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

Three distinct sections of the ultraviolet mutation frequency response (MFR) curve toward tryptophan prototrophy have been demonstrated in Excherichia coli B/r WP2 trp thy and its uvrA derivative in log-phase growth in minimal medium. The initial section, which appears fluence-squared, may reflect the necessity, if mutation is to result, for induction of two lesions, one located within the potentially mutated genetic locus and the other damaging deoxyribonucleic acid replication and resulting in inducation of the error-prone SOS repair function. A second linear section is ascribed to the continued induction, after exposure above that sufficient for complete SOS expression, of isolated lesions which lead to mutation in potentially mutated loci. The third section demonstrates an increased rate of mutagenesis and suggests the induction of two lesions in proximity which result in additional mutations. Split-exposure studies support the inducible nature of the SOS function and suggest that mutation frequency decline (MFD) is due to exicion resulting from or related to the prevention of SOS induction by inhibition of protein synthesis. Preirradiation tryptophan starvation of the uvr+ strain for 30 min decrease MFR in the first and second sections of the curve. Reduction of MFR in the third section requires more prestarvation time and is blocked by nalidixic acid. The decreased MFR of the first and second sections ascribed to promotion of postirradiation MFD based on excision and that of third section to completion of the chromosome during the prestarvation period.
 ...
PMID:Complexity of the ultraviolet mutation frequency response curve in Escherichia coli B/r: SOS induction, one-lesion and two-lesion mutagenesis. 79 35

The daily flux of amino acids in the body is extensive. Protein synthesis is estimated to be 300 g daily in an adult man. This requires uptake and release of 150 g essential amino acids, yet the dietary requirement for essential amino acids in only 6 g. This indicates extensive and efficient recycling of essential amino acids released by protein breakdown. The catabolism of essential amino acids by the liver is sensitively regulated in relation to requirements. A study of availability of tryptophan to rats receiving various levels of tryptophan in the diet shows that plasma tryptophan increases only when intake exceeds requirements and at these higher levels of intake tryptophan oxygenase activity in the liver becomes increased shortly after meals. In addition, the carbohydrate content of the diet causes tryptophan to become deposited in the free amino acid pool of muscle through an insulin-dependent mechanism. Dietary carbohydrate also effects plasma tryptophan due to a fall in the plasma level of non-esterified fatty acids which compete with tryptophan for binding sites on serum albumin. Consequently, after carbohydrate the proportion of plasma tryptophan bound to serum albumin increases, so that there is less nonbound tryptophan in the plasma. The metabolic significance of this has yet to be demonstrated. Finally, protein metabolism in skeletal muscle exhibits considerable efficiency of reutilization of essential amino acids, since the main products passing into the blood are alanine and glutamine. It has been shown that 3-methylhistidine present in muscle protein in not reutilized for synthesis of protein and that its excretion in the urine can provide a useful index of muscle catabolism. In prolonged starvation of adults or protein deficiency in children, output of 3-methylhistidine is much reduced, suggesting an adaptive reduction in muscle protein catabolism. It is emphasized that, because of its function in monitoring dietary amino acid intake, liver protein metabolism responds rapidly to changes in protein intake and in consequence protein deficiency causes early depletion, whereas muscle protein undergoes depletion later and is subject to adaptive processes that restrict the loss.
 ...
PMID:Regulation of protein metabolism in relation to adequacy of intake. 81 Apr 22

In Acinetobacter calcoaceticus the seven genes coding for the enzymes responsible for tryptophan synthesis map at three chromosomal locations. Two three-gene clusters, one (trpGDC) specifying the small subunit of anthranilate synthase, phosphoribosyl transferase, and indoleglycerol phosphate synthase and the other (trpFBA) specifying phosphoribosyl anthranilate isomerase and both tryptophan synthase subunits, are not linked to each other or to the trpE gene specifying the large anthranilate synthase subunit. When regulation of trp gene expression is studied in the wild type, only the level of the trpF gene product decreases upon addition of tryptophan to the medium. Tryptophan starvation of tryptophan auxotrophs, however, results in increased levels of all the tryptophan enzymes; this and additional evidence suggests that the expression of all the trp genes is subject to repression. The trpGDC genes are coordinately controlled, and the trpE gene is regulated in parallel with them. The trpFBA genes are controlled neither coordinately nor in parallel with the other trp genes, but respond proportionally when compared with each other. So far, two types of constitutive mutants have been found. The first class of mutants apparently occurs in the structural gene for a repressor protein; this repressor locus is unlinked to any of the biosynthetic trp genes and affects only the expression of trpE and the trpGDC cluster. The second class contains mutants closely linked to the trpGDC region; they overproduce only the gene products of this cluster.
 ...
PMID:Regulation of enzyme synthesis in the tryptophan pathway of Acinetobacter calcoaceticus. 93 50

Tryptophan was measured in the cisternal CSF and brains of rats. In untreated rats there was a significant but not very close correlation between the tryptophan concentration in these two compartments. Factors that change the brain tryptophan concentration such as starvation, glucose feeding, and lithium treatment affected the CSF tryptophan in the same way as the brain tryptophan. Diurnal changes were parallel for brain and CSF. When we take into account our knowledge of the disposition of tryptophan in human CSF, these data suggest that measurement of lumbar CSF tryptophan in man may be a useful approach to the study of human brain tryptophan. However, because the correlation between brain and CSF is not very close, measurements on CSF tryptophan would be more meaningful in groups of patients than in individuals.
 ...
PMID:Relationship between rat brain and cisternal CSF tryptophan concentrations. 94 32

Cardiac: Cardiac protein synthesis is influenced by the state of nutrition with reduction of cardiac size in starvation. Ethanol per se may not affect this synthesis directly, but the metabolite of ethanol, acetaldehyde, profoundly decreases normal protein synthesis in the heart in vitro. The interference with the synthetic process may play a role in the ultimate cardiomyopathies of malnutrition and alcoholism. Hepatic: In vivo albumin synthesis is sensitive to environment, oncotic pressure, normal balance, nutrition, as well as toxins and state of health. Thus, to study the acute effects of alcohol alone, it was necessary to employ the isolated perfused liver. Fasting reduced albumin synthesis 50%, with loss of RNA and a disaggregation of the endoplasmic membrane bound polysome. Tryptophan, arginine and ornithine added to the perfusate at a final concentration of 10 mM reversed these findings. Alcohol likewise reduced albumin synthesis; disaggregates the bound polysome without a marked loss of RNA. Ornithine, arginine and tryptophan are able to reverse this loss in albumin synthesizing capacity. The combination of fasting and alcohol, while not lowering albumin synthesis below that seen with either stress alone, prevents the recovery from either stress.
 ...
PMID:Effects of ethanol on protein synthesis. 109 51

Striated ducts in cats after 24 hours starvation normally contained glycogen, especially in the basal regions. They also contained neutral mucin and tryptophan in apical parts of "light" cells and small irregular "secretory" granules were found in a similar distribution by electron microscopy.--Parasympathetic nerve stimulation caused a loss of glycogen but no apparent change in the apical secretory material, despite a copious secretion.--Sympathetic stimulation caused a loss of glycogen and an extensive depletion of apical secretory material, although the salivary flow was small.--Parasympathetic denervation caused progressive atrophy of striated ducts and oedematous degeneration of some cells occurred. Persisting "light" cells tended to contain few basal infoldings, few mitochondria and little apical secretory material.--Sympathetic denervation caused a loss of apical secretory material between 2-4 days, which may have been due to "degeneration activation". Thereafter little change was evident but some ductal atrophy had occurred by 32 days.--These changes in ductal secretory material correspond more closely than acinar changes to the alterations in glandular and salivary kallikrein resulting from similar experiments by other workers. It therefore seems likely that submandibular salivary kallikrein in the cat is present in the secretory material of striated ducts.
 ...
PMID:Effects of nerve stimulation and denervation on secretory material in submandibular striated duct cells of cats, and the possible role of these cells in the secretion of salivary kallikrein. 114 39

1. Phosphoenolpyruvate carboxykinase was assayed by three methods: (i) incorporation of H(14)CO(3) (-) into oxaloacetate: (ii) conversion of oxaloacetate into phosphoenolpyruvate, subsequently assayed enzymically; and (iii) transfer of (32)P from [gamma-(32)P]GTP to oxaloacetate. 2. Enzyme activity is increased in liver and epididymal adipose tissue in alloxan-diabetes and starvation, and in kidney in starved, acidotic and steroid-treated animals. 3. The ratios of the ;back' to the ;forward' reactions in liver, kidney and epididymal adipose tissue are different and characteristic of each tissue; they differ markedly from values reported for the purified mitochondrial enzyme. 4. The ratio of the ;back' to ;forward' reaction in any one tissue is constant in adrenalectomized, diabetic, acidotic and steroid-treated animals. 5. In starved animals, the ratio is increased in liver and kidney, but decreased in epididymal adipose tissue. 6. Administration of l-tryptophan results in an acute (1h) increase in activity measured in the ;forward' direction alone in liver and epididymal adipose tissue, but not in kidney.
 ...
PMID:The activity of phosphoenolpyruvate carboxykinase in rat tissues. Assay techniques and effects of dietary and hormonal changes. 122 Jun 93

In phenylalanine administered rat, tryptophan chiefly metabolized to xanthurenic acid and in nicotinic acid administration to 5-hydroxy indole acetic acid mainly. MAO reaction inhibited by quinoline compound and the inhibition of kynurenine aminotransferase activity through the injection of epinephrine or serotonin were observed. And also the induction of tryptophanpyrrolase in starvation was discussed.
 ...
PMID:Tryptophan metabolism in various nutritive conditions. 124 91

The effect of different patterns of starvation (acute and intermittent) on the in vivo intestinal absorption of glucose and tryptophan during the first days of Gallus domesticus chicks life was measured. Both acute and intermittent starvation increase duodenal absorption of glucose and jejunal absorption of tryptophan. Intermittent starvation tends to reduce the effect of age which normally decreases intestinal uptake of nutrients. This effect is clearer for glucose absorption than for tryptophan absorption.
 ...
PMID:Effect of starvation on the in vivo intestinal absorption of sugars and amino acids in young chickens (Gallus domesticus). 137 93

The R gene coding for phage lambda lysozyme (lambda L), cloned under the control of the PL promoter on a multicopy vector, is expressed in an Escherichia coli strain auxotrophic for tryptophan. Induction by a thermal shift after tryptophan supplementation in a culture initially brought into stationary phase by tryptophan starvation leads to highly increased expression. A thermally unstable mutant protein, difficult to obtain under standard conditions, can be easily produced by post-stationary-phase expression. It is shown that this is due to a drastic decrease in the heat-shock-induced proteolysis normally observed on thermal induction. These data are discussed in relation to our present knowledge of stringent and heat-shock responses.
 ...
PMID:A large decrease in heat-shock-induced proteolysis after tryptophan starvation leads to increased expression of phage lambda lysozyme cloned in Escherichia coli. 138 88


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>