849 resultados para Net Adhesion Force
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Mode of access: Internet.
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Description based on: 1963; title from cover
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Includes index.
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"PB94-928013"--Stamped cover.
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"11 April 1994"--Vol. 4.
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"GAO/NSIAD-93-128."
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Includes bibliographies.
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Mode of access: Internet.
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Loose-leaf for updating by periodic change publications.
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The anterior adhesive mechanism was studied for Merizocotyle icopae (Monogenea: Monocotylidae). Adult anterior apertures can open and close. In addition, duct endings terminating within the apertures are everted or retracted depending on the stage of attachment. Adhesive in adults is synthesized from all 3 secretory types (rod-shaped, small and large spheroidal bodies) found within anterior apertures. All exit together and undergo mixing to produce the adhesive matrix, a process that depletes duct contents. A greater number of ducts carrying rod-shaped bodies is depleted than ducts containing spheroidal bodies which changes the ratio of secretory types present on detachment. Detachment involves elongation of duct endings and secretion of additional matrix as the worm pulls away from the substrate. The change in secretory type ratio putatively modifies the properties of the secreted matrix enabling detachment. Only after detachment do ducts refill. During attachment, individual secretory bodies undergo morphological changes. The larval and adult adhesive matrix differs. Anterior adhesive in oncomiracidia does not show fibres with banding whereas banded fibres comprise a large part of adult adhesive. The data Suggest that this is the result of adult spheroidal secretions modifying the way in which the adult adhesive matrix forms.
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We are using polymer templates to grow artificial artery grafts in vivo for the replacement of diseased blood vessels. We have previously shown that adhesion of macrophages to the template starts the graft formation. We present a study of the mechanics of macrophage adhesion to these templates on a single cell and single bond level with optical tweezers. For whole cells, in vitro cell adhesion densities decreased significantly from polymer templates polyethylene to silicone to Tygon (167, 135, and 65 cells/mm(2)). These cell densities were correlated with the graft formation success rate (50%, 25%, and 0%). Single-bond rupture forces at a loading rate of 450 pN/s were quantified by adhesion of trapped 2-mm spheres to macrophages. Rupture force distributions were dominated by nonspecific adhesion (forces, < 40 pN). On polystyrene, preadsorption of fibronectin or presence of serum proteins in the cell medium significantly enhanced adhesion strength from a mean rupture force of 20 pN to 28 pN or 33 pN, respectively. The enhancement of adhesion by fibronectin and serum is additive (mean rupture force of 43 pN). The fraction of specific binding forces in the presence of serum was similar for polystyrene and polymethyl-methacrylate, but specific binding forces were not observed for silica. Again, we found correlation to in vivo experiments, where the density of adherent cells is higher on polystyrene than on silica templates, and can be further enhanced by fibronectin adsorption. These findings show that in vitro adhesion testing can be used for template optimization and to substitute for in-vivo experiments.
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Surface modification techniques have been used to develop biomimetic scaffolds by incorporating cell adhesion peptides, which facilitates cell adhesion, migration and proliferation. In this study, we evaluated the cell adhesion properties of a tailored laminin-332 alpha3 chain tethered to a type I collagen scaffold using microbial transglutaminase (mTGase) by incorporating transglutaminase substrate peptide sequences containing either glutamine (peptide A: PPFLMLLKGSTREAQQIVM) or lysine (peptide B: PPFLMLLKGSTRKKKKG). The degree of cross-linking was studied by amino acid analysis following proteolytic digestion and the structural changes in the modified scaffold further investigated using Fourier transform infrared spectroscopy and atomic force microscopy. Fibroblasts were used to evaluate the cellular behaviour of the functionalized collagen scaffold. mTGase supports cell growth but tethering of peptide A and peptide B to the mTGase cross-linked collagen scaffold caused a significant increase in cell proliferation when compared with native and mTGase cross-linked collagen scaffolds. Both peptides enabled cell-spreading, attachment and normal actin cytoskeleton organization with slight increase in the cell proliferation was observed in peptide A when compared with the peptide B and mTGase cross-linked scaffold. An increase in the amount of epsilon(gamma-glutamyl) lysine isopeptide was observed in peptide A conjugated scaffolds when compared with peptide B conjugated scaffolds, mTGase cross-linked scaffold without peptide. Changes in D-spacing were observed in the cross-linked scaffolds with tethered peptides. These results demonstrate that mTGase can play a bifunctional role in both conjugation of the glutamine and lysine containing peptide sequences and also in the cross-linking of the collagen scaffold, thus providing a suitable substrate for cell growth.
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A szerző az Európai Unióhoz az elmúlt évtizedben csatlakozott országok felzárkózásának összefüggéseit vizsgálja, rámutatva arra, hogy a kelet-közép-európai térség országainak természetes modernizációs központja az Európai Unió. Az európai integrációba történő szerves beépülésnek nem volt és a jövőben sincs reális alternatívája. Annak ellenére, hogy a nemzetközi pénzügyi és gazdasági válság rendkívül kedvezőtlen fordulatot hozott, az új tagországok többségében jelentős ütemű felzárkózási folyamat indult el: egy évtizeden belül relatív pozíciójuk az uniós átlaghoz képest átlagosan 15 százalékpont javult a vásárlóerő-paritáson mért egy főre jutó GDP-t tekintve. A tagság számos előnye közül ki kell emelni, hogy az uniós költségvetésből származó közvetlen transzferek hatására az új tagállamok számottevő külső forráshoz jutottak, aminek révén hosszú távú fejlődésüket és versenyképességüket befolyásoló területeken jelentős beruházásokat hajthattak végre. E transzferek kapcsán a szerző felhívja a figyelmet arra, hogy a szűk látókörűen számított nettó haszonélvezői pozíció valójában kölcsönös előnyöket rejt: az EU fejlettebb országai számára is komoly előnyök származnak a megnövekedett importkeresletből és általában a bővülés kereskedelemteremtő hatásaiból. _____ The author analyses some catch-up aspects of countries joining the EU in 2004 and 2007, pointing out that the EU is an obvious centre of modernization for the countries in East Central Europe. There was no realistic alternative to participating in the European integration process and this applies also to the future. Contrary to the extremely bad general environment caused by the international financial and economic crisis, most new member-states were able to converge on the EU average quite fast: within a decade the relative regional level of development measured in GDP per capita terms and compared with the EU average increased by 15 per cent. It should be stressed that among several advantages of EU membership, direct transfers from the EU-level budget played a crucial role in improving competitiveness through investment. Looking beyond narrow-minded net budgetary positions, the author sees mutual comprehensive benefits: the more developed member-states can enjoy additional demand for their products, and in general benefit from the trade-creating effects of enlargement.
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Acknowledgements V.B., N.K.G., and E.A. contributed with conception and experimental design. V.B. performed the experiments. V.B., R.H., A.G., and R.M.M. carried out analysis and interpretation of data. V.B., R.H., A.G., and E.A. wrote the manuscript. V.B. and R.H. contributed equally to this work. V.B. acknowledges funding by SPP 1420 of the German Science Foundation DFG. E.A., N.K.G., and R.H. acknowledge funding from the European Research Council under the European Union/ERC Advanced Grant “Switch2Stick,” Agreement No. 340929.
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Peer reviewed