Hormone-sensitive adenyl cyclase: cytochemical localization in rat liver

An electron microscopic procedure has been developed, using rat liver, for the localization of hormone-sensitive adenyl cyclase. Isoproterenol-sensitive adenyl cyclase is located almost exclusively in the parenchymal cells. In contrast, glucagon-sensitive adenyl cyclase is located primarily in the reticulo-endothelial cells but is also present in parenchymal cells. Sodium fluoride-sensitive adenyl cyclase is found in both cell types.     

Glucagon-sensitive adenyl cylase in plasma membrane of hepatic parenchymal cells

The plasma membrane of hepatic parenchymal cells contains an adenyl cyclase system that is stimulated by glucagon. Adrenocorticotropin and epinephrine do not stimulate this adenyl cyclase, and very little cyclic phospho-diesterase activity is present in the membrane. These findings support the concept that glucagon exerts its regulatory action in the liver by stimulating adenyl cyclase activity in the plasma membrane.     

Tyrosine aminotransferase: enzyme induction independent of adenosine 3', 5'-monophosphate

The importance of adenyl cyclase and adenosine 3',5'-monophosphate in the induction of tyrosine aminotransferase by adrenocorticosteroids has been tested in HTC cells derived from a rat hepatoma and grown in tissue culture. Adrenocorticosteroids cause a 10-to 15-fold increase in the rate of synthesis of tyrosine aminotransferase in these cells. Under various experimental conditions, with or without glucocorticoids, neither adenyl cyclase nor cyclic adenosine mono-phosphate could be detected in HTC cells. In addition, neither the cyclic nucleotide nor N(6), O(2')-dibutyryl cyclic adenosine monophosphate caused increased activity of the transaminase in HTC cells. We conclude that induction of tyrosine aminotransferase by glucocorticoids is not mediated by the adenyl cyclase-cyclic adenosine monophosphate system.     

Renal adenyl cyclase: anatomically separate sites for parathyroid hormone and vasopressin

Adenyl cyclase from plasma membrane fractions of rat renal cortex or medulla was assayed by measuring conversion of adenosine triphosphate labeled at the alpha-phosphate with (32)P to cyclic 3',5'-adenosine monophosphate labeled with 32P. Parathyroid hormone activated the enzyme primarily in cortex; vasopressin acted primarily in medulla. These experiments support the conclusion that cyclic adenosine monophosphate mediates the action of parathyroid hormone on the kidney and show that parathyroid hormone and vasopressin stimulate adenyl cyclase at anatomically separable areas within the kidney.     

Isolated adrenal cells: adrenocorticotropic hormone, calcium, steroidogenesis, and cyclic adenosine monophosphate

Corticosterone production by isolated adrenal cells in response to adrenocorticotropic hormone is reduced when the cells are incubated in a medium that contains no calcium. This reduction is associated with an equal reduction of accumulation of cyclic adenosine monophosphate. Production of corticosterone and accumulation of cyclic adenosine monophosphate are increased when the calcium concentration in the medium is increased (from zero to 7.65 millimolar). This is in contrast to the situation in "subcellular membrane fragments" of adrenal tissue where high calcium in the medium (> 1.0 millimolar) inhibits cyclic adenosine monophosphate accumulation. We propose that adenyl cyclase in the intact plasma membrane is located in a compartment wherein calcium concentration is low and remains unaffected by the concentration of calcium in the extracellular space. It is proposed that, as the concentration of calcium in the incubation medium is increased from zero to 7.65 millimolar, the strength of the signal generated by the interaction of adrenocorticotropic hormone with its receptor and transmitted to the adenyl cyclase compartment is proportionately increased.     

Epinephrine: effect on uptake of iodine by dispersed cells of calf thyroid gland

In isolated thyroid cells I-epinephrine (0.1 and 10.0 micrograms per milliliter), norepinephrine and isoproterenol consistently stimulated the accumulation and organic binding of iodine. The effect was partially inhibited by phentolamine, but not propranolol, and hence may be mediated by alpha receptors. Theophylline did not mimic or enhance the epinephrine effect, suggesting that the latter may not result from activation of adenyl cyclase.     

Adenyl cyclase of cultured mammalian cells: activation by catecholamines

Chang's liver cells and 3T6 mouse embryo fibroblasts contain high amounts of catecholamine-sensitive adenyl cyclase, whereas HeLa cells contain relatively low amounts of activity. Both epinephrine and fluoride ion stimulate activity of each cell line. In contrast to normal liver, Chang's liver cells show greater response to epinephrine and no detectable stimulation by glucagon.     

Dopamine-sensitive adenyl cyclase: possible role in synaptic transmission

An adenyl cyclase activated by low concentrations of dopamine has been found in the mammalian superior cervical sympathetic ganglion. The existence of this enzyme may account for the increased amount of adenosine 3',5' monophosphate associated with synaptic activity in the ganglion. The results suggest that the physiological effects of dopamine in the ganglion, and possibly elsewhere in the nervous system, may be mediated by stimulating the synthesis of adenosine 3',5'-monophosphate.     

Thyroid-stimulating hormone and prostaglandin E1 stimulation of cyclic 3',5'-adenosine monophosphate in thyroid slices

Thyroid-stimulating hormone increased the cyclic 3',5'-adenosine monophosphate concentration in dog thyroid slices during a 1-minute incubation period and produced a maximum effect soon thereafter. The elevation persisted for at least 30 minutes. The concentrations of the cyclic 3',5'-adenosine monophosphate increased as the TSH concentration was increased from 0.125 to 50 milliunits per milliliter. Prostaglandin E(1), which increases glucose oxidation in dog thyroid slices, also increased the concentration of cyclic 3',5'-adenosine monophosphate. Although sodium fluoride stimulates thyroid adenyl cyclase, it did not increase concentration of cyclic 3',5'-adenosine monophosphate. Carbamylcholine and menadiol sodium diphosphate augment glucose oxidation in dog thyroid slices but do not change concentrations of cyclic 3',5'-adenosine monophosphate.     

Vitamin B12 requirement of a marine blue-green alga

A species of Synechocystis isolated from a marine mud has an absolute requirement for vitamin B(12). Analogues of B(12), including cobinamide and alpha-(adenyl) cobamide cyanide, satisfactorily substitute for vitamin B(12). Methionine alone or in combination with other compounds supports only a low level of growth.     

Mutations of the adenylyl cyclase gene that block RAS function in Saccharomyces cerevisiae

The interaction between RAS proteins and adenylyl cyclase was studied by using dominant interfering mutations of adenylyl cyclase from the yeast Saccharomyces cerevisiae. RAS proteins activate adenylyl cyclase in this organism. A plasmid expressing a catalytically inactive adenylyl cyclase was found to interfere dominantly with this activation. The interfering region mapped to the leucine-rich repeat region of adenylyl cyclase, which is homologous to domains present in several other proteins and is thought to participate in protein-protein interactions.     

家兔绒毛的显微结构研究

[目的]了解家兔绒毛的显微形态结构,[方法]选择具有典型特征的单根家兔绒毛,从尖部到根部对其进行显微结构观察,并检测其纤维直径.[结果]家兔绒毛的毛尖由鳞片层和皮质层组成,无髓质层;中部一般由鳞片层、皮质层和髓质层组成;根部无髓质层,鳞片层呈麦穗状.这是家兔绒毛的特性,可用于与其他动物纤维的比较研究及种类鉴别.兔毛具有发达的髓质层,纤维直径与髓腔列数成正相关.绒毛一般为单列,粗毛为多列.单根兔绒的尖部最细,中部变粗,根部又变细,且各部分直径差异较大,外形生长特性呈纺锤形.[结论]利用生物显微镜法鉴别不同动物毛皮及其产品种类是较为客观、简便的方法.     

Effect of forskolin on voltage-gated K+ channels is independent of adenylate cyclase activation

Forskolin is commonly used to stimulate adenylate cyclase in the study of modulation of ion channels and other proteins by adenosine 3',5'-monophosphate (cAMP)-dependent second messenger systems. In addition to its action on adenylate cyclase, forskolin directly alters the gating of a single class of voltage-dependent potassium channels from a clonal pheochromocytoma (PC12) cell line. This alteration occurred in isolated cell-free patches independent of soluble cytoplasmic enzymes. The effect of forskolin was distinct from those of other agents that raise intracellular cAMP levels. The 1,9-dideoxy derivative of forskolin, which is unable to activate the cyclase, was also effective in altering the potassium channel activity. This direct action of forskolin can lead to misinterpretation of results in experiments in which forskolin is assumed to selectively activate adenylate cyclase.     

Catecholamine-induced alteration in sedimentation behavior of membrane bound beta-adrenergic receptors

Incubation of astrocytoma cells with catecholamines results in a decrease in catecholamine-stimulated adenylate cyclase activity and a concomitant alteration in the sedimentation properties of particulate beta-adrenergic receptors. The altered receptors exhibit agonist binding properties similar to those of receptors that are "uncoupled" from adenylate cyclase.     

Effects of extracellular egg factors on sperm guanylate cyclase

Extracellular factors from the sea urchin egg induce a change in the electrophoretic mobility of an abundant sperm membrane phosphoprotein. The modified protein was identified as guanylate cyclase. The mobility shift of the cyclase was shown to be associated with a decrease in its enzymatic activity.     

东方白鹳与家禽腔上囊的形态学比较

利用光镜和透射电镜,观察了２只东方白鹳和鸡、鸭腔上囊的形态结构。东方白鹳腔上囊壁内的淋巴组织结构与家禽明显不同。东方白鹳腔上囊壁内的淋巴小结多呈扁椭圆形,皮质与髓质各位于小结的一侧,中间区呈窄条状、位于小结中间。多见２～３个淋巴小结对合成一个淋巴小叶。小叶中间是淋巴小结的髓质,两侧或周围是淋巴小结的皮质。淋巴小结的髓质外侧表面付有单层上皮。小叶内淋巴小结之间有窄的腔隙。家禽的淋巴小结中髓质位于中央,而皮质包于周围。中间区在皮髓交界处,呈环形包围在髓质周围。     

From epinephrine to cyclic AMP

Binding of catecholamines to the beta-adrenergic receptor results in the activation of adenylate cyclase and the intracellular formation of adenosine 3',5'-monophosphate (cAMP). In the past 20 years the events that lead from hormone binding at the cell surface receptor site to the synthesis of cAMP at the inner layer of the membrane have been intensively studied. Signal transduction in this system involves the sequential interaction of the beta-adrenergic receptor with the guanine nucleotide-binding protein (Gs) and the adenylate cyclase catalyst (C). The mechanism of signal transduction from the receptor through Gs to C, as well as the role of the adenylate cyclase inhibitory G protein Gi, is discussed.     

3种犬科动物直针毛显微形态学特征观察

应用扫描电镜及偏振光显微镜对沙狐、狼和貉的背部和腹部直针毛的髓质指数及鳞片花纹类型进行研究。结果表明。沙狐2个部位的髓质指数区间为71．4％～82．9％,狼的为43．6％一62．9％,貉的为51．2％～66．7％;毛鳞片形态在属间和种间存在差异,同一种类身体不同部位毛的鳞片形态也有差异,同一根毛的不同部位也存在差异,沙狐背毛主要鳞片类型为方瓣型,腹毛主要鳞片类型为长瓣型;狼背毛的主要鳞片类型为方瓣型,腹毛的主要鳞片类型为杂波形;貉背毛的主要鳞片类型为杂波型、杂瓣型,腹毛的主要鳞片类型为杂波形。用毛的显微形态学特征对3种动物进行识别具有可行性,但有一定的难度。     

Modulation of adenylate cyclase activity in liver and fat cell membranes by insulin

Insulin depresses both the activity of adenylate cyclase stimulated by glucagon, epinephrine, and sodium fluoride in liver cell membranes and the activity of adenylate cyclase stimulated by epinephrine and adrenocorticotropin in particulate preparations from homogenates of isolated fat cells. Significant inhibition is detected with very low concentrations (10(-11) molar) of insulin but not with unphysiologically high (10(-9)molar) concentrations of the hormone. These direct effects of insulin on an enzymatic system in broken-cell -preparations suggest a fundamental role of adenylate cyclase activity and of cyclic adenosine monophosphate in the mechanism of action of insulin.     

Adenylate cyclase activation shifts the phase of a circadian pacemaker

Forskolin, a highly specific activator of adenylate cyclase, produced both delay and advance phase shifts of the circadian rhythm recorded from the isolated eye of the marine mollusk Aplysia. The phase dependence of the response to forskolin was identical to that with serotonin, which also stimulates adenylate cyclase in the eye. The ability of agents to activate adenylate cyclase in homogenates was correlated with their ability to shift the phase of the circadian oscillator. These results along with earlier findings show that adenosine 3',5'-monophosphate mediates the effect of serotonin on the rhythm and regulates the phase of the circadian pacemaker in the eye of Aplysia.