Androgen Level in the Sheep Fetus During Gestation

Pomerantz, David K.; Nalbandov, A. V.

doi:10.3181/00379727-149-38818

Cited by 46 publications

(39 citation statements)

References 1 publication

(1 reference statement)

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“…Fetal males have higher circulating concentrations of testosterone at G65 to G70 than do fetal females (Pomerantz and Nalbandov, 1975). Concentrations of testosterone in males decline between G70 and G90, and are not significantly greater than in female until late in gestation and during postnatal life (Pomerantz and Nalbandov, 1975;Roselli et al, 2006). Thus, it appears, in sheep, that testicular androgen is available to sexually differentiate males as early as the first trimester of pregnancy.…”

Section: Sexual Differentiation Of Reproductive Behavior In Sheepmentioning

confidence: 81%

“…Gonadal differentiation occurs between gestational day 25 (G25) and G35 and the external genitalia begin to differentiate on G45 (Clarke et al, 1976a). The fetal testes synthesize elevated levels of testosterone starting around G35 (Attal, 1969;Pomerantz and Nalbandov, 1975) and the testicular content of testosterone continues to increase from this time until birth. Fetal males have higher circulating concentrations of testosterone at G65 to G70 than do fetal females (Pomerantz and Nalbandov, 1975).…”

Section: Sexual Differentiation Of Reproductive Behavior In Sheepmentioning

confidence: 99%

“…The fetal testes synthesize elevated levels of testosterone starting around G35 (Attal, 1969;Pomerantz and Nalbandov, 1975) and the testicular content of testosterone continues to increase from this time until birth. Fetal males have higher circulating concentrations of testosterone at G65 to G70 than do fetal females (Pomerantz and Nalbandov, 1975). Concentrations of testosterone in males decline between G70 and G90, and are not significantly greater than in female until late in gestation and during postnatal life (Pomerantz and Nalbandov, 1975;Roselli et al, 2006).…”

Section: Sexual Differentiation Of Reproductive Behavior In Sheepmentioning

confidence: 99%

See 2 more Smart Citations

The ram as a model for behavioral neuroendocrinology

Perkins

Roselli

2007

Hormones and Behavior

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The sheep offers a unique model to study male sexual behavior and sexual partner preference. Rams are seasonal breeders and show the greatest libido during short days coincident with the resumption of ovarian cyclicity in the ewe. Threshold concentrations of testosterone are required for the acquisition and display of adult sexual behavior. In addition, estrogens produced from circulating testosterone by cytochrome P450 aromatase in the preoptic area are critical for the maintenance of sexual behaviors in rams. Sex differences in adult reproductive behaviors and hormone responsiveness are the result of permanent organizational effects exerted by testosterone and its metabolites on brain development. Early exposure to ewes enhances ram sexual performance, but cannot prevent some rams from exhibiting male-oriented sexual partner preferences. Neurochemical and neuroanatomical studies suggest that male-oriented ram behavior may be a consequence of individual variations in brain sexual differentiation.

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Section: Sexual Differentiation Of Reproductive Behavior In Sheepmentioning

confidence: 81%

Section: Sexual Differentiation Of Reproductive Behavior In Sheepmentioning

confidence: 99%

Section: Sexual Differentiation Of Reproductive Behavior In Sheepmentioning

confidence: 99%

See 1 more Smart Citation

The ram as a model for behavioral neuroendocrinology

Perkins

Roselli

2007

Hormones and Behavior

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“…Other gonadal factors such as estradiol [11,12] and testosterone [13,14] have been reported to have a negative effect on the synthesis and/or release of gonado tropins by the sheep fetal pituitary. The aim of the present study was to delineate further the influence of the fetal gonads on the variability of the different gonadotrope cell populations in the fetal sheep pituitary in late gestation.…”

Section: Introductionmentioning

confidence: 99%

Castration Effects on the Gonadotrope Cell Populations of the Fetal Sheep Pituitary in Late Gestation

Messaoud-Toumi

Taragnat²,

Durand³

1993

Neuroendocrinology

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This immunocytochemical study focused on the role of fetal gonads in the regulation of gonadotrope cell populations in the fetal sheep pituitary in late gestation. Male and female sheep fetuses were castrated at 112–115 days of gestation and maintained in utero until 139–140 days gestation when their pituitaries were collected. Intact twins served as controls. The percentages of the different gonadotrope cell populations (i.e. the number of gonadotrope cells vs. the total number of the pituitary cell counted) and the mean cell area were determined. Castration did not affect the LH cell percentage in either sex but resulted in a decrease in the individual LH cell areas of both males and females (46.4 ± 0.6 vs. 51.6 ± 0.4 µm², p < 0.01, in males and 43.0 ± 0.5 vs. 50.0 ± 1.1 µm², p < 0.01 in females). By contrast, the FSH cell percentage was increased about twofold in castrated fetuses when compared to intact animals (3.5 ± 0.3 vs. 1.6 ± 0.3, p < 0.01, in males and 2.3 ± 0.1 vs. 1.1 ± 0.3, p < 0.02, in females). Moreover, castrated males had higher FSH cell percentages than castrated females (p < 0.02). The individual FSH cell area was smaller in castrated fetuses than that in controls (44.7 ± 1.4 vs. 51.2 ± 1.4 µm², p < 0.05, in males and 42.1 ± 0.8 vs. 51.6 ± 0.8 µm², p < 0.01, in females). The LH-FSH cell percentage was slightly higher in castrated males than in control males (0.9 ± 0.01 vs. 0.8 ± 0.06, p < 0.05) and twofold lower in castrated females than in intact females (0.5 ± 0.05 vs. 0.9 ± 0.03, p < 0.01). These results suggest that the fetal ovary as well as the fetal testis are involved in the variations of the percentages of the different gonadotrope cell populations of the fetal sheep pituitary previously observed in late gestation.

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“…Circulating LH levels in the fetal sheep are low at the end of gestation [Foster et al, 1972a;Foster 1974], but conflicting data con-1 Fellow of the 'Conseil de Recherches en Santé du Québec '. ceming the evolution of plasma androgen levels have been published [Colas and Curet, 1978;Pomerantz and Nalbandov, 1975], Re cently we have demonstrated that the hypothalamic-pituitary-adrenal axis is quite ac tive at the end of gestation, while the hypo thalamic-pituitary-gonadal axis is relatively quiescent [Savoie et al, 1981], Nevertheless, the administration of LHRH to the ovine fetus does induce pituitary gonadotropin re lease from the second trimester of gestation to term [Foster et al, 1972b;Mueller et al, 1981], In addition, luteinizing hormone re leasing hormone (LHRH) [Lee et al, 1976] and human chorionic gonadotropins (hCG) can increase T secretion in the newborn sheep , The present study was undertaken to determine whether lack of responsiveness of the testis or the absence of hypothalamic-pituitary stimuli are responsi ble for the low levels of circulating T found in the fetal sheep.…”

Section: Introductionmentioning

confidence: 99%

Testicular Responsiveness to hCG of the Ovine Fetus in the Last Third of Gestation

et al. 1983

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The in vivo and in vitro testicular responsiveness to hCG of hemicastrated lamb fetuses 95-99, 110-118 and 130-141 days of gestational age was studied. Basal plasma testosterone (T) levels were similar at all ages ( < 0.25 ng/ml), while the mean testicular concentrations of dehydroepiandrosterone sulfate (DHA-S), 17α-hydroxyprogesterone (17-OHP) and T were higher in 95- to 99-day-fold fetuses. Plasma T levels and the concentration of T, DHA-S, 17-OHP, androstenedione (A) and cyclic adenosine 3’5’-monophosphate (cAMP) were increased by hCG in the hemicastrated animal at all ages. cAMP and T production by enriched preparations of dispersed interstitial cells from control testes was increased by hCG in all groups. In fetuses pretreated with hCG in vivo the addition of hCG in vitro failed to modify cAMP and T production. 100 µg of LHRH to a 130-day-old fetus increased plasma LH and T levels. From these experiments, it is suggested that the low plasma LH and T levels found throughout the last trimester of fetal life reflect a relative lack of endogenous LHRH synthesis and/or release, rather than reduced testicular steroidogenic capacity.

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Androgen Level in the Sheep Fetus During Gestation

Cited by 46 publications

References 1 publication

The ram as a model for behavioral neuroendocrinology

The ram as a model for behavioral neuroendocrinology

Castration Effects on the Gonadotrope Cell Populations of the Fetal Sheep Pituitary in Late Gestation

Testicular Responsiveness to hCG of the Ovine Fetus in the Last Third of Gestation

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