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Biomedical subjects

S Yasui

Publications and source records attributed to S Yasui.

At least 91 records · Page 5Linked to original sources
PubMed1990

Significance of discordant ST alternans in ventricular fibrillation.

With the use of epicardial mapping, we investigated the electrical alternans of the ST segment during acute myocardial ischemia and studied the difference in ST alternans between dogs with resultant ventricular fibrillation and those without it. During the 7-minute occlusion of the left anterior descending coronary artery below its first diagonal branch, 60 epicardial unipolar electrograms were recorded simultaneously at 1-minute intervals by a computerized mapping system. ST alternans was found in the eight dogs we observed. The amplitude of ST alternans (difference in the ST segment elevation of two consecutive electrograms) was greater in dogs with ventricular fibrillation (n = 4) than in those without it (n = 4) (3.92 +/- 1.24 versus 0.58 +/- 0.49 mV, p less than 0.05). Three of the four dogs with ventricular fibrillation demonstrated discordant ST alternans (i.e., adjacent leads were out of phase). Results from the present study indicate that an increased amplitude and discordance of ST alternans during acute myocardial ischemia are related to ventricular fibrillation and act as indicators of time and spatial unevenness of ventricular repolarization.

Animals↗
PubMed1990

The role of late potentials in the assessment of myocardial degeneration in idiopathic dilated cardiomyopathy.

In order to determine whether or not late potentials indicate either a degree of myocardial fibrosis or necrosis, the relationship between late potentials and thallium-201 myocardial perfusion images was studied in 13 patients with idiopathic dilated cardiomyopathy. Late potentials were defined as low-amplitude waveforms having duration of over 20 msec after the end of the QRS complex using a high-resolution ECG (Marquette electronics, MAC 1). In the T1-201 myocardial perfusion image, the segmental perfusion state was assessed by use of a parameter called the uptake index (= normalized sector counts/maximal normalized sector counts) of each of 6 different segments. Segments which showed an uptake index of -2SD less than the normal value were judged to be abnormal. Late potentials were detected in 8 (61.5%) of the 13 patients. All of the patients showing late potentials also had ventricular tachycardia. Among the patients showing no late potential, ventricular tachycardia was observed in only one patient. Seven of the 8 patients showing late potentials and 3 of 5 patients not showing late potentials, however, had both a higher degree and a greater extent of abnormal perfusion images than the patients not showing late potentials. Therefore, late potentials may reflect a degree of myocardial fibrosis or necrosis in patients with dilated cardiomyopathy, those showing abnormal thallium images are apt to show late potentials, and these patients seem to be also at a high risk of suffering from ventricular tachycardia.

Adult↗
PubMed1990

Body surface electrocardiographic mapping to assess left ventricular diastolic overload in valvular heart disease.

In order to assess diastolic overload by electrocardiogram (ECG), we performed body surface ECG mapping (MAP), and then compared the results with echocardiographic, roentgenographic and cardiac catheterization findings. Eighty-seven unipolar electrocardiograms were simultaneously recorded for the following groups: 1) 40 normal subjects, 2) 46 patients with diastolic overload [32 patients with aortic regurgitation (AR) and 14 patients with mitral regurgitation (MR)]. QRS isopotential maps were constructed at 10, 20, 30, 40, 50 and 60 msec from the QRS onset. On the potential departure map, the area where the QRS voltage was greater than the normal limits (mean + 2SD of normal control) was designated as "+2SD area". In patients with diastolic overload, +2SD area was found on the left anterior chest and back at 40, 50 and 60 msec from QRS onset. Subjects were classified into the following 3 groups according to the location of their +2SD area: 1) group A (n = 23) in which the +2SD area was found on the left anterior chest and back, 2) group B (n = 17) in which the +2SD area was found only on the back, and 3) group N (n = 6) in which no +2SD area was found. Group A had a markedly greater left ventricular end-diastolic internal dimension than the other groups (A 63.6 +/- 6.8 mm, B 53.9 +/- 5.5 mm, N 50.7 +/- 6.0 mm, A vs. B, N p less than 0.01), and a greater cardiothoracic ratio than the other groups (A 58.5 +/- 5.6%, B 52.5 +/- 7.0%, N 52.3 +/- 4.7%, A vs. B, N p less than 0.01). There was no significant difference in wall thickness among the 3 groups. The regurgitation severity assessed by cardiac catheterization was greater in group A than in the other groups. Among AR patients, the +2SD area was located on the upper back and the upper anterior chest, whereas among MR patients, it tended to be located on the lower portions. The potential departure map is a useful noninvasive analytic method for determining the extent and grade of diastolic overload. Furthermore, the location of the +2SD area may be used to discriminate between AR and MR.

Adolescent↗
PubMed1990

Pulmonary vascular response to acetylcholine in isolated rat lungs treated with intratracheal bleomycin.

We tested the hypothesis that during alveolar hypoxia the vasodilator response to acetylcholine (ACh) is impaired in lungs injured by intratracheal bleomycin. Isolated rat lungs were ventilated with normoxic (21% O2) or hypoxic (2% O2) gas and perfused with homologous blood. The effect of ACh on pulmonary vascular resistance was estimated during ongoing hypoxic pulmonary vasoconstriction (HPVC) after the temporal pattern of HPVC was established. The magnitude of the decrease in pulmonary vascular resistance was significantly smaller in the bleomycin-treated group (group B, n = 7) than in the saline-treated group (group S, n = 7) (p less than 0.05). The magnitude of HPVC itself did not differ between groups. The pulmonary vascular reactivities to angiotensin II and KCl were similar in the two groups (group S, n = 4, group B, n = 5). At any given transpulmonary pressure the lung volumes of group B (n = 5) were significantly smaller than those of group S (n = 4) (p less than 0.01). We conclude that vascular dilation in response to ACh during ongoing HPVC was impaired in bleomycin-injured rat lungs.

Acetylcholine↗
PubMed1990

[123I-IMP accumulation in the lung with bronchial asthma--early uptake and delayed washout].

123I-IMP is taken up by the pulmonary capillary endothelial cells during the first pass through the lung, and is slowly released from them. To look up the factors which influence on the prolonged 123I-IMP retention in the diseased lung, we examined the correlation between the 123I-IMP uptake during the first pass and the 123I-IMP retention. Patients with bronchial asthma had no abnormal finding in the chest X-ray photograph. However 123I-IMP release from their lungs was delayed. Some patients show a tendency that 123I-IMP uptake during the first pass was uneven, which suggested the change in amine uptake function of endothelial cells. However their correlation coefficients between the uptake during the first pass and the prolonged retention were very small. It was considered that the prolonged 123I-IMP retention in the diseased lung was not explained only by the change in uptake function of pulmonary capillary endothelial cell.

Amphetamines↗
PubMed1990

[Analysis of 123I IMP retention in the lung and application to the diagnosis of lung disease].

The movement of N-isopropyl-p[123I] iodoamphetamine (I-123 IMP) in the lungs was studied. The half time of I-123 IMP release (T 1/2) was delayed in the fibrosis and the sarcoidosis. There was a relation between the prolongation of T 1/2 and the radiographic finding. It was considered that T 1/2 was useful for the objective estimation of the change in the lungs. The adsorption of I-123 IMP to the alveolar cells was much higher than to the circulating leukocytes. It was considered that the accumulation and retention of I-123 IMP in the lungs had relation to the alveolar cells.

Amphetamines↗
PubMed1990

[Effects of lung volume levels and trapidil on transdiaphragmatic pressure in young healthy subjects].

Effects of lung volume levels, and effect of intravenous administration of Trapidil on the maximal force developed by the diaphragm were investigated by the measurement of transdiaphragmatic pressure (Pdi) in 10 healthy young subjects. To evaluate transdiaphragmatic pressure, delta Pdimax was used. delta Pdimax was calculated by the subtraction of the transdiaphragmatic pressure at FRC (Pdi FRC) from the maximal transdiaphragmatic pressure (Pdimax) at each lung-volume level. Regardless of the administration of Trapidil, delta Pdimax was highest at FRC in each subject. When Trapidil was administered, Pdimax increased in cases where absolute Pdimax FRC was initially low. The relation between changes of delta Pdimax at FRC after Trapidil administration and delta Pdimax showed significant linear correlation (r = -0.85, p less than 0.002). These results suggest that FRC is the most adequate lung volume level to produce an effective transdiaphragmatic pressure, and that Trapidil increases the muscle force of the diaphragm in cases where the force is initially low in young healthy subjects.

Adult↗
PubMed1989

Alpha-chloralose opens the chloride channel of frog isolated sensory neurons.

The effect of alpha-chloralose on the sensory neurons isolated enzymatically and mechanically from frog dorsal root ganglia was studied using a suction-pipette technique. The threshold concentration of alpha-chloralose was around 3 x 10(-5) M and the current produced by alpha-chloralose saturated at the concentration of 3 x 10(-3) M or more. The dose-response curve for alpha-chloralose provided a Ka value of 6 x 10(-4) M and a Hill coefficient of 1.8. The reversal potential of the response elicited by alpha-chloralose was close to the equilibrium potential for Cl- (ECl), indicating that the current was carried through Cl- channels. The current-voltage relationship indicated that there was little voltage dependence in the alpha-chloralose-induced response. The analysis of the variance of the alpha-chloralose-induced Cl- current fluctuations showed two types of the receptor-ionophore complexes with different channel conductances.

Animals↗
PubMed1989

H1 horizontal cells of carp retina have different postsynaptic mechanisms to mediate short- versus long-wavelength visual signals.

Vertebrate photoreceptors release neurotransmitter substance(s) tonically in the dark and this release is curtailed by light. Recently, we have become increasingly aware of the possibility that short- and long-wavelength visual signals are mediated differently during the synaptic transmission to second-order retinal neurons. The experiment described here advances this notion further by demonstrating a postsynaptic difference. Treatment of the carp retina by dopamine reduced the gap-junctional coupling of horizontal cells, and we made use of this known effect to measure the input resistance (Rin) of H1-type horizontal cells. Flashes of light increased Rin. This increase, however, was found to be smaller with short wavelengths, even though the comparison was made when voltage responses were equal in amplitude. Often, Rin was even found to decrease at the blue end of spectrum. No single postsynaptic mechanism can account for any equal-voltage Rin difference such as this. The synaptic spectral segregation thus revealed is probably subserved by a dual scheme wherein the transmitter from blue-sensitive cone photoreceptors acts to decrease the membrane conductance of H1 cells whereas the synapses made by red- and green-sensitive cones are of a classical excitatory type.

Animals↗
PubMed1989

Prolonged lung retention of 123I-IMP in pulmonary disease.

The accumulation of venously injected 123I-IMP in the lung was studied. Between 30 and 50 min after the injection of the 1.5 mCi 123I-IMP, the concentration of 123I-IMP in the broncho-alveolar lavage fluid were much higher than in the blood. It was considered that 123I-IMP was transported into the alveolar spaces and was absorbed by the alveolar cells. The half time (T1/2) of the 123I-IMP release from the lung between 10 and 25 min immediately after the injection was calculated. In normal subjects the T1/2 ranged between 25 and 44 min and was prolonged in subjects with pulmonary fibrosis, sarcoidosis, and allergic alveolitis. It was considered that the retention of 123I-IMP was related not only to the endothelial cells, but also to the alveolar cells. It was considered that the analysis of the lung release of 123I-IMP forms a new lung dysfunction index.

Amphetamines↗
PubMed1989

Effect of diltiazem on coronary blood flow distribution in dog heart under ischemia.

Effect of intracoronary infusion of diltiazem (1 microgram/min) on regional myocardial blood flow (RMBF) was studied using 15-microns radioactive microspheres in 11 excised cross-circulated canine left ventricles. With total coronary blood flow (CBF) and heart rate (HR) held constant, regional ischemia was induced by ligating the left anterior descending coronary artery (LAD). Diltiazem at the dose used had no effects on ventricular Emax before and after LAD ligation. RMBF expressed by the counts divided by the counts averaged in all segments in each layer significantly (p less than 0.05) increased under diltiazem only in the low-flow region that had less than 50% RMBF before diltiazem; from 21% (+/- 12%) to 35% (+/- 18%) in the epicardial, from 22% (+/- 12%) to 32% (+/- 18%) in the midwall, and from 24% (+/- 10%) to 31% (+/- 12%) in the endocardial layers. We conclude that the beneficial effect of diltiazem on the ischemic heart involves a direct action on the coronary vascular system and does not necessarily depend on the concomitant changes in hemodynamics.

Animals↗
PubMed1989

A plethysmographic technique for direct measurement of airway resistance in hamsters.

We have developed a new technique to directly measure airway resistance (Raw) in small animals with a pressure-type body plethysmograph equipped with a hot-wire microflow sensor. Seventeen male golden hamsters weighing 70-84 g were studied. Change in alveolar pressure (delta PA) was calculated from total gas volume and the respired volume difference through the flow sensor between the midpoints of the tidal excursion curve, reflecting the thorax movement. The ratio of delta PA to the flow difference between those two midpoints gave Raw. Raw was compared with pulmonary resistance, and inspiratory and expiratory resistances were also compared. Raw was 0.44 +/- 0.06 (SE) cmH2O.ml-1.s. Mean of the coefficients of variation of Raw was 19.6 +/- 3.2% (SE). Raw was well correlated with pulmonary resistance (r = 0.93). We demonstrated that Raw could be directly measured in small animals with a hot-wire flow sensor and a plethysmographic technique, and the values were well correlated with previously reported pulmonary resistance.

Airway Resistance↗
PubMed1989

Improved diagnostic performance on the severity of left ventricular hypertrophy with body surface mapping.

To improve the diagnostic usefulness of electrocardiography (ECG) in determining the severity of left ventricular hypertrophy (LVH) with body surface mapping, 87 unipolar ECGs were recorded from 57 patients with left ventricular (LV) concentric hypertrophy and 30 with LV dilatation. Body surface ECG features due to LVH were evaluated by increase of QRS voltage and delayed local activation. We measured for each lead R voltage, net area of QRS (AQRS), ventricular activation time (VAT), and departure index (DI) of AQRS and VAT (DI = mean/SD). From these measurements, seven parameters were calculated for each patient: Rmax, the maximal R wave voltage; AQRSmax, the maximal AQRS; AQRS-Dmax, the maximal AQRS DI; AQRS-Darea, the area size where DIs of AQRS are more than 2; VATmax, the maximal VAT; VAT-Dmax, the maximal VAT DI; and VAT-Darea, the area size where DIs of VAT are more than 2. Among these parameters, the most effective for diagnosis of LVH were selected by stepwise multiple regression analysis. In the concentric hypertrophy group, the combination of VAT-Darea and Rmax was determined to be the best for estimating wall thickness. The regression equation determined from them correlated well to wall thickness (r = 0.73). In the LV dilatation hypertrophy group, only AQRSmax was selected for estimating LV dilatation. A good correlation between AQRSmax and LV internal dimension was observed (r = 0.73). With the body surface distribution of VAT prolongation, septal hypertrophy was separated from the other LVH. These were superior to the conventional method of 12-lead ECGs. ECG diagnosis of LVH severity improved by incorporating a mapping study. Also, prolongation of VAT and increase in QRS voltage were shown to be important when determining the severity of LVH.

Adolescent↗
PubMed1989

Detection of diseased coronary artery by exercise ST-T maps in patients with effort angina pectoris, single-vessel disease, and normal ST-T wave on electrocardiogram at rest.

To examine the clinical significance of ST-T isopotential maps, 87-lead body surface mapping was performed after treadmill exercise in 21 patients with effort angina pectoris, single-vessel disease, and normal ST-T waves on the resting electrocardiogram. Single-vessel disease was found in the left anterior descending artery (LAD) (nine patients), in the right coronary artery (RCA) (seven patients), and in the left circumflex artery (LCx) (five patients). At 40 msec after the J point, the isopotential maps showed the site of the minimum to be in the left anterior chest in all patients. According to the changes in the position of the minimum from the ST segment to the T wave, postexercise maps were classified into four types. Type A maps (n = 8) were characterized by the persistence of the minimum in the left anterior chest until its negativity decreased and until it became less negative than another minimum that subsequently appeared in a different position. Type B maps (n = 6) were characterized by the gradual movement of the minimum toward the lower thoracic surface. Type C maps (n = 5) were characterized by the gradual movement of the minimum to the left upper direction and then to the back. Type D maps (n = 2) did not show any of the characteristics of A, B, or C. All patients with type A, type B, or type C maps had single-vessel disease of LAD, RCA, or LCx, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Effect of left ventricular volume on right ventricular end-systolic pressure-volume relation. Resetting of regional preload in right ventricular free wall.

Effect of left ventricular (LV) volume on right ventricular (RV) end-systolic pressure-volume relation (ESPVR) was investigated, and the mechanism was examined from a standpoint of the alteration of RV free wall mean fiber length. Twelve cross-circulated isovolumically contracting canine hearts in which both ventricular volumes were controlled independently were used, and RV-ESPVR was determined at three different LV volume levels. At small (10.2 +/- 0.6 ml), middle (15.3 +/- 1.0 ml), and large (20.5 +/- 1.4 ml) LV volume, the slope of the RV-ESPVR was 2.63 +/- 0.13, 2.74 +/- 0.13, and 2.89 +/- 0.12 mm Hg/ml, respectively, and each value was significantly different from the others (p less than 0.01). The volume intercept (V0) of the relation (RV-V0) was significantly decreased with the increment of LV volume (RV-V0 in small, middle, and large LV volume; 3.92 +/- 0.68, 3.39 +/- 0.67, and 2.87 +/- 0.71 ml, respectively; p less than 0.01). In nine hearts, RV free wall lengths in latitudinal and meridional direction were measured at three LV volume levels when RV volume was held constant (16.1 +/- 1.1 ml). RV latitudinal end-diastolic length was significantly augmented with increasing LV volume (latitudinal length in small, middle, and large LV volume; 9.68 +/- 0.55, 9.81 +/- 0.56, and 9.92 +/- 0.55 mm, respectively). RV meridional end-diastolic length also increased significantly with increasing LV volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗