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Biomedical subjects

J W Stevens

Publications and source records attributed to J W Stevens.

27 records · Page 2Linked to original sources
PubMed1992

Isolation and characterization of bovine gingival proteoglycans versican and decorin.

1. We have isolated, chemically and immunologically characterized versican and decorin from bovine gingiva. 2. Versican was of large molecular weight and the molecular size of the core protein was estimated to be greater than 200 kDa. 3. The glycosaminoglycan chains were susceptible to chondroitinase ABC and N-linked oligosaccharides were present on the protein core of the molecule. 4. Immunological studies provided evidence that a hyaluronic acid binding region was present in the core protein of versican. 5. The overall structure was similar to that of versican isolated from bovine sclera. 6. Decorin had a molecular weight of 102 kDa and its glycosaminoglycan chain was completely digested by specific glycosidases. 7. The partially deglycosylated core protein had a molecular weight of 55 kDa and N-linked oligosaccharides were present on the molecule.

Amino Acids↗
PubMed1989

Molecular cloning of rat and human type IX collagen cDNA and localization of the alpha 1(IX) gene on the human chromosome 6.

Type IX collagen is found in hyaline cartilage, where it is associated with type II collagen in quarter-staggered collagen fibrils. Chicken type IX collagen has been extensively characterized and shown to contain molecules with three triple-helical domains, interspersed with non-triple-helical sequences. The molecule contains three, genetically distinct, subunits and one of these subunits carries a covalently bound glycosaminoglycan side chain. In the present report, we describe for the first time the primary structure of mammalian type IX collagen chains, based on cloning and sequencing of cDNA from rat and human cDNA libraries. The results suggest that mammalian alpha 1(IX) chains have the same multi-domain structure as the avian protein. We also demonstrate, by in situ hybridization of chromosome spreads, that the human alpha 1(IX) collagen gene is located on the long arm of chromosome 6. The cloning of human type IX collagen cDNA provides a probe for molecular studies of human chondrodysplasias that may involve abnormalities in this extracellular collagen-proteoglycan.

Amino Acid Sequence↗
PubMed1986

N-terminal carbamylation of the hyaluronic acid-binding region and the link protein from the chondrosarcoma proteoglycan aggregate.

The ternary complex consisting of a 65-kDa peptide originating from the proteoglycan core protein and a 43-kDa link protein bound to hyaluronic acid was purified from a clostripain digest of the rat chondrosarcoma aggregating proteoglycan and 14C-carbamylated with potassium [14C]cyanate. At a pH of 8.0, 14C-carbamylation of the alpha-NH2 groups in the N-terminal amino acids was favored over carbamylation of epsilon-NH2 groups in the lysinyl residues for both the 65- and 43-kDa species. Two-dimensional tryptic peptide maps revealed a single major, distinctly different, fluorographic spot for each. These tryptic peptides had approximate masses of 4.5 kDa (from the 65-kDa species) and 3.0 kDa (from the 43-kDa species) on sodium dodecyl sulfate-polyacrylamide gel electrophoresis gels and each contained greater than 60% of the total radioactivity associated with its original polypeptide. Primary amino acid sequencing of the 65-kDa species gave a defined sequence for the first 4 N-terminal residues, whereas sequencing through the first 4 residues of a fully carbamylated species gave no dabsylated derivative for the first residue but identical residues in position 2-4 as for the noncarbamylated species and loss of radioactive derivative. Digests of 14C-carbamylated ternary complex with alpha-chymotrypsin resulted in a limit 14C-carbamylated 55-kDa species which contained greater than 85% of the radiolabel originally in the 65-kDa peptide. Similarly, trypsin generated two radiolabeled species, 60 and 58 kDa. These limit digest peptides (55, 60, 58 kDa) all contained the 4.5-kDa N-terminal tryptic peptide. Thus peptides removed from the 65-kDa peptide digestion with either alpha-chymotrypsin or trypsin were on the carboxyl end of the molecule.

Animals↗
PubMed1984

Characteristics of the core protein of the aggregating proteoglycan from the Swarm rat chondrosarcoma.

A ternary complex of hyaluronic acid-binding region and link protein bound to hyaluronic acid was isolated from limit clostripain digests of proteoglycan aggregates isolated from the Swarm rat chondrosarcoma. Under these conditions, the hyaluronic acid-binding region has a molecular weight of approximately equal to 65,000 (HA-BR65). N-terminal amino acids in the complex were selectively 14C-carbamylated. The resulting derivatized HA-BR65 was isolated, and tryptic peptide maps were prepared and developed on two-dimensional TLC sheets. A single, labeled peptide was obtained which gave a Mr by approximately equal to 8,000 by SDS-PAGE. Chymotrypsin digestion of the ternary complex reduced the molecular weight of HA-BR65 to a polypeptide of approximately equal to 55,000 (HA-BR55) which still retains the same N-terminal tryptic peptide. Partial digestion of proteoglycan aggregates with clostripain generated a series of larger intermediates with the hyaluronic acid-binding region. Direct SDS-PAGE analysis revealed one major intermediate with approximately equal to 109,000 (HA-BR109) as well as HA-BR65. After chondroitinase digestion, two additional prominent intermediates were observed on a SDS-PAGE gel at Mr approximately equal to 120,000 (HA-BR120) and approximately equal to 140,000 (HA-BR140). All the intermediates were recognized by a monoclonal antibody specific for the hyaluronic acid-binding region, and all of them contained the same N-terminal tryptic peptide. The results indicate that the N terminus of the core protein is at the hyaluronic acid-binding end of the proteoglycan and that the chondroitin sulfate chains are first present on the core protein in a region between 109,000 and 120,000 molecular weight away from the N terminus.

Amino Acid Sequence↗
PubMed1981

Proteoglycan structure and metabolism in normal and osteoarthritic cartilage of guinea pigs.

Sulfated proteoglycan structure and metabolism in osteoarthritic articular cartilage from the hind-limb joints of guinea pigs in which the disease had been surgically induced were evaluated and compared with those from nonoperated or sham-operated controls. In these studies, conducted on animals receiving high and low dietary levels of ascorbic acid, the effect of vitamin C on these variables was also examined. Sulfated proteoglycan biosynthesis per unit of DNA as reflected by in vivo uptake of 35S-sulfate was stimulated both by arthritic development and high dietary vitamin C. Under these conditions, the specific activities, 35S-cpm/micrograms uronic acid, of the proteoglycans were elevated. Neither arthritic development nor variation in dietary levels of vitamin C altered the structure of the proteoglycans. Two species of proteoglycans that exhibited the same electrophoretic mobilities in agarose/acrylamide gels, the same elution profiles on high performance liquid chromatography,, and the same galactosamine/glucosamine ratios were found in all normal and osteoarthritic cartilage specimens tested. The specific activities of these two specimens tested. The specific activities of these two species were dissimilar. In all samples, the larger of the two species had a higher specific activity.

Animals↗
PubMed1979

L-ascorbic acid: effects on aortic glycosaminoglycan 35S incorporation in rabbit-induced atherogenesis.

The effects of L-ascorbic acid on 35S-incorporation into thoracic aorta glycosaminoglycans and upon aorta cholesterol levels were determined in hypercholesterolemic rabbits. No significant difference was observed in serum free or esterified cholesterol levels between animals receiving L-ascorbic acid supplementation or saline while maintained on a cholesterol diet (0.5%). A 15-fold higher serum cholesterol was observed in animals on the cholesterol diet to those animals which received a normal rabbit (Purina) diet. L-Ascorbic acid increased sulfated glycosaminoglycans concentrations in hypercholesterolemic rabbits which paralleled lower tissue free and esterified cholesterol levels. The 35S-specific activity of glycosaminoglycans in hypercholesterolemic animals receiving saline was much greater than in those animals receiving L-ascorbic acid. This suggests that L-ascorbic acid plays a role in the maintenance of adequate levels of aortic sulfated glycosaminoglycans. This then is a suggested biochemical mechanism of L-ascorbic acids interaction in the atherogenic process.

Animals↗
PubMedDate not supplied

Bayesian assessment of sample size for clinical trials of cost-effectiveness.

The authors present an analysis of the choice of sample sizes for demonstrating cost-effectiveness of a new treatment or procedure, when data on both cost and efficacy will be collected in a clinical trial. The Bayesian approach to statistics is employed, as well as a novel Bayesian criterion that provides insight into the sample size problem and offers a very flexible formulation.

Bayes Theorem↗
PubMedDate not supplied

African American female adolescent identity development: a three-dimensional perspective.

African American female adolescents have unique identity issues that structure developmental tasks. Qualitative data from a longitudinal research project are used to explicate a three-dimensional model of the identity developmental process in early-age African American female adolescents. The limitations of a gender analysis model of voice and connection are noted. It is suggested that the African American female adolescent experiences a relational crisis in both racial and gender identity development. Moreover, African American female adolescents develop skillful, unique, expressionistic, and assertive styles of relating to negotiating perceived hostile environments. Practice implications for child welfare are outlined.

Adolescent↗