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

Adhesion of platelets to several polymer- and protein-coated glass surfaces has been studied in vitro. The apparatus consists of a cylindrical probe rotating in a test tube containing the platelet medium and allows close control of fluid shear and mass transport. Suspensions of washed pig platelets constitute the basic platelet medium, and can be modified by adding back red cells and plasma proteins. Adhesion is measured via 51Cr-labeling of platelets. In the absence of red cells, identical low levels of adhesion were seen on all surfaces and saturation was reached within 2 min. In the presence of red cells, adhesion was greater. Saturation on all surfaces except fibrinogen and collagen again occurred within 2 min. The adhesion levels on polymer surfaces and glass were indistinguishable, while those on albumin were lower and those on fibrinogen were higher. Collagen was the most reactive surface. It did not equilibrate within 15 min., and kinetic data indicated a platelet diffusivity strongly dependent on hematocrit. These effects were attributed to rotational and translational motion of the red cells causing increased diffusion and surface-platelet collision energy.
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PMID:Adhesion of platelets to artificial surfaces: effect of red cells. 127 Apr 59

Adhesion durability between dentin pretreated with 10-3 and 4-META/MMA-TBB resin was studied. Reduction of etching periods with 10-3 was not so effective as expected. The weakening of bond strength during immersion in water at 37 degrees C to the dentin pretreated for 1 sec occurred faster than those for either 5 sec or 10 sec. The strength decreased from 12 MPa at 1 day to 9 MPa at 3 months, 3 MPa at 6 months and finally 2 MPa at 1 year in the case of 1 sec pretreated dentin. On the other hand, the strength became half after the storage in water for 1 year in the cases of 5 and 10 sec pretreated dentins. Combination of 10-3 pretreatment and subsequent glutaraldehyde treatment could stabilize the decrease but not completely. SEM and TEM examinations suggested that dentinal collagen exposed by the etching but not entangled and impregnated by poly (4-META-co-MMA) easily deteriorated by water during the longer immersion. Collagen modified with 10-3 and then with glutaraldehyde was also changed by the longer immersion.
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PMID:[Durability of bonding between 4-META/MMA-TBB resin to dentin pretreated with 10-3. The effect of 10-3 pretreating period and subsequent glutaraldehyde treatment]. 213 46

In vitro assays using endothelial cells (EC, bovine corneal) were performed to study adhesion and spreading on collagen types I and IV. Adhesion was quantitatively analyzed by counting the EC under a light microscope. Spreading was determined by measuring cell area using a scanning electron microscope (SEM). Collagen types I, IV, and IV-F, a mixture of 70, 120, and 140 KD fragments of type IV, all promoted EC adhesion, Types IV and IV-F showed evidence of giving a more marked adhesion than type I. A study of cell area, carried out under identical conditions, such as those in the adhesion assay, showed that types I and IV-F, but not type IV, promoted cell spreading. This provides evidence that cell adhesion and spreading are indeed separate biological phenomena. Furthermore, the ability of fragments of type IV collagen to promote both cell adhesion and spreading may represent an inherent repair mechanism in damaged endothelium.
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PMID:Adhesion and spreading of corneal endothelial cells on collagens type I and IV in vitro: a model to study mechanisms of endothelial repair. 236 45

A simple turbidimetric method is described that permits quantitation of both the number and the rate at which human fixed washed platelets adhere to fibrillar collagen in suspension. Fixed washed platelets were mixed with buffer or test sample in an aggregometer cuvette. Collagen was added, and the change in light transmission was recorded at 37 degrees C. Percent adhesion was obtained from the maximum change in light transmission within 5 minutes, and the adhesion rate was calculated from the initial slope of the adhesion curve. In this system, the percent adhesion was optimal at ionic strengths of 0.1 to 0.15 in a pH range of 7.0 to 8.0. Percent adhesion could be increased either by lowering the platelet number or by increasing the collagen concentration. No adherence of fixed washed platelets to heat-denatured collagen or Cytodex 3 beads was observed. Adhesion rate increased with greater stirring speed, but decreased with increasing concentrations of bovine serum albumin or normal human plasma, but the percent adhesion remained relatively constant. The rate of adhesion in 20% normal human plasma was greater than that in 1% to 4% bovine serum albumin buffer. This suggests that normal plasma contains some factor(s) that can overcome the inhibitory effect of protein on the rate of adhesion of fixed washed platelets to fibrillar collagen.
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PMID:A quantitative method for studying platelet adhesion to collagen. 671 55

Collagen is one of the major constituents of glomerular basal lamina. Its thrombogenecity has been systematically studied in our laboratory by aggregometry, adenine nucleotide release assay, and electron microscopy. The purified human glomerular basal lamina (HGBL) preparation does not induce platelet degranulation, nucleotide release, or aggregation, although adhesion and spreading of platelets on HGBL are observed. Isolated monomeric HGBL collagen or insoluble HGBL collagen in its native state of organization are similarly inactive. Modification of carbohydrate moieties by sialase, alpha-glucosidase, or sodium periodate oxidation has no effect on HGBL's inability to induce platelet release reaction or aggregation. Therefore, HGBL collagen is not thrombogenic as has been suspected. Adhesion and spreading of platelets on HGBL, which require the noncollagen constituents of HGBL and divalent cations, represent a temporary capillary pavement for endothelial defect distinct from thrombogenic activity of platelets.
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PMID:Human platelets and glomerular basal lamina interaction. 732 14

Collagen type VI, which forms characteristic microfibrillar structures, is assembled from three individual alpha(VI) chains that form a short triple helix and two adjacent globular domains. Expression of all three alpha (VI) collagen chains in the human bone marrow (BM) microenvironment could be detected by chain-specific antibodies in tissue sections and in the adherent stromal layer of long-term BM cultures. In functional studies, collagen type VI was shown to be a strong adhesive substrate for various hematopoietic cell lines and light-density BM mononuclear cells. The adhesive site within the molecule seems to be restricted to the triple helical domain of all three alpha (VI) chains, because individual alpha (VI) chains were not active in the attachment assays. Adhesion of the hematopoietic cell lines to collagen VI was dose-dependent and could be inhibited by heparin. Although the triple helix contains several RGD sequences, adhesion of the hematopoietic cell types to collagen VI could be blocked neither by RGD-containing peptides nor by a neutralizing antibody to the beta 1 integrin subunit. In combination with an antiadhesive substrate, the binding properties of collagen VI could be downregulated. These data suggest that this collagen type may play an important role in the adhesion of hematopoietic cells within the BM microenvironment.
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PMID:Collagen type VI in the human bone marrow microenvironment: a strong cytoadhesive component. 765 6

Platelet membrane glycoprotein IV (GPIV) is a cell-surface glycoprotein that has been proposed as a receptor for collagen. Recently, it has been shown that platelets with the Naka-negative phenotype lack GPIV on their surface, whereas donors with this phenotype are healthy and do not suffer from hematologic disorders. In this study, we compared Naka-negative platelets with normal platelets in adhesion to collagen types I, III, IV, and V and the extracellular matrix of endothelial cells (ECM) under static and flow conditions. No differences in platelet adhesion and subsequent aggregate formation on the collagens types I, III, and IV were observed under static and flow conditions. Adhesion of both homozygous and heterozygous Naka-negative platelets to collagen type V was strongly reduced under static conditions. Collagen type V was not adhesive under flow conditions. No difference in platelet adhesion to ECM was observed, which suggests that GPIV is not important in adhesion to subendothelium, for which ECM may serve as a model. These results indicate that GPIV is not a functional receptor for collagen under flow conditions.
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PMID:Platelet adhesion to collagen and endothelial cell matrix under flow conditions is not dependent on platelet glycoprotein IV. 819 59

A device based on the cone-and-plate flow geometry commonly employed for viscometry was developed for the investigation of cell-surface interactions. The cone-and-plate geometry is capable of generating uniform, constant shear-rate flow fields, and control of cone rotational speed allows for easy variation of fluid shear rate. The current design is adapted for use with any material that is available in the form of a flat plate (film or coating). It also allows for replicate samples (the same or different surfaces) to be evaluated simultaneously. The device was tested under varying flow conditions for its ability to measure platelet adhesion from suspensions of washed platelets containing red cells. Collagen- and albumin-coated polymer materials were used as "standard" surfaces of known platelet reactivity (high and low, respectively). Adhesion to the collagen-coated surface was measured over a range of shear rate from 0 to 300 s(-1) and times up to 15 min. Platelet adhesion was observed to increase with increasing shear rate and time. Adhesion was significantly higher in the presence of red cells as has been observed by others. Effective platelet diffusion coefficients, calculated from the data on adhesion to the collagen surface, increased with increasing shear rate. Very little platelet adhesion to the albumin-coated surface, known to be unreactive to platelets, was observed when measured over a 15 min time period at 300 s(-1) shear rate, indicating that the device itself does not stimulate the platelets in the flow field. The data generated provide validation for this device as a simple means of measuring cell adhesion under controlled flow conditions to any smooth surface available in flat plate form.
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PMID:A cone-and-plate device for the investigation of platelet biomaterial interactions. 905 27

Prostate cancer selectively metastasises to the bone. To investigate the importance of prostate epithelial cell adhesion to bone marrow cells in this process we examined the binding of human primary prostatic epithelial cells (PEC) to human bone marrow stromal cultures (BMS). We found that PEC derived from both malignant and benign tissue showed greater adhesion to BMS than to benign prostatic fibroblasts (median difference was 340% and 200% respectively), skin fibroblasts or plastic tissue culture plates. Adhesion to BMS grown from the bone marrow of patients with prostatic skeletal metastases was no different from those grown from normal bone marrow. The role of integrin molecules in these cell interactions was determined. Collagen type I and fibronectin were found to increase PEC adhesion whereas vitronectin and laminin did not. Inhibition studies demonstrated that although there was heterogeneity between samples, antibodies against the integrins alpha2 and beta1 consistently inhibited PEC binding to BMS. This result was more marked for PEC derived from malignant tissue. However studies investigating the effects of disintegrins and anti-alpha3 and anti-alpha5 integrins indicated that for a percentage of patients these integrins and RGD (arginine, glycine, aspartamine)-dependent binding pathways were also involved. In summary, the results indicate that BMS are adherent to primary PEC derived from both malignant and benign tissue. The integrin alpha2beta1 is a major contributor to this interaction.
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PMID:Primary prostatic epithelial cell binding to human bone marrow stroma and the role of alpha2beta1 integrin. 917 23

Collagen-platelet interaction, occurring in hemostasis but also a cause of thrombosis, is a two-step process of adhesion and activation involving the sequential recognition of distinct receptors. Adhesion involves first the reversible recognition of collagen-bound von Willebrand factor by the platelet receptor complex Gp Ib/IX/V, followed by direct interaction between collagen and the platelet integrin receptor alpha2beta1, which binds to specific sequences in collagen in which the GER motif appears important. Platelet activation then follows from the recognition by the receptor Gp VI of GPP* sequences in collagen, culminating in signalling events unique to collagen as a platelet agonist: Gp VI leads via the novel platelet Fc receptor gamma-chain to p72syk and phospholipase Cgamma2.
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PMID:The collagen-platelet interaction. 977 9


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