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Biomedical subjects

R Hirota

Publications and source records attributed to R Hirota.

10 recordsLinked to original sources
PubMed1991

Production of corticosterone and testosterone in scorbutic mutant rats: difference of in vivo production between adrenal gland and testis.

Effects of deficiency in ascorbic acid on in vivo production of corticosterone and testosterone were examined using a mutant strain of rats unable to synthesize ascorbic acid. The adrenal weight of scorbutic rats was larger, and corticosterone levels in plasma and adrenal tissues were higher than those of ascorbic acid-supplied (ascorbutic) rats. Acute and chronic stimulation with ACTH increased corticosterone levels in both ascorbutic and scorbutic rats. In contrast, weights of seminal vesicles and ventral prostates in unstimulated scorbutic rats were smaller, and testosterone levels in plasma and testicular tissues were lower than those in ascorbutic rats. Acute stimulation with hCG increased testosterone levels only slightly in plasma and not in testicular tissues of scorbutic rats, when testosterone levels in ascorbutic rats reached a maximum. Chronic stimulation with hCG increased testosterone levels remarkably in both ascorbutic and scorbutic rats. These findings seem to indicate that ascorbic acid is not essential for the synthesis of steroid hormones. The scurvy seems to increase plasma ACTH levels secondary to the stress, resulting in the stimulation of the adrenals. In contrast, a prolonged deficiency in ascorbic acid appears to decrease plasma gonadotropin levels, and may reduce the sensitivity of testes to gonadotropins.

Adrenal Glands↗
PubMed1989

Effect of physical training on thrombotic tendency in rats: decrease in thrombotic tendency measured by the He-Ne laser-induced thrombus formation method.

The effect of physical training on thrombotic tendency was assessed in rats. Exercise was done on a flat treadmill for 30 min at a rate of 1,400 m/h (submaximal speed), 5 times a week for either 1.5 or 3 months. The thrombotic tendency was measured by the He-Ne laser-induced thrombus formation method in microvessels of mesentery, i.e. measurement of the number of laser irradiations necessary to induce stasis of blood flow by occlusive thrombus formation. An increase in the number of irradiations necessary to induce occlusive thrombus formation was observed in arterioles, but not in venules after physical training for 1.5 and 3 months.

Animals↗
PubMed1979

Suppressive effect of pentagastrin on pituitary-adrenocortical secretion.

The effect of pentagastrin on the pituitary-adrenocortical secretion was examined in male rats. In the morning the intraperitoneal injection of this peptide produced a slight, but significant, decrease in the plasma corticosterone levels, but it had no effect on the evening rise due to circadian periodicity and the stress-induced elevation of the plasma corticosterone level. Following intracerebroventricular administration of pentagastrin, plasma corticosterone tended to decrease and in in vitro incubation of rat pituitary tissue the addition of pentagastrin elicited a suppressive effect on the ACTH release from the tissue into the medium. It was suggested that gastrin-like peptide might control the secretion of ACTH.

Adrenocorticotropic Hormone↗
PubMed1978

[Postnatal development of adrenocortical circadian rhythm in neonatally cortisol- and estriol-treated rats (author's transl)].

The effect of a single neonatal administration of cortisol and estriol on the development of the adrenocortical circadian rhythm was investigated in immature rats. In normal control rats of both sexes, the plasma corticosterone rhythm was discernible on day 21. In male rats the adult pattern was observed on day 28, but in females as the plasma corticosterone level elevated progressively during puberty, the rhythm increased in amplitude and the adult pattern was established at 8 weeks of age. In neonatally cortisol-treated rats, the plasma corticosterone rhythm appeared at 4 weeks of age, but the plasma level was significantly lower than that of the controls until 6 weeks and attained a level similar to the controls at 8 weeks. Neonatally estriol-treated rats exhibited the rhythm as early as 2 weeks of age, but this was temporary. It disappeared at 3 weeks and reappeared a 4 weeks. Although 5-week-old males showed normal rhythm as seen in the controls, in females the plasma corticosterone level remained low for weeks and approached the control level at 8 weeks of age. The development of circadian periodicity of adrenal corticosterone content almost paralleled that of plasma corticosterone not only in the controls but also in steroid-treated groups, but the rhythm was occasionally equivocal. In neonatally estriol-treated rats, stress response of plasma and adrenal corticosterone to ether was similar to that of the controls, but the response to exposure to a strange environment was significantly small.

Adrenal Cortex↗
PubMed1977

[Changes in adrenal gland and thymus induced by sex steroid administration in newborn rats (author's transl)].

Testosterone, dehydroepiandrosterone (DHEA), progesterone, estradiol-17beta, estrone, estriol, 2-hydroxyestradiol-17beta, 2-hydroxyestriol, deoxyestrone and diethylstilbestrol were injected s.c. in a dose of 0.5 mg each into newborn rats on the first day of life, and changes in the adrenal gland, thymus and spleen were examined 3 days later. Increase in the body weight during the 3 days was less in rats treated with DHEA, 2-hydroxyestriol and deoxyestrone, as compared with that in controls. Development of the thymus was significantly impaired in rats injected with various kinds of sex steroids, except progesterone and diethylstilbestrol. Reduction of the spleen weight by sex steroid treatment was not marked. The weight of adrenal gland decreased in rats injected with DHEA and progesterone, while the weight increased in those given estrone and diethylstilbestrol. Estrogens, particularly estriol, induced a marked increase in adrenal corticosterone content, while 2-hydroxyestriol caused only slight elevation and 2-hydroxyestradiol and deoxyestrone had no influence on the content. Suppressive effect of cortisol on the adrenal gland of newborn rats was slightly, but significantly, lessened by estriol treatment. From the results, physiological role of estriol and DHEA in adrenal secretion was discussed.

Adrenal Glands↗
PubMed1976

[Postnatal development of the adrenal gland in the rat (author's transl)].

Postnatal development of adrenocortical function of rats was studied. During the first week after birth the increase in adrenal weight was very slight. Consequently, the relative weight of the gland per body weight decreased progressively during the postnatal 14 days. However, adrenal corticosterone concentration showed a gradual elevation over this period of postnatal days. Adrenal corticosterone response to ether stress did not appear in male rats at 12 days of age, but a distinct response was observed in female ones at the same age. A sex difference in the duration of the stress-nonresponsive period is likely to exist in newborn rats. In accord with the stress-nonresponsive period, the thymus-lymphatic system showed a marked development. The pattern of circadian periodicity of plasma corticosterone levels in 21-day-old rats was somewhat different from that in adult rats. Peak value of the corticosterone rhythm was attained at 0300 in the infant rats. A sex difference was again noticed in the evening rise of plasma corticosterone level in these infant rats: the rise was steeper in females than in males. A significant circadian periodicity was observed in female rats at 14 days of age, but the periodicity was equivocal in male ones at the same age.

Adrenal Glands↗
PubMed1976

[Atrophy of adrenal gland and thymus following cortisol treatment in newborn rats (author's transl)].

Effects of neonatal treatment with cortisol on the mortality, growth rate, the weight of thymus, spleen and adrenal gland, blood lymphocyte counts and stress responses were examined in the rat. In rats treated with 1 mg cortisol the survival rate was only 13 percent, and in those given 0.75 mg the rate was 47 percent. Large doses of cortisol produced "wasting syndrome" and the animals died during a period from 5 to 13 days after the injection. Over the first week the body weight did not increase in rats injected with cortisol in doses of 1 and 0.75 mg. A marked atrophy of the thymus and a great reduction of the blood lymphocyte counts were observed in rats treated with large doses of cortisol. The development of spleen was temporarily inhibited. The adrenal gland was remarkably atrophied: the gland weight at 21 days of age was similar to that at birth and only 22 percent of the control value. In rats injected with 0.5 mg cortisol plasma corticosterone response to ether inhalation was not different from that of normal controls at 21 days of age. However, rats treated with 0.75 and 1 mg cortisol did not show plasma corticosterone response on exposure to a strange environment. The effect of several kinds of corticoids was also examined. Dexamethasone and betamethasone caused a marked atrophy of the thymus and spleen. Cortisol and deoxycorticosterone produced a large decrease in the adrenal corticosterone content. The effect of exogenous corticosterone was less in extent as compared with that of cortisol.

Adrenal Glands↗