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

Gluconeogenesis from isotopically substituted (3-13C)alanine (Ala) was demonstrated in the last larval instar of an insect, Manduca sexta, when maintained on low carbohydrate diets. 13C was incorporated into all carbons of the blood sugar trehalose (Tre), but enrichments of C1 and C6, and C2 and C5 were greatest. Relative to the amount of [3-13C]Ala metabolized, larvae maintained on a low carbohydrate diet supplemented with casein displayed the greatest enrichment of Tre. Very little de novo synthesis of Tre was observed in larvae maintained on a complete-balanced diet containing calorically equivalent amounts of sucrose and casein. Starvation failed to induce gluconeogenesis and 13C was not incorporated into Tre in starved insects. Activity of the TCA cycle contributed approximately 10% of the 13C incorporated into Tre in larvae on low carbohydrate diets, while the TCA cycle contribution in larvae on the complete diet approached 70%. The pattern of 13C enrichment of glucose in larvae on the low carbohydrate diets indicated that cytoplasmic carboxylation, possibly due to 'malic enzyme'-like activity, contributed significantly to the synthesis of Tre. The pentose phosphate pathway was evidenced in insects on all diets. Glucose labelling ratios indicated a pentose cycling flux of 10 to 20% in insects on the low carbohydrate diets and 50% in larvae on the complete diet. Glutamine together with lesser amounts of glutamate and glutathione were also products of the labelled Ala. The distribution of label in these products under different dietary conditions demonstrated shifts in the relative contribution of pyruvate carboxylase and pyruvate dehydrogenase activities for providing substrate to the TCA cycle. In the expected fashion starved insects and insects on the low carbohydrate diets incorporated a greater proportion of 13C into the TCA cycle via carboxylation while incorporation by the two pathways was similar in insects on the complete diet. The significance of these findings with regard to the regulation of gluconeogenesis in M. sexta and comparison of the present results with those obtained from studies of hepatic gluconeogenesis are discussed.
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PMID:Gluconeogenesis and effect of nutritional status on TCA cycle activity in the insect Manduca sexta. 854 15

Previous work has shown that clinical Escherichia coli strains, starved in seawater, are able to present residual growth, with subsequent alterations to their enzymatic activities and metabolism. Gelatinolytic activity of starved cells is of importance because it appears and increases gradually with time. In this work, several forms of gelatinolytic activity were detected by SDS-polyacrylamide gel electrophoresis, differing in molecular masses and appearance, before and after starvation of E. coli cells. The enzymic forms are classified into 4 categories according to the effect of certain inhibitors on the appearance of gelatinolytic activity: a. those whose appearance is inhibited by the chelating factors EDTA, 1,10-phenanthroline and whose presence is also inhibited by N-ethylmaleimide (metalloproteinases with thiol group active); b. those affected by the presence of chelators, N-ethylmaleimide and Ca2+ (Ca2(+)-dependent metalloproteinases with thiol group active); c. those inhibited by chelators and activated in the presence of Ca2+ (Ca2(+)-dependent metalloproteinases) and d. those whose appearance is independent of the presence of inhibitors used. The forms of gelatinolytic activity of the fourth category coincide with enzyme forms that can also use casein as substrate in electrophoresis. These data suggest that there are considerable differences in the gelatinolytic pattern of clinical strains of E.coli cells before and after starvation in seawater.
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PMID:Study of the gelatinolytic activities Escherichia coli cells before and after starvation in seawater by substrate gel electrophoresis. 881 23

The effects of acute food deprivation and subsequent refeeding with isonitrogenous oral liquid diets supplemented with arginine (ARG), ARG alpha-ketoglutarate (AKG), or ARG alpha-ketoisocaproate (AKIC) were examined in a Sprague-Dawley rat trauma model (bilateral femur fracture). Both control and trauma rats were starved for 2 days and then pair-fed for 4 days with one of four liquid isonitrogenous diets: diet 1 was a basal casein-based diet, and diets 2, 3, and 4 were the basal diet in which 10% of the nitrogen was replaced by ARG, AKG, or AKIC nitrogen. Two days of starvation resulted in a 13% loss of body weight and also a 27% decrease in the excretion of orotic acid (OA) in control and trauma rats. Although the ARG content of diets 2, 3, and 4 was the same, ARG- and AKIC-supplemented rats excreted significantly (P < .05) more OA than AKG-fed rats. The low level of OA excretion in AKG-fed rats indicates greater use of ARG for metabolic purposes, including efficient urea cycle operation. The metabolic adaptation and nutritional efficacy, i.e., Increased nitrogen retention, larger weight gain, and altered amino acid (AA) metabolism, of AKIC rats seem to be better than in ARG- or AKG-fed rats.
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PMID:Nutritional and metabolic effects and significance of mild orotic aciduria during dietary supplementation with arginine or its organic salts after trauma injury in rats. 922 32

The binding of insulin to its receptor rapidly induces intrinsic insulin receptor tyrosine kinase activity, resulting in tyrosine phosphorylation of various cytosolic substrates, such as insulin receptor substrate-1 (IRS-1) which, in turn, associates with a p85 subunit of phosphatidylinositol 3-kinase (PI 3-kinase) followed by activation of this enzyme. In the present study, we have examined these early steps of insulin signalling in rat liver in vivo after food ingestion. After fasting for 22 h, a 12% casein diet was available ad libitum throughout the 8-h experimental period. Plasma insulin concentrations increased within 45 min after feeding, reached a maximum at 1.5 h and gradually decreased until 8 h. Autophosphorylation of the insulin receptor beta-subunit in liver was detected even during fasting and increased about 1.5-fold at 1.5 h after feeding. Basal tyrosine phosphorylation of IRS-1 was detectable during starvation, increased about twofold at 3 h after feeding and levels were maintained until 8 h. The content of the p85 subunit of PI 3-kinase associated with IRS-1 also increased after feeding in parallel with the changes in tyrosine phosphorylation of IRS-1. Because tyrosine phosphorylation of the insulin receptor beta-subunit and IRS-1 and the association of the p85 subunit of PI 3-kinase with IRS-1 in liver were closely correlated with the changes in the plasma concentration of insulin, we concluded that endogenous insulin secreted in response to eating caused these insulin-dependent intracellular changes in the liver.
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PMID:Changes in tyrosine phosphorylation of insulin receptor and insulin receptor substrate-1 (IRS-1) and association of p85 of phosphatidylinositol 3-kinase with IRS-1 after feeding in rat liver in vivo. 929 37

Glutamine release by the liver constitutes a process of nitrogen salvage through the recycling of a part of the nitrogen, which prevents irreversible nitrogen losses as urea. The aim of this work was to study the nitrogen cycling in the splanchnic bed under different nutritional conditions: fed state, postabsorptive state (16 h food deprivation) or prolonged starvation (24 or 40 h). Rats were adapted to a 15% casein diet for 15 d and then sampled. The digestive, hepatic and splanchnic balances of glucose, lactate, ketone bodies, urea and amino acids were determined. There was a net release of lactate and alanine by the digestive tract, due to the high rate of glycolysis and glutaminolysis. During prolonged starvation, ketone bodies became major energy fuel for the intestine. In fed rats, there was a net uptake of most amino acids by the liver, except for glutamine and glutamate. Urea, glutamine and glutamate released represented 33, 24 and 6% of total nitrogen taken up by the liver, respectively. In postabsorptive rats, compared with fed rats, there was a significant reduction of ureagenesis, and glutamine became the major form of nitrogen released by the liver. In fact, nitrogen cycling in the form of glutamine or glutamate in the liver may be interpreted as a nitrogen salvage process, rather than as an acid-base control process. In the splanchnic area, in parallel with a highly active cycling of glucose as lactate, there exists a nitrogen cycling involving opposite fluxes of glutamine and alanine.
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PMID:Opposite fluxes of glutamine and alanine in the splanchnic area are an efficient mechanism for nitrogen sparing in rats. 973 9

The sigma factor RpoS (sigmaS) has been described as a general stress response regulator that controls the expression of genes which confer increased resistance to various stresses in some gram-negative bacteria. To elucidate the role of RpoS in Pseudomonas aeruginosa physiology and pathogenesis, we constructed rpoS mutants in several strains of P. aeruginosa, including PAO1. The PAO1 rpoS mutant was subjected to various environmental stresses, and we compared the resistance phenotype of the mutant to that of the parent. The PAO1 rpoS mutant was slightly more sensitive to carbon starvation than the wild-type strain, but this phenotype was obvious only when the cells were grown in a medium supplemented with glucose as the sole carbon source. In addition, the PAO1 rpoS mutant was hypersensitive to heat shock at 50 degrees C, increased osmolarity, and prolonged exposure to high concentrations of H2O2. In accordance with the hypersensitivity to H2O2, catalase production was 60% lower in the rpoS mutant than in the parent strain. We also assessed the role of RpoS in the production of several exoproducts known to be important for virulence of P. aeruginosa. The rpoS mutant produced 50% less exotoxin A, but it produced only slightly smaller amounts of elastase and LasA protease than the parent strain. The levels of phospholipase C and casein-degrading proteases were unaffected by a mutation in rpoS in PAO1. The rpoS mutation resulted in the increased production of the phenazine antibiotic pyocyanin and the siderophore pyoverdine. This increased pyocyanin production may be responsible for the enhanced virulence of the PAO1 rpoS mutant that was observed in a rat chronic-lung-infection model. In addition, the rpoS mutant displayed an altered twitching-motility phenotype, suggesting that the colonization factors, type IV fimbriae, were affected. Finally, in an alginate-overproducing cystic fibrosis (CF) isolate, FRD1, the rpoS101::aacCI mutation almost completely abolished the production of alginate when the bacterium was grown in a liquid medium. On a solid medium, the FRD1 rpoS mutant produced approximately 70% less alginate than did the wild-type strain. Thus, our data indicate that although some of the functions of RpoS in P. aeruginosa physiology are similar to RpoS functions in other gram-negative bacteria, it also has some functions unique to this bacterium.
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PMID:Effect of rpoS mutation on the stress response and expression of virulence factors in Pseudomonas aeruginosa. 1038 54

A diet containing adequate amounts of protein rapidly suppresses myofibrillar protein degradation in rats and mice. This study determined whether dietary amino acids inhibit postprandial protein degradation in rat skeletal muscle. When rats fed on a 20% casein diet for 1 h after 18 h starvation, the rate of myofibrillar protein degradation measured by N(tau)-methylhistidine release from the isolated extensor digitorum longus muscle was significantly (p < 0.05) decreased at 4 h after refeeding. A diet containing an amino acid mixture which is the same composition as casein also reduced myofibrillar protein degradation at 4 h after refeeding (p < 0.05). An essential amino acid mixture (15.1%, corresponding to casein composition) and a leucine (2.9%) diets reduced the rate of myofibrillar protein degradation after refeeding (p < 0.05), whereas a protein free diet did not. Administration of leucine alone (0.135 g/100 g body weight) by a feeding tube induced a decrease in the rate of myofibrillar protein degradation at 2 h after administration (p < 0.05), whereas the serum insulin concentration was constant after leucine administration. These results suggested that leucine is one of regulating factors of myofibrillar protein degradation after refeeding of a protein diet.
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PMID:Rapid suppression of protein degradation in skeletal muscle after oral feeding of leucine in rats. 1183 28

Glutamate is concentrated within RBC, but this intracellular glutamate is often ignored in studies of glutamate metabolism in vivo. The objective of this work was to determine the size of the plasma and cellular glutamate pools in rat blood and to clarify the role of RBC in the interorgan transport of glutamate. Approximately 20% of whole-blood glutamate was associated with isolated RBC membranes, but this was easily removed by washing with high salt solutions. Arterial plasma glutamate levels were relatively stable and did not show marked differences with starvation, streptozotocin diabetes or feeding 60% casein diets. In rats fed 5% casein, the plasma glutamate level was slightly higher (P < 0.05) than in most other groups. In contrast, RBC glutamate levels showed considerable variation. In rats consuming 5% casein, cellular glutamate levels were approximately 100% higher (P < 0.05) than in control, starved, diabetic or 20 or 60% casein-fed rats. Cellular glutamate levels were also higher (P < 0.05) in rats fed 60% casein than in those consuming 20% casein or the control diet. Rat erythrocytes in vitro did not take up or release free glutamate, confirming that they do not possess a glutamate transporter. Arteriovenous difference measurements across the portal drained viscera indicated a net glutamate release into the portal vein in control, 60% casein-fed and diabetic rats. In all cases, the net change in blood glutamate across the tissue occurred via the plasma, with no change in cellular glutamate levels. Therefore analyses of glutamate metabolism in rats in vivo may be made confidently using measurements of either whole-blood or plasma glutamate concentrations.
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PMID:Net interorgan transport of L-glutamate in rats occurs via the plasma, not via erythrocytes. 1198 20

The response of tobacco (Nicotiana tabacum) suspension-cultured cells (BY-2) to nutrient starvation was investigated. When the cells that were grown in Murashige-Skoog medium containing 3% (w/v) sucrose were transferred to the same medium without sucrose, 30 to 45% of the intracellular proteins were degraded in 2 d. An analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that proteins were degraded nonselectively. With the same treatment, protease activity in the cell, which was measured at pH 5.0 using fluorescein thiocarbamoyl-casein as a substrate, increased 3- to 7-fold after 1 d. When the cysteine protease inhibitor (2S,3S)-trans-epoxysuccinyl-L-leucylamido-3-methyl-butane (10 [mu]M) was present in the starvation medium, both the protein degradation and the increase in the protease activity were effectively inhibited. Light microscopy analysis showed that many small spherical bodies accumulated in the perinuclear region of the cytosol 8 h after the start of the inhibitor treatment. These bodies were shown to be membrane-bound vesicles of 1 to 6 [mu]m in diameter that contained several particles. Quinacrine stained these vesicles and the central vacuole; thus, both organelles are acidic compartments. Cytochemical enzyme analysis using 1-naphthylphosphate and [beta]-glycerophosphate as substrates showed that these vesicles contained an acid phosphatase(s). We suggest that these vesicles contribute to cellular protein degradation stimulated under sucrose starvation conditions.
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PMID:Autophagy in Tobacco Suspension-Cultured Cells in Response to Sucrose Starvation. 1222 58

Eisenstadt, Jerome M. (Brandeis University, Waltham, Mass.) and Harold P. Klein. Evidence for the de novo synthesis of the alpha-amylase of Pseudomonas saccharophila. J. Bacteriol. 82:798-807. 1961.-Chloramphenicol at a concentration of 20 mug per ml inhibited the appearance of the inducible alpha-amylase of Pseudomonas saccharophila. This inhibition was observed when induction was attempted in buffer or in a complete medium. Preinduced cells were also prevented from forming this enzyme under similar conditions. Under all the conditions tested, there was no lag in chloramphenicol inhibition, thus suggesting an absence of any protein precursor in amylase formation. Cells suspended in a complete medium without a nitrogen source lost their capacity to form this enzyme when subsequently induced in buffer. When cells were grown in the presence of radioactive sulfate and then subjected to starvation, the radioactivity of the amino acid pool diminished only slightly. However, examination of the free amino acid pool by paper chromatography showed that the loss of enzyme inducibility was accompanied by the disappearance of glutamine, aspartic acid, and a third, unidentified, compound. Enzyme-forming ability was restored by the addition, to starved cells of casein hydrolysate, glutamate, glutamine, or aspartate. Other amino acids tested were ineffective in this regard. When cells were induced in buffer in the presence of labeled methionine, amylase was formed at a linear rate over a 3-hr period. Furthermore, both the cellular proteins and the extracellular amylase became labeled at a linear rate. These observations are discussed in relation to the problem of protein turnover, and are interpreted as evidence for the de novo synthesis of alpha-amylase in this organism.
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PMID:Evidence for the de novo synthesis of the alpha-amylase of Pseudomonas saccharophila. 1388 95


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