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

Acute nitrogen normobaric hypoxic challenges, resulting in an approximately 50% overall survival, were performed in young adult male and female heterozygous OF1 mice under various environmental conditions. The time required to obtain 50% survival was 20 min for a constant pO2 of 42 Torr, and 151 min when pO2 was progressively lowered by nitrogen flushing from 159 to 16.5 Torr. In LD12:12 synchronized animals, survival was significantly (P less than 0.001) less when hypoxia was performed during the light (L) than during the dark (D) phase. Lowering the ambient temperature from 33.8 to 13.2 degrees C increased the length of the progressive hypoxia necessary to obtain a 50% survival of the mice by 1.7 times, and diminished the final pO2 from 35 to 12 Torr. Grouping and crowding both decreased hypoxic survival. A previous stress (starvation) diminished hypoxic resistance of mice, while a preceding hypoxia, carbon monoxide inhalation, or sodium cyanide injection had the opposite effect. In all instances, OF1 females were more resistant than males. Most of these variations can be related to differences in respiratory exchanges, locomotor activity and aggressiveness, which are dependent upon the various experimental environmental parameters.
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PMID:Environmental parameters in the experimental evaluation of a respiratory aggression. 667 64

Vegetative hyphae of Fusarium oxysporum differentiate into chlamydospore by triggering with carbon-starvation. The current changes in the cellular detoxifying defenses against superoxide and hydrogen peroxide: superoxide dismutase (SOD) and catalase, were examined. Although there was a little change in catalase, a dramatic change in SOD was observed during the differentiation. In vegetative hyphae of F. oxysporum f. sp. raphani, three isozymes of SOD, all of which were not inhibited by hydrogen peroxide and cyanide, were present whereas in chlamydospore an isoenzyme, which was inhibited by hydrogen peroxide but not by cyanide, was present. Thus, as differentiation proceeded, Mn-type SOD disappeared and an Fe-type SOD appeared. The results suggest that the Fe-type SOD is specifically expressed during chlamydospore formation and that active intermediates of oxygen and/or its scavenging enzymes participate in the differentiation of Fusarium oxysporum.
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PMID:Alterations in superoxide dismutase and catalase in Fusarium oxysporum during starvation-induced differentiation. 762 60

Glutamate excretion due to amino acid starvation was investigated in "stringent" and "relaxed" strains of Escherichia coli. The observed excretion process is relA-dependent, carrier-mediated, and glutamate-specific. After induction, excretion was detected within less than 2 min and continued for more than 5 h with a rate of 7-10 nmol (mg dry weight)-1 min-1. Using carbonyl cyanide m-chlorophenylhydrazone or polymyxin B nonapeptide, together with valinomycin, it was shown that glutamate excretion is driven by the membrane potential.
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PMID:Glutamate excretion in Escherichia coli: dependency on the relA and spoT genotype. 764 16

Nitric oxide (NO) synthase, the enzyme responsible for the generation of the cytotoxic compound NO from L-arginine, is induced in macrophages during activation. Previous work demonstrated that the cytotoxicity of NO extends to the macrophages that produce it, because the activity of NO synthase in these cells correlates inversely with their life span in culture. Data presented here demonstrate that the NO-dependent death of murine peritoneal macrophages activated in vitro with IFN-gamma and LPS is mediated through apoptosis. Evidence in this direction was provided by microscopic examination of the cells, which revealed the presence of nuclear and cytoplasmic alterations characteristic of apoptosis, and by the specific pattern of internucleosomal DNA fragmentation detected by electrophoresis. That these alterations resulted from the production of NO was confirmed by the preventive effects of cell activation in L-arginine-restricted medium or in medium containing an inhibitor of NO synthase, NG-monomethy L-arginine, and more directly by the induction of apoptosis by exposure of the cells to authentic NO gas. Additional results demonstrated that glucose starvation, the inhibition of the tricarboxylic acid cycle with fluorocitrate or of glycolysis with iodoacetate, but not the suppression of the electron transport chain with potassium cyanide, also induced macrophage apoptosis. The potential role of metabolic inhibition as a mechanism for NO-mediated apoptosis, as well as the relationship of these findings with events occurring in wounds and other sites of macrophage infiltration are discussed.
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PMID:Nitric oxide-mediated apoptosis in murine peritoneal macrophages. 768 18

The stringent halobacterial strain Haloferax volcanii was subjected to a set of physiological conditions different from amino acid starvation that are known to cause production of guanosine polyphosphates [(p)pp Gpp] in eubacteria via the relA-independent (spoT) pathway. The conditions used were temperature upshift, treatment with cyanide, and total starvation. Under none of these conditions were detectable levels of (p)ppGpp observed. This result, in conjunction with our previous finding that (p)ppGpp synthesis does not occur under amino acid starvation, leads to the conclusion that in halobacteria both growth rate control and stringency are probably governed by mechanisms that operate in the absence of ppGpp. During exponential growth, a low level of phosphorylated compounds with electrophoretic mobilities similar, but not identical, to that of (p)ppGpp were observed. The intracellular concentration of these compounds increased considerably during the stationary phase of growth and with all of the treatments used. The compounds were identified as short-chain polyphosphates identical to those found under similar conditions in Saccharomyces cerevisiae.
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PMID:Lack of production of (p)ppGpp in Halobacterium volcanii under conditions that are effective in the eubacteria. 779 53

Fatty acid beta-oxidation was studied in organellar fractions from maize root tips by h.p.l.c. and radiometric analysis of the products of incubations with [1-14C]octanoate and [1-14C]palmitate. In crude organellar fractions containing both mitochondria and peroxisomes, octanoate and palmitate beta-oxidation, as determined by the production of acetyl-CoA, was functional and, for palmitate, was activated 4-12-fold after subjecting the root tips to 48 h of glucose starvation. The sensitivity to a 'cocktail' of respiratory-chain inhibitors containing cyanide, azide and salicylhydroxamate depended on the conditions of incubation, with no inhibition in a medium facilitating peroxisomal beta-oxidation and a significant inhibition in a medium potentially facilitating mitochondrial beta-oxidation. Indeed, preparations of highly purified mitochondria from glucose-starved root tips were able to oxidize octanoate and palmitate to give organic acids of the tricarboxylic acid cycle. This activity was inhibited 5-10-fold by the above cocktail of respiratory-chain inhibitors, with no parallel accumulation of acetyl-CoA, thus showing that the inhibition affected beta-oxidation rather than the pathway from acetyl-CoA to the organic acids. This provides the first evidence that the complete beta-oxidation pathway from fatty acids to citrate was functional in mitochondria from a higher plant. Moreover, an acyl-CoA dehydrogenase activity was shown to be present in the purified mitochondria. In contrast with the peroxisomal activity, mitochondrial beta-oxidation showed the same efficiency with octanoate and palmitate and was strictly dependent on glucose starvation.
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PMID:Effects of glucose starvation on the oxidation of fatty acids by maize root tip mitochondria and peroxisomes: evidence for mitochondrial fatty acid beta-oxidation and acyl-CoA dehydrogenase activity in a higher plant. 825 Aug 43

The gram negative bacterium Escherichia coli has evolved a highly specific system for the transport of exogenous long-chain fatty acids (C12-C18) across the cell envelope that requires the outer membrane protein FadL and the inner membrane associated fatty acyl CoA synthetase. The transport of oleate (C18:1) across the cell envelop responds to metabolic energy. In order to define the source of metabolic energy which drives this process, oleate transport was measured in wild-type and ATP synthase-defective (Deltaatp) strains which were (i) subjected to osmotic shock and (ii) starved and energized with glucose or d-lactate in the presence of different metabolic inhibitors. Osmotic shock did not eliminate transport but rather reduced the rate to 33-55% of wild-type levels. These results suggested a periplasmic protein may participate in this process or that osmotic shock disrupts the energized state of the cell which in turn reduces the rate of oleate transport. Transport systems which are osmotically sensitive also require ATP. The process of long-chain fatty acid transport requires ATP generated either by substrate-level or oxidative phosphorylation. Following starvation, the basal rate of transport for wild-type cells was 340.4 pmol/min/mg protein compared to 172.0 pmol/min/mg protein for the Deltaatp cells. When cells are energized with glucose, the rates of transport were increased and comparable (1242.6 and 1293.8 pmol/min/mg protein, respectively). This was in contrast to cells energized with d-lactate in which only the wild-type cells were responsive. The role of ATP is likely due to the ATP requirement of fatty acyl CoA synthetase for catalytic activity. The process of oleate transport is also influenced by the energized state of the inner membrane. In the presence of carbonyl cyanide-m-chlorophenylhydrazone oleate transport is depressed to 30-50% of wild-type levels in wild-type and Deltaatp strains under starvation conditions. These results are mirrored in cells energized with glucose and d-lactate, indicating that an energized membrane is required for optimal levels of oleate transport. These data support the hypothesis that the fatty acid transport system of E. coli responds to both intracellular pools of ATP and an energized membrane for maximal proficiency.
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PMID:Energetics underlying the process of long-chain fatty acid transport. 1032 25

Rhizobium tropici forms nitrogen-fixing nodules on the roots of the common bean (Phaseolus vulgaris). Like other legume-Rhizobium symbioses, the bean-R. tropici association is sensitive to the availability of phosphate (P(i)). To better understand phosphorus movement between the bacteroid and the host plant, P(i) transport was characterized in R. tropici. We observed two P(i) transport systems, a high-affinity system and a low-affinity system. To facilitate the study of these transport systems, a Tn5B22 transposon mutant lacking expression of the high-affinity transport system was isolated and used to characterize the low-affinity transport system in the absence of the high-affinity system. The K(m) and V(max) values for the low-affinity system were estimated to be 34 +/- 3 microM P(i) and 118 +/- 8 nmol of P(i) x min(-1) x mg (dry weight) of cells(-1), respectively, and the K(m) and V(max) values for the high-affinity system were 0.45 +/- 0.01 microM P(i) and 86 +/- 5 nmol of P(i) x min(-1) x mg (dry weight) of cells(-1), respectively. Both systems were inducible by P(i) starvation and were also shock sensitive, which indicated that there was a periplasmic binding-protein component. Neither transport system appeared to be sensitive to the proton motive force dissipator carbonyl cyanide m-chlorophenylhydrazone, but P(i) transport through both systems was eliminated by the ATPase inhibitor N,N'-dicyclohexylcarbodiimide; the P(i) transport rate was correlated with the intracellular ATP concentration. Also, P(i) movement through both systems appeared to be unidirectional, as no efflux or exchange was observed with either the wild-type strain or the mutant. These properties suggest that both P(i) transport systems are ABC type systems. Analysis of the transposon insertion site revealed that the interrupted gene exhibited a high level of homology with kdpE, which in several bacteria encodes a cytoplasmic response regulator that governs responses to low potassium contents and/or changes in medium osmolarity.
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PMID:Characterization of two inducible phosphate transport systems in Rhizobium tropici. 1061 97

Cells of Listeria monocytogenes display sub-lethal injury when subjected to long-term chill-storage in a nutrient-poor environment. The physical and metabolic causes of sub-lethal injury to two meat (L61 and L62) and two clinical (L98 and L99) L. monocytogenes strains chill-stored (4 degrees C) for 4 weeks in phosphate-buffered saline at pH 7.0 and pH 5.5, and pH 5.5 in the presence of 0.3% potassium sorbate, were characterized. Causes of sub-lethal injury were determined by examining changes in the cell structure, leakage of nucleic acids and proteins from the cells, and cell recovery from injury in the presence of the metabolic inhibitors rifampicin, D-cycloserine, carbonyl cyanide m-chlorophenylhydrazone and chloramphenicol. Visible shrinkage of the cytoplasm and slight cell wall damage were apparent over the 4 week storage period by electron microscopy for all four strains and three storage conditions. By contrast, over the same storage period, only three of the strains (L62, L98 and L99) displayed slight leakage of cellular content in all three storage media, while one strain (L61) displayed greater leakage. The three strains also displayed similar storage media-dependent metabolic damage. For these strains, phosphate-buffered saline pH 5.5 caused the least damage and potassium sorbate, the most. Recovery experiments also indicated that at pH 5.5, the energy transduction system of these three strains remained undamaged, and that injury to the cell transcription machinery was greatest at pH 7.0. The fourth strain, L61, displayed less damage than the others but this was attributed to the death of the injured cell sub-population in this strain. In this study, damage to sub-lethally injured chill-stored L. monocytogenes was different from that caused by other agents, such as heat. Therefore, cells injured by chill-storage under starvation conditions may require novel protocols to assure their effective recovery.
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PMID:Physical and metabolic causes of sub-lethal damage in Listeria monocytogenes after long-term chilled storage at 4 degrees C. 1066 14

This study reports on the construction, calibration and use of recombinant cells of Rhodobacter capsulatus expressing the luciferase gene of the North American firefly Photinus pyralis to detect, by bioluminescence, variations of endogenous ATP levels under various physiological conditions. We show that the antibiotic polymyxin B allows luciferin to rapidly move into cell cytosol, but does not make external ATP freely accessible to intracellular luciferase. Notably, in toluene:ethanol-permeabilized cells, the apparent K(mATP) for luciferase (50 microM) is similar to that measured in soluble cell fractions. This finding limits the applicability of the firefly luciferase for monitoring intracellular maximal ATP concentration because dark/aerobic-grown recombinant cells of Rba. capsulatus contain approximately 1.3-2.6+/-0.5 mM ATP. Therefore, the effects of chemical and physical factors such as oxygen, light, carbonyl cyanide m-chlorophenyl hydrazone and antimycin A on ATP synthesis were examined in cells subjected to different starvation periods to reduce the endogenous ATP pool below the luciferase ATP saturation level (< or =0.2 mM). We conclude that the amount of endogenous ATP generated by light is maximal in the presence of oxygen, which is required to optimize the membrane redox poise.
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PMID:Assay of ATP in intact cells of the facultative phototroph Rhodobacter capsulatus expressing recombinant firefly luciferase. 1179 39


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