UMLS:C0038187 - FACTA Search

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

Data are presented on the metabolic and endocrine effects of intravenous infusions in normal fasting man observed under highly controlled conditions over a period of six to eight days duration. There are comparative data on a variety of intravenous feeding programs. The data on total starvation are based on studies from the literature, some of which were carried out in this laboratory. The data on low dose glucose, high dose glucose, glycerol, fat emulsion, and amino acids, each given separately, demonstrate changes seen with simple infusion of a single substrate in fasting. These data are now compared with the utilization of amino acid infusions when accompanied by low dose glucose, high dose glucose, glycerol, and fat emulsion. In all, nine experimental intravenous feeding programs are presented, based on data from 35 subjects observed over a total of 370 subject-days. The findings show a strong interaction between glucose or lipid and protein metabolism. In fasting, glucose had protein sparing effect, most evident when given at high dose. Glycerol, in an amount equal to that contained in 2000 ml of ten per cent fat emulsion, had a mild protein sparing effect. Fat emulsion was no more effective. When amino acids were given alone, normal fasting human subjects were always in negative nitrogen balance with the daily nitrogen loss half that seen in starvation alone. Although amino acids given alone have a protein sparing effect, this is accomplished only at the expense of a high nitrogen excretion including an amount equivalent to the entire infusion plus an additional loss from the body's native proteins. The provision of energy yielding non-protein substrates with the amino acids markedly improved nitrogen economy in the following order: glycerol, low dose glucose, fat emulsion and high dose glucose. When caloric provision with glucose approached the isocaloric level for normal diet, the utilization of amino acids was maximized. When given with amino acids, fat emulsion was more effective than the available glycerol alone. THE ACCOMPANYING ENDOCRINE AND BIOCHEMICAL CHANGES SUGGEST THAT THE MILIEU FOR IDEAL UTILIZATION OF INFUSED AMINO ACIDS IS VARIABLE: ketones at low range (carbohydrate) or moderately elevated (fat emulsion); insulin elevated (carbohydrate) or unchanged (fat emulsion). The utilization of the infused amino acids was markedly improved in both endocrine settings, suggesting that it is the provision of energy as substrate as well as the endocrine setting that determines amino acid utilization. There were other changes in plasma intermediates, particularly fatty acids, glucose and urea, all consistent with the concept that when amino acids are given without other substrates, the amino acids must be maximally utilized for gluconeogenesis. When other substrates are provided (particularly glucose at high dose) then this mandate no longer exists and protein synthesis from the amino acids is favored. Several of the plasma amino acid concentrations responded to glucose when added to amino acid infusion. Amino acids alone produced increases in concentration of all the amino acids found in the infusion with the exception of alanine, arginine, and threonine. Many of these increases were abated by the addition of glucose to the amino acid infusion, suggesting an increased utilization rate. Glycerol and fat emulsion, while modulating increases in the plasma amino acid concentration, did so to a lesser extent than did glucose. This lowering of amino acid concentration was unaccompanied by an increase in urinary excretion. The assumption is therefore made that the provision of the added glucose favors the incorporation of amino acid into protein. There is no evidence from these data to suggest that a rising concentration of ketones in the blood favors amino acid utilization or protein synthesis.
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PMID:Substrate interaction in intravenous feeding: comparative effects of carbohydrate and fat on amino acid utilization in fasting man. 41 Mar 76

Sulfur-deficient tRNA, isolated from Escherichia coli HfrC, rel-, met-, cys-, lambda, after cysteine starvation, was found to have an increased acceptance of isoleucine in proportion to the deficiency of 4-thiouridine. Isoleucine acceptance was not altered in the presence of other amino acids of CTP, and the higher acceptance was observed over a wide range of magnesium, isoleucine, tRNA and enzyme concentrations. The Vmax value for sulfur-deficient tRNA was more than three times greater than observed for normal tRNA. Methylated albumin kieselguhr (MAK) chromatography revealed three isoacceptor peak for normal tRNA, while sulfur-deficient tRNA was missing tRNAile, and exhibited a larger, shifted peaks for tRNA normal tRNA, while sulfur-deficient tRNA was missing tRNAille 2, and exhibited a large shifted peak for tRNAile 3 . Treatment with crude RNA sulfurtransferase both lowered the isoleucine acceptance for sulfur-deficient tRNA to that seen for normal tRNA, and restored the missing isoacceptor on MAK. The possibility that thionucleotides may play a role in the aminoacylation of tRNAile in E. coli is discussed.
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PMID:Increased isoleucine acceptance by sulfur-deficient transfer RNA from Escherichia coli. 78 31

Carnitine is synthesized from lysine and methionine. In the rat, inadequate intake of either of these essential amino acids causes carnitine depletion. Inasmuch as protein deficiency is common in the hospital population, we have investigated the possible occurrence of nosocomial carnitine deficiency. Fasting serum carnitine concentration was measured in 16 normal and 247 patients in 16 disease groups. Normal range of carnitine was 55-103 muM. Only the cirrhotic group showed significant (P < 0.05) hypocarnitinemia. 14 of 36 hospitalized cirrhotics had subnormal values for serum carnitine. The creatinine/height index, midarm muscle circumference, and triceps skin-fold thickness indicated protein-calorie starvation in the 14 hypocarnitinemic liver patients. In six of the hypocarnitinemic cirrhotics (average serum level 50% of normal), spontaneous dietary intakes of carnitine, lysine, and methionine were measured and found to be only 5-15% as great as in six normocarnitinemic, healthy controls. When these six cirrhotic and six normal subjects were given the same lysine-rich, methionine-rich, and carnitine-free nutritional intake, the normals maintained normal serum carnitine levels and excreted 100 mumol/day, whereas the cirrhotics' serum level fell to 25% of normal, and urinary excretion declined to 15 mumol/day. Seven hypocarnitinemic cirrhotics died. Postmortem concentrations of carnitine in liver, muscle, heart, kidney, and brain averaged only one-fourth to one-third those in corresponding tissues of eight normally nourished nonhepatic patients who died after an acute illness of a 1-3-day duration. THESE DATA SHOW THAT CARNITINE DEPLETION IS COMMON IN PATIENTS HOSPITALIZED FOR ADVANCED CIRRHOSIS, AND THAT IT RESULTS FROM THREE FACTORS: substandard intake of dietary carnitine; substandard intake of lysine and methionine, the precursors for endogenous carnitine synthesis; and loss of capacity to synthesize carnitine from lysine and methionine.
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PMID:Deficiency of carnitine in cachectic cirrhotic patients. 89 75

It has been shown that the net rate of gluconeogenesis from cysteine was only 10% the rate observed from pyruvate. This suggested that the rate limiting step in gluconeogenesis from cysteine was between cysteine and pyruvate. Evidence is presented showing that the cysteine-sulfinate pathway does not play a regulating role in the conversion of cysteine to glucose. Thus, liver cysteine desulfhydrase (CDS) activity and hydrogen sulfide production were evaluated for their potential effects. Liver CDS activity was increased by a 3 day starvation, by feeding a 90% casein diet or a 4% cysteine + 86% casein diet. In all cases the activity of the enzyme was in excess of that required to account for the rate of conversion of cysteine to glucose observed, thus the potential activity of this enzyme was not a rate limiting factor. The possible effect of H2S, an end product of the CDS reaction, on gluconeogenesis from cysteine was evaluated. The addition of NaHS abolished the glucogenic response observed from cysteine, but had very little effect on glucoeogenesis from lactate, suggesting that accumulated H2S may inhibit CDS, marking CDS rate limiting in the conversion of cysteine to pyruvate.
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PMID:Fractors affecting the rate of gluconeogenesis from L-cysteine in the perfused rat liver. 95 11

Transfer RNA from Escherichia coli C6, a Met-, Cys-, relA- mutant, was previously shown to contain an altered tRNA(Ile) which accumulates during cysteine starvation (Harris, C.L., Lui, L., Sakallah, S. and DeVore, R. (1983) J. Biol. Chem. 258, 7676-7683). We now report the purification of this altered tRNA(Ile) and a comparison of its aminoacylation and chromatographic behavior and modified nucleoside content to that of tRNA(Ile) purified from cells of the same strain grown in the presence of cysteine. Sulfur-deficient tRNA(Ile) (from cysteine-starved cells) was found to have a 5-fold increased Vmax in aminoacylation compared to the normal isoacceptor. However, rates or extents of transfer of isoleucine from the [isoleucyl approximately AMP.Ile-tRNA synthetase] complex were identical with these two tRNAs. Nitrocellulose binding studies suggested that the sulfur-deficient tRNA(Ile) bound more efficiently to its synthetase compared to normal tRNA(Ile). Modified nucleoside analysis showed that these tRNAs contained identical amounts of all modified bases except for dihydrouridine and 4-thiouridine. Normal tRNA(Ile) contains 1 mol 4-thiouridine and dihydrouridine per mol tRNA, while cysteine-starved tRNA(Ile) contains 2 mol dihydrouridine per mol tRNA and is devoid of 4-thiouridine. Several lines of evidence are presented which show that 4-thiouridine can be removed or lost from normal tRNA(Ile) without a change in aminoacylation properties. Further, tRNA isolated from E. coli C6 grown with glutathione instead of cysteine has a normal content of 4-thiouridine, but its tRNA(Ile) has an increased rate of aminoacylation. We conclude that the low content of dihydrouridine in tRNA(Ile) from E. coli cells grown in cysteine-containing medium is most likely responsible for the slow aminoacylation kinetics observed with this tRNA. The possibility that specific dihydrouridine residues in this tRNA might be necessary in establishing the correct conformation of tRNA(Ile) for aminoacylation is discussed.
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PMID:Modified nucleosides and the chromatographic and aminoacylation behavior of tRNA(Ile) from Escherichia coli C6. 245 69

Choline-O-sulfate uptake by Penicillium notatum showed the following characteristics. (i) Transport was mediated by a permease which is highly specific for choline-O-sulfate. No significant inhibition of transport was caused by choline, choline-O-phosphate, acetylcholine, ethanolamine-O-phosphate, ethanolamine-O-sulfate, methanesulfonyl choline, 2-aminoethane thiosulfate, or the monomethyl or dimethyl analogues of choline-O-sulfate. Similarly, no significant inhibition was caused by any common sulfur amino acid or inorganic sulfur compound. Mutants lacking the inorganic sulfate permease possessed the choline-O-sulfate permease at wild-type levels. (ii) Choline-O-sulfate transport obeyed saturation kinetics (K(m) = 10(-4) to 3 x 10(-4)m; V(max) = 1 to 6 mumoles per g per min). The kinetics of transport between 10(-9) and 10(-1)m external choline-O-sulfate showed that only one saturable mechanism is present. (iii) Transport was sensitive to 2,4-dinitrophenol, azide, N-ethylmaleimide, p-chloromercuribenzoate, and cyanide. Ouabain, phloridzin, and eserine had no effect. (iv) Transport was pH-dependent with an optimum at pH 6. Variations in the ionic strength of the incubation medium had no effect. (v) Transport was temperature-dependent with a Q(10) of greater than 2 between 3 and 40 C. Transport decreased rapidly above 40 C. (vi) Ethylenediaminetetraacetate (sodium salts, pH 6) had no effect, nor was there any stimulation by metal or nonmetal ions. Cu(++), Ag(+), and Hg(++) were inhibitory. (vii) The initial rate at which the ester is transported was independent of intracellular hydrolysis. After long periods of incubation (> 10 min), a significant proportion of the transported choline-O-sulfate was hydrolyzed intracellulary. In the presence of 5 x 10(-3)m external choline-O-sulfate, the mycelia accumulated choline-O-sulfate to an apparent intracellular concentration of 0.075 m by 3 hr. Transport was unidirectional. No efflux or exchange of (35)S-choline-O-sulfate was observed when preloaded mycelia were suspended in buffer alone or in buffer containing a large excess of unlabeled choline-O-sulfate. (viii) The specific transport activity of the mycelium depended on the sulfur source used for growth. (ix) Sulfur starvation of sulfur-sufficient mycelium resulted in an increase in the specific transport activity of the mycelium. This increase was prevented by cycloheximide, occurred only when a metabolizable carbon source was present, and resulted from an increase in the V(max) of the permease, rather than from a decrease in K(m). The increase could be partially reversed by refeeding the mycelia with unlabeled choline-O-sulfate, sulfide, sulfite, l-homocysteine, l-cysteine, or compounds easily converted to cysteine. The results strongly suggested that the choline-O-sulfate permease is regulated primarily by repression-derepression, but that intracellular choline-O-sulfate and cysteine can act as feedback inhibitors.
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PMID:Specificity and control of choline-O-sulfate transport in filamentous fungi. 572 99

As was shown using various reagents (Ag+, Cd2+) and solvents (ethanol, methanol), Thiobacillus ferrooxidans cells accumulate colloidal sulfur when they grow in the medium 9K containing elemental sulfur. Colloidal sulfur is accumulated in the periplasmic space, in large, bipolarly arranged spherical structures and in simple invaginates of the cytoplasmic membrane. T. ferrooxidans cells accumulate the sulfur at a highest rate during the stationary phase of growth and can use it as a source of energy under the conditions of starvation. The factors causing sulfur accumulation in T. ferrooxidans cells are discussed.
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PMID:[Nature of the sulfur-containing component and its function in Thiobacillus ferrooxidans]. 664 91

Saccharomyces cerevisiae wine-producing yeast cultures grown under model winemaking conditions could be induced to liberate hydrogen sulfide (H2S) by starvation for assimilable nitrogen. The amount of H2S produced was dependent on the yeast strain, the sulfur precursor compound, the culture growth rate, and the activity of the sulfite reductase enzyme (EC 1.8.1.2) immediately before nitrogen depletion. Increased H2S formation relative to its utilization by metabolism was not a consequence of a de novo synthesis of sulfite reductase. The greatest amount of H2S was produced when nitrogen became depleted during the exponential phase of growth or during growth on amino acids capable of supporting short doubling times. Both sulfate and sulfite were able to act as substrates for the generation of H2S in the absence of assimilable nitrogen; however, sulfate reduction was tightly regulated, leading to limited H2S liberation, whereas sulfite reduction appeared to be uncontrolled. In addition to ammonium, most amino acids were able to suppress the liberation of excess H2S when added as sole sources of nitrogen, particularly for one of the strains studied. Cysteine was the most notable exception, inducing the liberation of H2S at levels exceeding that of the nitrogen-depleted control. Threonine and proline also proved to be poor substitutes for ammonium. These data suggest that any compound that can efficiently generate sulfide-binding nitrogenous precursors of organic sulfur compounds will prevent the liberation of excess H2S.
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PMID:Regulation of hydrogen sulfide liberation in wine-producing Saccharomyces cerevisiae strains by assimilable nitrogen. 757 81

The liberation of H2S is a common problem afflicting wine fermentation. Sulphite reductase activity of a commercial wine yeast was investigated to define its involvement in this process. The activity studied here differed from those characterized previously from cider and bakers' yeasts by displaying a greater sensitivity to cold, low ionic strength and possibly, proteolytic action. These differences necessitated the development of a new method of quantification. Through this method, the onset of H2S liberation was shown not to be a result of variations in the levels of sulphite reductase activity. Thus, high levels of activity which occurred during the exponential phase of growth were not necessarily accompanied by the liberation of H2S. Similarly, nitrogen-starved cultures which liberated H2S showed no corresponding increase in sulphite reductase activity from prestarvation levels. In fact, rates of H2S liberation from cultures and in enzyme assays agreed closely. A short-term independence of sulphite reductase activity from culture nitrogen status was therefore evident. The only influence of nitrogen was achieved in its absence when enzyme activity decayed with a half-life (4.25 h) which was comparable to that induced by the presence of cycloheximide (5.75 h). A proposed transcriptional control mechanism mediated by methionine derivatives was only partly effective in this strain although an in vitro inhibitory effect of methionine was implicated. These data therefore support the notion that H2S liberation in response to nitrogen starvation stems from a failure of metabolism to sequester H2S which continues to be formed, at least initially, at prestarvation rates.
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PMID:Determination of sulphite reductase activity and its response to assimilable nitrogen status in a commercial Saccharomyces cerevisiae wine yeast. 881 60

O-Acetylserine(thiol)lyase (OASTL) enzyme catalyzes the cysteine biosynthesis in photosynthetic organisms. In mature Arabidopsis thaliana the highest activity level is observed in non-photosynthetic tissues like roots, that also show significant amount of protein detected by Western blot analysis. By means of specific probes for cytosolic and plastidic OASTL isoenzyme transcripts, cytosolic isoenzyme has been determined to be predominantly expressed in roots, while the expression of the plastidic isoform is high in both green and non-green tissues. Sulfur starvation produces an increase on the OASTL activity level in all the Arabidopsis organs examined, this effect being particularly significant in the aerial parts of the plant.
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PMID:The role of roots in cysteine biosynthesis by Arabidopsis thaliana. 1022 10

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