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Biomedical subjects

M Monsigny

Publications and source records attributed to M Monsigny.

At least 163 records · Page 9Linked to original sources
PubMed1983

Evolution of the surface of mouse myocardial cells during ontogenesis. II. Changes of fluorescent lectin-binding sites.

Fluorescein isothiocyanate-conjugated lectins (FTC-lectins) have been used to study the occurrence and the distribution of their receptors in the coating of mouse myocardial cells throughout their differentiation (from 10 days post-coitum to the adult stage). FTC-Con A, -WGA and -PNA specifically inhibited by alpha-mannosyl, beta-N-acetylglucosaminyl and beta-galactosyl residues, respectively, bind to the cell surface whatever the stage of differentiation. FTC-SBA and -HPA, specifically inhibited by alpha-N-acetylgalactosaminyl residues, bind to the coating of adult cells; their receptor sites appear only at day 18 of development. FTC-UeA, specifically inhibited by fucosyl residues also binds to adult cells. In sections of embryonic hearts, FTC-UeA is trapped by a lectin-like component; this UeA binding can be prevented with mannosyl-substituted serum albumin. Isolated embryonic myocardial cells do not bind FTC-UeA. FTC-BS I-A4 and -BS I-B4, specifically inhibited by alpha-N-acetylgalactosaminyl and alpha-galactosyl residues, respectively, bind only to the capillaries of adult heart. These results show that the differentiation of myocardial cells is accompanied by the sequential acquisition of lectin-binding sites. These changes express the maturation of cell coating glycoconjugates.

Age Factors↗
PubMed1983

Red cell ageing: phagocytosis and life-span of young and old erythrocytes fractionated by centrifugation.

Young and old red blood cells, separated by centrifugation on the basis of differences in cell density, were submitted to phagocytosis by either autologous human alveolar macrophages or syngeneic murine bone-marrow macrophages. Young cells adhere to macrophages, but to a much smaller extent than old ones. The influence of both type and quality of the separation procedure on the differences observed between the two erythrocyte subpopulations is discussed in the light of the half-life times of murine young and old red blood cells. Fractionation according to age was obtained following the method of Murphy (1973) and glutamate oxalo-acetate transaminase activity was measured and used as an indicator of both cell age and separation.

Animals↗
PubMed1982

Assay for proteolytic activity using a new fluorogenic substrate (peptidyl-3-amino-9-ethyl-carbazole); quantitative determination of lipopolysaccharide at the level of one picogram.

A new sensitive fluorimetric assay has been developed using peptidyl-3-amino-9-ethyl-carbazole as substrate. The fluorescence intensity of free 3-amino-9-ethyl-carbazole (AEC) at 460 nm is between two and three orders of magnitude higher than the fluorescence intensity of acyl-AEC. The release of AEC from a peptidyl derivative by proteases may be monitored continuously during the hydrolysis step or may be quantified upon addition of a general inhibitor such as benzamidinium chloride. Using N-benzoyl-arginyl-AEC as substrate, as little as 1 ng trypsin may be detected. Using t-butyloxycarbonyl-Val-Leu-Gly-Arg-AEC and the amoebocyte lysate of Limulus polyphemus, as little as 1 pg lipopolysaccharide can be detected. This fluorimetric method allows detection of trace amounts of lipopolysaccharide (endotoxins) in various biological materials, including sera.

Animals↗
PubMed1981

Cell surface receptors for wheat germ agglutinin and limulin in baby hamster kidney cells and ricin resistant variants.

The cell surface glycoconjugates of Baby Hamster Kidney cells and of four ricin resistant variants were investigated by the use of 125I-substituted ricin (Ricinus communis toxin) which binds galactose residues, and by the use of fluorescein labelled lectins which bind N-acetylneuraminic acid and/or N-acetylglucosamine: Limulin (Limulus polyphemus agglutinin), wheat germ agglutinin (Triticum vulgare agglutinin) and succinylated wheat germ agglutinin. Striking differences in the number of lectin and/or ricin receptors were found between the cell surface of wild type cells and that of ricin resistant variants. The results are discussed on the basis of the main glycopeptide structure, and of the specificity of the sugar binding proteins used. The ricin resistance of variant cells is concomitant to modifications of the concentration of certain glycoconjugate structures which are accessible to the sugar binding proteins. Depending on the variants, N-asparaginyl glycopeptide types and/or O-glycosidic glycopeptide types are affected.

Animals↗
PubMed1981

Specificities of limulin and wheat-germ agglutinin towards some derivatives of GM3 gangliosides.

Lipid vesicles containing derivatives of GM3 ganglioside (II3-N-acetylneuraminosyllactosyl ceramide) were used to study the specificities of two lectins (limulin and wheat germ agglutinin) towards N-acetyl neuraminic acid and N-glycoloylneuraminic acid and some of their natural and chemically modified derivatives. The extent of the lectin binding to the gangliosides was related to the aggregation process of the lipid vesicles which was monitored as an absorbance increase. Limulin binds specifically to lipid vesicles containing N-glycoloyl derivatives of GM3. The hydroxyl group at C-4 and the carboxyl group of neuraminic acid have to be free for the binding to limulin. The side chain of neuraminic acid is not involved in the binding site of limulin. Wheat germ agglutinin binds to GM3 ganglioside only when the hydrophilic tail of the neuraminic group is cut off (C7 analogues). The acetamido group but not the carboxyl group is involved in the binding to wheat germ agglutinin. The wheat-germ-agglutinin-induced aggregation of vesicles containing derivatives of GM3-ganglioside is dependent on the pH, on the ionic strength and on the presence of Ca2+ ions. The dependence on ionic strength and Ca2+ is a consequence of the electrostatic repulsion of the vesicles. The wheat-germ-agglutinin-induced aggregation process of vesicles containing any suitable GM3-ganglioside derivative was reversed by the addition of N-acetylglucosamine showing that the N-acetylneuraminic acid derivatives bind to the N-acetylglucosamine binding site.

Calcium↗
PubMed1981

Intraindividual variability of concanavalin A binding to the plasmalemma of human spermatozoa.

Certain characteristics of the sperm plasmalemma were studied using 10 ejaculates from the same subject. Measurements of membrane glycoconjugates binding by FTC Con A were made on samples with equal numbers of motile spermatozoa which had been selected by migration in phosphate buffered saline (pH 7.4). Scatchard plots showed that the association constant for Con A binding to membrane glycoconjugate varied between ejaculates, but in 9 of 10 cases the number of receptor sites for this lectin was constant with only one class of receptor.

Cell Membrane↗
PubMed1980

Sugar-lectin interactions: how does wheat-germ agglutinin bind sialoglycoconjugates?

The specific binding of N-acetylneuraminic acid to wheat-germ agglutinin is based on configuration similarities between N-acetylneuraminic acid and N-acetylglucosamine. The N-acetamido group and an adjacent hydroxyl group, both in an equatorial position are shown to be the main determinants. The N-acetylneuraminic acid--wheat-germ agglutinin interaction is increased by the removal of the last two carbons C8 and C9. The interaction between wheat-germ agglutinin and glycoconjugates containing N-acetylneuraminic acid is shown to be dependent on a charge effect and on an avidity effect. Succinylated wheat-germ agglutinin which is negatively charged at physiological pH, in contrast with wheat-germ agglutinin which is positively charged, does not bind cell surface glycoconjugates containing N-acetylneuraminic acid but does bind cell surface glycoconjugates containing N-acetylglucosamine. The use of wheat-germ agglutinin and of succinylated wheat-germ agglutinin leads to the determination of the number of cell surface receptors containing N-acetylneuraminic acid.

Acetylglucosamine↗
PubMed1979

Quantitative fluorimetric determination of cell-surface glycoconjugates with fluorescein-substituted lectins.

Fluorescein-substituted lectins, which can be used to visualize cell surface glycoconjugates, are shown to be usable in the quantitative determination of the number of receptor sites and of their association constant. The fluorescence measurements of the fluorescein-substituted lectins released from the cell surface with the related inhibitor, give quantitative data in a large range of fluorescein-substituted lectin concentration (0.1 to 100 microgram/ml). Using fluorescein-substituted concanavalin A or [3H]acetyl-concanavalin A, it was found that baby hamster kidney cells (BHK 21, wild-type) bind 10 +/- 2 x 10(6) lectin molecules per cell with an apparent association constant of 1.8 or 1.7 x 10(6) 1 x mol-1, respectively. Using the fluoresceinyl and [3H]acetyl-substituted wheat germ agglutinin, we found 40 +/- 5 x 10(6) sites per cell with an apparent binding constant of 1 and 1.3 +/- 0.3 x 10(6) 1 x mol-1, respectively. When fluorescein-substituted succinyl wheat germ agglutinin was used instead of the unsuccinylated wheat germ agglutinin derivatives, the number of binding sites was reduced 7 times, while the binding constant was very slightly lowered. Concanavalin A derivatives gave monotonic Scatchard plots; on the opposite, wheat germ agglutinin derivatives gave biphasic Scatchard plots suggesting that wheat germ agglutinin binds to two classes of receptors.

Animals↗
PubMed1979

Properties of succinylated wheat-germ agglutinin.

The physicochemical and binding properties of succinylated wheat germ agglutinin are described in comparison with these of unmodified wheat germ agglutinin. Succinylated wheat germ agglutinin is an acidic protein with a pI of 4.0 +/- 0.2 while the native lectin is basic, pI of 8.5. The solubility of succinylated wheat germ agglutinin is about 100 times higher than that of the unmodified lectin at neutral pH. Both lectins are dimeric at pH down to 5, and the dissociation occurs at pH lower than 4.5. The binding of oligosaccharides of N-acetylglucosamine to both lectins is very similar on the basis of fluorescence and phosphorescence studies. The minimal concentration required to agglutinate rabbit red blood cells is about 2 microgram/ml with both lectins and the concentrations of N-acetylglucosamine and di-N-acetylchitobiose which inhibit agglutination are similar with both lectins. The number of succinylated wheat germ agglutinin molecules bound to the surface of mouse thymocytes was ten times lower than that of the unmodified lectin although the apparent binding constant was only slightly different between the two lectins. The dramatic decrease of the apparent number of cell surface receptors upon succinylation of the lectin is discussed on the basis of the decrease of the isoelectric point and of the acidic properties of the cell surface.

Fluoresceins↗