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Biomedical subjects

S Yasui

Publications and source records attributed to S Yasui.

At least 145 records · Page 8Linked to original sources
PubMed1987

Elastic recoil pressure arising from surface tension in hamster lungs treated with intratracheal bleomycin.

Lung elastic recoil pressure arising from surface tension (Ps) was evaluated in normal and bleomycin-treated lungs. Twenty two male golden hamsters were separated into a control group (group A, n = 10) and a bleomycin group (group B, n = 12). Group B was given a single intratracheal instillation of bleomycin and group A was given normal saline as a control. Thirty days after instillation, three cycles of static air -and saline-filled pressure-volume curves (P-V curve) were measured. Ps was graphically derived from air- and saline-filled P-V curves. The Ps of groups A and B were compared at the same lung volumes. Mean body weight and nose-to-tail length of the two groups did not differ significantly. Total lung capacity, defined as lung air volume at a transpulmonary pressure of 25 cmH2O, was significantly smaller in group B (mean +/- S.E. was 4.08 +/- 0.20 ml) than in group A (mean +/- S.E. was 5.23 +/- 0.12 ml) (p less than 0.01). The Ps of group B was significantly larger than that of group A at all lung volumes studied (p less than 0.01-0.05). These results indicate that the lung elastic recoil pressure component due to the surface tension was increased by intratracheal instillation of bleomycin in hamsters.

Animals↗
PubMed1987

Cigarette smoke modifies bleomycin-induced lung injury to produce lung emphysema.

The effect of cigarette smoke exposure on the development of bleomycin (BLM)-induced pulmonary fibrosis was studied. Hamsters 3 weeks of age were divided into four groups, control (C), BLM treated (B), cigarette smoke exposure (T), and cigarette smoke plus BLM (TB). Cigarette smoke exposure was started 5 days after the beginning of feeding in a desiccator which received a flow of smoke. A single intratracheal dose of 0.5 mg of BLM per 100 g body weight was administered 30 days after feeding. Sixty days after feeding the animals were killed for measurement of pressure-volume (P-V) relationships and microscopic observations. At 60 days the deflation P-V curves in B and TB were shifted significantly downward and to the right of that of C and T, respectively. P-V curves in TB were shifted significantly upward and to the left of that of B, almost returning to that of C. Light-microscopic examination showed no evidence of emphysema in the lung of T. In contrast, in the lung of TB there were destruction of the alveolar walls, varying degrees of enlargement of alveolar spaces and fibrous thickening of the alveolar septa. These results suggest that BLM-induced lung injury may be modified by cigarette smoke to produce lung emphysema.

Animals↗
PubMed1987

[Predictability of stress-induced myocardial ischemia from coronary arteriography in patients with organic coronary artery stenosis].

A quantitative index for describing the severity and extent of coronary artery disease has not been established yet, although it is certain that the stenosis causes myocardial ischemia induced by stress. To establish the most meaningful scoring system, we developed the grading of stenosis which is "critical" or significant in the single-, double-, and triple-vessel method (SDT), and the extent of improvement in the predictive value which may be induced by accounting for the predominance of the three major coronary arteries nourishing the left ventricle. Thirty-three patients (six were women), whose average age was 58.6 years, all having exertional angina pectoris and fixed organic coronary artery stenosis documented by coronary arteriography, but no old myocardial infarction, were the subjects of this study. For these patients the mean redistribution index (RDI) was determined by ergometer stress myocardial perfusion imaging using 201T1. The number (nST) of significant ST segment depressions by body surface ECG mapping after treadmill stress tests was compared with the sigma Pujadas grade, which is the sum of each grade assigned to each of the three major coronary arteries, and with the Pujadas score, which is the weighted sum of grades by dominance in the coronary artery distribution. The SDT method was a better predictor of ischemia if the criterion for critical stenosis is selected at a more severe stenosis (greater than 90% diameter stenosis). Among factors predicting ischemia, the length of the stenosis and the presence of collaterals did not seem to be definitive. However, the distribution of the arteries was an important factor.(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Angiography↗
PubMed1986

Alterations in myocardial perfusion during exercise after isosorbide dinitrate infusion in patients with coronary disease: assessment by thallium-201 scintigraphy.

We studied the effect of intravenous isosorbide dinitrate (ISDN) on myocardial perfusion of patients with coronary artery disease, by using exercise thallium-201 (TI-201) myocardial scintigraphy. A control study was conducted initially to assess regional myocardial perfusion rate. Left ventricular myocardium was divided into six parts: anterior, lateral, apical, inferior, posterior, and septal segments. The segmental myocardial perfusion was characterized according to TI-201 initial uptake index (IUI) of relative distribution and redistribution index (RDI) of TI-201 washout. The normal limit of IUI and RDI was established from the data of 17 persons with normal coronary arteries, and then the IUI less than or equal to 84% and the RDI greater than or equal to 1.12 was defined as abnormal. Based on IUI and RDI, each segment was characterized into three types: A type = IUI less than or equal to 84%, RDI greater than or equal to 1.12; B type = IUI less than or equal to 84%, RDI less than 1.12; and C type = IUI greater than 84%, RDI less than 1.12. ISDN was given as a dose of 0.1 mg/kg/hr, and then treadmill testing was repeated for the same duration of exercise time using the same protocol as in the control period. The segments of A type showed a significant improvement in IUI and RDI after receiving ISDN infusion, while the B and C type segments showed no change. It was also shown that the improvement of IUI and RDI of the A type segments was not as marked in multivessel disease as in cases of single-vessel disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Horizontal cell signal is smaller with texture-like nonuniform patterns than with uniform fields of the same space-average illuminance.

While measurement of the pertinent response as a function of flash intensity has been a standard procedure in vision research, we ask here what happens to horizontal cells in the vertebrate retina if the flash energy is varied through the density of a large number of small light spots rather than through the intensity of uniform illumination. The experiment described here demonstrates that the electrical response of horizontal cells in the turtle retina is consistently smaller with the present dot-density modulation than with the usual intensity modulation, even though the comparison is made when the mean irradiance per photoreceptor is equal in the two methods of modulation. Thus, the spatial summation, an important retinal function often thought to provide a base signal level for contrast detection, is affected significantly by how the visual pattern is structured at a level of microscopic dimension far smaller than the receptive field. The present finding, which seems to be a new form of area-intensity effect, can be explained if the dendritic membrane conductance of horizontal cells at each synaptic site increases at a progressively higher rate with decreases of the corresponding local illuminance. This possibility is discussed in the light of relevant photoreceptor response data, the presumed sigmoidal trend of the postsynaptic chemosensitivity and a simple electrical analog of contiguous horizontal cells.

Animals↗
PubMed1986

Non-invasive detection of coronary artery disease by body surface electrocardiographic mapping after dipyridamole infusion.

Electrocardiographic changes after dipyridamole infusion (0.568 mg/kg/4 min) were studied in 41 patients with coronary artery disease and compared with those after submaximal treadmill exercise by use of the body surface mapping technique. Patients were divided into three groups; 19 patients without myocardial infarction (non-MI group), 14 with anterior infarction (ANT-MI) and eight with inferior infarction (INF-MI). Eighty-seven unipolar electrocardiograms (ECGs) distributed over the entire thoracic surface were simultaneously recorded. After dipyridamole, ischemic ST-segment depression (0.05 mV or more) was observed in 84% of the non-MI group, 29% of the ANT-MI group, 63% of the INF-MI group and 61% of the total population. Exercise-induced ST depression was observed in 84% of the non-MI group, 43% of the ANT-MI group, 38% of the INF-MI group and 61% of the total. For individual patients, there were no obvious differences between the body surface distribution of ST depression in both tests. The increase in pressure rate product after dipyridamole was significantly less than that during the treadmill exercise. The data suggest that the dipyridamole-induced myocardial ischemia is caused by the inhomogenous distribution of myocardial blood flow. We conclude that the dipyridamole ECG test is as useful as the exercise ECG test for the assessment of coronary artery disease.

Adult↗
PubMed1986

Acute effects of oral captopril on hemodynamics in patients with cor pulmonale.

The cause of pulmonary hypertension in chronic obstructive pulmonary disease (COPD) is considered to be hypoxic pulmonary vasoconstriction, which may be mediated in part by angiotensin II. We administered captopril (25 mg, orally) to seven patients with COPD and complicating cor pulmonale in stable state. Hemodynamic responses were recorded before and one hour after the administration of the drug. Captopril increased cardiac output by 23% (p less than 0.025) and reduced mean systemic pressure by 12% (p less than 0.004), but did not alter mean pulmonary arterial pressure. Pulmonary and systemic vascular resistance fell, respectively, by 14% (p less than 0.035) and 31% (p less than 0.03). There was an increase in pulmonary/systemic vascular resistance ratio (p less than 0.007). Heart rate, mean right atrial, pulmonary capillary wedge pressure, arterial oxygen tension and dioxide tension, and alveolar- arterial oxygen tension difference remained unchanged. These results suggest that captopril is successful in reducing pulmonary vascular resistance without affecting arterial blood gases, but does not change mean pulmonary arterial pressure probably because of the concurrent increase in pulmonary blood flow. In addition, results indicate that captopril has more effects on the systemic vasculature than on the pulmonary circulation.

Administration, Oral↗
PubMed1986

Comparison of the electrocardiographic changes induced by dipyridamole infusion and treadmill exercise in patients with coronary artery disease.

To determine whether dipyridamole infusion can be used as an alternative method to physical exercise, 87 lead body surface mapping was performed to compare the distribution patterns of ST-segment depression after 0.568 mg/kg/4 min dipyridamole infusion (D) and after submaximal treadmill exercise (T) in 21 patients with coronary artery disease. Significant ST-segment depression (greater than or equal to 0.05 mV) was observed in 19 patients after D and in 18 after T. After D and T, each patient showed a similar distribution pattern of ST-segment depression. There were no significant differences in the number of leads which showed ST-segment depression (nST: D, 15.6 +/- 11.1 vs T, 15.2 +/- 10.8) and in the maximal value of ST-segment depression (STmax: D, -0.24 +/- 0.16 vs T, -0.20 +/- 0.13 mV). Good correlations were observed in nST (r = 0.84) and in STmax (r = 0.87) between D and T. The increase in mean pressure-rate product after T was 89%, while the increase after D was only 22%. Our results suggest that this pharmacologic test to induce myocardial ischemia may be useful in the evaluation of coronary artery disease in patients who are physically unable to perform adequate exercise.

Aged↗