Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Thyroid cells from euthyroid patients with Graves' disease were cultured in a chemically defined medium. The cells preserved the ability to respond to TSH with 8-fold increase in cyclic AMP concentration. This cyclic AMP response to TSH was diminished by prior exposure of cells to TSH. The decrease in cyclic AMP response to TSH induced to TSH was reversible, was not associated with a similar decrease to cyclic AMP response to PGE1, and could not be attributed to increased phosphodiesterase activity or to decreased adenyl cyclase activity. The partial resistence to TSH stimulation of thyroid cells previously exposed to TSH may be due to changes in the TSH receptor, possibly caused by TSH itself.
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PMID:Cyclic AMP level of human thyroid cells in monolayer culture. TSH induced refractoriness to TSH action. 18 6

Expression of the L-arabinose regulon in Escherichia coli B/r requires, among other things, cyclic adenosine-3', 5'-monophosphate (cAMP) and the cAMP receptor protein (CRP). Mutants deficient in adenyl cyclase (cya-), the enzyme which synthesizes cAMP, or CRP (crp-) are unable to utilize a variety of carbohydrates, including L-arabinose. Ara+ revertants of a cya-crp- strain were isolated on 0.2% minimal L-arabinose plates, conditions which require the entire ara regulon to be activated in the absence of cAMP and CRP. Evidence from genetic and physiological studies is consistent with placing these mutations in the araC regulatory gene. Deletion mapping with one mutant localized the site within either araO or araC, and complementation tests indicated the mutants acted trans to confer the ability to utilize L-arabinose in a cya-crp- genetic background. Since genetic analysis supports the conclusion, that the mutant sites are in the araC regulatory gene, the mutants were designated araCi, indicating a mutation in the regulatory gene affecting the cAMP-CRP requirement. Physiological analysis of one mutant, araCi1, illustrates the trans-acting nature of the mutation. In a cya-crp- genetic background, araCi1 promoted synthesis of both isomerase, a product of the araBAD operon, and permease, a product of the araE operon. Isomerase and permease levels in araCi1 cya+ crp+ were hyperinducible, and the sensitivity of each to cAMP was altered. Two models are presented that show the possible mutational lesion in the araCi strains.
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PMID:Mutations affecting catabolite repression of the L-arabinose regulon in Escherichia coli B/r. 18 62

1. Giant fibres of the barnacle Balanus nubilus have been used as a preparation for studying the mode of action of cAMP on sodium transport. 2. It is shown that a concentration of cAMP as low as 10(-6)M, when micro-injected, causes a sharp rise in the radio-Na efflux. Ouabain fails to reverse the cAMP effect. 3. The magnitude of the response of the Na efflux to cAMP is markedly reduced by pre-injecting 100 or 500 mM-EGTA solutions or by omitting Ca2+ from the bathing medium. Both together fail to bring about a greater reduction in the response. 4. The response to cAMP is greatly reduced by pre-injecting the protein inhibitor of Walsh and practically abolished by pre-injecting 500 mM-EGTA and soaking in Ca-free artificial sea water, ASW. 5. The Ca2+-independent component of the Na efflux which is also stimulated by cAMP is shown to involve Na for H exchange. The magnitude of this exchange is governed by external pH. 6. The Na efflux into Ca2+-free, Li+-ASW is shown to be markedly stimulated by injecting cAMP, an effect which is enhanced by reducing external pH. 7. The Na efflux at 0 degrees C is stimulated by injecting cAMP. This is shown to be related to activation of the protein kinase by cAMP and to depend on the presence of external Ca2+. 8 (i) Ethacrynic acid when injected reduces the ouabain-insensitive Na efflux into HEPES-Ca2+-free ASW at pH 6-3. These same fibres show a marked response to cAMP. (II) The ouabain-insensitive Na efflux into HCO3-, Ca2+-free ASW from fibres pre-treated with ethacrynic acid fails to respond to external acidification. This is interpreted as indicating that ethacrynic acid inactivates the CO2-sensitive adenyl cyclase system. These same fibres when injected with cAMP show a marked response. (iii) Stimulation of the ouabain-insensitive Na efflux into HCO-3, Ca2+-free ASW by external acidification is reversed by injecting ethacrynic acid. These fibres when injected with cAMP show a reduced response. 9. It is concluded that: (i) stimulation of the Na efflux by injected cAMP is mainly due to activation of cAMP-dependent protein kinase; (ii) the underlying exchange mechanism consists of Na:Ca and Na:H exchange. Interaction of Ca2+ with a phosphorylated membrane, thereby modifying permeability remains as a real possibility; (iii) the site of action of CO2 and ethacrynic acid is the adenyl cyclase system. 10. The implications of activation of the adenyl cyclase system by CO2 and Na:H exchange are briefly touched upon.
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PMID:Mode of stimulation by adenosine 3':5'-cyclic monophosphate of the sodium efflux in barnacle muscle fibres. 18 61

Effects of externally applied cyclic AMP and other adrenergic stimulants on the electrical and mechanical activities of the cat small intestine were observed by using pressure electrodes. The electrical and mechanical activities were suppressed by cyclic AMP and beta-stimulants. Those inhibitory actions of cyclic AMP and beta-stimulants were potentiated under the treatment with caffeine, theophylline and papaverine which inhibits the phosphodiesterase activity. On the other hand, the inhibitory action of cyclic AMP and beta-stimulants was decreased in imidazole, an agent that increases phosphodiesterase activity. Exogenous applied concanavalin A, an agent that inhibits the adenyl cyclase activity, showed no observable changes in both activities but the effects of beta-stimulants were decreased after treatment with concanavalin A. No obvious changes on both activities were obtained in cyclic GMP and dibutyryl cyclic GMP. These findings tentatively support the hypothesis that cyclic AMP is a second messenger in the inhibitory responses to beta-stimulants on the intestinal smooth muscle. However, it is also concluded that the inhibition of mechanical activity caused by cyclic AMP is partially due to suppression of the membrane activity.
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PMID:Further studies of the action of cyclic AMP on the electrical and mechanical activities of intestinal smooth muscle. 18 23

Insulin accelerates the entry of glucose and amino acids into muscle cells by acting upon the 'carrier-facilitated' transport mechanism. For glucose this process is passive and leads to equilibration of intracellular and extracellular concentrations. In heart muscle, glucose transport is a rate-limiting step for glucose uptake. During hypoxia and ischemia the heart turns to anaerobic glycolysis for energy production and therefore, maximal glucose transport becomes important. Insulin is necessary to insure proper protein synthesis, probably at the level of membrane-bound polyribosomes. However, during myocardial hypoxia, insulin alone cannot restore the associated depression in protein synthesis. Although insulin hyperpolarizes the cell, a change in the ratio of intracellular to extracellular activities of potassium is not its primary mode of action. An insulin-induced configurational change in the plasma membrane could simultaneously account for the effects of insulin on sodium and potassium permeability and the action on facilitated transport. Intracellular levels of cyclic adenylate may be reduced by insulin in adipose tissue because of inhibition of adenyl cyclase or stimulation of phosphodiesterase. However, at this time there is little evidence that insulin alters cyclic AMP levels in the heart. Insulin secretion is depressed in patients with heart disease in proportion to the reduction of cardiac index sustained. Since the ischemic heart is dependent upon glucose as the major fuel, insulin lack may deprive the heart of adequate substrate.
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PMID:Insulin: fundamental mechanism of action and the heart. 18 67

Changes in adenosine triphosphatase (ATPase) activity of the peripheral blood leukocytes were investigated in patients with bronchial asthma. Estimation of the leukocyte Mg++- and Ca++- dependent ATPases was carried out according to Hadden's method, incubating ATP with the membrane fraction of the leukocyte. The leukocyte ATPase activity was significantly elevated among asthmatic patients compared with control subjects. This elevated ATPase was seen in all asthmatics irrespective of acute attacks or the drug treatment. There was no clear correlation between the activity of ATPase and the percentage of leukocytes, neutrophils and eosinophils. There was no relationship between ATPase activity and adenyl cyclase activity of the same leukocytes from asthmatic patients.
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PMID:Leukocyte adenosine triphosphatase activity in human bronchial asthma. 18 9

Changes in cyclic-3', 5'-nucleotide phosphodiesterase activity of the peripheral blood leukocytes were investigated in patients with bronchial asthma. Leukocyte phosphodiesterase activity was significantly elevated during asthmatic attacks. Elevated activity was seen in most active asthmatics irrespective of the drug treatment. The ratio of the adenyl cyclase activity to the phosphodiesterase activity of the same leukocyte decreased to less than 1.0 during asthmatic attacks.
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PMID:Leukocyte cyclic-3', 5'-nucleotide phosphodiesterase activity in human bronchial asthma. 18 72

1. Physiological concentrations of antidiuretic hormone increase diffusional water permeability but not measurable cyclic AMP content in the isolated papilla of the rat's kidney. 2. Theophylline (6 mM) increases diffusional water permeability and cyclic AMP content in the isolated papilla of the rat's kidney. 3. The increase in water permeability is detected with 5 muunits.ml-1 of ADH and is maximal with 50 muunits.ml-1. The same maximum was achieved with 6 mM theophylline. 4. Cyclic AMP and dibutyryl cyclic AMP both increase water permeability, but to a lesser extent than theophylline or ADH. 5. In the presence of theophylline, ADH causes a dose related generation of tissue cyclic AMP up to a dose of 2,000,000 muunits.ml-1. 6. Adenyl cyclase is increasingly activated by ADH up to doses of 2,000,000 muunits.ml-1. 7. These results suggest that while ADH activates the adenyl cyclase system and changes water permeability there are sufficient disparities to cast doubt on an exclusive role for cyclic AMP as the second messenger.
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PMID:The interrelationships between antidiuretic hormone, adenyl cyclase, tissue cyclic AMP and diffusional water permeability. 18 92

The levels of cylic AMP and adenyl cyclase in swarming and non-swarming cells of Proteus mirabilis and the effect of glucose on swarming have been investigated. The results indicate the cAMP is required for swarming, but that the flagellar derepression characteristic of swarming does not result from increased cAMP levels.
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PMID:The role of cyclic adenosine monophosphate in the swarming phenomenon of Proteus mirabilis. 18 81

The effect of different environmental temperatures on adenyl cyclase was studied. An increase in temperature appears to increase TRH-induced activity of adenyl cyclase, and possible causes an increases sensitivity to the hormone. Cyclic AMP levels of the pituitaries showed change at different environmental temperatures.
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PMID:Adenyl cyclase activity at different environmental temperatures in the isolated rat anterior pituitary membranes. 18 84


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