Search PubMed⌕ Search

Biomedical subjects

L D Bergelson

Publications and source records attributed to L D Bergelson.

At least 91 records · Page 5Linked to original sources
PubMed1978

Manipulation of phospholipid composition of membranes with the aid of lipid exchange proteins. Incorporation of phosphatidylcholine into protoplasts of Micrococcus lysodeikticus.

Incubation of Micrococcus lysodeikticus protoplasts with phosphatidylcholine liposomes and rat liver exchange proteins (pH 5.1 supernatant fraction) resulted in replacement of about one half of the bacterial total phospholipids by phosphatidylcholine. Protoplasts modified by phosphatidylcholine showed a decreased rate of oxidation of exogenous substrates (NADH, malate) and decreased ferricyanide reductase activity as compared to the initial protoplasts. At the same time incorporation of phosphatidylcholine had no influence on the level of endogeneous respiration. Protoplasts modified by phosphatidylcholine were osmotically more stable than the initial protoplasts. After osmotic lysis of the phosphatidylcholine protoplasts their NADH (malate) oxidase and ferricyanide reductase activities were restored. Incorporation of phosphatidylcholine into membrane ghosts, obtained by osmotic rupture of the initial protoplasts had only small if any effect on the malate and NADH oxidase and dehydrogenase activities. It is concluded that phosphatidylcholine in incorporated predominantly into the outer part of cytoplasmic membrane and that proteinmediated transfer of phosphatidylcholine results in restoration of the permeability barrier due to repair of local defects in the initial protoplast membrane.

Cell Membrane↗
PubMed1976

Gangliosides of hepatoma 27, normal and regenerating rat liver.

The highly malignant rat hepatoma 27 was found to have increased amounts of lipid-bound sialic acid as compared with normal liver whereas in regenerating liver the lipid-bound sialic acid level was reduced. In contrast to the liver the hepatoma contained higher amounts of disialogangliosides and no trisialogangliosides, which are abundant in the liver. The main disialoganglioside of the hepatoma had no analogue among the liver gangliosides and was identified as Gal-GalNAc(AcNeu-AcNeu)-Glc-Cer (GD1b), which in other tissues is known to be a precursor of trisialogangliosides. These findings may be explained by a reduced activity of glycosyltransferases in the hepatoma and apparently do not simply reflect differences in growth rate since the ganglioside pattern of regenerating rat liver was not altered significantly in comparison with the liver. Liver and hepatoma microsomes were found to be enriched in gangliosides as compared with whole cells, liver mitochondria were slightly poorer, while the ganglioside level of hepatoma mitochondria was much higher than that of the hepatoma cells. It thus appears that the existing image of the plasma membranes as the only sites of high ganglioside concentration may not hold true for weakly differentiated hepatomas of high malignancy.

Animals↗
PubMed1976

Diol lipids. Acylated ethyleneglycol glycosides. A new type of natural glycolipid.

A new type of glycolipid has been detected in ripening corn seeds. The presence of ethyleneglycol, galactose, glucose and fatty acids was shown by degradation studies. The products of alkaline deacylation were identified as galactosyl- and glycosylethyleneglycol by thin-layer chromatography and combined gas-liquid chromatography-mass spectrometry. The native ethyleneglycol galactolipid was isolated by distribution of the total lipids between heptane and 95% methanol, following silica gel column chromatography of the methanol soluble fraction. Analysis of the alkaline deacylation products of the isolated ethyleneglycol lipid as well as examination of the mass-spectrum of its tetraacetate showed the new lipid to have the structure of 1-acyl-2-(O-beta-D-galacto-pyranosyl)ethyleneglycol with palmitic, oleic and stearic acids as the main fatty acid components. The fragmentation patterns under electron impact of trimethylsilyl ethers of synthetic ethyleneglycol glycopyranosides and of 1-palmitoyl-2-(O-beta-D-tetraacetylgalactopyranosyl)ethyleneglycol are described.

Ethylene Glycols↗
PubMed1975

Intervesicular phospholipid exchange. An NMR study.

Phospholipid exchange between phosphatidylinositol and phosphatidylcholine ?vesicles has been studied by NMR spectroscopy with use of hydrophilic paramagnetic lanthanide probes (Pr-3+ and Eu-3+ ions). The dependence of the lanthanide induced shifts in the1-H and 31-P NMR spectra on the phospholipid composition of the vesicles could be used for its quantitative evaluation. The method has been proved to be applicable for studying phospholipid exchange stimulated by soluble proteins (postmicrosomal supernatant fraction) from rat liver. Furthermore it has been shown that the phospholipid molecules newly introduced by protein-stimulated exchange are predominantly incorporated into the outermonolayer of the vesicular bilayer membrane. This makes it possible to produce liposomes with asymmetric distribution of the phospholipids across the bilayer.

Biological Transport↗
PubMed1975

13-C NMR investigation of phospholipid membranes with the aid of shift reagents.

13-C NMR spectra of sonicated phospholipid dispersions have been investigated with the aid of paramagnetic ions (Pr-3+) as shift reagents. This method permits discrimination between the outer and the inner surfaces of the vesicular membrane and gives a larger variety of signals than 1-H NMR. The lanthanide induced shifts have been found to depend on other ions present and on the lipid composition of the membrane.

Carbon Isotopes↗
PubMed1972

Tumor lipids.

Explore the source record for details and available documents.

Animals↗