Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:1.4.1.2 (glutamate dehydrogenase)
 4,380 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Male Wistar rats administered repetitively with pentylenetetrazol developed a dose-dependent enhancement of seizure behaviour referred to as pentylenetetrazol kindling. After a daily dose of 40 mg pentylenetetrazol/kg or physiological saline (control rats) injected intraperitoneally for a period of two weeks, hippocampal tissue was studied autoradiographically for high-affinity uptake of [3H]glutamate and, by activity staining, for aspartate aminotransferase and glutamate dehydrogenase. Most prominent changes were found in neuropil areas known to be endowed with glutamatergic structures. The uptake capacity of glutamate decreased by 48% (maximum rate), whilst activities of aspartate aminotransferase and glutamate dehydrogenase elevated to 140 and 130%, respectively. Cytochrome c oxidase activity was found to be unaffected. The findings indicate an important role of factors of the glutamate metabolism in the kindling process with respect to the production, utilization, and availability of transmitter glutamate.
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PMID:Pentylenetetrazol kindling and factors of glutamate transmitter metabolism in rat hippocampus. 135 55

C57BL/10Bg sps/sps mice display behavioral arrest, similar to generalized absence seizures. Compared with the parent strain C57BL/10Bg SPS/SPS, the activities of glutamate decarboxylase (GAD, E. C. 2.6.1.15), GABA aminotransferase (GABA-T, E. C. 2.6.1.19), aspartate aminotransferase (ASP-T, E. C. 2.6.1.1), and glutamate dehydrogenase (GDH, E. C. 1.4.1.3) in whole brain crude supernatant were significantly reduced in the sps/sps mice. Alanine aminotransferase activity (ALA-T, E. C. 2.6.1.2), was not altered in any of the strains, and normalization of GAD, GABA-T and GDH activities by that of ALA-T, further revealed significant differences between the normal strain (SPS/SPS), the heterozygotes (SPS/sps), and behavioral arrest (sps/sps) mice. These results suggest the possible involvement of GABAergic and glutamatergic neurotransmission in the absence-like behavior displayed by sps/sps mice. Open field behavior of C57BL/10Bg sps/sps mice is characterized by periods of marked inactivity which easily distinguish affected homozygotes, from their heterozygotes littermates.
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PMID:The C57BL/10Bg sps/sps mouse: a mutant with absence-like seizures; neurochemical and behavioral correlates. 239 34

The activity of glutamate related enzymes and the concentration of glutamine, glutamate and gamma-amino n-butyric acid (GABA) were investigated in the cerebral cortex of rats, in different stages of insulin-induced hypoglycemia. Hypoglycemia was produced by intraperitoneal injection of insulin 0.05-100 units per kg body weight. The minimum required dose to produce irreversible severe hypoglycemia was 0.5 units/kg. In 85% of the cases an insulin induced hypoglycemic convulsion, was achieved 130-150 minutes after injection. Blood glucose levels during insulin induced seizures ranged between 8-15 mg%. In the range of 0.5-100 u insulin/kg the degree of hypoglycemia and the onset of convulsions were identical. The concentration of glutamine was significantly reduced during convulsive and postconvulsive stages. Glutamate and GABA concentrations were reduced significantly in all stages of insulin-induced hypoglycemia. The decrease in glutamine concentration was concurrent with an increase in the activity of its degradative enzyme, glutaminase. This was apparent at the preconvulsive, convulsive and postconvulsive stages. The activity of other enzymes related to energy production such as glutamate dehydrogenase (GDH), glutamate transaminase (GPT) and aspartate aminotransferase (AAT) were also increased. The activity of glutamine synthase (GS) was unaffected by hypoglycemia. Insulin induced changes in glutamine, glutamate and their related enzymes could not be attributed to convulsion since a similar pattern of changes was observed in the preconvulsive and postconvulsive stages, and no changes were detected following picrotoxin-induced seizures.
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PMID:Changes in the activity of glutamate related enzymes in cerebral cortex, during insulin-induced seizures. 257 18

Studies of various parameters of amino acid and catecholamine metabolism in human cerebral cortex have provided a number of biochemical markers that appear to delineate areas of focal epileptic activity. These observations have been consolidated further by investigations of a number of experimental models of epilepsy in animals. In appraising this data, it is important to take into consideration whether the tissue samples were obtained during an actual seizure state or in an interictal period. It is also important when possible to assess the extent of astrogliosis and neuronal loss. Sites of spontaneously active epileptic spiking in the cerebral neocortex have a somewhat different amino acid profile when compared to gray matter obtained from surrounding nonspiking gyri several centimeters away. There is an elevation in glycine content, a relative diminution in taurine, and a trend towards lowered glutamic acid levels. However, the concentrations of the eight amino acids measured appear in both the foci and surround to still be within the general range for normal tissue. Measurements of key enzymes involved in the synthesis and regulation of neurotransmitters provide a complementary method of evaluating functional changes in epileptic brain as they are generally less labile than their substrates. There is a moderate increase in the activity of glutamic acid dehydrogenase, an enzyme that plays an important role in the synthesis of glutamic acid from glucose. In some patients a decrease in glutamic acid decarboxylase has also been reported: this enzyme forms gamma-aminobutyric acid (GABA) from glutamic acid and is thus important for inhibition in the central nervous system. Moreover, there is a striking increase in the activity of tyrosine hydroxylase, the rate-limiting enzyme responsible for catecholamine synthesis. The possibility of a focal abnormality in catecholamine metabolism is reinforced by the simultaneous finding of a relative decrease in the number of alpha-1 postsynaptic receptor sites. An important marker of energy metabolism in neural tissue, Na+,K+-ATPase activity, has also been found to be decreased in actively spiking human cerebral cortex. Data from experimental animal foci produced by topical application of convulsant agents show a consistent drop in glutamic acid tissue content. This can be matched to an efflux of glutamic acid from the cortical surface, which in turn is proportional to the electrographic activity of the spike focus. In addition, there is often also a decrease in taurine and GABA in such foci, as well as an increase in the levels of a number of neutral amino acids.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Amino acid and catecholamine markers of metabolic abnormalities in human focal epilepsy. 287 18

The experiments on (CBA X C57BL/6)F1 mice have shown that regular corazol injections in subliminal doses stimulated seizure susceptibility (pharmacological kindling). Cytophotometric assay of the activity of oxidative metabolism enzymes (glutamate dehydrogenase, malate dehydrogenase, succinate dehydrogenase, alpha-oxoglutarate dehydrogenase, lactate dehydrogenase) and GABA-transaminase in the sensorimotor cortex of kindled mice in post-convulsive period, and 24 hours or 30 days after corazol injections were discontinued, has revealed some specific alterations of the enzymes under study, that suggest the existence of two phases of energy metabolism disturbances. The first phase (24 hours after corazol injections were discontinued) is characterized by intensified succinic acid oxidation, while the second phase (30 days after the last injection) is characterized by anaerobic glycolysis in neuronal and glial cells. Inhibition of GABA-transaminase activity was particularly marked in postconvulsive period. From a molecular point of view these data may be considered as enzyme disturbances during stimulation of seizure susceptability or seizure activity and as a compensation component ensuring anticonvulsive mechanisms and reparative processes (antagonistic principle of molecular mechanism regulation) during activation of antiepileptic system.
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PMID:[Changes in the dehydrogenase and GABA transaminase activity in the cerebral cortex during corazol kindling]. 394 8

The efficacy of phenobarbital and primidone against canine epilepsy was compared in a controlled study. Thirty-five dogs showing generalized tonic-clonic seizures (grand mal), treated for a minimum of 6 months, were included in the study; fifteen of these were treated with phenobarbital, the other twenty with primidone. Both drugs were dosed according to the clinical requirement; the daily doses ranged from 5-17 mg/kg phenobarbital and from 17-70 mg/kg primidone. The plasma concentrations of phenobarbital, or of primidone and its metabolites phenobarbital and phenylethylmalondiamide (PEMA), were routinely monitored. Complete control of tonic-clonic seizures for 6 months, at least, was attained in six out of fifteen dogs of the phenobarbital group, and in five out of twenty dogs in the primidone group. A further six dogs on phenobarbital, and seven dogs on primidone, were classified as 'improved', i.e. the rate of seizures was reduced by at least 50%. The rest of the dogs were not improved by the treatment. The difference between the efficacy of phenobarbital and primidone was not significant, but primidone gave rise to signs of liver toxicity in fourteen out of twenty dogs, as indicated by considerable elevations of liver enzyme values (alanine transferase, glutamate dehydrogenase, alkaline phosphatase). Phenobarbital is, therefore, regarded as the drug of first choice for the treatment of canine epilepsy.
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PMID:Therapeutic efficacy of phenobarbital and primidone in canine epilepsy: a comparison. 402 Sep 42

It has been demonstrated in (CBA X C57BL/6) F1 mice that daily corazole injections (30 mg/kg) lead to the development of pharmacological kindling that manifests in a progressive increase of seizure susceptibility, seizure occurrence in response to the subthreshold convulsant dose and in demonstrable seizures. Cytophotometric study of the histological specimens of the sensorimotor cortex discovered the reduced enzymatic activity of glutamate dehydrogenase and GABA transaminase in the neurons. In the neuroglial cells, the activity of glutamate dehydrogenase also declined, whereas that of GABA transaminase tended on the contrary, towards increase.
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PMID:[Cytophotometric study of changes in glutamate dehydrogenase and GABA transaminase in the cerebral cortex during corazole kindling]. 672 1

This study is an investigation into the validity of calculating the mitochondrial redox state in brain in vivo using models of seizure and anoxia in rats. At six intervals following electroconvulsive seizure (0.5-10 min) and after 5 min of complete anoxia, multiple metabolites were measured in freeze-blown or freeze-clamped brain. From substrate ratios, the apparent changes in the mitochondrial free [NAD+]/[NADH] [H+] ratio were calculated from the L-glutamate dehydrogenase reaction [EC 1.4.1.3] and compared with shifts in the oxidized to reduced ratio of total ubiquinone (a component of the mitochondrial phosphorylation chain). During complete anoxia the calculated mitochondrial free [NAD+]/[NADH] [H+] ratio and the ubiquinone redox ratio both became more reduced by a factor of approximately 7. In contrast, following seizure the two indicators of the mitochondrial redox state moved in opposite directions. Mainly because of a large increase in tissue NH4+, the calculated mitochondrial free [NAD+]/[NADH] [H+] ratio paradoxically became more oxidized, plateauing between 2 and 10 min post seizure at a value approximately double that of the control. At the same time, however, the ubiquinone redox state fell to one-half the control value at two min and moved back towards normal between 5 and 10 min after the onset of the seizure. The results have been taken to be evidence against the applicability of the calculation of the mitochondrial free [NAD+]/[NADH] [H+] ratio from the L-glutamate dehydrogenase reaction in brain at least under conditions of rapid change. The results also suggest the possibility that the NH4+ produced during seizure is extra-mitochondrial and has relatively little tendency to diffuse into the matrix.
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PMID:The calculation of the mitochondrial free [NAD+]/[NADH][H+] ratio in brain: effect of electroconvulsive seizure. 709 92

A 4.5-year-old boy with chronic progressive encephalopathy is described. The clinical presentation initially included seizures and hypotonia which later evolved into severe extrapyramidal disease and dementia. The gas chromatography/mass spectrometry (GC/MS) analysis of urine indicated that alpha-ketoglutarate was increased 210 times and aconitic acid 80 times. No disturbance of acid/base balance, lactic acid or ammonia metabolism accompanied this clinical picture. The fibroblasts contained 29% of normal alpha-ketoglutarate dehydrogenase activity, while the activity of another mitochondrial marker enzyme, glutamate dehydrogenase, was normal. The neuroimaging studies revealed bilateral striatal necrosis. The clinical and biochemical findings were almost identical to two previously reported patients. Experience with this patient emphasizes the need for detailed organic acid biochemical investigation in any progressive encephalopathy and that extrapyramidal tract signs should evoke the possibility of alpha-ketoglutaric aciduria, among other 'neurologic organic acidemias'.
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PMID:A new patient with alpha-ketoglutaric aciduria and progressive extrapyramidal tract disease. 772 79

Studies of neuroactive amino acids and their regulatory enzymes in surgically excised focally epileptic human brain are reviewed. Concentrations of glutamate, aspartate and glycine are significantly increased in epileptogenic cerebral cortex. The activities of the enzymes, glutamate dehydrogenase and aspartate aminotransferase, involved in glutamate and aspartate metabolism are also increased. Polyamine synthesis is enhanced in epileptogenic cortex and may contribute to the activation of N-methyl-D-aspartate (NMDA) receptors. Nuclear magnetic resonance spectroscopy (NMRS) reveals that patients with poorly controlled complex partial seizures have a significant diminution in occipital lobe gamma aminobutyric acid (GABA) concentration. The activity of the enzyme GABA-aminotransaminase (GABA-T) which catalyzes GABA degradation is not altered in epileptogenic cortex. NMRS studies show that vigabatrin, a GABA-T inhibitor and effective antiepileptic, significantly increases brain GABA. Glutamate decarboxylase (GAD), responsible for GABA synthesis, is diminished in interneurons in discrete regions of epileptogenic cortex and hippocampus. In vivo microdialysis performed in epilepsy surgery patients provides measurements of extracellular amino acid levels during spontaneous seizures. Glutamate concentrations are higher in epileptic hippocampi and increase before seizure onset reaching potentially excitotoxic levels. Frontal or temporal cortical epileptogenic foci also release aspartate, glutamate and serine particularly during intense seizures or status epilepticus. GABA in contrast, exhibits a delayed and feeble rise in the epileptic hippocampus possibly due to a reduction in the number and/or efficiency of GABA transporters.
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PMID:Neuroactive amino acids in focally epileptic human brain: a review. 1055 79


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