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Biomedical subjects

M Ueda

Publications and source records attributed to M Ueda.

At least 1,459 records · Page 81Linked to original sources
PubMed1978

Effect of atrial fibrillation on coronary circulation and blood flow distribution across the left ventricular wall in anesthetized open-chest dogs.

Effects of atrial fibrillation on coronary circulation and on blood flow distribution across the left ventricular wall were studied in anesthetized open-chest dogs. Atrial fibrillation was induced by pressing down mechanically the left atrial appendage or by stimulating electrically the left atrial appendage. Heated cross-thermocouples were used for measuring regional myocardial blood flow. The results showed a marked decrease in coronary blood flow with a significant increase in coronary vascular resistance; average values (SD) of flow and resistance during control simus rhythm were 71.6 +/- 7.36 ml/min . 100g heart muscle and 1.38 +/- 0.15 mmHg/ml/min . 100g heart muscle, respectively, and 54.0 +/- 13.60 ml/min . 100g and 1.54 +/- 0.18 mmHg/ml/min . 100gjust prior to cessation of atrial fibrillation. The termination of fibrillation caused a remarkable rise in coronary flow and a fall in coronary resistance. Pacing-induced tachycardia, similar to the average ventricular rate during atrial fibrillation, increased coronary blood flow and decreased coronary vascular resistance. These show that active coronary vasodilatation and an increase in extravascular support of coronary bed are produced by atrial fibrillation. Subendocardial myocardial blood flow during atrial fibrillation was reduced 22.0 +/- 14.8% from control levels followed by marked increase in flow after cessation of fibrillation, while subepicardial flow decreased only slightly. Thus, atrial fibrillation itself diminishes coronary flow reserve, especially in the subendocardial layer, partly due to the increase in myocardial component of coronary vascular resistance, and it is possible that irregular ventricular rhythm may play an important part in a rise in extravascular support.

Animals↗
PubMed1978

Antihypertensive effect of trichlormethiazide in spontaneously hypertensive rats.

Antihypertensive and diuretic effects of trichlormethiazide (TCM) were investigated in the spontaneously hypertensive rats (SHR). The antihypertensive effect of TCM in an acute experiment was observed in male SHR only at a dose over 10 mg/kg given intraperitoneally and not in female SHR and normotensive Kyoto Wistar rats. In a subacute experiment (6 weeks), TCM retarded the development of hypertension in the male SHR loaded with 1% saline solution at an oral dose over 1 mg kg-1 day-1 and such had a diuretic effect. Oral administration of TCM and hydrochlorothiazide (HCT) at 10 mg kg-1 day-1 retarded the development of hypertension in the saline loaded female SHR to the same degree, but the relationship between antihypertensive and diuretic effects of both compounds was obscure. Except for decreases of water contents in the thoracic artery and wet weights of hearts, the electrolyte, uric acid, catecholamine and 5-hydroxytryptamine contents in the serum or/and organs were not affected by either TCM or HCT. It is concluded that the antihypertensive effect of TCM and HCT can be observed in SHR with a saline-load, and that the effect may be due to diuretic actions in the male. The relationship was not apparent in female SHR.

Animals↗
PubMed1978

Comparative vasodilator effects of nitroprusside, phentolamine, and nitroglycerin on hemodynamics, regional myocardial function and epicardial electrogram in dogs with acute myocardial ischemia.

The effects of nitroprusside (NP), phentolamine (PH), and nitroglycerin (NTG) were studied on systemic hemodynamics, regional contraction and epicardial ST segment in the border and non-ischemic zones of the left ventricle of anesthetized open chest dogs. The anterior descending coronary artery (LAD) was completely occluded. NP (5 microgram/Kg/min) or PH (100 microgram/Kg/min) was drip-infused, or a bolus injection of NTG (20 microgram/Kg) was administered intravenously. The 3 vasodilator agents produced somewhat similar reductions in systemic arterial pressure. However, NP caused a greater reduction in total peripheral resistance (TPR) than in left ventricular end-diastolic pressure (LVEDP), and caused a decline, in the ischemic marginal zone, in both ST segment eievation and paradoxical systolic lengthening. PH decreased TRP without reducing LVEDP and elevated the ST segment. NTG markedly reduced LVEDP and TPR slightly. NTG improved the elevated ST segment and paradoxical systolic expansion of the segmental myocardium in the border zone. Cardiac output rose with NP and PH, whereas injected NTG caused a reduction in cardiac output. These findings suggest that NP favourably affects the ischemic myocardium mainly by reducing the afterload and that the NTG-induced improvement of myocardial ischemia can be attributed mainly to preload reduction, while PH enhances cardiac function with slight or no improvement of myocardial ischemia in the border zone.

Acute Disease↗
PubMed1978

Effects of calcium and magnesium ions on the interaction of corticosterone with rat brain cytosol receptor(s).

The apparent maximum corticosterone binding (B max) with rat brain cytosol and the apparent dissociation constant of this steroid-receptor binding (Kd) estimated with a Scatchard plot was 2.9 X 10(-13) moles/mg cytosol protein and 4.0 X 10(-9) M, respectively. When increasing amounts of CaCl2 or MgCl2 up to 5.0 mM were added, a specific [3H] corticosterone binding increased 4-fold by CaCl2 at concentrations of 1.0-2.0 mM and 1.5-fold by MgCl2 at concentrations of 0.5-5.0 mM. The addition of MnCl2 and KCl did not affect this binding. Binding of corticosterone with rat brain cytosol receptor(s) were decreased by increasing amounts of EGTA and complete inhibition was observed at concentrations equal to and greater than 2.5 mM. Inhibition of this binding by EDTA was less than by EGTA. Either theophylline or dibutyryl cyclic AMP had no effect on this binding.

Adrenalectomy↗
PubMed1978

Effect of myocardial ischemia and nitroglycerin on systolic time intervals in the segmental myocardium.

Effects of ischemia and nitroglycerin on systolic time intervals in the segmental myocardial length were studied in anesthetized open-chest dogs. Two strain-gauges were sutured on the surface of the left ventricular wall; one was in the central area perfused by the left circumflex coronary artery (LCX) and the other was in the area perfused by the left anterior descending coronary artery. LCX was partially occluded with a screw type constrictor to the degree at which reactive hyperemia after the transient total coronary occlusion almost disappeared. After the hemodynamics stabilized nitroglycerin (20 microgram/kg) was injected into the femoral vein. In the ischemic area, contraction time was shortened and precontraction time was prolonged in association with an elongation of end-systolic and early systolic segment-length, respectively. The systolic time intervals in the ischemic segment were improved as a result of the recovery in the segment-length toward the control. The results suggest the usefulness of analyzing the segmental myocardial systolic time intervals for verifying the asynchronous contraction of the ventricle and the favourable effects of nitroglycerin on segmental myocardial function in the ischemic area.

Animals↗
PubMed1978

Correlation of systolic time interval with abnormal myocardial contraction by coronary occlusion in anesthetized open-chest dogs.

The correlation between the systolic time interval and abnormal contraction in ischemic myocardium was studied in anesthetized open-chest dogs. A strain-gauge was sutured on the surface of the left ventricular wall perfused by the left anterior descending coronary artery (LAD) for measuring segment-length. The left ventricular stroke volume decreased progressively after occlusion of LAD. The left ventricular ejection time (LVET) was progressively shortened in close correlation with the elongation of segment-length at the onset of isometric relaxation in 20 seconds after LAD occlusion when early systolic myocardial contraction and isometric contraction time (ICT) were not affected. ICT was gradually prolonged and closely related with the lengthening of the early systolic segment-length, while LVET recovered toward the control level in spite of further decrease in stroke volume. A close relationship was observed between ICT/LVET and stroke volume (gamma = 0.76, P less than 0.01). The results suggested the possibility that LVET was normalized even when the left ventricular function was impaired, and ICT/LVET ratio was the most sensitive index of LV dysfunction.

Animals↗
PubMed1978

Effect of propranolol on regional myocardial function in anesthetized open-chest dogs with myocardial ischemia.

Effects of propranolol on ischemic segmental function were studied in anesthetized open-chest dogs. Two segment-length gauges were used for measuring the regional myocardial function: one was sutured on to the left ventricular surface perfused by the anterior descending coronary artery (ischemic zone) and the other was on to that perfused by the circumflex coronary artery (normal zone). A bolus of propranolol (0.5 mg/kg) was injected into the right femoral vein. Five min later, the left anterior descending coronary artery (LAD) was completely occluded for one mine and thereafter released. Then a second coronary occlusion for 20 min was performed; an interval of 20 min was allowed between two occlusions. Propranolol, in the ischemic segment, apparently decreased the extent of paradoxical lengthening in the late systole following one min LAD occlusion, and facilitated improvement of segmental function after release of the occlusion. Moreover, the extent of abnormal stretching induced by 20 min occlusion during early systole, was also reduced by propranolol pretreatment. In contrast, compensatory increase in shortening by the normal segment was disturbed by propranolol. These results suggest that propranolol might exert a favourable influence on the segmental myocardial function during either transient or maintained myocardial ischemia.

Animals↗