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Sample records for vivo tethered toxin

  1. Rolling neutrophils form tethers and slings under physiologic conditions in vivo.

    Science.gov (United States)

    Marki, Alex; Buscher, Konrad; Mikulski, Zbigniew; Pries, Axel; Ley, Klaus

    2017-08-18

    Human and mouse neutrophils are known to form tethers when rolling on selectins in vitro. Tethers are ∼0.2 μm thin, ∼5-10 μm-long structures behind rolling cells that can swing around to form slings that serve as self-adhesive substrates. Here, we developed a mouse intravital imaging method, where the neutrophil surface is labeled by injecting fluorescently labeled mAb to Ly-6G. Venules in the cremaster muscle of live mice were imaged at a high frame rate using a confocal microscope equipped with a fast resonant scanner. We observed 270 tethers (median length 3.5 μm) and 31 slings (median length 6.9 µm) on 186 neutrophils of 15 mice. Out of 199 tether break events, 123 were followed by immediate acceleration of the rolling cell, which shows that tethers are load-bearing structures in vivo. In venules with a high wall shear stress (WSS; > 12 dyn/cm2), median rolling velocity was higher (19 μm/s), and 43% of rolling neutrophils had visible tethers. In venules with WSS < 12 dyn/cm2, only 26% of rolling neutrophils had visible tethers. We conclude that neutrophil tethers are commonly present and stabilize rolling in vivo. © Society for Leukocyte Biology.

  2. Anthrax toxin receptor 2-dependent lethal toxin killing in vivo.

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    Heather M Scobie

    2006-10-01

    Full Text Available Anthrax toxin receptors 1 and 2 (ANTXR1 and ANTXR2 have a related integrin-like inserted (I domain which interacts with a metal cation that is coordinated by residue D683 of the protective antigen (PA subunit of anthrax toxin. The receptor-bound metal ion and PA residue D683 are critical for ANTXR1-PA binding. Since PA can bind to ANTXR2 with reduced affinity in the absence of metal ions, we reasoned that D683 mutant forms of PA might specifically interact with ANTXR2. We show here that this is the case. The differential ability of ANTXR1 and ANTXR2 to bind D683 mutant PA proteins was mapped to nonconserved receptor residues at the binding interface with PA domain 2. Moreover, a D683K mutant form of PA that bound specifically to human and rat ANTXR2 mediated killing of rats by anthrax lethal toxin, providing strong evidence for the physiological importance of ANTXR2 in anthrax disease pathogenesis.

  3. Analysis of Single Locus Trajectories for Extracting In Vivo Chromatin Tethering Interactions.

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    Assaf Amitai

    2015-08-01

    Full Text Available Is it possible to extract tethering forces applied on chromatin from the statistics of a single locus trajectories imaged in vivo? Chromatin fragments interact with many partners such as the nuclear membrane, other chromosomes or nuclear bodies, but the resulting forces cannot be directly measured in vivo. However, they impact chromatin dynamics and should be reflected in particular in the motion of a single locus. We present here a method based on polymer models and statistics of single trajectories to extract the force characteristics and in particular when they are generated by the gradient of a quadratic potential well. Using numerical simulations of a Rouse polymer and live cell imaging of the MAT-locus located on the yeast Saccharomyces cerevisiae chromosome III, we recover the amplitude and the distance between the observed and the interacting monomer. To conclude, the confined trajectories we observed in vivo reflect local interaction on chromatin.

  4. Coupling of vesicle tethering and Rab binding is required for in vivo functionality of the golgin GMAP-210.

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    Sato, Keisuke; Roboti, Peristera; Mironov, Alexander A; Lowe, Martin

    2015-02-01

    Golgins are extended coiled-coil proteins believed to participate in membrane-tethering events at the Golgi apparatus. However, the importance of golgin-mediated tethering remains poorly defined, and alternative functions for golgins have been proposed. Moreover, although golgins bind to Rab GTPases, the functional significance of Rab binding has yet to be determined. In this study, we show that depletion of the golgin GMAP-210 causes a loss of Golgi cisternae and accumulation of numerous vesicles. GMAP-210 function in vivo is dependent upon its ability to tether membranes, which is mediated exclusively by the amino-terminal ALPS motif. Binding to Rab2 is also important for GMAP-210 function, although it is dispensable for tethering per se. GMAP-210 length is also functionally important in vivo. Together our results indicate a key role for GMAP-210-mediated membrane tethering in maintaining Golgi structure and support a role for Rab2 binding in linking tethering with downstream docking and fusion events at the Golgi apparatus. © 2015 Sato, Roboti, 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).

  5. Comparative in vitro and in vivo assessment of toxin neutralization by anti-tetanus toxin monoclonal antibodies

    Science.gov (United States)

    Yousefi, Mehdi; Khosravi-Eghbal, Roya; Reza Mahmoudi, Ahmad; Jeddi-Tehrani, Mahmood; Rabbani, Hodjatallah; Shokri, Fazel

    2014-01-01

    Tetanus is caused by the tetanus neurotoxin (TeNT), a 150 kDa single polypeptide molecule which is cleaved into an active two-chain molecule composed of a 50 kDa N-terminal light (L) and a 100 kDa C-terminal heavy (H) chains. Recently, extensive effort has focused on characterization of TeNT binding receptors and toxin neutralization by monoclonal antibodies (mAbs). Toxin binding inhibition and neutralization is routinely assessed either in vitro by the ganglioside GT1b binding inhibition assay or in vivo using an animal model. These two assay systems have never been compared. In the present study, we report characterization of eleven mAbs against different parts of TeNT. The toxin inhibitory and neutralization activity of the mAbs was assessed in vitro and in vivo respectively. Our data demonstrated that seven mAbs bind to fragment C of the heavy chain, two mAbs react with the light chain, one mAb recognizes both chains and one mAb reacts with neither light chain nor fragment C. Six fragment C specific mAbs were able to inhibit TeNT binding to GT1b ganglioside in vitro but three failed to neutralize the toxin in vivo. One in vitro inhibitory mAb (1F3E3) was found to synergize with the in vivo neutralizing mAbs to reduce toxin lethal activity in vivo. Sequencing of the immunoglobulin heavy and light chain variable region genes revealed that the three in vivo neutralizing mAbs were derived from a common origin. Altogether, our data suggests that fragment C specific mAbs contribute to toxin neutralization in both systems, though some of the GT1b binding inhibitory mAbs may not be able to neutralize TeNT in vivo. PMID:24126015

  6. Probing and Quantifying the Food-Borne Pathogens and Toxins: From In Vitro to In Vivo.

    Science.gov (United States)

    Liu, Jing-Min; Wang, Zhi-Hao; Ma, Hui; Wang, Shuo

    2018-02-07

    Development of real-time and in situ analytical methods for determination of food-borne pathogens and toxins ingested into the human body would be a promising research direction in the food-safety area. The present perspective starts with summarization of the up-to-date progress of the nanomaterial-assisted in vitro detection methods for pathogens and toxins and finally focuses on application of animal bioimaging to in vivo study, including prospective strategies for in vivo quantification of target pathogens or toxins and in vivo investigation of their behaviors inside the living body, with the assistance of real-time and non-invasive optical bioimaging. This perspective provides the advisory direction for food-safety research, from in vitro to in vivo, along with a prospective discussion of the further development roadmap of the food-safety detection techniques, especially the bioimaging-guided methods for investigation and mediation of the food contamination effect to human health.

  7. Mouse in Vivo Neutralization of Escherichia coli Shiga Toxin 2 with Monoclonal Antibodies

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    Larry H. Stanker

    2013-10-01

    Full Text Available Shiga toxin-producing Escherichia coli (STEC food contaminations pose serious health concerns, and have been the subject of massive food recalls. STEC has been identified as the major cause of the life-threatening complication of hemolytic uremic syndrome (HUS. Besides supportive care, there currently are no therapeutics available. The use of antibiotics for combating pathogenic E. coli is not recommended because they have been shown to stimulate toxin production. Clearing Stx2 from the circulation could potentially lessen disease severity. In this study, we tested the in vivo neutralization of Stx2 in mice using monoclonal antibodies (mAbs. We measured the biologic half-life of Stx2 in mice and determined the distribution phase or t1/2 α to be 3 min and the clearance phase or t1/2 β to be 40 min. Neutralizing mAbs were capable of clearing Stx2 completely from intoxicated mouse blood within minutes. We also examined the persistence of these mAbs over time and showed that complete protection could be passively conferred to mice 4 weeks before exposure to Stx2. The advent of better diagnositic methods and the availability of a greater arsenal of therapeutic mAbs against Stx2 would greatly enhance treatment outcomes of life threatening E. coli infections.

  8. Natural history of Helicobacter pylori VacA toxin in human gastric epithelium in vivo: vacuoles and beyond.

    Science.gov (United States)

    Necchi, Vittorio; Sommi, Patrizia; Vanoli, Alessandro; Fiocca, Roberto; Ricci, Vittorio; Solcia, Enrico

    2017-11-06

    Uptake, intracellular trafficking and pathologic effects of VacA toxin from Helicobacter pylori have been widely investigated in vitro. However, no systematic analysis investigated VacA intracellular distribution and fate in H. pylori-infected human gastric epithelium in vivo, using ultrastructural immunocytochemistry that combines precise toxin localization with analysis of the overall cell ultrastructure and intercompartimental/interorganellar relationships. By immunogold procedure, in this study we investigated gastric biopsies taken from dyspeptic patients to characterize the overall toxin's journey inside human gastric epithelial cells in vivo. Endocytic pits were found to take up VacA at sites of bacterial adhesion, leading to a population of peripheral endosomes, which in deeper (juxtanuclear) cytoplasm enlarged and fused each other to form large VacA-containing vacuoles (VCVs). These directly opened into endoplasmic reticulum (ER) cisternae, which in turn enveloped mitochondria and contacted the Golgi apparatus. In all such organelles we found toxin molecules, often coupled with structural damage. These findings suggest direct toxin transfer from VCVs to other target organelles such as ER/Golgi and mitochondria. VacA-induced cytotoxic changes were associated with the appearance of auto(phago)lysosomes containing VacA, polyubiquitinated proteins, p62/SQSTM1 protein, cathepsin D, damaged mitochondria and bacterial remnants, thus leading to persistent cell accumulation of degradative products.

  9. Tethered Lubricants

    Energy Technology Data Exchange (ETDEWEB)

    Archer, Lynden

    2010-09-15

    We have performed extensive experimental and theoretical studies of interfacial friction, relaxation dynamics, and thermodynamics of polymer chains tethered to points, planes, and particles. A key result from our tribology studies using lateral force microscopy (LFM) measurements of polydisperse brushes of linear and branched chains densely grafted to planar substrates is that there are exceedingly low friction coefficients for these systems. Specific project achievements include: (1) Synthesis of three-tiered lubricant films containing controlled amounts of free and pendent PDMS chains, and investigated the effect of their molecular weight and volume fraction on interfacial friction. (2.) Detailed studies of a family of hairy particles termed nanoscale organic hybrid materials (NOHMs) and demonstration of their use as lubricants.

  10. Role of 6-Gingerol in Reduction of Cholera Toxin Activity In Vitro and In Vivo

    Science.gov (United States)

    Saha, Pallashri; Das, Bornita

    2013-01-01

    Vibrio cholerae is one of the major bacterial pathogens responsible for the devastating diarrheal disease called cholera. Chemotherapy is often used against V. cholerae infections; however, the emergence of V. cholerae with multidrug resistance (MDR) toward the chemotherapeutic agents is a serious clinical problem. This scenario has provided us with the impetus to look into herbal remediation, especially toward blocking the action of cholera toxin (CT). Our studies were undertaken to determine the antidiarrheal potential of 6-gingerol (6G) on the basis of its effect on CT, the virulence factor secreted by V. cholerae. We report here that 6G binds to CT, hindering its interaction with the GM1 receptor present on the intestinal epithelial cells. The 50% inhibitory concentration (IC50) was determined to be 10 μg/ml. The detailed mechanistic study was conducted by enzyme-linked immunosorbent assay (ELISA), fluorescence spectroscopy, and isoelectric focusing. These results were validated with in vitro studies performed with the CHO, HeLa, and HT-29 cell lines, whereas a rabbit ileal loop assay was done to estimate the in vivo action, which confirms the efficacy of 6G in remediation of the choleragenic effects of CT. Thus, 6G can be an effective adjunctive therapy with oral rehydration solution for severe CT-mediated diarrhea. PMID:23817372

  11. Tethering a new technology

    Science.gov (United States)

    Stone, Nobie H.; Candidi, Maurizio

    1993-01-01

    In a tethered-satellite system, two satellites travelling in different orbits are forced to circle the earth in the same time period. The lower satellite is dragged by the tether to a higher orbital speed, while the upper one tends to move higher. This generates a tension which maintains the system in a stable configuration; the tether is aligned with a radius projecting outward from the earth's center. Such a system has been demonstrated by the TSS-1 tethered satellite carried by the Space Shuttle's STS-46 mission. The dynamic and the electrodynamic behavior of the system at long tether lengths were not, however, evaluated due to system malfunctions.

  12. Activation of the unfolded protein response is required for defenses against bacterial pore-forming toxin in vivo.

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    Larry J Bischof

    2008-10-01

    Full Text Available Pore-forming toxins (PFTs constitute the single largest class of proteinaceous bacterial virulence factors and are made by many of the most important bacterial pathogens. Host responses to these toxins are complex and poorly understood. We find that the endoplasmic reticulum unfolded protein response (UPR is activated upon exposure to PFTs both in Caenorhabditis elegans and in mammalian cells. Activation of the UPR is protective in vivo against PFTs since animals that lack either the ire-1-xbp-1 or the atf-6 arms of the UPR are more sensitive to PFT than wild-type animals. The UPR acts directly in the cells targeted by the PFT. Loss of the UPR leads to a normal response against unrelated toxins or a pathogenic bacterium, indicating its PFT-protective role is specific. The p38 mitogen-activated protein (MAPK kinase pathway has been previously shown to be important for cellular defenses against PFTs. We find here that the UPR is one of the key downstream targets of the p38 MAPK pathway in response to PFT since loss of a functional p38 MAPK pathway leads to a failure of PFT to properly activate the ire-1-xbp-1 arm of the UPR. The UPR-mediated activation and response to PFTs is distinct from the canonical UPR-mediated response to unfolded proteins both in terms of its activation and functional sensitivities. These data demonstrate that the UPR, a fundamental intracellular pathway, can operate in intrinsic cellular defenses against bacterial attack.

  13. Effects of Amanita phalloides toxins on insulin release: in vivo and in vitro studies.

    Science.gov (United States)

    De Carlo, Eugenio; Milanesi, Anna; Martini, Chiara; Maffei, Pietro; Tamagno, Gianluca; Parnigotto, Pier Paolo; Scandellari, Cesare; Sicolo, Nicola

    2003-08-01

    The clinical picture of Amanita phalloides poisoning includes hypoglycaemia, usually related to hepatic damage. In fact, Amanita toxins induce hepatic glycogen depletion in humans and animals. However, in animals morphological changes of pancreatic beta cells are reported, suggesting that an alteration of insulin secretion might be involved in the pathogenesis of hypoglycaemia. Therefore, we determined fasting glucose, insulin and C-peptide levels in ten patients intoxicated by Amanita phalloides and in ten control subjects. Fasting blood samples were drawn on 3 consecutive days, beginning 48-72 h after mushroom ingestion, and glucose, insulin and C-peptide concentrations were determined by routine methods. Serum glucose concentrations did not differ between poisoned subjects and controls, whereas insulin and C-peptide concentrations were significantly higher in poisoned subjects ( PAmanita toxins might play a role in the clinical context of Amanita poisoning. We demonstrate, for the first time, that alpha-amanitin induces insulin release and may exert a cytotoxic effect on beta cells.

  14. Circadian Dysfunction in Response to in Vivo Treatment with the Mitochondrial Toxin 3-Nitropropionic Acid

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    Takashi Kudo

    2013-12-01

    Full Text Available Sleep disorders are common in neurodegenerative diseases including Huntington's disease (HD and develop early in the disease process. Mitochondrial alterations are believed to play a critical role in the pathophysiology of neurodegenerative diseases. In the present study, we evaluated the circadian system of mice after inhibiting mitochondrial complex II of the respiratory chain with the toxin 3-nitropropionic acid (3-NP. We found that a subset of mice treated with low doses of 3-NP exhibited severe circadian deficit in behavior. The temporal patterning of sleep behavior is also disrupted in some mice with evidence of difficulty in the initiation of sleep behavior. Using the open field test during the normal sleep phase, we found that the 3-NP-treated mice were hyperactive. The molecular clockwork responsible for the generation of circadian rhythms as measured by PER2::LUCIFERASE was disrupted in a subset of mice. Within the SCN, the 3-NP treatment resulted in a reduction in daytime firing rate in the subset of mice which had a behavioral deficit. Anatomically, we confirmed that all of the treated mice showed evidence for cell loss within the striatum but we did not see evidence for gross SCN pathology. Together, the data demonstrates that chronic treatment with low doses of the mitochondrial toxin 3-NP produced circadian deficits in a subset of treated mice. This work does raise the possibility that the neural damage produced by mitochondrial dysfunction can contribute to the sleep/circadian dysfunction seen so commonly in neurodegenerative diseases.

  15. Tethered Spinal Cord Syndrome

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    ... SEARCH Definition Treatment Prognosis Clinical Trials Organizations Publications Definition Tethered spinal cord syndrome is a neurological disorder caused by tissue attachments that limit the movement of the spinal cord within the ...

  16. GRASP : A Multitasking Tether

    OpenAIRE

    Catherine eRabouille; Adam eLinstedt

    2016-01-01

    Originally identified as Golgi stacking factors in vitro, the Golgi reassembly stacking protein (GRASP) family has been shown to act as membrane tethers with multiple cellular roles. As an update to previous comprehensive reviews of the GRASP family (Giuliani et al., 2011; Vinke et al., 2011; Jarvela and Linstedt, 2012), we outline here the latest findings concerning their diverse roles. New insights into the mechanics of GRASP-mediated tethering come from recent crystal structures. The model...

  17. Glycerol monolaurate and dodecylglycerol effects on Staphylococcus aureus and toxic shock syndrome toxin-1 in vitro and in vivo.

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    Ying-Chi Lin

    Full Text Available Glycerol monolaurate (GML, a 12 carbon fatty acid monoester, inhibits Staphylococcus aureus growth and exotoxin production, but is degraded by S. aureus lipase. Therefore, dodecylglycerol (DDG, a 12 carbon fatty acid monoether, was compared in vitro and in vivo to GML for its effects on S. aureus growth, exotoxin production, and stability.Antimicrobial effects of GML and DDG (0 to 500 microg/ml on 54 clinical isolates of S. aureus, including pulsed-field gel electrophoresis (PFGE types USA200, USA300, and USA400, were determined in vitro. A rabbit Wiffle ball infection model assessed GML and DDG (1 mg/ml instilled into the Wiffle ball every other day effects on S. aureus (MN8 growth (inoculum 3x10(8 CFU/ml, toxic shock syndrome toxin-1 (TSST-1 production, tumor necrosis factor-alpha (TNF-alpha concentrations and mortality over 7 days. DDG (50 and 100 microg/ml inhibited S. aureus growth in vitro more effectively than GML (p<0.01 and was stable to lipase degradation. Unlike GML, DDG inhibition of TSST-1 was dependent on S. aureus growth. GML-treated (4 of 5; 80% and DDG-treated rabbits (2 of 5; 40% survived after 7 days. Control rabbits (5 of 5; 100% succumbed by day 4. GML suppressed TNF-alpha at the infection site on day 7; however, DDG did not (<10 ng/ml versus 80 ng/ml, respectively.These data suggest that DDG was stable to S. aureus lipase and inhibited S. aureus growth at lower concentrations than GML in vitro. However, in vivo GML was more effective than DDG by reducing mortality, and suppressing TNF-alpha, S. aureus growth and exotoxin production, which may reduce toxic shock syndrome. GML is proposed as a more effective anti-staphylococcal topical anti-infective candidate than DDG, despite its potential degradation by S. aureus lipase.

  18. Design of an EGFR-targeting toxin for photochemical delivery: in vitro and in vivo selectivity and efficacy.

    Science.gov (United States)

    Berstad, M B; Cheung, L H; Berg, K; Peng, Q; Fremstedal, A S V; Patzke, S; Rosenblum, M G; Weyergang, A

    2015-10-29

    The number of epidermal growth factor receptor (EGFR)-targeting drugs in the development for cancer treatment is continuously increasing. Currently used EGFR-targeted monoclonal antibodies and tyrosine kinase inhibitors have specific limitations related to toxicity and development of resistance, and there is a need for alternative treatment strategies to maximize the clinical potential of EGFR as a molecular target. This study describes the design and production of a novel EGFR-targeted fusion protein, rGel/EGF, composed of the recombinant plant toxin gelonin and EGF. rGel/EGF was custom-made for administration by photochemical internalization (PCI), a clinically tested modality for cytosolic release of macromolecular therapeutics. rGel/EGF lacks efficient mechanisms for endosomal escape and is therefore minimally toxic as monotherapy. However, PCI induces selective and efficient cytosolic release of rGel/EGF in EGFR-expressing target cells by light-directed activation of photosensitizers accumulated selectively in tumor tissue. PCI of rGel/EGF was shown to be highly effective against EGFR-expressing cell lines, including head and neck squamous cell carcinoma (HNSCC) cell lines resistant to cetuximab (Erbitux). Apoptosis, necrosis and autophagy were identified as mechanisms of action following PCI of rGel/EGF in vitro. PCI of rGel/EGF was further shown as a highly tumor-specific and potent modality in vivo, with growth inhibitory effects demonstrated on A-431 squamous cell carcinoma (SCC) xenografts and reduction of tumor perfusion and necrosis induction in SCC-026 HNSCC tumors. Considering the small amount of rGel/EGF injected per animal (0.1 mg/kg), the presented in vivo results are highly promising and warrant optimization and production of rGel/EGF for further preclinical evaluation with PCI.

  19. In vivo and in vitro toxicity of nanogold conjugated snake venom protein toxin GNP-NKCT1

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    Partha Pratim Saha

    2014-01-01

    Full Text Available Research on nanoparticles has created interest among the biomedical scientists. Nanoparticle conjugation aims to target drug delivery, increase drug efficacy and imaging for better diagnosis. Toxicity profile of the nanoconjugated molecules has not been studied well. In this communication, the toxicity profile of snake venom cytotoxin (NKCT1, an antileukemic protein toxin, was evaluated after its conjugation with gold nanoparticle (GNP-NKCT1. Gold nanoparticle conjugation with NKCT1 was done with NaBH4 reduction method. The conjugated product GNP-NKCT1 was found less toxic than NKCT1 on isolated rat lymphocyte, mice peritoneal macrophage, in culture, which was evident from the MTT/Trypan blue assay. Peritoneal mast cell degranulation was in the order of NKCT1 > GNP-NKCT1. The in vitro cardiotoxicity and neurotoxicity were increased in case of NKCT1 than GNP-NKCT1. On isolated kidney tissue, NKCT1 released significant amount of ALP and γ-GT than GNP-NKCT1. Gold nanoconjugation with NKCT1 also reduced the lethal activity in mice. In vivo acute/sub-chronic toxicity studies in mice showed significant increase in molecular markers due to NKCT1 treatment, which was reduced by gold nanoconjugation. Histopathology study showed decreased toxic effect of NKCT1 in kidney tissue after GNP conjugation. The present study confirmed that GNP conjugation significantly decreased the toxicity profile of NKCT1. Further studies are in progress to establish the molecular mechanism of GNP induced toxicity reduction.

  20. Impacts of microcystin, a cyanobacterial toxin, on laboratory rodents in vivo

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    Andrea Ziková

    2008-01-01

    Full Text Available Cyanobacterial water blooms became a global problem/issue because beside a dramatic deterioration of water quality parameters they also produce cyanobacterial toxins being harmful for animals and humans. Cyanotoxins especially the most prominent one, microcystin-LR (MC-LR, are of major concern and they have been reported to cause even death of mammals following ingestion or ingurgitation due to hepatotoxic modes of action. The aim of the recent study is to summarize briefly the impacts of microcystin on laboratory rodents, mice and rats, being used as models for other mammals including human beings. Most experimental approaches used intraperitoneal rather than oral and intratracheal application of microcystins, especially MC-LR, being the most efficient way to induce adverse impacts on different target organs. However, no matter how the exposure of rodents was performed, microcystins induced severe harmful impacts on the different target organs, preferentially the liver, for instances hemorrhages and apoptosis in liver, liver tumours, adverse effects on gut, kidney, testis and epididymis including spermatogenesis, on lung, on serum parameters and on progeny. In addition to these histological findings, microcystin was found to affect specifically biochemical parameters of target organs such as enzymes e.g. GST, CAT, GR, GPX, SOD, AST, ALT, γ-GT, protein phosphatases, SDH, SoDH and LDH or stress proteins such as HSP-70 and further parameters such as hepatic sulfhydryl content, GSH depletion, total bilirubin, urea nitrogen, and creatinine. Gene array analyses revealed that microcystin affects genes related to actin organization, cell cycle, apoptosis, cellular redox potential, cell signalling, albumin metabolism, glucose homeostasis pathway and organic anion transport polypeptide system. In combination with a further proteomics approach the proteomic analyses indicate that liver apoptosis induced by microcystin can be induced by two pathways: the

  1. Botulinum Toxin

    Science.gov (United States)

    2009-01-01

    intercostal muscle (Hilmas, unpublished data). All serotypes showed a similar ability to produce complete muscular paralysis in ex vivo human intercostal...routes of exposure include, in order of descending frequency: dysphagia, xerostomia, diplopia, dysarthria, fatigue , ptosis of the eyelids...Medical and Public Health Manage- ment. JAMA 285: 1059-70. Bakry, N., Kamata, Y., Simpson, L. (1997). Expression of botu- linum toxin binding sites in

  2. Effect of in vivo injection of cholera and pertussis toxin on glucose transport in rat skeletal muscle

    DEFF Research Database (Denmark)

    Ploug, Thorkil; Han, X; Petersen, L N

    1997-01-01

    Cholera toxin (CTX) and pertussis toxin (PTX) were examined for their ability to inhibit glucose transport in perfused skeletal muscle. Twenty-five hours after an intravenous injection of CTX, basal transport was decreased approximately 30%, and insulin- and contraction-stimulated transport...

  3. Proposed Mechanisms of Tethered Antimicrobial Peptide Chrysophsin-1 as a Function of Tether Length Using QCM-D.

    Science.gov (United States)

    Lozeau, Lindsay D; Alexander, Todd E; Camesano, Terri A

    2015-10-15

    Rising antibiotic resistance has led to a call for the development of alternative antibiotics. Antimicrobial peptides (AMPs) are promising, but their potential has not been fully explored because of toxicity and lack of stability in vivo. Multiple recent studies have focused on surface immobilization of AMPs to maximize antimicrobial activity and stability while mitigating toxicity. We covalently tethered cysteine-modified chrysophsin-1 (C-CHY1) via PEG of three molecular weights, 866, 2000, and 7500. Quartz crystal microbalance with dissipation (QCM-D) was used to characterize thickness and grafting density of tethered C-CHY1, which were related to its activity against Staphylococcus aureus and Escherichia coli and found to be important in determining mechanisms leading to activity. The PEG 866 tether promoted an antimicrobial mechanism that caused displacement of positive cations from bacterial membranes. The PEG 7500 tether maintained C-CHY1's ability to effectively form membrane pores, promoting the highest activity. When AMP was tethered with PEG 2000, antimicrobial activity was limited, apparently because neither mechanism of AMP activity was able to occur with this tether. Using QCM-D, we calculated thickness and density of PEG-tethered C-CHY1 and correlated it with antimicrobial effectiveness to determine the mechanisms by which tethered C-CHY1 acts against bacteria.

  4. GRASP: A multitasking tether

    Directory of Open Access Journals (Sweden)

    Catherine eRabouille

    2016-01-01

    Full Text Available Originally identified as Golgi stacking factors in vitro, the Golgi reassembly stacking protein (GRASP family has been shown to act as membrane tethers with multiple cellular roles. As an update to previous comprehensive reviews of the GRASP family (Vinke et al., 2011 (Giuliani et al., 2011;Jarvela and Linstedt, 2012, we outline here the latest findings concerning their diverse roles. New insights into the mechanics of GRASP-mediated tethering come from recent crystal structures. The models of how GRASP65 and GRASP55 tether membranes relate directly to their role in Golgi ribbon formation in mammalian cells and the unlinking of the ribbon at the onset of mitosis. However, it is also clear that GRASPs act outside the Golgi with roles at the ER and ER exit sites (ERES. Furthermore, the proteins of this family display other roles upon cellular stress, especially in mediating unconventional secretion of both transmembrane proteins (Golgi bypass and cytoplasmic proteins (through secretory autophagosomes.

  5. GRASP: A Multitasking Tether.

    Science.gov (United States)

    Rabouille, Catherine; Linstedt, Adam D

    2016-01-01

    Originally identified as Golgi stacking factors in vitro, the Golgi reassembly stacking protein (GRASP) family has been shown to act as membrane tethers with multiple cellular roles. As an update to previous comprehensive reviews of the GRASP family (Giuliani et al., 2011; Vinke et al., 2011; Jarvela and Linstedt, 2012), we outline here the latest findings concerning their diverse roles. New insights into the mechanics of GRASP-mediated tethering come from recent crystal structures. The models of how GRASP65 and GRASP55 tether membranes relate directly to their role in Golgi ribbon formation in mammalian cells and the unlinking of the ribbon at the onset of mitosis. However, it is also clear that GRASPs act outside the Golgi with roles at the ER and ER exit sites (ERES). Furthermore, the proteins of this family display other roles upon cellular stress, especially in mediating unconventional secretion of both transmembrane proteins (Golgi bypass) and cytoplasmic proteins (through secretory autophagosomes).

  6. Modelling Tethered Enzymatic Reactions

    Science.gov (United States)

    Solis Salas, Citlali; Goyette, Jesse; Coker-Gordon, Nicola; Bridge, Marcus; Isaacson, Samuel; Allard, Jun; Maini, Philip; Dushek, Omer

    Enzymatic reactions are key to cell functioning, and whilst much work has been done in protein interaction in cases where diffusion is possible, interactions of tethered proteins are poorly understood. Yet, because of the large role cell membranes play in enzymatic reactions, several reactions may take place where one of the proteins is bound to a fixed point in space. We develop a model to characterize tethered signalling between the phosphatase SHP-1 interacting with a tethered, phosphorylated protein. We compare our model to experimental data obtained using surface plasmon resonance (SPR). We show that a single SPR experiment recovers 5 independent biophysical/biochemical constants. We also compare the results between a three dimensional model and a two dimensional model. The work gives the opportunity to use known techniques to learn more about signalling processes, and new insights into how enzyme tethering alters cellular signalling. With support from the Mexican Council for Science and Technology (CONACyT), the Public Education Secretariat (SEP), and the Mexican National Autonomous University's Foundation (Fundacion UNAM).

  7. GRASP : A Multitasking Tether

    NARCIS (Netherlands)

    Rabouille, Catherine; Linstedt, Adam D

    2016-01-01

    Originally identified as Golgi stacking factors in vitro, the Golgi reassembly stacking protein (GRASP) family has been shown to act as membrane tethers with multiple cellular roles. As an update to previous comprehensive reviews of the GRASP family (Giuliani et al., 2011; Vinke et al., 2011;

  8. Electrodynamic Tethers for Spacecraft Propulsion

    Science.gov (United States)

    Johnson, Les

    2009-01-01

    Electrodynamic (Drag) Tether Thrust Principles: a) Uses both solar energy and consumes no propellant. b) Tether's orbital velocity v (approx. 7500 m/s) through North-pointing geomagnetic field B(sub north) (0.18 - 0.32 Gauss) induces voltage (35 - 160 V/km) in tether. c) Return current is through surrounding plasma. d) Current I produces a drag thrust force F on the tether. e) Magnetic force F from current I through insulated tether of length l: F = lI x B(sub north).

  9. Rate limit of protein elastic response is tether dependent

    Science.gov (United States)

    Berkovich, Ronen; Hermans, Rodolfo I.; Popa, Ionel; Stirnemann, Guillaume; Garcia-Manyes, Sergi; Berne, Bruce J.; Fernandez, Julio M.

    2012-01-01

    The elastic restoring force of tissues must be able to operate over the very wide range of loading rates experienced by living organisms. It is surprising that even the fastest events involving animal muscle tissues do not surpass a few hundred hertz. We propose that this limit is set in part by the elastic dynamics of tethered proteins extending and relaxing under a changing load. Here we study the elastic dynamics of tethered proteins using a fast force spectrometer with sub-millisecond time resolution, combined with Brownian and Molecular Dynamics simulations. We show that the act of tethering a polypeptide to an object, an inseparable part of protein elasticity in vivo and in experimental setups, greatly reduces the attempt frequency with which the protein samples its free energy. Indeed, our data shows that a tethered polypeptide can traverse its free-energy landscape with a surprisingly low effective diffusion coefficient Deff ∼ 1,200 nm2/s. By contrast, our Molecular Dynamics simulations show that diffusion of an isolated protein under force occurs at Deff ∼ 108 nm2/s. This discrepancy is attributed to the drag force caused by the tethering object. From the physiological time scales of tissue elasticity, we calculate that tethered elastic proteins equilibrate in vivo with Deff ∼ 104–106 nm2/s which is two to four orders magnitude smaller than the values measured for untethered proteins in bulk. PMID:22895787

  10. Emerging insights into the roles of membrane tethers from analysis of whole organisms: The tip of an iceberg?

    Directory of Open Access Journals (Sweden)

    Wei Hong eToh

    2016-02-01

    Full Text Available Membrane tethers have been identified throughout different compartments of the endomembrane system. It is now well established that a number of membrane tethers mediate docking of membrane carriers in anterograde and retrograde transport and in regulating the organization of membrane compartments. Much of our information on membrane tethers have been obtained from the analysis of individual membrane tethers in cultured cells. In the future it will be important to better appreciate the network of interactions mediated by tethers and the potential co-ordination of their collective functions in vivo. There are now a number of studies which have analyzed membrane tethers in tissues and organisms which are providing new insights into the role of this class of membrane protein at the physiological level. Here we review recent advances in the understanding of the function of membrane tethers from knock outs (or knock downs in whole organisms and from mutations in tethers associated with disease.

  11. Monoclonal Antibody and an Antibody-Toxin Conjugate to a Cell Surface Proteoglycan of Melanoma Cells Suppress in vivo Tumor Growth

    Science.gov (United States)

    Bumol, T. F.; Wang, Q. C.; Reisfeld, R. A.; Kaplan, N. O.

    1983-01-01

    A monoclonal antibody directed against a cell surface chondroitin sulfate proteoglycan of human melanoma cells, 9.2.27, and its diphtheria toxin A chain (DTA) conjugate were investigated for their effects on in vitro protein synthesis and in vivo tumor growth of human melanoma cells. The 9.2.27 IgG and its DTA conjugate display similar serological activities against melanoma target cells but only the conjugate can induce consistent in vitro inhibition of protein synthesis and toxicity in M21 melanoma cells. However, both 9.2.27 IgG and its DTA conjugate effect significant suppression of M21 tumor growth in vivo in an immunotherapy model of a rapidly growing tumor in athymic nu/nu mice, suggesting that other host mechanisms may mediate monoclonal antibody-induced tumor suppression.

  12. Use of porcine vaginal tissue ex-vivo to model environmental effects on vaginal mucosa to toxic shock syndrome toxin-1

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Catherine C.; Baccam, Mekhine [Feminine Care Global Product Stewardship, 6110 Center Hill Road, The Procter and Gamble Company, Cincinnati, OH 45224 (United States); Mantz, Mary J. [Dows Institute for Dental Research, The University of Iowa, Iowa City, IA 52242 (United States); Osborn, Thomas W.; Hill, Donna R. [Feminine Care Product Development, 6110 Center Hill Road, The Procter and Gamble Company, Cincinnati, OH 45224 (United States); Squier, Christopher A. [Dows Institute for Dental Research, The University of Iowa, Iowa City, IA 52242 (United States)

    2014-01-15

    Menstrual toxic shock syndrome (mTSS) is a rare, recognizable, and treatable disease that has been associated with tampon use epidemiologically. It involves a confluence of microbial risk factors (Staphylococcus aureus strains that produce the superantigen—TSST-1), as well as environmental characteristics of the vaginal ecosystem during menstruation and host susceptibility factors. This paper describes a series of experiments using the well-characterized model of porcine vaginal mucosa ex-vivo to assess the effect of these factors associated with tampon use on the permeability of the mucosa. The flux of radiolabeled TSST-1 and tritiated water ({sup 3}H{sub 2}O) through porcine vaginal mucosa was determined at various temperatures, after mechanical disruption of the epithelial surface by tape stripping, after treatment with surfactants or other compounds, and in the presence of microbial virulence factors. Elevated temperatures (42, 47 and 52 °C) did not significantly increase flux of {sup 3}H{sub 2}O. Stripping of the epithelial layers significantly increased the flux of labeled toxin in a dose-dependent manner. Addition of benzalkonium chloride (0.1 and 0.5%) and glycerol (4%) significantly increased the flux of {sup 3}H{sub 2}O but sodium lauryl sulfate at any concentration tested did not. The flux of the labeled toxin was significantly increased in the presence of benzalkonium chloride but not Pluronic® L92 and Tween 20 and significantly increased with addition of α-hemolysin but not endotoxin. These results show that the permeability of porcine vagina ex-vivo to labeled toxin or water can be used to evaluate changes to the vaginal environment and modifications in tampon materials, and thus aid in risk assessment. - Highlights: • Model assessed local effects of tampon use on vaginal mucosa. • Risks were evaluated using two tracers to assess permeability in an ex vivo model. • Mechanical damage to the epithelial surface increased tracer penetration.

  13. Electrodynamic Tethers for Spacecraft Propulsion

    Science.gov (United States)

    Johnson, Les; Estes, Robert D.; Lorenzini, Enrico; Martinez-Sanchez, Manuel; Sanmartin, Juan; Vas, Irwin

    1998-01-01

    Relatively short electrodynamic tethers can use solar power to 'push' against a planetary magnetic field to achieve propulsion without the expenditure of propellant. The groundwork has been laid for this type of propulsion. NASA began developing tether technology for space applications in the 1960's. Important recent milestones include retrieval of a tether in space (TSS-1, 1992), successful deployment of a 20-km-long tether in space (SEDS-1, 1993), and operation of an electrodynamic tether with tether current driven in both directions-power and thrust modes (PMG, 1993). The planned Propulsive Small Expendable Deployer System (ProSEDS) experiment will demonstrate electrodynamic tether thrust during its flight in early 2000. ProSEDS will use the flight-proven Small Expendable Deployer System (SEDS) to deploy a 5 km bare copper tether from a Delta II upper stage to achieve approximately 0.4 N drag thrust, thus deorbiting the stage. The experiment will use a predominantly 'bare' tether for current collection in lieu of the endmass collector and insulated tether approach used on previous missions. Theory and ground-based plasma chamber testing indicate that the bare tether is a highly-efficient current collector. The flight experiment is a precursor to utilization of the technology on the International Space Station for reboost application and the more ambitious electrodynamic tether upper stage demonstration mission which will be capable of orbit raising, lowering and inclination changes - all using electrodynamic thrust. In addition, the use of this type of propulsion may be attractive for future missions at Jupiter and any other planetary body with a magnetosphere.

  14. In Vitro and In Vivo Measurement of Percutaneous Penetration of Low Molecular Weight Toxins of Military Interest

    Science.gov (United States)

    1989-12-15

    results in the release of toxins. Blooms of P. brevis are responsible for massive fish kills in the Gulf of Mexico and along the Florida coast [1]. The...isolated from several Streptomyces strains (fungus- like bacteria). Teleocidin was isolated from Streptomyces medio - cidicus as a strong skin irritant and

  15. Ts8 scorpion toxin inhibits the Kv4.2 channel and produces nociception in vivo.

    Science.gov (United States)

    Pucca, Manuela Berto; Cerni, Felipe Augusto; Cordeiro, Francielle Almeida; Peigneur, Steve; Cunha, Thiago Mattar; Tytgat, Jan; Arantes, Eliane Candiani

    2016-09-01

    The venom from the scorpion Tityus serrulatus (Ts) has been extensively studied mainly because of its rich cocktail of neurotoxins. Neurotoxins are the major and the most known components based on their modulation of voltage-gated ion channels. Until now, electrophysiological studies demonstrated that the Ts venom comprises toxins that affect Nav and Kv channels. However, although many studies have been conducted in this field, many peptides from Ts venom await further studies, including Ts8 toxin. Here we report the isolation and electrophysiological study of Ts8. The toxin Ts19 Frag-II was used as negative control. Ts8 demonstrates, among 20 tested channels, to be a selective modulator of Kv4.2 channels. Based on studies investigating the involvement of Kv4.2 on controlling nociception, we further investigated the modulation of pain by Ts8. Using intraplantar injections, Ts8 induced overt nociception (licking and lifting behaviors) and decreased the mechanical nociceptive threshold (hyperalgesia). Furthermore, the hyperalgesia was prolonged when intrathecal injections were performed. Independent of the severity, most of the victims stung by Ts scorpions report an intense and persistent pain as the major manifestation. The new role of Ts8 on nociception could explain, at least partially, this phenomenon. Additionally, our study also stresses the involvement of toxins specific to Nav channels and inflammatory mediators on the Ts painful sting. This work provides useful insights for a better understanding of the prolonged and intense pain associated with Ts envenoming for the development of specific therapies. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Space Station tethered elevator system

    Science.gov (United States)

    Haddock, Michael H.; Anderson, Loren A.; Hosterman, K.; Decresie, E.; Miranda, P.; Hamilton, R.

    1989-01-01

    The optimized conceptual engineering design of a space station tethered elevator is presented. The tethered elevator is an unmanned, mobile structure which operates on a ten-kilometer tether spanning the distance between Space Station Freedom and a platform. Its capabilities include providing access to residual gravity levels, remote servicing, and transportation to any point along a tether. The report discusses the potential uses, parameters, and evolution of the spacecraft design. Emphasis is placed on the elevator's structural configuration and three major subsystem designs. First, the design of elevator robotics used to aid in elevator operations and tethered experimentation is presented. Second, the design of drive mechanisms used to propel the vehicle is discussed. Third, the design of an onboard self-sufficient power generation and transmission system is addressed.

  17. The rGel/BLyS Fusion Toxin Inhibits Diffuse Large B-cell Lymphoma Growth In Vitro and In Vivo

    Directory of Open Access Journals (Sweden)

    Mi-Ae Lyu

    2010-05-01

    Full Text Available Diffuse large B-cell lymphoma (DLBCL is an aggressive subtype of B-cell non-Hodgkin lymphoma (NHL and accounts for 30%to 40%of NHL. Molecules targeting nuclear factor-κB (NF-κB are expected to be of therapeutic value in those tumors where NF-κB seems to play a unique survival role such as activated B-cell (ABC-subtype DLBCL. We previously generated a rGel/BLyS fusion toxin for receptor-mediated delivery of the rGel toxin specifically to malignant B cells. In this study, we examined this fusion toxin for its ability to suppress DLBCL growth in vitro and in vivo. rGel/BLyS was specifically cytotoxic to DLBCL lines expressing all three BLyS receptors and constitutively active NF-κB. Treatment with rGel/BLyS induced down-regulation of the phosphorylation of inhibitory subunit of NF-κB (IκB-α, inhibition of NF-κB DNA-binding activity, and accumulation of IκB-α. In agreement with these results, we additionally found that rGel/BLyS downregulated levels of several NF-κB targets including Bcl-xL, Mcl-1, survivin, and x-chromosome linked inhibitor-of-apoptosis. Treatment also induced up-regulation of Bax and apoptosis through caspase-3 activation and poly ADP-ribose polymerase cleavage. Importantly, rGel/BLyS significantly inhibited tumor growth (P < .05 in a DLBCL xenograft model. Thus, our results indicate that rGel/BLyS is an excellent candidate for the treatment of aggressive NHLs that are both dependent on NF-κB and are resistant to conventional chemotherapeutic regimens.

  18. Stool C difficile toxin

    Science.gov (United States)

    Antibiotic associated colitis - toxin; Colitis - toxin; Pseudomembranous - toxin; Necrotizing colitis - toxin; C difficile - toxin ... not recently taken antibiotics. This condition is called pseudomembranous colitis .

  19. Modeling and Control of a Tethered Rotorcraft

    Science.gov (United States)

    2010-07-30

    compared to the tether sway and surge . This report models the tether using a chain of N bodies connected by spherical joints rather than using stiff...tether drag coefficient CS = tether damping coefficient Cv = viscous damping coefficient d = diameter of the tether En = n x n identity matrix FA...viscous damper with damping coefficient Cv. Visco-elastic line force is written in terms of components Δx, Δy, and Δz, of the difference vector formed

  20. New high-affinity monoclonal antibodies against Shiga toxin 1 facilitate the detection of hybrid Stx1/Stx2 in vivo

    Science.gov (United States)

    Background: Shiga-like toxins (Stxs) are important virulence factors in gastrointestinal infections caused by Shiga toxin-producing Eschericia coli (STEC). Stx1 is almost identical to the Shiga toxin (STx) from Shigella dysenteriae, a very prevalent disease-causing microorganism in the developing wo...

  1. In Vitro and In Vivo Measurement of Percutaneous Penetration of Low Molecular Weight Toxins of Military Interest

    Science.gov (United States)

    1990-10-21

    acetylsalicylic acid and urea (Bronaugh et al., 1982). However, it has been proposed that partition coefficients near one favor skin penetration by allowing the...Weanling pig skin was used as a model for human skin because it has similar permeability properties (3). EXPERIMENTAL METHODS MATERIALS Unlabeled PbTx-3...barrier properties of these two skin types were found to be similar (results not shown). In vivo percutaneous penetration of PbTx-3 This study was

  2. Charge-dependent translocation of Bordetella pertussis adenylate cyclase toxin into eukaryotic cells: implication for the in vivo delivery of CD8(+) T cell epitopes into antigen-presenting cells.

    Science.gov (United States)

    Karimova, G; Fayolle, C; Gmira, S; Ullmann, A; Leclerc, C; Ladant, D

    1998-10-13

    Bordetella pertussis secretes a calmodulin-activated adenylate cyclase toxin, CyaA, that is able to deliver its N-terminal catalytic domain (400-aa residues) into the cytosol of eukaryotic target cells, directly through the cytoplasmic membrane. We have previously shown that CyaA can be used as a vehicle to deliver T cell epitopes, inserted within the catalytic domain of the toxin, into antigen-presenting cells and can trigger specific class I-restricted CD8(+) cytotoxic T cell responses in vivo. Here, we constructed a series of recombinant toxins harboring at the same insertion site various peptide sequences of 11-25 amino acids, corresponding to defined CD8(+) T cell epitopes and differing in the charge of the inserted sequence. We show that inserted peptide sequences containing net negative charges (-1 or -2) decreased or completely blocked (charge of -4) the internalization of the toxin into target cells in vitro and abolished the induction of cytotoxic T cell responses in vivo. The blocking of translocation due to the inserted acidic sequences can be relieved by appropriate mutations in the flanking region of CyaA that counterbalance the inserted charges. Our data indicate that (i) the electrostatic charge of the peptides inserted within the catalytic domain of CyaA is critical for its translocation into eukaryotic cells and (ii) the delivery of T cell epitopes into the cytosol of antigen-presenting cells by recombinant CyaA toxins is essential for the in vivo stimulation of specific cytotoxic T cells. These findings will help to engineer improved recombinant CyaA vectors able to stimulate more efficiently cellular immunity.

  3. Charge-dependent translocation of Bordetella pertussis adenylate cyclase toxin into eukaryotic cells: Implication for the in vivo delivery of CD8+ T cell epitopes into antigen-presenting cells

    Science.gov (United States)

    Karimova, G.; Fayolle, C.; Gmira, S.; Ullmann, A.; Leclerc, C.; Ladant, D.

    1998-01-01

    Bordetella pertussis secretes a calmodulin-activated adenylate cyclase toxin, CyaA, that is able to deliver its N-terminal catalytic domain (400-aa residues) into the cytosol of eukaryotic target cells, directly through the cytoplasmic membrane. We have previously shown that CyaA can be used as a vehicle to deliver T cell epitopes, inserted within the catalytic domain of the toxin, into antigen-presenting cells and can trigger specific class I-restricted CD8+ cytotoxic T cell responses in vivo. Here, we constructed a series of recombinant toxins harboring at the same insertion site various peptide sequences of 11–25 amino acids, corresponding to defined CD8+ T cell epitopes and differing in the charge of the inserted sequence. We show that inserted peptide sequences containing net negative charges (−1 or −2) decreased or completely blocked (charge of −4) the internalization of the toxin into target cells in vitro and abolished the induction of cytotoxic T cell responses in vivo. The blocking of translocation due to the inserted acidic sequences can be relieved by appropriate mutations in the flanking region of CyaA that counterbalance the inserted charges. Our data indicate that (i) the electrostatic charge of the peptides inserted within the catalytic domain of CyaA is critical for its translocation into eukaryotic cells and (ii) the delivery of T cell epitopes into the cytosol of antigen-presenting cells by recombinant CyaA toxins is essential for the in vivo stimulation of specific cytotoxic T cells. These findings will help to engineer improved recombinant CyaA vectors able to stimulate more efficiently cellular immunity. PMID:9770520

  4. HLA-DR polymorphisms influence in vivo responses to staphylococcal toxic shock syndrome toxin-1 in a transgenic mouse model.

    Science.gov (United States)

    Krogman, A; Tilahun, A; David, C S; Chowdhary, V R; Alexander, M P; Rajagopalan, G

    2017-01-01

    Toxic shock syndrome toxin-1 (TSST-1) is a potent superantigen produced by Staphylococcus aureus. In addition to menstrual and nonmenstrual toxic shock syndromes, TSST-1 is also implicated in the immunopathogenesis of pneumonia, infective endocarditis, neonatal exanthematous disease, and atopic dermatitis among others. Superantigens first bind to major histocompatibility complex (MHC) class II molecules and then activate a large proportion of T cells by cross-linking their T cell receptor. As binding to MHC class II molecules is a critical step in the robust activation of the immune system by TSST-1 and other superantigens, polymorphic variations between different HLA-DR alleles could potentially influence the magnitude of immune activation and immunopathology caused by TSST-1. As TSST-1 is highly toxic to humans and given that multiple variations of alleles of HLA-DR and HLA-DQ are expressed in each individual, it is difficult to determine how HLA-DR polymorphisms quantitatively and qualitatively impact immune activation caused by TSST-1 in humans. However, such investigations can be conducted on transgenic mice lacking all endogenous MHC class II molecules and expressing specific HLA class II alleles. Therefore, transgenic mice expressing different HLA-DRB1 alleles (HLA-DRB1*15:01, HLA-DRB1*15:02, HLA-DRB1*03:01, HLA-DRB1*04:01), and sharing HLA-A1*01:01 chain, were systemically challenged with purified TSST-1 and multiple immune parameters were assessed. Among the HLA-DR alleles, mice expressing HLA-DRB1*15:01 allele elicited a significantly higher serum cytokine/chemokine response; greater splenic T cell expansion and most severe organ pathology. Our study highlights the potential utility of human leukocyte antigen (HLA) transgenic mice in understanding the impact of HLA polymorphisms on the outcomes of diseases caused by TSST-1 and other superantigens. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  5. Giardia duodenalis infection reduces granulocyte infiltration in an in vivo model of bacterial toxin-induced colitis and attenuates inflammation in human intestinal tissue.

    Directory of Open Access Journals (Sweden)

    James A Cotton

    Full Text Available Giardia duodenalis (syn. G. intestinalis, G. lamblia is a predominant cause of waterborne diarrheal disease that may lead to post-infectious functional gastrointestinal disorders. Although Giardia-infected individuals could carry as much as 106 trophozoites per centimetre of gut, their intestinal mucosa is devoid of overt signs of inflammation. Recent studies have shown that in endemic countries where bacterial infectious diseases are common, Giardia infections can protect against the development of diarrheal disease and fever. Conversely, separate observations have indicated Giardia infections may enhance the severity of diarrheal disease from a co-infecting pathogen. Polymorphonuclear leukocytes or neutrophils (PMNs are granulocytic, innate immune cells characteristic of acute intestinal inflammatory responses against bacterial pathogens that contribute to the development of diarrheal disease following recruitment into intestinal tissues. Giardia cathepsin B cysteine proteases have been shown to attenuate PMN chemotaxis towards IL-8/CXCL8, suggesting Giardia targets PMN accumulation. However, the ability of Giardia infections to attenuate PMN accumulation in vivo and how in turn this effect may alter the host inflammatory response in the intestine has yet to be demonstrated. Herein, we report that Giardia infection attenuates granulocyte tissue infiltration induced by intra-rectal instillation of Clostridium difficile toxin A and B in an isolate-dependent manner. This attenuation of granulocyte infiltration into colonic tissues paralled decreased expression of several cytokines associated with the recruitment of PMNs. Giardia trophozoite isolates that attenuated granulocyte infiltration in vivo also decreased protein expression of cytokines released from inflamed mucosal biopsy tissues collected from patients with active Crohn's disease, including several cytokines associated with PMN recruitment. These results demonstrate for the first time

  6. Giardia duodenalis Infection Reduces Granulocyte Infiltration in an In Vivo Model of Bacterial Toxin-Induced Colitis and Attenuates Inflammation in Human Intestinal Tissue

    Science.gov (United States)

    Cotton, James A.; Motta, Jean-Paul; Schenck, L. Patrick; Hirota, Simon A.; Beck, Paul L.; Buret, Andre G.

    2014-01-01

    Giardia duodenalis (syn. G. intestinalis, G. lamblia) is a predominant cause of waterborne diarrheal disease that may lead to post-infectious functional gastrointestinal disorders. Although Giardia-infected individuals could carry as much as 106 trophozoites per centimetre of gut, their intestinal mucosa is devoid of overt signs of inflammation. Recent studies have shown that in endemic countries where bacterial infectious diseases are common, Giardia infections can protect against the development of diarrheal disease and fever. Conversely, separate observations have indicated Giardia infections may enhance the severity of diarrheal disease from a co-infecting pathogen. Polymorphonuclear leukocytes or neutrophils (PMNs) are granulocytic, innate immune cells characteristic of acute intestinal inflammatory responses against bacterial pathogens that contribute to the development of diarrheal disease following recruitment into intestinal tissues. Giardia cathepsin B cysteine proteases have been shown to attenuate PMN chemotaxis towards IL-8/CXCL8, suggesting Giardia targets PMN accumulation. However, the ability of Giardia infections to attenuate PMN accumulation in vivo and how in turn this effect may alter the host inflammatory response in the intestine has yet to be demonstrated. Herein, we report that Giardia infection attenuates granulocyte tissue infiltration induced by intra-rectal instillation of Clostridium difficile toxin A and B in an isolate-dependent manner. This attenuation of granulocyte infiltration into colonic tissues paralled decreased expression of several cytokines associated with the recruitment of PMNs. Giardia trophozoite isolates that attenuated granulocyte infiltration in vivo also decreased protein expression of cytokines released from inflamed mucosal biopsy tissues collected from patients with active Crohn’s disease, including several cytokines associated with PMN recruitment. These results demonstrate for the first time that certain

  7. Giardia duodenalis infection reduces granulocyte infiltration in an in vivo model of bacterial toxin-induced colitis and attenuates inflammation in human intestinal tissue.

    Science.gov (United States)

    Cotton, James A; Motta, Jean-Paul; Schenck, L Patrick; Hirota, Simon A; Beck, Paul L; Buret, Andre G

    2014-01-01

    Giardia duodenalis (syn. G. intestinalis, G. lamblia) is a predominant cause of waterborne diarrheal disease that may lead to post-infectious functional gastrointestinal disorders. Although Giardia-infected individuals could carry as much as 106 trophozoites per centimetre of gut, their intestinal mucosa is devoid of overt signs of inflammation. Recent studies have shown that in endemic countries where bacterial infectious diseases are common, Giardia infections can protect against the development of diarrheal disease and fever. Conversely, separate observations have indicated Giardia infections may enhance the severity of diarrheal disease from a co-infecting pathogen. Polymorphonuclear leukocytes or neutrophils (PMNs) are granulocytic, innate immune cells characteristic of acute intestinal inflammatory responses against bacterial pathogens that contribute to the development of diarrheal disease following recruitment into intestinal tissues. Giardia cathepsin B cysteine proteases have been shown to attenuate PMN chemotaxis towards IL-8/CXCL8, suggesting Giardia targets PMN accumulation. However, the ability of Giardia infections to attenuate PMN accumulation in vivo and how in turn this effect may alter the host inflammatory response in the intestine has yet to be demonstrated. Herein, we report that Giardia infection attenuates granulocyte tissue infiltration induced by intra-rectal instillation of Clostridium difficile toxin A and B in an isolate-dependent manner. This attenuation of granulocyte infiltration into colonic tissues paralled decreased expression of several cytokines associated with the recruitment of PMNs. Giardia trophozoite isolates that attenuated granulocyte infiltration in vivo also decreased protein expression of cytokines released from inflamed mucosal biopsy tissues collected from patients with active Crohn's disease, including several cytokines associated with PMN recruitment. These results demonstrate for the first time that certain

  8. A novel plant toxin, persin, with in vivo activity in the mammary gland, induces Bim-dependent apoptosis in human breast cancer cells.

    Science.gov (United States)

    Butt, Alison J; Roberts, Caroline G; Seawright, Alan A; Oelrichs, Peter B; Macleod, John K; Liaw, Tracy Y E; Kavallaris, Maria; Somers-Edgar, Tiffany J; Lehrbach, Gillian M; Watts, Colin K; Sutherland, Robert L

    2006-09-01

    Phytochemicals have provided an abundant and effective source of therapeutics for the treatment of cancer. Here we describe the characterization of a novel plant toxin, persin, with in vivo activity in the mammary gland and a p53-, estrogen receptor-, and Bcl-2-independent mode of action. Persin was previously identified from avocado leaves as the toxic principle responsible for mammary gland-specific necrosis and apoptosis in lactating livestock. Here we used a lactating mouse model to confirm that persin has a similar cytotoxicity for the lactating mammary epithelium. Further in vitro studies in a panel of human breast cancer cell lines show that persin selectively induces a G2-M cell cycle arrest and caspase-dependent apoptosis in sensitive cells. The latter is dependent on expression of the BH3-only protein Bim. Bim is a sensor of cytoskeletal integrity, and there is evidence that persin acts as a microtubule-stabilizing agent. Due to the unique structure of the compound, persin could represent a novel class of microtubule-targeting agent with potential specificity for breast cancers.

  9. Enabling Tethered Exploration on Mars Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Strong science motivations exist for exploring hard to reach terrain on Mars and the leading systems proposed to do so require tethers. While tethers are used...

  10. Rationally designed chemokine-based toxin targeting the viral G protein-coupled receptor US28 potently inhibits cytomegalovirus infection in vivo

    DEFF Research Database (Denmark)

    Spiess, Katja; Jeppesen, Mads G.; Malmgaard-Clausen, Mikkel

    2015-01-01

    The use of receptor-ligand interactions to direct toxins to kill diseased cells selectively has shown considerable promise for treatment of a number of cancers and, more recently, autoimmune disease. Here we move the fusion toxin protein (FTP) technology beyond cancer/autoimmune therapeutics to t...

  11. Pre-clinical studies of toxin-specific Nanobodies: Evidence of in vivo efficacy to prevent fatal disturbances provoked by scorpion envenoming

    Energy Technology Data Exchange (ETDEWEB)

    Hmila, Issam [Laboratoire des Venins et Toxines, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis (Tunisia); Cosyns, Bernard [Laboratory of In Vivo Cellular and Molecular Imaging, Vrije Universiteit Brussel (Belgium); Tounsi, Hayfa [Service d' Anatomo-Pathologie, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis (Tunisia); Roosens, Bram; Caveliers, Vicky [Laboratory of In Vivo Cellular and Molecular Imaging, Vrije Universiteit Brussel (Belgium); Abderrazek, Rahma Ben [Laboratoire des Venins et Toxines, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis (Tunisia); Boubaker, Samir [Service d' Anatomo-Pathologie, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis (Tunisia); Muyldermans, Serge [Laboratory of Cellular and Molecular Immunology, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel (Belgium); Department of Structural Biology, VIB, Brussels (Belgium); El Ayeb, Mohamed [Laboratoire des Venins et Toxines, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis (Tunisia); Bouhaouala-Zahar, Balkiss, E-mail: balkiss.bouhaouala@pasteur.rns.tn [Laboratoire des Venins et Toxines, Institut Pasteur de Tunis, 13 Place Pasteur, BP-74, 1002 Tunis (Tunisia); Faculté de Médecine de Tunis, Université de Tunis-El Manar (Tunisia); Lahoutte, Tony [Laboratory of In Vivo Cellular and Molecular Imaging, Vrije Universiteit Brussel (Belgium)

    2012-10-15

    Scorpions represent a significant threat to humans and animals in various countries throughout the world. Recently, we introduced Nanobodies (Nbs) to combat more efficiently scorpion envenoming and demonstrated the performance of NbAahIF12 and NbAahII10 to neutralize scorpion toxins of Androctonus australis hector venom. A bispecific Nb construct (NbF12-10) comprising these two Nbs is far more protective than the classic Fab′{sub 2} based therapy and is the most efficient antivenom therapy against scorpion sting in preclinical studies. Now we investigate the biodistribution and pharmacokinetics of {sup 99m}Tc labeled Nbs by in vivo imaging in rodents and compared these data with those of the Fab′{sub 2} product (PAS). The pharmacodynamics of the Nbs was investigated in rats by in vivo echocardiography and it is shown that NbF12-10 prevents effectively the hemodynamic disturbances induced by a lethal dose of venom. Moreover, even a late injection of NbF12-10 restores the heart rate and brings the blood pressure to baseline values. Histology confirms that NbF12-10 prevents lung and heart lesions of treated mice after envenoming. In conjunction, in this preclinical study, we provide proof of concept that NbF12-10 prevents effectively the fatal disturbances induced by Androctonus venom, and that the Nanobody based therapeutic has a potential to substitute the classic Fab′{sub 2} based product as immunotherapeutic in scorpion envenoming. Further clinical study using larger cohorts of animals should be considered to confirm the full protecting potential of our NbF12-10. -- Highlights: ► Nanobody therapy prevents the hemodynamic disturbances induced by a lethal dose. ► Late injection of Nanobody restores hemodynamic parameters to baseline values. ► Nanobody therapy prevents lung and heart lesions of treated mice after envenoming. ► Labeled Nanobody and Fab’2 pharmacokinetics curves reach plateau in favour of Nanobody.

  12. Pertussis toxin

    Energy Technology Data Exchange (ETDEWEB)

    Sekura, R.D.; Moss, J.; Vaughan, M.

    1985-01-01

    This book contains 13 selections. Some of the titles are: Genetic and Functional Studies of Pertussis Toxin Substrates; Effect of Pertussis Toxin on the Hormonal Responsiveness of Different Tissues; Extracellular Adenylate Cyclase of Bordetella pertussis; and GTP-Regulatory Proteins are Introcellular Messagers: A Model for Hormone Action.

  13. Polyamine toxins

    DEFF Research Database (Denmark)

    Strømgaard, Kristian; Jensen, Lars S; Vogensen, Stine B

    2005-01-01

    Polyamine toxins, isolated from spiders and wasps, have been used as pharmacological tools for the study of ionotropic receptors, but their use have so far been hampered by their lack of selectivity. In this mini-review, we describe how careful synthetic modification of native polyamine toxins have...

  14. Botulinum toxin.

    Science.gov (United States)

    The National Institutes of Health Consensus Development Conference on Clinical Use of Botulinum Toxin brought together neurologists, ophthalmologists, otolaryngologists, speech pathologists, and other health care professionals as well as the public to address: the mechanisms of action of botulinum toxin, the indications and contraindications for botulinum toxin treatment, the general principles of technique of injection and handling for its safe and effective use, and the short-term and long-term side effects and complications of therapy. Following 2 days of presentations by experts and discussion by the audience, a consensus panel weighed the evidence and prepared their consensus statement. Among their findings, the panel recommended that (1) botulinum toxin therapy is safe and effective for treating strabismus, blepharospasm, hemifacial spasm, adductor spasmodic dysphonia, jaw-closing oromandibular dystonia, and cervical dystonia; (2) botulinum toxin is not curative in chronic neurological disorders; (3) the safety of botulinum toxin therapy during pregnancy, breast feeding, and chronic use during childhood is unknown; (4) the long-term effects of chronic treatment with botulinum toxin remain unknown; and (5) botulinum toxin should be administered by committed interdisciplinary teams of physicians and related health care professionals with appropriate instrumentation. The full text of the consensus panel's statement follows.

  15. Tether dynamics and control results for tethered satellite system's initial flight

    Science.gov (United States)

    Chapel, Jim D.; Flanders, Howard

    The recent Tethered Satellite System-1 (TSS-1) mission has provided a wealth of data concerning the dynamics of tethered systems in space and has demonstrated the effectiveness of operational techniques designed to control these dynamics. In this paper, we review control techniques developed for managing tether dynamics, and discuss the results of using these techniques for the Tethered Satellite System's maiden flight on STS-46. In particular, the flight results of controlling libration dynamics, string dynamics, and slack tether are presented. These results show that tether dynamics can be safely managed. The overall stability of the system was found to be surprisingly good even at relatively short tether lengths. In fact, the system operated in passive mode at a tether length of 256 meters for over 9 hours. Only monitoring of the system was required during this time. Although flight anomalies prevented the planned deployment to 20 km, the extended operations at shorter tether lengths have proven the viability of using tethers in space. These results should prove invaluable in preparing for future missions with tethered objects in space.

  16. Hypervelocity impact experiments on tether materials

    Science.gov (United States)

    Sabath, D.; Paul, K. G.

    Tethered systems are new and exciting means for various applications, such as the re-entry of small payloads from the space station. Due to payload mass constraints of the launch vehicle, the mass of the tethered system should be minimised. Therefore, fibres are the choice for tether materials. The probability of a severe impact into the tether is very high due its large surface area despite its small diameter. Hence, the risk of an impact of a micrometeoroid or a space debris particle cutting the tether should be investigated prior to flight. This work reports first observations of hypervelocity impact experiments on three different braided materials used for tether applications. The tether samples -- Dyneema, Kevlar and Spectra -- were tested using the plasma drag accelerator (PDA) facility of the Fachgebiet Raumfahrttechnik (LRT), Technische Universität München (TUM). An overview of the morphology of such impacts is presented. The extent of damage is compared to other materials commonly found on spacecraft. A risk assessment of an impact cutting the tether with current meteoroid and debris models and data from LDEF, Eureca and HST solar arrays, is also given.

  17. Modeling and position control of tethered octocopters

    Directory of Open Access Journals (Sweden)

    de Castro Davi Ferreira

    2016-01-01

    Full Text Available This work presents the modeling and control of a multirotor aerial vehicle with tethered configuration. It is considered an octocopter with a saturated proportional-plus-derivative position control. A viscoelastic model is considered for the tether, which has a tension control. Numerical simulations are carried out to compare the performance of the tethred configuration with the vehicle in free flight.

  18. Mobile tethering: Overview, perspectives and challengess

    NARCIS (Netherlands)

    Constantinescu, M.; Onur, E.; Durmus, Y.; Nikou, S.; Reuver, M. de; Bouwman, H.; Djurica, M.; Glatz, P.M.

    2014-01-01

    Purpose: The purpose of this paper is to analyze mobile tethering from technological and social perspectives. Mobile tethering allows us to share cellular data connection with others over WiFi, Bluetooth or USB. Although the technology is ready and has promising outcomes, service providers and the

  19. BOTULINUM TOXIN

    Science.gov (United States)

    Nigam, P K; Nigam, Anjana

    2010-01-01

    Botulinum toxin, one of the most poisonous biological substances known, is a neurotoxin produced by the bacterium Clostridium botulinum. C. botulinum elaborates eight antigenically distinguishable exotoxins (A, B, C1, C2, D, E, F and G). All serotypes interfere with neural transmission by blocking the release of acetylcholine, the principal neurotransmitter at the neuromuscular junction, causing muscle paralysis. The weakness induced by injection with botulinum toxin A usually lasts about three months. Botulinum toxins now play a very significant role in the management of a wide variety of medical conditions, especially strabismus and focal dystonias, hemifacial spasm, and various spastic movement disorders, headaches, hypersalivation, hyperhidrosis, and some chronic conditions that respond only partially to medical treatment. The list of possible new indications is rapidly expanding. The cosmetological applications include correction of lines, creases and wrinkling all over the face, chin, neck, and chest to dermatological applications such as hyperhidrosis. Injections with botulinum toxin are generally well tolerated and side effects are few. A precise knowledge and understanding of the functional anatomy of the mimetic muscles is absolutely necessary to correctly use botulinum toxins in clinical practice. PMID:20418969

  20. Botulinum toxin

    Directory of Open Access Journals (Sweden)

    Nigam P

    2010-01-01

    Full Text Available Botulinum toxin, one of the most poisonous biological substances known, is a neurotoxin produced by the bacterium Clostridium botulinum. C. botulinum elaborates eight antigenically distinguishable exotoxins (A, B, C 1 , C 2 , D, E, F and G. All serotypes interfere with neural transmission by blocking the release of acetylcholine, the principal neurotransmitter at the neuromuscular junction, causing muscle paralysis. The weakness induced by injection with botulinum toxin A usually lasts about three months. Botulinum toxins now play a very significant role in the management of a wide variety of medical conditions, especially strabismus and focal dystonias, hemifacial spasm, and various spastic movement disorders, headaches, hypersalivation, hyperhidrosis, and some chronic conditions that respond only partially to medical treatment. The list of possible new indications is rapidly expanding. The cosmetological applications include correction of lines, creases and wrinkling all over the face, chin, neck, and chest to dermatological applications such as hyperhidrosis. Injections with botulinum toxin are generally well tolerated and side effects are few. A precise knowledge and understanding of the functional anatomy of the mimetic muscles is absolutely necessary to correctly use botulinum toxins in clinical practice.

  1. New high-affinity monoclonal antibodies against Shiga toxin 1 facilitate the detection of hybrid Stx1/Stx2 in vivo.

    Directory of Open Access Journals (Sweden)

    Craig Skinner

    Full Text Available BACKGROUND: Shiga toxin-producing E. coli (STEC are a group of common and potentially deadly intestinal pathogens expressing Shiga toxin (Stx as a primary virulence factor. Of the two types of Stx, Stx2 is responsible for more severe symptoms during infection, while Stx1 is almost identical to the Shiga toxin from Shigella dysenteriae, a ubiquitous pathogen in developing countries. Although antibodies against Stx1 have been reported, few have reached the affinity needed for assembling highly sensitive immunoassays. Sensitive and affordable immunoassays for Stx1 and Stx2 could help improve detection of STEC in livestock, food, the environment, and in clinical samples resulting in improved food safety and human health. METHOD AND FINDINGS: Three new monoclonal antibodies (mAbs against the B subunit of Stx1 were generated using recombinant toxoid Stx1E167Q and hybridoma technology. These new mAbs recognize all subtypes of Stx1, but do not cross-react with any subtype of Stx2. In addition, they exhibited the ability to neutralize Stx1 toxicity in Vero cell assays. An optimized sandwich ELISA using of a pair of these mAbs had a limit of detection of 8.7 pg/mL, which is superior to any existing assay of this kind. Using one of these Stx1 mAbs in concert with Stx2 mAbs, the presence of hybrid Stx1/Stx2 toxin in the culture media of STEC strains that express both Stx1 and Stx2 was demonstrated. CONCLUSIONS: These new mAbs provide a mix of availability, utility, versatility, and most importantly, increased sensitivity for detection of Stx1. There are numerous potential applications for these mAbs, including low-cost detection assays and therapeutic use. Analysis of hybrid Stx1/2 could provide new insights on the structure, activity, and cellular targets of Shiga toxins.

  2. Electrodynamic tethers for energy conversion

    Science.gov (United States)

    Nobles, W.

    1986-01-01

    Conductive tethers have been proposed as a new method for converting orbital mechanical energy into electrical power for use on-board a satellite (generator mode) or conversely (motor mode) as a method of providing electric propulsion using electrical energy from the satellite. The operating characteristics of such systems are functionally dependent on orbit altitude and inclination. Effects of these relationships are examined to determine acceptable regions of application. To identify system design considerations, a specific set of system performance goals and requirements are selected. The case selected is for a 25 kW auxiliary power system for use on Space Station. Appropriate system design considerations are developed, and the resulting system is described.

  3. Golgi GRASPs: moonlighting membrane tethers

    Directory of Open Access Journals (Sweden)

    Jarvela T

    2012-05-01

    Full Text Available Timothy Jarvela, Adam D LinstedtDepartment of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, USAAbstract: The identification of mammalian Golgi reassembly stacking proteins (GRASPs 15 years ago was followed by experiments implicating them in diverse functions, including two differing structural roles in Golgi biogenesis and at least two distinct roles in the secretion of proteins. GRASP55 and GRASP65 are localized to cis and medial/trans Golgi cisternae, respectively. They are both required for stacking of Golgi membranes in a Golgi reassembly assay. Depletion of either GRASP from cultured cells prevents the linking of Golgi membranes into their normal ribbon-like network. While GRASPs are not required for transport of secretory cargo per se, they are required for ER-to-Golgi transport of certain specific cargo, such as those containing a C-terminal valine motif. Surprisingly, GRASPs also promote secretion of cargo by the so-called unconventional secretory pathway, which bypasses the Golgi apparatus where the GRASPs reside. Furthermore, regulation of GRASP activity is now recognized for its connections to cell cycle control, development, and disease. Underlying these diverse activities is the structurally conserved N-terminal GRASP domain whose crystal structure was recently determined. It consists of a tandem array of atypical PSD95–DlgA–Zo–1 (PDZ domains, which are well-known protein–protein interaction motifs. The GRASP PDZ domains are used to localize the proteins to the Golgi as well as GRASP-mediated membrane tethering and cargo interactions. These activities are regulated, in part, by phosphorylation of the large unstructured C-terminal domain.Keywords: GRASP, review, membrane, tether, PDZ domain, secretory chaperone, unconventional secretion

  4. The space station tethered elevator system

    Science.gov (United States)

    Anderson, Loren A.

    1989-01-01

    The optimized conceptual engineering design of a space station tethered elevator is presented. The elevator is an unmanned mobile structure which operates on a ten kilometer tether spanning the distance between the Space Station and a tethered platform. Elevator capabilities include providing access to residual gravity levels, remote servicing, and transportation to any point along a tether. The potential uses, parameters, and evolution of the spacecraft design are discussed. Engineering development of the tethered elevator is the result of work conducted in the following areas: structural configurations; robotics, drive mechanisms; and power generation and transmission systems. The structural configuration of the elevator is presented. The structure supports, houses, and protects all systems on board the elevator. The implementation of robotics on board the elevator is discussed. Elevator robotics allow for the deployment, retrieval, and manipulation of tethered objects. Robotic manipulators also aid in hooking the elevator on a tether. Critical to the operation of the tethered elevator is the design of its drive mechanisms, which are discussed. Two drivers, located internal to the elevator, propel the vehicle along a tether. These modular components consist of endless toothed belts, shunt-wound motors, regenerative power braking, and computer controlled linear actuators. The designs of self-sufficient power generation and transmission systems are reviewed. Thorough research indicates all components of the elevator will operate under power provided by fuel cells. The fuel cell systems will power the vehicle at seven kilowatts continuously and twelve kilowatts maximally. A set of secondary fuel cells provides redundancy in the unlikely event of a primary system failure. Power storage exists in the form of Nickel-Hydrogen batteries capable of powering the elevator under maximum loads.

  5. Tethered satellite thermal design and test

    Science.gov (United States)

    Chapter, John J.

    1991-01-01

    The Tethered Satellite System (TSS) is the first Shuttle Orbiter mission that investigates electrodynamic phenomenon of a 20 km conductive tether, in space. The TSS Mission is planned for January 1992. The 'Deployer' that provides the mechanisms that control a tethered satellite is mounted on a Spacelab Pallet. The Deployer thermal design uses Multilayer Insulation (MLI), heaters, and the Spacelab payload freon loop. The pallet and Deployer are isolated from the space thermal environment with MLI that forms an enclosure that is a unique part of the thermal design. This paper describes the TSS thermal design, presents the analysis approach, and details the Deployer thermal balance test.

  6. A biomimetic nanosponge that absorbs pore-forming toxins

    Science.gov (United States)

    Hu, Che-Ming J.; Fang, Ronnie H.; Copp, Jonathan; Luk, Brian T.; Zhang, Liangfang

    2013-05-01

    Detoxification treatments such as toxin-targeted anti-virulence therapy offer ways to cleanse the body of virulence factors that are caused by bacterial infections, venomous injuries and biological weaponry. Because existing detoxification platforms such as antisera, monoclonal antibodies, small-molecule inhibitors and molecularly imprinted polymers act by targeting the molecular structures of toxins, customized treatments are required for different diseases. Here, we show a biomimetic toxin nanosponge that functions as a toxin decoy in vivo. The nanosponge, which consists of a polymeric nanoparticle core surrounded by red blood cell membranes, absorbs membrane-damaging toxins and diverts them away from their cellular targets. In a mouse model, the nanosponges markedly reduce the toxicity of staphylococcal alpha-haemolysin (α-toxin) and thus improve the survival rate of toxin-challenged mice. This biologically inspired toxin nanosponge presents a detoxification treatment that can potentially treat a variety of injuries and diseases caused by pore-forming toxins.

  7. Dynamics analysis of electrodynamic satellite tethers. Equations of motion and numerical solution algorithms for the tether

    Science.gov (United States)

    Nacozy, P. E.

    1984-01-01

    The equations of motion are developed for a perfectly flexible, inelastic tether with a satellite at its extremity. The tether is attached to a space vehicle in orbit. The tether is allowed to possess electrical conductivity. A numerical solution algorithm to provide the motion of the tether and satellite system is presented. The resulting differential equations can be solved by various existing standard numerical integration computer programs. The resulting differential equations allow the introduction of approximations that can lead to analytical, approximate general solutions. The differential equations allow more dynamical insight of the motion.

  8. Numerical modelling of elastic space tethers

    DEFF Research Database (Denmark)

    Kristiansen, Kristian Uldall; Palmer, P. L.; Roberts, R. M.

    2012-01-01

    In this paper the importance of the ill-posedness of the classical, non-dissipative massive tether model on an orbiting tether system is studied numerically. The computations document that via the regularisation of bending resistance a more reliable numerical integrator can be produced. Furthermore......, the numerical experiments of an orbiting tether system show that bending may introduce significant forces in some regions of phase space. Finally, numerical evidence for the existence of an almost invariant slow manifold of the singularly perturbed, regularised, non-dissipative massive tether model is provided....... It is also shown that on the slow manifold the dynamics of the satellites are well-approximated by the finite dimensional slack-spring model....

  9. Tether as a dynamic transmission line

    Science.gov (United States)

    Gullahorn, Gordon E.; Hohlfeld, Robert G.

    1988-01-01

    The effect of longitudinal impulses on a satellite when a continuum tether from the Shuttle or Space Station is included is investigated. It is demonstrated that, taking the continuum nature of the tether into account, the sharp onset of a forcing impulse at the Shuttle end is perceived on board the satellite. The magnitude of the satellite response is diminished from that of the forcing impulse, and the response exhibits a broadened exponential tailoff. These are due primarily to the coupling between the tether and the satellite and its influence on an impinging impulsive wave, and not on the whole system as in the spring-mass model. The full impulse response function can be quite complex, showing repeated impulses as the tether wave bounces back and forth between the satellite and Shuttle, and having a different shape at each impingement on the satellite.

  10. FCAPD Protective Coating for Space Tethers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Alameda Applied Sciences Corporation (AASC) proposes to demonstrate extended service lifetime of space tethers in the Low Earth Orbit (LEO) environment by using...

  11. [Phalloidian toxins].

    Science.gov (United States)

    Larcan, A; Lamarche, M; Lambert, H

    1979-01-01

    The phalloidian toxins are very complex. The classification proposed by Wieland distinguishes between the various amatoxins and phallotoxins. The authors study successively: Methods of isolation, the general structure and chemical composition, their localization and concentration in mushrooms. This is an analytical study of the phallotoxins and amadoxins. Various experimental intoxication protocols using total extracts of the toxins purified with different doses and different animals have revealed the main signs of experimental intoxication with phallotoxins. This is characterized especially by hepatic and renal lesions. The phallotoxins have a more specific action on the cell membrane and metabolism. The amatoxins have a more specific action on the cell nucleus and protein synthesis. The action on DNA dependent RNA polymerases is particularly characteristic.

  12. Developing New Tools for the in vivo Generation/Screening of Cyclic Peptide Libraries. A New Combinatorial Approach for the Detection of Bacterial Toxin Inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Camarero, J A

    2006-11-28

    A new combinatorial approach for the biosynthesis and screening of small drug-like toxin inhibitors inside living cells is presented. This approach has been initially used as proof of principle for finding inhibitors against the LF factor from Bacillus anthracis. Key to our ''living combinatorial'' approach is the use of a living cell as a micro-chemical factory for both synthesis and screening of potential inhibitors for a given molecular recognition event (see Scheme 1). This powerful technique posses the advantage that both processes synthesis and screening happen inside the cell thus accelerating the whole screening/selection process.

  13. Development of the flight tether for ProSEDS

    Science.gov (United States)

    Curtis, Leslie; Vaughn, Jason; Welzyn, Ken; Carroll, Joe

    2002-01-01

    The Propulsive Small Expendable Deployer System (ProSEDS) space experiment will demonstrate the use of an electrodynamic tether propulsion system to generate thrust in space by decreasing the orbital altitude of a Delta II Expendable Launch Vehicle second stage. ProSEDS will use the flight-proven Small Expendable Deployer System to deploy a newly designed and developed tether which will provide tether generated drag thrust of ~0.4 N. The development and production of very long tethers with specific properties for performance and survivability will be required to enable future tether missions. The ProSEDS tether design and the development process may provide some lessons learned for these future missions. The ProSEDS system requirements drove the design of the tether to have three different sections of tether each serving a specialized purpose. The tether is a total of 15 kilometers long: 10 kilometers of a non-conductive Dyneema lead tether; 5 km of CCOR conductive coated wire; and 220 meters of insulated wire with a protective Kevlar overbraid. Production and joining of long tether lengths involved many development efforts. Extensive testing of tether materials including ground deployment of the full-length ProSEDS tether was conducted to validate the tether design and performance before flight. .

  14. Laser-induced tether & spouts

    Science.gov (United States)

    Delville, Jean-Pierre

    2004-03-01

    Since the seminal work of Ashkin and Dziedzic on the deformation of transparent free-surfaces induced by laser waves, the optical radiation pressure has been recognized as very appealing to locally manipulate liquid interfaces. While the first developments essentially exploited the interface bending for optical applications in adaptive lensing, radiation pressure effects have recently received renewed interest in connection with nano/bio-technologies, as a non-intrusive tool to probe microscopic surface properties of soft materials including cell stretching, or membrane and interface visco-elasticity. However, as the optical bending of a fluid interface is generally weak, these experiments were essentially limited to the linear regime in deformation. Non-linear behaviors can nevertheless be investigated using very soft transparent liquid interfaces to enhance light effects. At large optical excitation, either a large stable tether is formed, or else a break-up of the interface occurs, depending on the direction of the beam propagation. Physically, the reason for this asymmetry can be traced to whether total reflection of light at deformed interface occurs or not. Laser-induced interface instability leads to the formation of a stationary beam-centered liquid micro-jet emitting droplets, which anticipates the bases for new applications in micro-fluidics and liquid micro-spraying. On the other hand, the method can be extended to form microscopic liquid bridges of very large aspect ratio, because optical forces are able to overcome the fundamental Rayleigh-Plateau limitation. As laser-induced micro-jets, laser-sustained liquid columns are tunable in aspect ratio and adjustable in direction. Consequently, the applications range of "opto-hydrodynamic" interface instability is wide, going from micro-optics (i.e. liquid columns also behave as soft optical fibers) to micro-fluidics, as fluid transfer can be optically monitored and directed in three dimensions.

  15. A Child with Tethered Cord Syndrome

    Directory of Open Access Journals (Sweden)

    Bekti Safarini

    2012-06-01

    Full Text Available Tethered Cord Syndome (TCS refers to a group of neurological disorders related to malformations of the spinal cord, pulling of the spinal cord at the base of spinal canal. Tethered cord syndrome can be seen at any age but most often during childhood. A few children complain of diffuse pain in lower extremitiesor urological symptoms, 20% - 30 % of the patients will have a neurogenic bladder. A 9 years old girl, complained to have a flank pain and eneuresis. A mass is palpable at right flank. Ultrasound revealed duplex hydronephrosis and hydroureter with trabeculated bladder. Voiding Cystouretrography showed grade V vesicoureteral reflux (VUR and neurogenic bladder appearance. Lumbosacral MRI demonstrated tethered cord with adjacent lipoma and spina bifida (Sains Medika, 4(1:89-96.

  16. Tethers in Space : A propellantless propulsion in-orbit demonstration

    NARCIS (Netherlands)

    Kruijff, M.

    2011-01-01

    Space tethers are cables that connect satellites or other endmasses in orbit. The emptiness of space and the near-weightlessness there make it possible to deploy very long and thin tethers. By exploiting basic principles of physics, tethers can provide propellantless propulsion and enable unique

  17. Dynamics and offset control of tethered space-tug system

    Science.gov (United States)

    Zhang, Jingrui; Yang, Keying; Qi, Rui

    2018-01-01

    Tethered space-tug system is regarded as one of the most promising active debris removal technologies to effectively decrease the steep increasing population of space debris. In order to suppress the spin of space debris, single-tethered space-tug system is employed by regulating the tether. Unfortunately, this system is underactuated as tether length is the only input, and there are two control objectives: the spinning debris and the vibration of tether. Thus, it may suffer great oscillations and result in failure in space debris removal. This paper presents the study of attitude stabilization of the single-tethered space-tug system using not only tether length but also the offset of tether attachment point to suppress the spin of debris, so as to accomplish the space debris removal mission. Firstly, a precise 3D mathematical model in which the debris and tug are both treated as rigid bodies is developed to study the dynamical evolution of the tethered space-tug system. The relative motion equation of the system is described using Lagrange method. Secondly, the dynamic characteristic of the system is analyzed and an offset control law is designed to stabilize the spin of debris by exploiting the variation of tether offset and the regulation of tether length. Besides, an estimation formula is proposed to evaluate the capability of tether for suppressing spinning debris. Finally, the effectiveness of attitude stabilization by the utilization of the proposed scheme is demonstrated via numerical case studies.

  18. Shiga toxin-producing Escherichia coli (STEC) O22:H8 isolated from cattle reduces E. coli O157:H7 adherence in vitro and in vivo.

    Science.gov (United States)

    Martorelli, L; Albanese, A; Vilte, D; Cantet, R; Bentancor, A; Zolezzi, G; Chinen, I; Ibarra, C; Rivas, M; Mercado, E C; Cataldi, A

    2017-09-01

    Shiga toxin-producing Escherichia coli (STEC) are a group of bacteria responsible for food-associated diseases. Clinical features include a wide range of symptoms such as diarrhea, hemorrhagic colitis and the hemolytic uremic syndrome (HUS), a life-threatening condition. Our group has observed that animals naturally colonized with STEC strains of unknown serotype were not efficiently colonized with E. coli O157:H7 after experimental infection. In order to assess the basis of the interference, three STEC strains were isolated from STEC persistently-colonized healthy cattle from a dairy farm in Buenos Aires, Argentina. The three isolated strains are E. coli O22:H8 and carry the stx1 and stx2d genes. The activatable activity of Stx2d was demonstrated in vitro. The three strains carry the adhesins iha, ehaA and lpf O113 . E. coli O22:H8 formed stronger biofilms in abiotic surface than E. coli O157:H7 (eae+, stx2+) and displayed a more adherent phenotype in vitro towards HeLa cells. Furthermore, when both serotypes were cultured together O22:H8 could reduce O157:H7 adherence in vitro. When calves were intragastrically pre-challenged with 10 8 CFU of a mixture of the three STEC strains and two days later challenged with the same dose of the strain E. coli O157:H7 438/99, the shedding of the pathogen was significantly reduced. These results suggest that E. coli O22:H8, a serotype rarely associated with human illness, might compete with O157:H7 at the bovine recto-anal junction, making non-O157 carrying-calves less susceptible to O157:H7 colonization and shedding of the bacteria to the environment. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Tethered spacecraft in asteroid gravitational environment

    Science.gov (United States)

    Burov, Alexander A.; Guerman, Anna D.; Kosenko, Ivan I.; Nikonov, Vasily I.

    2018-02-01

    Relative equilibria of a pendulum attached to the surface of a uniformly rotating celestial body are considered. The locations of the tether anchor that correspond to a given spacecraft position are defined. The domains, where the spacecraft can be held with the help of such a pendulum, are also described. Stability of the found relative equilibria is studied.

  20. Ionic-Liquid-Tethered Nanoparticles: Hybrid Electrolytes

    KAUST Repository

    Moganty, Surya S.

    2010-10-22

    A new class of solventless electrolytes was created by tethering ionic liquids to hard inorganic ZrO2 nanostructures (see picture; NIM=nanoscale ionic material). These hybrid fluids exhibit exceptional redox stability windows, excellent thermal stability, good lithium transference numbers, long-term interfacial stability in the presence of a lithium anode and, when doped with lithium salt, reasonable ionic conductivities.

  1. Tethered "kiteplane" design for the Laddermill project

    NARCIS (Netherlands)

    Breukels, J.; Ockels, W.

    2005-01-01

    The Laddermill is an innovative concept for generating energy from wind using large kite-like wings on a tether. The wings are able to fly in both the regime of airplanes and kites. We therefore call these structures "kiteplanes". By providing a recurring motion with a large lift during ascending

  2. Nanomechanics of HaloTag tethers.

    Science.gov (United States)

    Popa, Ionel; Berkovich, Ronen; Alegre-Cebollada, Jorge; Badilla, Carmen L; Rivas-Pardo, Jaime Andrés; Taniguchi, Yukinori; Kawakami, Masaru; Fernandez, Julio M

    2013-08-28

    The active site of the Haloalkane Dehydrogenase (HaloTag) enzyme can be covalently attached to a chloroalkane ligand providing a mechanically strong tether, resistant to large pulling forces. Here we demonstrate the covalent tethering of protein L and I27 polyproteins between an atomic force microscopy (AFM) cantilever and a glass surface using HaloTag anchoring at one end and thiol chemistry at the other end. Covalent tethering is unambiguously confirmed by the observation of full length polyprotein unfolding, combined with high detachment forces that range up to ∼2000 pN. We use these covalently anchored polyproteins to study the remarkable mechanical properties of HaloTag proteins. We show that the force that triggers unfolding of the HaloTag protein exhibits a 4-fold increase, from 131 to 491 pN, when the direction of the applied force is changed from the C-terminus to the N-terminus. Force-clamp experiments reveal that unfolding of the HaloTag protein is twice as sensitive to pulling force compared to protein L and refolds at a slower rate. We show how these properties allow for the long-term observation of protein folding-unfolding cycles at high forces, without interference from the HaloTag tether.

  3. Yielding elastic tethers stabilize robust cell adhesion.

    Directory of Open Access Journals (Sweden)

    Matt J Whitfield

    2014-12-01

    Full Text Available Many bacteria and eukaryotic cells express adhesive proteins at the end of tethers that elongate reversibly at constant or near constant force, which we refer to as yielding elasticity. Here we address the function of yielding elastic adhesive tethers with Escherichia coli bacteria as a model for cell adhesion, using a combination of experiments and simulations. The adhesive bond kinetics and tether elasticity was modeled in the simulations with realistic biophysical models that were fit to new and previously published single molecule force spectroscopy data. The simulations were validated by comparison to experiments measuring the adhesive behavior of E. coli in flowing fluid. Analysis of the simulations demonstrated that yielding elasticity is required for the bacteria to remain bound in high and variable flow conditions, because it allows the force to be distributed evenly between multiple bonds. In contrast, strain-hardening and linear elastic tethers concentrate force on the most vulnerable bonds, which leads to failure of the entire adhesive contact. Load distribution is especially important to noncovalent receptor-ligand bonds, because they become exponentially shorter lived at higher force above a critical force, even if they form catch bonds. The advantage of yielding is likely to extend to any blood cells or pathogens adhering in flow, or to any situation where bonds are stretched unequally due to surface roughness, unequal native bond lengths, or conditions that act to unzip the bonds.

  4. Yielding Elastic Tethers Stabilize Robust Cell Adhesion

    Science.gov (United States)

    Whitfield, Matt J.; Luo, Jonathon P.; Thomas, Wendy E.

    2014-01-01

    Many bacteria and eukaryotic cells express adhesive proteins at the end of tethers that elongate reversibly at constant or near constant force, which we refer to as yielding elasticity. Here we address the function of yielding elastic adhesive tethers with Escherichia coli bacteria as a model for cell adhesion, using a combination of experiments and simulations. The adhesive bond kinetics and tether elasticity was modeled in the simulations with realistic biophysical models that were fit to new and previously published single molecule force spectroscopy data. The simulations were validated by comparison to experiments measuring the adhesive behavior of E. coli in flowing fluid. Analysis of the simulations demonstrated that yielding elasticity is required for the bacteria to remain bound in high and variable flow conditions, because it allows the force to be distributed evenly between multiple bonds. In contrast, strain-hardening and linear elastic tethers concentrate force on the most vulnerable bonds, which leads to failure of the entire adhesive contact. Load distribution is especially important to noncovalent receptor-ligand bonds, because they become exponentially shorter lived at higher force above a critical force, even if they form catch bonds. The advantage of yielding is likely to extend to any blood cells or pathogens adhering in flow, or to any situation where bonds are stretched unequally due to surface roughness, unequal native bond lengths, or conditions that act to unzip the bonds. PMID:25473833

  5. Tethered Aerostat Effects on Nearby Seismometers

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, Daniel [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-12-01

    This report assesses seismic interference generated by a tethered aerostat. The study was motivated by a planned aerostat deployment within the footprint of the Dry Alluvium Geology seismic network. No evidence was found for seismic interference generated by the aerostat, and thus the e ects on the Dry Alluvium Geology sensors will be negligible.

  6. Coordinated coupling control of tethered space robot using releasing characteristics of space tether

    Science.gov (United States)

    Huang, Panfeng; Zhang, Fan; Xu, Xiudong; Meng, Zhongjie; Liu, Zhengxiong; Hu, Yongxin

    2016-04-01

    Tethered space robot (TSR) is a new concept of space robot, which is released from the platform satellite, and retrieved via connected tether after space debris capture. In this paper, we propose a new coordinate control scheme for optimal trajectory and attitude tracking, and use releasing motor torque to instead the tension force, since it is difficult to track in practical. Firstly, the 6-DOF dynamics model of TSR is derived, in which the dynamics of tether releasing system is taken into account. Then, we propose and design the coordinated coupled controller, which is composed of a 6-DOF sliding mode controller and a PD controller tether's releasing. Thrust is treated as control input of the 6-DOF sliding mode controller to control the in-plane and out-of-plane angle of the tether and attitude angles of the TSR. The torque of releasing motor is used as input of PD controller, which controls the length rate of space tether. After the verification of the control scheme, finally, the simulation experiment is presented in order to validate the effectiveness of this control method. The results show that TSR can track the optimal approaching trajectory accurately. Simultaneously, the attitude angles can be changed to the desired attitude angles in control period, and the terminal accuracy is ±0.3°.

  7. Theory and Modeling in Support of Tether

    Science.gov (United States)

    Chang, C. L.; Bergeron, G.; Drobot, A. D.; Papadopoulos, K.; Riyopoulos, S.; Szuszczewicz, E.

    1999-01-01

    This final report summarizes the work performed by SAIC's Applied Physics Operation on the modeling and support of Tethered Satellite System missions (TSS-1 and TSS-1R). The SAIC team, known to be Theory and Modeling in Support of Tether (TMST) investigation, was one of the original twelve teams selected in July, 1985 for the first TSS mission. The accomplishments described in this report cover the period December 19, 1985 to September 31, 1999 and are the result of a continuous effort aimed at supporting the TSS missions in the following major areas. During the contract period, the SAIC's TMST investigation acted to: Participate in the planning and the execution on both of the TSS missions; Provide scientific understanding on the issues involved in the electrodynamic tether system operation prior to the TSS missions; Predict ionospheric conditions encountered during the re-flight mission (TSS-lR) based on realtime global ionosounde data; Perform post mission analyses to enhance our understanding on the TSS results. Specifically, we have 1) constructed and improved current collection models and enhanced our understanding on the current-voltage data; 2) investigated the effects of neutral gas in the current collection processes; 3) conducted laboratory experiments to study the discharge phenomena during and after tether-break; and 4) perform numerical simulations to understand data collected by plasma instruments SPES onboard the TSS satellite; Design and produce multi-media CD that highlights TSS mission achievements and convey the knowledge of the tether technology to the general public. Along with discussions of this work, a list of publications and presentations derived from the TMST investigation spanning the reporting period is compiled.

  8. Optimal control of electrodynamic tether satellites

    Science.gov (United States)

    Stevens, Robert E.

    Low thrust propulsion systems offer a fuel-efficient means to maneuver satellites to new orbits, however they can only perform such maneuvers when they are continuously operated for a long time. Such long-term maneuvers occur over many orbital revolutions often rendering short time scale trajectory optimization methods ineffective. An approach to multirevolution, long time scale optimal control of an electrodynamic tether is investigated for a tethered satellite system in Low Earth Orbit with atmospheric drag. Control is assumed to be periodic over several orbits since under the assumptions of a nearly circular orbit, periodic control yields the only solution that significantly contributes to secular changes in the orbital parameters. The optimal control problem is constructed in such a way as to maneuver the satellite to a new orbit while minimizing a cost function subject to the constraints of the time-averaged equations of motion by controlling current in the tether. To accurately capture the tether orbital dynamics, libration is modeled and controlled over long time scales in a similar manner to the orbital states. Libration is addressed in two parts; equilibrium and stability analysis, and control. Libration equations of motion are derived and analyzed to provide equilibrium and stability criteria that define the constraints of the design. A new libration mean square state is introduced and constrained to maintain libration within an acceptable envelope throughout a given maneuver. Optimal control solutions are achieved using a pseudospectral method that maneuver an electrodynamic tether to new orbits over long time scales while managing librational motion using only current in a wire.

  9. Precision tethered satellite attitude control. Ph.D. Thesis

    Science.gov (United States)

    Kline-Schoder, Robert J.

    1990-01-01

    Tethered spacecraft possess unique dynamic characteristics which make them advantageous for certain classes of experiments. One use for which tethers are particularly well suited is to provide an isolated platform for spaceborne observatories. The advantages of tethering a pointing platform 1 or 2 km from a space shuttle or space station are that, compared to placing the observatory on the parent spacecraft, vibrational disturbances are attenuated and contamination is eliminated. In practice, all satellites have some requirement on the attitude control of the spacecraft, and tethered satellites are no exception. It has previously been shown that conventional means of performing attitude control for tethered satellites are insufficient for any mission with pointing requirements more stringent than about 1 deg. This is due mainly to the relatively large force applied by the tether to the spacecraft. A particularly effective method of implementing attitude control for tethered satellites is to use this tether tension force to generate control torques by moving the tether attach point relative to the subsatellite center of mass. A demonstration of this attitude control technique on an astrophysical pointing platform has been proposed for a space shuttle flight test project and is referred to as the Kinetic Isolation Tether Experiment (KITE).

  10. AAV.shRNA-mediated downregulation of ROCK2 attenuates degeneration of dopaminergic neurons in toxin-induced models of Parkinson's disease in vitro and in vivo.

    Science.gov (United States)

    Saal, Kim-Ann; Koch, Jan C; Tatenhorst, Lars; Szegő, Eva M; Ribas, Vinicius Toledo; Michel, Uwe; Bähr, Mathias; Tönges, Lars; Lingor, Paul

    2015-01-01

    Parkinson's disease (PD) is a neurodegenerative disorder with prominent neuronal cell death in the substantia nigra (SN) and other parts of the brain. Previous studies in models of traumatic and neurodegenerative CNS disease showed that pharmacological inhibition of Rho-associated kinase (ROCK), a molecule involved in inhibitory signaling in the CNS, by small-molecule inhibitors improves neuronal survival and increases regeneration. Most small-molecule inhibitors, however, offer only limited target specificity and also inhibit other kinases, including both ROCK isoforms. To establish the role of the predominantly brain-expressed ROCK2 isoform in models of regeneration and PD, we used adeno-associated viral vectors (AAV) to specifically knockdown ROCK2 in neurons. Rat primary midbrain neurons (PMN) were transduced with AAV expressing short-hairpin-RNA (shRNA) against ROCK2 and LIM-domain kinase 1 (LIMK1), one of the downstream targets of ROCK2. While knock-down of ROCK2 and LIMK1 both enhanced neurite regeneration in a traumatic scratch lesion model, only ROCK2-shRNA protected PMN against 1-methyl-4-phenylpyridinium (MPP+) toxicity. Moreover, AAV.ROCK2-shRNA increased levels of the pro-survival markers Bcl-2 and phospho-Erk1. In vivo, AAV.ROCK2-shRNA vectors were injected into the ipsilateral SN and a unilateral 6-OHDA striatal lesion was performed. After four weeks, behavioral, immunohistochemical and biochemical alterations were investigated. Downregulation of ROCK2 protected dopaminergic neurons in the SN from 6-OHDA-induced degeneration and resulted in significantly increased TH-positive neuron numbers. This effect, however, was confined to nigral neuronal somata as striatal terminal density, dopamine and metabolite levels were not significantly preserved. Interestingly, motor behavior was improved in the ROCK2-shRNA treated animals compared to control after four weeks. Our studies thus confirm ROCK2 as a promising therapeutic target in models of PD and

  11. Lipoproteins tethered dendrimeric nanoconstructs for effective targeting to cancer cells

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Anupriya; Jain, Keerti, E-mail: keertijain02@gmail.com; Mehra, Neelesh Kumar, E-mail: neelesh81mph@gmail.com; Jain, N. K., E-mail: dr.jnarendr@gmail.com [Dr. H. S. Gour University, Pharmaceutics Research Laboratory, Department of Pharmaceutical Sciences (India)

    2013-10-15

    In the present investigation, poly (propylene imine) dendrimers up to fifth generation (PPI G5.0) were synthesized using ethylene diamine and acrylonitrile. Lipoproteins (high-density lipoprotein; HDL and low-density lipoprotein; LDL) were isolated from human plasma by discontinuous density gradient ultracentrifugation, characterized and tethered to G5.0 PPI dendrimers to construct LDL- and HDL-conjugated dendrimeric nanoconstructs for tumor-specific delivery of docetaxel. Developed formulations showed sustained release characteristics in in vitro drug release and in vivo pharmacokinetic studies. The cancer targeting potential of lipoprotein coupled dendrimers was investigated by ex vivo cytotoxicity and cell uptake studies using human hepatocellular carcinoma cell lines (HepG2 cells) and biodistribution studies in albino rats of Sprague-Dawley strain. Lipoprotein anchored dendrimeric nanoconstructs showed significant uptake by cancer cells as well as higher biodistribution of docetaxel to liver and spleen. It is concluded that these precisely synthesized engineered dendrimeric nanoconstructs could serve as promising drug carrier for fighting with the fatal disease, i.e., cancer, attributed to their defined targeting and therapeutic potential.

  12. Lipoproteins tethered dendrimeric nanoconstructs for effective targeting to cancer cells

    Science.gov (United States)

    Jain, Anupriya; Jain, Keerti; Mehra, Neelesh Kumar; Jain, N. K.

    2013-10-01

    In the present investigation, poly (propylene imine) dendrimers up to fifth generation (PPI G5.0) were synthesized using ethylene diamine and acrylonitrile. Lipoproteins (high-density lipoprotein; HDL and low-density lipoprotein; LDL) were isolated from human plasma by discontinuous density gradient ultracentrifugation, characterized and tethered to G5.0 PPI dendrimers to construct LDL- and HDL-conjugated dendrimeric nanoconstructs for tumor-specific delivery of docetaxel. Developed formulations showed sustained release characteristics in in vitro drug release and in vivo pharmacokinetic studies. The cancer targeting potential of lipoprotein coupled dendrimers was investigated by ex vivo cytotoxicity and cell uptake studies using human hepatocellular carcinoma cell lines (HepG2 cells) and biodistribution studies in albino rats of Sprague-Dawley strain. Lipoprotein anchored dendrimeric nanoconstructs showed significant uptake by cancer cells as well as higher biodistribution of docetaxel to liver and spleen. It is concluded that these precisely synthesized engineered dendrimeric nanoconstructs could serve as promising drug carrier for fighting with the fatal disease, i.e., cancer, attributed to their defined targeting and therapeutic potential.

  13. Tethered constellation, their utilization as microgravity platforms and relevant features

    Science.gov (United States)

    Napolitano, L. G.; Bevilacqua, F.

    1984-10-01

    The gravitational, thermal, and dynamic docking effects on tethered platforms were studied. The near-earth environment has gravitational effects such as g-jitters and intermittencies, g-noise, and frequency and amplitude features which may influence life science, materials processing, and fluid processes research and commercial activities. Artificial gravity is produced by minute accelerations imparted by tethers. The magnitudes of gravitational forces produced by tethers 100 and 100,000 m long at various altitudes from 463-35,786 km are calculated. Thermal analyses were performed for stainless steel and Kevlar tethers, showing the steel tether could vary 300 m in length and the polyamide 25 m during one orbit. Finally, consideration given to docking with a tethered platform revealed that the center of mass could change, which would produce, however, negligible changes in orbit and therefore gravity.

  14. Orbital oscillations of an elastic vertically-tethered satellite

    Science.gov (United States)

    Aslanov, V. S.

    2011-10-01

    The motion of a satellite in a circular orbit with respect to its center of mass is considered. The satellite bears an elastic tether system unrolled along the local vertical. The load at the end of the tether oscillates harmonically. The satellite motion under the action of the gravitational moment and the moment due to the tether tension force is studied. The bifurcation diagram is constructed and the hetero- and homoclinic separatrix trajectories are determined. Mel'nikov's method is used to study the satellite chaotic behavior near separatrices under the action of the periodic tether tension force. The results of the present paper can be used to analyze tether systems of gravitational stabilization and to study the orbital behavior of a satellite with an unrolled tether system with respect to the satellite center of mass.

  15. Nano-mechanics of HaloTag Tethers

    OpenAIRE

    Popa, Ionel; Berkovich, Ronen; Alegre-Cebollada, Jorge; Badilla, Carmen L.; Rivas-Pardo, Jaime Andres; Taniguchi, Yukinori; Kawakami, Masaru; Fernandez, Julio M.

    2013-01-01

    The active site of the Haloalkane Dehydrogenase (HaloTag) enzyme can be covalently attached to a chloroalkane ligand providing a mechanically strong tether, resistant to large pulling forces. Here we demonstrate the covalent tethering of protein L and I27 polyproteins between an AFM cantilever and a glass surface using HaloTag anchoring at one end, and thiol chemistry at the other end. Covalent tethering is unambiguously confirmed by the observation of full length polyprotein unfolding, combi...

  16. Chaotic motions of a tethered satellite system in circular orbit

    Science.gov (United States)

    Jin, D. P.; PANG, Z. J.; Wen, H.; Yu, B. S.

    2016-09-01

    This paper studies the chaotic motions of a tethered satellite system by utilizing a ground-based experimental system. Based on dynamics similarity principle, a dynamical equivalent model between the on-orbit tethered satellite and its ground physical model is obtained. As a result, the space dynamics environment of the tethered satellite can be simulated via the thrust forces and the torque of a momentum wheel on the satellite simulator. The numerical results of the on-orbit tethered satellite show the chaotic motions of the attitude motion of mother satellite. The experiment shows that the torque of momentum wheel as a negative damping is able to suppress the chaotic motion.

  17. Electrodynamic Tether Propulsion for Spacecraft and Upper Stages

    Science.gov (United States)

    Johnson, Les; Gilchrist, Brian; Estes, Robert D.; Lorenzini, Rnrico; Martinez-Sanchez, Manuel; Sanmartin, Juan

    1998-01-01

    Relatively short electrodynamic tethers can use solar power to 'push' against a planetary magnetic field to achieve propulsion without the expenditure of propellant. The groundwork has been laid for this type of propulsion. Important recent milestones include retrieval of a tether in space (TSS-1, 1992), successful deployment of a 20-km-long tether in space (SEDS-1, 1993), and operation of an electrodynamic tether with tether current driven in both directions (PMG, 1993). The planned Propulsive Small Expendable Deployer System (ProSEDS) experiment will use the flight-proven Small Expendable Deployer System (SEDS) to deploy a 5 km bare copper tether from a Delta II upper stage to achieve approximately 0.4 N drag thrust, thus deorbiting the stage. The experiment will use a predominantly 'bare' tether for current collection in lieu of the endmass collector and insulated tether approach used on previous missions. The flight experiment is a precursor to utilization of the technology on the International Space Station for reboost and the electrodynamic tether upper stage demonstration mission which will be capable of orbit raising, lowering and inclination changes, all using electrodynamic thrust. In addition, the use of this type of propulsion may be attractive for future missions at Jupiter.

  18. Lyapunov Orbits in the Jupiter System Using Electrodynamic Tethers

    Science.gov (United States)

    Bokelmann, Kevin; Russell, Ryan P.; Lantoine, Gregory

    2013-01-01

    Various researchers have proposed the use of electrodynamic tethers for power generation and capture from interplanetary transfers. The effect of tether forces on periodic orbits in Jupiter-satellite systems are investigated. A perturbation force is added to the restricted three-body problem model and a series of simplifications allows development of a conservative system that retains the Jacobi integral. Expressions are developed to find modified locations of equilibrium positions. Modified families of Lyapunov orbits are generated as functions of tether size and Jacobi integral. Zero velocity curves and stability analyses are used to evaluate the dynamical properties of tether-modified orbits.

  19. Joint ASI/NASA efforts on tether flight demonstrations

    Science.gov (United States)

    Loria, Alberto; Harrison, James K.

    1989-01-01

    Technological and organizational aspects of joint efforts by NASA and the Italian space agency ASI to develop tethered spacecraft systems are briefly discussed. The members of the ASI/NASA Task Group for Tether Flight Demonstrations are listed; the history of Task Group activities since 1986 is reviewed; and the current status of the main projects is indicated in a series of charts. Particular attention is given to the Tether Initiated Space Recovery System, a 450-lb spacecraft with a 20-km tether scheduled for Space Shuttle or Delta II launch to a 250-km 27.5-deg circular orbit in 1992.

  20. Neutralising Antibodies against Ricin Toxin

    Science.gov (United States)

    Prigent, Julie; Panigai, Laetitia; Lamourette, Patricia; Sauvaire, Didier; Devilliers, Karine; Plaisance, Marc; Volland, Hervé; Créminon, Christophe; Simon, Stéphanie

    2011-01-01

    The Centers for Disease Control and Prevention have listed the potential bioweapon ricin as a Category B Agent. Ricin is a so-called A/B toxin produced by plants and is one of the deadliest molecules known. It is easy to prepare and no curative treatment is available. An immunotherapeutic approach could be of interest to attenuate or neutralise the effects of the toxin. We sought to characterise neutralising monoclonal antibodies against ricin and to develop an effective therapy. For this purpose, mouse monoclonal antibodies (mAbs) were produced against the two chains of ricin toxin (RTA and RTB). Seven mAbs were selected for their capacity to neutralise the cytotoxic effects of ricin in vitro. Three of these, two anti-RTB (RB34 and RB37) and one anti-RTA (RA36), when used in combination improved neutralising capacity in vitro with an IC50 of 31 ng/ml. Passive administration of association of these three mixed mAbs (4.7 µg) protected mice from intranasal challenges with ricin (5 LD50). Among those three antibodies, anti-RTB antibodies protected mice more efficiently than the anti-RTA antibody. The combination of the three antibodies protected mice up to 7.5 hours after ricin challenge. The strong in vivo neutralising capacity of this three mAbs combination makes it potentially useful for immunotherapeutic purposes in the case of ricin poisoning or possibly for prevention. PMID:21633505

  1. Neutralising antibodies against ricin toxin.

    Directory of Open Access Journals (Sweden)

    Julie Prigent

    Full Text Available The Centers for Disease Control and Prevention have listed the potential bioweapon ricin as a Category B Agent. Ricin is a so-called A/B toxin produced by plants and is one of the deadliest molecules known. It is easy to prepare and no curative treatment is available. An immunotherapeutic approach could be of interest to attenuate or neutralise the effects of the toxin. We sought to characterise neutralising monoclonal antibodies against ricin and to develop an effective therapy. For this purpose, mouse monoclonal antibodies (mAbs were produced against the two chains of ricin toxin (RTA and RTB. Seven mAbs were selected for their capacity to neutralise the cytotoxic effects of ricin in vitro. Three of these, two anti-RTB (RB34 and RB37 and one anti-RTA (RA36, when used in combination improved neutralising capacity in vitro with an IC(50 of 31 ng/ml. Passive administration of association of these three mixed mAbs (4.7 µg protected mice from intranasal challenges with ricin (5 LD(50. Among those three antibodies, anti-RTB antibodies protected mice more efficiently than the anti-RTA antibody. The combination of the three antibodies protected mice up to 7.5 hours after ricin challenge. The strong in vivo neutralising capacity of this three mAbs combination makes it potentially useful for immunotherapeutic purposes in the case of ricin poisoning or possibly for prevention.

  2. Dynamic control of the space tethered system

    Science.gov (United States)

    Malashin, A. A.; Smirnov, N. N.; Bryukvina, O. Yu.; Dyakov, P. A.

    2017-02-01

    We discuss the problem of simultaneous dynamical stabilization and suppression of transverse and longitudinal vibrations of the space tethered system deployed along a certain trajectory. The dynamics of the system is described by a system of nonlinear partial differential equations for the longitudinal and transverse waves and we consider a non-classical version of the problem with one moving boundary. We formulate a mathematical model and perform the analytic and numerical analysis of the boundary control problem based on the Lyapunov method. A scheme of the deployment mechanism is suggested. It includes a control torque and transverse displacement of the boundary and ensures stable deployment of the whole system.

  3. Tether enabled spacecraft systems for ultra long wavelength radio astronomy

    Science.gov (United States)

    Gemmer, Thomas; Yoder, Christopher D.; Reedy, Jacob; Mazzoleni, Andre P.

    2017-09-01

    This paper describes a proposed CubeSat mission to perform unique experiments involving interferometry and tether dynamics. A 3U CubeSat is to be placed in orbit where it will separate into three 1U CubeSats connected by a total of 100 m of tether. The separation between the three units will allow for the demonstration of high resolution radio interferometry. The increased resolution will provide access to the Ultra-Long Wavelength (ULW) scale of the electromagnetic spectrum, which is largely unexplored. During and after completion of the primary experiment, the CubeSat will be able to gather data on tethered dynamics of a space vehicle. Maneuvers to be performed and studied include direct testing of tether deployment and tethered formation flying. Tether deployment is a vital area where more data is needed as this is the phase where many tethered missions have experienced complications and failures. There are a large number of complex dynamical responses predicted by the theory associated with the deployment of an orbiting tethered system. Therefore, it is imperative to conduct an experiment that provides data on what dynamic responses actually occur.

  4. Climber Motion Optimization for the Tethered Space Elevator

    NARCIS (Netherlands)

    Williams, P.; Ockels, W.J.

    The tethered space elevator could provide a revolutionary means for enabling cheap transportation to geostationary altitude and beyond. Assuming that such a system can be built, one of the dynamic design problems is determining a means of moving the elevator along the tether so as to minimize the

  5. Effects tethering feeding management system on carcass, organ ...

    African Journals Online (AJOL)

    Sixteen (16) growing West African dwarf goats comprising eight bucks and eight does aged between 8 – 12 months were used in this study to monitor the effect of periodic tethering ... The tethered goats in treatment group T 1 showed higher weight values of the liver (0.95 + 0.1 kg) and kidneys weight of (0.42 + 0.17 kg).

  6. Tethered Contactless Mobile Nuclear Environment Monitoring Robot

    Energy Technology Data Exchange (ETDEWEB)

    Choi, S. Y.; Lee, E. S.; Lee, Kun J.; Kim, Su H.; Rim, C. T. [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2013-05-15

    In fact, the nuclear environment monitoring is significantly crucial for early detection of NPP accident, radiological emergency, the estimation of radiation exposure to nearby residents as well as the long term radioactivity. In the UAE, the nuclear environment monitoring is, however, quite challenging because sampling locations are far from NPPs and the outdoor temperature and humidity are very high for NPP workers to collect soil, air, and water samples. Therefore, nuclear environment monitoring robots (Nubos) are strongly needed for the NPPs in the UAE. The Nubos can be remotely controlled to collect samples in extreme environment instead of NPP workers. Moreover, the Nubos can be unmanned ground vehicles (UGVs), unmanned aerial vehicles (UAVs) and unmanned marine vehicles (UMVs) to collect soil, air, and water samples, respectively. In this paper, the prototype development of UGV type Nubos using power cable for a long distance power delivery, called Tethered contactless mobile Nubo is introduced and validated by experiments. In this paper, the prototype development of Tethered Contactless Mobile (TeCoM) Nubo, which can be powered continuously within several km distance and avoid tangled cable, and the indoor test are finished. As further works, outdoor demonstration and a grand scale R and D proposal of practical Nubo will be proceeded.

  7. [Hemolysis of Scolopendra toxins].

    Science.gov (United States)

    Deng, F; Fang, H; Wang, K

    1997-01-01

    The hemolysis of toxins from alive Scolopendra subspinipes mutilans, medicinal material of Scolopendra subspimipes mutilans and S. multidens have been compared. The result shows that all the toxins have hemolytic activity. The hemolytic activity of the toxin from the medicinal materials of S. subspinipes mutilans is obviously lower than that from alive ones, and that from fresh medicinal materials are twice as high that from old ones, and that from S. multidens is higher than that from S. subspinipes multilans.

  8. A space tethered towing method using tension and platform thrusts

    Science.gov (United States)

    Meng, Zhongjie; Wang, Bingheng; Huang, Panfeng

    2017-01-01

    Orbit maneuver via tether is a promising countermeasure for space debris removal and satellite orbit transfer. A space tethered towing method is explored that utilizes thrust to fulfill transfer and bounded tension to stabilize tether heading. For this purpose, a time-energy optimal orbit is designed by Gauss pseudospectral method. The theoretical attitude commands are obtained by equilibria analysis. An effective attitude control strategy is presented where the commands are optimized first and then feedback controller is designed. To deal with the underactuated problem with tension constraint, hierarchical sliding mode theory is employed and an adaptive anti-windup module is added to mitigate the actuator saturation. Simulation results show that the target is towed effectively by the thrusts, and a smooth tracking for the commands of tether length and in-plane tether heading is guaranteed by the bounded tension. In addition, the designed controller also presents appreciable robustness to model error and determination error.

  9. Novel Clostridium difficile Anti-Toxin (TcdA and TcdB) Humanized Monoclonal Antibodies Demonstrate In Vitro Neutralization across a Broad Spectrum of Clinical Strains and In Vivo Potency in a Hamster Spore Challenge Model.

    Science.gov (United States)

    Qiu, Hongyu; Cassan, Robyn; Johnstone, Darrell; Han, Xiaobing; Joyee, Antony George; McQuoid, Monica; Masi, Andrea; Merluza, John; Hrehorak, Bryce; Reid, Ross; Kennedy, Kieron; Tighe, Bonnie; Rak, Carla; Leonhardt, Melanie; Dupas, Brian; Saward, Laura; Berry, Jody D; Nykiforuk, Cory L

    2016-01-01

    Clostridium difficile (C. difficile) infection (CDI) is the main cause of nosocomial antibiotic-associated colitis and increased incidence of community-associated diarrhea in industrialized countries. At present, the primary treatment of CDI is antibiotic administration, which is effective but often associated with recurrence, especially in the elderly. Pathogenic strains produce enterotoxin, toxin A (TcdA), and cytotoxin, toxin B (TcdB), which are necessary for C. difficile induced diarrhea and gut pathological changes. Administration of anti-toxin antibodies provides an alternative approach to treat CDI, and has shown promising results in preclinical and clinical studies. In the current study, several humanized anti-TcdA and anti-TcdB monoclonal antibodies were generated and their protective potency was characterized in a hamster infection model. The humanized anti-TcdA (CANmAbA4) and anti-TcdB (CANmAbB4 and CANmAbB1) antibodies showed broad spectrum in vitro neutralization of toxins from clinical strains and neutralization in a mouse toxin challenge model. Moreover, co-administration of humanized antibodies (CANmAbA4 and CANmAbB4 cocktail) provided a high level of protection in a dose dependent manner (85% versus 57% survival at day 22 for 50 mg/kg and 20 mg/kg doses, respectively) in a hamster gastrointestinal infection (GI) model. This study describes the protective effects conferred by novel neutralizing anti-toxin monoclonal antibodies against C. difficile toxins and their potential as therapeutic agents in treating CDI.

  10. Novel Clostridium difficile Anti-Toxin (TcdA and TcdB Humanized Monoclonal Antibodies Demonstrate In Vitro Neutralization across a Broad Spectrum of Clinical Strains and In Vivo Potency in a Hamster Spore Challenge Model.

    Directory of Open Access Journals (Sweden)

    Hongyu Qiu

    Full Text Available Clostridium difficile (C. difficile infection (CDI is the main cause of nosocomial antibiotic-associated colitis and increased incidence of community-associated diarrhea in industrialized countries. At present, the primary treatment of CDI is antibiotic administration, which is effective but often associated with recurrence, especially in the elderly. Pathogenic strains produce enterotoxin, toxin A (TcdA, and cytotoxin, toxin B (TcdB, which are necessary for C. difficile induced diarrhea and gut pathological changes. Administration of anti-toxin antibodies provides an alternative approach to treat CDI, and has shown promising results in preclinical and clinical studies. In the current study, several humanized anti-TcdA and anti-TcdB monoclonal antibodies were generated and their protective potency was characterized in a hamster infection model. The humanized anti-TcdA (CANmAbA4 and anti-TcdB (CANmAbB4 and CANmAbB1 antibodies showed broad spectrum in vitro neutralization of toxins from clinical strains and neutralization in a mouse toxin challenge model. Moreover, co-administration of humanized antibodies (CANmAbA4 and CANmAbB4 cocktail provided a high level of protection in a dose dependent manner (85% versus 57% survival at day 22 for 50 mg/kg and 20 mg/kg doses, respectively in a hamster gastrointestinal infection (GI model. This study describes the protective effects conferred by novel neutralizing anti-toxin monoclonal antibodies against C. difficile toxins and their potential as therapeutic agents in treating CDI.

  11. Changes in Polymeric Tether Properties Due to Atomic Oxygen

    Science.gov (United States)

    Finckenor, Miria M.; Vaughn, Jason A.; Watts, Edward W.

    2003-01-01

    The Propulsive Small Expendable Deployer System (ProSEDS) mission is designed to provide an on-orbit demonstration of the electrodynamic propulsion capabilities of tethers in space. The ProSEDS experiment will be a secondary payload on a Delta II unmanned expendable booster. A 5-km conductive tether is attached to the Delta II second stage and collects current fiom the low Earth orbit (LEO) plasma to facilitate de-orbit of the spent stage. The conductive tether is attached to a 10-km non-conductive tether, which is then attached to an endmass containing several scientific instruments. Atomic oxygen (AO) erodes most organic materials. As the orbit of the Delta II second stage decas, the AO flux (atoms/sq cm sec) increases. A nominal AO fluence of 1 x l0(exp 21) atoms/sq cm was agreed upon by the investigators as an adequate level for evaluating the performance of the tether materials. A test series was performed to determine the effect of atomic oxygen (AO) on the mechanical integrity and possible strength loss of ProSEDS tether materials. The tether materials in this study were Dyneema, an ultra-high molecular weight polyethylene material used as the non-conducting portion of the ProSEDS tether, and the Kevlar core strength fiber used in the conductive tether. Samples of Dyneema and Kevlar were exposed to various levels of atomic oxygen up to 1.07 x 10(exp 21) atoms/sq cm in the Marshall Space Flight Center Atomic Oxygen Beam Facility (AOBF). Changes in mass were noted after AO exposure. The tethers were then tensile-tested until failure. AO affected both the Dyneema and Kevlar tether material strength. Dyneema exposed to 1.07 x 10(exp 21) atoms/sq cm of atomic oxygen failed due to normal handling when removed fiom the AOBF and was not tensile-tested. Another test series was performed to determine the effect of AO on the electrical properties of the ProSEDS conductive tether. The conductive tether consists of seven individually coated strands of 28 AWG 1350

  12. Assessing Tether Anchor Labeling and Usability in Pickup Trucks.

    Science.gov (United States)

    Klinich, Kathleen D; Manary, Miriam A; Malik, Laura A; Flannagan, Carol A; Jermakian, Jessica S

    2017-10-30

    Investigate vehicle factors associated with child restraint tether use and misuse in pickup trucks and evaluate four labeling interventions designed to educate consumers on proper tether use. Volunteer testing was performed with 24 subjects and four different pickup trucks. Each subject performed eight child restraint installations among the four pickups using two forward-facing restraints: a Britax Marathon G4.1 and an Evenflo Triumph. Vehicles were selected to represent four different implementations of tether anchors among pickups: plastic loop routers (Chevrolet Silverado), webbing routers (Ram), back wall anchors (Nissan Frontier), and webbing routers plus metal anchors (Toyota Tundra). Interventions included a diagram label, QR Code linked to video instruction, coordinating text label, and contrasting text tag. Subjects used the child restraint tether in 93 percent of trials. However, tether use was completely correct in only 9 percent of trials. An installation was considered functional if the subject attached the tether to a tether anchor and had a tight installation (ignoring routing and head restraint position); 28 percent of subjects achieved a functional installation. The most common installation error was attaching the tether hook to the anchor/router; directly behind the child restraint (near the top of the seatback) rather than placing the tether through the router and attaching it to the anchor in the adjacent seating position. The Nissan Frontier, with the anchor located on the back wall of the cab, had the highest rate of correct installations but also had the highest rate of attaching the tether to components other than the tether anchor (seat adjustor, child restraint storage hook, around head restraint). None of the labeling interventions had a significant effect on correct installation; not a single subject scanned the QR Code to access the video instruction. Subjects with the most successful installations spent extensive time reviewing the

  13. Project 'VOLCANO': Electronics of tethered satellite system

    Science.gov (United States)

    Savich, N. A.

    The main goal of the 'VOLCANO' project developed jointly by the Institute of Radio Engineering and Electronics and space concern 'ENERGIA' is experimental investigation of the current-voltage characteristics of the 'Collector-Boom-Emitter' system simulating the long Tethered Satellite System (TSS) in the real space flight conditions on the transport ship 'PROGRESS'. These measurements will allow scientists to determine the attainable current values for different combinations of collectors and emitters (passive metallic sphere, thermocathode, hollow cathodes and show up some prospects of active TSS. The report is concerned with the concept, purpose and tasks of the project, the planned set up of the measurement equipment on the 'PROGRESS' ship and in the container extended on the deployable 100 m long boom end.

  14. Protection against Shiga Toxins

    Directory of Open Access Journals (Sweden)

    Simona Kavaliauskiene

    2017-02-01

    Full Text Available Shiga toxins consist of an A-moiety and five B-moieties able to bind the neutral glycosphingolipid globotriaosylceramide (Gb3 on the cell surface. To intoxicate cells efficiently, the toxin A-moiety has to be cleaved by furin and transported retrogradely to the Golgi apparatus and to the endoplasmic reticulum. The enzymatically active part of the A-moiety is then translocated to the cytosol, where it inhibits protein synthesis and in some cell types induces apoptosis. Protection of cells can be provided either by inhibiting binding of the toxin to cells or by interfering with any of the subsequent steps required for its toxic effect. In this article we provide a brief overview of the interaction of Shiga toxins with cells, describe some compounds and conditions found to protect cells against Shiga toxins, and discuss whether they might also provide protection in animals and humans.

  15. Interaction of the Space Shuttle on-orbit autopilot with tether dynamics

    Science.gov (United States)

    Bergmann, Edward V.

    1988-01-01

    The effect of Orbiter flight control on tether dynamics is studied by simulation. Open-loop effects of Orbiter jet firing on tether dynamics are shown, and the potential for closed-loop interaction between tether dynamics and Orbiter flight control is determined. The significance of these effects on Orbiter flight control and tether control is assessed.

  16. Passivity-Based Control of a Rigid Electrodynamic Tether

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2011-01-01

    parts, a feedback connection, which stabilizes the open-loop equilibrium, and a bias term, which is able to drive the system trajectory away from this equilibrium, a feature necessary to obtain orbit adjustment capabilities of the electrodynamic tether. It is then shown how the periodic solutions......Electrodynamic tethers provide actuation for performing orbit correction of spacecrafts. When an electrodynamic tether system is orbiting the Earth in an inclined orbit, periodic changes in the magnetic field result in a family of unstable periodic solutions in the attitude motion. This paper shows...

  17. Microalgal toxin(s): characteristics and importance

    African Journals Online (AJOL)

    Prokaryotic and eukaryotic microalgae produce a wide array of compounds with biological activities. These include antibiotics, algicides, toxins, pharmaceutically active compounds and plant growth regulators. Toxic microalgae, in this sense, are common only among the cyanobacteria and dinoflagellates. The microalgal ...

  18. Human alpha-defensins inhibit Clostridium difficile toxin B.

    Science.gov (United States)

    Giesemann, Torsten; Guttenberg, Gregor; Aktories, Klaus

    2008-06-01

    Clostridium difficile toxins A and B are major virulence factors implicated in pseudomembranous colitis and antibiotic-associated diarrhea. The toxins are glucosyltransferases, which inactivate Rho proteins involved in cellular signaling. Human alpha-defensins as part of the innate immune system inactivate various microbial pathogens as well as specific bacterial exotoxins. Here, we studied the effects of alpha-defensins human neutrophil protein (HNP)-1, HNP-3, and enteric human defensin (HD)-5 on the activity of C difficile toxins A and B. Inactivation of C difficile toxins by alpha-defensins in vivo was monitored by microscopy, determination of the transepithelial resistance of CaCo-2 cell monolayers, and analysis of the glucosylation of Rac1 in toxin-treated cells. In vitro glucosylation was used to determine K(m) and median inhibitory concentration (IC(50)) values. Formation of defensin-toxin complexes was analyzed by precipitation and turbidity studies. Treatment of cells with human alpha-defensins caused loss of cytotoxicity of toxin B, but not of toxin A. Only alpha-defensins, but not beta-defensin-1 or cathelicidin LL-37, inhibited toxin B-catalyzed in vitro glucosylation of Rho guanosine triphosphatases in a competitive manner, increasing K(m) values for uridine 5'-diphosphate-glucose up to 10-fold. The IC(50) values for inhibition of toxin B-catalyzed glucosylation by the alpha-defensins were 0.6-1.5 micromol/L. At high concentrations, defensins (HNP-1 > or = 2 micromol/L) caused high-molecular-mass aggregates, comparable to Bacillus anthracis protective antigen and lethal factor. Our data indicate that toxin B interacts with high affinity with alpha-defensins and suggest that defensins may provide a defense mechanism against some types of clostridial glucosylating cytotoxins.

  19. Fiber Optic Shape Sensing for Tethered Marsupial Rovers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Building upon the successful proof of concept work in Phase I, Luna Innovations Incorporated is proposing to design, build, and test a sensing tether for marsupial...

  20. An updated review of nanotechnologies for the space elevator tether

    OpenAIRE

    Brambilla, G.

    2010-01-01

    The space elevator tether requires an extraordinary specific ultimate strength (ratio between ultimate strength and density) and carbon nanotubes (CNTs) have been identified as the ideal candidate because of their astonishing strength. This paper reviews CNT manufacture and measured strengths.

  1. Fiber Optic Shape Sensing for Tethered Marsupial Rovers Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Luna Innovations Incorporated is proposing to design, build, and test a shape, length, and tension sensing tether for robotic exploration and sample-gathering...

  2. Stationary Tether Device for Buoy Apparatus and System for Using

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — A rigid, neutrally buoyant hydrodynamicaly-faired tether and associated fastening hardware that loosely holds a bathymetric float at a predetermined distance from a...

  3. Reconstitution of Cholesterol-Dependent Vaginolysin into Tethered Phospholipid Bilayers

    DEFF Research Database (Denmark)

    Budvytyte, Rima; Pleckaityte, M.; Zvirbliene, A.

    2013-01-01

    Functional reconstitution of the cholesterol-dependent cytolysin vaginolysin (VLY) from Gardnerella vaginalis into artificial tethered bilayer membranes (tBLMs) has been accomplished. The reconstitution of VLY was followed in real-time by electrochemical impedance spectroscopy (EIS). Changes...

  4. Development of a Tethered Formation Flight Testbed for ISS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The development of a testbed for the development and demonstration of technologies needed by tethered formation flying satellites is proposed. Such a testbed would...

  5. Precession and circularization of elliptical space-tether motion

    Science.gov (United States)

    Chapel, Jim D.; Grosserode, Patrick

    1993-01-01

    In this paper, we present a simplified analytic model for predicting motion of long space tethers. The perturbation model developed here addresses skip rope motion, where each end of the tether is held in place and the middle of the tether swings with a motion similar to that of a child's skip rope. If the motion of the tether midpoint is elliptical rather than circular, precession of the ellipse complicates the procedures required to damp this motion. The simplified analytic model developed in this paper parametrically predicts the precession of elliptical skip rope motion. Furthermore, the model shows that elliptic skip rope motion will circularize when damping is present in the longitudinal direction. Compared with high-fidelity simulation results, this simplified model provides excellent predictions of these phenomena.

  6. Tethered catalysts for the hydration of carbon dioxide

    Science.gov (United States)

    Valdez, Carlos A; Satcher, Jr., Joe H; Aines, Roger D; Wong, Sergio E; Baker, Sarah E; Lightstone, Felice C; Stolaroff, Joshuah K

    2014-11-04

    A system is provided that substantially increases the efficiency of CO.sub.2 capture and removal by positioning a catalyst within an optimal distance from the air-liquid interface. The catalyst is positioned within the layer determined to be the highest concentration of carbon dioxide. A hydrophobic tether is attached to the catalyst and the hydrophobic tether modulates the position of the catalyst within the liquid layer containing the highest concentration of carbon dioxide.

  7. The effects of tether placement on antibody stability on surfaces

    Science.gov (United States)

    Grawe, Rebecca W.; Knotts, Thomas A.

    2017-06-01

    Despite their potential benefits, antibody microarrays have fallen short of performing reliably and have not found widespread use outside of the research setting. Experimental techniques have been unable to determine what is occurring on the surface of an atomic level, so molecular simulation has emerged as the primary method of investigating protein/surface interactions. Simulations of small proteins have indicated that the stability of the protein is a function of the residue on the protein where a tether is placed. The purpose of this research is to see whether these findings also apply to antibodies, with their greater size and complexity. To determine this, 24 tethering locations were selected on the antibody Protein Data Bank (PDB) ID: 1IGT. Replica exchange simulations were run on two different surfaces, one hydrophobic and one hydrophilic, to determine the degree to which these tethering sites stabilize or destabilize the antibody. Results showed that antibodies tethered to hydrophobic surfaces were in general less stable than antibodies tethered to hydrophilic surfaces. Moreover, the stability of the antibody was a function of the tether location on hydrophobic surfaces but not hydrophilic surfaces.

  8. Dynamics of the Space Tug System with a Short Tether

    Directory of Open Access Journals (Sweden)

    Jiafu Liu

    2015-01-01

    Full Text Available The dynamics of the space tug system with a short tether similar to the ROGER system during deorbiting is presented. The kinematical characteristic of this system is significantly different from the traditional tethered system as the tether is tensional and tensionless alternately during the deorbiting process. The dynamics obtained based on the methods for the traditional tethered system is not suitable for the space tug system. Therefore, a novel method for deriving dynamics for the deorbiting system similar to the ROGER system is proposed by adopting the orbital coordinates of the two spacecraft and the Euler angles of ROGER spacecraft as the generalized coordinates instead of in- and out-plane librations and the length of the tether and so forth. Then, the librations of the system are equivalently obtained using the orbital positions of the two spacecraft. At last, the geostationary orbit (GEO and the orbit whose apogee is 300 km above GEO are chosen as the initial and target orbits, respectively, to perform the numerical simulations. The simulation results indicate that the dynamics can describe the characteristic of the tether-net system conveniently and accurately, and the deorbiting results are deeply affected by the initial conditions and parameters.

  9. Botulinum Toxin Therapy

    Science.gov (United States)

    ... AADA Health System Reform Principles Drug pricing and availability CVS dermatologic formulary restrictions Access to compounded medications ... Botulinum toxin therapy: Overview Also called botulinum rejuvenation Brand names: Botox® Cosmetic, Dysport®, MYOBLOC®, and XEOMIN® When ...

  10. Wallpaper May Breed Toxins

    Science.gov (United States)

    ... https://medlineplus.gov/news/fullstory_166850.html Wallpaper May Breed Toxins: Study Fungus on the walls might ... 2017 FRIDAY, June 23, 2017 (HealthDay News) -- Wallpaper may contribute to "sick building syndrome," a new study ...

  11. Staphylococcus aureus toxins.

    Science.gov (United States)

    Otto, Michael

    2014-02-01

    Staphylococcus aureus is a dangerous pathogen that causes a variety of severe diseases. The virulence of S. aureus is defined by a large repertoire of virulence factors, among which secreted toxins play a preeminent role. Many S. aureus toxins damage biological membranes, leading to cell death. In particular, S. aureus produces potent hemolysins and leukotoxins. Among the latter, some were recently identified to lyse neutrophils after ingestion, representing an especially powerful weapon against bacterial elimination by innate host defense. Furthermore, S. aureus secretes many factors that inhibit the complement cascade or prevent recognition by host defenses. Several further toxins add to this multi-faceted program of S. aureus to evade elimination in the host. This review will give an overview over S. aureus toxins focusing on recent advances in our understanding of how leukotoxins work in receptor-mediated or receptor-independent fashions. Published by Elsevier Ltd.

  12. Computerized video analysis of tethered bacteria

    Science.gov (United States)

    Berg, Howard C.; Block, Steven M.; Conley, M. Patricia; Nathan, Andrew R.; Power, John N.; Wolfe, Alan J.

    1987-03-01

    When a flagellar filament of a bacterial cell such as Escherichia coli is fixed to a glass surface, the cell body spins alternately clockwise and counterclockwise at speeds of up to 15 Hz. In cells wild type for chemotaxis, reversals occur about once per second. A typical experiment on bacterial behavior involves data collected from as many as 30 such cells over periods of about an hour. A system is described that makes practical detailed analysis of such a large body of data. Microscopic fields, each containing many tethered cells, were recorded on VHS cassettes with a shuttered multiframe video camera. The tapes were played back through hardware that encoded information from successive images of a given cell and passed that information on to a minicomputer. This computer, following instructions provided in an editing session, identified intervals during which the cell was rotating clockwise, rotating counterclockwise, or remained stationary. Output files were generated listing the times at which transitions between these states occurred and the speeds of the cell averaged over successive time periods. This output was then combined with that from other cells and/or processed by various applications programs.

  13. Factors affecting tether use and correct use in child restraint installations.

    Science.gov (United States)

    Jermakian, Jessica S; Klinich, Kathleen D; Orton, Nichole R; Flannagan, Carol A C; Manary, Miriam A; Malik, Laura A; Narayanaswamy, Prabha

    2014-12-01

    Field studies show that top tethers go unused in half of forward-facing child restraint installations. In this study, parent volunteers were asked to use the Lower Anchors and Tethers for Children (LATCH) to install child restraints in several vehicles to identify tether anchor characteristics that are associated with tether use. Thirty-seven volunteers were assigned to four groups. Each group tested two forward-facing child restraints in four of 16 vehicle models. Logistic regression models were used to identify predictors of tether use and correct use. Subjects used the tether in 89% of the 294 forward-facing child restraint installations and attached the tether correctly in 57% of the installations. Tethers were more likely to be used when the anchor was located on the rear deck as typically found in sedans compared with the seatback, floor, or roof. Tethers were less likely to be attached correctly when there was potentially confusing hardware present. No vehicle tether hardware characteristics or vehicle manual directions were associated specifically with correct tether routing and head restraint position. This study provides laboratory evidence that specific vehicle features are associated with tether use and correct use. Modifications to vehicles that make tether anchors easier to find and identify likely will result in increases in tether use and correct use. Copyright © 2014 Elsevier Ltd. All rights reserved.

  14. Adult idiopathic scoliosis: the tethered spine.

    Science.gov (United States)

    Whyte Ferguson, Lucy

    2014-01-01

    This article reports on an observational and treatment study using three case histories to describe common patterns of muscle and fascial asymmetry in adults with idiopathic scoliosis (IS) who have significant scoliotic curvatures that were not surgically corrected and who have chronic pain. Rather than being located in the paraspinal muscles, the myofascial trigger points (TrPs) apparently responsible for the pain were located at some distance from the spine, yet referred pain to locations throughout the thoracolumbar spine. Asymmetries in these muscles appear to tether the spine in such a way that they contribute to scoliotic curvatures. Evaluation also showed that each of these individuals had major ligamentous laxity and this may also have contributed to development of scoliotic curvatures. Treatment focused on release of TrPs found to refer pain into the spine, release of related fascia, and correction of related joint dysfunction. Treatment resulted in substantial relief of longstanding chronic pain. Treatment thus validated the diagnostic hypothesis that myofascial and fascial asymmetries were to some extent responsible for pain in adults with significant scoliotic curvatures. Treatment of these patterns of TrPs and muscle and fascial asymmetries and related joint dysfunction was also effective in relieving pain in each of these individuals after they were injured in auto accidents. Treatment of myofascial TrPs and asymmetrical fascial tension along with treatment of accompanying joint dysfunction is proposed as an effective approach to treating both chronic and acute pain in adults with scoliosis that has not been surgically corrected. Copyright © 2013 Elsevier Ltd. All rights reserved.

  15. Botulinum Toxin (Botox) for Facial Wrinkles

    Science.gov (United States)

    ... Eye Health / Eye Health A-Z Botulinum Toxin (Botox) for Facial Wrinkles Sections Botulinum Toxin (Botox) for ... How Does Botulinum Toxin (Botox) Work? Botulinum Toxin (Botox) for Facial Wrinkles Leer en Español: La toxina ...

  16. Novel Structure and Function of Typhoid Toxin

    Science.gov (United States)

    ... Matters NIH Research Matters July 29, 2013 Novel Structure and Function of Typhoid Toxin Structure of typhoid toxin, showing the 2 A subunits ( ... to cultured cells. The scientists next determined the structure of the typhoid toxin. The toxin was already ...

  17. Tethered Pyrotechnic Apparatus for Acquiring a Ground Sample

    Science.gov (United States)

    Jones, Jack; Zimmerman, Wayne; Wu, Jiunn Jenq; Badescu, Mircea; Sherrit, Stewart

    2009-01-01

    A proposed alternative design for the balloon-borne ground-sampling system described in the immediately preceding article would not rely on free fall to drive a harpoonlike sample-collecting device into the ground. Instead, the harpoon-like sample-collecting device would be a pyrotechnically driven, tethered projectile. The apparatus would include a tripod that would be tethered to the gondola. A gun for shooting the projectile into the ground would be mounted at the apex of the tripod. The gun would include an electronic trigger circuit, a chamber at the breech end containing a pyrotechnic charge, and a barrel. A sabot would be placed in the barrel just below the pyrotechnic charge, and the tethered projectile would be placed in the barrel just below the sabot. The tripod feet would be equipped with contact sensors connected to the trigger circuit. In operation, the tripod would be lowered to the ground on its tether. Once contact with the ground was detected by the sensors on all three tripod feet, the trigger circuit would fire the pyrotechnic charge to drive the projectile into the ground. (Requiring contact among all three tripod feet and the ground would ensure that the projectile would be fired into the ground, rather than up toward the gondola or the balloon.) The tethered projectile would then be reeled back up to the gondola for analysis of the sample.

  18. Tethered Nanoparticle–Polymer Composites: Phase Stability and Curvature

    KAUST Repository

    Srivastava, Samanvaya

    2012-04-17

    Phase behavior of poly(ethylene glycol) (PEG) tethered silica nanoparticles dispersed in PEG hosts is investigated using small-angle X-ray scattering. Phase separation in dispersions of densely grafted nanoparticles is found to display strikingly different small-angle X-ray scattering signatures in comparison to phase-separated composites comprised of bare or sparsely grafted nanoparticles. A general diagram for the dispersion state and phase stability of polymer tethered nanoparticle-polymer composites incorporating results from this as well as various other contemporary studies is presented. We show that in the range of moderate to high grafting densities the dispersion state of nanoparticles in composites is largely insensitive to the grafting density of the tethered chains and chemistry of the polymer host. Instead, the ratio of the particle diameter to the size of the tethered chain and the ratio of the molecular weights of the host and tethered polymer chains (P/N) are shown to play a dominant role. Additionally, we find that well-functionalized nanoparticles form stable dispersions in their polymer host beyond the P/N limit that demarcates the wetting/dewetting transition in polymer brushes on flat substrates interacting with polymer melts. A general strategy for achieving uniform nanoparticle dispersion in polymers is proposed. © 2012 American Chemical Society.

  19. Numerical Simulation of Tethered Underwater Kites for Power Generation

    Science.gov (United States)

    Ghasemi, Amirmahdi; Olinger, David; Tryggvason, Gretar

    2015-11-01

    An emerging renewable energy technology, tethered undersea kites (TUSK), which is used to extract hydrokinetic energy from ocean and tidal currents, is studied. TUSK systems consist of a rigid-winged ``kite,'' or glider, moving in an ocean current which is connected by tethers to a floating buoy on the ocean surface. The TUSK kite is a current speed enhancement device since the kite can move in high-speed, cross-current motion at 4-6 times the current velocity, thus producing more power than conventional marine turbines. A computational simulation is developed to simulate the dynamic motion of an underwater kite and extendable tether. A two-step projection method within a finite volume formulation, along with an Open MP acceleration method, is employed to solve the Navier-Stokes equations. An immersed boundary method is incorporated to model the fluid-structure interaction of the rigid kite (with NACA 0012 airfoil shape in 2D and NACA 0021 airfoil shape in 3D simulations) and the fluid flow. PID control methods are used to adjust the kite angle of attack during power (tether reel-out) and retraction (reel-in) phases. Two baseline simulations (for kite motions in two and three dimensions) are studied, and system power output, flow field vorticity, tether tension, and hydrodynamic coefficients (lift and drag) for the kite are determined. The simulated power output shows good agreement with established theoretical results for a kite moving in two-dimensions.

  20. CORVET and HOPS tethering complexes - coordinators of endosome and lysosome fusion.

    Science.gov (United States)

    Balderhaar, Henning J kleine; Ungermann, Christian

    2013-03-15

    Protein and lipid transport along the endolysosomal system of eukaryotic cells depends on multiple fusion and fission events. Over the past few years, the molecular constituents of both fission and fusion machineries have been identified. Here, we focus on the mechanism of membrane fusion at endosomes, vacuoles and lysosomes, and in particular on the role of the two homologous tethering complexes called CORVET and HOPS. Both complexes are heterohexamers; they share four subunits, interact with Rab GTPases and soluble NSF attachment protein receptors (SNAREs) and can tether membranes. Owing to the presence of specific subunits, CORVET is a Rab5 effector complex, whereas HOPS can bind efficiently to late endosomes and lysosomes through Rab7. Based on the recently described overall structure of the HOPS complex and a number of in vivo and in vitro analyses, important insights into their function have been obtained. Here, we discuss the general function of both complexes in yeast and in metazoan cells in the context of endosomal biogenesis and maturation.

  1. Multifunctional inulin tethered silver-graphene quantum dots nanotheranostic module for pancreatic cancer therapy.

    Science.gov (United States)

    Nigam Joshi, Preeti; Agawane, Sachin; Athalye, Meghana C; Jadhav, Vrushali; Sarkar, Dhiman; Prakash, Rajiv

    2017-09-01

    Cancer nanotechnology is an emerging area of cancer diagnosis and therapy. Although considerable progress has been made for targeted drug delivery systems to deliver anticancer agents to particular site of interest, new nanomaterials are frequently being developed and explored for better drug delivery efficiency. In the present work, we have explored a novel nanoformulation based on silver-graphene quantum dots (Ag-GQDs) nanocomposite for its successful implementation for pancreatic cancer specific drug delivery in wistar rats. Carboxymethyl inulin (CMI); a modified variant of natural polysaccharide inulin is tethered with the nanocomposite via carbodiimide coupling to enhance the biocompatibility of nanoformulation. Experiments are performed to investigate the cytotoxicity reduction of silver nanoparticles after inulin tethering as well as anticancer efficacy of the system using 5-Fluorouracil (5-FU) as model drug. SEM, TEM, FT-IR, UV-vis, photoluminescence and anti proliferative assays (MTT) are performed for characterisation of the nanocomposite. Hyaluronic acid (HA) is conjugated as targeting moiety for CD-44 (cancer stem cell marker) to fabricate a complete targeted drug delivery vehicle specific for pancreatic cancer. In the present work two prime objectives were achieved; mitigation the toxicity of silver nanoparticles by inulin coating and it's in vivo application for pancreatic cancer. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Marine Toxins: An Overview

    Science.gov (United States)

    Fusetani, Nobuhiro

    Oceans provide enormous and diverse space for marine life. Invertebrates are conspicuous inhabitants in certain zones such as the intertidal; many are soft-bodied, relatively immobile and lack obvious physical defenses. These animals frequently have evolved chemical defenses against predators and overgrowth by fouling organisms. Marine animals may accumulate and use a variety of toxins from prey organisms and from symbiotic microorganisms for their own purposes. Thus, toxic animals are particularly abundant in the oceans. The toxins vary from small molecules to high molecular weight proteins and display unique chemical and biological features of scientific interest. Many of these substances can serve as useful research tools or molecular models for the design of new drugs and pesticides. This chapter provides an initial survey of these toxins and their salient properties.

  3. Marine and freshwater toxins.

    Science.gov (United States)

    Hungerford, James M

    2006-01-01

    In a very busy and exciting year, 2005 included First Action approval of a much needed official method for paralytic shellfish toxins and multiple international toxin symposia highlighted by groundbreaking research. These are the first-year milestones and activities of the Marine and Freshwater Toxins Task Force and Analytical Community. Inaugurated in 2004 and described in detail in last year's General Referee Report (1) this international toxins group has grown to 150 members from many regions and countries. Perhaps most important they are now making important and global contributions to food safety and to providing alternatives to animal-based assays. Official Method 2005.06 was first approved in late 2004 by the Task Force and subsequently Official First Action in 2005 (2) by the Methods Committee on Natural Toxins and Food Allergens and the Official Methods Board. This nonproprietary method (3) is a precolumn oxidation, liquid chromatographic method that makes good use of fluorescence detection to provide high sensitivity detection of the saxitoxins. It has also proven to be rugged enough for regulatory use and the highest level of validation. As pointed out in the report of method principle investigator and Study Director James Lawrence, approval of 2005.06 now provides the first official alternative to the mouse bioassay after many decades of shellfish monitoring. This past year in April 2005 the group also held their first international conference, "Marine and Freshwater Toxins Analysis: Ist Joint Symposium and AOAC Task Force Meeting," in Baiona, Spain. The 4-day conference consisted of research and stakeholder presentations and symposium-integrated subgroup sessions on ciguatoxins, saxitoxin assays and liquid chromatography (LC) methods for saxitoxins and domoic acids, okadaiates and azaspiracids, and yessotoxins. Many of these subgroups were recently formed in 2005 and are working towards their goals of producing officially validated analytical methods

  4. [Determination of tetanus toxin and toxoid by ELISA using monoclonal antibodies].

    Science.gov (United States)

    Burkin, M A; Sviridov, V V; Perelygina, O V

    2004-01-01

    The procedure of obtaining monoclonal antibodies TT-1, TT-2, and TT-3 against tetanus toxin/toxoid is described. It is shown that both commercial DTP vaccine and tetanus toxoid conjugated with a low-molecular-weight hapten can be used an immunogens. Monoclonal antibodies TT-1 and TT-2 neutralized tetanus toxin in vivo. The monoclonal antibodies obtained were used to design and compare several schemes of quantitative determination of tetanus toxoid and toxin by ELISA. A more sensitive competitive ELISA allowed detecting as much as 0.01 EC/ml toxoid and 50 LD50/ml toxin.

  5. Modeling of tethered satellite formations using graph theory

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Smith, Roy S; Blanke, Mogens

    2011-01-01

    Tethered satellite formations have recently gained increasing attention due to future mission proposals. Several different formations have been investigated for their dynamic properties and control schemes have been suggested. Formulating the equations of motion and investigation which geometries...... satellite formation and proposes a method to deduce the equations of motion for the attitude dynamics of the formation in a compact form. The use of graph theory and Lagrange mechanics together allows a broad class of formations to be described using the same framework. A method is stated for finding...... could form stable formations in space are cumbersome when done at a case to case basis, and a common framework providing a basic model of the dynamics of tethered satellite formations can therefore be advantageous. This paper suggests the use of graph theoretical quantities to describe a tethered...

  6. Reliability of tethered swimming evaluation in age group swimmers.

    Science.gov (United States)

    Amaro, Nuno; Marinho, Daniel A; Batalha, Nuno; Marques, Mário C; Morouço, Pedro

    2014-06-28

    The aim of the present study was to examine the reliability of tethered swimming in the evaluation of age group swimmers. The sample was composed of 8 male national level swimmers with at least 4 years of experience in competitive swimming. Each swimmer performed two 30 second maximal intensity tethered swimming tests, on separate days. Individual force-time curves were registered to assess maximum force, mean force and the mean impulse of force. Both consistency and reliability were very strong, with Cronbach's Alpha values ranging from 0.970 to 0.995. All the applied metrics presented a very high agreement between tests, with the mean impulse of force presenting the highest. These results indicate that tethered swimming can be used to evaluate age group swimmers. Furthermore, better comprehension of the swimmers ability to effectively exert force in the water can be obtained using the impulse of force.

  7. Reliability of Tethered Swimming Evaluation in Age Group Swimmers

    Directory of Open Access Journals (Sweden)

    Amaro Nuno

    2014-07-01

    Full Text Available The aim of the present study was to examine the reliability of tethered swimming in the evaluation of age group swimmers. The sample was composed of 8 male national level swimmers with at least 4 years of experience in competitive swimming. Each swimmer performed two 30 second maximal intensity tethered swimming tests, on separate days. Individual force-time curves were registered to assess maximum force, mean force and the mean impulse of force. Both consistency and reliability were very strong, with Cronbach's Alpha values ranging from 0.970 to 0.995. All the applied metrics presented a very high agreement between tests, with the mean impulse of force presenting the highest. These results indicate that tethered swimming can be used to evaluate age group swimmers. Furthermore, better comprehension of the swimmers ability to effectively exert force in the water can be obtained using the impulse of force.

  8. Progressive coxa vara by eccentric growth tethering in immature pigs.

    Science.gov (United States)

    Chang, Chia-Hsieh; Chi, Chau-Hwa; Lee, Zhon-Liau

    2006-07-01

    The present study tested progressive coxa vara by eccentric growth tethering that might be used to correct coxa valga in cerebral palsy. Eight young pigs received screw fixation at inferior portion of right femoral head at age 4 months and were killed at age 7.25 months for bilateral femurs for comparison. The neck-shaft angle at the tethered side was significantly less than that at the control side (129.8 vs. 138.3 degrees , P<0.05). Histological study showed bony bar formation. Eccentric growth tethering by one screw resulted in a reduction of neck-shaft angle by 8.5 degrees and shortening of femoral length by 4%.

  9. Behavior During Tethered Kicking in Infants With Periventricular Brain Injury.

    Science.gov (United States)

    Campbell, Suzann K; Cole, Whitney; Boynewicz, Kara; Zawacki, Laura A; Clark, April; Gaebler-Spira, Deborah; deRegnier, Raye-Ann; Kuroda, Maxine M; Kale, Dipti; Bulanda, Michele; Madhavan, Sangeetha

    2015-01-01

    To describe behavior of children with periventricular brain injury (PBI) in a tethered-kicking intervention. Sixteen infants with PBI were randomly assigned to exercise or no-training in a longitudinal pilot study. Frequencies of leg movements and interlimb coordination were described from videos at 2 and 4 months' corrected age (CA). Eight of the 13 children (62%) with longitudinal data increased the frequency of leg movements while tethered to a mobile between 2 and 4 months' CA. Movement frequency was correlated with scores on the Test of Infant Motor Performance, but no differences between experimental groups were found. Children with typical development at 12 months' CA increased the proportion of leg movements that were synchronous between 2 and 4 months, as did a child with cerebral palsy in the experimental group. The tethered-kicking intervention facilitates movement in infants with PBI, but effects on development remain to be demonstrated.

  10. [Toxins as a biological weapon].

    Science.gov (United States)

    Płusa, Tadeusz

    2015-09-01

    The criteria for recognizing a chemical compound for the toxin are vague and gave it the possibility of inclusion in this group a number of biological agents. Toxins list is extensive, but the interest is focused on bacterial toxins, poisons derived from snake venoms, algae and plant proteins, and small molecules. Particular attention is focused on the so-called "sea" toxins, which include tetrodotoxin, brevetoxin and saxitoxin. This indicates the search for a new hitherto unknown potential bioterrorist threats. © 2015 MEDPRESS.

  11. Anchoring a Leviathan: How the Nuclear Membrane Tethers the Genome

    Directory of Open Access Journals (Sweden)

    Rafal eCzapiewski

    2016-05-01

    Full Text Available It is well established that the nuclear envelope has many distinct direct connections to chromatin that contribute to genome organization. The functional consequences of genome organization on gene regulation are less clear. Even less understood is how interactions of lamins and nuclear envelope transmembrane proteins (NETs with chromatin can produce anchoring tethers that can withstand the physical forces of and on the genome. Chromosomes are the largest molecules in the cell, making megadalton protein structures like the nuclear pore complexes and ribosomes seem small by comparison. Thus to withstand strong forces from chromosome dynamics an anchoring tether is likely to be much more complex than a single protein-protein or protein-DNA interaction. Here we will briefly review known NE-genome interactions that likely contribute to spatial genome organization, postulate in the context of experimental data how these anchoring tethers contribute to gene regulation, and posit several hypotheses for the physical nature of these tethers that need to be investigated experimentally. Significantly, disruption of these anchoring tethers and the subsequent consequences for gene regulation could explain how mutations in nuclear envelope proteins cause diseases ranging from muscular dystrophy to lipodystrophy to premature ageing progeroid syndromes. The two favored hypotheses for nuclear envelope protein involvement in disease are 1 weakening nuclear and cellular mechanical stability, and 2 disrupting genome organization and gene regulation. Considerable experimental support has been obtained for both. The integration of both mechanical and gene expression defects in the disruption of anchoring tethers could provide a unifying hypothesis consistent with both.

  12. Bioassays for evaluation of medical products derived from bacterial toxins.

    Science.gov (United States)

    Sesardic, Thea

    2012-06-01

    Bioassays play central role in evaluation of biological products and those derived from bacterial toxins often rely exclusively on in vivo models for assurance of safety and potency. This chapter reviews existing regulatory approved methods designed to provide information on potency and safety of complex biological medicines with an insight into strategies considered for alternative procedures. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. An experimental study of tether reel system: A laboratory model

    OpenAIRE

    Yoshimura, Shoichi; Okamoto, Osamu; 吉村 庄市; 岡本 修

    1992-01-01

    A laboratory prototype model of a reel system has been made as the first step of an in-house hardware study of the tether system in space. The model is consisted of two main parts, i. e., a Reel Drum Driving (RDD) unit (25 kg weight) and a Power Supply/Signal Processing (PSSP) unit (32 kg weight). The tether (0.8 mm in diameter and 300 m long) consists of a Kevlar fiber core and a nylon fiber jacket. Following the preliminary functional test, a computer-controlled functional test has been car...

  14. Protein tethering enables rapid and label-free SERS platform for screening drugs of abuse (Conference Presentation)

    Science.gov (United States)

    Siddhanta, Soumik; Wróbel, Maciej S.; Barman, Ishan

    2017-02-01

    A quick, cost-effective method for detection of drugs of abuse in biological fluids would be of great value in healthcare, law enforcement, and home testing applications. The alarming rise in narcotics abuse has led to considerable focus on developing potent and versatile analytical tools that can address this societal problem. While laboratory testing plays a key role in the current detection of drug misuse and the evaluation of patients with drug induced intoxication, these typically require expensive reagents and trained personnel, and may take hours to complete. Thus, a significant unmet need is to engineer a facile method that can rapidly detect drugs with little sample preparation, especially the bound fraction that is typically dominant in the blood stream. Here we report an approach that combines the exquisite sensitivity of surface enhanced Raman spectroscopy (SERS) and a facile protein tethering mechanism to reliably detect four different classes of drugs, barbiturate, benzodiazepine, amphetamine and benzoylecgonine. The proposed approach harnesses the reliable and specific attachment of proteins to both drugs and nanoparticle to facilitate the enhancement of spectral markers that are sensitive to the presence of the drugs. In conjunction with chemometric tools, we have shown the ability to quantify these drugs lower than levels achievable by existing clinical immunoassays. Through molecular docking simulations, we also probe the mechanistic underpinnings of the protein tethering approach, opening the door to detection of a broad class of narcotics in biological fluids within a few minutes as well as for groundwater analysis and toxin detection.

  15. Membrane tethers formed from blood cells with available area and determination of their adhesion energy.

    OpenAIRE

    Hochmuth, Robert M; Marcus, Warren D.

    2002-01-01

    Fundamental to all mammalian cells is the adherence of the lipid bilayer membrane to the underlying membrane associated cytoskeleton. To investigate this adhesion, we physically detach the lipid membrane from the cell by mechanically forming membrane tethers. For the most part these have been tethers formed from either neutrophils or red cells. Here we do a simple thermodynamic analysis of the tether formation process using the entire cell, including tether, as the control volume. For a neutr...

  16. Optimal Trajectories for Tethered Kite Mounted on a Vertical Axis Generator

    NARCIS (Netherlands)

    Williams, P.; Lansdorp, B.; Ockels, W.

    2007-01-01

    Tethered kite technology promises the enable the efficient extraction of energy from high altitude winds. One possible concept for converting the wind energy into electricity is to generate useful work at the ground by using a tether. The tether is able to drive a generator in one of two ways:

  17. Nonlinear Control of Electrodynamic Tether in Equatorial or Somewhat Inclined Orbits

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2007-01-01

    This paper applies different control design methods to a tethered satellite system (TSS) to investigate essential control properties of this under-actuated and nonlinear system. When the tether position in the orbit plane is controlled by the tether current, out of orbit plane motions occur...

  18. Toxins Best Paper Award 2015

    Directory of Open Access Journals (Sweden)

    Vernon L. Tesh

    2015-03-01

    Full Text Available In order to recognize outstanding papers related to biotoxins and toxinology that have been published in Toxins, the Editorial Board established an annual “Toxins Best Paper Award”. We are pleased to announce the first “Toxins Best Paper Award” for 2015. Nominations were selected by the Editorial Board members, with all papers published in 2011 eligible for consideration. Reviews and original research articles were evaluated separately. Following review and voting by the Toxins Best Paper Award Committee, the following three papers have won Toxins Best Paper Awards for 2015:[...

  19. [Protein toxins of Staphylococcus aureus].

    Science.gov (United States)

    Shamsutdinov, A F; Tiurin, Iu A

    2014-01-01

    Main scientific-research studies regarding protein bacterial toxins of the most widespread bacteria that belong to Staphylococcus spp. genus and in particular the most pathogenic species for humans--Staphylococcus aureus, are analyzed. Structural and biological properties of protein toxins that have received the name of staphylococcus pyrogenic toxins (PTSAg) are presented. Data regarding genetic regulation of secretion and synthesis of these toxins and 3 main regulatory genetic systems (agr--accessory gene regulator, xpr--extracellular protein regulator, sar--staphylococcal accessory regulator) that coordinate synthesis of the most important protein toxins and enzymes for virulence of S. aureus, are presented.

  20. Autoproteolytic Activation of Bacterial Toxins

    Directory of Open Access Journals (Sweden)

    Aimee Shen

    2010-05-01

    Full Text Available Protease domains within toxins typically act as the primary effector domain within target cells. By contrast, the primary function of the cysteine protease domain (CPD in Multifunctional Autoprocessing RTX-like (MARTX and Clostridium sp. glucosylating toxin families is to proteolytically cleave the toxin and release its cognate effector domains. The CPD becomes activated upon binding to the eukaryotic-specific small molecule, inositol hexakisphosphate (InsP6, which is found abundantly in the eukaryotic cytosol. This property allows the CPD to spatially and temporally regulate toxin activation, making it a prime candidate for developing anti-toxin therapeutics. In this review, we summarize recent findings related to defining the regulation of toxin function by the CPD and the development of inhibitors to prevent CPD-mediated activation of bacterial toxins.

  1. Dominant negative mutants of Bacillus thuringiensis Cry1Ab toxin function as anti-toxins: demonstration of the role of oligomerization in toxicity.

    Directory of Open Access Journals (Sweden)

    Claudia Rodríguez-Almazán

    Full Text Available Bacillus thuringiensis Cry toxins, that are used worldwide in insect control, kill insects by a mechanism that depends on their ability to form oligomeric pores that insert into the insect-midgut cells. These toxins are being used worldwide in transgenic plants or spray to control insect pests in agriculture. However, a major concern has been the possible effects of these insecticidal proteins on non-target organisms mainly in ecosystems adjacent to agricultural fields.We isolated and characterized 11 non-toxic mutants of Cry1Ab toxin affected in different steps of the mechanism of action namely binding to receptors, oligomerization and pore-formation. These mutant toxins were analyzed for their capacity to block wild type toxin activity, presenting a dominant negative phenotype. The dominant negative phenotype was analyzed at two levels, in vivo by toxicity bioassays against susceptible Manduca sexta larvae and in vitro by pore formation activity in black lipid bilayers. We demonstrate that some mutations located in helix alpha-4 completely block the wild type toxin activity at sub-stoichiometric level confirming a dominant negative phenotype, thereby functioning as potent antitoxins.This is the first reported case of a Cry toxin dominant inhibitor. These data demonstrate that oligomerization is a fundamental step in Cry toxin action and represent a potential mechanism to protect special ecosystems from the possible effect of Cry toxins on non-target organisms.

  2. The value of intraoperative neurophysiological monitoring in tethered cord surgery

    NARCIS (Netherlands)

    Hoving, Eelco W.; Haitsma, Esther; Ophuis, Charlotte M. C. Oude; Journee, Henricus L.

    The value of intraoperative neurophysiological monitoring (IONM) with surgical detethering in dysraphic patients has been questioned. A retrospective analysis of our series of 65 patients is presented with special focus on technical set-up and outcome. All patients were diagnosed with a tethered

  3. 75 FR 47316 - Centennial Challenges 2010 Strong Tether Challenge

    Science.gov (United States)

    2010-08-05

    ... Challenge will be conducted at the 2010 Space Elevator Conference held at the Microsoft Conference Center... SPACE ADMINISTRATION Centennial Challenges 2010 Strong Tether Challenge AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice. SUMMARY: This notice is issued in accordance with 42 U.S.C...

  4. 76 FR 41526 - Centennial Challenges 2011 Strong Tether Challenge

    Science.gov (United States)

    2011-07-14

    ... Challenge will be conducted at the 2011 Space Elevator Conference held at the Microsoft Conference Center... SPACE ADMINISTRATION Centennial Challenges 2011 Strong Tether Challenge AGENCY: National Aeronautics and Space Administration (NASA). ACTION: Notice. SUMMARY: This notice is issued in accordance with 42 U.S.C...

  5. Three dimensional dynamics of a flexible Motorised Momentum Exchange Tether

    Science.gov (United States)

    Ismail, N. A.; Cartmell, M. P.

    2016-03-01

    This paper presents a new flexural model for the three dimensional dynamics of the Motorised Momentum Exchange Tether (MMET) concept. This study has uncovered the relationships between planar and nonplanar motions, and the effect of the coupling between these two parameters on pragmatic circular and elliptical orbits. The tether sub-spans are modelled as stiffened strings governed by partial differential equations of motion, with specific boundary conditions. The tether sub-spans are flexible and elastic, thereby allowing three dimensional displacements. The boundary conditions lead to a specific frequency equation and the eigenvalues from this provide the natural frequencies of the orbiting flexible motorised tether when static, accelerating in monotonic spin, and at terminal angular velocity. A rotation transformation matrix has been utilised to get the position vectors of the system's components in an assumed inertial frame. Spatio-temporal coordinates are transformed to modal coordinates before applying Lagrange's equations, and pre-selected linear modes are included to generate the equations of motion. The equations of motion contain inertial nonlinearities which are essentially of cubic order, and these show the potential for intricate intermodal coupling effects. A simulation of planar and non-planar motions has been undertaken and the differences in the modal responses, for both motions, and between the rigid body and flexible models are highlighted and discussed.

  6. Tethered Nanoparticle -Polymer Composites: Phase behavior and rheology

    Science.gov (United States)

    Mangal, Rahul; Archer, Lynden A.

    2014-03-01

    Polymer nanocomposites with particle radius (a) approaching the radius of gyration (Rg) of entangled host polymer have been reported to exhibit an unusual negative reinforcement effect, which leads to an anomalous reduction in relative an anomalous reduction in relative viscosity at low particle loadings (φ) . This so-called Non-Einsteinian flow behavior is understood to be sensitive to the dispersion state of particles in host polymer. We studied suspensions of SiO2 nanoparticles tethered with polethylene glycol (PEG) in polymethylmethacralate (PMMA) with molecular weights (Mw) from 17 KDa to 280 KDa. Due to strong enthalpic interactions between PEG and PMMA (χ = -0.65), nanoparticles are expected to be well-dispersed, independent of Mw of PMMA. Using small angle x-ray scattering measurements we show that the phase stability of suspensions depends on Mw of the tethered PEG, host PMMA, and φ. Particles functionalized with low molecular weight PEG aggregate at low φ, but disperse at high φ. In contrast, nanoparticles functionalized with higher molecular weight PEG are well dispersed for host chain lengths (P) to tethered chain length (N), (P/N), is as high as 160. The stability boundary of these suspensions extends well beyond expectations for nanocomposites based on tethered PEG chains suspended in PEG. Through in-depth analysis of rheology and x-ray photon correlation spectra we explore the fundamental origins of non-Einsteinian flow behavior. King Abdullah University of Science and Technology (KAUST), Advanced Photon Source (APS).

  7. Power and charge dissipation from an electrodynamic tether

    Science.gov (United States)

    Hite, Gerald E.

    1987-01-01

    The Plasma Motor-Generator project utilizes the influence of the geomagnetic field on a conductive tether attached to a LEO spacecraft to provide a reversible conversion of orbital energy into electrical energy. The behavior of the current into the ionospheric plasma under the influence of the geomagnetic field is of significant experimental and theoretical interest. Theoretical calculations are reviewed which start from Maxwell's equations and treat the ionospheric plasma as a linear dielectric medium. These calculations show a charge emitting tether moving in a magnetic field will generate electromagnetic waves in the plasma which carry the charge in the direction of the magnetic field. The ratio of the tether's speed to the ion cyclotron frequency which is about 25 m for a LEO is a characteristic length for the phenomena. Whereas for the dimensions of the contact plasma much larger than this value the waves are the conventional Alfven waves, when the dimensions are comparable or smaller, diffraction effects occur similar to those associated with Fresnel diffraction in optics. The power required to excite these waves for a given tether current is used to estimate the impedance associated with this mode of charge dissipation.

  8. Metal-ligand cooperation at tethered pi-ligands

    NARCIS (Netherlands)

    Verhoeven, Dide G. A.; Moret, Marc-Etienne

    2016-01-01

    Metal–ligand cooperativity in homogeneous catalysis is emerging as a powerful tool for the design of efficient transition-metal catalysts. This perspective highlights recent advances in the use of neutral π-coordinating ligands, tethered to a transition-metal center by other donor ligands, as

  9. Hierarchical Structure in Semicrystalline Polymers Tethered to Nanospheres

    KAUST Repository

    Kim, Sung A

    2014-01-28

    We report on structural and dynamic transitions of polymers tethered to nanoparticles. In particular, we use X-ray diffraction, vibrational spectroscopy, and thermal measurements to investigate multiscale structure and dynamic transitions of poly(ethylene glycol) (PEG) chains densely grafted to SiO2 nanoparticles. The approach used for synthesizing these hybrid particles leads to homogeneous SiO2-PEG composites with polymer grafting densities as high as 1.5 chains/nm2, which allows the hybrid materials to exist as self-suspended suspensions with distinct hierarchical structure and thermal properties. On angstrom and nanometer length scales, the tethered PEG chains exhibit more dominant TTG conformations and helix unit cell structure, in comparison to the untethered polymer. The nanoparticle tethered PEG chains are also reported to form extended crystallites on tens of nanometers length scales and to exhibit more stable crystalline structure on small dimensions. On length scales comparable to the size of each hybrid SiO 2-PEG unit, the materials are amorphous presumably as a result of the difficulty fitting the nanoparticle anchors into the PEG crystal lattice. This structural change produces large effects on the thermal transitions of PEG molecules tethered to nanoparticles. © 2014 American Chemical Society.

  10. Nano-mechanics of HaloTag Tethers

    Science.gov (United States)

    Popa, Ionel; Berkovich, Ronen; Alegre-Cebollada, Jorge; Badilla, Carmen L.; Rivas-Pardo, Jaime Andres; Taniguchi, Yukinori; Kawakami, Masaru; Fernandez, Julio M.

    2013-01-01

    The active site of the Haloalkane Dehydrogenase (HaloTag) enzyme can be covalently attached to a chloroalkane ligand providing a mechanically strong tether, resistant to large pulling forces. Here we demonstrate the covalent tethering of protein L and I27 polyproteins between an AFM cantilever and a glass surface using HaloTag anchoring at one end, and thiol chemistry at the other end. Covalent tethering is unambiguously confirmed by the observation of full length polyprotein unfolding, combined with high detachment forces that range up to ~2000 pN. We use these covalently anchored polyproteins to study the remarkable mechanical properties of HaloTag proteins. We show that the force that triggers unfolding of the HaloTag protein exhibits a four-fold increase, from 131 pN to 491 pN, when the direction of the applied force is changed from the C-terminus to the N-terminus. Force-clamp experiments reveal that unfolding of the HaloTag protein is twice more sensitive to pulling force compared to protein L, and refolds at a slower rate. We show how these properties allow for the long-term observation of protein folding-unfolding cycles at high forces, without interference from the HaloTag tether. PMID:23909704

  11. Fortissimo: A Japanese Space Test Of Bare Wire Anode Tethers

    Science.gov (United States)

    Johnson, Les; Fujii, H. A.; Sanmartin, J. R.

    2008-01-01

    A Japanese led international team is developing a suborbital test of orbital-motion-limited (OML) bare wire anode current collection for application to electrodynamic tether (EDT) propulsion. The tether is a tape with a width of 25 mm, thickness of 0.05 mm, and is 300 m in length. This will be the first space test of OML theory. The mission will launch in the summer of 2009 using an S520 Sounding Rocket. During ascent, and above approx. 100 km in attitude, the tape tether will be deployed at a rate of approx. 8 m/s. Once deployed, the tape tether will serve as an anode, collecting ionospheric electrons. The electrons will be expelled into space by a hollow cathode device, thereby completing the circuit and allowing current to flow. The total amount of current collected will be used to assess the validity of OML theory. This paper will describe the objectives of the proposed mission, the technologies to be employed, and the application of the results to future space missions using EDTs for propulsion or power generation.

  12. Flight control and stability of a multiple kites tethered system

    NARCIS (Netherlands)

    Podgaets, A.R.; Ockels, W.J.

    2006-01-01

    One of novel concepts to use the energy of high altitude winds is by launching a series of kite on a long rope and let them pull the rope thus driving the generator. A mathematical model of tethered kites system has been developed consisting of models of kites and of the cable that links them

  13. Position Control of an X4-Flyer Using a Tether

    Directory of Open Access Journals (Sweden)

    , Keigo Watanabe

    2014-10-01

    Full Text Available In Japan, aging of infrastructures, such as roads, bridges, and water and sewer services, etc. poses a problem, and it is required to extend the life-span of such infrastructures by maintenance. Among infrastructures, especially bridges are periodically inspected by short range visual observations, which check the damage and deterioration of the surface. However, since there are some cases where the short range visual observation is difficult, an alternative method is required so as to replace the short range visual observation with it. So, "X4-Flyer" is very attractive because of realizing a movement at high altitude easily. The objective of this study is to develop a tethered X4- Flyer, so that the conventional short range visual observation of bridges is replaced by it. In this paper, a method for the measurement and control of the position is described by using a tether for controlling the position of the X4-Flyer. In addition, it is checked whether the tethered X4-Flyer can control the position using the proposed method or not, letting it fly in a state in which a tether is being attached.

  14. Clostridium Perfringens Toxins Involved in Mammalian Veterinary Diseases

    Science.gov (United States)

    Uzal, F. A.; Vidal, J. E.; McClane, B. A.; Gurjar, A. A.

    2013-01-01

    . perfringens in animal disease. These research tools are helping us to establish the role of each C. perfringens toxin in animal disease, to investigate the in vivo mechanism of action of these toxins, and to develop more effective vaccines against diseases produced by these microorganisms. PMID:24511335

  15. T-Rex: A Japanese Space Tether Experiment

    Science.gov (United States)

    Johnson, Les

    2009-01-01

    Electrodynamic tether (EDT) thrusters work by virtue of the force a magnetic field exerts on a wire carrying an electrical current. The force, which acts on any charged particle moving through a magnetic field (including the electrons moving in a current-carrying wire), were concisely expressed by Lorentz in 1895 in an equation that now bears his name. The force acts in a direction perpendicular to both the direction of current flow and the magnetic field vector. Electric motors make use of this force: a wire loop in a magnetic field is made to rotate by the torque the Lorentz Force exerts on it due to an alternating current in the loop times so as to keep the torque acting in the same sense. The motion of the loop is transmitted to a shaft, thus providing work. Although the working principle of EDT thrusters is not new, its application to space transportation may be significant. In essence, an EDT thruster is just a clever way of getting an electrical current to flow in a long orbiting wire (the tether) so that the Earth s magnetic field will accelerate the wire and, consequently the payload attached to the wire. The direction of current flow in the tether, either toward or away from the Earth along the local vertical, determines whether the magnetic force will raise or lower the orbit. The bias voltage of a vertically deployed metal tether, which results just from its orbital motion (assumed eastward) through Earth s magnetic field, is positive with respect to the ambient plasma at the top and negative at the bottom. This polarization is due to the action of the Lorentz force on the electrons in the tether. Thus, the natural current flow is the result of negative electrons being attracted to the upper end and then returned to the plasma at the lower end. The magnetic force in this case has a component opposite to the direction of motion, and thus leads to a lowering of the orbit and eventually to re-entry. In this generator mode of operation the Lorentz Force

  16. Autonomous Vision-Based Tethered-Assisted Rover Docking

    Science.gov (United States)

    Tsai, Dorian; Nesnas, Issa A.D.; Zarzhitsky, Dimitri

    2013-01-01

    Many intriguing science discoveries on planetary surfaces, such as the seasonal flows on crater walls and skylight entrances to lava tubes, are at sites that are currently inaccessible to state-of-the-art rovers. The in situ exploration of such sites is likely to require a tethered platform both for mechanical support and for providing power and communication. Mother/daughter architectures have been investigated where a mother deploys a tethered daughter into extreme terrains. Deploying and retracting a tethered daughter requires undocking and re-docking of the daughter to the mother, with the latter being the challenging part. In this paper, we describe a vision-based tether-assisted algorithm for the autonomous re-docking of a daughter to its mother following an extreme terrain excursion. The algorithm uses fiducials mounted on the mother to improve the reliability and accuracy of estimating the pose of the mother relative to the daughter. The tether that is anchored by the mother helps the docking process and increases the system's tolerance to pose uncertainties by mechanically aligning the mating parts in the final docking phase. A preliminary version of the algorithm was developed and field-tested on the Axel rover in the JPL Mars Yard. The algorithm achieved an 80% success rate in 40 experiments in both firm and loose soils and starting from up to 6 m away at up to 40 deg radial angle and 20 deg relative heading. The algorithm does not rely on an initial estimate of the relative pose. The preliminary results are promising and help retire the risk associated with the autonomous docking process enabling consideration in future martian and lunar missions.

  17. The International Tethered Cord Partnership: Beginnings, process, and status

    Science.gov (United States)

    Mulholland, Celene B.; Aranda, Guzmán; Arredondo, Luis Angel; Calgua, Erwin; Contreras, Fernando; Espinoza, Dulce Maria; Gonzalez, Juan Bosco; Hoil, Jose A.; Komolafe, Edward; Lazareff, Jorge A.; Liu, Yunhui; Soto-Mancilla, Juan Luis; Mannucci, Graciela; Nan, Bao; Portillo, Santiago; Zhao, Hongyu

    2011-01-01

    Background: Spina bifida presents a significant cause of childhood morbidity in lower- and middle-income nations. Unfortunately, there is a paucity of literature examining outcomes among children with spina bifida in these countries. The goal of the International Tethered Cord Parternship is twofold: (1) to establish an international surveillance database to examine the correlation between time of repair and clinical outcomes in children with spina bifida and tethered cord; and (2) to foster collaboration among international institutions around pediatric neurosurgical concerns. Methods: Twelve institutions in 7 countries committed to participating in the International Tethered Cord Partnership. A neurosurgeon at each institution will evaluate all children presenting with spina bifida and/or tethered cord using the survey instrument after appropriate consent is obtained. The instrument was developed collaboratively and based on previous measures of motor and sensory function, ambulation, and continence. All institutions who have begun collecting data received appropriate Institutional Review Board approval. All data will be entered into a Health Insurance Portability and Accountability Act (HIPAA) compliant database. In addition, a participant restricted internet forum was created to foster communication and includes non–project-specific communications, such as case and journal article discussion. Results: From October 2010 to December 2010, 82 patients were entered from the various study sites. Conclusion: To our knowledge this is the first international pediatric neurosurgical database focused on clinical outcomes and predictors of disease progression. The collaborative nature of the project will not only increase knowledge of spina bifida and tethered cord, but also foster discussion and further collaboration between neurosurgeons internationally. PMID:21541204

  18. The International Tethered Cord Partnership: Beginnings, process, and status.

    Science.gov (United States)

    Mulholland, Celene B; Aranda, Guzmán; Arredondo, Luis Angel; Calgua, Erwin; Contreras, Fernando; Espinoza, Dulce Maria; Gonzalez, Juan Bosco; Hoil, Jose A; Komolafe, Edward; Lazareff, Jorge A; Liu, Yunhui; Soto-Mancilla, Juan Luis; Mannucci, Graciela; Nan, Bao; Portillo, Santiago; Zhao, Hongyu

    2011-03-23

    Spina bifida presents a significant cause of childhood morbidity in lower- and middle-income nations. Unfortunately, there is a paucity of literature examining outcomes among children with spina bifida in these countries. The goal of the International Tethered Cord Parternship is twofold: (1) to establish an international surveillance database to examine the correlation between time of repair and clinical outcomes in children with spina bifida and tethered cord; and (2) to foster collaboration among international institutions around pediatric neurosurgical concerns. Twelve institutions in 7 countries committed to participating in the International Tethered Cord Partnership. A neurosurgeon at each institution will evaluate all children presenting with spina bifida and/or tethered cord using the survey instrument after appropriate consent is obtained. The instrument was developed collaboratively and based on previous measures of motor and sensory function, ambulation, and continence. All institutions who have begun collecting data received appropriate Institutional Review Board approval. All data will be entered into a Health Insurance Portability and Accountability Act (HIPAA) compliant database. In addition, a participant restricted internet forum was created to foster communication and includes non-project-specific communications, such as case and journal article discussion. From October 2010 to December 2010, 82 patients were entered from the various study sites. To our knowledge this is the first international pediatric neurosurgical database focused on clinical outcomes and predictors of disease progression. The collaborative nature of the project will not only increase knowledge of spina bifida and tethered cord, but also foster discussion and further collaboration between neurosurgeons internationally.

  19. Relaxation Dynamics of Nanoparticle-Tethered Polymer Chains

    KAUST Repository

    Kim, Sung A

    2015-09-08

    © 2015 American Chemical Society. Relaxation dynamics of nanoparticle-tethered cis-1,4-polyisoprene (PI) are investigated using dielectric spectroscopy and rheometry. A model system composed of polymer chains densely grafted to spherical SiO2 nanoparticles to form self-suspended suspensions facilitates detailed studies of slow global chain and fast segmental mode dynamics under surface and geometrical confinement-from experiments performed in bulk materials. We report that unentangled polymer molecules tethered to nanoparticles relax far more slowly than their tethered entangled counterparts. Specifically, at fixed grafting density we find, counterintuitively, that increasing the tethered polymer molecular weight up to values close to the entanglement molecular weight speeds up chain relaxation dynamics. Decreasing the polymer grafting density for a fixed molecular weight has the opposite effect: it dramatically slows down chain relaxation, increases interchain coupling, and leads to a transition in rheological response from simple fluid behavior to viscoelastic fluid behavior for tethered PI chains that are unentangled by conventional measures. Increasing the measurement temperature produces an even stronger elastic response and speeds up molecular relaxation at a rate that decreases with grafting density and molecular weight. These observations are discussed in terms of chain confinement driven by crowding between particles and by the existence of an entropic attractive force produced by the space-filling constraint on individual chains in a self-suspended material. Our results indicate that the entropic force between densely grafted polymer molecules couples motions of individual chains in an analogous manner to reversible cross-links in associating polymers.

  20. Modelling a tethered mammalian sperm cell undergoing hyperactivation

    KAUST Repository

    Curtis, M.P.

    2012-09-01

    The beat patterns of mammalian sperm flagella can be categorised into two different types. The first involves symmetric waves propagating down the flagellum with a net linear propulsion of the sperm cell. The second, hyperactive, waveform is classified by vigorous asymmetric waves of higher amplitude, lower wavenumber and frequency propagating down the flagellum resulting in highly curved trajectories. The latter beat pattern is part of the capacitation process whereby sperm prepare for the prospective penetration of the zona pellucida and fusion with the egg. Hyperactivation is often observed to initiate as sperm escape from epithelial and ciliary bindings formed within the isthmic regions of the female oviducts, leading to a conjecture in the literature that this waveform is mechanically important for sperm escape. Hence, we explore the mechanical effects of hyperactivation on a tethered sperm, focussing on a Newtonian fluid. Using a resistive force theory model we demonstrate that hyperactivation can indeed generate forces that pull the sperm away from a tethering point and consequently a hyperactivated sperm cell bound to an epithelial surface need not always be pushed by its flagellum. More generally, directions of the forces generated by tethered flagella are insensitive to reductions in beat frequency and the detailed flagellar responses depend on the nature of the binding at the tethering point. Furthermore, waveform asymmetry and amplitude increases enhance the tendency for a tethered flagellum to start tugging on its binding. The same is generally predicted to be true for reductions in the wavenumber of the flagellum beat, but not universally so, emphasising the dynamical complexity of flagellar force generation. Finally, qualitative observations drawn from experimental data of human sperm bound to excised female reproductive tract are also presented and are found to be consistent with the theoretical predictions. © 2012 Elsevier Ltd.

  1. Toxins of Amanita phalloides.

    Science.gov (United States)

    Vetter, J

    1998-01-01

    The most poisonous mushroom toxins are produced by Amanita phalloides (death cap). The occurrence and chemistry of three groups of toxins (amatoxins, phallotoxins and virotoxins) are summarized. The concentration and distribution of toxins in certain species are variable, with the young fruit body containing lower, and the well-developed fungus higher concentrations, but there is a high variability among specimens collected in the same region. Regarding phallotoxins, the volva (the ring) is the most poisonous. The most important biochemical effect of amatoxins is the inhibition of RNA polymerases (especially polymerase II). This interaction leads to a tight complex and the inhibition is of a non-competitive type. Non-mammalian polymerases show little sensitivity to amanitins. The amatoxins cause necrosis of the liver, also partly in the kidney, with the cellular changes causing the fragmentation and segregation of all nuclear components. Various groups of somatic cells of emanation resistance have been isolated, including from a mutant of Drosophila melanogaster. The phallotoxins stimulate the polymerization of G-actin and stabilize the F-actin filaments. The interaction of phallotoxins occurs via the small, 15-membered ring, on the left side of the spatial formula. The symptoms of human poisoning and the changes in toxin concentrations in different organs are summarized. Conventional therapy includes: (1) stabilization of patient's condition with the correction of hypoglycaemia and electrolytes; (2) decontamination; and (3) chemotherapy with different compounds. Finally, certain antagonists and protective compounds are reviewed, bearing in mind that today these have more of a theoretical than a practical role.

  2. In vivo

    Science.gov (United States)

    Freudenblum, Julia; Iglesias, José A; Hermann, Martin; Walsen, Tanja; Wilfinger, Armin; Meyer, Dirk; Kimmel, Robin A

    2018-02-08

    The three-dimensional architecture of the pancreatic islet is integral to beta cell function, but the process of islet formation remains poorly understood due to the difficulties of imaging internal organs with cellular resolution. Within transparent zebrafish larvae, the developing pancreas is relatively superficial and thus amenable to live imaging approaches. We performed in vivo time-lapse and longitudinal imaging studies to follow islet development, visualizing both naturally occurring islet cells and cells arising with an accelerated timecourse following an induction approach. These studies revealed previously unappreciated fine dynamic protrusions projecting between neighboring and distant endocrine cells. Using pharmacological compound and toxin interference approaches, and single-cell analysis of morphology and cell dynamics, we determined that endocrine cell motility is regulated by phosphoinositide 3-kinase (PI3K) and G-protein-coupled receptor (GPCR) signaling. Linking cell dynamics to islet formation, perturbation of protrusion formation disrupted endocrine cell coalescence, and correlated with decreased islet cell differentiation. These studies identified novel cell behaviors contributing to islet morphogenesis, and suggest a model in which dynamic exploratory filopodia establish cell-cell contacts that subsequently promote cell clustering. © 2018. Published by The Company of Biologists Ltd.

  3. Tether-mission design for multiple flybys of moon Europa

    Science.gov (United States)

    Sanmartin, J. R. S.; Charro, M. C.; Sanchez-Arriaga, G. S. A.; Sanchez-Torres, A. S. T.

    2015-10-01

    A tether mission to carry out multiple flybys of Jovian moon Europa is here presented. There is general agreement on elliptic-orbit flybys of Europa resulting in cost to attain given scientific goals lower than if actually orbiting the moon, tethers being naturally fit to fly-by rather than orbit moons1. The present mission is similar in this respect to the Clipper mission considered by NASA, the basic difference lying in location of periapsis, due to different emphasis on mission-challenge metrics. Clipper minimizes damaging radiation-dose by avoiding the Jupiter neighborhood and its very harsh environment; periapsis would be at Europa, apoapsis as far as moon Callisto. As in all past outer-planet missions, Clipper faces, however, critical power and propulsion needs. On the other hand, tethers can provide both propulsion and power, but must reach near the planet to find high plasma density and magnetic field values, leading to high induced tether current, and Lorentz drag and power. The bottom line is a strong radiation dose under the very intense Radiation Belts of Jupiter. Mission design focuses on limiting dose. Perijove would be near Jupiter, at about 1.2-1.3 Jovian radius, apojove about moon Ganymede, corresponding to 1:1 resonance with Europa, so as to keep dose down: setting apojove at Europa, for convenient parallel flybys, would require two perijove passes per flyby (the Ganymede apojove, resulting in high eccentricity, about 0.86, is also less requiring on tether operations). Mission is designed to attain reductions in eccentricity per perijove pass as high as Δe ≈ - 0.04. Due the low gravity-gradient, tether spinning is necessary to keep it straight, plasma contactors placed at both ends taking active turns at being cathodic. Efficiency of capture of the incoming S/C by the tether is gauged by the ratio of S/C mass to tether mass; efficiency is higher for higher tape-tether length and lower thickness and perijove. Low tether bowing due to the Lorentz

  4. Toxin Plasmids of Clostridium perfringens

    Science.gov (United States)

    Li, Jihong; Adams, Vicki; Bannam, Trudi L.; Miyamoto, Kazuaki; Garcia, Jorge P.; Uzal, Francisco A.; Rood, Julian I.

    2013-01-01

    SUMMARY In both humans and animals, Clostridium perfringens is an important cause of histotoxic infections and diseases originating in the intestines, such as enteritis and enterotoxemia. The virulence of this Gram-positive, anaerobic bacterium is heavily dependent upon its prolific toxin-producing ability. Many of the ∼16 toxins produced by C. perfringens are encoded by large plasmids that range in size from ∼45 kb to ∼140 kb. These plasmid-encoded toxins are often closely associated with mobile elements. A C. perfringens strain can carry up to three different toxin plasmids, with a single plasmid carrying up to three distinct toxin genes. Molecular Koch's postulate analyses have established the importance of several plasmid-encoded toxins when C. perfringens disease strains cause enteritis or enterotoxemias. Many toxin plasmids are closely related, suggesting a common evolutionary origin. In particular, most toxin plasmids and some antibiotic resistance plasmids of C. perfringens share an ∼35-kb region containing a Tn916-related conjugation locus named tcp (transfer of clostridial plasmids). This tcp locus can mediate highly efficient conjugative transfer of these toxin or resistance plasmids. For example, conjugative transfer of a toxin plasmid from an infecting strain to C. perfringens normal intestinal flora strains may help to amplify and prolong an infection. Therefore, the presence of toxin genes on conjugative plasmids, particularly in association with insertion sequences that may mobilize these toxin genes, likely provides C. perfringens with considerable virulence plasticity and adaptability when it causes diseases originating in the gastrointestinal tract. PMID:23699255

  5. Tether pointing platform and space elevator mechanisms analysis of the key concepts for SATP and scaled SATP

    Science.gov (United States)

    Turci, E.

    1986-01-01

    The key concepts for a scaled and full model Science and Applications Tethered Platform (SATP) are analysized. This includes a tether pointing platform and a space elevator. The mechanism concepts and technological solutions are given. The idea of the tether pointing platform mechanism is to control and stabilize the attitude of a platform by means of a movable tether. The idea of the space elevator mechanism for a scaled SATP is to drag the tether gripping it between two rotating wheels.

  6. Effects of Clostridium perfringens iota toxin in the small intestine of mice.

    Science.gov (United States)

    Redondo, Leandro M; Redondo, Enzo A; Dailoff, Gabriela C; Leiva, Carlos L; Díaz-Carrasco, Juan M; Bruzzone, Octavio A; Cangelosi, Adriana; Geoghegan, Patricia; Fernandez-Miyakawa, Mariano E

    2017-12-01

    Iota toxin is a binary toxin solely produced by Clostridium perfringens type E strains, and is structurally related to CDT from C. difficile and CST from C. spiroforme. As type E causes hemorrhagic enteritis in cattle, it is usually assumed that associated diseases are mediated by iota toxin, although evidence in this regard has not been provided. In the present report, iota toxin intestinal effects were evaluated in vivo using a mouse model. Histological damage was observed in ileal loops treated with purified iota toxin after 4 h of incubation. Luminal iota toxin induced fluid accumulation in the small intestine in a dose dependent manner, as determined by the enteropooling and the intestinal loop assays. None of these changes were observed in the large intestine. These results suggest that C. perfringens iota toxin alters intestinal permeability, predominantly by inducing necrosis and degenerative changes in the mucosal epithelium of the small intestine, as well as changes in intestinal motility. The obtained results suggest a central role for iota toxin in the pathogenesis of C. perfringens type E hemorrhagic enteritis, and contribute to remark the importance of clostridial binary toxins in digestive diseases. Published by Elsevier Ltd.

  7. Tethered elevator: A unique opportunity for space processing

    Science.gov (United States)

    Monti, R.

    1986-01-01

    The latest fluid dynamic and material science experiments in the microgravity environment have emphasized the importance of the residual gravity level and of the g-jitter on fluid physics phenomena. The tethered elevator presents the possibility of providing variable g-levels (both steady and g-jitter) around a very low steady g-level (that can be realized when the elevator is near the center of mass of the space station-tether complex). When positioning a variable periodic oscillation to the payload a clean g-jitter disturbance can be obtained that would not be otherwise obtainable by other systems. These two possibilities make the elevator a facility to help resolve a number of still open questions that are preventing wider utilization of the space environment in the microgravity area.

  8. Tethered naphthalene diimide intercalators enhance DNA triplex stability.

    Science.gov (United States)

    Gianolio, D A; McLaughlin, L W

    2001-09-01

    Naphthalene diimides function as effective intercalators and when tethered to the 5'-terminus of a pyrimidine-rich oligonucleotide can contribute significantly to the overall stabilization of DNA triplexes. This stabilization can be further enhanced by alterations to the linker tethering the DNA sequence and the intercalator. Less flexible linkers, and particularly one with a phenyl ring present, appear to permit the stabilization afforded by the bound intercalator to be transferred more effectively to the three-stranded complex. The conjugate containing the phenyl linker exhibits a T(M) value that is increased by 28 degrees C relative to the unconjugated triplex. That the linker itself contributes to the observed stabilization is clear since introduction of the phenyl linker increases the observed T(M) by 11 degrees C relative to a simple flexible linker.

  9. Synthesis and insertion chemistry of mixed tether uranium metallocene complexes

    Energy Technology Data Exchange (ETDEWEB)

    Siladke, Nathan A.; LeDuc, Jennifer; Ziller, Joseph W.; Evans, William J. [Department of Chemistry, University of California, Irvine, CA (United States)

    2012-11-12

    The synthesis of mixed tethered alkyl uranium metallocenes has been investigated by examining the reactivity of the bis(tethered alkyl) metallocene [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC){sub 2}U] (1) with substrates that react with only one of the U-C linkages. The effect of these mixed tether coordination environments on the reactivity of the remaining U-C bond has been studied by using CO insertion chemistry. One equivalent of azidoadamantane (AdN{sub 3}) reacts with 1 to yield the mixed tethered alkyl triazenido complex [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC)U(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}-CH{sub 2}NNN-Ad-κ{sup 2}N{sup 1,3})]. Similarly, a single equivalent of CS{sub 2} reacts with 1 to form the mixed tethered alkyl dithiocarboxylate complex [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC)U(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}- CH{sub 2}C(S){sub 2}-κ{sup 2}S,S{sup '})], a reaction that constitutes the first example of CS{sub 2} insertion into a U{sup 4+}-C bond. Complex 1 reacts with one equivalent of pyridine N-oxide by C-H bond activation of the pyridine ring to form a mixed tethered alkyl cyclometalated pyridine N-oxide complex [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC)(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 3})U(C{sub 6}H{sub 4}NO-κ{sup 2} C,O)]. The remaining (η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}-κC){sup 2-} ligand in each of these mixed tethered species show reactivity towards CO and tethered enolate ligands form by insertion. Subsequent rearrangement have been identified in [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 3})U(C{sub 5}H{sub 4}NO-κ{sup 2}C,O)(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}C(=CH{sub 2})O- κO)] and [(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}CH{sub 2}NNN-Ad-κ{sup 2}N{sup 1,3})U(η{sup 5}-C{sub 5}Me{sub 4}SiMe{sub 2}C(=CH{sub 2})O-κO)]. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. The tethered satellite system for low density aerothermodynamics studies

    Science.gov (United States)

    Carlomagno, Giovanni M.; De Luca, Luigi; Siemers, P. M., III; Wood, George M., Jr.

    1986-01-01

    The feasibility of the operation of the Tethered Satellite System (TSS) as a continuous open wind tunnel for low-density aerothermodynamic studies (applicable to the design of hypersonic space vehicles including STARFAC, AOTV, and ERV) is considered. The Shuttle Continuous Open Wind Tunnel (SCOWT) program, for the study of the energy and momentum transfer between the tethered satellite and its environmental medium during the TSS/2 mission, is described. Instrumentation and TSS design requirements to meet SCOWT objectives are also considered. SCOWT will provide information on the gasdynamic processes occurring downstream of the bow wave standing in front of the TS, the chemistry and physics of the upper atmosphere related to satellite aerothermodynamics, and TSS's overall experimental envelope of operation.

  11. Asteroid rotation control via a tethered solar sail

    Science.gov (United States)

    Gao, Youtao; Wu, Jingyun

    2016-12-01

    The rotation of asteroids causes difficulties in the exploration of asteroids or prevention of asteroids impact on the Earth. We propose to use a solar sail to control, i.e., slow down or stop the rotational motion of an asteroid. First, the dynamic model of a tethered solar sail in the rotating gravitational field of an asteroid is presented. An optimal control method is employed to determine the control law of the tethered solar sail. The optimal control problem is converted into a nonlinear programming problem with the Gauss pseudospectral method. Simulation results show that this method can effectively slow down or even stop the rotation of an asteroid. A solar sail of 105 m2 can stop the rotation of the asteroid Apophis in 1000 days.

  12. Comprehensive analysis of LANA interacting proteins essential for viral genome tethering and persistence.

    Directory of Open Access Journals (Sweden)

    Subhash C Verma

    Full Text Available Kaposi's sarcoma associated herpesvirus is tightly linked to multiple human malignancies including Kaposi's sarcoma (KS, Primary Effusion Lymphoma (PEL and Multicentric Castleman's Disease (MCD. KSHV like other herpesviruses establishes life-long latency in the infected host by persisting as chromatin and tethering to host chromatin through the virally encoded protein Latency Associated Nuclear Antigen (LANA. LANA, a multifunctional protein, is capable of binding to a large number of cellular proteins responsible for transcriptional regulation of various cellular and viral pathways involved in blocking cell death and promoting cell proliferation. This leads to enhanced cell division and replication of the viral genome, which segregates faithfully in the dividing tumor cells. The mechanism of genome segregation is well known and the binding of LANA to nucleosomal proteins, throughout the cell cycle, suggests that these interactions play an important role in efficient segregation. Various biochemical methods have identified a large number of LANA binding proteins, including histone H2A/H2B, histone H1, MeCP2, DEK, CENP-F, NuMA, Bub1, HP-1, and Brd4. These nucleosomal proteins may have various functions in tethering of the viral genome during specific phases of the viral life cycle. Therefore, we performed a comprehensive analysis of their interaction with LANA using a number of different assays. We show that LANA binds to core nucleosomal histones and also associates with other host chromatin proteins including histone H1 and high mobility group proteins (HMGs. We used various biochemical assays including co-immunoprecipitation and in-vivo localization by split GFP and fluorescence resonance energy transfer (FRET to demonstrate their association.

  13. Currents between tethered electrodes in a magnetized laboratory plasma

    Science.gov (United States)

    Stenzel, R. L.; Urrutia, J. M.

    1989-01-01

    Laboratory experiments on important plasma physics issues of electrodynamic tethers were performed. These included current propagation, formation of wave wings, limits of current collection, nonlinear effects and instabilities, charging phenomena, and characteristics of transmission lines in plasmas. The experiments were conducted in a large afterglow plasma. The current system was established with a small electron-emitting hot cathode tethered to an electron-collecting anode, both movable across the magnetic field and energized by potential difference up to V approx.=100 T(sub e). The total current density in space and time was obtained from complete measurements of the perturbed magnetic field. The fast spacecraft motion was reproduced in the laboratory by moving the tethered electrodes in small increments, applying delayed current pulses, and reconstructing the net field by a linear superposition of locally emitted wavelets. With this technique, the small-amplitude dc current pattern is shown to form whistler wings at each electrode instead of the generally accepted Alfven wings. For the beam electrode, the whistler wing separates from the field-aligned beam which carries no net current. Large amplitude return currents to a stationary anode generate current-driven microinstabilities, parallel electric fields, ion depletions, current disruptions and time-varying electrode charging. At appropriately high potentials and neutral densities, excess neutrals are ionized near the anode. The anode sheath emits high-frequency electron transit-time oscillations at the sheath-plasma resonance. The beam generates Langmuir turbulence, ion sound turbulence, electron heating, space charge fields, and Hall currents. An insulated, perfectly conducting transmission line embedded in the plasma becomes lossy due to excitation of whistler waves and magnetic field diffusion effects. The implications of the laboratory observations on electrodynamic tethers in space are discussed.

  14. Crowded, Confined, and Frustrated: Dynamics of Molecules Tethered to Nanoparticles

    KAUST Repository

    Agarwal, Praveen

    2012-12-01

    Above a critical chemistry-dependent molecular weight, all polymer molecules entangle and, as a result, exhibit slow dynamics, enhanced viscosity, and elasticity. Herein we report on the dynamics of low molecular weight polymers tethered to nanoparticles and find that even conventionally unentangled chains manifest dynamical features similar to entangled, long-chain molecules. Our findings are shown to imply that crowding and confinement of polymers on particles produce topological constraints analogous to those in entangled systems. © 2012 American Physical Society.

  15. Deorbit efficiency assessment through numerical simulation of electromagnetic tether devices

    Directory of Open Access Journals (Sweden)

    Alexandru IONEL

    2016-03-01

    Full Text Available This paper examines the deorbit efficiency of an electromagnetic tether deorbit device when used to deorbit an upper stage at end of mission from low Earth orbit. This is done via a numerical simulation in Matlab R2013a, using ode45, taking into account perturbations on the upper stage’s trajectory. The perturbations taken into account are the atmospheric drag, the 3rd body (Sun and Moon, and Earth’s gravitational potential expanded into spherical harmonics.

  16. Looking at the end of the ROV tether

    Energy Technology Data Exchange (ETDEWEB)

    Grange, P.

    1983-06-01

    It is expected that eventually the remotely operated vehicle (ROV) will discard its clumsy, expensive, and restrictive umbilical, but for the moment virtually all these vehicles remain tethered to their mother service vessels. Lack of power has been the persistent problem with these vehicles but this could be effectively overcome with the development of closed loop internal combustion engines. The development of these engines for integration into ROV's is discussed.

  17. Cracking pressure control of parylene checkvalve using slanted tensile tethers

    OpenAIRE

    Lin, Jeffrey Chun-Hui; Yu, Feiqiao; Tai, Yu-Chong

    2010-01-01

    MEMS check valves with fixed cracking pressures are important in micro-fluidic applications where the pressure, flow directions and flow rates all need to be carefully controlled. This work presents a new surface-micromachined parylene check valve that uses residual thermal stress in the parylene to control its cracking pressure. The new check valve uses slanted tethers to allow the parylene tensile stress to apply a net downward force on the valving seat against the orifice. The angle of the...

  18. Shuttle Tethered Aerothermodynamics Research Facilty (STARFAC) instrumentation requirements

    Science.gov (United States)

    Wood, G. M.; Siemers, P. M.; Carlomagno, G. M.; Hoffman, J.

    1986-01-01

    The instrumentation requirements for the Shuttle Tethered Aerothermodynamic Research Facility (STARFAC) are presented. The typical physical properties of the terrestrial atmosphere are given along with representative atmospheric daytime ion concentrations and the equilibrium and nonequilibrium gas property comparison from a point away from a wall. STARFAC science and engineering measurements are given as are the TSS free stream gas analysis. The potential nonintrusive measurement techniques for hypersonic boundary layer research are outlined along with the quantitative physical measurement methods for aerothermodynamic studies.

  19. Downward-deployed tethered platforms for high enthalpy aerothermodynamic research

    Science.gov (United States)

    Wood, George M.; Siemers, Paul M.; Squires, R. Kenneth; Wolf, Henry; Carlomagno, Giovanni M.

    1988-01-01

    The data on aerothermodynamic and aerodynamic interactions at altitudes above 50 km is extremely limited because of the relative inaccessibility of the region to research vehicles of any sort. This paper addresses the practicability of using downward deployed satellites tethered to an orbiting host vehicle in order to obtain steady-state data in the upper reaches of the region above 80 or 90 km.

  20. Review of the ProSEDS Electrodynamic Tether Mission Development

    Science.gov (United States)

    Vaughn, Jason A.; Curtis, Leslie; Gilchrist, Brian E.; Bilen, Sven; Lorenzini, Enrico

    2004-01-01

    The Propulsive Small Expendable Deployer System (ProSEDS) space experiment was ready to fly as a secondary payload on a Delta-II expendable launch vehicle in late March 2003. Concerns raised in February 2003 by the International Space Station resulted in the delay of the launch of ProSEDS. Issues associated with the delayed launch date and a change in starting altitude resulted in the cancellation of the mission. ProSEDS was intended to deploy a tether (5 km bare wire plus 10 km non-conducting Dyneema) from a Delta I1 second stage to achieve adequate drag thrust that would lower the orbit of the system over days as opposed to months due to atmospheric drag. It was also designed to utilize the tether-generated current to provide limited spacecraft power. Considerable effort and testing went in to developing the ProSEDS system by a dedicated team. Through this effort, important technological issues were identified and addressed and this presentation will discuss some of the important technical issues and hurdles that had to be addressed to successfully prepare for flight. It is intended that this information will be of use for future tether mission and experiment designers.

  1. A Tether-Based Variable-Gravity Research Facility Concept

    Science.gov (United States)

    Sorensen, Kirk

    2006-01-01

    The recent announcement of a return to the Moon and a mission to Mars has made the question of human response to lower levels of gravity more important. Recent advances in tether technology spurred by NASA s research in MXER tethers has led to a re-examination of the concept of a variable-gravity research facility (xGRF) for human research in low Earth orbit. Breakthroughs in simplified inertial tracking have made it possible to consider eliminating the despun section of previous designs. This, in turn, improves the prospect of a facility based entirely around a tether, with the human module on one end and a countermass on the other. With such a configuration, propellantless spinup and spindown is also possible based on the conservation of angular momentum from a gravity-gradient configuration to a spinning configuration. This not only saves large amounts of propellant but vastly simplifies crew and consumable resupply operations, since these can now be done in a microgravity configuration. The importance of the science to be obtained and the performance improvements in this new design argue strongly for further investigation.

  2. Position Control of an X4-Flyer Using a Tether

    Directory of Open Access Journals (Sweden)

    Yusuke Ouchi

    2016-05-01

    Full Text Available In Japan, aging of infrastructures, such as roads,bridges, and water and sewer services, etc. poses a problem, andit is required to extend the life-span of such infrastructures bymaintenance. Among infrastructures, especially bridges areperiodically inspected by short range visual observations, whichcheck the damage and deterioration of the surface. However,since there are some cases where the short range visualobservation is difficult, an alternative method is required so as toreplace the short range visual observation with it. So, "X4-Flyer"is very attractive because of realizing a movement at high altitudeeasily. The objective of this study is to develop a tethered X4-Flyer, so that the conventional short range visual observation ofbridges is replaced by it. In this paper, a method for themeasurement and control of the position is described by using atether for controlling the position of the X4-Flyer. In addition, itis checked whether the tethered X4-Flyer can control the positionusing the proposed method or not, letting it fly in a state in whicha tether is being attached

  3. Artificial auroral effects from a bare conducting tether

    Science.gov (United States)

    Martínez-Sanchez, M.; Sanmartín, J. R.

    1997-12-01

    An electrically floating metallic bare tether in a low Earth orbit would be highly negative with respect to the ambient plasma over most of its length, and would be bombarded by ambient ions. This would liberate secondary electrons, which, after acceleration through the same voltage, would form a magnetically guided two-sided planar e beam, and result in auroral effects (ionization and light emission) upon impact on the atmospheric E layer, at about 120-140 km altitude. This paper examines in a preliminary way the feasibility of using this effect as an upper atmospheric probe. Ionization rates can reach up to 105cm-3s-1 if a tape, instead of a wire, is used as tether. Contrary to standard e beams, the beam from the tether is free of spacecraft charging and plasma interaction problems, and its energy flux varies across the cross section, which is quite large; this would make possible continuous observation from the satellite, with high resolution, both spectral and vertical, of the induced optical emissions. Ground observation might be possible at latitudes around 40°, for night, magnetically quiet conditions.

  4. Investigation of force approximations in tethered cells simulations

    CERN Document Server

    Zakrisson, Johan; Axner, Ove; Andersson, Magnus

    2015-01-01

    Simulations of tethered cells in viscous sub-layers are frequently performed using the Stokes drag force, but without taking into account contributions from surface corrections, lift forces, buoyancy, the Basset force, the cells finite inertia, or added mass. In this work, we investigate to which extent such contributions influence, under a variety of hydrodynamic conditions, the force at the anchor point of a tethered cell and the survival probability of a bacterium that is attached to a host by either a slip or a catch bond via a tether with a few different biomechanical properties. We show that a consequence of not including some of these contributions is that the force to which a bond is exposed can be significantly underestimated; in general by ~32-46 %, where the influence of the surface corrections dominate (the parallel and normal correction coefficients contribute with ~5-8 or 23-26 %, respectively). The Basset force is a major contributor, up to 20 %, for larger cells and shear rates. The lift force...

  5. SATB1 tethers multiple gene loci to reprogram expression profiledriving breast cancer metastasis

    Energy Technology Data Exchange (ETDEWEB)

    Han, Hye-Jung; Kohwi, Yoshinori; Kohwi-Shigematsu, Terumi

    2006-07-13

    Global changes in gene expression occur during tumor progression, as indicated by expression profiling of metastatic tumors. How this occurs is poorly understood. SATB1 functions as a genome organizer by folding chromatin via tethering multiple genomic loci and recruiting chromatin remodeling enzymes to regulate chromatin structure and expression of a large number of genes. Here we show that SATB1 is expressed at high levels in aggressive breast cancer cells, and is undetectable in non-malignant breast epithelial cells. Importantly, RNAi-mediated removal of SATB1 from highly-aggressive MDA-MB-231 cells altered the expression levels of over 1200 genes, restored breast-like acinar polarity in three-dimensional cultures, and prevented the metastastic phenotype in vivo. Conversely, overexpression of SATB1 in the less-aggressive breast cancer cell line Hs578T altered the gene expression profile and increased metastasis dramatically in vivo. Thus, SATB1 is a global regulator of gene expression in breast cancer cells, directly regulating crucial metastasis-associated genes, including ERRB2 (HER2/NEU), TGF-{beta}1, matrix metalloproteinase 3, and metastasin. The identification of SATB1 as a protein that re-programs chromatin organization and transcription profiles to promote breast cancer metastasis suggests a new model for metastasis and may provide means of therapeutic intervention.

  6. Clostridium perfringens Epsilon Toxin: A Malevolent Molecule for Animals and Man?

    Science.gov (United States)

    Stiles, Bradley G.; Barth, Gillian; Barth, Holger; Popoff, Michel R.

    2013-01-01

    Clostridium perfringens is a prolific, toxin-producing anaerobe causing multiple diseases in humans and animals. One of these toxins is epsilon, a 33 kDa protein produced by Clostridium perfringens (types B and D) that induces fatal enteric disease of goats, sheep and cattle. Epsilon toxin (Etx) belongs to the aerolysin-like toxin family. It contains three distinct domains, is proteolytically-activated and forms oligomeric pores on cell surfaces via a lipid raft-associated protein(s). Vaccination controls Etx-induced disease in the field. However, therapeutic measures are currently lacking. This review initially introduces C. perfringens toxins, subsequently focusing upon the Etx and its biochemistry, disease characteristics in various animals that include laboratory models (in vitro and in vivo), and finally control mechanisms (vaccines and therapeutics). PMID:24284826

  7. The Typhoid Toxin Promotes Host Survival and the Establishment of a Persistent Asymptomatic Infection

    DEFF Research Database (Denmark)

    Del Bel Belluz, Lisa; Guidi, Riccardo; Pateras, Ioannis S.

    2016-01-01

    analysis confirmed the toxin-mediated suppression of the intestinal inflammatory response. The presence of a functional typhoid toxin further induced an increased frequency of asymptomatic carriers. Our data indicate that the typhoid toxin DNA damaging activity increases host survival and favours long......Bacterial genotoxins, produced by several Gram-negative bacteria, induce DNA damage in the target cells. While the responses induced in the host cells have been extensively studied in vitro, the role of these effectors during the course of infection remains poorly characterized. To address...... this issue, we assessed the effects of the Salmonella enterica genotoxin, known as typhoid toxin, in in vivo models of murine infection. Immunocompetent mice were infected with isogenic S. enterica, serovar Typhimurium (S. Typhimurium) strains, encoding either a functional or an inactive typhoid toxin...

  8. A Method to Predict the Orbital Lifetimes of Free Tethers and Tether-Trailing Satellites using Artificial Neural Networks

    Science.gov (United States)

    1992-08-28

    done by Freud .’ Prior to his psychoanalysis investigations, Freud attempted to ".... represent psychical processes as quantitatively determinate states...parent vehicle for (1) tether initiated reentry or orbit transfer of a subsatellite, and/or (2) local area operations requiring return to the space...performing flow analyses routinely use empirically- derived expressions to calculate convection heat transfer coefficients.ś Another example occurs in

  9. Dynamic analysis of the tether transportation system using absolute nodal coordinate formulation

    Science.gov (United States)

    Sun, Xin; Xu, Ming; Zhong, Rui

    2017-10-01

    Long space tethers are becoming a rising concern as an alternate way for transportation in space. It benefits from fuel economizing. This paper focuses on the dynamics of the tether transportation system, which consists of two end satellites connected by a flexible tether, and a movable vehicle driven by the actuator carried by itself. The Absolute Nodal Coordinate Formulation is applied to the establishment of the equation of motion, so that the influence caused by the distributed mass and elasticity of the tether is introduced. Moreover, an approximated method for accelerating the calculation of the generalized gravitational forces on the tether is proposed by substituting the volume integral every step into summation of finite terms. Afterwards, dynamic evolutions of such a system in different configurations are illustrated using numerical simulations. The deflection of the tether and the trajectory of the crawler during the transportation is investigated. Finally, the effect on the orbit of the system due to the crawler is revealed.

  10. New tool for spreading proteins to the environment: Cry1Ab toxin immobilized to bioplastics.

    Science.gov (United States)

    Moldes, Cristina; Farinós, Gema P; de Eugenio, Laura I; García, Pedro; García, José L; Ortego, Félix; Hernández-Crespo, Pedro; Castañera, Pedro; Prieto, María A

    2006-08-01

    A new tool to provide an environmentally friendly way to deliver active proteins to the environment has been developed, based on the use of polyhydroxyalkanoate (PHA, bioplastic) granules. To illustrate this novel approach, a derived Cry1Ab insect-specific toxin protein was in vivo immobilized into PHA granules through the polypeptide tag BioF. The new toxin, named Fk-Bt1, was shown to be active against Sesamia nonagrioides (Lepidoptera: Noctuidae). The dose-mortality responses of the new toxin granule formulation (PFk-Bt1) and purified Cry1Ab have been compared, demonstrating the effectiveness of PFk-Bt1 and suggesting a common mode of action.

  11. Tethered elevator and platforms as space station facilities: Systems studies and demonstrative experiments

    Science.gov (United States)

    1986-01-01

    Several key concepts of the science and applications tethered platforms were studied. Some conclusions reached are herein listed. Tether elevator and platform could improve the space station scientific and applicative capabilities. The space elevator presents unique characteristics as microgravity facility and as a tethered platform servicing vehicle. Pointing platforms could represent a new kind of observation facility for large class of payloads. The dynamical, control and technological complexity of these concepts advised demonstrative experiments. The on-going tethered satellite system offers the opportunity to perform such experiments. And feasibility studies are in progress.

  12. Novel Roaming and Stationary Tethered Aerial Robots for Continuous Mobile Missions in Nuclear Power Plants

    Directory of Open Access Journals (Sweden)

    Beom W. Gu

    2016-08-01

    Full Text Available In this paper, new tethered aerial robots including roaming tethered aerial robots (RTARs for radioactive material sampling and stationary tethered aerial robots (STARs for environment monitoring are proposed to meet extremely-long-endurance missions of nuclear power plants. The flight of the proposed tethered aerial robots may last for a few days or even a few months as long as the tethered cable provides continuous power. A high voltage AC or DC power system was newly adopted to reduce the mass of the tethered cable. The RTAR uses a tethered cable spooled from the aerial robot and an aerial tension control system. The aerial tension control system provides the appropriate tension to the tethered cable, which is accordingly laid down on the ground as the RTAR roams. The STAR includes a tethered cable spooled from the ground and a ground tension control system, which enables the STAR to reach high altitudes. Prototypes of the RTAR and STAR were designed and successfully demonstrated in outdoor environments, where the load power, power type, operating frequency, and flight attitude of the RTAR and STAR were: 180 W, AC 100 kHz, and 20 m; and 300 W, AC or DC 100 kHz, and 80 m, respectively.

  13. Configuration maintaining control of three-body ring tethered system based on thrust compensation

    Science.gov (United States)

    Huang, Panfeng; Liu, Binbin; Zhang, Fan

    2016-06-01

    Space multi-tethered systems have shown broad prospects in remote observation missions. This paper mainly focuses on the dynamics and configuration maintaining control of space spinning three-body ring tethered system for such mission. Firstly, we establish the spinning dynamic model of the three-body ring tethered system considering the elasticity of the tether using Newton-Euler method, and then validate the suitability of this model by numerical simulation. Subsequently, LP (Likins-Pringle) initial equilibrium conditions for the tethered system are derived based on rigid body's equilibrium theory. Simulation results show that tether slack, snapping and interaction between the tethers exist in the three-body ring system, and its' configuration can not be maintained without control. Finally, a control strategy based on thrust compensation, namely thrust to simulate tether compression under LP initial equilibrium conditions is designed to solve the configuration maintaining control problem. Control effects are verified by numerical simulation compared with uncontrolled situation. Simulation results show that the configuration of the three-body ring tethered system could maintain under this active control strategy.

  14. Three-dimensional characterization of tethered microspheres by total internal reflection fluorescence microscopy

    Science.gov (United States)

    Blumberg, Seth; Gajraj, Arivalagan; Pennington, Matthew W.; Meiners, Jens-Christian

    2005-01-01

    Tethered particle microscopy is a powerful tool to study the dynamics of DNA molecules and DNA-protein complexes in single-molecule experiments. We demonstrate that stroboscopic total internal reflection microscopy can be used to characterize the three-dimensional spatiotemporal motion of DNA-tethered particles. By calculating characteristic measures such as symmetry and time constants of the motion, well-formed tethers can be distinguished from defective ones for which the motion is dominated by aberrant surface effects. This improves the reliability of measurements on tether dynamics. For instance, in observations of protein-mediated DNA looping, loop formation is distinguished from adsorption and other nonspecific events.

  15. Novel roaming and stationary tethered aerial robots for continuous mobile missions in nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Beom W.; Choi, Su Y.; Rim, Chun T. [Dept. of Nuclear and Quantum Engineering, KAIST, Daejeon (Korea, Republic of); Choi, Young Soo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Cai, Guowei; Seneviratne, Lakmal [Dept. of Aerospace Engineering, Khalifa University, Abu Dhabi (United Arab Emirates)

    2016-08-15

    In this paper, new tethered aerial robots including roaming tethered aerial robots (RTARs) for radioactive material sampling and stationary tethered aerial robots (STARs) for environment monitoring are proposed to meet extremely-long-endurance missions of nuclear power plants. The flight of the proposed tethered aerial robots may last for a few days or even a few months as long as the tethered cable provides continuous power. A high voltage AC or DC power system was newly adopted to reduce the mass of the tethered cable. The RTAR uses a tethered cable spooled from the aerial robot and an aerial tension control system. The aerial tension control system provides the appropriate tension to the tethered cable, which is accordingly laid down on the ground as the RTAR roams. The STAR includes a tethered cable spooled from the ground and a ground tension control system, which enables the STAR to reach high altitudes. Prototypes of the RTAR and STAR were designed and successfully demonstrated in outdoor environments, where the load power, power type, operating frequency, and flight attitude of the RTAR and STAR were: 180 W, AC 100 kHz, and 20 m; and 300 W, AC or DC 100 kHz, and 80 m, respectively.

  16. Bile salt inhibition of host cell damage by Clostridium difficile toxins.

    Directory of Open Access Journals (Sweden)

    Charles Darkoh

    Full Text Available Virulent Clostridium difficile strains produce toxin A and/or toxin B that are the etiological agents of diarrhea and pseudomembranous colitis. Treatment of C. difficile infections (CDI has been hampered by resistance to multiple antibiotics, sporulation, emergence of strains with increased virulence, recurrence of the infection, and the lack of drugs that preserve or restore the colonic bacterial flora. As a result, there is new interest in non-antibiotic CDI treatments. The human conjugated bile salt taurocholate was previously shown in our laboratory to inhibit C. difficile toxin A and B activities in an in vitro assay. Here we demonstrate for the first time in an ex vivo assay that taurocholate can protect Caco-2 colonic epithelial cells from the damaging effects of the C. difficile toxins. Using caspase-3 and lactate dehydrogenase assays, we have demonstrated that taurocholate reduced the extent of toxin B-induced apoptosis and cell membrane damage. Confluent Caco-2 cells cultured with toxin B induced elevated caspase-3 activity. Remarkably, addition of 5 mM taurocholate reduced caspase-3 activity in cells treated with 2, 4, 6, and 12 µg/ml of toxin B by 99%, 78%, 64%, and 60%, respectively. Furthermore, spent culture medium from Caco-2 cells incubated with both toxin B and taurocholate exhibited significantly decreased lactate dehydrogenase activity compared to spent culture medium from cells incubated with toxin B only. Our results suggest that the mechanism of taurocholate-mediated inhibition functions at the level of toxin activity since taurocholate did not affect C. difficile growth and toxin production. These findings open up a new avenue for the development of non-antibiotic therapeutics for CDI treatment.

  17. Food toxin detection with atomic force microscope

    Science.gov (United States)

    Externally introduced toxins or internal spoilage correlated pathogens and their metabolites are all potential sources of food toxins. To prevent and protect unsafe food, many food toxin detection techniques have been developed to detect various toxins for quality control. Although several routine m...

  18. [Shiga toxin and tetanus toxin as a potential biologic weapon].

    Science.gov (United States)

    Toczyska, Izabela; Płusa, Tadeusz

    2015-09-01

    Toxins produced by the bacteria are of particular interest as potential cargo combat possible for use in a terrorist attack or war. Shiga toxin is usually produced by shiga toxigenic strains of Escherichia coli (STEC - shigatoxigenic Escherichia coli). To infection occurs mostly after eating contaminated beef. Clinical syndromes associated with Shiga toxin diarrhea, hemorrhagic colitis, hemolytic uremic syndrome (HUS - hemolytic uremic syndrome) or thrombotic thrombocytopenic purpura. Treatment is symptomatic. In HUS, in which mortality during an epidemic reaches 20%, extending the kidney injury dialysis may be necessary. Exposure to tetanus toxin produced by Clostridium tetani, resulting in the most generalized tetanus, characterized by increased muscle tension and painful contractions of individual muscle groups. In the treatment beyond symptomatic behavior (among others spasticity medications, anticonvulsants, muscle relaxants) is used tetanus antitoxin and antibiotics (metronidazole choice). A common complication is acute respiratory failure - then it is necessary to implement mechanical ventilation. © 2015 MEDPRESS.

  19. Tethered Transition Metals Promoted Photocatalytic System for Efficient Hydrogen Evolutions

    KAUST Repository

    Takanabe, Kazuhiro

    2015-03-05

    The present invention is directed, at least in part, to a process for improving the efficiency of a photocatalyst (a semiconductor photocatalyst) by tethering (depositing) a metal (e.g., metal ions of a late transition metal, such as nickel) to the semiconductor (photocatalyst) surface through the use of an organic ligand. More specifically, 1,2-ethanedithiol (EDT) functions as an excellent molecular linker (organic ligand) to attach a transition metal complex (e.g., nickel (Ni.sup.2+ ions)) to the semiconductor surface, which can be in the form of a cadmium sulfide surface. The photocatalyst has particular utility in generating hydrogen from H.sub.2S.

  20. Flight control and stability of a multiple kites tethered system

    OpenAIRE

    Podgaets, A.R.; Ockels, W.J.

    2006-01-01

    One of novel concepts to use the energy of high altitude winds is by launching a series of kite on a long rope and let them pull the rope thus driving the generator. A mathematical model of tethered kites system has been developed consisting of models of kites and of the cable that links them together and to the generator on the ground energy station. The model described is then investigated for stability in various wind conditions including random wind gusts which require stochastic stabilit...

  1. Tethered bimolecular lipid membranes - A novel model membrane platform

    Energy Technology Data Exchange (ETDEWEB)

    Knoll, Wolfgang; Koeper, Ingo; Naumann, Renate; Sinner, Eva-Kathrin [Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz (Germany)

    2008-10-01

    This contribution summarizes some of our efforts in designing, synthesizing, assembling, and characterizing functional tethered bimolecular lipid membranes (tBLMs) as a novel platform for biophysical studies of and with artificial membranes or for sensor development employing, e.g., membrane integral receptor proteins. Chemical coupling schemes based on thiol groups for Au substrates or silanes used in the case of oxide surfaces allow for the covalent and, hence, chemically and mechanically robust attachment of anchor lipids to the solid support, stabilizing the proximal layer of a tethered membrane on the transducer surface. Surface plasmon optics, the quartz crystal microbalance, fluorescence- and IR spectroscopies, and electrochemical techniques are used to characterize the build-up of these complex supramolecular interfacial architectures. We demonstrate, in particular, that bilayers with a specific electrical resistance of better than 10 M{omega} cm{sup 2} can be achieved routinely with this approach. The functionalization of the lipid membranes by the incorporation of peptides is demonstrated for the carrier valinomycin which shows in our tBLMs the expected discrimination by four orders of magnitude between the translocation of K{sup +}- and Na{sup +}-ions across the hydrophobic barrier. For the synthetic channel-forming peptide M2 the high electrical resistance of the bilayer with the correspondingly low background current allows for the recording of even single channel current fluctuations. From the many membrane proteins that we reconstituted so far we describe results obtained with the redox-protein cytochrome c oxidase. Here, we also use a genetically modified mutant with a His-tag at either the C- or the N-terminus for the oriented attachment of the protein via the NTA/Ni{sup 2+} approach. With this strategy, we not only can control the density of the immobilized functional units, we introduce a completely new and alternative concept for the

  2. Dynamic modeling and Super-Twisting Sliding Mode Control for Tethered Space Robot

    Science.gov (United States)

    Zhao, Yakun; Huang, Panfeng; Zhang, Fan

    2018-02-01

    Recent years, tethered space capturing systems have been considered as one of the most promising solutions for active space debris removal due to the increasing threat of space debris to spacecraft and astronauts. In this paper, one of the tethered space capturing systems, Tethered Space Robot (TSR), is investigated. TSR includes a space platform, a space tether, and a gripper as the terminal device. Based on the assumptions that the platform and the gripper are point masses and the tether is rigid, inextensible and remaining straight, the dynamic model of TSR is presented, in which the disturbances from space environment is considered. According to the previous study, the in-plane and out-of-plane angles of the tether oscillate periodically although the tether is released to the desired length. A super-twisting adaptive sliding mode control scheme is designed for TSR to eliminate the vibration of the tether to assure a successful capture in station-keeping phase. Both uncontrolled and controlled situations are simulated. The simulation results show that the proposed controller is effective. Additionally, after comparing with normal sliding mode control algorithm, it is verified that the proposed control scheme can avoid the chattering of normal sliding mode control and is robust for unknown boundary perturbations.

  3. Label-free measurements of membrane tether thickness using optical tweezers combined with SLIM

    Science.gov (United States)

    Sarshar, Mohammad; Wong, Winson T.; Anvari, Bahman

    2015-03-01

    Various cellular activities such as motility, division, and endocytosis involve a change in the cell shape. The mechanical interactions between the cell membrane and cytoskeleton play an important role in regulating changes in the cell shape. Tether formation from cell membranes provides a technique to characterize the mechanical properties of cell membranes and membrane-cytoskeleton interactions. Accurate measurement of the nano-scale tether diameter is relevant to quantification of membrane tension, bending modulus, and adhesion energy of the membrane-cytoskeleton structure. We have integrated optical tweezers with quantitative phase imaging, based on spatial light interference microscopy (SLIM), to simultaneously form tethers from HEK-293 cells and measure their diameters. Tether thickness along the illumination axis was measured using the quantitative phase map of the sample, and the refractive index (RI) mismatch between the sample and the surrounding media. The RI of the tethers ranged from 1.354 to 1.368 (cell culture medium RI=1.337). Our SLIM imaging system provided a 38 nm resolution in tether thickness measurements. Tether diameter fluctuations of <100 nm were resolved on tethers that ranged between 600-900 nm in diameter. Our integrated platform also provides the ability to simultaneously manipulate and image cell organelles in a non-contact and marker-free manner at nanometer spatial resolution.

  4. The development and significance of abnormal stereotyped behaviours in tethered sows

    NARCIS (Netherlands)

    Cronin, G.M.

    1985-01-01

    The development and performance of abnormal stereotyped behaviours (stereotypies) by tethered sows were studied in order to investigate the consequences of the behaviours for animal welfare and sow productivity.

    In Chapter 2, the behaviour of 36 tethered sows in a commercial herd

  5. Long-term evaluation of intraoperative neurophysiological monitoring-assisted tethered cord surgery

    NARCIS (Netherlands)

    Dulfer, S E; Drost, G; Lange, F; Journee, H L; Wapstra, F H; Hoving, E W

    2017-01-01

    PURPOSE: Patients with tethered spinal cord have been investigated for short-term effects after tethered spinal cord surgery in the past. However, little is known about the long-term effects in this patient group. In this retrospective, longitudinal, observational study, a patient sample of a

  6. Tethered Cord Syndrome with Syrinx in A Nigerian Adult Female: A ...

    African Journals Online (AJOL)

    Alasia Datonye

    modern imaging tools like MRI, the diagnosis of TCS is no more as rare as it is ... Keywords: Tethered cord; Syringomyelia; MRI; Adult;. Nigeria. ... DISCUSSION. Tethered cord syndrome (TCS) is a pull-induced functional disease of the spinal cord with its caudal part anchored by an. 3 inelastic structure . Garcean first ...

  7. Acquisition of Ice-Tethered Profilers with Velocity (ITP-V) Instruments for Future Arctic Studies

    Science.gov (United States)

    2016-11-15

    San Diego, CA, IEEE Xplore . Toole, J. M., R. A. Krishfield, M.-L. Timmennans, and A. Proshutinsky, 2011: The Ice-Tethered Profiler: Argo ofthe Arctic, Oceanogr., 24, 126-135. 4 ...observations from Ice-Tethered Profilers, MTS/ IEEE Oceans’ 2015, Washington DC, 1-10. Krishfield, R., J. Toole, A. Proshutinsky, and M.-L. Timmennans, 2008

  8. Tethered Cord Syndrome with Syrinx in A Nigerian Adult Female: A ...

    African Journals Online (AJOL)

    There were no cutaneous stigmata (hypertrichosis). Laboratory investigations showed normal hematological indices. Urinalysis was also normal. An impression of acute transverse myelitis was made. Magnetic resonance imaging showed tethered cord and syrinx in the lumbar region. Conclusion: Tethered cord association ...

  9. Flexible Tethered Kite with Moveable Attachment Points, Part I: Dynamics and Control

    NARCIS (Netherlands)

    Williams, P.; Lansdorp, B.; Ockels, W.

    2007-01-01

    Tethered kite technology is one potential means of harnessing energy available in high altitude winds. In an efficient and practical system, the kite is required to fly in cyclic patterns that maximize net power produced per cycle. At the same time, the tether length must be controlled to ensure the

  10. In-plane adaptive retrieval control for a noncooperative target by tethered space robots

    Directory of Open Access Journals (Sweden)

    Zhongjie Meng

    2016-09-01

    Full Text Available Using tether to replace rigid arms, the tethered space robot has more flexibility and security than the traditional space robot, which gives it a wide application prospect in the satellite retrieval. After a noncooperative satellite is captured by the tethered space robot, the tethered space robot and the satellite compose a combination with uncertain mass, inertia, and tether junction position. The tether length, tether deflection, and combination attitude are coupled seriously and control inputs are strictly limited, which make the retrieval of tethered space robot very difficult. First, a retrieval dynamic model of in-plane motion is derived using Lagrangian method. Then, in order to solve the uncertainty problems of dynamics parameters, an adaptive controller and its parameter updating law are proposed using the dynamic inversion theory. Moreover, an anti-windup strategy with auxiliary variables is derived to compensate the limited control inputs. Simulation results validate the feasibility of the proposed adaptive anti-windup control method. The noncooperative satellite is retrieved along the desired trajectory effectively.

  11. Yolk granule tethering: a role in cell resealing and identification of several protein components.

    Science.gov (United States)

    McNeil, Anna; McNeil, Paul L

    2005-10-15

    Homotypic fusion among echinoderm egg yolk granules has previously been reconstituted in vitro, and shown to be a rapid, Ca2+-triggered reaction that can produce extremely large (>10 microm diameter) fusion products. We here show that, prior to Ca2+-triggered fusion, yolk granules in vitro, if isolated in an appropriate buffer, became tethered to one another, forming large aggregates of more than 100 granules. Granule washing with mildly chaotropic salt abolished this tethering reaction, and prevented Ca2+-triggered formation of the large fusion products characteristic of tethered granules. Protein factors present in the wash restored tethering activity and these factors could be substantially enriched by anion exchange chromatography. The enriched fraction behaved under native conditions as a high molecular weight (approximately 670 kDa), multisubunit complex of at least seven proteins. Monoclonal antibodies directed against this complex of proteins were capable of immunodepleting tethering activity, confirming the role of the complex in granule tethering. These antibodies selectively stained the surface of yolk granules in the intact egg. We therefore propose a new role for tethering: it can promote the formation of large vesicular fusion products, such as those required for successful resealing. We have, moreover, identified several proteins that may be critical to this tethering mechanism.

  12. Cellulose Microfibril Formation by Surface-Tethered Cellulose Synthase Enzymes.

    Science.gov (United States)

    Basu, Snehasish; Omadjela, Okako; Gaddes, David; Tadigadapa, Srinivas; Zimmer, Jochen; Catchmark, Jeffrey M

    2016-02-23

    Cellulose microfibrils are pseudocrystalline arrays of cellulose chains that are synthesized by cellulose synthases. The enzymes are organized into large membrane-embedded complexes in which each enzyme likely synthesizes and secretes a β-(1→4) glucan. The relationship between the organization of the enzymes in these complexes and cellulose crystallization has not been explored. To better understand this relationship, we used atomic force microscopy to visualize cellulose microfibril formation from nickel-film-immobilized bacterial cellulose synthase enzymes (BcsA-Bs), which in standard solution only form amorphous cellulose from monomeric BcsA-B complexes. Fourier transform infrared spectroscopy and X-ray diffraction techniques show that surface-tethered BcsA-Bs synthesize highly crystalline cellulose II in the presence of UDP-Glc, the allosteric activator cyclic-di-GMP, as well as magnesium. The cellulose II cross section/diameter and the crystal size and crystallinity depend on the surface density of tethered enzymes as well as the overall concentration of substrates. Our results provide the correlation between cellulose microfibril formation and the spatial organization of cellulose synthases.

  13. Piperidinium tethered nanoparticle-hybrid electrolyte for lithium metal batteries

    KAUST Repository

    Korf, Kevin S.

    2014-06-23

    We report on the synthesis of novel piperidinium-based ionic liquid tethered nanoparticle hybrid electrolytes and investigate their physical and electrochemical properties. Hybrid electrolytes based on the ionic liquid 1-methyl-1-propylpiperidinium bis(trifluoromethanesulfone) imide covalently tethered to silica nanoparticles (SiO2-PP-TFSI) were blended with propylene carbonate-1 M lithium bis(trifluoromethanesulfone) imide (LiTFSI). We employed NMR analysis to confirm the successful creation of the hybrid material. Dielectric and rheological measurements show that these electrolytes exhibit exceptional room-temperature DC ionic conductivity (10-2 to 10 -3 S cm-1) as well as high shear mechanical moduli (105 to 106 Pa). Lithium transference numbers were found to increase with particle loading and to reach values as high as 0.22 at high particle loadings where the particle jam to form a soft glassy elastic medium. Analysis of lithium electrodeposits obtained in the hybrid electrolytes using SEM and EDX spectra show that the SiO2-PP-TFSI nanoparticles are able to smooth lithium deposition and inhibit lithium dendrite proliferation in Li metal batteries. LTOSiO2-PP-TFSI/PC in 1 M LiTFSILi half-cells based on the SiO2-PP-TFSI hybrid electrolytes exhibit attractive voltage profiles and trouble-free extended cycling behavior over more than 1000 cycles of charge and discharge. This journal is © the Partner Organisations 2014.

  14. Dynamics of tethered versus free-swimming animals: A wake structure comparison in jellyfish

    Science.gov (United States)

    Katija, Kakani; Dabiri, John O.

    2006-11-01

    Previous research has shown that jellyfish utilize the formation and shedding of vortices to help feed and move the animal. Laboratory experiments often require restricting the motion of an animal by tethering/fluming to allow for repeatable results. However, past research has not addressed the differences that arise when the motion of an animal is restricted/confined. This presentation will attend to this issue by comparing the wake structure of a tethered and free-swimming Aurelia aurita. Digital Particle Image Velocimetry is used to collect measurements of the velocity field surrounding an animal that is either tethered or swimming freely. Dynamical systems methods are used to compute Lagrangian coherent structures (LCS), which is used to identify the geometries of structures in the wake of the animal. Using LCS, a comparison between the wake of a tethered and free-swimming animal can be made. This research provides a quantitative measure of the differences between a tethered and freely moving jellyfish.

  15. Transport vesicle tethering at the trans Golgi network: coiled coil proteins in action

    Directory of Open Access Journals (Sweden)

    Pak-yan Patricia Cheung

    2016-03-01

    Full Text Available The Golgi complex is decorated with so-called Golgin proteins that share a common feature: a large proportion of their amino acid sequences are predicted to form coiled-coil structures. The possible presence of extensive coiled coils implies that these proteins are highly elongated molecules that can extend a significant distance from the Golgi surface. This property would help them to capture or trap inbound transport vesicles and to tether Golgi mini-stacks together. This review will summarize our current understanding of coiled coil tethers that are needed for the receipt of transport vesicles at the trans Golgi network. How do long tethering proteins actually catch vesicles? Golgi-associated, coiled coil tethers contain numerous binding sites for small GTPases, SNARE proteins, and vesicle coat proteins. How are these interactions coordinated and are any or all of them important for the tethering process? Progress towards understanding these questions and remaining, unresolved mysteries will be discussed.

  16. Interplay of matrix stiffness and protein tethering in stem cell differentiation.

    Science.gov (United States)

    Wen, Jessica H; Vincent, Ludovic G; Fuhrmann, Alexander; Choi, Yu Suk; Hribar, Kolin C; Taylor-Weiner, Hermes; Chen, Shaochen; Engler, Adam J

    2014-10-01

    Stem cells regulate their fate by binding to, and contracting against, the extracellular matrix. Recently, it has been proposed that in addition to matrix stiffness and ligand type, the degree of coupling of fibrous protein to the surface of the underlying substrate, that is, tethering and matrix porosity, also regulates stem cell differentiation. By modulating substrate porosity without altering stiffness in polyacrylamide gels, we show that varying substrate porosity did not significantly change protein tethering, substrate deformations, or the osteogenic and adipogenic differentiation of human adipose-derived stromal cells and marrow-derived mesenchymal stromal cells. Varying protein-substrate linker density up to 50-fold changed tethering, but did not affect osteogenesis, adipogenesis, surface-protein unfolding or underlying substrate deformations. Differentiation was also unaffected by the absence of protein tethering. Our findings imply that the stiffness of planar matrices regulates stem cell differentiation independently of protein tethering and porosity.

  17. The development of optimal control laws for orbiting tethered platform systems

    Science.gov (United States)

    Bainum, P. M.

    1986-01-01

    A mathematical model of the open and closed loop in orbit plane dynamics of a space platform-tethered-subsatellite system is developed. The system consists of a rigid platform from which an (assumed massless) tether is deploying (retrieving) a subsatellite from an attachment point which is, in general, offset from the platform's mass center. A Langrangian formulation yields equations describing platform pitch, subsatellite tetherline swing, and varying tether length motions. These equations are linearized about the nominal station keeping motion. Control can be provided by both modulation of the tether tension level and by a momentum type platform-mounted device; system controllability depends on the presence of both control inputs. Stability criteria are developed in terms of the control law gains, the platform inertia ratio, and tether offset parameter. Control law gains are obtained based on linear quadratic regulator techniques. Typical transient responses of both the state and required control effort are presented.

  18. Diffusive transport of molecular cargo tethered to a DNA origami platform.

    Science.gov (United States)

    Kopperger, Enzo; Pirzer, Tobias; Simmel, Friedrich C

    2015-04-08

    Fast and efficient transport of molecular cargoes along tracks or on supramolecular platforms is an important prerequisite for the development of future nanorobotic systems and assembly lines. Here, we study the diffusive transport of DNA cargo strands bound to a supramolecular DNA origami structure via an extended tether arm. For short distances (on the order of a few nanometers), transport from a start to a target site is found to be less efficient than for direct transfer without tether. For distances on the scale of the origami platform itself, however, cargo transfer mediated by a rigid tether arm occurs very fast and robust, whereas a more flexible, hinged tether is found to be considerably less efficient. Our results suggest diffusive motion on a molecular tether as a highly efficient mechanism for fast transfer of cargoes over long distances.

  19. Shortest Path Planning for a Tethered Robot or an Anchored Cable

    Energy Technology Data Exchange (ETDEWEB)

    Xavier, P.G.

    1999-02-22

    We consider the problem of planning shortest paths for a tethered robot with a finite length tether in a 2D environment with polygonal obstacles. We present an algorithm that runs in time O((k{sub 1} + 1){sup 2}n{sup 4}) and finds the shortest path or correctly determines that none exists that obeys the constraints; here n is the number obstacle vertices, and k{sub 1} is the number loops in the initial configuration of the tether. The robot may cross its tether but nothing can cross obstacles, which cause the tether to bend. The algorithm applies as well for planning a shortest path for the free end of an anchored cable.

  20. Targeted toxins in brain tumor therapy.

    Science.gov (United States)

    Li, Yan Michael; Hall, Walter A

    2010-11-01

    Targeted toxins, also known as immunotoxins or cytotoxins, are recombinant molecules that specifically bind to cell surface receptors that are overexpressed in cancer and the toxin component kills the cell. These recombinant proteins consist of a specific antibody or ligand coupled to a protein toxin. The targeted toxins bind to a surface antigen or receptor overexpressed in tumors, such as the epidermal growth factor receptor or interleukin-13 receptor. The toxin part of the molecule in all clinically used toxins is modified from bacterial or plant toxins, fused to an antibody or carrier ligand. Targeted toxins are very effective against cancer cells resistant to radiation and chemotherapy. They are far more potent than any known chemotherapy drug. Targeted toxins have shown an acceptable profile of toxicity and safety in early clinical studies and have demonstrated evidence of a tumor response. Currently, clinical trials with some targeted toxins are complete and the final results are pending. This review summarizes the characteristics of targeted toxins and the key findings of the important clinical studies with targeted toxins in malignant brain tumor patients. Obstacles to successful treatment of malignant brain tumors include poor penetration into tumor masses, the immune response to the toxin component and cancer heterogeneity. Strategies to overcome these limitations are being pursued in the current generation of targeted toxins.

  1. An Overview of Helicobacter pylori VacA Toxin Biology

    Science.gov (United States)

    Foegeding, Nora J.; Caston, Rhonda R.; McClain, Mark S.; Ohi, Melanie D.; Cover, Timothy L.

    2016-01-01

    The VacA toxin secreted by Helicobacter pylori enhances the ability of the bacteria to colonize the stomach and contributes to the pathogenesis of gastric adenocarcinoma and peptic ulcer disease. The amino acid sequence and structure of VacA are unrelated to corresponding features of other known bacterial toxins. VacA is classified as a pore-forming toxin, and many of its effects on host cells are attributed to formation of channels in intracellular sites. The most extensively studied VacA activity is its capacity to stimulate vacuole formation, but the toxin has many additional effects on host cells. Multiple cell types are susceptible to VacA, including gastric epithelial cells, parietal cells, T cells, and other types of immune cells. This review focuses on the wide range of VacA actions that are detectable in vitro, as well as actions of VacA in vivo that are relevant for H. pylori colonization of the stomach and development of gastric disease. PMID:27271669

  2. Removal of Paralytic Shellfish Toxins by Probiotic Lactic Acid Bacteria

    Directory of Open Access Journals (Sweden)

    Mari Vasama

    2014-07-01

    Full Text Available Paralytic shellfish toxins (PSTs are non-protein neurotoxins produced by saltwater dinoflagellates and freshwater cyanobacteria. The ability of Lactobacillus rhamnosus strains GG and LC-705 (in viable and non-viable forms to remove PSTs (saxitoxin (STX, neosaxitoxin (neoSTX, gonyautoxins 2 and 3 (GTX2/3, C-toxins 1 and 2 (C1/2 from neutral and acidic solution (pH 7.3 and 2 was examined using HPLC. Binding decreased in the order of STX ~ neoSTX > C2 > GTX3 > GTX2 > C1. Removal of STX and neoSTX (77%–97.2% was significantly greater than removal of GTX3 and C2 (33.3%–49.7%. There were no significant differences in toxin removal capacity between viable and non-viable forms of lactobacilli, which suggested that binding rather than metabolism is the mechanism of the removal of toxins. In general, binding was not affected by the presence of other organic molecules in solution. Importantly, this is the first study to demonstrate the ability of specific probiotic lactic bacteria to remove PSTs, particularly the most toxic PST-STX, from solution. Further, these results warrant thorough screening and assessment of safe and beneficial microbes for their usefulness in the seafood and water industries and their effectiveness in vivo.

  3. In Situ Capture of Bacterial Toxins for Antivirulence Vaccination.

    Science.gov (United States)

    Wei, Xiaoli; Gao, Jie; Wang, Fei; Ying, Man; Angsantikul, Pavimol; Kroll, Ashley V; Zhou, Jiarong; Gao, Weiwei; Lu, Weiyue; Fang, Ronnie H; Zhang, Liangfang

    2017-09-01

    Antivirulence vaccination is a promising strategy for addressing bacterial infection that focuses on removing the harmful toxins produced by bacteria. However, a major challenge for creating vaccines against biological toxins is that the vaccine potency is often limited by lack of antigenic breadth, as most formulations have focused on single antigens, while most bacteria secrete a plethora of toxins. Here, a facile approach for generating multiantigenic nanotoxoids for use as vaccines against pathogenic bacteria by leveraging the natural affinity of virulence factors for cellular membranes is reported. Specifically, multiple virulent toxins from bacterial protein secretions are concurrently and naturally entrapped using a membrane-coated nanosponge construct. The resulting multivalent nanotoxoids are capable of delivering virulence factors together, are safe both in vitro and in vivo, and can elicit functional immunity capable of combating live bacterial infections in a mouse model. Despite containing the same bacterial antigens, the reported nanotoxoid formulation consistently outperforms a denatured protein preparation in all of the metrics studied, which underscores the utility of biomimetic nanoparticle-based neutralization and delivery. Overall this strategy helps to address major hurdles in the design of antivirulence vaccines, enabling increased antigenic breadth while maintaining safety. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Inositol hexakisphosphate-dependent processing of Clostridium sordellii lethal toxin and Clostridium novyi alpha-toxin.

    Science.gov (United States)

    Guttenberg, Gregor; Papatheodorou, Panagiotis; Genisyuerek, Selda; Lü, Wei; Jank, Thomas; Einsle, Oliver; Aktories, Klaus

    2011-04-29

    Clostridium sordellii lethal toxin and Clostridium novyi α-toxin, which are virulence factors involved in the toxic shock and gas gangrene syndromes, are members of the family of clostridial glucosylating toxins. The toxins inactivate Rho/Ras proteins by glucosylation or attachment of GlcNAc (α-toxin). Here, we studied the activation of the autoproteolytic processing of the toxins by inositol hexakisphosphate (InsP(6)) and compared it with the processing of Clostridium difficile toxin B. In the presence of low concentrations of InsP(6) (<1 μM), toxin fragments consisting of the N-terminal glucosyltransferase (or GlcNAc-transferase) domains and the cysteine protease domains (CPDs) of C. sordellii lethal toxin, C. novyi α-toxin, and C. difficile toxin B were autocatalytically processed. The cleavage sites of lethal toxin (Leu-543) and α-toxin (Leu-548) and the catalytic cysteine residues (Cys-698 of lethal toxin and Cys-707 of α-toxin) were identified. Affinity of the CPDs for binding InsP(6) was determined by isothermal titration calorimetry. In contrast to full-length toxin B and α-toxin, autocatalytic cleavage and InsP(6) binding of full-length lethal toxin depended on low pH (pH 5) conditions. The data indicate that C. sordellii lethal toxin and C. novyi α-toxin are InsP(6)-dependently processed. However, full-length lethal toxin, but not its short toxin fragments consisting of the glucosyltransferase domain and the CPD, requires a pH-sensitive conformational change to allow binding of InsP(6) and subsequent processing of the toxin.

  5. Inositol Hexakisphosphate-dependent Processing of Clostridium sordellii Lethal Toxin and Clostridium novyi α-Toxin*

    Science.gov (United States)

    Guttenberg, Gregor; Papatheodorou, Panagiotis; Genisyuerek, Selda; Lü, Wei; Jank, Thomas; Einsle, Oliver; Aktories, Klaus

    2011-01-01

    Clostridium sordellii lethal toxin and Clostridium novyi α-toxin, which are virulence factors involved in the toxic shock and gas gangrene syndromes, are members of the family of clostridial glucosylating toxins. The toxins inactivate Rho/Ras proteins by glucosylation or attachment of GlcNAc (α-toxin). Here, we studied the activation of the autoproteolytic processing of the toxins by inositol hexakisphosphate (InsP6) and compared it with the processing of Clostridium difficile toxin B. In the presence of low concentrations of InsP6 (<1 μm), toxin fragments consisting of the N-terminal glucosyltransferase (or GlcNAc-transferase) domains and the cysteine protease domains (CPDs) of C. sordellii lethal toxin, C. novyi α-toxin, and C. difficile toxin B were autocatalytically processed. The cleavage sites of lethal toxin (Leu-543) and α-toxin (Leu-548) and the catalytic cysteine residues (Cys-698 of lethal toxin and Cys-707 of α-toxin) were identified. Affinity of the CPDs for binding InsP6 was determined by isothermal titration calorimetry. In contrast to full-length toxin B and α-toxin, autocatalytic cleavage and InsP6 binding of full-length lethal toxin depended on low pH (pH 5) conditions. The data indicate that C. sordellii lethal toxin and C. novyi α-toxin are InsP6-dependently processed. However, full-length lethal toxin, but not its short toxin fragments consisting of the glucosyltransferase domain and the CPD, requires a pH-sensitive conformational change to allow binding of InsP6 and subsequent processing of the toxin. PMID:21385871

  6. Alpha-Toxin Promotes Mucosal Biofilm Formation by Staphylococcus aureus

    Directory of Open Access Journals (Sweden)

    Michele J Anderson

    2012-05-01

    Full Text Available Staphylococcus aureus causes numerous diseases in humans ranging from the mild skin infections to serious, life-threatening, superantigen-mediated Toxic Shock Syndrome (TSS. S. aureus may also be asymptomatically carried in the anterior nares, vagina or on the skin, which serve as reservoirs for infection. Pulsed-field gel electrophoresis clonal type USA200 is the most widely disseminated colonizer and a major cause of TSS. Our prior studies indicated that α-toxin was a major epithelial proinflammatory exotoxin produced by TSS S. aureus USA200 isolates. It also facilitated the penetration of TSS Toxin-1 (TSST-1 across vaginal mucosa. However, the majority of menstrual TSS isolates produce low α-toxin due to a nonsense point mutation at codon 113, designated hly, suggesting mucosal adaptation. The aim of this study was to characterize the differences between TSS USA200 strains [high (hla+ and low (hly+ α-toxin producers] in their abilities to infect and disrupt vaginal mucosal tissue. A mucosal model was developed using ex vivo porcine vaginal mucosa, LIVE/DEAD® staining and confocal microscropy to characterize biofilm formation and tissue viability of TSS USA 200 isolates CDC587 and MN8, which contain the α-toxin pseudogene (hly, MNPE (hla+ and MNPE isogenic hla knockout (hlaKO. All TSS strains grew to similar bacterial densities (1-5 x 108 CFU on the mucosa and were proinflammatory over 3 days. However, MNPE formed biofilms with significant reductions in the mucosal viability whereas neither CDC587, MN8 (hly+, or MNPE hlaKO, formed biofilms and were less cytotoxic. The addition of exogenous, purified α-toxin to MNPE hlaKO restored the biofilm phenotype. Our studies suggest α-toxin affects S. aureus phenotypic growth on vaginal mucosa, by promoting tissue disruption and biofilm formation; and α–toxin mutants (hly are not benign colonizers, but rather form a different type of infection, which we have termed high density pathogenic

  7. DNA aptamers as a novel approach to neutralize Staphylococcus aureus α-toxin.

    Science.gov (United States)

    Vivekananda, Jeevalatha; Salgado, Christi; Millenbaugh, Nancy J

    2014-02-14

    Staphylococcus aureus is a versatile pathogen capable of causing a broad spectrum of diseases ranging from superficial skin infections to life threatening conditions such as endocarditis, septicemia, pneumonia and toxic shock syndrome. In vitro and in vivo studies identified an exotoxin, α-toxin, as a major cause of S. aureus toxicity. Because S. aureus has rapidly evolved resistance to a number of antibiotics, including methicillin, it is important to identify new therapeutic strategies, other than antibiotics, for inhibiting the harmful effects of this pathogen. Aptamers are single-stranded DNA or RNA oligonucleotides with three-dimensional folded conformations that bind with high affinity and selectivity to targets and modulate their biological functions. The goal of this study was to isolate DNA aptamers that specifically inhibit the cytotoxic activity of α-toxin. After 10 rounds of Systematic Evolution of Ligands by EXponential Enrichment (SELEX), 49 potential anti-α-toxin aptamers were identified. In vitro neutralization assays demonstrated that 4 of these 49 aptamers, AT-27, AT-33, AT-36, and AT-49, significantly inhibited α-toxin-mediated cell death in Jurkat T cells. Furthermore, RT-PCR analysis revealed that α-toxin increased the transcription of the inflammatory cytokines TNF-α and IL-17 and that anti-α-toxin aptamers AT-33 and AT-36 inhibited the upregulation of these genes. Collectively, the data suggest the feasibility of generating functionally effective aptamers against α-toxin for treatment of S. aureus infections. Published by Elsevier Inc.

  8. Delayed toxicity associated with soluble anthrax toxin receptor decoy-Ig fusion protein treatment.

    Directory of Open Access Journals (Sweden)

    Diane Thomas

    Full Text Available Soluble receptor decoy inhibitors, including receptor-immunogloubulin (Ig fusion proteins, have shown promise as candidate anthrax toxin therapeutics. These agents act by binding to the receptor-interaction site on the protective antigen (PA toxin subunit, thereby blocking toxin binding to cell surface receptors. Here we have made the surprising observation that co-administration of receptor decoy-Ig fusion proteins significantly delayed, but did not protect, rats challenged with anthrax lethal toxin. The delayed toxicity was associated with the in vivo assembly of a long-lived complex comprised of anthrax lethal toxin and the receptor decoy-Ig inhibitor. Intoxication in this system presumably results from the slow dissociation of the toxin complex from the inhibitor following their prolonged circulation. We conclude that while receptor decoy-Ig proteins represent promising candidates for the early treatment of B. anthracis infection, they may not be suitable for therapeutic use at later stages when fatal levels of toxin have already accumulated in the bloodstream.

  9. Recognition and tethering of transport vesicles at the Golgi apparatus.

    Science.gov (United States)

    Witkos, Tomasz M; Lowe, Martin

    2017-08-01

    The Golgi apparatus occupies a central position within the secretory pathway where it is a hub for vesicle trafficking. Distinct classes of transport vesicles traffic diverse cargoes into and out of this organelle, as well as between the different Golgi subcompartments. A key feature of Golgi trafficking is the specific recognition of transport vesicles at the different regions of the Golgi apparatus, required for the correct cargo delivery. Specificity is ensured by coiled-coil golgins and multi-subunit tethering complexes (MTCs), which act together to capture vesicles and promote their subsequent fusion with the Golgi membrane. In this review we discuss our current understanding of how golgins and MTCs function together to mediate the specific recognition of vesicles at the Golgi apparatus. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Metal-ligand cooperation at tethered π-ligands.

    Science.gov (United States)

    Verhoeven, Dide G A; Moret, Marc-Etienne

    2016-10-12

    Metal-ligand cooperativity in homogeneous catalysis is emerging as a powerful tool for the design of efficient transition-metal catalysts. This perspective highlights recent advances in the use of neutral π-coordinating ligands, tethered to a transition-metal center by other donor ligands, as cooperative reaction centers. The state-of-the-art organometallic complexes, including π-coordinating ligands originating from C[double bond, length as m-dash]C, C[double bond, length as m-dash]E (E = O, N) and boron containing moieties, are described here, with special attention on their specific reactivity. Geometric and electronic aspects of ligand design and their influence on the coordination mode and reactivity of the π-system are discussed.

  11. Physisorbed Polymer-Tethered Lipid Bilayer with Lipopolymer Gradient

    Directory of Open Access Journals (Sweden)

    Christoph A. Naumann

    2012-11-01

    Full Text Available Physisorbed polymer-tethered lipid bilayers consisting of phospholipids and lipopolymers represent an attractive planar model membrane platform, in which bilayer fluidity and membrane elastic properties can be regulated through lipopolymer molar concentration. Herein we report a method for the fabrication of such a planar model membrane system with a lateral gradient of lipopolymer density. In addition, a procedure is described, which leads to a sharp boundary between regions of low and high lipopolymer molar concentrations. Resulting gradients and sharp boundaries are visualized on the basis of membrane buckling structures at elevated lipopolymer concentrations using epifluorescence microscopy and atomic force microscopy. Furthermore, results from spot photobleaching experiments are presented, which provide insight into the lipid lateral fluidity in these model membrane architectures. The presented experimental data highlight a planar, solid-supported membrane characterized by fascinating length scale-dependent dynamics and elastic properties with remarkable parallels to those observed in cellular membranes.

  12. DOE Geothermal Data Repository - Tethering Data to Information: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Weers, J.; Anderson, A.

    2014-02-01

    Data are not inherently information. Without context, data are just numbers, figures, names, or points on a line. By assigning context to data, we can validate ideas, form opinions, and generate knowledge. This is an important distinction to information scientists, as we recognize that the context in which we keep our data plays a big part in generating its value. The mechanisms used to assign this context often include their own data, supplemental to the data being described and defining semantic relationships, commonly referred to as metadata. This paper provides the status of the DOE Geothermal Data Repository (DOE GDR), including recent efforts to tether data submissions to information, discusses the important distinction between data and information, outlines a path to generate useful knowledge from raw data, and details the steps taken in order to become a node on the National Geothermal Data System (NGDS).

  13. Circular Orbit Target Capture Using Space Tether-Net System

    Directory of Open Access Journals (Sweden)

    Guang Zhai

    2013-01-01

    Full Text Available The space tether-net system for on-orbit capture is proposed in this paper. In order to research the dynamic behaviors during system deployment, both free and nonfree deployment dynamics in circular orbit are developed; the system motion with respect to Local Vertical and Local Horizontal frame is also researched with analysis and simulation. The results show that in the case of free deployment, the capture net follows curve trajectories due to the relative orbit dynamic perturbation, and the initial deployment velocities are planned by state transformation equations for static and floating target captures; in the case of non-free deployment, the system undergoes an altitude libration along the Local Vertical, and the analytical solutions that describe the attitude libration are obtained by using variable separation and integration. Finally, the dynamics of postdeployment system is also proved marginally stable if the critical initial conditions are satisfied.

  14. Tethered and Polymer Supported Bilayer Lipid Membranes: Structure and Function

    Directory of Open Access Journals (Sweden)

    Jakob Andersson

    2016-05-01

    Full Text Available Solid supported bilayer lipid membranes are model systems to mimic natural cell membranes in order to understand structural and functional properties of such systems. The use of a model system allows for the use of a wide variety of analytical tools including atomic force microscopy, impedance spectroscopy, neutron reflectometry, and surface plasmon resonance spectroscopy. Among the large number of different types of model membranes polymer-supported and tethered lipid bilayers have been shown to be versatile and useful systems. Both systems consist of a lipid bilayer, which is de-coupled from an underlying support by a spacer cushion. Both systems will be reviewed, with an emphasis on the effect that the spacer moiety has on the bilayer properties.

  15. Determination of low tetanus or diphtheria antitoxin titers in sera by a toxin neutralization assay and a modified toxin-binding inhibition test

    Directory of Open Access Journals (Sweden)

    M.H. Sonobe

    2007-01-01

    Full Text Available A method for the screening of tetanus and diphtheria antibodies in serum using anatoxin (inactivated toxin instead of toxin was developed as an alternative to the in vivo toxin neutralization assay based on the toxin-binding inhibition test (TOBI test. In this study, the serum titers (values between 1.0 and 19.5 IU measured by a modified TOBI test (Modi-TOBI test and toxin neutralization assays were correlated (P < 0.0001. Titers of tetanus or diphtheria antibodies were evaluated in serum samples from guinea pigs immunized with tetanus toxoid, diphtheria-tetanus or triple vaccine. For the Modi-TOBI test, after blocking the microtiter plates, standard tetanus or diphtheria antitoxin and different concentrations of guinea pig sera were incubated with the respective anatoxin. Twelve hours later, these samples were transferred to a plate previously coated with tetanus or diphtheria antitoxin to bind the remaining anatoxin. The anatoxin was then detected using a peroxidase-labeled tetanus or diphtheria antitoxin. Serum titers were calculated using a linear regression plot of the results for the corresponding standard antitoxin. For the toxin neutralization assay, L+/10/50 doses of either toxin combined with different concentrations of serum samples were inoculated into mice for anti-tetanus detection, or in guinea pigs for anti-diphtheria detection. Both assays were suitable for determining wide ranges of antitoxin levels. The linear regression plots showed high correlation coefficients for tetanus (r² = 0.95, P < 0.0001 and for diphtheria (r² = 0.93, P < 0.0001 between the in vitro and the in vivo assays. The standardized method is appropriate for evaluating titers of neutralizing antibodies, thus permitting the in vitro control of serum antitoxin levels.

  16. The Effect of Tethers on Artificial Cell Membranes: A Coarse-Grained Molecular Dynamics Study.

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    William Hoiles

    Full Text Available Tethered bilayer lipid membranes (tBLMs provide a stable platform for modeling the dynamics and order of biological membranes where the tethers mimic the cytoskeletal supports present in biological cell membranes. In this paper coarse-grained molecular dynamics (CGMD is applied to study the effects of tethers on lipid membrane properties. Using results from the CGMD model and the overdamped Fokker-Planck equation, we show that the diffusion tensor and particle density of water in the tBLM is spatially dependent. Further, it is shown that the membrane thickness, lipid diffusion, defect density, free energy of lipid flip-flop, and membrane dielectric permittivity are all dependent on the tether density. The numerically computed results from the CGMD model are in agreement with the experimentally measured results from tBLMs containing different tether densities and lipids derived from Archaebacteria. Additionally, using experimental measurements from Escherichia coli bacteria and Saccharomyces Cerevisiae yeast tethered membranes, we illustrate how previous molecular dynamics results can be combined with the proposed model to estimate the dielectric permittivity and defect density of these membranes as a function of tether density.

  17. Probing tethered targets of a single biomolecular complex with atomic force microscopy.

    Science.gov (United States)

    Wu, Na; Wang, Qi; Zhou, Xingfei; Jia, Si Si; Fan, Youjie; Hu, Jun; Li, Bin

    2013-12-01

    DNA origami shows tremendous promise as templates for the assembly of nano-components and detection of molecular recognition events. So far, the method of choice for evaluating these structures has been atomic force microscopy (AFM), a powerful tool for imaging nanoscale objects. In most cases, tethered targets on DNA origami have proven to be highly effective samples for investigation. Still, while maximal assembly of the nanostructures might benefit from the greatest flexibility in the tether, AFM imaging requires a sufficient stability of the adsorbed components. The balance between the tether flexibility and sample stability is a major, poorly understood, concern in such studies. Here, we investigated the dependence of the tethering length on molecular capture events monitored by AFM. In our experiments, single biotin molecules were attached to DNA origami templates with various linker lengths of thymidine nucleotides, and their interaction with streptavidin was observed with AFM. Our results show that the streptavidin-biotin complexes are easily detected with short tethered lengths, and that their morphological features clearly change with the tethering length. We identify the functionally useful tether lengths for these investigations, which are also expected to prove useful in the construction and further application of DNA origami in bio-nanotechnology studies. Copyright © 2013 John Wiley & Sons, Ltd.

  18. Viewpoint animation with a dynamic tether for supporting navigation in a virtual environment.

    Science.gov (United States)

    Wang, Wenbi; Milgram, Paul

    2009-06-01

    This study examined the concept of dynamic viewpoint tethering for enhancing performance in 3-D avatar control tasks. Dynamic viewpoint tethering refers to a viewpoint animation technique that couples a display viewpoint to a controlled avatar through a virtual tether. A dynamic tether, modeled as a mass spring damper system, can potentially generate desirable viewpoint behavior because of its ability to produce frequency-separated viewpoint responses. This study investigated the impact of a tether's rigidity and damping properties on users' navigational performance. Twelve participants took part in a simulated 3-D aerial navigational task. Performance was evaluated with respect to local guidance and global awareness. Root mean square error scores revealed a decrease in local guidance performance when (a) the tether was either severely underdamped or overdamped and (b) the tether's rigidity approached either zero or infinity. In addition, (c) global performance was better for higher-frequency forcing functions. Critical damping and medium rigidity can be optimized during design for enhancing users' navigational efficiency. Guidelines generated from this study support future viewpoint design in interactive virtual reality applications.

  19. Serine protease EspP from enterohemorrhagic Escherichia coli is sufficient to induce shiga toxin macropinocytosis in intestinal epithelium.

    Directory of Open Access Journals (Sweden)

    Julie In

    Full Text Available Life-threatening intestinal and systemic effects of the Shiga toxins produced by enterohemorrhagic Escherichia coli (EHEC require toxin uptake and transcytosis across intestinal epithelial cells. We have recently demonstrated that EHEC infection of intestinal epithelial cells stimulates toxin macropinocytosis, an actin-dependent endocytic pathway. Host actin rearrangement necessary for EHEC attachment to enterocytes is mediated by the type 3 secretion system which functions as a molecular syringe to translocate bacterial effector proteins directly into host cells. Actin-dependent EHEC attachment also requires the outer membrane protein intimin, a major EHEC adhesin. Here, we investigate the role of type 3 secretion in actin turnover occurring during toxin macropinocytosis. Toxin macropinocytosis is independent of EHEC type 3 secretion and intimin attachment. EHEC soluble factors are sufficient to stimulate macropinocytosis and deliver toxin into enterocytes in vitro and in vivo; intact bacteria are not required. Intimin-negative enteroaggregative Escherichia coli (EAEC O104:H4 robustly stimulate Shiga toxin macropinocytosis into intestinal epithelial cells. The apical macropinosomes formed in intestinal epithelial cells move through the cells and release their cargo at these cells' basolateral sides. Further analysis of EHEC secreted proteins shows that a serine protease EspP alone is able to stimulate host actin remodeling and toxin macropinocytosis. The observation that soluble factors, possibly serine proteases including EspP, from each of two genetically distinct toxin-producing strains, can stimulate Shiga toxin macropinocytosis and transcellular transcytosis alters current ideas concerning mechanisms whereby Shiga toxin interacts with human enterocytes. Mechanisms important for this macropinocytic pathway could suggest new potential therapeutic targets for Shiga toxin-induced disease.

  20. Serine protease EspP from enterohemorrhagic Escherichia coli is sufficient to induce shiga toxin macropinocytosis in intestinal epithelium.

    Science.gov (United States)

    In, Julie; Lukyanenko, Valeriy; Foulke-Abel, Jennifer; Hubbard, Ann L; Delannoy, Michael; Hansen, Anne-Marie; Kaper, James B; Boisen, Nadia; Nataro, James P; Zhu, Chengru; Boedeker, Edgar C; Girón, Jorge A; Kovbasnjuk, Olga

    2013-01-01

    Life-threatening intestinal and systemic effects of the Shiga toxins produced by enterohemorrhagic Escherichia coli (EHEC) require toxin uptake and transcytosis across intestinal epithelial cells. We have recently demonstrated that EHEC infection of intestinal epithelial cells stimulates toxin macropinocytosis, an actin-dependent endocytic pathway. Host actin rearrangement necessary for EHEC attachment to enterocytes is mediated by the type 3 secretion system which functions as a molecular syringe to translocate bacterial effector proteins directly into host cells. Actin-dependent EHEC attachment also requires the outer membrane protein intimin, a major EHEC adhesin. Here, we investigate the role of type 3 secretion in actin turnover occurring during toxin macropinocytosis. Toxin macropinocytosis is independent of EHEC type 3 secretion and intimin attachment. EHEC soluble factors are sufficient to stimulate macropinocytosis and deliver toxin into enterocytes in vitro and in vivo; intact bacteria are not required. Intimin-negative enteroaggregative Escherichia coli (EAEC) O104:H4 robustly stimulate Shiga toxin macropinocytosis into intestinal epithelial cells. The apical macropinosomes formed in intestinal epithelial cells move through the cells and release their cargo at these cells' basolateral sides. Further analysis of EHEC secreted proteins shows that a serine protease EspP alone is able to stimulate host actin remodeling and toxin macropinocytosis. The observation that soluble factors, possibly serine proteases including EspP, from each of two genetically distinct toxin-producing strains, can stimulate Shiga toxin macropinocytosis and transcellular transcytosis alters current ideas concerning mechanisms whereby Shiga toxin interacts with human enterocytes. Mechanisms important for this macropinocytic pathway could suggest new potential therapeutic targets for Shiga toxin-induced disease.

  1. Minimally invasive tethered cord release in children: A technical note

    Directory of Open Access Journals (Sweden)

    S. Kağan Başarslan

    2014-03-01

    Full Text Available Tethered cord release is commonly performed in pediatric neurosurgery. Nowadays, minimally invasive procedures are created growing interest due to its highly tolerable nature for surgery. It has been main purpose a minimal damaging on access route and maximum protection of normal structures in surgery. We present a surgical treatment of tethered cord syndrome, by which is provided the cord releasing unlike the many methods being applied with tissue removal. The main advantage of performing this surgery through 2 cm hole is to avoid removing ligamentum flavum and bony structure like lamina in addition to reduce the length of the incision and the related scar tissue. J Clin Exp Invest 2014; 5 (1: 115-117 Technical note: the patient was taken on the operating table in the sitting-prone position, and L5-S1 distance was determined by fluoroscopy. The skin and subcutaneous tissues was passed via a 2 cm vertical incision settled in 0.5 cm laterally from midline. L5-S1 distance and its covering ligamentum flavum are displayed by the guidance of L5 lamina. Williams’s retractor was placed in the distance after fetching microscope. The foregoing procedures are the same with microdiscectomic surgery. By a vertical incision made on the flavum, its both layer was lifted up and hanged with simple suture on the back tissue for a comfortable exposure of the Dura. Thecal sac was opened by 0.5 cm long vertical incision on the Dura after obtaining secure CSF drainage with the help of yellow-tipped syringe needle. With finding by a nerve hook, the phylum was burned and released securely. Then the Dura was sutured primarily for the closure by means of microsurgery instruments, and flavum was laid on it again.

  2. Heterobifunctional crosslinkers for tethering single ligand molecules to scanning probes

    Energy Technology Data Exchange (ETDEWEB)

    Riener, Christian K.; Kienberger, Ferry; Hahn, Christoph D.; Buchinger, Gerhard M.; Egwim, Innocent O.C.; Haselgruebler, Thomas; Ebner, Andreas; Romanin, Christoph; Klampfl, Christian; Lackner, Bernd; Prinz, Heino; Blaas, Dieter; Hinterdorfer, Peter; Gruber, Hermann J

    2003-11-14

    Single molecule recognition force microscopy (SMRFM) is a versatile atomic force microscopy (AFM) method to probe specific interactions of cognitive molecules on the single molecule level. It allows insights to be gained into interaction potentials and kinetic barriers and is capable of mapping interaction sites with nm positional accuracy. These applications require a ligand to be attached to the AFM tip, preferably by a distensible poly(ethylene glycol) (PEG) chain between the measuring tip and the ligand molecule. The PEG chain greatly facilitates specific binding of the ligand to immobile receptor sites on the sample surface. The present study contributes to tip-PEG-ligand tethering in three ways: (i) a convenient synthetic route was found to prepare NH{sub 2}-PEG-COOH which is the key intermediate for long heterobifunctional crosslinkers; (ii) a variety of heterobifunctional PEG derivatives for tip-PEG-ligand linking were prepared from NH{sub 2}-PEG-COOH; (iii) in particular, a new PEG crosslinker with one thiol-reactive end and one terminal nitrilotriacetic acid (NTA) group was synthesized and successfully used to tether His{sub 6}-tagged protein molecules to AFM tips via noncovalent NTA-Ni{sup 2+}-His{sub 6} bridges. The new crosslinker was applied to link a recombinant His{sub 6}-tagged fragment of the very-low density lipoprotein receptor to the AFM tip whereupon specific docking to the capsid of human rhinovirus particles was observed by force microscopy. In a parallel study, the specific interaction of the small GTPase Ran with the nuclear import receptor importin {beta}1 was studied in detail by SMRFM, using the new crosslinker to link His{sub 6}-tagged Ran to the measuring tip [Nat. Struct. Biol. (2003), 10, 553-557].

  3. Fate of tetanus toxin bound to the surface of primary neurons in culture: evidence for rapid internalization.

    Science.gov (United States)

    Critchley, D R; Nelson, P G; Habig, W H; Fishman, P H

    1985-05-01

    We examined the nature of the tetanus toxin receptor in primary cultures of mouse spinal cord by ligand blotting techniques. Membrane components were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and transferred to nitrocellulose sheets, which were overlaid with 125I-labeled tetanus toxin. The toxin bound only to material at or near the dye front, which was lost when the cells were delipidated before electrophoresis. Gangliosides purified from the lipid extract were separated by thin-layer chromatography and the chromatogram was overlaid with 125I-toxin. The toxin bound to gangliosides corresponding to GD1b and GT1b. Similar results were obtained with brain membranes; thus, gangliosides rather than glycoproteins appear to be the toxin receptors both in vivo and in neuronal cell cultures. To follow the fate of tetanus toxin bound to cultured neurons, we developed an assay to measure cell-surface and internalized toxin. Cells were incubated with tetanus toxin at 0 degree C, washed, and sequentially exposed to antitoxin and 125I-labeled protein A. Using this assay, we found that much of the toxin initially bound to cell surface disappeared rapidly when the temperature was raised to 37 degrees C but not when the cells were kept at 0 degree C. Some of the toxin was internalized and could only be detected by our treating the cells with Triton X-100 before adding anti-toxin. Experiments with 125I-tetanus toxin showed that a substantial amount of the toxin bound at 0 degree C dissociated into the medium upon warming of the cells. Using immunofluorescence, we confirmed that some of the bound toxin was internalized within 15 min and accumulated in discrete structures. These structures did not appear to be lysosomes, as the cell-associated toxin had a long half-life and 90% of the radioactivity released into the medium was precipitated by trichloroacetic acid. The rapid internalization of tetanus toxin into a subcellular compartment where it escapes

  4. Experiments and simulation of a net closing mechanism for tether-net capture of space debris

    Science.gov (United States)

    Sharf, Inna; Thomsen, Benjamin; Botta, Eleonora M.; Misra, Arun K.

    2017-10-01

    This research addresses the design and testing of a debris containment system for use in a tether-net approach to space debris removal. The tether-net active debris removal involves the ejection of a net from a spacecraft by applying impulses to masses on the net, subsequent expansion of the net, the envelopment and capture of the debris target, and the de-orbiting of the debris via a tether to the chaser spacecraft. To ensure a debris removal mission's success, it is important that the debris be successfully captured and then, secured within the net. To this end, we present a concept for a net closing mechanism, which we believe will permit consistently successful debris capture via a simple and unobtrusive design. This net closing system functions by extending the main tether connecting the chaser spacecraft and the net vertex to the perimeter and around the perimeter of the net, allowing the tether to actuate closure of the net in a manner similar to a cinch cord. A particular embodiment of the design in a laboratory test-bed is described: the test-bed itself is comprised of a scaled-down tether-net, a supporting frame and a mock-up debris. Experiments conducted with the facility demonstrate the practicality of the net closing system. A model of the net closure concept has been integrated into the previously developed dynamics simulator of the chaser/tether-net/debris system. Simulations under tether tensioning conditions demonstrate the effectiveness of the closure concept for debris containment, in the gravity-free environment of space, for a realistic debris target. The on-ground experimental test-bed is also used to showcase its utility for validating the dynamics simulation of the net deployment, and a full-scale automated setup would make possible a range of validation studies of other aspects of a tether-net debris capture mission.

  5. Electrodynamic Tether Operations beyond the Ionosphere in the Low-Density Magnetosphere

    Science.gov (United States)

    Stone, Nobie H.

    2007-01-01

    In the classical concept for the operation of electrodynamic tethers in space, a voltage is generated across the tether, either by the tether's orbital motion through the earth's planetary magnetic field or by a power supply; electrons are then collected from the ionospheric plasma at the positive pole; actively emitted back into space at the negative pole; and the circuit is closed by currents driven through the ambient conducting ionosphere. This concept has been proven to work in space by the Tethered Satellite System TSS-1 and TSS-1R Space Shuttle missions; and the Plasma Motor-Generator (PMG) tether flight experiment. However, it limits electrodynamic tether operations to the F-region of the ionosphere where the plasma density is sufficient to conduct the required currents--in other words, between altitudes of approximately 200 to 1000 km in sunlight. In the earth's shadow, the ionospheric density drops precipitously and tether operations, using the above approach, are not effective--even within this altitude range. There are numerous missions that require in-space propulsion in the Earth's shadow and/or outside of the above altitude range. This paper will, therefore, present the fundamentals of a concept that would allow electrodynamic tethers to operate almost anywhere within the magnetosphere, the region of space containing the earth's planetary magnetic field. In other words, because operations would be virtually independent of any ambient plasma, the range of electrodynamic operations would be extended into the earth's shadow and out to synchronous orbit--forty times the present operational range. The key to this concept is the active generation of plasma at each pole of the tether so that current generation ,does not depend on the conductivity of the ambient ionosphere. Arguments will be presented, based on ,existing flight data, which shed light on the behavior of charge emissions in space and show the plausibility of the concept.

  6. Entry of Shiga toxin into cells

    DEFF Research Database (Denmark)

    Sandvig, Kirsten; van Deurs, Bo

    1994-01-01

    Cellebiologi, Shiga toxin, receptors, glycolipids, endocytosis, trans-Golgi network, endoplasmic reticulum, retrograde transport......Cellebiologi, Shiga toxin, receptors, glycolipids, endocytosis, trans-Golgi network, endoplasmic reticulum, retrograde transport...

  7. Inhibition of cholera toxin and other AB toxins by polyphenolic compounds

    Science.gov (United States)

    All AB-type protein toxins have intracellular targets despite an initial extracellular location. These toxins use different methods to reach the cytosol and have different effects on the target cell. Broad-spectrum inhibitors against AB toxins are therefore hard to develop because the toxins use dif...

  8. Neutralising Antibodies against Ricin Toxin

    OpenAIRE

    Julie Prigent; Laetitia Panigai; Patricia Lamourette; Didier Sauvaire; Karine Devilliers; Marc Plaisance; Hervé Volland; Christophe Créminon; Stéphanie Simon

    2011-01-01

    The Centers for Disease Control and Prevention have listed the potential bioweapon ricin as a Category B Agent. Ricin is a so-called A/B toxin produced by plants and is one of the deadliest molecules known. It is easy to prepare and no curative treatment is available. An immunotherapeutic approach could be of interest to attenuate or neutralise the effects of the toxin. We sought to characterise neutralising monoclonal antibodies against ricin and to develop an effective therapy. For this pur...

  9. Toxin synergism in snake venoms

    DEFF Research Database (Denmark)

    Laustsen, Andreas Hougaard

    2016-01-01

    Synergism between venom toxins exists for a range of snake species. Synergism can be derived from both intermolecular interactions and supramolecular interactions between venom components, and can be the result of toxins targeting the same protein, biochemical pathway or physiological process. Few...... simple systematic tools and methods for determining the presence of synergism exist, but include co-administration of venom components and assessment of Accumulated Toxicity Scores. A better understanding of how to investigate synergism in snake venoms may help unravel strategies for developing novel...

  10. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    Science.gov (United States)

    Angelici, Robert J.; Gao, Hanrong

    1998-08-04

    The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilation, olefin oxidation, isomerization, hydrocyanation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical.

  11. Toxin yet not toxic: Botulinum toxin in dentistry

    Directory of Open Access Journals (Sweden)

    Archana M.S.

    2016-04-01

    Full Text Available Paracelsus contrasted poisons from nonpoisons, stating that “All things are poisons, and there is nothing that is harmless; the dose alone decides that something is a poison”. Living organisms, such as plants, animals, and microorganisms, constitute a huge source of pharmaceutically useful medicines and toxins. Depending on their source, toxins can be categorized as phytotoxins, mycotoxins, or zootoxins, which include venoms and bacterial toxins. Any toxin can be harmful or beneficial. Within the last 100 years, the perception of botulinum neurotoxin (BTX has evolved from that of a poison to a versatile clinical agent with various uses. BTX plays a key role in the management of many orofacial and dental disorders. Its indications are rapidly expanding, with ongoing trials for further applications. However, despite its clinical use, what BTX specifically does in each condition is still not clear. The main aim of this review is to describe some of the unclear aspects of this potentially useful agent, with a focus on the current research in dentistry.

  12. Comparative toxicity and efficacy of engineered anthrax lethal toxin variants with broad anti-tumor activities

    Energy Technology Data Exchange (ETDEWEB)

    Peters, Diane E. [Proteases and Tissue Remodeling Section, Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD (United States); Program of Pharmacology and Experimental Therapeutics, Tufts University School of Medicine, Boston, MA (United States); Hoover, Benjamin [Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD (United States); Cloud, Loretta Grey [Proteases and Tissue Remodeling Section, Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD (United States); Liu, Shihui [Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD (United States); Molinolo, Alfredo A. [Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD (United States); Leppla, Stephen H. [Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD (United States); Bugge, Thomas H., E-mail: thomas.bugge@nih.go [Proteases and Tissue Remodeling Section, Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD (United States)

    2014-09-01

    We have previously designed and characterized versions of anthrax lethal toxin that are selectively cytotoxic in the tumor microenvironment and which display broad and potent anti-tumor activities in vivo. Here, we have performed the first direct comparison of the safety and efficacy of three engineered anthrax lethal toxin variants requiring activation by either matrix-metalloproteinases (MMPs), urokinase plasminogen activator (uPA) or co-localized MMP/uPA activities. C57BL/6J mice were challenged with six doses of engineered toxins via intraperitoneal (I.P.) or intravenous (I.V.) dose routes to determine the maximum tolerated dose for six administrations (MTD6) and dose-limiting toxicities. Efficacy was evaluated using the B16-BL6 syngraft model of melanoma; mice bearing established tumors were treated with six I.P. doses of toxin and tumor measurements and immunohistochemistry, paired with terminal blood work, were used to elaborate upon the anti-tumor mechanism and relative efficacy of each variant. We found that MMP-, uPA- and dual MMP/uPA-activated anthrax lethal toxins exhibited the same dose-limiting toxicity; dose-dependent GI toxicity. In terms of efficacy, all three toxins significantly reduced primary B16-BL6 tumor burden, ranging from 32% to 87% reduction, and they also delayed disease progression as evidenced by dose-dependent normalization of blood work values. While target organ toxicity and effective doses were similar amongst the variants, the dual MMP/uPA-activated anthrax lethal toxin exhibited the highest I.P. MTD6 and was 1.5–3-fold better tolerated than the single MMP- and uPA-activated toxins. Overall, we demonstrate that this dual MMP/uPA-activated anthrax lethal toxin can be administered safely and is highly effective in a preclinical model of melanoma. This modified bacterial cytotoxin is thus a promising candidate for further clinical development and evaluation for use in treating human cancers. - Highlights: • Toxicity and anti

  13. Fibrinogenolytic toxin from Indian monocled cobra

    Indian Academy of Sciences (India)

    A fibrinogenolytic toxin of molecular weight 6.5 kDa has been purified from the venom of Indian monocled cobra (Naja kaouthia) by repeated cation exchange chromatography on CM-sephadex C-50. The purified toxin did not show any phospholipase activity but was mildly hemolytic on human erythrocytes. This toxin, called ...

  14. Risk Assessment of Shellfish Toxins

    Directory of Open Access Journals (Sweden)

    Rex Munday

    2013-11-01

    Full Text Available Complex secondary metabolites, some of which are highly toxic to mammals, are produced by many marine organisms. Some of these organisms are important food sources for marine animals and, when ingested, the toxins that they produce may be absorbed and stored in the tissues of the predators, which then become toxic to animals higher up the food chain. This is a particular problem with shellfish, and many cases of poisoning are reported in shellfish consumers each year. At present, there is no practicable means of preventing uptake of the toxins by shellfish or of removing them after harvesting. Assessment of the risk posed by such toxins is therefore required in order to determine levels that are unlikely to cause adverse effects in humans and to permit the establishment of regulatory limits in shellfish for human consumption. In the present review, the basic principles of risk assessment are described, and the progress made toward robust risk assessment of seafood toxins is discussed. While good progress has been made, it is clear that further toxicological studies are required before this goal is fully achieved.

  15. Botulinum toxin for vaginismus treatment.

    Science.gov (United States)

    Ferreira, Juliana Rocha; Souza, Renan Pedra

    2012-01-01

    Vaginismus is characterized by recurrent or persistent involuntary contraction of the perineal muscles surrounding the outer third of the vagina when penile, finger, tampon, or speculum penetration is attempted. Recent results have suggested the use of botulinum toxin for the treatment of vaginismus. Here, we assessed previously published data to evaluate the therapeutic effectiveness of botulinum toxin for vaginismus. We have carried out a systematic review followed by a meta-analysis. Our results indicate that botulinum toxin is an effective therapeutic option for patients with vaginismus (pooled odds ratio of 8.723 with 95% confidence interval limits of 1.942 and 39.162, p = 0.005). This may hold particularly true in treatment-refractory patients because most of the studies included in this meta-analysis have enrolled these subjects in their primary analysis. Botulinum toxin appears to bea reasonable intervention for vaginismus. However, this conclusion should be read carefully because of the deficiency of placebo-controlled randomized clinical trials and the quality issues presented in the existing ones.

  16. Shigella Sonnei and Shiga Toxin

    Centers for Disease Control (CDC) Podcasts

    2016-07-28

    Katherine Lamba, an infectious disease epidemiologist with the California Department of Public Health, discusses Shiga Toxin producing Shigella sonnei.  Created: 7/28/2016 by National Center for Emerging and Zoonotic Infectious Diseases (NCEZID).   Date Released: 7/28/2016.

  17. The pore-forming toxin proaerolysin is activated by furin.

    Science.gov (United States)

    Abrami, L; Fivaz, M; Decroly, E; Seidah, N G; Jean, F; Thomas, G; Leppla, S H; Buckley, J T; van der Goot, F G

    1998-12-04

    Aerolysin is secreted as an inactive dimeric precursor by the bacterium Aeromonas hydrophila. Proteolytic cleavage within a mobile loop near the C terminus of the protoxin is required for oligomerization and channel formation. This loop contains the sequence KVRRAR432, which should be recognized by mammalian proprotein convertases such as furin, PACE4, and PC5/6A. Here we show that these three proteases cleave proaerolysin after Arg-432 in vitro, yielding active toxin. We also investigated the potential role of these enzymes in the in vivo activation of the protoxin. We found that Chinese hamster ovary cells were able to convert the protoxin to aerolysin in the absence of exogenous proteases and that activation did not require internalization of the toxin. The furin inhibitor alpha1-antitrypsin Portland reduced the rate of proaerolysin activation in vivo, and proaerolysin processing was even further reduced in furin-deficient FD11 Chinese hamster ovary cells. The cells were also less sensitive to proaerolysin than wild type cells; however, transient transfection of FD11 cells with the cDNA encoding furin conferred normal sensitivity to the protoxin. Together these findings argue that furin catalyzes the cell-surface activation of proaerolysin in vivo.

  18. Tethered gravity laboratories study - The center-of-gravity management concept

    Science.gov (United States)

    Bevilacqua, Franco; Merlina, Pietro; Lorenzini, Enrico Carlo; Cosmo, Mario; Bergamaschi, Silvio

    A tether system deployed from the Space Station (SS) can provide a facility for controlling the vertical position of the system center of mass at low frequencies or in the dc mode. A review of the force field on board the SS is presented, and a classification is given of the sources of external perturbations modifying the g-field at the microgravity laboratory. This provides a set of constraints to be taken into account. A complete analysis of possible configurations (single tether system, double tether system) is performed, including design criteria, SS impacts, and configuration tradeoff. Basic results are presented from an analysis aimed at identifying the acceleration noise level transmitted to the SS when a tethered system is acted upon by environmental perturbations. Possible benefits achievable by implementing the center-of-graivty management concept are assessed on the basis of development risks and expected hardware complexity.

  19. UV-Curable Hybrid Nanocomposite Coating to Protect Tether Polymer Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To address the NASA need for coatings to protect and strengthen tether materials for Momentum-exchange Electrodynamic Reboost (MXER) technology, Luminit, LLC,...

  20. Computational study of small molecule binding for both tethered and free conditions.

    Science.gov (United States)

    Ytreberg, F Marty

    2010-04-29

    Using a calix[4]arene-benzene complex as a test system, we compare the potential of mean force for when the calix[4]arene is tethered versus free. When the complex is in vacuum, our results show that the difference between tethered and free is primarily due to the entropic contribution to the potential of mean force resulting in a significant binding free energy difference of 6.6 kJ/mol. By contrast, when the complex is in water, our results suggest that there is no appreciable difference between tethered and free. This study elucidates the roles of entropy and enthalpy for this small molecule system and emphasizes the point that tethering the receptor has the potential to dramatically impact the binding properties. These findings should be taken into consideration when using calixarene molecules in nanosensor design.

  1. Materials for Advancement of MXER Tether Design (1000-549) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — There exist a need to develop, identify, and classify various materials that can be used in the fabrication of electrodynamic tethers for various applications. These...

  2. Materials for advancement of MXER tether design (1000-371) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — There exist a need to develop, identify, and classify various materials that can be used in the fabrication of electrodynamic tethers for various applications. These...

  3. The use of the Tethered Satellite System to perform low density aerothermodynamics studies

    Science.gov (United States)

    Carlomagno, Giovanni M.; De Luca, Luigi; Siemers, Paul M.; Wood, George M., Jr.

    1988-01-01

    The Tethered Satellite System (TSS) is a cooperative space system development activity being carried out by USA and Italy. Within TSS, the Shuttle Tethered Aerothermodynamic Research Facility (STARFAC) concept has the potential to provide access to vast portions of the upper atmosphere for the purpose of atmospheric and aerothermodynamic research. The implementation of this capability will push Tether System (TS) state of the art to its limits; the primary problems being tether/satellite drag, heating, tension control, deployment/retrieval control. In this paper parametric studies are accomplished to assess some of these problems and to delineate the tradeoffs available to missions design to meet the engineering constraints. The utilization of aerodynamic rather than spherical shapes - (TSS) - as well as elementary satellite thrusting and lift are included in the present study.

  4. Advanced Particle-in-Cell (PIC) Tools for Simulation of Electrodynamic Tether Plasma Interactions Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Electrodynamic tethers are optimally suited for use in Low-Earth-Orbit (LEO) to generate thrust or drag maneuver satellites. LEO region is polluted with space debris...

  5. Inactivation of allergens and toxins.

    Science.gov (United States)

    Morandini, Piero

    2010-11-30

    Plants are replete with thousands of proteins and small molecules, many of which are species-specific, poisonous or dangerous. Over time humans have learned to avoid dangerous plants or inactivate many toxic components in food plants, but there is still room for ameliorating food crops (and plants in general) in terms of their allergens and toxins content, especially in their edible parts. Inactivation at the genetic rather than physical or chemical level has many advantages and classical genetic approaches have resulted in significant reduction of toxin content. The capacity, offered by genetic engineering, of turning off (inactivating) specific genes has opened up the possibility of altering the plant content in a far more precise manner than previously available. Different levels of intervention (genes coding for toxins/allergens or for enzymes, transporters or regulators involved in their metabolism) are possible and there are several tools for inactivating genes, both direct (using chemical and physical mutagens, insertion of transposons and other genetic elements) and indirect (antisense RNA, RNA interference, microRNA, eventually leading to gene silencing). Each level/strategy has specific advantages and disadvantages (speed, costs, selectivity, stability, reversibility, frequency of desired genotype and regulatory regime). Paradigmatic examples from classical and transgenic approaches are discussed to emphasize the need to revise the present regulatory process. Reducing the content of natural toxins is a trade-off process: the lesser the content of natural toxins, the higher the susceptibility of a plant to pests and therefore the stronger the need to protect plants. As a consequence, more specific pesticides like Bt are needed to substitute for general pesticides. Copyright © 2010 Elsevier B.V. All rights reserved.

  6. The evaluation of brake mechanisms in the deployment of Electrodynamic Tether for space debris removal

    Science.gov (United States)

    2016-03-30

    increase of space debris is becoming a serious problem and active removal of large debris is required. The Japan Aerospace Exploration Agency (JAXA...mechanism, Deployment friction, Electrodynamic tether system, Space debris , Tether. Introduction The increase of space debris , which are defunct or...to exponentially increase [1] [2]. Consequently, the active removal of large space debris from crowded economically useful orbits (800-1500km alt

  7. Control by damping Injection of Electrodynamic Tether System in an Inclined Orbit

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2009-01-01

    Control of a satellite system with an electrodynamic tether as actuator is a time-periodic and underactuated control problem. This paper considers the tethered satellite in a Hamiltonian framework and determines a port-controlled Hamiltonian formulation that adequately describes the nonlinear...... of the closed loop system is treated using Floquet theory, investigating the closed loop properties for their dependency of the controller gain and orbit inclination....

  8. Simulation of a tethered microgravity robot pair and validation on a planar air bearing

    Science.gov (United States)

    Mantellato, R.; Lorenzini, E. C.; Sternberg, D.; Roascio, D.; Saenz-Otero, A.; Zachrau, H. J.

    2017-09-01

    A software model has been developed to simulate the on-orbit dynamics of a dual-mass tethered system where one or both of the tethered spacecraft are able to produce propulsive thrust. The software simulates translations and rotations of both spacecraft, with the visco-elastic tether being simulated as a lumped-mass model. Thanks to this last feature, tether longitudinal and lateral modes of vibration and tether tension can be accurately assessed. Also, the way the spacecraft motion responds to sudden tether tension spikes can be studied in detail. The code enables the simulation of different scenarios, including space tug missions for deorbit maneuvers in a debris mitigation context and general-purpose tethered formation flight missions. This study aims to validate the software through a representative test campaign performed with the MIT Synchronized Position Hold Engage and Reorient Experimental Satellites (SPHERES) planar air bearing system. Results obtained with the numerical simulator are compared with data from direct measurements in different testing setups. The studied cases take into account different initial conditions of the spacecraft velocities and relative attitudes, and thrust forces. Data analysis is presented comparing the results of the simulations with direct measurements of acceleration and Azimuth rate of the two bodies in the planar air bearing test facility using a Nylon tether. Plans for conducting a microgravity test campaign using the SPHERES satellites aboard the International Space Station are also being scheduled in the near future in order to further validate the simulation using data from the relevant operational environment of extended microgravity with full six degree of freedom (per body) motion.

  9. Magnetically Tuning Tether Mobility of Integrin Ligand Regulates Adhesion, Spreading, and Differentiation of Stem Cells.

    Science.gov (United States)

    Wong, Dexter S H; Li, Jinming; Yan, Xiaohui; Wang, Ben; Li, Rui; Zhang, Li; Bian, Liming

    2017-03-08

    Cells sense and respond to the surrounding microenvironment through binding of membranous integrin to ligands such as the Arg-Gly-Asp (RGD) peptide. Previous studies show that the RGD tether properties on substrate influence cell adhesion and spreading, but few studies have reported strategies to control the tether mobility of RGD on substrate via a physical and noncontact approach. Herein, we demonstrate a novel strategy to tune the tether mobility of RGD on substrate via magnetic force. We conjugate a monolayer of RGD-bearing magnetic nanoparticles (MNPs) on a glass substrate via the flexible and coiled poly(ethylene glycol) linker of large molecular weight (PEG, average MW: 2000), and this increases the RGD tether mobility, which can be significantly reduced by applying magnetic attraction on MNPs. Our data show that high RGD tether mobility delays the early adhesion and spreading of human mesenchymal stem cells (hMSCs), leading to compromised osteogenic differentiation at later stage. In contrast, hMSCs cultured on substrate with restricted RGD tether mobility, achieved either via a shorter PEG linker (MW: 200) or magnetic force, show significantly better adhesion, spreading, and osteogenic differentiation. The control utilizing RGD-bearing nonmagnetic nanoparticles shows no such enhancing effect of magnetic field on cellular events, further supporting our conjecture of magnetic tuning of RGD tether mobility. We hypothesize that high tether mobility of RGD entails additional time and effort by the cells to fully develop traction force and mechanical feedback, thereby delaying the maturation of FAs and activation of subsequent mechanotransduction signaling. Our staining results of vinculin, a critical component of FAs, and Yes-associated protein (YAP), an important mechanosensitive transcriptional factor, support our hypothesis. We believe that our work not only sheds light on the impact of dynamic presentation of cell adhesive ligands on cellular behaviors

  10. Data Tethers: Preventing Information Leakage by Enforcing Environmental Data Access Policies

    OpenAIRE

    Fleming, Charles

    2013-01-01

    Protecting data from accidental loss or theft is crucial in today's world ofmobile computing. Data Tethers provides environmental policy control of information at the data level, rather than the file level. Data Tethers uses dynamic recompilation to add label tracking instructions to existing applications in the OpenSolaris operating system, allowing fine-grain data flow tracking in legacy applications without the need to recompile from source. We demonstrate the system's feasibility with mi...

  11. Neuronal sensitivity to tetanus toxin requires gangliosides.

    Science.gov (United States)

    Williamson, L C; Bateman, K E; Clifford, J C; Neale, E A

    1999-08-27

    Tetanus toxin produces spastic paralysis in situ by blocking inhibitory neurotransmitter release in the spinal cord. Although di- and trisialogangliosides bind tetanus toxin, their role as productive toxin receptors remains unclear. We examined toxin binding and action in spinal cord cell cultures grown in the presence of fumonisin B(1), an inhibitor of ganglioside synthesis. Mouse spinal cord neurons grown for 3 weeks in culture in 20 microM fumonisin B(1) develop dendrites, axons, and synaptic terminals similar to untreated neurons, even though thin layer chromatography shows a greater than 90% inhibition of ganglioside synthesis. Absence of tetanus and cholera toxin binding by toxin-horseradish peroxidase conjugates or immunofluorescence further indicates loss of mono- and polysialogangliosides. In contrast to control cultures, tetanus toxin added to fumonisin B(1)-treated cultures does not block potassium-stimulated glycine release, inhibit activity-dependent uptake of FM1-43, or abolish immunoreactivity for vesicle-associated membrane protein, the toxin substrate. Supplementing fumonisin B(1)-treated cultures with mixed brain gangliosides completely restores the ability of tetanus toxin to bind to the neuronal surface and to block neurotransmitter release. These data demonstrate that fumonisin B(1) protects against toxin-induced synaptic blockade and that gangliosides are a necessary component of the receptor mechanism for tetanus toxin.

  12. Mechanism of Shiga Toxin Clustering on Membranes

    DEFF Research Database (Denmark)

    Pezeshkian, Weria; Gao, Haifei; Arumugam, Senthil

    2017-01-01

    The bacterial Shiga toxin interacts with its cellular receptor, the glycosphingolipid globotriaosylceramide (Gb3 or CD77), as a first step to entering target cells. Previous studies have shown that toxin molecules cluster on the plasma membrane, despite the apparent lack of direct interactions...... toxin molecules. By contrast, in coarse-grained computer simulations, a correlation was found between clustering and toxin nanoparticle-driven suppression of membrane fluctuations, and experimentally we observed that clustering required the toxin molecules to be tightly bound to the membrane surface....... The most likely interpretation of these findings is that a membrane fluctuation-induced force generates an effective attraction between toxin molecules. Such force would be of similar strength to the electrostatic force at separations around 1 nm, remain strong at distances up to the size of toxin...

  13. Role of UPR Pathway in Defense Response of Aedes aegypti against Cry11Aa Toxin from Bacillus thuringiensis

    Directory of Open Access Journals (Sweden)

    Alejandra Bravo

    2013-04-01

    Full Text Available The insecticidal Cry toxins are pore-forming toxins produced by the bacteria Bacillus thuringiensis that disrupt insect-midgut cells. Cells can trigger different survival mechanisms to counteract the effects of sub-lytic doses of pore forming toxins. Particularly, two signaling pathways have been demonstrated to play a role in the defense mechanism to other toxins in Caenorhabditis elegans and in mammalian cells. These are the unfolded protein response (UPR and the sterol regulatory element binding proteins (SREBP pathways, which are proposed to facilitate membrane repair responses. In this work we analyzed the role of these pathways in Aedes aegypti response to intoxication with Cry11Aa toxin. We show that UPR is activated upon toxin ingestion. The role of these two pathways was analyzed in vivo by using RNA interference. We silenced the expression of specific proteins in A. aegypti larvae. Gene silencing of Ire-1 and Xbp-1 proteins from UPR system, resulted in hypersensitive to Cry11Aa toxin action. In contrast, silencing of Cas-1, Scap and S2P from SREBP pathway had no affect on Cry11Aa toxicity in A. aegypti larvae. However, the role of SREBP pathway requires further studies to be conclusive. Our data indicate that the UPR pathway is involved in the insect defense against Cry toxins.

  14. Biomimicry enhances sequential reactions of tethered glycolytic enzymes, TPI and GAPDHS.

    Science.gov (United States)

    Mukai, Chinatsu; Gao, Lizeng; Bergkvist, Magnus; Nelson, Jacquelyn L; Hinchman, Meleana M; Travis, Alexander J

    2013-01-01

    Maintaining activity of enzymes tethered to solid interfaces remains a major challenge in developing hybrid organic-inorganic devices. In nature, mammalian spermatozoa have overcome this design challenge by having glycolytic enzymes with specialized targeting domains that enable them to function while tethered to a cytoskeletal element. As a step toward designing a hybrid organic-inorganic ATP-generating system, we implemented a biomimetic site-specific immobilization strategy to tether two glycolytic enzymes representing different functional enzyme families: triose phosphoisomerase (TPI; an isomerase) and glyceraldehyde 3-phosphate dehydrogenase (GAPDHS; an oxidoreductase). We then evaluated the activities of these enzymes in comparison to when they were tethered via classical carboxyl-amine crosslinking. Both enzymes show similar surface binding regardless of immobilization method. Remarkably, specific activities for both enzymes were significantly higher when tethered using the biomimetic, site-specific immobilization approach. Using this biomimetic approach, we tethered both enzymes to a single surface and demonstrated their function in series in both forward and reverse directions. Again, the activities in series were significantly higher in both directions when the enzymes were coupled using this biomimetic approach versus carboxyl-amine binding. Our results suggest that biomimetic, site-specific immobilization can provide important functional advantages over chemically specific, but non-oriented attachment, an important strategic insight given the growing interest in recapitulating entire biological pathways on hybrid organic-inorganic devices.

  15. Biomimicry enhances sequential reactions of tethered glycolytic enzymes, TPI and GAPDHS.

    Directory of Open Access Journals (Sweden)

    Chinatsu Mukai

    Full Text Available Maintaining activity of enzymes tethered to solid interfaces remains a major challenge in developing hybrid organic-inorganic devices. In nature, mammalian spermatozoa have overcome this design challenge by having glycolytic enzymes with specialized targeting domains that enable them to function while tethered to a cytoskeletal element. As a step toward designing a hybrid organic-inorganic ATP-generating system, we implemented a biomimetic site-specific immobilization strategy to tether two glycolytic enzymes representing different functional enzyme families: triose phosphoisomerase (TPI; an isomerase and glyceraldehyde 3-phosphate dehydrogenase (GAPDHS; an oxidoreductase. We then evaluated the activities of these enzymes in comparison to when they were tethered via classical carboxyl-amine crosslinking. Both enzymes show similar surface binding regardless of immobilization method. Remarkably, specific activities for both enzymes were significantly higher when tethered using the biomimetic, site-specific immobilization approach. Using this biomimetic approach, we tethered both enzymes to a single surface and demonstrated their function in series in both forward and reverse directions. Again, the activities in series were significantly higher in both directions when the enzymes were coupled using this biomimetic approach versus carboxyl-amine binding. Our results suggest that biomimetic, site-specific immobilization can provide important functional advantages over chemically specific, but non-oriented attachment, an important strategic insight given the growing interest in recapitulating entire biological pathways on hybrid organic-inorganic devices.

  16. Study of dynamical stability of tethered systems during space tug maneuvers

    Science.gov (United States)

    Mantellato, R.; Olivieri, L.; Lorenzini, E. C.

    2017-09-01

    The dynamics of a space tether system composed of one active spacecraft, an uncontrolled large debris (e.g., a defunct satellite), and a visco-elastic tether connecting the two bodies are investigated in this paper. The active spacecraft is assumed to be equipped with a propulsive system for carrying out a tug maneuver that forces the orbital decay of the debris. The dynamical stability and the eigenfrequencies of the tethered system under the action of the thrust are investigated with both numerical and analytical models. A more complex numerical lumped-masses model provides the reference to validate the results hailing from the simplified models. Simplified models of orbital decay, tether, and debris attitude motions were derived using the Clohessy-Wiltshire equations. The results obtained with the simplified models fit very well with those from the lumped-masses model for a wide range of initial conditions. Thanks to the analytical models two resonance conditions were found, both of them affecting the attitude dynamics of the debris, that could represent a serious issue for the safety of the tug maneuver. Also, an instability mechanism that could induce the dual mass system to rotate around its center of mass under certain conditions was identified. These findings make it possible to pinpoint the set of initial conditions of the tethered system at the beginning of the thrust event that provides a dynamically stable tug maneuver for different configurations of the system (e.g., low/high thrust, stiff/elastic tethers).

  17. Tethered cord syndrome with spina bifida aperta in cats: two case reports of different types

    Science.gov (United States)

    Tamura, Masahiro; Oji, Takashi; Une, Satoshi; Mukaino, Makiko; Bekki, Tatsuro; Tado, Masaki; Koyama, Hiromi; Kagawa, Yumiko; Kawata, Mutsumi

    2017-01-01

    Case summary Two castrated male cats, aged 8 months old (case 1) and 10 months old (case 2), showed a history of progressive paraparesis, an over-reaching pelvic limb gait, urinary incontinence and a palpable dermoid fistula. In case 1, the fistula was connected to the dural sac on the conus medullaris, and the tethered spinal cord was retracted caudally. In case 2, the tubular structure was connected to the dural sac on the thoracic spinal cord, and the tethered spinal cord was retracted dorsally. Tethered cord syndrome secondary to spina bifida aperta was suspected in both cats. Excision of the fistula and release of the tethered spinal cord was performed. A histopathological examination confirmed the diagnosis of a meningomyelocele in case 1 and a meningocele in case 2. Paraparesis improved postoperatively in both cats. However, urinary incontinence in case 1 remained partially unresolved. Relevance and novel information This is the first report to describe the imaging characteristics, surgical treatments and outcomes of two different types of tethered cord syndrome with spina bifida aperta in cats. Tethered cord syndrome with spina bifida aperta needs to be included in the differential diagnosis of slowly progressive paraparesis in younger cats with or without vesicorectal failure and a palpable dermoid fistula. PMID:28546867

  18. Tethered cord syndrome with spina bifida aperta in cats: two case reports of different types

    Directory of Open Access Journals (Sweden)

    Masahiro Tamura

    2017-05-01

    Full Text Available Case summary Two castrated male cats, aged 8 months old (case 1 and 10 months old (case 2, showed a history of progressive paraparesis, an over-reaching pelvic limb gait, urinary incontinence and a palpable dermoid fistula. In case 1, the fistula was connected to the dural sac on the conus medullaris, and the tethered spinal cord was retracted caudally. In case 2, the tubular structure was connected to the dural sac on the thoracic spinal cord, and the tethered spinal cord was retracted dorsally. Tethered cord syndrome secondary to spina bifida aperta was suspected in both cats. Excision of the fistula and release of the tethered spinal cord was performed. A histopathological examination confirmed the diagnosis of a meningomyelocele in case 1 and a meningocele in case 2. Paraparesis improved postoperatively in both cats. However, urinary incontinence in case 1 remained partially unresolved. Relevance and novel information This is the first report to describe the imaging characteristics, surgical treatments and outcomes of two different types of tethered cord syndrome with spina bifida aperta in cats. Tethered cord syndrome with spina bifida aperta needs to be included in the differential diagnosis of slowly progressive paraparesis in younger cats with or without vesicorectal failure and a palpable dermoid fistula.

  19. Tethered motion of uniflagellated bacteria at the liquid-solid surface

    Science.gov (United States)

    Bell, Jordan; Tang, Jay

    Direct evidence of the bacterial flagellar motor's rotation was first noted when multiflagellated bacterial cells were observed (under the optical microscope) to rotate when tethered to glass by a single flagellum. The tethered cell assay has continued to play a significant role throughout the subsequent studies of motor characteristics and behavior. Such studies have expanded to include uniflagellated bacteria, such as Vibrio alginolyticus, Pseudomonas aeruginosa, and Caulobacter crescentus. Here we show that such cells are not necessarily tethered by their flagellum, but rather elsewhere on the cell body. The observed cell body rotation is actually due to the flagellum either ``rolling'' against the glass surface, or pushing the cell body at the flagellar base. These motions are directly observed for Vibrio alginolyticus with darkfield microscopy. Additionally, our recently measured distributions of intervals between motor switches for tethered Caulobacter crescentus also confirm this more complicated mode of tethering. Therefore, the rotational speed of tethered uniflagellated bacteria may not equate to that of the motor itself, as is commonly assumed.

  20. Tethered Swimming for the Evaluation and Prescription of Resistance Training in Young Swimmers.

    Science.gov (United States)

    Papoti, Marcelo; da Silva, Adelino S R; Kalva-Filho, Carlos Augusto; Araujo, Gustavo Gomes; Santiago, Vanessa; Martins, LuizEduardo Barreto; Cunha, Sérgio Augusto; Gobatto, Claudio Alexandre

    2017-02-01

    The aims of the present study were 1) to evaluate the effects of 11 weeks of a typical free-swimming training program on aerobic and stroke parameters determined in tethered swimming (Study 1; n=13) and 2) to investigate the responses of tethered swimming efforts, in addition to free-swimming sessions, through 7 weeks of training (Study 2; n=21). In both studies, subjects performed a graded exercise test in tethered swimming (GET) to determine anaerobic threshold (AnT), stroke rate at AnT (SRAnT), peak force at GET (PFGET) and peak blood lactate ([La-]GET). Participants also swam 100-, 200- and 400-m lengths to evaluate performance. In Study 2, swimmers were divided into control (i. e., only free-swimming; GC [n=11]) and tethered swimming group (i. e., 50% of the main session; GTS [n=10]). The results of Study 1 demonstrate that AnT, PFGET, [La(-)]GET and 200-m performance were improved with free-swimming training. The SRAnT decreased with training. In Study 2, free-swimming performance and most of the graded exercise test parameters were not altered in either group. However, [La-]GET improved only for GTS. These results demonstrate that aerobic parameters obtained in tethered swimming can be used to evaluate free-swimming training responses, and the addition of tethered efforts during training routine improves the lactate production capacity of swimmers. © Georg Thieme Verlag KG Stuttgart · New York.

  1. AFM/TIRF force clamp measurements of neurosecretory vesicle tethers reveal characteristic unfolding steps.

    Directory of Open Access Journals (Sweden)

    Mark C Harris

    Full Text Available Although several proteins have been implicated in secretory vesicle tethering, the identity and mechanical properties of the components forming the physical vesicle-plasma membrane link remain unknown. Here we present the first experimental measurements of nanomechanical properties of secretory vesicle-plasma membrane tethers using combined AFM force clamp and TIRF microscopy on membrane sheets from PC12 cells expressing the vesicle marker ANF-eGFP. Application of pulling forces generated tether extensions composed of multiple steps with variable length. The frequency of short (<10 nm tether extension events was markedly higher when a fluorescent vesicle was present at the cantilever tip and increased in the presence of GTPγS, indicating that these events reflect specifically the properties of vesicle-plasma membrane tethers. The magnitude of the short tether extension events is consistent with extension lengths expected from progressive unfolding of individual helices of the exocyst complex, supporting its direct role in forming the physical vesicle-plasma membrane link.

  2. AFM/TIRF force clamp measurements of neurosecretory vesicle tethers reveal characteristic unfolding steps.

    Science.gov (United States)

    Harris, Mark C; Cislo, Dillon; Lenz, Joan S; Umbach, Christopher; Lindau, Manfred

    2017-01-01

    Although several proteins have been implicated in secretory vesicle tethering, the identity and mechanical properties of the components forming the physical vesicle-plasma membrane link remain unknown. Here we present the first experimental measurements of nanomechanical properties of secretory vesicle-plasma membrane tethers using combined AFM force clamp and TIRF microscopy on membrane sheets from PC12 cells expressing the vesicle marker ANF-eGFP. Application of pulling forces generated tether extensions composed of multiple steps with variable length. The frequency of short (<10 nm) tether extension events was markedly higher when a fluorescent vesicle was present at the cantilever tip and increased in the presence of GTPγS, indicating that these events reflect specifically the properties of vesicle-plasma membrane tethers. The magnitude of the short tether extension events is consistent with extension lengths expected from progressive unfolding of individual helices of the exocyst complex, supporting its direct role in forming the physical vesicle-plasma membrane link.

  3. Beta2 toxin is not involved in in vitro cell cytotoxicity caused by human and porcine cpb2-harbouring Clostridium perfringens.

    Science.gov (United States)

    Allaart, Janneke G; van Asten, Alphons J A M; Vernooij, Johannes C M; Gröne, Andrea

    2014-06-25

    Clostridium perfringens is a common cause of intestinal disease in animals and humans. Its pathogenicity is attributed to the toxins it can produce, including the beta2 toxin. The presence of cpb2, the gene encoding the beta2 toxin, has been associated with diarrhoea in neonatal piglets and humans. However, the exact role of the beta2 toxin in the development of diarrhoea is still unknown. In this study we investigated the level of cytotoxicity to porcine IPI-21 and human Caco-2 cell-lines caused by porcine and human cpb2-harbouring C. perfringens and the significance of the beta2 toxin for the induction of cell cytotoxicity. Supernatants of porcine cpb2-harbouring C. perfringens strains were cytotoxic to both cell lines. Cell cytotoxicity caused by supernatant of human cpb2-harbouring C. perfringens strains was variable among strains. However, removal of the beta2 toxin by anti-beta2 toxin antibodies or degradation of the beta2 toxin by trypsin did not reduce the cytotoxic effect of any of the supernatants. These data suggest that beta2 toxin does not play a role in the development of cell cytotoxicity in in vitro experiments. In vivo studies are necessary to definitely define the role of beta2 toxin in the development of cell cytotoxicity and subsequent diarrhoea. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Virus evolution reveals an exclusive role for LEDGF/p75 in chromosomal tethering of HIV.

    Directory of Open Access Journals (Sweden)

    Anneleen Hombrouck

    2007-03-01

    Full Text Available Retroviruses by definition insert their viral genome into the host cell chromosome. Although the key player of retroviral integration is viral integrase, a role for cellular cofactors has been proposed. Lentiviral integrases use the cellular protein LEDGF/p75 to tether the preintegration complex to the chromosome, although the existence of alternative host proteins substituting for the function of LEDGF/p75 in integration has been proposed. Truncation mutants of LEDGF/p75 lacking the chromosome attachment site strongly inhibit HIV replication by competition for the interaction with integrase. In an attempt to select HIV strains that can overcome the inhibition, we now have used T-cell lines that stably express a C-terminal fragment of LEDGF/p75. Despite resistance development, the affinity of integrase for LEDGF/p75 is reduced and replication kinetics in human primary T cells is impaired. Detection of the integrase mutations A128T and E170G at key positions in the LEDGF/p75-integrase interface provides in vivo evidence for previously reported crystallographic data. Moreover, the complementary inhibition by LEDGF/p75 knockdown and mutagenesis at the integrase-LEDGF/p75 interface points to the incapability of HIV to circumvent LEDGF/p75 function during proviral integration. Altogether, the data provide a striking example of the power of viral molecular evolution. The results underline the importance of the LEDGF/p75 HIV-1 interplay as target for innovative antiviral therapy. Moreover, the role of LEDGF/p75 in targeting integration will stimulate research on strategies to direct gene therapy vectors into safe landing sites.

  5. Characterization of recombinant Bordetella pertussis adenylate cyclase toxins carrying passenger proteins.

    Science.gov (United States)

    Gmira, S; Karimova, G; Ladant, D

    2001-12-01

    Bordetella pertussis secretes a calmodulin-activated adenylate cyclase toxin, CyaA, that is able to deliver its N-terminal catalytic domain (400 amino acid residues) into the cytosol of eukaryotic target cells, directly through the cytoplasmic membrane. We have previously shown that CyaA can be used as a vehicle to deliver CD8+ T-cell epitopes, inserted within the catalytic domain of the toxin, into antigen-presenting cells and can trigger specific class I-restricted cytotoxic T-cell (CTL) responses in vivo. To explore the tolerance of CyaA to insertion of polypeptides of larger size, we constructed and characterized different recombinant CyaA toxins with protein inserts of 87 to 206 amino acids in length. Several of these recombinant CyaA toxins were found to be invasive. Furthermore, we showed that the unfolding of the passenger protein is a prerequisite for the translocation of the recombinant toxins into eukaryotic cells. Our results highlight the remarkable tolerance of the CyaA toxin and suggest that CyaA might be used to deliver proteins into eukaryotic cells.

  6. Mutagenic Deimmunization of Diphtheria Toxin for Use in Biologic Drug Development

    Directory of Open Access Journals (Sweden)

    Joerg U. Schmohl

    2015-10-01

    Full Text Available Background: Targeted toxins require multiple treatments and therefore must be deimmunized. We report a method of protein deimmunization based on the point mutation of highly hydrophilic R, K, D, E, and Q amino acids on the molecular surface of truncated diphtheria-toxin (DT390. Methods: Based on their surface position derived from an X-ray-crystallographic model, residues were chosen for point mutation that were located in prominent positions on the molecular surface and away from the catalytic site. Mice were immunized with a targeted toxin containing either a mutated DT390 containing seven critical point mutations or the non-mutated parental toxin form. Results: Serum analysis revealed a significant 90% reduction in anti-toxin antibodies in mice immunized with the mutant, but not the parental drug form despite multiple immunizations. The experiment was repeated in a second strain of mice with a different MHC-haplotype to address whether point mutation removed T or B cell epitopes. Findings were identical indicating that B cell epitopes were eliminated from DT. The mutant drug form lost only minimal activity in vitro as well as in vivo. Conclusion: These findings indicate that this method may be effective for deimmunizing of other proteins and that discovery of a deimmunized form of DT may lead to the development of more effective targeted toxin.

  7. Proteolytic processing of the Cyt1Ab1 toxin produced by Bacillus thuringiensis subsp. medellin

    Directory of Open Access Journals (Sweden)

    Elizabeth Escobar

    2000-10-01

    Full Text Available Bacillus thuringiensis produces d-endotoxins that require proteolytic processing to become active. The activation of the B. thuringiensis subsp. medellin 28 kDa (Cyt1Ab1 cytolytic toxin by trypsin, chymotrypsin and gut extract from Culex quinquefasciatus larvae was analyzed. The Cyt1Ab1 toxin of B. thuringiensis subsp. medellin was processed by all proteases tested to fragments between 23 and 25 kDa, while processing of the Cyt1Aa1 toxin produce fragments between 22.5 and 24.5 kDa. The Cyt1Ab1 toxin was preferentially processed at the alkaline pH of 12. The in vitro proteolytic processing of the Cyt1Ab1 toxin by C. quinquefasciatus larvae midgut extract showed a 25 kDa fragment; a similar result was observed when the activation was performed in the in vivo experiments. The solubilized Cyt1Ab1 toxin and the protease resistant cores generated by in vitro processing showed hemolytic activity but not mosquitocidal activity. Amino terminal sequence of the C. quinquefasciatus gut extract resistant fragment indicated that the cutting site was located between Lys31 and Asp32, with a sequence DDPNEKNNHNS; while for the trypsin-resistant fragment the cutting site was determined between Leu29 and Arg30, and for the chymotrypsin-resistant fragment between Arg30 and Lys31.

  8. Functional characteristics of the Staphylococcus aureus δ-toxin allelic variant G10S.

    Science.gov (United States)

    Cheung, Gordon Y C; Yeh, Anthony J; Kretschmer, Dorothee; Duong, Anthony C; Tuffuor, Kwame; Fu, Chih-Lung; Joo, Hwang-Soo; Diep, Binh A; Li, Min; Nakamura, Yuumi; Nunez, Gabriel; Peschel, Andreas; Otto, Michael

    2015-12-10

    Staphylococcus aureus δ-toxin is a member of the phenol-soluble modulin (PSM) peptide family. PSMs have multiple functions in staphylococcal pathogenesis; for example, they lyse red and white blood cells and trigger inflammatory responses. Compared to other PSMs, δ-toxin is usually more strongly expressed but has only moderate cytolytic capacities. The amino acid sequences of S. aureus PSMs are well conserved with two exceptions, one of which is the δ-toxin allelic variant G10S. This variant is a characteristic of the subspecies S. argenteus and S. aureus sequence types ST1 and ST59, the latter representing the most frequent cause of community-associated infections in Asia. δ-toxin G10S and strains expressing that variant from plasmids or the genome had significantly reduced cytolytic and pro-inflammatory capacities, including in a strain background with pronounced production of other PSMs. However, in murine infection models, isogenic strains expressing the two δ-toxin variants did not cause measurable differences in disease severity. Our findings indicate that the widespread G10S allelic variation of the δ-toxin locus has a significant impact on key pathogenesis mechanisms, but more potent members of the PSM peptide family may overshadow that impact in vivo.

  9. Cardiorenal syndrome: the emerging role of protein-bound uremic toxins.

    Science.gov (United States)

    Lekawanvijit, Suree; Kompa, Andrew R; Wang, Bing H; Kelly, Darren J; Krum, Henry

    2012-11-09

    Cardiorenal syndrome is a condition in which a complex interrelationship between cardiac dysfunction and renal dysfunction exists. Despite advances in treatment of both cardiovascular and kidney disease, cardiorenal syndrome remains a major global health problem. Characteristic of the pathophysiology of cardiorenal syndrome is bidirectional cross-talk; mediators/substances activated by the disease state of 1 organ can play a role in worsening dysfunction of the other by exerting their biologically harmful effects, leading to the progression of the syndrome. Accumulation of uremic toxins is a hallmark of renal excretory dysfunction. Removal of some toxins by conventional dialysis is particularly problematic because of their high protein binding. In this review, we demonstrate that protein-bound uremic toxins may play an important role in progression of cardiovascular disease in the setting of chronic kidney disease. The highly protein-bound uremic toxin indoxyl sulfate has emerged as a potent toxin adversely affecting both the kidney and heart. Direct cardiac effects of this toxin have been recently demonstrated both in vitro and in vivo. Specifically, potent fibrogenic and prohypertrophic effects, as well as oxidative stress-inducing effects, appear to play a central role in both renal and cardiac pathology. Many of these adverse effects can be suppressed by use of a gut adsorbent, AST-120. Potential mechanisms underlying indoxyl sulfate-induced cardiorenal fibrosis are discussed. Future research and clinical implications conclude this review.

  10. Scorpion Toxins Specific for Potassium (K+ Channels: A Historical Overview of Peptide Bioengineering

    Directory of Open Access Journals (Sweden)

    Zachary L. Bergeron

    2012-11-01

    Full Text Available Scorpion toxins have been central to the investigation and understanding of the physiological role of potassium (K+ channels and their expansive function in membrane biophysics. As highly specific probes, toxins have revealed a great deal about channel structure and the correlation between mutations, altered regulation and a number of human pathologies. Radio- and fluorescently-labeled toxin isoforms have contributed to localization studies of channel subtypes in expressing cells, and have been further used in competitive displacement assays for the identification of additional novel ligands for use in research and medicine. Chimeric toxins have been designed from multiple peptide scaffolds to probe channel isoform specificity, while advanced epitope chimerization has aided in the development of novel molecular therapeutics. Peptide backbone cyclization has been utilized to enhance therapeutic efficiency by augmenting serum stability and toxin half-life in vivo as a number of K+-channel isoforms have been identified with essential roles in disease states ranging from HIV, T-cell mediated autoimmune disease and hypertension to various cardiac arrhythmias and Malaria. Bioengineered scorpion toxins have been monumental to the evolution of channel science, and are now serving as templates for the development of invaluable experimental molecular therapeutics.

  11. Tethered naphthalene diimide-based intercalators for DNA triplex stabilization

    Science.gov (United States)

    Gianolio, Diego A.; Segismundo, Joanna M.; McLaughlin, Larry W.

    2000-01-01

    The synthesis and triplex stabilizing properties of oligodeoxyribonucleotides functionalized at the 5′- and/or 3′-termini with a naphthalene diimide-based (NDI) intercalator is described. The NDI intercalator was prepared in a single step from the corresponding dianhydride and was attached to the 5′-terminus of an oligodeoxyribonucleotide following a reverse coupling procedure. The DMT protecting group was removed and the sequence phosphitylated to generate the phosphoramidite derivative on the 5′-terminus of the support-bound oligodeoxyribonucleotide. The NDI intercalator with a free hydroxyl was then added in the presence of tetrazole. Attachment of the NDI to the 3′-terminus relied upon a tethered amino group that could be functionalized first with the naphthalene dianhydride, which was subsequently converted to the diimide. Using both procedures, an oligonucleotide conjugate was prepared having the NDI intercalator at both the 5′- and 3′-termini. Thermal denaturation studies were used to determine the remarkable gain in stability for triplexes formed when the NDI-conjugated oligonucleotide was present as the third strand in the complex. PMID:10773082

  12. Critical adsorption of copolymer tethered on selective surfaces

    Science.gov (United States)

    Li, Hong; Qian, Chang-Ji; Luo, Meng-Bo

    2016-04-01

    Critical adsorption behaviors of flexible copolymer chains tethered to a flat homogeneous surface are studied by using Monte Carlo simulations. We have compared the critical adsorption temperature Tc, estimated by a finite-size scaling method, for different AB copolymer sequences with A the attractive monomer and B the inert monomer. We find that Tc increases with an increase in the fraction of monomers A, fA, in copolymers, and it increases with an increase in the length of block A for the same fA. In particular, Tc of copolymer (AnBn)r can be expressed as a function of the block length, n, and Tc of copolymer (AnB)r and (ABm)r can be expressed as a linear function of fA. Tc of random copolymer chains also can be expressed as a linear function of fA and it can be estimated by using weight-average of Tc of different diblocks in the random copolymer. However, the crossover exponent is roughly independent of AB sequence distributions either for block copolymers or for random copolymers.

  13. Flow structures around a beetle in a tethered flight

    Science.gov (United States)

    Lee, Boogeon; Oh, Sehyeong; Park, Hyungmin; Choi, Haecheon

    2017-11-01

    In the present study, through a wind-tunnel experiment, we visualize the flow in a tethered flight of a rhinoceros beetle using a smoke-wire visualization technique. Measurements are done at five side planes along the wind span while varying the body angle (angle between the horizontal and the body axis) to investigate the influence of the stroke plane angle that was observed to change depending on the flight mode such as hovering, forward and takeoff flights so on. Observing that a large attached leading-edge vortex is only found on the hindwing, it is inferred that most of the aerodynamic forces would be generated by hindwings (flexible inner wings) compared to the elytra (hard outer wings). In addition, it is observed to use unsteady lift-generating mechanisms such as clap-and-fling, wing-wing interaction and wake capture. Finally, we discuss the relation between the advance ratio and Strouhal number by adjusting free-stream velocity and the body angle (i.e., angle of wake-induced flow). Supported by a Grant to Bio-Mimetic Robot Research Center Funded by Defense Acquisition Program Administration, and by ADD, Korea (UD130070ID).

  14. Repurposing bacterial toxins for intracellular delivery of therapeutic proteins.

    Science.gov (United States)

    Beilhartz, Greg L; Sugiman-Marangos, Seiji N; Melnyk, Roman A

    2017-10-15

    Despite enormous efforts, achieving efficacious levels of proteins inside mammalian cells remains one of the greatest challenges in biologics-based drug discovery and development. The inability of proteins to readily cross biological membranes precludes access to the wealth of intracellular targets and applications that lie within mammalian cells. Existing methods of delivery commonly suffer from an inability to target specific cells and tissues, poor endosomal escape, and limited in vivo efficacy. The aim of the present commentary is to highlight the potential of certain classes of bacterial toxins, which naturally deliver a large protein into the cytosolic compartment of target cells after binding a host cell-surface receptor with high affinity, as robust protein delivery platforms. We review the progress made in recent years toward demonstrating the utility of these systems at delivering a wide variety of protein cargo, with special attention paid to three distinct toxin-based platforms. We contend that with recent advances in protein deimmunization strategies, bacterial toxins are poised to introduce biologics into the inner sanctum of cells and treat a wealth of heretofore untreatable diseases with a new generation of therapeutics. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Why do we study animal toxins?

    Science.gov (United States)

    ZHANG, Yun

    2015-01-01

    Venom (toxins) is an important trait evolved along the evolutionary tree of animals. Our knowledges on venoms, such as their origins and loss, the biological relevance and the coevolutionary patterns with other organisms are greatly helpful in understanding many fundamental biological questions, i.e., the environmental adaptation and survival competition, the evolution shaped development and balance of venoms, and the sophisticated correlations among venom, immunity, body power, intelligence, their genetic basis, inherent association, as well as the cost-benefit and trade-offs of biological economy. Lethal animal envenomation can be found worldwide. However, from foe to friend, toxin studies have led lots of important discoveries and exciting avenues in deciphering and fighting human diseases, including the works awarded the Nobel Prize and lots of key clinic therapeutics. According to our survey, so far, only less than 0.1% of the toxins of the venomous animals in China have been explored. We emphasize on the similarities shared by venom and immune systems, as well as the studies of toxin knowledge-based physiological toxin-like proteins/peptides (TLPs). We propose the natural pairing hypothesis. Evolution links toxins with humans. Our mission is to find out the right natural pairings and interactions of our body elements with toxins, and with endogenous toxin-like molecules. Although, in nature, toxins may endanger human lives, but from a philosophical point of view, knowing them well is an effective way to better understand ourselves. So, this is why we study toxins. PMID:26228472

  16. Toxins-antitoxins: diversity, evolution and function.

    Science.gov (United States)

    Hayes, Finbarr; Van Melderen, Laurence

    2011-10-01

    Genes for toxin-antitoxin (TA) complexes are widespread in prokaryote genomes, and species frequently possess tens of plasmid and chromosomal TA loci. The complexes are categorized into three types based on genetic organization and mode of action. The toxins universally are proteins directed against specific intracellular targets, whereas the antitoxins are either proteins or small RNAs that neutralize the toxin or inhibit toxin synthesis. Within the three types of complex, there has been extensive evolutionary shuffling of toxin and antitoxin genes leading to considerable diversity in TA combinations. The intracellular targets of the protein toxins similarly are varied. Numerous toxins, many of which are sequence-specific endoribonucleases, dampen protein synthesis levels in response to a range of stress and nutritional stimuli. Key resources are conserved as a result ensuring the survival of individual cells and therefore the bacterial population. The toxin effects generally are transient and reversible permitting a set of dynamic, tunable responses that reflect environmental conditions. Moreover, by harboring multiple toxins that intercede in protein synthesis in response to different physiological cues, bacteria potentially sense an assortment of metabolic perturbations that are channeled through different TA complexes. Other toxins interfere with the action of topoisomersases, cell wall assembly, or cytoskeletal structures. TAs also play important roles in bacterial persistence, biofilm formation and multidrug tolerance, and have considerable potential both as new components of the genetic toolbox and as targets for novel antibacterial drugs.

  17. Exfoliative Toxins of Staphylococcus aureus

    Directory of Open Access Journals (Sweden)

    Michal Bukowski

    2010-05-01

    Full Text Available Staphylococcus aureus is an important pathogen of humans and livestock. It causes a diverse array of diseases, ranging from relatively harmless localized skin infections to life-threatening systemic conditions. Among multiple virulence factors, staphylococci secrete several exotoxins directly associated with particular disease symptoms. These include toxic shock syndrome toxin 1 (TSST-1, enterotoxins, and exfoliative toxins (ETs. The latter are particularly interesting as the sole agents responsible for staphylococcal scalded skin syndrome (SSSS, a disease predominantly affecting infants and characterized by the loss of superficial skin layers, dehydration, and secondary infections. The molecular basis of the clinical symptoms of SSSS is well understood. ETs are serine proteases with high substrate specificity, which selectively recognize and hydrolyze desmosomal proteins in the skin. The fascinating road leading to the discovery of ETs as the agents responsible for SSSS and the characterization of the molecular mechanism of their action, including recent advances in the field, are reviewed in this article.

  18. Botulinum toxin: mechanisms of action

    OpenAIRE

    Dirk Dressler; Fereshte Adib Saberi; Egberto Reis Barbosa

    2005-01-01

    This review describes therapeutically relevant mechanisms of action of botulinum toxin (BT). BT's molecular mode of action includes extracellular binding to glycoproteine structures on cholinergic nerve terminals and intracellular blockade of the acetylcholine secretion. BT affects the spinal stretch reflex by blockade of intrafusal muscle fibres with consecutive reduction of Ia/II afferent signals and muscle tone without affecting muscle strength (reflex inhibition). This mechanism allows fo...

  19. Botulinum neurotoxin serotype D is poorly effective in humans: an in vivo electrophysiological study.

    Science.gov (United States)

    Eleopra, Roberto; Montecucco, Cesare; Devigili, Grazia; Lettieri, Christian; Rinaldo, Sara; Verriello, Lorenzo; Pirazzini, Marco; Caccin, Paola; Rossetto, Ornella

    2013-05-01

    Botulinum neurotoxins act on nerve endings and block neurotransmitter release. Their potency is due to their enzymatic activity and high affinity binding to neurons. Botulinum toxin type A is used in the treatment of human diseases characterized by hyperactivity of peripheral cholinergic nerve terminals, but some patients are or become resistant to it. This can be overcome by using other botulinum toxins, and studies have been performed with different toxin serotypes. Botulinum neurotoxin type D has never been tested in humans in vivo, and, therefore, we investigated the action of this toxin in mouse and human muscles. Botulinum toxin type D potency was determined on mouse hemidiaphragm and on rat neuronal cultures. From these experiments, doses to be injected in human volunteers were decided. The compound muscle action potential of toxin-injected Extensor Digitorum Brevis muscle was measured at different times points after injection in human volunteers. Botulinum toxin type D is poorly effective in inducing human skeletal muscle paralysis. Botulinum toxin type D is very potent in mice and almost ineffective in humans in vivo. The results shed new light on the mechanism of toxin type D binding to the neuronal surface receptors. Copyright © 2012 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

  20. Human Rab small GTPase- and class V myosin-mediated membrane tethering in a chemically defined reconstitution system.

    Science.gov (United States)

    Inoshita, Motoki; Mima, Joji

    2017-11-10

    Membrane tethering is a fundamental process essential for the compartmental specificity of intracellular membrane trafficking in eukaryotic cells. Rab-family small GTPases and specific sets of Rab-interacting effector proteins, including coiled-coil tethering proteins and multisubunit tethering complexes, are reported to be responsible for membrane tethering. However, whether and how these key components directly and specifically tether subcellular membranes remains enigmatic. Using chemically defined proteoliposomal systems reconstituted with purified human Rab proteins and synthetic liposomal membranes to study the molecular basis of membrane tethering, we established here that Rab-family GTPases have a highly conserved function to directly mediate membrane tethering, even in the absence of any types of Rab effectors such as the so-called tethering proteins. Moreover, we demonstrate that membrane tethering mediated by endosomal Rab11a is drastically and selectively stimulated by its cognate Rab effectors, class V myosins (Myo5A and Myo5B), in a GTP-dependent manner. Of note, Myo5A and Myo5B exclusively recognized and cooperated with the membrane-anchored form of their cognate Rab11a to support membrane tethering mediated by trans-Rab assemblies on opposing membranes. Our findings support the novel concept that Rab-family proteins provide a bona fide membrane tether to physically and specifically link two distinct lipid bilayers of subcellular membranes. They further indicate that Rab-interacting effector proteins, including class V myosins, can regulate these Rab-mediated membrane-tethering reactions. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  1. Failure of manganese to protect from Shiga toxin.

    Directory of Open Access Journals (Sweden)

    Marsha A Gaston

    Full Text Available Shiga toxin (Stx, the main virulence factor of Shiga toxin producing Escherichia coli, is a major public health threat, causing hemorrhagic colitis and hemolytic uremic syndrome. Currently, there are no approved therapeutics for these infections; however manganese has been reported to provide protection from the Stx1 variant isolated from Shigella dysenteriae (Stx1-S both in vitro and in vivo. We investigated the efficacy of manganese protection from Stx1-S and the more potent Stx2a isoform, using experimental systems well-established for studying Stx: in vitro responses of Vero monkey kidney cells, and in vivo toxicity to CD-1 outbred mice. Manganese treatment at the reported therapeutic concentration was toxic to Vero cells in culture and to CD-1 mice. At lower manganese concentrations that were better tolerated, we observed no protection from Stx1-S or Stx2a toxicity. The ability of manganese to prevent the effects of Stx may be particular to certain cell lines, mouse strains, or may only be manifested at high, potentially toxic manganese concentrations.

  2. Natural toxins and their therapeutic potential.

    Science.gov (United States)

    Kapoor, V K

    2010-03-01

    Plants have been extensively investigated for exploring their therapeutic potentials, but there are comparatively scanty reports on drugs derived from animal kingdom, except for hormones. During last decade, the toxins that are used for defense by the animals, have been isolated and found useful tools for physiological and pharmacological studies, besides giving valuable leads to drug development. Toxins with interesting results have been isolated from the venoms of snakes, scorpions, spiders, snails, lizards, frogs and fish. The present review describe about some toxins as drugs and their biological activities. Some fungal, bacterial and marine toxins have also been covered in this article.

  3. Thrust Control During Towing of Space Debris using an Elastic Tether

    Directory of Open Access Journals (Sweden)

    A. D. Ledkov

    2014-01-01

    Full Text Available The paper considers a maneuver for deorbiting the large space debris using an active spacecraft connected with the debris by an elastic tether. Tether slacking during the maneuver can lead to the tether rupture, kinking, and winding on the descending object. Therefore it is important to prevent slacking. The objective of this work is to find the law of thrust force control of the active spacecraft to ensure a continuously strained tether during the maneuver.Using Lagrange formalism a mathematical model to describe the system plane motion is developed. This model considers the active spacecraft as a mass point, the space debris as a rigid body, and the tether as a weightless elastic rod. A thrust force is directed along the local horizon of the spacecraft. Linearization of nonlinear differential equation describing longitudinal oscillations of the tether length is performed. Its phase portrait is analyzed. An approximate expression describing the position of the center on the phase portrait is obtained. A time-optimal control with full feedback to ensure that the tether is in the strained state is found by solving the Bellman equation. To use the obtained optimal law it is necessary to set the measuring equipment on the spacecraft, which is capable of accurate measuring a distance to the space debris and its relative velocity. An alternative control law, which is simpler in terms of the practical implementation, is proposed. As an example, the descent from an orbit of nonfunctioning Soviet satellite Meteor-2 is considered. It is shown that both proposed laws provide continuous strain of the tether during deorbiting of the satellite. Moreover, slack does not occur even at the first period of oscillation of the tether length. It is shown that the use of the proposed control laws leads to slight increase of deorbiting time as compared to the case of using the constant thrust.The results can be used to develop the control systems of small spacecrafts

  4. The shear flow processing of controlled DNA tethering and stretching for organic molecular electronics.

    Science.gov (United States)

    Yu, Guihua; Kushwaha, Amit; Lee, Jungkyu K; Shaqfeh, Eric S G; Bao, Zhenan

    2011-01-25

    DNA has been recently explored as a powerful tool for developing molecular scaffolds for making reproducible and reliable metal contacts to single organic semiconducting molecules. A critical step in the process of exploiting DNA-organic molecule-DNA (DOD) array structures is the controlled tethering and stretching of DNA molecules. Here we report the development of reproducible surface chemistry for tethering DNA molecules at tunable density and demonstrate shear flow processing as a rationally controlled approach for stretching/aligning DNA molecules of various lengths. Through enzymatic cleavage of λ-phage DNA to yield a series of DNA chains of various lengths from 17.3 μm down to 4.2 μm, we have investigated the flow/extension behavior of these tethered DNA molecules under different flow strengths in the flow-gradient plane. We compared Brownian dynamic simulations for the flow dynamics of tethered λ-DNA in shear, and found our flow-gradient plane experimental results matched well with our bead-spring simulations. The shear flow processing demonstrated in our studies represents a controllable approach for tethering and stretching DNA molecules of various lengths. Together with further metallization of DNA chains within DOD structures, this bottom-up approach can potentially enable efficient and reliable fabrication of large-scale nanoelectronic devices based on single organic molecules, therefore opening opportunities in both fundamental understanding of charge transport at the single molecular level and many exciting applications for ever-shrinking molecular circuits.

  5. Shuttle tethered operations: The effect on orbital trajectory and inertial navigation

    Science.gov (United States)

    Lardas, Mark N.

    1989-01-01

    The first full scale test of a large tethered satellite system is planned. The Orbiter will be linked to a 500 kg payload by a 20 km tether, an action with a profound effect on the trajectory of the Orbiter. For the first time in the history of the Shuttle program, the vehicle will conduct prolonged operations with the center of mass of the orbiting system a significant distance from the center of mass of the Space Shuttle Orbiter, a violation of the fundamental assumption made in both the Orbiter ground-based and onboard navigation software. Inertial navigation of tethered operations with the Shuttle is further complicated by the presence of non-conservative forces in the system: Reaction Control System (RCS) translational effects, atmospheric drag, and electro-magnetic dynamics. These can couple with the conservative tether dynamics effects, and degrade the navigation software performance. The primary effects are examined on the Orbiter's trajectory, coupling by conservative forces during tethered operations, and the impact of both on the ability to meet inertial navigation constraints. The impact of electrodynamics, different RCS control modes, commanded attitudes, and attitude deadbands are presented. Operational guidelines which optimize successful mission navigation, and necessary navigation constraints are discussed.

  6. Determination of a quantitative parameter to evaluate swimming technique based on the maximal tethered swimming test.

    Science.gov (United States)

    Soncin, Rafael; Mezêncio, Bruno; Ferreira, Jacielle Carolina; Rodrigues, Sara Andrade; Huebner, Rudolf; Serrão, Julio Cerca; Szmuchrowski, Leszek

    2017-06-01

    The aim of this study was to propose a new force parameter, associated with swimmers' technique and performance. Twelve swimmers performed five repetitions of 25 m sprint crawl and a tethered swimming test with maximal effort. The parameters calculated were: the mean swimming velocity for crawl sprint, the mean propulsive force of the tethered swimming test as well as an oscillation parameter calculated from force fluctuation. The oscillation parameter evaluates the force variation around the mean force during the tethered test as a measure of swimming technique. Two parameters showed significant correlations with swimming velocity: the mean force during the tethered swimming (r = 0.85) and the product of the mean force square root and the oscillation (r = 0.86). However, the intercept coefficient was significantly different from zero only for the mean force, suggesting that although the correlation coefficient of the parameters was similar, part of the mean velocity magnitude that was not associated with the mean force was associated with the product of the mean force square root and the oscillation. Thus, force fluctuation during tethered swimming can be used as a quantitative index of swimmers' technique.

  7. Optimal Trajectory Planning and Coordinated Tracking Control Method of Tethered Space Robot Based on Velocity Impulse

    Directory of Open Access Journals (Sweden)

    Panfeng Huang

    2014-09-01

    Full Text Available The tethered space robot (TSR is a new concept of space robot which consists of a robot platform, space tether and operation robot. This paper presents a multi-objective optimal trajectory planning and a coordinated tracking control scheme for TSR based on velocity impulse in the approaching phase. Both total velocity impulse and flight time are included in this optimization. The non-dominated sorting genetic algorithm is employed to obtain the optimal trajectory Pareto solution using the TSR dynamic model and optimal trajectory planning model. The coordinated tracking control scheme utilizes optimal velocity impulse. Furthermore, the PID controller is designed in order to compensate for the distance measurement errors. The PID control force is optimized and distributed to thrusters and the space tether using a simulated annealing algorithm. The attitude interferential torque of the space tether is compensated a using time-delay algorithm through reaction wheels. The simulation results show that the multi-objective optimal trajectory planning method can reveal the relationships among flight time, fuel consumption, planar view angle and velocity impulse number. This method can provide a series of optimal trajectory according to a number of special tasks. The coordinated control scheme can significantly save thruster fuel for tracking the optimal trajectory, restrain the attitude interferential torque produced by space tether and maintain the relative attitude stability of the operation robot.

  8. Myo1c binding to submembrane actin mediates insulin-induced tethering of GLUT4 vesicles

    Science.gov (United States)

    Boguslavsky, Shlomit; Chiu, Tim; Foley, Kevin P.; Osorio-Fuentealba, Cesar; Antonescu, Costin N.; Bayer, K. Ulrich; Bilan, Philip J.; Klip, Amira

    2012-01-01

    GLUT4-containing vesicles cycle between the plasma membrane and intracellular compartments. Insulin promotes GLUT4 exocytosis by regulating GLUT4 vesicle arrival at the cell periphery and its subsequent tethering, docking, and fusion with the plasma membrane. The molecular machinery involved in GLUT4 vesicle tethering is unknown. We show here that Myo1c, an actin-based motor protein that associates with membranes and actin filaments, is required for insulin-induced vesicle tethering in muscle cells. Myo1c was found to associate with both mobile and tethered GLUT4 vesicles and to be required for vesicle capture in the total internal reflection fluorescence (TIRF) zone beneath the plasma membrane. Myo1c knockdown or overexpression of an actin binding–deficient Myo1c mutant abolished insulin-induced vesicle immobilization, increased GLUT4 vesicle velocity in the TIRF zone, and prevented their externalization. Conversely, Myo1c overexpression immobilized GLUT4 vesicles in the TIRF zone and promoted insulin-induced GLUT4 exposure to the extracellular milieu. Myo1c also contributed to insulin-dependent actin filament remodeling. Thus we propose that interaction of vesicular Myo1c with cortical actin filaments is required for insulin-mediated tethering of GLUT4 vesicles and for efficient GLUT4 surface delivery in muscle cells. PMID:22918957

  9. Structure of purotoxin-2 from wolf spider: modular design and membrane-assisted mode of action in arachnid toxins.

    Science.gov (United States)

    Oparin, Peter B; Nadezhdin, Kirill D; Berkut, Antonina A; Arseniev, Alexander S; Grishin, Eugene V; Vassilevski, Alexander A

    2016-10-01

    Traditionally, arachnid venoms are known to contain two particularly important groups of peptide toxins. One is disulfide-rich neurotoxins with a predominance of β-structure that specifically target protein receptors in neurons or muscle cells. The other is linear cationic cytotoxins that form amphiphilic α-helices and exhibit rather non-specific membrane-damaging activity. In the present paper, we describe the first 3D structure of a modular arachnid toxin, purotoxin-2 (PT2) from the wolf spider Alopecosa marikovskyi (Lycosidae), studied by NMR spectroscopy. PT2 is composed of an N-terminal inhibitor cystine knot (ICK, or knottin) β-structural domain and a C-terminal linear cationic domain. In aqueous solution, the C-terminal fragment is hyper-flexible, whereas the knottin domain is very rigid. In membrane-mimicking environment, the C-terminal domain assumes a stable amphipathic α-helix. This helix effectively tethers the toxin to membranes and serves as a membrane-access and membrane-anchoring device. Sequence analysis reveals that the knottin + α-helix architecture is quite widespread among arachnid toxins, and PT2 is therefore the founding member of a large family of polypeptides with similar structure motifs. Toxins from this family target different membrane receptors such as P2X in the case of PT2 and calcium channels, but their mechanism of action through membrane access may be strikingly similar. © 2016 The Author(s); published by Portland Press Limited on behalf of the Biochemical Society.

  10. The HOPS/class C Vps complex tethers membranes by binding to one Rab GTPase in each apposed membrane.

    Science.gov (United States)

    Ho, Ruoya; Stroupe, Christopher

    2015-07-15

    Many Rab GTPase effectors are membrane-tethering factors, that is, they physically link two apposed membranes before intracellular membrane fusion. In this study, we investigate the distinct binding factors needed on apposed membranes for Rab effector-dependent tethering. We show that the homotypic fusion and protein-sorting/class C vacuole protein-sorting (HOPS/class C Vps) complex can tether low-curvature membranes, that is, liposomes with a diameter of ∼100 nm, only when the yeast vacuolar Rab GTPase Ypt7p is present in both tethered membranes. When HOPS is phosphorylated by the vacuolar casein kinase I, Yck3p, tethering only takes place when GTP-bound Ypt7p is present in both tethered membranes. When HOPS is not phosphorylated, however, its tethering activity shows little specificity for the nucleotide-binding state of Ypt7p. These results suggest a model for HOPS-mediated tethering in which HOPS tethers membranes by binding to Ypt7p in each of the two tethered membranes. Moreover, because vacuole-associated HOPS is presumably phosphorylated by Yck3p, our results suggest that nucleotide exchange of Ypt7p on multivesicular bodies (MVBs)/late endosomes must take place before HOPS can mediate tethering at vacuoles. © 2015 Ho and Stroupe. 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).

  11. Synthesis and biology of cyclic imine toxins, an emerging class of potent, globally distributed marine toxins.

    Science.gov (United States)

    Stivala, Craig E; Benoit, Evelyne; Aráoz, Rómulo; Servent, Denis; Novikov, Alexei; Molgó, Jordi; Zakarian, Armen

    2015-03-01

    From a small group of exotic compounds isolated only two decades ago, Cyclic Imine (CI) toxins have become a major class of marine toxins with global distribution. Their distinct chemical structure, biological mechanism of action, and intricate chemistry ensures that CI toxins will continue to be the subject of fascinating fundamental studies in the broad fields of chemistry, chemical biology, and toxicology. The worldwide occurrence of potent CI toxins in marine environments, their accumulation in shellfish, and chemical stability are important considerations in assessing risk factors for human health. This review article aims to provide an account of chemistry, biology, and toxicology of CI toxins from their discovery to the present day.

  12. Diamond surface functionalization with biomimicry – Amine surface tether and thiol moiety for electrochemical sensors

    Energy Technology Data Exchange (ETDEWEB)

    Sund, James B., E-mail: jim@jamessund.com [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Causey, Corey P. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Wolter, Scott D. [Department of Physics, Elon University, Elon, NC 27244 (United States); Parker, Charles B., E-mail: charles.parker@duke.edu [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Stoner, Brian R. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States); Research Triangle Institute (RTI) International, Research Triangle Park, NC (United States); Toone, Eric J. [Departments of Chemistry and Biochemistry, Duke University, Durham, NC (United States); Glass, Jeffrey T. [Department of Electrical and Computer Engineering, Duke University, Durham, NC (United States)

    2014-05-01

    Highlights: • Diamond surfaces were functionalized with organic molecules using a novel approach. • Used biomimicry to select a molecule to bind NO, similar to the human body. • Molecular orbital theory predicted the molecule-analyte oxidation behavior. • A thiol moiety was attached to an amine surface tether on the diamond surface. • XPS analysis verified each surface functionalization step. - Abstract: The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen–oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

  13. Modeling and Control of Electrodynamic Tethers - an Energy and Topology Approach

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund

    , and separate derivations of the dynamical equations can be cumbersome. It can therefore be advantageous to be able to model a formation independent of its topology, i.e. the way tethers and satellites are interconnected. The thesis treats a class of formations in a generic framework, using graph theory......-flying spacecrafts, since a predetermined geometry of spacecrafts is easily maintained. This thesis investigates the use of electrodynamic tethers for such tethered satellite formaii tions with focus on the modeling and control aspects. One can think of many different structures for solving tasks in space...... to describe the topology of the formations. The framework can be used both to deduce the equations of motion for the attitude motion of the formation and for control design regarding the same motion. The main part of the thesis consists of five scientific papers which have been submitted for international...

  14. Low density aerothermodynamics studies performed by means of the tethered satellite system

    Science.gov (United States)

    Carlomagno, Giovanni M.; De Luca, Luigi; Siemers, Paul M.; Wood, George M., Jr.

    1986-01-01

    Low density gas flow modeling and current ground wind-tunnel technologies are not presently able to produce fully reliable data concerning low density flow regimes. In order to answer some of these issues, the Shuttle Continuous Open Wind Tunnel (SCOWT) program has been proposed, which makes use of the tethered satellite system (TSS). SCOWT's objective is to investigate the energy and momentum transfer between the tethered satellite and its environmental medium within the range of the thermofluid-dynamic conditions experienced by TSS during its atmospheric flights. The feasibility and capability of SCOWT to perform low density aerothermodynamics studies are investigated. Some of the results, obtained by means of a tether simulation program, and the instrumentation and TSS design main requirements to meet SCOWT objectives are described.

  15. Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

    Science.gov (United States)

    Stevens, Tyler E.; Pearce, Charles J.; Whitten, Caleah N.; Grant, Richard P.; Monson, Todd C.

    2017-03-01

    Many challenges must be overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. To begin addressing these challenges (and others), we report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers. The tethered array of nanoparticles, MnO in this case, bound directly to a gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). This strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles.

  16. Vth Pan American Symposium on Animal, Plant and Microbial Toxins

    National Research Council Canada - National Science Library

    Ownby, Charlotte

    1996-01-01

    ..., cardiotoxins, and antihemorrhagic factors. Presentations on plant and microbial toxins include work done on ricin, Clostridium perfringens enterotoxin, cone snail peptides, sea anemone toxins, proteinase inhibitors and maitotoxin...

  17. Unilateral pedicle screws asymmetric tethering: an innovative method to create idiopathic deformity

    Directory of Open Access Journals (Sweden)

    Zhang Xuesong

    2007-10-01

    Full Text Available Abstract Objective To evaluate the feasibility of the method that unilateral pedicle screws asymmetric tethering in concave side in combination with convex rib resection for creating idiopathic deformity. Summary of background data Various methods are performed to create idiopathic deformity. Among these methods, posterior asmmetric tethering of the spine shows satisfying result, but some drawbacks related to the current posterior asymmetric tether were still evident. Materials and methods Unilateral pedicle screws asymmetric tethering was performed to 14 female goats (age: 5–8 week-old, weight: 6–8 kg in concave side in combination with convex rib resection. Dorsoventral and lateral plain radiographs were taken of each thoracic spine in the frontal and sagittal planes right after the surgery and later every 4 weeks. Results All animals ambulated freely after surgery. For technical reasons, 2 goats were excluded (one animal died for anesthetic during the surgery, and one animal was lost for instrumental fail due to postoperative infection. Radiography showed that 11 goats exhibited scoliosis with convex toward to the right side, and as the curve increased with time, only 1 goat showed nonprogressive. The initial scoliosis generated in the progressors after the procedures measured 29.0° on average (range 23.0°–38.5° and increased to 43.0° on average (range 36.0°–58.0° over 8 to 10 weeks. The average progression of 14.0° was measured. The curvature immediately after tethering surgery (the initial Cobb angle did have a highly significant correlation with the final curvature (p Conclusion Unilateral pedicle screws asymmetric tethering is a practical method to create experimental scoliosis, especially for those who would like to study the correction of this deformity.

  18. Differential regulation of synaptic vesicle tethering and docking by UNC-18 and TOM-1

    Directory of Open Access Journals (Sweden)

    Elena O Gracheva

    2010-10-01

    Full Text Available The assembly of SNARE complexes between syntaxin, SNAP-25 and synaptobrevin is required to prime synaptic vesicles for fusion. Since Munc18 and tomosyn compete for syntaxin interactions, the interplay between these proteins is predicted to be important in regulating synaptic transmission. We explored this possibility, by examining genetic interactions between C. elegans unc-18(Munc18, unc-64(syntaxin and tom-1(tomosyn. We have previously demonstrated that unc-18 mutants have reduced synaptic transmission, whereas tom-1 mutants exhibit enhanced release. Here we show that the unc-18 mutant release defect is associated with loss of two morphologically distinct vesicle pools; those tethered within 25nm of the plasma membrane and those docked with the plasma membrane. In contrast, priming defective unc-13 mutants accumulate tethered vesicles, while docked vesicles are greatly reduced, indicating tethering is UNC-18-dependent and occurs in the absence of priming. C. elegans unc-64 mutants phenocopy unc-18 mutants, losing both tethered and docked vesicles, whereas overexpression of open syntaxin preferentially increases vesicle docking, suggesting UNC-18/closed syntaxin interactions are responsible for vesicle tethering. Given the competition between vertebrate tomosyn and Munc18, for syntaxin binding, we hypothesized that C. elegans TOM-1 may inhibit both UNC-18-dependent vesicle targeting steps. Consistent with this hypothesis, tom-1 mutants exhibit enhanced UNC-18 plasma membrane localization and a concomitant increase in both tethered and docked synaptic vesicles. Furthermore, in tom-1;unc-18 double mutants the docked, primed vesicle pool is preferentially rescued relative to unc-18 single mutants. Together these data provide evidence for the differential regulation of two vesicle targeting steps by UNC-18 and TOM-1 through competitive interactions with syntaxin

  19. The Disulfide Bonds within BST-2 Enhance Tensile Strength during Viral Tethering.

    Science.gov (United States)

    Du Pont, Kelly E; McKenzie, Aidan M; Kokhan, Oleksandr; Sumner, Isaiah; Berndsen, Christopher E

    2016-02-16

    Human BST-2/tetherin is a host factor that inhibits the release of enveloped viruses, including HIV-1, HIV-2, and SIV, from the cell surface by tethering viruses to the host cell membrane. BST-2 has an α-helical ectodomain that forms disulfide-linked dimers between two monomers forming a coiled coil. The ectodomain contains three cysteine residues that can participate in disulfide bond formation and are critical for viral tethering. The role of the disulfides in viral tethering is unknown but proposed to be for maintaining the dimer. We explored the role of the disulfides in the structure of BST-2 using experimental, biophysical methods. To understand the role of the disulfides in viral tethering, we used a new approach in viral tethering, steered molecular dynamics. We find that the disulfides coordinate the unfolding of the BST-2 monomers, which adds tensile strength to the coiled coil. Structural differences between oxidized and reduced BST-2 are apparent during unfolding, showing the monomers slide past each other in the absence of the disulfides. We found no evidence to support dissociation of the dimer upon reduction of the disulfide bonds. Moreover, the structure of BST-2 in the absence of the disulfides is similar to that of the oxidized form of BST-2, supporting previous X-ray crystallography and cellular work that showed the disulfides are not required for expression of BST-2. These data provide new insights into viral tethering by using novel techniques in the analysis of BST-2 to give amino acid level insight into functions of BST-2.

  20. Conserved TCP domain of Sas-4/CPAP is essential for pericentriolar material tethering during centrosome biogenesis

    Science.gov (United States)

    Zheng, Xiangdong; Gooi, Li Ming; Wason, Arpit; Gabriel, Elke; Mehrjardi, Narges Zare; Yang, Qian; Zhang, Xingrun; Debec, Alain; Basiri, Marcus L.; Avidor-Reiss, Tomer; Pozniakovsky, Andrei; Poser, Ina; Šarić, Tomo; Hyman, Anthony A.; Li, Haitao; Gopalakrishnan, Jay

    2014-01-01

    Pericentriolar material (PCM) recruitment to centrioles forms a key step in centrosome biogenesis. Deregulation of this process leads to centrosome aberrations causing disorders, one of which is autosomal recessive primary microcephaly (MCPH), a neurodevelopmental disorder where brain size is reduced. During PCM recruitment, the conserved centrosomal protein Sas-4/CPAP/MCPH6, known to play a role in centriole formation, acts as a scaffold for cytoplasmic PCM complexes to bind and then tethers them to centrioles to form functional centrosomes. To understand Sas-4’s tethering role, we determined the crystal structure of its T complex protein 10 (TCP) domain displaying a solvent-exposed single-layer of β-sheets fold. This unique feature of the TCP domain suggests that it could provide an “extended surface-like” platform to tether the Sas-4–PCM scaffold to a centriole. Functional studies in Drosophila, human cells, and human induced pluripotent stem cell-derived neural progenitor cells were used to test this hypothesis, where point mutations within the 9–10th β-strands (β9–10 mutants including a MCPH-associated mutation) perturbed PCM tethering while allowing Sas-4/CPAP to scaffold cytoplasmic PCM complexes. Specifically, the Sas-4 β9–10 mutants displayed perturbed interactions with Ana2, a centrosome duplication factor, and Bld-10, a centriole microtubule-binding protein, suggesting a role for the β9–10 surface in mediating protein–protein interactions for efficient Sas-4–PCM scaffold centriole tethering. Hence, we provide possible insights into how centrosomal protein defects result in human MCPH and how Sas-4 proteins act as a vehicle to tether PCM complexes to centrioles independent of its well-known role in centriole duplication. PMID:24385583

  1. Recent insights into Pasteurella multocida toxin and other G-protein-modulating bacterial toxins.

    Science.gov (United States)

    Wilson, Brenda A; Ho, Mengfei

    2010-08-01

    Over the past few decades, our understanding of the bacterial protein toxins that modulate G proteins has advanced tremendously through extensive biochemical and structural analyses. This article provides an updated survey of the various toxins that target G proteins, ending with a focus on recent mechanistic insights in our understanding of the deamidating toxin family. The dermonecrotic toxin from Pasteurella multocida (PMT) was recently added to the list of toxins that disrupt G-protein signal transduction through selective deamidation of their targets. The C3 deamidase domain of PMT has no sequence similarity to the deamidase domains of the dermonecrotic toxins from Escherichia coli (cytotoxic necrotizing factor [CNF]1-3), Yersinia (CNFY) and Bordetella (dermonecrotic toxin). The structure of PMT-C3 belongs to a family of transglutaminase-like proteins, with active site Cys-His-Asp catalytic triads distinct from E. coli CNF1.

  2. MARTX Toxin in the Zoonotic Serovar of Vibrio vulnificus Triggers an Early Cytokine Storm in Mice

    Directory of Open Access Journals (Sweden)

    Celia Murciano

    2017-07-01

    Full Text Available Vibrio vulnificus biotype 2-serovar E is a zoonotic clonal complex that can cause death by sepsis in humans and fish. Unlike other biotypes, Bt2 produces a unique type of MARTXVv (Multifunctional-Autoprocessive-Repeats-in-Toxin; RtxA13, which is encoded by a gene duplicated in the pVvBt2 plasmid and chromosome II. In this work, we analyzed the activity of this toxin and its role in human sepsis by performing in vitro, ex vivo, and in vivo assays. First, we demonstrated that the ACD domain, present exclusively in this toxin variant, effectively has an actin-cross-linking activity. Second, we determined that the whole toxin caused death of human endotheliocytes and monocytes by lysis and apoptosis, respectively. Finally, we tested the hypothesis that RtxA13 contributes to human death caused by this zoonotic serovar by triggering an early cytokine storm in blood. To this end, we used a Bt2-SerE strain (R99 together with its rtxA13 deficient mutant, and a Bt1 strain (YJ016 producing RtxA11 (the most studied MARTXVv together with its rtxA11 deficient mutant, as controls. Our results showed that RtxA13 was essential for virulence, as R99ΔΔrtxA13 was completely avirulent in our murine model of infection, and that R99, but not strain YJ016, induced an early, strong and dysregulated immune response involving the up-regulation of a high number of genes. This dysregulated immune response was directly linked to RtxA13. Based on these results and those obtained ex vivo (human blood, we propose a model of infection for the zoonotic serovar of V. vulnificus, in which RtxA13 would act as a sepsis-inducing toxin.

  3. Stealth and mimicry by deadly bacterial toxins

    DEFF Research Database (Denmark)

    Yates, S.P.; Jørgensen, Rene; Andersen, Gregers Rom

    2006-01-01

    Diphtheria toxin and exotoxin A are well-characterized members of the ADP-ribosyltransferase toxin family that serve as virulence factors in the pathogenic bacteria, Corynebacterium diphtheriae and Pseudomonas aeruginosa.  New high-resolution structural data of the Michaelis complex of the Pseudo...

  4. Botulinum toxin — therapeutic effect in cosmetology

    Directory of Open Access Journals (Sweden)

    Morrison A.V.

    2016-09-01

    Full Text Available This review presents the data from published literatures and the research works conducted by the authors about mechanisms of action of botulinum toxin and its use in the practical medicine (particularly in dermatology and cosmetology. Indications and contraindications of botulinum toxin use in cosmetology are also considered in this work.

  5. Botulinum toxin — therapeutic effect in cosmetology

    OpenAIRE

    Morrison A.V.; Bocharova Y.M.; Morrison V.V.

    2016-01-01

    This review presents the data from published literatures and the research works conducted by the authors about mechanisms of action of botulinum toxin and its use in the practical medicine (particularly in dermatology and cosmetology). Indications and contraindications of botulinum toxin use in cosmetology are also considered in this work.

  6. Toxin-Antitoxin Battle in Bacteria

    DEFF Research Database (Denmark)

    Cataudella, Ilaria

    This PhD thesis consists of three research projects revolving around the common thread of investigation of the properties and biological functions of Toxin-Antitoxin loci. Toxin-Antitoxin (TA) loci are transcriptionally regulated via an auto-inhibition mechanism called conditional cooperativity, ...

  7. T-2 toxin adsorption by hectorite

    Directory of Open Access Journals (Sweden)

    ALEKSANDRA DAKOVIĆ

    2009-11-01

    Full Text Available The adsorption of T-2 toxin by the natural smectite mineral – hectorite at pH 3.0, 7.0 and 9.0 was investigated. The results of T-2 toxin adsorption on hectorite showed that the T-2 adsorption capacity decreased with increasing concentration of adsorbent in the suspension for all the investigated pH values. From the adsorption isotherms, an increase in T-2 toxin adsorption with increasing initial T-2 toxin concentration was observed for all the investigated pH values. The T-2 toxin adsorption by hectorite followed a non-linear (Langmuir type of isotherm at pH 3.0, 7.0 and 9.0, with correlation coefficients (r2 of 0.943 at pH 3.0, 0.919 at pH 7.0 and 0.939 at pH 9.0. The estimated maximum T-2 toxin adsorption by hectorite based on the Langmuir fit to the data (9.178 mg/g at pH 3.0, 9.930 mg/g at pH 7.0, and 19.341 mg/g at pH 9.0, indicated that the adsorption of T-2 toxin by hectorite is pH dependent. The obtained data suggest the existence of specific active sites in hectorite onto which the T-2 toxin is adsorbed.

  8. Tetra- versus Pentavalent Inhibitors of Cholera Toxin

    NARCIS (Netherlands)

    Fu, Ou; Pukin, Aliaksei V.; Quarles Van Ufford, Linda; Branson, Thomas R.; Thies-Weesie, Dominique M E; Turnbull, W. Bruce; Visser, Gerben M.; Pieters, Roland J.

    2015-01-01

    The five B-subunits (CTB5) of the Vibrio cholerae (cholera) toxin can bind to the intestinal cell surface so the entire AB5 toxin can enter the cell. Simultaneous binding can occur on more than one of the monosialotetrahexosylganglioside (GM1) units present on the cell surface.

  9. Plant Insecticidal Toxins in Ecological Networks

    Directory of Open Access Journals (Sweden)

    Sébastien Ibanez

    2012-04-01

    Full Text Available Plant secondary metabolites play a key role in plant-insect interactions, whether constitutive or induced, C- or N-based. Anti-herbivore defences against insects can act as repellents, deterrents, growth inhibitors or cause direct mortality. In turn, insects have evolved a variety of strategies to act against plant toxins, e.g., avoidance, excretion, sequestration and degradation of the toxin, eventually leading to a co-evolutionary arms race between insects and plants and to co-diversification. Anti-herbivore defences also negatively impact mutualistic partners, possibly leading to an ecological cost of toxin production. However, in other cases toxins can also be used by plants involved in mutualistic interactions to exclude inadequate partners and to modify the cost/benefit ratio of mutualism to their advantage. When considering the whole community, toxins have an effect at many trophic levels. Aposematic insects sequester toxins to defend themselves against predators. Depending on the ecological context, toxins can either increase insects’ vulnerability to parasitoids and entomopathogens or protect them, eventually leading to self-medication. We conclude that studying the community-level impacts of plant toxins can provide new insights into the synthesis between community and evolutionary ecology.

  10. Plant insecticidal toxins in ecological networks.

    Science.gov (United States)

    Ibanez, Sébastien; Gallet, Christiane; Després, Laurence

    2012-04-01

    Plant secondary metabolites play a key role in plant-insect interactions, whether constitutive or induced, C- or N-based. Anti-herbivore defences against insects can act as repellents, deterrents, growth inhibitors or cause direct mortality. In turn, insects have evolved a variety of strategies to act against plant toxins, e.g., avoidance, excretion, sequestration and degradation of the toxin, eventually leading to a co-evolutionary arms race between insects and plants and to co-diversification. Anti-herbivore defences also negatively impact mutualistic partners, possibly leading to an ecological cost of toxin production. However, in other cases toxins can also be used by plants involved in mutualistic interactions to exclude inadequate partners and to modify the cost/benefit ratio of mutualism to their advantage. When considering the whole community, toxins have an effect at many trophic levels. Aposematic insects sequester toxins to defend themselves against predators. Depending on the ecological context, toxins can either increase insects' vulnerability to parasitoids and entomopathogens or protect them, eventually leading to self-medication. We conclude that studying the community-level impacts of plant toxins can provide new insights into the synthesis between community and evolutionary ecology.

  11. MARTX toxins as effector delivery platforms.

    Science.gov (United States)

    Gavin, Hannah E; Satchell, Karla J F

    2015-12-01

    Bacteria frequently manipulate their host environment via delivery of microbial 'effector' proteins to the cytosol of eukaryotic cells. In the case of the multifunctional autoprocessing repeats-in-toxins (MARTX) toxin, this phenomenon is accomplished by a single, >3500 amino acid polypeptide that carries information for secretion, translocation, autoprocessing and effector activity. MARTX toxins are secreted from bacteria by dedicated Type I secretion systems. The released MARTX toxins form pores in target eukaryotic cell membranes for the delivery of up to five cytopathic effectors, each of which disrupts a key cellular process. Targeted cellular processes include modulation or modification of small GTPases, manipulation of host cell signaling and disruption of cytoskeletal integrity. More recently, MARTX toxins have been shown to be capable of heterologous protein translocation. Found across multiple bacterial species and genera--frequently in pathogens lacking Type 3 or Type 4 secretion systems--MARTX toxins in multiple cases function as virulence factors. Innovative research at the intersection of toxin biology and bacterial genetics continues to elucidate the intricacies of the toxin as well as the cytotoxic mechanisms of its diverse effector collection. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  12. Analysis of the effect of attachment point bias during large space debris removal using a tethered space tug

    Science.gov (United States)

    Chu, Zhongyi; Di, Jingnan; Cui, Jing

    2017-10-01

    Space debris occupies a valuable orbital resource and is an inevitable and urgent problem, especially for large space debris because of its high risk and the possible crippling effects of a collision. Space debris has attracted much attention in recent years. A tethered system used in an active debris removal scenario is a promising method to de-orbit large debris in a safe manner. In a tethered system, the flexibility of the tether used in debris removal can possibly induce tangling, which is dangerous and should be avoided. In particular, attachment point bias due to capture error can significantly affect the motion of debris relative to the tether and increase the tangling risk. Hence, in this paper, the effect of attachment point bias on the tethered system is studied based on a dynamic model established based on a Newtonian approach. Next, a safety metric of avoiding a tangle when a tether is tensioned with attachment point bias is designed to analyse the tangling risk of the tethered system. Finally, several numerical cases are established and simulated to validate the effects of attachment point bias on a space tethered system.

  13. Wall effect on fluid–structure interactions of a tethered bluff body

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Sumant; Raghav, Vrishank, E-mail: vrishank@gatech.edu; Komerath, Narayanan, E-mail: komerath@gatech.edu; Smith, Marilyn

    2013-11-01

    Wind tunnel experiments have shown an unexplained amplification of the free motion of a tethered bluff body in a small wind tunnel relative to that in a large wind tunnel. The influence of wall proximity on fluid–structure interaction is explored using a compound pendulum motion in the plane orthogonal to a steady freestream with a doublet model for aerodynamic forces. Wall proximity amplifies a purely symmetric single degree of freedom oscillation with the addition of an out-of-phase force. The success of this simple level of simulation enables progress to develop metrics for unsteady wall interference in dynamic testing of tethered bluff bodies.

  14. Diamond surface functionalization with biomimicry - Amine surface tether and thiol moiety for electrochemical sensors

    Science.gov (United States)

    Sund, James B.; Causey, Corey P.; Wolter, Scott D.; Parker, Charles B.; Stoner, Brian R.; Toone, Eric J.; Glass, Jeffrey T.

    2014-05-01

    The surface of conducting diamond was functionalized with a terminal thiol group that is capable of binding and detecting nitrogen-oxygen species. The functionalization process employed multiple steps starting with doped diamond films grown by plasma enhanced chemical vapor deposition followed by hydrogen termination and photochemical attachment of a chemically protected amine alkene. The surface tether was deprotected to reveal the amine functionality, which enabled the tether to be extended with surface chemistry to add a terminal thiol moiety for electrochemical sensing applications. Each step of the process was validated using X-ray photoelectron spectroscopy analysis.

  15. Tethered satellite system dynamics and control review panel and related activities, phase 3

    Science.gov (United States)

    1991-01-01

    Two major tests of the Tethered Satellite System (TSS) engineering and flight units were conducted to demonstrate the functionality of the hardware and software. Deficiencies in the hardware/software integration tests (HSIT) led to a recommendation for more testing to be performed. Selected problem areas of tether dynamics were analyzed, including verification of the severity of skip rope oscillations, verification or comparison runs to explore dynamic phenomena observed in other simulations, and data generation runs to explore the performance of the time domain and frequency domain skip rope observers.

  16. Stabilization of periodic solutions in a tethered satellite system by damping injection

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2009-01-01

    A spacecraft with electrodynamic tether orbiting the Earth will be subject to a periodic forcing term induced by the variation of the magnetic field along the orbit. The periodic forcing term leads to a family of unstable periodic solutions for a tether carrying a constant current. This paper...... to affect the orbit parameters. An approximation of the periodic solutions of the closed loop system is found as a series expansion in the parameter plane spanned by the controller gain and the bias term. The stability of the solutions is investigated using linear Floquet analysis of the variational...

  17. Electron Emitter for small-size Electrodynamic Space Tether using MEMS Technology

    DEFF Research Database (Denmark)

    Fleron, René A. W.; Blanke, Mogens

    2004-01-01

    Adjustment of the orbit of a spacecraft using the forces created by an electro-dynamic space-tether has been shown as a theoretic possibility in recent literature. Practical implementation is being pursued for larger scale missions where a hot filament device controls electron emission and the cu......Adjustment of the orbit of a spacecraft using the forces created by an electro-dynamic space-tether has been shown as a theoretic possibility in recent literature. Practical implementation is being pursued for larger scale missions where a hot filament device controls electron emission...... and other orbit parameters can be controlled for small sized missions, without on-board propulsion....

  18. Elasticity, adhesion and tether extrusion on breast cancer cells provide a signature of their invasive potential.

    Science.gov (United States)

    Smolyakov, Georges; Thiebot, Bénédicte; Campillo, Clément C; Labdi, Sid; Séverac, Childérick; Pelta, Juan; Dague, Etienne

    2016-10-05

    We use single cell force spectroscopy to compare elasticity, adhesion and tether extrusion on four breast cancer cell lines with an increasing invasive potential. We perform cell attachment/detachment experiments either on fibronectin or on another cell using an Atomic Force Microscope. Our study on the membrane tether formation from cancer cells show that they are easier to extrude from aggressive invasive cells. Measured elastic modulus values confirm that more invasive cells are softer. Moreover, the adhesion force increases with the invasive potential. Our results provide a mechanical signature of breast cancer cells that correlates with their invasivity.

  19. Botulinum toxin in poststroke spasticity.

    Science.gov (United States)

    Ozcakir, Suheda; Sivrioglu, Koncuy

    2007-06-01

    Poststroke hemiparesis, together with abnormal muscle tone, is a major cause of morbidity and disability. Although most hemiparetic patients are able to reach different ambulatory levels with rehabilitation efforts, upper and lower limb spasticity can impede activities of daily living, personal hygiene, ambulation and, in some cases, functional improvement. The goals of spasticity management include increasing mobility and range of motion, attaining better hygiene, improving splint wear and other functional activities. Conservative measures, such as positioning, stretching and exercise are essential in spasticity management, but alone often are inadequate to effectively control it. Oral antispastic medications often provide limited effects with short duration and frequent unwanted systemic side effects, such as weakness, sedation and dry mouth. Therefore, neuromuscular blockade by local injections have become the first choice for the treatment of focal spasticity, particularly in stroke patients. Botulinum toxin (BTX), being one of the most potent biological toxins, acts by blocking neuromuscular transmission via inhibiting acetylcholine release. Currently, focal spasticity is being treated successfully with BTX via injecting in the spastic muscles. Two antigenically distinct serotypes of BTX are available on the market as type A and B. Clinical studies of BTX used for spastic hemiplegic patients are reviewed in this article in two major categories, upper and lower limb applications. This review addresses efficacy in terms of outcome measures, such as muscle tone reduction and functional outcome, as well as safety issues. Application modifications of dose, dilutions, site of injections and combination therapies with BTX injections are also discussed.

  20. Bordetella Adenylate Cyclase-Hemolysin Toxins

    Science.gov (United States)

    Guiso, Nicole

    2017-01-01

    Adenylate cyclase-hemolysin toxin is secreted and produced by three classical species of the genus Bordetella: Bordetella pertussis, B. parapertussis and B. bronchiseptica. This toxin has several properties such as: (i) adenylate cyclase activity, enhanced after interaction with the eukaryotic protein, calmodulin; (ii) a pore-forming activity; (iii) an invasive activity. It plays an important role in the pathogenesis of these Bordetella species responsible for whooping cough in humans or persistent respiratory infections in mammals, by modulating host immune responses. In contrast with other Bordetella toxins or adhesins, lack of (or very low polymorphism) is observed in the structural gene encoding this toxin, supporting its importance as well as a potential role as a vaccine antigen against whooping cough. In this article, an overview of the investigations undertaken on this toxin is presented. PMID:28892012

  1. Immunotoxins: The Role of the Toxin

    Directory of Open Access Journals (Sweden)

    David FitzGerald

    2013-08-01

    Full Text Available Immunotoxins are antibody-toxin bifunctional molecules that rely on intracellular toxin action to kill target cells. Target specificity is determined via the binding attributes of the chosen antibody. Mostly, but not exclusively, immunotoxins are purpose-built to kill cancer cells as part of novel treatment approaches. Other applications for immunotoxins include immune regulation and the treatment of viral or parasitic diseases. Here we discuss the utility of protein toxins, of both bacterial and plant origin, joined to antibodies for targeting cancer cells. Finally, while clinical goals are focused on the development of novel cancer treatments, much has been learned about toxin action and intracellular pathways. Thus toxins are considered both medicines for treating human disease and probes of cellular function.

  2. Novel receptors for bacterial protein toxins.

    Science.gov (United States)

    Schmidt, Gudula; Papatheodorou, Panagiotis; Aktories, Klaus

    2015-02-01

    While bacterial effectors are often directly introduced into eukaryotic target cells by various types of injection machines, toxins enter the cytosol of host cells from endosomal compartments or after retrograde transport via Golgi from the ER. A first crucial step of toxin-host interaction is receptor binding. Using optimized protocols and new methods novel toxin receptors have been identified, including metalloprotease ADAM 10 for Staphylococcus aureus α-toxin, laminin receptor Lu/BCAM for Escherichia coli cytotoxic necrotizing factor CNF1, lipolysis stimulated lipoprotein receptor (LSR) for Clostridium difficile transferase CDT and low-density lipoprotein receptor-related protein (LRP) 1 for Clostridium perfringens TpeL toxin. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Toxins and Secretion Systems of Photorhabdus luminescens

    Directory of Open Access Journals (Sweden)

    Athina Rodou

    2010-06-01

    Full Text Available Photorhabdus luminescens is a nematode-symbiotic, gram negative, bioluminescent bacterium, belonging to the family of Enterobacteriaceae.Recent studies show the importance of this bacterium as an alternative source of insecticides, as well as an emerging human pathogen. Various toxins have been identified and characterized in this bacterium. These toxins are classified into four major groups: the toxin complexes (Tcs, the Photorhabdus insect related (Pir proteins, the “makes caterpillars floppy” (Mcf toxins and the Photorhabdus virulence cassettes (PVC; the mechanisms however of toxin secretion are not fully elucidated. Using bioinformatics analysis and comparison against the components of known secretion systems, multiple copies of components of all known secretion systems, except the ones composing a type IV secretion system, were identified throughout the entire genome of the bacterium. This indicates that Photorhabdus luminescens has all the necessary means for the secretion of virulence factors, thus it is capable of establishing a microbial infection.

  4. Interplay between toxin transport and flotillin localization

    DEFF Research Database (Denmark)

    Pust, Sascha; Dyve, Anne Berit; Torgersen, Maria L

    2010-01-01

    The flotillin proteins are localized in lipid domains at the plasma membrane as well as in intracellular compartments. In the present study, we examined the importance of flotillin-1 and flotillin-2 for the uptake and transport of the bacterial Shiga toxin (Stx) and the plant toxin ricin and we...... investigated whether toxin binding and uptake were associated with flotillin relocalization. We observed a toxin-induced redistribution of the flotillins, which seemed to be regulated in a p38-dependent manner. Our experiments provide no evidence for a changed endocytic uptake of Stx or ricin in cells silenced...... for flotillin-1 or -2. However, the Golgi-dependent sulfation of both toxins was significantly reduced in flotillin knockdown cells. Interestingly, when the transport of ricin to the ER was investigated, we obtained an increased mannosylation of ricin in flotillin-1 and flotillin-2 knockdown cells. The toxicity...

  5. Toxins and secretion systems of Photorhabdus luminescens.

    Science.gov (United States)

    Rodou, Athina; Ankrah, Dennis O; Stathopoulos, Christos

    2010-06-01

    Photorhabdus luminescens is a nematode-symbiotic, gram negative, bioluminescent bacterium, belonging to the family of Enterobacteriaceae. Recent studies show the importance of this bacterium as an alternative source of insecticides, as well as an emerging human pathogen. Various toxins have been identified and characterized in this bacterium. These toxins are classified into four major groups: the toxin complexes (Tcs), the Photorhabdus insect related (Pir) proteins, the "makes caterpillars floppy" (Mcf) toxins and the Photorhabdus virulence cassettes (PVC); the mechanisms however of toxin secretion are not fully elucidated. Using bioinformatics analysis and comparison against the components of known secretion systems, multiple copies of components of all known secretion systems, except the ones composing a type IV secretion system, were identified throughout the entire genome of the bacterium. This indicates that Photorhabdus luminescens has all the necessary means for the secretion of virulence factors, thus it is capable of establishing a microbial infection.

  6. Integrated test rig for tether hardware, real-time simulator and control algorithms: Robust momentum transfer validated

    Science.gov (United States)

    Kruijff, Michiel; van der Heide, Erik Jan

    2001-02-01

    In preparation of the ESA demonstration mission for a tethered sample return capability from ISS, a breadboard test has been performed to validate the robust StarTrack tether dynamics control algorithms in conjunction with the constructed hardware. The proposed mission will use hardware inherited from the YES mission (Kruijff, 1999). A tether spool is holding a 7 kg, 35 km Dyneema tether. A 45 kg re-entry capsule will be ejected by springs and then deployed by gravity gradient. The dynamics are solely controlled by a barberpole type friction brake, similar to the SEDS hardware. This hardware is integrated in a test rig, based on the TMM&M stand, that has been upgraded to accommodate both a Space Part (abruptly applied initial tether deployment speed, fine tensiometer, real-time space tether simulator using the tensiometer measurements as input, take-up roller deploying the tether at a simulator-controlled speed) and a Satellite Part (infra-red beams inside the tether canister, control computer estimating deployed length and required extra braking from the IRED interrupts, `barberpole' friction brake). So the set-up allows for a tether deployment with closed loop control, all governed by a real-time comprehensive tether dynamics simulation. The tether deployment is based on the two-stage StarTrack deployment. This scheme stabilizes the tether at an intermediate vertical stage (with 3 km deployed). When the orbit and landing site have synchronized, a high-speed deployment follows to a large angle. When the fully deployed 35-km tether swings to the vertical at approximately 40 m/s, it is cut at a prefixed time optimized for landing site accuracy. The paper discusses the tests performed to characterize the designed hardware, maturing of the developed algorithms with respect to the hardware noise levels and the difficulties and limitations of the test rig. It is found that the set-up can be applied to a variety of tether pre-mission tests. It is shown that the performed

  7. Electron Tomography and Simulation of Baculovirus Actin Comet Tails Support a Tethered Filament Model of Pathogen Propulsion

    Science.gov (United States)

    Mueller, Jan; Pfanzelter, Julia; Winkler, Christoph; Narita, Akihiro; Le Clainche, Christophe; Nemethova, Maria; Carlier, Marie-France; Maeda, Yuichiro; Welch, Matthew D.; Ohkawa, Taro; Schmeiser, Christian; Resch, Guenter P.; Small, J. Victor

    2014-01-01

    Several pathogens induce propulsive actin comet tails in cells they invade to disseminate their infection. They achieve this by recruiting factors for actin nucleation, the Arp2/3 complex, and polymerization regulators from the host cytoplasm. Owing to limited information on the structural organization of actin comets and in particular the spatial arrangement of filaments engaged in propulsion, the underlying mechanism of pathogen movement is currently speculative and controversial. Using electron tomography we have resolved the three-dimensional architecture of actin comet tails propelling baculovirus, the smallest pathogen yet known to hijack the actin motile machinery. Comet tail geometry was also mimicked in mixtures of virus capsids with purified actin and a minimal inventory of actin regulators. We demonstrate that propulsion is based on the assembly of a fishbone-like array of actin filaments organized in subsets linked by branch junctions, with an average of four filaments pushing the virus at any one time. Using an energy-minimizing function we have simulated the structure of actin comet tails as well as the tracks adopted by baculovirus in infected cells in vivo. The results from the simulations rule out gel squeezing models of propulsion and support those in which actin filaments are continuously tethered during branch nucleation and polymerization. Since Listeria monocytogenes, Shigella flexneri, and Vaccinia virus among other pathogens use the same common toolbox of components as baculovirus to move, we suggest they share the same principles of actin organization and mode of propulsion. PMID:24453943

  8. Evaluation of antidiphtheria toxin nanobodies

    Directory of Open Access Journals (Sweden)

    Ghada H Shaker

    2010-06-01

    Full Text Available Ghada H ShakerDepartment of Microbiology and Immunology, Faculty of Pharmacy, King Saud University, Riyadh, Kingdom of Saudi ArabiaAbstract: Nanobodies are the smallest fragments of naturally occurring single-domain antibodies that have evolved to be fully functional in the absence of a light chain. Conventional antibodies are glycoproteins comprising two heavy and two light chains. Surprisingly, all members of the Camelidae family possess a fraction of antibodies devoid of both light chains and the first constant domain. These types of antibodies are known as heavy-chain antibody (HcAb nanobodies. There are three subclasses of IgG in dromedaries, namely IgG1, IgG2, and IgG3 of which IgG2 and IgG3 are of the HcAb type. These heavy chain antibodies constitute approximately 50% of the IgG in llama serum and as much as 75% of the IgG in camel serum. In the present work, the different IgG subclasses from an immunized camel (Camelus dromedarius with divalent diphtheria-tetanus vaccine were purified using their different affinity for protein A and protein G and their absorbance measured at 280 nm. Purity control and characterization by 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis of IgG subclasses was done under reducing conditions. Protein bands were visualized after staining with Coomassie Blue, showing two bands at 50 kDa and 30 kDa for IgG1, while IgG2 and IgG3 produced only one band at 46 kDa and 43 kDa, respectively. An enzyme-linked immunosorbent assay test using diphtheria toxin and purified IgG subclasses from the immunized camel were performed to evaluate their efficiency. Compared with conventional IgG1, heavy chain antibodies (nanobodies were shown to be more efficient in binding to diphtheria toxin antigen. This study revealed the possibility of using IgG2 and IgG3 nanobodies as an effective antitoxin for the treatment of diphtheria in humans.Keywords: camel, heavy chain antibody, HcAb, nanobodies, immunoglobulin, Ig

  9. Occurrence of a stonefish toxin-like toxin in the venom of the rabbitfish Siganus fuscescens.

    Science.gov (United States)

    Kiriake, Aya; Ishizaki, Shoichiro; Nagashima, Yuji; Shiomi, Kazuo

    2017-12-15

    Rabbitfish belonging to the order Perciformes are well-known venomous fish that are frequently involved in human accidents. However little research has been done into either the whole venom toxicities or the structures and properties of their venom toxins. In this study, we first examined biological activities of the crude venom extract prepared from dorsal spines of Siganus fuscescens, a rabbitfish most commonly found along the coasts of Japan. As a result, the crude venom extract was shown to have mouse-lethal activity, hemolytic activity against rabbit erythrocytes, edema-forming activity and nociceptive activity, similar to the known scorpaeniform fish toxins (stonefish toxins and their analogues). Then, the primary structure of the S. fuscescens toxin was successfully elucidated by the same cDNA cloning strategy as previously employed for the toxins of some scorpaeniform fish (lionfish, devil stinger and waspfish). The S. fuscescens toxin is obviously an analogue of stonefish toxins, being composed of two kinds of subunits, an α-subunit of 703 amino acid residues and a β-subunit of 699 amino acid residues. Furthermore, the genes encoding both subunits were cloned from genomic DNA and shown to have an architecture of three exons and two introns, as reported for those of the scorpaeniform fish toxins. This study is the first to demonstrate the occurrence of stonefish toxin-like toxins in perciform fish. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Botulinum toxin for the treatment of bruxism.

    Science.gov (United States)

    Tinastepe, Neslihan; Küçük, Burcu Bal; Oral, Koray

    2015-10-01

    Botulinum toxin, the most potent biological toxin, has been shown to be effective for a variety of disorders in several medical conditions, when used both therapeutically and cosmetically. In recent years, there has been a rising trend in the use of this pharmacological agent to control bruxing activity, despite its reported adverse effects. The aim of this review was to provide a brief overview to clarify the underlying essential ideas for the use of botulinum toxin in bruxism based on available scientific papers. An electronic literature search was performed to identify publications related to botulinum toxin and its use for bruxism in PubMed. Hand searching of relevant articles was also made to identify additional studies. Of the eleven identified studies, only two were randomized controlled trials, compared with the effectiveness of botulinum toxins on the reduction in the frequency of bruxism events and myofascial pain after injection. The authors of these studies concluded that botulinum toxin could be used as an effective treatment for reducing nocturnal bruxism and myofascial pain in patients with bruxism. Evidence-based research was limited on this topic. More randomized controlled studies are needed to confirm that botulinum toxin is safe and reliable for routine clinical use in bruxism.

  11. Interplay between toxin transport and flotillin localization.

    Directory of Open Access Journals (Sweden)

    Sascha Pust

    Full Text Available The flotillin proteins are localized in lipid domains at the plasma membrane as well as in intracellular compartments. In the present study, we examined the importance of flotillin-1 and flotillin-2 for the uptake and transport of the bacterial Shiga toxin (Stx and the plant toxin ricin and we investigated whether toxin binding and uptake were associated with flotillin relocalization. We observed a toxin-induced redistribution of the flotillins, which seemed to be regulated in a p38-dependent manner. Our experiments provide no evidence for a changed endocytic uptake of Stx or ricin in cells silenced for flotillin-1 or -2. However, the Golgi-dependent sulfation of both toxins was significantly reduced in flotillin knockdown cells. Interestingly, when the transport of ricin to the ER was investigated, we obtained an increased mannosylation of ricin in flotillin-1 and flotillin-2 knockdown cells. The toxicity of both toxins was twofold increased in flotillin-depleted cells. Since BFA (Brefeldin A inhibits the toxicity even in flotillin knockdown cells, the retrograde toxin transport is apparently still Golgi-dependent. Thus, flotillin proteins regulate and facilitate the retrograde transport of Stx and ricin.

  12. Tethering a laminin peptide to a crosslinked collagen scaffold for biofunctionality.

    Science.gov (United States)

    Damodaran, Gopinath; Collighan, Russell; Griffin, Martin; Pandit, Abhay

    2009-06-15

    Cell adhesion peptide regulates various cellular functions like proliferation, attachment, and spreading. The cellular response to laminin peptide (PPFLMLLKGSTR), a motif of laminin-5 alpha3 chain, tethered to type I collagen, crosslinked using microbial transglutaminase (mTGase) was investigated. mTGase is an enzyme that initiates crosslinking by reacting with the glutamine and lysine residues on the collagen fibers stabilizing the molecular structure. In this study that tethering of the laminin peptide in a mTGase crosslinked collagen scaffold enhanced cell proliferation and attachment. Laminin peptide tethered crosslinked scaffold showed unaltered cell morphology of 3T3 fibroblasts when compared with collagen and crosslinked scaffold. The triple helical structure of collagen remained unaltered by the addition of laminin peptide. In addition a dose-dependent affinity of the laminin peptide towards collagen was seen. The degree of crosslinking was measured by amino acid analysis, differential scanning calorimeter and fourier transform infrared spectroscopy. Increased crosslinking was observed in mTGase crosslinked group. mTGase crosslinking showed higher shrinkage temperature. There was alteration in the fibrillar architecture due to the crosslinking activity of mTGase. Hence, the use of enzyme-mediated linking shows promise in tethering cell adhesive peptides through biodegradable scaffolds. Copyright 2008 Wiley Periodicals, Inc.

  13. Analysis and design of a friction brake for momentum exchange propulsion tethers

    Science.gov (United States)

    Lennert, Simone; Cartmell, Matthew P.

    2006-10-01

    The purpose of this paper is to present an engineering assessment of a proposal for a deployment brake for a momentum exchange tether. Tethers have attracted considerable interest amongst the propulsion community for many years for orbit raising, energy conversion, de-orbiting, and injection into interplanetary transfers, and the motivation for the work described in the paper is directly mission-oriented. The YES2 SpaceMail mission has been planned as a low-cost international effort to provide a facility for the return of small samples from the ISS back to Earth, based on an inflatable re-entry capsule and a mechanical tether system. The system will be lofted into orbit as part of a payload on a Foton/Bion rocket launcher. The brake design concept is based on the use of friction between the deploying tether and a short pole onto which several turns are wound, and the paper summarises the modelling work that has been done, and then discusses an experiment in which the premise was tested in the laboratory. The paper concludes with certain practical proposals for implementation.

  14. A kinetic Monte Carlo analysis for the production of singularly tethered carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Hilmer, Andrew J; Strano, Michael S [Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Nair, Nitish, E-mail: strano@mit.edu [Department of Chemical and Biological Engineering, University of Colorado, Boulder, CO 80309 (United States)

    2010-12-10

    Nanoparticles that possess a single covalent tether to either another particle or a surface play an increasingly important role in nanotechnology, serving as a foundation for aggregation-based plasmonic sensors, chemically assembled framework structures, and scanning probe tips. Using a theoretical approach, we explore the reaction conditions necessary to maximize singular tethering for several cases of homogeneously dispersed nanoparticles, with a particular focus on single-walled carbon nanotubes. In the limit of particles of monodisperse size and equal site reactivity, the number of tethers versus the reaction conversion is statistically described by the well-known binomial distribution, with a variance that is minimal for the single tether case. However, solutions of nanoparticles often deviate from this ideal, and reaction events can introduce steric hindrance to neighboring sites or alter particle electronic properties, both of which can influence local reactivity. In order to study these cases we use the electron transfer reactions of single-walled carbon nanotubes. We find that the distribution in the number of monofunctional tubes, as a function of conversion, is largely dependent on the distribution of nanotube rate constants, and therefore tube chiralities, in the initial solution. As a contemporary example, we examine the implications of this result on the metallic-semiconductor separation of carbon nanotubes using electron transfer chemistry.

  15. APTEC: aptamer-tethered enzyme capture as a novel rapid diagnostic test for malaria.

    Science.gov (United States)

    Dirkzwager, Roderick M; Kinghorn, Andrew B; Richards, Jack S; Tanner, Julian A

    2015-03-18

    We report the rapid diagnosis of malaria by aptamer-tethered enzyme capture (APTEC) whereby an aptamer captures biomarker Plasmodium falciparum lactate dehydrogenase (PfLDH) then activity is measured colorimetrically. The robust test was sensitive (limit of detection = 4.9 ng mL(-1)) and could reliably diagnose malaria in clinical blood samples.

  16. Delivery of bFGF for Tissue Engineering by Tethering to the ECM

    Directory of Open Access Journals (Sweden)

    Chawapun Suttinont

    2015-01-01

    Full Text Available Delivery of growth factors to target cells is an important subject in tissue engineering. Towards that end, we have developed a growth factor-tethered extracellular matrix (ECM. Here, basic fibroblast growth factor (bFGF was tethered to extracellular matrix noncovalently. The designed ECM was comprised of 12 repeats of the APGVGV peptide motif derived from elastin as a stable structural unit and included the well-known cell adhesive RGD peptide as an active functional unit. To bind bFGF to the ECM, an acidic amino acid-rich sequence was introduced at the C-terminus of the ECM protein. It consisted of 5 repeats of 4 aspartic acids and a serine, DDDDS. bFGF has a highly basic amino acid domain. Therefore, bFGF was tethered to the ECM protein by electrostatic interaction. Cells cultured on bFGF-tethered ECM were well attached to the ECM and induced proliferation without addition of soluble bFGF.

  17. Optimal Cross-Wind Towing and Power Generation with Tethered Kites

    NARCIS (Netherlands)

    Williams, P.; Lansdorp, B.; Ockels, W.

    2007-01-01

    Non-powered flight vehicles such as kites can provide a means of transmitting wind energy from higher altitudes to the ground via tethers. Although there have been many proposals for systems to extract wind energy from higher altitudes, this paper focuses on the use of a light lifting body at the

  18. Titanium-tethered vancomycin prevents resistance to rifampicin in Staphylococcus aureus in vitro.

    Directory of Open Access Journals (Sweden)

    Martin Rottman

    Full Text Available Rifampicin is currently recognized as the most potent drug against Gram positive implant related infections. The use of rifampicin is limited by the emergence of bacterial resistance, which is often managed by coadministration of a second antibiotic. The purpose of this study was to determine the effectiveness of soluble rifampicin in combination with vancomycin tethered to titanium metal as a means to control bacterial growth and resistance in vitro. Bacterial growth was inhibited when the vancomycin-tethered titanium discs were treated with Staphylococcus aureus inocula of ≤2×10⁶ CFU, however inocula greater than 2×10⁶ CFU/disc adhered and survived. The combination of surface-tethered vancomycin with soluble rifampicin enhanced the inhibitory effect of rifampicin for an inoculum of 10⁶ CFU/cm² by one dilution (combination MIC of 0.008 mg/L versus 0.015 mg/L for rifampicin alone. Moreover, surface tethered vancomycin prevented the emergence of a rifampicin resistant population in an inoculum of 2×10⁸ CFU.

  19. Technical and economical assessment on tethered wind-energy systems (TWES)

    Energy Technology Data Exchange (ETDEWEB)

    Furuya, O.; Maekawa, S.

    1982-06-01

    The objective of the work reported was to establish the potential of tethered wind energy systems for energy conversion in the upper atmosphere. Of the concepts investigated, the Vertical Takeoff and Landing (VTOL) lift generation concept had the highest potential as compared to balloon, wind and hybrid concepts.

  20. Folding of multidomain proteins: biophysical consequences of tethering even in apparently independent folding.

    Science.gov (United States)

    Arviv, Oshrit; Levy, Yaakov

    2012-12-01

    Most eukaryotic and a substantial fraction of prokaryotic proteins are composed of more than one domain. The tethering of these evolutionary, structural, and functional units raises, among others, questions regarding the folding process of conjugated domains. Studying the folding of multidomain proteins in silico enables one to identify and isolate the tethering-induced biophysical determinants that govern crosstalks generated between neighboring domains. For this purpose, we carried out coarse-grained and atomistic molecular dynamics simulations of two two-domain constructs from the immunoglobulin-like β-sandwich fold. Each of these was experimentally shown to behave as the "sum of its parts," that is, the thermodynamic and kinetic folding behavior of the constituent domains of these constructs seems to occur independently, with the folding of each domain uncoupled from the folding of its partner in the two-domain construct. We show that the properties of the individual domains can be significantly affected by conjugation to another domain. The tethering may be accompanied by stabilizing as well as destabilizing factors whose magnitude depends on the size of the interface, the length, and the flexibility of the linker, and the relative stability of the domains. Accordingly, the folding of a multidomain protein should not be viewed as the sum of the folding patterns of each of its parts, but rather, it involves abrogating several effects that lead to this outcome. An imbalance between these effects may result in either stabilization or destabilization owing to the tethering. Copyright © 2012 Wiley Periodicals, Inc.

  1. LBR and lamin A/C sequentially tether peripheral heterochromatin and inversely regulate differentiation.

    Science.gov (United States)

    Solovei, Irina; Wang, Audrey S; Thanisch, Katharina; Schmidt, Christine S; Krebs, Stefan; Zwerger, Monika; Cohen, Tatiana V; Devys, Didier; Foisner, Roland; Peichl, Leo; Herrmann, Harald; Blum, Helmut; Engelkamp, Dieter; Stewart, Colin L; Leonhardt, Heinrich; Joffe, Boris

    2013-01-31

    Eukaryotic cells have a layer of heterochromatin at the nuclear periphery. To investigate mechanisms regulating chromatin distribution, we analyzed heterochromatin organization in different tissues and species, including mice with mutations in the lamin B receptor (Lbr) and lamin A (Lmna) genes that encode nuclear envelope (NE) proteins. We identified LBR- and lamin-A/C-dependent mechanisms tethering heterochromatin to the NE. The two tethers are sequentially used during cellular differentiation and development: first the LBR- and then the lamin-A/C-dependent tether. The absence of both LBR and lamin A/C leads to loss of peripheral heterochromatin and an inverted architecture with heterochromatin localizing to the nuclear interior. Myoblast transcriptome analyses indicated that selective disruption of the LBR- or lamin-A-dependent heterochromatin tethers have opposite effects on muscle gene expression, either increasing or decreasing, respectively. These results show how changes in NE composition contribute to regulating heterochromatin positioning, gene expression, and cellular differentiation during development. Copyright © 2013 Elsevier Inc. All rights reserved.

  2. Titanium-tethered vancomycin prevents resistance to rifampicin in Staphylococcus aureus in vitro.

    Science.gov (United States)

    Rottman, Martin; Goldberg, Joel; Hacking, S Adam

    2012-01-01

    Rifampicin is currently recognized as the most potent drug against Gram positive implant related infections. The use of rifampicin is limited by the emergence of bacterial resistance, which is often managed by coadministration of a second antibiotic. The purpose of this study was to determine the effectiveness of soluble rifampicin in combination with vancomycin tethered to titanium metal as a means to control bacterial growth and resistance in vitro. Bacterial growth was inhibited when the vancomycin-tethered titanium discs were treated with Staphylococcus aureus inocula of ≤2×10⁶ CFU, however inocula greater than 2×10⁶ CFU/disc adhered and survived. The combination of surface-tethered vancomycin with soluble rifampicin enhanced the inhibitory effect of rifampicin for an inoculum of 10⁶ CFU/cm² by one dilution (combination MIC of 0.008 mg/L versus 0.015 mg/L for rifampicin alone). Moreover, surface tethered vancomycin prevented the emergence of a rifampicin resistant population in an inoculum of 2×10⁸ CFU.

  3. Defined subunit arrangement and rab interactions are required for functionality of the HOPS tethering complex.

    Science.gov (United States)

    Ostrowicz, Clemens W; Bröcker, Cornelia; Ahnert, Franziska; Nordmann, Mirjana; Lachmann, Jens; Peplowska, Karolina; Perz, Angela; Auffarth, Kathrin; Engelbrecht-Vandré, Siegfried; Ungermann, Christian

    2010-10-01

    Within the endomembrane system of eukaryotic cells, multisubunit tethering complexes together with their corresponding Rab-GTPases coordinate vesicle tethering and fusion. Here, we present evidence that two homologous hexameric tethering complexes, the endosomal CORVET (Class C core vacuole/endosome transport) and the vacuolar HOPS (homotypic vacuole fusion and protein sorting) complex, have similar subunit topologies. Both complexes contain two Rab-binding proteins at one end, and the Sec1/Munc18-like Vps33 at the opposite side, suggesting a model on membrane bridging via Rab-GTP and SNARE binding. In agreement, HOPS activity can be reconstituted using purified subcomplexes containing the Rab and Vps33 module, but requires all six subunits for activity. At the center of HOPS and CORVET, the class C proteins Vps11 and Vps18 connect the two parts, and Vps11 binds both HOPS Vps39 and CORVET Vps3 via the same binding site. As HOPS Vps39 is also found at endosomes, our data thus suggest that these tethering complexes follow defined but distinct assembly pathways, and may undergo transition by simple subunit interchange. © 2010 John Wiley & Sons A/S.

  4. Tethered Cord Syndrome with Syrinx in A Nigerian Adult Female: A ...

    African Journals Online (AJOL)

    Alasia Datonye

    system did not show scoliosis. The respiratory and gastrointestinal systems were all normal. There were no cutaneous stigmata (hypertrichosis). Laboratory investigations showed normal haematogical indices. Urinalysis was also normal. An impression of transverse myelitis was made to exclude tethered cord syndrome.

  5. Mast Cell Targeted Chimeric Toxin Can Be Developed as an Adjunctive Therapy in Colon Cancer Treatment

    Directory of Open Access Journals (Sweden)

    Shan Wang

    2016-03-01

    Full Text Available The association of colitis with colorectal cancer has become increasingly clear with mast cells being identified as important inflammatory cells in the process. In view of the relationship between mast cells and cancer, we studied the effect and mechanisms of mast cells in the development of colon cancer. Functional and mechanistic insights were gained from ex vivo and in vivo studies of cell interactions between mast cells and CT26 cells. Further evidence was reversely obtained in studies of mast cell targeted Fcε-PE40 chimeric toxin. Experiments revealed mast cells could induce colon tumor cell proliferation and invasion. Cancer progression was found to be related to the density of mast cells in colonic submucosa. The activation of MAPK, Rho-GTPase, and STAT pathways in colon cancer cells was triggered by mast cells during cell-to-cell interaction. Lastly, using an Fcε-PE40 chimeric toxin we constructed, we confirmed the promoting effect of mast cells in development of colon cancer. Mast cells are a promoting factor of colon cancer and thus also a potential therapeutic target. The Fcε-PE40 chimeric toxin targeting mast cells could effectively prevent colon cancer in vitro and in vivo. Consequently, these data may demonstrate a novel immunotherapeutic approach for the treatment of tumors.

  6. Ex vivo

    Science.gov (United States)

    Matsuda, Kant M; Lopes-Calcas, Ana; Honke, Michael L; O'Brien-Moran, Zoe; Buist, Richard; West, Michael; Martin, Melanie

    2017-07-01

    To advance magnetic resonance imaging (MRI) technologies further for in vivo tissue characterization with histopathologic validation, we investigated the feasibility of ex vivo tissue imaging of a surgically removed human brain tumor as a comprehensive approach for radiology-pathology correlation in histoanatomically identical fashion in a rare case of pigmented ganglioglioma with complex paramagnetic properties. Pieces of surgically removed ganglioglioma, containing melanin and hemosiderin pigments, were imaged with a small bore 7-T MRI scanner to obtain T1-, T2-, and T2*-weighted image and diffusion tensor imaging (DTI). Corresponding histopathological slides were prepared for routine hematoxylin and eosin stain and special stains for melanin and iron/hemosiderin to correlate with MRI signal characteristics. Furthermore, mean diffusivity (MD) maps were generated from DTI data and correlated with cellularity using image analysis. While the presence of melanin was difficult to interpret in in vivo MRI with certainty due to concomitant hemosiderin pigments and calcium depositions, ex vivo tissue imaging clearly demonstrated pieces of tissue exhibiting the characteristic MR signal pattern for melanin with pathologic confirmation in a histoanatomically identical location. There was also concordant correlation between MD and cellularity. Although it is still in an initial phase of development, ex vivo tissue imaging is a promising approach, which offers radiology-pathology correlation in a straightforward and comprehensive manner.

  7. The Transcriptome of the Zoanthid Protopalythoa variabilis (Cnidaria, Anthozoa) Predicts a Basal Repertoire of Toxin-like and Venom-Auxiliary Polypeptides.

    Science.gov (United States)

    Huang, Chen; Morlighem, Jean-Étienne Rl; Zhou, Hefeng; Lima, Érica P; Gomes, Paula B; Cai, Jing; Lou, Inchio; Pérez, Carlos D; Lee, Simon Ming; Rádis-Baptista, Gandhi

    2016-10-05

    Protopalythoa is a zoanthid that, together with thousands of predominantly marine species, such as hydra, jellyfish, and sea anemones, composes the oldest eumetazoan phylum, i.e., the Cnidaria. Some of these species, such as sea wasps and sea anemones, are highly venomous organisms that can produce deadly toxins for preying, for defense or for territorial disputes. Despite the fact that hundreds of organic and polypeptide toxins have been characterized from sea anemones and jellyfish, practically nothing is known about the toxin repertoire in zoanthids. Here, based on a transcriptome analysis of the zoanthid Protopalythoa variabilis, numerous predicted polypeptides with canonical venom protein features are identified. These polypeptides comprise putative proteins from different toxin families: neurotoxic peptides, hemostatic and hemorrhagic toxins, membrane-active (pore-forming) proteins, protease inhibitors, mixed-function venom enzymes, and venom auxiliary proteins. The synthesis and functional analysis of two of these predicted toxin products, one related to the ShK/Aurelin family and the other to a recently discovered anthozoan toxin, displayed potent in vivo neurotoxicity that impaired swimming in larval zebrafish. Altogether, the complex array of venom-related transcripts that are identified in P. variabilis, some of which are first reported in Cnidaria, provides novel insight into the toxin distribution among species and might contribute to the understanding of composition and evolution of venom polypeptides in toxiferous animals. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  8. Clostridium perfringens type A–E toxin plasmids

    Science.gov (United States)

    Freedman, John C.; Theoret, James R.; Wisniewski, Jessica A.; Uzal, Francisco A.; Rood, Julian I.; McClane, Bruce A.

    2014-01-01

    Clostridium perfringens relies upon plasmid-encoded toxin genes to cause intestinal infections. These toxin genes are associated with insertion sequences that may facilitate their mobilization and transfer, giving rise to new toxin plasmids with common backbones. Most toxin plasmids carry a transfer of clostridial plasmids locus mediating conjugation, which likely explains the presence of similar toxin plasmids in otherwise unrelated C. perfringens strains. The association of many toxin genes with insertion sequences and conjugative plasmids provides virulence flexibility when causing intestinal infections. However, incompatibility issues apparently limit the number of toxin plasmids maintained by a single cell. PMID:25283728

  9. Dorsal Cervical Spinal Cord Herniation Precipitated by Kyphosis Deformity Correction for Spinal Cord Tethering.

    Science.gov (United States)

    Heller, Robert S; Hwang, Steven W; Riesenburger, Ron I

    2017-04-01

    Cervical spinal cord herniation is a rare clinical entity. Reported after previous intradural surgery or surgery complicated by durotomy, patients return several months to years later with symptoms of worsening myelopathy. Herein is presented a case of a 51-year-old female patient with spinal cord herniation in the cervical spine after kyphosis deformity correction. A 51-year old female patient presented to the neurosurgery clinic with worsening cervical myelopathy due to cervical spinal cord tethering and adhesions from previous intradural surgery for Chiari malformation. Conservative treatment initially was recommended but ultimately unsuccessful, as her neurologic function continued to deteriorate. Follow-up imaging demonstrated progressive cervical kyphotic deformity with stability of the tethered spinal cord. The patient underwent cervical deformity correction to reduce tension on the spinal cord, after which her neurologic symptoms stabilized and began to improve with physical therapy. Four months after surgery, she returned to clinic with recurrence of cervical myelopathy. Repeat imaging demonstrated herniation of the cervical spinal cord through a dorsal defect, and the patient was treated successfully with a wide cervical duraplasty to recreate an intact thecal sac. The inability of the spinal cord to compensate for changes in spinal alignment in cases of tethering makes it susceptible to increased pressure and tension at the point of tethering. Caution is urged when attempting deformity correction in the presence of spinal cord tethering, which may limit the capacity of the spinal cord and surrounding tissue to compensate for alterations in spinal alignment. Copyright © 2017 Elsevier Inc. All rights reserved.

  10. Nonfouling poly(ethylene oxide) layers end-tethered to polydopamine.

    Science.gov (United States)

    Pop-Georgievski, Ognen; Verreault, Dominique; Diesner, Mark-Oliver; Proks, Vladimír; Heissler, Stefan; Rypáček, František; Koelsch, Patrick

    2012-10-09

    Nonfouling surfaces capable of reducing protein adsorption are highly desirable in a wide range of applications. Coating of surfaces with poly(ethylene oxide) (PEO), a water-soluble, nontoxic, and nonimmunogenic polymer, is most frequently used to reduce nonspecific protein adsorption. Here we show how to prepare dense PEO brushes on virtually any substrate by tethering PEO to polydopamine (PDA)-modified surfaces. The chain lengths of hetero-bifunctional PEOs were varied in the range of 45-500 oxyethylene units (M(n) = 2000-20,000). End-tethering of PEO chains was performed through amine and thiol headgroups from reactive polymer melts to minimize excluded volume effects. Surface plasmon resonance (SPR) was applied to investigate the adsorption of model protein solutions and complex biologic medium (human blood plasma) to the densely packed PEO brushes. The level of protein adsorption of human serum albumin and fibrinogen solutions was below the detection limit of the SPR measurements for all PEO chains end-tethered to PDA, thus exceeding the protein resistance of PEO layers tethered directly on gold. It was found that the surface resistance to adsorption of lysozyme and human blood plasma increased with increasing length and brush character of the PEO chains end-tethered to PDA with a similar or better resistance in comparison to PEO layers on gold. Furthermore, the chain density, thickness, swelling, and conformation of PEO layers were determined using spectroscopic ellipsometry (SE), dynamic water contact angle (DCA) measurements, infrared reflection-absorption spectroscopy (IRRAS), and vibrational sum-frequency-generation (VSFG) spectroscopy, the latter in air and water.

  11. Retrograde transport of protein toxins through the Golgi apparatus

    DEFF Research Database (Denmark)

    Sandvig, Kirsten; Skotland, Tore; van Deurs, Bo

    2013-01-01

    A number of protein toxins from plants and bacteria take advantage of transport through the Golgi apparatus to gain entry into the cytosol where they exert their action. These toxins include the plant toxin ricin, the bacterial Shiga toxins, and cholera toxin. Such toxins bind to lipids or proteins...... at the cell surface, and they are endocytosed both by clathrin-dependent and clathrin-independent mechanisms. Sorting to the Golgi and retrograde transport to the endoplasmic reticulum (ER) are common to these toxins, but the exact mechanisms turn out to be toxin and cell-type dependent. In the ER......, the enzymatically active part is released and then transported into the cytosol, exploiting components of the ER-associated degradation system. In this review, we will discuss transport of different protein toxins, but we will focus on factors involved in entry and sorting of ricin and Shiga toxin into and through...

  12. Bacterial Toxins for Oncoleaking Suicidal Cancer Gene Therapy.

    Science.gov (United States)

    Pahle, Jessica; Walther, Wolfgang

    For suicide gene therapy, initially prodrug-converting enzymes (gene-directed enzyme-producing therapy, GDEPT) were employed to intracellularly metabolize non-toxic prodrugs into toxic compounds, leading to the effective suicidal killing of the transfected tumor cells. In this regard, the suicide gene therapy has demonstrated its potential for efficient tumor eradication. Numerous suicide genes of viral or bacterial origin were isolated, characterized, and extensively tested in vitro and in vivo, demonstrating their therapeutic potential even in clinical trials to treat cancers of different entities. Apart from this, growing efforts are made to generate more targeted and more effective suicide gene systems for cancer gene therapy. In this regard, bacterial toxins are an alternative to the classical GDEPT strategy, which add to the broad spectrum of different suicide approaches. In this context, lytic bacterial toxins, such as streptolysin O (SLO) or the claudin-targeted Clostridium perfringens enterotoxin (CPE) represent attractive new types of suicide oncoleaking genes. They permit as pore-forming proteins rapid and also selective toxicity toward a broad range of cancers. In this chapter, we describe the generation and use of SLO as well as of CPE-based gene therapies for the effective tumor cell eradication as promising, novel suicide gene approach particularly for treatment of therapy refractory tumors.

  13. Urea, a true uremic toxin: the empire strikes back.

    Science.gov (United States)

    Lau, Wei Ling; Vaziri, Nosratola D

    2017-01-01

    Blood levels of urea rise with progressive decline in kidney function. Older studies examining acute urea infusion suggested that urea was well-tolerated at levels 8-10× above normal values. More recent in vitro and in vivo work argue the opposite and demonstrate both direct and indirect toxicities of urea, which probably promote the premature aging phenotype that is pervasive in chronic kidney disease (CKD). Elevated urea at concentrations typically encountered in uremic patients induces disintegration of the gut epithelial barrier, leading to translocation of bacterial toxins into the bloodstream and systemic inflammation. Urea induces apoptosis of vascular smooth muscle cells as well as endothelial dysfunction, thus directly promoting cardiovascular disease. Further, urea stimulates oxidative stress and dysfunction in adipocytes, leading to insulin resistance. Finally, there are widespread indirect effects of elevated urea as a result of the carbamylation reaction, where isocyanic acid (a product of urea catabolism) alters the structure and function of proteins in the body. Carbamylation has been linked with renal fibrosis, atherosclerosis and anaemia. In summary, urea is a re-emerging Dark Force in CKD pathophysiology. Trials examining low protein diet to minimize accumulation of urea and other toxins suggest a clinical benefit in terms of slowing progression of CKD. © 2016 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society.

  14. Identification of a VapBC toxin-antitoxin system in a thermophilic bacterium Thermus thermophilus HB27.

    Science.gov (United States)

    Fan, Yuqi; Hoshino, Takayuki; Nakamura, Akira

    2017-01-01

    There are 12 putative toxin-antitoxin (TA) loci in the Thermus thermophilus HB27 genome, including four VapBC and three HicBA families. Expression of these seven putative toxin genes in Escherichia coli demonstrated that one putative VapC toxin TTC0125 and two putative HicA toxins, TTC1395 and TTC1705, inhibited cell growth, and co-expression with cognate antitoxin genes rescued growth, indicating that these genes function as TA loci. In vitro analysis with the purified TTC0125 and total RNA/mRNA from E. coli and T. thermophilus showed that TTC0125 has RNase activity to rRNA and mRNA; this activity was inhibited by the addition of the purified TTC0126. Translation inhibition assays showed that TTC0125 inhibited protein synthesis by degrading mRNA but not by inactivating ribosomes. Amino acid substitutions of 14 predicted catalytic and conserved residues in VapC toxins to Ala or Asp in TTC0125 indicated that nine residues are important for its in vivo toxin activity and in vitro RNase activity. These data demonstrate that TTC0125-TTC0126 functions as a VapBC TA module and causes growth inhibition by degrading free RNA. This is the first study to identify the function of TA systems in T. thermophilus.

  15. Plasma membrane association of three classes of bacterial toxins is mediated by a basic-hydrophobic motif.

    Science.gov (United States)

    Geissler, Brett; Ahrens, Sebastian; Satchell, Karla J F

    2012-02-01

    Plasma membrane targeting is essential for the proper function of many bacterial toxins. A conserved fourhelical bundle membrane localization domain (4HBM) was recently identified within three diverse families of toxins: clostridial glucosylating toxins, MARTX toxins and Pasteurella multocida-like toxins. When expressed in tissue culture cells or in yeast, GFP fusions to at least one 4HBM from each toxin family show significant peripheral membrane localization but with differing profiles. Both in vivo expression and in vitro binding studies reveal that the ability of these domains to localize to the plasma membrane and bind negatively charged phospholipids requires a basic-hydrophobic motif formed by the L1 and L3 loops. The different binding capacity of each 4HBM is defined by the hydrophobicity of an exposed residue within the motif. This study establishes that bacterial effectors utilize a normal host cell mechanism to locate the plasma membrane where they can then access their intracellular targets. © 2011 Blackwell Publishing Ltd.

  16. Amino-acid sequence of a coelenterate toxin: toxin II from Anemonia sulcata.

    Science.gov (United States)

    Wunderer, G; Fritz, H; Wachter, E; Machleidt, W

    1976-09-01

    Toxin II from Anemonia sulcata, the main component of the sea anemone venom, consists of 47 amino acid residues which are interconnected by three disulfide bridges. The S-aminoethylated polypeptide was coupled to activated glass beads and sequenced to position 33 by automated solid-phase Edman degradation. Blanks arising from anchor points and the rest of the sequence were determined from tryptic peptides of the [14C]carboxymethylated toxin. Toxin II shows no significant homologies with other known sequences of neurotoxins or cardiotoxins. It might constitute a new class of polypeptide toxins.

  17. Cholera Toxin B: One Subunit with Many Pharmaceutical Applications

    Directory of Open Access Journals (Sweden)

    Keegan J. Baldauf

    2015-03-01

    Full Text Available Cholera, a waterborne acute diarrheal disease caused by Vibrio cholerae, remains prevalent in underdeveloped countries and is a serious health threat to those living in unsanitary conditions. The major virulence factor is cholera toxin (CT, which consists of two subunits: the A subunit (CTA and the B subunit (CTB. CTB is a 55 kD homopentameric, non-toxic protein binding to the GM1 ganglioside on mammalian cells with high affinity. Currently, recombinantly produced CTB is used as a component of an internationally licensed oral cholera vaccine, as the protein induces potent humoral immunity that can neutralize CT in the gut. Additionally, recent studies have revealed that CTB administration leads to the induction of anti-inflammatory mechanisms in vivo. This review will cover the potential of CTB as an immunomodulatory and anti-inflammatory agent. We will also summarize various recombinant expression systems available for recombinant CTB bioproduction.

  18. Shiga-Like Toxin 2 of Enterohemorrhagic Escherichia Coli (EHEC): Genetic Organization and Effects of Toxin in a Murine Model of EHEC Infection

    Science.gov (United States)

    1990-04-27

    Shiga toxin of Shigella dysenteriae type 1. Shiga toxin has been recognized as one of the most potent bacterial toxins for eucaryotic cells . Shiga toxin...Shiga toxin transcription or the efficiency of toxin release from the bacterial cell . IV SHIGA-LIKE TOXIN TYPE 11 OF ENTEROHEMORRHAGIC...2 rabbits (Conradi, 1903). Subsequent reports demonstrated that crude prepara- tions of Shiga toxin were cytotoxic for selected mammalian cells

  19. INVESTIGATOIN OF CYANOBACTERIA TOXINS IN WATER

    Science.gov (United States)

    Introduction:Approximately 80 alkaloid and cyclic peptide toxins produced by various freshwater and marine cyanobacteria (blue-green algae) have been identified and their structures determined. The U. S. Environmental Protection Agency has identified two neurotoxin alkalo...

  20. Peptide toxin components of Amanita exitialis basidiocarps

    National Research Council Canada - National Science Library

    Wang-Qiu Deng; Tai-Hui Li; Ping-Gen Xi; Li-Xia Gan; Zheng-Duan Xiao; Zi-De Jiang

    2011-01-01

    .... The molecular weight (729.5 Da) of the eighth compound did not match that of any reported Amanita toxins and, although the UV absorption spectrum indicated it to be a phallotoxin, further studies are required to identify this component...

  1. Bacterial toxins as pathogen weapons against phagocytes

    Directory of Open Access Journals (Sweden)

    Ana edo Vale

    2016-02-01

    Full Text Available Bacterial toxins are virulence factors that manipulate host cell functions and take over the control of vital processes of living organisms to favour microbial infection. Some toxins directly target innate immune cells, thereby annihilating a major branch of the host immune response. In this review we will focus on bacterial toxins that act from the extracellular milieu and hinder the function of macrophages and neutrophils. In particular, we will concentrate on toxins from Gram-positive and Gram-negative bacteria that manipulate cell signalling or induce cell death by either imposing direct damage to the host cells cytoplasmic membrane or enzymatically modifying key eukaryotic targets. Outcomes regarding pathogen dissemination, host damage and disease progression will be discussed.

  2. Botulinum A toxin utilizations in obstetric palsy

    Directory of Open Access Journals (Sweden)

    Atakan Aydin

    2012-12-01

    Conclusion: We conclude that with the help of botulinum A toxin and physyotherapy, obstetrical palsy patient with cocontractions can significantly improve movements and may have less surgery. [Hand Microsurg 2012; 1(3.000: 89-94

  3. Toxin Detection by Surface Plasmon Resonance

    Directory of Open Access Journals (Sweden)

    2009-02-01

    Full Text Available Significant efforts have been invested in the past years for the development of analytical methods for fast toxin detection in food and water. Immunochemical methods like ELISA, spectroscopy and chromatography are the most used in toxin detection. Different methods have been linked, e.g. liquid chromatography and mass spectrometry (LC-MS, in order to detect as low concentrations as possible. Surface plasmon resonance (SPR is one of the new biophysical methods which enables rapid toxin detection. Moreover, this method was already included in portable sensors for on-site determinations. In this paper we describe some of the most common methods for toxin detection, with an emphasis on SPR.

  4. NNDSS - Table II. Shiga toxin to Shigellosis

    Data.gov (United States)

    U.S. Department of Health & Human Services — NNDSS - Table II. Shiga toxin to Shigellosis - 2016. In this Table, provisional* cases of selected†notifiable diseases (≥1,000 cases reported during the...

  5. NNDSS - Table II. Shiga toxin to Shigellosis

    Data.gov (United States)

    U.S. Department of Health & Human Services — NNDSS - Table II. Shiga toxin to Shigellosis - 2015. In this Table, provisional cases of selected notifiable diseases (≥1,000 cases reported during the preceding...

  6. Ultrasound-guided botulinum toxin injections

    OpenAIRE

    S. E. Khatkova; A. A. Balbert

    2016-01-01

    One of the key conditions for achieving the desirable result during botulinum toxin therapy for muscular dystonia, spasticity, and other diseases accompanied by spasm, pain, and autonomic dysfunction (dystonias, spasticity, etc.) is the proper administration of the agent into the muscles directly involved in the pathological process. The exact entry of botulinum toxin into the target muscles is essential for successful and safe treatment because its injection into a normal muscle may cause si...

  7. Botulinum toxin treatment of hemifacial spasm.

    OpenAIRE

    Elston, J S

    1986-01-01

    Six patients with hemifacial spasm were treated with injections of botulinum toxin A into the orbicularis oculi; the abnormal movements around the eye were relieved for an average of 15 weeks. There were no systemic or significant local side effects, and in view of the risks involved in neurosurgical treatment, a trial of botulinum toxin injections is recommended in the first instance in this condition.

  8. Botulinum toxin treatment of hemifacial spasm.

    Science.gov (United States)

    Elston, J S

    1986-01-01

    Six patients with hemifacial spasm were treated with injections of botulinum toxin A into the orbicularis oculi; the abnormal movements around the eye were relieved for an average of 15 weeks. There were no systemic or significant local side effects, and in view of the risks involved in neurosurgical treatment, a trial of botulinum toxin injections is recommended in the first instance in this condition. PMID:3746313

  9. Biodegradation of the Polyketide Toxin Cercosporin

    OpenAIRE

    Mitchell, Thomas K.; Chilton, William Scott; Daub, Margaret E.

    2002-01-01

    Cercosporin is a non-host-specific polyketide toxin produced by many species of plant pathogens belonging to the genus Cercospora. This red-pigmented, light-activated toxin is an important pathogenicity determinant for Cercospora species. In this study, we screened 244 bacterial isolates representing 12 different genera for the ability to degrade cercosporin. Cercosporin degradation was determined by screening for the presence of cleared zones surrounding colonies on cercosporin-containing cu...

  10. [Amanita phalloides toxins in dried mushrooms].

    Science.gov (United States)

    Klán, J; Baudisová, D

    1993-08-05

    The content of toxins from Amanita phalloides in dried carpophores is decreasing in the dependence on time. The content of alpha-amanitin found after 20 years was about one half. A mere trace of alpha-amanitin which is the most stable of all toxins was detected in a carpophore 50 years old. Degradation of amatoxins and phallotoxins by light (mainly the UV part) and high temperatures was observed.

  11. Toxicological Perspective on Climate Change: Aquatic Toxins.

    Science.gov (United States)

    Botana, Luis M

    2016-04-18

    In recent years, our group and several others have been describing the presence of new, not previously reported, toxins of high toxicity in vectors that may reach the human food chain. These include tetrodotoxin in gastropods in the South of Europe, ciguatoxin in fish in the South of Spain, palytoxin in mussels in the Mediterranean Sea, pinnatoxin all over Europe, and okadaic acid in the south of the U.S. There seem to be new marine toxins appearing in areas that are heavy producers of seafood, and this is a cause of concern as most of these new toxins are not included in current legislation and monitoring programs. Along with the new toxins, new chemical analogues are being reported. The same phenomenom is being recorded in freshwater toxins, such as the wide appearance of cylindrospermopsin and the large worldwide increase of microcystin. The problem that this phenomenon, which may be linked to climate warming, poses for toxicologists is very important not only because there is a lack of chronic studies and an incomplete comprehension of the mechanism driving the production of these toxins but also because the lack of a legal framework for them allows many of these toxins to reach the market. In some cases, it is very difficult to control these toxins because there are not enough standards available, they are not always certified, and there is an insufficient understanding of the toxic equivalency factors of the different analogues in each group. All of these factors have been revealed and grouped through the massive increase in the use of LC-MS as a monitoring tool, legally demanded, creating more toxicological problems.

  12. Updates on tetanus toxin: a fundamental approach

    Directory of Open Access Journals (Sweden)

    Md. Ahaduzzaman

    2015-03-01

    Full Text Available Clostridium tetani is an anaerobic bacterium that produces second most poisonous protein toxins than any other bacteria. Tetanus in animals is sporadic in nature but difficult to combat even by using antibiotics and antiserum. It is crucial to understand the fundamental mechanisms and signals that control toxin production for advance research and medicinal uses. This review was intended for better understanding the basic patho-physiology of tetanus and neurotoxins (TeNT among the audience of related field.

  13. Sensitivity of cancer cells to truncated diphtheria toxin.

    Directory of Open Access Journals (Sweden)

    Yi Zhang

    2010-05-01

    Full Text Available Diphtheria toxin (DT has been utilized as a prospective anti-cancer agent for the targeted delivery of cytotoxic therapy to otherwise untreatable neoplasia. DT is an extremely potent toxin for which the entry of a single molecule into a cell can be lethal. DT has been targeted to cancer cells by deleting the cell receptor-binding domain and combining the remaining catalytic portion with targeting proteins that selectively bind to the surface of cancer cells. It has been assumed that "receptorless" DT cannot bind to and kill cells. In the present study, we report that "receptorless" recombinant DT385 is in fact cytotoxic to a variety of cancer cell lines.In vitro cytotoxicity of DT385 was measured by cell proliferation, cell staining and apoptosis assays. For in vivo studies, the chick chorioallantoic membrane (CAM system was used to evaluate the effect of DT385 on angiogenesis. The CAM and mouse model system was used to evaluate the effect of DT385 on HEp3 and Lewis lung carcinoma (LLC tumor growth, respectively.Of 18 human cancer cell lines tested, 15 were affected by DT385 with IC(50 ranging from 0.12-2.8 microM. Furthermore, high concentrations of DT385 failed to affect growth arrested cells. The cellular toxicity of DT385 was due to the inhibition of protein synthesis and induction of apoptosis. In vivo, DT385 diminished angiogenesis and decreased tumor growth in the CAM system, and inhibited the subcutaneous growth of LLC tumors in mice.DT385 possesses anti-angiogenic and anti-tumor activity and may have potential as a therapeutic agent.

  14. Sea Anemone Toxins Affecting Potassium Channels

    Science.gov (United States)

    Diochot, Sylvie; Lazdunski, Michel

    The great diversity of K+ channels and their wide distribution in many tissues are associated with important functions in cardiac and neuronal excitability that are now better understood thanks to the discovery of animal toxins. During the past few decades, sea anemones have provided a variety of toxins acting on voltage-sensitive sodium and, more recently, potassium channels. Currently there are three major structural groups of sea anemone K+ channel (SAK) toxins that have been characterized. Radioligand binding and electrophysiological experiments revealed that each group contains peptides displaying selective activities for different subfamilies of K+ channels. Short (35-37 amino acids) peptides in the group I display pore blocking effects on Kv1 channels. Molecular interactions of SAK-I toxins, important for activity and binding on Kv1 channels, implicate a spot of three conserved amino acid residues (Ser, Lys, Tyr) surrounded by other less conserved residues. Long (58-59 amino acids) SAK-II peptides display both enzymatic and K+ channel inhibitory activities. Medium size (42-43 amino acid) SAK-III peptides are gating modifiers which interact either with cardiac HERG or Kv3 channels by altering their voltage-dependent properties. SAK-III toxins bind to the S3C region in the outer vestibule of Kv channels. Sea anemones have proven to be a rich source of pharmacological tools, and some of the SAK toxins are now useful drugs for the diagnosis and treatment of autoimmune diseases.

  15. Botulinum toxin for the treatment of strabismus.

    Science.gov (United States)

    Rowe, Fiona J; Noonan, Carmel P

    2017-03-02

    The use of botulinum toxin as an investigative and treatment modality for strabismus is well reported in the medical literature. However, it is unclear how effective it is in comparison to other treatment options for strabismus. The primary objective was to examine the efficacy of botulinum toxin therapy in the treatment of strabismus compared with alternative conservative or surgical treatment options. This review sought to ascertain those types of strabismus that particularly benefit from the use of botulinum toxin as a treatment option (such as small angle strabismus or strabismus with binocular potential, i.e. the potential to use both eyes together as a pair). The secondary objectives were to investigate the dose effect and complication rates associated with botulinum toxin. We searched CENTRAL (which contains the Cochrane Eyes and Vision Trials Register) (2016, Issue 6), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to July 2016), Embase (January 1980 to July 2016), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to July 2016), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov), and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 11 July 2016. We handsearched the British and Irish Orthoptic Journal, Australian Orthoptic Journal, proceedings of the European Strabismological Association (ESA), International Strabismological Association (ISA) and International Orthoptic Association (IOA) (www.liv.ac.uk/orthoptics/research/search.htm) and American Academy of Paediatric Ophthalmology and Strabismus meetings (AAPOS). We contacted researchers who are active in this field for information about further

  16. [Botulinum toxin therapy for spasticity].

    Science.gov (United States)

    Masakado, Yoshihisa

    2014-09-01

    Botulinum toxin (BTX) administered as an adjunct to other interventions for spasticity can act as a useful and effective therapeutic tool for treating patients disabled by spasticity. Presence of other non-reflex motor disorders (muscle stiffness, shortness, and contracture) can complicate the clinical course and disturb rehabilitative process of patients with spasticity. Treatment of spasticity using BTX can improve paralysis by correcting muscular imbalance that follows these diseases. In patients with chronic severe spasticity, we also have to address unique and difficult-to-treat clinical conditions such as abnormal posture and movement disorders. The effectiveness of BTX in treating some of these conditions is discussed. Because patients with neurological disabilities can show complex dysfunctions, specific functional limitations, goals, and expected outcomes of treatment should be evaluated and discussed with the patient, family members, and caregivers, prior to initiating BTX therapy. BTX therapy might improve not only care, passive function, but also motor functions in these patients by supplementing intensive rehabilitation with repetitive transcranial magnetic stimulation, transcranial direct-current stimulation, peripheral electrical stimulation, muscle stretching, and other rehabilitation strategies.

  17. Identification of the cellular receptor of Clostridium spiroforme toxin.

    Science.gov (United States)

    Papatheodorou, Panagiotis; Wilczek, Claudia; Nölke, Thilo; Guttenberg, Gregor; Hornuss, Daniel; Schwan, Carsten; Aktories, Klaus

    2012-04-01

    Clostridium spiroforme produces the binary actin-ADP-ribosylating toxin CST (C. spiroforme toxin), which has been proposed to be responsible for diarrhea, enterocolitis, and eventually death, especially in rabbits. Here we report on the recombinant production of the enzyme component (CSTa) and the binding component (CSTb) of C. spiroforme toxin in Bacillus megaterium. By using the recombinant toxin components, we show that CST enters target cells via the lipolysis-stimulated lipoprotein receptor (LSR), which has been recently identified as the host cell receptor of the binary toxins Clostridium difficile transferase (CDT) and Clostridium perfringens iota toxin. Microscopic studies revealed that CST, but not the related Clostridium botulinum C2 toxin, colocalized with LSR during toxin uptake and traffic to endosomal compartments. Our findings indicate that CST shares LSR with C. difficile CDT and C. perfringens iota toxin as a host cell surface receptor.

  18. Metabolism of HT-2 Toxin and T-2 Toxin in Oats

    Directory of Open Access Journals (Sweden)

    Jacqueline Meng-Reiterer

    2016-12-01

    Full Text Available The Fusarium mycotoxins HT-2 toxin (HT2 and T-2 toxin (T2 are frequent contaminants in oats. These toxins, but also their plant metabolites, may contribute to toxicological effects. This work describes the use of 13C-assisted liquid chromatography–high-resolution mass spectrometry for the first comprehensive study on the biotransformation of HT2 and T2 in oats. Using this approach, 16 HT2 and 17 T2 metabolites were annotated including novel glycosylated and hydroxylated forms of the toxins, hydrolysis products, and conjugates with acetic acid, putative malic acid, malonic acid, and ferulic acid. Further targeted quantitative analysis was performed to study toxin metabolism over time, as well as toxin and conjugate mobility within non-treated plant tissues. As a result, HT2-3-O-β-d-glucoside was identified as the major detoxification product of both parent toxins, which was rapidly formed (to an extent of 74% in HT2-treated and 48% in T2-treated oats within one day after treatment and further metabolised. Mobility of the parent toxins appeared to be negligible, while HT2-3-O-β-d-glucoside was partly transported (up to approximately 4% through panicle side branches and stem. Our findings demonstrate that the presented combination of untargeted and targeted analysis is well suited for the comprehensive elucidation of mycotoxin metabolism in plants.

  19. Chaotic attitude motion of a low-thrust tug-debris tethered system in a Keplerian orbit

    Science.gov (United States)

    Aslanov, Vladimir S.; Misra, Arun K.; Yudintsev, Vadim V.

    2017-10-01

    Chaotic motion of the tethered towing of debris using a low-thrust tug is considered. Stable and unstable stationary solutions are presented for the in-plane motion of the system in a circular orbit, which depend on the value of the tug's thrust. The unstable solutions give rise to the chaotic motion of the system in the presence of additional disturbances. The chaotic behavior of the system, caused by the eccentricity of the orbit and out-of-orbital plane roll motion of the tether system, is investigated based on the equations of spatial motion of tethered satellites developed in previous works. It is shown that the chaotic motions of the system depend on the value of the tug's thrust, so that using the tug with low thrust and starting the active phase of the active debris removal from unsuitable initial conditions for the pitch and roll angles of the tether can lead to chaotic motion of the system.

  20. In vivo

    Science.gov (United States)

    Berkowitz, Bruce A; Lenning, Jacob; Khetarpal, Nikita; Tran, Catherine; Wu, Johnny Y; Berri, Ali M; Dernay, Kristin; Haacke, E Mark; Shafie-Khorassani, Fatema; Podolsky, Robert H; Gant, John C; Maimaiti, Shaniya; Thibault, Olivier; Murphy, Geoffrey G; Bennett, Brian M; Roberts, Robin

    2017-09-01

    Hippocampus oxidative stress is considered pathogenic in neurodegenerative diseases, such as Alzheimer disease (AD), and in neurodevelopmental disorders, such as Angelman syndrome (AS). Yet clinical benefits of antioxidant treatment for these diseases remain unclear because conventional imaging methods are unable to guide management of therapies in specific hippocampus subfields in vivo that underlie abnormal behavior. Excessive production of paramagnetic free radicals in nonhippocampus brain tissue can be measured in vivo as a greater-than-normal 1/ T 1 that is quenchable with antioxidant as measured by quench-assisted (Quest) MRI. Here, we further test this approach in phantoms, and we present proof-of-concept data in models of AD-like and AS hippocampus oxidative stress that also exhibit impaired spatial learning and memory. AD-like models showed an abnormal gradient along the CA1 dorsal-ventral axis of excessive free radical production as measured by Quest MRI, and redox-sensitive calcium dysregulation as measured by manganese-enhanced MRI and electrophysiology. In the AS model, abnormally high free radical levels were observed in dorsal and ventral CA1. Quest MRI is a promising in vivo paradigm for bridging brain subfield oxidative stress and behavior in animal models and in human patients to better manage antioxidant therapy in devastating neurodegenerative and neurodevelopmental diseases.-Berkowitz, B. A., Lenning, J., Khetarpal, N., Tran, C., Wu, J. Y., Berri, A. M., Dernay, K., Haacke, E. M., Shafie-Khorassani, F., Podolsky, R. H., Gant, J. C., Maimaiti, S., Thibault, O., Murphy, G. G., Bennett, B. M., Roberts, R. In vivo imaging of prodromal hippocampus CA1 subfield oxidative stress in models of Alzheimer disease and Angelman syndrome. © FASEB.

  1. Toxin ζ Triggers a Survival Response to Cope with Stress and Persistence

    Directory of Open Access Journals (Sweden)

    María Moreno-del Álamo

    2017-06-01

    Full Text Available Bacteria have evolved complex regulatory controls in response to various environmental stresses. Protein toxins of the ζ superfamily, found in prominent human pathogens, are broadly distributed in nature. We show that ζ is a uridine diphosphate-N-acetylglucosamine (UNAG-dependent ATPase whose activity is inhibited in vitro by stoichiometric concentrations of ε2 antitoxin. In vivo, transient ζ expression promotes a reversible multi-level response by altering the pool of signaling purine nucleotides, which leads to growth arrest (dormancy, although a small cell subpopulation persists rather than tolerating toxin action. High c-di-AMP levels (absence of phosphodiesterase GdpP decrease, and low c-di-AMP levels (absence of diadenylate cyclase DisA increase the rate of ζ persistence. The absence of CodY, a transition regulator from exponential to stationary phase, sensitizes cells to toxin action, and suppresses persisters formed in the ΔdisA context. These changes, which do not affect the levels of stochastic ampicillin (Amp persistence, sensitize cells to toxin and Amp action. Our findings provide an explanation for the connection between ζ-mediated growth arrest (with alterations in the GTP and c-di-AMP pools and persistence formation.

  2. Handling of Drugs, Metabolites, and Uremic Toxins by Kidney Proximal Tubule Drug Transporters.

    Science.gov (United States)

    Nigam, Sanjay K; Wu, Wei; Bush, Kevin T; Hoenig, Melanie P; Blantz, Roland C; Bhatnagar, Vibha

    2015-11-06

    The proximal tubule of the kidney plays a crucial role in the renal handling of drugs (e.g., diuretics), uremic toxins (e.g., indoxyl sulfate), environmental toxins (e.g., mercury, aristolochic acid), metabolites (e.g., uric acid), dietary compounds, and signaling molecules. This process is dependent on many multispecific transporters of the solute carrier (SLC) superfamily, including organic anion transporter (OAT) and organic cation transporter (OCT) subfamilies, and the ATP-binding cassette (ABC) superfamily. We review the basic physiology of these SLC and ABC transporters, many of which are often called drug transporters. With an emphasis on OAT1 (SLC22A6), the closely related OAT3 (SLC22A8), and OCT2 (SLC22A2), we explore the implications of recent in vitro, in vivo, and clinical data pertinent to the kidney. The analysis of murine knockouts has revealed a key role for these transporters in the renal handling not only of drugs and toxins but also of gut microbiome products, as well as liver-derived phase 1 and phase 2 metabolites, including putative uremic toxins (among other molecules of metabolic and clinical importance). Functional activity of these transporters (and polymorphisms affecting it) plays a key role in drug handling and nephrotoxicity. These transporters may also play a role in remote sensing and signaling, as part of a versatile small molecule communication network operative throughout the body in normal and diseased states, such as AKI and CKD. Copyright © 2015 by the American Society of Nephrology.

  3. Selenium promotes metabolic conversion of T-2 toxin to HT-2 toxin in cultured human chondrocytes.

    Science.gov (United States)

    Yu, Fang-Fang; Lin, Xia-Lu; Wang, Xi; Liu, Huan; Yang, Lei; Goldring, Mary B; Lammi, Mikko J; Guo, Xiong

    2017-12-01

    To explore the metabolism of T-2 toxin in human chondrocytes (HCs) and determine the impact of selenium supplementation. For determination of cytotoxicity using the MTT assay, optical density values were read with an automatic enzyme-linked immunosorbent assay reader at 510nm. Cell survival was calculated and the cytotoxicity estimated. To identify the metabolites of T-2 toxin, the medium supernatants and C28/I2 cells were analyzed by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) separately. For HPLC-MS/MS, the mobile phase A was water and phase B was 98% methanol. The gradient for the elution was: 0-0.5min, 50% of B; 0.5-2.0min, 100% of B; 2.0-3.5min, 100% of B; 3.6-6min, 50% of B. T-2 toxin increased the toxicity to C28/I2 cells significantly in a dose- and time-dependent manner (viability range 91.5-22.0%). Supplementation with selenium (100ng/mL) could increase the cell viability after the 24h incubation. The concentration of T-2 toxin in the cell medium decreased from 20 to 6.67±1.02ng/mL, and the concentration of HT-2 toxin increased from 0 to 6.88±1.23ng/mL during the 48h incubation, whereas the relative concentration of T-2 toxin in cells increased from 0 to 12.80±1.84ng/g. Supplementary selenium in the HCs cultures reduced the cytotoxicity induced by T-2 toxin significantly, and was associated with rapid conversion of T-2 toxin in the culture medium to HT-2 toxin. T-2 toxin was more toxic to HCs than HT-2 toxin at equivalent concentrations. HT-2 toxin was a detectable metabolite of T-2 toxin in cultured HCs, and selenium enhanced the metabolic conversion of T-2 toxin, reducing its cytotoxicity to HCs. Copyright © 2017 Elsevier GmbH. All rights reserved.

  4. Toxin production in Dinophysis and the fate of these toxins in marine mussels

    DEFF Research Database (Denmark)

    Nielsen, Lasse Tor

    Diarrhetic shellfish poisoning (DSP) poses a considerable threat to food safety and to the economy of shellfish fishers and farmers in many parts of the world. Thousands of DSP intoxications have been reported, and bivalve harvesting can sometimes be closed down several months in a row. The toxins...... are primarily produced by the marine mixotrophic dinoflagellates Dinophysis spp., known to occur in most parts of the world. Dinophysis can, along with other planktonic organisms, be consumed by filter-feeding bivalves, and thus the toxins can accumulate. Dinophysis can produce the three toxin groups, okadaic...... acid (OA), dinophysistoxins (DTX) and pectenotoxins (PTX) – the latter two in a few different isomers. Toxin profiles, as well as cellular toxin quotas, vary tremendously between Dinophysis populations in situ, both within and between species, and the toxicity of a Dinophysis population is obviously...

  5. The HOPS/Class C Vps Complex Tethers High-Curvature Membranes via a Direct Protein-Membrane Interaction.

    Science.gov (United States)

    Ho, Ruoya; Stroupe, Christopher

    2016-10-01

    Membrane tethering is a physical association of two membranes before their fusion. Many membrane tethering factors have been identified, but the interactions that mediate inter-membrane associations remain largely a matter of conjecture. Previously, we reported that the homotypic fusion and protein sorting/Class C vacuolar protein sorting (HOPS/Class C Vps) complex, which has two binding sites for the yeast vacuolar Rab GTPase Ypt7p, can tether two low-curvature liposomes when both membranes bear Ypt7p. Here, we show that HOPS tethers highly curved liposomes to Ypt7p-bearing low-curvature liposomes even when the high-curvature liposomes are protein-free. Phosphorylation of the curvature-sensing amphipathic lipid-packing sensor (ALPS) motif from the Vps41p HOPS subunit abrogates tethering of high-curvature liposomes. A HOPS complex without its Vps39p subunit, which contains one of the Ypt7p binding sites in HOPS, lacks tethering activity, though it binds high-curvature liposomes and Ypt7p-bearing low-curvature liposomes. Thus, HOPS tethers highly curved membranes via a direct protein-membrane interaction. Such high-curvature membranes are found at the sites of vacuole tethering and fusion. There, vacuole membranes bend sharply, generating large areas of vacuole-vacuole contact. We propose that HOPS localizes via the Vps41p ALPS motif to these high-curvature regions. There, HOPS binds via Vps39p to Ypt7p in an apposed vacuole membrane. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Development of Tethered Hsp90 Inhibitors Carrying Radioiodinated Probes to Specifically Discriminate and Kill Malignant Breast Tumor Cells

    Science.gov (United States)

    2016-05-01

    tethered Hsp90 inhibitor capable of carrying various radioactive iodine isotopes for early detection and ablation of metastatic breast cancers . These...imaging agents in mouse models of breast cancer . 15. SUBJECT TERMS Radiodination, tethered Hsp90 inhibitor, malignant breast tumor , ectopic Hsp90 16...and 324 ER- tumors ) showed increased Hsp90 expression in all breast cancer cell lines, and in nearly 90% of primary breast cancers (2). A recent

  7. Use of Site-Specifically Tethered Chemical Nucleases to Study Macromolecular Reactions

    Directory of Open Access Journals (Sweden)

    Mukherjee Srabani

    2003-01-01

    Full Text Available During a complex macromolecular reaction multiple changes in molecular conformation and interactions with ligands may occur. X-ray crystallography may provide only a limited set of snapshots of these changes. Solution methods can augment such structural information to provide a more complete picture of a macromolecular reaction. We analyzed the changes in protein conformation and protein:nucleic acid interactions which occur during transcription initiation by using a chemical nuclease tethered to cysteines introduced site-specifically into the RNA polymerase of bacteriophage T7 (T7 RNAP. Changes in cleavage patterns as the polymerase steps through transcription reveal a series of structural transitions which mediate transcription initiation. Cleavage by tethered chemical nucleases is seen to be a powerful method for revealing the conformational dynamics of macromolecular reactions, and has certain advantages over cross-linking or energy transfer approaches.

  8. p12 Tethers the Murine Leukemia Virus Pre-integration Complex to Mitotic Chromosomes

    Science.gov (United States)

    Elis, Efrat; Ehrlich, Marcelo; Prizan-Ravid, Adi; Laham-Karam, Nihay; Bacharach, Eran

    2012-01-01

    The p12 protein of the murine leukemia virus (MLV) is a constituent of the pre-integration complex (PIC) but its function in this complex remains unknown. We developed an imaging system to monitor MLV PIC trafficking in live cells. This allowed the visualization of PIC docking to mitotic chromosomes and its release upon exit from mitosis. Docking occurred concomitantly with nuclear envelope breakdown and was impaired for PICs of viruses with lethal p12 mutations. Insertion of a heterologous chromatin binding module into p12 of one of these mutants restored PICs attachment to the chromosomes and partially rescued virus replication. Capsid dissociated from wild type PICs in mitotic cells but remained associated with PICs harboring tethering-negative p12 mutants. Altogether, these results explain, in part, MLV restriction to dividing cells and reveal a role for p12 as a factor that tethers MLV PIC to mitotic chromosomes. PMID:23300449

  9. Surface activity of polypeptide toxins isolated from Anemonia sulcata.

    Science.gov (United States)

    Ash, P; Hider, R C; Ménez, A; Wunderer, G

    1981-07-28

    Circular dichroism spectra and surface activities are reported for toxins II and III isolated from Anemonia sulcata. Toxin II is highly surface active and as a result possesses a synergistic effect with phospholipase A2. In complete contrast, toxin III lacks detectable surface activity. The presence of sodium dodecyl sulfate (2.5 mg.ml-1) failed to trigger large conformation changes in both toxins II and III. From a comparison of the sequences of toxins II and III it is suggested that the hydrophobic region 17-27 is responsible for the surface activity of toxin II.

  10. Lifting options for stratospheric aerosol geoengineering: advantages of tethered balloon systems.

    Science.gov (United States)

    Davidson, Peter; Burgoyne, Chris; Hunt, Hugh; Causier, Matt

    2012-09-13

    The Royal Society report 'Geoengineering the Climate' identified solar radiation management using albedo-enhancing aerosols injected into the stratosphere as the most affordable and effective option for geoengineering, but did not consider in any detail the options for delivery. This paper provides outline engineering analyses of the options, both for batch-delivery processes, following up on previous work for artillery shells, missiles, aircraft and free-flying balloons, as well as a more lengthy analysis of continuous-delivery systems that require a pipe connected to the ground and supported at a height of 20 km, either by a tower or by a tethered balloon. Towers are shown not to be practical, but a tethered balloon delivery system, with high-pressure pumping, appears to have much lower operating and capital costs than all other delivery options. Instead of transporting sulphuric acid mist precursors, such a system could also be used to transport slurries of high refractive index particles such as coated titanium dioxide. The use of such particles would allow useful experiments on opacity, coagulation and atmospheric chemistry at modest rates so as not to perturb regional or global climatic conditions, thus reducing scale-up risks. Criteria for particle choice are discussed, including the need to minimize or prevent ozone destruction. The paper estimates the time scales and relatively modest costs required if a tethered balloon system were to be introduced in a measured way with testing and development work proceeding over three decades, rather than in an emergency. The manufacture of a tether capable of sustaining the high tensions and internal pressures needed, as well as strong winds, is a significant challenge, as is the development of the necessary pumping and dispersion technologies. The greatest challenge may be the manufacture and launch of very large balloons, but means have been identified to significantly reduce the size of such balloons or aerostats.

  11. Otolith tethering in the zebrafish otic vesicle requires Otogelin and ?-Tectorin

    OpenAIRE

    Stooke-Vaughan, Georgina A.; Obholzer, Nikolaus D.; Baxendale, Sarah; Megason, Sean G.; Whitfield, Tanya T.

    2015-01-01

    Otoliths are biomineralised structures important for balance and hearing in fish. Their counterparts in the mammalian inner ear, otoconia, have a primarily vestibular function. Otoliths and otoconia form over sensory maculae and are attached to the otolithic membrane, a gelatinous extracellular matrix that provides a physical coupling between the otolith and the underlying sensory epithelium. In this study, we have identified two proteins required for otolith tethering in the zebrafish ear, a...

  12. Otolith tethering in the zebrafish otic vesicle requires Otogelin and alpha-Tectorin

    OpenAIRE

    Stooke-Vaughan, G.A.; Obholzer, N.D.; Baxendale, S.; Megason, S.G.; Whitfield, T.T.

    2015-01-01

    Otoliths are biomineralised structures important for balance and hearing in fish. Their counterparts in the mammalian inner ear, otoconia, have a primarily vestibular function. Otoliths and otoconia form over sensory maculae and are attached to the otolithic membrane, a gelatinous extracellular matrix that provides a physical coupling between the otolith and the underlying sensory epithelium. In this study, we have identified two proteins required for otolith tethering in the zebrafish ear, a...

  13. A Rapidly-Incremented Tethered-Swimming Test for Defining Domain-Specific Training Zones

    Directory of Open Access Journals (Sweden)

    Pessôa Filho Dalton M.

    2017-06-01

    Full Text Available The purpose of this study was to investigate whether a tethered-swimming incremental test comprising small increases in resistive force applied every 60 seconds could delineate the isocapnic region during rapidly-incremented exercise. Sixteen competitive swimmers (male, n = 11; female, n = 5 performed: (a a test to determine highest force during 30 seconds of all-out tethered swimming (Favg and the ΔF, which represented the difference between Favg and the force required to maintain body alignment (Fbase, and (b an incremental test beginning with 60 seconds of tethered swimming against a load that exceeded Fbase by 30% of ΔF followed by increments of 5% of ΔF every 60 seconds. This incremental test was continued until the limit of tolerance with pulmonary gas exchange (rates of oxygen uptake and carbon dioxide production and ventilatory (rate of minute ventilation data collected breath by breath. These data were subsequently analyzed to determine whether two breakpoints defining the isocapnic region (i.e., gas exchange threshold and respiratory compensation point were present. We also determined the peak rate of O2 uptake and exercise economy during the incremental test. The gas exchange threshold and respiratory compensation point were observed for each test such that the associated metabolic rates, which bound the heavy-intensity domain during constant-work-rate exercise, could be determined. Significant correlations (Spearman’s were observed for exercise economy along with (a peak rate of oxygen uptake (ρ = .562; p < 0.025, and (b metabolic rate at gas exchange threshold (ρ = −.759; p < 0.005. A rapidly-incremented tethered-swimming test allows for determination of the metabolic rates that define zones for domain-specific constant-work-rate training.

  14. Tethered 3-min all-out test did not predict the traditional critical force parameters in inexperienced swimmers.

    Science.gov (United States)

    Kalva-Filho, Carlos A; Zagatto, Alessandro M; da Silva, Adelino S; Castanho de Araújo, Monique Y; de Almeida, Pablo B; Papoti, Marcelo

    2017-09-01

    Critical power model can be performed in tethered swimming (i.e. critical force model). Although critical force can be used to prescribe aerobic training, its determination depends on at least three exhaustive efforts in altered days. In this context, previously studies have demonstrate that critical power model can be estimated by a single 3-min all-out test (3MT), which was not investigated in swimming yet. Thus, the aim of this study was to compare the parameters obtained during the tethered swimming 3MT to those obtained during the traditional critical force model. Seven swimmers (four female and three male) underwent a tethered swimming 3MT and three exhaustive efforts to determine the traditional critical force parameters (i.e. critical force [CF] and anaerobic impulse capacity [AIC]). The critical force (CF3-MIN) and force-time integral above the CF3-MIN (AIC3-MIN) determined during the tethered 3MT were not different to CF and AIC, respectively (P value >0.55). However, these parameters were not correlated (P value >0.45). In addition, we verified large limits of agreement between CF3MIN and CF (±19.7 N), which was also observed between AIC3MIN and AIC (±0.84 Log[N·min]). These findings demonstrated that tethered 3MTs should not be used to predict traditional critical force parameters, at least when the swimmers are inexperienced in long tethered all-out efforts.

  15. Role of the Mannose Receptor (CD206 in Innate Immunity to Ricin Toxin

    Directory of Open Access Journals (Sweden)

    Emily Gage

    2011-09-01

    Full Text Available The entry of ricin toxin into macrophages and certain other cell types in the spleen and liver results in toxin-induced inflammation, tissue damage and organ failure. It has been proposed that uptake of ricin into macrophages is facilitated by the mannose receptor (MR; CD206, a C-type lectin known to recognize the oligosaccharide side chains on ricin’s A (RTA and B (RTB subunits. In this study, we confirmed that the MR does indeed promote ricin binding, uptake and killing of monocytes in vitro. To assess the role of MR in the pathogenesis of ricin in vivo, MR knockout (MR−/− mice were challenged with the equivalent of 2.5× or 5× LD50 of ricin by intraperitoneal injection. We found that MR−/− mice were significantly more susceptible to toxin-induced death than their age-matched, wild-type control counterparts. These data are consistent with a role for the MR in scavenging and degradation of ricin, not facilitating its uptake and toxicity in vivo.

  16. Conformation and stretching of end-tethered polymers in pressure-driven flow under confinement

    Science.gov (United States)

    Roy, Tamal; Hardt, Steffen; InstituteNano-; Microfludics, Technische Universität Darmstadt Team

    2016-11-01

    Understanding of the conformation and dynamics of polymers under confinement is important for both fundamental studies and applications. We experimentally study the conformation and stretching of surface-tethered polymer chains confined between parallel surfaces and exposed to a pressure-driven flow. λ-DNA molecules are tethered to the wall of a microchannel of height smaller than the contour lengths of the molecules. The DNA molecules, stained with a fluorescent dye, are visualized by epifluorescence and laser-scanning confocal microscopy (LSCM). The effects of the channel height, flow rate and contour length on the extension of the molecules are determined from epifluorescence images. From LSCM images the complete conformation and orientation of the DNA molecules is inferred. We find that the fractional extension of the molecules is uniquely determined by the fluid shear stress at the tethering surface and the chain contour length. There is no explicit influence of the channel height in the range of contour lengths we consider. We also derive analytical scaling relationships (in the weak and strong extension limits) that explain the experimentally observed stretching characteristics. This work is supported by Deutsche Forschungsgemeinschaft (Grant No. HA 2696/33-1).

  17. Finite time attitude takeover control for combination via tethered space robot

    Science.gov (United States)

    Lu, Yingbo; Huang, Panfeng; Meng, Zhongjie; Hu, Yongxin; Zhang, Fan; Zhang, Yizhai

    2017-07-01

    Up to April 6, 2016, there are 17,385 large debris in orbit around the Earth, which poses a serious hazard to near-Earth space activities. As a promising on-orbit debris capture strategy, tethered space robots (TSRs) have wide applications in future on-orbit service owing to its flexibility and great workspace. However, lots of problems may arise in the Tethered Space Robots (TSRs) system from the approaching, capturing, postcapturing and towing phases. The postcapture combination attitude takeover control by the TSR is studied in this paper. Taking control constraints, tether oscillations and external disturbances into consideration, a fast terminal sliding mode control (FTSMC) methodology with dual closed loops for the flexible combination attitude takeover control is designed. The unknown upper bounds of the uncertainties, external disturbances are estimated through adaptive techniques. Stability of the dual closed loop control system and finite time convergence of system states are proved via Lyapunov stability theory. Besides, null space intersection control allocation was adopted to distribute the required control moment over TSR's redundant thrusters. Simulation studies have been conducted to demonstrate the effectiveness of the proposed controller with the conventional sliding mode control(SMC).

  18. Tethered Satellites as an Enabling Platform for Operational Space Weather Monitoring Systems

    Science.gov (United States)

    Gilchrist, Brian E.; Krause, Linda Habash; Gallagher, Dennis Lee; Bilen, Sven Gunnar; Fuhrhop, Keith; Hoegy, Walt R.; Inderesan, Rohini; Johnson, Charles; Owens, Jerry Keith; Powers, Joseph; hide

    2013-01-01

    Tethered satellites offer the potential to be an important enabling technology to support operational space weather monitoring systems. Space weather "nowcasting" and forecasting models rely on assimilation of near-real-time (NRT) space environment data to provide warnings for storm events and deleterious effects on the global societal infrastructure. Typically, these models are initialized by a climatological model to provide "most probable distributions" of environmental parameters as a function of time and space. The process of NRT data assimilation gently pulls the climate model closer toward the observed state (e.g., via Kalman smoothing) for nowcasting, and forecasting is achieved through a set of iterative semi-empirical physics-based forward-prediction calculations. Many challenges are associated with the development of an operational system, from the top-level architecture (e.g., the required space weather observatories to meet the spatial and temporal requirements of these models) down to the individual instruments capable of making the NRT measurements. This study focuses on the latter challenge: we present some examples of how tethered satellites (from 100s of m to 20 km) are uniquely suited to address certain shortfalls in our ability to measure critical environmental parameters necessary to drive these space weather models. Examples include long baseline electric field measurements, magnetized ionospheric conductivity measurements, and the ability to separate temporal from spatial irregularities in environmental parameters. Tethered satellite functional requirements are presented for two examples of space environment observables.

  19. Relationship between anaerobic capacity estimated using a single effort and 30-s tethered running outcomes.

    Science.gov (United States)

    Zagatto, Alessandro Moura; Miyagi, Willian Eiji; Sousa, Filipe Antônio de Barros; Gobatto, Claudio Alexandre

    2017-01-01

    The purpose of the current study was to investigate the relationship between alternative anaerobic capacity method (MAODALT) and a 30-s all-out tethered running test. Fourteen male recreational endurance runners underwent a graded exercise test, a supramaximal exhaustive effort and a 30-s all-out test on different days, interspaced by 48h. After verification of data normality (Shapiro-Wilk test), the Pearson's correlation test was used to verify the association between the anaerobic estimates from the MAODALT and the 30-s all-out tethered running outputs. Absolute MAODALT was correlated with mean power (r = 0.58; P = 0.03), total work (r = 0.57; P = 0.03), and mean force (r = 0.79; P = 0.001). In addition, energy from the glycolytic pathway (E[La-]) was correlated with mean power (r = 0.58; P = 0.03). Significant correlations were also found at each 5s interval between absolute MAODALT and force values (r between 0.75 and 0.84), and between force values and E[La-] (r between 0.73 to 0.80). In conclusion, the associations between absolute MAODALT and the mechanical outputs from the 30-s all-out tethered running test evidenced the importance of the anaerobic capacity for maintaining force during the course of time in short efforts.

  20. Tensile radial stress in the spinal cord related to arachnoiditis or tethering: a numerical model.

    Science.gov (United States)

    Bertram, C D; Bilston, L E; Stoodley, M A

    2008-07-01

    Spinal arachnoiditis comprises fibrous scarring of the subarachnoid space, following spinal trauma or inflammation, and is often associated with syringomyelia. We hypothesised that cord-to-dura attachments could cause transient tensile cord radial stress, as pressure waves propagate. This was tested in a fluid-structure interaction model, simulating three types of cord tethering, with 'arachnoiditis' confined to a short mid-section of the cord. The annular system was excited abdominally with a short transient, and the resulting Young and Lamb waves and reflections were analysed. Radial mid-section tethering was less significant than axial tethering, which gave rise to tensile radial stress locally when the cord was not fixed cranially. Simulated as inextensible string connections to the dura, arachnoiditis caused both localised tensile radial stress and localised low pressure in the cord as the transient passed. The extent of these effects was sensitive to the relative stiffness of the dura and cord. Tensile radial stress may create a syrinx in previously normal cord tissue, and transiently lowered pressure may draw in interstitial fluid, causing the syrinx to enlarge if fluid exit is inhibited. The suggested mechanism could also explain the juxtaposition of syrinxes to regions of arachnoiditis.

  1. Clustering of tethered satellite system simulation data by an adaptive neuro-fuzzy algorithm

    Science.gov (United States)

    Mitra, Sunanda; Pemmaraju, Surya

    1992-01-01

    Recent developments in neuro-fuzzy systems indicate that the concepts of adaptive pattern recognition, when used to identify appropriate control actions corresponding to clusters of patterns representing system states in dynamic nonlinear control systems, may result in innovative designs. A modular, unsupervised neural network architecture, in which fuzzy learning rules have been embedded is used for on-line identification of similar states. The architecture and control rules involved in Adaptive Fuzzy Leader Clustering (AFLC) allow this system to be incorporated in control systems for identification of system states corresponding to specific control actions. We have used this algorithm to cluster the simulation data of Tethered Satellite System (TSS) to estimate the range of delta voltages necessary to maintain the desired length rate of the tether. The AFLC algorithm is capable of on-line estimation of the appropriate control voltages from the corresponding length error and length rate error without a priori knowledge of their membership functions and familarity with the behavior of the Tethered Satellite System.

  2. System Dynamics and Feedforward Control for Tether-Net Space Robot System

    Directory of Open Access Journals (Sweden)

    Guang Zhai

    2009-06-01

    Full Text Available A new concept using flexible tether-net system to capture space debris is presented in this paper. With a mass point assumption the tether-net system dynamic model is established in orbital frame by applying Lagrange Equations. In order to investigate the net in-plane trajectories during after cast, the non-control R-bar and V-bar captures are simulated with ignoring the out-of-plane libration, the effect of in-plane libration on the trajectories of the capture net is demonstrated by simulation results. With an effort to damp the in-plane libration, the control scheme based on tether tension is investigated firstly, after that an integrated control scheme is proposed by introduced the thrusters into the system, the nonlinear close-loop dynamics is linearised by feedforward strategy, the simulation results show that feedforward controllor is effective for in-plane libration damping and enable the capture net to track an expected trajectory.

  3. System Dynamics and Feedforward Control for Tether-Net Space Robot System

    Directory of Open Access Journals (Sweden)

    Bin Liang

    2009-11-01

    Full Text Available A new concept using flexible tether-net system to capture space debris is presented in this paper. With a mass point assumption the tether-net system dynamic model is established in orbital frame by applying Lagrange Equations. In order to investigate the net in-plane trajectories during after cast, the non-control R-bar and V-bar captures are simulated with ignoring the out-of-plane libration, the effect of in-plane libration on the trajectories of the capture net is demonstrated by simulation results. With an effort to damp the in-plane libration, the control scheme based on tether tension is investigated firstly, after that an integrated control scheme is proposed by introduced the thrusters into the system, the nonlinear close-loop dynamics is linearised by feedforward strategy, the simulation results show that feedforward controllor is effective for in-plane libration damping and enable the capture net to track an expected trajectory.

  4. Effects of Asymmetries on the Dynamics of Motorized Momentum Exchange Tether and Payloads Injection Precision

    Directory of Open Access Journals (Sweden)

    Naiming Qi

    2015-01-01

    Full Text Available This paper presents the error dynamic model of motorized momentum exchange tether (MMET based on the momentum exchange principle of space tether. The error dynamics are caused by the structural bias of the differences in tethers’ length and the difference in payloads’ mass. After that, the coupling analysis between orbit and attitude is presented. It is shown that, with increasing the differences in tethers’ length and payloads’ mass, the COM deviation of the MMET increases linearly. The numerical simulations of the MMET by considering the structural asymmetries are presented; the results show that the asymmetries have tiny influences on the orbit of the chief satellite by decreasing the apogee, which will change the instantaneous velocity at the apogee and affect the payload injection precision. What is more, the structural asymmetries have effects on the attitude elements (including the pitch angle and yaw angle; however, the effects could be weakened by the external torque. The structural asymmetries and gravity gradient torque have composite effects on the angular velocity of the propulsion tether.

  5. Development of dynamic analysis program for tethered type deep-sea ROV (remotely operated vehicle) system

    Energy Technology Data Exchange (ETDEWEB)

    Takasugi, Noriyuki; Taniuchi, Takuya; Fukuda, Yutaka; Ito, Reiji; Kawakami, Hajime; Yoshikawa, Takao

    1987-08-20

    Nowadays, the development of the tethered type deep-sea ROV system using optical communication techniques, automated control techniques and robotics has been conducted and it is becoming possible to do safe and comparatively inexpensive investigations. However, since it constitutes problems that the power and light cables which hang an unmanned submarine (vehicle) receive the fluid dynamic actions and that due to the above effect, and the free movements of a mother ship and the vehicle are restricted, the technique of analyzing these behaviors is indispensable for the design of the vehicle system. Kawasaki Heavy Industries developed a program which can analyze in the time domain by the finite element method the three dimensional behaviors of the system in which mothership, tethering cable, launcher and vehicle are deemed to be an entirety and the tension of the tethering cables, etc. This article introduces this program. Thanks for this, the simulation of dynamic behavior of the above system and the simulation of total deep-sea operation supporting system have become feasible. (11 figs, 1 tab, 2 refs)

  6. Tethered Satellites as an Enabling Platform for Operational Space Weather Monitoring Systems

    Science.gov (United States)

    Gilchrist, B. E.; Habash Krause, L.; Gallagher, D. L.; Bilen, S. G.; Fuhrhop, K.; Johnson, C.; Owens, J. K.; Powers, J.; Voronka, N.

    2013-12-01

    Tethered satellites offer the potential to be an important enabling technology to support operational space weather monitoring systems. Space weather 'nowcasting' and forecasting models rely on assimilation of near-real-time (NRT) space environment data to provide warnings for storm events and deleterious effects on the global societal infrastructure. Typically, these models are initialized by a climatological model to provide "most probable distributions" of environmental parameters as a function of time and space. The process of NRT data assimilation gently pulls the climate model closer toward the observed state (e.g., via Kalman smoothing) for nowcasting, and forecasting is achieved through a set of iterative semi-empirical physics-based forward-prediction calculations. Many challenges are associated with the development of an operational system, from the top-level architecture (e.g., the required space weather observatories to meet the spatial and temporal requirements of these models) down to the individual instruments capable of making the NRT measurements. This study focuses on the latter challenge: we present some examples of how tethered satellites are uniquely suited to address certain shortfalls in our ability to measure critical environmental parameters necessary to drive these space weather models. Examples include very-long-baseline electric field measurements, magnetized ionospheric conductivity measurements, and the ability to separate temporal from spatial irregularities in environmental parameters. Tethered satellite functional requirements will be presented for each space environment observable considered in this study.

  7. Fluorescence Enhancement of Fluorophores Tethered to Different Sized Silver Colloids Deposited on Glass Substrate

    Science.gov (United States)

    Lukomska, Joanna; Malicka, Joanna; Gryczynski, Ignacy; Leonenko, Zoya; Lakowicz, Joseph R.

    2009-01-01

    We studied fluorescence enhancements of fluorescein tethered to silver colloids of different size. Thiolated 23-mer oligonucleotide (ss DNA-SH) was bound selectively to silver colloids deposited on 3-aminopropyltriethoxysilane (APS)-treated quartz slides. Fluoresceinlabeled complementary oligonucleotide (ss Fl-DNA) was added in an amount significantly lower than the amount of unlabeled DNA tethered to the colloids. The hybridization kinetics, observed as an increase in fluorescence emission, on small (30-40 nm) and large (> 120 nm) colloids were similar. However, the final fluorescence intensity of the sample with large colloids was about 50% higher than that observed for the sample with small colloids. The reference sample without ss DNA-SH was used to estimate the fluorescence enhancements of fluorescein tethered to the small colloids (E = 2.7) and to the large colloids (E = 4.1) due to its steady fluorescence signal. The proposed method, based on controlled hybridization with minimal amount of fluorophore labeled ss DNA, can be used to reliably estimate the fluorescence enhancements on any silver nanostructures. PMID:15578680

  8. Probing the effects of surface hydrophobicity and tether orientation on antibody-antigen binding

    Science.gov (United States)

    Bush, Derek B.; Knotts, Thomas A.

    2017-04-01

    Antibody microarrays have the potential to revolutionize molecular detection for many applications, but their current use is limited by poor reliability, and efforts to change this have not yielded fruitful results. One difficulty which limits the rational engineering of next-generation devices is that little is known, at the molecular level, about the antibody-antigen binding process near solid surfaces. Atomic-level structural information is scant because typical experimental techniques (X-ray crystallography and NMR) cannot be used to image proteins bound to surfaces. To overcome this limitation, this study uses molecular simulation and an advanced, experimentally validated, coarse-grain, protein-surface model to compare fab-lysozyme binding in bulk solution and when the fab is tethered to hydrophobic and hydrophilic surfaces. The results show that the tether site in the fab, as well as the surface hydrophobicity, significantly impacts the binding process and suggests that the optimal design involves tethering fabs upright on a hydrophilic surface. The results offer an unprecedented, molecular-level picture of the binding process and give hope that the rational design of protein-microarrays is possible.

  9. Relationship between anaerobic capacity estimated using a single effort and 30-s tethered running outcomes.

    Directory of Open Access Journals (Sweden)

    Alessandro Moura Zagatto

    Full Text Available The purpose of the current study was to investigate the relationship between alternative anaerobic capacity method (MAODALT and a 30-s all-out tethered running test. Fourteen male recreational endurance runners underwent a graded exercise test, a supramaximal exhaustive effort and a 30-s all-out test on different days, interspaced by 48h. After verification of data normality (Shapiro-Wilk test, the Pearson's correlation test was used to verify the association between the anaerobic estimates from the MAODALT and the 30-s all-out tethered running outputs. Absolute MAODALT was correlated with mean power (r = 0.58; P = 0.03, total work (r = 0.57; P = 0.03, and mean force (r = 0.79; P = 0.001. In addition, energy from the glycolytic pathway (E[La-] was correlated with mean power (r = 0.58; P = 0.03. Significant correlations were also found at each 5s interval between absolute MAODALT and force values (r between 0.75 and 0.84, and between force values and E[La-] (r between 0.73 to 0.80. In conclusion, the associations between absolute MAODALT and the mechanical outputs from the 30-s all-out tethered running test evidenced the importance of the anaerobic capacity for maintaining force during the course of time in short efforts.

  10. Gd³⁺ Tethered Gold Nanorods for Combined Magnetic Resonance Imaging and Photo-Thermal Therapy.

    Science.gov (United States)

    Pitchaimani, Arunkumar; Duong, Tuyen; Nguyen, Thanh; Maurmann, Leila; Key, Jaehong; Bossmann, Stefan H; Aryal, Santosh

    2017-04-01

    Near infrared (NIR) mediated photothermal therapy and magnetic resonance imaging (MRI) are promising treatment and imaging modalities in the field of cancer theranostics. Gold nanorods are the first choice of materials for NIR-mediated photothermal therapy due to their strong localized surface plasmon resonance (LSPR) at NIR region. Similarly, gadolinium based MRI contrast agents have an ability to increase the ionic and molecular relaxivity, thereby enhancing the solvent proton relaxation rate resulting in contrast enhancement. Herein, the effort has been made to engineer a dual front theranostic agent with combined photothermal and magnetic resonance imaging capacity using gadolinium tethered gold nanorods (Gd3+-AuNR). NIR-responsive gold nanorods were surface fabricated by means of Au-thiol interaction using a thiolated macrocyclic chelator that chelates Gd3+ ions, and further stabilized by thiolated polyethylene glycol (PEG-SH). The magnetic properties of the Gd3+-AuNR displayed an enhanced r 1 relaxivity of 12.1 mM–1s–1, with higher biological stability, and contrast enhancement in both solution state and in cell pellets. In-vitro (cell-free) and ex-vivo (on pig skin) analysis of the Gd3+-AuNR shows enhanced photothermal properties as equivalent to that of the raw AuNR. Furthermore, Gd3+-AuNR showed competent cellular entry and intracellular distribution as revealed by hyperspectral microscopy. In addition, Gd3+-AuNR also exhibits significant thermal ablation of B16–F10 cells in the presence of NIR. Thus, Gd3+-AuNR features a significant theranostic potential with combined photothermal and imaging modality, suggesting a great potential in anticancer therapy.

  11. Tethering IL2 to Its Receptor IL2Rβ Enhances Antitumor Activity and Expansion of Natural Killer NK92 Cells.

    Science.gov (United States)

    Jounaidi, Youssef; Cotten, Joseph F; Miller, Keith W; Forman, Stuart A

    2017-11-01

    IL2 is an immunostimulatory cytokine for key immune cells including T cells and natural killer (NK) cells. Systemic IL2 supplementation could enhance NK-mediated immunity in a variety of diseases ranging from neoplasms to viral infection. However, its systemic use is restricted by its serious side effects and limited efficacy due to activation of T regulatory cells (Tregs). IL2 signaling is mediated through interactions with a multi-subunit receptor complex containing IL2Rα, IL2Rβ, and IL2Rγ. Adult natural killer (NK) cells express only IL2Rβ and IL2Rγ subunits and are therefore relatively insensitive to IL2. To overcome these limitations, we created a novel chimeric IL2-IL2Rβ fusion protein of IL2 and its receptor IL2Rβ joined via a peptide linker (CIRB). NK92 cells expressing CIRB (NK92CIRB) were highly activated and expanded indefinitely without exogenous IL2. When compared with an IL2-secreting NK92 cell line, NK92CIRB were more activated, cytotoxic, and resistant to growth inhibition. Direct contact with cancer cells enhanced the cytotoxic character of NK92CIRB cells, which displayed superior in vivo antitumor effects in mice. Overall, our results showed how tethering IL2 to its receptor IL2Rβ eliminates the need for IL2Rα and IL2Rβ, offering a new tool to selectively activate and empower immune therapy. Cancer Res; 77(21); 5938-51. ©2017 AACR. ©2017 American Association for Cancer Research.

  12. Botulinum Toxin in Management of Limb Tremor

    Directory of Open Access Journals (Sweden)

    Elina Zakin

    2017-11-01

    Full Text Available Essential tremor is characterized by persistent, usually bilateral and symmetric, postural or kinetic activation of agonist and antagonist muscles involving either the distal or proximal upper extremity. Quality of life is often affected and one’s ability to perform daily tasks becomes impaired. Oral therapies, including propranolol and primidone, can be effective in the management of essential tremor, although adverse effects can limit their use and about 50% of individuals lack response to oral pharmacotherapy. Locally administered botulinum toxin injection has become increasingly useful in the management of essential tremor. Targeting of select muscles with botulinum toxin is an area of active research, and muscle selection has important implications for toxin dosing and functional outcomes. The use of anatomical landmarks with palpation, EMG guidance, electrical stimulation, and ultrasound has been studied as a technique for muscle localization in toxin injection. Earlier studies implemented a standard protocol for the injection of (predominantly wrist flexors and extensors using palpation and EMG guidance. Targeting of muscles by selection of specific activators of tremor (tailored to each patient using kinematic analysis might allow for improvement in efficacy, including functional outcomes. It is this individualized muscle selection and toxin dosing (requiring injection within various sites of a single muscle that has allowed for success in the management of tremors.

  13. Crystal structure of Clostridium difficile toxin A

    Energy Technology Data Exchange (ETDEWEB)

    Chumbler, Nicole M.; Rutherford, Stacey A.; Zhang, Zhifen; Farrow, Melissa A.; Lisher, John P.; Farquhar, Erik; Giedroc, David P.; Spiller, Benjamin W.; Melnyk, Roman A.; Lacy, D. Borden

    2016-01-11

    Clostridium difficile infection is the leading cause of hospital-acquired diarrhoea and pseudomembranous colitis. Disease is mediated by the actions of two toxins, TcdA and TcdB, which cause the diarrhoea, as well as inflammation and necrosis within the colon. The toxins are large (308 and 270 kDa, respectively), homologous (47% amino acid identity) glucosyltransferases that target small GTPases within the host. The multidomain toxins enter cells by receptor-mediated endocytosis and, upon exposure to the low pH of the endosome, insert into and deliver two enzymatic domains across the membrane. Eukaryotic inositol-hexakisphosphate (InsP6) binds an autoprocessing domain to activate a proteolysis event that releases the N-terminal glucosyltransferase domain into the cytosol. Here, we report the crystal structure of a 1,832-amino-acid fragment of TcdA (TcdA1832), which reveals a requirement for zinc in the mechanism of toxin autoprocessing and an extended delivery domain that serves as a scaffold for the hydrophobic α-helices involved in pH-dependent pore formation. A surface loop of the delivery domain whose sequence is strictly conserved among all large clostridial toxins is shown to be functionally important, and is highlighted for future efforts in the development of vaccines and novel therapeutics.

  14. Toxin inhibition in C. crescentus VapBC1 is mediated by a flexible pseudo-palindromic protein motif and modulated by DNA binding

    DEFF Research Database (Denmark)

    Bendtsen, Kirstine Louise; Xu, Kehan; Luckmann, Majbritt

    2017-01-01

    Expression of bacterial type II toxin-antitoxin (TA) systems is regulated at the transcriptional level through direct binding of the antitoxin to pseudo-palindromic sequences on operator DNA. In this context, the toxin functions as a co-repressor by stimulating DNA binding through direct...... for binding and inactivation of the VapC1 toxin dimer. Sequence analysis of 4127 orthologous VapB sequences reveals that such palindromic protein sequences are widespread and unique to bacterial and archaeal VapB antitoxins suggesting a general principle governing regulation of VapBC TA systems. Finally......, a structure of C-terminally truncated VapB1 bound to VapC1 reveals discrete states of the TA interaction that suggest a structural basis for toxin activation in vivo....

  15. Magnetic resonance imaging in the prone position and the diagnosis of tethered spinal cord.

    Science.gov (United States)

    Stamates, Melissa M; Frim, David M; Yang, Carina W; Katzman, Gregory L; Ali, Saad

    2018-01-01

    OBJECTIVE Tethered cord syndrome (TCS) is a neurosurgical disorder with varied clinical manifestations believed to result from vascular compromise due to stretch forces on the spinal cord. Conventional supine MRI findings may include a low-lying conus medullaris, thickened or fat-infiltrated filum terminale, or lipoma; however, imaging sensitivity and specificity for tethered cord can be low. The purpose of this study was to evaluate the utility of prone MRI in the diagnosis of tethered and retethered spinal cord. METHODS Medical records were reviewed in 41 patients who underwent surgical release of tethered cord and in whom preoperative prone MRI sequences were available. Patients were divided into Group 1 (new TCS diagnosis) and Group 2 (recurrent TCS after previous untethering). Absolute conus ventral motion and motion as a percentage of canal width between supine and prone positions was measured in these 2 groups via sagittal T2-weighted sequences; these groups were compared with 30 consecutive patients (Group 3) who were classified as the normal control group. RESULTS The mean ventral motion was as follows: Group 1 (absolute: 0.5 ± 0.5 mm [range 0-2.4 mm]; canal percentage: 3.7% ± 3.9% [range 0%-16.3%]); Group 2 (absolute: 0.4 ± 0.7 mm [range 0-2.6 mm]; canal percentage: 2.2% ± 3.7% [range 0%-14.0%]); and Group 3 (absolute: 3.4 ± 1.3 mm [range 1.4-5.6 mm]; canal percentage: 22.0% ± 7.2% [range 10.5%-36.1%]). Whereas 38/41 surgically treated patients with TCS had diminished ( 10% canal width motion. Sensitivity and specificity were thereby calculated as 92.7% and 100%, respectively. CONCLUSIONS In the present series, prone imaging is found to be a sensitive and specific tool, and the authors believe it may have a role as supportive evidence in the diagnosis of tethered and retethered spinal cord.

  16. Nuclear envelope localization of LEMD2 is developmentally dynamic and lamin A/C dependent yet insufficient for heterochromatin tethering.

    Science.gov (United States)

    Thanisch, Katharina; Song, Congdi; Engelkamp, Dieter; Koch, Jeannette; Wang, Audrey; Hallberg, Einar; Foisner, Roland; Leonhardt, Heinrich; Stewart, Colin L; Joffe, Boris; Solovei, Irina

    Peripheral heterochromatin in mammalian nuclei is tethered to the nuclear envelope by at least two mechanisms here referred to as the A- and B-tethers. The A-tether includes lamins A/C and additional unknown components presumably INM protein(s) interacting with both lamins A/C and chromatin. The B-tether includes the inner nuclear membrane (INM) protein Lamin B-receptor, which binds B-type lamins and chromatin. Generally, at least one of the tethers is always present in the nuclear envelope of mammalian cells. Deletion of both causes the loss of peripheral heterochromatin and consequently inversion of the entire nuclear architecture, with this occurring naturally in rod photoreceptors of nocturnal mammals. The tethers are differentially utilized during development, regulate gene expression in opposite manners, and play an important role during cell differentiation. Here we aimed to identify the unknown chromatin binding component(s) of the A-tether. We analyzed 10 mouse tissues by immunostaining with antibodies against 7 INM proteins and found that every cell type has specific, although differentially and developmentally regulated, sets of these proteins. In particular, we found that INM protein LEMD2 is concomitantly expressed with A-type lamins in various cell types but is lacking in inverted nuclei of rod cells. Truncation or deletion of Lmna resulted in the downregulation and mislocalization of LEMD2, suggesting that the two proteins interact and pointing at LEMD2 as a potential chromatin binding mediator of the A-tether. Using nuclei of mouse rods as an experimental model lacking peripheral heterochromatin, we expressed a LEMD2 transgene alone or in combination with lamin C in these cells and observed no restoration of peripheral heterochromatin in either case. We conclude that in contrary to the B-tether, the A-tether has a more intricate composition and consists of multiple components that presumably vary, at differing degrees of redundancy, between cell

  17. Clostridium perfringens delta toxin is sequence related to beta toxin, NetB, and Staphylococcus pore-forming toxins, but shows functional differences.

    Directory of Open Access Journals (Sweden)

    Maria Manich

    Full Text Available Clostridium perfringens produces numerous toxins, which are responsible for severe diseases in man and animals. Delta toxin is one of the three hemolysins released by a number of C. perfringens type C and possibly type B strains. Delta toxin was characterized to be cytotoxic for cells expressing the ganglioside G(M2 in their membrane. Here we report the genetic characterization of Delta toxin and its pore forming activity in lipid bilayers. Delta toxin consists of 318 amino acids, its 28 N-terminal amino acids corresponding to a signal peptide. The secreted Delta toxin (290 amino acids; 32619 Da is a basic protein (pI 9.1 which shows a significant homology with C. perfringens Beta toxin (43% identity, with C. perfringens NetB (40% identity and, to a lesser extent, with Staphylococcus aureus alpha toxin and leukotoxins. Recombinant Delta toxin showed a preference for binding to G(M2, in contrast to Beta toxin, which did not bind to gangliosides. It is hemolytic for sheep red blood cells and cytotoxic for HeLa cells. In artificial diphytanoyl phosphatidylcholine membranes, Delta and Beta toxin formed channels. Conductance of the channels formed by Delta toxin, with a value of about 100 pS to more than 1 nS in 1 M KCl and a membrane potential of 20 mV, was higher than those formed by Beta toxin and their distribution was broader. The results of zero-current membrane potential measurements and single channel experiments suggest that Delta toxin forms slightly anion-selective channels, whereas the Beta toxin channels showed a preference for cations under the same conditions. C. perfringens Delta toxin shows a significant sequence homolgy with C. perfringens Beta and NetB toxins, as well as with S. aureus alpha hemolysin and leukotoxins, but exhibits different channel properties in lipid bilayers. In contrast to Beta toxin, Delta toxin recognizes G(M2 as receptor and forms anion-selective channels.

  18. Marine Toxins Targeting Ion Channels

    Directory of Open Access Journals (Sweden)

    Hugo R. Arias

    2006-04-01

    Full Text Available Abstract: This introductory minireview points out the importance of ion channels for cell communication. The basic concepts on the structure and function of ion channels triggered by membrane voltage changes, the so-called voltage-gated ion channels (VGICs, as well as those activated by neurotransmitters, the so-called ligand-gated ion channel (LGICs, are introduced. Among the most important VGIC superfamiles, we can name the voltage-gated Na+ (NaV, Ca2+ (CaV, and K+ (KV channels. Among the most important LGIC super families, we can include the Cys-loop or nicotinicoid, the glutamate-activated (GluR, and the ATP-activated (P2XnR receptor superfamilies. Ion channels are transmembrane proteins that allow the passage of different ions in a specific or unspecific manner. For instance, the activation of NaV, CaV, or KV channels opens a pore that is specific for Na+, Ca2+, or K+, respectively. On the other hand, the activation of certain LGICs such as nicotinic acetylcholine receptors, GluRs, and P2XnRs allows the passage of cations (e.g., Na+, K+, and/or Ca2+, whereas the activation of other LGICs such as type A γ-butyric acid and glycine receptors allows the passage of anions (e.g., Cl− and/or HCO3−. In this regard, the activation of NaV and CaV as well as ligand-gated cation channels produce membrane depolarization, which finally leads to stimulatory effects in the cell, whereas the activation of KV as well as ligand-gated anion channels induce membrane hyperpolarization that finally leads to inhibitory effects in the cell. The importance of these ion channel superfamilies is emphasized by considering their physiological functions throughout the body as well as their pathophysiological implicance in several neuronal diseases. In this regard, natural molecules, and especially marine toxins, can be potentially used as modulators (e.g., inhibitors or prolongers of ion channel functions to treat or to alleviate a specific

  19. Marine toxins and their toxicological significance: An overview

    Digital Repository Service at National Institute of Oceanography (India)

    Sarkar, A.

    This article presents an overview of various types of marine toxins and their toxicological significance in the context of biotechnological research and development. The characteristics and toxic potentials of different marine toxins highlighted...

  20. Amino-acid sequence of toxin I from Anemonia sulcata.

    Science.gov (United States)

    Wunderer, G; Eulitz, M

    1978-08-15

    Toxin I from Anemonia sulcata, a major component of the sea anemone venom, consists of 46 amino acid residues which are linked by three disulfide bridges. The [14C]carboxymethylated polypeptide was sequenced to position 29 by automated Edman degradation. The remaining sequence was determined from cyanogen bromide peptides and from tryptic peptides of the citraconylated [14C]carboxymethylated toxin. Toxin I is homologous to toxin II from Anemonia sulcata and to anthopleurin A, a toxin from the sea anemone Anthopleura xanthogrammica. These toxins constitute a new class of polypeptide toxins. No significant homologies exist with toxin III from Anemonia sulcata nor with known sequences of neurotoxins or cardiotoxins of various origin.

  1. Retrograde trafficking of AB₅ toxins: mechanisms to therapeutics.

    Science.gov (United States)

    Mukhopadhyay, Somshuvra; Linstedt, Adam D

    2013-10-01

    Bacterial AB5 toxins are a clinically relevant class of exotoxins that include several well-known members such as Shiga, cholera, and pertussis toxins. Infections with toxin-producing bacteria cause devastating human diseases that affect millions of individuals each year and have no definitive medical treatment. The molecular targets of AB5 toxins reside in the cytosol of infected cells, and the toxins reach the cytosol by trafficking through the retrograde membrane transport pathway that avoids degradative late endosomes and lysosomes. Focusing on Shiga toxin as the archetype member, we review recent advances in understanding the molecular mechanisms involved in the retrograde trafficking of AB5 toxins and highlight how these basic science advances are leading to the development of a promising new therapeutic approach based on inhibiting toxin transport.

  2. Beyond Beauty : Botulinum Toxin Use in Anal Fissure

    National Research Council Canada - National Science Library

    Mehrotra, S

    2009-01-01

    .... In this scenario chemical sphincterotomy using Botulinum toxin offers an alternative modality. A total of 30 patients of chronic fissure in ano were treated with Botulinum toxin injection in the internal sphincter...

  3. An Automated System for Measuring Microphysical and Radiative Cloud Characteristics from a Tethered Balloon

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Paul Lawson

    2004-03-15

    OAK-B135 The rate of climate change in polar regions is now felt to be a harbinger of possible global warming. Long-lived, relatively thin stratus clouds play a predominant role in transmitting solar radiation and trapping long wave radiation emitted from open water and melt ponds. In situ measurements of microphysical and radiative properties of Arctic and Antarctic stratus clouds are needed to validate retrievals from remote measurements and simulations using numerical models. While research aircraft can collect comprehensive microphysical and radiative data in clouds, the duration of these aircraft is relatively short (up to about 12 hours). During the course of the Phase II research, a tethered balloon system was developed that supports miniaturized meteorological, microphysical and radiation sensors that can collect data in stratus clouds for days at a time. The tethered balloon system uses a 43 cubic meter balloon to loft a 17 kg sensor package to altitudes u p to 2 km. Power is supplied to the instrument package via two copper conductors in the custom tether. Meteorological, microphysical and radiation data are recorded by the sensor package. Meteorological measurements include pressure, temperature, humidity, wind speed and wind direction. Radiation measurements are made using a 4-pi radiometer that measures actinic flux at 500 and 800 nm. Position is recorded using a GPS receiver. Microphysical data are obtained using a miniaturized version of an airborne cloud particle imager (CPI). The miniaturized CPI measures the size distribution of water drops and ice crystals from 9 microns to 1.4 mm. Data are recorded onboard the sensor package and also telemetered via a 802.11b wireless communications link. Command signals can also be sent to the computer in the sensor package via the wireless link. In the event of a broken tether, a GMRS radio link to the balloon package is used to heat a wire that burns 15 cm opening in the top of the balloon. The balloon and

  4. Regulation of Toxin Production in Clostridium perfringens.

    Science.gov (United States)

    Ohtani, Kaori; Shimizu, Tohru

    2016-07-05

    The Gram-positive anaerobic bacterium Clostridium perfringens is widely distributed in nature, especially in soil and the gastrointestinal tracts of humans and animals. C. perfringens causes gas gangrene and food poisoning, and it produces extracellular enzymes and toxins that are thought to act synergistically and contribute to its pathogenesis. A complicated regulatory network of toxin genes has been reported that includes a two-component system for regulatory RNA and cell-cell communication. It is necessary to clarify the global regulatory system of these genes in order to understand and treat the virulence of C. perfringens. We summarize the existing knowledge about the regulatory mechanisms here.

  5. Snake venom toxins: toxicity and medicinal applications.

    Science.gov (United States)

    Chan, Yau Sang; Cheung, Randy Chi Fai; Xia, Lixin; Wong, Jack Ho; Ng, Tzi Bun; Chan, Wai Yee

    2016-07-01

    Snake venoms are complex mixtures of small molecules and peptides/proteins, and most of them display certain kinds of bioactivities. They include neurotoxic, cytotoxic, cardiotoxic, myotoxic, and many different enzymatic activities. Snake envenomation is a significant health issue as millions of snakebites are reported annually. A large number of people are injured and die due to snake venom poisoning. However, several fatal snake venom toxins have found potential uses as diagnostic tools, therapeutic agent, or drug leads. In this review, different non-enzymatically active snake venom toxins which have potential therapeutic properties such as antitumor, antimicrobial, anticoagulating, and analgesic activities will be discussed.

  6. Regulation of Toxin Production in Clostridium perfringens

    Directory of Open Access Journals (Sweden)

    Kaori Ohtani

    2016-07-01

    Full Text Available The Gram-positive anaerobic bacterium Clostridium perfringens is widely distributed in nature, especially in soil and the gastrointestinal tracts of humans and animals. C. perfringens causes gas gangrene and food poisoning, and it produces extracellular enzymes and toxins that are thought to act synergistically and contribute to its pathogenesis. A complicated regulatory network of toxin genes has been reported that includes a two-component system for regulatory RNA and cell-cell communication. It is necessary to clarify the global regulatory system of these genes in order to understand and treat the virulence of C. perfringens. We summarize the existing knowledge about the regulatory mechanisms here.

  7. Use of botulinum toxin in dentistry.

    Science.gov (United States)

    Hoque, Afreen; McAndrew, Maureen

    2009-11-01

    A growing number of dentists are providing botulinum toxin to patients. The research presented here outlines potential uses of Botox related to oral health and facial problems as compared to traditional treatment methods. The administration of Botox (historically done by dermatologists and neurologists) may fall under dentists' jurisdiction, as their training and knowledge encompasses the entire head and neck. A review is made of the literature, based on Ovid and PubMed searches, selecting articles describing the injection of botulinum toxin A in areas related to the oral cavity and the face, excluding cosmetic purposes.

  8. Streptococcal toxins: role in pathogenesis and disease.

    Science.gov (United States)

    Barnett, Timothy C; Cole, Jason N; Rivera-Hernandez, Tania; Henningham, Anna; Paton, James C; Nizet, Victor; Walker, Mark J

    2015-12-01

    Group A Streptococcus (Streptococcus pyogenes), group B Streptococcus (Streptococcus agalactiae) and Streptococcus pneumoniae (pneumococcus) are host-adapted bacterial pathogens among the leading infectious causes of human morbidity and mortality. These microbes and related members of the genus Streptococcus produce an array of toxins that act against human cells or tissues, resulting in impaired immune responses and subversion of host physiological processes to benefit the invading microorganism. This toxin repertoire includes haemolysins, proteases, superantigens and other agents that ultimately enhance colonization and survival within the host and promote dissemination of the pathogen. © 2015 John Wiley & Sons Ltd.

  9. Regulation of Toxin Production in Clostridium perfringens

    Science.gov (United States)

    Ohtani, Kaori; Shimizu, Tohru

    2016-01-01

    The Gram-positive anaerobic bacterium Clostridium perfringens is widely distributed in nature, especially in soil and the gastrointestinal tracts of humans and animals. C. perfringens causes gas gangrene and food poisoning, and it produces extracellular enzymes and toxins that are thought to act synergistically and contribute to its pathogenesis. A complicated regulatory network of toxin genes has been reported that includes a two-component system for regulatory RNA and cell-cell communication. It is necessary to clarify the global regulatory system of these genes in order to understand and treat the virulence of C. perfringens. We summarize the existing knowledge about the regulatory mechanisms here. PMID:27399773

  10. Cellular Entry of Clostridium perfringens Iota-Toxin and Clostridium botulinum C2 Toxin

    Directory of Open Access Journals (Sweden)

    Masaya Takehara

    2017-08-01

    Full Text Available Clostridium perfringens iota-toxin and Clostridium botulinum C2 toxin are composed of two non-linked proteins, one being the enzymatic component and the other being the binding/translocation component. These latter components recognize specific receptors and oligomerize in plasma membrane lipid-rafts, mediating the uptake of the enzymatic component into the cytosol. Enzymatic components induce actin cytoskeleton disorganization through the ADP-ribosylation of actin and are responsible for cell rounding and death. This review focuses upon the recent advances in cellular internalization of clostridial binary toxins.

  11. Host cell-induced signaling causes Clostridium perfringens to upregulate production of toxins important for intestinal infections

    Science.gov (United States)

    Chen, Jianming; Ma, Menglin; Uzal, Francisco A; McClane, Bruce A

    2014-01-01

    Clostridium perfringens causes enteritis and enterotoxemia in humans and livestock due to prolific toxin production. In broth culture, C. perfringens uses the Agr-like quorum sensing (QS) system to regulate production of toxins important for enteritis/enterotoxemia, including beta toxin (CPB), enterotoxin, and epsilon toxin (ETX). The VirS/VirR two-component regulatory system (TCRS) also controls CPB production in broth cultures. Both the Agr-like QS and VirS/VirR systems are important when C. perfringens senses enterocyte-like Caco-2 cells and responds by upregulating CPB production; however, only the Agr-like QS system is needed for host cell-induced ETX production. These in vitro observations have pathophysiologic relevance since both the VirS/VirR and Agr-like QS signaling systems are required for C. perfringens strain CN3685 to produce CPB in vivo and to cause enteritis or enterotoxemia. Thus, apparently upon sensing its presence in the intestines, C. perfringens utilizes QS and TCRS signaling to produce toxins necessary for intestinal virulence. PMID:24061146

  12. The CDI toxin of Yersinia kristensenii is a novel bacterial member of the RNase A superfamily

    Energy Technology Data Exchange (ETDEWEB)

    Batot, Gaëlle; Michalska, Karolina; Ekberg, Greg; Irimpan, Ervin M.; Joachimiak, Grazyna; Jedrzejczak, Robert; Babnigg, Gyorgy; Hayes, Christopher S.; Joachimiak, Andrzej; Goulding, Celia W.

    2017-04-10

    Contact-dependent growth inhibition (CDI) is an important mechanism of inter-bacterial competition found in many Gram-negative pathogens. CDI+ cells express cell-surface CdiA proteins that bind neighboring bacteria and deliver C-terminal toxin domains (CdiA-CT) to inhibit target-cell growth. CDI+ bacteria also produce CdiI immunity proteins, which specifically neutralize cognate CdiA-CT toxins to prevent self-inhibition. Here, we present the crystal structure of the CdiA-CT/CdiI(Ykris) complex from Yersinia kris-tensenii ATCC 33638. CdiA-CTYkris adopts the same fold as angiogenin and other RNase A paralogs, but the toxin does not share sequence similarity with these nucleases and lacks the characteristic disulfide bonds of the superfamily. Consistent with the structural homology, CdiA-CTYkris has potent RNase activity in vitro and in vivo. Structure-guided mutagenesis reveals that His175, Arg186, Thr276 and Tyr278 contribute to CdiA-CTYkris activity, suggesting that these residues participate in substrate binding and/or catalysis. CdiI(Ykris) binds directly over the putative active site and likely neutralizes toxicity by blocking access to RNA substrates. Significantly, CdiA-CTYkris is the first non-vertebrate protein found to possess the RNase A superfamily fold, and homologs of this toxin are associated with secretion systems in many Gram-negative and Gram-positive bacteria. These observations suggest that RNase Alike toxins are commonly deployed in inter-bacterial competition.

  13. Shellfish toxicity: human health implications of marine algal toxins.

    Science.gov (United States)

    James, K J; Carey, B; O'Halloran, J; van Pelt, F N A M; Skrabáková, Z

    2010-07-01

    Five major human toxic syndromes caused by the consumption of shellfish contaminated by algal toxins are presented. The increased risks to humans of shellfish toxicity from the prevalence of harmful algal blooms (HABs) may be a consequence of large-scale ecological changes from anthropogenic activities, especially increased eutrophication, marine transport and aquaculture, and global climate change. Improvements in toxin detection methods and increased toxin surveillance programmes are positive developments in limiting human exposure to shellfish toxins.

  14. Antiproliferative effect of the jararhagin toxin on B16F10 murine melanoma.

    Science.gov (United States)

    Maria, Durvanei Augusto; da Silva, Manuela Garcia Laveli; Correia Junior, Mario Cesar; Ruiz, Itamar Romano Garcia

    2014-11-18

    Malignant melanoma is a less common but highly dangerous form of skin cancer; it starts in the melanocytes cells found in the outer layer of the skin. Jararhagin toxin, a metalloproteinase isolated from Bothrops jararaca snake venom acts upon several biological processes, as inflammation, pain, platelet aggregation, proliferation and apoptosis, though not yet approved for use, may one day be employed to treat tumors. B16F10 murine melanoma cells were treated with jararhagin (jara), a disintegrin-like metalloproteinase isolated from Bothrops jararaca snake venom, and jari (catalytic domain inactivated with 1,10-phenanthroline). Viability and adhesion cells were evaluated by MTT assay. The expression of caspase-3 active, phases of the cell cycle and apoptosis were assessed by flow cytometry. We analyze in vivo the effects of jararhagin on melanoma growth, apoptosis and metastasis. The tumor cells acquired round shapes, lost cytoplasmic expansions, formed clusters in suspension and decreased viability. Jari was almost 20 times more potent toxin than jara based on IC50 values and on morphological changes of the cells, also observed by scanning electron microscopy. Flow cytometry analysis showed 48.3% decrease in the proliferation rate of cells and 47.2% increase in apoptosis (jara) and necrosis (jari), following 1.2 μM jara and 0.1 μM jari treatments. Caspase-3 activity was increased whereas G0/G1 cell cycle phase was on the decline. Proliferative rate was assessed by staining with 5,6-carboxyfluoresceindiacetate succinimidyl ester, showing a significant decrease in proliferation at all concentrations of both toxins. In vivo treatment of the toxins was observed reduction in the incidence of nodules, and metastasis and antiproliferative inhibition capacity. This data strengthens the potential use jararhagin as an anti-neoplastic drug.

  15. 42 CFR 73.4 - Overlap select agents and toxins.

    Science.gov (United States)

    2010-10-01

    ... Equine Encephalitis virus (c) Genetic Elements, Recombinant Nucleic Acids, and Recombinant Organisms: (1... occurring environment provided that the select agent or toxin has not been intentionally introduced... toxin against theft, loss, or release, and reports any theft, loss, or release of such agent or toxin...

  16. Cholera toxin B subunit induces local curvature on lipid bilayers

    DEFF Research Database (Denmark)

    Pezeshkian, Weria; Nåbo, Lina J.; Ipsen, John H.

    2017-01-01

    The B subunit of the bacterial cholera toxin (CTxB) is responsible for the toxin binding to the cell membrane and its intracellular trafficking. CTxB binds to the monosialotetrahexosyl ganglioside at the plasma membrane of the target cell and mediates toxin internalization by endocytosis. CTx...

  17. 77 FR 9888 - Shiga Toxin-Producing Escherichia coli

    Science.gov (United States)

    2012-02-21

    ... Food Safety and Inspection Service Shiga Toxin-Producing Escherichia coli in Certain Raw Beef Products... manufacturing trimmings for six non-O157 Shiga toxin-producing Escherichia coli (STEC) serogroups (O26, O45..., non-intact product, that are contaminated with Shiga toxin-producing Escherichia coli (STEC) O26, O45...

  18. Bacterial protein toxins : tools to study mammalian molecular cell biology

    NARCIS (Netherlands)

    Wüthrich, I.W.

    2014-01-01

    Bacterial protein toxins are genetically encoded proteinaceous macromolecules that upon exposure causes perturbation of cellular metabolism in a susceptible host. A bacterial toxin can work at a distance from the site of infection, and has direct and quantifiable actions. Bacterial protein toxins

  19. EFFECTS OF MARINE ALGAL TOXINS ON THERMOREGULATION IN MICE.

    Science.gov (United States)

    Hypothermia is often seen in mice and rats exposed acutely to marine algal toxins, but the mechanism of action of these toxins on thermoregulation is not well understood. Our laboratory has assessed the thermoregulatory mechanisms of two marine algal toxins, maitotoxin and brevet...

  20. Reduction of caudal traction force using dural sac opening rather than spinal cord detethering for tethered cord syndrome caused by lipomyelomeningocele: a case report.

    Science.gov (United States)

    Murata, Yasuaki; Kanaya, Kohichi; Wada, Hiroyoshi; Wada, Keiji; Shiba, Masahiro; Kato, Yoshiharu

    2014-10-01

    A few reports have addressed tethered cord syndrome. Detethering surgery has been performed in these cases because abnormal tension on the spinal cord causes neurologic and urologic symptoms. To discuss the surgical treatment of tethered cord syndrome with the belief that the tension on the cord can be decreased by shifting tethered cord to the dorsal side. A patient with tethered cord syndrome was surgically treated by shifting the tethered cord to the dorsal side by harnessing the lumbar lordosis instead of detethering. We performed surgery to shift the tethered cord to the dorsal side by harnessing the lumbar lordosis to decrease the tension on the spinal cord. The tethered cord that was pressed to the ventral side because of a lipoma was shifted dorsally by laminectomy and opening of the dural sac. Pain and numbness were alleviated immediately after surgery. The method used in the present case, that is, shifting the tethered cord and lipoma to the dorsal side by harnessing the lumbar lordosis instead of detethering, is a viable treatment option for tethered cord syndrome. Copyright © 2014 Elsevier Inc. All rights reserved.

  1. Molecular basis for tetanus toxin coreceptor interactions.

    Science.gov (United States)

    Chen, Chen; Baldwin, Michael R; Barbieri, Joseph T

    2008-07-08

    Tetanus toxin (TeNT) elicits spastic paralysis through the cleavage of vesicle-associated membrane protein-2 (VAMP-2) in neurons at the interneuronal junction of the central nervous system. While TeNT retrograde traffics from peripheral nerve endings to the interneuronal junction, there is limited understanding of the neuronal receptors utilized by tetanus toxin for the initial entry into nerve cells. Earlier studies implicated a coreceptor for tetanus toxin entry into neurons: a ganglioside binding pocket and a sialic acid binding pocket and that GT1b bound to each pocket. In this study, a solid phase assay characterized the ganglioside binding specificity and functional properties of both carbohydrate binding pockets of TeNT. The ganglioside binding pocket recognized the ganglioside sugar backbone, Gal-GalNAc, independent of sialic acid-(5) and sialic acid-(7) and GM1a was an optimal substrate for this pocket, while the sialic acid binding pocket recognized sialic acid-(5) and sialic acid-(7) with "b"series of gangliosides preferred relative to "a" series gangliosides. The high-affinity binding of gangliosides to TeNT HCR required functional ganglioside and sialic acid binding pockets, supporting synergistic binding to coreceptors. This analysis provides a model for how tetanus toxin utilizes coreceptors for high-affinity binding to neurons.

  2. Toxins of molds from decaying tomato fruit.

    Science.gov (United States)

    Harwig, J; Scott, P M; Stoltz, D R; Blanchfield, B J

    1979-01-01

    Among 27 mold isolates from decaying tomatoes, culture filtrates or ethyl acetate extracts of 8 isolates grown in yeast extract-sucrose medium were markedly toxic (mortality, greater than 50%) to brine shrimp larvae. The toxicity of six of these isolates could be attributed to the presence of citrinin, tenuazonic acid, or T-2 toxin. Ethyl acetate extracts of five Alternaria isolates and one Fusarium isolate were mutagenic for Salmonella typhimurium strains. In ripe tomatoes inoculated with toxin-producing isolates and incubated at 25 degrees C, one Alternaria alternata isolate produced tenuazonic acid in seven of seven tomatoes at levels of up to 106 micrograms/g and alternariol methyl ether in one of the seven tomatoes at 0.8 microgram/g. Another A. alternata isolate produced tenuazonic acid or alternariol methyl ether at much lower levels in only three of seven tomatoes. Patulin and citrinin were produced by a Penicillium expansum isolate at levels of up to 8.4 and 0.76 microgram/g, respectively. In tomatoes incubated at 15 degrees C, a Fusarium sulphureum isolate produced T-2 toxin, HT-2 toxin, and neosolaniol at levels of up to 37.5, 37.8 and 5.6 micrograms/g, respectively. If these mycotoxins are thermostable, they may occur at detectable levels in tomato products whenever partially moldy tomatoes are used as raw material. PMID:391152

  3. Okadaic Acid: More than a Diarrheic Toxin

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    Josefina Méndez

    2013-10-01

    Full Text Available Okadaic acid (OA is one of the most frequent and worldwide distributed marine toxins. It is easily accumulated by shellfish, mainly bivalve mollusks and fish, and, subsequently, can be consumed by humans causing alimentary intoxications. OA is the main representative diarrheic shellfish poisoning (DSP toxin and its ingestion induces gastrointestinal symptoms, although it is not considered lethal. At the molecular level, OA is a specific inhibitor of several types of serine/threonine protein phosphatases and a tumor promoter in animal carcinogenesis experiments. In the last few decades, the potential toxic effects of OA, beyond its role as a DSP toxin, have been investigated in a number of studies. Alterations in DNA and cellular components, as well as effects on immune and nervous system, and even on embryonic development, have been increasingly reported. In this manuscript, results from all these studies are compiled and reviewed to clarify the role of this toxin not only as a DSP inductor but also as cause of alterations at the cellular and molecular levels, and to highlight the relevance of biomonitoring its effects on human health. Despite further investigations are required to elucidate OA mechanisms of action, toxicokinetics, and harmful effects, there are enough evidences illustrating its toxicity, not related to DSP induction, and, consequently, supporting a revision of the current regulation on OA levels in food.

  4. Immunogenicity of toxins during Staphylococcus aureus infection

    NARCIS (Netherlands)

    N.J. Verkaik (Nelianne); O. Dauwalder (Olivier); K. Antri (Kenza); I. Boubekri (Ilhem); C.P. de Vogel (Corné); C. Badiou (Cédric); M. Bes (Michèle); F. Vandenesch (François); M. Tazir (Mohammed); H. Hooijkaas (Herbert); H.A. Verbrugh (Henri); A.F. van Belkum (Alex); J. Etienne (Jerome); G. Lina (Gérard); N. Ramdani-Bouguessa (Nadjia); W.J.B. van Wamel (Willem)

    2010-01-01

    textabstractAB - BACKGROUND: Toxins are important Staphylococcus aureus virulence factors, but little is known about their immunogenicity during infection. Here, additional insight is generated. METHODS: Serum samples from 206 S. aureus-infected patients and 201 hospital-admitted control subjects

  5. Shiga toxin-producing Escherichia coli

    DEFF Research Database (Denmark)

    Pedersen, Rune Micha; Nielsen, Marc Trunjer Kusk; Möller, Sören

    2018-01-01

    OBJECTIVES: Shiga toxin-producing Escherichia coli (STEC) causes diarrhoeal disease, bloody diarrhoea and haemolytic uraemic syndrome. The aim of this study was to describe the incidence of STEC and the clinical features of STEC patients from a well-defined Danish population in which all fecal...

  6. Protein-bound toxins: has the Cinderella of uraemic toxins turned into a princess?

    Science.gov (United States)

    Liabeuf, Sophie; Villain, Cédric; Massy, Ziad A

    2016-12-01

    Chronic kidney disease (CKD) has emerged as a global public health problem. Although the incidence and prevalence of CKD vary from one country to another, the estimated worldwide prevalence is 8-16%. The complications associated with CKD include progression to end-stage renal disease (ESRD), mineral and bone disorders, anaemia, cognitive decline and elevated all-cause and cardiovascular (CV) mortality. As a result of progressive nephron loss, patients with late-stage CKD are permanently exposed to uraemic toxins. These toxins have been classified into three groups as a function of the molecular mass: small water-soluble molecules, middle molecules and protein-bound uraemic toxins. The compounds can also be classified according to their origin (i.e. microbial or not) or their protein-binding ability. The present review will focus on the best-characterized protein-bound uraemic toxins, namely indoxylsulfate (IS), indole acetic acid (IAA) and p-cresylsulfate (PCS, a cresol metabolite). Recent research suggests that these toxins accelerate the progression of CV disease, kidney disease, bone disorders and neurological complications. Lastly, we review therapeutic approaches that can be used to decrease toxin levels. © 2016 The Author(s). published by Portland Press Limited on behalf of the Biochemical Society.

  7. Radiation induced changes in alpha toxin of Staphylococcus aureus 3750

    Energy Technology Data Exchange (ETDEWEB)

    Sherekar, S.V.; Bhushan, B.; Gore, M.S. (Bhabha Atomic Research Centre, Bombay (India). Biochemistry and Food Technology Div.)

    1981-06-01

    Influence of ..gamma..-radiation and heat on haemolytic activity of purified alpha toxin from staphylococcus aureus 3750 cells was studied. Heat treatment at 60deg C for 1 min resulted in 99% inactivation of alpha toxin, while exposure to ..gamma..-radiation caused linear decline in activity, 40 krad causing 50% inactivation. Urea treatment reversed the heat induced inactivation but did not reactivate the irradiated toxin. However, the irradiated toxin retained its antigenicity, thus indicating its potential for the preparation of toxoid against alpha toxin.

  8. General Aspects and Recent Advances on Bacterial Protein Toxins

    Science.gov (United States)

    Lemichez, Emmanuel; Barbieri, Joseph T.

    2013-01-01

    Bacterial pathogens produce protein toxins to influence host–pathogen interactions and tip the outcome of these encounters toward the benefit of the pathogen. Protein toxins modify host-specific targets through posttranslational modifications (PTMs) or noncovalent interactions that may inhibit or activate host cell physiology to benefit the pathogen. Recent advances have identified new PTMs and host targets for toxin action. Understanding the mechanisms of toxin action provides a basis to develop vaccines and therapies to combat bacterial pathogens and to develop new strategies to use toxin derivatives for the treatment of human disease. PMID:23378599

  9. Characterization of Hemagglutinin Negative Botulinum Progenitor Toxins

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    Suzanne R. Kalb

    2017-06-01

    Full Text Available Botulism is a disease involving intoxication with botulinum neurotoxins (BoNTs, toxic proteins produced by Clostridium botulinum and other clostridia. The 150 kDa neurotoxin is produced in conjunction with other proteins to form the botulinum progenitor toxin complex (PTC, alternating in size from 300 kDa to 500 kDa. These progenitor complexes can be classified into hemagglutinin positive or hemagglutinin negative, depending on the ability of some of the neurotoxin-associated proteins (NAPs to cause hemagglutination. The hemagglutinin positive progenitor toxin complex consists of BoNT, nontoxic non-hemagglutinin (NTNH, and three hemagglutinin proteins; HA-70, HA-33, and HA-17. Hemagglutinin negative progenitor toxin complexes contain BoNT and NTNH as the minimally functional PTC (M-PTC, but not the three hemagglutinin proteins. Interestingly, the genome of hemagglutinin negative progenitor toxin complexes comprises open reading frames (orfs which encode for three proteins, but the existence of these proteins has not yet been extensively demonstrated. In this work, we demonstrate that these three proteins exist and form part of the PTC for hemagglutinin negative complexes. Several hemagglutinin negative strains producing BoNT/A, /E, and /F were found to contain the three open reading frame proteins. Additionally, several BoNT/A-containing bivalent strains were examined, and NAPs from both genes, including the open reading frame proteins, were associated with BoNT/A. The open reading frame encoded proteins are more easily removed from the botulinum complex than the hemagglutinin proteins, but are present in several BoNT/A and /F toxin preparations. These are not easily removed from the BoNT/E complex, however, and are present even in commercially-available purified BoNT/E complex.

  10. Differential neutralizing activities of a single domain camelid antibody (VHH specific for ricin toxin's binding subunit (RTB.

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    Cristina Herrera

    Full Text Available Ricin, a member of the A-B family of ribosome-inactivating proteins, is classified as a Select Toxin by the Centers for Disease Control and Prevention because of its potential use as a biothreat agent. In an effort to engineer therapeutics for ricin, we recently produced a collection of alpaca-derived, heavy-chain only antibody VH domains (VHH or "nanobody" specific for ricin's enzymatic (RTA and binding (RTB subunits. We reported that one particular RTB-specific VHH, RTB-B7, when covalently linked via a peptide spacer to different RTA-specific VHHs, resulted in heterodimers like VHH D10/B7 that were capable of passively protecting mice against a lethal dose challenge with ricin. However, RTB-B7 itself, when mixed with ricin at a 1 ∶ 10 toxin:antibody ratio did not afford any protection in vivo, even though it had demonstrable toxin-neutralizing activity in vitro. To better define the specific attributes of antibodies associated with ricin neutralization in vitro and in vivo, we undertook a more thorough characterization of RTB-B7. We report that RTB-B7, even at 100-fold molar excess (toxin:antibody was unable to alter the toxicity of ricin in a mouse model. On the other hand, in two well-established cytotoxicity assays, RTB-B7 neutralized ricin with a 50% inhibitory concentration (IC50 that was equivalent to that of 24B11, a well-characterized and potent RTB-specific murine monoclonal antibody. In fact, RTB-B7 and 24B11 were virtually identical when compared across a series of in vitro assays, including adherence to and neutralization of ricin after the toxin was pre-bound to cell surface receptors. RTB-B7 differed from both 24B11 and VHH D10/B7 in that it was relatively less effective at blocking ricin attachment to receptors on host cells and was not able to form high molecular weight toxin:antibody complexes in solution. Whether either of these activities is important in ricin toxin neutralizing activity in vivo remains to be determined.

  11. Tether-directed synthesis of highly substituted oxasilacycles via an intramolecular allylation employing allylsilanes

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    Cox Liam R

    2007-02-01

    Full Text Available Abstract Background Using a silyl tether to unite an aldehyde electrophile and allylsilane nucleophile into a single molecule allows a subsequent Lewis-acid-mediated allylation to proceed in an intramolecular sense and therefore receive all the benefits associated with such processes. However, with the ability to cleave the tether post allylation, a product that is the result of a net intermolecular reaction can be obtained. In the present study, four diastereoisomeric β-silyloxy-α-methyl aldehydes, which contain an allylsilane tethered through the β-carbinol centre, have been prepared, in order to probe how the relative configuration of the two stereogenic centres affects the efficiency and selectivity of the intramolecular allylation. Results Syn-aldehydes, syn-4a and syn-4b, both react poorly, affording all four possible diastereoisomeric oxasilacycle products. In contrast, the anti aldehydes anti-4a and anti-4b react analogously to substrates that lack substitution at the α-site, affording only two of the four possible allylation products. Conclusion The outcome of the reaction with anti-aldehydes is in accord with reaction proceeding through a chair-like transition state (T.S.. In these systems, the sense of 1,3-stereoinduction can be rationalised by the aldehyde electrophile adopting a pseudoaxial orientation, which will minimise dipole-dipole interactions in the T.S. The 1,4-stereoinduction in these substrates is modest and seems to be modulated by the R substituent in the starting material. In the case of the syn-substrates, cyclisation through a chair T.S. is unlikely as this would require the methyl substituent α to the reacting carbonyl group to adopt an unfavourable pseudoaxial position. It is therefore proposed that these substrates react through poorly-defined T.S.s and consequently exhibit essentially no stereoselectivity.

  12. Role of Double-Strand Break End-Tethering during Gene Conversion in Saccharomyces cerevisiae

    Science.gov (United States)

    Haber, James E.

    2016-01-01

    Correct repair of DNA double-strand breaks (DSBs) is critical for maintaining genome stability. Whereas gene conversion (GC)-mediated repair is mostly error-free, repair by break-induced replication (BIR) is associated with non-reciprocal translocations and loss of heterozygosity. We have previously shown that a Recombination Execution Checkpoint (REC) mediates this competition by preventing the BIR pathway from acting on DSBs that can be repaired by GC. Here, we asked if the REC can also determine whether the ends that are engaged in a GC-compatible configuration belong to the same break, since repair involving ends from different breaks will produce potentially deleterious translocations. We report that the kinetics of repair are markedly delayed when the two DSB ends that participate in GC belong to different DSBs (termed Trans) compared to the case when both DSB ends come from the same break (Cis). However, repair in Trans still occurs by GC rather than BIR, and the overall efficiency of repair is comparable. Hence, the REC is not sensitive to the “origin” of the DSB ends. When the homologous ends for GC are in Trans, the delay in repair appears to reflect their tethering to sequences on the other side of the DSB that themselves recombine with other genomic locations with which they share sequence homology. These data support previous observations that the two ends of a DSB are usually tethered to each other and that this tethering facilitates both ends encountering the same donor sequence. We also found that the presence of homeologous/repetitive sequences in the vicinity of a DSB can distract the DSB end from finding its bona fide homologous donor, and that inhibition of GC by such homeologous sequences is markedly increased upon deleting Sgs1 but not Msh6. PMID:27074148

  13. EVIDENCE FOR SOLAR TETHER-CUTTING MAGNETIC RECONNECTION FROM CORONAL FIELD EXTRAPOLATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chang; Deng, Na; Lee, Jeongwoo; Wang, Haimin [Space Weather Research Laboratory, Center for Solar-Terrestrial Research, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States); Wiegelmann, Thomas [Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Strasse 2, D-37191 Katlenburg-Lindau (Germany); Moore, Ronald L., E-mail: chang.liu@njit.edu [Heliophysics and Planetary Science Office, ZP13, Marshall Space Flight Center, Huntsville, AL 35812-9900 (United States)

    2013-12-01

    Magnetic reconnection is one of the primary mechanisms for triggering solar eruptive events, but direct observation of this rapid process has been a challenge. In this Letter, using a nonlinear force-free field (NLFFF) extrapolation technique, we present a visualization of field line connectivity changes resulting from tether-cutting reconnection over about 30 minutes during the 2011 February 13 M6.6 flare in NOAA AR 11158. Evidence for the tether-cutting reconnection was first collected through multiwavelength observations and then by analysis of the field lines traced from positions of four conspicuous flare 1700 Å footpoints observed at the event onset. Right before the flare, the four footpoints are located very close to the regions of local maxima of the magnetic twist index. In particular, the field lines from the inner two footpoints form two strongly twisted flux bundles (up to ∼1.2 turns), which shear past each other and reach out close to the outer two footpoints, respectively. Immediately after the flare, the twist index of regions around the footpoints diminishes greatly and the above field lines become low-lying and less twisted (≲0.6 turns), overarched by loops linking the two flare ribbons formed later. About 10% of the flux (∼3 × 10{sup 19} Mx) from the inner footpoints undergoes a footpoint exchange. This portion of flux originates from the edge regions of the inner footpoints that are brightened first. These rapid changes of magnetic field connectivity inferred from the NLFFF extrapolation are consistent with the tether-cutting magnetic reconnection model.

  14. Feasibility Study of Space Based Solar Power to Tethered Aerostat Systems

    Science.gov (United States)

    Blank, Stephen J.; Leete, Stephen J.; Jaffe, Paul

    2013-01-01

    The feasibility of two-stage Space-Based Solar Power to Tethered Aerostat to Earth (SSP-TA) system architectures that offer significant advantages over conventional single stage space-to-earth architectures is being studied. There have been many proposals for the transmission of solar power collected in space to the surface of the earth so that solar energy could provide a major part of the electric power requirements on earth. There are, however, serious difficulties in implementing the single stage space-based solar power systems that have been previously studied. These difficulties arise due to: i) the cost of transporting the components needed for the extremely large microwave transmit beaming aperture into space orbit, ii) the even larger collection apertures required on earth, iii) the potential radiation hazard to personnel and equipment on earth, and iv) a lack of flexibility in location of the collection station on the earth. Two candidate system architectures are described here to overcome these difficulties. In both cases a two-stage space to tethered aerostat to earth transmission system (SSP-TA) is proposed. The use of high altitude tethered aerostats (or powered airships) avoids the effects of attenuation of EM energy propagating through the earth s lower atmosphere. This allows the use of beaming frequencies to be chosen from the range of high millimeter (THz) to near-infra-red (NIR) to the visible. This has the potential for: i) greatly reduced transportation costs to space, ii) much smaller receiver collection apertures and ground stations, iii) elimination of the potential radiation hazard to personnel and equipment on earth, and iv) ease in transportation and flexibility in location of the collection station on the earth. A preliminary comparison of system performance and efficiencies is presented.

  15. Role of Double-Strand Break End-Tethering during Gene Conversion in Saccharomyces cerevisiae.

    Directory of Open Access Journals (Sweden)

    Suvi Jain

    2016-04-01

    Full Text Available Correct repair of DNA double-strand breaks (DSBs is critical for maintaining genome stability. Whereas gene conversion (GC-mediated repair is mostly error-free, repair by break-induced replication (BIR is associated with non-reciprocal translocations and loss of heterozygosity. We have previously shown that a Recombination Execution Checkpoint (REC mediates this competition by preventing the BIR pathway from acting on DSBs that can be repaired by GC. Here, we asked if the REC can also determine whether the ends that are engaged in a GC-compatible configuration belong to the same break, since repair involving ends from different breaks will produce potentially deleterious translocations. We report that the kinetics of repair are markedly delayed when the two DSB ends that participate in GC belong to different DSBs (termed Trans compared to the case when both DSB ends come from the same break (Cis. However, repair in Trans still occurs by GC rather than BIR, and the overall efficiency of repair is comparable. Hence, the REC is not sensitive to the "origin" of the DSB ends. When the homologous ends for GC are in Trans, the delay in repair appears to reflect their tethering to sequences on the other side of the DSB that themselves recombine with other genomic locations with which they share sequence homology. These data support previous observations that the two ends of a DSB are usually tethered to each other and that this tethering facilitates both ends encountering the same donor sequence. We also found that the presence of homeologous/repetitive sequences in the vicinity of a DSB can distract the DSB end from finding its bona fide homologous donor, and that inhibition of GC by such homeologous sequences is markedly increased upon deleting Sgs1 but not Msh6.

  16. Management of concomitant scoliosis and tethered cord syndrome in non-spina bifida pediatric population.

    Science.gov (United States)

    Yaltırık, Kaan; El Tecle, Najib E; Pierson, Matthew J; Puryear, Aki; Atalay, Basar; Elbabaa, Samer K

    2017-11-01

    The management of concomitant scoliosis and tethered cord syndrome in the non-spina bifida pediatric population is challenging. In the present study, we evaluate the efficacy of different treatment modalities and propose a treatment plan for the management of affected patients. A systematic literature review was conducted by querying the MEDLINE, PubMed, Cochrane, EMBASE, Scopus, and Web of Science databases for papers published between January 1996 and June 2016 and reporting on concomitant scoliosis and tethered cord. We excluded animal studies, non-English papers as well as papers reporting on patients with multiple concomitant intraspinal anomalies such as spina bifida. Out of 1993 articles, only 13 met our inclusion criteria. These 13 articles described six main management approaches: Observation, cord untethering only, cord untethering followed by deformity correction, simultaneous cord untethering and deformity correction, and deformity correction without untethering. Selection of the best approach is a function of the patient's symptomatology and Cobb angle. We propose treatment plan for the management of patients with concomitant tethered cord syndrome and spinal deformity. Asymptomatic patients can be followed conservatively and managed as scoliosis patients with no need for untethering. Surgical management in a staged fashion seems appropriate in symptomatic patients with a Cobb angle less than 35°. In these patients, deformity can improve following untethering, thus sparing the patient the risks of surgical correction of scoliosis. Staged or non-staged cord untethering and curve correction seem to be adequate in symptomatic patients with Cobb angle >35° as these patients are likely to require both untethering and deformity correction.

  17. Discovery of novel bacterial toxins by genomics and computational biology.

    Science.gov (United States)

    Doxey, Andrew C; Mansfield, Michael J; Montecucco, Cesare

    2018-02-10

    Hundreds and hundreds of bacterial protein toxins are presently known. Traditionally, toxin identification begins with pathological studies of bacterial infectious disease. Following identification and cultivation of a bacterial pathogen, the protein toxin is purified from the culture medium and its pathogenic activity is studied using the methods of biochemistry and structural biology, cell biology, tissue and organ biology, and appropriate animal models, supplemented by bioimaging techniques. The ongoing and explosive development of high-throughput DNA sequencing and bioinformatic approaches have set in motion a revolution in many fields of biology, including microbiology. One consequence is that genes encoding novel bacterial toxins can be identified by bioinformatic and computational methods based on previous knowledge accumulated from studies of the biology and pathology of thousands of known bacterial protein toxins. Starting from the paradigmatic cases of diphtheria toxin, tetanus and botulinum neurotoxins, this review discusses traditional experimental approaches as well as bioinformatics and genomics-driven approaches that facilitate the discovery of novel bacterial toxins. We discuss recent work on the identification of novel botulinum-like toxins from genera such as Weissella, Chryseobacterium, and Enteroccocus, and the implications of these computationally identified toxins in the field. Finally, we discuss the promise of metagenomics in the discovery of novel toxins and their ecological niches, and present data suggesting the existence of uncharacterized, botulinum-like toxin genes in insect gut metagenomes. Copyright © 2018. Published by Elsevier Ltd.

  18. In Vivo

    Science.gov (United States)

    Lau, Melissa; Li, Jianli; Cline, Hollis T

    2017-01-01

    The neurovascular niche is a specialized microenvironment formed by the interactions between neural progenitor cells (NPCs) and the vasculature. While it is thought to regulate adult neurogenesis by signaling through vascular-derived soluble cues or contacted-mediated cues, less is known about the neurovascular niche during development. In Xenopus laevis tadpole brain, NPCs line the ventricle and extend radial processes tipped with endfeet to the vascularized pial surface. Using in vivo labeling and time-lapse imaging in tadpoles, we find that intracardial injection of fluorescent tracers rapidly labels Sox2/3-expressing NPCs and that vascular-circulating molecules are endocytosed by NPC endfeet. Confocal imaging indicates that about half of the endfeet appear to appose the vasculature, and time-lapse analysis of NPC proliferation and endfeet-vascular interactions suggest that proliferative activity does not correlate with stable vascular apposition. Together, these findings characterize the neurovascular niche in the developing brain and suggest that, while signaling to NPCs may occur through vascular-derived soluble cues, stable contact between NPC endfeet and the vasculature is not required for developmental neurogenesis.

  19. IN VIVO

    Science.gov (United States)

    Jamila, Nargis; Khan, Naeem; Khan, Amir Atlas; Khan, Imran; Khan, Sadiq Noor; Zakaria, Zainal Amiruddin; Khairuddean, Melati; Osman, Hasnah; Kim, Kyong Su

    2017-01-01

    Garcinia hombroniana , known as "manggis hutan" (jungle mangosteen) in Malaysia, is distributed in tropical Asia, Borneo, Thailand, Andaman, Nicobar Islands, Vietnam and India. In Malaysia, its ripened crimson sour fruit rind is used as a seasoning agent in curries and culinary dishes. Its roots and leaves decoction is used against skin infections and after child birth. This study aimed to evaluate in vivo hepatoprotective and in vitro cytotoxic activities of 20% methanolic ethyl acetate (MEA) G. hombroniana bark extract. In hepatoprotective activity, liver damage was induced by treating rats with 1.0 mL carbon tetrachloride (CCl 4 )/kg and MEA extract was administered at a dose of 50, 250 and 500 mg/kg 24 h before intoxication with CCl 4 . Cytotoxicity study was performed on MCF-7 (human breast cancer), DBTRG (human glioblastoma), PC-3 (human prostate cancer) and U2OS (human osteosarcoma) cell lines. 1 H, 13 C-NMR (nuclear magnetic resonance), and IR (infrared) spectral analyses were also conducted for MEA extract. In hepatoprotective activity evaluation, MEA extract at a higher dose level of 500 mg/kg showed significant (pIR spectra exhibited bands, signals and J (coupling constant) values representing aromatic/phenolic constituents. From the results, it could be concluded that MEA extract has potency to inhibit hepatotoxicity and MCF-7 and DBTRG cancer cell lines which might be due to the phenolic compounds depicted from NMR and IR spectra.

  20. Botulinum toxin for treatment of blepharospasm and hemifacial spasm

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    Soltanzadeh A

    1997-04-01

    Full Text Available Botulinum toxin produced by Clostridium butolinum in one of the most fatal toxins known. Botulism is the name given to condition produced by this toxin. In recent years the diluted form of this toxin has been produced in injection form and used for treatment of hemifacial spasm and blepharospasm. This toxin blocks neuromuscular junction and inhibits acetylcholine release. In this article we reported 36 patients suffering from hemifacial & blepharospasm treated by injections of botulinum A toxin. 85 to 90 percent of patients responded well. The common complications of this drug were ptosis, hemifacial paresis, burning of the mouth and discoloration of the injection site. Generally speaking the patients preferred this toxin to taking oral medications which were less effective.