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Biomedical subjects

R Hirota

Publications and source records attributed to R Hirota.

34 records · Page 2Linked to original sources
PubMed1980

Effect of neonatal hydrocortisone treatment on brain monoamines in developing rats.

In our previous study, neonatal treatment with hydrocortisone was shown to produce a marked retardation of pituitary-adrenocortical development in infant rats. The present investigation was an attempt to determine whether or not the retarded activity is caused by functional changes in brain monoamine systems. In rats treated with hydrocortisone (0.5 mg/rat, s.c.) on the 2nd day of life, the development of whole brain was suppressed significantly. However, norepinephrine, dopamine and serotonin contents in the brain were higher in these rats than controls. These changes of monoamine contents were apparent in the hypothalamus, diencephalon and pons-medulla oblongata. Our data suggest that monoaminergic nervous systems are potentiated with hydrocortisone in these brain regions, although the results do not necessarily explain the retarded hypothalamo-pituitary function.

Animals↗
PubMed1980

Conditioned circadian rhythm of plasma corticosterone in the rat induced by food restriction.

Earlier observations that food restriction for a short period of time in the morning produced an altered circadian rhythm of plasma corticosterone having the peak just before feeding time, and that the elevated plasma corticosterone levels declined promptly immediately after food presentation were confirmed. After a 14-day restricted feeding schedule, where food was given from 11:00 to 13:00, if food was not given, elevated levels of plasma corticosterone were sustained for at least 1 hr and then declined gradually. On the other hand, if food was given 2 hr earlier than the scheduled time, the peak at 11:00 disappeared. The conditioned peak of plasma corticosterone was maintained for at least 3 days after the restricted feeding schedule if hypertonic saline, but not tap water, was given without food in male rats and ovariectomized female ones. When female rats were treated with lysine vasopressin for 5 days 10 min before the food presentation, highly elevated levels of plasma corticosterone were found at the time of food presentation. However, administration of cortisol 2 hr before the feeding time blocked the effect of vasopressin. The results suggest that vasopressin is involved in the acquisition and consolidation of the conditioned circadian rhythm of plasma corticosterone induced by restricted feeding.

Animals↗
PubMed1980

The rate of phase shift of plasma corticosterone circadian rhythm during early developmental stages in neonatally blinded rats.

The phase shift of circadian periodicity of pituitary-adrenocortical activity was studied in neonatally blinded infant rats. The phase shift of the rhythm was surprisingly rapid during the early stage of prepubertal period, while changes in the rhythm pattern were rather small after puberty, as indicated by a slight shift of the acrophase. Low amplitude was observed in the group data of blinded rats after puberty.

Age Factors↗
PubMed1980

Effect of a cholecystokinin preparation on brain monoamines in the rat.

In order to elucidate the central action mechanism of cholecystokinin (CCK), effects of this peptide on norepinephrine, dopamine and serotonin contents in the brain were observed in saline control, alpha-methyl-p-tyrosine-, L-DOPA- and pargyline-pretreated rats. Intraperitoneal injection of CCK in a dose of 40 U/kg did not produce any significant changes in the monoamine contents. However, since a tendency to increase in norepinephrine turnover rate after CCK injection was noticed, the possibility that brain monoamines are involved in the central action of CCK could not be excluded.

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↗
PubMedDate not supplied

Clinical evaluation of taste dysfunction using a salt-impregnated taste strip.

We have used special tests to investigate taste function in detail. To evaluate acuity for a salty taste, we used a paper with salt crystals, Salsave. The procedure is simple and takes only a few minutes. We analyzed the relationships between the magnitude of the threshold of response to this test and the results of other taste function tests in 126 patients who visited our clinic. The mean magnitude of the response to Salsave significantly correlated with the results of other taste tests. Thus, this is a useful method for screening the detection and recognition threshold of a salty taste.

Adult↗