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Biomedical subjects

S Asakuma

Publications and source records attributed to S Asakuma.

32 records · Page 2Linked to original sources
PubMed1988

[Clinical significance of precordial ST segment depression during acute inferior myocardial infarction].

To investigate the mechanisms and clinical significance of precordial (V1-V4) ST segment depression during acute inferior myocardial infarction, stress thallium-201 scintigrams and coronary angiograms were obtained within four to eight weeks after the onset of myocardial infarction in 37 patients experiencing their first acute inferior myocardial infarction. Among 18 patients with precordial ST depression (group 1), 11 with concomitant disease of the left anterior descending artery (LAD) had positive results on exercise test, whereas in seven patients without LAD lesion, only two had positive exercise test (p less than 0.01). In 19 patients without precordial ST depression (group 2), 11 had severe stenosis in the LAD. However, among these 11 patients, only two had positive exercise tests. Patients with precordial ST depression demonstrated a higher frequency of positive exercise tests than those without it (p less than 0.01). On stress thallium-201 scintigraphy, a perfusion defect involving the inferior wall was present in all patients, but additional anterior wall ischemia was present in only five of the 18 patients in group 1. These five patients had chest pain on exercise tests and a severe stenosis greater than 90% in the LAD. There was no significant difference in the frequency of additional posterolateral wall infarction between groups 1 and 2. In 18 patients in group 1, sigma ST (total degrees of ST segment depression in leads V1, V2, V3, and V4 in the acute stage) was significantly greater in 11 patients with LAD lesion than in seven without (p less than 0.05), and sigma ST greater than five mm was observed in 12 of 13 patients who had additional anterior wall ischemia and posterolateral wall infarction on stress thallium-201 scintigraphy (p less than 0.05). Myocardial revascularization, such as aortocoronary bypass surgery or percutaneous transluminal coronary angioplasty (PTCA), was performed in six of the 18 patients in group 1 in the chronic stage, but in only one of the 19 patients in group 2. Thus, in patients with initial acute inferior myocardial infarction, those with precordial ST depression seemed to be a high-risk group. It was suggested that, during the early stage of myocardial infarction, this abnormality on electrocardiograms is related to the summation of effects of anterior wall ischemia and posterolateral wall infarction. Furthermore, the sigma ST evaluation is useful in differentiating a mirror image of inferior wall infarction from anterior wall ischemia and posterolateral wall infarction as the mechanism of precordial ST depression.

Angiography↗
PubMed1981

Comparative ototoxicity of chloramphenicol and kanamycin with ethacrynic acid.

Chloramphenicol is not ototoxic if administered for systemic effect, but topical applications of it to the middle ear produce severe cochlear toxic effects. Ethacrynic acid potentiates the ototoxicity of aminoglycosides. Guinea pigs were administered chloramphenicol or kanamycin sulfate with ethacrynic acid to compare the ototoxicity of chloramphenicol and ethacrynic acid with the ototoxicity of kanamycin and ethacrynic acid. Preyer's reflex audiometry and measurement of the endocochlear dc potential, the cochlear microphonics, and the negative potential of the organ of Corti indicate that ethacrynic acid does not potentiate the ototoxicity of chloramphenicol. There is not even indirect evidence that the blood-cochlear barrier for chloramphenicol is altered by ethacrynic acid. Assuming that the ototoxicity of chloramphenicol and ethacrynic acid are similar for man and guinea pig, the combination of the administration of chloramphenicol and ethacrynic acid of systemic effect in dosages commonly used clinically should not produce greater ototoxicity than either agent administered alone.

Animals↗
PubMed1979

Effect of kanamycin sulfate on the endocochlear dc potential of guinea pigs.

The magnitudes of the endocochlear dc potential (EP) during adequate ventilation and during five minutes of anoxia were recorded in control guinea pigs and guinea pigs administered various dosages of kanamycin sulfate. The magnitudes of the EP after five minutes of anoxia were -44.6 +/- 5.9 mV in the controls and +26.6 +/- 9.9 mV in the guinea pigs that received kanamycin for seven or ten days. This change occurred after five or six days of administration of kanamycin. However, there was no significant change in the magnitude ot the EP with adequate ventilation with kanamycin intoxication. There is a significant correlation between the magnitude of the negative EP and the maximum output of the cochlear microphonics (r = -.770, P less than .001). These results suggest that the EP may not be the mathematical summation of the positive electrogenic potential and the negative diffusion potential. The mechanism for generating the negative EP during anoxia may have some relationship to hair cell integrity.

Animals↗
PubMed1978

Gastric response to meat extract stimulation in patients with gastroduodenal ulcer and patients after vagotomy or antrectomy.

Gastric acid secretion basally and in response to intragastric meat extract instillation or to tetragastrin, and circulating gastrin concentration basally and after meat extract stimulation were studied in 67 patients with gastroduodenal ulcer, 30 patients after highly selective vagotomy or selective vagotomy for duodenal ulcer, 12 patients after antrectomy for or gastric ulcer and 10 control subjects. Circulating gastrin concentration increased significantly after meat extract stimulation in control subjects, patients with ulceration and patients after highly selective vagotomy, and acid secretion in each group was increased significantly above basal level. In patients after selective vagotomy, significant increase of circulating gastrin concentration was observed, but it was not associated with significant increase of acid secretion. After antrectomy, neither gastrin nor acid secretion increased significantly after meat extract stimulation. In conclusion, present study suggested that (1) gastric acid secretion in response to intragastric meat extract is chiefly affected by the responsiveness of oxyntic cells and release of antral gastrin and that (2) the presence of the antrum is almost essential for acid secretion after a test meal, and release of duodenal gastrin after antrectomy would not be so potent biologically as to result in an acid secretion.

Adult↗
PubMed1978

Electrical resistance of the cochlear partition.

The relationship between the calculated value of the effective electrical resistance of the cochlear partition and the distance between the electrode for measuring the EP and the stimulating electrodes has been studied. The calculated value of the effective electrical resistance of the cochlear partition declines linearly with increasing distance between these electrodes. The correlation coefficient (r) is -0.806. In calculations of the effective electrical resistance of the cochlear partition, attention must be paid to the distance between the microelectrodes.

Animals↗
PubMedDate not supplied

Simple methods of assessing physical activity in patients with chronic heart failure.

This article reviews simple, noninvasive ways to assess physical activity in patients with chronic heart failure. Six- or 9-minute walk tests appear to be useful not only for selecting patients with relatively advanced heart failure but also as prognostic screening tests. The Master-Borg test (Master's two-step testing and 10-point Borg scale) is useful for assessing symptoms during exercise. Weekly pedometer counts show that the level of activity in patients with heart failure is dramatically less than in healthy controls. Physical activity can be determined directly by an ambulatory calorie counter that measures step scores and energy expenditure using specific accelerometers. Careful clinical interviewing regarding symptoms, together with submaximal exercise testing and use of motion sensors, are recommended as useful, simple, noninvasive alternatives for assessing physical activity in this patient population. (c)2000 by CHF, Inc.

Journal Article↗
PubMedDate not supplied

Bioelectric phenomena in the ototoxicity of nitrogen mustard.

The effects of nitrogen mustard on the electrical potentials of the inner ear were studied, and the results were correlated with the histopathologic findings which have been reported in nitrogen mustard ototoxicity. The endocochlear DC potential (EP) decreased rapidly after an injection of nitrogen mustard (NM). The amplitude of the cochlear microphonics potential (CM) diminished rapidly, and no substantial recoveries were observed. No significant changes in the magnitude of the negative potential of organ of Corti (NPOC) were observed. A large negative summating potential (SP) was recorded even when the amplitude of the CM had diminished.

Acoustic Stimulation↗
PubMedDate not supplied

Pathophysiology of the ototoxicity of cis-diamminedichloroplatinum.

The electrophysiologic and histopathologic changes in the inner ear caused by the administration of cis-diamminedichloroplatinum (CP) were studied in guinea pigs. The endocochlear dc potential (EP) gradually decreased after the intravenous injection of CP and reached approximately 0 mV on the fourth day, but the EP did not become negative. The cochlear microphonics also diminished and could not be recorded on the fourth day. The negative potential of the organ of Corti remained in the normal range during the experiment. A large negative summating potential (SP) was observed one day after injection, but the amplitude of the negative SP became small on the second day. Light microscopic examination demonstrated that the outer hair cells are destroyed in the basal turn of the cochlea and are preserved in the upper turns, while the inner hair cells are almost completely preserved in all turns. The stria vascularis was found to be slightly atrophic. Severe collapse of Reissner's membrane was observed in the basal turn.

Animals↗
PubMedDate not supplied

Experimental study of the mechanism of the decrease in endocochlear d.c. potential after administration of nitrogen mustard-N-oxide.

20 mg/kg of body weight of nitrogen mustard-N-oxide hydrochloride ( NMNO ) causes a transient decrease in the magnitude of the endocochlear d.c. potential (EP) in the same manner as does nitrogen mustard (NM). NMNO does not, however, change the electrical resistance of the cochlear partition. When the administered dose of NMNO is increased to 40, 60 and 80 mg/kg body weight, a corresponding diminution in the EP is not observed. No ultrastructural changes in the stria vascularis are observed, even in animals administered 80 mg/kg body weight. The reduction of the EP with NMNO could not be attributed to a loss of the electrical insulator effect of the cochlear partition, or to a functional derangement of the stria vascularis. In the experimental animals whose organ of Corti was already destroyed with kanamycin sulfate (KM), NMNO did not reduce the magnitude of the EP. The organ of Corti may be central in understanding the mechanism of NMNO -induced reduction of the EP.

Animals↗
PubMedDate not supplied

Effects of furosemide and ethacrynic acid on the endocochlear direct current potential in normal and kanamycin sulfate-treated guinea pigs.

The effects of loop diuretics on the endocochlear direct current (DC) potential and the effective electrical resistance of the cochlear partition were studied. The effective electrical resistance was increased, and the endocohlear DC potential was decreased. The decrease in the endocohlear DC potential must not be caused by breaks in the electrical insulation of the cochlear partition. With loop diuretics the endocochlear DC potential decreased less in guinea pigs treated with kanamycin sulfate than it did in the control group. Two interpretations of these phenomena are presented.

Animals↗