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)

The effect of riboflavin and iron on 6-hydroxy-2,4,5-triaminopyrimidine synthesis rate was investigated in the cultures of the yeast Pichia guilliermondii (rib2 mutants) with the blocked second reaction to flavinogenesis. It was shown that riboflavin inhibited the 6-hydroxy-2,4,5-triaminopyrimidine synthesis rate in iron-rich and iron-deficient cells of mutants with low riboflavin requirements. Cycloheximide did not prevent the stimulation of 6-hydroxy-2,4,5-triaminopyrimidine synthesis caused by riboflavin starvation. 7-methyl-8-trifluoromethyl-10-(1'-D-ribityl)isoalloxazine strongly inhibited the 6-hydroxy-2,4,5-triaminopyrimidine synthesis, while 7-methyl-8-trifluoro-methyl-10-(beta-hydroxyethyl)izoalloxazine and galactoflavin exerted only a slight effect on this process. The 6-hydroxy-2,4,5-triaminopyrimidine synthesis rate in iron-deficient cells was significantly higher than in iron-rich cells. The 2,2'-dipyridyl treatment of iron-rich cells caused the stimulation of 6-hydroxy-2,4,5-triaminopyrimidine synthesis and cycloheximide abolished this effect. The results suggest that the activity of the first enzyme of flavinogenesis (guanylic cyclohydrolase) is under the control of feedback inhibition by flavins and the biosynthesis of this enzyme is regulated by iron.
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PMID:Regulation of 6-hydroxy-2,4,5-triaminopyrimidine synthesis by riboflavin and iron in riboflavin-deficient mutants of Pichia guilliermondii yeast. 0 53

The activity of Ca2+-dependent ATP pyrophosphohydrolase was found to fluctuate during spherule formation of the acellular slime mold Physarum polycephalum under starving incubation. The enzyme activity increased up to 16-fold at the 3rd day of the starvation, then decreased drastically to less than its original level. Column chromatography of the enzyme preparation suggested that the increase in the activity was due to de novo synthesis of a new isozyme. Cycloheximide inhibited the synthesis. The two isozymes were different in their Ca2+ sensitivity, the new one being less sensitive.
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PMID:Change in ATP-pyrophosphohydrolase activity during spherule formation of Physarum polycephalum. 17 39

Inositol auxotrophs of yeast developing on isositol-deficient medium continue protein synthesis for 4-6 h, lose viability rapidly after 6 h, and show an increase in cytoplasmic viscosity as measured by spin label rotational motion. Cycloheximide prevents the rapid loss of cell viability, stops protein synthesis, and simultaneously prevents an increase in cytoplasmic viscosity. From these observations, we infer that intracellular translational diffusion is upset as a consequence of inositol starvation. Cell death may be caused by a modified intracellular diffusion environment.
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PMID:Inositol-less death in yeast results in a simultaneous increase in intracellular viscosity. 19 Nov 18

A study was made of the transport of a variety of amino acids by uninfected and Rous sarcoma virus-infected chicken embryo fibroblasts. Following a period of amino acid starvation, transformed, but not normal cells, showed increased levels of transport for alpha-aminoisobutyric acid, proline and alanine, three amino acids which are transported primarily by the A transport system. There was no starvation-induced increase in the transport of leucine, phenylalanine, lysine, or cycloleucine. In the absence of starvation, normal and transformed cells exhibited comparable rates of amino acid transport. Cycloheximide was able to block the increase in uptake. The enhanced uptake was characterized by an increase in Vmax for transport and little change in Km. The data demonstrate that an alteration in the regulation of the A amino acid transport system is an early event in malignant transformation by Rous sarcoma virus. However, since this alteration in made manifest only following a period of starvation, our findings suggest that increased amino acid uptake does not play a role in generating the other manifestations of the transformed state seen in cell culture.
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PMID:Amino acid transport in normal and Rous sarcoma virus-transformed chicken embryo fibroblasts. 22 76

In chick embryo fibroblast cultures the 15- to 30-fold enhancement of D-glucose uptake observed when cells are starved of glucose for 24 hours is not duplicated for derivatives of glucose that compete effectively for uptake and have generally been considered to use the same carrier. 2-deoxy-D-glucose, D-mannose, D-galactose and D-glucosamine are derepressed progressively less sharply in that order with glucosamine uptake never more than doubled by starvation. D-glucose at a concentration of 5.5 mM in the 24-hour conditioning medium is a strong "repressor" resulting in low "transport" behavior for each of the five sugars cited. D-glucosamine is equally effective at the same concentration. A 10-fold reduction in the concentration of glucosamine (0.55 mM) allows for the escape from repression of mannose, glucose, and deoxyglucose uptake while the others remain repressed. Mannose uptake escapes as well when the glucose concentration in the "conditioning" medium is similarly reduced. Under certain conditions of starvation and cell density dramatic effects of supplemental stimulation by insulin can be achieved. Insulin withdrawal interrupts the supplemental stimulation process. Cycloheximide, actinomycin D and cordycepin block both non-insulin and insulin-induced derepression. Short exposure (15-30 minutes) of 24-hour starved cells to glucose (5.5 mM) reduces glucose sharply but does not affect 3-O-methyl glucose uptake. If the exposure is to 2-deoxyglucose (5.5 mM) further derepression of glucose uptake results.
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PMID:Transport enhancement and reversal: glucose and 3-O-methyl glucose. 30 Nov 42

Studies were undertaken to determine if mitochondrial rRNA synthesis in yeast is regulated by general cellular stringent control mechanism. Those variables affecting the relaxation of a cycloheximide-induced stringent response as a result of medium-shift-down or tyrosine limitation include: 1) the stage of cell growth, 2) carbon source, 3) strain differences and, 4) integrity of the cell wall. The extent of phenotypic relaxation decreased or was eliminated entirely in a strain dependent manner as cells entered stationary phase of growth or by growth of cells on galactose or in osmotically stabilized spheroplast cultures. Cytoplasmic and mitochondrial RNA species were extracted from regrowing spheroplast cultures subjected to different experimental regimens and analyzed by electrophoresis on 2.5% polyacrylamide gels. Relative rates of synthesis were determined in pulse experiments and normalized by double-label procedures to longterm label material. Tyrosine starvation was found to inhibit synthesis of the large and small rRNA species of both cytoplasmic and mitochondrial rRNAs to about 5-20% of the control values. Chloramphenicol inhibits mitochondrial and cytoplasmic rRNA synthesis to 60-80% of control; however, chloramphenicol addition does not relax the stringent inhibition of either class of rRNAs. Cycloheximide addition results in 70-80% inhibition of synthesis of both cellular speceis of rRNAs. As noted above, cycloheximide does not relax the stringent response of cytoplasmic rRNA synthesis in spheroplasts, and also does not relax the stringent inhibition of mitochondrial rRNA synthesis. From these studies, we conclude that both cytoplasmic and mitochondrial rRNA synthesis share common control mechanisms related to regulation of protein synthesis by shift-down or amino acid limitation.
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PMID:Regulation of mitochondrial ribosomal RNA synthesis in yeast. I. In search of a relaxation of stringency. 38 47

The lipoprotein lipase activity of rat epididymal adipose tissue falls on starvation and increases on refeeding. Studies with fat cells isolated from this tissue have shown that increases in the activity of the enzyme occur under appropriate incubation conditions in vitro. The present study compares the responses of cells isolated from the adipose tissue of fed and 48-h starved rats. Fat cells from rats starved for 48 h display a lower initial lipoprotein lipase activity than cells from fed rats. When cells from rats in both nutritional states are incubated in a suitable medium at 25 degrees C, there is a progressive increase in the medium lipoprotein lipase activity. The absolute increase in the total activity of the incubation system during incubations of cells from 48-h starved rats is significantly less than during incubations of cells from fed rats. However, when expressed as a percentage of the initial cell activity, the rises in total activity are similar in the two nutritional states. Cycloheximide has no significant effect on the increase in activity of lipoprotein lipase that occurs with cells from 48-h starved rats. However, it does partially block the increase in activity seen with cells from fed rats and in a manner similar to that previously reported for cells from 24-h starved rats. The significance of the results is discussed in relation to previous studies with both intact adipose tissue and isolated fat cells.
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PMID:The effect of nutritional state on the lipoprotein lipase activity of isolated fat cells. 69 38

The ATP sulfurylase of cultured tobacco cells is repressed during growth on readily assimiliated sulfur sources, such as sulfate, L-cysteine, or L-methionine, but it is derepressed during growth on slowly assimiliated sulfur sources, such as L-djenkolate or glutathione, or during sulfur starvation. The enzyme is not induced by sulfate. The enzyme level in the cells begins to rise 12 to 24 h after the derepression conditions are initiated and continues to rise for 3 to 4 days, up to as much as 25 times above the initial specific activity. Addition of a repressing sulfur source to derepressed cells causes the enzyme to decay. Derepression by sulfur limitation does not occur in cells starved for nitrogen, a circumstance in which turnover synthesis of protein is known to continue. Upon addition of a nitrogen source to such cells, the development of the enzyme begins within 12 h, along with the resumption of growth and net protein synthesis. Derepression occurs in cells growing on the slowly assimilated nitrogen in urea, reaching specific activities very similar to those which develop in cells grown on nitrate, in spite of the lower protein accumulation rate on urea. Thus the ATP sulfurylase of tobacco cells appears to be regulated by both a negative feedback mechanism in which an end product of the sulfate assimilation pathway is the effector, and by a positive mechanism which serves to couple the regulation of the sulfate assimilation pathway to the cells' potential for nitrogen assimilation, i.e. net protein synthesis. The sulfur compounds which affect the development of ATP sulfurylase in vivo have no effect on the enzyme activity in vitro. Furthermore, extracts with high activity contain no activator and extracts with low activity contain no inhibitor of ATP sulfurylase. Cycloheximide, at a concentration which strongly inhibits amino acid incorporation into protein, inhibits derepression. ATP sulfurylase does not decay in cells inhibited by cycloheximide. Therefore, the changes in ATP sulfurylase of tobacco cells appear to involve changes in the rate of formation or degradation of the enzyme.
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PMID:Regulation of adenosine triphosphate sulfurylase in cultured tobacco cells. Effects of sulfur and nitrogen sources on the formation and decay of the enzyme. 84 48

Meal-feeding of a high sucrose diet produces a diurnal cycle (i.e., food response) in glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) levels resulting in an elevated level of these enzymes at approximately 12 hours after the start of a 2-hour meal and a return to base level by 24 hours. The effects of actinomycin D and cycloheximide on the 12-hour increases in G6PD and 6GPD were determined. Cycloheximide completely blocked the increase in G6PD if administered 2 or 4 hours after start of the meal, while actinomycin D completely blocked the increase in G6PD if administered at 2 hours and almost completely at 4 hours after start of the meal. These results were obtained previously with starved rats refed a sucrose diet. The diurnal increases in G6PD and 6PGD in meal-fed rats and the induction of G6PD in starved-refed rats thus appear to be regulated by the same mechanism requires RNA synthesis within 4 hours after start of re-feeding. The response of 6PGD to cycloheximide and to actinomycin D at 2 or 4 hours after start of the meal is essentially the same as that of G6PD. These data suggest that the increases in G6PD and 6PGD (and other enzymes) brought about by carbohydrate refeeding AFTER starvation or by carbohydrate meal-feeding on a diurnal cycle are mediated by a rapid change in RNA synthesis. This appears most compatible with a coordinate control of gene expression through messenger RNA synthesis.
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PMID:Regulation of glucose-6 phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in the meal-fed rat. 117 Feb 87

The genome of Neurospora crassa contains at least one natural fusion gene encoding a single ubiquitin (UBI) unit with a 78-amino acid C-terminal extension. The predominantly basic tail sequence corresponds to a highly conserved ribosomal protein identified in other organisms. The 0.7-kb UBI fusion transcript is mainly expressed in germinating conidia and other stages of active cell replication. Under starvation conditions attained by nutrient depletion, or after polyamine depletion, the UBI fusion gene is shut off while the polyUBI transcript is preserved. Cycloheximide addition promotes polyUBI, but not UBI fusion transcript accumulation in N. crassa.
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PMID:The cDNA sequence and expression of an ubiquitin-tail gene fusion in Neurospora crassa. 165 Jul 31


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