Search PubMed⌕ Search

Biomedical subjects

P Mandel

Publications and source records attributed to P Mandel.

At least 307 records · Page 17Linked to original sources
PubMed1979

High-affinity uptake of gamma-aminobutyric acid in cultured glial and neuronal cells.

Both glial and neuronal cells maintained in primary culture were found to accumulate [3H]GABA by an efficient "high-affinity" uptake system (apparent Km = 9 muM, Vmax = 0.018 and 0.584 nmol/mg/min, respectively) which required sodium ions and was inhibited by 1 mM ouabain. Strychnine and parachloromercuriphenylsulfonate (pCS) (both at 1mM) also strongly inhibited uptake of [3H]GABA, but metabolic inhibitors (2,4-dinitrophenol, potassium cyanide, and malonate) were without effect. Only three structural analogs of GABA (nipecotate, beta-alanine, and 2,4-diaminobutyrate) inhibited uptake of [3H]GABA, while several other compounds with structural similarities to GABA (e.g. glycine, L-proline, and taurine) did not interact with the system. The kinetic studies indicated presence of a second uptake (Km = 92 muM, Vmax = 0.124 nmol/mg/min) in the primary cultures containing predominantly glioblasts. On the other hand, only one of the neuronal cell lines transformed by simian virus SV40 appeared to accumulate [3H]GABA against a concentration gradient. Apparent Km of this uptake was relatively high (819 muM), and it was only weakly inhibited by 1 mM ouabain and 1 mM pCS. The structural specificity also differed from that of the uptake observed in the primary cultures. Significantly, non of the nontransformed continuous cell lines of either tumoral (glioma, C6; neuroblastoma, M1; M1NN) or normal (NN;I6) origin actively accumulated [3H]GABA. It is suggested that for the neurochemical studies related to GABA and requiring homogeneous cell populations, the primary cultures offer a better experimental model than the continuous cell lines.

4-Chloromercuribenzenesulfonate↗
PubMed1979

Comparison of high-affinity binding of [3H]GABA to subcellular particles of rat brain and liver.

The binding of [3H]GABA and retention of [14C]sucrose have been studied in freshly prepared "synaptosomal-mitochondrial" (P2) fractions of rat cerebral cortex and liver using bicarbonate-buffered medium (containing 147 mEq/liter of Na+), and in frozen/thawed crude membrane fractions of rat whole brain and liver using Na+-free Tris HCl medium. GABA-sensitive sites (GSS) and bicuculline-methiodide- (BMI-) sensitive sites (BMI-SS) were defined as those amounts of [3H]GABA that were sensitive to the displacement by 10(-3) M unlabeled GABA or BMI. In the presence of added Na+, two high-affinity GABA-binding processes were detected in the P2 fraction of cerebral cortex. The lower-affinity process (likely related mainly to uptake sites) had KB approximately equal to 10(-5) M, Bmax for GSS approximately equal to 3 nmol/mg protein, and Bmax for BMI-SS approximately equal to 0.5 nmol/mg protein, whereas the higher-affinity process (likely related to synaptic GABA receptors) had KB approximately equal to 10(-7) M, BMAX for GSS approximately equal to 43 pmol/mg protein, and BMAX for BMI-SS approximately equal to 2 pmol/mg proteins. Only the higher-affinity process was detected in the liver P2 fraction, and it had KB approximately equal to 3.7 x 10(-8) M, BMAX for GSS approximately equal to 0.48 pmol/mg protein, and BMAX for BMI-SS approximately equal to 0.1 pmol/mg protein (i.e., about 1/100 and 1/20 the receptive BMAX values of cerebral cortex). This binding process of the liver P2 fraction could represent sites involved in mitochondrial GABA transport. In Na+-free Tris HCl medium, high-affinity [3H]GABA binding appeared to exist in frozen/thawed membrane preparations of both brain and liver when data were expressed on a protein basis. However, this binding to liver membranes was not displaceable by 10(-5) M unlabeled GABA, and when these data were expressed on a weight basis and corrected for [3H]GABA present in trapped supernatant fluid of the pellets, no [3H]GABA binding was detected in the liver preparation.

Animals↗
PubMed1979

Development and mechanism of barbiturate tolerance in glial cell cultures.

The effects of exposure of glial cells in primary culture and in continuous line (clone NN) to pentobarbital over various periods of time on cellular respiration and activities of enzymes involved in carbohydrate metabolism were studied. The results obtained in glial cells in primary culture were qualitatively identical to those obtained in glial cells in clonal line (NN). Both types of glial cells were shown to develop biochemical tolerance to pentobarbital as defined by an attenuated response to the depressant effects of a challenging dose of pentobarbital on cellular respiration in barbiturate-cultivated cells compared to those grown in drug-free medium. The biochemical tolerance was evident in the presence of glucose and succinate but not malate as substrate. This tolerance to pentobarbital was accompanied by increased activities of hexokinase, glucose-6-phosphate dehydrogenase, succinate dehydrogenase, and glutamate dehydrogenase and by a marked increase in the number of glial cell mitochondria as observed in electron micrographs. The results are interpreted to indicate a compensation of glial cells to the continuous presence of PB by an accelerated glucose uptake and metabolism, an accelerated metabolism of succinate, and an increased mitochondrial activity.

Animals↗
PubMed1979

Membrane lipids in bromodeoxyuridine-differentiated astroglial cells in culture.

Embryonic hamster astroblasts (NN strain) grown in continuous line were cultivated in the presence of bromodeoxyuridine (BrdU). A decrease in the growth rate of the cells and striking changes in their morphology were observed, the morphology of the cells resembling that of mature astrocytes. Membrane lipids of BrdU-differentiated and standard cells were compared. No modification of the lipid/protein ratio was observed. Phospholipids and cholesterol were increased in the same proportions in the cells, and no modification of the phospholipid distribution was observed. Ganglioside sialic acid remained at the same level, but the ganglioside distribution was highly modified. Complex gangliosides appeared (GM1 and GD1a), while the proportion of simple gangliosides (GM3 and GD3) decreased. However, neither GT1 nor GQ1 were detected in differentiated cells. The distribution of phosphoglyceride acyl groups was highly modified, the proportion of arachidonic and docosapentaenoic acids being 2 to 3 times higher in BrdU-treated cells than in proliferating ones. These results were compared to those obtained with another clonal line of glial cells (C6) which exhibited no morphological differentiation in the presence of BrdU; the lipids of these cells were not modified by such a treatment.

Animals↗
PubMed1979

High-affinity binding of [3H]muscimol to subcellular particles of a neurone-enriched culture of embryonic rat brain.

High-affinity, Na+-independent binding of [3H]muscimol (KB approximately equal to 1.6 x 10(-8) M; Bmax approximately equal to 0.14 nmol/g pellet) occurred to a frozen-thawed particulate fraction of 74-h-old neurone-enriched cultures prepared from the cerebra of 12-13-day-old rat embryos. This finding provides evidence that GABA-receptors exist on cultured neurones which contain only a few synaptic connections.

Animals↗
PubMed1979

Effects of apomorphine and sodium Di-n-propylacetate on the aggressive behaviour of three strains of mice.

1. The effects of apomorphine and sodium Di-n-propylacetate (DPA, sodium valproate) on pain-induced aggressive behavior were investigated in three inbred strains of mice: BALB/c, C57B1/6 and DBA/2, which exhibited spontaneously low levels of aggression. 2. Apomorphine elicited aggressive behavior in the three strains, the range of effective doses being different for each strain of mice. 3. Di-n-propylacetate was effective in inhibiting apomorphine elicited aggression but the three strains exhibited a different sensitivity to this drug. 4. The effects of Di-n-propylacetate were not related to pain sensitivity, posture and locomotion. Only C57 strain exhibited a slight postural and locomotor impairment when injected with a higher dose of Di-n-propylacetate. 5. The results are discussed in terms of a genetic inference and of biological differences existing between these three strains.

Aggression↗
PubMed1979

Lack of linkage between acute intermittent porphyria and the A and B loci of the HLA system.

Forty-six members of a family known to have Porphyria were studied. As the disease is often latent clinically, erythrocyte uroporphyrinogen I synthetase activity was determined to classify the subjects as being healthy or carriers. HLA--A, B, C, Bf, GLO antigens were determined. No linkage between acute intermittent Porphyria and the HLA system was noted in this family.

Acute Disease↗
PubMed1979

Properties of purified calf thymus poly(adenosine diphosphate ribose) polymerase. Comparison of the DNA-independent and the DNA-dependent enzyme.

The physicochemical properties of the purified calf thymus poly(ADP-ribose) polymerase were investigated. The enzyme purified to homogeneity was shown to contain about 10% DNA on a weight basis and its activity to be DNA independent. After removing this fragment of DNA, called the sDNA fraction, the enzyme becomes DNA dependent. The activity of this enzyme preparation was entirely dependent on, and completely restored by, added calf thymus DNA or sDNA. However, the calf thymus DNA concentration needed was a hundred times higher than that of sDNA. The properties of the two enzyme preparations, DNA independent and DNA dependent, were essentially the same. They both reacted against the specific antibody obtained with the DNA-independent poly(ADP-ribose) polymerase. The pH optimum was around 8; the activity was stimulated by Mg2+, Mn2+ and Ca2+, and inhibited by high ionic strength, p-chloromercuribenzoate, ADP-ribose, AMP and polylysine. Nicotinamide, thymidine and NADP were shown to be competitive inhibitors. The enzymatic activity was stimulated by histone H1 when the ratio of DNA to histone H1 was 2. Histones H2A, H2B, H3 and H4 had little effect on the DNA-independent enzyme activity, but were strongly inhibitory for the DNA-dependent enzyme. This inhibitory effect could be reversed by allowing the DNA-dependent enzyme to react with the sDNA fraction before adding histone subfractions. The apparent Km for NAD of the DNA-dependent poly(ADP-ribose) polymerase was shown to vary with the DNA concentration. It was minimum when the amount of sDNA was 10% of that of the enzyme. The ratio of the apparent Km for sDNA to the enzyme concentration was constant at any enzyme concentration. The minimum estimation of the number of base pairs of sDNA required for maximal activation of one enzyme molecule was 16. For calf thymus DNA, this estimation was of 640. These results suggest that the activation of the enzyme needs the formation of some complex between the protein and a specific part of the DNA. This complex was preserved in the DNA-independent enzyme preparation.

Animals↗