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Biomedical subjects

T Yasui

Publications and source records attributed to T Yasui.

At least 289 records · Page 16Linked to original sources
PubMed1981

Effect of angiotensin I converting enzyme inhibitor, SQ 14225, on renin production and release.

Renin production and release induced by angiotensin I converting enzyme inhibitor (CEI), SQ 14225, were studied in male Wistar rats. Acute studies on the effects of CEI (4.6 mumol/kg, i.m. every 6 h for 48 H) in rats revealed a significant reduction in angiotensin II levels and a marked increase in plasma renin activity (PRA). There were no appreciable changes in renal content (RRC) and the juxtaglomerular cell granulation index (JGI). In rats which had received CEI in their drinking water (0.92 mumol/ml) for 12 days, angiotensin II levels were decreased markedly and urinary excretion of sodium was increased, but the reduction in blood pressure was slight. PRA, JGI and RRC were markedly increased in these animals. The kidneys of CEI-treated rats exhibited conspicuous vascular dilatation. CEI treatment of sodium-depleted rats resulted in a reduction of the increased JGI and RRC and in a further increase in PRA. Our findings suggest that CEI administration may initially effect stimulation of renin release from the juxtaglomerular apparatus and that prolonged CEI administration results in a gradual stimulation of renin production.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1981

Central and peripheral effects of dopamine on the renin-angiotensin-aldosterone system in conscious rats.

To investigate the role of the central and peripheral dopaminergic systems in the control of the renin-angiotensin-aldosterone system in conscious rats, dopamine or its antagonist, metoclopramide, was injected intravenously (i.v.) and intracerebroventricularly (i.c.v.). Dopamine (100 micrograms/kg), when injected i.c.v., decreased plasma renin activity (PRA) and plasma aldosterone concentration (PA), while metoclopramide (50 micrograms/kg, i.c.v.) increased both of them. Intravenous administration of dopamine (1 microgram/kg/min) did not produce significant changes in either PRA or PA. In contrast, metoclopramide (500 micrograms/kg, i.v.) increased PA, which was not accompanied by any change in PRA. Blood pressure was decreased by i.c.v. administration of dopamine and increased by i.c.v. injection of metoclopramide, whereas no change in blood pressure was observed when these compounds were administered i.v. Dopamine and metoclopramide, injected i.v. or i.c.v., did not produce significant changes in plasma sodium, potassium and corticosterone concentrations. These results suggest that the dopaminergic system in the brain regulates renin secretion, thereby changing PA. In contrast, dopamine receptors of the adrenal glands may inhibit aldosterone secretion, which is not mediated by changes in the renin-angiotensin system, plasma potassium and ACTH.

Aldosterone↗
PubMed1980

[Studies on the mechanism of secretion of adrenal steroid hormones from adenomas of primary aldosteronism and Cushing's syndrome (author's transl)].

The mechanism of secretion of adrenal steroid hormones from adenomas of primary aldosteronism and Cushing's syndrome was studied in 10 patients with primary aldosteronism and in 3 patients with Cushing's syndrome in in vivo and in vitro experiments. In all of the 10 patients with primary aldosteronism, ACTH stimulated aldosterone secretion from the adenomas more significantly than did angiotensin II and III. DOC and cortisol which were contained in the adenomas were also stimulated more significantly by ACTH than by angiotensin II and III. Responses of the adenomas of Cushing's syndrome to various stimulations were less than those of primary aldosteronism. Secretion of cortisol and aldosterone from the adenomas of Cushing's syndrome was stimulated by ACTH and angiotensin II to a similar degree. From these studies, it seems that secretion of adrenal steroid hormones from adenomas of primary aldosteronism is more sensitive to extradrenal stimulations than that of Cushing's syndrome, and ACTH is the main factor in the control of the secretion of adrenal steroid hormones from the adenomas.

Adenoma↗
PubMed1980

Vascular action of high dose estrogen in rats.

Effects of estradiol hemisuccinate and diethylstilbestrol diphosphate on the cardiovascular system in male rats were examined in vivo and in vitro. In conscious rats, intravenously administered estradiol or diethylstilbestrol inhibited vascular responses to norepinephrine in a dose-dependent manner. Diethylstilbestrol in high doses significantly lowered the blood pressure of conscious rats. In the isolated mesenteric arteries perfused with Krebs bicarbonate solution, estradiol or diethylstilbestrol in the perfusate similarly inhibited vascular reactivity to norepinephrine in a dose-dependent manner. As in the in vivo experiments, a decrease in the basal pressure of the mesenteric vascular bed was observed when diethylstilbestrol was added to the perfusate at high concentrations. The results of these in vivo and in vitro studies strongly suggest that estradiol and diethylstilbestrol act directly on the vascular beds and attenuate vascular response to norepinephrine. It is also suggested that diethylstilbestrol by itself causes vasodilatation and a reduction in blood pressure when present at high concentrations.

Animals↗
PubMed1980

Action of rennin on casein. III. Effect of alpha s- and beta-casein on the secondary phase.

The action of rennin on kappa-casein was studied as a function of time, employing turbidity measurements at 610 nm and the release of nonprotein nitrogen. kappa-Casein was converted to para-kappa-casein by the action of rennin. The para-kappa-casein aggregated to increase turbidity and then precipitated. Turbidity development was enhanced initially and then retarded severely by increasing concentrations of added alpha s- and beta-casein. The addition of selected amino acids and salts had variable effects on increase of turbidity.

Amino Acids↗
PubMed1979

Occurrence of GTP cyclohydrolase I in Bacillus stearothermophilus.

A GTP cyclohydrolase which catalyzes the removal of carbon 8 of GTP as formic acid to yield a single pteridine compound occurs in an obligate thermophile Bacillus stearothermophilus ATCC 8005. The enzyme was purified 5.5-fold. Its molecular weight and Stoke's radius were estimated as 105,000 and 45.3 A, respectively. The Km for GTP was 0.98 microM. The temperature and pH optima for activity were 60-65 degrees C and 8.0-8.4, respectively. No divalent cation was required for the reaction. The pteridine product was 3'-triphosphate of 2-amino-4-hydroxy-6-(D-erythro-1',2',3'-trihydroxypropyl)-7,8-dihydropteridine (dihydroneopterin triphosphate), identified by isolating its immediate derivative, 2',3'-cyclic phosphate of 2-amino-4-hydroxy-6-(D-erythro-1',2',3'-trihydroxypropyl)pteridine (neopterin cyclic phosphate). The radioactive product from [8-14C]GTP agreed with 14C-formate. Molar ratio of formate release to pteridine formation was 1.0.

Aminohydrolases↗
PubMed1979

Central hypertensive actions of angiotensin I, II and III in conscious rats.

The effects of intracerebroventricular administrations of three natural angiotensins, angiotensin I (ANG I 3.8 X 10-11-9.4 X10-10 mol/kg body weight), II (9.6 X 10-12-2.4 X 10-10 mol/kg body weight) and III (2.7 X 10-10 2.5 X 10-9 mol/kg body weight) on systemic blood pressure were investigated in conscious rats. Angiotensin II (ANG II), ANG I and angiotensin III (ANG III), increased blood pressure in a dose-related manner. The order of potency of angiotensins was ANG II greater than ANG I greater than ANG III. The intraventricular administration of a converting enzyme inhibitor (SQ 14225, 6.9 X10-8 mol/kg) abolished the central effect of ANG I, while an angiotensin II analogue ([Sar1-Ala8]ANG II, 1.1 X 10-8 mol/kg) administered intraventricularly inhibited the central pressor effects of these three angiotensins. These results suggest that ANG II is a main mediator of the renin-angiotensin system in the central nervous system.

Angiotensin I↗
PubMed1979

Molecular adaptability of carp myosin: a study of some physico-chemical properties and their comparison with those of rabbit myosin.

During thermal inactivation, the addition of as low as M urea resulted in the reduction of delta G identical to barrier of the inactivation of carp myosin Ca2+-ATPase, whereas that of rabbit myosin remained unaffected. In the absence of urea, a four-hour incubation of carp myosin was accompanied by the release of light chains at 30 degrees C, a value 10 degrees C lower than that for rabbit myosin. Electron micrographs revealed that carp myosin forms artificial thick filaments, which were uniform in size and may differ in a few details from those of rabbit. Not only that helical content of carp myosin was about 4% less than those of rabbit myosin, but it showed more sensitivity to thermal and urea denaturation; and its reversibility upon subsequent cooling or removal of urea was rather poor. The loss in helicity of myosins by urea was a concentration- and temperature-dependent biphasic reaction, with the most obvious effect observed on carp myosin. That carp myosin has increased tendency of unfolding in urea solutions was confirmed by viscosity data and the exposure of thiols also. Even in the absence of urea more SH groups of carp myosin were incorporated by DTNB, and more epsilon-amino groups reacted with NQS. Carp myosin remained in solution till the modification of about 52 surface myosin remained in solution till the modification of about 52 surface amino groups, whereas no precipitation effect was noted in case of rabbit myosin. Neither amino-acid composition nor some parameters derived from it, such as average hydrophobicity polarity index and number of polar side chains, revealed any difference pertinent to the relative stability of the two myosins. On the contrary, the contractile efficiency of carp myosin in the near physiological range was high and thus inversely related with the thermostability. This relationship along with the above evidence has been regarded to demonstrate the adaptability of carp myosin through a loose molecular conformation, which has probably been achieved by the addition of weak interactions in the course of evolution.

Animals↗
PubMed1978

Electron microscopic study of the response of the adrenocortical X-zone in mice treated with sex steroids.

In the adrenal cortex of 23- to 27-day-old C3H/Tw female mice, the eosinophilic X-zone became increasingly increasingly undetectable after 3 injections of 100 microgram testosterone propionate (TP). Whorls of smooth endoplasmic reticulum (sER) and peculiar complexes of mitochondria and sER, characteristics of X-zone cell, were no longer present in mice given 7 daily injections of TP. The ordinary mitochondria, although reduced in number, became swollen and actually increased in percent area occupied. They had well-developed tubulovesicular cristae. The lipid droplets increased in size and number after 3 daily TP injections, but decreased after 7 daily injections. Rough endoplasmic reticulum and sER were reduced in area in mice receiving 7 daily injections. The X-zone also became indistinguishable from the zona fasciculata after 7 daily injections of 5alpha-dihydrotestosterone propionate. Injections of progesterone or estradiol-17 beta had no effect on the X-zone.

Adrenal Glands↗
PubMed1978

Purification and some properties of a neutral muscle pyrophosphatase.

In the water-soluble fraction of rabbit skeletal muscle, at least two types of inorganic pyro phosphatase (PPase) are distinguishable on ion exchange column chromatography. One of them, pyrophosphatase-A (PPase-A), was isolated in an electrophoretically homogeneous form. This enzyme catalyzed the hydrolysis of PPi but not that of other phosphate esters. Only Mg2+ was required for activity and stability. Other cations such as Ca2+, Co2+, Mn2+, and Zn2+ had no activating effect. The activity of this PPase was optimum at pH 7.4. ATP, ADP, sodium imidodiphosphate (PNP), p-chloromercuribenzoate, and Ca2+ inhibited its enzymic activity. The enzyme was protected by dithiothreitol (DTT) against heat denaturation. The molecular weight was estimated to be 67,000 by gel filtration and the molecular size of the subunit was found to be 35,000 by gel electrophoresis in the presence of sodium dodecyl sulfate (SDS). The enzyme probably consists of two identical subunits of 35,000 daltons.

Animals↗