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

We have used transcriptional and translational fusions between various vir gene promoters and the lacZ gene to study the regulation of vir genes. Like other vir promoters, the virA promoter was induced by acetosyringone in a virA virG-dependent fashion. In addition to being induced by acetosyringone, the virG promoter was partially induced by acidic growth conditions and by starvation for inorganic phosphate. These two conditions appeared to act synergistically. The response to low pH and to phosphate starvation occurred in the absence of the Ti plasmid and must therefore have been mediated by chromosomal genes. Two transposon-generated mutations were obtained which attenuated induction by low pH. One of these transposons was cloned along with flanking DNA; the flanking DNA was sequenced (858 base pairs total), and the predicted amino acid sequence showed homology with a family of proteins including the Rhizobium leguminosarum nodI gene, many of whose members bind ATP and have been implicated in active transport systems. These results are discussed as possible explanations for previous observations that the induction of the octopine vir regulon (i) occurs only in acidic media and (ii) shows hyperbolic kinetics after a long lag phase.
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PMID:Transcriptional regulation of the virA and virG genes of Agrobacterium tumefaciens. 284

The growth of transformed mouse fibroblasts (3T6 cells) in medium containing 5% fetal bovine serum was inhibited after treatment with concentrations greater than 50 microM ATP, ADP, or AMP. Adenosine, the common catabolite of the nucleotides, had no effect on cell growth at concentrations below 1 mM. However, the following results indicate that the toxicity of ATP, ADP, and AMP is mediated by serum- and cell-associated hydrolysis of the nucleotides to adenosine. 1) ADP and AMP, but not ATP, were toxic to 3T6 cells grown in serum-free medium or medium in which phosphohydrolase activity of serum was inactivated. Under these conditions, the cells exhibited cell-associated ADPase and 5'-nucleotidase activity, but little ecto-ATPase activity. 2) Inhibition of adenosine transport in 3T6 cells by dipyridamole or S-(p-nitrobenzyl)-6-thioinosine prevented the toxicity of ATP in serum-containing medium and of ADP and AMP in serum-free medium. 3) A 16-24-h exposure to 125 microM AMP or ATP was needed to inhibit cell growth under conditions where serum- and cell-associated hydrolysis of the nucleotides generated adenosine in the medium continuously over the same time period. In contrast, 125 microM adenosine was completely degraded to inosine and hypoxanthine within 8-10 h. Furthermore, multiple doses of adenosine added to the cells at regular intervals over a 16-h period were significantly more toxic than an equivalent amount of adenosine added in one dose. Treatment of 3T6 cells with AMP elevated intracellular ATP and ADP levels and reduced intracellular UTP levels, effects which were inhibited by extracellular uridine. Uridine also prevented growth inhibition by ATP, ADP, and AMP. These and other results indicate that serum- and cell-associated hydrolysis of adenine nucleotides to adenosine suppresses growth by adenosine-dependent pyrimidine starvation.
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PMID:Growth inhibition of transformed mouse fibroblasts by adenine nucleotides occurs via generation of extracellular adenosine. 284 30

Significant increase in the activity of an acetyl-CoA hydrolase (ATP-stimulated, ADP-inhibited enzyme) in the supernatant fraction of rat liver was observed after 44-68 h of starvation (about 2-fold), and in the early stage of diabetes (about 1.6-fold), but not in the chronic stage of diabetes. The increased enzymatic activity in starved rats returned to the control level within 20 h when the animals were given laboratory chow, but not when they were given fat-free diet with a high carbohydrate content, and the enzyme activity was increased by the latter diet containing 1% thyroid powder. A single intraperitoneal injection of 3,3'5-triiodo-L-thyronine or 3,3',5,5'-tetraiodo-L-thyronine resulted in twice the normal enzyme activity two days later, and conversely 7 days after thyroidectomy, the enzyme activity was about 60% of the control level. A single subcutaneous injection of alpha-(p-chlorophenoxy)isobutyric acid, a hypolipidemic drug, doubled the enzyme activity in euthyroid rats, but not in thyroidectomized rats. Of the various tissues tested besides the liver, only the kidney had detectable ATP-stimulated and ADP-inhibited enzyme activity (5% of the activity in liver cytosol). The kidney enzyme had similar kinetic and immunochemical properties to the liver enzyme. Changes in the enzyme activity in the liver in various states were closely related to the amount of enzyme present, judging from results obtained by enzyme-linked immunosorbent assay. The physiological role of this enzyme (which hydrolyzes acetyl-CoA to acetate and CoASH) may be in maintenance of the cytosolic acetyl-CoA concentration and CoASH pool for both fatty acid synthesis and oxidation.
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PMID:Physiological changes in the activities of extramitochondrial acetyl-CoA hydrolase in the liver of rats under various metabolic conditions. 286 34

The state of adenylylation, n, of glutamine synthetase (GS) in Pseudomonas fluorescens has been determined as a function of growth conditions. Compared to the behavior of Escherichia coli, atypical responses to either carbon or nitrogen starvation were observed when P. fluorescens was grown with either succinate, malate, or fumarate as the sole source of carbon and energy. Under conditions of carbon starvation (high NH4+, low dicarboxylic acid substrate), the value of n falls rapidly from 10 to 1.0 during prolonged incubation in the stationary phase, whereas the value of n is unexpectedly high (ca. 10) in extracts of nitrogen-starved cells. These abnormal responses are attributable to particular permeability properties of P. fluorescens cells compared to E. coli. The unusual changes in nitrogen-starved cells are related to the release of alpha-ketoglutarate by such cells during incubation or washing procedures. These changes can be prevented by the addition of cetyltrimethylammonium bromide (CTAB) to the cultures 5 min prior to harvesting the cells, or by freezing the cell pellets just after centrifugation and sonication within 3 min of suspension in buffer, or by suspending freshly harvested cells in buffer containing alpha-ketoglutarate and orthophosphate (i.e., effectors that favor deadenylylation of glutamine synthetase). The abnormal changes which occur during carbon starvation in the presence of excess NH4+ can be prevented by addition of ATP and glutamine to the buffer in which the freshly harvested cells are suspended prior to sonication. The results suggest that during the stationary phase of growth on succinate, fumarate, or malate (but not on glucose), the cellular membrane becomes permeable to small molecules that regulate the adenylylation cascade, and indeed, it was observed that such whole cells expressed, without any chemical or physical treatment, more than 50% of the glutamine synthetase activity they contained. Such cells may be useful in studies to examine the effects of multiple metabolites on the regulation of glutamine synthetase adenylylation in situ.
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PMID:Adenylylation state of glutamine synthetase and permeability properties of Pseudomonas fluorescens. 287 12

A single-gene nuclear mutant has been selected from the yeast Schizosaccharomyces pombe for growth resistance to Dio-9, a plasma membrane H+-ATPase inhibitor. From this mutant, called pma1, an ATPase activity has been purified. It contains a Mr = 100,000 major polypeptide which is phosphorylated by [gamma-32P] ATP. Proton pumping is not impaired since the isolated mutant ATPase is able, in reconstituted proteoliposomes, to quench the fluorescence of the delta pH probe 9-amino-6-chloro-2-methoxy acridine. The isolated mutant ATPase is sensitive to Dio-9 as well as to seven other plasma membrane H+-ATPase inhibitors. The mutant H+-ATPase activity tested in vitro is, however, insensitive to vanadate. Its Km for MgATP is modified and its ATPase specific activity is decreased. The pma1 mutation decreases the rate of extracellular acidification induced by glucose when cells are incubated at pH 4.5 under nongrowing conditions. During growth, the intracellular mutant pH is more acid than the wild type one. The derepression by ammonia starvation of methionine transport is decreased in the mutant. The growth rate of pma1 mutants is reduced in minimal medium compared to rich medium, especially when combined to an auxotrophic mutation. It is concluded that the H+-ATPase activity from yeast plasma membranes controls the intracellular pH as well as the derepression of amino acid, purine, and pyrimidine uptakes. The pma1 mutation modifies several transport properties of the cells including those responsible for the uptake of Dio-9 and other inhibitors (Ulaszewski, S., Coddington, A., and Goffeau, A. (1986) Curr. Genet. 10, 359-364).
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PMID:A single mutation confers vanadate resistance to the plasma membrane H+-ATPase from the yeast Schizosaccharomyces pombe. 287 25

High-field pulsed Fourier-transform nuclear magnetic resonance spectroscopy (NMR) was used to quantify the adenylate levels of sea anemones (Aiptasia pulchella) with and without symbiotic dinoflagellates (Symbiodinium sp.). Animals were fed to repletion, then starved in darkness for up to six days before collection of in vivo NMR spectra. The host adenylate ratio of ATP: (ATP + ADP) declined significantly with increasing periods of starvation in both symbiotic and aposymbiotic hosts (P less than 0.05). However, the decline in the animal adenylate ratio was significantly more rapid in animals bearing symbiotic algae (P less than 0.05). This suggests that symbiotic algae in darkness cause more rapid depletion of host energy reserves, possibly by drawing on host pools of organic substrates. In vivo NMR spectroscopy was also used to evaluate the effect on A. pulchella of photosynthesis by zooxanthellae. Symbiotic anemones were fed to repletion, then starved under high irradiance (300 to 320 mu Ein m-2 s-1) or low irradiance (70 to 80 mu Ein m-2 s-1) conditions for up to five days. The host adenylate ratio declined significantly (P less than 0.01) with starvation under both treatments, but no significant difference was detected between treatments (P greater than 0.35). Blotted wet weight of anemones under high and low irradiance declined by 50% over eight days of starvation, but there was no significant difference in the rate of weight loss by anemones in the two treatments. There results suggest that translocation of photosynthate from symbiotic zooxanthellae does not significantly affect host adenylate ratio or have a sparing effect on host biomass during starvation in this symbiotic sea anemone.
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PMID:Impact of symbiotic algae on sea anemone metabolism: analysis by in vivo 31P nuclear magnetic resonance spectroscopy. 287 64

The effects of thermal injury (72 h post-injury), 72 h-partial (20% less food) or full starvation on the regulation of phosphofructokinase in the mucosa of rat small intestine were studied. Thermal injury and 72 h-partial or full starvation decreased the activity ratio v0.5/V, but the ratios obtained for thermally injured or fully starved rats were significantly lower than those of controls or partially starved rats. The susceptibility of phosphofructokinase to ATP inhibition was increased after thermal injury and 72 h-partial or full starvation compared to that of normal controls. However, these changes that occurred in the enzyme activities of the rat small intestine were mainly specific to injury per se but do not exclude the contribution of partial starvation during the same period of time.
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PMID:The effect of thermal injury on the regulation of phosphofructokinase in the mucosa of rat small intestine. 294 80

We report in this paper the effect of metabolic depletion on several modes of furosemide-sensitive (FS) Na and K transport in human red blood cells. The reduction of ATP content below 100 mumol/liter cells produced a marked decrease in the maximal activation (Vmax) of the outward, FS transport of Na and K into choline medium in the presence of ouabain (0.1 mM) and 1 mM MgCl2. The K0.5 for internal Na to activate the FS Na efflux was not altered by metabolic depletion. However, metabolic depletion markedly decreased the Ki for external K (Ko) to inhibit the FS Na efflux into choline medium (from 25 to 11 mM). Repletion of ATP content by incubation of cells in a substrate-rich medium recovered control levels of Vmax of the FS Na and K fluxes and of Ki for external K to inhibit FS Na efflux. The Vmax of FS Na and K influxes was also markedly decreased when the ATP content dropped below 100 mumol/liter cells. This was mainly due to a decrease in the inward-coupled transport of K and Na (NaO-stimulated K influx and the Ko-stimulated Na influx). The FS Ki/Ko exchange pathway of the Na-K cotransport, estimated from the FS K influx from choline-20 mM Ko medium into cells containing 22 mmol Na/liter cells, was also reduced by starvation. Starvation did not inhibit the FS Nai/Nao exchange pathway, estimated as FS Na influx from a medium containing 130 mM NaCl into cells containing 22 mmol Na/liter cells. The unidirectional FS 22Na efflux and influx were also measured in control and starved cells containing 22 mmol Na/liter cells, incubated in a Na medium (130 mM) at varying external K (0 to 20 mM). In substrate-fed cells, incubated in the absence of external K, FS Na efflux was larger than Na influx. This FS net Na extrusion (400 to 500 mumol/liter cells X hr) decreased when external K was increased, approaching zero around 15 mM Ko. In starved cells the net Na extrusion was markedly decreased and it approached zero at lower Ko than in substrate-fed cells. Our results indicate that the FS Na and K fluxes, and their major component, the gradient driven Na-K-Cl cotransport system, are dependent on the metabolic integrity of the cells.
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PMID:Effect of metabolic depletion on the furosemide-sensitive Na and K fluxes in human red cells. 299 28

The lon gene of Escherichia coli codes for an ATP-dependent protease. Mutations in lon cause a defect in the intracellular degradation of abnormal and mutant proteins and lead to a number of phenotypic changes, such as UV sensitivity and overproduction of capsular polysaccharide. We have isolated lambda transducing phage carrying the lon gene and used the lon phage as a target for insertional mutagenesis by a defective transposon Tn10 to produce lon::delta 16 delta 17Tn10 derivatives. The delta 16 delta 17Tn10 (hereafter called delta Tn10) elements were inserted at sites throughout the lon gene and disrupted the coding region between 15 and 75% of the distance from the amino-terminal end. Radioactive labeling of proteins in vivo in cells infected with different lambda lon::delta Tn10 phage demonstrated that the insertions resulted in the synthesis of truncated Lon proteins. The lon::delta Tn10 mutations, when crossed from the phage into the bacterial chromosome, abolished the synthesis of intact Lon protein, as assayed by antibody on Western blots. An analysis of the protein-degradative ability of lon::delta Tn10 cells suggests that although the insertions in lon caused a reduction in ATP-dependent protein degradation, they did not completely eliminate such degradation either in vivo or in vitro. The lon::delta Tn10 mutations and a lon deletion retaining only the amino-terminal 25% of the gene did not affect the energy-dependent degradation of proteins during starvation and led to only a 40 to 60% reduction in the ATP-dependent degradation of canavanine-containing proteins and puromycyl peptides. Our data provide clear evidence that energy-dependent proteolytic enzymes other than Lon exist in E. coli.
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PMID:Insertional mutagenesis of the lon gene in Escherichia coli: lon is dispensable. 299 72

AMP deaminase, the activity that catalyzes the deamination of AMP to form IMP and NH3 has been measured in Dictyostelium discoideum. A new procedure to assay the activity of this enzyme was developed using formycin 5'-monophosphate, a fluorescent analog of AMP as the substrate, and ion-paired reverse phase HPLC to separate the reactants and products. Quantitation of the formycin containing compounds was accomplished at 290 nm. At this wavelength adenosine containing compounds were not detected and activity could be monitored in the presence of its activator ATP. The AMP deaminase activity in vegetative cells was 7.4 nmols/min/mg proteins while the activity in cells measured at 2 and 6 hrs after starvation-induced growth-arrest was 376 nmols/min/mg protein...a 51-fold increase. When vegetative cells were treated with hadacidin, a drug that restricts de novo AMP synthesis and pinocytosis, the activity of the AMP deaminase was 511 nmols/min/mg protein...a 70-fold increase compared to that in untreated vegetative cells. Smaller increases were noted following the inhibition of growth with the drugs cerulenin and vinblastine, as well as after the inhibition of de novo GMP synthesis with the drug mycophenolic acid or the partial inhibition of de novo AMP synthesis with analogs of hadacidin, N-hydroxyglycine and N-formylglycine. In addition, when the activity of two other enzymes involved in purine metabolism, namely adenosine kinase and hypoxanthine-guanine phosphoribosyl transferase, was measured in vegetative cells, and the activity of both compared to that measured in starvation and hadacidin induced growth-arrested cells, showed no significant changes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:AMP deaminase in Dictyostelium discoideum: increase in activity following nutrient deprivation induced by starvation or hadacidin. 301 11


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