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Biomedical subjects

B Obrink

Publications and source records attributed to B Obrink.

At least 73 records · Page 4Linked to original sources
PubMed1981

Substrate adhesion of rat hepatocytes: mechanism of attachment to collagen substrates.

Attachment of rat hepatocytes to collagen, which occurs without the aid of fibronectin, was found to be a time-dependent reaction characterized by an initial lag phase of 10-20 min before stable attachment bonds began to form. Increasing the density of molecules in the collagen substrates enhanced the rate of cell attachment. The hepatocytes attached essentially equally well to all the collagen types tested (types I, II, III, IV and V). The initial rate of cell attachment was more rapid to native collagen than to denatured collagen or alpha 1(I) chains, apparently indicating different affinities of the cells for these substrates. However, if cells were incubated for 60 min or more, efficient attachment occurred to the alpha 1(I) chain and to all cyanogen-bromide-treated peptides tested (alpha 1-CB2, alpha 1-CB3, alpha 1-CB4, alpha 1-CB5, alpha 1-CB6A, alpha 1-CB7, alpha 1-CB8, alpha 2-CB2, alpha 2-CB3 and alpha 2-CB4) but not to the aminopropeptide of type I procollagen. A low but significant degree of attachment also took place to substrates made of synthetic peptides with the collagen-like structures (Gly-Ala-Pro)n, (Gly-Pro-Pro)n and (Gly-Pro-Hyp)n, whereas no attachment was observed to polyproline. We suggest that the cell-binding sites in collagen have a simple structure and occur in multiple copies along the collagen molecule. Addition of collagen in solution inhibited initial cell attachment, an effect that persisted longer on substrates made of alpha 1(I) chain than on denatured collagen. The collected data are interpreted in terms of a model for cell-to-collagen adhesion where the formation of stable attachment bonds requires the binding of several low-affinity receptors, clustered at the site of adhesion, to collagen molecules in the substrate.

Animals↗
PubMed1979

Surface properties of cultured endothelial cells.

Vascular endothelial cells (EC) are non-thrombogenic. The basis for this property is still essentially unknown. This paper summarizes our previous studies on EC associated glycosaminoglycans and on the specific binding of heparin to EC and describes the preventive effect of heparin sulphate (HS) on platelet adhesion to collagen; attempts to affect the binding of platelets to EC by specific removal of endogenous HS were, however, unsuccessful. The possible importance of EC surface HS for interactions with coagulation factors is discussed.

Aspirin↗
PubMed1977

Structure and metabolism of rat liver heparan sulphate.

Rat liver cells grown in primary cultures in the presence of [(35)S]sulphate synthesize a labelled heparan sulphate-like glycosaminoglycan. The characterization of the polysaccharide as heparan sulphate is based on its resistance to digestion with chondroitinase ABC or hyaluronidase and its susceptibility to HNO(2) treatment. The sulphate groups (including sulphamino and ester sulphate groups) are distributed along the polymer in the characteristic block fashion. In (3)H-labelled heparan sulphate, isolated after incubation of the cells with [(3)H]galactose, 40% of the radioactive uronic acid units are l-iduronic acid, the remainder being d-glucuronic acid. The location of heparan sulphate at the rat liver cell surface is demonstrated; part of the labelled polysaccharide can be removed from the cells by mild treatment with trypsin or heparitinase. Further, a purified plasma-membrane fraction isolated from rats previously injected with [(35)S]sulphate contains radioactively labelled heparan sulphate. A proteoglycan macromolecule composed of heparan sulphate chains attached to a protein core can be solubilized from the membrane fraction by extraction with 6m-guanidinium chloride. The proteoglycan structure is degraded by treatment with papain, Pronase or alkali. The production of heparan [(35)S]sulphate by rat liver cells incubated in the presence of [(35)S]sulphate was followed. Initially the amount of labelled polysaccharide increased with increasing incubation time. However, after 10h of incubation a steady state was reached where biosynthetic and degradative processes were in balance.

Animals↗
PubMed1977

Adhesive specificity of juvenile rat and chicken liver cells and membranes.

Liver cells, isolated from either juvenile rats or chickens by a collagenase perfusion technique, reaggregated when maintained in suspension. The cells exhibited marked adhesive specificity; when suspensions contained both cell types, the aggregates consisted primarily of either rat or chicken cells. Adhesive specificity was also observed with plasma membrane fractions isolated from rat liver homogenates, and with comparable fractions from chicken liver. These membranes stimulated aggregation of the homologous but not the heterologous cell type. Other membrane fractions had little or no effect on the aggregation of the homologous cell type. These and other properties of the liver cell and membrane preparations suggest that biochemical studies on cell-cell recognition and adhesion can most effectively be conducted with cells from juvenile and adult animals.

Animals↗