Experimental research on the morphofunctional differentiation of the rat ventral prostate: roles of the gonads at birth.

In the male rat, a dramatic increase in serum testosterone (T) of testicular origin occurs during the first few hours of postnatal life. This experiment sought to determine whether this increase affects the physiology of the adult rat ventral prostate. Male rats were castrated at the time of caesarean delivery performed at different precise stages between 21 days and 22 days of gestation (0h males).

[Variations in the testicular response to HCG during the perinatal period in the rat: influence of estrogens].

The variations of the testicular responsiveness to hCG and the implication of the maternal estrogens in the functioning of the testes were studied in the perinatal male rat. Male rat fetuses treated with hCG at the end of gestation failed to show an increase in serum testosterone (T). The lack of testicular responsiveness to hCG in the fetus is neither due to anesthesia nor to a blocking effect of estrogens directly on the testes.

Changes in plasma testosterone levels during the peri-hatching period in the chicken.

Blood was obtained by heart puncture from 19-day-old Black Sex link chicken embryos and from Black Sex link chickens at 1.5, 6, or 24 h post-hatching. Plasma testosterone was determined by gas chromatography-mass spectrometry associated with stable isotope dilution.

The neonatal testosterone surge: a comparative study.

In the rat an abrupt discharge of testicular testosterone in the newborn male figures prominently in the development of mechanisms controlling gonadotropin secretion, sexual behavior, and also promotes the functional differentiation of the accessory sex glands. In this study we detail the temporal characteristics of this surge in the rat, and we provide comparative data documenting a similar surge-like appearance of testosterone in neonatal male mice, recently foaled male horses, and newborn human infants. Although the physiological and behavioral significance of this phenomenon for species other than the rat remains to be determined, the apparently ubiquitous appearance of the neonatal testosterone surge suggests that it may be of special significance in the sexual differentiation of many mammalian species.

Sex differences in serum luteinizing hormone and testosterone in the human neonate during the first few hours after birth.

Blood was obtained from human male and female neonates within a few minutes after birth, and at intervals thereafter for up to 21 h. Serum LH was substantially higher at birth for boys than girls. For most boys, serum LH fell precipitously during the next hour; serum LH remained low for the remainder of the period sampled in both boys and girls.

Testosterone levels in plasma and testes of neonatal mice.

Newborn female and male C57BL6 mice were decapitated at birth or at different times during the first 24 h after birth and testosterone was determined by radioimmunoassay in plasma and testes. In newborn females, plasma testosterone is low and does not significantly change over the first 24 h after birth. In contrast, in newborn males, plasma testosterone more than doubles during the first 2 h after birth and then falls rapidly to remain relatively low for the remainder of the 24 h period after birth.

Influence of the environmental temperature on the post-partum testosterone surge in the rat.

In the neonatal male rat, a rapid and transient increase in serum testosterone occurs about 2 h after birth. This post-partum testosterone surge (PPTS) has been implicated in the masculinization and defeminization of the central nervous system. The present study shows that environmental temperature can have a profound influence on the PPTS.

Testicular hormones during the first few hours after birth augment the tendency of adult male rats to mount receptive females.

In the male rat, a dramatic increase in serum testosterone of testicular origin occurs during the first two hours of postnatal life. This experiment was designed to determine whether this increase contributes to the development of the propensity for adult male rats to mount sexually receptive females. Male rats were castrated at either 0-hours (virtually at the moment of birth), or at 6 hours, or at 24 hours after birth.

[Effect of newborn rat testes on the male sexual behavior of the testosterone-treated adult].

Neonatal male rats were castrated either at 0, 6 or 24 hrs. after birth. As adults, testosterone was delivered by subcutaneous implantation of a Silastic capsule containing this hormone.

Differential effects of the perinatal steroid environment on three sexually dimorphic parameters of the rat brain.

Gonadectomy of male rats was performed at 0, 6-7 (6h), 12-13 (12h), or 24 h postnatally in order to examine the influence of testosterone exposure on sexual differentiation of the brain. The indices examined were: the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) and luteinizing hormone (LH) and follicle-stimulating hormone (FSH) titers following estradiol benzoate (EB) and progesterone (P) administration. Control animals were sham-operated at 0 h and gonadectomized at 29 days of age (sham).

Sexual differentiation of positive feedback: effect of hour of castration at birth on estradiol-induced luteinizing hormone secretion in immature male rats.

In the male rat, a dramatic increase in hypothalamic testosterone and estradiol concentrations occurs during the first few hours of postnatal life. These experiments sought to determine whether such increases participate in the defeminization of positive estrogen feedback effects on LH secretion. Newborn male rats were castrated either in utero (0 h males), or 10 or 24 h after birth.

Gonadal steroid concentrations in serum and hypothalamus of the rat at birth: aromatization of testosterone to 17 beta-estradiol.

Endogenous concentrations of testosterone (T), 5 alpha-dihydrotestosterone, progesterone (P), and estradiol-17 beta (E2) were determined with specific RIAs in serum and hypothalami of male and female rats before, during, and up to 24 h after birth. In the male, a dramatic and transient increase in T concentration was observed in the serum and the hypothalamus between 0 h in utero and 2 h after delivery. At all times studied, T levels were undetectable in the female.

Female sexual behavior in male rats: effect of hour of castration at birth.

In the male rat, a dramatic increase in serum testosterone occurs during the first four hours of postnatal life. The experiments sought to determine whether such an increase would participate directly on the defeminization process. Newborn male rats were castrated either at 0 hr in utero (literally at the moment of birth) or at 6 or 12 hrs after birth.

Hypothalamic testosterone increase in the male rat at birth.

In the male rat, a dramatic increase in serum testosterone occurs during the first 2 h of postnatal life. Since the hypothalamus is known to be an important site for sexual differentiation of the brain, this early testosterone surge was a good model to use to study the transfer of serum testosterone to the hypothalamus and cerebral cortex. Endogenous testosterone was measured by radioimmunoassay in the hypothalamus and the cerebral cortex of the foetus and newborn rats during the first 6 h following birth.

[Increase in estradiol level in the male rat hypothalamus at birth].

In the newborn male Rat, hypothalamic estradiol levels suddenly increase during the first hour following birth and decrease between 2 and 24 hr. This surge is absent in the female or in the male gonadectomized at 0 hr. Serum estradiol levels decrease between fetal stage 21 days 8 hr.

[Female sex behavior of male rats castrated at birth and given female sex hormones: effects of hour of castration].

Female sexual behaviour of male Rats castrated at birth and treated with female sexual hormones: effects of hour of castration. Male Rats castrated at 0 hr and injected with aestradiol and progesterone as adults display a typical female sexual behaviour. The probability of them showing the lordotic reflex is significantly lower when castration is performed at 6 or 12 hrs.

[Increase in endogenous testosterone in the hypothalamus of the male rat at birth].

The evolution of serum and hypothalamic concentrations of endogenous testosterone was measured in newborn male and female Rats, from 0 up to 6 hrs. after birth. The serum testosterone surge observed in males between 0 and 2 hrs.

Changes in testicular weight and serum gonadotropin and testosterone levels before, during, and after birth in the perinatal rat.

Changes in serum and pituitary LH and FSH concentrations have been measured in the newborn male rat before, during, and up to 24 h after birth. A sudden and transient increase of serum and pituitary gonadotropins is observed at birth, which is followed by a rapid increase of absolute and relative testicular weights between 2--12 h (P less than 0.0001) and by a transient increase of serum testosterone between 0 h in utero (810 +/- 26 pg/ml) and 2 h (2820 +/- 318 pg/ml; P less than 0.

[Comparison between serum LH and FSH levels in male and female rats during the perinatal period].

In the newborn female Rat, no transient LH and FSH serum surges were observed between 0 and 2 hrs., as compared with the newborn male. In the newborn female, a progressive increase in serum gonadotropins was observed between 2 and 6 hrs.

Pituitary adrenocortical response to stress during the first day of post-natal life in the rat.

During the first hours of post-natal life, the newborn rat does not respond to ether stress by a rapid increase of ACTH secretion. Ether inhalation by 5- and 12-hour-old animals slightly but significantly increases plasma and adrenal corticosterone levels, but only 30 min after the onset of stress. At 1 day of age, adrenal response is established.

[Increase in serum testosterone in newborn rats].

The changes in serum testosterone and dihydrotestosterone concentrations have been measured in the newborn Rat, before, during and up to 6 hrs after birth. A sudden and transient increase of serum testosterone has been found between 0 and 2 hrs. At 4 hrs, the value returns to that found in the foetus at the end of gestation.

[Stimulation of the secretion of LH and FSH and increase in testicular weight at birth in rats].

The evolutions of serum LH and FSH concentrations and of testicular weight have been measured in the newborn Rat before, during and up to 24 hrs. after birth. A sudden and transient increase of LH and FSH is observed at birth.