Altricial and precocial species follow different developmental trajectories possibly reflecting different reproductive strategies. This chapter describes evidence that this distinction may have heuristic value in understanding the nature of steroidal influences on masculinization and defeminization. Across both types of mammals, defeminization was found to utilize estrogenic metabolites of andr...

Masculinization of a female foetus by androgenic hormones produced by an arrhenoblastoma in the mother during pregnancy was described by Brentnall (1945). Masculinization and pseudohermaphroditism caused by the administration of 17-methyltestosterone to the mother during pregnancy was reported by Hayles and Nolan (1957), Grunwaldt and Bates (1957) and others. Since Wilkins, Jones, Holman and St...

The spinal nucleus of the bulbocavernosus (SNB) and its target muscles are reduced or absent in normal female rats (Breedlove, S. M., and A. P. Arnold (1980) Science 210: 564-566). We now report that prenatal treatment of females with testosterone propionate (TP) significantly increases the number of SNB neurons found in adulthood. Dihydrotesterone propionate (DHTP) treatment just after but not...

Sociosexual orientation reflects individual differences in openness to short-term sexual relationships. We predicted that women with less restricted sociosexuality would be differentially attracted to highly masculinized male faces and bodies. In 2 studies, we investigated preference for male masculinization as a function of female sociosexuality. In Study 1, 40 female university students rated...

Brain sexual differentiation in rodents results from the perinatal testicular androgen surge. In the preoptic area (POA), estradiol aromatized from testosterone upregulates the production of the proinflammatory molecule, prostaglandin E(2) (PGE(2)) to produce sex-specific brain development. PGE(2) produces a two-fold greater density of dendritic spines in males than in females and masculinizes ...

Studies have shown that female mosquitofish living downstream of a paper mill located on the Fenholloway River, Florida, have masculinized secondary sex characteristics, including altered anal fin development and reproductive behavior. Masculinization can be caused by exposure to androgens in the water or from an alteration in aromatase activity in the fish. We hypothesized that aromatase activ...

Epigenetic regulation of the nuclear estrogen and androgen receptors, ER and AR, constitutes the molecular basis for the long-lasting effects of sex steroids on gene expression in cells. The effects prevail at hundreds of gene loci in the proximity of estrogen- and androgen-responsive elements and many more such loci through intra- and even inter-chromosomal level regulation. Such a memory syst...

Sexually dimorphic behavior in nonhuman primates results from behavioral predispositions organized by prenatal androgens. The rhesus monkey has been the primary primate model for understanding the hormonal organization of sexually dimorphic behavior. Historically, female fetuses have received high prenatal androgen doses to investigate the masculinizing and defeminizing effects of androgens. Su...

Otoacoustic emissions (OAEs) differ between the sexes in humans, rhesus and marmoset monkeys, and sheep. OAEs also are different in a number of special populations of humans. Those basic findings are reviewed and discussed in the context of possible prenatal-androgen effects on the auditory system. A parsimonious explanation for several outcomes is that prenatal exposure to high levels of andro...

We have evaluated whether the arachidonic acid cascade may be involved in the folding and fusion of the penis and scrotum in masculine differentiation, a possibility raised by recent observations of the involvement of the arachidonic acid cascade in the analogous embryonic processes of elevation and fusion of the palatal shelves and of folding and fusion of the neural tube. To test this hypothe...