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Biomedical subjects

L Rodén

Publications and source records attributed to L Rodén.

At least 73 records · Page 4Linked to original sources
PubMed1977

The covalent linkage of protein to carbohydrate in the extracellular protein-polysaccharide from the red alga Porphyridium cruentum.

The extracellular anionic polysaccharide isolated from cultures of a unicellular red alga, Porphyridium cruentum, contains a small amount of protein after extensive purification. The polysaccharide and protein are recovered in the same fraction after isopycnic CsCl-density-gradient centrifugation in 4M-guanidinium chloride, under conditions designed to separate proteins from polysaccharide. The peptide portion of the protein-polysaccharide is released from the polysaccharide by alkali under conditions for beta-elimination. The released peptide is non-diffusible, but in can be separated from the polysaccharide by precipitation of the polysaccharide as the cetylpyridinium complex. Under conditions for beta-elimination of certain O-glycosidic carbohydrate-protein linkages, selective destruction of serine and threonine occurs. The addition of a reducing agent to the alkali mixture produces a selective increase in alanine and alpha-aminobutyric acid. Addition of a tritiated reducing agent to the alkali mixture produces radioactive alanine and alpha-aminobutyric acid, and xylitol as the only sugar alcohol. Similar results are obtained from glycopeptides isolated from partial acid hydrolysates. A macromolecular structure of the protein-polysaccharide is suggested by a comparison of the intrinsic viscosity of material before and after treatment with alkali and proteolytic enzymes.

Amino Acids↗
PubMed1977

The effects of acetylation on the binding region of cartilage proteoglycans to hyaluronic acid.

Proteoglycans in cartilage are found as aggregates and as monomers. Evidence has been obtained indicating that hyaluronic acid, normally present in this tissue, binds together monomers into large molecular weight aggregates. In this investigation, the interacting region of the protein backbone has been studied. The results unequivocally demonstrated that the epsilon amino groups of lysine are involved in hyaluronic acid binding to proteoglycans and that their blocking by acetylation either prevents reaggregation or disaggregates the high mol.w aggregates.

Acetylation↗
PubMed1975

Biosynthesis of chondroitin sulfate. Solubilization of chondroitin sulfate glycosyltransferases and partial purification of uridine diphosphate-D-galactose:D-xylose galactosyltrans.

UDP-D-Galactose:D-xylose galactosyltransferase, a membrane-bound enzyme which catalyzes the second glycosyl transfer reaction in the biosynthesis of chondroitin sulfate chains, has been solubilized and partially purified from embryonic chick cartilage. Solubilization was effected by treatment of a particulate fraction of a homogenate (sedimenting between 10,000 and 100,000 times g) with the nonionic detergent Nonidet P-40 (0.5%) and KCl (0.5 M) or by the alkali-detergent method described previously (Helting, T. (1971) J. Biol. Chem. 246, 815-822). The applicability of the salt-detergent procedure as a general method for solubilization of membrane-bound glycosyltransferases was tested by assay of four other glycosyltransferases involved in chondroitin sulfate synthesis (UDP-D-xylose:core protein xylosyltransferase, UDP-D-galactose:4-O-beta-D-galactosyl-D-xylose galactosyltransferase, UDP-D-glucuronic acid: 3-O-beta-D-galactosyl-D-galactose glucuronosyltransferase, and UDP-N-acetyl-D-galactosamine: (GlcUA-GalNAc-4-sulfate)4 N-acetylgalactosaminyltransferase). In each case, greater than 70% of the activity was solubilized and, on gel chromatography on Sephadex G-200, the enzymes appeared largely in included positions and partially separated from each other. After partial purification by gel chromatography on Sephadex G-200, UDP-D-galactose:D-xylose galactosyltransferase was purified further by chromatography on one of several affinity matrices, i.e. xylosylated core protein of cartilage proteoglycan coupled to CNBr-activated Sepharose, a core protein matrix saturated with UDP-D-xylose:core protein xylosyltransferase or UDP-D-xylose:core protein xylosyltransferase covalently bound to Sepharose. The specific activities of the enzyme preparations obtained by these procedures were approximately 1000-fold greater than that of the crude homogenate.

Animals↗
PubMed1975

The linkage of corneal keratan sulfate to protein.

The linkage of corneal keratan sulfate to protein has been investigated. After exhaustive digestion of bovine corneas with papain and pronase, a product was obtained in which aspartic acid was the predominant amino acid and constituted 59% of the total amino acids. A carbohydrate-protein linkage fragment was isolated from this preparation by a relatively simple procedure involving the following steps: (1) partial acid hydrolysis, adsorption of glycopeptides and other cationic material on Dowex 50-X2 (H+) and elution with 0.25 M HCl: (2) paper electrophoresis of the eluted fraction at pH 6.5 and pH 1.9; (3) paper chromatography; and (4) final purification by column chromatography on Aminex A"-5 resin. The structure of the linkage fragment was established as 2-acetamido-1-(L-beta-aspartamido)-1,2-dideoxy-beta-D-glucose (Asn-GlcNAc). Evidence for this structure was obtained from qualitative and quantitative analyses as well as from the migration characteristics in several chromatographic anc electrophoretic systems. Further support for the identity of the isolated compound was provided by treatment with beta-aspartyl N-acetylglucosyl-amine amidohydrolase which specifically cleaves Asn-GlcNAc or asparaginyl-oligosaccharides. It is concluded that corneal keratan sulfate is bound to protein via a N-glycosylamine linkage between N-acetylglucosamine and asparagine: this type of linkage is common to many glycoproteins.

Acetylglucosamine↗
PubMed1975

Age-dependent changes on the state of aggregation of cartilage matrix.

The state of aggregation of cartilage matrix and its variations with age have been studied by biochemical, cytochemical, and ultrastructural methods. Determination of proteoglycans and collagen in costal cartilage from newborn, 4-week-, and 4-year-old rabbits showed that marked changes occurred during the first 4 weeks, i.e., a 30 percent decrease in proteoglycan content and a 3-fold increase in collagen. No significant changes were observed thereafter. The extractability of the proteoglycans after treatment with 4 M guanidinium chloride varied drastically, depending upon the age of the animal. Whereas 73 per cent of the proteoglycans was extracted from the neonatal tissue, the yield from old tissue was only 10 per cent. It is suggested that the decrease in extractability with age is related to the increase in collagen content. Cytochemical observations demonstrated that, in the neonatal tissue, metachromatic staining of the matrix was lost after guanidinium chloride treatment, with the exception of chromotropic granules still present in the lacunae. In the 1-month-old animals, a general decrease in the staining reaction ensued, except in the perilacunar areas. In the extracted tissues, instead, the picture changed drastically in that metachromasia was decreased in the interterritory but was not modified, as in the neonatal tissue, in the areas adjacent to the cell nests. In the old tissue, the patchy and irregular staining, typical of the cartilage of this age, was not modified by extraction with the guanidium salt. At the ultrastructural level, the proteoglycans in the neonatal tissue appeared as granules of different size, the largest having dimensions of about 900 A, In the 1-month-old animals, degenerative changes were already observed in the chondrocytes, including loss of the perilacunar space, reduction of the endoplasmic reticulum, and an increase of intracellular glycogen and lipids. The proteoglycan droplets, so prominent at the neonatal stage, were no longer evident. In the older animals, apart from the many foci of mineralization, the chondrocytes were almost all degenerated and showed signs of extensive vacuolation and lipid infiltration.

Aging↗