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

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

We have described in D. discoideum a highly organized cell aggregation that is mediated by cAMP. After suitable differentiation induced by starvation, the cells develop the capacity to orient in gradients of cAMP and to secrete cAMP in response to cAMP. This signaling response sets up the cell-cell relay of cAMP waves that transiently orients the cells toward the center. Both the signaling response and the chemotactic response, measured in isolated cells, adapt. The kinetics and properties of adaptation of the two responses are similar and may be due to the same mechanism. The mechanism does not involve protein synthesis, a change in the number or affinity of surface receptors, or the activation of adenylate cyclase. Adaptation of signaling is essential for the oscillatory production of cAMP at the aggregation centers and ensures that the cAMP waves move steadily toward the edge of the aggregation territories. Adaptation of the chemotactic response also ensures that cells do not reorient away from the center in the gradient presented by the trailing edge of the wave. We have demonstrated that both chemotaxis and cAMP signaling are mediated by the same surface receptor. The polypeptide containing the binding site of the receptor has been identified by photoaffinity labeling with [32P]-8-N3-cAMP as a diffuse band of 41,000-45,000 Mr. The receptor and adenylate cyclase copurify on a homogeneous class of vesicles resistant to extraction by nonionic detergents. A GTP-binding protein that is a substrate for cholera toxin-catalyzed ADP ribosylation is found in supernatants and membranes and may be similar to the Gs regulatory protein of adenylate cyclase in higher organisms. The mechanism of activation of the adenylate cyclase and chemotactic machinery is unknown. We have been able to inhibit the activation of the adenylate cyclase selectively and rapidly with agents acting to crosslink cell surface components, which may give a clue to the activation mechanism. The elaborate mechanisms of cell-cell communication occurring in D. discoideum are without precedent in biological literature, although models of oscillatory wave propagation have been proposed to account for pattern formation. Although it is unlikely that extracellular cAMP would be involved, it is not inconceivable that such mechanisms occur during the development of more evolutionarily advanced organisms. The organized communication system in D. discoideum is only apparent when cells are plated uniformly on a flat surface; such organized movements occurring in a three-dimensional structure such as an embryo would be very difficult to discern.
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PMID:Cell-cell interactions in the development of Dictyostelium. 285 27

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

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

ADP-ribosyl transferase (ADPRT) is a DNA-dependent chromatin-associated enzyme which covalently attaches ADP-ribose moieties derived from NAD+ to protein acceptors to form poly(ADP-ribose). ADPRT activity is strongly stimulated by breaks in DNA, and it is suggested that its activity is required for efficient DNA excision repair. In this paper, a cell-cycle-dependent fluctuation of basal ADPRT activity was demonstrated by measuring it in permeabilized FL cells. The cell used was subjected to arginine starvation for 48 h before being released from the block by replacement of deficient medium with complete medium and cells in different proliferating stages were traced by [3H]TdR pulse labelling and obtained at different intervals after block release. The peak basal ADPRT activity appeared 4-6 h after the appearance of the peak of DNA synthesis. After treating the cells with MNNG (10(-4) M), MMS (10(-3)-10(-4) M) and 4NQO (10(-5) M) for 90 min just after release of the block, the ADPRT activity was markedly stimulated. It was further demonstrated that the effects of MNNG/4NQO and cell cycle influence on the level of poly(ADP-ribose) synthesis appear to be additive. While concerning MMS, quite a different pattern of ADPRT stimulation in the cell cycle was demonstrated, i.e., the activity of ADPRT stimulation of 10(-3) M MMS was found to be completely dependent on the basal ADPRT activity. In the cells with the highest basal ADPRT activity 12 h after block release, the MMS-induced ADPRT stimulation could not be observed. It was suggested that more than one pathway might be present in ADPRT stimulation induced by DNA-damaging chemicals, and the cells synchronized in late G1 stage might be the most suitable for demonstrating poly(ADP-ribose) synthesis after DNA damage.
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PMID:Cell cycle effects on the basal and DNA-damaging-agent-stimulated ADPRT activity in cultured mammalian cells. 308 45

The quantitative determination of adenyl nucleotides based on the separation of their dansyl derivatives by thin layer chromatography has made it possible to study the dynamics of changes in the pool of ATP, ADP and AMP in Escherichia coli K-12 during its synchronous growth after glucose starvation. The energy parameters (the adenylate pool, energy charge, teh ATP/ADP ratio, the rates of oxygen uptake and ATP generation, the economic coefficients of oxygen and ATP utilization) were compared with changes in the growth characteristics (the rate of growth and biomass concentration). This comparison allowed the authors to draw the conclusion about the uncoupled constructive and energy metabolism and about the possible regulatory role of energy parameters in the synchronised culture growth.
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PMID:[Energy aspects of the growth of Escherichia coli synchronized by starvation]. 329 94

The effects of riboflavin deficiency on mitochondrial and peroxisomal substrate oxidation were examined in young (treatment begun at weaning) and adult Sprague-Dawley rats that were fed diets low and high in fat. State 3 respiration rates (ADP-stimulated) were used as an estimate of mitochondrial oxidation rates. The oxidation of palmitoyl-CoA and palmitoylcarnitine, and to a lesser extent, glutamate, pyruvate and succinate, by hepatic mitochondria isolated from the young rats was depressed with riboflavin deficiency. There was no effect of dietary fat level on mitochondrial substrate oxidation. Carnitine palmitoyltransferase-A (CPT-A) Vmax was increased with riboflavin deficiency and with increasing dietary fat. Cyanide-insensitive palmitoyl-CoA oxidation was used to estimate peroxisomal palmitate oxidation. Expressed as total hepatic capacity, peroxisomal palmitate oxidation was depressed with riboflavin deficiency. This effect was the result of the reduced feed intake rather than riboflavin deficiency per se. Increasing dietary fat resulted in increased peroxisomal palmitate oxidation. Starvation of young rats did not change mitochondrial oxidation rates, although riboflavin-deficient starved rats exhibited increased rates of palmitoyl-CoA oxidation as well as increased CPT-A Vmax. In adult rats, after 5 wk of deficiency, only palmitoyl-CoA and palmitoylcarnitine oxidation rates were depressed. Dietary fat level did not interact with riboflavin deficiency. However, CPT-A Vmax was increased with riboflavin deficiency and with increased dietary fat level. Further, depressed hepatic fatty acid oxidation can occur in adult rats as a sequel to the feeding of riboflavin-deficient diets.
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PMID:Hepatic mitochondrial and peroxisomal oxidative capacity in riboflavin deficiency: effect of age, dietary fat and starvation in rats. 377 26

Starvation of the mouse hepatoma cell line Hepa for an essential amino acid (Trp, His, Leu, Ile or Phe) stimulated the incorporation of [3H]adenosine as ADP-ribose monomer into an 80,000-Mr protein, P80. Two-dimensional electrophoresis of Hepa proteins showed that P80 was the only protein labeled under starvation conditions. Time course experiments showed that the ADP-ribosylation of P80 was a consequence rather than the cause of reduced translational activity. Cycloheximide treatment and incubation at reduced temperatures also reduced the rate of protein synthesis and stimulated the ADP-ribosylation of P80. Starvation-dependent ADP-ribosylation of P80 was shown to occur in three other cell lines (Chang, Neuro-2a, and chick comb fibroblasts).
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PMID:Translational control of ADP-ribosylation in eucaryotic cells. 379 12

In incubated colonocytes isolated from rat colons, the rates of utilization O2, glucose or glutamine were linear with respect to time for over 30 min, and the concentrations of adenine nucleotides plus the ATP/ADP or ATP/AMP concentration ratios remained approximately constant for 30 min. Glutamine, n-butyrate or ketone bodies were the only substrates that caused increases in O2 consumption by isolated incubated colonocytes. The maximum activity of hexokinase in colonic mucosa is similar to that of 6-phosphofructokinase. Starvation of the donor animal decreased the activities of hexokinase and 6-phosphofructokinase, whereas it increased those of glucose-6-phosphatase and fructose-bisphosphatase. Isolated incubated colonocytes utilized glucose at about 6.8 mumol/min per g dry wt., with lactate accounting for 83% of glucose removed. These rates were not affected by the addition of glutamine, acetoacetate or n-butyrate, and starvation of the donor animal. Isolated incubated colonocytes utilized glutamine at about 5.5 mumol/min per g dry wt., which is about 21% of the maximum activity of glutaminase. The major end-products of glutamine metabolism were glutamate, aspartate, alanine and ammonia. Starvation of the donor animal decreased the rate of glutamine utilization by colonocytes, which is accompanied by a decrease in glutamate formation and in the maximum activity of glutaminase. Isolated incubated colonocytes utilized acetoacetate at about 3.5 mumol/min per g dry wt. This rate was not markedly affected by addition of glucose or by starvation of the donor animal. When colonocytes were incubated with n-butyrate, both acetoacetate and 3-hydroxybutyrate were formed, with the latter accounting for only about 19% of total ketones produced.
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PMID:Fuel utilization in colonocytes of the rat. 407 34

1. Glucose uptake or glucose formation has been studied in kidney cortex slices to investigate metabolic control of phosphofructokinase and fructose-diphosphatase activities. 2. Glucose uptake is increased and glucose formation is decreased by anoxia, cyanide or an uncoupling agent. Under these conditions the intracellular concentrations of glucose 6-phosphate and ATP decreased whereas that of fructose diphosphate either increased or remained constant, and the concentrations of AMP and ADP increased. 3. Glucose uptake was decreased, and glucose formation from glycerol or dihydroxyacetone was increased, by the presence of ketone bodies or fatty acids, or after starvation of the donor animal. Under these conditions, the concentrations of glucose 6-phosphate and citrate were increased, whereas those of fructose diphosphate and the adenine nucleotides were unchanged (see also Newsholme & Underwood, 1966). 4. It is concluded that anoxia and cell poisons increase glucose uptake and decrease gluconeogenesis by stimulating phosphofructokinase and inhibiting fructose diphosphatase, whereas ketone bodies, fatty acids or starvation increase gluconeogenesis and decrease glucose uptake through the citrate inhibition of phosphofructokinase.
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PMID:Control of glycolysis and gluconeogenesis in rat kidney cortex slices. 429


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