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Biomedical subjects

Y Iwayama

Publications and source records attributed to Y Iwayama.

At least 55 records · Page 3Linked to original sources
PubMed1981

Dopamine receptor in anterior byssus retractor muscle of Mytilus edulis.

Effects of dopamine, N-methyl-, ethyl- and propyl-derivatives of dopamine, and alpha- and beta-adrenoceptor stimulants on catch contraction of anterior byssus retractor muscle of Mytilus edulis were tested. The test drugs except the beta-adrenoceptor stimulants relaxed catch contraction. Dopamine was most active and substitution of amino group in dopamine with ethyl and propyl decreased activity considerably. The concentration-curves of dopamine, its derivatives and norepinephrine shifted in parallel with application of haloperidol but were not influenced by the alpha- and beta-adrenoceptor antagonists. These results suggest that relaxation of catch contraction by catecholamines is mediated through a dopamine receptor. This muscle is considered to be suitable for a study of the dopamine receptor.

Animals↗
PubMed1980

Cardiotonic effect of phthalazinol (EG-626) in the isolated guinea pig by myocardium: mechanical and electrophysiological study.

EG-626, 7-ethoxycarbonyl-6, 8-dimethyl-4-hydroxymethyl-1 (2H)-phthalazinone, was found to be a considerably potent cardiotonic agent. It produced both the positive chronotropic and inotropic actions in the guinea pig heart muscle. Positive inotropic action of isoproterenol was potentiated by EG-626 at the concentration which did not produce a substantial positive inotropic action by itself. Cardiac action potential was not modified by EG-626 at concentrations sufficient to produce positive inotropic actions. EG-626 has a strong activity to produce slow responses in the depolarized myocardium, indicating that it can increase the density of the slow channels. The possibility was shown that the increase in the density of the slow channel may play an important role in the positive inotropic action of EG-626. The increase in the intracellular cyclic AMP due to the phosphodiesterase inhibition is tentatively most likely to be the cause of the EG-626 induced in the density of the slow channels.

Adrenergic alpha-Agonists↗
PubMed1980

Controlled clinical evaluation of a 10% strontium chloride dentifrice in treatment of dentin hypersensitivity following periodontal surgery.

Sixty adult patients were examined for dentin hypersensitivity prior to periodontal surgery. Stimuli used included mechanical, cold water and compressed air blasts. A subjective assessment of the degree of hypersensitivity for each stimulus was recorded. This presurgical examination revealed 249 hypersensitive areas among 60 subjects. Following surgery there was over a 100% increase in the pain (hypersensitivity) score. Desensitization with a 10% strontium chloride hexahydrate dentifrice was begun 1 week after surgical treatment. After 7 weeks of dentifrice use the pain score was reduced 75.5% in the test group. This was a reduction to a point below the preoperative level. The placebo group showed a reduction of 34.2% which was still above the preoperative level. These results agree with other clinical studies that have demonstrated a desensitizing effect of strontium chloride.

Adult↗
PubMed1979

Inhibitory alpha-adrenergic action of phenylephrine in guinea pig taenia caecum.

Phenylephrine, a selective alpha-adrenergic stimulant, caused a maximal relaxation of the taenia from guinea pig caecum in the concentration of 10(-6) g/ml. Phenylephrine in this concentration did not influence intracellular cyclic AMP and cyclic GMP levels. Although phenylephrine abolished the spontaneous spike discharge, no change was detected in 45Ca-uptake and 45Ca-efflux on the tissue level after phenylephrine. Ca-uptake and Ca-release on the subcellular level were also not influenced by phenylephrine. In Ca free-solution phenylephrine inhibited the response to CaCl2. Phenylephrine increased 42K-efflux in the normally polarized taenia and also in the K-depolarized taenia.

Action Potentials↗