Search PubMed⌕ Search

Biomedical subjects

J Asayama

Publications and source records attributed to J Asayama.

84 records · Page 5Linked to original sources
PubMed1985

Electrophysiological effects of bethanidine sulfate on guinea-pig papillary muscle.

Bethanidine, a chemical analog of bretylium, increased the plateau phase of the action potential of guinea-pig papillary muscle in 2.7 mM K+ Tyrode solution without changing other electrophysiological parameters. In 25 mM K+ Tyrode solution, the amplitude, duration and Vmax of the Ca2+-dependent action potential were increased in a dose-dependent manner by bethanidine. It is speculated that the mechanism of antiarrhythmic effect of bethanidine might be due to the prolongation of action potential by an increase of the slow inward current.

Action Potentials↗
PubMed1984

Pulmonary varix.

Pulmonary varix is rare, only 53 cases having been reported. A brief review of the literature is given. Because its radiologic appearance may be indistinguishable from mediastinal or pulmonary lesions, pulmonary angiography is necessary to avoid exploratory thoracotomy, mediastinoscopy, and unnecessary antituberculous therapy.

Aged↗
PubMed1983

Relationship between sarcoplasmic reticulum volume and calcium capacity in skinned frog skeletal muscle fibres.

Semitendinosus fibres from Rana pipiens were examined in the electron microscope. When the aqueous solutions in which the fibres were prepared contained no sucrose, the sarcoplasmic reticulum was markedly swollen and possibly fragmented. When as little as 50 mM sucrose was included in the aqueous solution, the sarcoplasmic reticulum retained the flattened appearance characteristic of intact fibres. The degree of flattening was not substantially different with concentrations of sucrose ranging from 50 to 300 mM, suggesting that the flattened volume may be determined by structural elements. In all the fibre segments, the regularity of the hexagonal filament lattice was disrupted and the disruption was not affected by sucrose. Radioactive calcium uptake was measured in the presence and absence of 200 mM sucrose. The capacity of the sarcoplasmic reticulum (SR) was depressed by about 30% by the sucrose but the initial uptake was not significantly affected. This finding suggests that most of the calcium within the SR is bound and not free in solution.

Animals↗
PubMed1982

A sensitive photoelectric force transducer with a resonant frequency of 6 kHz.

A displacement-type photoelectric force transducer with a projection arm and a resonant frequency of 6 kHz is described. A vane on a moving element partially interrupts a light beam shining on a pair of phototransistors. Movement of the vane causes changes in the phototransistor currents, which are amplified to give an overall sensitivity of 10 mV/mg. Most of the half of each phototransistor not under the vane is covered by a mask, the edge of which is parallel to the edge of the vane. This increases the sensitivity of the transducer so that stiffer moving elements can be used. Compliance of the transducer at the tip of the projection arm is about 10 micrometers/g. The inertia of the lightweight moving element is minimized by having it rotate about a twisting strip hinge. The equivalent mass of the moving element at the tip, 6 mm from the pivot, is about 0.9 mg. The principal advantages of the transducer over other types is that it is nearly impervious to moisture.

Animals↗
PubMed1977

Idiopathic enlargement of the right atrium.

A huge saccular idiopathic dilatation of the right atrium was detected with angiography and echocardiography in a 75 year old man. Cardiac catheterization data were compared with data obtained 4 years earlier. Idiopathic right atrial enlargement is not usually accompanied by tricuspid valve disease, but in this case tricuspid insufficiency did occur over a period of 4 years, possibly as a complication in the late stage of idiopathic right atrial enlargement.

Aged↗
PubMed1977

Echocardiographic measurement of right ventricular wall thickness. A new application of subxiphoid echocardiography.

The feasibility of subxiphoid echocardiography to measure the thickness of the right ventricular wall (RVWT) was investigated. In 87 (90.6%) of the 96 patients studied, adequate visualization of the echoes from the right ventricular wall was obtained using the subxiphoid technique. RVWT averaged 0.34 +/- 0.08 cm (mean +/- 1 SD), ranging from 0.2 to 0.5 cm in 25 normal individuals. This was not significantly different from the values in the left ventricular overload group (0.36 +/- 0.10 cm). However, the RVWT was increased significantly (P less than 0.001) in the combined group (0.62 0.18 cm), the right ventricular (RV) pressure overload group (0.60 +/- 0.13 cm) and the RV volume overload group (0.53 +/- 0.11 cm). Thirty-two patients underwent diagnosis right heart catheterization which revealed a good correlation between the RVWT measured echocardiographically and the right ventricular peak systolic pressure (r = 0.84). Subxiphoid echocardiography was considered to be useful in diagnosing right ventricular hypertrophy in adults.

Adolescent↗
PubMed1977

The study of the third heart sound in relation to the left ventricular filling and wall movement by echocardiography.

The left ventricular filling and wall movement were investigated in subjects with a third heart sound or ventricular gallop by echocardiography. Nine patients with ventricular gallop, who had left ventricular volume overload disease, and 6 normal subjects with a third heart sound had higher normalized peak rate of increase of the left ventricular dimension (peak dD/dT/D) than 10 normal subjects without a third heart sound (p less than 0.01). The normalized lengthening rate in the rapid filling phase was also higher in patients with ventricular gallop than in normal subjects without a third heart sound (p less than 0.05). The time from the second heart sound to peak dD/dT/D and rapid filling time did not show statistically significant values between subjects with ventricular gallop or a third heart sound and those without a third heart sound. These results suggest that higher peak filling, larger filling volume in the rapid filling phase and more abrupt cessation of the outward movement of the left ventricular wall may be a cause of the production of ventricular gallop in patients with left ventricular volume overload and of the physiological third heart sound.

Adolescent↗
PubMedDate not supplied

Release kinetics of cardiac troponin T in coronary effluent from isolated rat hearts during hypoxia and reoxygenation.

A newly developed troponin T (TnT) test for the detection of myocardial cell necrosis has been reported to be very efficient in the detection of acute myocardial infarction. The aim of the present study was to determine whether cardiac TnT in coronary effluent from isolated heart perfused with albumin-free perfusion medium could be detected using the enzyme-linked immuno-sorbent assay developed by Katus et al. Isolated rat hearts were perfused according to the method of Langendorff. Coronary flow rate was measured by timed collection of the coronary perfusate that dripped from the hearts during 5 h of hypoxia (protocol A) or 4 h of hypoxia followed by 1 h of reoxygenation (protocol B). Creatine kinase (CK) and lactate dehydrogenase (LD) levels were compared with that of TnT. Myocardial adenine nucleotides were measured by HPLC. There was a strong correlation between TnT levels in albumin-free coronary effluent and TnT levels in coronary effluent diluted 1:1 with 5% bovine serum albumin (r = 0.996, N = 72). The coefficients of correlation between TnT and CK or LD during hypoxia and reoxygenation were 0.891 (N = 88) and 0.871 (N = 88), respectively. The coefficient of correlation between CK and LD was 0.993 (N = 88). There were no significant differences in either the decrease of coronary flow or the increase of TnT content between the hearts in the two protocols. There was no significant correlation between sigma TnT and energy charge of adenine nucleotides. These results indicate that cardiac TnT levels can be easily measured in albumin-free coronary effluent of isolated heart preparations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Effects of ischemic preconditioning on the release of cardiac troponin T in isolated rat hearts.

The aim of this study was to examine the effect of ischemic preconditioning on the releases of cardiac troponin T (TnT) during reperfusion in isolated rat hearts. Experiments were done on 22 rat hearts, which were perfused according to the method of Langendorff and were divided into the control group (n = 14) and the preconditioning group (n = 8). Double 5 min of ischemia each followed by 5 min reflow were applied as ischemic preconditioning. After 20 min of global ischemia, the releases of TnT, creatine kinase (CK), and lactate dehydrogenase (LD) in coronary effluent and the left ventricular developed pressure (LVP) were measured during 60 min of reperfusion. Ischemic preconditioning significantly suppressed the amounts of TnT released during reperfusion, as with those of CK and LD, and also improved contractile dysfunction (nine hearts in which ventricular fibrillation was sustained were excluded from the evaluation for hemodynamics), though the release kinetics of TnT was different from that of CK and LD. There were good inverse relationships between the LVP and the total amounts of TnT released during reperfusion period (sigma TnT) or TnT levels at 60 min of reperfusion. Cardiac TnT can be used as a useful biochemical marker for hemodynamics and myocardial damage after reperfusion.

Animals↗
PubMedDate not supplied

Release kinetics and correlation with hemodynamic dysfunction of cardiac troponin T in coronary effluent from isolated rat hearts during reperfusion.

Previously, we reported that cardiac troponin T (TnT) can be detected and measured in coronary effluent from isolated rat hearts during hypoxia. The present study was designed to evaluate the release kinetics of TnT from post-ischemic rat hearts. Using the Langendorff technique, the hearts were reperfused for 4 h after 20 min or 60 min of global ischemia. Coronary flow was measured by timing the collection of the coronary perfusate that dripped from the hearts, and left ventricular pressure (LVP) was monitored continuously during the experiments. The amount of TnT released in 1 min was compared with the release of creatine kinase (CK) and lactate dehydrogenase (LD). The release kinetics of CK and LD showed a monophasic pattern and the levels at 4 h after reperfusion returned to baseline levels. By contrast, the release kinetics of TnT showed a small peak followed by a larger and more sustained peak. There were good negative correlations between developed pressure of LVP and both sigma TnT and the amount of TnT released within 1 min at 4 h after reperfusion. These results indicate that the release kinetics of TnT is different from that of CK and LD during reperfusion, and further that cardiac TnT is a useful indicator of myocardial cell damage and can be used to evaluate the degree of myocardial cell damage in both the early and late phase of acute myocardial infarction.

Animals↗