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

The effects of starvation, feeding and pentagastrin on gastric mucosal adenylate cyclase (AC) and phosphodiesterase (PDE) activity were studied in the rat. 1. Starvation for 24 hrs and 48 hrs reduced both NaF stimulated and basal AC activities. 2. Feeding of starved rats slowly raised the AC activity up to 430% within 4 hrs after feeding. This effect was more pronounced under basal conditions than with NaF stimulation. 3. A single i.p. injection of pentagastrin (125 mug/kg) caused a stimulation of basal AC lasting 45 min, which was followed by a subsequent decrease in the basal and NaF stimulated enzyme activity. 4. PDE activity was not influenced by starvation and feeding but underwent a transient inhibition by pentagastrin. Accordingly gastric mucosal cAMP levels after starvation, feeding and pentagastrin are regulated by changes in AC and not in PDE activity. The rise in AC activity after feeding appears to be related to functions other than H+ and pepsin secretion.
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PMID:Adenylate cyclase and phosphodiesterase in the rat gastric mucosa after starvation, feeding and pentagastrin. 16 82

Cyclic adenosine 3':5'-monophosphate added to the starvation media of Dictyostelium discoideum amoebae induces both intracellular and extracellular phosphodiesterase activities of these cells. The induced enzyme activity appears several hours earlier than that in starved cells which have not been induced with cyclic nucleotide. In both cases, the appearance of enzyme is inhibited by cycloheximide, and actinomycin D, and daunomycin. The KmS for the extracellular enzyme(s) of nucleotide-induced and uninduced control cells are identical. The induction of enzyme activity seems specific for cyclic adenosine 3':5'-monophosphate since cyclic guanosine 3':5'-monophosphate, as well as other nucleotides, have no effect. No differences in the activity or excretion of either N-acetylglucosaminidase or the inhibitory of the extracellular phosphodiesterase are observed between cyclic adenosine 3':5'-monophosphate-induced and control cells. A direct activation of phosphodiesterase by cyclic adenosine 3':5'-monophosphate can be excluded, since the addition of this nucleotide to cell lysates has no effect on the enzyme activity.
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PMID:Induction of phosphodiesterase by cyclic adenosine 3':5'-monophosphate in differentiating Dictyostelium discoideum amoebae. 17 Feb 56

Treatment during starvation of D. discoideum amoebae with micromolar amounts of A23187 causes an enhanced aggregation. Cells develop the properties of differentiated, aggregation competent amoebae earlier than untreated populations. Ionophore increases the release of calcium, and prevents the excretion of the phosphodiesterase ihibitor normally released in the media. A23187 suppresses the morphogenetic block of some aggregates mutants, suggesting that the ionophore either activates cAMP synthesis and excretion, or increases the cellular sensitivity to extracellular cAMP signals. This might result from the enhanced mobilisation of intracellular calcium
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PMID:[The effect of an ionophore on the aggregation of Dictyostelium discoideum]. 17 27

The dose as well as the time kinetics of insulin and adenosine-3', 5' -monophosphate (cyclic AMP) responses to glucose were compared in pancreatic islets of fed and starved rats. There was a preferential impairment of the early phase of glucose-induced insulin release in perifused islets of rats starved for 16 and 48 h. Similarly, the accumulation of 3H cyclic AMP in islets prelabeled with 3H-2-adenine was less in islets of 48 h starved than fed rats, during the first 10-min of stimulation with 26.7 mM glucose in the presence of 0.1 mM of the phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine, whereas at 30 and 60 min 3H cyclic AMP responses to glucose were similar in fed and starved islets. Also, in 10-min incubations with glucose 3.3, 6.7, 10.0, 13.3, and 26.7 mM without and with 0.1 mM and 1.0 mM 3-isobutyl-1-methylxanthine, insulin release correlated strongly with the accumulation of 3H cyclic AMP in the islets of fed as well as starved rats. The thresholds for glucose-induced insulin and 3H cyclic AMP responses were higher and the maximal responses were lower in starved than fed islets. Preincubation of islets of 48-h starved rats with 16.7 mM glucose for 60 min corrected the impaired insulin and 3H cyclic AMP responses to glucose. Starvation-induced impairment of insulin secretory responses to glucose, and their restoration by preincubation with glucose in vitro, may represent acute regulatory effects of glucose on the adenylate cyclase-cyclic AMP system in the pancreatic beta cell.
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PMID:Insulin release and cyclic AMP accumulation in response to glucose in pancreatic islets of fed and starved rats. 18 86

The regulation of three Salmonella typhimurium phosphatases in reponse to different nutritional limitations has been studied. Two enzymes, an acid hexose phosphatase (EC 3.1.3.2) and a cyclic phosphodiesterase (EC 3.1.4.d), appear to be regulated by the cyclic adenosine 3' ,5'-monophosphate (AMP) catabolite repression system. Levels of these enzymes increased in cells grown on poor carbon sources but not in cells grown on poor nitrogen or phosphorus sources. Mutants lacking adenyl cyclase did not produce elevated levels of these enzymes in response to carbon limitation unless cyclic AMP was supplied. Mutants lacking the cyclic AMP receptor protein did not produce elevated levels of these enzymes in response to carbon limitation regardless of the presence of cyclic AMP. Since no specific induction of either enzyme could be demonstrated, these enzymes appear to be controlled solely by the cyclic AMP system. Nonspecific acid phsphatase activity (EC 3.1.3.2) increased in response to carbon, nitrogen, phosphorus, or sulfur limitation. The extent of the increase depended on growth rate, with slower growth rates favoring greater increases, and on the type of limitation. Limitation for either carbon or phosphorus resulted in maximum increases, whereas severe limitation of Mg2+ caused only a slight increase. The increase in nonspecific acid phosphatase during carbon limitation was apparently not mediated by the catabolite repression system since mutants lacking adenyl cyclase or the cyclic AMP receptor protein still produced elevated levels of this enzyme during carbon starvation. Nor did the increase during phosphorus limitation appear to be mediated by the alkaline phosphatase regulatory system. A strain of Salmonella bearing a chromosomal mutation, which caused constitutive production of alkaline phosphatase (introduced by an episome from Escherichia coli), did not have constitutive levels of nonspecific acid phosphatase.
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PMID:Regulation of two phosphatases and a cyclic phosphodiesterase of Salmonella typhimurium. 19 13

1. Insulin biosynthesis in isolated rat islets of Langerhans was determined by the incorporation of [(3)H]leucine into newly synthesized islet proteins. Anti-insulin serum covalently coupled to a solid phase (CNBr-activated Sepharose 4B) was used to separate the immunoreactive proinsulin and insulin from other islet proteins. This method was applied to a study of the regulation of insulin biosynthesis in isolated rat islets of Langerhans during pregnancy, and immediately after a period of food deprivation. 2. Islets isolated from pregnant rats showed an increased basal rate of synthesis compared with the non-pregnant controls. In addition, they showed a significant increase in biosynthesis of proinsulin and insulin in comparison with the normal islets over a range of glucose concentrations of 2-20mm. 3. Addition of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine significantly increased the insulin-synthetic response of normal islets over the glucose range 5-20mm, so that their glucose response approached that of islets from pregnant rats. 4. Normal female rates were injected with a long-acting progesterone derivative (hydroxyprogesterone hexanoate), to investigate the role of progesterone on the increased insulin biosynthesis observed in islets in pregnancy. There appeared to be no marked difference in insulin biosynthesis between the islets from the progesterone-injected and control rats in the presence of 2mm- or 6mm-glucose alone. However, in the presence of 4mm- or 6mm-glucose and 3-isobutyl-1-methylxanthine there was a significant increase in insulin biosynthesis in the progesterone-treated animals. 5. Total islet protein biosynthesis was determined by the incorporation of [(3)H]leucine into trichloroacetic acid-precipitable islet proteins. Islets isolated from normal rats showed a 1.6-fold increase in incorporation over the glucose concentration range 2-20mm, and this value remained unchanged during starvation; however, rates of incorporation were significantly raised in islets isolated from pregnant rats in the presence of 20mm-glucose. 6. Islets from starved and fed control rats were incubated in the presence of increasing concentrations of glucose or glucose+3-isobutyl-1-methylxanthine. The islets isolated from the starved animals showed a diminished insulin-synthetic response to glucose as compared with the controls; this response was partially restored to normal values by elevation of cyclic AMP concentrations by using 3-isobutyl-1-methylxanthine. 7. It is suggested that the alterations in glucose-stimulated insulin biosynthesis observed in islets during pregnancy and after a period of starvation could be attributable, at least in part, to a long-term alteration of the cyclic AMP system, and in pregnancy to a direct or indirect effect of progesterone on beta-cell function.
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PMID:Alterations in regulation of insulin biosynthesis in pregnancy and starvation studied in isolated rat islets of langerhans. 20 48

A cyclic nucleotide-binding phosphohydrolase that possesses both a phosphomonoesterase and a phosphodiesterase catalytic function has been partially purified from Aspergillus nidulans. The enzyme hydrolyzes both p-nitrophenylphosphate and bis-(p-nitrophenyl)-phosphate. o'-Nucleoside monophosphates are the best physiological phosphomonesterase substrates but 5'- and 2'-nucleoside monophosphates are also hydrolyzed. The enzyme catalyzes the hydrolysis of adenosine 5'-triphosphate, adenosine 5'-diphosphate, and 2',3'- and 3'5'-cyclic nucleotides, but not of ribonucleic acid, deoxyribonucleic acid, or nicotinamide adenine dinucleotide. The enzyme has acid pH optima and is not activated by divalent cations. Nucleosides and nucleotides inhibit the enzyme. Cyclic nucleotides are competitive inhibitors of the phosphodiesterase-phosphomonoesterase. The enzyme can occur extracellularly. The phosphodiesterase-phosphomonoesterase is present at high levels in nitrogen-starved mycelium, and it is strongly repressed during growth in media containing ammonium or glutamine and weakly repressed during growth in glutamate-containing medium. Experiments with various area mutants show that this regulatory gene is involved in the control of the enzyme. No evidence for regulation of the enzyme by carbon or phosphorus starvation has been found.
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PMID:Enzymology and genetic regulation of a cyclic nucleotide-binding phosphodiesterase-phosphomonoesterase from Aspergillus nidulans. 24 43

Schizosaccharomyces pombe initiates sexual development in response to nutritional starvation. The level of cAMP in S. pombe cells changed during the transition from exponential growth to stationary phase. It also changed in response to a shift from nitrogen-rich medium to nitrogen-free medium. A decrease of approximately 50% was observed in either case, suggesting that S. pombe cells contain less cAMP when they initiate sexual development. S. pombe cells that expressed the catalytic domain of Saccharomyces cerevisiae adenylyl cyclase from the S. pombe adh1 promoter contained 5 times as much cAMP as the wild type and could not initiate mating and meiosis. These observations, together with previous findings that exogenously added cAMP inhibits mating and meiosis and that cells with little cAMP are highly derepressed for sexual development, strongly suggest that cAMP functions as a key regulator of sexual development in S. pombe. The pde1 gene, which encodes a protein homologous to S. cerevisiae cAMP phosphodiesterase I, was isolated as a multicopy suppressor of the sterility caused by a high cAMP level. Disruption of pde1 made S. pombe cells partially sterile and meiosis-deficient, indicating that this cAMP phosphodiesterase plays an important role in balancing the cAMP level in vivo.
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PMID:Reduction in the intracellular cAMP level triggers initiation of sexual development in fission yeast. 131 97

The Schizosaccharomyces pombe gpa2 gene was cloned by hybridization with a cDNA for Dictyostelium discoideum G alpha 1. It encodes a homolog of G-protein alpha-subunits with 354 amino acids and a predicted molecular mass of 40,522. Disruption of gpa2 slows cell growth but is not lethal. Cells defective in gpa2 mate and sporulate readily in the presence of plentiful nutrition, bypassing the requirement of nitrogen starvation for the initiation of sexual development. These phenotypes mimic those of cells defective in cyr1 encoding adenylyl cyclase. The level of cAMP in gpa2 null mutants is only one-third of the wild-type level. Mutations in gpa2 that are likely to inhibit the GTPase activity of the gene product cause a slight increase in intracellular cAMP levels and result in leaky sterility. The cAMP level reaches 20 times as high as the wild-type level if a cell carries both this type of gpa2 mutation and a null mutation in pde1 encoding phosphodiesterase. Cells defective in gpa2 fail to produce cAMP in response to glucose stimulation. These results suggest that Gpa2 is involved in the determination of the cAMP level according to nutritional conditions, most likely as a positive regulator of adenylyl cyclase.
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PMID:Characterization of a fission yeast gene, gpa2, that encodes a G alpha subunit involved in the monitoring of nutrition. 134 Apr 62

Cyclic AMP can profoundly influence the growth and differentiation of neuronal cells in culture. In this study, the relationship between this second messenger signal transduction pathway, cell differentiation, and the expression of a retinoid-responsive, thymosin beta-10 gene was examined. Thymosin beta-10 and cognate mRNA were expressed at high levels in actively proliferating rat B104 neuroblastoma cells cultured in medium containing 10% FCS. These cells were induced to differentiate in the presence of the cAMP analog N6, 2'-O-dibutyryladenosine 3':5'-cyclic monophosphate (Bt2-cAMP) (1 mM) and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) (100 microM). Expression of thymosin beta-10 mRNA was markedly inhibited (greater than 90% and 70%, respectively) by these compounds. Addition of sodium butyrate (NaB, 1 mM) indicated that at least part of the inhibitory actions of Bt2-cAMP were due to esterase-induced release of butyrate from this compound. Adenosine (50 microM), a metabolic precursor to endogenous cyclic AMP, also inhibited accumulation of thymosin beta-10 mRNA (to less than 70% of control levels). The inhibitory action of Bt2-cAMP upon thymosin beta-10 mRNA levels was time dependent; levels were inhibited by greater than 50% 24 hours after addition of the cAMP analog and by greater than 90% after 72 hours. Serum starvation (0.2% FCS for seven days) provoked a marked increase in neurite out-growth; this morphological change was also accompanied by a modest inhibition of thymosin beta-10 mRNA accumulation. These findings together with previous observations imply that both cyclic AMP-dependent and retinoid-responsive mechanisms coordinate thymosin beta-10 gene expression during neuroembryogenesis.
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PMID:Influence of cyclic AMP and serum factors upon expression of a retinoid-responsive gene in neuroblastoma cells. 137 94


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