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Biomedical subjects

M Horisberger

Publications and source records attributed to M Horisberger.

At least 55 records · Page 3Linked to original sources
PubMed1979

Fluorescent colloidal gold: a cytochemical marker for fluorescent and electron microscopy.

The gold method was further developed for fluorescent microscopy. Gold granules (12 nm in size) were labelled with rhodamine conjugates of Concanavalin A and avidin. The fluorescent markers were used to mark cell wall mannan on the yeast Saccharomyces cerevisiae either by the one-step, or by the two-step method via a biotinyl derivative of ConA. By fluorescence or transmission electron microscopy, the two-step method was found to achieve a higher density of marking.

Avidin↗
PubMed1979

Multiple marking of cell surface receptors by gold granules: simultaneous localization of three lectin receptors on human erythrocytes.

A method is described for transmission electron microscopy which allows high resolution mapping of three lectin receptors on the same cell. As a model, receptors for Concanavalin A, soya bean and wheat germ agglutinins have been simultaneously localized on human erythrocytes using lectin-labelled gold markers of different sizes (5, 17 and 26 nm, respectively). Quantitative binding data and examination of stereoscopic micrographs of thin sections of marked erythrocytes indicated that the greatest part of these lectin markers was bound by receptors spatially separated. As gold granules are electron dense and uniform in size, they are well suited for multiple marking of cell surface components. The method is simple and leads to a better understanding of the topography of cell membranes.

Cell Membrane↗
PubMed1978

Localization of alpha-galactomannan and of wheat germ agglutinin receptors in Schizosaccharomyces pombe.

The location of galactomannan on the surface of Schizosaccharomyces pombe cells was reexamined by scanning electron microscopy by an indirect but specific method using gold markers. The polysaccharide was found on the cell surface and at the end beginning to grow but not on the wall established by division. Galactomannan was also localized on S. pombe thin sections by transmission electron microscopy using the same method. The polysaccharide was found deposited in two layers in the cell wall, i.e. at the periphery of the wall and near the plasmalemma. The septum was also marked but mainly near the plasmalemma. These results indicated that the polysaccharide is elaborated onto the outside of the wall during extension but not during septum formation. When thin sections of S. pombe were marked with gold granules labeled with wheat germ agglutinin, marking was found in vacuoles but not in the cell wall. This confirmed that S. pombe cell wall is devoid of chitin.

Ascomycota↗
PubMed1978

Ultrastructural localization of beta-D-galactan in the nuclei of the myxomycete Physarum polycephalum.

The acellular slime mold Physarum polycephalum produces an extracellular sulfated and phosphorylated beta-D-galactan which was recently isolated from the nuclei of this organism. This polysaccharide has now been localized in the nuclei of P. polycephalum by electron microscopy using a specific "sandwich" technique: thin sections of P. polycephalum microplasmodia were incubated with the Ricinus communis lectin specific for D-galactose residues. The bound lectin was then localized with gold granules labeled with a galactose-terminated glycoprotein (desialylated ceruloplasmin). The galactan was found in the nuclei mainly associated with chromatin and, also, but to a smaller extent, in the cytoplasm and in some vacuoles. The specificity of the method was assessed by marking under the same condition the galactomannan present in the cell wall of the yeast Schizosaccharomyces pombe.

Cell Nucleus↗
PubMed1978

Agglutination of erythrocytes using lectin-labeled spacers.

The mechanism of agglutination of human erythrocytes by lectin, studied using lectin-labeled gold granules as spacers (5--64 nm in size), was found to depend upon the size of the spacer but not upon the number and the mobility of the receptors.

Gold↗
PubMed1978

Structure of a beta-galactan isolated from the nuclei of Physarum polycephalum.

A sulfated and phosphorylated beta-D-galactan ([alpha]D+8degrees) was isolated from the nuclei of the acellular slime mould Physarum polycephalum. The polysaccharide was isolated from cesium chloride gradients during the preparation of ribosomal DNA and purified. The purified galactan contained 89% galactose, 2.5% phosphate and 9.6% sulfate groups and had an average degree of polymerisation of 560. Periodate degradation and permethylation studies indicated the presence of mainly (1 leads to 4)-, but also of (1 leads to 3)-, and (1 leads to 6)-linked galactose units with one branch every 13 units. These results suggested that the intranuclear galactan, apart from its higher sulfate content, is similar to the extracellular polysaccharide produced by P. polycephalum.

Chemical Phenomena↗
PubMed1978

Simultaneous localization of an hepatic binding protein specific for galactose and of galactose-containing receptors on rat hepatocytes.

The hepatic binding protein, specific for galactose-terminated glycoproteins (asialoglycoproteins) and the receptors for the Ricinus communis lectin, specific for galactose residues (RCA1), were simultaneously localized on isolated rat hepatocytes by the gold method. The marker for the binding protein was prepared from gold granules (5 nm in diam.) labeled with ceruloplasmin and desialylated. The marker specific for galactose-containing receptors consisted of granules (17 nm in diameter) labeled with RCA1. It was established that both markers did not interact. Hepatocytes (fresh or briefly fixed with glutaraldehyde) were successively incubated with the asialoceruloplasmin and the RCA1 marker. Examination of thin sections by electron microscopy indicated that the binding protein and the RCA1 receptors were often in the proximity of each other on the plasmamembrane. Using the same technique, wheat germ agglutinin (WGA) receptors were generally found on area of the plasmamembrane poorly marked by the RCA1 gold marker. The binding of asialoceruloplasmin gold markers was studied as a function of the size of the granules. It became insignificant when the size was above 17 nm. Previous results have shown that the binding of RCA1 is low when the marker reaches 50 nm in size while WGA markers up to 75 nm are well bound by hepatocytes. It is therefore hypothesized that the binding protein and RCA1 receptors are located between glycoprotein brushes of increasing spacing while part or all of the WGA receptors are located at the periphery of the brushes.

Animals↗
PubMed1977

Location of mannan and chitin on thin sections of budding yeasts with gold markers.

Mannan was located on thin sections of Saccharomyces cerevisiae and Candida utilis with the homologous anti-mannan antibodies or with Concanavalin A, both labelled with gold granules. Fully synthesized mannan was found in the cell walls, on the plasmalemma and within the cytoplasm sometimes associated with vesicles and vacuoles. Chitin or its oligomers were located with wheat germ agglutinin in the bud scars but also in the cell wall and the cytoplasm near the plasmalemma. Both mannan and chitin or its oligomers were found in the forming septum and are synthesized within the cytoplasm. The gold method was also suitable for marking mannan and chitin simultaneously.

Candida↗
PubMed1977

Structure of the peptidoglycans of Moraxella glucidolytica and Moraxella lwoffi grown on hydrocarbons.

The peptidoglycans of Moraxella glucidolytica and Moraxella lwoffi grown on aliphatic hydrocarbons were isolated. They contained muramic acid, glucosamine, alanine, D-glutamic acid and mesodiaminoimelic acid in a molar ratio of about 0.5:0.5:1.6:1.0:1.0 (M. glucidolytica) and 0.8:0.7:1.3:1.0:1.0 (M. lwoffi). The peptidoglycans were lysozyme-resistant. However, when treated with formanide, they could be partially degraded by lysozyme. The fragments were purified and their structure determined. In both strains, the peptide subunits consisted mainly of tripeptides (L-Ala-D-Glu-meso-DAP) and tetrapeptides (L-Ala-D-glu-meso-DAP-D-Ala), most of them being directly cross-linked. It is concluded that in both strains the primary structures of the peptidoglycans are closely related.

Amino Acids↗
PubMed1977

Polysaccharides immobilized in polyacrylamide gel as high-capacity adsorbents for Bandeiraea simplicifolia lectin and concanavalin A.

A high-capacity adsorbent for lectins was easily prepared by immobilization of polysaccharides in a polyacrylamide gel. The properties of granulated guaran gel, used to purify by affinity chromatography the alpha-D-galactose-binding lectin from the seeds of Bandeiraea simplicifolia, were studied, as well as the binding of Concanavalin A (tetrameric) and succinylated Concanavalin A (dimeric) to a yeast mannan gel.

Acrylamides↗
PubMed1977

Cell-free coupling of influenza virus RNA transcription and translation.

A cell-free coupled system for the transcription and translation of fowl plague virus RNA is described. The system utilizes a new nuclease-preincubated rabbit reticulocyte lysate that has a high sensitivity to exogenous mRNA and a very low level of nuclease activity. Translation of the viral proteins in the coupled system is strictly dependent upon the viral transcriptase activity. In the coupled system the optimal concentration of magnesium is intermediate between the optimum for transcription and that for translation. Translation of the viral proteins seems faithful. The products represent the major viral peptides M and NP and two peptides with the same electrophoretic mobility as HA and P2. Viron NA is not resolved in the kind of polyacrylamide gels described. Proteins M and NP were immunoprecipitable with monospecific antisera. It is concluded that the virion-associated RNA polymerase transcribes the negative-stranded segments of the viral genome coding for these major structural proteins into fully functional mRNA's.

Animals↗
PubMed1977

Colloidal gold, a useful marker for transmission and scanning electron microscopy.

Electron dense markers of a size suitable for transmission electron microscopy and scanning electron microscopy have been prepared with gold granules labeled with a monolayer of specific macromolecules. The optimum conditions for preparing the markers have been ascertained. The method is simple, rapid and seems to be general since gold granules have been labeled with polysaccharides and proteins. As homogeneous populations of gold granules having different sizes can be prepared, the method is also suitable for double marking experiments. The gold technique is illustrated by the localization of polysaccharides and glycoproteins on yeast cell walls and erythrocyte membranes by transmission electron microscopy and on yeast cells and intact erythrocytes by scanning electron microscopy. Good spatial resolution of the marker was achieved in all cases. The method is also suitable for marking thin sections. Spectrophotometric measurements were used to determine the number of gold granules adsorbed per cell.

Candida↗