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1
Stewart, Alasdair Gwilym. "Studies of focal adhesion kinase in epithelial cells : involvement in cell-cell adhesion". Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1446839/.
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Epithelial cell-cell adhesion is mediated by tight junctions, adherens junctions and desmosomes. Epithelial cell-matrix adhesion is mediated by hemidesmosomes and focal contacts. These complexes exhibit great plasticity, and each contains molecular components which are able to participate in one or more of the other adhesive complexes. Focal adhesion kinase (FAK/pl25FAK) is a non-receptor tyrosine kinase which transduces signals from integrins at sites of focal contact to promote adhesion, spreading and migration. FAK possesses a central kinase domain which is flanked by large, non-catalytic, amino- and carboxy-terminal domains. Whereas the functions of the carboxy-terminal and kinase domains of FAK are well understood, the role of the amino-terminal domain remains unclear. FAK expression was examined in the human epithelial cell line, HEK 293. Amino-terminal FAK immunoreactivity was noted at sites of cell-cell contacts and in the nucleus, in contrast to carboxy-terminal immunoreactivity, which was largely cytoplasmic and perinuclear. Western blot analysis of endogenous FAK revealed expression of a presumptive proteolytic cleavage fragment corresponding to the amino- terminal domain. A series of FAK constructs was generated to test the hypothesis that the observed amino-terminal FAK localisation was due to this proteolytic fragment. Epitope- tagged Amino-Terminal FAK (ATF) constructs localised primarily at areas of cell-cell contact and in the nucleus in HEK 293 cells. This localisation was independent of Tyrosine 397, the major FAK autophosphorylation site. This sub-cellular distribution was confirmed in another epithelial cell line, MDCK, in which transiently transfected ATF constructs also localised primarily to the nucleus and at cell-cell contacts. HEK 293 cells were characterised with respect to expression of adhesive proteins, and ATF was found to co- localise with the tight junction protein occludin, with cortical actin and with junctional ?1 integrin. Immunoprecipitation data suggests that none of these proteins forms a precipitable complex with ATF. These findings indicate that the amino-terminal domain of FAK is capable of localising at epithelial cell-cell contacts and suggest a novel role for FAK in mediating cross-talk between focal contacts and cell-cell contacts through endogenously expressed amino-terminal FAK fragments.
2
Armstrong, Nicola J. "Continuum modelling of cell-cell adhesion". Thesis, Heriot-Watt University, 2008. http://hdl.handle.net/10399/2167.
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Cells adhere to each other through the binding of cell adhesion molecules at the cell surface. This process, known as cell-cell adhesion, is fundamental in many areas of biology, including early embryo development, tissue homeostasis and tumour growth. Here \~e present a new continuum mathematical model of this phenomenon by considering · the movement of cells in response to the adhesive forces generated through binding. We demonstrate that the model predicts aggregative behaviour, characteristic of an adhesive cell population. Further, when extended to two cell populations, the model predicts cell sorting behaviour dependent on the strengths of adhesive bonds between cells. While cell sorting has been demonstrated previously with discrete approaches, we believe that this is the first continuous model to capture this behaviour. In the latter part of this work we apply the model of cell-cell adhesion to somitogenesis and tumour growth. In applying the model to somitogenesis we demonstrate that the model predicts somite formation under particular parameter constraints. We suggest that these parameter constraints may provide a means by which to test competing theories of the mechanisms responsible for somitogenesis. In applying the model to tumour growth and invasion we demonstrate that the model predicts that mutations which alter cells adhesive properties have a significant influence on tumour dynamics. In particular, the model predicts that irregular invasion patterns are the consequence of increased cell-matrix adhesion and an inhomogeneous host environment.
3
Muniz, Maisonet Maritza. "Topographical Enhancement of Cell Adhesion on Poorly Adhesive Materials". Scholar Commons, 2015. https://scholarcommons.usf.edu/etd/5748.
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The overall thrust of this dissertation is to gain a fundamental understanding of the synergistic effects between surface topography and chemical functionality of poorly adhesive materials on enhancing the adhesion of mouse embryonic fibroblasts. Cellular response to surface topography and chemical functionality have been extensively studied on their own providing valuable information that helps in the design of new and improved biomaterials for tissue engineering applications. However, there is a lack of understanding of the synergistic effect of microscale and nanoscale topography with chemical functionality and the relative impact and contribution of each in modulating cellular behavior. By understanding the relationship between these cues, in particular using materials that are poorly adhesive, this study will provide new clues as to how cells adapt to their environment and also suggest new dimensions of biomaterial design for fine-tuning cellular control.
A microstructure that combined non adhesive materials with defined surface topography and surface chemistry is presented, to assess and correlate the enhancement of mouse embryonic fibroblasts cell adhesion and spreading. Poly (N-isopropylacrylamide) or PNIPAAm electrospun fibers were overlaid on PNIPAAm thin films (100 nm) at various time points to investigate the role of topography on such coatings by keeping the chemical functionality the same. After doing this, several topographical patterns were developed, spanning from sparse to dense fiber mats, and cell adhesion strongly depended on the relative available areas for attachment on either the fibers or the supporting surface. To gain a better understanding of this finding, two surface chemistries, non-adhesive (self-assembled monolayer of polyethylene glycol (PEGSAM) alkanethiol on gold) or an adhesive coating (3-aminopropyltriethoxysilane (APTES) on glass) with well characterized adhesive properties were included in this study to assess the effect of topographical cues provided by the PNIPAAm electrospun fibers on cellular responses. With the deposition of the PNIPAAm fibers onto a PEGSAM surface, cell adhesion increased to almost 100%, and unlike the PNIPAAm surface, cell spreading was significantly enhanced. With the deposition of PNIPAAm fibers onto APTES, both cell adhesion and spreading were unaffected up to 60% fiber coverage. For both surfaces, PNIPAAm fiber densities above 60% coverage lead to adhesion and spreading independent of the underlying surface. These findings indicate the presence of a sparse topographical feature can stimulate cell adhesion on a typically non-adhesive material, and that a chemical dissimilarity between the topographic features and the background enhances this effect through greater cell-surface interaction.
In addition to the aforementioned studies, cell response was also assessed on PNIPAAm thin films coatings with thicknesses ranging from 100 nm to 7 nm. Cell adhesion and spreading was enhanced as the thickness of the thin film decreased. This change was more noticeable below 30 nm, wherein 7 nm shows the highest cell adhesion and spreading enhancement. The results reported are preliminary results and further experiments will be conducted, to support the data. It is believed that cellular response was enhanced due to a change in surface topography at the nanoscale level.
4
Maghzal, Nadim. "The epithelial cell adhesion molecule (EpCAM) regulates cell motility and cell-cell adhesion by inhibiting PKC signaling". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114215.
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Tissue cohesion is achieved in part by a large family of plasma membrane-bound cell adhesion molecules (CAMs). During morphogenesis, CAM-mediated interactions provide adhesive forces required for cells to aggregate and form tissues. CAM-mediated adhesions in developing cells are highly dynamic, which provides the fluidity required for cellular movements that drive morphogenesis. Xenopus laevis gastrulation is an established model to study morphogenetic movements. During this phase of development, the mesoderm moves inside the embryo through involution, and migrates along the inner surface of the ectoderm while remaining separated from this tissue. Members of the Fagotto lab have identified the Xenopus orthologue of the Epithelial Cell Adhesion Molecule (EpCAM) in a gain-of-function screen to find gene products that cause aberrant ectoderm/mesoderm tissue mixing in the gastrula. EpCAM is a well known tumor-associated antigen that is specifically expressed in epithelial tissues, where its overexpression often correlates with malignancy. The initial aim of this thesis was to understand the molecular mechanism through which EpCAM promotes ectoderm/mesoderm tissue mixing. Overexpression of EpCAM in cells at the boundary increases their "invasive" behavior via a signaling property of its cytoplasmic domain (EpTAIL) that inhibits PKC signaling to promote cell motility. The most important findings of this thesis are that 1) EpTAIL inhibits PKC activity to promote cell motility and cell-cell adhesion by acting as a PKC pseudosubstrate domain that binds the enzyme on its catalytic site, and 2) this previously unknown mode of PKC inhibition is not specific to EpCAM as other PKC pseudosubstrate-mimicking plasma membrane proteins were identified and could potentially play important roles in the regulation of PKC activity. The data presented in this thesis further our understanding of EpCAM biology and unravel a new mode of PKC regulation that is valuable as PKCs are one of the major families of cytoplasmic kinases in cells.Les mécanismes de liaison cellulaire sont établis en partie par une vaste famille de protéines d'adhésion cellulaire ou CAMs. Lors de la morphogenèse, les interactions induites par les CAMs créent des forces d'adhésion nécessaires afin que les cellules puissent s'agréger et former des tissues. Les adhésions induites par les CAMs dans les cellules en développement sont très dynamiques et offrent ainsi la fluidité nécessaire aux mouvements cellulaires qui régissent la morphogenèse. La gastrulation chez la grenouille Xenopus laevis sert de modèle d'étude des mouvements morphogéniques. Durant ce stade de développement, le mésoderme se déplace vers l'intérieur de l'embryon via un mouvement d'involution et migre le long de la paroi interne de l'ectoderme tout en maintenant une séparation des deux tissues. Des membres du laboratoire de Dr. Fagotto ont réussi à identifier un orthologue de la protéine «Epithelial Cell Adhesion Molecule (EpCAM) » chez Xenopus dans un tri de gain de fonction permettent d'identifier des protéines pouvant être à l'origine d'aberrations au niveau du maintien de la séparation de l'ectoderme et du mésoderme durant la gastrulation. EpCAM est un antigène associé aux tumeurs exprimé dans les cellules épithéliales et dont la surexpression corrèle avec des tumeurs malignes. L'objectif initial de cette thèse était de découvrir les mécanismes moléculaires pouvant expliquer l'effet de EpCAM sur les aberrations entre la séparation des tissues de l'ectoderme et du mésoderme. Une surexpression de EpCAM dans les cellules à la bordure de l'ectoderme et du mésoderme cause une augmentation du comportement « invasif » entre les deux tissues, via la fonction de transduction du signal de son domaine cytoplasmique (EpTAIL), qui inhibe le signal de la protéine PKC afin de promouvoir le mouvement cellulaire. Les principales contributions de cette thèse ont été 1) EpTAIL inhibe l'activité de PKC en jouant le rôle d'un pseudosubstrat de PKC en interagissant avec le site catalytique de l'enzyme, et 2) ce mécanisme d'inhibition jusqu'à présent inconnu pour PKC n'est pas seulement spécifique à EpCAM, car d'autres protéines membranaires possède également cette capacité à imiter le pseudosubstrat de PKC et pourraient potentiellement avoir un rôle important à jouer au niveau de la régulation de l'activité de PKC. Les donnée présentées dans cette thèse contribuent à approfondir davantage notre connaissance d'EpCAM et dévoilent un nouveau mécanisme de régulation de PKC qui pourrait être important puisque les molécules PKC forment l'une des plus importantes familles de kinases cytoplasmiques dans les cellules.
5
Théard, Delphine Francine. "P27Kip1 in cell-cell adhesion and cell polarity". [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2006. http://irs.ub.rug.nl/ppn/291442056.
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Dix, Christina Lyn. "Adhesion-dependent cell division". Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10044469/.
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Animal cells undergo a dramatic series of cell shape changes as they pass through mitosis and divide which depend both on remodelling of the contrac- tile actomyosin cortex and on the release of cell-substrate adhesions. Here, I use the adherent, non-transformed, human RPE1 cell line as a model system in which to explore the dynamics of these shape changes, and the function of mitotic adhesion remodelling. Although these cells are highly motile, and therefore polarised in interphase, many pause migration and elongate to be- come bipolar prior to mitosis. Interestingly, and in contrast to most reported cell types, these cells do not round fully, and many leave long adhesive tails con- nected to the underlying substrate. These are typically bipolar, persist through- out mitosis, and guide cell respreading following mitotic exit. Further analysis shows that while many proteins are lost from focal adhesion complexes during mitotic rounding, integrin-rich contacts remain in place along these tails as well as defining the tips of retraction fibres. These adhesions are functionally impor- tant in RPE1 cells, since these cells fail to divide when removed from the sub- strate prior to entry into mitosis. The restoration of cell-substrate adhesions at anaphase are sufficient to rescue division in control cells. However, adhesions must persist into mitotic exit for division in cells compromised in their ability to construct an actomyosin ring. Division in these cells depends on respreading, since Ect2 RNAi cells fail to divide on small adhesive islands, but successfully divide on larger patterns with the cytoplasmic bridge connecting daughter cells narrowing as they migrate away from one another. Together these results re- veal the importance of coupling adhesion remodeling to mitotic progression.
7
Pouliot, Yannick 1963. "Study of L6 myoblast cell-cell adhesion". Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61797.
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Betson, Martha Elizabeth. "Regulation of cell-cell adhesion in keratinocyes". Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274930.
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Zhao, Lee Cheng. "Cell adhesion characterization of adhesive forces and effect of topography /". [Gainesville, Fla.] : University of Florida, 2000. http://etd.fcla.edu/etd/uf/2000/ana7043/LCZhao%5FThesis.pdf.
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Thesis (M.S.)--University of Florida, 2000.Title from first page of PDF file. Document formatted into pages; contains ix, 79 p.; also contains graphics. Vita. Includes bibliographical references (p. 69-77).
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Elineni, Kranthi Kumar. "Regulation of Cell Adhesion Strength by Spatial Organization of Focal Adhesions". Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3088.
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Cell adhesion to extracellular matrix (ECM) is critical to various cellular processes like cell spreading, migration, growth and apoptosis. At the tissue level, cell adhesion is important in the pathological and physiological processes that regulate the tissue morphogenesis. Cell adhesion to the ECM is primarily mediated by the integrin family of receptors. The receptors that are recruited to the surface are reinforced by structural and signaling proteins at the adhesive sites forming focal adhesions that connect the cytoskeleton to further stabilize the adhesions. The functional roles of these focal adhesions extend beyond stabilizing adhesions and transduce mechanical signals at the cell-ECM interface in various signaling events. The objective of this research is to analyze the role of the spatial distribution of the focal adhesions in stabilizing the cell adhesion to the ECM in relation to cell's internal force balance. The central hypothesis was that peripheral focal adhesions stabilize cell adhesion to ECM by providing for maximum mechanical advantage for resisting detachment as explained by the membrane peeling mechanism. Micropatterning techniques combined with robust hydrodynamic shear assay were employed to test our hypothesis. However, technical difficulties in microcontact printing stamps with small and sparse features made it challenging to analyze the role of peripheral focal adhesions in stabilizing cell adhesion. To overcome this limitation, the roof collapse phenomenon in stamps with small and sparse features (low fill factor stamps) that was detrimental to the reproduction of the adhesive geometries required to test the hypothesis was analyzed. This analysis lead to the valuable insight that the non-uniform pressure distribution during initial contact caused by parallelism error during manual microcontact printing prevented accurate replication of features on the substrate. To this end, the template of the stamp was modified so that it included an annular column around the pattern zone that acted as a collapse barrier and prevented roof collapse propagation into the pattern zone. Employing this modified stamp, the required geometries for the cell adhesion analysis were successfully reproduced on the substrates with high throughput. Adhesive areas were engineered with circular and annular patterns to discern the contribution of peripheral focal adhesions towards cell adhesion strength. The patterns were engineered such that two distinct geometries with either constant adhesive area or constant spreading area were obtained. The significance of annular patterns is that for the same total adhesive area as the circular pattern, the annular pattern provided for greater cell spreading thereby increasing the distance of the focal adhesions from the cell's center. The adhesion strength analysis was accomplished by utilizing hydrodynamic shear flow in a spinning disk device that was previously developed. The results indicate that for a constant total adhesive area, the annular patterns provide for greater adhesion strength by enhancing cell spreading area and providing for greater moment arm in resisting detachment due to shear. The next examination was the effect of the cell's internal force balance in stabilizing the cell adhesion. The working hypothesis was that microtubules provide the necessary forces to resist the tensile forces expressed by the cell contractile machinery, thereby stabilizing cell adhesion. Since microtubule disruption is known to enhance cell contractility, its effect on the cell adhesion strength was examined. Moreover, the force balance in cells was altered by engineering adhesive areas so that the cells were either spherical or completely spread and then disrupted microtubules to understand the significance of the force balance in modulating the cell adhesion strength. The results indicated that disruption of microtubules in cells on adhesive islands resulted in a 10 fold decrease in adhesion strength compared to untreated controls whereas no significant change was observed in completely spread cells between treated and untreated controls. This is in surprising contrast to the previous contractility inhibition studies which indicate a less pronounced regulation of adhesion strength for both micropatterned and spread cells. Taken together, these findings suggest that the internal force balance regulated by cell shape strongly modulates the adhesion strength though the microtubule network. In summary, this project elucidates the role of peripheral focal adhesions in regulating the cell adhesion strength. Furthermore, this study also establishes the importance of the internal force balance towards stabilizing the cell adhesion to the ECM through the microtubule network.
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Burthem, John. "Hairy cell adhesion and migration". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240394.
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Yildirim, Ali. "Measurement of cultured cell adhesion". Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760660.
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Sarwar, Muhammad. "Measurement of mammalian cell adhesion". Thesis, University of Bath, 1992. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314527.
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Krieg, Michael. "Cell adhesion and cell mechanics during zebrafish development". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-26093.
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During vertebrate development, gastrulation leads to the formation of three distinct germlayers. In zebrafish a central process is the delamination and the ingression of single cells from a common ancestor tissue - that will lead to the formation of the germlayers. Several molecules have been identified to regulate this process but the precise cellular mechanisms are poorly understood. Differential adhesiveness, a concept first introduced by Steinberg over 40 years ago, has been proposed to represent a key phenomena by which single hypoblast cells separate from the epiblast to form the mesendoderm at later stages. In this work it is shown that differential adhesion among the germlayer progenitor cells alone cannot predict germlayer formation. It is a combination of several mechanical properties such as cell cortex tension, cell adhesion and membrane mechanical properties that influence the migratory behavior of the constituent cells.
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Krieg, Michael. "Cell adhesion and cell mechanics during zebrafish development". Doctoral thesis, Technische Universität Dresden, 2009. https://tud.qucosa.de/id/qucosa%3A25182.
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During vertebrate development, gastrulation leads to the formation of three distinct germlayers. In zebrafish a central process is the delamination and the ingression of single cells from a common ancestor tissue - that will lead to the formation of the germlayers. Several molecules have been identified to regulate this process but the precise cellular mechanisms are poorly understood. Differential adhesiveness, a concept first introduced by Steinberg over 40 years ago, has been proposed to represent a key phenomena by which single hypoblast cells separate from the epiblast to form the mesendoderm at later stages. In this work it is shown that differential adhesion among the germlayer progenitor cells alone cannot predict germlayer formation. It is a combination of several mechanical properties such as cell cortex tension, cell adhesion and membrane mechanical properties that influence the migratory behavior of the constituent cells.
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Amin, Bakr. "Dynamics of E-cadherin mediated cell-cell adhesion". Thesis, Boston University, 2013. https://hdl.handle.net/2144/21122.
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Thesis (M.A.) PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.In epithelial cells, formation of stable adherens junction is essential for a number of important cell processes. The central protein responsible for creating cell-cell adhesion is known as E-cadherin. When the lamellipodia of migratory cells make contact, the cell is signaled to send E-cadherin/β-catenin complexes to the point of contact. Upon proper binding of two E-cadherin molecules further E-cadherins are signaled to cluster at the point of contact through cis lateral interactions and a passive diffusion trap mechanism. The actin cytoskeleton is also signaled through Rac1 to interact with the nascent adherens junction. As the adherens junction matures there are further actin cytoskeleton rearrangements and alterations to cell shape due to variable expression of the Rho GTPases. When adhesion in the adherens junction is stable the cell is able to become polarized by the assembly of tight junctions. Interference with any of the steps that lead to the development of a stable, mature, adherens junction results in various disease states such as cancer. Cancer can develop in epithelial cells due to E-cadherin dysfunction, particularly gastric, breast, ovarian, head and neck, and prostate cancer are seen. E-cadherin dysfunction can be caused by interference with proper transcription, N-glycosylation, and recycling. Transcription is most commonly disrupted due to acetylation of the E-cadherin promoter by improperly modulated transcriptional repressor, such as Snail. Aberrant Nglycosylation and/or modification with branching β1, 6 GlcNAc can interfere with the creation of stable adherens junction by interfering with E-cadherin binding. Increased endocytosis of E-cadherin via irregular Rho GTPase activity destabilizes adherens junctions. These interferences effect an epithelial to mesenchymal transition that can act as a metastatic cancer phenotype. E-cadherin serves a crucial function in cell-cell adhesion and preventing cells from exhibiting malignancy. It has been shown that restoration of its function in cancer cell lines reduces the invasiveness of cancer cells and returns to the cell to a normal epithelial phenotype. Knowledge of E-cadherin, its regulators, and association with the actin cytoskeleton will undoubtedly have clinical impacts in cancer treatment. However, understanding of E-cadherin is still incomplete, in particularly more studies need to be done in the area of Rho GTPases and N-glycosylation, There has also been recent controversy in identifying the principal molecule that links the actin cytoskeleton and α- catenin to mediate the binding of the E-cadherin/β-catenin complex to actin.
2031-01-01
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Hadjisavas, Michael. "Induction of mitogenesis and cell-cell adhesion by porcine seminal plasma". Title page, contents and abstract only, 1992. http://web4.library.adelaide.edu.au/theses/09PH/09phh1293.pdf.
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Includes list of publications by the author. Includes bibliographical references (leaves 103-123) Evaluates the nature of the interactions occurring between semen and cells of the uterus that occur following mating in pigs. Describes a novel ability of porcine seminal plasma to induce dose dependent cell-cell adhesion and mitogenesis amongst peripheral blood lymphocytes in vitro.
18
Pearce, Kristen (Kristen Joanne) 1974. "Regulation of adhesion between round spermatids and Sertoli cells in the testis". Monash University, Dept. of Obstetrics and Gynaecology, 2003. http://arrow.monash.edu.au/hdl/1959.1/6606.
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Miyahara, Ryo. "Expression of neural cell adhesion molecules(polysialated form of neural cell adhesion molecule and L1-cell adhesion molecule)on resected small cell lung cancer specimens : in relation to proliferation state". Kyoto University, 2001. http://hdl.handle.net/2433/150163.
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Coyer, Sean R. "Modulation of cell adhesion strengthening by nanoscale geometries at the adhesive interface". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34763.
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Cell adhesion to extracellular matrices (ECM) is critical to many cellular processes including differentiation, proliferation, migration, and apoptosis. Alterations in adhesive mechanisms are central to the behavior of cells in pathological conditions including cancer, atherosclerosis, and defects in wound healing. Although significant progress has been made in identifying molecules involved in adhesion, the mechanisms that dictate the generation of strong adhesive forces remain poorly understood. Specifically, the role of nanoscale geometry of the adhesive interface in integrin recruitment and adhesion forces remains elusive due to limitations in the techniques available for engineering cell adhesion environments. The objective of this project was to analyze the role of nanoscale geometry in cell adhesion strengthening to ECM. Our central hypothesis was that adhesive interactions are regulated by integrin clusters whose recruitment is determined by the nanoscale geometry of the adhesive interface and whose heterogeneity in size, spacing, and orientation modulates adhesion strength.
The objective of this project was accomplished by 1) developing an experimental technique capable of producing nanoscale patterns of proteins on surfaces for cell adhesion arrays, 2) assessing the regulation of integrin recruitment by geometry of the adhesive interface, and 3) determining the functional implications of adhesive interface geometry by systematically analyzing the adhesion strengthening response to nanoscale patterns of proteins. A printing technique was developed that patterns proteins into features as small as 90nm with high contrast and high reproducibility. Cell adhesion arrays were produced by directly immobilizing proteins into patterns on mixed-SAMs surfaces with a protein-resistant background. Colocalization analysis of integrin recruitment to FN patterns demonstrated a concentrating effect of bound integrins at pattern sizes with areas equivalent to small nascent focal adhesions. At adhesion areas below 333 × 333 nm2, the frequency of integrin recruitment events decreased significantly indicating a threshold size for integrin clustering. Functionally, pattern sizes below the threshold were unable to participate in generation of adhesion strength. In contrast, patterns between the threshold and micron sizes showed a relationship between adhesion strength and area of individual adhesion points, independent of the total available adhesion area. These studies introduce a robust platform for producing nanoscale patterns of proteins in biologically relevant geometries. Results obtained using this approach yielded new insights on the role of nanoscale organization of the adhesive interface in modulating adhesion strength and integrin recruitment.
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Schwarz, Ulrich. "Forces and elasticity in cell adhesion". [S.l. : s.n.], 2004. http://pub.ub.uni-potsdam.de/2004/0034/schwarz.pdf.
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Schwarz, Ulrich Sebastian. "Forces and elasticity in cell adhesion". Thesis, Universität Potsdam, 2004. http://opus.kobv.de/ubp/volltexte/2005/110/.
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Das Verhalten adhärenter Zellen hängt stark von den chemischen, topographischen und mechanischen Eigenschaften ihrer Umgebung ab. Experimentelle Untersuchungen der letzten Jahre haben gezeigt, dass adhärente Zellen aktiv die elastischen Eigenschaften ihrer Umgebung erkunden, indem sie an dieser ziehen. Der resultierende Kraftaufbau hängt von den elastischen Eigenschaften der Umgebung ab und wird an den Adhäsionskontakten in entsprechende biochemische Signale umgewandelt, die zelluläre Programme wie Wachstum, Differenzierung, programmierten Zelltod und Zellbewegung mitbestimmen. Im Allgemeinen sind Kräfte wichtige Einflussgrößen in biologischen Systemen. Weitere Beispiele dafür sind Hör- und Tastsinn, Wundheilung sowie die rollende Adhäsion von weißen Blutkörperchen auf den Wänden der Blutgefäße. In der Habilitationsschrift von Ulrich Schwarz werden mehrere theoretische Projekte vorgestellt, die die Rolle von Kräften und Elastizität in der Zelladhäsion untersuchen.(1) Es wurde eine neue Methode entwickelt, um die Kräfte auszurechnen, die Zellen an den Kontaktpunkten auf mikro-strukturierte elastische Substrate ausüben. Das Hauptergebnis ist, dass Zell-Matrix-Kontakte als Mechanosensoren funktionieren, an denen interne Kräfte in Proteinaggregation umgewandelt werden.
(2) Eine Ein-Schritt-Master-Gleichung, die die stochastische Dynamik von Adhäsionsclustern als Funktion von Clustergröße, Rückbindungsrate und Kraft beschreibt, wurde sowohl analytisch als auch numerisch gelöst. Zudem wurde dieses Modell auf Zell-Matrix-Kontakte, dynamische Kraftspektroskopie sowie die rollende Adhäsion angewandt.
(3) Im Rahmen der linearen Elastizitätstheorie und mit Hilfe des Konzepts der Kraftdipole wurde ein Modell formuliert und gelöst, das die Positionierung und Orientierung von Zellen in weicher Umgebung vorhersagt. Diese Vorhersagen sind in guter Übereinstimmung mit zahlreichen experimentellen Beobachtungen für Fibroblasten auf elastischen Substraten und in Kollagen-Gelen.
The behaviour of an adhering cell is strongly influenced by the chemical, topographical and mechanical properties of the surface it attaches to. During recent years, it has been found experimentally that adhering cells actively sense the elastic properties of their environment by pulling on it through numerous sites of adhesion. The resulting build-up of force at sites of adhesion depends on the elastic properties of the environment and is converted into corresponding biochemical signals, which can trigger cellular programmes like growth, differentiation, apoptosis, and migration. In general, force is an important regulator of biological systems, for example in hearing and touch, in wound healing, and in rolling adhesion of leukocytes on vessel walls. In the habilitation thesis by Ulrich Schwarz, several theoretical projects are presented which address the role of forces and elasticity in cell adhesion.
(1) A new method has been developed for calculating cellular forces exerted at sites of focal adhesion on micro-patterned elastic substrates. The main result is that cell-matrix contacts function as mechanosensors, converting internal force into protein aggregation.
(2) A one-step master equation for the stochastic dynamics of adhesion clusters as a function of cluster size, rebinding rate and force has been solved both analytically and numerically. Moreover this model has been applied to the regulation of cell-matrix contacts, to dynamic force spectroscopy, and to rolling adhesion.
(3) Using linear elasticity theory and the concept of force dipoles, a model has been introduced and solved which predicts the positioning and orientation of mechanically active cells in soft material, in good agreement with experimental observations for fibroblasts on elastic substrates and in collagen gels.
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McClure, Diane. "Cell adhesion mechanisms in colon cancer". Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=57005.
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Cell adhesion molecules are thought to have an important role in neoplastic progression as they are likely to be involved in the multiple steps of the metastatic cascade. We have focused on two adhesion molecules, E-cadherin and CD44, looking for changes in their expression in human colon cancer. The intercellular adhesion mediated by E-cadherin has been shown to be altered in cancer. We have investigated the expression of E-cadherin in normal and tumorigenic colorectal mucosa by immunohistochemistry. Tumor samples showed a down-regulation of expression correlating with the degree of tumor dedifferentiation. The second adhesion molecule, CD44, has been previously associated with metastasis in animal models. We have shown by Northern blotting that mRNA splice variants with domains IV + V are specifically over expressed in carcinomas. Immunohistochemistry showed redistribution of CD44 to the cellular basal membrane. Thus, the aberrant expression of E-cadherin and CD44 could be associated with malignant progression in colorectal cancer.
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May, Andrew Paul. "Structural studies on cell adhesion molecules". Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298346.
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Wright, Karen. "Synthesis of oligosaccharides affecting cell adhesion". Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267483.
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Minett, William T. "Cell adhesion on synthetic polymer substrates". Thesis, Aston University, 1986. http://publications.aston.ac.uk/14512/.
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Kang, Youn-Jung. "Cell adhesion and signalling at implantation". Thesis, University of Oxford, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.711653.
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Welf, Erik Steven. "Integrative modeling of cell adhesion processes". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 285 p, 2009. http://proquest.umi.com/pqdweb?did=1833641671&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Thesis (Ph.D.)--University of Delaware, 2009.Principal faculty advisors: Babatunde Ogunnaike, Dept. of Chemical Engineering, and Ulhas P. Naik, Dept. of Biological Sciences. Includes bibliographical references.
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Jones, Mara. "N-cadherin mediated cell-cell adhesion in the arterial wall". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ58830.pdf.
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Steelant, Wim Floris Albert. "Role of antitumor lipids in cell-cell adhesion and invasion". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2000. http://dare.uva.nl/document/56986.
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Brown, Marena Dessette. "Sickle cell-endothelial interactions : modulation of cell adhesion molecule expression". Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/11306.
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Wongchaowart, Michael B. "Optimization of cell adhesion environments for a liver cell bioreactor". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34156.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Biological Engineering Division, February 2006.Includes bibliographical references (p. 40-44).
The MilliF bioreactor offers great potential for the formation of i vivo-like liver tissue outside the body, making it a valuable tool for applications such as drug toxicity models and biosensors. Cell adhesion is an important factor in the maintenance of differentiated hepatocyte functions. Hepatocyte adhesion environments were examined in two settings: spheroid culture prior to seeding in the bioreactor and 2D surface culture methods that could be applied to the bioreactor scaffold. Spheroids were formed either by culturing in spinning suspension or on a static, non-adherent surface. In spheroid culture, the addition of extracellular matrix (ECM) signaling through the use of soluble Matrigel or adhesion protein-coated microspheres did not improve hepatocyte viability or function as assessed by liver-specific gene expression. These results suggest the importance of cell-cell rather than cell-surface interactions in maintaining hepatocytes. Optimal culturing of spheroids in spinning suspension without the ECM addition was found to be 3 days without media changes. 2D surfaces were treated with an adhesion peptide-conjugated comb polymer, preventing nonspecific cell adhesion and allowing attachment through the [alpha]₅[beta]₁ integrin.
(cont.) Varying the proportion of adhesion peptide presented to cells was found to regulate hepatocyte morphology and function; a surface with decreased hepatocyte spreading and liver-specific gene expression closer to in vivo was characterized. Immunoblotting for activated focal adhesion kinase (FAK) revealed that FAK signaling was not induced by attachment to the comb polymer surfaces. Immunostaining for other liver cell types demonstrated that the surface allowed hepatic stellate cell and Kupffer cell adhesion.
by Michael B. Wongchaowart.
M.Eng.
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McCormack, Jessica. "The regulation of cell-cell adhesion by GTPase activating proteins". Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/28574.
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Adherens junctions (AJs) are responsible for the adhesion of cells to their neighbours and influence a range of cellular processes. The formation and maintenance of AJs is governed by members of the Rho subfamily of small GTPases. Activation of the GTPases Rac1 and RhoA is necessary for the formation of cell-cell contacts in keratinocytes. However, how the GTPases themselves are regulated is not well understood. Rho GTPase activating proteins (GAPs) inactivate GTPases by promoting the hydrolysis of GTP to GDP. Whilst a large number of proteins containing Rho GAP domains have been identified, knowledge of this large family of proteins remains limited. It is predicted that multiple Rho GAPs are required in order to coordinate precise processes that are necessary for the formation and maintenance of cell-cell contacts to occur. However, relatively few Rho GAPs have been identified as regulators of cell-cell contacts. The aims of this project are to 1) identify GAPs involved in the regulation of cell-cell contact formation in keratinocytes and 2) to specifically investigate the role of CdGAP in junction formation and maintenance. To this end, 20 GAPs have been identified from a siRNA screen as potential regulators of junction formation, the vast majority of which have not previously been linked to this process. Subsequently, two Rho-specific GAPs have been investigated to probe their roles in the regulation of Rho in both junction formation and maintenance. The second part of this thesis focuses on the Rac and Cdc42-specific GAP CdGAP, which I demonstrate is an important regulator of AJs in keratinocytes. I show that CdGAP is able to interact with the scaffold protein Ajuba. Ajuba is known to localise to cell-cell adhesions, where it is necessary for maintaining Rac activation at junctions. However, Ajuba itself has no catalytic activity. My data suggests cooperation between CdGAP and Ajuba allows Rac levels to be fine-tuned at AJs. Overall, this data identifies numerous Rho GAPs as potential regualtors of junction formation, and confirms for the first time the importance of three Rho GAPs, ARAP1, ARHGAP6 and CdGAP, in the regulation of cell-cell contact formation and maintenance. Ultimately, this work provides further insight into the regulation of AJs by GAPs and enhances our understanding of how scaffold proteins, such as Ajuba, are able to influence this tightly controlled process.
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Lynn, Miriam Elen. "Enterocyte maturity influences adhesion by lactobacillus". Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.481471.
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Piper, James Wilson. "Force dependence of cell bound E-selectin/carbohydrate ligand binding characteristics". Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/18388.
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Yates, Luke Alexander. "Structural studies in cell adhesion and division". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:d66f5602-7e49-4042-8ebf-9457e61d56c3.
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Cell adhesion is a critical process that allows the organisation and functioning of tissues in three-dimensions. However, the replenishing of cells, via cell division, within tissues is equally important for functioning complex life. Both cell adhesion and division are tightly controlled processes and rely on a complex network of signals that, as yet, are not wholly understood. This Thesis presents a structural analysis of several proteins involved in these processes. In the case of cell adhesion, we have made use of high-throughput (HTP) cloning and expression screening technologies in the Oxford Protein Production Facility (OPPF) for the study of the Kindlin protein family – a recently discovered set of proteins essential for integrin-mediated cell adhesion. As a direct result of the HTP pipeline used we were able to determine the high resolution crystal structure of a single domain, the Pleckstrin Homology Domain, from the isoform Kindlin-1. Deletion of this domain in the full-length protein resulted in impaired integrin activation in vivo. This structure, in combination with molecular dynamics simulation demonstrated that, unlike other well characterised PH domains, the binding of secondary messenger lipids (phosphoinositides) is dictated by a, previously unseen, salt bridge that occludes the putative binding site. Mutation of the salt bridge alters the binding characteristics of this domain in vitro. In addition to the PH domain, we have also studied and biophysically characterised full-length Kindlin-3, a blood cell specific isoform. By optimising baculovirus-infected Sf9 cell expression systems we were able to obtain, for the first time, sufficient quantities of protein for characterisation. Furthermore, by using small-angle X-ray scattering (SAXS) in solution we were able to determine a low resolution solution structure of Kindlin-3, revealing a linear arrangement of its FERM domain - a novel conformation known only otherwise in talin. We characterised the interaction of full-length Kindlin-3 with β-integrin cytoplasmic tails using nuclear magnetic resonance spectroscopy, which confirmed that a direct interaction with a membrane distal NPxY motif occurs, and demonstrated the importance of a preceding Serine/Threonine rich region in peptide binding. In the case of cell division, we have determined the crystal structure of the cell cycle checkpoint control related protein, Cid1, a terminal uridine tranferase from Schizzosaccharomyces pombe, alone and in complex with UTP. Structural and biochemical analysis of Cid1 identified a novel Uridine selection mechanism that is suggested to be conserved in metazoan ZCCHC enzymes involved in let-7 miRNA biogenesis, which are important for proliferation, differentiation and cell fate. We have also demonstrated that Cid1 is an RNA binding protein, a property essential for activity that employs a novel mechanism of RNA binding in the absence of RNA binding motifs. The structural work undertaken in this thesis has focussed on two distinct, but interwoven, aspects of cell biology and has significantly added to both fields of research. Excitingly, this has opened many new avenues of investigation and, in the case of Cid1, has the strong potential to lead to the development of novel anticancer therapies.
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Demetriou, Manolis C. "Integrin clipping: A novel adhesion switch". Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290063.
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We previously identified a novel structural variant of the alpha6 integrin called alpha6p. This variant was produced on the cell surface and was missing the β-barrel extracellular domain. Using several different concentrations of amiloride, aminobenzamidine and PAI-1 and the urokinase-type plasminogen Activator (uPA) function blocking antibody (3689) we showed that uPA, acting as a protease, is responsible for production of α6p. We also showed that addition of uPA in the culture media of cells that do not produce α6p, resulted in a dose dependent α6p production. In contrast, the addition of uPA did not result in the cleavage of other integrins. Using α2-antiplasmin and plasmin depleted media, we observed that uPA cleaves the alpha6 integrin directly. Further, 12-O-tetradecanoyl-phorbol-13-acetate (TPA) induced the production of alpha6p, and this induction was abolished by PAI-1 but not α2-antiplasmin. Using site directed mutagenesis we have identified the site of cleavage to be at arginines 594 and 595. We have also shown that while a fraction of α6 integrin is normally associated with CD151, the α6p form is not. In order to determine whether α6 integrin clipping occurs in tissue, we have found that α6p is present in human prostate cancer tissue, in normal mouse epidermis, in mouse papillomas and squamous cell carcinomas induced by DMBA, TPA and MNNG treatments and in mouse melanomas induced by activated ras. Interestingly, subcutaneous injection into athymic nude mice of a malignant mouse keratinocyte derived cell line (6M90) that is α6p negative, results in the development of tumors that contain α6p integrin. Furthermore, we have shown that PC3N cells transfected with an uncleavable mutant of the α6 integrin grew smaller tumors when injected subcutaneously in SCID mice compared to wildtype α6 transfected cells. In addition, the tumors from the uncleavable mutant alpha6 transfected PC3N cells had higher levels of activated caspase 3 indicating higher levels of apoptosis. This finding suggests that the α6 integrin clipping is important for integrin signaling for survival. Collectively, all these data suggest that the cell surface clipping of the α6 integrin is a novel mechanism for altering integrin-laminin interactions during skin tissue remodeling and carcinogenesis.
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Gallant, Nathan D. "Analysis of Integrin-mediated Cell Adhesion Strengthening Using Surfaces Engineered to Control Cell Shape and Focal Adhesion Assembly". Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/7601.
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Cell adhesion to extracellular matrix proteins is critical to physiological and pathological processes as well as biomedical and biotechnological applications. Cell adhesion is a highly regulated process involving initial receptor-ligand binding, and subsequent clustering of these receptors and rapid association with the actin cytoskeleton as focal adhesions are assembled. Focal adhesions enhance adhesion, functioning as structural links between the cytoskeleton and the extracellular matrix and triggering signaling pathways that direct cell function. The objective of this thesis research is to develop a mechanical and biochemical analysis of the adhesion strengthening response.
Our central hypothesis was that focal adhesion size and position regulate cell adhesion strength by controlling the distribution of mechanical loading. We engineered micropatterned surfaces to control the size and position of focal adhesions in order to analyze the contributions of these specialized adhesive structures to adhesion strengthening. By applying surface micropatterning techniques, we showed robust control over cell-substrate contact area and focal adhesion assembly. Using a hydrodynamic shear assay to quantify adhesion strength to micropatterned substrates, we observed significant adhesive area- and time-dependent increases in adhesion strength. Complimentary biochemical assays allowed us to probe the role of structural proteins recruited to focal adhesions and examine the structure-function relationships between these adhesive structures and adhesion strength. These findings provide insights into the role of focal adhesions in adhesion strengthening, and may contribute to tissue engineering and biomaterials applications.
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Belusa, Roger. "Role of Na⁺, K⁺-ATPase in cell adhesion and cell volume regulation : mutagenesis of Na⁺, K⁺-ATPase and transfection in embryonic kidney cell line /". Stockholm, 2001. http://diss.kib.ki.se/2001/91-628-4874-7/.
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Carrasco, Sabino Dora Isabel. "Adhesion-associated proteins in Drosophila". Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612142.
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Wurff, A. A. M. van der. "Cell differentiation and adhesion in colorectal cancer". [Maastricht : Maastricht : Universiteit Maastricht] ; University Library, Maastricht University [Host], 1998. http://arno.unimaas.nl/show.cgi?fid=8253.
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Telci, Dilek. "Tissue transglutaminase : a novel cell adhesion protein". Thesis, Nottingham Trent University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410526.
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Montefort, Stephen. "Cell adhesion in airway mucosal allergic inflammation". Thesis, University of Southampton, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240611.
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Chen, Yun-Ju. "The role of dystroglycan in cell adhesion". Thesis, University of Glasgow, 2003. http://theses.gla.ac.uk/30966/.
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Dystroglycan is a heterodimeric transmembrane glycoprotein protein of α and β subunits that links the extracellular matrix to the cytoskeleton. Recent data tend to suggest that the role of dystroglycan in non-muscle cells is for cell adhesion, and cytoskeleton reorganisation signalling. To study the relationship between dystroglycan signalling and ERK signalling in focal adhesions, an YFP-ERK construct was expressed in REF52 cells. YFP-ERK was expressed with ERK activity and formed adhesion-like structures in the REF52 cells, however, no ERK activity was detected in the adhesion-like structures in the REF52 cells. To determine the function of dystroglycan for adhesion or cytoskeleton organisation in non-muscle cells, a GFP-tagged full-length dystroglycan (αβDG-GFP) or its deletion mutants was expressed in REF52 cells. Expression of αβDG-GFP markedly altered cell phenotype on a laminin or fibronectin substrate, resulting in the induction of actin-rich filopodia. The β-dystroglycan cytoplasmic domain is determined as the mediator for the dystroglycan-dependent filopodia formation mediated partly by integrin signalling. The dystroglycan deletion mutants lacking α-dystroglycan failed to target to the plasma membrane. Expression of an alkaline phosphate-tagged β-dystroglycan cytoplasmic domain construct (AP-cβ), which targeted the β-dystroglycan cytoplasmic domain to the membrane without the α-dystroglycan, was sufficient to induce the filopodia phenotype, indicating that with the proper membrane localisation, β-dystroglycan can regulate filopodia formation independently of α-dystroglycan. However, α-dystroglycan might be necessary for β-dystroglycan to target to the plasma membrane. These distinct morphologies strongly implied that β-dystroglycan mediates Cdc42 regulated cytoskeleton reorganisation. By cotransfecting dominant negative Cdc42 (Cdc42N17) or constitutively activated Cdc42 (V12Cdc42) constructs with αβDG-GFP or the mutants, Cdc42 was determined to be a mediator for dystroglycan-dependent filopodia formation. Therefore a signalling cycle of dystroglycan-Cdc42-PAK-ezrin-dystroglycan is identified. With this signalling cycle, dystroglycan plays a role in inducing actin filopodia formation and, at the same time, might also inhibit focal adhesion and stress fibre formation.
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Nwachukwu, Cynthia Chinwe. "Electrospinning Protein Nanofibers to Control Cell Adhesion". Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1727.
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The structural and mechanical properties of a surface often play an integral part in the determination of the cell adhesion strength and design parameters for creating a biodegradable electrospun scaffold. Nanofibers composed of the globular proteins bovine serum albumin (BSA) and fibronectin were produced by electrospinning with the electrospun protein scaffold serving as an extracellular matrix to which adhesion interaction will exist with cells via cell surface integrin. This interaction is vital in regulation cell differentiation, growth and migration and cell adhesion.
We will demonstrate the ability to manipulate ligand-receptor interaction, the properties of the electrospun fibers, control and the formation of focal adhesions sites in cells cultured on the fibers with the ultimate goal of developing a biomimetric scaffold to investigate how cell adhesion molecules modulate cell behavior in a 3-dimentional culture.
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Palovuori, R. (Riitta). "Regulation of cell-cell adhesion and actin cytoskeleton in non-transformed and transformed epithelial cells". Doctoral thesis, University of Oulu, 2003. http://urn.fi/urn:isbn:9514269306.
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Abstract
Epithelial cell-cell adhesions have a critical role in morphogenesis, establishment and maintenance of tissue architecture, cell-cell communication, normal cell growth and differentiation. These adhesions are disrupted during malignant transformation and tumour cell invasion. Several kinases, phosphatases and small GTPases regulate cell-cell contacts. In the present work we investigated the dynamics of cell-cell adhesion structures after microinjection of fluorophore tagged vinculin, during transformation caused by an active Src tyrosine kinase and during Helicobacter pylori infection. The regulatory role of Rac GTPase as well as the behaviour of actin and cadherin were analysed in all these conditions.
Microinjection of vinculin into bovine kidney epithelial MDBK cells induced release of actin, cadherin and plakoglobin to cytoplasm of the cells, caused disruption of protein complexes at adherens and tight junctions that finally led to formation of polykaryons. Activated Rac GTPase, in turn, enhanced accumulation of cadherin to membranes and thereby diminished the formation of polykaryons, whereas inactive Rac removed cadherin from membranes. Incorporation of vinculin to lateral membranes took place also in acidifying and depolarising conditions where cell fusions were prevented. Thus, the membrane potential seemed to control fusion ability. In src-MDCK cells, activation of Src kinase led to disintegration of adherens junctions. Clusters of junctional components and bundles of actin were seen at the basal surface already within 30 min after Src activation. p120ctn was the only component of adherens junction whose relocation correlated to its phosphorylation. Inhibition of Src by a specific inhibitor PP2 restored the cubic morphology of the cells and accumulated cadherin back to lateral walls. Still p120ctn remained in cytoplasm and thereby was not responsible for the epithelial phenotype. Activation of Rac GTPase by Tiam1 also increased the amount of cadherin at lateral membranes and maintained the morphology of src-MDCK cells practically normal after activation of Src kinase. In the same way, actin cytoskeleton was reorganised in gastric carcinoma cells in response to infection with H. pylori via activation of Rac signalling pathway. Hence, Rac and cadherin seem to be the major players in the maintenance of epithelial cell morphology.
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Santos, Tedim Sousa Pedrosa António José. "Chlamydia trachomatis, a cell adhesion architect : the role of TarP and CT228 in Chlamydia trachomatis modulation of host cell focal adhesions". Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=233419.
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Bacterial infection of mucosal epithelial cells triggers cell exfoliation to limit the dissemination of infection within the tissue. Therefore, mucosal pathogens must possess strategies to counteract cell extrusion in response to infection. Chlamydia trachomatis L2 spends most of its intracellular development in the non-infectious form, and premature extrusion of the host cell is detrimental to the pathogen. Here I show that Chlamydia trachomatis L2-infected cells exhibited increase adhesion as demonstrated by increased resistance to detachment by mild trypsinization. In addition, I observed an increase in the number and size of the focal adhesions of the Chlamydia trachomatis L2-infected cells. I demonstrated that this phenotype was not exclusive of C. trachomatis serovar L2 and that it was not restricted to a single type of cell line. Quantitative confocal and live-cell TIRF microscopy revealed that this bacterium actively modulated host cell focal adhesions by enhancing their stability. Infection conferred resistance to disassembly upon inhibition of myosin II or ROCK1 activity. Furthermore, I was able to demonstrate that the Chlamydia trachomatis effector TarP is able to colocalize to the sites of focal adhesions when ectopically expressed in mammalian cells. This resulted in increased number of the host cell focal adhesions. TarP was also able to confer resistance to myosin II inhibition, in a VBD-dependent manner. Also, I have found that C. trachomatis transmembrane protein CT228 cooperates with TarP to confer resistance to ROCK1 inhibition. Super resolution microscopy revealed a reorganisation of focal adhesions in Chlamydia trachomatis L2-infected cells. In summary, this work shows for the first time that Chlamydia trachomatis L2 uses TarP and CT228 to modulate the host cell focal adhesions. Finally, I have also described that both Chlamydia trachomatis L2 and TarP are able to alter the nanoscale architecture, this has never been reported in any other system.
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Källström, Helena. "Molecular and cellular mechanisms during adherence and cell signaling of pathogenic Neisseria to host cells /". Stockholm, 1999. http://diss.kib.ki.se/1999/91-628-3848-2/.
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Redmann, Anna-Lena. "Kinetics of cell attachment and spreading on hard and soft substrates". Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/290385.
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A very important aspect for the functioning of an organism is that cells adapt their behaviour to external stimuli. They continuously interact with their environment, and biochemical and physical cues can activate cellular signalling, which leads to changes in cell behaviour such as proliferation and shape. Understanding cells' interactions with their environment is also important for understanding diseases. For example mechanosensing, which is the sensing of the cell's mechanical environment, has been associated with cancer development. In order for a cell to be able to sense its mechanical environment, it needs to form attachments to the environment. In my thesis, I have worked on three different tasks: the development of a new measurement technique and the study of initial cell adhesion and of cell spreading. When a cell from suspension first comes into contact with a substrate, it forms initial attachment bonds with proteins on the substrate surface. These bonds are mediated through integrins, which are transmembrane heterodimers, binding to the cell's environment on one side and to the cell's cytoskeleton on the other side. I study this initial cell attachment by measuring the force needed to detach cells, called cell adhesion strength. For these experiments I built a detachment device, which allows the detachment of cells from a substrate by vibrating the substrate in liquid. The device combines cell incubation, detachment and imaging. I measured the dependence of initial integrin bond formation on external factors such as incubation temperature and substrate stiffness. Once initial integrin bonds are formed, many different proteins are recruited to the adhesion site in order to form stronger adhesions. Amongst these proteins are signalling proteins, which direct the behaviour of the cell as a whole. One of the first cellular reactions to a substrate after initial integrin binding is cell spreading. This can be seen by the cell changing its shape from spherical to dome-like on the substrate. Because cell spreading is a very early response of a cell to a substrate, the onset time of spreading can be used as a quantitative measure for the time it takes the cell to sense a substrate and signal shape change. In my work, I look at the distribution of the time of initial cell spreading in a population of cells. I measure this distribution under different growth conditions such as pH, change of incubation medium from DMEM to PBS, substrate stiffness and incubation temperature. In my detachment experiments, I observe that vibration accelerates cell spreading in those cells which remain on the substrate. This is a connection between the detachment experiments and the cell spreading experiments and it shows how cells react to external forces. By changing the medium temperature in the cell detachment and cell spreading experiments, I am able to analyse the kinetics of these two processes. I use a signalling network model to analyse the internal cellular signalling path that leads from a spherical to a spread cell.
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Franke, Katja. "Adhesion and Single Cell Tracking of Hematopoietic Stem Cells on Extracellular Matrices". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-77290.
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The local microenvironment of hematopoietic stem cells (HSCs) in the bone marrow -referred to as stem cell niche- is thought to regulate the balance of stem cell maintenance and differentiation by a complex interplay of extrinsic signals including spatial constraints, extracellular matrix (ECM) components and cell-cell interactions. To dissect the role of niche ECM components, a set of well-defined matrix biomolecular coatings including fibronectin, laminin, collagen IV, tropocollagen I, heparin, heparan sulphate, hyaluronic acid and co-fibrils of collagen I with heparin or hyaluronic acid were prepared and analyzed with respect to adhesive interactions of human CD133+ HSCs in vitro. ECM molecule dependent adhesion areas as well as fractions of adherent HSCs were assessed by reflection interference contrast microscopy and differential interference contrast microscopy. HSCs, so far mostly classified as suspension cells, exhibited intense adhesive interactions with fibronectin, laminin, collagen IV, heparin, heparan sulphate, and collagen I based co-fibrils. An integrin mediated adhesion on fibronectin and a L-selectin mediated adhesion on heparin pointed to specific interactions based on different adhesion mechanisms. As a consequence of HSC adhesion to molecules of the vascular and the endosteal regions, both regions were confirmed as possible stem cell niches and adhesive signals were suggested as potential regulators of stem cell fate. Furthermore, the impact of a spatially organized ECM on the HSC behavior was analyzed by single cell tracking. These studies required the development of engineered three-dimensional, ECM coated microcavities with the option for single cell tracking. A semi-automated cell-tracking tool was established to accelerate data access from time-lapse image sequences. From this analysis it was possible to reveal the genealogy, localization, morphology and migration of single HSCs over a time period of 4 days. A decreased cycling frequency was observed depending on the HSC localization in the spatially constraining microcavities. Besides the revealed impact of spatial constraints on HSC fate, the newly engineered ECM-coated microcavity setup and the semi-automated cell tracking tool provide new options to study the cell fate in engineered microenvironments at single cell level for other cell types ex vivoDie lokale Mikroumgebung von Blutstammzellen (BSZ) im Knochenmark, bezeichnet als Stammzellnische, reguliert das Gleichgewicht von Stammzellerhaltung und -differenzierung durch ein komplexes Zusammenspiel von extrinsischen Signalen wie räumliche Beschränkungen, Komponenten der extrazellulären Matrix (EZM) und Zell-Zell Wechselwirkungen. Um die Rolle der EZM-Komponenten zu analysieren, wurden definierte Beschichtungen von Fibronektin, Laminin, Kollagen IV, monomerem Kollagen I, Heparin, Heparan Sulphat, Hyaluronsäure und Co-Fibrillen aus Kollagen I und Heparin oder Hyaluronsäure hergestellt und in vitro bezüglich der adhäsiven Wechselwirkungen von humanen CD133+ BSZ untersucht. Die Adhäsionsflächen und der Anteil adhärenter Zellen wurden in Abhängigkeit von der EZM-Beschichtung mittels Reflexions- Interferenz-Kontrast-Mikroskopie und Differentieller Interferenz Kontrast Mikroskopie bestimmt. BSZ, bisher als Suspensionszellen definiert, zeigten intensive adhäsive Wechselwirkungen mit Fibronektin, Laminin, Kollagen IV, Heparin, Heparan Sulphat und den Co-Fibrillen. Eine Integrin abhängige Adhäsion auf Fibronektin und eine L-Selektin abhängige Adhäsion auf Heparin, wiesen auf spezifische Wechselwirkungen hin, die auf unterschiedlichen Mechanismen basieren. Aufgrund der Adhäsion von BSZ sowohl zu Molekülen der vaskulären als auch der endostealen Knochenmarkregion, wurden beide Bereiche als mögliche Stammzellnische bestätigt. Adhäsive Signale sind potentielle Regulatoren der Stammzellentwicklung. Im Weiteren wurde der Einfluss einer räumlich beschränkenden EZM auf das Verhalten der BSZ durch Einzelzellverfolgung untersucht. Diese Studien erforderten die Entwicklung von dreidimensionalen EZM-beschichteten Mikrokavitäten, die das Verfolgen einzelner Zellen ermöglichten. Es wurde ein halbautomatischer Algorithmus für die Zellverfolgung etabliert, um die Datengenerierung von den Zeitreihenaufnahmen zu beschleunigen. Die Analysen ermöglichten Aussagen über die Genealogie, Lokalisierung, Morphologie und Migration einzelner BSZ während einer Analysenzeit von 4 Tagen. Eine verringerte Zellteilungsaktivität wurde in Abhängigkeit von der BSZ Lokalisierung innerhalb der räumlich einschränkenden Mikrokavitäten festgestellt. Neben diesen Erkenntnissen bieten die entwickelten Mikrokavitäten und die etablierte Einzelzellverfolgung neue Möglichkeiten auch andere Zelltypen auf Einzelzellniveau ex vivo zu untersuchen