Biomedical subjects

A Saeki

Publications and source records attributed to A Saeki.

65 records · Page 4Linked to original sources

PubMed1992

Constant efficiency versus variable economy of cardiac contraction.

An intriguing aspect of cardiac mechanoenergetics is the smaller variability of the contractile efficiency than the energy economy of force. We theoretically speculated about this dissociation by relating the mechanical efficiency with Po/a (the curvature of the force-velocity curve) in Hill's characteristic equation of muscle; Po/a is known to change with the energy economy and inversely with Vmax and myosin ATPase activity. The analysis showed that the variability is smaller for the mechanical efficiency than for Po/a and that the energy economy changes approximately with (Po/a)3. These theoretical relations may partly explain the small variability of the empirically observed contractile efficiency under various experimental conditions which are known to widely change the energy economy.

Animals↗

PubMed1990

Pollution by the fungicide pentachloronitrobenzene in an intensive farming area in Japan.

Environmental pollution by pentachloronitrobenzene (PCNB) was investigated at Tsumagoi, an intensive farming area, where a great amount of PCNB has been applied. High concentrations of PCNB were detected in river water near an area of cabbage cultivation. Further, pentachloroaniline (PCA) and pentachlorothioanisole (PCTA), which are the principal biodegradation products of PCNB, were also detected, and their ratios to PCNB were higher in autumn than in summer. PCNB concentrations in soil were similar to those of river sediment, in which PCNB was concentrated 5000-10,000 times over levels in river water. The biodegradation rate of PCNB in river water was higher than in river sediment and soil. The formation rates of PCA from PCNB were higher in river sediment and soil than in river water. It is considered that PCA remains for a long time in the environment and accumulates in river sediment and soil.

Agriculture↗

PubMed1990

Increased dependence on slow filling for left ventricular diastolic filling in patients with coronary artery disease and a depressed systolic function--assessment with radionuclide ventriculography.

Contributions of rapid filling, slow filling and atrial systole to the left ventricular (LV) filling volume were analyzed with the use of radionuclide ventriculography at rest, both globally and regionally, in 34 patients with isolated disease of the left anterior descending coronary artery. The patients included 17 with a normal ejection fraction (EF greater than or equal to 50%; group 1) and 17 with a depressed EF (less than 50%; group 2), and the data were compared with those obtained from 13 normal subjects. A computer program subdivided the LV image into 4 regions, and time-activity curves were constructed globally and regionally by reverse-gating from the R wave. In both groups the contribution of rapid filling to the LV filling volume was decreased significantly in the affected septal and apical regions, and in the global left ventricle compared with that in normal subjects. In group 1, the contribution of atrial systole showed an increase in these affected regions and in the global left ventricle. In contrast, in group 2, the atrial contribution was not increased globally or regionally as much as was expected. However, the contribution of slow filling was either increased significantly or tended to increase in the affected regions and in the global left ventricle. There were negative correlations between the contribution of rapid filling and that of slow filling in the global left ventricle (r = -0.73, p less than 0.001) and in each of the septal, apical and lateral regions (r greater than or equal to -0.60, p less than 0.001), which suggested that the contribution of slow filling as well as of atrial systole undergoes an increase as rapid filling is impaired. Thus, in patients with coronary artery disease, the left ventricle relies on slow filling as well as atrial systole to affect diastolic LV filling in the affected regions and in the global left ventricle in the presence of LV systolic dysfunction.

Adult↗

PubMed1990

[Effects of anteroseptal myocardial infarction on systolic and diastolic filling function of the right ventricle].

To assess the effects of wall motion abnormalities of the anterior left ventricle and interventricular septum on right ventricular (RV) systolic and diastolic filling function, multiple-gated radionuclide angiography was performed at rest in 53 patients with previous anteroseptal myocardial infarction and 14 normal subjects. There were 26 patients with left ventricular ejection fraction (LVEF) greater than or equal to 45% (group 1) and 27 with LVEF less than 45% (group 2). Six measurements were obtained simultaneously in both ventricles: 1) EF, 2) peak ejection rate, 3) duration of systole, 4) peak filling rate, 5) time to the peak filling rate, and 6) ratio of the peak filling rate to the peak ejection rate. The mean RV ejection fraction and the peak ejection rate in groups 1 and 2 were similar to those in the normal subjects. The ratio of the peak RV filling rate to the peak RV ejection rate, a sensitive indicator of diastolic filling function, decreased significantly in group 1 (0.61 +/- 0.15, p less than 0.02) and group 2 (0.59 +/- 0.15, p less than 0.02) as compared with that in the normal subjects (0.74 +/- 0.14). This indicates an impairment of early diastolic RV filling compared with RV systolic function. Thus, RV systolic function appears to be normally maintained even when anteroseptal wall motion is severely impaired; however, even in the presence of mild anteroseptal wall motion abnormality, RV filling may be impaired without reduced RV systolic function.

Aged↗

PubMed1987