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

Neurospora crassa (bdA) mycelia were kept in liquid culture. Without rhythmic conidiation the levels of adenine nucleotides undergo circadian changes in constant darkness. Maxima occur 12-17 hr and 33-35 hr after initiation of the rhythm, i.e., at CT 0-6 hr. Pulses of metabolic inhibitors such as vanadate (Na3Vo4), molybdate (Na2MoO4 : 2 H2O), N-ethylmaleimide (NEM), azide (NaN3), cyanide (NaCN) and oligomycin phase shift the circadian conidiation rhythm of Neurospora crassa. Maximal advance phase shifts are observed at about CT 6 with all inhibitors. Pulses of N,N'dicyclohexylcarbodiimide (DCCD) and light phase shift the conidiation rhythm following a phase response curve different from those of the other agents (maximal advance at about CT 18-24). The phase shifts with DCCD and light are significantly larger in the wild type compared to the mitochrondrial mutant poky. Such differences are not found in PRCs of the protein synthesis inhibitor cycloheximide. [31P] NMR spectra of wild type Neurospora crassa and the clock mutants frq 1 and frq 7 which differ in their circadian period lengths did not reveal differences in the concentrations of adenine nucleotides, pyridine nucleotides or sugar phosphates. Starvation causes drastic changes of the levels of adenine nucleotides, phosphate and mobile polyphosphate without effecting phase or period length of the circadian rhythm.
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PMID:On the role of energy metabolism in Neurospora circadian clock function. 296 87

The changes in cyanide-resistant and SHAM-sensitive respiration have been examined in the cell cycle of yeast cells synchronized by nutrient starvation. The changing of the cyanide-resistant respiration of cells proliferating in synchronizing fermentor, where the glucose concentration was continuously decreasing, was associated with the stage in cell cycle rather than with the alteration of environment. The cyanide-resistant alternative respiration may be attributed characteristic of a certain part of the cell cycle termed "A" phase. This hypothesis is supported by the observation that in cultures proliferating, synchronously under constant conditions, the cyanide-resistant respiration changes periodically and reaches its maximum in the "A" phase after the cell division.
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PMID:Changes of alternative respiration during the division cycle of Candida tropicalis. 306 1

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

The hemolysis of sheep red blood cells by typhus rickettsiae is initiated by a temperature-sensitive adsorption process that is dependent on the energy-generating metabolism of the rickettsaie but not that of the erythrocyte. Adsorption is followed by events dependent on the metabolism of both the rickettsaie and red blood cells. At 34 C the adsorption step is complete after about 4 min, at lower temperatures the time required for adsorption is increased. At 0 C no adsorption occurred. The addition of cyanide inhibited the catabolism of glutamate by the rickettsiae and, consequently, both adsorption and the subsequent steps in hemolysis. The starvation of the rickettsiae for glutamate also prevented adsorption. Fluoride had no demonstrable effect on rickettsial metabolism nor the adsorption step but inhibited glycolysis in the erythrocytes and the hemolysis of the erythrocytes by rickettsiae.
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PMID:Rickettsial hemolysis: effect of metabolic inhibitors upon hemolysis and adsorption. 420 61

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

The reorganization of the bacterial nucleoid of an Escherichia coli mutant, MX74T2 ts52, was studied by electron microscopy after protein synthesis inhibition by using whole mounts of cell ghosts, ultrathin-sectioning, and freeze-etching. The bacterial nucleoid showed two morphological changes after chloramphenicol addition: deoxyribonucleic acid (DNA) localization and DNA condensation. DNA localization was observed 10 min after chloramphenicol addition; the DNA appeared as a compact, solid mass. DNA condensation was observed at 25 min; the nucleoid appeared as a cytoplasm-filled sphere, often opened at one end. Ribosomes were observed in the center. Giant nucleoids present in some mutant filaments showed fused, spherical nucleoids arranged linearly, suggesting that the tertiary structure of the nucleoid reflects the number of replicated genomes. Inhibitors which directly or indirectly blocked protein synthesis and caused DNA condensation were chloramphenicol, puromycin, amino acid starvation, rifampicin, or carbonyl cyanide m-chlorophenyl hydrazone. All inhibitors that caused cell division in the mutant also caused condensation, although some inhibitors caused condensation without cell division. Nucleoid condensation appears to be related to chromosome structure rather than to DNA segregation upon cell division.
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PMID:Nucleoid condensation and cell division in Escherichia coli MX74T2 ts52 after inhibition of protein synthesis. 458 May 61

Manganese is accumulated in Bacillus subtilis by a highly specific active transport system. This trace element "pump" is insensitive to added magnesium or calcium and preferentially accumulates manganese in the presence of cobalt, iron, and copper. Manganese uptake in B. subtilis is inhibited by cyanide, azide, pentachlorophenol, and m-chlorophenyl carbonylcyanide hydrazone. The uptake of manganese follows Michaelis-Menten kinetics, and the net accumulation of manganese is regulated by increasing the V(max) after exposure to manganese-starvation conditions and by decreasing the V(max) for manganese uptake during growth in excess manganese. The K(m) remains constant during these regulatory changes in V(max). Manganese accumulated during growth is exchangeable for exogenous manganese and can be released from the cells by toluene (which causes leakage but not lysis) or by lysis with lysozyme. Two stages can be distinguished with regard to intracellular manganese during the process of growth and sporulation. During logarithmic growth, B. subtilis maintains a relatively constant internal manganese content, which is a function of the external manganese concentration following approximately a Langmuir adsorption isotherm. At the end of log phase, net accumulation of manganese slows. A second phase of net manganese accumulation begins at about the same time during sporulation as the accumulation of calcium begins. The manganese accumulated during growth and early sporulation is exchangeable and therefore relatively "free"; intracellular manganese is converted later during sporulation into a bound form that cannot be released by toluene or lysozyme.
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PMID:Manganese transport in Bacillus subtilis W23 during growth and sporulation. 463

Choline-O-sulfate uptake by Penicillium notatum showed the following characteristics. (i) Transport was mediated by a permease which is highly specific for choline-O-sulfate. No significant inhibition of transport was caused by choline, choline-O-phosphate, acetylcholine, ethanolamine-O-phosphate, ethanolamine-O-sulfate, methanesulfonyl choline, 2-aminoethane thiosulfate, or the monomethyl or dimethyl analogues of choline-O-sulfate. Similarly, no significant inhibition was caused by any common sulfur amino acid or inorganic sulfur compound. Mutants lacking the inorganic sulfate permease possessed the choline-O-sulfate permease at wild-type levels. (ii) Choline-O-sulfate transport obeyed saturation kinetics (K(m) = 10(-4) to 3 x 10(-4)m; V(max) = 1 to 6 mumoles per g per min). The kinetics of transport between 10(-9) and 10(-1)m external choline-O-sulfate showed that only one saturable mechanism is present. (iii) Transport was sensitive to 2,4-dinitrophenol, azide, N-ethylmaleimide, p-chloromercuribenzoate, and cyanide. Ouabain, phloridzin, and eserine had no effect. (iv) Transport was pH-dependent with an optimum at pH 6. Variations in the ionic strength of the incubation medium had no effect. (v) Transport was temperature-dependent with a Q(10) of greater than 2 between 3 and 40 C. Transport decreased rapidly above 40 C. (vi) Ethylenediaminetetraacetate (sodium salts, pH 6) had no effect, nor was there any stimulation by metal or nonmetal ions. Cu(++), Ag(+), and Hg(++) were inhibitory. (vii) The initial rate at which the ester is transported was independent of intracellular hydrolysis. After long periods of incubation (> 10 min), a significant proportion of the transported choline-O-sulfate was hydrolyzed intracellulary. In the presence of 5 x 10(-3)m external choline-O-sulfate, the mycelia accumulated choline-O-sulfate to an apparent intracellular concentration of 0.075 m by 3 hr. Transport was unidirectional. No efflux or exchange of (35)S-choline-O-sulfate was observed when preloaded mycelia were suspended in buffer alone or in buffer containing a large excess of unlabeled choline-O-sulfate. (viii) The specific transport activity of the mycelium depended on the sulfur source used for growth. (ix) Sulfur starvation of sulfur-sufficient mycelium resulted in an increase in the specific transport activity of the mycelium. This increase was prevented by cycloheximide, occurred only when a metabolizable carbon source was present, and resulted from an increase in the V(max) of the permease, rather than from a decrease in K(m). The increase could be partially reversed by refeeding the mycelia with unlabeled choline-O-sulfate, sulfide, sulfite, l-homocysteine, l-cysteine, or compounds easily converted to cysteine. The results strongly suggested that the choline-O-sulfate permease is regulated primarily by repression-derepression, but that intracellular choline-O-sulfate and cysteine can act as feedback inhibitors.
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PMID:Specificity and control of choline-O-sulfate transport in filamentous fungi. 572 99

The total activity of pyruvate dehydrogenase (PDH) complex in rat hind-limb muscle mitochondria was 76.4 units/g of mitochondrial protein. The proportion of complex in the active form was 34% (as isolated), 8-14% (incubation with respiratory substrates) and greater than 98% (incubation without respiratory substrates). Complex was also inactivated by ATP in the presence of oligomycin B and carbonyl cyanide m-chlorophenylhydrazone. Ca2+ (which activates PDH phosphatase) and pyruvate or dichloroacetate (which inhibit PDH kinase) each increased the concentration of active PDH complex in a concentration-dependent manner in mitochondria oxidizing 2-oxoglutarate/L-malate. Values giving half-maximal activation were 10 nM-Ca2+, 3 mM-pyruvate and 16 microM-dichloroacetate. Activation by Ca2+ was inhibited by Na+ and Mg2+. Mitochondria incubated with [32P]Pi/2-oxoglutarate/L-malate incorporated 32P into three phosphorylation sites in the alpha-chain of PDH; relative rates of phosphorylation were sites 1 greater than 2 greater than 3, and of dephosphorylation, sites 2 greater than 1 greater than 3. Starvation ( 48h ) or induction of alloxan-diabetes had no effect on the total activity of PDH complex in skeletal-muscle mitochondria, but each decreased the concentration of active complex in mitochondria oxidizing 2-oxoglutarate/L-malate and increased the concentrations of Ca2+, pyruvate or dichloracetate required for half-maximal reactivation. In extracts of mitochondria the activity of PDH kinase was increased 2-3-fold by 48 h starvation or alloxan-diabetes, but the activity of PDH phosphatase was unchanged.
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PMID:Reversible phosphorylation of pyruvate dehydrogenase in rat skeletal-muscle mitochondria. Effects of starvation and diabetes. 633 93

We describe an NH4+-specific transport system in the N2-fixing symbiotic actinomycete Frankia sp. strain CpI1. [14C]methylammonium was used as an NH4+ analog. No specific transport process was detected when cells were grown on high concentrations of NH4+. A transport system with a high affinity for CH3NH3+ was synthesized after 3 to 4 h of nitrogen starvation. Methylammonium transport was not significantly inhibited by a variety of amino acids, primary amines, and polyamines. Ammonium completely eliminated CH3NH3+ transport. The Km for CH3NH3+ transport was around 2 +/- 1.8 microM with a Vmax of 4 to 5 nmol/min per mg of protein. The electron transport inhibitors cyanide and azide eliminated uptake, as did the uncoupler carbonyl cyanide-m-chlorophenylhydrazone. The sulfydryl reagent p-chloromercuribenzoic acid and the heavy metal thallium also inhibited uptake, suggesting the presence of an NH4+-specific permease. Concentration of CH3NH3+ across the membrane was demonstrated by conducting uptakes at low temperature to slow the metabolism of CH3NH3+ by glutamine synthetase. At 7 degrees C most of the label was concentrated inside the cells in a form that could be chased from the cells by adding excess NH4+ to the medium. At 30 degrees C most of the label was present as an impermeant metabolite. Thin-layer chromatography of cell extracts confirmed that the radioactivity inside the cells was mainly in the form of CH3NH3+ at 7 degrees C but was present as an unidentified metabolite at 30 degrees C. These studies demonstrate that Frankia sp. strain CpI1 has a high-affinity NH4+ transport system that is synthesized in response to NH4+ starvation.
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PMID:[14C]methylammonium transport by Frankia sp. strain CpI1. 650 Dec 18


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