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

The stimulatory effect of starvation on omega oxidation of stearate by the 20,000 X g supernatant fluid of rat liver homogenates was studied. The effect was obtained after starvation for 24 hours. Starvation for longer times did not further increase omega oxidation. The stimulatory effect of starvation on omega oxidation of stearic acid was accompanied by a reduced incorporation of stearic acid into phosphatidic acid, diglycerides, and triglycerides. Substitution of the 100,000 X g supernatant fluid from liver homogenate of starved rats with 100,000 X g supernatant fluid from liver homogenates of control rats reduced the microsomal omega oxidation of stearic acid with a simultaneous increase in incorporation of stearic acid into the different glycerides. Under the latter conditions almost no free stearic acid could be isolated from the incubation mixture after the incubation. Of three different soluble factors necessary for glyceride formation, ATP appeared to be the most important from a regulatory point of view. Thus the soluble fraction of liver homogenate from a starved rat was shown to contain suboptimal concentrations of ATP. Addition of physiological amounts of ATP to the 20,000 X g supernatant fluid of homogenate of liver of starved rats had the same effect as addition of 100, 000 X g supernatant fluid from liver homogenate of control rats, i.e. decrease in omega oxidation and increase in formation of glycerides. Addition of sn-glycerol 3-phosphate and CoA-SH in amounts optimal for glyceride formation to the 20,000 X g supernatant fluid of liver homogenate of starved rats had only small effects on omega oxidation and glyceride formation. The results are consistent with a competition for free fatty acids between the acyl-CoA synthetases involved in biosynthesis of glycerides and the microsomal hydroxylase(s) involved in omega oxidation of fatty acids. The concentration of ATP in the soluble fraction is of importance in this competition. The possibility is discussed that this competition is of importance also under in vivo conditions and that a decreased rate of esterification in the starved state is responsible for the higher excretion of omega-oxidized fatty acids in urine in the ketotic state.
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PMID:On the mechanism of regulation of omega oxidation of fatty acids. 95 85

In 30 obese subjects three different methods for weight, reduction were applicated over a period of 14 days. One group (n=10) was treated with total starvation, the other group (n=10) with total starvation and 80 mval potassium in addition and the third group (n=10) with a 700 cal. diet. In total starvation the balance of sodium, potassium and phosphate amounted to -9 mval/d, -34,9/d and -8,8 mval/d respectively. Whereas calcium showed a positive balance of 4,4 mval/d. During addition of 80 mval potassium sodium excretion increased whereas potassium excretion was diminished resulting in a potassium balance less negative. During treatment with the 700 calorie diet the highest negative sodium and a high positive potassium balance were observed,
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PMID:[Electrolyte metabolism in obese subjects with various forms of therapy]. 102 Mar 70

Decay of pre-existing ribonucleic acid was studied in Escherichia coli cells subjected to high temperature or to starvation for nitrogen, phosphate, amino acids, or a carbon source. In these studies a series of mutants affected in ribonucleic I(RNase I, EC 3.1.4.22) polynucleotide phosphorylase (EC 2.7.7.8) or ribonuclease II (RNase II, EC 3.1.4.23) were used. Degradation of total RNA and the disappearance of 23 S and 16 S rRNA were followed. The results obtained indicated that, by and large, decay of 23 S and 16 S RNA parallels that of total RNA. Decay of RNA depended on the nuclease content of the cells as well as on the treatment of applied. It was most pronounced during carbon starvation and least in cells deprived of phosphate ions. It was most effective in strains containing all three nucleases and least in the strain defective in all three. The exonucleases polynucleotide phosphorylase and RNase II did not seem to affect the extent of 23 S and 16 S RNA disappearance. Strains with modified exonucleases did accumulate low molecular weight RNA species during treatments which induced considerable degradation of 23 S and 16 S RNA. Based on the above date and previous observations, we suggest that during various starvations a similar mechanism is operative. The 23 S and 16 S RNAs are degraded endonucleolytically, and this is the rate-limiting step during starvation. The exonucleases polynucleotide phosphorylase and RNase II seem to participate primarily in the decay of the low molecular weight RNA species formed by the endonuclease(s), not as yet identified.
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PMID:Decay of ribosomal ribonucleic acid in Escherichia coli cells starved for various nutrients. 109 48

Quantitative measurements of alkaline phosphatase activity in various merozygotic combinations and electrophoretic analyses of periplasmic proteins derepressed by phosphate-starvation show that phoB is a positive regulatory gene.
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PMID:The regulatory nature of the phoB gene for alkaline phosphatase synthesis in Escherichia coli. 110 Oct 27

An enzyme capable of hydrolyzing the substrate L-alanine p-nitroanilide has been found in the various Escherichia coli strains tested. This enzyme has been called aminoendopeptidase since it shows both activities (see accompanying paper). It is released from the cells by osmotic shock and by lysozyme -- EDTA spheroplasting treatment, and 50% of the total activity is directly detectable with suspensions of intact cells. However, the release by osmotic shock or spheroplasting is not as efficient as it is for alkaline phosphatase. This periplasmic aminoendopeptidase is constitutively produced but the differential rate of synthesis is increased 4-fold when the cell growth is limited by Pi. The occurrence of this 'derepression' is simultaneous with that of alkaline phosphatase. Increasing the concentration of inorganic phosphate in the medium has no effect on the constitutive aminoendopeptidase synthesis. The effect of phosphate starvation is specific since starvation for neither nitrogen nor carbon and energy source are effective in derepressing aminoendopeptidase.
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PMID:Evidence for an aminoendopeptidase localized near the cell surface of Escherichia coli. Regulation of synthesis by inorganic phosphate. 110 39

Candida tropicalis has two phosphate transport systems, one of which is constitutive and has a low affinity for its substrate (Kmapp 1.2.10(-3) M). The other one characterized by a high affinity for H2PO4- (Kmapp = 4.5.10(-6) M) appears only under phosphate starvation conditions. The regulation of the latter would act on the one hand on the synthesis of binding proteins for P1 (repression-derepression) and on the other on the activation or inactivation of the carriers.
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PMID:[Demonstration of 2 phosphate transport systems in Candida tropicalis]. 127 39

Experiments were carried out to assess the physiological significance of the charging level of tRNA. Histidinol, a competitve inhibitor of charging of tRNAHis, was used to induce uncharged tRNA in mammalian cells. It is demonstrated that both in the presence of histidinol and under histidine depletion about 40% of the tRNAHis is uncharged. Concomitant with this appearance of uncharged tRNA(a) the pools of GTP and ATP are decreased rapidly by 25--30%; (b) the synthesis of both protein and ribosomal RNA is inhibited, whereas that of nucleoplasmic RNA is not affected; (c) the uptake of 2-deoxyglucose, phosphate, Ca2+; uridine and adenosine is inhibited; and (d) the growth of 3T6 fibroblasts is arrested. It is suggested that the appearence of uncharged tRNA is one of the earliest events occurring under conditions of amino acid starvation, which in turn causes the various metabolic changes observed.
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PMID:Studies on the role of uncharged tRNA in pleiotypic response of animal cells. 127 58

The effect of human recombinant tumor necrosis factor (TNF)-alpha on enzymes of gluconeogenesis in the rat was investigated by determining the activity of glucose 6-phosphatase, fructose 1,6-diphosphatase (FDP), and phosphoenolpyruvate carboxykinase in the liver and kidney of fed and fasted rats. The activity of transaldolase in the pentose phosphate pathway was also measured. Starvation of rats for 24 hr resulted in a 1.6- to 3.1-fold increase in liver and kidney glucose 6-phosphatase and phosphoenolpyruvate carboxykinase (P less than or equal to 0.05), a decrease in liver and kidney FDP (P less than 0.002), and an increase in liver and kidney transaldolase (P = 0.0001). Injection of 50 and 100 micrograms/kg/day of TNF for 5 days resulted in a significant (P less than or equal to 0.03) decrease in kidney FDP only. Injection of 100 micrograms/kg/day of TNF for 5 days with a 24-hr fast on Day 5 resulted in a significant (P = 0.04) increase in liver transaldolase, and a significant decrease in kidney FDP and phosphoenolpyruvate carboxykinase. Comparison of the enzyme activities of rats injected with 100 micrograms/kg/day of TNF for 5 days with those of their pair-fed control partners revealed additionally a significant decrease in glucose 6-phosphatase in the liver (P less than 0.001). It is concluded that TNF administration in the rat has different effects on the enzymes of gluconeogenesis in the liver and kidney, and these effects differ from those seen in starved or tumor-bearing rats.
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PMID:Effect of tumor necrosis factor on enzymes of gluconeogenesis in the rat. 130 99

It has been shown previously that the otsA and otsB mutations block osmoregulatory trehalose synthesis in Escherichia coli. We report that the transcription of these osmoregulated ots genes is dependent on KatF (AppR), a putative sigma factor for certain stationary phase- and starvation-induced genes. The transcription of the osmoregulated bet and proU genes was not katF dependent. Our genetic analysis showed that katF carries an amber mutation in E. coli K-12 and many of its derivatives but that katF has reverted to an active form in the much-used strain MC4100. This amber mutation in katF leads to strain variations in trehalose synthesis and other katF-dependent functions of E. coli. We have performed a molecular cloning of the otsBA genes, and we present evidence that they constitute an operon encoding trehalose-6-phosphate phosphatase and trehalose-6-phosphate synthase. A cloning and restriction site analysis, performed by comparing the cloned fragments with the known physical map of the E. coli chromosome, revealed that the otsBA genes are situated on a 2.9-kb HindIII fragment located 8 to 11 kb clockwise of tar (41.6 min).
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PMID:Molecular cloning and physical mapping of the otsBA genes, which encode the osmoregulatory trehalose pathway of Escherichia coli: evidence that transcription is activated by katF (AppR) 131 94

A series of deletions removing progressively larger parts of the 5' flanking region of the Escherichia coli pepD gene was constructed. After fusing the resulting promoter fragments to the chromosomal malPQ operon, their activities were determined by assaying for amylomaltase, the product of the malQ gene. Transcription from the pepD promoter region in exponentially growing cells was estimated to be about 5 times less efficient than transcription from the induced lac promoter. Approximately 115 bp preceding the translation start site of the pepD gene are important for regular promoter functioning, whereas the more distal sequences could be deleted without any significant effects. In bacterial cultures containing limiting amounts of inorganic phosphate, the rate of de novo synthesis of peptidase D, simultaneously with the derepression of alkaline phosphatase, increased about fivefold as a consequence of phosphate starvation. This regulation was shown to occur at the transcriptional level by the use of chromosomal pepD promoter-malPQ fusions. The inducibility by phosphate limitation was conserved in all of the deletion clones in which the pepD promoter region was still functional. As demonstrated by the use of phoB, R, and M mutants, the modulation of pepD expression is independent of the genetic system controlling the pho regulon.
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PMID:The promoter region of the Escherichia coli pepD gene: deletion analysis and control by phosphate concentration. 131 42


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