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Biomedical subjects

M Swamy

Publications and source records attributed to M Swamy.

9 recordsLinked to original sources
PubMed2005

Effects of acute ammonia toxicity on nitric oxide (NO), citrulline-NO cycle enzymes, arginase and related metabolites in different regions of rat brain.

Nitric oxide (NO) is involved in many pathophysiological processes in the brain. NO is synthesized from arginine by nitric oxide synthase (NOS) enzymes. Citrulline formed as a by-product of the NOS reaction, can be recycled to arginine by successive actions of argininosuccinate synthetase (ASS) and argininosuccinate lyase (ASL) via the citrulline-NO cycle. Hyperammonemia is known to cause poorly understood perturbations of the citrulline-NO cycle. To understand the role of citrulline-NO cycle in hyperammonemia, NOS, ASS, ASL and arginase activities, as well as nitrate/nitrite (NOx), arginine, ornithine, citrulline, glutamine, glutamate and GABA were estimated in cerebral cortex (CC), cerebellum (CB) and brain stem (BS) of rats subjected to acute ammonia toxicity. NOx concentration and NOS activity were found to increase in all the regions of brain in acute ammonia toxicity. The activities of ASS and ASL showed an increasing trend whereas the arginase was not changed. The results of this study clearly demonstrated the increased formation of NO, suggesting the involvement of NO in the pathophysiology of acute ammonia toxicity. The increased activities of ASS and ASL suggest the increased and effective recycling of citrulline to arginine in acute ammonia toxicity, making NO production more effective and contributing to its toxic effects.

Amino Acids↗
PubMed1993

Antibody-induced alterations of Na+/K(+)-ATPase activity in rabbit red blood cells during experimental thyroglobulin immunization.

Thyroid hormone modulates cell membrane Na+/K(+)-ATPase. A detailed study of erythrocyte membrane Na+/K(+)-ATPase activity was carried out during experimental thyroglobulin immunization. During the process of immunization there was a sharp decline in Na+/K(+)-ATPase activity until the 98th day of immunization, when the thyroglobulin antibody titer was at its peak. This enzyme activity retained a lower level although a fall in antibody titer occurred up to the 147th day.

Animals↗
PubMed1992

Studies on urea cycle enzyme levels in the human fetal liver at different gestational ages.

Urea cycle enzymes involved in the detoxification of ammonia were studied in liver tissues of 57 male and 49 female fetuses of different age groups ranging from 13 to 36 wk of gestation. Surgical wedge biopsies of liver from 18 male and 12 female adults were used as controls. Significant enzyme activity was found to be present as early as the 13th wk of gestation. As gestational age advanced, enzyme activity gradually increased, reaching about 90% of the adult activity by the 36th wk of gestation.

Adult↗
PubMed1989

Covalent change in the major intrinsic polypeptide (MIP26K) during cataract development in the streptozotocin-induced diabetic rat.

Antisera to synthetic peptides corresponding to residues 229-237, 252-259, and 256-263 have been used to quantitatively bind to the 19.5K, 24.0K, and 26.5K forms of the Major Intrinsic Polypeptide (MIP26K) of lens membrane from the streptozotocin-induced diabetic rat. The binding ratio of anti-229/anti-252 for the 19.5K component, and the binding ratio of anti-252/anti-256 for the 26.5K component, both increase only during the opacification process of the diabetic lens. Together, these results demonstrate that various forms of the MIP26K molecule undergo covalent modification during cataractogenesis of the diabetic rat lens, and that the degree of this change as monitored by binding of the anti-MIP26K peptide sera correlates with severity of the lens opacification.

Animals↗
PubMed1984

Possible occurrence of ornithine-omega-aminotransferase in GABAergic neurons.

The specific precursors for neurotransmitter pools of glutamate giving rise to GABA in GABAergic neurons and nerve endings have not been clearly established. Glutamate is the immediate precursor for the production of GABA and it is suggested that ornithine (from arginine) might be serving as one of the precursors of glutamate for the formation of neurotransmitter pool of GABA. Damage to GABAergic neurons in different regions of the brain in anoxia is well known. If arginine and ornithine act as precursors for GABA in GABAergic neurons, a decrease in the activities of arginase and ornithine-omega-transferase (Orn-T) is possible in areas having the lesions involving the GABAergic neurons due to anoxia. Estimation of Orn-T and arginase in different regions of the brain of rats exposed to anoxia revealed such a possibility.

Animals↗
PubMed1983

Studies on acetylcholinesterase and gamma-glutamyltranspeptidase in mouse brain in ammonia toxicity.

Short- and long-term ammonia toxicity was induced in mice by intraperitoneal injection, respectively, of single and six doses of 0.6 mM ammonium acetate per 100 g of body weight. The animals were sacrificed half an hour after either the single injection or after the last injection of six doses. Under these experimental conditions the ammonia levels were found to be elevated twofold in cerebral cortex, brain stem, and basal ganglia after the administration of a single dose of ammonium acetate. A fourfold increase in the content of ammonia was observed in cerebral cortex, brain stem, and basal ganglia after six injections. An elevation in the activity of pseudocholinesterase (enzyme localized in brain capillaries and glial cells) in all the above four regions resulted as a short-term effect of ammonia toxicity. True acetylcholinesterase was found to be elevated in all the four regions in short-term and in long-term ammonia toxicity. Gamma-glutamyltranspeptidase (GGTP), another enzyme localized in cerebral capillaries and glial cells, was found to be depressed in all the regions of the brain in both short- and long-term ammonia toxicity. The implications of these results are discussed in relation to glial cell function.

Acetylcholinesterase↗
PubMed1983

Activities of arginase, transamidinase, and ornithine aminotransferase in glia, neurons, and synaptosomes.

The regional, cellular, and subcellular distribution of some enzymes of the urea cycle in brain is not clearly known. Glia, neurons, and synaptosomes have been prepared from rat cerebral cortex and arginase (EC 3.5.3.1), transamidinase (EC 2.1.4.1), and ornithine aminotransferase (EC 2.6.1.13) have been estimated in order to understand the metabolic and functional role of these enzymes. It has been observed that arginase is predominantly localized in synaptosomes and neurons. The ornithine aminotransferase was found to be high in glial cells and very high in synaptosomes (higher than arginase). Transamidinase was mostly localized in glial cells. The implication of these results has been discussed in relation to a possible role of ornithine acting as a precursor of glutamate in glutametargic nerve endings and its possible participation in the glutamate-glutamine cycle.

Acyltransferases↗
PubMed1982

Studies on metabolism of branched chain amino acids in brain and other tissues of rat with special reference to leucine.

Leucine aminotransferase (EC 2.6.1.6) and 2-oxoisocaproate dehydrogenase (EC 1.2.4.3) were studied in rat cerebral cortex, cerebellum, brain stem, liver, and muscle in normal and animals starved for 48 hours. In the brain, leucine aminotransferase, valine aminotransferase, and 2-oxoisocaproate dehydrogenase showed a significant increase in starvation only in cerebellum while there was increase in 2-oxoisocaproate dehydrogenase in cerebral cortex only. A significantly high increase in the activity of 2-oxoisocaproate dehydrogenase was observed in muscle in starvation. A significant decrease in the activity of leucine aminotransferase was observed in liver in starvation. The increase in the activity of 2-oxoisocaproate dehydrogenase in muscle and a decrease in the activity of leucine aminotransferase in liver in starvation indicate that the leucine is predominantly metabolized in extra hepatic tissues particularly in muscle. As a result of intraperitoneal administration of 2 ml of leucine (5 mM), a significant increase in 2-oxoisocaproate dehydrogenase occurred in cerebral cortex, liver, and muscle while a profound increase in the activity of glutamate dehydrogenase (EC 1.4.1.2) was observed in all the brain regions and liver under these conditions. A significant increase in the content of glutamic acid, alanine, and GABA was observed in all the three regions of the brain after the administration of leucine. A significant increase in the content of glutamine was observed only in the cerebellum and cerebral cortex after leucine administration. These results indicate that leucine in brain might contribute to the formation of glutamate, not only by transamination, but also by promoting glutamate dehydrogenase activity. Thus, there is a change in the metabolism of glutamate family of amino acids and energy depletion. These results are discussed in relation to the brain function.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗