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Glandular physiology --- Gynaecology. Obstetrics --- Endocrinology, Experimental. --- Fetus --- Sheep --- Laboratory animals. --- Physiology. --- Fetuses

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Following either a) castration or b) both castration and implantation with capsules releasing a constant, physiological dose of testosterone, adult male Mongolian gerbils that had matured in intrauterine positions between two male fetuses still scent marked with greater frequency than did male gerbils that had matured in intrauterine positions between two female fetuses. We also found significant positive correlations between the relative frequency of scent marking exhibited by individual male gerbils when intact, after castration and after both castration and implantation with capsules releasing testosterone. Each of these findings is consistent with the view that differential exposure to testosterone, as a consequence of fetal intrauterine position, has lasting effects on the organization of scent-marking by male gerbils

Adult. --- Castration. --- Exposure. --- Female. --- Fetuses. --- Frequency. --- Gerbil. --- Gerbils. --- Implantation. --- Intrauterine position. --- Intrauterine positions. --- Male mongolian gerbils. --- Male. --- Marking. --- Mongolian gerbil. --- Mongolian gerbils. --- Mongolian-gerbil. --- Organization. --- Physiological. --- Position. --- Positions. --- Scent marking. --- Scent-marking. --- Scent. --- Territorial marking. --- Testosterone. --- Time. --- Uterine position.

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Two experiments were undertaken to investigate the cause of the observed tendency of Mongolian gerbil dams to gestate more male than female fetuses in their right uterine hems and more female than male fetuses in their left uterine hems. It was found in Expt I that female gerbils that had both ovaries removed and portions of their right ovary placed in both ovarian capsules gestated significantly more male fetuses than did females that had both ovaries removed and portions of their left ovaries placed in both ovarian capsules. Expt 2 showed that female gerbils that had both their ovaries removed and then returned to their original locations gestated more males in their right uterine hems than in their left, while females that had the positions of their ovaries exchanged gestated more male fetuses in their left uterine hems than in their right. The data were consistent with the hypothesis that lateral asymmetries in gerbil ovaries rather than in gerbil uterine hems cause partial uterine segregation of gerbil fetuses by sex

Asymmetries. --- Asymmetry. --- Experiment. --- Experiments. --- Female. --- Females. --- Fetuses. --- Gerbil. --- Gerbils. --- Horns. --- Implantation. --- Male. --- Males. --- Meriones unguiculatus. --- Meriones-unguiculatus. --- Mongolian gerbil. --- Mongolian gerbils. --- Mongolian-gerbil. --- Position. --- Positions. --- Sex ratio. --- Sex ratios. --- Sex. --- Sexes. --- Time. --- Uterus.

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A series of experiments was undertaken to both discover and explore the causes of sexually dimorphic phenotypic asymmetries in infant and adult Mongolian gerbils. We found that (1) the order in which the eyes of individual gerbil pups opened varied with their gender; right eves of female pups opened before left eyes, while left eyes of male pups opened before right eves, and (2) the paw that adult gerbils held in the air while maintaining a species-typical tripedal stance varied with gender: female gerbils held their right paws in the air significantly more often than did male gerbils. Both order of eye opening and laterality of paw use while in a tripedal stance varied significantly as a function of the intrauterine position which subjects had occupied as fetuses. These data implicate exposure to testosterone as a mediator of the development of asymmetries exhibited by Mongolian gerbils

Adult. --- Asymmetries. --- Asymmetry. --- Bias. --- Development. --- Experiment. --- Experiments. --- Exposure. --- Eye. --- Female. --- Fetuses. --- Function. --- Gender. --- Gerbil. --- Gerbils. --- Infant. --- Intrauterine position. --- Male. --- Mongolian gerbil. --- Mongolian gerbils. --- Mongolian-gerbil. --- Paw preference. --- Position. --- Preference. --- Pups. --- Rat. --- Testosterone. --- Time.

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Sex steroid concentrations in the plasma of 24-day pregnant Mongolian gerbils (Meriones unguiculatus) and their male and female fetuses were measured using radioimmunoassays. It was found that, on Day 24 of gestation: (a) androgen levels were higher in those male fetuses developing adjacent to no female fetuses than in those male fetuses developing between two female fetuses and (b) androgen levels were higher in those female fetuses developing between two male fetuses than in those female fetuses with no immediate, male neighbours. Further, plasma taken from 24-day pregnant dams that had exhibited vaginal opening at a relatively early age had significantly lower androgen levels and significantly higher estradiol levels than did plasma taken from 24-day pregnant dams that had exhibited relatively late vaginal opening. The data provide direct evidence of hormonal mediation of previously described differences both in the morphology and reproductive biology of male and female adult gerbils as a function both of their fetal intrauterine locations relative to members of the other sex and of the age at vaginal introitus of their respective dams

Adult female mice. --- Adult. --- Age. --- Androgen. --- Behavior. --- Biology. --- Contiguity. --- Estradiol. --- Female. --- Fetal sex steroids. --- Fetuses. --- Function. --- Gerbil. --- Gerbils. --- Gestation. --- Hormonal. --- Intrauterine position. --- Level. --- Life. --- Male. --- Maternal sex steroids. --- Meriones unguiculatus. --- Meriones-unguiculatus. --- Mongolian gerbil. --- Mongolian gerbils. --- Mongolian-gerbil. --- Morphology. --- Neonatal androgen. --- Plasma. --- Proximity. --- Radioimmunoassay. --- Rats. --- Sex ratio. --- Sex. --- Sexes. --- Sexual maturation. --- Steroid-hormones. --- Steroid. --- Time. --- Unguiculatus. --- Uterine position.