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Biomedical subjects

N Yoshimoto

Publications and source records attributed to N Yoshimoto.

51 records · Page 3Linked to original sources
PubMed1978

Electrographic changes associated with cyclical reduction of coronary blood flow.

Electrographic changes associated with cyclical reduction of blood flow in partially constricted one or two coronary arteries of anesthetized dogs were examined. In the preparations with single vessel constriction, cyclical ST elevation occurred along with cyclical reduction of coronary blood flow below 25% of the control value. The ST elevation was associated with reciprocal ST depression in the contralateral ventricular surface. In the preparations with double vessel constriction, cyclical reduction of flow frequently occurred in both vessels. The reduction of flow in one vessel occurred not synchronously with that in another vessel in the majority of preparations. The reduction of flow in both vessels was associated with ST elevation in the corresponding areas of the left ventricle. Premature ventricular contractions frequently occurred at the beginning of or immediately after disappearance of ST elevation, or when ST elevation persisted for more than 10 min. Ventricular fibrillation frequently occurred in the preparations with double vessel constriction.

Angina Pectoris↗
PubMed1978

Effects of anti-anginal agents on cyclical reductions of coronary blood flow.

The effects of coronary vasodilating agents and alpha- and beta-adrenergic blocking agents on cyclical reductions of blood flow in the partially constricted coronary artery of anesthetized dogs were examined. Intravenous injections of nitroglycerin (50 microgram/Kg), SG 75 (150 microgram/Kg), papaverine (1 mg/Kg), and nicotinic acid (10 mg/Kg) eliminated both cyclical reductions of flow and ST elevation (group 1). Nifedipine (10 microgram/Kg), verapamil (500 microgram/Kg), diltiazem (500 microgram/Kg), and propranolol (500 microgram/Kg) suppressed ST elevation, but they could not eliminate cyclical reductions of flow (group 2). Dipyridamole (1 mg/Kg) and phenotolamine (500 microgram/Kg) augmented both ST elevation and cyclical reductions of flow (group 3). The results indicate that ST elevation due to cyclical reductions of coronary blood flow was eliminated by spasmolytic actions of group 1 on coronary artery, was suppressed by negative chronotropic and/or inotropic actions of group 2, and was augmented by peripheral actions of group 3.

Adrenergic alpha-Antagonists↗
PubMed1977

Cyclical reduction in blood flow of partially constricted coronary artery in dogs. II. An arteriographic study.

Mechanisms for cyclical reduction in peripheral blood pressure and flow of partially constricted coronary artery of anesthetized dogs has been examined. In 64 of 97 preparations, cyclical reduction in coronary blood pressure and flow developed 3 to 32 min after the beginning of constriction. Period duration of the cyclical reduction ranged from 1 to 32 min. The cyclical reduction was frequently associated with elevation of the ST segment of surface electrocardiogram, systolic bulge of the left ventricle and excitation of afferent cardiac sympathetic nerve fibers. In the preparations in which cyclical reduction was not produced by constriction, a brief stretching of the constricted portion provoked the cyclical reduction. Segmental or diffuse narrowing of the constricted coronary artery which occurred during the reduction in pressure and flow was demonstrated by selective arteriography. Also, segmental spasm in the constricted coronary artery was demonstrated by photography. No obvious difference in the constricted of the artery was observed histologically between the preparations in which cyclical reduction developed and those in which cyclical reduction was not produced. The results indicate participation of vasospasm in the cyclical reduction of blood pressure and flow in partially constricted coronary artery.

Action Potentials↗
PubMed1977

Instantaneous assessments of left ventricular dimensions by ultrasonic analogue conversion system. I. An experimental study.

A new time-to-voltage analogue converter of ultrasound echo was made. The converter samples the echoes from the septal endocardium and the endocardium of the posterior wall of the left ventricle. The converter also enables automatic calculates left ventricular minor axis, volume, and work. In fixed human hearts, the left ventricular minor axis and volume calculated by the converter were close to the actual ones. In anesthetized dogs, left ventricular minor axis, volume, ejection fraction and stroke work calculated by the converter were close to those calculated by cineventriculography. The results indicate applicability of the ultrasonic analogue converter for instantaneous assessments of left ventricular dimensions and function.

Analog-Digital Conversion↗
PubMed1975

Cyclic fluctuations in coronary blood pressure and flow induced by coronary artery constriction.

Slow cyclic fluctuations were frequently observed in blood pressure of the distal portion of the partially constricted coronary artery of anesthetized dogs. Lowering the mean peripheral coronary blood pressure below 50% of the control value was required for initiation of fluctuations. Each fluctuation in pressure was composed of 2 phases; the phase of rise and phase of fall. Almost invariably, the phase of rise and phase of fall were accompanied by increase and decrease in coronary blood flow, respectively. When the mean peripheral coronary blood pressure fell below 20% of the control value during the phase of fall, systolic bulge and elevation of the ST segment of surface ventriculra electrocardiogram occurred. Period duration of each fluctuation ranged from 30 sec to 14 min. The cyclic fluctuations in pressure, flow, electrocardiogram and left ventricular wall motion were eliminated by nitroglycerin, but were not affected by phentolamine, propranolol, atropine, cervical vagotomy, and stellectomy.

Animals↗
PubMed1975

Excitation of afferent cardiac sympathetic nerve fibers induced by vagal stimulation.

The effect of vagal stimulation on activity of afferent sympathetic nerve fibers from the dog's left ventricle has been examined. During partial constriction of the coronary artery, a brief electrical stimulation of the cervical vagus nerves resulted in a decrease in blood flow of the constricted artery, systolic bulge of the left ventricle, elevation of the ST segment of electrocardiogram and excitation of the afferent nerve fibers, which continued for up to 15 min. These changes were not produced without coronary artery constriction. Intravenous injection of phentolamine eliminated the decrease in blood flow, and suppressed systolic bulge, elevation of the ST segment and excitation of afferent fibers. Propranolol could not eliminate the decrease in blood flow while suppressed the other changes. Atropine eliminated all of these changes. The results indicate participation of adrenergic alpha-receptors in sustained decrease of coronary blood flow and excitation of afferent cardiac sympathetic nerve fibers which can be produced by a brief vagal excitation.

Action Potentials↗
PubMedDate not supplied

Effects of heart rate on hemodynamic severity of coronary artery stenosis in the dog.

In 14 open-chest mongrel dogs, the effects of heart rate on hemodynamic severity of proximal coronary artery stenosis were studied. Stenosis was produced by a circumferential wire snare on left circumflex coronary artery. An intermediate stenosis was defined by reduction of peak reactive hyperemia response to 200% of control flow, a critical stenosis by prevention of any reactive hyperemia flow to a 15-s occlusion. Heart rate was increased stepwise from control to 160 and 200 beats/min by left atrial pacing. In intermediate stenosis, increased pacing rate reduced peripheral coronary pressure distal to the stenosis from 77 +/- 3 to 73 +/- 4 to 65 +/- 3 mm Hg (p less than 0.05) and increased stenosis resistance from 0.30 +/- 0.05 to 0.34 +/- 0.05 to 0.35 +/- 0.05 resistance units (p less than 0.05). In critical stenosis, increased heart rate changed peripheral coronary pressure from 45 +/- 5 to 49 +/- 5 to 48 +/- 5 mm Hg (p less than 0.01) and reduced stenotic resistance from 1.24 +/- 0.19 to 1.08 +/- 0.18 to 1.15 +/- 0.19 resistance units (p less than 0.005). A significant correlation between changes in stenotic resistance and peripheral coronary pressure was obtained (r = -0.71, p less than 0.001). In maximally dilated coronary arteries, a circumferential stenosis decreased circumflex artery flow to 50%. Increased pacing rate up to nearly 200 beats/min raised peripheral coronary pressure distal to the stenosis from 51 +/- 4 to 56 +/- 4 mm Hg (p less than 0.005) and changed stenotic resistance from 0.41 +/- 0.13 to 0.30 +/- 0.06 to 0.33 +/- 0.10 resistance units (p less than 0.05). It is assumed that the changes in peripheral coronary pressure alter the luminal area of the stenosis and hence calculated stenotic resistance. Other possible mechanisms like turbulent streaming, vasomotion or platelet aggregation appear to be of minor importance in the present experimental conditions.

Animals↗
PubMedDate not supplied

ECG-gated NMR-CT for cardiovascular disease.

We have developed an ECG-gated NMR-CT, and used it with 16 patients. The saturation recovery images are not able to separate heart muscle from the blood pool, but in inversion recovery images, heart muscle can be differentiated from the ventricles. The region of myocardial infarction is revealed as wall thinning and/or wall motion abnormality. From the two-gated inversion recovery images (the end-diastole and end-systole images) we obtained, we evaluated a wall motion abnormality in the left ventricle, and calculated the ejection fraction of the left ventricle. This information was then compared with the findings of a nuclear medicine study carried out one week interval and which included 10 of the 16 patients tested with the ECG-gated NMR-CT. The wall motions in both methods are well correlated, with the exception of the inferior wall. The values of the ejection fraction in the NMR image were moderately low, but two modalities showed a satisfactory correlation (r = 0.85).

Adult↗