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Biomedical subjects

A Linker

Publications and source records attributed to A Linker.

11 recordsLinked to original sources
PubMed1992

Topography of proteoglycan and glycosaminoglycan free chain expression in 3T3 fibroblasts and human keratinocytes.

Synthesis of heparan sulfate-free chains by human keratinocytes is upregulated during terminal differentiation. The cellular location of this product class and the significance of the differentiation effect are unknown. Differential plasma membrane shearing with cationized colloidal silica was used to evaluate the compartmentalization of the heparan and chondroitin sulfate free chains and their respective proteoglycans in 3T3 fibroblasts and human keratinocytes. The method exploits the topologic segregation of plasma membranes of adherent cells into ventral, dorsal, and intracellular domains and the selective binding of the silica to the dorsal membranes, which by shearing can be separated from ventral membranes adherent to the substratum. Analysis of membrane preparations from sheared cells that had been prelabeled with [35S]-sulfate revealed the proteoglycans to be predominantly ventral, at which location a matrix binding function could be accommodated. Proteoglycans were also recovered from dorsal and intracellular membranes, suggesting active trafficking between intra- and extra-cellular sites. In contrast, the major fraction of heparan and chondroitin sulfate free chains was either cytosolic or associated with intracellular membranes, with the remaining approximately 20% segregated to dorsal and ventral membranes. These results suggest different cellular functions for the proteoglycans and glycosaminoglycan free chains. The partial localization of the free chains to peripheral membranes is compatible with our prior hypothesis that they arise by processing of precursor proteoglycans on cell surfaces. Following this origin, the free glycosaminoglycan polymers could be available to bind ligands such as cytokines prior to transport to intracellular sites of action.

3T3 Cells↗
PubMed1979

Structure of heparan sulphate oligosaccharides and their degradation by exo-enzymes.

Oligosaccharides obtained from heparan sulphate by nitrous acid degradation were shown to be degraded sequentially by beta-D-glucuronidase or alpha-L-iduronidase followed by alpha D-N-acetylglucosaminidase. Structural analysis of the tetrasaccharide fraction showed the following. (1) N-Acetylglucosamine is preceded by a non-sulphated uronic acid residue that can be either D-glucuronic of L-iduronic acid, but followed by a glucuronic acid residue. (2) The N-acetylglucosamine in the major fraction is sulphated. (3) Very few if any of the uronic acid residues are sulphated (4). The results indicate that the area of the heparan sulphate chain where disaccharides containing N-acetylglucosamine and N-sulphated glucosamine residues alternate is higher in sulphate content than expected and that the sulphate groups are mainly located on the hexosamine units.

Acetylglucosaminidase↗
PubMed1979

Structure of the antithrombin-binding site in heparin.

Heparin preparations from pig intestinal mucosa and from bovine lung were separated by chromatography on antithrombin-Sepharose into a high-affinity fraction (with high anticoagulant activity) and a low-affinity fraction (with low anticoagulant). Antithrombin-binding heparin fragments (12-16 monosaccharide units) were prepared, either by digesting a high-affinity heparin-antithrombin complex with bacterial heparinase or by partial deaminative cleavage of the unfractionated polysaccharide with nitrous acid followed by affinity chromatography on immobilized antithrombin. Compositional analysis based on separation and identification of deamination products reduced with sodium boro[3H]hydride showed that nonsulfated L-iduronic acid occurred in larger amounts in high-affinity heparin than in low-affinity heparin; furthermore, this component was concentrated in the antithrombin-binding regions of the high-affinity heparin molecules, amounting to approximately one residue per binding site. It is suggested that nonsulfated L-iduronic acid is essential for the anticoagulant activity of heparin. The location of the non-sulfated uronic acid in the antithrombin-binding site was determined by periodate oxidation of antithrombin-binding fragments containing a terminal 2,5-anhydro-D-[1-3H]mannitol unit. Tentative structures for antithrombin-binding sequences in heparin are proposed, including some structural variants believed to be compatible with, but not required for, activity.

Animals↗
PubMed1978

Gelatinous transformation of the bone marrow.

A study of so-called gelatinous transformation of the bone marrow in 14 patients is presented. The condition is characterized by the presence of extracellular "gelatinous" material, fat atrophy, and associated focal marrow hypoplasia and is often mistaken as representing edema, necrosis, or amyloid. Histochemical studies indicate that the extracellular substance is hyaluronic acid. Though the lesion is usually associated with severe weight loss and cachexia, it appears that factors other than malnutrition must play a significant role in the pathogenesis of gelatinous transformation. Anemia, frequently seen in these patients, does not appear to be a consequence of gelatinous transformation.

Adipose Tissue↗
PubMed1977

Specificity of flavobacterial glycuronidases acting on disaccharides derived from glycosaminoglycans.

The specificity of the unusual flavobacterial glycuronidases that act on disaccharides containing delta4,5-unsaturated uronic acids was reinvestigated. The results show that the enzyme that hydrolyses the uronidic bond in disaccharides from hyaluronic acid and the chondroitin sulphates appears to be mainly specific for beta-D-(1 leads to 3)-derived linkages. The enzyme that hydrolyses the uronidic bond in a variety of disaccharides obtained from heparan sulphate and heparin appears to be specific for beta-D-(1 leads to 4)- and alpha-L-(1 leads to 4)- derived linkages. Thus the glycuronidases seem to be specific for linkage position rather than anomeric configuration, as had been thought previously. In addition, the data confirm other evidence that the major glucuronidic linkages in heparan sulphate and heparin have the beta-D-configuration, and the iduronidic linkages the alpha-L-configuration.

Chondroitin Sulfates↗
PubMed1975

Structural studies of heparitin sulfates.

Heparitin sulfate fractions with a large range in sulfate content were subjected to degradation by Flavobacterium heparinase and by nitrous acid. The products obtained were fractionated by chromatography, characterized, and used to arrive at tentative structures for these complex polysaccharides. The heparitin sulfate chains examined appear to be composed of: 1. uninterrupted blocks of N-acetylglucosamine containing disaccharides; 2. larger blocks with a molecular weight range of 5000 to 6000 which include the N-acetyl block but do not contain heparinase sensitive linkages; 3. segments containing mainly areas where N-acetyl, N-sulfate and some disulfated units alternate in the chain. The size and arrangement of these polymer segments seem to vary with the sulfate content of a particular heparitin sulfate. For instance, the polysaccharides with the highest degree of sulfation do not appear to contain N-acetyl blocks of significant size.

Acetates↗
PubMed1975

The uronidic linkages in heparitin sulfate.

Beta-glucuronidase preparations obtained from various sources were shown to liberate free D-glucuronic acid from heparitin sulfate oligosaccharides. Some free L-iduronic acid could also be detected in the hydrolyzates indicating the presence of an iduronidase in the preparations. The data presented indicate that heparitin sulfate contains a substantial amount of beta-D-glucuronidic and some alpha-L-iduronidic linkages.

Animals↗