|Effects of perinatal bisphenol A exposure during early development on radial arm maze behavior in adult male and female rats.|
Sadowski, RN; Park, P; Neese, SL; Ferguson, DC; Schantz, SL; Juraska, JM
Neurotoxicology and teratology
Previous work has shown that exposure to bisphenol A (BPA) can affect anxiety behavior. However, no studies have examined whether administration of this endocrine disruptor during the perinatal period has the potential to induce alterations in cognitive behavior in both adult males and females as assessed in an appetitive task. The goal of the current study was to determine whether exposure to different doses of BPA during early development alters performance on the 17-arm radial maze in adulthood in Long-Evans rats. Oral administration of corn oil (vehicle), 4 μg/kg, 40 μg/kg, or 400 μg/kg BPA to the dams occurred daily throughout pregnancy, and the pups received direct oral administration of BPA between postnatal days 1-9. Blood was collected from offspring at weaning age to determine levels of several hormones (thyroxine, thyroid stimulating hormone, follicle stimulating hormone, luteinizing hormone). One male and one female from each litter were evaluated on the 17-arm radial maze, a working/reference memory task, in adulthood. Results indicated that after exposure to BPA at both 4 and 400 μg/kg/day, rats of both sexes had decreased levels of FSH at weaning. There were no significant effects of BPA on performance on the radial arm maze in males or females. In conclusion, exposure to BPA during early development had modest effects on circulating hormones but did not affect performance on a spatial learning and memory task.
|Dynamic changes in fetal Leydig cell populations influence adult Leydig cell populations in mice.|
Barsoum, IB; Kaur, J; Ge, RS; Cooke, PS; Yao, HH
FASEB journal : official publication of the Federation of American Societies for Experimental Biology
Testes contain two distinct Leydig cell populations during development: fetal and adult Leydig cells (FLCs and ALCs, respectively). ALCs are not derived from FLCs, and it is unknown whether these two populations share common progenitors. We discovered that hedgehog (Hh) signaling is responsible for transforming steroidogenic factor 1-positive (SF1(+)) progenitors into FLCs. However, not all SF1(+) progenitors become FLCs, and some remain undifferentiated through fetal development. We therefore hypothesized that if FLCs and ALCs share SF1(+) progenitors, increased Hh pathway activation in SF1(+) progenitor cells could change the dynamics and distribution of SF1(+) progenitors, FLCs, and ALCs. Using a genetic model involving constitutive activation of Hh pathway in SF1(+) cells, we observed reduced numbers of SF1(+) progenitor cells and increased FLCs. Conversely, increased Hh activation led to decreased ALC populations prepubertally, while adult ALC numbers were comparable to control testes. Hence, reduction in SF1(+) progenitors temporarily affects ALC numbers, suggesting that SF1(+) progenitors in fetal testes are a potential source of both FLCs and ALCs. Besides transient ALC defects, adult animals with Hh activation in SF1(+) progenitors had reduced testicular weight, oligospermia, and decreased sperm mobility. These defects highlight the importance of properly regulated Hh signaling in Leydig cell development and testicular functions.
|Global but not gonadotrope-specific disruption of Bmal1 abolishes the luteinizing hormone surge without affecting ovulation.|
Chu, A; Zhu, L; Blum, ID; Mai, O; Leliavski, A; Fahrenkrug, J; Oster, H; Boehm, U; Storch, KF
Although there is evidence for a circadian regulation of the preovulatory LH surge, the contributions of individual tissue clocks to this process remain unclear. We studied female mice deficient in the Bmal1 gene (Bmal1(-/-)), which is essential for circadian clock function, and found that they lack the proestrous LH surge. However, spontaneous ovulation on the day of estrus was unaffected in these animals. Bmal1(-/-) females were also deficient in the proestrous FSH surge, which, like the LH surge, is GnRH-dependent. In the absence of circadian or external timing cues, Bmal1(-/-) females continued to cycle in constant darkness albeit with increased cycle length and time spent in estrus. Because pituitary gonadotropes are the source of circulating LH and FSH, we assessed hypophyseal circadian clock function and found that female pituitaries rhythmically express clock components throughout all cycle stages. To determine the role of the gonadotrope clock in the preovulatory LH and FSH surge process, we generated mice that specifically lack BMAL1 in gonadotropes (GBmal1KO). GBmal1KO females exhibited a modest elevation in both proestrous and baseline LH levels across all estrous stages. BMAL1 elimination from gonadotropes also led to increased variability in estrous cycle length, yet GBmal1KO animals were otherwise reproductively normal. Together our data suggest that the intrinsic clock in gonadotropes is dispensable for LH surge regulation but contributes to estrous cycle robustness. Thus, clocks in the suprachiasmatic nucleus or elsewhere must be involved in the generation of the LH surge, which, surprisingly, is not required for spontaneous ovulation.