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The effects of ammonium chloride (3 mM) and beta-methylene-DL-aspartate (BMA; 5 mM) (an inhibitor of aspartate aminotransferase, a key enzyme of the malate-aspartate shuttle (MAS] on the metabolism of glutamate and related amino acids were studied in primary cultures of astrocytes and neurons. Both ammonia and BMA inhibited 14CO2 production from [U-14C]-(More)
Activity levels of pyruvate dehydrogenase, enzymes of citric acid cycle, aspartate and alanine aminotransferases were estimated in mitochondria, synaptosomes and cytosol isolated from brains of normal rats and those injected with acute and subacute doses of ammonium acetate. In mitochondria isolated from animals treated with acute dose of ammonium acetate,(More)
Effects of 1 and 5 mM ammonium acetate on glucose metabolism were studied in astrocytes. But for an elevation in the levels of fructose-6-phosphate, phosphoenol pyruvate, and pyruvate, glucose metabolism was unaltered in the presence of 1 mM ammonium acetate. With 5 mM ammonium acetate, but for unaltered lactate, ADP, ATP and decreased aspartate, levels of(More)
Release and uptake of neurotransmitter amino acids, glutamate and aspartate, were studied in the synaptosomes, astrocytes and in the perikarya of granule neurons isolated from the cerebella of normal and hyperammonemic rats. During acute hyperammonemia, depolarization-induced release of both the amino acids from the synaptosomes was elevated. The Vmax(More)
Activity levels of enzymes of glycolytic pathway viz., hexokinase (EC., phosphofructokinase (EC., aldolase (EC., glyceraldehyde-3-phosphate dehydrogenase (EC., enolase (EC., pyruvate kinase (EC. and lactate dehydrogenase (EC. were estimated in cerebral cortex, cerebellum and brainstem of the rats(More)
Some metabolic effects on primary cultures of neurons or astrocytes were studied following acute or chronic exposure to pathophysiological concentrations (usually 3 mM) of ammonia. Three parameters were investigated: (1) 14CO2 production from 14C-labeled substrates [glucose, pyruvate, branched-chain amino acids (leucine, valine, isoleucine), and glutamate];(More)
Binding of glutamate and muscimol (an agonist for GABAA receptors) to their respective receptors has been studied in the cerebellum of normal and hyperammonemic rats. There was a decrease in both high- and low-affinity binding of glutamate in the cerebellum during hyperammonemia. Kinetic studies revealed that the decrease is due to a reduction in the number(More)
A simplified method was developed for the bulk separation of neuronal perikarya and astroglial cells from adult rat brain without the involvement of density gradients. Activities of various enzymes involved in glutamate metabolism were estimated and compared with those of synaptosomes. The activities of glutamate dehydrogenase and aspartate aminotransferase(More)
14CO2 production and incorporation of label into proteins from the labeled branched-chain amino acids, leucine, valine, and isoleucine, were determined in primary cultures of neurons and of undifferentiated and differentiated astrocytes from mouse cerebral cortex in the absence and presence of 3 mM ammonium chloride. Production of 14CO2 from [1-14C]leucine(More)
A comparison was made of acute and chronic effects of ammonia on production of 14CO2 from the [U-14C] labeled branched-chain amino acids (BCAA) leucine, isoleucine, and valine as well as from [1-14C] leucine, and on the incorporation of radioactivity from these amino acids into a perchloric-acid-precipitable protein fraction in astrocytes and neurons in(More)