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Query: UMLS:C0001511 (Adhesion)
 5,955 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Platelet adhesion to collagens immobilized on plastic has been measured, with the following results. (1) Human, but not rabbit, platelets adhered readily to pepsin-extracted monomeric collagens in an Mg2(+)-dependent manner. (2) Rabbit platelets adhered to a monomeric collagen extracted without pepsin by a process that was cation-independent; human platelet adhesion to this collagen exhibited a cation-independent element. (3) Human platelet adhesion to polymeric collagens, including intact native fibres and those reconstituted from pepsin-extracted monomeric collagens, exhibited appreciable cation-independence; adhesion of rabbit platelets to these collagens occurred only by a cation-independent process; pepsin treatment of the intact fibres caused a reduction in cation-independent binding. Two mechanisms of adhesion can therefore be distinguished, one Mg2(+)-dependent, expressed by human, but not rabbit, platelets, the other cation-independent and exhibited by platelets of both species. Mg2(+)-dependent and cation-independent adhesion sites are located within the triple helix of collagen, but the latter sites are only expressed in collagen in polymeric form. In neither case is the helical conformation of the sites essential for their binding activity. Cation-independent adhesion sites are also located in the pepsin-sensitive non-helical telopeptides of collagen and can be expressed in both monomeric and polymeric collagens. Chemical modification of collagen lysine residues indicates that specific lysine residues may be involved in Mg2(+)-dependent adhesion. Adhesion using human citrated platelet-rich plasma is Mg2(+)-independent. Plasma contains factors, conceivably the adhesive proteins fibronectin and von Willebrand factor, that promote the Mg2(+)-independent mechanism.
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PMID:Platelet adhesion to collagen. Factors affecting Mg2(+)-dependent and bivalent-cation-independent adhesion. 211 94

Human erythroblastic progenitors (colony-forming unit-erythroid [CFU-E] and burst-forming unit-erythroid [BFU-E]) have been shown to attach to fibronectin (Fn), a property that might be involved in the local regulation of erythropoiesis. In this study, we have investigated changes in cell attachment to Fn upon terminal erythroid differentiation. We first purified CFU-E from human marrow by avidin-biotin immune rosetting. This negative selection procedure yielded a cell population containing approximately 80% blasts that, after characterization by colony-assays and electron microscopy, appeared to consist of CFU-E (10% to 15%) and their immediate progeny (85% to 90%), here defined as "preproerythroblasts." In the presence of erythropoietin, purified cells differentiated into reticulocytes in 7 to 10 days. Cell attachment to Fn was inversely correlated to the stage of differentiation of the erythroid cell: more than 50% of the CFU-E population reproducibly adhered to Fn, whereas at most 30% of the preproerythroblasts had the same capacity. Adhesion was further lost at late maturation stages, and a constant finding was the inability of reticulocytes to adhere to Fn. Finally, CFU-E adhesion to Fn was blocked by polyclonal lgG raised against the Fn receptor and by a monoclonal antibody against VLA-5. These results demonstrate that adhesion to Fn is developmentally regulated during normal human erythropoiesis. Restriction of its expression to CFU-E and its first divisions strikingly correlates with the migratory capacity of these cells.
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PMID:Loss of attachment to fibronectin with terminal human erythroid differentiation. 213 53

In previous studies it was shown that transformation of AKR fibroblasts with 3-methylcholanthrene was associated with a loss of surface fibronectin and that induction of differentiation of the transformed cells with N,N-dimethylformamide (DMF) was associated with reacquisition of surface fibronectin (Chakrabarty et al., J. Cell. Physiol. 133:415, 1987). It is shown in the present study that changes in surface fibronectin reflect altered fibronectin synthesis and altered fibronectin binding. Both the nontransformed cells (AKR-2B) and their transformed counterparts (AKR-MCA) bound 125I-fibronectin in a receptor-like fashion, but the AKR-MCA cells had only 20% of the receptors found on the AKR-2B cells. Whole cell extracts prepared from the AKR-2B cells and separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions were examined for 125I-fibronectin binding. Under these conditions, the majority of binding occurred to moieties with molecular weights of 180 kD, 150 kD, and 97 kD. Binding to similar moieties on the AKR-MCA cells was virtually absent but occurred rapidly after treatment with DMF. The appearance of these moieties paralleled the acquisition of 125I-fibronectin binding activity by whole cells. Antibodies to the fibronectin receptor isolated from human placenta reacted with the DMF-sensitive moieties in immunoblot assays. Both the appearance of the fibronectin binding moieties and the acquisition of 125I-fibronectin binding activity by whole cells occurred within 6 hr of DMF treatment and increased over the subsequent 4 day period. The time course of these events paralleled closely the time course for induction of fibronectin biosynthesis by DMF. These changes in fibronectin binding and fibronectin production were associated with alterations in cell-substrate adhesion. The AKR-2B cells rapidly attached and spread on bovine serum albumin-coated dishes and on fibronectin-coated dishes, whereas the AKR-MCA cells were less adhesive on both substrates. Capacity to attach and spread was regained concomitantly with the induction of fibronectin binding and fibronectin production. Adhesion on both substrates was partially inhibited by antibodies to the fibronectin receptor and by RGDS. These studies suggest that fibronectin production and fibronectin binding are coregulated in AKR fibroblasts and that they function together to bring about changes in cell-substrate adhesion.
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PMID:Modulation of fibronectin synthesis and fibronectin binding during transformation and differentiation of mouse AKR fibroblasts. 214 11

Adhesion has been evaluated for tumor cell populations derived from Kirsten murine sarcoma virus (KiMSV)-transformed BALB/c 3T3 cells responding to substrata coated with intact plasma fibronectin (pFN), a family of related proteolytic fragments from pFN or cellular fibronectins (FNs), and the heparan sulfate-binding platelet factor-4 (PF4). Both early-passage KiMSV cells, harboring the viral Kirsten ras oncogene (v-Ki-ras+), and late-passage KiMSV cells, in which most cells have lost the oncogene (v-Ki-ras-), are compared with primary tumor and lung metastatic tumor cells after three routes of injection into nude mice; nontumorigenic v-Ki-ras- revertant cells have been cloned from the late-passage KiMSV population. Attachment of early-passage KiMSV, primary tumor, and lung metastatic tumor cells was optimal and resistant to soluble RGDS peptide in the medium on intact pFN, on fragment F-155 from pFN containing the RGDS cell-binding domain and the heparinII domain, and on PF4 but decreased for metastatic cells on F110 containing only the RGDS domain (and sensitive to RGDS peptide). Cytoplasmic spreading of early-passage KiMSV and all tumor cells was good to excellent in polygonal patterns on pFN and on F155, while most cells remained round on F110. Responses for KiMSV and tumor cells varied on different heparin-binding proteins; cells remained rounded or detached on F38 derived from pFN or on PF4 but spread effectively with long linear process extension on cellular FN-derived fragments F44 + 47 harboring the extra domaina sequence. That F44 + 47 may contain a new cell-binding site for v-Ki-ras+ cells was also indicated by resistance to bacterial heparitanase in cell responses on F44 + 47 but not on PF4 and extensive catabolism of proteoglycans in the substratum-attached material of these cells. v-Ki-ras- revertant cells, nontumorigenic in nude mice, have reacquired 3T3-like responses to proteolytic fragments, including much more effective spreading on PF4 or on F38 substrata, and have reverted in generating microfilament stress fibers on pFN, a competence lacking in all v-Ki-ras+ cells. These results indicate that (a) v-Ki-ras+ primary and metastatic tumor cells respond similarly to most proteolytic fragments of FNs harboring known binding domains, with a few exceptions; (b) v-Ki-ras gene expression correlates with a new cell surface receptor activity recognized by extra domaina-containing fragments from cellular FNs; and (c) loss of the viral oncogene to generate v-Ki-ras- revertant cells reverts their FN-mediated adhesion responses.
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PMID:Adhesion of Kirsten-ras+ tumor-progressing and Kirsten-ras- revertant 3T3 cells on fibronectin proteolytic fragments. 216 49

Adhesion of human umbilical vein endothelial cells (ECs) to various extracellular matrix proteins is mostly mediated by receptors of the integrin family. The interaction of ECs with extracellular matrix proteins is accompanied by cell spreading, cytoskeletal organization, and clustering of the specific integrin receptors in complex supramolecular structures known as adhesion plaques or focal contacts. Little is known on the functional role of focal contacts in EC adhesion and motility and on the possibility to modulate their organization. In this article we report that an increase in intracellular cAMP levels severely impaired focal contact formation. This process did not affect cell attachment, but increased cell adhesion and strongly inhibited cell motility. ECs were treated with the cAMP-increasing agents forskolin and 2-chloro-adenosine or with the cAMP analogue 8-bromo-cAMP. When treated cells were seeded on purified vitronectin, fibrinogen, or fibronectin little modification in the number of attached cell was observed. In contrast ECs showed impaired organization of microfilaments and poorly developed clusters of beta 3- and beta 1-integrin receptors. On a vitronectin substrate, vinculin followed the distribution of beta 3-receptors. It was typically enriched at the focal contacts in control cells but was fragmented in small dots at the cell periphery in treated cells, as were bundles of actin stress fibers. Similarly, when forskolin was added to ECs spread on vitronectin or on fibrinogen, there was a progressive but reversible disruption of actin microfilaments and diffusion of beta 3 receptors. This was accompanied by a tighter adhesion of the cells to substrata. Migration of ECs in response to different matrix proteins was severely inhibited by cAMP-increasing agents. These data indicate that EC adhesion can occur very efficiently in the absence of fully developed beta 3- or beta 1-integrin receptor-containing focal contacts but suggest that the capacity to normally assemble focal contacts and cytoskeletal proteins is required for full cell spreading and migration.
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PMID:Endothelial cell motility, integrin receptor clustering, and microfilament organization are inhibited by agents that increase intracellular cAMP. 217 48

Adhesion of pathogens to proteins and glycoconjugates on the host cell plasma membrane or to components of the extracellular matrix is a critical early step in the initiation of infection. For intracellular pathogens, adhesion to the cell surface is a prerequisite to gaining entry into the cell. In all cases, adhesion to host tissue prevents elimination of the pathogens by normal clearance processes and may help the organism to evade immune surveillance by the host. Many laboratories are investigating the ligand binding specificities of bacterial receptors or adhesions and have described diverse binding specificities for adhesive proteins in the host extracellular matrix including laminin and fibronectin. Many bacteria also have adhesins that bind to carbohydrates occurring on glycolipids and glycoproteins in the apical membranes of epithelia in tissues that are targets for infection. Definition of these binding specificities and identification of the receptors that mediate adhesion may lead to development of a novel class of antibiotics whose mechanism of action is to compete with the endogenous ligands for binding to the pathogen receptors or to otherwise prevent adhesion to host tissues and thereby prevent infection.
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PMID:Interactions of respiratory pathogens with host cell surface and extracellular matrix components. 220 37

C1q binds through its collagen-like domain to specific surface receptors of fibroblasts and to adhesive elements of extracellular matrix including fibronectin, collagens, proteoglycans, and laminin. To determine whether C1q participates in fibroblast adhesion, cells in serum-free medium were plated on surfaces coated with purified C1q at physiologic ionic strength and pH. Surfaces coated with fibronectin or collagen type I served as positive controls, and those coated with BSA were negative controls. Substratum-adsorbed C1q promoted fibroblast adhesion to a maximum of 73% of available cells within 90 min at 37 degrees C. Adhesion was C1q concentration dependent, saturable, specific, and dependent on the collagen-like domain of the molecule. De novo protein synthesis plays a role in adhesion: pretreatment of fibroblasts with cycloheximide reduced adherence about 50% of controls. Addition of exogenous fibronectin, collagen type I, or C1q as soluble mediators did not affect adhesion of the cycloheximide-treated cells to C1q substrate. Adhesion could be accounted for primarily, although not completely, by the C1q receptors. Antibodies raised against the Raji cell C1q receptors (alpha C1qR Ab) specifically inhibited fibroblast adhesion to C1q substrates about 60% of controls. The binding of fibroblasts to C1q substrates could be inhibited about 24% of controls with the GRGDTP cell recognition peptide. GRGDTP and alpha C1q Ab had an additive effect on adhesion that was inhibited 77 to 80% of controls. We conclude from these data that aggregated rather than monomeric C1q may be the natural ligand of the fibroblast C1q receptor, and the biologic function of the receptor in cells of the connective tissue may be cell adhesion.
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PMID:Participation of C1q and its receptor in adherence of human diploid fibroblast. 221 51

The adhesion of leukocytes to endothelium is a physiological phenomenon which is the first step for leukocyte emigration. The adhesion can be dramatically increased in pathological situations such as inflammation and vascular diseases. The molecular basis of leukocyte-endothelium interaction has been largely investigated in the last ten years. Using monoclonal antibodies it is possible to characterize the leukocyte adhesion molecule (LeuCAM) also named CD11/CD18 complex. These molecules responsible for leukocyte adhesion are heterodimers consisting of a common beta subunit and different subunit CD11a/CD18 corresponding to LFA-1; CD11b/CD18 to Mac1/Mol; CD11c/CD18 to GP150-95. Beside these receptors, other leukocyte structures such as the fibronectin receptors are involved in the adhesive process. On the endothelial cell side specialized structures implicated in leukocyte adhesion have been identified. Structures like Intercellular Adhesion Molecule (ICAM) are expressed on endothelial cells in the absence of stimulation, while other receptors Endothelial Leukocyte Adhesion Molecule (ELAM) are only detectable on activated endothelial cells. Cytokines such as IL-1 induced the expression of ELAM, increased the number of ICAM and Human Leukocyte Antigens (HLA) DR, DP, DQ. In various pathological circumstances, namely extracorporeal circulation, Acute Respiratory Distress Syndrome (ARDS), hypercholesterolemia and diabetes mellitus increased leukocyte adhesion has been reported and is potentially responsible for vascular damage. Therefore, the modulation of leukocyte-endothelial cell interactions is a possible target for antithrombotic and antiatherosclerotic therapy.
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PMID:Leukocyte adhesion to endothelial cells. 226 8

The interaction between granulocytes and endothelial walls may be influenced by the blood flow. This possibility was investigated by studying the influence of fluid flow on the adhesion and detachment of 51Cr-labeled rat granulocytes interacting with protein-coated glass surfaces. It is concluded that: i) Adhesion is markedly decreased when the wall shear rate becomes higher than about 20 s-1. ii) Pretreating glass with concanavalin A or polylysine significantly decreased adhesion, whereas fibronectin had little effect on binding. iii) Very high flow rates (about one thousandfold higher than those compatible with bond formation) were required to provoke substantial detachment of substrate-bound cells. iv) Coating glass with laminin or polylysine decreased binding strength whereas fibronectin or concanavalin A did not substantially influence this parameter. v) Exposing granulocytes to phorbol myristate acetate might increase the cell ability to form strong adhesions, whereas labile adhesion was unaffected or even decreased by this treatment.
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PMID:Mechanisms of leukocyte adhesion. 226 9

A method was developed to study the adhesion of platelets to fibrillar collagen at 37 degrees C in the absence of aggregation. Human platelets were labeled with [3H]-oleic acid, gel-filtered, and incubated with collagen in the presence of receptor antagonists to thromboxane A2, 5-hydroxytryptamine, and platelet-activating factor, as well as a fibrinogen/fibronectin inhibitor and an ADP-removing system. Those platelets that adhered to collagen were separated from those that did not by filtration through a 10-microns nylon mesh and the extent of platelet adhesion was quantitated by determination of the radioactivity retained by the mesh. The extent of platelet adhesion was proportional to the amount of collagen added up to 100 micrograms/ml and was essentially complete by 1 min. At least 80-90% of the platelets were capable of adhering to collagen. Adhesion was potentiated by the presence of extracellular Mg2+ and this potentiation was inhibited by extracellular Ca2+. Phosphatidic acid increased markedly in those platelets that adhered to collagen and this was associated with increases in cytosolic free Ca2+ levels that could be detected using the fluorescent Ca2+ indicator fura-2.
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PMID:Determination of platelet adhesion to collagen and the associated formation of phosphatidic acid and calcium mobilization. 237 14


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