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

A single-gene nuclear mutant has been selected from the yeast Schizosaccharomyces pombe for growth resistance to Dio-9, a plasma membrane H+-ATPase inhibitor. From this mutant, called pma1, an ATPase activity has been purified. It contains a Mr = 100,000 major polypeptide which is phosphorylated by [gamma-32P] ATP. Proton pumping is not impaired since the isolated mutant ATPase is able, in reconstituted proteoliposomes, to quench the fluorescence of the delta pH probe 9-amino-6-chloro-2-methoxy acridine. The isolated mutant ATPase is sensitive to Dio-9 as well as to seven other plasma membrane H+-ATPase inhibitors. The mutant H+-ATPase activity tested in vitro is, however, insensitive to vanadate. Its Km for MgATP is modified and its ATPase specific activity is decreased. The pma1 mutation decreases the rate of extracellular acidification induced by glucose when cells are incubated at pH 4.5 under nongrowing conditions. During growth, the intracellular mutant pH is more acid than the wild type one. The derepression by ammonia starvation of methionine transport is decreased in the mutant. The growth rate of pma1 mutants is reduced in minimal medium compared to rich medium, especially when combined to an auxotrophic mutation. It is concluded that the H+-ATPase activity from yeast plasma membranes controls the intracellular pH as well as the derepression of amino acid, purine, and pyrimidine uptakes. The pma1 mutation modifies several transport properties of the cells including those responsible for the uptake of Dio-9 and other inhibitors (Ulaszewski, S., Coddington, A., and Goffeau, A. (1986) Curr. Genet. 10, 359-364).
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PMID:A single mutation confers vanadate resistance to the plasma membrane H+-ATPase from the yeast Schizosaccharomyces pombe. 287 25

The liver is the "glucostat" of the organism and serves at the same time as an "ammonia-sink and pH stat". The key enzymes involved in glucose uptake and release and in urea and glutamine formation are reciprocally distributed over the liver parenchyma: The glucogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK), fructosebisphosphatase (FBPase) and glucose-6-phosphatase (G6Pase) as well as the ureagenic enzyme carbamoylphosphate synthetase (CAPS) are predominant in the periportal zone. The glycolytic enzymes glucokinase (GK) and pyruvate kinase type L (PKL) as well as the glutaminogenic enzyme glutamine synthetase (GluNS) are prevalent in the perivenous zone. This heterogeneity appears to be a prerequisite for the normal "glucostat, ammonia-sink and pH-stat" function of the liver. After birth the liver is a gluconeogenic organ, only with weaning it becomes a "glycolytic/gluconeogenic" glucostat. In the rat zonation of PEPCK, G6Pase and CAPS developed gradually after birth and was completed before weaning, i.e. before it would be functionally required. After 2/3 partial hepatectomy the liver looses its normal glucostat function and becomes a gluconeogenic organ. With this change the zonation of PEPCK and PKL were also lost; it was restored only during the second week after operation. During starvation the liver also looses its glucostat function to become the major glucose supplier of the organism. Zonation of PEPCK and PKL were diminished to such an extent that the major function of the perivenous zone was altered from glucose uptake to release. In diabetes the liver does not loose its glucostat function; however, the function is severely impaired. Zonation of PEPCK was increased and that of PKL decreased in such a manner that the major function of the perivenous zone, glucose uptake, was not entirely changed but only diminished. It can be concluded that in the various physiological states studied the zonation of enzymes correlated well with the glucostat function of the liver.
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PMID:Dynamics of zonal hepatocyte heterogeneity. Perinatal development and adaptive alterations during regeneration after partial hepatectomy, starvation and diabetes. 301 Mar 76

AMP deaminase, the activity that catalyzes the deamination of AMP to form IMP and NH3 has been measured in Dictyostelium discoideum. A new procedure to assay the activity of this enzyme was developed using formycin 5'-monophosphate, a fluorescent analog of AMP as the substrate, and ion-paired reverse phase HPLC to separate the reactants and products. Quantitation of the formycin containing compounds was accomplished at 290 nm. At this wavelength adenosine containing compounds were not detected and activity could be monitored in the presence of its activator ATP. The AMP deaminase activity in vegetative cells was 7.4 nmols/min/mg proteins while the activity in cells measured at 2 and 6 hrs after starvation-induced growth-arrest was 376 nmols/min/mg protein...a 51-fold increase. When vegetative cells were treated with hadacidin, a drug that restricts de novo AMP synthesis and pinocytosis, the activity of the AMP deaminase was 511 nmols/min/mg protein...a 70-fold increase compared to that in untreated vegetative cells. Smaller increases were noted following the inhibition of growth with the drugs cerulenin and vinblastine, as well as after the inhibition of de novo GMP synthesis with the drug mycophenolic acid or the partial inhibition of de novo AMP synthesis with analogs of hadacidin, N-hydroxyglycine and N-formylglycine. In addition, when the activity of two other enzymes involved in purine metabolism, namely adenosine kinase and hypoxanthine-guanine phosphoribosyl transferase, was measured in vegetative cells, and the activity of both compared to that measured in starvation and hadacidin induced growth-arrested cells, showed no significant changes.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:AMP deaminase in Dictyostelium discoideum: increase in activity following nutrient deprivation induced by starvation or hadacidin. 301 11

The addition of DL-7-azatryptophan (AZAT), a tryptophan analog, to continuous cultures of Anabaena sp. strain CA grown with 10 mM nitrate as the nitrogen source resulted in the differentiation of heterocysts. Analysis of the intracellular amino acid pools of Anabaena sp. strain CA after the addition of AZAT showed a marked decline in the intracellular glutamate pool and a slight increase in the levels of glutamine. The in vitro activity of glutamate synthase, the second enzyme involved in primary ammonia assimilation in Anabaena spp., was partially inhibited by the presence of AZAT at concentrations which are effective in triggering heterocyst formation (15% inhibition at 10 microM AZAT and up to 85% inhibition at 1.0 mM AZAT). Azaserine, a glutamine analog and potent glutamate synthase inhibitor, had no effect on the triggering of heterocyst development from undifferentiated batch and continuous cultures of Anabaena sp. strain CA. However, the presence of 1.0 microM azaserine significantly decreased the intracellular glutamate pool and increased the glutamine pool. The addition of AZAT also caused a decrease in the C-phycocyanin content of Anabaena sp. strain CA as a result of its proteolytic degradation. AZAT also had an inhibitory effect on the nitrogenase activity of Anabaena sp. strain CA. All these results suggest that AZAT causes a general nitrogen starvation of Anabaena sp. strain CA filaments, triggering heterocyst synthesis.
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PMID:Nitrogen starvation mediated by DL-7-azatryptophan in the cyanobacterium Anabaena sp. strain CA. 310 56

1. The effect of starvation on the metabolism of gut glutamine and ketone-bodies of peak lactating, non-lactating and virgin rats was investigated. 2. The arterial blood ketone-body concentration was increased by approximately 7-, 6- and 13-fold in 48 h-starved virgin, non-lactating and lactating rats, respectively. 3. The arterial blood glutamine concentration was decreased by approximately 32% in 48 h-starved lactating rats (p less than 0.001). 4. The maximal activity of phosphate-dependent glutaminase was increased or decreased in the small intestine of fed or 48 h-starved peak-lactating rats, respectively. 5. Portal drained viscera blood flow increased by approximately 25% in peak-lactating rats. 6. Arteriovenous difference measurements for ketone-bodies across the gut of 48 h-starved rats showed an increase in net uptake of ketone-bodies by approximately 10-, 17- and 29-fold in virgin, non-lactating and lactating rats, respectively. 7. Glutamine was extracted by the gut of peak-lactating rats at a rate of 487 nmol/100 g of body wt. which was greater by approximately 33% (p less than 0.001) than that of virgin or non-lactating animals. In peak lactating rats, 48 h-starvation resulted in marked decreases in the rates of glutamine removal from the circulation (p less than 0.001) which was accompanied by decreased rates of release of glutamate, alanine and ammonia.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Glutamine and ketone-body metabolism in the small intestine of starved peak-lactating rats. 313 91

Measurement of the arteriovenous differences for free amino acids across rat kidney reveals that glycine and citrulline are removed and serine and arginine are added to the circulation. In addition, glutamine is taken up in large quantities by kidneys of animals that need to excrete large quantities of acid (e.g., diabetic animals, NH4Cl-fed animals, and animals fed a high protein diet). Glutamine is the major precursor of urinary ammonia and thus renal glutamine metabolism plays a key role in acid-base homeostasis. This process occurs primarily in the cells of the convoluted proximal tubule. Glutamine carbon is converted to glucose in acidotic rats and is totally oxidized in dogs. Regulation of glutamine metabolism occurs at two levels: acute regulation and chronic regulation. Acute regulation is, in part, mediated through a fall in intracellular [H+]. This activates alpha-ketoglutarate dehydrogenase and, ultimately, glutaminase. Chronic regulation involves induction of key enzymes, including, in the rat, glutaminase, glutamate dehydrogenase, and phosphoenolpyruvate carboxykinase. During the acidosis of prolonged starvation, the kidneys' requirement for glutamine must be met from muscle proteolysis and thus becomes a drain on lean body mass. Serine synthesis occurs by two separate pathways: from glycine by the combined actions of the glycine cleavage enzyme and serine hydroxymethyltransferase and from gluconeogenic precursors using the phosphorylated-intermediate pathway. Both pathways are located in the cells of the proximal tubule. Conversion of glycine to serine is ammoniagenic and the activity of the glycine cleavage enzyme is increased in acidosis. The function of serine synthesis by the phosphorylated-intermediate pathway is not apparent.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The 1986 Borden award lecture. The role of the kidney in amino acid metabolism and nutrition. 332 68

The provision of small amounts of glucose during fasting is known to spare body protein and to attenuate markedly the metabolic response to starvation. These actions, which are not shared by fat, are generally thought to depend on the ability of exogenous glucose to stimulate insulin secretion. To determine whether fructose, a very weak insulin secretagogue, will also conserve nitrogen and alter the response to fasting, we infused small amounts of fructose, 100 g/d (375 kcal), into 7 obese subjects during a 10-day fast: 4 received fructose days 7 to 10, and 3 received fructose days 1 to 7. Fructose virtually abolished (all P less than 0.05-0.01) the fasting induced: (a) fall in glucose and insulin and rise in glucagon, (b) fall in triiodothyronine, (c) ketosis and acidosis, (d) increased ammonia excretion, (e) hyperuricemia (and hypouricosuria), and (f) fall in plasma alanine and rise in branched chain amino acids. Fructose also significantly reduced urinary sodium loss. Moreover, fructose exerted a prominent protein-sparing action, even though plasma insulin concentrations never exceeded postabsorptive levels. Excretion of total nitrogen was reduced by 40% to 50% during periods of fructose infusion, reflecting significant suppression of both urea and ammonia generation (all P less than 0.05-0.01). Most plasma glucogenic amino acids rose significantly during fructose administration. We conclude that low-dose fructose infusion essentially abolishes the entire hormone-substrate response to fasting, and spares body protein without raising insulin above postabsorptive levels.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nitrogen conservation in starvation revisited: protein sparing with intravenous fructose. 351 Mar 63

When mixed ruminal bacteria were provided with growth rate limiting amounts of mixed carbohydrates, more than 50 mg ammonia/L were required for maximal protein synthesis. Microbial protein synthesis declined when ammonia concentration was less than 50 mg/L and unfermented carbohydrates increased. Ammonia starvation also decreased growth efficiency. Intracellular ammonia increased as a linear function of extracellular ammonia, but the intracellular concentration was always at least 160 mg/L higher than the extracellular concentration. Maximal protein synthesis was not observed until intracellular ammonia was greater than 220 mg/L. The concentration gradient of ammonia across cell membranes ranged from 15-fold to 1.8-fold and indicated that some of the ruminal bacteria may have active transport mechanisms for ammonia. These concentration gradients were, however, far less than those reported for bacteria from other habitats. The ruminal bacteria left more than 12 mg ammonia/L when carbohydrates were still available, and this observation was consistent with the assumption that active ammonium transport was not readily or maximally induced.
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PMID:Concentration of ammonia across cell membranes of mixed rumen bacteria. 359 37

The study of uterine metabolism in pregnancy under chronic steady-state conditions has been confined to large mammals and, more recently, to the guinea pig. The pregnant rabbit is of interest because of its short gestation and large litter size. We developed an indirect approach involving retrograde catheterization of the uterine venous drainage, permitting measurement of both uterine metabolic quotients and uterine uptakes. Radioactive microspheres were used to measure blood flow. A large lactate and ammonia efflux from the uterus was found. In the fed state, ketogenic substrates were taken up in small amounts. However, during starvation a significant increase in ketoacid uptake was observed with a concurrent fall in acetate uptake. There was a large glucose/oxygen quotient across the uterus, but the glucose plus lactate/oxygen quotient was comparable to that found in the sheep and guinea pig (0.6 +/- 0.1). It is apparent that in all three species studied under chronic steady-state conditions (sheep, guinea pig, and rabbit) there is a large glucose uptake associated with a net lactate production, and fuels other than glucose and lactate must be used by the uterus.
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PMID:Uterine metabolism of the pregnant rabbit under chronic steady-state conditions. 370 43

Studies were conducted to determine whether rainbow trout fingerlings possess the ability to synthesize arginine via the urea cycle. Several urea cycle enzymes were detected in trout tissues. An experiment was conducted to determine whether the enzymes increase in response to starvation or in response to dietary protein level (0, 30, 40, 50% protein). Although some effects were observed, they did not appear to be consistent with the function of the urea cycle as a mechanism of detoxifying ammonia in the fish. The activities of kidney arginase and liver and muscle carbamoyl phosphate synthetase (CPS) were higher (P less than 0.05) when protein was omitted from the diet (P less than 0.05) than when it was present but were unaffected by protein level otherwise. The activities of liver arginase and kidney and muscle CPS and ornithine transcarbamoylase (OTC) were higher (P less than 0.05) in starved fish than in fish that received adequate levels of protein. Liver CPS and OTC were lower in starved fish than in fish fed 30% protein. L-[l-14C]ornithine hydrochloride and L-[carbamoyl-14C]citrulline, injected intraperitoneally, were incorporated into tissue arginine, a finding consistent with arginine biosynthesis via the urea cycle. When one-half of dietary arginine was replaced by equimolar amounts of glutamic acid, ornithine or citrulline, glutamic acid markedly reduced growth (P less than 0.05), whereas growth was depressed only slightly by ornithine (P less than 0.05) and not depressed by citrulline (P greater than 0.05). We conclude that trout have a urea cycle that provides for potential arginine biosynthesis.
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PMID:Urea cycle activity and arginine formation in rainbow trout (Salmo gairdneri) 376 Oct 21


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