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Biomedical subjects

F Okada

Publications and source records attributed to F Okada.

At least 145 records · Page 8Linked to original sources
PubMed1983

Regulation of noradrenergic receptor systems in brain that are coupled to adenylate cyclase.

The current status of regulation of norepinephrine (NE) receptor systems in brain that are coupled to adenylate cyclase is briefly reviewed. The availability of NE and the formation of the NE receptor complex is one prerequisite for the regulation of both the sensitivity of the system and the density of its beta-adrenoceptor population. Serotonergic neuronal input is corequired with NE for the down-regulation of the number of beta-adrenoceptors, which in the absence of serotonergic input, show a marked decrease in agonist affinity. Steroid hormones influence either the sensitivity of the NE receptor system (adrenocorticoids) or the biological responsiveness and the density of beta-adrenoceptors (sex steroids) while preliminary data indicate that 3,5,3'-triiodothyronine can convert a "DMI resistant" to a "DMI responsive" receptor system. The complex neurohormonal and endocrine regulation of the biological responsiveness of NE receptor systems, the number of receptors and the efficacy of their coupling to adenylate cyclase appear to represent control mechanisms for the intensity of signal transfer.

Adenylyl Cyclases↗
PubMed1982

Role of serotonergic input in the regulation of the beta-adrenergic receptor-coupled adenylate cyclase system.

The action of desipramine on the norepinephrine-sensitive adenylate cyclase system and the density of beta-adrenergic receptors in rat cortex was studied after selective lesioning of serotonergic neurons with 5,7-dihydroxytryptamine. In animals with lesions desipramine failed to reduce the density of beta-adrenoceptors but decreased the response of adenosine 3',5'-monophosphate to isoproterenol and norepinephrine to the same degree as in animals without lesions. The results demonstrate a functional linkage between serotonergic and noradrenergic systems in the rat cortex, with beta-adrenergic receptors and neurohormonal sensitivity of the adenosine 3',5'-monophosphate-generating system being under separate regulatory control.

Adenylyl Cyclases↗
PubMed1982

Dopamine-beta-hydroxylase activity in the locus coeruleus and hypothalamus in cold-stressed rats.

Dopamine-beta-hydroxylase (DBH) activity was determined in the locus coeruleus, anterior hypothalamus and posterior hypothalamus of cold-stressed rats. In the acute cold stress, rats were exposed to an ambient temperature of 5 degrees C in a cold room for 5-20 min. In the chronic cold stress, rats were exposed to the same cold temperature for 4 hr once every day in the morning for periods ranging from 1 to 3 weeks. There was decreased DBH activity in the locus coeruleus following acute cold stress and increased activity in both the locus coeruleus and the anterior hypothalamus following the chronically repeated cold stress.

Animals↗
PubMed1982

Plasma guanosine 3',5'-monophosphate responses to methacholine and epinephrine in humans.

The im injection of methacholine into healthy volunteers caused a dose-dependent increase in plasma cGMP levels; this increase was antagonized by atropine, while it was not affected by phentolamine or propranolol. The im injection of epinephrine caused a small but significant rise in plasma cGMP concentrations; this rise was completely blocked by the simultaneous injection of phentolamine, while it was not affected by atropine or propranolol. These data show that changes in the plasma concentration of cGMP may reflect not only cholinergic but also alpha-adrenergic functions in humans.

Adolescent↗
PubMed1981

Plasma cyclic AMP hyper-response to glucagon in manic patients on lithium treatment.

We have measured the rise in plasma cyclic AMP induced by glucagon and adrenaline in manic patients on lithium therapy. Glucagon-induced increases in the concentration of plasma cyclic AMP were larger, but the adrenaline-induced increases were smaller, in lithium-treated manic patients than in normal controls. In 3 manic patients, the enhanced response to glucagon was normalized 3 weeks after the cessation of lithium treatment. Though the underlying mechanism is unknown, the unusual plasma cyclic AMP responses may reflect altered receptor sensitivity which would be closely related to the curative effect of lithium on symptoms of mania.

Adult↗
PubMed1980

Anomalous plasma cyclic AMP responses to glucagon in patients with liver disease.

The purpose of the present study is to show anomalies of the plasma cAMP response of patients with hepatic disorders to a single injection of a low dose of glucagon (1 microgram/kg body wt). The response was markedly blunted in patients with liver cirrhosis and potentiated in patients with acute or chronic hepatitis. This glucagon test is, therefore, promising for development as a simple diagnostic means without undertaking liver biopsy to distinguish cirrhosis from chronic hepatitis.

Adult↗
PubMed1980

Changes in plasma cyclic nucleotides levels during various acute physical stresses.

Studies were performed with healthy volunteers to determine the effects of various stresses known to increase sympathetic nerve activity on the plasma concentration of cyclic AMP and cyclic GMP. Plasma cyclic AMP rose promptly in response to exercise; the elevation was completely abolished by a simultaneous injection of propranolol. Plasma cyclic GMP rose slightly after exercise; the elevation was completely abolished by a simultaneous injection of atropine. No significant changes occurred during tilting and cold pressor stress. The increase in plasma concentrations of cyclic AMP and cyclic GMP may serve as putative indices for beta-adrenergic, and cholinergic functions respectively during exercise of humans.

Adolescent↗
PubMed1980

Plasma cyclic nucleotide responses to insulin-induced hypoglycaemia and methacholine in patients with hyperthyroidism.

The effect of insulin-induced hypoglycaemia and methacholine on plasma cAMP and cGMP levels was studied in normal volunteers, hyperthyroid and hypothyroid patients. A significant positive correlation existed between the maximal increase in plasma cAMP and the maximal decrease in plasma glucose in normals during insulin-induced hypoglycaemia. Therefore, the plasma cAMP response is considered to be dependent on the degree of hypoglycaemia, rather than the dose of insulin. The cAMP response to hypoglycaemia was significantly higher in hyperthyroid patient, and was lower in patients with hypothyroidism than in normals. The cAMP response of the hyperthyroid patients was normalized when their hyperthyroidism was controlled after 3 months of treatment. The plasma level of cGMP was slightly elevated during hypoglycaemia, but there was no significant difference between controls and hyperthyroid patients. The cGMP response to methacholine, which is probably mediated by cholinergic receptors, was significantly potentiated in hyperthyroid patients. The cAMP response, which is presumably dependent on endogenous catecholamines secreted during methacholine-induced hypotension, was also enhanced in hyperthyroid patients. It is likely that beta-adrenergic receptor responses and cholinergic receptor responses are both enhanced in hyperthyroidism.

Adolescent↗
PubMed1978

Pupillary abnormalities in schizophrenic patients during long-term administration of psychotropic drugs: dissociation between light and near vision reactions.

Pupillographic studies were made of the reactions to light and near vision in 12 schizophrenic patients under long-term administration of psychotropic drugs. The results showed a significant reduction in the light reaction, while the near vision reaction was preserved. The pupillographic study revealed not only reduction in amplitude of the light reaction but also changes in dynamic aspects of the reaction, i.e., prolonged latency time, shortened constriction time, and half redilatation time after the light stimulus. The mechanisms underlying the dissociation between light reaction and near vision reaction induced by long-term administration of psychotropic drugs are obscure, but both the peripheral and central actions of these drugs may be involved.

Adult↗
PubMed1975

[Studies of the relationship between renin secretion and the sympathetic nervous system responsiveness in man (author's transl)].

In recent years many investigators have reported the role of the sympathetic nervous system and the catecholamines in the regulation of renin secretion. It has been recently reported that plasma dopamine-beta-hydroxylase (DBH) excreted through the mechanism of the exocytosis with noradrenaline from the sympathetic postganglionic nervous endings is a mirror of the function of the sympathetic nervous system. In this investigation, blood pressure, urinary catecholamine excretion, plasma DBH activity and plasmsa renin activity (RPA) have been determined in normal individuals during the mecholyl test and insulin-induced hypoglycaemia. In the mecholyl test, plasma DBH activity and PRA markedly increased in five males who showed prominent responses of systolic blood pressure to mecholyl (S type) and changed slightly in eight males who showed minimal responses of systolic blood pressure to mecholyl (N type). It showed that there was a significant relationship between the maximal percent increases from their respective control values of plasma DBH activity and those of PRA following mecholyl. In insulin-induced hypoglycaemia, plasma DBH activity, blood pressure and PRA remarkably increased following a large dose of insulin administration (0.15 u/kg). In a dose of 0.1 u/kg, there was no significant increase of plasma DBH activity and blood pressure. PRA singificantly increased but was lower than a large dose of insulin. Also, it showed that their was a significant relationship between maximal percent increases from their respective control values of plasma DBH activity and those of PRA following insulin administration. These data indicate a close correlation between changes in plasma DBH activity and those of PRA during mecholyl and insulin-induced hypoglycaemia and lend additional support to the concept of sympathetic nervous system mechanism of renin secretion.

Adult↗