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

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.
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PMID:The redox state of free nicotinamide-adenine dinucleotide phosphate in the cytoplasm of rat liver. 439 Oct 39

The effects of transcription and translation inhibitors on NADP-glutamate dehydrogenase and glutamine synthetase synthesis in nitrogen-starving Ankistrodesmus braunii cells have been studied. Considering the results obtained one can suggest that both enzymes are coded in a chloroplast genome and that during nitrogen starvation specific mRNA's are partly transferred from chloroplast into cytoplasm and can be translated there on 80S ribosomes.
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PMID:The role of chloroplast and cytoplasm in the NADP-glutamate dehydrogenase and glutamine synthetase synthesis in Ankistrodesmus cells. 612 70

The effects of transcription and translation inhibitors on NADP-glutamate dehydrogenase and glutamine synthetase synthesis in nitrogen-starving Ankistrodesmus braunii cells have been studied. Considering the results obtained one can suggest that both enzymes are coded in the chloroplast genome and that during nitrogen starvation specific mRNA's are partly transferred from the chloroplast into the cytoplasm and can be translated there on 80S ribosomes.
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PMID:The role of chloroplast and cytoplasm in the NADP-glutamate dehydrogenase and glutamine synthetase synthesis in Ankistrodesmus cells. 613 76

The activity of some NAD- and NADP-dependent dehydrogenases involved in generation of the reducing equivalents for lipogenesis and the activity and some kinetic parameters of ATP-citrate (pro-3S)-lyase from rat liver, i. e. the enzyme involved in the formation of CoASAc, the primary substrate of fatty acid biosynthesis, were studied. The changes in the activity of NADP-dependent dehydrogenase and ATP-citrate(pro-3S)-lyase, as well as the affinity of the latter for sitrate and CoA and the rate of lipogenesis in starved rats and in rats kept on a carbohydrate-rich diet after starvation appeared to be parallel. Nicotinamide decreased the activity of all NADP-dependent dehydrogenases under study, which was especially well-pronounced after nicotinamide addition against increased lipogenesis. The affinity of ATP-citrate(pro-3S)-lyase for citrate and CoA decreased simultaneously with the decrease in the concentration of the latter. These changes can possibly induce the decrease of lipogenesis rate in rat liver after addition of nicotinamide.
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PMID:[Possible mechanisms of the inhibiting effect of nicotinamide on lipogenesis in rat liver]. 645 46

Malic enzyme [L-malate-NADP oxidoreductase (decarboxylating), EC 1.1.1.40] and fatty acid synthase activities were barely detectable in the uropygial gland of duck embryos until 4 or 5 days before hatching, when they began to increase. These activities increased about 30- and 140-fold, respectively, by the day of hatching. Malic enzyme and fatty acid synthase activities were also very low in embryonic liver. However, hepatic malic enzyme activity did not increase until the newly hatched ducklings were fed. Hepatic fatty acid synthase began to increase the day before hatching and the rate of increase in enzyme activity accelerated markedly when the newly hatched ducklings were fed. Starvation of newly hatched or 12-day-old ducklings had no effect on the activities of malic enzyme and fatty acid synthase in the uropygial gland but markedly inhibited these activities in liver. Changes in the concentrations of both enzymes and in the relative synthesis rates of fatty acid synthase correlated with enzyme activities in both uropygial gland and liver. Developmental patterns for sequence abundance of malic enzyme and fatty acid synthase mRNAs in uropygial gland and liver were similar to those for their respective enzyme activities. Starvation of 4-day-old ducklings had no significant effect on the abundance of these mRNAs in uropygial gland but caused a pronounced decrease in their abundance in liver. It is concluded that developmental and nutritional regulation of these enzymes is tissue specific and occurs primarily at a pretranslational level in both uropygial gland and liver.
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PMID:Malic enzyme and fatty acid synthase in the uropygial gland and liver of embryonic and neonatal ducklings. Tissue-specific regulation of gene expression. 671 47

We have examined the interconversion of cortisone (E) and cortisol (F) in rat lung homogenate and microsomal fraction and in the isolated rat lung perfused with Krebs bicarbonate solution containing 4.5% albumin. In the perfused lung the apparent Km was 5.1 microM E and the Vmax was 9 nmol . g(-1) . min-1. The ability of the lung to reduce E to F was enhanced both by 7 days prior exposure of the rat to an ambient temperature of 2 degrees C and by starvation of the rat for 3 days. The activity was inhibited by adrenalectomy and castration of 7 days duration. Whereas little steroid oxidation occurred in the perfused lung, preparations of lung homogenates and microsomal fraction readily reduced or oxidised the 11-position of the corticoid molecule depending on the preponderance of either NADPH or NADP, respectively. We conclude, that the predominance of the reductive reaction in the whole rat lung under physiological conditions reflects the very active pentose-phosphate shunt in the lung, which produces NADPH. We suggest that this ability of the lung to activate E to F may exert a fine control over the arterial concentration of unbound, physiologically active, 11-hydroxylated steroid.
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PMID:The physiological significance of 11 beta-hydroxysteroid dehydrogenase in the rat lung. 695 69

We examined the relationship between glucose-induced insulin release and the intermediary metabolism of islets from fed and fasted rats. Isolated islets were perifused and insulin release measured in the effluent. At various times after switching islets from 2.4 to 8.6 or 14.5 mM glucose or from 2.4 to 14.5 and back to 2.4 mM glucose, islets were quickly frozen, freeze dried, and subsequently analyzed for tissue content of glucose-6-P, fructose-1,6-P2 plus triose-P, Pi, ATP, ADP, 5'-AMP, NADH, NADPH, total NAD, and total NADP using enzymatic fluorometric procedures. When islets from fed rats were exposed to high glucose, there were concomitant increases of insulin release and islet content of glucose-6-P, fructose-1,6-P2 plus triose-P, NADH, and NADPH. During stimulation Pi and 5'-AMP content fell markedly. The total adenine nucleotide content remained constant. Similar secretory and metabolic changes occurred when 1.5 mM Pi was added to the perifusion fluid. When glucose-stimulated islets were switched back to low glucose for 10 min, all substances but fructose-1,6-P2 plus triose-P, 5'-AMP, NADPH, and possibly ATP returned to the prestimulatory level. Starvation of rats for 3 days blocked the secretory response to 8.6 mM glucose. Fructose-1,6-P2 plus triose-P rose but it did not attain the level existing in islets from fed rats. The ratios (ATP)/(5'-AMP) and (ATP)/(Pi)(adp) increased to the values observed in glucose-stimulated islets of fed rats. The metabolic changes in islets from fed rats exposed to high glucose are consistent with an activation of glycolysis occurring concomitantly with stimulated rates of insulin release. This occurs despite the decrease of important activators of glycolysis--Pi and 5'-AMP. The enhanced glycolysis possibly results from P-fructokinase activation by increased fructose-6-P levels. Activation of glycolysis with 8.6 mM glucose was not as pronounced in islets from starved rats. Despite the different secretory response of islets from fet and fasted rats, the changes of phosphorylation state in the islets, in particular, Pi and 5'-AMP levels, were similar.
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PMID:Effects of glucose on insulin release and on intermediary metabolism of isolated perifused pancreatic islets from fed and fasted rats. 699 11

1. Deoxycorticosterone, which does not enhance tryptophan pyrrolase activity, also fails to alter the concentrations of the NAD(P) couples in livers of fed rats, whereas corticosterone increases both pyrrolase activity and dinucleotide concentrations. 2. Starvation of rats increases serum corticosterone concentration, lipolysis, tryptophan availability to the liver, tryptophan pyrrolase activity and liver [NADP(H)]. Glucose prevents all these changes. 3. The beta-adrenoceptor-blocking agent propranolol prevents the starvation-induced lipolysis and the consequent increase in tryptophan availability to the liver, but does not influence the increase in serum corticosterone concentration, liver pyrrolase activity and [NADP(H)]. 4. Actinomycin D, which prevents the starvation-induced increases in liver pyrrolase activity and [NADP(H)], does not affect those in serum corticosterone concentration and tryptophan availability to the liver. 5. Allopurinol, which blocks the starvation-induced enhancement of pyrrolase activity, also abolishes the increases in liver [NADP(H)], but not those in serum corticosterone concentration or tryptophan availability to the liver. 6. It is suggested that liver tryptophan pyrrolase activity plays an important role in NAD+ synthesis from tryptophan in the rat.
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PMID:Possible involvement of the enhanced tryptophan pyrrolase activity in the corticosterone- and starvation-induced increases in concentrations of nicotinamide-adenine dinucleotides (phosphates) in rat liver. 730 70

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.
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PMID:Cloning and expression analysis of the cytosolic NADP(+)-dependent isocitrate dehydrogenase from potato. Implications for nitrogen metabolism. 771 47

A small-scale functional analysis screen has revealed several new phenotypes associated with a large deletion of GDH3, one of two Saccharomyces cerevisiae genes known to encode NADP-linked glutamate dehydrogenase. Diploids heterozygous for the deletion are able to sporulate in rich media, while haploid deletants produce dark, wrinkled colonies containing pseudohyphal cells. The haploid cells rapidly lose viability upon starvation.
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PMID:Partial deletion of the Saccharomyces cerevisiae GDH3 gene results in novel starvation phenotypes. 875 31


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