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

Cells of Arthrobacter globiformis grown in carbohydrate-rich media were found to contain large quantities of low-Mr carbohydrates (800 micrograms/mg protein) and only small amounts of amino acids, in addition to high amounts of glycogen (2 mg/mg protein). At increasing osmotic values of the medium, low-Mr carbohydrate levels increased to 1300 micrograms/mg protein. Low-Mr pools were extracted from the cells with hot 75% ethanol, and subjected to thin layer, gel and gas-liquid chromatography. They turned out to consist mainly of alpha,alpha-trehalose. Levels of trehalose in Arthrobacter cells have the tendency to remain constant, both during nutrient exhaustion (resulting in glycogen consumption), and on addition of excess of carbon source to the medium (resulting in an increased glycogen content of the cells). The stress-tolerant properties of Arthrobacter (resistance to nutrient starvation, desiccation and high salt concentration) are discussed with respect to the high glycogen and trehalose contents of the cells.
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PMID:Levels of trehalose and glycogen in Arthrobacter globiformis under conditions of nutrient starvation and osmotic stress. 157 69

Four strains of Rhizobium japonicum (61A76 and USDA 110, 123, and 138) were grown in eight different defined media. Regardless of the carbon or nitrogen source supplied, alpha, alpha-trehalose was the major carbohydrate (among mono- and disaccharides) accumulated by all four strains. After 7 to 9 days of growth, trehalose generally accounted for 90 to 100% of the mono- and disaccharides detected. None of the four strains would grow with trehalose as a carbon source, but the utilization of endogenous trehalose was demonstrated under carbon starvation conditions in water culture or when the carbon supply in a defined medium was exhausted. Under these conditions, a small amount of trehalose was lost from cells to the medium. In a survey of most of the serogroups of R. japonicum and several strains of other Rhizobium species, all strains tested were found to accumulate some trehalose. Trehalose concentrations varied widely; the highest concentration recorded was 41 micrograms/mg of dry weight. In all but six strains trehalose accounted for greater than 80% of the mono- and disaccharides in cells. Fast-growing strains of R. japonicum also accumulated small amounts trehalose. R. japonicum bacteroids also synthesized trehalose; the quantity in nodules varied in approximate correspondence to accumulation of trehalose by cultured bacteria. In young soybean nodules (29 days after planting), 45 to 80% of the trehalose was recovered in the cytosol. There were differences among R. japonicum strains in the retention of trehalose, and the proportion of trehalose retained by bacteroids increased with increasing plant age for all strains.
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PMID:Accumulation of alpha,alpha-trehalose by Rhizobium bacteria and bacteroids. 404 31

The uptake of nutrients (glucose, glutamine, and N-acetylglucosamine), the intracellular concentrations of metabolites (glucose-6-phosphate, cyclic AMP, amino acids, trehalose, and glycogen) and cell wall composition were studied in Candida albicans. These analyses were carried out with exponential-phase, stationary-phase, and starved yeast cells, and during germ-tube formation. Germ tubes formed during a 3-h incubation of starved yeast cells (0.8 X 10(8) cells/mL) at 37 degrees C during which time the nutrients glucose plus glutamine or N-acetylglucosamine (2.5 mM of each) were completely utilized. Control incubations with these nutrients at 28 degrees C did not form germ tubes. Uptake of N-acetylglucosamine and glutamine was inhibited by cycloheximide which suggests that de novo protein synthesis was required for the induction of these uptake systems. The glucose-6-phosphate content varied from 0.4 nmol/mg dry weight for starved cells to 2-3 nmol/mg dry weight for growing yeast cells and germ tube forming cells. Trehalose content varied from 85 nmol/mg dry weight (growing yeast cells and germ tube forming cells) to 165 nmol/mg weight (stationary-phase cells). The glycogen content decreased during germ-tube formation (from 800 to 600 nmol glucose equivalent/mg dry weight) but increased (to 1000 nmol glucose equivalent/mg dry weight) in the control incubation of yeast cells. Cyclic AMP remained constant throughout germ-tube formation at 4-6 pmol/mg dry weight. The total amino acid pool was similar in exponential, starved, and germ tube forming cells but there were changes in the amounts of individual amino acids. The overall cell wall composition of yeast cells and germ tube forming cells were similar: lipid (2%, w/w); protein (3-6%), and carbohydrate (77-85%). The total carbohydrates were accounted for as the following fractions: alkali-soluble glucan (3-8%), mannan (20-23%), acid-soluble glucan (24-27%), and acid-insoluble glucan (18-26%). The relative amounts of the alkali-soluble and insoluble glucan changed during starvation of yeast cells, reinitiation of yeast-phase growth, and germ-tube formation. Analysis of the insoluble glucan fraction from cells labelled with [14C]glucose during germ-tube formation showed that the chitin content of the cell wall increased from 0.6% to 2.7% (w/w).
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PMID:An analysis of the metabolism and cell wall composition of Candida albicans during germ-tube formation. 632 47

Addition of glucose to cells of the yeast Saccharomyces cerevisiae growing on a nonfermentable carbon source triggers a rapid, transient increase in the cAMP level. The occurrence of this cAMP spike appears to be correlated inversely with the glucose-repression state of the cells. This was also observed for the hex2 mutant, which is deficient in glucose repression and which displayed the cAMP signal constitutively. When cells of the hex2 mutant were starved for nitrogen on a glucose-containing medium, they rapidly lost viability, similarly to mutants with overactivation of the Ras-adenylate cyclase pathway. Flow cytometry measurements showed that G1 arrest of the hex2 mutant under such conditions was incomplete. Trehalose accumulation, a typical feature of cells entering the stationary phase G0, was very short-lived in the hex2 mutant under the same conditions. These results are in agreement with the presence of continuous glucose-triggered activation of cAMP synthesis in hex2 cells on a glucose-containing nitrogen-starvation medium. In the course of these experiments a spontaneous suppressor mutant, shx (for suppressor of hex2), was isolated which survived nitrogen starvation on a glucose-containing medium much better than the hex2 strain. It also showed normal G1 arrest and much longer accumulation of trehalose. The suppressor mutation also caused inability to grow on nonfermentable carbon sources and absence of invertase depression, and it was epistatic to hex2 for these characteristics also. The isolation of this epistatic depression mutation supports the idea that the defect in glucose repression of the hex2 mutant is the cause of its rapid loss of viability during nitrogen starvation on a glucose-containing medium.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Constitutive glucose-induced activation of the Ras-cAMP pathway and aberrant stationary-phase entry on a glucose-containing medium in the Saccharomyces cerevisiae glucose-repression mutant hex2. 755 Oct 24

Trehalose and glycogen accumulate in Saccharomyces cerevisiae when growth conditions deteriorate. It has been suggested that aside from functioning as storage factors and stress protectants, these carbohydrates may be required for cell cycle progression at low growth rates under carbon limitation. By using a mutant unable to synthesize trehalose and glycogen, we have investigated this requirement of trehalose and glycogen under carbon-limited conditions in continuous cultures. Trehalose and glycogen levels increased with decreasing growth rates in the wild-type strain, whereas no trehalose or glycogen was detected in the mutant. However, the mutant was still able to grow and divide at low growth rates with doubling times similar to those for the wild-type strain, indicating that trehalose and glycogen are not essential for cell cycle progression. Nevertheless, upon a slight increase of extracellular carbohydrates, the wild-type strain degraded its reserve carbohydrates and was able to enter a cell division cycle faster than the mutant. In addition, wild-type cells survived much longer than the mutant cells when extracellular carbon was exhausted. Thus, trehalose and glycogen have a dual role under these conditions, serving as storage factors during carbon starvation and providing quickly a higher carbon and ATP flux when conditions improve. Interestingly, the CO2 production rate and hence the ATP flux were higher in the mutant than in the wild-type strain at low growth rates. The possibility that the mutant strain requires this steady higher glycolytic flux at low growth rates for passage through Start is discussed.
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PMID:Function of trehalose and glycogen in cell cycle progression and cell viability in Saccharomyces cerevisiae. 988 51

The dynamic responses of reserve carbohydrates with respect to shortage of either carbon or nitrogen source was studied to obtain a sound basis for further investigations devoted to the characterization of mechanisms by which the yeast Saccharomyces cerevisiae can cope with nutrient limitation during growth. This study was carried out in well-controlled bioreactors which allow accurate monitoring of growth and frequent sampling without disturbing the culture. Under glucose limitation, genes involved in glycogen and trehalose biosynthesis (GLG1, GSY1, GSY2, GAC1, GLC3, TPS1), in their degradation (GPH1, NTHI), and the typical stress-responsive CTT1 gene were coordinately induced in parallel with glycogen, when the growth has left the pure exponential phase and while glucose was still plentiful in the medium. Trehalose accumulation was delayed until the diauxic shift, although TPS1 was induced much earlier, due to hydrolysis of trehalose by high trehalase activity. In contrast, under nitrogen limitation, both glycogen and trehalose began to accumulate at the precise time when the nitrogen source was exhausted from the medium, coincidentally with the transcriptional activation of genes involved in their metabolism. While this response to nitrogen starvation was likely mediated by the stress-responsive elements (STREs) in the promoter of these genes, we found that these elements were not responsible for the co-induction of genes involved in reserve carbohydrate metabolism during glucose limitation, since GLG1, which does not contain any STRE, was coordinately induced with GSY2 and TPS1.
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PMID:Dynamic responses of reserve carbohydrate metabolism under carbon and nitrogen limitations in Saccharomyces cerevisiae. 1007 86

The effect of starvation on carbohydrate metabolism in the last instar larvae of the silkworm Bombyx mori was examined. Trehalose concentration in the hemolymph increased slightly during the first 6 h of starvation and decreased thereafter, whereas glucose concentration decreased rapidly immediately after diet deprivation. Starvation-induced hypertrehalosemia was completely inhibited by neck ligation, suggesting that starvation stimulates the release of a hypertrehalosemic factor(s) from the head. The percentage of active glycogen phosphorylase in the fat body increased within 3 h of starvation and its glycogen content decreased gradually. These observations suggest that production of trehalose from glycogen is enhanced in starved larvae. However, hypertrehalosemia during starvation cannot be explained by the increased supply of trehalose into hemolymph alone, as similar changes in phosphorylase activity and glycogen content in the fat body were observed in neck-ligated larvae, in which hemolymph trehalose concentration did not increase but decreased gradually. When injected into larvae, trehalose disappeared from hemolymph at a rate about 40% lower in starved larvae than neck-ligated larvae. The hemolymph lipid concentration increased during starvation, suggesting that an increased supply of lipids to tissues suppresses the consumption of hemolymph trehalose and this is an important factor in hypertrehalosemia.
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PMID:Carbohydrate metabolism during starvation in the silkworm Bombyx mori. 1086 69

Panagrolaimus davidi is a freeze-tolerant Antarctic nematode which survives extensive intracellular freezing. This paper describes the development of culture techniques which provide clean samples, with a high degree of freeze tolerance and in sufficient quantities for the analysis of potential cryoprotectants. Cultures grown at 20 degrees C survived a short-term freezing stress but survival declined with the time spent frozen. Acclimation of cultures at 5 degrees C enhanced the long-term survival of freezing. Starvation, however, reduced the nematode's ability to survive short-term freezing. The principal cryoprotectants detected by gas chromatography were trehalose and glycerol. The levels of trehalose, but not those of glycerol, increased significantly after acclimation. Trehalose may stabilise membranes and protect them against the dehydrating effects of the osmotic stresses resulting from freeze concentration effects but other factors, such as recrystallisation inhibition, may be involved in long-term survival.
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PMID:Cold acclimation and cryoprotectants in a freeze-tolerant Antarctic nematode, Panagrolaimus davidi. 1093 23

The physiological hallmark of heat-shock response in yeast is a rapid, enormous increase in the concentration of trehalose. Normally found in growing yeast cells and other organisms only as traces, trehalose becomes a crucial protector of proteins and membranes against a variety of stresses, including heat, cold, starvation, desiccation, osmotic or oxidative stress, and exposure to toxicants. Trehalose is produced from glucose 6-phosphate and uridine diphosphate glucose in a two-step process, and recycled to glucose by trehalases. Even though the trehalose cycle consists of only a few metabolites and enzymatic steps, its regulatory structure and operation are surprisingly complex. The article begins with a review of experimental observations on the regulation of the trehalose cycle in yeast and proposes a canonical model for its analysis. The first part of this analysis demonstrates the benefits of the various regulatory features by means of controlled comparisons with models of otherwise equivalent pathways lacking these features. The second part elucidates the significance of the expression pattern of the trehalose cycle genes in response to heat shock. Interestingly, the genes contributing to trehalose formation are up-regulated to very different degrees, and even the trehalose degrading trehalases show drastically increased activity during heat-shock response. Again using the method of controlled comparisons, the model provides rationale for the observed pattern of gene expression and reveals benefits of the counterintuitive trehalase up-regulation.
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PMID:Biochemical and genomic regulation of the trehalose cycle in yeast: review of observations and canonical model analysis. 1278 17

Adipokinetic hormone (AKH) is a metabolic neuropeptide principally known for its mobilization of energy substrates, notably lipid and trehalose during energy-requiring activities, such as flight and locomotion. Drosophila melanogaster AKH cell localization in corpora cardiaca, as in other insect species, was confirmed by immunoreactivity and by a genetic approach using the UAS/GAL4 system. To assess AKH general physiological rules, we ablated AKH endocrine cells by specifically driving the expression of apoptosis transgenes in AKH cells. Trehalose levels were decreased in larvae and starved adults, when the stimulation by AKH of the production of trehalose from fat body glycogen is no longer possible. Moreover, we show that these adults without AKH cells become progressively hypoactive. Finally, under starvation conditions, those hypoactive AKH-knockout cell flies survived approximately 50% longer than control wild-type flies, suggesting that the slower rate at which AKH-ablated flies mobilize their energy resources extends their survival.
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PMID:AKH-producing neuroendocrine cell ablation decreases trehalose and induces behavioral changes in Drosophila. 1537 18


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