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

The nature, kinetics and cofactor requirements of leukocyte adhesion to cultured vascular cells have been investigated in vitro, using a model system in which leukocyte suspensions are in continuous motion over the cultured cells. Adhesion is assessed by histological examination or by using 51Cr-labelled leukocytes. Leukocytes adhere preferentially to endothelial cell monolayers rather than to smooth muscle cells, adventitial fibroblasts or serum-coated glass. Arterial and venous endothelium are equally good substrates for leukocyte adhesion, and lymphocytes and granulocytes at the same suspension density adhere to endothelial cells in similar numbers. Adherence is greatest during the first 10 min, and is inversely related to flow rate. Numbers of leukocytes adhering to the cell monolayer are proportional to the initial concentration of leukocytes in suspension, although only 2--10% of the leukocytes adhere. Leukocytes that have adhered to the cell monolayer spread over the cells and then migrate, apparently through intercellular junctions. Adhesion requires Ca2+ or Mg2+ ions, but not plasma protein cofactors. Fewer leukocytes adhere to endothelial cells grown for 48 h in rapidly stirred medium than to cells grown under conventional, static conditions.
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PMID:Interaction of leukocytes with vascular cells in culture. 72 10

Adhesion of N-formyl-methionyl-leucylphenylalanine-stimulated human polymorphonuclear leukocytes (PMNs) to dishes coated with laminin, fibronectin, or collagen types I and IV was dependent on the presence of magnesium (Mg2+) but not calcium (Ca2+). Addition of manganese (Mn2+) in combination with Ca2+ and Mg2+ further increased the number of PMNs adhering to the matrix proteins. Monoclonal antibody 60.3 (mAb 60.3) was equally effective at inhibiting adhesion of PMNs to all the matrix proteins. The presence of Mn2+ (50 microM), in addition to 1 mM Ca2+ and Mg2+, required higher concentrations of mAb 60.3 to inhibit adhesion of PMNs to collagens type I or IV, suggesting increased affinity of PMNs for these substrates. These findings suggest that the PMNs may regulate the affinity of CD11/CD18 for multiple ligands by binding different divalent cations to the receptor.
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PMID:Effect of divalent cations on adhesion of polymorphonuclear leukocytes to matrix molecules in vitro. 135 18

In this study, the putative laminin receptor function of the alpha 6 beta 4 integrin was assessed. For this purpose, we used a human cell line, referred to as clone A, that was derived from a highly invasive, colon adenocarcinoma. This cell line, which expresses the alpha 6 beta 4 integrin, adheres to the E8 and not to the P1 fragment of laminin. The adhesion of clone A cells to laminin is extremely rapid with half-maximal adhesion observed at 5 min after plating. Adhesion to laminin is blocked by GoH3, and alpha 6 specific antibody (60% inhibition), as well as by A9, a beta 4 specific antibody (30% inhibition). Most importantly, we demonstrate that alpha 6 beta 4 binds specifically to laminin-Sepharose columns in the presence of either Mg2+ or Mn2+ and it is eluted from these columns with EDTA but not with NaCl. The alpha 6 beta 4 integrin does not bind to collagen-Sepharose, but the alpha 2 beta 1 integrin does bind. Clone A cells do not express alpha 6 beta 1 as evidenced by the following observations: (a) no beta 1 integrin is detected in beta 1 immunoblots of GoH3 immunoprecipitates; and (b) no alpha 6 beta 1 integrin is seen in GoH3 immunoprecipitates of clone A extracts that had been immunodepleted of all beta 4 containing integrin using the A9 antibody. These data establish that laminin is a ligand for the alpha 6 beta 4 integrin and that this integrin can function as a laminin receptor independently of alpha 6 beta 1.
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PMID:The integrin alpha 6 beta 4 is a laminin receptor. 153 98

The recognition of exposed collagen by circulating platelets is an initial step in the formation of the hemostatic plug or a thrombus after vascular injury. Theoretical calculations of the speed of platelet function required for effective hemostasis have suggested very short reaction times. However, it is not known how fast platelets can adhere to collagen under arterial flow conditions or which membrane proteins are involved. We have used a continuous-flow, microaffinity column linked to a resistive-particle counter to detect platelet adhesion. Adhesion of human platelets to native type I collagen was extremely rapid, with exponential half-times as short as 240 ms, and was nearly complete by 2 s. This RGD-independent process was not associated with platelet aggregation or secretion. The monoclonal antibody 6F1 directed against the glycoprotein Ia/IIa complex inhibited adhesion, suggesting that this complex plays an important role in the initial phases of platelet-collagen interaction under flow conditions. In addition, divalent cations were required for adhesion, as indicated by inhibition with EDTA in plasma and the dependence on Mg2+ for washed platelets.
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PMID:High-speed platelet adhesion under conditions of rapid flow. 163 Oct 56

The adhesion of platelets to purified laminin under flow conditions was investigated. Adhesion to laminin was strongly dependent on the presence of divalent cations. In the absence of cations platelet adhesion (8% coverage in 5 minutes) was maximal at a shear rate of 100/s and no adhesion could be detected at shear rates above 800/s. In the presence of 0.8 mmol/L Mg2+ and 2 mmol/L Ca2+ platelet adhesion reached its maximum (30% coverage) around 800/s. At 1,800/s platelets still adhered to purified laminin (coverage of 6%). Antibodies against the E8 domain of laminin and antibodies against the alpha 6 and beta 1 chains of platelet membrane glycoprotein very late activation antigen-6 (VLA-6), completely inhibited adhesion. No inhibition was found with antibodies against glycoprotein IIb:IIIa, against the alpha 2 chain of VLA-2, and against the alpha 5 chain of VLA-5. Fibronectin and von Willebrand factor were not involved in laminin-dependent adhesion. Anti-VLA-6 partly inhibited platelet adhesion to the extracellular matrix of endothelial cells at shear rates below 800/s. Preincubation of the matrices with antilaminin E8 antibodies did not influence the adhesion. These results show that purified laminin supports platelet adhesion and that the presence of VLA-6 is important for platelet adhesion under flow conditions. The protein in the matrix with which VLA-6 interacts is currently unknown.
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PMID:Platelet adhesion to laminin: role of Ca2+ and Mg2+ ions, shear rate, and platelet membrane glycoproteins. 173 1

Cerebral involvement in Plasmodium falciparum malaria is associated with sequestration of infected red blood cells and occlusion of cerebral vessels. Adhesion of infected erythrocytes along the vascular endothelium as well as binding of uninfected erythrocytes to cells infected with late-stage asexual parasites (rosetting) may be important in erythrocyte sequestration. We report that the recently discovered rosetting phenomenon shares characteristics with other human cell-cell interactions (heparin sensitivity, temperature independence, Ca2+/Mg2+ and pH dependence). Mono- and polyclonal antibodies specific for PfHRP1, a histidine-rich protein present in the membrane of P. falciparum-infected erythrocytes, disrupt rosettes but do not affect attachment of infected erythrocytes to endothelial cells. The inhibitory anti-PfHRP1 antibodies reacted with rosetting parasites in indirect immunofluorescence and with P. falciparum polypeptides of Mr 28,000 and Mr 90,000 in immunoprecipitation and immunoblotting, respectively. No inhibitory effects on erythrocyte rosetting were obtained with antibodies to related histidine-rich or other antigens of P. lophurae or P. falciparum. Whether the epitope that mediates rosetting, and is recognized by the anti-PfHRP1 antibodies, is located on PfHRP1 or on a crossreactive antigen remains to be established. The results suggest that endothelial cytoadherence and erythrocyte rosetting involve different molecular mechanisms.
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PMID:Antibodies to a histidine-rich protein (PfHRP1) disrupt spontaneously formed Plasmodium falciparum erythrocyte rosettes. 210 39

The immunological properties of cerebral microvascular endothelium were directly compared with those of an extra-cerebral endothelium in vitro. Lymphocyte adhesion to cerebral endothelium is normally low, but is sensitive to induction by interferon-gamma (IFN gamma) and tumour necrosis factor-alpha (TNF alpha). Conversely adhesion to aortic endothelium is normally much higher but it is only marginally sensitive to induction by cytokines. Adhesion to both cell types is Ca2+ and Mg2+ dependent. Mitogen-activated lymphocytes bind more strongly to both endothelia, but adhesion to aortic endothelium is not enhanced further by activation of the endothelium. The observed low binding of lymphocytes to brain endothelium and its rapid induction by cytokines suggest a mechanism to explain why lymphocyte accumulation in brain is normally very low but rapidly increases during immune responses. Both cell types express similar levels of class I major histocompatibility complex (MHC) molecules, and this is enhanced by IFN gamma with similar responsiveness to different levels of IFN gamma. MHC class II molecules are absent from these cells but may be induced: although both endothelia respond to similar levels of cytokines, the surface density induced on brain endothelium is approximately 2- to 3-fold higher at all levels of IFN gamma.
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PMID:Comparison of the immunological properties of rat cerebral and aortic endothelium. 212 97

Polycationic polymers have been noted for their effects in promoting cell adhesion to various surfaces, but previous studies have failed to describe a mechanism dealing with this type of adhesion. In the present study, three polycationic polymers (chitosan, poly-L-lysine, and lysozyme) were tested for their effects on microbial hydrophobicity, as determined by adhesion to hydrocarbon and polystyrene. Test strains (Escherichia coli, Candida albicans, and a nonhydrophobic mutant, MR-481, derived from Acinetobacter calcoaceticus RAG-1) were vortexed with hexadecane in the presence of the various polycations, and the extent of adhesion was measured turbidimetrically. Adhesion of all three test strains rose from near zero values to over 90% in the presence of low concentrations of chitosan (125 to 250 micrograms/ml). Adhesion occurred by adsorption of chitosan directly to the cell surface, since E. coli cells preincubated in the presence of the polymer were highly adherent, whereas hexadecane droplets pretreated with chitosan were subsequently unable to bind untreated cells. Inorganic cations (Na+, Mg2+) inhibited the chitosan-mediated adhesion of E. coli to hexadecane, presumably by interfering with the electrostatic interactions responsible for adsorption of the polymer to the bacterial surface. Chitosan similarly promoted E. coli adhesion to polystyrene at concentrations slightly higher than those which mediated adhesion to hexadecane. Poly-L-lysine also promoted microbial adhesion to hexadecane, although at concentrations somewhat higher than those observed for chitosan. In order to study the effect of the cationic protein lysozyme, adhesion was studied at 0 degree C (to prevent enzymatic activity), using n-octane as the test hydrocarbon. Adhesion of E. coli increased by 70% in the presence of 80 micrograms of lysozyme per ml. When the negatively charged carboxylate residues on the E. coli cell surface were substituted for positively charged ammonium groups, the resulting cells became highly hydrophobic, even in the absence of polycations. The observed "hydrophobicity" of the microbial cells in the presence of polycations is thus probably due to a loss of surface electronegativity. The data suggest that enhancement of hydrophobicity by polycationic polymers is a general phenomenon.
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PMID:Mechanism of enhancement of microbial cell hydrophobicity by cationic polymers. 221 2

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

Adhesion and spreading of BHK21 cells on adsorbed bovine and foetal bovine serum require addition to the medium of a divalent cation. Divalent cations are effective in the order Mn2+ greater than Co2+ greater than Mg2+ greater than Ca2+, with Ca2+ ineffective below 10(-4)M. On purified fibronectin, however, no added divalent cation is required, since the requirement is largely met by adventitious Ca2+ (circa 10(-5)M) in nominally divalent cation-free saline. In such background Ca2+, adhesion and spreading on fibronectin are only slightly slower than in optimal Mg2+, and appear identical, morphologically, and in sensitivity to cytochalasin D. Cells also spread on fibronectin in response to Mg2+, when Ca2+ is buffered below 10(-6)M, showing that external Ca2+ is not needed as a source for an increase in internal Ca2+. Cells can be induced to spread on serum in low Ca2+ by substantially increasing the fibronectin concentration; this supports other evidence that at its unsupplemented concentration, fibronectin contributes little to the spreading of these cells on serum. The Ca2+ requirement for spreading on preparations of vitronectin (serum spreading factor), partially purified from bovine serum, is similar to that on whole serum. Thus the difference in divalent cation requirement between serum and fibronectin may arise because, on serum, the dominant protein responsible for induction of spreading is vitronectin rather than fibronectin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:A major difference between serum and fibronectin in the divalent cation requirement for adhesion and spreading of BHK21 cells. 244 8


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