above 50 years of age assessed between 2009 and 2011. Cases were defined as those who had been under regular use of oral acetylsalicylic acid for more than six consecutive months. The assessment focused on: age, sex, skin-type, tobacco smoking, use of medication, occurrence of individual or family skin cancer, and sunscreen and sun exposure habits. Actinic keratoses were counted in the medial region of the face and upper limbs. Counts were adjusted by co-variables based on a generalized linear model. A total of 74 cases and 216 controls were assessed. The median time of acetylsalicylic acid use was 36 months. Cases differed from controls as to the highest age, highest prevalence of use of angiotensin-converting enzyme inhibitors and fewer keratosis on the face and on the upper limbs (pkeratosis and upper-limb erythematous actinic keratosis (pkeratosis, especially facial and erythematous ones.

  8. New Topical Treatment Options for Actinic Keratosis: A Systematic Review.

    Science.gov (United States)

    Stockfleth, Eggert; Sibbring, Gillian C; Alarcon, Ivette

    2016-01-01

    This systematic review compared the relative efficacy of 5-fluorouracil 0.5% in salicylic acid 10% (5-FU/SA), ingenol mebutate (IMB) and imiquimod 2.5%/3.75% (IMI) for actinic keratosis on the face, forehead or scalp. Only 11 publications, relating to 7 randomised controlled trials, met inclusion criteria and it was only possible to compare the effect of all 3 treatments on complete clinical clearance, and the effect of 5-FU/SA and IMB on actinic keratosis recurrence rate. Despite a higher vehicle response rate for 5-FU/SA, complete clinical clearance was higher than IMB and IMI (55.4, 42.2, and 25.0-30.6/34.0-35.6%, [corrected] respectively). 5-FU/SA was also associated with lower actinic keratosis recurrence rate than IMB at 12 months post-treatment (32.7 vs. 53.9%). Although qualitative assessment suggested a numerical advantage of 5-FU/SA over IMB and IMI in terms of complete clinical clearance and sustained clearance, clinical data from longer term trials, with comparable outcome measures, are required to corroborate these findings.

  9. Antibodies to filamentous actin (F-actin) in type 1 autoimmune hepatitis.

    Science.gov (United States)

    Granito, A; Muratori, L; Muratori, P; Pappas, G; Guidi, M; Cassani, F; Volta, U; Ferri, A; Lenzi, M; Bianchi, F B

    2006-03-01

    To evaluate the diagnostic significance of anti-filamentous actin antibodies (A-FAA) assessed with a commercial ELISA in comparison with immunofluorescence reactivity and patterns of anti-smooth muscle antibodies (SMA); and to correlate A-FAA positivity with clinical, immunogenetic, laboratory, and histological features in patients with autoimmune hepatitis type 1 (AIH-1). We studied 78 consecutive untreated AIH-1 patients and 160 controls: 22 with autoimmune hepatitis type 2 (AIH-2), 51 with hepatitis C, 17 with coeliac disease (CD), 20 with primary biliary cirrhosis (PBC) and 50 blood donors. SMA was evaluated by indirect immunofluorescence (IIF) on frozen sections of rat tissues, and A-FAA with a modified commercial ELISA. SMA was detected by IIF in 61 (78%) of 78 AIH-1 patients, of whom 47 (60%) had the SMA-T/G and 14 (18%) the SMA-V pattern. Of the pathological controls, 32 (20%) had the SMA-V pattern (25 with hepatitis C, 2 with AIH-2, 2 with PBC, 3 with CD). A-FAA were present in 55 AIH-1 patients (70.5%; 46 with SMA-T/G, 7 with SMA-V, and 2 SMA-negative), and in 10 controls (6%), of whom five had hepatitis C, two AIH-2, two PBC and one CD. The association between A-FAA and the SMA-T/G pattern was statistically significant (p<0.0001). A-FAA levels were higher in SMA-T/G positive than SMA-V positive AIH-1 patients and controls (p<0.0001). A-FAA positivity was significantly associated with higher gamma-globulin and IgG levels, but did not correlate with other considered parameters. The modified A-FAA ELISA strictly correlates with the SMA-T/G pattern and is a reliable and operator independent assay for AIH-1. Detection of A-FAA, even if devoid of prognostic relevance, may be useful when interpretative doubts of standard IIF arise.

  10. Antibodies to filamentous actin (F‐actin) in type 1 autoimmune hepatitis

    Science.gov (United States)

    Granito, A; Muratori, L; Muratori, P; Pappas, G; Guidi, M; Cassani, F; Volta, U; Ferri, A; Lenzi, M; Bianchi, F B

    2006-01-01

    Aims To evaluate the diagnostic significance of anti‐filamentous actin antibodies (A‐FAA) assessed with a commercial ELISA in comparison with immunofluorescence reactivity and patterns of anti‐smooth muscle antibodies (SMA); and to correlate A‐FAA positivity with clinical, immunogenetic, laboratory, and histological features in patients with autoimmune hepatitis type 1 (AIH‐1). Methods We studied 78 consecutive untreated AIH‐1 patients and 160 controls: 22 with autoimmune hepatitis type 2 (AIH‐2), 51 with hepatitis C, 17 with coeliac disease (CD), 20 with primary biliary cirrhosis (PBC) and 50 blood donors. SMA was evaluated by indirect immunofluorescence (IIF) on frozen sections of rat tissues, and A‐FAA with a modified commercial ELISA. Results SMA was detected by IIF in 61 (78%) of 78 AIH‐1 patients, of whom 47 (60%) had the SMA‐T/G and 14 (18%) the SMA‐V pattern. Of the pathological controls, 32 (20%) had the SMA‐V pattern (25 with hepatitis C, 2 with AIH‐2, 2 with PBC, 3 with CD). A‐FAA were present in 55 AIH‐1 patients (70.5%; 46 with SMA‐T/G, 7 with SMA‐V, and 2 SMA‐negative), and in 10 controls (6%), of whom five had hepatitis C, two AIH‐2, two PBC and one CD. The association between A‐FAA and the SMA‐T/G pattern was statistically significant (p<0.0001). A‐FAA levels were higher in SMA‐T/G positive than SMA‐V positive AIH‐1 patients and controls (p<0.0001). A‐FAA positivity was significantly associated with higher γ‐globulin and IgG levels, but did not correlate with other considered parameters. Conclusion The modified A‐FAA ELISA strictly correlates with the SMA‐T/G pattern and is a reliable and operator independent assay for AIH‐1. Detection of A‐FAA, even if devoid of prognostic relevance, may be useful when interpretative doubts of standard IIF arise. PMID:16505279

  11. The Hierarchy of Brain Networks Is Related to Insulin Growth Factor-1 in a Large, Middle-Aged, Healthy Cohort: An Exploratory Magnetoencephalography Study.

    Science.gov (United States)

    Sorrentino, Pierpaolo; Nieboer, Dagmar; Twisk, Jos W R; Stam, Cornelis J; Douw, Linda; Hillebrand, Arjan

    2017-06-01

    Recently, a large study demonstrated that lower serum levels of insulin growth factor-1 (IGF-1) relate to brain atrophy and to a greater risk for developing Alzheimer's disease in a healthy elderly population. We set out to test if functional brain networks relate to IGF-1 levels in the middle aged. Hence, we studied the association between IGF-1 and magnetoencephalography-based functional network characteristics in a middle-aged population. The functional connections between brain areas were estimated for six frequency bands (delta, theta, alpha1, alpha2, beta, gamma) using the phase lag index. Subsequently, the topology of the frequency-specific functional networks was characterized using the minimum spanning tree. Our results showed that lower levels of serum IGF-1 relate to a globally less integrated functional network in the beta and theta band. The associations remained significant when correcting for gender and systemic effects of IGF-1 that might indirectly affect the brain. The value of this exploratory study is the demonstration that lower levels of IGF-1 are associated with brain network topology in the middle aged.

  12. Annual Research Review: Growth connectomics – the organization and reorganization of brain networks during normal and abnormal development

    Science.gov (United States)

    Vértes, Petra E; Bullmore, Edward T

    2015-01-01

    Background We first give a brief introduction to graph theoretical analysis and its application to the study of brain network topology or connectomics. Within this framework, we review the existing empirical data on developmental changes in brain network organization across a range of experimental modalities (including structural and functional MRI, diffusion tensor imaging, magnetoencephalography and electroencephalography in humans). Synthesis We discuss preliminary evidence and current hypotheses for how the emergence of network properties correlates with concomitant cognitive and behavioural changes associated with development. We highlight some of the technical and conceptual challenges to be addressed by future developments in this rapidly moving field. Given the parallels previously discovered between neural systems across species and over a range of spatial scales, we also review some recent advances in developmental network studies at the cellular scale. We highlight the opportunities presented by such studies and how they may complement neuroimaging in advancing our understanding of brain development. Finally, we note that many brain and mind disorders are thought to be neurodevelopmental in origin and that charting the trajectory of brain network changes associated with healthy development also sets the stage for understanding abnormal network development. Conclusions We therefore briefly review the clinical relevance of network metrics as potential diagnostic markers and some recent efforts in computational modelling of brain networks which might contribute to a more mechanistic understanding of neurodevelopmental disorders in future. PMID:25441756

  13. Integration of a laterally acquired gene into a cell network important for growth in a strain of Vibrio rotiferianus

    Directory of Open Access Journals (Sweden)

    Labbate Maurizio

    2011-11-01

    Full Text Available Abstract Background Lateral Gene Transfer (LGT is a major contributor to bacterial evolution and up to 25% of a bacterium's genome may have been acquired by this process over evolutionary periods of time. Successful LGT requires both the physical transfer of DNA and its successful incorporation into the host cell. One system that contributes to this latter step by site-specific recombination is the integron. Integrons are found in many diverse bacterial Genera and is a genetic system ubiquitous in vibrios that captures mobile DNA at a dedicated site. The presence of integron-associated genes, contained within units of mobile DNA called gene cassettes makes up a substantial component of the vibrio genome (1-3%. Little is known about the role of this system since the vast majority of genes in vibrio arrays are highly novel and functions cannot be ascribed. It is generally regarded that strain-specific mobile genes cannot be readily integrated into the cellular machinery since any perturbation of core metabolism is likely to result in a loss of fitness. Results In this study, at least one mobile gene contained within the Vibrio rotiferianus strain DAT722, but lacking close relatives elsewhere, is shown to greatly reduce host fitness when deleted and tested in growth assays. The precise role of the mobile gene product is unknown but impacts on the regulation of outermembrane porins. This demonstrates that strain specific laterally acquired mobile DNA can be integrated rapidly into bacterial networks such that it becomes advantageous for survival and adaptation in changing environments. Conclusions Mobile genes that are highly strain specific are generally believed to act in isolation. This is because perturbation of existing cell machinery by the acquisition of a new gene by LGT is highly likely to lower fitness. In contrast, we show here that at least one mobile gene, apparently unique to a strain, encodes a product that has integrated into central

  14. 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.

  15. 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.

  16. 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

  17. The actin cytoskeleton may control the polar distribution of an auxin transport protein

    Science.gov (United States)

    Muday, G. K.; Hu, S.; Brady, S. R.; Davies, E. (Principal Investigator)

    2000-01-01

    The gravitropic bending of plants has long been linked to the changes in the transport of the plant hormone auxin. To understand the mechanism by which gravity alters auxin movement, it is critical to know how polar auxin transport is initially established. In shoots, polar auxin transport is basipetal (i.e., from the shoot apex toward the base). It is driven by the basal localization of the auxin efflux carrier complex. One mechanism for localizing this efflux carrier complex to the basal membrane may be through attachment to the actin cytoskeleton. The efflux carrier protein complex is believed to consist of several polypeptides, including a regulatory subunit that binds auxin transport inhibitors, such as naphthylphthalamic acid (NPA). Several lines of experimentation have been used to determine if the NPA binding protein interacts with actin filaments. The NPA binding protein has been shown to partition with the actin cytoskeleton during detergent extraction. Agents that specifically alter the polymerization state of the actin cytoskeleton change the amount of NPA binding protein and actin recovered in these cytoskeletal pellets. Actin-affinity columns were prepared with polymers of actin purified from zucchini hypocotyl tissue. NPA binding activity was eluted in a single peak from the actin filament column. Cytochalasin D, which fragments the actin cytoskeleton, was shown to reduce polar auxin transport in zucchini hypocotyls. The interaction of the NPA binding protein with the actin cytoskeleton may localize it in one plane of the plasma membrane, and thereby control the polarity of auxin transport.

  18. 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

  19. Actin Nemaline Myopathy Mouse Reproduces Disease, Suggests Other Actin Disease Phenotypes and Provides Cautionary Note on Muscle Transgene Expression

    Science.gov (United States)

    Ravenscroft, Gianina; Jackaman, Connie; Sewry, Caroline A.; McNamara, Elyshia; Squire, Sarah E.; Potter, Allyson C.; Papadimitriou, John; Griffiths, Lisa M.; Bakker, Anthony J.; Davies, Kay E.; Laing, Nigel G.; Nowak, Kristen J.

    2011-01-01

    Mutations in the skeletal muscle α-actin gene (ACTA1) cause congenital myopathies including nemaline myopathy, actin aggregate myopathy and rod-core disease. The majority of patients with ACTA1 mutations have severe hypotonia and do not survive beyond the age of one. A transgenic mouse model was generated expressing an autosomal dominant mutant (D286G) of ACTA1 (identified in a severe nemaline myopathy patient) fused with EGFP. Nemaline bodies were observed in multiple skeletal muscles, with serial sections showing these correlated to aggregates of the mutant skeletal muscle α-actin-EGFP. Isolated extensor digitorum longus and soleus muscles were significantly weaker than wild-type (WT) muscle at 4 weeks of age, coinciding with the peak in structural lesions. These 4 week-old mice were ∼30% less active on voluntary running wheels than WT mice. The α-actin-EGFP protein clearly demonstrated that the transgene was expressed equally in all myosin heavy chain (MHC) fibre types during the early postnatal period, but subsequently became largely confined to MHCIIB fibres. Ringbinden fibres, internal nuclei and myofibrillar myopathy pathologies, not typical features in nemaline myopathy or patients with ACTA1 mutations, were frequently observed. Ringbinden were found in fast fibre predominant muscles of adult mice and were exclusively MHCIIB-positive fibres. Thus, this mouse model presents a reliable model for the investigation of the pathobiology of nemaline body formation and muscle weakness and for evaluation of potential therapeutic interventions. The occurrence of core-like regions, internal nuclei and ringbinden will allow analysis of the mechanisms underlying these lesions. The occurrence of ringbinden and features of myofibrillar myopathy in this mouse model of ACTA1 disease suggests that patients with these pathologies and no genetic explanation should be screened for ACTA1 mutations. PMID:22174871

  20. The structure of the actin-smooth muscle myosin motor domain complex in the rigor state.

    Science.gov (United States)

    Banerjee, Chaity; Hu, Zhongjun; Huang, Zhong; Warrington, J Anthony; Taylor, Dianne W; Trybus, Kathleen M; Lowey, Susan; Taylor, Kenneth A

    2017-12-01

    Myosin-based motility utilizes catalysis of ATP to drive the relative sliding of F-actin and myosin. The earliest detailed model based on cryo-electron microscopy (cryoEM) and X-ray crystallography postulated that higher actin affinity and lever arm movement were coupled to closure of a feature of the myosin head dubbed the actin-binding cleft. Several studies since then using crystallography of myosin-V and cryoEM structures of F-actin bound myosin-I, -II and -V have provided details of this model. The smooth muscle myosin II interaction with F-actin may differ from those for striated and non-muscle myosin II due in part to different lengths of important surface loops. Here we report a ∼6 Å resolution reconstruction of F-actin decorated with the nucleotide-free recombinant smooth muscle myosin-II motor domain (MD) from images recorded using a direct electron detector. Resolution is highest for F-actin and the actin-myosin interface (3.5-4 Å) and lowest (∼6-7 Å) for those parts of the MD at the highest radius. Atomic models built into the F-actin density are quite comparable to those previously reported for rabbit muscle actin and show density from the bound ADP. The atomic model of the MD, is quite similar to a recently published structure of vertebrate non-muscle myosin II bound to F-actin and a crystal structure of nucleotide free myosin-V. Larger differences are observed when compared to the cryoEM structure of F-actin decorated with rabbit skeletal muscle myosin subfragment 1. The differences suggest less closure of the 50 kDa domain in the actin bound skeletal muscle myosin structure. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. 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

  2. Updates on drug-target network; facilitating polypharmacology and data integration by growth of DrugBank database.

    Science.gov (United States)

    Barneh, Farnaz; Jafari, Mohieddin; Mirzaie, Mehdi

    2016-11-01

    Network pharmacology elucidates the relationship between drugs and targets. As the identified targets for each drug increases, the corresponding drug-target network (DTN) evolves from solely reflection of the pharmaceutical industry trend to a portrait of polypharmacology. The aim of this study was to evaluate the potentials of DrugBank database in advancing systems pharmacology. We constructed and analyzed DTN from drugs and targets associations in the DrugBank 4.0 database. Our results showed that in bipartite DTN, increased ratio of identified targets for drugs augmented density and connectivity of drugs and targets and decreased modular structure. To clear up the details in the network structure, the DTNs were projected into two networks namely, drug similarity network (DSN) and target similarity network (TSN). In DSN, various classes of Food and Drug Administration-approved drugs with distinct therapeutic categories were linked together based on shared targets. Projected TSN also showed complexity because of promiscuity of the drugs. By including investigational drugs that are currently being tested in clinical trials, the networks manifested more connectivity and pictured the upcoming pharmacological space in the future years. Diverse biological processes and protein-protein interactions were manipulated by new drugs, which can extend possible target combinations. We conclude that network-based organization of DrugBank 4.0 data not only reveals the potential for repurposing of existing drugs, also allows generating novel predictions about drugs off-targets, drug-drug interactions and their side effects. Our results also encourage further effort for high-throughput identification of targets to build networks that can be integrated into disease networks. © The Author 2015. Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  3. Platelet rich plasma promotes skeletal muscle cell migration in association with up-regulation of FAK, paxillin, and F-Actin formation.

    Science.gov (United States)

    Tsai, Wen-Chung; Yu, Tung-Yang; Lin, Li-Ping; Lin, Mioa-Sui; Tsai, Ting-Ta; Pang, Jong-Hwei S

    2017-11-01

    Platelet rich plasma (PRP) contains various cytokines and growth factors which may be beneficial to the healing process of injured muscle. The aim of this study was to investigate the effect and molecular mechanism of PRP on migration of skeletal muscle cells. Skeletal muscle cells intrinsic to Sprague-Dawley rats were treated with PRP. The cell migration was evaluated by transwell filter migration assay and electric cell-substrate impedance sensing. The spreading of cells was evaluated microscopically. The formation of filamentous actin (F-actin) cytoskeleton was assessed by immunofluorescence staining. The protein expressions of paxillin and focal adhesion kinase (FAK) were assessed by Western blot analysis. Transfection of paxillin small-interfering RNA (siRNAs) to muscle cells was performed to validate the role of paxillin in PRP-mediated promotion of cell migration. Dose-dependently PRP promotes migration of and spreading and muscle cells. Protein expressions of paxillin and FAK were up-regulated dose-dependently. F-actin formation was also enhanced by PRP treatment. Furthermore, the knockdown of paxillin expression impaired the effect of PRP to promote cell migration. It was concluded that PRP promoting migration of muscle cells is associated with up-regulation of proteins expression of paxillin and FAK as well as increasing F-actin formation. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2506-2512, 2017. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

  4. High level of reactive oxygen species impaired mesenchymal stem cell migration via overpolymerization of F-actin cytoskeleton in systemic lupus erythematosus.

    Science.gov (United States)

    Shi, D; Li, X; Chen, H; Che, N; Zhou, S; Lu, Z; Shi, S; Sun, L

    2014-12-01

    Some lines of evidence have demonstrated abnormalities of bone marrow mesenchymal stem cells (MSCs) in systemic lupus erythematosus (SLE) patients, characterized by defective phenotype of MSCs and slower growth with enhanced apoptosis and senescence. However, whether SLE MSCs demonstrate aberrant migration capacity or abnormalities in cytoskeleton are issues that remain poorly understood. In this study, we found that MSCs from SLE patients did show impairment in migration capacity as well as abnormalities in F-actin cytoskeleton, accompanied by a high level of intracellular reactive oxygen species (ROS). When normal MSCs were treated in vitro with H2O2, which increases intracellular ROS level as an oxidant, both reorganization of F-actin cytoskeleton and impairment of migration capability were observed. On the other hand, treatment with N-acetylcysteine (NAC), as an exogenous antioxidant, made F-actin more orderly and increased migration ratio in SLE MSCs. In addition, oral administration of NAC markedly reduced serum autoantibody levels and ameliorated lupus nephritis (LN) in MRL/lpr mice, partially reversing the abnormalities of MSCs. These results indicate that overpolymerization of F-actin cytoskeleton, which may be associated with high levels of ROS, causes impairment in the migration capacity of SLE MSCs and that oral administration of NAC may have potential therapeutic effects on MRL/lpr mice. Copyright © 2014 Elsevier Masson SAS. All rights reserved.

  5. Network cohesion

    OpenAIRE

    Cavalcanti, Tiago V. V.; Giannitsarou, Chryssi; Johnson, Charles R.

    2016-01-01

    This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00199-016-0992-1 We define a measure of network cohesion and show how it arises naturally in a broad class of dynamic models of endogenous perpetual growth with network externalities. Via a standard growth model, we show why network cohesion is crucial for conditional convergence and explain that as cohesion increases, convergence is faster. We prove properties of network cohesion and d...

  6. Microwave assisted rapid growth of Mg(OH){sub 2} nanosheet networks for ethanol chemical sensor application

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hazmi, Faten [Department of Physics, College of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21569 (Saudi Arabia); Umar, Ahmad, E-mail: ahmadumar786@gmail.com [Promising Centre for Sensors and Electronic Devices (PCSED) and Centre for Advanced Materials and Nano-Research (CAMNR), Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Dar, G.N. [Promising Centre for Sensors and Electronic Devices (PCSED) and Centre for Advanced Materials and Nano-Research (CAMNR), Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Al-Ghamdi, A.A.; Al-Sayari, S.A. [Department of Physics, College of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21569 (Saudi Arabia); Al-Hajry, A. [Promising Centre for Sensors and Electronic Devices (PCSED) and Centre for Advanced Materials and Nano-Research (CAMNR), Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Department of Physics, College of Science and Arts, Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Kim, S.H. [Promising Centre for Sensors and Electronic Devices (PCSED) and Centre for Advanced Materials and Nano-Research (CAMNR), Najran University, P.O. Box 1988, Najran 11001 (Saudi Arabia); Al-Tuwirqi, Reem M. [Department of Physics, College of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21569 (Saudi Arabia); Alnowaiserb, Fowzia [Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah (Saudi Arabia); El-Tantawy, Farid [Department of Physics, Faculty of Science, Suez Canal University, Ismailia (Egypt)

    2012-04-05

    Highlights: Black-Right-Pointing-Pointer A facile microwave-assisted synthesis and characterizations of magnesium hydroxide (Mg(OH){sub 2}) nanosheet networks. Black-Right-Pointing-Pointer Fabrication of ethanol sensor based on (Mg(OH){sub 2}) nanosheet networks. Black-Right-Pointing-Pointer Good sensitivity ({approx}3.991 {mu}A cm{sup -2} mM{sup -1}) and lower detection limit (5 {mu}M). Black-Right-Pointing-Pointer This research opens a way to utilize Mg(OH){sub 2} nanostructures for chemical sensors applications. - Abstract: This paper reports a facile microwave-assisted synthesis of magnesium hydroxide (Mg(OH){sub 2}) nanosheet networks and their utilization for the fabrication of efficient ethanol chemical sensor. The synthesized nanosheets networks were characterized in terms of their morphological, structural and optical properties using various analysis techniques such as field emission scanning electron microscopy (FESEM), X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. The detailed morphological and structural investigations reveal that the synthesized (Mg(OH){sub 2}) products are nanosheet networks, grown in high density, and possessing hexagonal crystal structure. The optical band gap of as-synthesized Mg(OH){sub 2} nanosheet networks was examined by UV-Vis absorption spectrum, and found to be 5.76 eV. The synthesized nanosheet networks were used as supporting matrices for the fabrication of I-V technique based efficient ethanol chemical sensor. The fabricated ethanol sensor based on nanosheet networks exhibits good sensitivity ({approx}3.991 {mu}A cm{sup -2} mM{sup -1}) and lower detection limit (5 {mu}M), with linearity (R = 0.9925) in short response time (10.0 s). This work demonstrate that the simply synthesized Mg(OH){sub 2} nanosheet networks can effectively be used for the fabrication of efficient ethanol chemical sensors.

  7. Envisaging the Regulation of Alkaloid Biosynthesis and Associated Growth Kinetics in Hairy Roots of Vinca minor Through the Function of Artificial Neural Network.

    Science.gov (United States)

    Verma, Priyanka; Anjum, Shahin; Khan, Shamshad Ahmad; Roy, Sudeep; Odstrcilik, Jan; Mathur, Ajay Kumar

    2016-03-01

    Artificial neural network based modeling is a generic approach to understand and correlate different complex parameters of biological systems for improving the desired output. In addition, some new inferences can also be predicted in a shorter time with less cost and labor. As terpenoid indole alkaloid pathway in Vinca minor is very less investigated or elucidated, a strategy of elicitation with hydroxylase and acetyltransferase along with incorporation of various precursors from primary shikimate and secoiridoid pools via simultaneous employment of cyclooxygenase inhibitor was performed in the hairy roots of V. minor. This led to the increment in biomass accumulation, total alkaloid concentration, and vincamine production in selected treatments. The resultant experimental values were correlated with algorithm approaches of artificial neural network that assisted in finding the yield of vincamine, alkaloids, and growth kinetics using number of elicits. The inputs were the hydroxylase/acetyltransferase elicitors and cyclooxygenase inhibitor along with various precursors from shikimate and secoiridoid pools and the outputs were growth index (GI), alkaloids, and vincamine. The approach incorporates two MATLAB codes; GRNN and FFBPNN. Growth kinetic studies revealed that shikimate and tryptophan supplementation triggers biomass accumulation (GI = 440.2 to 540.5); while maximum alkaloid (3.7 % dry wt.) and vincamine production (0.017 ± 0.001 % dry wt.) was obtained on supplementation of secologanin along with tryptophan, naproxen, hydrogen peroxide, and acetic anhydride. The study shows that experimental and predicted values strongly correlate each other. The correlation coefficient for growth index (GI), alkaloids, and vincamine was found to be 0.9997, 0.9980, 0.9511 in GRNN and 0.9725, 0.9444, 0.9422 in FFBPNN, respectively. GRNN provided greater similarity between the target and predicted dataset in comparison to FFBPNN. The findings can provide future

  8. Microscale force response and morphology of tunable co-polymerized cytoskeleton networks

    Science.gov (United States)

    Ricketts, Shea; Yadav, Vikrant; Ross, Jennifer L.; Robertson-Anderson, Rae M.

    The cytoskeleton is largely comprised of actin and microtubules that entangle and crosslink to form complex networks and structures, giving rise to nonlinear multifunctional mechanics in cells. The relative concentrations of semiflexible actin filaments and rigid microtubules tune cytoskeleton function, allowing cells to move and divide while maintaining rigidity and resilience. To elucidate this complex tunability, we create in vitro composites of co-polymerized actin and microtubules with actin:microtubule molar ratios of 0:1-1:0. We use optical tweezers and confocal microscopy to characterize the nonlinear microscale force response and morphology of the composites. We optically drag a microsphere 30 μm through varying actin-microtubule networks at 10 μm/s and 20 μm/s, and measure the force the networks exerts to resist the strain and the force relaxation following strain. We use dual-color confocal microscopy to image distinctly-labeled filaments in the networks, and characterize the integration of actin and microtubules, network connectivity, and filament rigidity. We find that increasing the fraction of microtubules in networks non-monotonically increases elasticity and stiffness, and hinders force relaxation by suppressing network mobility and fluctuations. NSF CAREER Award (DMR-1255446), Scialog Collaborative Innovation Award funded by Research Corporation for Scientific Advancement (Grant No. 24192).

  9. Empirical Study on Growth of Evil Forces in Land Requisition and Relocation in City G of Hubei Province Based on Social Network Analysis

    Institute of Scientific and Technical Information of China (English)

    Hongxia ZHANG; Xia ZHOU; Yanan LI

    2015-01-01

    Using social network analysis method,this paper made an empirical study on growth of evil forces in land requisition and relocation in City G of Hubei Province. It obtained following results:(i) lawless developers and inefficient public security organs form interested parties of evil forces. Besides,the inward closeness centrality of evil forces is high,manifesting that evil forces independently possess decentralized power of network and have unscrupulous behavior in land requisition and relocation to a certain extent.(ii) Activities of evil forces have complicated spatial correlation and their geographical distribution is uneven,taking on irregular characteristics. In the field of land requisition and relocation,some evil forces are expandi Xng and spreading,while other forces are relatively weak. In conclusion,growth of evil forces comes from premeditation and collaboration of lawless developers,lack of functions and weak attack of public security organs; growth of evil forces has periodic changes,when in power,they will take opportunity to expand,while losing power,they will hide or even disappear.

  10. Actin Waves Do Not Boost Neurite Outgrowth in the Early Stages of Neuron Maturation

    Directory of Open Access Journals (Sweden)

    Simone Mortal

    2017-12-01

    Full Text Available During neurite development, Actin Waves (AWs emerge at the neurite base and move up to its tip, causing a transient retraction of the Growth Cone (GC. Many studies have shown that AWs are linked to outbursts of neurite growth and, therefore, contribute to the fast elongation of the nascent axon. Using long term live cell-imaging, we show that AWs do not boost neurite outgrowth and that neurites without AWs can elongate for several hundred microns. Inhibition of Myosin II abolishes the transient GC retraction and strongly modifies the AWs morphology. Super-resolution nanoscopy shows that Myosin IIB shapes the growth cone-like AWs structure and is differently distributed in AWs and GCs. Interestingly, depletion of membrane cholesterol and inhibition of Rho GTPases decrease AWs frequency and velocity. Our results indicate that Myosin IIB, membrane tension, and small Rho GTPases are important players in the regulation of the AW dynamics. Finally, we suggest a role for AWs in maintaining the GCs active during environmental exploration.

  11. Initiation and growth of thermal fatigue crack networks in an AISI 304 L type austenitic stainless steel (X2 CrNi18-09)

    International Nuclear Information System (INIS)

    Maillot, V.

    2004-01-01

    We studied the behaviour of a 304 L type austenitic stainless steel submitted to thermal fatigue. Using the SPLASH equipment of CEA/SRMA we tested parallelepipedal specimens on two sides: the specimens are continuously heated by Joule effect, while two opposites faces are cyclically. cooled by a mixed spray of distilled water and compressed air. This device allows the reproduction and the study of crack networks similar to those observed in nuclear power plants, on the inner side of circuits fatigued by mixed pressurized water flows at different temperatures. The crack initiation and the network constitution at the surface were observed under different thermal conditions (Tmax = 320 deg C, ΔT between 125 and 200 deg C). The experiment produced a stress gradient in the specimen, and due to this gradient, the in-depth growth of the cracks finally stopped. The obtained crack networks were studied quantitatively by image analysis, and different parameters were studied: at the surface during the cycling, and post mortem by step-by-step layer removal by grinding. The maximal depth obtained experimentally, 2.5 mm, is relatively coherent with the finite element modelling of the SPLASH test, in which compressive stresses appear at a depth of 2 mm. Some of the crack networks obtained by thermal fatigue were also tested in isothermal fatigue crack growth under 4-point bending, at imposed load. The mechanisms of the crack selection, and the appearance of the dominating crack are described. Compared to the propagation of a single crack, the crack networks delay the propagation, depending on the severity of the crack competition for domination. The dominating crack can be at the network periphery, in that case it is not as shielded by its neighbours as a crack located in the center of the network. It can also be a straight crack surrounded by more sinuous neighbours. Indeed, on sinuous cracks, the loading is not the same all along the crack path, leading to some morphological

  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. 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.

  14. Genome-scale reconstruction of the Streptococcus pyogenes M49 metabolic network reveals growth requirements and indicates potential drug targets

    NARCIS (Netherlands)

    Levering, J.; Fiedler, T.; Sieg, A.; van Grinsven, K.W.A.; Hering, S.; Veith, N.; Olivier, B.G.; Klett, L.; Hugenholtz, J.; Teusink, B.; Kreikemeyer, B.; Kummer, U.

    2016-01-01

    Genome-scale metabolic models comprise stoichiometric relations between metabolites, as well as associations between genes and metabolic reactions and facilitate the analysis of metabolism. We computationally reconstructed the metabolic network of the lactic acid bacterium Streptococcus pyogenes

  15. 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 ...

  16. 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.

  17. 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.

  18. G-actin sequestering protein thymosin-β4 regulates the activity of myocardin-related transcription factor.

    Science.gov (United States)

    Morita, Tsuyoshi; Hayashi, Ken'ichiro

    2013-08-02

    Myocardin-related transcription factors (MRTFs) are robust coactivators of serum response factor (SRF). MRTFs contain three copies of the RPEL motif at their N-terminus, and they bind to monomeric globular actin (G-actin). Previous studies illustrate that G-actin binding inhibits MRTF activity by preventing the MRTFs nuclear accumulation. In the living cells, the majority of G-actin is sequestered by G-actin binding proteins that prevent spontaneous actin polymerization. Here, we demonstrate that the most abundant G-actin sequestering protein thymosin-β4 (Tβ4) was involved in the regulation of subcellular localization and activity of MRTF-A. Tβ4 competed with MRTF-A for G-actin binding; thus, interfering with G-actin-MRTF-A complex formation. Tβ4 overexpression induced the MRTF-A nuclear accumulation and activation of MRTF-SRF signaling. The activation rate of MRTF-A by the Tβ4 mutant L17A, whose affinity for G-actin is very low, was lower than that by wild-type Tβ4. In contrast, the β-actin mutant 3DA, which has a lower affinity for Tβ4, more effectively suppressed MRTF-A activity than wild-type β-actin. Furthermore, ectopic Tβ4 increased the endogenous expression of SRF-dependent actin cytoskeletal genes. Thus, Tβ4 is an important MRTF regulator that controls the G-actin-MRTFs interaction. Copyright © 2013 Elsevier Inc. All rights reserved.

  19. Cooperative and non-cooperative conformational changes of F-actin induced by cofilin

    Energy Technology Data Exchange (ETDEWEB)

    Aihara, Tomoki; Oda, Toshiro, E-mail: toda@spring8.or.jp

    2013-05-31

    Highlights: •Mobility of MTSL attached to C374 in F-actin became high upon addition of cofilin. •Change of motility of MTSL attached to C374 with cofilin-binding was cooperative. •Mobility of MTSL attached to V43C in F-actin became high upon addition of cofilin. •Change of motility of MTSL attached to V43C with cofilin-binding was linear. -- Abstract: Cofilin is an actin-binding protein that promotes F-actin depolymerization. It is well-known that cofilin-coated F-actin is more twisted than naked F-actin, and that the protomer is more tilted. However, the means by which the local changes induced by the binding of individual cofilin proteins proceed to the global conformational changes of the whole F-actin molecule remain unknown. Here we investigated the cofilin-induced changes in several parts of F-actin, through site-directed spin-label electron paramagnetic resonance spectroscopy analyses of recombinant actins containing single reactive cysteines. We found that the global, cooperative conformational changes induced by cofilin-binding, which were detected by the spin-label attached to the Cys374 residue, occurred without the detachment of the D-loop in subdomain 2 from the neighboring protomer. The two processes of local and global changes do not necessarily proceed in sequence.

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

    Science.gov (United States)

    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.

  1. Plant vegetative and animal cytoplasmic actins share functional competence for spatial development with protists.

    Science.gov (United States)

    Kandasamy, Muthugapatti K; McKinney, Elizabeth C; Roy, Eileen; Meagher, Richard B

    2012-05-01

    Actin is an essential multifunctional protein encoded by two distinct ancient classes of genes in animals (cytoplasmic and muscle) and plants (vegetative and reproductive). The prevailing view is that each class of actin variants is functionally distinct. However, we propose that the vegetative plant and cytoplasmic animal variants have conserved functional competence for spatial development inherited from an ancestral protist actin sequence. To test this idea, we ectopically expressed animal and protist actins in Arabidopsis thaliana double vegetative actin mutants that are dramatically altered in cell and organ morphologies. We found that expression of cytoplasmic actins from humans and even a highly divergent invertebrate Ciona intestinalis qualitatively and quantitatively suppressed the root cell polarity and organ defects of act8 act7 mutants and moderately suppressed the root-hairless phenotype of act2 act8 mutants. By contrast, human muscle actins were unable to support prominently any aspect of plant development. Furthermore, actins from three protists representing Choanozoa, Archamoeba, and green algae efficiently suppressed all the phenotypes of both the plant mutants. Remarkably, these data imply that actin's competence to carry out a complex suite of processes essential for multicellular development was already fully developed in single-celled protists and evolved nonprogressively from protists to plants and animals.

  2. A function for filamentous alpha-smooth muscle actin: Retardation of motility in human breast fibroblasts

    DEFF Research Database (Denmark)

    Rønnov-Jessen, Lone; Petersen, Ole William

    1996-01-01

    .8 and 3.0 microns/h, respectively. To knock out the alpha-sm actin protein, several antisense phosphorothioate oligodeoxynucleotide (ODNs) were tested. One of these, 3'UTI, which is complementary to a highly evolutionary conserved 3' untranslated (3'UT) sequence of alpha-sm actin mRNA, was found to block...... alpha-sm actin synthesis completely without affecting the synthesis of any other proteins as analyzed by two-dimensional gel electrophoresis. Targeting by antisense 3'UTI significantly increased motility compared with the corresponding sense ODN. alpha-Sm actin inhibition also led to the formation...

  3. Diversity Networks

    Science.gov (United States)

    and professional growth of women through networking, mentoring and training. We strive to ensure that will be used. National Processing Center Seniors Leader: Jo Anne Hankins Champion: Eric Milliner NO

  4. 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.

  5. 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.

  6. Isoliquiritigenin induces growth inhibition and apoptosis through downregulating arachidonic acid metabolic network and the deactivation of PI3K/Akt in human breast cancer

    International Nuclear Information System (INIS)

    Li, Ying; Zhao, Haixia; Wang, Yuzhong; Zheng, Hao; Yu, Wei; Chai, Hongyan; Zhang, Jing; Falck, John R.; Guo, Austin M.; Yue, Jiang; Peng, Renxiu; Yang, Jing

    2013-01-01

    Arachidonic acid (AA)-derived eicosanoids and its downstream pathways have been demonstrated to play crucial roles in growth control of breast cancer. Here, we demonstrate that isoliquiritigenin, a flavonoid phytoestrogen from licorice, induces growth inhibition and apoptosis through downregulating multiple key enzymes in AA metabolic network and the deactivation of PI3K/Akt in human breast cancer. Isoliquiritigenin diminished cell viability, 5-bromo-2′-deoxyuridine (BrdU) incorporation, and clonogenic ability in both MCF-7 and MDA-MB-231cells, and induced apoptosis as evidenced by an analysis of cytoplasmic histone-associated DNA fragmentation, flow cytometry and hoechst staining. Furthermore, isoliquiritigenin inhibited mRNA expression of multiple forms of AA-metabolizing enzymes, including phospholipase A2 (PLA2), cyclooxygenases (COX)-2 and cytochrome P450 (CYP) 4A, and decreased secretion of their products, including prostaglandin E 2 (PGE 2 ) and 20-hydroxyeicosatetraenoic acid (20-HETE), without affecting COX-1, 5-lipoxygenase (5-LOX), 5-lipoxygenase activating protein (FLAP), and leukotriene B 4 (LTB 4 ). In addition, it downregulated the levels of phospho-PI3K, phospho-PDK (Ser 241 ), phospho-Akt (Thr 308 ), phospho-Bad (Ser 136 ), and Bcl-x L expression, thereby activating caspase cascades and eventually cleaving poly(ADP-ribose) polymerase (PARP). Conversely, the addition of exogenous eicosanoids, including PGE 2 , LTB 4 and a 20-HETE analog (WIT003), and caspase inhibitors, or overexpression of constitutively active Akt reversed isoliquiritigenin-induced apoptosis. Notably, isoliquiritigenin induced growth inhibition and apoptosis of MDA-MB-231 human breast cancer xenografts in nude mice, together with decreased intratumoral levels of eicosanoids and phospho-Akt (Thr 308 ). Collectively, these data suggest that isoliquiritigenin induces growth inhibition and apoptosis through downregulating AA metabolic network and the deactivation of PI3K/Akt in

  7. An imputation/copula-based stochastic individual tree growth model for mixed species Acadian forests: a case study using the Nova Scotia permanent sample plot network

    Directory of Open Access Journals (Sweden)

    John A. KershawJr

    2017-09-01

    Full Text Available Background A novel approach to modelling individual tree growth dynamics is proposed. The approach combines multiple imputation and copula sampling to produce a stochastic individual tree growth and yield projection system. Methods The Nova Scotia, Canada permanent sample plot network is used as a case study to develop and test the modelling approach. Predictions from this model are compared to predictions from the Acadian variant of the Forest Vegetation Simulator, a widely used statistical individual tree growth and yield model. Results Diameter and height growth rates were predicted with error rates consistent with those produced using statistical models. Mortality and ingrowth error rates were higher than those observed for diameter and height, but also were within the bounds produced by traditional approaches for predicting these rates. Ingrowth species composition was very poorly predicted. The model was capable of reproducing a wide range of stand dynamic trajectories and in some cases reproduced trajectories that the statistical model was incapable of reproducing. Conclusions The model has potential to be used as a benchmarking tool for evaluating statistical and process models and may provide a mechanism to separate signal from noise and improve our ability to analyze and learn from large regional datasets that often have underlying flaws in sample design.

  8. Osteogenic stimulatory conditions enhance growth and maturation of endothelial cell microvascular networks in culture with mesenchymal stem cells

    Directory of Open Access Journals (Sweden)

    Torbjorn O Pedersen

    2012-12-01

    Full Text Available To optimize culture conditions for in vitro prevascularization of tissue-engineered bone constructs, the development of organotypic blood vessels under osteogenic stimulatory conditions (OM was investigated. Coculture of endothelial cells and mesenchymal stem cells was used to assess proangiogenic effects of mesenchymal stem cells on endothelial cells. Four different culture conditions were evaluated for their effect on development of microvascular endothelial cell networks. Mineralization, deposition of extracellular matrix, and perivascular gene expression were studied in OM. After 3 days, endothelial cells established elongated capillary-like networks, and upregulated expression of vascular markers was seen. After 15 days, all parameters evaluated were significantly increased for cultures in OM. Mature networks developed in OM presented lumens enveloped by basement membrane-like collagen IV, with obvious mineralization and upregulated perivascular gene expression from mesenchymal stem cells. Our results suggest osteogenic stimulatory conditions to be appropriate for in vitro development of vascularized bone implants for tissue engineering.

  9. Altered small-world topology of structural brain networks in infants with intrauterine growth restriction and its association with later neurodevelopmental outcome.

    Science.gov (United States)

    Batalle, Dafnis; Eixarch, Elisenda; Figueras, Francesc; Muñoz-Moreno, Emma; Bargallo, Nuria; Illa, Miriam; Acosta-Rojas, Ruthy; Amat-Roldan, Ivan; Gratacos, Eduard

    2012-04-02

    Intrauterine growth restriction (IUGR) due to placental insufficiency affects 5-10% of all pregnancies and it is associated with a wide range of short- and long-term neurodevelopmental disorders. Prediction of neurodevelopmental outcomes in IUGR is among the clinical challenges of modern fetal medicine and pediatrics. In recent years several studies have used magnetic resonance imaging (MRI) to demonstrate differences in brain structure in IUGR subjects, but the ability to use MRI for individual predictive purposes in IUGR is limited. Recent research suggests that MRI in vivo access to brain connectivity might have the potential to help understanding cognitive and neurodevelopment processes. Specifically, MRI based connectomics is an emerging approach to extract information from MRI data that exhaustively maps inter-regional connectivity within the brain to build a graph model of its neural circuitry known as brain network. In the present study we used diffusion MRI based connectomics to obtain structural brain networks of a prospective cohort of one year old infants (32 controls and 24 IUGR) and analyze the existence of quantifiable brain reorganization of white matter circuitry in IUGR group by means of global and regional graph theory features of brain networks. Based on global and regional analyses of the brain network topology we demonstrated brain reorganization in IUGR infants at one year of age. Specifically, IUGR infants presented decreased global and local weighted efficiency, and a pattern of altered regional graph theory features. By means of binomial logistic regression, we also demonstrated that connectivity measures were associated with abnormal performance in later neurodevelopmental outcome as measured by Bayley Scale for Infant and Toddler Development, Third edition (BSID-III) at two years of age. These findings show the potential of diffusion MRI based connectomics and graph theory based network characteristics for estimating differences in the

  10. Growth of zinc cobaltate nanoparticles and nanorods on reduced graphene oxide porous networks toward high-performance supercapacitor electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yaling; Zhao, Changhui; Fu, Wenbin; Zhang, Zemin; Zhang, Mingxiang; Zhou, Jinyuan; Pan, Xiaojun, E-mail: xjpan@lzu.edu.cn; Xie, Erqing

    2016-05-25

    A type of composite network constructed from zinc cobaltate (ZnCo{sub 2}O{sub 4}) nanoparticles and nanorods on reduced graphene oxide (rGO) nanosheets has been prepared by a facile hydrothermal method. Transmission electron microscope results reveal that the rGO nanosheets are covered by ZnCo{sub 2}O{sub 4} nanoparticles evenly due to the abundant surface functional groups on surface of original GO, and supported by some cross-linked ZnCo{sub 2}O{sub 4} nanorods in the entire structures. With a rational combination, the composite networks present a meso-/macroporous architecture with a larger specific surface area than those of pristine ZnCo{sub 2}O{sub 4} nanorods. As expected, the prepared ZnCo{sub 2}O{sub 4}/rGO electrode exhibits improved electrochemical performances, which shows a high specific capacitance (626 F g{sup −1} at 1 A g{sup −1}), excellent rate capability (81% retention of the initial capacitance at 30 A g{sup −1}), and long-term cycling stability (99.7% retention after 3000 cycles at 10 A g{sup −1}). Such remarkable electrochemical performances of ZnCo{sub 2}O{sub 4}/rGO electrode can be due to the effective pathways for both electronic and ionic transport in these porous networks. - Highlights: • Porous ZnCo{sub 2}O{sub 4}/rGO composite networks can be prepared by a hydrothermal method. • These networks are mainly constructed from ZnCo{sub 2}O{sub 4} nanorods and rGO nanosheets. • The rGO nanosheets are uniformly covered by ZnCo{sub 2}O{sub 4} nanoparticles. • The composite networks can promote capacitive performances as electrode materials.

  11. Suppression of progranulin expression inhibits bladder cancer growth and sensitizes cancer cells to cisplatin

    OpenAIRE

    Buraschi, Simone; Xu, Shi-Qiong; Stefanello, Manuela; Moskalev, Igor; Morcavallo, Alaide; Genua, Marco; Tanimoto, Ryuta; Birbe, Ruth; Peiper, Stephen C.; Gomella, Leonard G.; Belfiore, Antonino; Black, Peter C.; Iozzo, Renato V.; Morrione, Andrea

    2016-01-01

    We have recently demonstrated a critical role for progranulin in bladder cancer. Progranulin contributes, as an autocrine growth factor, to the transformed phenotype by modulating Akt-and MAPK-driven motility, invasion and anchorage-independent growth. Progranulin also induces F-actin remodeling by interacting with the F-actin binding protein drebrin. In addition, progranulin is overexpressed in invasive bladder cancer compared to normal tissue controls, suggesting that progranulin might play...

  12. The effects of near-UV radiation on elasmobranch lens cytoskeletal actin.

    Science.gov (United States)

    Zigman, S; Rafferty, N S; Scholz, D L; Lowe, K

    1992-08-01

    The role of near-UV radiation as a cytoskeletal actin-damaging agent was investigated. Two procedures were used to analyse fresh smooth dogfish (Mustelus canis) eye lenses that were incubated for up to 22 hr in vitro, with elasmobranch Ringer's medium, and with or without exposure to a near-UV lamp (emission principally at 365 nm; irradiance of 2.5 mW cm-2). These were observed histologically using phalloidin-rhodamine specific staining and by transmission electron microscopy. In addition, solutions of purified polymerized rabbit muscle actin were exposed to the same UV conditions and depolymerization was assayed by ultracentrifugation and high-pressure liquid chromatography. While the two actins studied do differ very slightly in some amino acid sequences, they would react physically nearly identically. The results showed that dogfish lenses developed superficial opacities due to near-UV exposure. Whole mounts of lens epithelium exhibited breakdown of actin filaments in the basal region of the cells within 18 hr of UV exposure. TEM confirmed the breakdown of actin filaments due to UV exposure. SDS-PAGE and immunoblotting positively identified actin in these cells. Direct exposure of purified polymerized muscle actin in polymerizing buffer led to an increase in actin monomer of approximately 25% in the UV-exposed solutions within 3-18 hr, whether assayed by ultracentrifugation or HPLC. The above indicates that elasmobranch lens epithelial cells contain UV-labile actin filaments, and that near-UV radiation, as is present in the sunlit environment, can break down the actin structure in these cells. Furthermore, breakdown of purified polymerized muscle actin does occur due to near-UV light exposure.(ABSTRACT TRUNCATED AT 250 WORDS)

  13. Human myosin VIIa is a very slow processive motor protein on various cellular actin structures.

    Science.gov (United States)

    Sato, Osamu; Komatsu, Satoshi; Sakai, Tsuyoshi; Tsukasaki, Yoshikazu; Tanaka, Ryosuke; Mizutani, Takeomi; Watanabe, Tomonobu M; Ikebe, Reiko; Ikebe, Mitsuo

    2017-06-30

    Human myosin VIIa (MYO7A) is an actin-linked motor protein associated with human Usher syndrome (USH) type 1B, which causes human congenital hearing and visual loss. Although it has been thought that the role of human myosin VIIa is critical for USH1 protein tethering with actin and transportation along actin bundles in inner-ear hair cells, myosin VIIa's motor function remains unclear. Here, we studied the motor function of the tail-truncated human myosin VIIa dimer (HM7AΔTail/LZ) at the single-molecule level. We found that the HM7AΔTail/LZ moves processively on single actin filaments with a step size of 35 nm. Dwell-time distribution analysis indicated an average waiting time of 3.4 s, yielding ∼0.3 s -1 for the mechanical turnover rate; hence, the velocity of HM7AΔTail/LZ was extremely slow, at 11 nm·s -1 We also examined HM7AΔTail/LZ movement on various actin structures in demembranated cells. HM7AΔTail/LZ showed unidirectional movement on actin structures at cell edges, such as lamellipodia and filopodia. However, HM7AΔTail/LZ frequently missed steps on actin tracks and exhibited bidirectional movement at stress fibers, which was not observed with tail-truncated myosin Va. These results suggest that the movement of the human myosin VIIa motor protein is more efficient on lamellipodial and filopodial actin tracks than on stress fibers, which are composed of actin filaments with different polarity, and that the actin structures influence the characteristics of cargo transportation by human myosin VIIa. In conclusion, myosin VIIa movement appears to be suitable for translocating USH1 proteins on stereocilia actin bundles in inner-ear hair cells. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  14. Chronologic and actinically induced aging in human facial skin

    International Nuclear Information System (INIS)

    Gilchrest, B.A.; Szabo, G.; Flynn, E.; Goldwyn, R.M.

    1983-01-01

    Clinical and histologic stigmata of aging are much more prominent in habitually sun-exposed skin than in sun-protected skin, but other possible manifestations of actinically induced aging are almost unexplored. We have examined the interrelation of chronologic and actinic aging using paired preauricular (sun-exposed) and postauricular (sun-protected) skin specimens. Keratinocyte cultures derived from sun-exposed skin consistently had a shorter in vitro lifespan but increased plating efficiency compared with cultures derived from adjacent sun-protected skin of the same individual, confirming a previous study of different paired body sites. Electron microscopic histologic sections revealed focal abnormalities of keratinocyte proliferation and alignment in vitro especially in those cultures derived from sun-exposed skin and decreased intercellular contact in stratified colonies at late passage, regardless of donor site. One-micron histologic sections of the original biopsy specimens revealed no striking site-related keratinocyte alterations, but sun-exposed specimens had fewer epidermal Langerhans cells (p less than 0.001), averaging approximately 50 percent the number in sun-protected skin, a possible exaggeration of the previously reported age-associated decrease in this cell population. These data suggest that sun exposure indeed accelerates aging by several criteria and that, regardless of mechanism, environmental factors may adversely affect the appearance and function of aging skin in ways amenable to experimental quantitation

  15. Nano-assembly of nanodiamonds by conjugation to actin filaments.

    Science.gov (United States)

    Bradac, Carlo; Say, Jana M; Rastogi, Ishan D; Cordina, Nicole M; Volz, Thomas; Brown, Louise J

    2016-03-01

    Fluorescent nanodiamonds (NDs) are remarkable objects. They possess unique mechanical and optical properties combined with high surface areas and controllable surface reactivity. They are non-toxic and hence suited for use in biological environments. NDs are also readily available and commercially inexpensive. Here, the exceptional capability of controlling and tailoring their surface chemistry is demonstrated. Small, bright diamond nanocrystals (size ˜30 nm) are conjugated to protein filaments of actin (length ˜3-7 µm). The conjugation to actin filaments is extremely selective and highly target-specific. These unique features, together with the relative simplicity of the conjugation-targeting method, make functionalised nanodiamonds a powerful and versatile platform in biomedicine and quantum nanotechnologies. Applications ranging from using NDs as superior biological markers to, potentially, developing novel bottom-up approaches for the fabrication of hybrid quantum devices that would bridge across the bio/solid-state interface are presented and discussed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Bacterial actin MreB forms antiparallel double filaments.

    Science.gov (United States)

    van den Ent, Fusinita; Izoré, Thierry; Bharat, Tanmay Am; Johnson, Christopher M; Löwe, Jan

    2014-05-02

    Filaments of all actin-like proteins known to date are assembled from pairs of protofilaments that are arranged in a parallel fashion, generating polarity. In this study, we show that the prokaryotic actin homologue MreB forms pairs of protofilaments that adopt an antiparallel arrangement in vitro and in vivo. We provide an atomic view of antiparallel protofilaments of Caulobacter MreB as apparent from crystal structures. We show that a protofilament doublet is essential for MreB's function in cell shape maintenance and demonstrate by in vivo site-specific cross-linking the antiparallel orientation of MreB protofilaments in E. coli. 3D cryo-EM shows that pairs of protofilaments of Caulobacter MreB tightly bind to membranes. Crystal structures of different nucleotide and polymerisation states of Caulobacter MreB reveal conserved conformational changes accompanying antiparallel filament formation. Finally, the antimicrobial agents A22/MP265 are shown to bind close to the bound nucleotide of MreB, presumably preventing nucleotide hydrolysis and destabilising double protofilaments.DOI: http://dx.doi.org/10.7554/eLife.02634.001. Copyright © 2014, van den Ent et al.

  17. 5-ALA induced fluorescent image analysis of actinic keratosis

    Science.gov (United States)

    Cho, Yong-Jin; Bae, Youngwoo; Choi, Eung-Ho; Jung, Byungjo

    2010-02-01

    In this study, we quantitatively analyzed 5-ALA induced fluorescent images of actinic keratosis using digital fluorescent color and hyperspectral imaging modalities. UV-A was utilized to induce fluorescent images and actinic keratosis (AK) lesions were demarcated from surrounding the normal region with different methods. Eight subjects with AK lesion were participated in this study. In the hyperspectral imaging modality, spectral analysis method was utilized for hyperspectral cube image and AK lesions were demarcated from the normal region. Before image acquisition, we designated biopsy position for histopathology of AK lesion and surrounding normal region. Erythema index (E.I.) values on both regions were calculated from the spectral cube data. Image analysis of subjects resulted in two different groups: the first group with the higher fluorescence signal and E.I. on AK lesion than the normal region; the second group with lower fluorescence signal and without big difference in E.I. between two regions. In fluorescent color image analysis of facial AK, E.I. images were calculated on both normal and AK lesions and compared with the results of hyperspectral imaging modality. The results might indicate that the different intensity of fluorescence and E.I. among the subjects with AK might be interpreted as different phases of morphological and metabolic changes of AK lesions.

  18. Chronic actinic dermatitis - A study of clinical features

    Directory of Open Access Journals (Sweden)

    Somani Vijay

    2005-01-01

    Full Text Available Background: Chronic actinic dermatitis (CAD, one of the immune mediated photo-dermatoses, comprises a spectrum of c