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Biomedical subjects

Y Kasuya

Publications and source records attributed to Y Kasuya.

At least 397 records · Page 22Linked to original sources
PubMed1976

The effect of denervation on the synchronization of contraction of the rat vas deferens.

Denervation of the rat vas deferens results in both quantitative and qualtitative changes in the contraction of the isolated smooth muscle. The maximum contraction induced by norepinephrine, acetylcholine or serotonin is enhanced by denervation. The response of the tissue to 2 X 10(-4) M BaCl2 initiates a contraction which is more synchronized than the response of the control tissue. By use of 14C-sorbitol and Co-EDTA for estimating extracellular space and from fluorescence histochemical observations, it appears that facilitation of drug diffusion through the extracellular space plays an unimportant role in the altered response to drugs. In experiments which utilized a double-compartment tissue bath it was found that denervation enhanced the propagation of the contraction in the longitudinal direction. From measurements of the longitudinal tissue impedance it was determined that the resistance between smooth muscle cells was significantly decreased by denervation. These results suggest that denervation improves the propagation of excitation in this smooth muscle.

Animals↗
PubMed1976

Antiarrhythmic action of a new beta-adrenergic blocking agent, 6-(2-hydroxy-3-isopropylaminopropyloxy)-benzothiazole succinate (KF-577), compared with that of propranolol.

The antiarrhythmic activity of a new beta-adrenergic blocking agent, 6-(2-hydroxy-3-isopropylaminopropyloxy)-benzothiazole succinate (KF-577), was compared with that of propranolol. KF-577 antagonized ouabain-induced arrhythmias in normal and bilaterally vagotomized guinea pigs; its antagonistic activity was equal to that of propranolol. Reserpinization greatly reduced ouabain intoxication and neither of the two beta-blockers produced further reduction. Aconitine-induced arrhythmias in rats were not antagonized by the two agents. In intact guinea pigs, the reduction of ouabain intoxication by both beta-blockers could not exceed that produced by simulataneous infusion of KCl, and vice versa. In isolated guinea pig atria, propranolol was about 10 times more effective than KF-577 in reducing the ouabain intoxication. The antiaarhythmic activity of KF-577 paralleled its beta-blocking activity in the isolated preparations but not in the intact animals.

Aconitine↗
PubMed1976

Desensitization of guinea pig tracheal muscle preparation to beta-adrenergic stimulants by a preceding exposure to a high dose of catecholamines.

When a given concentration of a catecholamine was applied to guinea pig tracheal preparation contracted by 20 muM histamine or by 30 mM-K+-Tyrode's solution, constant relaxations were observed, if the relaxation was submaximal. When a high concentration of catecholamine, 200 times the ED50, was once applied, subsequent responses to beta-stimulants (ED80) was reduced by about 30-40%, in spite of repeated washings. The response was gradually recovered in 2 hr. Thus 45 muM epinephrine and 1 muM isoproterenol could cause desensitization to 0.65 muM EPINEPHRINE AND 0.03 muM isoproterenol, respectively. Epinephrine and isoproterenol could cause densensitization to isoprophenamine, a non-catechol beta-stimulant. Epinephrine did not affect the response to cyclic AMP, dibutyryl cyclic AMP, aminophylline and prostaglandin E1. This densensitization was not affected by phentolamine, normetanephrine nor by Ca2+ deprivation from the bathing solution. The mechanisms of the desensitization may relate to some step(s) between the receptor-drug interaction and cyclic AMP accumulation in the process of tracheal muscle relaxation induced by beta-stimulants.

Adrenergic beta-Agonists↗
PubMed1976

Electrophysiologically determined quinidine-like actions of a beta-adrenergic blocking agent, 1-(7-indenyloxy)-3-isopropylaminopropane-2-ol hydrochloride (YB-2).

Since 1-(7-indenyloxy)-3-isopropylaminopropane-2-ol hydrochloride (YB-2) has been reported to be a potent beta-adrenergic blocking agent with antiarrhythmic effects, the electrophysiological effects of this compound on guinea-pig and canine heart muscle were examined. YB-2 was found to have typical quinidine-like actions such as decrease in rate of rise of the action potential, prolongation of refractory period and decrease in conduction velocity.

Action Potentials↗