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Biomedical subjects

H Kotake

Publications and source records attributed to H Kotake.

At least 145 records · Page 8Linked to original sources
PubMed1988

[Coronary artery tone assessed by the administration of ergonovine maleate and nitrates].

Angiographic changes caused by administering ergonovine maleate (EM) and nitrates were quantitated in 136 patients without significant coronary artery disease. Percent coronary artery (CA) narrowing was calculated in 67 patients with a negative EM test (Group A) and 69 patients with a positive EM test (Group B) as follows: (Formula; see text) In both groups, coronary artery narrowing before and after EM did not differ among the proximal, middle or distal segments of each coronary artery. The measurements of the right coronary artery were greater than those of the left anterior descending artery (p less than 0.01 after EM, p less than 0.05 before EM), and those of the left main trunk were markedly less than those of the other coronary arteries (p less than 0.01). In both groups, coronary narrowing after EM administration was greater than before administration (p less than 0.01). Initial coronary narrowing in Group B was also greater than in Group A (p less than 0.01), similar to the responses for EM. In 19 patients with coronary artery spasm provoked by EM coronary artery narrowing before and after EM was 37 +/- 12% and 69 +/- 23% for coronary arteries with spasm, and 30 +/- 13% and 42 +/- 16% for those without spasm. Not only after, but also before EM administration, coronary narrowing was greater in the arteries with spasm than in those without spasm (p less than 0.01). Furthermore, the arteries without spasm showed greater sensitivity to EM and nitrates than did the arteries of the control patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Vessels↗
PubMed1987

Effect of trimebutine maleate on sinus node pacemaker activity of the rabbit.

The electrophysiological effects of trimebutine maleate were studied on rabbit sinus node cells with the two-microelectrode voltage clamp method. Trimebutine (above 10 microM) produced a negative chronotropic effect accompanied by decreases in the maximum upstroke velocity at phase 0, slope of phase 4 depolarization and action potential amplitude. The effects on the current systems were depression of the slow inward current and a decrease in the current oscillations induced by elevating [Ca]0. It is concluded that trimebutine exerts a Ca2+ channel blocking effect on the sinus node pacemaker cells.

Action Potentials↗
PubMed1987

On the ionic mechanism of cyproheptadine-induced bradycardia in a rabbit sinoatrial node preparation.

The effects of cyproheptadine (0.1-10 microM) on the membrane potentials and currents of rabbit sinoatrial node were examined with the double-microelectrode voltage clamp technique. Cyproheptadine reduced the heart rate, maximum rate of depolarization and action potential amplitude. It also decreased the slope of phase 4 depolarization. On the current systems, cyproheptadine decreased the slow inward current (Isi), the time-dependent potassium outward current (Ik) and the hyperpolarization-activated current (Ih). The reduction of Isi was the major effect. Furthermore, Isi was progressively decreased by repetitive membrane depolarization during administration of cyproheptadine, an effect suggestive of frequency-dependent block of Isi. These electrophysiological observations indicate that cyproheptadine has a calcium antagonistic property, and additionally, decreases Ik and Ih in rabbit sinoatrial node.

Action Potentials↗
PubMed1987

Inhibition of Ca2+ inward current in rabbit sinoatrial node by bunazosin, an alpha-adrenoceptor antagonist.

The electrophysiological effects of bunazosin, a novel alpha-adrenoceptor antagonist, were examined on isolated spontaneously beating sinoatrial node preparations of the rabbit by means of a double-microelectrode voltage clamp method. Bunazosin (above 10 microM) reduced the beating frequency, and the maximum rate of rise and the amplitude of action potentials. The slope of the diastolic depolarization (phase 4) was also decreased by the drug whereas the action potential duration at 50% repolarization was prolonged. Bunazosin decreased the slow inward current (Isi) and the time-dependent potassium outward current (IK). However, the major effect was the reduction of Isi. The results indicate that bunazosin, an alpha-adrenoceptor antagonist, depresses the action potential and automaticity of the sinoatrial node by inhibition of Ca channels.

Action Potentials↗
PubMed1987

Inhibitory action of 711389-S on the electrical activity of rabbit sinoatrial node.

The effects of 711389-S (0.1-10 mumol.litre-1) on membrane potentials and currents of rabbit sinoatrial node preparations were studied using a conventional double microelectrode voltage-clamp method. The agent 711389-S decreased the heart rate, the maximum rate of depolarisation, and the amplitude of the action potential and increased the action potential duration in a dose dependent manner. The slope of the diastolic depolarisation was also reduced. Of the current systems of sinoatrial node, 711389-S depressed the slow inward current (Isi), the potassium outward current (IK), and the hyperpolarisation activated current (Ih) dose dependently. The kinetics of IK were not altered significantly by the drug. It is concluded that 711389-S does not have an effect on a single current system but that the drug exerts a depressant effect on the electrical activity of the sinoatrial node.

Animals↗
PubMed1987

A case of four coronary artery fistulae originating from three vessels associated with aneurysm.

A case of an aneurysm associated with four coronary artery fistulae originating from three vessels is reported. The patient, a 52-year-old woman, had chest heaviness and palpitations. Coronary arteriography revealed the four fistulae originating from three coronary vessels with an aneurysm draining into the left ventricle and the main pulmonary artery. The patient's symptoms were relieved after fistulectomy and the aneurysmectomy, suggesting that a coronary steal phenomenon through the fistulae was the cause of her symptoms. This case is of interest because of its rarity, since this is the first case report of an aneurysm associated with four coronary artery fistulae from three vessels.

Arterio-Arterial Fistula↗
PubMed1987

Estimation of catecholamine potencies on the myocardium by means of a new method.

A simple method is described for evaluating the potencies of catecholamines on the slow response of myocardium. Catecholamines depolarize guinea pig ventricular muscle cells exposed to the high K+ (27 mmol/l) Tyrode's solution containing 0.2 mmol/l Ba through an increase in slow channel conductance. Higher concentrations of catecholamines in addition induce spontaneous action potentials. This model was used to estimate and compare catecholamine potencies on myocardium. Catecholamine concentrations needed for depolarization alone or for depolarization plus automatic activity were taken as basis for comparison. The order of potency obtained by means of this new method was: l-isoproterenol greater than l-adrenaline greater than or equal to dl-noradrenaline greater than or equal to dobutamine greater than or equal to dopamine. This is similar to the order reported with other methods.

Action Potentials↗
PubMed1987

Cardiac involvement in a patient with limb-girdle muscular dystrophy.

A case of limb-girdle muscular dystrophy with cardiomegaly, electrocardiographic abnormalities, and paroxysmal ventricular tachycardia was described. Some of the interesting electrocardiographic features were discussed, and the importance of serial electrocardiograms for the detection of cardiac involvement is emphasized, since acute disturbances in cardiac rhythm may indicate that the patient is in immediate danger of sudden death.

Cardiomegaly↗
PubMed1987

Comparison of the chronotropic responses to tri- and tetracyclic antidepressants in isolated sinoatrial node preparations from the rabbit.

The effects of maprotiline and mianserin, tetracyclic antidepressant agents, on membrane potentials and currents of rabbit sinoatrial node cells were studied and compared to those of a tricyclic antidepressant compound, imipramine. Imipramine (10 microM), maprotiline (30 microM) and mianserin (100 microM) significantly decreased the spontaneous rate, the maximum rate of rise and the action potential amplitude. The slope of the diastolic depolarization was also decelerated by these drugs. On the current systems, imipramine (10 microM), maprotiline (10-30 microM) and mianserin (40-100 microM) decreased the slow inward current, the time-dependent potassium outward current and the hyperpolarization-activated inward current. Although all these antidepressant agents have qualitatively similar depressant effects, the inhibitory potency on the electrical activity of sinoatrial node was: imipramine greater than maprotiline greater than mianserin. These electrophysiological observations suggest that tetracyclic antidepressant agents might have less pronounced cardiotoxicity than did tricyclic antidepressants in slow response fibers.

Action Potentials↗
PubMed1987

[Metastatic tumor of the heart from gall bladder cancer detected by echocardiography: a case report].

Cardiac metastases have been reported increasingly partly because of the longevity of cancer patients, but its antemortem diagnosis is frequently missed. This is due to the nonspecific clinical manifestations or relative lack of characteristic signs which are masked by the underlying disease. This is a report of a 42-year-old man diagnosed as having a metastatic cardiac tumor by echocardiography, six months after operation for squamous cell carcinoma of the gall bladder. Echocardiography revealed abnormal structures in the regions of the posterior and lateral walls of the left ventricle and interventricular septum, suggesting metastatic tumors. The cytological findings of a fine-needle aspiration biopsy specimen were squamous cell carcinoma. The patient died of cardiac failure eight months after the echocardiographic diagnosis. At autopsy, the abnormal structures in the heart were identified as cardiac metastatic tumors from gall bladder cancer. Reports of cardiac metastasis of gall bladder cancer is very rare (0-3%). The myocardial metastasis may have a more serious prognostic importance than the primary neoplasm itself; thus, its definite diagnosis is mandatory.

Adult↗
PubMed1987

Effect of bepridil on membrane currents of rabbit sinoatrial node cells.

Effect of 1-[3-isobutoxy-2-(benzylphenyl) amino]propyl pyrrolidine hydrochloride (bepridil), a new antianginal agent, on membrane potentials and membrane currents of sinoatrial node cells of rabbits was examined using conventional microelectrode and double microelectrode voltage clamp methods. Bepridil at a concentration of 10 mumol/l caused an increase in spontaneous cycle length, and a decrease in maximum rate of rise of the action potential and action potential amplitude. The rate of diastolic depolarization (phase 4) was also decreased by the drug. In the voltage clamp experiment, bepridil reduced both the slow inward current (Isi) and the hyperpolarization activated current (Ih), and increased the recovery time constant of Isi, whereas the time-dependent potassium current (IK) was not altered significantly. The major effect, however, was the reduction of Isi. These electrophysiological findings suggest that bepridil has a depressant effect on the electrical activity of sinoatrial node mainly by mediating the depression of slow channel.

Action Potentials↗
PubMed1987

Electrophysiological study of cibenzoline in voltage-clamped rabbit sinoatrial node preparations.

Effects of cibenzoline (0.1-30 microM) on membrane potentials and currents were investigated in rabbit sinoatrial node cells using conventional microelectrode and double microelectrode voltage clamp methods. Cibenzoline reduced the heart rate, the maximum rate of rise and the action potential amplitude in a dose-dependent manner. At the same time, the action potential duration at half-amplitude was prolonged, and the slope of phase 4 depolarization was decelerated. The voltage clamp experiment revealed that cibenzoline (7-30 microM) depressed the slow inward current, the time-dependent potassium outward current and the hyperpolarization activated current. Neither the kinetic variable of the time-dependent potassium outward current nor the decay time of the outward current tail was altered by the drug perfusion. The results suggest that cibenzoline exerts a depressant effect on the electrical activity of sinoatrial node cells and that the depression of the currents induced by cibenzoline is due to a reduction in conductances of the current systems.

Action Potentials↗
PubMed1987

Complete atrioventricular block with a 22-month history of ocular sarcoidosis: a case report.

A 52-year-old woman with acute uveitis associated with ocular sarcoidosis developed complete atrioventricular block 22 months after the initial diagnosis was made. Cardiac sarcoidosis is a serious and, not infrequently, a fatal disease. Although it is difficult to establish the clinical diagnosis of cardiac sarcoidosis, a serial ECG is considered necessary in patients with any kind of sarcoidosis.

Cardiomyopathies↗
PubMed1986

Electrophysiological actions of mexiletine on rabbit sinoatrial node cells.

The effects of mexiletine (1-100 microM) were examined on membrane potential and current of rabbit sinoatrial node cells by means of conventional microelectrode and double microelectrode voltage clamp techniques. Mexiletine decreased, in a dose-dependent manner, the maximum rate of depolarization of the action potential and the action potential amplitude, and increased the spontaneous cycle length. The slope of the diastolic depolarization (phase 4) was also reduced. In the voltage clamp experiment, mexiletine (40-100 microM) reduced the slow inward current (Isi), the potassium outward current (IK) and the hyperpolarization-activated current (Ih). The kinetic variable of IK was not altered by the drug. These results suggest that mexiletine does not have a specific effect on a single-current system, but that relatively high concentrations of mexiletine exert an inhibitory effect on the electrical activity of the sinoatrial node cells.

Action Potentials↗
PubMed1986

Histomorphometric study of trabecular channels in normal iliac bone.

Cancellous bone channels in the normal iliac crest have been studied histologically and by histomorphometry, and their biological role has been considered. Eighty percent of trabecular channels were typical osteons with the same structural and remodeling features as cortical osteons. The similarity of osteons in these two locations was corroborated by the comparability of morphometric features. The points of difference between osteons in the two types of bone were irregular configurations of trabecular osteons and marrow cells in the central canal in some. Since the number of trabecular osteons decreases with age, and since active trabecular resorption cavities were few in number, it is unlikely that additional osteons are formed in normal bone after the active modeling phase of bone growth. It is improbable that they make a significant contribution to bone remodeling since their number decreases with age, and since the available surface of trabecular channels for remodeling is extremely small. However, it is probable that they aid the intraosseous microcirculation and mineral exchange in thick trabecula and bifurcations, where they are mainly located. The demarcation curves at the 95% confidence interval, which suggest the normal range for numbers of channels, was calculated from the scatter diagram against bone area.

Adolescent↗
PubMed1986

Rate-force relationship and calcium overload in canine Purkinje fibers.

The relationship between driving rate and contractile force was studied in calcium-overloaded canine cardiac Purkinje fibers perfused in vitro. The following results were obtained. In Tyrode solution (2.7 mM Ca), increasing the drive rate ('overdrive') induced an initial decrease followed by a progressive increase in force; the initial decrease was more pronounced and the subsequent increase slower when the driving rate was faster; returning to the basal slow rate caused a transient increase in force above control and this increase was greater when overdrive was faster; a stepwise increase and decrease in rate led to an initial decrease in force with each increment in rate and an initial increase with each decrement in rate; increasing [Ca]o up to 16.2 mM reversed both the initial fall during and the transient increase in force after overdrive; these changes in force were associated with oscillatory potentials, a sign of calcium overload; similar results were obtained by inducing calcium overload with a low [Na]o solution or strophanthidin; the altered force patterns and the oscillatory potentials were reduced or eliminated if calcium load was reduced by decreasing the basal rate or [Ca]o, by increasing [K]o or by administering tetrodotoxin. It is concluded that in Purkinje fibers the force-frequency relationship is markedly altered in the presence of calcium overload because overdrive further increases the calcium load and this results in a reversal of the relation between calcium and force.

Animals↗