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

Polysomes were extracted from Bacillus subtilis cells starved for a required amino acid. The monosome peak appeared soon after starvation; no difference in the rate of degradation was detected when the cells were starved for arginine or tryptophan in a double auxotroph. RNA production during starvation was not inhibited by actinomycin, but the molecular weight of the product made in the presence of the antibiotic was much lower. Indications that stable messenger ribonucleic acid is present for up to 90 min after amino acid starvation are also presented.
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PMID:Polyribosomes from Bacillus subtilis during amino acid starvation in the presence and in the absence of actinomycin. 419 20

Plasma was filtered on G50 Sephadex, and two components of circulating insulin, "little" insulin and "big" insulin, were measured by immunoassay. The former component is indistinguishable from insulin, whereas the latter more closely resembles proinsulin and the other insulin-like substances isolated from the pancreas. In thin normal subjects, the fraction of plasma insulin that was big insulin (per cent "big"). 15-30 min after oral glucose, was less than 5%; per cent big rose 2- to 8-fold over the next hour and by 90-120 min represented 5-29% of the plasma insulin. In young thin subjects with idiopathic glucose intolerance associated with normal concentrations of plasma insulin, an identical pattern of big insulin was observed. In thin subjects in whom elevations of per cent big at 90-120 min during the standard test were only modest, starvation for 48 hr before the glucose administration resulted in a more pronounced rise in the per cent big insulin. Early after glucose administration to obese and acromegalic subjects, the per cent big was higher than in thin subjects. The magnitude of the elevation was roughly correlated with elevations in the fasting plasma insulin concentration. By 90-120 min, the per cent big in obese and acromegalic patients was the same range as in the thin subjects. Intravenously administered arginine and tolbutamide in a small number of subjects yielded a response that was similar to oral glucose; the per cent big was low early after stimulation and increased with time. In two patients with islet cell carcinomas, the per cent big was in the same range as in normal subjects.
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PMID:Plasma insulin: fluctuations in the "big" insulin component in man after glucose and other stimuli. 431 Dec 36

Heme oxygenase (HO), the enzyme system catalyzing the conversion of heme to bilirubin, was studied in the liver and spleen of fed, fasted, and refed rats. Fasting up to 72 hr resulted in a threefold increase in hepatic HO activity, while starvation beyond this period led to a gradual decline in enzyme activity. Refeeding of rats fasted for 48 hr depressed hepatic HO activity to basal values within 24 hr. Splenic HO was unaffected by fasting and refeeding. Hypoglycemia induced by injections of insulin or mannose was a powerful stimulator of hepatic HO. Glucose given together with the insulin abolished the stimulatory effect of the latter. Parenteral treatment with glucagon led to a twofold, and with epinephrine to a fivefold, increase of hepatic HO activity; arginine, which releases endogenous glucagon, stimulated the enzyme fivefold. These stimulatory effects of glucagon and epinephrine could be duplicated by administration of cyclic adenosine monophosphate (AMP), while thyroxine and hydroxortisone were ineffective. Nicotinic acid, which inhibits lipolysis, failed to modify the stimulatory effect of epinephrine. None of these hormones altered HO activity in the spleen. These findings demonstrate that the enzymatic mechanism involved in the formation of bilirubin from heme in the liver is stimulated by fasting, hypoglycemia, epinephrine, glucagon, and cyclic AMP. They further suggest that the enzyme stimulation produced by fasting may be mediated by glucagon released in response to hypoglycemia. The possibility is considered that the enhanced HO activity in the liver may increase hepatic heme turnover and hence, bilirubin production, which may explain the rise of unconjugated serum bilirubin observed in fasting or hypoglycemic individuals.
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PMID:Metabolic regulation of heme catabolism and bilirubin production. I. Hormonal control of hepatic heme oxygenase activity. 433 19

In a wild-type strain of Saccharomyces cerevisiae the tryptophan analogue dl-5-methyl-tryptophan (5MT) causes only a slight reduction of the growth rate. Uptake experiments indicate that the limited inhibition is partly due to low levels of 5MT inside the cell. On the other hand, this low concentration of 5MT leads to an increase in the activity of the tryptophan-biosynthetic enzymes. Evidence is presented that suggests that 5MT acts primarily through feedback inhibition of anthranilate synthase, the first enzyme of the pathway. A number of 5MT-sensitive mutants have been isolated, characterized, and assigned to one of the following three classes: class I, strains with altered activity and/or feedback sensitivity of anthranilate synthase; class II, strains with elevated uptake of 5MT; class III, mutants with altered regulation of the tryptophan-biosynthetic enzymes, which do not exhibit increases in activity in the presence of 5MT. This failure to exhibit increased enzyme activities in mutants of class III can also be observed after tryptophan starvation. Two mutants of class III show high sensitivity towards 3-amino-1,2,4-triazole. They can not exhibit derepression of some histidine- and arginine-biosynthetic enzymes under conditions that lead to an increase in these same enzymes in the wild-type strain.
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PMID:Regulation of tryptophan biosynthesis in Saccharomyces cerevisiae: mode of action of 5-methyl-tryptophan and 5-methyl-tryptophan-sensitive mutants. 436 May 39

In Neurospora crassa, histidine starvation of histidine mutants resulted in derepression of histidine, tryptophan, and arginine biosynthetic enzymes. The same tripartite derepression occurred in wild-type strain 74A when it was grown in medium supplemented with 3-amino-1,2,4-triazole, an inhibitor of histidine biosynthesis. Histidine-mediated derepression of tryptophan and arginine biosynthetic enzymes was not due to a lowered intracellular concentration of tryptophan or arginine, respectively. A discussion of possible mechanisms and of similar studies in prokaryotic and eukaryotic organisms is presented.
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PMID:Cross-pathway regulation: histidine-mediated control of histidine, tryptophan, and arginine biosynthetic enzymes in Neurospora crassa. 436 40

In Neurospora crassa, the starvation of tryptophan mutants for tryptophan resulted in the derepression of tryptophan, histidine, and arginine biosynthetic enzymes. This tryptophan-mediated derepression of histidine and arginine biosynthetic enzymes occurred despite the fact that the tryptophan-starved cells had a higher intracellular concentration of histidine and arginine than did nonstarved cells.
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PMID:Cross-pathway regulation: tryptophan-mediated control of histidine and arginine biosynthetic enzymes in Neurospora crassa. 436 41

Pyridoxineless mutants of Escherichia coli B stopped incorporation of nucleosides into trichloroacetic acid-insoluble material about 40 to 60 min after pyridoxine starvation was initiated, whereas incorporation of amino acids (measured the same way) slowed but did not stop for several hours. Both these incorporations and cell density were increased most effectively by the presence of either threonine or isoleucine. Arginine, glutamate, histidine, methionine, tryptophan, and tyrosine also caused significant but less dramatic increases. Inducibility of beta-galactosidase continued beyond the point where nucleic acids appeared to stop their synthesis, suggesting that messenger ribonucleic acid synthesis continued beyond ribosomal ribonucleic acid synthesis. This inducibility was also increased by isoleucine and threonine. The overall results suggest that the threonine-isoleucine biosynthetic pathway is the most sensitive to starvation for pyridoxine.
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PMID:Isoleucine and threonine can prolong protein and ribonucleic acid synthesis in pyridoxine-starved mutants of Escherichia coli B. 456 72

The concentration of rifampin necessary to affect the initiation of ribonucleic acid (RNA) synthesis quickly in Escherichia coli strains K-12 and 15TAU was about 200 mug/ml, as determined by extrapolation of the effect of the drug on the induction of beta-galactosidase synthesis. A lag in the action of rifampin of about 10 s was confirmed. Rifampin was then used as a probe to compare RNA synthesis in growing and amino acid-starved E. coli. Restoring arginine to arginine-starved strain 15TAU immediately after rifampin inhibition did not detectably restore the rate of uracil uptake to that of uninhibited cells. The residual rate of RNA synthesis (corrected for acid-soluble triphosphate specific activities) after rifampin treatment of both growing and isoleucine-starved (valine-inhibited) cultures of strain K-12 showed similar decay kinetics. These findings support the notion that amino acid starvation blocks the initiation of some RNA transcription units, but do not rule out other possibilities.
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PMID:Decay of ribonucleic acid synthesis in amino acid-starved Escherichia coli after rifampin treatment. 459 64

To clarify the relationship between thymineless death and thymineless mutagenesis, the induction of arginine revertants of Escherichia coli TAU-bar by thymine starvation was examined in physiological terms. Induced revertants were detectable both on minimal medium lacking arginine and minimal medium supplemented with 1 mug of arginine per ml. Substantial thymineless mutagenesis occurred during the period before the onset of thymineless death. Mutagenesis and loss of viability were observed upon incubation in medium lacking thymine and arginine, and both were inhibited upon incubation in medium lacking thymine and uracil. Mutagenesis also occurred during thymine starvation at 25 C, where there was relatively little loss of viability. At 37 C thymineless mutagenesis did not require complete thymine starvation, and the induction of revertants appeared to be initiated at the same suboptimal thymine concentration at which lethality was first detectable. Mutagenesis was found not to occur preferentially at the growing point of deoxyribonucleic acid replication. These results suggest that thymineless mutagenesis does not involve simply errors in base pairing due to the absence of thymine. The data also suggest that the induction of mutations and thymineless death are due to the same primary event but that mutagenesis is the more sensitive response.
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PMID:Thymineless mutagenesis in Escherichia coli. 460 83

Albumin synthesis was measured in the isolated perfused rat liver by using the livers of both well-fed and starved rats. Starvation markedly decreased albumin synthesis. The livers from starved rats were unable to increase synthesis rates after the addition to the perfusates of single amino acids or the addition of both glucagon and tryptophan. Arginine, asparagine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan and valine, added together to ten times their normal peripheral blood concentrations, restored synthesis rates to normal. The plasma aminogram (i.e. the relative concentrations, of amino acids) was altered by depriving rats of protein for 48h. The use of blood from the deprived rats as perfusate, instead of normal blood, decreased albumin synthesis rates significantly by livers obtained from well-fed rats. The addition of single amino acids, including the non-metabolizable amino acid, alpha-aminoisobutyric acid, to the above mixture increased albumin synthesis rates to normal values. It is concluded that amino acids play an important role in the control of albumin synthesis and that more than one mechanism is probably involved.
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PMID:The effects of amino acids on albumin synthesis by the isolated perfused rat liver. 465 17


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