In the rat a reciprocal relationship between the secretion of luteotropin and that of gonadotropins has been reported by a number of workers. In persistentdiestrous rats secured by 30 daily injections of estradiol from the day of birth, the ovaries remained infantile and the vaginal smear was characterized by a state of constant diestrus. Corpora lutea induced in such animals by injections of gonadotropins did not secrete progesterone spontaneously, at least in an amount sufficient to counteract the cornifying effect of excessive doses of estradiol. However, if the adenohypophysis of these rats was autografted under the kidney capsule, corpora lutea secreted enough progesterone to induce strong mucification in the vaginal epithelium in the presence of excess estradiol. These findings indicate that in persistent-diestrous rats, although the production of LH-releasing factor by the hypothalamus and consequently that of LH by the adenohypophysis are impaired (Arai, 1963), the secretion of luteotropin is inhibited by the hypothalamus.

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The effects of gonadal hormones-estradiol, progesterone and testosterone on the activity of choline acetylase in relation to the synthesis of acetylcholine in the hypothalamus of the spayed rats were studied to clarify the feedback mechanism of those gonadal steroids on the central nervous system. The following results were obtained: The elevation in the choline acetylase activity in the hypothalamus following ovariectomy was reduced to the level of the normal control by daily injection of estradiol benzoate in a range of doses of 0.1μg to 10μg. Attention should be given to the finding that the posterior hypothalamus is mainly responsible for the inhibitory effect of estradiol. However, no definite effect of estradiol was observed in the rats on the 20th day and the 100th day after castration which showed the lowered enzyme activity in the hypothalamus. Progesterone or testosterone had no demonstrable effect on the choline acetylase activity in the hypothalamus except that as small as 10μg of testosterone caused an increase in the activity of the rat on the 20th day after castration. It seems reasonable to conclude from the results mentioned above and those from the studies on cholinesterase and acetylcholine in this laboratory that there is the estrogen sensitive structure of cholinergic nature in the hypothalamus, especially in its posterior part, and the structure is closely involved in the mechanism of the secretion of gonadotropins as well as in the feedback mechanism of the steroid.

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The relation between the salt intake and the time of adrenal enucleation in Skelton's hypertension was investigated.
Neither increase of salt nor elevation of the blood pressure into hypertensive range occurred, if there is a 2-weeks-interval between the uninephroadenalectomy and the contralateral adrenal enucleation.
Under the same procedure increasing the concentration of sodium chloride in the drinking fluid to 2% caused increase of salt intake, but it brought the animals into the state of salt intoxication without hypertension.
The reasonable explanation for these results remains unresolved.

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The effect of level of feeding on spontaneous alveolar formation (SAF) was investigated using 35 litters of KP group of mice.
Each litter was divided into 2 groups after weaning till 70days of age; free fed group (group F) and restricted fed one (group R).
The day of vaginal opening was about 33days after birth in group F and about 51days in group R. On the 70th day, frequency of SAF in group F was about 53%, on the other hand, it was 0% in group R.
From the day of 71 th to 90th, some of the SAF positive mice in group F were given restricted food (group FR) and the rest and all of SAF negative mice continued to be fed freely (groups FF and FF'). Some of the group R were fed freely (group RF) and the rest continued to be fed as before (group RR).
On the 90th day, half of the mice in group FF' showed positive SAF, frequency of SAF elevated then to 69% in the pooled data of groups FF and FF', and no animals showed positive SAF in group FR. The frequency of SAF in group RF was 44%, while all animals in group RR remained to be negative in SAF.
The estrous cycles of some mice in each group were examined throughout the experiment, and it was ascertained that the ovary was active irrespective of feeding conditions. The SAF positive mice had always at least one long cycle.
There were some differences among groups in body weights either on the 70th or 90th day and some organ weights on the 90th day. The significance of these findings was discussed.

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Using the Sprague-Dawley strain of pregnant rats stressed with sham hypophysectomy as a trauma, the reactions of the maternal adrenals, the fetal pituitary and the fetal adrenals were examined quantitatively comparing with the data on fetuses after maternal hypophysectomy. Some of the animals were hypophysectomized on 141/2 days (group D), and 181/2 days (group B) of pregnancy.
Other pregnant rats were treated with sham hypophysectomy at the same times (groups E and C). In groups E and C, it was found that the maternal adrenal weight showed a remarkable increase. On the contrary, the fetuses in these groups showed a remarkable decline in the volume of the adrenal and in the volume of the pituitary, especially in the adrenals.
From these results, it may be suggested that the increased cortical steroid in the circulation of the mother treated with sham hypophysectomy as stress does cross the placental barrier, enter the fetus and give an inhibiting effect on the development of the pituitary and adrenal of the fetus, especially on the adrenal.

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We studied the effect of salivary gland hormone and salivary gland hormonelike substances on the serum calcium of rats, but we could not find any statistically significant change.

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1. Extremely minute quantities of placental TSH could invariably be detected in placental tissue whether it was spontaneously delivered or removed at the time of caesarean section.
2. Blood TSH level of pregnant women was far higher than those of normal male or female adults.
3. The quantity of TSH in the pituitary of the pregnant rat was higher than in the non-pregnant, while gonadotropin was lesser in amount during the period of gestation than in the non-pregnant period. Hence, an assumption is made that the higher blood TSH level of pregnant women implies hypersecretion of TSH from the anterior pituitary.
4. The human fetal thyroid gland is filled with a colloidal substance early in the 4th month of gestation, and by the 8th month it develop lobes. The glandular organ structure is morphologically complete by the time of birth.
5. The fact that we have failed to observe histological differences between fetal thyroid glands of pregnant rats administered a TSH product and a group of animal without such a drug seems to substantiate the interpretation that no TSH is transmitted across the placenta.
6. Human fetal TSH in the pituitary could be estimated as soon as 12th week of gestation is past, and that the thyroid lobules are formed by the 23rd week of gestation at which time the TSH content increases rapidly with simultaneous appearance of PAS positive granules. Development of the fetal thyroid, therefore takes place solely under control of fetal TSH.

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The in vitro production of corticoids from human adrenals was studied in normal and pathological states such as Cushing's syndrome or primary aldosteronism.
1. Hyperplastic adrenals of Cushing's syndrome produced a large amount of cortisone, cortisol and corticosterone. In the adrenal adenoma of primary aldosteronism, the production of aldosterone and corticosterone was stimulated. Hyperplastic tissues of the adrenal, combined with adenoma, also produced relatively large amounts of aldosterone. Another case of primary aldosteronism without adenoma produced not only aldosterone but also cortisone, cortisol and corticosterone in large amounts.
2. When ACTH was added to the incubation medium, the production of every kind of corticoids determined increased in normal adrenals, while aldosterone production did not increase so much in hyperplastic adrenals of Cushing's syndrome as compared with other corticoids production.
3. The production of aldosterone and corticosterone was stimulated by addition of synthetic angiotensin II to the incubation medium in normal adrenals, but only aldosterone production was promoted by angiotensin II in the adrenal of primary aldosteronism.

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