Academic literature on the topic 'Fibronectin fibers'
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Journal articles on the topic "Fibronectin fibers"
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Christopher, R. A., A. P. Kowalczyk, and P. J. McKeown-Longo. "Localization of fibronectin matrix assembly sites on fibroblasts and endothelial cells." Journal of Cell Science 110, no. 5 (March 1, 1997): 569–81. http://dx.doi.org/10.1242/jcs.110.5.569.
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Polymerization of soluble fibronectin into extracellular matrix fibers occurs through the interaction between the amino terminus of fibronectin contained within a 70 kDa fragment and ‘matrix assembly sites’ on the cell surface. The present studies were performed to localize the ‘matrix assembly sites’ (defined by 70 kDa binding sites) on newly adherent cells and on cells containing preformed fibronectin matrix. Matrix nucleation sites on newly spread cells were visualized using Texas Red conjugated 70 kDa fragment and were found to colocalize with vinculin and substrate fibronectin fibrils. Cells plated onto vitronectin coated coverslips did not exhibit any 70 kDa binding sites although these cells were well-spread with fully developed focal adhesions. Time course studies indicated that 70 kDa binding sites could be detected on newly adherent cells within 30–40 minutes following cell plating onto fibronectin coated coverslips, prior to the reorganization of substrate fibronectin into fibrils. Similarly, exogenous fibronectin conjugated with Texas Red was also colocalized with vinculin when added to newly adherent cells. The disruption of actin filaments with cytochalasin D both prevented the expression of 70 kDa binding sites and also resulted in the loss of established 70 kDa binding sites on newly spread cells. After 3 days in culture, cells organized an extensive fibronectin matrix and 70 kDa was colocalized with two distinct types of matrix fibronectin fibers: fine linear cell-associated fibers which co-stained with the beta1 integrin and coarse extracellular fibers which did not stain for the beta1 integrin. There was also a third type of fibronectin fiber which was organized into a meshwork structure. There was no localization of either beta1 or 70 kDa to these structures. Treatment of 3-day cells with cytochalasin D resulted in the disruption of cell-matrix fibers and cell-associated 70 kDa binding sites. In contrast, the coarse extracellular matrix fibers as well as the meshwork fibers were unaffected by cytochalasin. In the presence of cytochalasin D, 70 kDa bound to sites which colocalized with the coarse extracellular matrix fibers. These data suggest that de novo assembly of fibronectin matrix occurs at sites of focal adhesion and as fibronectin polymerization proceeds, matrix nucleation sites colocalize along cell associated fibronectin fibers. At later times 70 kDa is localized to a subset of more mature fibronectin-containing fibers. These results suggest that there are at least three morphologically distinct 70 kDa binding sites on adherent cells: one which colocalizes with beta1 to focal adhesions, a second which colocalizes with beta1 and fibronectin in matrix contacts, and a third which localizes to extracellular matrix fibers.
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Ba, X., Y. Meng, Y. Huang, S. Y. Kwak, S. Ge, Y. Qin, E. DiMasi, Helga Füredi-Milhofer, N. Pernodet, and Miriam Rafailovich. "In Vitro Biomineralization Induced by Self-Assembled Extracellular Matrix Proteins." Key Engineering Materials 361-363 (November 2007): 427–30. http://dx.doi.org/10.4028/www.scientific.net/kem.361-363.427.
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Extracellular matrix (ECM) proteins play an essential role during biomineralization in bone and engineered tissues. In a previous study [1], we showed that calcite preferentially nucleated on pure elastin fibers. However, the actual cellular ECM fibers are composed of a combination of proteins, primarily collagen, fibronectin and some elastin. Here we follow the calcium carbonate- and calcium phosphate- mineralization process in vitro when these ECM proteins are combined and determine the differences between these proteins in the biomineralization process. The surface morphology and mechanical properties of the protein fibers during the early stages were probed by atomic force microscopy (AFM) and shear modulation force microscopy (SMFM). The nucleation of the mineral crystals on the protein matrices was investigated by scanning electron microscopy (SEM). Preliminary data showed that the moduli of all protein fibers increased at the early stages, with collagen having the largest increase in supersaturated calcium bicarbonate solution. In metastable calcium phosphate solutions the modulus of the mixed elastin-fibronectin fibres increased to a greater extent than the moduli of the fibers composed of the single proteins. Longer exposure in the mineral solutions led to the formation of crystals templated along the self-assembled fiber structures.
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Echtermeyer, F., P. C. Baciu, S. Saoncella, Y. Ge, and P. F. Goetinck. "Syndecan-4 core protein is sufficient for the assembly of focal adhesions and actin stress fibers." Journal of Cell Science 112, no. 20 (October 15, 1999): 3433–41. http://dx.doi.org/10.1242/jcs.112.20.3433.
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The formation of focal adhesions and actin stress fibers on fibronectin is dependent on signaling through (β)1 integrins and the heparan sulfate proteoglycan syndecan-4, and we have analyzed the requirement of the glycosaminoglycan chains of syndecan-4 during these events. Chinese hamster ovary cells with mutations in key enzymes of the glycanation process do not synthesize glycosaminoglycan chains and are unable to assemble actin stress fibers and focal contacts when cultured on fibronectin. Transfection of the mutant cells with a cDNA that encodes the core protein of chicken syndecan-4 leads to the production of unglycanated core protein. The overexpression of syndecan-4 core protein in these mutant cells increases cell spreading and is sufficient for these cells to assemble actin stress fibers and focal adhesions similar to wild-type cells seeded on fibronectin and vitronectin matrices. Syndecan-4 core protein colocalizes to focal contacts in mutant cells that have been transfected with the syndecan-4 core protein cDNA. These data indicate an essential role for the core protein of syndecan-4 in the generation of signals leading to actin stress fiber and focal contact assembly.
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Flück, Martin, Matthias Chiquet, Silvia Schmutz, Marie-Hélène Mayet-Sornay, and Dominique Desplanches. "Reloading of atrophied rat soleus muscle induces tenascin-C expression around damaged muscle fibers." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 284, no. 3 (March 1, 2003): R792—R801. http://dx.doi.org/10.1152/ajpregu.00060.2002.
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The hypothesis was tested that mechanical loading, induced by hindlimb suspension and subsequent reloading, affects expression of the basement membrane components tenascin-C and fibronectin in the belly portion of rat soleus muscle. One day of reloading, but not the previous 14 days of hindlimb suspension, led to ectopic accumulation of tenascin-C and an increase of fibronectin in the endomysium of a proportion (8 and 15%) of muscle fibers. Large increases of tenascin-C (40-fold) and fibronectin (7-fold) mRNA within 1 day of reloading indicates the involvement of pretranslational mechanisms in tenascin-C and fibronectin accumulation. The endomysial accumulation of tenascin-C was maintained up to 14 days of reloading and was strongly associated with centrally nucleated fibers. The observations demonstrate that an unaccustomed increase of rat soleus muscle loading causes modification of the basement membrane of damaged muscle fibers through ectopic endomysial expression of tenascin-C.
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Dugina, Vera, Lionel Fontao, Christine Chaponnier, Jury Vasiliev, and Giulio Gabbiani. "Focal adhesion features during myofibroblastic differentiation are controlled by intracellular and extracellular factors." Journal of Cell Science 114, no. 18 (September 15, 2001): 3285–96. http://dx.doi.org/10.1242/jcs.114.18.3285.
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Transforming growth factor β (TGFβ), the most established promoter of myofibroblast differentiation, induces ED-A cellular fibronectin and α-smooth muscle actin expression in fibroblastic cells in vivo and in vitro. ED-A fibronectin exerts a permissive action for α-smooth muscle actin expression. A morphological continuity (called fibronexus), a specialized form of focal adhesion, has been described between actin stress fibers that contain α-smooth muscle actin, and extracellular fibronectin, which contains the ED-A portion, in both cultured fibroblasts and granulation tissue myofibroblasts. We have studied the development of these focal adhesions in TGFβ-treated fibroblasts using confocal laser scanning microscopy, three-dimensional image reconstruction and western blots using antibodies against focal adhesion proteins. The increase in ED-A fibronectin expression induced by TGFβ was accompanied by bundling of ED-A fibronectin fibers and their association with the terminal portion of α-smooth muscle actin-positive stress fibers. In parallel, the focal adhesion size was importantly increased, and tensin and FAK were neoexpressed in focal adhesions; moreover, vinculin and paxillin were recruited from the cytoplasmic pool into focal adhesions. We have evaluated morphometrically the length and area of focal adhesions. In addition, we have evaluated biochemically their content of associated proteins and of α-smooth muscle actin after TGFβ stimulation and on this basis suggest a new focal adhesion classification, that is, immature, mature and supermature.When TGFβ-induced α-smooth muscle actin expression was blocked by soluble recombinant ED-A fibronectin, we observed that the fragment was localised into the fibronectin network at the level of focal adhesions and that focal adhesion supermaturation was inhibited. The same effect was also exerted by the ED-A fibronectin antibody IST-9. In addition, the antagonists of actin-myosin contractility BDM and ML-7 provoked the dispersion of focal adhesions and the decrease of α-smooth muscle actin content in stress fibers of pulmonary fibroblasts, which constitutively show large focal adhesions and numerous stress fibers that contain α-smooth muscle actin. These inhibitors also decreased the incorporation of recombinant ED-A into fibronectin network. Our data indicate that a three-dimensional transcellular structure containing both ED-A fibronectin and α-smooth muscle actin plays an important role in the establishment and modulation of the myofibroblastic phenotype. The organisation of this structure is regulated by intracellularly and extracellularly originated forces.
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Morris, S. M., P. J. Stone, and G. L. Snider. "Electron microscopic study of human lung tissue after in vitro exposure to elastase." Journal of Histochemistry & Cytochemistry 41, no. 6 (June 1993): 851–66. http://dx.doi.org/10.1177/41.6.8315277.
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Much of the experimental evidence supporting the hypothesis that pulmonary emphysema results from an imbalance between elastases and anti-elastases in the lung comes from animal models. The present study was designed to examine the effects on human lung tissue of the two elastases that have been most widely used to produce these animal models. Lung tissue was exposed in vitro to human neutrophil elastase (HNE) or porcine pancreatic elastase (PPE). Although both enzymes solubilized protein at similar rates, PPE solubilized elastin five times faster than did HNE. Ultrastructurally, HNE-exposed tissue exhibited fewer damaged elastic fibers as well as some fibers that were damaged at the edges, whereas the interior of the fiber appeared intact. Elastic fibers showing damage only at the periphery were not seen in tissue exposed to PPE. Immunocytochemical studies in which antibodies to HNE and PPE were applied to thin sections of Lowicryl-embedded tissue indicated that both of these elastases could be detected in association with elastic fibers, but only in areas of the fiber that showed morphological evidence of elastase injury. Both HNE and PPE removed fibronectin from basement membranes (as determined by loss of binding of fibronectin antibodies after exposure to elastase), but neither elastase was detected on basement membrane. Loss of epithelial cells usually accompanied elastic fiber damage by HNE but not PPE.
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Moyano, José V., Alfredo Maqueda, Benito Casanova, and Angeles Garcia-Pardo. "α4β1 Integrin/Ligand Interaction Inhibits α5β1-induced Stress Fibers and Focal Adhesions via Down-Regulation of RhoA and Induces Melanoma Cell Migration." Molecular Biology of the Cell 14, no. 9 (September 2003): 3699–715. http://dx.doi.org/10.1091/mbc.e02-10-0667.
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We have studied the function of the Hep III fibronectin domain in the cytoskeletal response initiated by alpha5beta1 integrin-mediated adhesion. Melanoma cells formed stress fibers and focal adhesions on the RGD-containing FNIII7–10 fragment. Coimmobilization of FNIII4–5, a fragment spanning Hep III and containing the alpha4beta1 ligand H2 with FNIII7–10, or addition of soluble FNIII4–5 to cells preattached to FNIII7–10, inhibited stress fibers and induced cytoplasmic protrusions. This effect involved alpha4beta1 since: 1) mutations in H2 reverted the inhibition; 2) other alpha4beta1 ligands (CS-1, VCAM-1), an anti-alpha4 mAb, or alpha4 expression in HeLa cells inhibited stress fibers. This activity was apparently cryptic in fibronectin or large fibronectin fragments, but exposed upon proteolytic degradation. Indeed purified peptic fragments containing H2, inhibited stress fibers when mixed with FNIII7–10 or fibronectin. RhoA activation with LPA or transfection with V14RhoA reverted the inhibitory effect and induced stress fibers on FNIII7–10+FNIII4–5. Furthermore, addition of alpha4beta1 ligands to FNIII7–10, down-regulated RhoA and activated p190RhoGAP, which localized to cytoplasmic protrusions. alpha4beta1/ligand interaction induced cell migration, monitored by video microscopy and wound healing assays. These data indicate that alpha4beta1 provides an antagonistic signal to alpha5beta1 by interfering with the RhoA activation pathway and this leads to melanoma cell migration.
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Litvinov, R. I. "Prospects for therapeutic use of fibronectin preparations." Kazan medical journal 67, no. 5 (September 15, 1986): 391–97. http://dx.doi.org/10.17816/kazmj70725.
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Blood plasma fibronectin is a glycoprotein with a molecular weight of 450 kD consisting of two almost identical polypeptide chains linked by disulfide bonds. The normal concentration of fibronectin in adult plasma is 0.3-0.4 g/l. Plasma fibronectin is synthesized by hepatocytes and possibly by endothelial cells. In its chemical structure and immunological properties it is similar to tissue fibronectin, which is formed mainly by connective tissue cells and is a part of extracellular matrix and collagen fibers.
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Yoneda, Atsuko, Dmitriy Ushakov, Hinke A. B. Multhaupt, and John R. Couchman. "Fibronectin Matrix Assembly Requires Distinct Contributions from Rho Kinases I and -II." Molecular Biology of the Cell 18, no. 1 (January 2007): 66–75. http://dx.doi.org/10.1091/mbc.e06-08-0684.
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Extracellular matrix is integral to tissue architecture and regulates many aspects of cell behavior. Fibronectin matrix assembly involves the actin cytoskeleton and the small GTPase RhoA, but downstream signaling is not understood. Here, down-regulation of either rho kinase isoform (ROCK I or -II) by small interfering RNA treatment blocked fibronectin matrix assembly, although the phenotypes were distinct and despite persistence of the alternate kinase. Remnant fibronectin on ROCK-deficient fibroblasts was mostly punctate and more deoxycholate soluble compared with controls. Fibronectin matrix assembly defects in ROCK-deficient cells did not result from decreased synthesis/secretion, altered fibronectin mRNA splicing, metalloproteinase activity, or α5β1 integrin dysfunction. Rescue could be effected by ROCK protein restoration or phosphomimetic myosin light chain expression. However, the effect of ROCK I deficiency on fibronectin matrix assembly was secondary to altered cell surface morphology, rich in filopodia, resulting from high GTP–Cdc42 levels. Total internal reflection microscopy revealed that a submembranous pool of myosin light chain in control cells was missing in ROCK II-deficient cells and replaced by stress fibers. Together, two rho kinases contribute to fibronectin matrix assembly in a different manner and cortical myosin II-driven contractility, but not stress fibers, may be critical in this activity.
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Sugimoto, K., S. Fujii, T. Takemasa, and K. Yamashita. "Factors inducing codistribution of marginal actin fibers and fibronectin in rat aortic endothelial cells." American Journal of Physiology-Heart and Circulatory Physiology 272, no. 5 (May 1, 1997): H2188—H2194. http://dx.doi.org/10.1152/ajpheart.1997.272.5.h2188.
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Rat endothelial cells have a unique arrangement of actin fibers running with subendothelial fibronectin along the cell margins. The present study was conducted to identify the factors that are associated with codistribution of these actin fibers and fibronectin in fetal rat aortic endothelial cells, mainly using rheological techniques. Fluorescence histochemistry revealed that the codistribution pattern was established between gestational days 14 and 15. The endothelial cells changed from polygonal to spindle shaped during this gestational period. Although the aortic length remained almost unchanged during this period of gestation, both the diameter and expansion ratio of the aorta increased, by 9 and 10%, respectively. On the other hand, the wall shear rate increased rapidly during gestational days 13-16. These results indicate that the codistribution of actin fibers and subendothelial fibronectin along the margins of endothelial cells in fetal rat aorta occurs in association with a rise in stretch and shear stress and that the endothelial cells may require this change to maintain structural integrity.
Dissertations / Theses on the topic "Fibronectin fibers"
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Zafar, Syed Muhammad Sohaib Zafar. "Differential Association of Vitronectin and Fibronectin with Glass and Electrospun Fibers of a Poly (D-Lysine) /Poly (Acrylic Acid)." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6444.
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Proteins represent major constituent of the extracellular matrix which plays an important role in the formation, maintenance and remodeling of tissues, this project focuses on adsorption of two specific serum proteins fibronectin (FN) and vitronectin (VTN) responsible for mediating cell matrix interaction through integrin binding, tripeptide Arg-Gly-Asp (RGD) sequence found in these protein features are recognized by αβV3 integrin which ultimately helps in clot formation.
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Ahmed, Zubair. "Peripheral nerve regeneration on fibronectin fibre substrates." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313836.
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Grapa, Anca-Ioana. "Caractérisation des réseaux de fibronectine représentés par des graphes de fibres à partir d'images de microscopie confocale 2D." Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4031.
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La fibronectine (FN) cellulaire, composante majeure de la matrice extracellulaire, est organisée en réseaux fibrillaires de maniéré différente suivant les deux extra-domaines EDB et EDA. Notre objectif a été le développement de biomarqueurs quantitatifs pour caractériser l'organisation géométrique des quatre variants de FN à partir d'images de microscopie confocale 2D, puis de comparer les tissus sains et cancéreux. Premièrement, nous avons montré à travers deux pipelines de classification fondés sur les curvelets et sur l'apprentissage profond, que les variants peuvent être distingués avec une performance similaire à celle d'un annotateur humain. Nous avons ensuite construit une représentation des fibres (détectées avec des filtres Gabor) fondée sur des graphes. Les variantes ont été classés en utilisant des attributs spécifiques aux graphes, prouvant que ceux-ci intègrent des informations pertinentes dans les images confocales. De plus, nous avons identifié différentes techniques capables de différencier les graphes, afin de comparer les variants de FN quantitativement et qualitativement. Une analyse des performances sur des exemples simples a montré la capacité des méthodes fondées sur l'appariement de graphes et le transport optimal, de comparer les graphes. Nous avons ensuite proposé différentes méthodologies pour définir le graphe représentatif d'une certaine classe. De plus, l'appariement de graphes nous a permis de calculer des cartes de déformation des paramètres entre tissus sains et cancéreux. Ces cartes ont ensuite été analysées dans un cadre statistique montrant si la variation du paramètre peut être expliquée ou non par la variance au sein d'une même classeA major constituent of the Extracellular Matrix is a large protein called the Fibronectin (FN). Cellular FN is organized in fibrillar networks and can be assembled differently in the presence of two Extra Domains, EDA and EDB. Our objective was to develop numerical quantitative biomarkers to characterize the geometrical organization of the four FN variants (that differ by the inclusion/exclusion of EDA/EDB) from 2D confocal microscopy images, and to compare sane and cancerous tissues. First, we showed through two classification pipelines, based on curvelet features and deep learning framework, that the FN variants can be distinguished with a similar performance to that of a human annotator. We constructed a graph-based representation of the fibers, which were detected using Gabor filters. Graphspecific attributes were employed to classify the variants, proving that the graph representation embeds relevant information from the confocal images. Furthermore, we identified various techniques capable to differentiate the graphs, allowing us to compare the FN variants quantitatively and qualitatively. Performance analysis using toy graphs showed that the methods, which are based on graph matching and optimal transport, can meaningfully compare graphs. Using the graph-matching framework, we proposed different methodologies for defining the prototype graph, representative of a certain FN class. Additionally, the graph matching served as a tool to compute parameter deformation maps between the variants. These deformation maps were analyzed in a statistical framework showing whether or not the variation of the parameters can be explained by the variance within the same class
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Hayes, Julie Marie. "Integrin alphα5/fibronectin1 and focal adhesion kinase are required for lens fiber morphogenesis in zebrafish." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-08-1966.
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Fibronectin (fn) and integrin α5 (itgα5) are both key players in cell adhesion and intracellar signaling, however the specific in vivo role of these proteins has never been analyzed in the vertebrate lens.
The results presented here indicate that Fn1 and Itgα5 proteins are essential for the proper development of the lens. The loss of Fn1 protein in the zebrafish embryo results in distinct adhesion defects, defects in lens fiber morphogenesis, and cataracts. These results were phenocopied in zebrafish itga5 mutants, thereby indicating an essential role for Fn1 and Itgα5 during lens development. Furthermore, embryos with reduced levels of ptk2.1 (focal adhesion kinase – FAK) also phenocopied the defective fn1 and itgα5 lens, suggesting that FAK is a major player in the intracellular signaling mediated by Fn1/Itgα5 interactions in the lens.text
Conference papers on the topic "Fibronectin fibers"
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Bradshaw, Mark J., and Michael L. Smith. "A Combined In Vitro and In Silico Approach to Estimate the Molecular Arrangement Within a Fibronectin Fiber." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53809.
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It has become apparent that the extracellular matrix (ECM) is a powerful modulator of cell behavior. Fibronectin (Fn) is of particular interest because it is a requisite cell adhesion molecule for development and wound healing and it is a promiscuous binding partner for many soluble signaling molecules. It was recently shown that the binding affinity of some molecules is dependent on the strain state of the Fn [2,3], reinvigorating our interest in the molecular mechanism of Fn fiber extension. The tertiary structure of the approximately 30 Fn type III domains of the protein has been shown to be capable of unfolding in single molecule force spectroscopy experiments, although evidence that unfolding occurs in Fn fibers has been indirect and has not been quantified. Nevertheless, unfolding of Fn molecules predicts a possible mechanism of strain dependant binding in Fn matrix and commensurate strain feedback to attached cells, contributing to the cellular mechanotransduction toolbox [3].
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McGarry, J. P., C. S. Chen, V. S. Deshpande, R. M. McMeeking, and A. G. Evans. "Cells on a Bed of Micro-Needles: Modeling of the Scaling of the Response." In ASME 2007 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2007. http://dx.doi.org/10.1115/sbc2007-176593.
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The behavior of a cell attached to a bed of micro-needles is investigated using a bio-chemo-mechanical model. In experiments, the cell is spread on the tips of the micro-needles to which it is attached by focal adhesions bonded to ligands in the fibronectin on the posts. Actin stress-fibers form and attach to the focal adhesion plaques and exert contractile force on the micro-needles. As a result, the posts deflect and their displacements are measured and used to calculate the applied forces. This step is straightforward, because the cells do not adhere to the flanks of the micro-needles, and Euler-Bernoulli beam theory can be used to convert the bending displacements to applied loads. The bio-chemo-mechanical model for the cytoskeleton incorporates a signal, the tension-stabilized formation of actomyosin stress fibers, and their myosin motor driven contractility. In conjunction, the focal adhesions are modeled to account for their mechanosensitivity, in which loads transmitted to them from the stress-fibers encourage the development of plaques attached to the fibronectin on the micro-needle tips. These features have been programmed into a finite element code (ABAQUS) and used to simulate the behavior of cells attached to a bed of micro-posts. The micro-needles themselves are modeled as elastic structures and, consequently, the contractile force applied by the cells causes them to bend. The model of a cell on micro-needles successfully reproduces the characteristics of the data from the experiments. The scaling of the behavior in terms of micro-needle height, diameter, spacing, and elastic stiffness is investigated. In addition, the parameters of the bio-chemo-mechanical model of the cytoskeleton and the focal adhesions are varied (contractile tension, rate of stress-fiber contraction, persistence time for the signal and the effective stiffness of the focal adhesions) and their effect on scaling of the response also investigated. The results provide insight into the bio-chemo-mechanical response of cells to biological stimuli. The scaling simulations also give guidance on how experiments utilizing cells on micro-needles can be designed to extend the understanding of the mechanosensitivity of cells.
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Whitehead, Tonya J., and Harini G. Sundararaghavan. "Electrospun Hyaluronic Acid Scaffolds Containing Microspheres for Protein Delivery to Support Peripheral Nerve Growth." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14630.
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Peripheral nerve injury can cause lifelong pain, loss of function, and decreased quality of life. The gold standard of repair is a nerve autograft; however this requires additional surgeries and can cause donor site morbidity. As an alternative, nerve growth conduits are being developed to guide he existing nerves to cross these injured gaps. Electrospinning has emerged as a popular method to produce fibrous scaffolds for use in tissue engineering applications. However, limited work has been done electrospinning Hyaluronic Acid (HA) a major component of the extra cellular matrix. Cells respond to several factors in their environment including chemical, mechanical, topographical and adhesion cues.1 Using electrospinning along with microspheres allows us to control mechanical, topographical, and chemical signals within our scaffold. Axons are known to respond to topographical cues, prefer ‘soft’ substrates and grow faster in the presence of Nerve Growth Factor (NGF). We can precisely control the mechanics of our scaffold by conjugating methacrylates to the HA backbone and crosslinking under UV light. We also use the rotation speed of the collection mandrel to create fibers that are aligned along one axis. Adhesivity is achieved by coating the finished scaffold with fibronectin. Microspheres are included to release protein and create a chemical signal. These characteristics combined mimic the natural environment of nervous tissue.
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Procyk, R., M. Block, and B. Blomback. "POLYMERIZATION OF FIBRINOGEN AND FIBRONECTIN CATALYZED BY FACTOR XIII." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643310.
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Factor XIII catalyzed the formation of gels in solutions containing physiological concentrations of fibrinogen and fibro-nectin. Oligomeric intermediates were isolated from reaction mixtures at early times prior to gel formation by chromatography on gelatin-Sepharose and by FPLC using Superose 6 columns. The products of two simultaneous polymerization reactions were characterized: fibrinogen oligomers (fibrinogenin) from the poly merization of fibrinogen, and conjugates of fibrinogen-fibro-nectin (heteronectin) from heteropolymer formation involving the two proteins.At a constant concentration of fibrinogen (2.5 mg/mL) and factor XIII (0.4 U/mL), the appearance of different sizes of fibrinogen polymers depended on the concentration of fibronectin added to the reaction mixture. At fibronectin concentrations in the range of the normal plasma level of 0.3 mg/mL, fibrinogen formed oligomers of various sizes up to heptamer before incorporating a molecule of fibronectin. At a high fibronectin concentration (3.2 mg/mL) most of the fibrinogen reacted with the fibronectin at the monomer stage, although small amounts of fibrinogen dimers and trimers were also formed.Heteronectin formation coincided with the appearance of filamentous and particulate matter. This material became incorporated into a gel structure if sufficient fibrinogen was present in the reaction mixture (about 0.5 mg/mL). If these factor XIII catalyzed polymerization reactions occur in the microvasculature under conditions where the fibrinogen concentration might be significantly lowered, the production of fibrinogen-fibronectin polymeric material without gel formation would be favored.
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Meusburger, S., R. Beckmann, J. Wojta, and B. R. Binder. "RELATION OP FIBRIN STIMULATION OF tPA MEDIATED PLASMINOGEN ACTIVATION AND FIBRIN BINDING TOWARDS FIBRONEKTIN AS REVEALED BY A MONOCLONAL ANTIBODY (MAB) AGAINST FCB-2 FIBRINOGEN FRAGMENTS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644403.
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Fibrin binds to the finger domain of fibronektin via the C-terminal end of the chain and it was reported previously by us that in a fluid phase assay fibronektin inhibits fibrin enhancement of plasminogen activation by tPA. However, other have shown that tPA binds to fibronectin thereby possibly mediating enhanced matrix bound plasmin formation. In the present study we tried to further characterize the interaction between fibronectin and fibrin in regard to fibrin dependent enhancement of plasminogen activation by tPA. For fibrin binding to fibronectin we have developed an ELISA system using fibronectin coated plates and antibodies against fibrin(ogen) to quantify bound fibrin. For determination of plasminogen activation we used a coupled spectrophotometric fluid phase assay with Glu-plasminogen as substrate and H-D-Val-Leu-Lys-pNA to quantify the formed plasmin. Fibrin binding to coated fibronectin was linear between 500ng and 1 mg/ml for fibrin monomers (reptilase), FCB-2 fragments and thrombin (3.3 U/ml) treated fibrinogen, respectively. A monoclonal antibody directed against the FCB-2 fibrinogen fragment which also could be shown to recognize fibirn but not fibrinogen did not recognize fibronectin bound fibrin and inhibited also the fibrin stimulatory effect on plasminogen activation indicating that the epitope against which the antibody is directed is closely related to both the fibronectin binding site and the site involved in t-PA stimulation.
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Nair, C. H., G. A. Shah, and D. P. Dhall. "ON THE DETERMINANTS OF FIBRE THICKNESS AND FIBRIN NETWORK CHARACTERISTICS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643314.
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Spectacular differences are found between characteristics of networks developed in plasma and those developed in pure fibrinogen solution. Networks in plasma have thicker fibres, are more permeable and have lower tensile strength. In this investigation determinants of network structure under "hycio-logical conditions of clotting have been examined in an attempt to account for differences in network structure in plasma and in fibrinogen solution.Two independent variations of mass-length ratio ( µp and µr-.) from permeability and turbidity respectively were used. Effect of varying fibrinogen and thrombin concentrations and the effect of physiological concentrations of Antithrombin III, fibronectin, albumin, γ-globulin and platelet extract on fibrin network structure was examined.Fibrinogen and thrombin alter network characteristics through the modification of kinetics of network development.In these and several other studies it has been found that the kinetics of fibrin formation ultimately determine the final network structure through events preceding the appearance of visible fibrin. In separate experiments it was found that spectacular differences in network structure developed in plasma and fibrinogen were not entirely accounted for by alterations induced in network properties by albumin, y-globulin, fibronectin, ATIII and platelet extract.It is concluded that the final network structure is determined by kinetics of fibrin fibre growth and is highly responsive to the presence of plasma proteins and platelets.The findings may have fundamental applications to haemostasis and thrombosis.
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Müller, N., and U. Velten. "FIBRONECTIN CONTENTS AND LEVELS IN BLOOD COMPONENTS DURING STORAGE." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1644155.
Full textAbstract:
Fibronectin has been proposed to have an antithrombotic effect, protecting against platelet and fibrinogen consumption after injury. For the supply of platelets the possibility of extending platelet storage is important forthe management of platelet logistics. This study was designed to determine the effect of storage on the contents and levels of fibro-nectin (FN) in whole blood and components suchas packed RBCs, PRPs and platelet concentrates (PC) in two different plastics. For care of critically ill patients the FN present in components often used in large amounts could supplement the use of purified FN as a source of this opsonic protein. FN protein was assayed using an electroimmunoassay as well as a turbidimetric assay for quantitative determination at 2 day intervals during storage of CPDA-1 stabilized red cells at 4° C for 35 days and daily during end-over-end rotational storage of platelets at 22° C in conventional plastic containers (I) and trimellitate plasticised polyvinylchlo-ride bags (II) (F-763 Biotest). Moreover platelet functional tests, fibrinogen, F XIII and F VIII-complex were tested. FN levels in red cell componentsgradually decreased during storage until to 40% of the initial levels. Platelets maintained a concentrationof 404 ±70 ug/dl (I) and 378±66 ug/dl(II). There were no significant differences between the values determined in the two differentbags over the 8-days storage period. This study demonstrate the stabilityof FN protein during storage and formore effective use of limited donor resources the FN content of each of these products should be considered when determing the dose of FN for replacement therapy in critically ill patients with FN depletion following trauma and surgery.