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Biomedical subjects

Y Yazaki

Publications and source records attributed to Y Yazaki.

At least 829 records · Page 46Linked to original sources
PubMed1981

[Two-dimensional echocardiographic findings during syncopal attack due to obstruction in the outflow tract of the left ventricle in a patient with hypertrophic obstructive cardiomyopathy (author's transl)].

The two-dimensional echocardiogram was successfully obtained during syncopal attack due to obstruction in the outflow tract of the left ventricle in a 52 years old male with hypertrophic obstructive cardiomyopathy (HOCM). The diagnosis of HOCM was confirmed by cardiac catheterization which revealed a pressure gradient of 65 mmHg in the outflow tract of the left ventricle during intravenous infusion of isoproterenol (2 micrograms/min). During the test, the patient developed convulsion as well as syncopal attack. The two-dimensional echocardiogram demonstrated a marked protrusion followed by a fixation of the whole mitral complex (SAM component) toward the hypertrophied interventricular septum throughout whole cardiac cycles. Although the mechanism of this phenomenon is not clear, it can be speculated that an abnormally sustained excitation and contraction of the papillary muscles (just like a muscle cramp) may be induced, resulting in the left ventricular outflow tract obstruction.

Blood Pressure↗
PubMed1981

[Hemodynamic responses to supine bicycle exercise in juvenile hypertensive subjects: an echocardiographic assessment (author's transl)].

Six juvenile hypertensive patients were studied by supine bicycle ergometer exercise during continuous echocardiographic recording. Thirteen normotensive young men were also studied for the control. Left ventricular end-diastolic dimensions (Dd) during exercise was significantly increased from 28.8 +/- 0.5 mm/m2 to 29.7 +/- 0.6 mm/m2 in normotensives, but the increase in Dd was not observed in hypertensives. Effects of propranolol on changes in Dd during exercise were almost equal in two groups. Left ventricular end-systolic dimensions (Ds) were decreased during exercise in both groups. After propranolol administration, Ds in hypertensives was significantly increased from 18.8 +/- 1.0 mm/m2 to 19.4 +/- 1.1 mm/m2 at rest, and during the following exercise it reached to 19.7 +/- 1.1 mm/m2, whereas Ds in normotensives was decreased during exercise even after propranolol. Peripheral vascular resistance at rest was almost equal between the two groups, but in hypertensives the reduction during exercise was restricted. These results suggest that sympathetic activities of cardiovascular system are accentuated in juvenile hypertensive subjects.

Adult↗
PubMed1980

Enzymatic activities, activation by actin, and synthesis of cardiac atrial myosin: distinctive enzymatic properties compared with cardiac ventricular myosin.

ATPase activity and synthesis of atrial and ventricular myosin were compared in the dog and rabbit heart. Atrial myosin showed enzymatic properties characterized by high Ca2+- and Mg2+-activated ATPase activities, low activation energy, lower rate of inactivation at alkaline pH, and no activation by N-ethylmalemide compared with the same properties in ventricular myosin. These findings suggest a difference in the myosin molecule at or near the active site involfing the SH-1 thiols. Also, actin activation of ATPase activities was studied to determine the physiological significance of this observation, since, in living muscle cell, MgATP is hydrolyzed by myosin under the activating effect of actin. Actin extracted from skeletal muscle was used in this experiment. Vmax for the actin-activated Mg2+-ATPase of atrial myosin was about twice that of ventricular myosin, whereas no significant difference was observed in the apparent dissociation constant for actin. This result suggests that the change in the enzymatic properties of myosin is reflected in the contractility of atrial and ventricular muscles. However, [3H]leucine incorporation into the myosin was approximately the same, suggesting that the difference in work load between atrium and ventricle is not associated with alteration of synthesis of cardiac myosin.

Actins↗
PubMed1980

Radioimmunoassay of cardiac myosin light chain II in the serum following experimental myocardial infarction.

A sensitive radioimmunoassay for cardiac myosin light chain II (LCII) was developed, and changes of serum LCII levels were studied in experimental myocardial infarction in dogs. This radioimmunoassay employed an antiserum which was prepared in rabbits against canine LCII. In our assay, 0.2-5.0 ng of LCII were effectively measurable. In normal dogs, LCII concentration in serum was less than 20 ng/ml. The serum LCII level began to rise within 6 hr after ligation of the left anterior descending coronary artery, reaching maximum level at 3-5 days (40-320 ng/ml). In eight out of ten cases with coronary occlusion, LCII could be detected as long as 7 days after operation. In one sham-operated dog, LCII was detected at 2 and 3 days, but its concentrations were less than 30 ng/ml. When LCII was injected intravenously, it dissipated from the blood stream within 48 hr. The time course curves of serum LCII level had two characteristics that had not been observed in serum enzyme studies: 1) LCII level rose rapidly and stayed up during a long period after coronary occlusion, and 2) changes of serum LCII levels were biphasic in six out of ten dogs with coronary occlusion. These results, and our previous studies of synthesis rate of light chains, suggest that when a coronary artery is occluded LCII may first be released from a pool of uncombined LCII in myocardial cells, and then continuously liberated from cardiac myosin molecules. This radioimmunoassay can be expected to be useful when applied to clinical use.

Animals↗
PubMed1979

Cardiac atrial myosin adenosine triphosphatase of animals and humans: distinctive enzymatic properties compared with cardiac ventricular myosin.

Cardiac myosin obtained from atria had a higher Ca2+-activated ATPase activity than did cardiac myosin from ventricles in various species of animals and in humans. The increased specific activity of Ca2+-activated adenosine triphosphatase (ATPase) of atrial myosin appeared to correlate with the level of the activity of ventricular myosin ATPase in the animal, since the same order in ATPase activity, as observed in ventricular myosins from various animals, was noted in atrial myosins. The enzymatic properties of atrial myosin also were characterized by no activation by N-ethylmaleimide, low activating energy, and a lower rate of inactivation at alkaline pH compared with the same properties of ventricular myosin. These findings suggest a difference in the myosin molecule at or near the active site, involving some sulfhydryl groups, between the two types of cardiac myosin. The Mg2+-activated ATPase activity, both in the presence and absence of actin (which is thought to be closely related to the basic contraction mechanism), also was enhanced in atrial myosin. Thus, the ATPase activities of atrial and ventricular myosins were different with special reference to the reaction pathway involving calcium and magnesium ions and appear to account for the difference in the velocity of contraction between the atria and the ventricles.

Adenosine Triphosphatases↗
PubMed1978

Binding sites for angiotensin II in human mononuclear leucocytes.

Angiotensin II binding sites were demonstrated in human mononuclear leucocytes by use of [125I]angiotensin II. The binding of [125I]angiotensin II to mononuclear leucocytes was rapid and reversible. The abilities of unlabeled compounds to displace [125I]angiotensin II were proportional to their abilities to displace labeled hormone in adrenal and smooth muscle membrane preparations. The Scatchard plot revealed two apparent orders of binding sites. The affinity constants were comparable with those for binding sites in other main target tissues of angiotensin II.

Adult↗
PubMed1978

The effect of thyroxine on (Na+, K+)-ATPase from the heart and the kidney of rabbit.

The effect of thyroxine on membrane bound (Na+, K+)-ATPase isolated as a microsomal fraction from rabbit heart and kidney was investigated. In the heart, thyroxine administration produced an increased Ki value (a concentration of ouabain required for half maximal inhibition of (Na+, K+)-ATPase activity) without alteration of the specific activity of cardiac (Na+, K+)-ATPase, indicating that the digitalis sensitivity of cardiac (Na+, K+)-ATPase was decreased. On the contrary, a significant increase of the specific activity of renal (Na+, K+)-ATPase was observed without change in its digitalis sensitivity. These results suggest that (1) a decreased sensitivity of cardiac (Na+, K+)-ATPase to digitalis glycosides in thyrotoxic animals may contribute to the decrease in the inotropic and toxic effects of the digitalis glycosides in the hyperthyroid state, and that (2) there may be an organ difference in (Na+, K+)-ATPase.

Animals↗
PubMed1978

[Studies on development of viral hepatitis with HBs antigenemia (author's transl)].

47 cases of viral hepatitis with HBs antigenemia, who were diagnosed by peritoneoscopy and biopsy, were studied. 41 cases were males, and 6 cases were females. The onset ages were mostly in 25--29 years old. The histories of blood transfusion were found in only 4.3%. On the other hand, the families clustered with HBs antigen were found in 68%. Recidivums were often seen (76%), and yet the intervals between recidivum were short (the neighborhood of 8 months). The transaminases at the recidivums were not so high (200 units or thereabout). 20 cases whom biopsies were performed more than twice, were studied histologically. 14 cases were prognessive. 5 were stationary. 1 was improved. In all of progressive cases, sublobular hepatic necrosis was seen. But in other cases, sublobular necrosis was not seen. After this sublobular necrosis, various distortion of the lobule architecture was appeared, and some of them progressed to liver cirrhosis. As to GOT and GPT, GPT was dominant before sublobular neerosis, but GOT was liable to be dominant after sublobular necrosis. Peritoneoscopically, peculiar red spots were found on liver surfaces at the time of sublobular necrosis.

Adult↗
PubMed1975

Effect of the thyroid state on the enzymatic characteristics of cardiac myosin. A difference in behavior of rat and rabbit cardiac myosin.

The effect of thyroid state on the activity of myosin adenosinetriphosphatase (ATPase) was examined in the rat and the rabbit. Cardiac myosin from thyroxine-treated rabbits showed enzymatic properties characterized by high Ca2plus-activated ATPase activity, low activation energy, lower rate of inactivation at alkaline pH, and no activation by N-ethylmaleimide compared with the same properties in the normal rabbit; thyroidectomy did not affect the enzymatic properties of rabbit cardiac myosin. These findings suggest a difference in the myosin molecule at or near the active site, involving some sulfhydryl groups, between hyperthyroid and euthyroid rabbits. However, rat cardiac myosin showed a pattern of activity in the euthyroid state similar to that of the hyperthyroid rabbit and changed to the euthyroid type after thyroidectomy. These changes were specific for cardiac myosin, since no change was observed in skeletal myosin. It is unlikely that there are major differences in the myosin molecule associated with the two types of activity, since similar proportion and amino acid composition of the subunits of cardiac myosin were observed in the different thyroid states. Thus, we concluded that the administration of thyroxine to the rabbit stimulates the synthesis of new cardiac myosin with altered enzymatic properties and that synthesis of this type of cardiac myosin is maintained by the normal level of thyroid hormone in the rat.

Adenosine Triphosphatases↗