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Biomedical subjects

S Morimoto

Publications and source records attributed to S Morimoto.

At least 685 records · Page 38Linked to original sources
PubMed1984

Dependence of conduction velocity on spike interval during voluntary muscular contraction in human motor units.

The dependence of the conduction velocity of the action potential on the spike interval from a preceding potential was studied using human single motor units during voluntary muscle contraction. The spike potential was recorded from the surface of the skin overlying M. vastus medialis by use of surface electrodes (diameter 5 mm). The results were as follows: Conduction velocity increased with a decrease in spike interval. The relation between conduction velocity and spike interval can be expressed as log v = kt + a, where v is conduction velocity (m X s-1), t is spike interval (ms) and k and a are constants. All data can be expressed by the above formula with a highly significant correlation. After arterial occlusion, there was little or no relation between conduction velocity and spike interval. This lack of correlation between these parameters was not restored to the initial correlation within a period of 15 min. Effects similar to occlusion could be seen in the result of prolonged isometric contraction. However the lack of correlation between these parameters was restored to the initial correlation within a 15 min recovery period. At low muscular temperature, the relation could not be described by a logarithmic regression. As the spike interval became shorter, the conduction velocity decreased. After cessation of cooling, the relation was restored to the initial correlation within 30 min. The mechanisms of these changes are still uncertain but some possible factors can be considered, for example, composition of the extracellular fluid, pH, temperature and permiability of the excitable membranes of the muscle.

Action Potentials↗
PubMed1984

Transplantation of extensor carpi radialis longus muscle in normal and dystrophic chicks.

The etiology of avian muscular dystrophy was examined by a cross-transplantation technique. Care was taken for the transplants to regenerate and develop under neural influence, by using the small extensor carpi radialis longus (ECRL) muscle. The ECRL muscles were exchanged between normal and dystrophic chicks 2 to 3 days ex ovo, and the muscle weight, number of muscle fibers, muscle fiber size, and contractile properties of the transplanted muscles were observed 60 to 65 days after operation when the tissue reconstitution was virtually complete. The results obtained for the physiologic, anatomic, and histologic parameters strongly suggested that there exists some failure in the host environment of the dystrophic chicken. The analyses of the histologic parameters suggested that a genetic disorder may also reside in the muscle tissue itself. The myotonic nature of the muscle membrane, however, probably does not contribute significantly to the abnormal behavior of dystrophic chickens. The importance of some neurogenic abnormalities in avian muscular dystrophy is discussed in relation to the results reported by other investigators.

Action Potentials↗
PubMed1984

Rice bran treatment for patients with hypercalciuric stones: experimental and clinical studies.

The purpose of this study is to confirm the hypocalciuric effect of rice bran experimentally and clinically. Urinary calcium excretion and its absorption in the intestine were reduced significantly by rice bran or phytin in rats fed high calcium diets, while there were no significant decreases with a low calcium diet. For the clinical study 70 patients with idiopathic hypercalciuria were treated with rice bran (10 gm. twice daily) for 1 month to 3 years. In almost all patients rice bran caused a significant decrease in urinary calcium excretion, which was maintained during treatment. Evidence of stones has decreased clearly among patients treated with rice bran for 1 to 3 years, although this might be a halfway judgment of the long-term treatment. We suggest that phytin should be the most effective substance to reduce the intestinal absorption of calcium and that rice bran treatment should be effective for prevention of recurrent urinary stone disease.

Animals↗
PubMed1984

Relation of doubling time of plasma calcitonin levels to prognosis and recurrence of medullary thyroid carcinoma.

Plasma calcitonin (CT) levels were measured serially in 54 patients surgically treated for medullary thyroid carcinoma. Patients with postoperative basal CT levels higher than 1 ng/ml measured within 1 month after surgery had a higher recurrence rate than those with lower CT levels (p less than 0.002). Patients with postoperative basal CT levels higher than 2 ng/ml had a lower survival rate than those with lower CT levels (p less than 0.01). However, preoperative basal CT levels had no significant correlation with life expectancy or recurrence during the present observation period. Serial measurements in 23 patients with elevated postoperative CT levels showed exponential increases in basal CT levels in 19 patients (p less than 0.05 in nine patients, 0.05 less than p less than 0.1 in four patients) and slight decreases in four (p less than 0.05 in one patient). Doubling time of CT levels calculated from the regression line in each patient showed the highest correlation with 3-year survival, recurrence within 5 years, and time interval between surgery and clinical recurrence of the tumor, allowing quantitative prediction of the prognosis.

Calcitonin↗
PubMed1984

Adrenal adenoma with 18-hydroxycorticosterone excess and hypertension: a variant of aldosteronomas.

A 46-year-old woman with hypertension, normokalemia, suppressed renin, normal catecholamines, and a left adrenal mass on the CT scan was found to have excessive 18-hydroxycorticosterone (18-OHB) and normal aldosterone levels in plasma, both of which responded poorly to sodium restriction and angiotension II, and supranormally to ACTH. Plasma 18-hydroxydeoxycorticosterone (18-OHDOC) was normal. After adrenalectomy, amelioration from hypertension occurred with a reduction in plasma 18-OHB and aldosterone. The plasma 18-OHDOC remained normal. The adrenal tumor was histologically an adenoma, containing a large amount of 18-OHB and a small amount of aldosterone. Thus, the present adenoma seems to be a variant of aldosteronomas.

18-Hydroxycorticosterone↗
PubMed1984

Inhibition of calcitonin secretion by exogenous calcitonin in the rat.

The effect of synthetic salmon calcitonin (CT) on calcium- and pentagastrin-stimulated plasma CT was investigated in male Sprague-Dawley rats. Plasma samples were obtained before and 3 and 6 min after calcium (1 mg/100 g BW, iv) or pentagastrin (5 micrograms/100 g BW, iv) infusion. Although salmon CT at the dose of 0.4 MRC U/100 g BW administered 15 min before either the calcium or pentagastrin infusion did not influence circulating endogenous CT levels, salmon CT in doses of 4 and 20 U/100 g BW administered 15 min before the injection of secretogogues significantly reduced the response of CT to either calcium or pentagastrin without significantly changing plasma calcium levels from those of control animals. Salmon CT (20 U/100 g BW) given 5 min before pentagastrin infusion again significantly suppressed the response of plasma CT to this stimulus. Similarly, salmon CT administered chronically in a dose of 2 U/100 g BW for 28 days significantly reduced the response of CT to the calcium infusion. These data suggest that in the rat, at least pharmacological dosage of CT modulates the production and/or secretion of glandular CT itself.

Animals↗
PubMed1984

Stimulant effects of W-7, a calmodulin-antagonist, on renin release from rat kidney cortical slices.

Effects of N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), a calmodulin-antagonist, on renin release was examined using rat kidney cortical slices. Although the amounts of renin release from the slices were stable during incubation of 3 consecutive 15 min periods in Krebs-Ringer bicarbonate solution (pH 7.4), the addition of W-7 to the incubation medium resulted in a concentration-dependent increase in renin release from the slices. The stimulant effect of W-7 on renin release was abolished by the removal of calcium from the incubation medium. These results suggest that the inhibition of the calcium-calmodulin system leads to the stimulation of renin release from rat kidney cortical slices.

Animals↗
PubMed1984

Conversion of low molecular weight renin into the high molecular weight form by Cu2+ in the rat kidney.

The low molecular weight form of renin (M.W. 40000) in the extract of rat kidney cortex was converted into the high molecular weight form (M.W. 60000) in the presence of Cu2+ and this conversion was abolished following pretreatment of the extract with disodium ethylenediaminetetraacetic acid. Fe3+, Fe(CN)6(3-), Cd2+ and Zn2+ had no effects on the reaction of the molecular weight conversion of this enzyme. The reactivity in the formation of high molecular weight renin catalyzed by Cu2+ increased when the extract was previously dialyzed, indicating the presence of substance(s) that interfere with the binding reaction of renin. The high molecular weight renin produced by Cu2+ was stable against dithiothreitol, suggesting that the formation of disulphide bridge(s) is not involved in the reaction of renin with the renin binding substance. We also confirmed that for formation of the high molecular weight renin, Cu2+ must react with both the renin enzyme and the renin binding substance. Our findings provide new evidence related to the mechanism of molecular weight conversion of renin in the rat kidney.

Animals↗
PubMed1984

Pseudohypoparathyroidism (PHP) type II and selective hypoaldosteronism in a patient with retinitis pigmentosa.

A 53-year-old man with retinitis pigmentosa, who had two years' complaints of general malaise and muscle weakness, noticed occasional attacks of the cramps of the lower legs about three months prior to admission. At that time, hypocalcemia (7.6 mg/dl) and hyperphosphatemia (5.2 mg/dl) were pointed out. On admission, serum potassium was high-normal or high (4.4 - 4.9 mEq/l). Endocrinological studies revealed the findings of pseudohypoparathyroidism (PHP) type II, including a normal urinary cyclic AMP but blunted phosphaturic response to synthetic human parathyroid hormone (PTH), a high level of serum amino-terminal fragment of PTH with a low level of serum calcium and its ionized form, and a high-normal level of nephrogenous cyclic AMP. This patient also had selective hypoaldosteronism, as shown by intermittent hyperkalemia, low plasma and urinary levels of aldosterone and normal glucocorticoid levels. Plasma renin activity was normal but responded to a greater extent to furosemide plus upright posture. Plasma aldosterone was low and responded poorly to furosemide plus upright posture and graded angiotensin II infusions. The possible explanations for the association of PHP type II and selective hypoaldosteronism in this patient with retinitis pigmentosa are discussed.

Aldosterone↗
PubMed1984

Sonographically guided needle biopsy for diagnosis of thoracic lesions.

Fluoroscopically guided percutaneous biopsy of thoracic lesions is widely accepted. However, some lesions are not sufficiently visible on fluoroscopy. When this is the case, sonographic guidance may be helpful. Real-time sonographically guided needle biopsy was performed in 38 such cases, including 27 pulmonary nodules adjacent to the chest wall, three mediastial tumors, five chest wall masses, and three pleural lesions. Definitive diagnoses were made in 30 cases (78.9%), including 21 (91.3%) of 23 malignancies and nine (60%) of 15 benign lesions. Sonographically guided needle biopsy could be performed safely and easily, taking advantage of the real-time monitoring of needle position for the pulmonary masses located adjacent to the chest wall, even when fluoroscopic or CT guidance was not effective. It is suitable for biopsying chest wall tumors, pleural lesions, and anterior mediastinal masses. It is particularly suited to biopsying small pulmonary nodules adjacent to the chest wall, nodules in the apical or juxtadiaphragmatic regions, and those obscured by pleural effusion.

Adult↗
PubMed1984

The characteristics of renal mineralocorticoid receptors in glycyrrhizinic acid or deoxycorticosterone-induced hypertensive rats.

The relationship between blood pressure and the characteristics of renal mineralocorticoid receptors was studied in glycyrrhizinic acid (GR) or deoxycorticosterone (DOC) induced hypertensive rats. The apparent maximum binding (Bmax) of aldosterone to renal mineralocorticoid receptors was 3.1 +/- 0.2 X 10(-13) mol/mg cytosol protein and the dissociation constant (Kd) was 1.6 +/- 0.5 nM. GR treatment reduced the concentration of cytosol mineralocorticoid receptors (Bmax) but did not affect the Kd. In unilaterally adreno-nephrectomized rats, GR induced hypertension and hypokalemia as seen in DOC treated rats. After the discontinuation of GR, blood pressure was normalized with concomitant recovery of free cytosol mineralocorticoid receptors in 14 weeks. On the contrary, in DOC treated rats, the characteristics of mineralocorticoid receptors in kidney were already normal one week after the cessation of DOC treatment. However, blood pressure remained high up to 15 weeks. These findings suggest that the persistence of hypertension after GR discontinuation might be caused by a long-standing effect of GR on renal mineralocorticoid receptor mechanisms.

Aldosterone↗