Search PubMed⌕ Search

Biomedical subjects

E Yavin

Publications and source records attributed to E Yavin.

At least 109 records · Page 6Linked to original sources
PubMed1980

Nervous system-specific proteins in developing rat cerebral cells in culture.

The nervous system-specific proteins; synaptin, D1, D2, D3, glial fibrillary acidic protein (GFA) and 14-3-2, were quantified in dissociated cerebral cells from the foetal rat brain at various times of growth in culture. By approximately 1 week in culture, the neuronal membrane markers synaptin, D1, D2, and D3 could all be demonstrated. A maximum concentration of 10-20% for synaptin, D1, and D3 and 160% for D2, in comparison with the levels in adult forebrain, was attained during the 2nd week in vitro. The astroglial gliofilament marker GFA increased continuously, reaching by 38 days of cultivation an 18-fold higher level than the concentration in adult forebrain. The neuronal cytoplasm marker 14-3-2 could be demonstrated in trace amounts, and only after more than 1 week in vitro. Neuronal cell bodies and processes stained by indirect immunofluorescence using an anti-D2 serum were strongly fluorescent after 1 week in vitro. Immunofluorescence staining for GFA revealed a cytoplasmic filamentous network in perinuclear areas and processes of, presumably, astroblasts.

Animals↗
PubMed1979

Translocation and turnover of phospholipid analogs in plasma membrane-derived vesicles from cell cultures.

The time-dependent accumulation of phosphatidyldimethylethanolamine in formaldehyde-induced vesicles obtained from a somatic cell hybrid line was investigated. From a number of considerations including a two-fold enrichment of cholesterol and sphingomyelin it was concluded that these vesicles were derived from the cell plasma membrane. A progressive depletion of phosphatidylcholine, the major vesicle phospholipid, was observed in cells supplemented for various time periods with dimethylethanolamine. This depletion was accompanied by a concomitant increase in the amount of lipid analog. The time-dependent alteration of the phospholipid polar head group in intact cells was almost identical to that observed in isolated plasma membrane vesicles, suggesting a rapid equilibration of the de novo synthesized phospholipid with the cell surface compartment. From the initial velocity rate, the time required for the phosphatidylcholine pool to double was about 12 h. Agarose-linked phospholipase A2 was used to measure the relative composition of choline- and dimethylethanolamine-phosphoglycerides in the outer surface of vesicles prepared from cells with different degrees of polar head group substitution. The gradual appearance of lysodimethylethanolamine lipid analog in vesicles treated with phospholipase A2 suggested an asymmetric distribution of the phospholipid between the interior and the exterior part of the vesicle. This asymmetry was maximal up to about 4 h following the addition of dimethylethanolamine to the culture medium and was of a transient nature as the lipid analog accumulated on both sides of the plasma membrane. Based on these measurements a fast followed by a slow translocation component could be distinguished with apparent doubling times of 7 and 43 h for the lipid analog, respectively. As the analog becomes the predominant cellular phospholipid a significant increase in the vesicle lipid fluidity was measured.

Animals↗
PubMed1978

Immunofluorescent patterns of dissociated rat embryo cerebral cells during development in surface culture: distinctive reactions with neurite and perikaryon cell membranes.

The presence of antigenic determinants on surface cultures of dissociated cells from rat embryo cerebral tissue has been investigated with the immunofluorescence technique. Antisera raised in rabbits against mature mouse brain reacted with the embryonic cells and enabled the identification of two distinct populations of immunofluorescent cells. One population clearly distinguishable by its ring fluorescence was involved in early cellular reaggregation and neurite formation. A second population which displayed dispersed fluorescence over the whole cell, did not establish intercellular contacts for prolonged periods of time in culture. Indirect evidence suggests that after several days in culture a great portion of the latter population was found in close proximity to the early aggregate, to form an immunofluorescent-heterotypic aggregate. A second antiserum, raised against embryonic rat cerebral cells, displayed immunofluorescent labeling patterns similar to those observed with the mature mouse brain antiserum, when reacted with freshly dissociated cerebral cells. As the cells differentiated in surface culture, distinctive patterns of immunofluorescent reactions developed. Large neuronal cells were labeled on their neuritic cell membranes by the antiserum to adult brain but not by the antiserum to embryonic cells. The results suggest that the anti-mature brain serum possess a class of antibodies which is able to react with antigenic determinants localized specifically on the neuritic plasma membrane.

Animals↗
PubMed1977

Base stimulation of phospholipid metabolism in neuroblastoma cells. I. Kinetics of incorporation of N-methylated ethanolamine bases.

The effects of nitrogen bases on the regulation of phospholipid metabolism in neuroblastoma cell cultures were investigated. An increase in the total cellular phospholipids was observed up to 24 h following plating. Addition of monomethyl- and dimethylethanolamine bases resulted in a stimulation of the synthesis of their corresponding phospholipids. The average rates of synthesis of phosphatidylmonomethyl- and phosphatidyldimethylethanolamine were 0.09 and 0.12 nmol/microgram DNA per h, respectively. The labeling patterns of the various phospholipid species from ortho[32P]phosphate have been determined. They suggest that the synthesis of the analogs proceeded entirely via a phosphate mediated pathway rather than through a base exchange mechanism. A number of distinct patterns for the incorporation of bases into acyl-, alkyl- and alkenyl-containing phosphoglyceride species were indicated. The polar head group composition appeared to be intimately related to the type of bond of the hydrocarbon residue.

Cell Line↗
PubMed1977

Synaptogenesis and myelinogenesis in dissociated cerebral cells from rat embryo on polylysine coated surfaces.

The appearance of myelinated axons and establishment of synaptic contracts in dissociated cells from rat embryo cerebral hemispheres grown on polylysine precoated surfaces were studied by light and electron microscopy. Typical myelin lamellae ensheathing axons were observed as early as the eighth day. Immature synaptic profiles exhibiting slight membrane thickening and few synaptic vesicles were observed after seven days. At 3 weeks, mature synapses containing many synaptic vesicles and the typical irregular membrane thickening could be seen. It is suggested that the presence of polylysine may provide a support which enhances the attachment and subsequent establishment of contacts between neuronal and glial cells, resulting in the early onset of myelin formation.

Animals↗
PubMed1977

Regulation of phospholipid metabolism in differentiating cells from rat brain cerebral hemispheres in culture. Serine incorporation into serine phosphoglycerides: base exchange and decarboxylation patterns.

The patterns of serine metabolism into phospholipids of cultured brain cells was examined. Labeled serine was incorporated predominantly into serine- ad ethanolamine-containing phospholipids and sphingolipids. The highest rates of labeling were observed in the (1)acyl-(2)acyl- and (1)alkyl-(2)acyl-serine phosphoglyceride fractions. Serine incorporation into both compounds appears to proceed via a base exchange mechanism. A decrease in the rate of serine phosphoglycerides labeling and a depletion of the ATP levels were observed when oligomycin or the calcium ionophore A23187 was added to the incubation medium. The inhibition of serine incorporation by A23187 could be partially reversed following addition of 10 mM CaCl2. Based on these findings it is suggested that in addition to demonstrating the energy-independent calcium-stimulated pathway, there may also be an energy related pathway. Formation of ethanolamine phosphoglycerides, as a result of serine phosphoglycerides decarboxylation, has been analyzed by using a simplified compartmental model. Of the 0.67 nmol/mg of protein turned over per h in the diacylserine phosphoglyceride compartment, 0.14 nmol/mg of protein are converted into the ethanolamine phosphoglycerides. In a similar manner, of the 0.09 nmol/mg of protein turned over per h in the (1)alkyl-(2)acyl-serine phosphoglyceride compartment, 0.014 nmol/mg of protein is converted into the (1)alkyl-(2)acyl-ethanolamine phosphoglyceride. These figures provide a first indication that a considerable portion of the ethanolamine phosphoglycerides in cultured brain cells is formed via a direct decarboxylation of the serine phosphoglycerides. In estimating the rates of (1)alkenyl-(2)acyl-ethanolamine phosphoglyceride formation from (1)alkyl-(2)acyl-ethanolamine phosphoglyceride the precursor-product specific activity crossover point could not be established. Mathematical analysis, however, enabled us to estimate the flux from the former into the latter as 0.04 nmol/mg of protein per h. A scheme for the possible metabolic interconversions of the ether bond containing serine and ethanolamine phosphoglycerides is proposed.

Adenosine Triphosphate↗
PubMed1976

Regulation of phospholipid metabolism in differentiating cells from rat brain cerebral hemispheres in culture. Patterns of acetylcholine phosphocholine, and choline phosphoglycerides labeling from (methyl-14C)choline.

The uptake and metabolism of [14C]choline in dissociated rat brain embryo cell cultures was examined as a function of the extracellular choline concentration. Choline uptake did not follow normal Michaelis-Menten kinetics, but rather exhibited two components with apparent Km of 0.016 mM and 0.96 mM. At low choline concentrations (high affinity uptake) most of the [14C]choline label was present in the phosphocholine fraction prior to the appearance of label in phospholipids. At high choline concentrations (low affinity uptake) a large proportion of the radioactivity was converted into acetylcholine. The dissimilarities between the formation of phosphocholine and acetylcholine as a function of choline concentration might be explained by the existence of two mutually independent enzymatic activities with different Km affinities for choline. Kinetic data augmented by double label studies, suggested that formation of choline phosphoglyceride proceeds entirely via a phosphocholine intermediate. Nearly all radioactivity in the lipid fraction is incorporated into choline phosphoglycerides. A higher turnover rate of choline incorporation into choline phosphoglycerides, accompanied by an increase in the levels of glycerophosphocholine, was observed in older cultures as compared to younger cultures. The metabolic implications of these findings in cultured brain cells in comparison with other in vitro systems are discussed.

Acetylcholine↗
PubMed1976

Cholesterol metabolism in cultured fibroblasts in adrenoleukodystrophy.

The basic biochemical defect of X-linked adrenoleukodystrophy (sudanophilic leukodystrophy, Schilder's disease) is unknown. To investigate reported abnormalities in cholesterol metabolism in vitro, we examined cultured skin fibroblasts of four patients and four normal control subjects. The kinetics of retention and accumulation of [14C]cholesterol by these cells was studied. After 3 days of exposure to tracer amounts of [14C]cholesterol, an apparent steady state between the medium and cellular cholesterol was established. The specific radioactivity expressed per mg of protein was similar for both Schilder and control fibroblasts. tafter labeling the pre-existing cellular cholesterol pool, the rate of loss of label was followed up for a 6-day period. About 23% and 14%, respectively, of the cellular radioactivity in both Schilder's disease and control cells were released into the medium after the consecutive change with fresh nonlabeled medium. No significant differences in [14C]cholesterol rates of uptake or release were observed between control and Schilder's disease fibroblasts. About 44% of the labeled cholesterol was present in an esterfied form after incubation in the presence of unheated serum in both Schilder's and control cultures.

Adolescent↗
PubMed1975

Regulation of phospholipid metabolism in differentiating cells from rat brain cerebral hemispheres in culture. I. Uptake and phosphorylation of [U-14C]ethanoloamine and the effect of various inhibitors.

Cultured dissociated cells from rat embryo cerebral hemispheres were incubated with [U-14C]ethanolamine and the resulting cellular labeled products were identified. A highly efficient uptake for ethanolamine with a Km of approximately 8.3 muM was calculated. A rapid labeling of phosphorylethanolamine was observed prior to the appearance of label in lipids. A lag period of 2.5 min for the phosphorylation reaction was observed, followed by an almost linear rate for up to 40 min. After a 1-min incubation, a plateau for free ethanolamine taken up by the cells was established. Respiratory inhibitiors such as cyanide, 2,4-dinitrophenol, and N-ethylmaleimide decreased by the formation of phosphorylethanolamine. However, the amount offree ethanolamine present in the cells increased 1.6-fold after 10 min of incubation with N-ethylmaleimide. 2-Chloroethylamine, a structural analog of ethanolamine, and choline were both competitive inhibitiors with an apparent Ki of 0.1 mM and 0.36 mM, respectively. Incubations of short duration suggest that both compounds affect ethanolamine transport into the cells. Based on these studies it is suggested that ethanolamine transport and the phosphorylation reaction are independent events. Evidence based on studies with hemicholinium-3 and chloroethylamine suggest that ethanolamine uptake may proceed by a pathway independent of either choline or serine uptake.

Animals↗