A. V. Nalbandov

Hypothalamic center influencing the release of LH in the cockerel

Abstract Lesions destroying the posterior part of the tuberal nucleus or the tracts from it to the posterior part of the anterior median eminence affected the interstitial cells of cockerel testes and inhibited comb growth. Lesions elsewhere in the ventral hypothalamus did not prevent comb growth. Lesions in the dorsal anterior part of the hypothalamus appeared to stimulate comb growth.

The effect of weanling and adult males on sexual maturation in female voles (Microtus ochrogaster).

Abstract Weanling iemale voles were paired with either litlermate males, nonlittermate weanling males or adult males. Vaginal opening was earliest in females with adult males, latest in females with littermate males, and intermediate in females with nonlittermate weanling males. Littering occurred at approximately the same time in females with adult or nonlittermate weanling males and was significantly delayed in females with littermate males.

The effect of hypothalamic lesions on adrenal function in intact and adenohypophysectomized cockerels

Electrolytic lesions in the ventral tuberal area of the hypothalamus had contrary effects upon adrenal function of intact and adenohypophysectomized cockerels, as measured by corticosterone concentration in adrenal vein plasma: adrenal function decreased in intact birds, while it increased in adenohypophysectomized birds. Lesions in any other area of the hypothalamus had no influence upon adrenal function. Interrenal tissue atrophied in adrenals of adenohypophysectomized cockerels, and there was loss of differentiation between interrenal and chromaffin tissue. The interrenal tissue at the periphery appeared stimulated and exhausted of its granulation. Adrenals of adenohypophysectomized birds which were also lesioned showed little change from those in adenohypophysectomized birds. Interrenal cells in the periphery of adrenals of intact birds which were lesioned showed a decrease in activity, and an increase in amount proportional to chromaffin tissue. The histology of adrenal interrenal cells lying between the periphery and the center of the gland appeared to reflect the levels of corticosterone concentration in adrenal vein plasma. While adenohypophysectomy caused a decrease in adrenal weight, hypothalamic lesions had no effect. While the data appears to support the current view of the role of the hypothalamo-hypophyseal axis in regulation of adrenal function in intact cockerels, there is no indication from this study that the extrahypophyseal support for adrenal function in adenohypophysectomized cockerels resides in the hypothalamus.

Androgen Level in the Sheep Fetus During Gestation

Summary The androgen content of amniotic fluid, plasma, and gonads from 107 fetal lambs was determined by radioimmunoassay in an attempt to understand the ontogeny of gonadal function. Testosterone (T) was too low to be reliably measured in the amniotic fluid from fetuses of either sex. Ovaries were without T activity at an ofy the stages of gestation studied. Testicular T-5α-dihydrotestosterone (T-DHT) concentration steadily decreased from 1.4 ± 0.2 to 0.08 ± 0.01 μg T-DHT/g testis during the last 80 days of gestation. This was due to both increasing gonadal size as well as a decline in the absolute amount of T-DHT/testis. T was detected in the plasma of fetuses of both sexes. In females, levels rose steadily from 112 ± 20 to 459 ± 223 pg/ml during the last 80 days of fetal development. The pattern in the male was different in that plasma T at 70 days of gestation was 658 ± 145 pg/ml; then fell to 279 ± 51 pg/ml at about 100 days of gestation. Plasma T then rose to 866 ± 141 pg/ml near term. It is suggested that nongonadal testosterone production increases during fetal life and that T secretion by the fetal testis may contribute steadily less to the plasma pool of T as gestation proceeds. The John R. Morrell Packing Company, Sioux Falls, South Dakota, was most cooperative in allowing us to obtain tissue and blood samples. H. Eiler and R. Curnock assisted in the collection of the samples. Mrs. Lei-Hwa Yen performed much of the technical work reported here.

A study of ACTH and CRF in chickens

Abstract Previous work had demonstrated that chicken pituitaries contained a substance which was able to cause corticosterone synthesis by adrenals in vitro . In the present study chicken pituitary glands were assayed by the adrenal ascorbic acid-depletion method in hypophysectomized rats. It was found that perfect parallelism existed between the doses of 1.5–96.0 μg/100g body weight of chicken adenohypophyses and 0.4–10.0 mU of a standard mammalian ACTH. The data presented show that chicken pituitary glands contain relatively more ACTH than do those of rats. When assayed on hypophysectomized rats, perfect parallelism was demonstrated between extracts of 10, 20, and 40 chicken hypothalamic fragments and 0.4, 2.0, and 10.0 mU of the ACTH standard. Similar data were obtained on intact blocked rats. These results led to the conclusion that chicken hypothalami contain ACTH or an ACTH-like substance. No activity was present in extracts of chicken cerebral cortices which were used as control test substances.

The role of vasotocin and of CRF in ACTH release in the chicken

Abstract Hypothalamic extracts (HE) of chickens have the ability to deplete adrenal ascorbic acid (AAAD assay) in hypophysectomized rats. These extracts can withstand boiling up to 60 min without loss of activity. Since 25.0, 50.0, or 300.0 mU of arginine vasotocin shows no significant AAA depletion and since the dose of HE used was estimated to contain at most 100 mU of lysine vasopressin equivalents (Dekanski), it was concluded that the depleting activity was not due to vasotocin. Since both the chicken pituitary and mammalian ACTH standard lose their ability to deplete ascorbic acid after boiling for 30–60 min, it was further concluded that the depleting substance in hypothalami was different from hypophyseal ACTH. It is speculated that α-MSH may be the substance responsible for the ACTH-like activity of chicken hypothalami. Data are also presented to show that chicken hypothalami contain a factor which fulfills all the requirements of a CRF and that 94% of the ACTH-releasing activity of hypothalami is due to CRF.

Neurosecretion in the White Leghorn cockerel

Abstract The median eminence and posterior pituitary of White Leghorn cockerels was examined to see if there was a relationship between the presence of aldehydefuchsin positive neurosecretory material (NSM) and activity of the testes or pituitary and photoperiod. No correlation was found between the presence of NSM in the median eminence (ME) and castration, adenohypophysectomy, dehydration, or exposure to light (24-hour lighting for one week). From hatching to 45–50 days of age there is little NSM in the ME; after that there is an increase in the ME although the testes are developing rapidly. Dehydration effects a depletion of NSM from the posterior pituitary (PP).

Testicular development and testosterone concentrations in the testis and plasma of young male shrews (Suncus murinus)

Abstract Testicular development and testosterone concentrations in the peripheral plasma and testes of young, adult, and castrated male musk shrews ( Suncus murinus ) were examined. Fifty immature, 24 adult, and eight castrated males were used. Immature males ranged from 5–45 days of age. Plasma and testis homogenates were assayed for testosterone by radioimmunoassay. Testes were examined histologically for spermatogenic development. Plasma testosterone concentrations increased gradually from Day 5 to Day 24, then rapidly to Day 30. There was a sharp decrease between Day 30 and 33, then a gradual increase to Day 45. Testis testosterone concentrations followed the same pattern, except that on Day 5, the concentration was significantly higher than on Day 10. Adult males had higher testis testosterone and lower plasma testosterone concentrations than Day 45 males. Castrated males had barely detectable plasma testosterone levels. Testis weights increased linearly with age, except for a slight decrease between Day 30 and 33. Spermatogenic development was already initiated by Day 5. Cap-phase spermatids were present on Day 23, acrosome-phase spermatids on Day 30, and mature spermatozoa on Day 31. Epididymal sperm were present by Day 45.

The duration and control of adrenal function in adenohypophysectomized cockerels

Abstract Corticosterone concentration in adrenal venous plasma of adenohypo-physectomized cockerels was about one-third of that found in intact birds. There was no change in the output of this steroid into the adrenal vein from 1.5 to 42 days after surgery. Corticosterone synthesis in vitro was not influenced by hypothalamic homogenate, suggesting that no corti-cotrophin was present in this tissue, although evidence supports the existence of an extrahypophyseal corticotrophin. ACTH was shown to act at step(s) in the metabolic pathway preceding progesterone. The significance of these results is discussed and it is concluded that adrenal regulation in cockerels cannot be explained by the traditional concepts associated with mammalian adrenal function.

Plasma steroid concentrations in conscious and anesthetized rabbits.

Summary The ovarian steroids, estrogen, androgen, and progestin, were measured in the peripheral plasma of adult female rabbits that were either conscious or anesthetized with sodium pentobarbital (nembutal) or halothane. Concentrations of estrogen, androgens, and progestin were determined before and at 10 and 45 min after systemic injection of either buffer or L.H. In the controls androgen levels were significantly different between animals anesthetized with nembutal and halothane. However, the greatest treatment effect was noted in plasma progestin concentrations which were significantly elevated in halothane-anesthetized animals in comparison to the conscious and nembutal-anesthetized animals. Following LH, the androgen and progestin levels were significantly elevated over basal levels. Most likely the treatment effect observed in the controls was still present but was overridden by the increased release of steroids following gonadotrophin stimulation. This study suggests that halothane, in contrast to nembutal, does significantly elevate peripheral progestin and androgen levels.