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

Administration of KC1 0.5 mmol/kg/day to subjects undergoin prolonged starvation reduced daily urinary ammonium and beta-hydroxybutyrate excretion by one-third. These changes were accompanied by an improvement in potassium balance and an increased rate of chloride excretion. A similar fall in ammonium excretion occurred in a second group of subjects after administration of KHCO3 0.5 mmol/kg/day. Ketone body and bicarbonate excretion remained unchanged in this group while potassium balance improved. In both the first and second groups urine pH fell significantly as the rate of excretion of urinary buffer (ammonium) decreased. When the dose of KHCO3 was increased to 1.5-2.0 mmol/kg/day in fasting subjects, the urine was alkalinized, and ammonium excretion fell to negligible levels, resulting in nitrogen sparing of 2.0 g/day. The results indicate that one-half of the increase in ammonium excretion observed in starvation is due to potassium deficiency. Nitrogen wastage caused by losses of urinary ammonium during starvation can be virtually eliminated by potassium supplementation and urinary alkalinization. The decrease in beta-hydroxybutyrate excretion after potassium chloride administration was not caused by a fall in the rate of nonionic diffusion of this organic acid related to the reduction in urine pH. The reason for the fall in beta-hydroxybutyrate excretion is not apparent, though it was associated with an increase in chloride excretion.
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PMID:The role of potassium in the control of ammonium excretion during starvation. 0 35

The intracellular levels of glutamine synthetase (GS) in Anacystis nidulans grown under different conditions were determined using a whole-cell assay. Nitrate-grown cells have 64% more GS than cells grown in ammonium sulfate. Nitrogen starvation does not affect GS levels appreciably. Incubation of nitrate-grown cells with ammonium sulfate does not change the ratio of gamma-glutamyl transferase activities stimulated by Mg2+ and Mn2+ ions. An in vitro test of adenylylation indicates that algae do not have an endogenous adenylyl transferase (ATase) and that algal GS is not adenylylatable by the Klebsiella aerogenes ATase. Some characteristics of the GS-membrane complex were determined by centrifugation of the complex under varying conditions of pH and ionic strength. In this way, it was shown that acid pH (4.5) stabilizes the complex and high ionic strength tends to solubilize the enzyme. A simple partial purification of GS (89-fold) was developed based on the sedimentation properties of GS.
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PMID:Distinctive properties of glutamine synthetase from the cyanobacterium Anacystis nidulans. 3 92

Urinary orotidine and orotic acid have been determined in a patient with purine nucleoside phosphorylase (PNP) deficiency under various dietary therapeutic conditions. For this purpose a new procedure for the analysis of both compounds has been developed, consisting of prefractionation with Dowex 1X8, followed by two HPLC steps on a micro Bondapak NH2 and a micro Bondapak C18 column. With this method normal as well as slightly elevated excretions of orotic acid have been found in our patient. No evidence was obtained for inhibition of OPRT by purine (deoxy)nucleosides as a cause of pyrimidine starvation. A significant increase of urinary orotidine was found after loading with allopurinol. For comparison excretory values in a patient with ornithine transcarbamylase deficiency and also in a patient with orotic aciduria type I are shown. The possible cause of the slight increase in urinary orotic acid in our patient has been discussed.
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PMID:Urinary excretion of orotic acid, orotidine and other pyrimidines in a patient with purine nucleoside phosphorylase deficiency. 10 38

When washed spleen slices from fed rats are incubated with 3 mm-[U-14C]glucose, the rate of glucose utilization (46.2 mumol/h per g dry wt.) is sufficient to account, theoretically, for 80% of the O2 consumption. Measurement of net lactate production, however, and the fate of the radioactive carbon, indicates that the contribution of glucose to the respiratory fuel of the tissue is only 25-30% whereas 60-70% of the glucose utilized is converted into lactate. At saturating glucose concentrations (above 5 mm) its contribution to the respiratory fuel of the slice is increased to a maximum value of 34-39%. Only 2% of the glucose utilized is metabolized via the oxidative steps of the pentose phosphate pathway. Starvation for 72 h marginally increases both the rate of glucose utilization (by 21%) and its net contribution to the respiratory fuel (by 29%). Insulin, glucagon, adrenaline and adenosine 3':5'-cyclic monophosphate have no significant effect on either the rate of glucose utilization or on the pattern of radioactive isotope distribution. The uptake of glucose is increased by only 20%, whereas the production of lactate doubles when slices are incubated under anaerobic conditions. In assessing the suitability of spleen slices for metabolic studies, the only serious major perturbation, compared with the freeze-clamped organ, is an elevated mitochondrial [NAD+]/[NADH] ratio (connected with increased endogenous NH3 production) that is partially restored to normal values on incubation with glucose. Equal proportions of erythrocytes and leucocytes are found in the washed spleen slice. Metabolic contributions of the constituent cell populations in the washed slice are calculated and it is concluded that lymphocytes account for the major part of the glycolytic metabolism (80-90%), whereas the contribution of erythrocytes is insignificant.
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PMID:Regulation of carbohydrate metabolism in lymphoid tissue. Quantitative aspects of [U-14C]glucose oxidation by rat spleen slices. 17 88

Methylamine (methylammonium ion) entered Saccharomyces cerevisiae X2180-A by means of a specific active transport system. Methylamine uptake was pH dependent (maximum rate between pH 6.0 and 6.5) and temperature dependent (increasing up to 35 C) and required the presence of a fermentable or oxidizable energy source in the growth medium. At 23 C the vmax for methylamine transport was similar 17 nmol/min per mg of cells (dry weight) and the apparent Km was 220 muM. The transport system exhibited maximal activity in ammonia-grown cells and was repressed 60 to 70 percent when glutamine or asparagine was added to the growth medium. There was no significant derepression of the transport system during nitrogen starvation. Ammonia (ammonium ion) was a strong competitive inhibitor of methylamine uptake, whereas other amines inhibited to a much lesser extent. Mutants selected on the basis of their reduced ability to transport methylamine (Mea-R) simultaneously exhibited a decreased ability to transport ammonia.
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PMID:Methylamine and ammonia transport in Saccharomyces cerevisiae. 23 81

Nitrogen-starved cultures of the alga Anabaena cylindrica 629 produced hydrogen and oxygen continuously for 7 to 19 days. Hydrogen production attained a maximum level after 1 to 2 days of starvation and was followed by a slow decline. The maximum rates were 30 ml of H2 evolved per liter of culture per h or 32 mul of H2 per mg of dry weight per h. In 5 to 7 days the rate of H2 evolution by the more productive cultures fell to one-half its maximum value. The addition of 10(-4) to 5 X 10(-4) M ammonium increased the rate of oxygen evolution and the total hydrogen production of the cultures. H2-O2 ratios were 4:1 under conditions of complete nitrogen starvation and about 1.7:1 after the addition of ammonium. Thus, oxygen evolution was affected by the extent of the nitrogen starvation. Thermodynamic efficiencies of converting incident light energy to free energy of hydrogen via algal photosynthesis were 0.4%. Possible factors limiting hydrogen production were decline of reductant supply and filament breakage. Hydrogen production by filamentous, heterocystous blue-green algae could be used for development of a biophotolysis system.
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PMID:Hydrogen production by nitrogen-starved cultures of Anabaena cylindrica. 40 9

1. Neither alloxan-diabetes nor starvation affected the rate of glucose production in hepatocytes incubated with lactate, pyruvate, propionate or fructose as substrates. In contrast, glucose synthesis with either alanine or glutamine was increased nearly 3- and 12-fold respectively, in comparison with that in fed rabbits. 2. The addition of amino-oxyacetate resulted in about a 50% decrease in glucose formation from lactate in hepatocytes isolated from fed, alloxan-diabetic and starved rats, suggesting that both mitochondrial and cytosolic forms of rabbit phosphoenolpyruvate carboxykinase function actively during gluconeogenesis. 3. Alloxan-diabetes resulted in about 2-3-fold stimulation of urea production from either amino acid studied or NH4Cl as NH3 donor, whereas starvation caused a significant increase in the rate of ureogenesis only in the presence of alanine as the source of NH3. 4. As concluded from changes in the [3-hydroxybutyrate]/[acetoacetate] ratio, in hepatocytes from diabetic animals the mitochondrial redox state was shifted toward oxidation in comparison with that observed in liver cells isolated from fed rabbits.
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PMID:Effect of alloxan-diabetes on gluconeogenesis and ureogenesis in isolated rabbit liver cells. 74 58

Yeast strains sigma1278b and Harden and Young, which synthesize only an internal constitutive form of L-asparaginase, do not grow on D-asparagine, as a sole source of nitrogen, and whole cell suspensions of these strains do not hydrolyze D-asparagine. Strains X2180-A2 and D273-10B, which possess an externally active form of asparaginase, are able to grow slowly on D-asparagine, and nitrogen-starved suspensions of these strains exhibit high activity toward the D-isomer. Nitrogen starvation of strain X218O-A2 results in coordinate increase of D- and L-asparaginase activity; the specific activity observed for the D-isomer is approximately 20% greater than that observed for the L-isomer. It was observed, in studies with cell extracts, that hydrolysis of D-asparagine occurred only with extracts from nitrogen-starved cells of strains that synthesize the external form of asparaginase. Furthermore, the activity of the extracts toward the D-isomer was always higher than that observed with the L-isomer. A 400-fold purified preparation of external asparaginase from Saccharomyces cerevisiae X218U-A2 hydrolyzed D-asparagine with an apparent Km of 0.23 mM and a Vmax of 38.7 mumol/min per mg of protein. D-Asparagine was a competitive inhibitor of L-asparagine hydrolysis and the Ki determined for this inhibition was approximately equal to its Km. These data suggest that D-asparagine is a good substrate for the external yeast asparaginase but is a poor substrate for the internal enzyme.
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PMID:Utilization of D-asparagine by Saccharomyces cerevisiae. 76 32

Pacaud and Uriel described an enzyme from Escherichia coli ("protease I") that hydrolyzes acetyl phenylalanine naphthyl ester (APNE). We examined the possible involvement of this enzyme in intracellular protein degradation, its subcellular distribution, and its proteolytic activity. Although the APNE-hydrolyzing activity is localized primarily in the periplasm, proteolytic activity against casein was found in the periplasm, membrane, and cytoplasm with similar specific activities. The APNE-hydrolyzing enzyme did not appear to contribute to the proteolytic activity of the periplasm. A mutant deficient in APNE-hydrolyzing activity lacked all activity in the periplasm but showed a slight percentage of residual activity in the cytoplasm. Extracts of such cells were normal in their ability to hydrolyze casein. The mutant was indistinguishable from wild-type cells in its rate of protein degradation during growth or glucose starvation and in the ability to rapidly degrade puromycin-containing polypeptides. Nitrogen starvation, which increased protein breakdown severalfold, affected neither the total amount nor the distribution of APNE-hydrolyzing activity. The mutant showed no defect in its ability to cleave small phenylalanine-containing peptides released during protein degradation. The mutant and wild-type cells are equally able to hydrolyze exogenously supplied phenylalanyl peptides. These experiments suggest that the APNE-hydrolyzing enzyme is not required for protein degradation and that "protease I" is probably not a protease.
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PMID:Role and location of "protease I" from Escherichia coli. 79 31

An asporogenous mutant of Bacillus megaterium KM, blocked at stage I of sporulation, is cultivated in different conditions which usually lead to sporulation (Nitrogen, carbon, phosphate starvation). Aklaline phosphatase appears only in inorganic phosphate starvation like the wild type, but a glucose dehydrogenase activity also appears in phosphate starvation and so, is dissociated from sporulation.
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PMID:[Variations of enzymatic activities in an asporogenic mutant of Bacillus megaterium for various nutritional deficiencies]. 82 32


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