1. Cell Culture Approach to the Study of Granulosa Cells In 1672, Regnier de Graaf first described the differentiation of ovarian follicles into the corpus luteum. He stated that “age and coitus cause very great changes in eggs (follicles). In young animals, they are very small and in more developed ones they are larger. After coitus, they (the follicles) so alter as to resemble the globules (the corpora lutea) …, being one or more according as the animal will produce one or more fetuses.” (1) Follicles as the functional unit: Ovarian follicles have since been shown to be the basic functional unit of the ovary and consist of an outer layer of theca interna cells which encircle inner layers of granulosa cells. Granulosa cells, in turn, surround the innermost oocyte-cumulus cell complex. The maturation of ovarian follicles and their transformation into corpora lutea is regulated by a specific set of hormones and has been a major research area for ovarian physiologists for several hundred years.

The objectives of this study were 1) to compare temperament assessments, using multiple techniques and over repeated observations, to gauge temperament over the long-term and 2) to evaluate the relationship of the temperament appraisals with serum concentrations of cortisol (CS). Measures of temperament were gathered over 3 repeated observations (60-d interval) of yearling, fall-born Brahman bulls (initial BW = 320 ± 4 kg; n = 66). Temperament assessments included exit velocity (EV), which was the rate at which the bulls exited the squeeze chute and traversed a fixed distance (1.83 m); pen scores (PEN; 1 = quiet to 5 = excited), ascertained from animal behavior while penned in small groups (n = 5); and chute scores (CHUTE; 1 = quiet to 5 = excited), determined from behavioral responses to restraint on the weigh scale. Temperament measures obtained during the initial data collection (d 0) were all positively correlated (r ≥0.35, P < 0.005) with one another. Additionally, PEN (r = 0.29, P < 0.05) and EV (r = 0.26, P < 0.05) were positively correlated with CS, whereas CHUTE was not (r = 0.09, P = 0.46). All serial EV measures were positively correlated (r > 0.31, P < 0.02). All PEN were positively correlated (r > 0.31, P < 0.01), whereas serial measures of CHUTE were not (P > 0.3). Exit velocity was positively correlated with CS within d 0 (r = 0.26, P = 0.04) and 120 (r = 0.44, P < 0.01). The EV data obtained at d 0 were transformed into a discrete variable, EV ranking (EV RANK; 1 to 3 scale), in which 1 equated to 1 SD above the mean. Mean EV (P < 0.01) decreased from d 0 (2.82 ± 0.07 m/sec) to 120 (2.11 ± 0.10 m/sec). Time also influenced (P < 0.01) CS; mean CS decreased between d 0 (14.6 ± 0.7 ng/mL) and 120 (11.1 ± 0.8 ng/mL). Measures of EV can be a valuable tool for the assessment of cattle temperament and a possible predictor of temperament and stress responsiveness to future animal handling events. Copyright © 2006. . Copyright 2006 Journal of Animal Science

Exposure to endocrine disrupting compounds (EDCs), such as bisphenol A (BPA), may cause adverse health effects in wildlife and humans, but controversy remains as to what traits are most sensitive to EDCs and might serve as barometers of exposure. Expression of sexually selected traits that have evolved through intrasexual competition for mates and intersexual choice of mating partner are more dependent on developmental and physical condition of an animal than naturally selected traits and thus might be particularly vulnerable to disruption by developmental exposure to EDCs. We have used the deer mouse ( Peromyscus maniculatus ) as a model to test this hypothesis. Adult male–male competition for mates in this species is supported by enhanced spatial navigational and exploratory abilities, which enable males to search for prospective, widely dispersed females. Male deer mice exposed to BPA or ethinyl estradiol (EE) through maternal diet showed no changes in external phenotype, sensory development, or adult circulating concentrations of testosterone and corticosterone, but spatial learning abilities and exploratory behaviors were severely compromised compared with control males. Because these traits are not sexually selected in females, BPA exposure predictably had no effect, although EE-exposed females demonstrated enhanced spatial navigational abilities. Both BPA-exposed and control females preferred control males to BPA-exposed males. Our demonstration that developmental exposure to BPA compromises cognitive abilities and behaviors essential for males to reproduce successfully has broad implications for other species, including our own. Thus, sexually selected traits might provide useful biomarkers to assess risk of environmental contamination in animal and human populations.

Epidermal growth factor (EGF), but not fibroblast growth factor, inhibits the gonadotropin stimulation of estrogen and testosterone production by primary cultures of ovarian granulosa and testicular Leydig cells, respectively. EGF also inhibits gonadal steroidogenesis induced by cholera toxin and (Bu)₂cAMP, and the inhibitory effect of EGF is not associated with cell proliferation. EGF may play an important endocrine role in the regulation of steroidogenic functions of gonadal cells.

The mechanism whereby glucocorticoids directly inhibit gonadotropin-stimulated testosterone production was studied by using primary cultures of testicular cells from adult hypophysectomized rats. Testicular cells were maintained in serum-free media with hormone treatments administered on Day 8 and media collected 48 h later for steroid and cAMP measurement. Highly purified human chorionic gonadotropin (hCG) increased testosterone production relative to controls. Concomitant administration of either natural (cortisone greater than deoxycorticosterone = aldosterone) or synthetic (dexamethasone greater than or equal to prednisolone) corticosteroids inhibited hCG-stimulated testosterone production in a dose-dependent manner. Dexamethasone at 10(-7) M decreased testosterone production by approximately 50-60% and this inhibitory effect was reversible upon removal of the glucocorticoid. In the presence or absence of a phosphodiesterase inhibitor, dexamethasone decreased hCG-stimulated cAMP production by approximately 60%. Dexamethasone also decreased testosterone production induced by cholera toxin and (Bu)2 cAMP by 43 and 63%, respectively. The dexamethasone suppression of testosterone production was accompanied by marked decreases in androstenedione (80% decrease) and 17 alpha-hydroxyprogesterone (57%) production, with a lesser effect on progesterone production (28% decrease) and no effect on pregnenolone production. Exogenous progesterone and 17 alpha-hydroxyprogesterone augmented hCG-stimulated testosterone production. Dexamethasone reduced the conversion of exogenous progesterone to testosterone by 33% but did not affect the conversion of 17 alpha-hydroxyprogesterone to androstenedione and testosterone, suggesting a specific inhibition of 17 alpha-hydroxylase. These results suggest that glucocorticoids directly suppress Leydig cell steroidogenesis by decreasing gonadotropin stimulation of cAMP production and the activity of 17 alpha-hydroxylase.