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Biomedical subjects

K Yanagihara

Publications and source records attributed to K Yanagihara.

At least 181 records · Page 10Linked to original sources
PubMed1980

Inward current activated during hyperpolarization in the rabbit sinoatrial node cell.

Inward current activated by hyperpolarization (ih) was dissected from the K-current by the difference in its activation voltage range and the selective blocking effect of Ba2+ on the K-current. The ih shows little specificity to any particular ion, and its reversal potential was -25 mV. The current system can be expressed well by Hodgkin-Huxley type kinetics. The time constant of ih ranged from 2-4 s at about -70 mV, but it became shorter at about -10 mV. The ih began to activate at -50 mV and fully saturated at about -100 mV. The fully activated current-voltage relation shows no rectifying property. Activation and deactivation time courses were fitted by a single exponential with the same time constant at a given membrane potential. Although ih plays only a small role during the normal action potential in the isolated preparation, it plays a significant role in keeping the pacemaker cell at a low membrane potential

Animals↗
PubMed1980

Potassium current during the pacemaker depolarization in rabbit sinoatrial node cell.

Voltage clamp experiments were carried out on the rabbit sinoatrial (S-A) node. The delayed outward current in the voltage range between --60 mV and --22 mV almost disappeared in the presence of 5 mM Ba2+. The slow inward current and the hyperpolarization-activated current remained unaffected. In the absence of the time-dependent potassium current the S-A node cell generated spontaneous action potentials, provided that the membrane was hyperpolarized by constant outward current. Therefore it seems unlikely that the potassium current plays an essential role in generating the pacemaker potential in the S-A node. The time course of the potassium current (iK) during the cardiac cycle was calculated using equations simulating the kinetics of iK. According to this computation, the change of iK in the S-A node is small during pacemaker depolarization. It is proposed that the gradual decay of potassium conductance is less important for the development of the pacemaker potential than the contribution of the slow inward current.

Action Potentials↗
PubMed1980

Ionic current and pacemaker activity of the S-A node cells.

1) Five membrane current (if, is, ik, ih, il) were observed in rabbit S-A node cells by the voltage clamp method. 2) The outward current (ik) was carried by k ion, while the inward current (is) was mainly carried by Na ion with some contribution of Ca ion. The inward current activated by hyperpolarization (ih) ws a mixed current system, but participation of Na and Cl ions was found to be existed. 3) Each current was analysed according to the Hodgkin-Huxley type equation. 4) Finally the action potential and pacemaker activity of S-A node were reconstructed. 5) In phase 4 diastolic depolarization, is played the major role, but the assistance of ik ws also important.

Animals↗
PubMed1980

Reconstruction of sino-atrial node pacemaker potential based on the voltage clamp experiments.

The pacemaker activity of the S-A node cell was explained by reconstructing the pacemaker potential using a Hodgkin-Huxley type mathematical model which was based on the reported voltage clamp data. In this model four dynamic currents, the sodium current iNa, the slow inward current, is, the potassium current, iK, and the hyperpolarization-activated current, ih, in addition to a time-dependent leak current, i1 were included. The model simulated the spontaneous action potential the current voltage relationship, and the voltage clamp experiment in normal Tyrode solution of the rabbit S-A node. Furthermore, the changes of activity induced by the potassium current blocker Ba2+, by applying constant current, acetylcholine, and epinephrine were also reconstructed. It was strongly suggested that the pacemaker depolarization in the S-A node cell is mainly due to a gradual increase of iS during diastole, and that the contribution of iK is much less compared to the potassium current iK2 in the Purkinje fiber pacemaker depolarization. The rising phase of the action potential was due to iS and the plateau phase is determined by both the inactivation of iS and activation of iK.

Acetylcholine↗
PubMed1979

Cross-sectional echocardiographic diagnosis of coronary artery aneurysms in patients with the mucocutaneous lymph node syndrome.

Real-time cross-sectional echocardiographic studies revealed the presence of coronary artery aneurysms in five patients with mucocutaneous lymph node syndrome. These lesions appeared as circular echo-free spaces with clearly-defined borders in sites corresponding to angiographically proven aneurysms. In 15 normal subjects who were studied only by noninvasive methods, and in 17 who had normal coronary arteriograms (including eight with the mucocutaneous lymph node syndrome), we found no similar echo findings. The aneurysms were in both right and left coronary arteries in three patients, and were confined to the left side in two. The mucocutaneous lymph node syndrome is an increasingly common condition in Japan which may be fatal due to myocardial infarction occurring in a setting of coronary aneurysm with thrombosis. Therefore, the ability to demonstrate coronary aneurysms noninvasively is of prognostic and potentially therapeutic value in this inadequately understood syndrome.

Adult↗
PubMed1979

Noninvasive diagnosis of pseudoaneurysm of the left ventricle.

The echocardiographic, scintigraphic, angiocardiographic and autopsy correlations in a patient with left ventricular pseudoaneurysm are presented. Interruption of the echo of the left ventricular wall and radioisotope image of pseudoaneurysm and its communication channel are demonstrated for the first time. The striking similarity of the radioisotope image to the angiographic image is noted. This study suggests that echocardiography has capability to visualize left ventricular wall defects, such as the perforation seen in this case and radioisotope ventriculography is equivalent to the invasive contrast technique. Both of the methods seem to be safe and specific for the diagnosis of left ventricular pseudoaneurysm.

Aged↗
PubMed1978

Cross-sectional echocardiographic diagnosis of large left atrial tumor and extracardiac tumor compressing the left atrium. Limitation of M mode echocardiography in distinguishing the two lesions.

A case of a left atrial fibrosarcoma arising from the posterior left atrial wall and two cases of an extracardiac tumor compressing the left atrium were studied with M mode and cross-sectional echocardiography. In all three cases, M mode echocardiography revealed a mass of echoes just behind the aorta and did not distinguish a left atrial from an extracardiac tumor. By contrast, cross-sectional echocardiography allowed direct visualization of the location, size and movement of the tumor in all three cases and contributed to distinguishing the two lesions. This study indicates that cross-sectional echocardiography is more accurate than M mode echocardiography in the differential diagnosis of a large left atrial tumor and extracardiac tumor compressing the left atrium.

Adult↗
PubMed1978

Ultrasonic features of anomalous origin of the left coronary artery from the pulmonary artery.

Two cases of anomalous origin of the left coronary artery from the pulmonary artery with and without marked dilatation of the right coronary artery were studied by M-mode echocardiography and cross-sectional echocardiography. The M-mode echocardiogram obtained from the case with the dilated right coronary artery demonstrated an abnormal structure anterior to the aortic root. The cross-sectional echocardiogram of the same case visualized the origin of the dilated right coronary artery. In addition, echocardiographic abnormalities suggesting the ischemia of the left ventricle were observed in both cases. Although many of the ultrasonic features are nonspecific, the combination of ultrasonic technique provides useful clues to the diagnosis of anomalous origin of the left coronary artery from the pulmonary artery.

Adult↗
PubMed1978

Echocardiographic features of congenital pulmonary regurgitation.

Eight patients with congenital pulmonary regurgitation documented by cardiac catheterization and angiography were studied by echocardiography. Echocardiographic features of the pulmonary valve observed in this condition included a) diastolic fluttering (5 cases), b) diastolic separation (2 cases), and c) increase of posterior motion during atrial systole (a wave). Maximum a wave depth exceeded the upper limit of the normal value in 2 cases and averaged 6.1 +/- 0.7 (standard error of the mean) mm. In addition, d) diastolic fluttering of the anterior tricuspid valve was seen in 5 cases and e) abnormal interventricular septal motion in 2 cases (one, paradoxical and the other, flat). Of these findings, the diastolic fluttering of the pulmonary valve, which results from the turbulent stream of blood in the outflow of the right ventricle striking the pulmonary valve, is pathognomonic for pulmonary regurgitation. Although the other findings are nonspecific, all patients had at least 1 of these 5 findings. Echocardiography, therefore, provides useful clues to the diagnosis of pulmonary regurgitation. Furthermore, echocardiography should be of use in differentiating congenital from functional pulmonary regurgitation and from aortic regurgitation.

Adolescent↗
PubMed1978

Cellular injury of adrenocorticotropic pituitary tumor (AtT-20) by corticosteroid in mice.

A transplantable ACTH-secreting pituitary tumor (AtT-20) in mice was studied for its growth in relation to adrenocortical steroid. The latency of transplanted tumor in LAF-1 mice with 10(6) tumor cells was about 2 weeks in adrenalectomized and in intact mice. In the former, however, tumor size reached 1.5 cm in diameter within 1 month, while it remained about 0.5 cm in the latter. Macroscopic and microscopic observation revealed that the tumor grafted in intact mice showed massive necrosis, leaving minimum intact tumor cells among necrotic foci. In contrast, the tumor grafted in adrenalectomized mice was healthy, soft, and showed adenomatous structure. It is concluded that excess of adrenocortical steroid produced in the grafted AtT-20 was inhibitory for the growth of transplanted tumor and removal of the adrenal glands was good for growth and survival of transplanted tumor. For the assessment of direct effect of adrenal steroid on AtT-20 cells, incorporation of 3H-thymidine in cultured AtT-20 cells was examined in a medium supplemented with glucocorticoid hormone. The autoradiographic study indicated that the inhibition of 3H-thymidine uptake was demonstrated at 24 hr after incubation with steroid and labeled cells were barely detectable on 3rd and 5th day.

Adenoma↗