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

The effects of one vs. two episodes of starvation-refeeding were studied in young male rats as a function of elapsed time between the two episodes of starvation-refeeding. Starved-refed rats ate more and gained weight faster than ad libitum-fed rats. The difference in weight gains could be attributed to the greater amount of body fat in the starved-refed rats. The responses of four NADP-linked liver dehydrogenases:isocitrate dehydrogenase (ICD)/LS-isocitrate:NADP oxidoreductase (decarboxylating) (EC 1.1.1.42), glucose-6-phosphate dehydrogenase (G6PD)/D-glucose-6-phosphate:NADP oxidoreductase (EC 1.1.1.49); 6-phosphogluconate dehydrogenase (6PGD/6-phospho-D-gluconate:NADP oxidoreductase (decarboxylating) (EC 1.1.1.44); and malic enzyme (ME)/L-malate:NADP oxidoreductase (decarboxylating) (EC 1.1.1.40) were studied. Starvation-refeeding caused an overshoot of G6PD, 6PGD, and ME, but not of ICD. A second episode of starvation caused an even greater enzyme overshoot; this difference persisted for 3 weeks with G6PD and for 2 weeks with 6PGD and ME. No significant differences in blood cholesterol were detected.
 ...
PMID:Long-term effects of starvation-refeeding in the rat. 122 70

Previous attempts to account for the labelling in vivo of liver metabolites associated with the citrate cycle and gluconeogenesis have foundered because proper allowance was not made for the heterogeneity of the liver. In the basal state (anaesthetized after 24h starvation) this heterogeneity is minimal, and we show that labelling by [14C]bicarbonate can be interpreted unambiguously. [14C]Bicarbonate was infused to an isotopic steady state, and measurements were made of specific radioactivities of blood bicarbonate, alanine, glycerol and lactate, of liver alanine and lactate, and of individual carbon atoms in blood glucose and liver aspartate, citrate and malate. (Existing methods for several of these measurements were extensively modified.) The results were combined with published rates of gluconeogenesis, uptake of gluconeogenic precursors by the liver, and citrate-cycle flux, all measured under similar conditions, and with estimates of other rates made from published data. To interpret the results, three ancillary measurements were made: the rate of CO2 exchange by phosphoenolpyruvate carboxykinase (PEPCK; EC 4.1.1.32) under conditions that simulated those in vivo; the 14C isotope effect in the pyruvate carboxylase (EC 6.4.1.1) reaction (14C/12C = 0.992 +/- 0.008; S.E.M., n = 8); the ratio of labelling by [2-14C]- to that by [1-14C]-pyruvate of liver glutamate 1.5 min after injection. This ratio, 3.38, is a measure of the disequilibrium in the mitochondria between malate and oxaloacetate. The data were analysed with due regard to experimental variance, uncertainties in values of fluxes measured in vitro, hepatic heterogeneity and renal glucose output. The following conclusions were reached. The results could not be explained if CO2 fixation was confined to pyruvate carboxylase and there was only one, well-mixed, pool of oxaloacetate in the mitochondria. Addition of the other carboxylation reactions, those of PEPCK, isocitrate dehydrogenase (EC 1.1.1.42) and malic enzyme (EC 1.1.1.40), was not enough. Incomplete mixing of mitochondrial oxaloacetate had to be assumed, i.e. that there was metabolic channelling of oxaloacetate formed from pyruvate towards gluconeogenesis. There was some evidence that malate exchange across the mitochondrial membrane might also be channelled, with incomplete mixing with that in the citrate cycle. Calculated rates of exchange of CO2 by PEPCK were in agreement with those measured in vitro, with little or no activation by Fe2+ ions.(ABSTRACT TRUNCATED AT 400 WORDS)
 ...
PMID:[14C]bicarbonate fixation into glucose and other metabolites in the liver of the starved rat under halothane anaesthesia. Metabolic channelling of mitochondrial oxaloacetate. 392 30

1. Optimum conditions were established for determining the activities of the NADP(+)-linked enzymes, glucose 6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and isocitrate dehydrogenase, in mosquito tissues. 2. The activity of each dehydrogenase was determined in samples of mosquitoes of different ages throughout the life-span. The specific-activity curves attained maximal values in the pupal or early adult period. From these maxima an 81% decrease in glucose 6-phosphate-dehydrogenase and 67% decrease in 6-phosphogluconate-dehydrogenase activities occurred after the tenth day of adult life; a 77% decrease in isocitrate-dehydrogenase activity occurred before the fifth day. 3. The activity differences were found in different body regions as well as in whole organisms. 4. Starvation of the larva or adult did not result in decreases in enzyme activity. 5. These findings support the hypothesis that the activities of enzymes that form NADPH are related to the biosynthetic activity, for the enzyme activities increased during the period of cellular growth and decreased during the aging period.
 ...
PMID:Nicotinamide-adenine dinucleotide phosphate enzymes in the mosquito during growth and aging. 438 47

1. The concentrations of the oxidized and reduced substrates of the ;malic' enzyme (EC 1.1.1.40) and isocitrate dehydrogenase (EC 1.1.1.42) were measured in freeze-clamped rat livers. By assuming that the reactants of these dehydrogenase systems are at equilibrium in the cytoplasm the [free NADP(+)]/[free NADPH] ratio was calculated. The justification of the assumption is discussed. 2. The values of this ratio obtained under different nutritional conditions (well-fed, 48hr.-starved, fed with a low-carbohydrate diet, fed with a high-sucrose diet) were all of the same order of magnitude although characteristic changes occurred on varying the diet. The value of the ratio fell on starvation and on feeding with the low-carbohydrate diet and rose slightly on feeding with the high-sucrose diet. 3. The mean values of the ratio were calculated to be between 0.001 and 0.015, which is about 100000 times lower than the values of the cytoplasmic [free NAD(+)]/[free NADH] ratio. 4. The differences in the redox state of the two nicotinamide-adenine dinucleotide couples can be explained on a simple physicochemical basis. The differences are the result of equilibria that are determined by the equilibrium constants of a number of highly active readily reversible dehydrogenases and transaminases and the concentrations of the substrates and products of these enzymes. 5. The decisive feature is the fact that the NAD and NADP couples share substrates. This sharing provides a link between the redox states of the two couples. 6. The application of the method of calculation to data published by Kraupp, Adler-Kastner, Niessner & Plank (1967), Goldberg, Passonneau & Lowry (1966) and Kauffman, Brown, Passonneau & Lowry (1968) shows that the redox states of the NAD and NADP couples in cardiac-muscle cytoplasm and in mouse-brain cytoplasm are of the same order as those in rat liver. 7. The determination of the equilibrium constant at 38 degrees , pH7.0 and I 0.25 (required for the calculation of the [free NADP(+)]/[free NADPH] ratio), gave a value of 3.44x10(-2)m for the ;malic' enzyme (with CO(2) rather than HCO(3) (-) as the reactant) and a value of 1.98x10(-2)m(-1) for glutathione reductase.
 ...
PMID:The redox state of free nicotinamide-adenine dinucleotide phosphate in the cytoplasm of rat liver. 439 Oct 39

1. The conversion of [U-(14)C]glucose into carbon dioxide, cholesterol and fatty acids in liver slices and the activities of ;malic' enzyme, citrate-cleavage enzyme, NADP-linked isocitrate dehydrogenase and hexose monophosphate-shunt dehydrogenases in the soluble fraction of homogenates of liver were measured in chicks that were starved or starved then fed. 2. In newly hatched chicks the incorporation of [U-(14)C]glucose and the activity of ;malic' enzyme did not increase unless the birds were fed. The response to feeding of [U-(14)C]glucose incorporation into fatty acids increased as the starved chicks grew older. 3. Citrate-cleavage enzyme activity increased slowly even when the newly hatched chicks were unfed. On feeding, citrate-cleavage enzyme activity increased at a much faster rate. 4. In normally fed 20-day-old chicks starvation decreased the incorporation of [U-(14)C]glucose into all three end products and depressed the activities of ;malic' enzyme and citrate-cleavage enzyme. Re-feeding increased all of these processes to normal or higher-than-normal levels. 5. In both newly hatched and 20-day-old chicks starvation increased the activity of isocitrate dehydrogenase and feeding or re-feeding decreased it. 6. Very little change in hexose monophosphate-shunt dehydrogenase activity was observed during the dietary manipulations. 7. The results indicate that increased substrate delivery to the liver is the principal stimulus to the increased rate of glucose metabolism observed in newly hatched chicks. The results also suggest that changes in the activities of ;malic' enzyme and citrate-cleavage enzyme are secondary to an increased flow of metabolites through the glucose-to-fatty acid pathway and that the dehydrogenases of the hexose monophosphate shunt play a minor role in NADPH production for fatty acid synthesis.
 ...
PMID:The effect of starvation and starvation followed by feeding on enzyme activity and the metabolism of [U-14C]glucose in liver from growing chicks. 566 80

A full-length cDNA (icdh-1) encoding a cytosolic NADP(+)-dependent isocitrate dehydrogenase (ICDH-1) from potato (Solanum tuberosum L.) has been isolated. Analysis of the deduced protein sequence revealed considerable homologies with the corresponding proteins from other eukaryotes such as tobacco, alfalfa, soybean, cattle, pig, and yeast. The gene was transcribed in all tissues tested, with the highest amount of icdh-1 transcript being found in green tissues, in flowers, and in roots. In leaves, enzyme activities were dependent on the age, with fully mature leaves showing the highest level of RNA expression and enzyme activity. This observation may indicate that NADP(+)-dependent ICDH is not only involved in amino acid biosynthesis via the glutamine synthetase/glutamine oxoglutarate aminotransferase cycle but also in cycling, redistribution, and export of amino acids. The latter assumption has been strengthened by our finding of a preferential expression of NADP(+)-dependent ICDH in leaf veins. Under in vivo conditions, the expression pattern paralleled the enzyme activity, indicating coarse control on the RNA level. Experiments carried out with detached leaves revealed an influence of light, nitrate, and sucrose on icdh-1 transcript levels and in some cases also on NADP(+)-dependent ICDH activity. In darkness, nitrate or sucrose induced icdh-1 mRNA expression. Leaves kept under starvation conditions exhibited a decrease of their protein content, whereas icdh-1 expression and ICDH activity increased significantly.
 ...
PMID:Cloning and expression analysis of the cytosolic NADP(+)-dependent isocitrate dehydrogenase from potato. Implications for nitrogen metabolism. 771 47

Using two-dimensional gel electrophoresis and N-terminal amino acid sequencing analysis, we demonstrate that a mutant of the global regulatory protein ArcA fails to decrease the synthesis of the TCA cycle enzymes malate dehydrogenase, isocitrate dehydrogenase, lipoamide dehydrogenase E3 and succinate dehydrogenase in response to stasis, while the increased production of the glycolysis enzymes phosphoglycerate mutase and pyruvate kinase is unaffected. Microcalorimetric and respiratory measurements show that the continued production of TCA cycle enzymes in the (delta)arcA mutant is manifested as an elevated rate of respiration and total metabolic activity during starvation. The (delta)arcA mutant is severely impaired in surviving prolonged periods of exogenous carbon starvation, a phenotype that can be alleviated by overproducing the superoxide dismutase SodA. In addition, flow cytometry demonstrates that starving (delta)arcA mutant cells, in contrast to wild-type cells, fail to perform reductive division, remain large and contain multiple chromosomal copies. We suggest that the ArcA-dependent reduced production of electron donors and the decreased level and activity of the aerobic respiratory apparatus during growth arrest is an integral part of a defense system aimed at avoiding the damaging effects of oxygen radicals and controlling the rate of utilization of endogenous reserves.
 ...
PMID:Bacterial defense against aging: role of the Escherichia coli ArcA regulator in gene expression, readjusted energy flux and survival during stasis. 867 Aug 22

NADP+-isocitrate dehydrogenase (NADP+-IDH) activity and protein levels in crude extracts from the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 and the filamentous, dinitrogen-fixing Anabaena sp. strain PCC 7120 were determined under different nitrogen conditions. The highest NADP+-IDH activity and protein accumulation were found under dinitrogen-fixing conditions for the Anabaena strain and under nitrogen starvation for Synechocystis sp. PCC 6803. The icd gene that encodes the NADP+-IDH from Synechocystis sp. strain PCC 6803 was cloned by heterologous hybridization with the previously isolated icd gene from Anabaena sp. strain PCC 7120. The two cyanobacterial icd genes show 81% sequence identity and share a typical 44-amino-acid region different from all the other icd genes sequenced so far. The icd gene seems to be essential for Synechocystis growth since attempts to generate a completely segregated icd mutant were unsuccessful. Transcripts of 2.0 and 1.6 kb were detected by Northern (RNA) blot analysis, for the Anabaena and Synecho-cystis icd genes, respectively. Maximal icd mRNA accumulation was reached after 5 It of nitrogen starvation in Synechocystis cells and under dinitrogen-fixing conditions in Anabaena cells. Primer extension analysis showed that the structure of the Synechocystis icd gene promoter resembles those of the NtcA-regulated promoters. In addition, mobility shift assays demonstrated that purified Synechocystis NtcA protein binds to the promoter of the icd gene. All these data suggest that the expression of the icd gene from Synechocystis sp. strain PCC 6803 may be subjected to nitrogen control mediated by the positively acting regulatory protein NtcA.
 ...
PMID:The NADP+-isocitrate dehydrogenase gene (icd) is nitrogen regulated in cyanobacteria. 876 33

Embryo axes isolated from germinating lupine seeds were cultivated in vitro for 24-96 h over media containing either 60 mmol/L sucrose or no sucrose. Ultrastructural studies showed that large vacuoles were accumulating in a central region of primary parenchyma cells in sucrose starved lupine embryo axes, whereas cytoplasm along with organelles were forced to a periphery of the cells. We suggest that the autolysis of cytoplasmic proteins contributes to the accumulation of the vacuoles and this suggestion is consistent with the results of the characterisation of protein content. The level of cytosolic proteins was reduced by 50% and the activity of cytosolic marker enzyme, PEP carboxylase, was reduced by 46% in starved embryos as compared to control. The mitochondria from starved tissues were not degraded. The level of mitochondrial proteins was reduced by only 10% and the activity of mitochondrial NAD-isocitrate dehydrogenase decreased by 8% as a result of starvation. As demonstrated by the results of Percoll density gradient centrifugation, sucrose starvation caused an increase of 49% in many of the higher density mitochondria fractions, whereas many of the lower density mitochondria fractions were decreased by 33%. The samples of mitochondria from starved embryo axes were determined to have higher respiration activity in the presence of glutamate and malate as compared to control samples. EPR-based analyses of free radicals showed the presence of free radicals with a signal at g = 2.0060 in embryo axes. The level of the radical was two times higher in sucrose-starved embryo axes than in control (the level of this radical increased in senescing plant tissues as well). The results of EPR-based quantitation of Mn2+ ions revealed that the level was a few times higher in starved material than in control. Starved embryo axes, however, do possess a number of adaptive mechanisms protecting them from oxidative damage. Densitometric analyses of gels revealed an increase in the activity of SOD in sugar-starved embryos, whereas CAT and POX activities were lower in axes grown without sucrose as compared to control. Superoxide dismutase, catalase and peroxidase zymogram analyses showed that synthesis of new isoforms was not induced by sugar starvation. An accumulation of phytoferritin was found in plastids of sucrose starved embryos. These results are discussed in relation to the metabolic changes observed in senescing plant tissues.
 ...
PMID:Metabolic and ultrastructural responses of lupine embryo axes to sugar starvation. 1274 88

In order to investigate the metabolic poise of the elasmobranch rectal gland, we conducted two lines of experimentation. First, we examined the effects of feeding on plasma metabolites and enzyme activities from several metabolic pathways in several tissues of the dogfish shark, Squalus acanthias, after starvation and at 6, 20, 30 and 48 h post-feeding. We found a rapid and sustained ten-fold decrease in plasma beta-hydroxybutyrate at 6 h and beyond compared with starved dogfish, suggesting an upregulation in the use of this substrate, a decrease in production, or both. Plasma acetoacetate levels remain unchanged, whereas there was a slight and transient decrease in plasma glucose levels at 6 h. Several enzymes showed a large increase in activity post-feeding, including beta-hydroxybutyrate dehydrogenase in rectal gland and liver, and in rectal gland, isocitrate dehydrogenase, citrate synthase, lactate dehydrogenase, aspartate amino transferase, alanine amino transferase, glutamine synthetase and Na(+)/K(+) ATPase. Also notable in these enzyme measurements was the overall high level of activity in the rectal gland in general. For example, activity of the Krebs' TCA cycle enzyme citrate synthase (over 30 U g(-1)) was similar to activities in muscle from other species of highly active fish. Surprisingly, lactate dehydrogenase activity in the gland was also high (over 150 U g(-1)), suggesting either an ability to produce lactate anaerobically or use lactate as an aerobic fuel. Given these interesting observations, in the second aspect of the study we examined the ability of several metabolic substrates (alone and in combination) to support chloride secretion by the rectal gland. Among the substrates tested at physiological concentrations (glucose, beta-hydroxybutyrate, lactate, alanine, acetoacetate, and glutamate), only glucose could consistently maintain a viable preparation. Whereas beta-hydroxybutyrate could enhance gland activity when presented in combination with glucose, surprisingly it could not sustain chloride secretion when used as a lone substrate. Our results are discussed in the context of the in vivo role of the gland and mechanisms of possible upregulation of enzyme activities.
 ...
PMID:Metabolic organization and effects of feeding on enzyme activities of the dogfish shark (Squalus acanthias) rectal gland. 1685 77


1 2 3 Next >>