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Biomedical subjects

N Sharon

Publications and source records attributed to N Sharon.

At least 19 recordsLinked to original sources
PubMed1992

Immunochemical studies on the combining site of the A + N blood type specific Moluccella laevis lectin.

The specificity of the anti A+N lectin of Moluccella laevis (MLL) was examined by hemagglutination experiments with enzyme-modified human erythrocytes and by inhibition of hemagglutination. In addition, binding to various glycoproteins and inhibition by different sugars and glycoproteins were examined by enzyme immunoassay with antibodies to the lectin. Treatment of AMM erythrocytes with proteolytic enzymes increased their agglutinability by MLL 4-16-fold; similar treatment of ONN cells decreased their agglutinability 8-16-fold. This is in line with the known location and enzyme sensitivity of A and N specificity determinants. Treatment of the erythrocytes with sialidase increased their agglutinability and abolished the distinction between N and M cells. Hapten inhibition of hemagglutination of AMM and ONN erythrocytes by the lectin, and its binding to glycoproteins measured by enzyme immunoassay, confirmed the high specificity of MLL for N-acetyl-D-galactosamine (200-500 times more than for D-galactose) and suggested the presence of hydrophobic interactions around HO-2 of the D-galactose unit. The methyl alpha-glycosides of D-galactose and of N-acetyl-D-galactosamine were better inhibitors than the corresponding beta-glycosides; this preference was abolished, and sometimes reversed, when the p-nitrophenyl glycosides of the same monosaccharides were tested, stressing again the importance of hydrophobic interactions in the binding of carbohydrates to MLL. The lectin reacted well with ONN substance and with glycophorin A of the N phenotype (GPAN), but did not react with OMM substance or GPAM. The strongest inhibitor was asialo ovine submaxillary mucin, which contains many unsubstituted alpha-D-GalpNAc-(1-->3)-Ser/Thr residues; calculated per N-acetyl-D-galactosamine residue, it was 1500 stronger than free N-acetyl-D-galactosamine. In accordance with this result, it was found that the lectin strongly agglutinates Tn cells. The specificity of MLL can, thus, be defined as anti-Tn, crossreactive with blood types A and N, and with sialosyl-Tn. The N-specificity can best be explained by assuming that GPAN contains a small number of unsubstituted or partially sialylated alpha-D-GalpNAc-(1-->3)-Ser/Thr residues, which are present in smaller proportions, if at all, in GPAM.

Antibody Specificity↗
PubMed1992

Cloning, sequence analysis and expression in Escherichia coli of the cDNA encoding a precursor of peanut agglutinin.

The cDNA coding for pre-peanut agglutinin (PNA) was isolated from a bacterial expression library. It codes for a polypeptide of 273 amino acids composed of a hydrophobic signal peptide of 23 amino acids and a mature protein of 250 amino acids. The sequence of the latter is identical to that of native PNA, determined very recently by conventional methods, except that it contains 14 additional amino acids at the C-terminus. Bacterial cells harboring a plasmid with the prePNA-cDNA, produced two PNA cross-reacting proteins: one migrated on SDS-PAGE identically with the native lectin (apparent mol. wt. 31 kDa); the other, at 35 kDa, was a beta-galactosidase pre-PNA fusion protein. The former protein possessed an N-terminal sequence identical to that of the mature, native PNA, suggesting that it was processed from the 35 kDa prePNA precursor. Only the 31 kDa protein was exported into the bacterial periplasmic space, and had the ability to bind to galactose-Sepharose. The isolated processed protein had the same hemagglutinating activity as the native lectin, when assayed with sialidase-treated human erythrocytes. Like the native lectin, it did not agglutinate the untreated cells, was not inhibited by N-acetylgalactosamine, and was inhibited by Gal beta 1----3GalNAc 30-times more strongly than by galactose.

Amino Acid Sequence↗
PubMed1992

Lectinophagocytosis of type 1 fimbriated (mannose-specific) Escherichia coli in the mouse peritoneum.

Bacteria can bind specifically to phagocytic cells via lectin-carbohydrate interactions and such binding is often followed by activation and degranulation of the phagocytes, as well as uptake and killing of the bacteria, a phenomenon designated lectinophagocytosis. Although extensively studied in vitro, no direct evidence for the occurrence of lectinophagocytosis in vivo has been available. To obtain such evidence, we injected type 1 fimbriated (mannose-specific) or nonfimbriated Escherichia coli into the peritoneal cavity of mice (10(7)-10(10) bacteria/animal) in the absence or presence of sugars and quantified the phagocytic activity by assaying the release of lysosomal N-acetyl-beta-D-glucosaminidase into the peritoneal fluid, up to 45 min after injection. Following injection of the type 1 fimbriated bacteria, significant release of the enzyme was observed which was time dependent and increased with the number of bacteria injected, whereas the nonfimbriated bacteria caused only little release. Methyl alpha-D-mannoside (50 mM), but not methyl alpha-D-galactoside or sucrose, inhibited the release by 60 to 100%. No release of N-acetyl-beta-D-glucosaminidase was induced by bacteria injected into a peritoneal cavity from which the macrophages had been removed. Our findings show that lectinophagocytosis can occur in vivo and may contribute to the host's defence against type 1 fimbriated bacteria.

Acetylglucosaminidase↗
PubMed1992

Synthesis of methyl alpha- and beta-N-dansyl-D-galactosaminides, probes for the combining sites of N-acetyl-D-galactosamine-specific lectins.

The synthesis of the methyl alpha- and beta-N-dansyl-D-galactosaminides is described using methyl alpha,beta-2-azido-2-deoxy-D-galactopyranoside as starting material. This was reduced to the corresponding methyl alpha,beta-2-amino-2-deoxy-D-galactopyranoside and then treated with dansyl chloride to yield a mixture of methyl alpha,beta-N-dansyl-D-galactosaminides which was separated into individual anomeric forms by flash chromatography on silica gel. Methyl alpha-N-dansyl-D-galactosaminide was used as a fluorescent indicator ligand in continuous substitution titrations to determine the association constants of nonchromophoric carbohydrates with the N-acetyl-D-galactosamine specific lectin from Erythrina corallodendron.

Acetylgalactosamine↗
PubMed1979

Thyroid carcinoma. Immunology, irradiation, and lymphocytic infiltration.

Patients undergoing thyroidectomies at Evanston (III) Hospital, during a six-month period had immunological studies performed preoperatively. No differential could be found between those with carcinoma or benign pathologic findings. T- and B-cell distribution and lymphocytic response to mitogens varied widely. Quantitative immunoglobulins showed slightly increased levels of IgG in patients with carcinoma and thyroiditis in comparison with those patients with adenomas. Antithyroglobulin antibodies were negative in all patients. Pathology slides from 107 patients with thyroid carcinoma between 1972 and 1978 at Evanston Hospital were reviewed for the presence of thyroiditis, either focal or diffuse. It was found that 50% of all carcinomas had either diffuse or focal thyroiditis. Diffuse thyroiditis was more common in patients with no history of irradiation and papillary carcinoma, and in younger age groups.

Adenoma↗
PubMed1979

Characterization of reactive and suppressive cells in the mouse embryonic liver by peanut agglutinin (PNA).

Embryonic liver cells suppressed the MLC response of adult mouse spleen cells and reactivity to mitogens Con A, PHA and LPS. Suppression was exerted by cells agglutinated by PNA (PNA+ cells). Cells reacting to LPS and to DxS were found in the nonagglutinated (PNA-) cell fraction. The PNA+ fraction did not react to DxS nor did it reduce the response of sdult spleen cells to this mitogen.

Animals↗
PubMed1979

Interaction of peanut agglutinin with normal human lymphocytes and with leukemic cells.

The interaction of peanut agglutinin (PNA) with human thymocytes, peripheral blood lymphocytes, and peripheral blood cells of various types of leukemia was investigated by using fluorescein isothiocyanate-conjugated PNA. The majority of human thymocytes (60-80%) bind the lectin. The major subpopulation of thymocytes that is PNA-positive was separated from the PNA-negative cells by differential agglutination with the lectin. The two thymocyte subpopulations were tested in the mixed lymphocyte reaction and with the phytohemagglutinin of Phaseolus vulgaris. The poor response of the PNA-positive thymocytes to these stimuli indicates that these thymocytes are functionally immature. The fluorescein isothiocyanate-PNA-binding test with peripheral blood lymphocytes of leukemic patients revealed that in most acute leukemias the PNA receptor is exposed on the blastic cells, whereas in most cases of chronic leukemia the peripheral blood lymphocytes are PNA-negative. The validity of PNA as a marker of immature blood cells and its potential clinical application are discussed.

Arachis↗
PubMed1979

Prevention of colonization of the urinary tract of mice with Escherichia coli by blocking of bacterial adherence with methyl alpha-D-mannopyranoside.

Methyl alpha-D-mannopyranoside (alpha MM), a competitor inhibitor of the binding of mannose by Escherichia coli, was tested for its ability to prevent infection of the urinary tract of mice with infective strains of the organisms. Injection of the bacteria in the presence of the drug resulted in a considerable reduction in the number of bacteriuric mice. In this system alpha MM was inactive against Proteus mirabilis in accordance with its inability to inhibit the adherence of this organism to epithelial cells in vitro, and methyl alpha-D-glucopyranoside proved inactive against both E. coli and P. mirabilis.

Adhesiveness↗
PubMed1978

Cooperativity of lectin binding to lymphocytes, and its relevance to mitogenic stimulation.

The relationship between the binding patterns of soybean agglutinin, peanut agglutinin (both in their native (unaggregated) form and in their polymerized form), and of Phaseolus vulgaris leucoagglutinin, to neuraminidase-treated lymphocytes from different sources, and the mitogenic activity of these lectins, was studied. In all cases investigated, binding of a lectin to lymphocytes which resulted in stimulation was a positive cooperative process. Our findings support the assumption that clustering of receptors and conformational changes in membrane structure are prerequisites for mitogenic stimulation.

Animals↗
PubMed1978

Studies on growth inhibition by lectins of Penicillia and Aspergilli.

It has previously been shown in our laboratory that wheat germ agglutinin (WGA) binds to Trichoderma viride and inhibits growth of this fungus. Here we report on the effect of WGA, soybean agglutinin (SBA) and peanut agglutinin (PNA) on Penicillia and Aspergilli. Binding of the lectins to the fungi was examined with the aid of their fluorescein isothiocyanate (FITC) conjugated derivatives. FITC-WGA bound to young hyphal walls of all species, in particular to the hyphal tips and septa, in agreement with the chitinous composition of the cell walls of the two genera. Hyphae of all species examined were labelled, though in different patterns, by FITC-SBA and FITC-PNA, suggesting the presence of galactose residues on their surfaces. Young conidiophores, metulae (of the Penicillia), vesicles (of the Aspergilli), sterigmata and young spores, were also labelled. The three lectins inhibited incorporation of [3H]acetate, N-acetyl-D-[3h]glucosamine and D-[14C]galactose into young hyphae of Aspergillus ochraceus, indicating interference with fungal growth. Inhibition of spore germination by the three lectins was also observed. Preincubation of the lectins with their specific saccharide inhibitors prevented binding and the inhibitory effects. We conclude that lectins are useful tools for the study of fungal cell surfaces, and may also serve as an important aid in fungal classification. The present findings also support the suggestion that one role of lectins in plants is protection against fungal pathogens.

Aspergillus↗