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Biomedical subjects

P Mandel

Publications and source records attributed to P Mandel.

At least 433 records · Page 24Linked to original sources
PubMed1977

Glycosphingolipids from cultured astroblasts.

The glycolipids of two clonal lines astroblasts, NN clone and C6 clone, were studied. Glucosylceramide and lactosylceramide were present at very low levels in both clones, but the most common myelin glycolipids galactosylceramide and sulfatide, were not detected. The ganglioside pattern of these cells was rather simple, with GM3 as main compoenent, accompained in one clone by GD3. These results are quite different from those observed on astroglia-enriched fractions isolated from brain. The fatty acid composition of these glycolipids was studied. Long chain fatty acids, up to lignoceric acid, were found in appreciable amounts, even in gangliosides. It is difficult to conclude if these glycolipid patterns are due to the properties of normal astroblasts, to transformation, or to a tumoral character of our cell lines.

Astrocytes↗
PubMed1976

Studies of soluble rat liver mitochondrial acid ATPases. I. Purification and catalytic properties of ATPase 1.

A method for isolation of a soluble ATPase from rat liver mitochondria after freeze thaw cycling is described. Two enzymatically active fractions were separated by DEAE-cellulose chromatography (ATPase 1 and ATPase 2). ATPase 1 has been purified 300 fold. ATPase 1 was homogenous as judged by polyacrylamide gel electrophoresis. The optimum pH of the enzyme was 5.8-6.0 and the optimum temperature was 45 degrees C. The enzyme follows Michaelis-Menten kinetics: Km (9 X 10(-4) M), Vmax (23,6 mumoles Pi released X min -1 X mg protein -1). The enzyme hydrolysed nucleoside triphosphates, but was inactive upon nucleoside di and monophosphates, glucose 6-phosphate, phosphoserine, pyrophosphate and glycerol 2-phosphate. In contrast to membrane bound ATPase, cations have no effect on the enzyme activity. Nucleoside di and mono phosphates and glycerol 2 phosphate inhibited competitively the enzyme. The enzyme was not affected by oligomycin, but was stimulated by lactate, 2-mercaptoethanol and dithiothreitol.

Adenosine Monophosphate↗
PubMed1976

[Effect of pentobarbital on the morphology and respiration of glial cells in primary culture].

Dissociated glial cells from cell-born Rat brains in primary culture were exposed to 5 X 10(-4) M pentobarbital-Na and 2.5 X 10(-5) M morphine. Only pentobarbital was found to induce a morphological change resembling a maturation into protoplasmic astrocytes. This modification was accompanied by an increase of oxygen consumption (50-75%). No evidence could be obtained for the presence of dependence on the barbiturate or morphine, but a certain degree of tolerance to pentobarbital was observed.

Animals↗
PubMed1976

[Effect of an irreversible inhibitor (RMI71645) of gamma-aminobutyric acid (GABA) transaminase on spontaneous and conditioned activities of mice].

The RMI, an irreversible inhibitor of GABA transaminase, inhibited, at the dose of 100 mg/kg, the activity of Mice placed in an open-field. At lower doses, RMI improved the activity in open-field and the number of conditioned avoidance reactions. Results are correlated with increase of the level of brain GABA, following administration of RMI.

4-Aminobutyrate Transaminase↗
PubMed1976

[Changes in cholinergic mechanisms and in learning in three strains of inbred mice after electric stimulation of the dorsal hippocampus].

Two experiments investigated the neurochemical correlates of hippocampal stimulation effects on learning in three inbred strains of Mice. In the 1st experiment, it was shown that subseizure electrical stimulation of the dorsal hippocampus, 30 sec. after a partial appetitive learning session (1) improved 24 hrs. delayed performances of BALB/c Mice (2) had little but significant effect on C57BL/6 (3) had no effect on C57BR animals. The second experiment was aimed at studying the stimulation effect on hippocampal cholinergic mechanisms by testing the two main enzymes involved in acetylcholine synthesis and degradation (choline acetyltransferase = ChAc and acetylcholinesterase = AChE). The major findings of this experiment were as follows: (1) stimulation induced a 3 hrs. delayed improvement of ChAc activity for the BALB/c strain (2) a similar but less important effect was observed in C57BL/6 Mice (3) there was no effect for C57BR animals. These result further support the view that cholinergic hippocampal mechanisms act upon memory consolidation.

Acetylcholinesterase↗
PubMed1976

[Inhibition of mouse-killing behavior by rats with taurine, GABA, and its analogues].

The injection of Gaba, of taurine or of a structural analog of GABA (n-dipropylacetate) in the olfactive bulb of "killer" Rats was found to inhibit the mouse-killing behaviour of the rat. The same effect was obtained when taurine or n-dipropylacetate (which increases GABA in the central nervous system), was injected intraperitoneally. The experiments reported here are interpreted to explain certain molecular mechanisms of muricidal behaviour.

Aggression↗
PubMed1976

The relative distribution of soluble and insoluble cholinesterases in rat excitable tissues.

Three ratios were studied here: bound to free AChE (R1), bound to free BChE (R2), and the ratios between these two (R3). The first one proved relevant in that it contributed to the division of the cholinergic tissues into 3 classes: high values (nicotinic tissues: skeletal muscle), low values (muscarinic tissues: small intestine, uterus, heart), and middle values (mixed, nicotinic and muscarinic cholinergic innervation: brain). The third ratio (R3) showed different values in the muscarinic tissues studied; no significant differences could, however, be found between the ratios of brain and skeletal muscle. Further exploration of this ratio should indicate whether it is of some importance for the characterization of excitable tissues.

Acetylcholinesterase↗
PubMed1976

Cholinesterase activity and choline uptake in intact nerve cell cultures.

Choline uptake and ecto-cholinesterase activities have been measured in intact astroblast and neuroblast cultures. The data show that choline uptake is dependent upon the ionic composition of the culture medium and is sensitive to metabolic inhibitors. However, the high concentrations of the inhibitors necessary for the inhibition of the uptake and some thermodynamic properties qould suggest a facilitated transport rather than an active uphill process. Preincubation of the cultures with various inhibitors of cholinesterases shows no direct parallelism between inhibition of choline high affinity uptake (apparent Km approximately equal to 10-6 M) and inhibition of ecto-acetylcholinesterase (EC 3.1.1.7).

Animals↗
PubMed1976

Plasma dopamine beta-hydroxylase in a noradrenalin-secreting pheochromocytoma.

Circulating dopamine beta-hydroxylase activity was studied in a case of a hypertensive patient bearing a pheochromocytoma. The tumour secreted noradrenalin. The enzyme activity was found to decrease gradually after removal of the tumour, and to reach a stable value, in correlation with the decrease of urinary catecholamines. It is concluded that some pheochromocytoma tumours are able to secrete dopamine beta-hydroxylase.

Adult↗
PubMed1976

Ecto-5'-nucleotidase of intact cultured C6 rat glioma cells.

The characteristics of 5'-nucleotidase in a clonal line (C6) of rat glioma cells has been examined in detail. The cells liberated 6.80 +/- 0.33 mumol of inorganic phosphate/mg of cell protein/hour, producing nearly equimolar amounts of adenosine and inorganic phosphate from AMP in the extracellular fluid. No 5'-nucleotidase was released by the cells into the medium. Most of the 5'-nucleotidase activity was found to be located in the outer surface of the plasma membrane of C6 cells and rapidly accessible to exogenous AMP, by experiments based upon differential labeling of extracellular and intracellular compartments with 32P and 33P. The ecto-enzyme was active in the absence of divalent cations. However, Mn2+ or Co2+ were somewhat stimulatory. Zn2+ suppressed activity very markedly. The relationship of enzymatic reaction velocity to pH was complex, with an optimum at pH 7.4 for all substrates tested. The ecto-5'-nucleotidase readily hydrolyzed 5'-AMP and 5'-UMP. Other 5'-nucleoside monophosphates, including 5'-deoxy-AMP, were also hydrolyzed, but more slowly; 2'- or 3'-nucleoside monophosphates were not attacked. The ecto-5'-nucleotidase in the intact cell obeyed Michaelis-Menten kinetics. Apparent Km for AMP was 0.22 mM; apparent Km values for other substrates were similar and ranged from 0.16 to 0.18 mM. ADP exerted a very powerful inhibitory effect, behaving as a competitive inhibitor, and 5'-UMP behaved as a strictly competitive substrate for 5'-AMP. ATP and ITP were inhibitory. Of these, ITP served to increase Km for AMP. ATP did likewise, but also greatly lowered Vmax. These findings indicate that the intact cell is capable of rapid hydrolysis of exogenous 5'-AMP, to produce adenosine at the cell surface at a rate which responds directly to extracellular AMP concentration but which can be suppressed by extracellular ADP or ATP.

Binding, Competitive↗
PubMed1976

Properties of soluble and particulate cysteine sulfinate decarboxylase of the adult and the developing rat brain.

Some properties of cysteine sulfinate decarboxylase (CSD) activity were studied in the pellet and supernatant of a 18,000 X g centrifugation of isotonic sucrose rat brain homogenates. About 50% of the enzyme activity was found associated to the particulate fraction and 16% of the activity remained particle bound after hypo-osmotic shock of the 18,000 X g pellet. The activity of the 18,000 X g supernatant showed a lower dependence on exogenous pyridoxal phosphate (PLP) than the activity in the particulate fraction. The CSD activity of these fractions also differed in optimal pH and in apparent kinetic constants. The enzyme associated to particles showed the highest Vmax and the lowest Km. The activity and kinetic characteristics of CSD were studied during brain postnatal development. In the newborn brain only a small amount of the enzyme activity was found associated to the 18,000 X g pellet. CSD in brain homogenates of immature rats was less dependent on free PLP and showed a higher Km and a lower Vmax as compared with the enzyme in the adult brain. Between birth and adulthood the enzyme activity increased more than 10-fold in the particulate fraction and 2-fold in the soluble fraction. It is concluded that the differences observed in CSD activity between newborn and adult brain are due to an increase of the particulate form of the enzyme during postnatal development.

Animals↗
PubMed1976

Brain UDPgalactose: ceramide galactosyltransferase Purification of a catalytically active protein obtained after proteolytic digestion.

A procedure for the purification of UDPgalactose--2-hydroxyacylsphingosine galactosyltransferase (EC 2.4.1.45) including detergent extraction, ion-excharge chromatography and proteolytic digestion was developed. The active fraction obtained by this procedure had about 100 times higher specific activity than microsomes. Enzymic activity resisted destruction by pronase treatment at 4 degrees C. Agarose gel chromatography indicated the presence of an enzyme-phospholipid-detergent complex with a molecular weight between 400 000 and 500 000. Intact phospholipids seemed to be required for full enzymic activity as evidenced by the drastic loss of activity upon treatment with phospholipase A or C.

Animals↗