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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phosphate-activated glutaminase (PAG) and glutamic acid decarboxylase (GAD) were assayed in homogenates and synaptosomes obtained from starved (48 hr or 120 hr) and diabetic (streptozotocin) rat brain cortex. Glutamine synthetase (GS) was assayed in homogenates, microsomal and soluble fractions, from brain cortex of similarly treated rats. L-Glutamate uptake and exit rates were determined in cortex slices and synaptosomes under the same conditions. The specific activity (s.a.) of PAG, a glutamate producing enzyme, decreased (50%) in the homogenate after 120-hr starvation. In synaptosomes it decreased (25%) only after 48-hr starvation. The s.a. of GAD and GS, which are glutamate-consuming enzymes, were progressively increased with time of starvation, reaching 39% and 55% respectively after 120 hr. GS in the microsomes or the soluble fraction and GAD in the synaptosomes showed no change in s.a. under these conditions. Diabetes increased (40%) microsomal GS s.a. and decreased GAD s.a. (18%) in the homogenate. The L-glutamate uptake rate was decreased (48%) by diabetes in slices but no in synaptosomes. It is suggested that a) enzymes of the glutamate system respond differently in different subcellular fractions towards diabetes or deprivation of food and b) diabetes may affect the uptake system in glial cells but not in neurons.
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PMID:Effects of fasting and diabetes on some enzymes and transport of glutamate in cortex slices or synaptosomes from rat brain. 289 38

The metabolic consequences of two defects in pyruvate metabolism of the hyphal fungus Aspergillus nidulans have been investigated by natural abundance 13C-NMR spectroscopy. A pyruvate dehydrogenase complex (pdh) mutant, grown on acetate, accumulates alanine upon starvation which is derived from mannitol reserves. The L-alanine level increases further upon incubation with the non-permissive substrate D-glucose. L-Glutamate is absent from these spectra as it is required both for the transamination of pyruvate and as a reaction on an impaired energy metabolism in such a pdh-deficient strain. A pyruvate carboxylase (pyc) mutant, grown upon acetate, only starts to accumulate alanine after a long incubation period with D-glucose, due to the long-lasting presence of phosphoenolpyruvate carboxykinase and malic enzyme, which are both induced by growth on acetate. When this strain is grown on D-fructose and L-glutamate, alanine also accumulates within 3 h upon transfer to D-glucose.
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PMID:13C-NMR analysis of Aspergillus mutants disturbed in pyruvate metabolism. 331 6

Some cultures of Escherichia coli BGA8, a mutant unable to synthesize putrescine, showed a change of behaviour and could grow almost equally well in either the absence or the presence of polyamines after repeated periods of polyamine starvation. Experiments in vivo with radioactive precursors showed that the bacteria which evaded the polyamine requirement had recovered their ability to synthesize putrescine from glucose or glutamic acid, but not from ornithine or arginine. These results are in agreement with the fact that the polyamine-independent cells were still deficient in the enzymes ornithine decarboxylase and agmatinase. Our findings seem to indicate the existence of a new pathway synthesize putrescine which does not involve ornithine or arginine as intermediates.
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PMID:A probable new pathway for the biosynthesis of putrescine in Escherichia coli. 352 93

Studies were conducted to determine whether rainbow trout fingerlings possess the ability to synthesize arginine via the urea cycle. Several urea cycle enzymes were detected in trout tissues. An experiment was conducted to determine whether the enzymes increase in response to starvation or in response to dietary protein level (0, 30, 40, 50% protein). Although some effects were observed, they did not appear to be consistent with the function of the urea cycle as a mechanism of detoxifying ammonia in the fish. The activities of kidney arginase and liver and muscle carbamoyl phosphate synthetase (CPS) were higher (P less than 0.05) when protein was omitted from the diet (P less than 0.05) than when it was present but were unaffected by protein level otherwise. The activities of liver arginase and kidney and muscle CPS and ornithine transcarbamoylase (OTC) were higher (P less than 0.05) in starved fish than in fish that received adequate levels of protein. Liver CPS and OTC were lower in starved fish than in fish fed 30% protein. L-[l-14C]ornithine hydrochloride and L-[carbamoyl-14C]citrulline, injected intraperitoneally, were incorporated into tissue arginine, a finding consistent with arginine biosynthesis via the urea cycle. When one-half of dietary arginine was replaced by equimolar amounts of glutamic acid, ornithine or citrulline, glutamic acid markedly reduced growth (P less than 0.05), whereas growth was depressed only slightly by ornithine (P less than 0.05) and not depressed by citrulline (P greater than 0.05). We conclude that trout have a urea cycle that provides for potential arginine biosynthesis.
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PMID:Urea cycle activity and arginine formation in rainbow trout (Salmo gairdneri) 376 Oct 21

1. Mg(2+) or Mn(2+) starvation causes suspensions of Bacillus subtilis strain W 23 to accumulate bound amino sugars that are soluble in trichloroacetic acid. 2. The presence of chloramphenicol or puromycin produces higher intracellular concentrations of amino sugars during Mg(2+) starvation, but neither compound can stimulate the accumulation when Mg(2+) is present. 3. The major component of the amino sugar fraction extracted from cells deprived of Mg(2+) is a nucleotide containing uridine, phosphorus, N-acetylmuramic acid, alanine, glutamic acid and alphain-diaminopimelic acid in the molar proportions of 1:2:1:3:1:1. This compound represents at least 80% of the bound N-acetylhexosamine extracted by trichloroacetic acid. 4. Studies of the binding of this nucleotide with vancomycin support the proposal that it is the mucopeptide precursor UDP-N-acetylmuramyl-l-alanyl-d-glutaminyl- alphain-diaminopimelyl-d-alanyl-d-alanine. 5. A method is described for the isolation of this material labelled with [(3)H]alphain-diaminopimelic acid. 6. When Mg(2+) is supplied to cells previously starved of Mg(2+), the accumulated pool of amino sugars rapidly decreases. 7. The biosynthesis of mucopeptide is inhibited by 35-50% under conditions of Mg(2+) starvation. The presence of EDTA increases this inhibition to 70%. The amount of N-acetylhexosamine that accumulates is balanced exactly by the associated fall in mucopeptide synthesis. 8. ;Chase' experiments show that the accumulated N-acetylhexosamine compound is utilized in mucopeptide synthesis.
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PMID:The effect of magnesium ion deprivation on the synthesis of mucopeptide and its precursors in Bacillus subtilis. 498 84

The transport of L-glutamic acid has been studied in skin-derived diploid human fibroblasts. Competition analysis in the presence and absence of Na+ and mathematical discrimination by nonlinear regression indicated that L-glutamic acid enters the cell by at least three transport systems: 1) a high affinity Na+-dependent system which has been found to be identical to the previously described system for anionic amino acids (Gazzola, G. C., Dall'Asta, V., Bussolati, O., Makowske, M., and Christensen, H. N. (1981) J. Biol. Chem. 256, 6054-6059) and which is provisionally designated as System X-AG; this route was shared by L-aspartic acid; 2) a low affinity Na+-dependent system resembling the ASC System for neutral amino acids (Franchi-Gazzola, R., Gazzola, G. C., Dall'Asta, V., and Guidotti, G. G. (1982) J. Biol. Chem. 257, 9582-9587); its reactivity toward L-glutamic acid was strongly inhibited by L-serine, but not by 2-(methyl-amino)isobutyric acid; and 3) a Na+-independent system similar to System XC- described in fetal human lung fibroblasts (Bannai, S., and Kitamura, E. (1980) J. Biol. Chem. 255, 2372-2376). The XC- system served for L-glutamic acid and L-cystine, the latter amino acid behaving as a potent inhibitor of L-glutamic acid uptake. Amino acid starvation did not change the uptake of L-glutamic acid by the two Na+-dependent systems, but enhanced the activity of System XC- by increasing its Vmax. L-Glutamic acid transport was also affected by the density of the culture. An increased cell density lowered the uptake of the amino acid by Systems ASC and XC- and promoted the uptake by System X-AG. All these variations were dependent upon changes in Vmax.
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PMID:Pathways of L-glutamic acid transport in cultured human fibroblasts. 613 63

In anorexia nervosa the pain of hunger or, alternatively (in bulemia), of glut recalls Freud's aphorism that the man with toothache cannot fall in love. But object longing remains and stimulates such envy that the anorectic must project her wishes; she is not be found wanting. The use of projection, in turn, complicates self-other boundaries, with the result that she experiences not only people but even food as overpowering. This, then, excites more envy, indeed an envy so ruinous that self-starvation or compulsive evacuations are employed additionally to make reparation. Because all of this condenses into Less is More, the anorexic poses particular problems for analytic treatment, which is the subject of a companion paper.
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PMID:The problem of anorexia nervosa. 657 8

The general control of amino acid biosynthesis was investigated in Candida spec. EH 15/D, using single and double mutant auxotrophic strains and prototrophic revertants starved for their required amino acids. These experiments show that starvation for lysine, histidine, arginine, leucine, threonine, proline, serine, methionine, homoserine, asparagine, glutamic acid or aspartic acid can result in derepression of enzymes. A correlation was found between the degree of derepression, growth of strains, and concentration of required amino acids. The amino acids pool pattern of mutants and revertants is different from that in the wild type strain.
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PMID:[General control of amino acid biosynthesis in mutants of Candida spec. EH 15/D]. 663 44

Folic acid is a chemoattractant for the slime mold Dictyostelium minutum V3. The activity of extracellular folic acid is regulated by a folic acid C9-N10 splitting enzyme (FAS). The products were identified as pterin-6-aldehyde and p-amino-benzoylglutamic acid. The enzyme was stabilized by EDTA. For the extracellular enzyme, the Km was 10(-7) M, and the optimal pH was 4.0. During starvation, FAS activity was mainly secreted into the medium; after 3 h, a plateau was reached. The membrane-bound activity was constant, but only 12% of the extracellular activity at 3 h. Intracellular activity also increased up to 3 h to a level of 23% of the extracellular FAS. The substrate recognition of FAS was found to be based on 4-O or N3 or both, N5 or N8 or both, N10, and the p-aminobenzoic acid moiety, whereas 2-NH2, N1, and the glutamic acid moiety were not recognized. Other slime mold species were found to secrete FAS with 20-fold or more reduced activity than D. minutum V3.
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PMID:Characterization of the folic acid C9-N10-cleaving enzyme of Dictyostelium minutum V3. 684 18

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.
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PMID:Studies on metabolism of branched chain amino acids in brain and other tissues of rat with special reference to leucine. 714 88


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