Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ribonucleotide reduction was measured in Chinese hamster ovary cells made permeable to nucleotides by treatment with the detergent Tween-80. When compared to the respective ribonucleotide reductase activity in partially purified cell extracts, CDP and GDP reductase activities in permeabilized cells responded in a similar fashion to dithiothreitol, pH, MgCl2, FeCl3, substrate concentration and the presence of positive or negative allosteric effectors. At low protein concentrations both CDP and GDP reduction with whole cells increased linearly with cell number and was greater than the activity in corresponding cell extracts. Permeabilized cells were used to measure the level of CDP and GDP reductase in a hamster cell line resistant to the cytotoxic effects of hydroxyurea. The hydroxyurea-resistant cell line contained four to ten times more CDP and GDP reductase activity compared to parental or revertant cell lines. The permeabilized cell assay was also used to measure CDP and GDP reductase activities in Chinese hamster ovary cells synchronized by isoleucine starvation. CDP reductase activity was low in G1 arrested cells but increased 10-fold by 16 hours after the readdition of isoleucine to the growth medium. GDP reductase, which is present at much higher levels, is similarly induced after isoleucine addition, but only by 2-fold. The maximum activity of both CDP and GDP reductase occurred from 14 to 16 hours after isoleucine addition, which corresponded to the period of maximum DNA synthesis.
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PMID:Assay of ribonucleotide reduction in nucleotide-permeable hamster cells. 62 Dec 24

The synthesis of histones and DNA was examined in BHK cells arrested in G1 by isoleucine starvation and in cells progressing into the S phase upon isoleucine refeeding. Approximately 2-3% of the cells were not arrested in G1 and synthesized DNA. The rate of synthesis of DNA and nucleosomal histones observed in cells starved for isoleucine could be accounted for by the presence of these asynchronous cells. Synthesis of H1 histones by cells in G1, however, was 3 times that of the nucleosomal histones and approximately 15% of the rate of H1 histone synthesis in mid-S. Upon entry into S, the histones were synthesized in the same molar ratio in which they are present in chromatin. The possible biological significance of H1 histone synthesis in G1 cells and its implications for the regulatory mechanisms controlling histome synthesis are discussed.
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PMID:Synthesis of H1 histones by BHK cells in G1. 69 40

Myeloma cells have been synchronized by isoleucine starvation. Changes in RNA synthetic rates as a result of starvation have been studied. The ability of isolated nuclei to synthesize RNA declines on starvation and increases subsequently on refeeding isoleucine. There is a coordinate drop in synthetic rate for all three polymerases both in vivo and in vitro. The chain elongation rate in vitro is the same in starved and normal cells, so the difference is in the number of active polymerases in vitro. However, the nuclei do not exactly parallel the state of the cell from which they were isolated, but the in vitro RNA synthesis increases more slowly than the in vivo RNA synthesis. There is no change in relative amounts of synthesis by the different RNA polymerases. The in vitro RNA product is similar in starved and growing cells.
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PMID:RNA synthesis in myeloma cells synchronized by isoleucine starvation. 72 11

We have investigated the kinetics of exit from the resting state of BHK cells which had been arrested by isoleucine deprivation, serum starvation, or high temperature in the case of three ts G1 mutants. In addition, we have studied the effect of imposing a secondary deprivation on cells which had been released from one of the above mentioned blocks. The results obtained show that the quiescent states reached by BHK cells following serum or isoleucine deprivation cannot be differentiated on the basis of the exit kinetics from Smith and Martin's probabilistic A-state. Nevertheless, the response of cells to secondary deprivation is different, depending on the nature of the primary arresting condition used, reflecting physiological differences between the different resting states. A model is presented which postulates that cycle transition specific genes require the presence of different proliferative agents for their expression.
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PMID:Requirements of BHK cells for the exit from different quiescent states. 73 Jul 78

The amino acid pattern following total hip replacement is characterized by increases in muscle of the branched chain amino acids (leucine, isoleucine and valine), the aromatics (phenylalanine and tyrosine) as well as methionine. The nonessential amino acids in muscle tend to decline, glutamine having the most marked change. Plasma levels of the essential amino acids increase while the nonessentials tend to decrease. This pattern differs from that observed in other catabolic states (uremia, starvation, untreated diabetes) and is significantly different from the effects of inactivity and starvation combined. This suggests that injury can be characterized by a unique pattern of muscle and plasma amino acids.
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PMID:Muscle and plasma amino acids after injury: the role of inactivity. 73 57

Sulfur-deficient tRNA, isolated from Escherichia coli HfrC, rel-, met-, cys-, lambda, after cysteine starvation, was found to have an increased acceptance of isoleucine in proportion to the deficiency of 4-thiouridine. Isoleucine acceptance was not altered in the presence of other amino acids of CTP, and the higher acceptance was observed over a wide range of magnesium, isoleucine, tRNA and enzyme concentrations. The Vmax value for sulfur-deficient tRNA was more than three times greater than observed for normal tRNA. Methylated albumin kieselguhr (MAK) chromatography revealed three isoacceptor peak for normal tRNA, while sulfur-deficient tRNA was missing tRNAile, and exhibited a larger, shifted peaks for tRNA normal tRNA, while sulfur-deficient tRNA was missing tRNAille 2, and exhibited a large shifted peak for tRNAile 3 . Treatment with crude RNA sulfurtransferase both lowered the isoleucine acceptance for sulfur-deficient tRNA to that seen for normal tRNA, and restored the missing isoacceptor on MAK. The possibility that thionucleotides may play a role in the aminoacylation of tRNAile in E. coli is discussed.
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PMID:Increased isoleucine acceptance by sulfur-deficient transfer RNA from Escherichia coli. 78 31

Plasma concentrations of the branched-chain amino acids (leucine, isoleucine, and valine) are more prominently affected than the concentrations of other amino acids by changes in dietary-caloric, protein, fat, and carbohydrate-intake in man. For example, within a day of starvation or protein deprivation, there are increases or decreases, respectively, in concentrations of these amino acids in the plasma of healthy human volunteers. The cellular mechanisms of these changes have been investigated in rats, since the changes in the plasma branched-chain amino acid concentrations in response to the previously stated dietary alterations are similar to those found in man. Among the tissues studied (liver, skeletal muscle, heart, kidney, and intestine) only liver and the skeletal muscle exhibit changes in branched-chain amino acid concentrations in response to dietary alteation. Changes in plasma concentrations appear to reflect more intimately those of the muscle than theliver. After 8 days of starvation, there is a 25% decrease in the muscle protein, but after 8 days of protein deprivation, there is no significant change in the muscle mass. Increases in concentrations of branched-chain amino acids in the muscle are much smaller than the amounts of these amino acids lost as protein constituents form the muscle during fasting. Changes in tissue transport, transamination, oxidation, or metabolic conversions of branched-chain amino acids in tissues. It is concluded that increased muscle protein breakdown, which provides substrates for enhanced gluconeogenesis in the liver and enhanced branched-chain amino acid oxidation in the muscle, is the major mechanism of hyperbranched-chain aminoacdemia in starvation. On the other hand, the principal factors in the development of hypobranched-chain aminoacidemia during protein deprivation are absence of exogenous amino acids as well as curtailed muscle protein breakdown.
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PMID:Metabolism of branched-chain amino acids in altered nutrition. 79 82

A spo T stringent strain of Escherichia coli rapidly accumulates guanosine 5'-triphosphate,3'-diphosphate (pppGpp) immediately after the onset of isoleucine starvation. Subsequently, its level rapidly falls, as guanosine 5'-diphosphate,3'-diphosphate (ppGpp) continues to rise to the maximum value, which is abnormally high compared with that in the spo T+ strain. The ppGpp level in the spo T strain never reaches a steady state as it does in the spo T+ strain. Immediately after starvation, pppGpp and ppGpp are labeled with [3H]guanosine at a similar differential rate in both the spo T and spo T+ strains, suggesting that the two strains synthesize these nucleotides by the same pathway. However, by 15 min after starvation, the synthesis of these nucleotides is nearly halted in the spo T strain, and is greatly reduced in the spo T+ strain. Since ppGpp is labeled with [3H]guanosine more slowly than pppGpp in the starved spo T+ strain, ppGpp cannot be a precursor of pppGpp. The kinetics of the GTP level during starvation suggests that GTP is a precursor of pppGpp. The observed differences between the spo T and spo T+ strains can be explained by postulating, firstly, that ppGpp negatively controls the conversion of GTP to pppGpp, which is subsequently converted to ppGpp; secondly, that a catabolite of ppGpp negatively controls the conversion of pppGpp to ppGpp; and thirdly, that the spo T mutation primarily reduces the rate of ppGpp catabolism.
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PMID:Synthesis of guanosine 5'-triphosphate,3'-diphosphate in a spo T strain of Escherichia coli. 79 88

Recent experience with three children who had non-ketotic hyperglycinemia suggested that interpretation of blood glycine levels in children is complex. The elevations of blood glycine in these children were quite modest, and comparable to those of other children admitted to hospital with other diseases. Often we find elevations of blood glycine in children who have had some degree of starvation before blood was taken for amino acid analysis. In a "typical" patient, valine, leucine, isoleucine and occasionally threonine are depressed, while the glycine level is raised. As nutrition improves all of the amino acids return to normal. Our data suggest that blood glycine levels in children with an acute episode of a debilitating disease need to be interpreted with respect to the immediate state of nutrition of the children.
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PMID:Interpretation of elevated blood glycine levels in children. 80 17

Mouse neuroblastoma cells derived from cholinergic clone NS 20 were synchronized by isoleucine plus glutamine starvation. Basal adenylate cyclase activity increased linearly during the different phases of the cell cycle. Pharmacological data are presented indicating that adenosine, dopamine and prostaglandin E1 control through distinct receptors the same adenylate cyclase activity. The demonstration that basal enzyme activity and its responsiveness to the three agonists tested followed different evolution patterns during the cell cycle suggests that enzyme activity (or content) and activity (or number) of enzyme coupled receptors can be independently modulated.
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PMID:[Adenylate cyclase in synchronized neuroblastoma cells: enzyme response during the cell cycle]. 82 49


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