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

A 24-h starvation markedly diminished the stimulant action of 8 mM glucose on insulin secretion from isolated perifused rat islets of Langerhans. The response to a supramaximal glucose stimulus (27.5 mM) remained normal, but prolonged fasting (48 or more) also reduced its efficacy. Refeeding of 24-h fasted animals resulted in complete restoration of glucose sensitivity within 24 h. The responses to glyceraldehyde (2 mM) and alpha-ketoisocaproate (8 mM) at concentrations which elicit approximately half-maximal stimulation were unaltered by a 24-h fast, while that to a half-maximally effective dose of mannose (15 mM) was decreased. Theophylline (5 mM) could not normalize the reduced secretory response to glucose seen in this state. The islets' ability to metabolize glucose, using various in vitro pretreatment protocols and different incubation times, was not affected by a 24-h fast. Mannose and glyceraldehyde metabolism were also unaltered. Prolonged fasting (48 h) reduced glucose metabolism by 25% at both 8 and 27.5 mM. The acute adaptive changes in islet sensitivity to moderate glucose and mannose concentrations during short term fasting (24 h) cannot be explained by an altered usage of the added hexoses.
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PMID:Starvation diabetes in the rat: onset, recovery, and specificity of reduced responsiveness of pancreatic beta-cells. 37 69

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

Fourteen well-nourished patients undergoing elective major surgery were maintained on intravenous, dextrose-free isotonic (3%) amino acid solution postoperatively. Seven patients developed fevers greater than 100 F due to a variety of mild infective complications. While all patients developed a negative nitrogen balance postoperatively in this ketonemic state, infection did not appear to increase nitrogen loss. This is in striking contrast to the response observed in the fed state. Adaptation to starvation, particulary the effect of ketones on muscle metabolism, would appear to reduce significantly the nitrogen loss during infection.
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PMID:Failure of postoperative infection to increase nitrogen excretion in patients maintained on peripheral amono acids. 40 77

Four patients from a larger group of 18 patients receiving dextrose-free isotonic (3%) amino acid solution as nutritional support, form the basis of this report. An additional seven patients received intravenous isotonic (5%) dextrose as their sole support in the postoperative period following major elective surgery (average nitrogen balance = -12.3 +/- 2.7 g). All patients were well-nourished as determined by anthropometric measurements. The nonseptic patients receiving infusions of isotonic amino acids demonstrated an improvement in nitrogen balance (= delta 8.5 +2, P less than 0.001) when compared to the postoperative use of 100 to 150 g of glucose. However, sepsis produced a decreased net utilization of the infused crystalline amino acids such that nitrogen balance was similar to the intravenous glucose group (- 10.6 +/- 2.1). This septic response was associated with decreased plasma free fatty acid concentrations and the absence of starvation ketosis and ketonuria. While the nitrogen balance was not different in the septic and the dextrose control groups, deficiencies in plasma amino acid concentrations were observed in the group receiving intravenous infusion of glucose.
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PMID:Effect of deep surgical sepsis on protein-sparing therapies and nitrogen balance. 40 78

Rates of uptake of glucose (measured with 3H-2-deoxy-d-glucose), galactose, and leucine after exposure of chick embryo cells to increasing concentrations of Na+ over the range 100 to 200 mM. Uptake of nucleosides was unaffected by [Na+] over this range. Prior exposure of cells was required for the [Na+] effect on uptake. Changes were measureable within two hours after changing [Na+], and although the capacity for deoxyglucose uptake remained constant thereafter, the capacity for leucine uptake continued to change during the next few hours. Inhibition of protein synthesis by cycloheximide, or of RNA synthesis by Actinomycin D, failed to prevent these uptake changes. Analysis of the kinetics of uptake showed that only the Km for uptake of deoxyglucose or leucine was affected by [Na+]; the maximum V for each compound remained the same. Effects of [Na+]; could be distinguished from the increased capacity for glucose uptake induced by glucose starvation. Incorporation of both radioactive uridine into RNA, and radioactive thymidine into DNA, were affected by [Na+[, but the differences were not correlated with uptake of other metoblites. No differences in countable mitoses were apparent, although the growth of chick embryo cells in increased slightly with increasing [Na+]. Changes in uptake due to differing [Na+] also were observed in mammalian (rat NRK) cells. However, no effects of [Na+] on rates of cell growth or saturation density were observed with these cells.
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PMID:Sodium concentrations affect metabolite uptake and cellular metabolism. 56 84

The kinetics of D-xylose transport were studied in Rhodotorula glutinis. Analysis of the saturation isotherm revealed the presence of at least two carriers for D-xylose in the Rhodotorula plasma membrane. These two carriers exhibited Km values differing by more than an order of magnitude. The low-Km carrier was repressed in rapidly growing cells and derepressed by starvation of the cells. Several hexoses were observed to inhibit D-xylose transport. In the studies reported here, the inhibitions produced by D-galactose and 2-deoxy-D-glucose were examined in some detail in order to define the interactions of these sugars with the D-xylose carriers. 2-Deoxy-D-glucose competitively inhibited both of the D-xylose carriers. In contrast, only the low-Km carrier was competitively inhibited by D-galactose.
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PMID:A kinetic analysis of D-xylose transport in Rhodotorula glutinis. 56 57

Each medium renewal of confluent primary heart cell cultures derived from new born rats induces a pleiotypic response which leads to active proliferation. The presence of serum in the culture medium is essential for this activation of growth. Nutrient starvation prior to the activation decreases the response of the cells to serum. Serum starvation prior to the activation increases the serum dependence of the incorporation of labelled leucine but leaves the serum dependence of DNA synthesis unchanged. Ageing in culture decreases the serum dependence of the incorporation of labelled thymidine and amino acids but maintains it for alpha amino isobutyric acid transport. Several active components in human serum were distinguished by fractionated dialysis. A single dialyzable component stimulates both thymidine and amino acid incorporations. The transport of 2 deoxy-D-glucose is activated by another rapidly dialyzing component. The activation of alpha amino isobutyric acid transport may result from several components that are distanct from the previous ones. These results imply that a multiplicity of controls underly the pleiotypic activation of heart cell cultures by medium changes.
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PMID:The growth of heart cells in culture. Evidences for a multiple activation of the pleiotypic program. 71 43

The nature of the endogenous reserves of Saccharomyces cerevisiae was examined with respect to conditions of growth, specifically extremes of oxygen tension and carbon source. Cells were grown in batch culture at 30 C under aerobic conditions on a galactose or glucose carbon source and under anaerobic conditions on glucose. The greatest effect of growth conditions on the chemical composition of the cells was on their fatty acid and sterol content. Cells grown under both aerobic and anaerobic conditions mobilised concurrently protein, glycogen, trehalose and fatty acids during a period of 72 hours' starvation under aerobic conditions. The viability of both types of the aerobically grown cells declined to 75% during this period and was not influenced by the initial fatty acid and sterol content of the cells. Cells grown anaerobically showed a more rapid decline in viability which was only 17% after 72 hours' starvation. This loss of viability was not due to a lack of available endogenous reserves but was probably due to an impaired membrane function caused by a deficiency of sterols and unsaturated fatty acids.
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PMID:The influence of conditions of growth on the endogenous metabolism of Saccharomyces cerevisiae: effect on protein, carbohydrate, sterol and fatty acid content and on viability. 79 16

Some methods for measuring the uptake of sugars by yeasts were investigated critically. A study was made of the effects of starvation of Pichia pinus, Candida utilis, Saccharomyces cerevisiae and Rhodosporidium toruloides on their uptake of D-glucose and 2-deoxy-D-glucose. Marked changes in the rates of uptake of these sugars occured during 10 h of starvation, including (a) an immediate increase of up to 75% above that for growing cells and (b) a continuous decline to as little as 4%. Each yeast behaved differently. The rates did not remain constant during the periods of starvation often used for studies on the transport of sugars into yeasts. For Pichia pinus, there were striking differences, associated with starvation, between the transport of 2-deoxy-D-glucose and D-glucose, despite evidence that the two sugars enter this yeast by means of the same carrier. Some physiological explanations for these findings are discussed.
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PMID:Some physiological observations on the uptake of D-glucose and 2-deoxy-D-glucose by starving and exponentially-growing yeasts. 79 35

On refeeding after starvation, the resynthesis of rabbit-liver glycogen proceeds inhomogeneously and over-produces material of low molecular weight. The fate of radioactivity incorporated into glycogen from D-glucose-14C can be explained if glycogen of high molecular weight is synthesised on a protein backbone. Confirmation of this view is given by the effect upon glycogen of reagents that break disulphide bonds; these cause loss of the polysaccharide of high molecular weight. Buoyant densities of glycogens are found to be independent of molecular weight and even of extensive degradation. It is concluded that glycogen synthesis proceeds by two routes; one results in the production of polysaccharide of high molecular weight which has a protein backbone capable of forming disulphide bonds, and another results in the production of polysaccharide of low molecular weight which has either no protein backbone or a protein backbone that is incapable of forming disulphide bridges. Apart from size, the two species are physicochemically indistinguishable.
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PMID:Molecular and metabolic heterogeneity of liver glycogen. 90 78


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