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Biomedical subjects

J Picard

Publications and source records attributed to J Picard.

At least 127 records · Page 7Linked to original sources
PubMed1981

Glycosaminoglycan biosynthesis in arterial wall. Sulfation of heparan sulfate in cell membrane of aortic media-intima.

Incubation of microsomal fractions with labelled 3'-phosphoadenylyl sulfate results in incorporation of [35S]sulfate into endogenous glycosaminoglycans. Specific radioactivity observed incorporated into heparan sulfate chains is 10-fold greater than that incorporated into chondroïtin sulfate chains. This is in agreement with the results obtained for glycosylation of glycosaminoglycans in arterial wall membrane fractions. Sulfation of heparan sulfate was studied since it contains N- and O-sulfate groups in contrast with the other sulfated glycosaminoglycans which contain only O-sulfate groups. Sulfation of heparan sulfate occurs rapidly, since sulfate incorporation is detected after exposure for only 0.5 min. Heparan sulfate was identified on the basis of its resistance to hyaluronidase and chondroïtin ABC lyase, its susceptibility to heparitinase, its sensitivity to nitrous acid and the presence of glucosamine as the only hexosamine. The chemical composition of the purified heparan sulfate fractions provides evidence for the high degree of sulfation of its chains. Studies into the distribution of sulfate residues on heparan sulfate at different times of sulfation indicate that N-sulfate groups are not randomly introduced into the polymer. The relationship between the processes of N- and O-sulfation was studied. The present results demonstrate that preferential N-sulfation is obtained for incorporation of labelled precursor over a short period, the O-sulfation occurring on previously N-sulfated heparan sulfate.

Animals↗
PubMed1981

[Heparan sulfate biosynthesis in swine arterial wall: glycosylation and sulfation].

We investigated "in vitro" incorporation of labelled (14C) - or (35S) - precursors into microsomal heparan sulfate of pig aortic media-intima. Heparan sulfate, predominantly located on the external surface of smooth muscle cells, may conceivably provide a mean for the selective binding of plasma components to the arterial wall; functional implications of such binding, have been proposed in atherogenesis and thrombogenesis processes. We demonstrated the great metabolic activity of heparan sulfate chains. By evaluation of radioactivity incorporated into monosaccharides residues, we showed that sugar was quantitatively transferred from UDPGlcNAc 14C into endogenous glycosaminoglycans. The relationship between the N- and O-sulfation processes into heparan sulfate chains was studied after different time of sulfation by labelled sulfate nucleotide: PAP(35S). Our results outlined that preferential N-sulfation is obtained with short time exposures to labelled precursor, the O-sulfation occurring on previously N-sulfated heparan sulfate.

Adenine Nucleotides↗
PubMed1980

Variations in the distribution of glycosaminoglycans in the uterine cervix of the pregnant woman.

A study was made of the modifications of glycosaminoglycans in the uterine cervix and the relationship to gestation. These substances are essential constituents of connective tissue, and a modification of their concentration could affect the physical and chemical characteristics of the cervix. Glycosaminoglycans were extracted from cervical biopsies obtained from pregnant and non-pregnant women. This study showed dermatan sulfte to be quantitatively the most important glycosaminoglycan in the cervix of both the groups studied, and that a significant decrease in the concentration of both dermatan sulfate and chondroitin sulfates occurred in the biopsies obtained just after delivery. This was related to a decrease of collagen in the cervix at the end of gestation, as the proteoglycans containing dermatan sulfate are principally associated with collagen.

Adult↗
PubMed1979

Changes in glycoproteins of liver plasma membranes from rats treated with D-galactosamine.

D-Galactosamine administration to rats (400 mg/kg) by intraperitoneal injection induced biochemical alterations in liver plasma membranes. Alterations were studied 4, 16 and 24 h after D-galactosamine injection. Plasma membrane 5'-mononucleotidase activity decreased to 40% of control values. Carbohydrate composition was significantly changed. After 24 h D-galactosamine administration, the diminution in plasma membrane sialic acids and hexoses reached 30% of control values. As detected by SDS-acrylamide gel electrophoresis, high molecular weight glycoproteins of D-galactosamine-treated plasma membranes were modified. Moreover, the incorporation of [35S]-sulfate into membrane glycoproteins decreased after D-galactosamine administration (40--60% of control). The present results show that biochemical alterations in rat liver plasma membranes appear soon after D-galactosamine injection. Marked changes are observed in cell surface glycoproteins, especially in sialoglycoproteins and sulfated glycoproteins.

Animals↗
PubMed1978

Involvement of glycoconjugates in insulin-receptor interactions. Studies in liver plasma membranes of control and diabetic mice.

The involvement of glycoconjugates in the insulin-receptor interactions in mouse liver is tested by digestions of membranes with various enzymes. Trypsin decreased the binding of [125I]insulin to liver membranes. After digestion with beta-galactosidase no ""high affinity'' receptor sites could be detected. The effects observed with plant lectins confirm the involvement of galactoconjugates in the insulin binding process. Sophora japonica and Ricinus communis lectins (with galactose specificity) and concanavalin A largely inhibit the binding process of insulin and those effects concern the ""high affinity'' receptor sites. Other lectins (wheat germ agglutinin, Dolichos) and enzymes (alpha-L-fucosidase, beta-N-acetyl-hexosaminidase and neuraminidase) are without effect on insulin binding. Comparative studies performed on diabetic mouse liver membrane (KK mice), previously characterized by decreased number of insulin receptors, are in good agreement with qualitatively similar receptor sites in both non-diabetic (control) and diabetic mice. Effects of enzymes and lectins yielded same results as compared to control membranes. Plasma membrane proteins and glycoproteins in both types of mouse are indistinguishable with respect to enzymic and chemical analysis. Sodium dodecyl sulphate acrylamide gel electrophoresis shows identical patterns. Moreover, the decrease in the number of insulin receptors is easily reversed with diet restriction. These data are consistent with the similarity of receptor sites in control and diabetic liver membrane.

Animals↗
PubMed1978

[Activity of gamma-glutamyl transferase of sheep cerebral cortex with respect to amino acids and glutathione].

gamma-glutamyl Transferase fron Sheep brain cortex capillaries was studied from the point of view of transport of aminoacids across blood brain barrier. Excess substrate inhibition was competitive and observed both with donor (glutathione) and various acceptors (methionine, alanine, tryptophan) but not with arginine. Excess glutathione inhibition of transfer reaction is concomitant with an increase of total reaction (transfer + hydrolysis + autotranspeptidation). With regard to aminoacids, the greater the K'm the stronger the inhibition. This inhibition is the result of formation of a dead complex. Lineweaver-Burk plots 1/v versus 1/[acceptor] give straight lines meeting at the same point, whereas 1/v verus 1/[donor] plots are roughly parallel for high aminoacid concentrations and become secant for the low ones. Replots of slopes vs. 1/[acceptor] are not linear: the lower the aminoacid affinity the more pronounced the slope replot curvature. Thus kinetic patterns are consistent with a branched ping-pong mechanism including a ternary complex (Enzyme-acceptor-H2O) at high or low relative concentration, which balances the two branches. The estimated value of kinetic parameters does not support the hypothesis of major implication of the enzyme in brain uptake of aminoacids.

Amino Acids↗
PubMed1978

Lysosomal N-acetyl-beta-hexosaminidase and beta-glucuronidase activities from arterial wall. Variations with aging.

Properties of two hydrolases: beta-glucuronidase and N-acetyl-beta-hexosaminidase were studied in lysosomal fractions of media-intima from arterial wall. These enzymatic activities change significantly with aging. In the arterial wall, the decrease in activities of beta-glucuronidase and N-acetyl-beta-hexosaminidase between young and old rats was highly significant while there no notable change in the activities of acid phosphatase. These data are in agreement with the metabolic slow-down and the modifications of the glycosaminoglycan distribution in the media-intima of arterial wall with aging.

Acid Phosphatase↗
PubMed1978

Isolation of glycosaminoglycans from lymphocytes in chronic lymphoic leukemia.

Glycosaminoglycans were isolated from type B chronic lymphoid leukemia lymphocytes. Their studies showed chondroitin sulfate A (C) and under-sulfated chondroitin sulfate, no heparan sulfate was found. These results were confirmed with 12 other chronic lymphoid leukemia patients. By the same method polyanionic glycopeptides distinct from glycosaminoglycans were obtained from lymphocyte glycoproteins. They showed similarities in composition with known cell receptors. The largest part of chondroitin sulfate was liberated from cells by mild hydrolysis with trypsin and thus appeared to be a cell-surface component.

B-Lymphocytes↗