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Biomedical subjects

H Kawata

Publications and source records attributed to H Kawata.

At least 109 records · Page 6Linked to original sources
PubMed1990

Effects of sodium depletion on the caffeine-induced contraction of frog's skeletal muscle.

Effects of depletion of Na ions from the environmental medium on the caffeine-induced contraction were investigated in both intact and skinned fibers prepared from the frog's fast twitch muscle. In intact muscle fibers, both the twitch and the contracture induced by 5 mM caffeine were enhanced by depleting the external Na at 9-10 degrees C. In contrast, in the mechanically skinned muscle fiber, which was used to examine the capability of the sarcoplasmic reticulum to take up Ca ions from the sarcoplasm and/or the superfusing medium, the contractile tension as well as its fractional area measured by applying 25 mM caffeine were markedly inhibited by Na-depletion at 5 degrees C. The apparent discrepancy between these two conditions is discussed.

Animals↗
PubMed1990

Dependence of contractile responses by some calcium antagonists on external calcium in the skeletal muscle.

Dependence of contractile potentiation by calcium antagonists on external calcium was investigated on the frog's twitch muscle. Low concentrations (10(-6) to 10(-5) M) of nicardipine and verapamil enhanced the peak tension of both twitch and electrically induced contracture in the presence of calcium. In the calcium-free media the drugs suppressed the contractile tension. Caffeine contracture was inhibited by the calcium antagonists at 20 degrees C. This inhibition was caused by an early onset of relaxation, which was not observed at 7 degrees C. The results suggest that some interaction between calcium ions and drug molecules at the voltage sensor on the transverse tubular membrane, which regulates E-C coupling but is not directly related to the functional calcium channel, may play an important role for the phenomena. The inhibitory action of calcium antagonists on the caffeine contracture in the presence of calcium is probably independent of the potentiating effect seen in the depolarization-induced contractions.

Animals↗
PubMed1990

Changes in contractile force by barium in the frog skeletal muscle.

Effects of Ba2+ ions on the contractility were investigated in the frog skeletal muscle under the current clamp condition. The membrane potential was depolarized by 10 to 20 mV by perfusing 2 mM Ba2+ for 5 to 10 min. Membrane resistance was first increased and then decreased. The mechanical threshold examined in TTX-containing solution was shifted to more positive potential by applying Ba2+. The electrically induced contracture in TTX-solution as well as twitch in normal Ringer were enhanced by superfusing Ba2+. In both types of contraction an afterpotentiation was observed on washing out of Ba2+ ions, reflecting the existence of an inhibitory action during Ba2+ perfusion which could be masked by potentiation. Caffeine was able to induce contracture even in muscles soaked in "zero" Ca2+ solution for 24 to 48 h. In these muscles Ba2+ was more effective than Ca2+ to potentiate the contracture tension presumably by releasing Ca2+ ions from the sarcoplasmic reticulum whereas Mg2+ inhibited it.

Animals↗
PubMed1990

[Double chambered right ventricle: surgical experience in a 60-year-old woman].

The patients reported as double chambered right ventricle are mainly children. A 60-year-old woman had been pointed out for her systolic cardiac murmur without any symptom. She was admitted to our hospital for her gradual onset of fatigue, lassitude. Cardiac catheterization data revealed a 105 mmHg peak-to-peak gradient within the right ventricular cavity with normal pulmonary pressures [20/5 (12) mmHg]. Right ventricular end-diastolic pressure was 4 mmHg. Right ventriculogram demonstrated double chambered right ventricle. Electrocardiogram showed neither right ventricular hypertrophy nor upright T wave in V3R. In order to release intraventricular pressure gradient and her symptom, the anomalous muscle bundles were resected through both the right atrium and the pulmonary artery. Surgical repair without right ventriculotomy is suitable for such an elder patient with double chambered right ventricle whose ventricular function may decrease.

Age Factors↗
PubMed1989

Twitch potentiation of frog (Rana japonica) skeletal muscle by antipyrine.

1. The effects of antipyrine on single muscle fibres from the frog Rana japonica were examined. Antipyrine potentiated the twitch tension, but did not affect the tetanus response or induce any contracture by itself. 2. The duration of the action potential was prolonged in a dose-dependent manner. 3. Antipyrine did not affect the mechanical threshold, the uptake of Ca2+, or the Ca2+ induced release of Ca2+ from the sarcoplasmic reticulum. 4. Ca2+-channel blockers did not affect the twitch potentiation by antipyrine.

Action Potentials↗
PubMed1989

[Analysis of the result of thyroid microsomal particle agglutination test by ELISA].

No accurate method to detect thyroid microsomal (MC) antibody (Ab) in serum has been generalized. In this study, the titer of MC Ab obtained by the method of MC autoantibody particle agglutination (MCPA) was analyzed by enzyme linked immunosorbent assay (ELISA). MC and thyroglobulin (Tg) were prepared from Graves' thyroid. ELISA was done by coating the plate with MC, adding Tg to buffer and using peroxidase-conjugated anti-h IgG. 1) The titer of MCPA correlated with the MC Ab ELISA index in serum without Tg Ab, but it did not in serum with Tg Ab. MC Ab was negative by ELISA while it was positive by MCPA in some of the sera with Tg Ab. 2) When ELISA was done using buffer without Tg, the amount of IgG bound to MC was greater in serum with TGPA: + and MCPA: - than in serum with MCPA: + and TGPA: -. 3) The zone phenomenon observed in MCPA did not always indicate an excess of MC Ab. 4) MC Ab was positive by ELISA in some of the negative MCPA sera obtained from patients with Hashimoto's disease in which diagnosis was confirmed by biopsy. In conclusion, the result obtained in MCPA now in use is strongly influenced by Tg Ab. Furthermore, since binding of Ab to MC is judged by agglutination of particles in MCPA, ELISA is superior in sensitivity and accuracy in detecting MC Ab.

Agglutination Tests↗
PubMed1989

[Subclavian flap aortoplasty with preservation of arterial blood flow to the left arm for coarctation repair--report of 2 cases].

Two infants with coarctation of the aorta were successfully repaired by the modified method of subclavian flap aortoplasty with preservation of arterial blood flow to the left arm. The left subclavian artery was detached from the aorta at its origin, opened longitudinally in its posterior wall and sutured over the coarctation site. Widening of the stenosis and preserving of the blood flow to the left arm were obtained. This operative technique seems advantageous without complications induced by sacrificing the continuity of the subclavian artery, reserving the advantages of the former subclavian flap aortoplasty.

Aortic Coarctation↗
PubMed1989

[A case of successful modified Fontan operation in pulmonary atresia and intact ventricular septum].

A 5 year-old girl with pulmonary atresia with intact ventricular septum underwent a modified Fontan operation successfully. In spite of the previous Brock and shunt procedures, the right ventricle remained hypoplastic as end diastolic volume of 50% of normal with hypoplastic tricuspid valve. A modified Fontan operation was performed as a definitive operation with main reason of hypoplastic tricuspid valve. The selection of the definitive procedures was discussed.

Child, Preschool↗
PubMed1988

Effects of external sodium removal on the contracture of frog skeletal muscle.

Effects of removal of the external sodium on the contractility of the frog's skeletal muscle were studied. Sodium-free solution, replaced by choline, strongly augmented the twitch tension before it abolished the action potential. A similar marked potentiation was also observed in the sustained contracture induced by a small depolarization under the current-clamped condition where generation of conductive action potential was blocked. On the other hand, the maximum contracture induced either by electrical stimulation or by high potassium solution was not modified by lowering the external sodium concentration. Furthermore, contraction threshold measured on the electrically induced contracture was shifted to more negative value of the membrane potential. Caffeine contracture, examined by a short-term application of 5 mM caffeine, was first inhibited by sodium-free solution but afterwards restored or even augmented during the sodium-free perfusion. From these observations it is concluded that a removal of external sodium lowered the mechanical threshold of the muscle by affecting some step of the coupling process at the T-SR junction without affecting the contractile machinery.

Animals↗
PubMed1988

Effects of extracellular calcium and other divalent cations on mechanical response of frog skeletal muscle.

In order to investigate the mechanism by which elevated extracellular Ca ions decrease twitch and tetanus tension in frog skeletal muscle we made mechanical and electrophysiological measurements on single fibers or small bundles from twitch muscles. High concentration of Ca caused a hyperpolarization and an increase in the duration of action potential. The mechanical threshold, estimated by using the strength-duration curve, was shifted upward by adding Ca ions. These effects were fully reversible. Steady state twitch tension was slightly increased by replacing Mg and Ni with Ca and decreased by elevating their concentrations, although Ba resulted in a marked twitch augmentation and a positive correlation with the ion concentration. By contrast, the strength-duration curve was shifted upward by Ni while Mg and Ba showed no shift. These evidences point to a failure of the early step of excitation-contraction coupling, including the T-membrane depolarization, as the primary mechanism of action of high concentration of Ca, Mg, and Ni ions, whereas Ba ion has an additional intracellular potentiating effect.

Action Potentials↗