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Biomedical subjects

M M Burger

Publications and source records attributed to M M Burger.

At least 127 records · Page 7Linked to original sources
PubMed1980

Fluorescent antibody localization of Microciona prolifera aggregation factor and its baseplate component.

Specific rabbit antisera were prepared against purified aggregation factor and its membrane-associated receptor, baseplate, derived from the marine sponge. Microciona prolifera. They were utilized in conjunction with fluorescent-labeled goat anti-rabbit IgG in an assay to demonstrate the surface localizations of both components. The specificity of antibody preparations for AF and BP was demonstrated through inhibition of the rotation-mediated assay by homotypic antibody. This study confirms the presence of aggregation factor on the surface of disaggregated sponge cells maintained in the presence of the divalent cations, Ca++ and Mg++, and its absence when cells are maintained in Ca++ and Mg++-free seawater. The location of BP could also be demonstrated on the cell surface. Aggregation factors and baseplate appear to be heavily distributed on archeocytes and choanocytes, but are localized less intensely on gray cells. Gray cells are typified by yellowish autofluorescence of their intracellular granules in stained and control preparations. The reaction of anti-Microciona aggregation factor with its homotypic factor appeared to be species specificity judged by immunofluorescence assays and by inhibition of rotation-mediated assay by anti-homotypic AF since antibodies prepared against heterotypic AF preparations were unreactive.

Animals↗
PubMed1980

Carbohydrate changes in glycoproteins of a poorly metastasizing wheat germ agglutinin-resistant melanoma clone.

Glycoproteins of a metastasizing line of B16 mouse melanoma and a poorly metastasizing wheat germ agglutinin-resistant clone were compared. Cell surface proteins and glycoproteins were isotopically labeled by lactoperoxidase-catalyzed iodination and by NaB3H4 reduction after oxidation by periodate or galactose oxidase and subsequently analyzed by gel electrophoresis and autoradiography. Differences were observed in the relative mobilities of several major cell surface components. Binding of 125I-labeled lectins to total cellular proteins on polyacrylamide gels following electrophoresis showed that the major wheat germ agglutinin-binding components of F1 cells were altered in Wa-4 cells. Similar differences were not observed in concanavalin A-binding components. Total cellular glycopeptides were analyzed after separation into structurally distinct classes. The acidic "complex" N-glycosidic glycopeptides from the resistant cells were of lower molecular weight than those from the parent cells. No differences were observed among the mannose-rich N-glycosidic glycopeptides or the alkali-labile O-glycosidic oligosaccharides. Structural studies involving methylation analysis revealed that in the altered glycopeptides of the resistant cells the amount of neuraminic acid residues was decreased to one-half, concomitant with an increase in the amount of fucose. The lost sialic acid was bound to C-3 of galactose, whereas the increased fucose was found on C-3 of 4-substituted N-acetylglucosamine. A possible basis for the glycosylation change and its relation to the biological behavior are discussed.

Animals↗
PubMed1979

Isolation of a protein from the plasma membrane of adrenal medulla which binds to secretory vesicles.

Solubilized proteins of the plasma membrane of bovine adrenal medulla were fractionated on the basis of their affinity for secretory vesicles. The isolation procedure included preparation of a highly purified fraction of plasma membranes, its solubilization in detergent, and application to a column prepared from glutaraldehyde-fixed chromaffin granules. Using this technique, one major polypeptide (80% of the material bound) was isolated. This protein has been shown to originate from the plasma membrane and has no affinity for fixed bovine adrenal medullary mitochondria or lysosomes. It is eluted most effectively by low pH (3.0) and can be rebound and re-eluted from fixed secretory granules. In sodium dodecyl sulfate and beta-mercaptoethanol it has an apparent molecular weight of 51,000. In addition, two minor components, comprising about 20% of the material bound were detected having apparent molecular weights in sodium dodecyl sulfate of 14,000 and 62,000. It is suggested that such a molecule could function as a plasma membrane-located receptor for chromaffin granules during the secretory process.

Adrenal Medulla↗
PubMed1979

Liver-colonizing melanoma cells selected from B-16 melanoma.

Liver-colonizing tumor cells were selected from B-16 melanoma by a stepwise procedure: (1) injection of the original cells through the portal circulation: (2) removal of tumor cells from the hepatic tumor nodules for culture in vitro; (3) reinjection of such cells through the portal circulation and repetition of steps 2 and 3 eight times. The predilection of these cells to form tumors in the liver was clearly demonstrated following injection of the cells intra-arterially. The accuracy of the injection technique was controlled by monitoring amonts of injected radioactively labelled Sephadex microspheres. This liver-colonizing preference was not exclusive, but relative.

Animals↗
PubMed1979

Effect of polyene antibiotics on the lectin-induced agglutination of transformed and untransformed cell lines.

Treatment of transformed Py3T3, SV101-3T3, and L1210 cells, as well as mitotic and Pronase-treated untransformed 3T3 cells, with the polyene antibiotics filipin, nystatin, and amphotericin B inhibited agglutination by wheat germ agglutinin. The effect of polyene antibiotic treatment was lectin and cell specific. Concanavalin A induced agglutination was not inhibited, wheat germ agglutination induced agglutination of untransformed 3T3 interphase cells was not influenced, and other aggregation phenomena, including those of erythrocytes with blood group specific antibodies or divalent cations, were unaffected by polyene treatments. This suggests that the formation of polyene-cholesterol complexes in transformed and erythrocyte cell membranes may specifically affect wheat germ agglutinin receptors and/or secondary events necessary for wheat germ agglutinin induced agglutination. Fluorescence studies of membrane filipin-cholesterol complexes showed that pretreating the cells with wheat germ agglutinin, but not concanavalin A, perturbed the fluorescence properties of filipin. Electron spin resonance studies with spin-labeled fatty acids revealed at best only a slight decrease in fatty acyl chain flexibility following filipin treatment. These studies indicate that there are not only quantitative differences between the agglutinability of transformed and untransformed cells with wheat germ agglutinin but that qualitative differences exist as well.

Agglutination↗
PubMed1979

Nerve fibers in culture and their interactions with non-neural cells visualized by immunofluorescence.

Cultures of embryonic mouse spinal cord explants, alone or in combination with rat myotubes, were stained by indirect immunofluorescence using antibodies against three structural proteins to: (a) reveal the distribution of these proteins among different cell types, and (b) test the usefulness of antibody staining to reveal the gross morphology of the neurite network in complex cultures. Affinity column purified antibodies were used against chicken gizzard actin, porcine brain tubulin, and skeletal muscle alpha-actinin. Neurites were stained intensely by anti-actin as was the stress fiber pattern of underlying fibroblasts. With anti-tubulin, the staining of neurites was an order of magnitude more intense than the staining of the microtubule pattern of background fibroblasts. Neurite cell bodies and astrocyte-like glia cells were stained with anti-tubulin and their nuclei remained unstained. Anti-tubulin could thus be used to trace even the finest extensions of nerve processes in spinal cord and spinal cord-muscle cultures. Furthermore, it could be combined with the histochemical reaction for acetylcholinesterase (AChE, EC 3.1.1.7) to demonstrate AChE-positive neurons and specialized nerve-muscle contact sites. The staining of neural elements with anti-alpha-actinin was generally much weaker than with anti-actin and anti-tubulin. Neurites were stained only moderately in comparison to myotube Z lines in the same culture. However, a distinct staining of the periphery of dorsal root ganglion cells was observed. Thus, a protein immunologically related to muscle alpha-actinin is present in the nervous system. In myotubes, Z lines were stained intensely with anti-alpha-actinin while I bands were only faintly stained with anti-actin. In isolated myofibrils, both structures were stained intensely with the same antibody preparations.

Actinin↗
PubMed1978

Growth inhibition of transformed cells with succinylated concanavalin A.

Succinylated concanavalin A reversibly inhibits the growth of SV40 transformed mouse 3T3 cells and thus causes an accumulation of the cells in the G1 phase of the cell cycle. In a soft substrate (methylcellulose) succinylated concanavalin A also restores in transformed cells the growth behavior typical of untransformed cells.

Cell Adhesion↗
PubMed1978

An efficient method to produce specific anti-actin.

The production of affinity column purified (specific) anti-actin is described. With the immunization scheme employed, all rabbits produced precipitating antibodies over several months, so that 30 mg specific anti-actin per rabbit could be isolated in 6 months. The antibodies against native and detergent denatured smooth muscle actin are characterized by immunodiffusion tests, staining of the I-band of isolated myofibrils and stress fibers in tissue culture cells, using indirect immunofluorescence.

Actins↗
PubMed1978

Similarities in the membrane fluidity of 3T3 and SV101-3T3 cells and its relation to concanavalin A- and wheat germ agglutinin-induced agglutination.

Intact, viable ultransformed 3T3 and transformed SV101-3T3 cells were labeled with fatty acid spin labels and with 2,2,6,6-tetramethylpiperidine-1-oxyl in order to measure the fluidity properties of membrane lipids. Both cell types were grown in regular calf serum and in a lipid-depleted serum supplemented with either oleate or elaidate. The temperature dependence of the spectra obtained revealed inflections that correlate with the temperature below which agglutination with concanavalin A is inhibited, and another inflection that correlates with the temperature below which agglutination with wheat germ agglutinin is inhibited, suggesting that (a) the lipid phase(s) in the vicinity of the receptor(s) for these two lectins differ, and (b) a fluid membrane in the vicinity of the lectin receptor(s) is necessary for agglutination with either concanavalin A or wheat germ agglutinin. Studies with a partially characterized plasma membrane fraction suggest that the plasma membrane fluidity parameters closely resemble those of the intact cell. 3T3 and SV101-3T3 cells show virtually identical fluidity profiles by all of the tests we have applied.

Agglutination↗
PubMed1977

Sugar-specific antibodies reactive towards cell-surface carbohydrates.

Antibodies generated against sugar-azoproteins have been purified by affinity chromatography using elution with monosaccharide. They have high specificity for monosaccharide and they react with terminal, non-reducing sugars on the surfaces of human erythrocytes. Some of them, either native or as Fab fragments, inhibit mitogenic stimulation of lymphocytes by concanavalin A.

Animals↗
PubMed1977

Stimulation of lymphocytes by concanavalin A. Temperature-dependent effect of fatty acid replacements.

The membrane fatty acyl composition of lymphocytes was altered by growth in lipid-depleted serum containing fatty acid supplements, as well as avidin to block endogenous synthesis of fatty acids. Under these growth conditions over 50% of the total fatty acid in membrane phospholipid were derived from the added fatty acid. Enrichment of lymphocyte membranes with oleate (cis C18:1) or elaidate (trans C18:1) shifted the optimum temperature for mitogenic stimulation by concanavalin A as measured by [3H]thymidine incorporation. These results suggest that the fluidity of the membrane lipid phase plays a role in the process of lymphocyte stimulation by lectins.

Animals↗