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Biomedical subjects

R G Spiro

Publications and source records attributed to R G Spiro.

At least 91 records · Page 5Linked to original sources
PubMed1981

Comparative studies on amniotic fluid and plasma fibronectins.

Human fibronectin was isolated from second-trimester amniotic fluid, from amniotic fluid obtained at term and from adult plasma. The amniotic-fluid fibronectins had a slightly higher apparent molecular weight on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis than the plasma fibronectin. Early- and late-amniotic-fluid fibronectin had 9.5 and 9.6% carbohydrate respectively, whereas plasma fibronectin had 5.8%. The amniotic-fluid fibronectins had similar mannose and sialic acid contents to plasma fibronectin, but greater amounts of glucosamine, galactosamine, galactose and fucose. There were no detectable differences in the amino-acid composition of amniotic-fluid and plasma fibronectins, and the patterns of peptides obtained after tryptic digestion of fibronectin from the two sources showed extensive similarities. Fibronectins from plasma and amniotic fluid were equally active in promoting cell attachment and were immunologically indistinguishable. These results show that fibronectin from amniotic fluid is more heavily glycosylated than plasma fibronectin or previously analysed fibronectins from cultured fibroblasts. The observed differences in glycosylation may be related to cell type and/or stage of development.

Amino Acids↗
PubMed1980

Isolation and characterization of three major glycoproteins from thyroid plasma membranes.

Three major glycoproteins of calf thyroid plasma membranes were preferentially solubilized by chloroform/methanol extraction and recovered along with glycolipids in the aqueous phase. After removal of lipid from this extract, a fraction was obtained which accounted for about 20% of the carbohydrate of the membrane but only 2% of its peptide weight. Partial resolution of the components could be achieved by filtration on Bio-Gel A-5m, while preparative polyacrylamide gel electrophoresis resulted in the isolation in homogeneous form of approximately equal amounts of the three glycoproteins which were designated as GP-1, GP-2, and GP-3, in order of their increasing mobility. These purified glycoproteins appeared on electrophoresis as single components by periodic acid-Schiff staining as well as by distribution of radioactivity following 3H or 14C labeling. Molecular weights of 100,000, 59,000, and 20,000 were estimated for the three components on the basis of their retardation coefficients. The total carbohydrate content by weight determined for GP-1, GP-2, and GP-3 was 56, 57, and 79%, respectively. The sugar constituents were mannose, galactose, fucose, glucosamine, galactosamine, and sialic acid, which were present in the following mol per cents: GP-1, 13:32:5:24:13:12; GP-2, 20:28:3:32:5:11; GP-3, 12:36:2:34:6:10. Studies performed with various lectins (Bandeiraea simplicifolia I and I (B4), wheat germ, Ricinus communis, and soybean) on the gycoproteins, either native or after treatment with glycosidases (alpha- or beta-galactosidase, neuraminidase), indicated that sialic acid and alpha-linked galactose were in terminal positions, beta-galactosyl residues were internally located, and chains containing the sequence sialic acid-N-acetylgalactosamine were present.

Amino Acids↗
PubMed1979

Glomerular basement membrane metabolism in the diabetic rat. In vivo studies.

The effect of diabetes on the metabolism of the renal glomerular basement membrane has been studied in the rat with the aid of injected tracer doses of tritiated proline. At various times after administration of the labeled amino acid, the specific radioactivities of the proline and hydroxyproline of the basement membranes from alloxan diabetic rats were determined and compared with those of age-matched normal rats. In both normal and diabetic animals the incorporation of radioactivity into the basement membrane was slow and, after a maximum was reached, an extended period of almost constant specific activity of proline and hydroxyproline was observed. The diabetic basement membrane, however, differed from the normal by attaining specific activities of the amino acids which were about twice as high as normal (P less than 0.001 at 42 h after injection of radioisotope). Although the proline concentration of serum and renal cortical fluid was the same in normal and diabetic rats, there were substantial differences in the specific activity of this precursor amino acid in these pools that had to be taken into account to compare the two types of animals. The results of the present study are consistent with an accelerated rate of glomerular basement membrane polypeptide synthesis and proline hydroxylation in diabetes.

Animals↗
PubMed1977

Studies on the metabolism of the renal glomerular basement membrane. Turnover measurements in the rat with the use of radiolabeled amino acids.

The synthesis and degradation of the renal glomerular basement membrane have been investigated in the rat with the aid of injected tracer doses of various tritiated amino acids including L-proline, L-lysine, L-phenylalanine, L-leucine, and glycine. After incorporation into the basement membrane the turnover times of these amino acid constituents, as well as of hydroxyproline and hydroxylysine, were determined from the decay in their specific radioactivities. The loss of radioactivity from the proline and hydroxyproline of the glomerular basement membrane was as slow as that from tail tendon collagen in the same animals (turnover time of more than 100 days) and contrasted with the radiodecay of the proline in other glomerular proteins (turnover time of 9 days). The glycine of the membrane similarly turned over at this very slow rate. The total replacement times of the leucine, hydroxylysine, lysine, and phenylalanine constituents of the basement membrane were determined to be somewhat shorter with a range of 65 to 23 days. The nonuniform turnover of these membrane components may be a function of the polydispersity of the peptide subunits of the basement membrane observed by polyacrylamide gel electrophoresis and may reflect a subtle morphological and functional heterogeneity. The amino acid and saccharide composition of the rat glomerular basement membrane used in these studies are also reported.

Amino Acids↗