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Biomedical subjects

Y Uchida

Publications and source records attributed to Y Uchida.

At least 829 records · Page 46Linked to original sources
PubMed1975

Afferent sympathetic nerve fibers with mechanoreceptors in the right heart.

Mechanosensitivity of afferent sympathetic nerve fibers from the right heart and the pulmonary artery has been examined. Action potentials of the afferent fibers that responded to tapping the right heart and the pulmonary artery were derived from upper thoracic communicating rami of both sides of anesthetized dogs. The fibers were composed of myelinated Adelta fibers and unmyelinated fibers. The receptive fields of both groups of fibers were located widely in the right heart and the pulmonary artery. Myelinated fibers ceased to fire quickly whereas unmyelinated fibers continued to fire after withdrawl of a brief mechanical stimulus. In the myelinated group, the pressure threshold was 3-50, 6-58, and 3-10 mmHg for right ventricular, pulmonary and right atrial threshold was 15-58, 22-34, and 4-8 mmHg for right ventricular, pulmonary, and right atrial fibers, respectively. Spontaneous discharge of myelinated fibers was synchronous with each rise and/or fall in intracardiac or pulmonary pressure whereas that of unmyelinated fibers was irregular and independent. A rise in pressure produced by pulmonary embolization or occlusion caused an augumented discharge whereas a fall caused by caval vein occulsion eliminated the discharge. The results indicate the existence of both myelinated and unmyelinated fibers with mechanoreceptors in the right heart and the pulmonary artery.

Acetylcholine↗
PubMed1975

Acid-induced excitation of afferent cardiac sympathetic nerve fibers.

The effect of acids on activity of afferent sympathetic nerve fibers from the left ventricle has been examined. Action potentials were derived from the upper thoracic communicating rami of the left side of anesthetized dogs. Application of a solution of lactic acid to the left ventricular surface caused excitation in both myelinated and unmyelinated fibers. The minimum concentration required for excitation was 7.5-75 mug/ml for the unmyelinated fibers and 375-750 mug/ml for the myelinated fibers. Excitation of the unmyelinated fibers induced by coronary occlusion was suppressed by pretreatment with sodium bicarbonate, 500 mg/kg. However, excitation of the myelinated fibers was influenced little by the agent. Pretreatment with a large dose of Trasylol failed to suppress excitation induced by coronary occlusion. The result suggests that acidosis plays a role in excitation of the unmyelinated fibers induced by myocardial ischemia, but not in excitation of the myelinated fibers.

Acids↗
PubMed1975

Afferent aortic nerve fibers with their pathways in cardiac sympathetic nerves.

The effect of mechanical and chemical stimulation on activity of afferent aortic nerve fibers with pathways in the cardiac sympathetic nerves has been examined. Action potentials were derived from the second or third thoracic communicating ramus of the left side of anesthetized dogs. Thirty myelinated and 19 unmyelinated fibers responded to tapping the ascending aorta, aortic arch, and descending aorta. Both groups of fibers also responded to a rise as well as to a fall in aortic pressure. Spontaneous discharge of myelinated fibers was related to aortic pressure pulse whereas that of unmyelinated fibers was related to respiration. Asphyxia caused excitation of unmyelinated fibers but not of myelinated fibers. Both groups of fibers responded to topical application of lactic acid. Mechanical and chemical stimulation of the aorta after vagotomy caused a rise in systemic blood pressure and extension of the limbs. The results indicate the existence of afferent aortic fibers in the cardiac sympathetic nerves that cause circulatory and somatic responses.

Action Potentials↗
PubMed1975

Non-uniform myocardial blood flow caused by stellate ganglion stimulation.

The blood flow through the anterior wall of the left ventricle has been studied during electrical stimulation of the left stellate ganglion of anesthetized dogs. The flow was continuously monitored by heated cross-thermocuple. Ganglion stimulation caused a significant increase in the flow through the outer half while producing relative ischemia of the inner half of the wall. Pretreatment with propranolol reduced regional difference of flow changes. Significantly augmented non-uniform flow changes, however, were produced by ganglion stimulation during hypertension caused by aortic constriction or by methoxamine. The results indicate non-uniform blood flow distribution which can be produced by sympathetic nerve excitation.

Animals↗
PubMed1975

Sustained decreased in coronary blood flow and excitation of cardiac sensory fibers following sympathetic stimulation.

The effect of electrical stimulation of the efferent cardiac sympathetic nerves on activity of afferent cardiac fibers in the sympathetic nerves and coronary hemodynamics of anesthetized dogs has been examined. During partial constriction of the coronary artery, a brief stimulation of the efferent cardiac sympathetic nerves resulted in sustained excitation of the afferent fibers and a sustained decrease in blood flow of the constricted artery which were associated with systolic bulge of the left ventricle and elevation of the ST segment of electrocardiogram. These changes were not produced without constriction. Pretreatment with phentolamine suppressed excitation of the afferent fibers, development of systolic bulge and elevation of the ST segment. Also, the decrease in coronary blood flow induced by stimulation was replaced by an increase after the administration of the agent. Propranolol suppressed excitation of the fibers, systolic bulge and elevation of the ST segment, but could not eliminate the decrease in blood flow. The results indicate that sympathetic stimulation caused a decrease in coronary blood flow through excitation of the alpha-adrenergic receptors while increasing cardiac work load and energy requirements through excitation of the beta-adrenergic receptors, leading to more severe myocardial ischemia and excitation of the afferent fibers.

Action Potentials↗
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↗
PubMed1975

[The characteristics of the antibacterial activity of garlic (author's transl)].

It has been found by Cavallito (1944) that garlic (Allium sativum L.) has a strong antibacterial activity and the active principle of garlic is named "Allicin" and it has been confirmed by Stoll et al. (1948) that the allicin is derived from the alliin-alliinase system. Nevertheless, one worker in Japan (1951) stands on another view point which the effective component of garlic is some sugar-proteim because he could not find alliin in the native garlic. We intend to make sure that the alliin is contained in the native garlic, by using Hitachi Amino acid Analyser with Fraction Collecter and compared with garlic of other countrys' production. As the result of examinations, we found that the good amounts of alliin is contained in the native garlic also. The contents of alliin in garlic is varied by the species, the cultivation mode, and the district of production. The form of alliin in the tissue is a free style, and thereupon it is easy to change its chemical conformation by the method of extraction. We compared the relative capacity between 1 allicin unit by Klein (1954) and 1 cup unit by Schmidt et al. (1947). Furthermore we tested the antibiotic spectrum, using the pure crystallized alliin with the sufficient amount of raw alliinase gained by the isoelectric point precipitation and checked upon wide spectrum for Mycobacterium tuberculosis, Gram-positive and negative bacteria, and some fungi.

Allyl Compounds↗