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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

An experimental arrangement was described that enables nuclear magnetic resonance spectra of compressed plant cells to be recorded while circulating a medium through the sample. The system provided a convenient arrangement for monitoring by 31P NMR the behavior of plant cells over a long period of time under different conditions such as sucrose starvation. Perfusion of compressed sycamore cells with sucrose-free culture medium triggered a progressive decrease in the glucose 6-P and uridine-5'-diphosphate-alpha-D-glucose resonances over 30 h. When almost all the intracellular carbohydrate pool had disappeared the nucleotide triphosphate resonances decline progressively. These changes were accompanied by a Pi accumulation in the vacuole and a phosphorylcholine (P-choline) accumulation in the cytoplasm. The very long lag phase observed for ATP and P-choline evolution was comparable with that observed for the progressive intracellular digestion of cytoplasmic constituents (Journet, E., Bligny, R. and Douce, R. (1986) J. Biol. Chem. 261, 3193-3199). Addition of sucrose in the circulating system after a long period of sucrose starvation led to a disappearance of the cytoplasmic Pi resonance and a marked increase in that of glucose 6-P. Under these conditions the vacuolar Pi pool did not fluctuate to buffer the Pi in the cytoplasm. The results suggest that Pi which has been sequestered in the vacuole during the course of sucrose starvation is not restored to the cytoplasm for rapid metabolic processes. Furthermore, the presence of P-choline in plant cells in large excess should be considered as a good marker of membrane utilization after a long period of sucrose starvation and is very likely related to stress.
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PMID:Biochemical changes during sucrose deprivation in higher plant cells. Phosphorus-31 nuclear magnetic resonance studies. 303 Oct 35

Nutrition is a factor which may affect the liver energy charge. Experiments were performed to determine the effect of starvation and of ATP precursors, adenine and ribose on liver energy stores. The 31P NMR spectra of well-fed and starved mice livers were studied in a perfusion system using Krebs-Henseleit buffer (KHB). The ATP precursors, adenine (20 mmol/l) and ribose (80 mmol/l), were then added to determine their effect. Their effect on the ATP dynamics during ischemia and reperfusion were then evaluated. The effects of adenine alone and ribose alone were then determined. The 31P spectra of well-fed mice demonstrated high ATP content relative to Pi, phosphoesters and phospholipids. Animals starved for 24 h showed very low ATP, high Pi and little or no detectable phospholipids. In starved animals, ATP rose steadily to approximately 50% above the baseline level when precursors were added. Pi decreased to 30% of the baseline after 40 min. Little change was noted in well-fed animals. The rate of ATP decay did not change with the onset of ischemia, whether the livers were perfused with KHB alone or KHB with precursors. Upon reperfusion, precursors improved the recovery of ATP (81% vs 49% after 20 min ischemia, 44% vs 34% after 30 min ischemia). Addition of adenine alone produced similar results, but addition of ribose alone did not significantly alter ATP recovery. In conclusion, supplying starved or post-ischemic livers with adenine or ribose and adenine does improve ATP levels.
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PMID:Liver adenosine triphosphate and pH in fasted and well-fed mice after infusion of adenine nucleotide precursors. 314 8

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

31P-NMR studies of Mycoplasma gallisepticum cells have been carried out using a continuous perfusion technique; these are the first such studies with this organism. Using this technique, glucose metabolism was monitored in the intact organisms, and cell extracts were prepared to identify the intermediates. Under glycolytic conditions, high levels of fructose-1,6-diphosphate were observed, indicating that this sugar may play a key role in the regulation of metabolism. The level of phosphoenolpyruvate was low under normal glycolytic conditions, and did not increase during starvation. From the position of the internal inorganic phosphate peak, the intracellular pH was estimated. The cells were found to maintain an intracellular pH of approximately 7.1 over an investigated external pH range of 6.6-8.6.
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PMID:31P-NMR studies of Mycoplasma gallisepticum cells using a continuous perfusion technique. 373 20

Natural-abundance high-resolution 13C NMR spectra (linewidth, 10 Hz) of the hyphal fungus Aspergillus nidulans have been obtained after growth on glycolytic or gluconeogenic carbon sources. Various polyols, some tricarboxylic acid-cycle intermediates and amino acids, and some phospholipids and fatty acyl compounds are present. The polyols found are mannitol, arabitol, erythritol, and glycerol. The nature of the carbon source has a pronounced effect on the pool sizes of the various polyols. All are present when the fungus is grown on sucrose or sucrose/acetate under strongly aerobic conditions. When grown on acetate, both arabitol and glycerol levels are low, whereas on glycerol erythritol is also hardly detectable. The effect of oxygen is most outspoken in glycolytically grown cultures. Limited oxygenation leads to low levels of arabitol and glycerol. Strong oxygenation changes the ratio of erythritol to mannitol, favoring the C4 polyol. An increase in oxygen supply leads to (i) stimulation of the fluxes through the pentose phosphate pathway and glycolysis, (ii) an overflow of reduced metabolites both at the pentose phosphate pathway level (erythritol and arabitol) and at the C3 level of the glycolytic pathway (glycerol), and (iii) the usual accumulation of mannitol. Upon starvation, glycerol, the other three polyols, and the tricarboxylic acid-cycle intermediates and their associated amino acids disappear in this order. As in yeast, gluconeogenic substrates lead to the synthesis of trehalose, which also occurs when mycelium is grown on acetate/sucrose under limiting aeration. A transient formation of trehalose has been observed upon incubation of starved mycelium, cultured on different substrates, with [13C]glucose.
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PMID:13C NMR studies of carbon metabolism in the hyphal fungus Aspergillus nidulans. 388 52

Aspartate transcarbamoylase labeled with 3-fluorotyrosine was purified from an Escherichia coli strain which was auxotrophic for tyrosine and overproduced aspartate transcarbamoylase upon uracil starvation. The labeled enzyme in which about 85% of the tyrosines were replaced by fluorotyrosine exhibited high enzyme activity that varied in a sigmoidal manner with respect to the aspartate concentration. Also, the labeled enzyme was inhibited by CTP, activated by ATP, and exhibited a 2.6% decrease in sedimentation coefficient upon the addition of the active-site ligand, N-(phosphonacetyl)-L-aspartate. Thus, despite extensive replacement of tyrosines by fluorotyrosine, the modified enzyme was similar to native aspartate transcarbamoylase. The 19F nuclear magnetic resonance spectrum of isolated regulatory subunits labeled with fluorotyrosine consisted of a single peak. Addition of the activator, ATP, or the inhibitor, CTP, caused a loss of intensity at about 61.3 ppm upfield from a trifluoroacetic acid reference and an increase at about 61.5 ppm, but CTP also caused an increase at about 61.0 ppm. Five overlapping resonances were observed in the 19F NMR spectrum of unliganded catalytic subunits containing fluorotyrosine. Although the binding of the bisubstrate analog, N-(phosphonacetyl)-L-aspartate, or the combination of carbamoylphosphate and succinate caused similar disappearances of resonances, the addition of N-(phosphonacetyl)-L-aspartate caused the appearance of resonances not observed with carbamoylphosphate plus succinate. Carbamoylphosphate alone perturbed three or four resonances and the subsequent addition of succinate affected at least two.
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PMID:19F nuclear magnetic resonance studies of fluorotyrosine-labeled aspartate transcarbamoylase. Properties of the enzyme and its catalytic and regulatory subunits. 404 74

A method for quantitative calculation of 31P-NMR spectra of tissues is proposed. Change dynamics of concentrations of phosphor-containing metabolites in the mouse liver under starvation, physical load (swimming) and glucose load (intraperitoneally) was investigated. It has been shown that using starvation as a method for object standardization 12-24 hours starvation is the optimal one.
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PMID:[31P-NMR study of P-compounds metabolism in the liver of mice under stress]. 683 Sep 8

The livers of gsd/gsd rats homozygous for the glycogen storage disease phosphorylase b kinase deficiency were observed by 13C NMR using a surface coil. Clear signals were detected from glycogen. The concentration of glycogen as determined by NMR was approximately 3-times that found in normal strains agreeing well with chemical determinations. Starvation did not significantly reduce the glycogen content of the livers with glycogen storage disease whereas it reduced the signal below detectability in normal rats. Difference spectra of starved normal rats from fed gsd/gsd rats gave spectra similar in appearance to that of purified glycogen. Glycogen both in vivo and in vitro is fully visible using 13C NMR.
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PMID:Detection of glycogen in a glycogen storage disease by 13C nuclear magnetic resonance. 696 87

A continuous-flow NMR culture system for mammalian cells has been developed on which 31P-NMR experiments under complete and strictly physiologic conditions have been performed. Observations on the response of the cellular metabolism to stresses such as starvation, low temperature and changes in environmental pH monitored by 31P-NMR are reported. The response of the intracellular pH relative to the external pH of the growth medium is studied. We find that under the experimental conditions used there exists a delta pH varying between less than 0.2 and more than 0.6 pH units. These results are compatible with those obtained using other techniques.
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PMID:Continuous-flow NMR culture system for mammalian cells. 710 97


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