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

The content of membrane-bound ribosomes in normal rat liver cells is 3 times as high as compared to that of free ribosomes. (K=membrane-bound ribosome RNAs divided by free ribosome RNAs=3, the opposite effect being observed in case of ascites hepatoma cells. A considerable increase in the free ribosome fraction in the liver of hepatoma-bearing rats occurs by the sixth day due to a decrease in the content of hepatoma-bearing rats occurs by the sixth day due to a decrease in the content of membrane-bound ribosomes (K=0.6). Similar, but less-pronounced changes were observed in liver cells of control animals after 48-hour starvation (K=0.9), simulating the condition occurring during the last days of tumour animals' life. Thus, changes in the rativ of membrane-bound to free ribosomes in liver during the ascites tumour growth are probably specifics and are not only due to anorexia in Zajdela hepatoma animals.
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PMID:[Correlation of membrane-bound and free ribosomes in normal rat liver, Zajdela hepatoma rat liver and ascite cells proper]. 19 Nov

Free and membrane-bound ribosomal ribonucleic acid (RNA) from maternal rat liver was measured in virgin rats and in variously dated pregnant animals that were either fed or starved for one to four days. The total amounts of free and membrane-bound ribosomal RNA differed between pregnant and nonpregnant rats, but the free ribosomal RNA progressively decreased only in the nonpregnant animals. A similar conservation of membrane-bound ribosomal RNA was observed with starvation among the pregnant rats except for the very early dated pregnant rats. Radioisotope labeling experiments using 3H-labeled orotic acid demonstrated a slower increase in specific activity among fed rats, irrespective of pregnancy state. However, metabolic and physiologic changes associated with pregnancy imposed additional complicating factors to the study.
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PMID:Changes in the free and membrane-bound ribosomes in maternal rat liver during starvation. 56 85

The distribution of free and membrane-bound ribosomes in liver in response to starvation has not been clearly defined. An investigation has been made of the effects of starvation on the content of DNA, RNA, protein, phospholipid and glycogen in rat liver, on the distribution of free and membrane-bound ribosomes, and on the content of phospholipid and glycogen in free and bound ribosome fractions. The results indicate that starvation can produce up to a 50% reduction in hepatic ribosomes without altering either the fraction of rRNA relative to the total RNA or the distribution of free and membrane-bound ribosomes. In addition, the degree of contamination of isolated ribosomes with membranous material does not fluctuate with changes in the nutritional status of the animal. The results suggest that the relative capacities for protein synthesis among the two ribosome compartments are maintained during the early stages of starvation. Further, co-sedimentation with glycogen is not responsible for the presence of membranous materials in purified ribosomes.
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PMID:Effect of starvation of the distribution of free and membrane-bound ribosomes in rat liver and on the content of phospholipid and glycogen in purified ribosomes. 97 28

1. The effect of phenobarbitone on the rate of protein synthesis and on the sedimentation patterns of various liver subcellular fractions containing ribosomes was studied in rats. 2. Phenobarbitone treatment increased the incorporation of [114C]leucine into protein by all preparations, provided they had not been subjected to preliminary treatment with Sephadex G-25. The phenobarbitone-induced effect on incorporation was associated with a gain in liver weight and a higher degree of polyribosomal aggregation. 3. Preparations that were treated with Sephadex G-25 incorporated more radioactivity into protein, but did not show the response to phenobarbitone treatment. 4. When the influence of starvation and phenobarbitone was studied separately on membrane-bound and membrane-free polyribosomes, it was shown that whereas both classes of polyribosomes were affected by starvation, apparently only the former class was susceptible to phenobarbitone stimulation of protein synthesis. 5. The decreased capacity for protein synthesis of polyribosomes from starved rats was independent of their association with the membranes of the endoplasmic reticulum, but resulted from polyribosomal disaggregation, from an intrinsic defect of the polyribosomes themselves and from changes in composition of the cell cap. 6. The results are discussed in relation to the problem of the control of protein biosynthesis and of the functional separation of membrane-bound and membrane-free polyribosomes.
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PMID:The effect of phenobarbitone on protein synthesis by liver polyribosomes in fed and starved rats. 114 92

Phenol oxidase enzymes, linked to virulence in Cryptococcus neoformans, were prepared from broken cells. More enzyme activity was found in the ultracentrifugation supernatant; less was found in the membrane fraction. Phenol oxidases were located in acrylamide gel electropherograms by activity staining with L-dihydroxyphenylalanine (DOPA). Mobility differences between soluble and solubilized membrane-bound phenol oxidases were not found. Comparison of enzymes produced at 25 and 37 degrees C revealed that the enzyme had lower activity and lower mobility at 37 degrees C. The mobility of 25 degrees C phenol oxidases from strains of C. neoformans var. gattii was lower than that of those from C. neoformans var. neoformans. Half of the phenol oxidase produced at 25 degrees C was bound by concanavalin A, while that produced at 37 degrees C was not bound. However, glucose starvation of cultures at 25 degrees C overnight resulted in increased amounts of enzyme which did not bind to concanavalin A. A given strain of C. neoformans produces different species of phenol oxidase under different culture conditions.
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PMID:Heterogeneity of phenol oxidases in Cryptococcus neoformans. 150 Jan 62

The occurrence of proton symport mechanisms for the transport of glucose, galactose, fructose, raffinose and sucrose in 21 yeast strains representing the species of the genus Kluyveromyces was surveyed. Proton symport of one or more sugars occurred in 57% of the strains. Similarly, all the sugars investigated were transported by symports by several strains. Symport systems for non-utilisable sugars were rare. Starvation of cells frequently resulted in the appearance of a symport absent in non-starved glucose-grown cells, indicating that repression of proton symports by glucose and subsequent derepression by starvation is a general phenomenon in members of Kluyveromyces. The addition of a sugar to cell suspensions resulted in acidification in 80% of cases, indicating the activity of a membrane-bound ATPase. Acidification was also observed with a number of sugars that cannot be utilised by the particular species. Interesting correlations between the number of proton symports and the abundance of other phenotypic characteristics in members of the genus emerged. Most members of the infertile group of species showing an increase in the number of small chromosomes, inability to produce well-developed pseudomycelium, linoleic and linolenic acid, a decrease in the number of carbon compounds utilised and inability to utilise ethylamine also had no proton symports, whereas most members of the interfertile species produced one or more proton symports. It was concluded that the distribution of the number of proton symports amongst Kluyveromyces species coincided with that of other positive characteristics and may therefore be of taxonomic value.
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PMID:Occurrence and taxonomic aspects of proton movements coupled to sugar transport in the yeast genus Kluyveromyces. 165 Oct 70

Type I iodothyronine 5'deiodinase (5'D-I) is a membrane-bound enzyme catalyzing the deiodination of T4 to T3. The affinity label, N-bromoacetyl-thyroxine (BrAcT4), has previously been used to characterize a 27 kilodalton protein (p27) from rat liver and kidney microsomes with characteristics of the catalytic subunit of the 5'D-I. We examined the effect of physiological conditions, known to alter 5'D-I activity, on affinity-labeled proteins in rat liver and kidney microsomes. To confirm that the affinity labeled protein was associated with the deiodinase, we treated rats with the active site directed enzyme inhibitor, propylthiouracil (PTU), in the absence and presence of 100-fold excess methimazole (MMI), an antithyroid drug which blocks PTU inhibition of 5'D-I in vivo. In addition, we used the affinity label as a probe to measure 5'D-I levels in membrane preparations from short and long term fasted rats. Rats were treated ip with PTU (50 micrograms/100 g BW) or MMI (5 mg/100 g BW); in a second experiment, groups of rats were fasted for 4 days (4 D), 1 day (1 D), or fed ad lib (C) and hepatic and kidney microsomes were prepared. 5'D-I activity and 5'D-I content, as judged by specific incorporation of the affinity label into p27, were determined. PTU decreased both 5'D-I activity and BrACT incorporation into p27 by 60-65%. Coadministration of MMI attenuated the effect of PTU on 5'D-I activity and p27 affinity labeling. No other affinity labeled proteins were affected. In fasting experiments, the changes in affinity labeling of p27 paralleled the changes in 5'D-I activity. 5'D-I activity was significantly decreased in hepatic microsomes obtained from 4 D-fasted rats as compared to C rats, but was unchanged in hepatic microsomes from 1 D-fasted rats or in kidney microsomes from 1 D or 4 D-fasted rats as compared to C. Maximal BrAcT4 incorporation into p27 decreased by 45% in hepatic microsomes from 4 D-starved rats as compared to C (6.7 +/- 0.9 vs. 11.9 +/- 1.5 pmol BrAcT4 incorporated/mg microsomal protein, respectively). There was no change in p27 content in hepatic microsomes from 1 D-starved rats (11.2 +/- 1.1). Starvation failed to alter the BrAcT4 labeling of kidney microsomes (16.7 +/- 4.4, 16.2 +/- 6.6, and 14.8 +/- 3.2 pmol BrAcT4 in 4 D, 1 D, and C rats, respectively). In this study, we have demonstrated that alterations in biological activity of 5'D-I correspond to alterations in affinity labeling of p27.
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PMID:Effect of biological alterations of type I 5'deiodinase activity on affinity labeled membrane proteins in rat liver and kidney. 229 72

Crithidia luciliae, a trypanosomatid protozoan readily grown in axenic cultures, was shown to possess low levels of a surface membrane-bound ectoenzyme capable of hydrolyzing both 3'-ribonucleotides and nucleic acids. The specific activities of this 3'-nucleotidase/nuclease, with both mononucleotide and nucleic acid substrates, were greatly enhanced when the protozoa were deprived of purines, an essential nutrient. The catalytic activities were exhibited by a polypeptide which migrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an Mr of 47,000. Starvation of these cells for inorganic phosphate (Pi), in media with or without purines, also led to an increase in the specific activity of the ectoenzyme compared to that of Pi- and purine-replete cells. In contrast, the level of enzyme activity was not increased when the protozoa were starved, under purine-replete conditions, for either arginine or hemin, two other essential nutrients. Cells starved simultaneously for either of the latter two nutrients and for purines also did not show increased levels of the 3'-nucleotidase/nuclease. The activation of the enzyme was also prevented by sodium arsenite, cycloheximide, actinomycin D, and tunicamycin indicating that the activation presumably required metabolic energy as well as new transcription, translation, and protein modification. The results demonstrate that the control of 3'-nucleotidase/nuclease expression is a regulated, adaptive response to growth-limiting levels of essential nutrients.
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PMID:Crithidia luciliae: factors affecting the expression of 3'-nucleotidase/nuclease activity. 283 57

Nongrowing Escherichia coli deprived of an essential amino acid continued to produce peptidoglycan at a rate approximately 30% of that of growing cells. The composition of this peptidoglycan was very different from that of growing cells and resembled that of peptidoglycan left undegraded during partial autolysis of the bacteria. Synthesis of this peptidoglycan of anomalous composition began at once upon the removal of the amino acid from the medium. Fifteen minutes of amino acid deprivation was sufficient to virtually completely prevent penicillin-induced autolytic wall degradation in vivo. During this time, although the specific activities of soluble and membrane-bound hydrolytic transglycosylases and endopeptidases remained high, the peptidoglycan produced showed decreased sensitivity to degradation in vitro. After more extensive (2-h) starvation, triggering of autolysis by chaotropic agents was also blocked. Autolysis in growing cells may be selective for peptidoglycan representing the cylindrical portion of the sacculus. It is suggested that at least part of the mechanism of the well-known lysis resistance of nongrowing E. coli is related to the deposition of structurally anomalous and relatively autolysin-resistant peptidoglycan at some strategically located sites on the bacterial surface.
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PMID:Autolysis-resistant peptidoglycan of anomalous composition in amino-acid-starved Escherichia coli. 289 87

The effect of Ep on different ATPases and acetylcholinesterase of rat RBC membrane was studied. Starvation caused a slight decrease in Mg2+-, Ca2+-, and Na+ + K+-ATPases. However, these enzyme activities were markedly increased on Ep treatment of starved rats. Specific activities of all three ATPases increased linearly with increasing concentration of Ep. Under identical conditions the hormone failed to stimulate the ATPase activity of liver plasma membrane. Desensitization by fluoride of allosteric inhibition of erythrocyte membrane-bound Na+ + K+-ATPase was observed under starvation which showed a return to normal n values on Ep administration. The enzyme from normal animals was inhibited almost completely at 0.1 mM fluoride whereas enzyme from starved and Ep-treated animals showed only about 50% inhibition at that fluoride concentration. Ep increased the acetylcholinesterase activity of normal RBC membrane to a small extent whereas the stimulation was much higher under starvation. The fluoride inhibition curve of this enzyme changed from sigmoidal to hyperbolic under starvation which again changed to allosteric on administration of Ep. These changes were closely correlated to n values. Red blood cells of Ep-treated animals became more susceptible to osmotic shock under the experimental conditions.
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PMID:Effect of erythropoietin on the different ATPases and acetylcholinesterase of rat RBC membrane. 302 76


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