doublesex (dsx) is unusual among the known sex-determination genes of Drosophila melanogaster in that functional homologs are found in distantly related species. In flies, dsx occupies a position near the bottom of the sex determination hierarchy. It is expressed in male- and female-specific forms and these proteins function as sex-specific transcription factors. In the studies reported here, w...

Sex differences in brain function underlie robust differences between males and females in both normal and disease states. Although alternative mechanisms exist, sexual differentiation of the male mammalian brain is initiated predominantly by testosterone secreted by the testes during the perinatal period. Despite considerable advances in understanding how testosterone and its metabolite estrad...

OBJECTIVE The aim of this study was to assess whether the joint effects of three androgen receptor antagonists (vinclozolin, flutamide, procymidone) on male sexual differentiation after in utero and postnatal exposures can be predicted based on dose-response data of the individual chemicals. METHODS Test chemicals and mixtures were administered by gavage to time-mated nulliparous, young adult...

Debate and controversy exists concerning the potential for the herbicide atrazine to cause gonadal malformations in developing Xenopus laevis. Following review of the existing literature the U.S. Environmental Protection Agency required a rigorous investigation conducted under standardized procedures. X. laevis tadpoles were exposed to atrazine at concentrations of 0.01, 0.1, 1, 25, or 100 micr...

Understanding environmental influences on sex ratios is important for the study of the evolution of sex-determining mechanisms and for evaluating the effects of global warming and chemical pollution. Fishes exhibit sexual plasticity, but the underlying mechanisms of environmental effects on their reproduction are unclear even in the well-established teleost research model, the zebrafish. Here w...

Genital malformations constitute the most common birth defects encountered in man and domestic animals. They occur more frequently in genetic males since the participation of many genes is required for sex differentiation to proceed in the male direction. The emerging insight, through the identification of genes involved in the sex differentiation cascade, is that over 85 percent of sex anomali...

Male and female social roles are predicated on the fact that male and female reproductive functions are separated in different individuals. This paper asks why. That is, why is gonochorism, not hermaphroditism, the rule among vertebrates. We argue that (simultaneous) hermaphroditism may be unstable in the face of heterogeneity. Building on the Bateman principle – access to eggs, not sperm, limi...

Sexual differentiation is essential for the transmission of Plasmodium to mosquitoes and therefore, for the spread of malaria. The molecular mechanisms underlying sexual differentiation are poorly understood but may be elucidated by a detailed study of the regulation of expression of sexual stage specific genes. In the present work we describe the differential expression of the gene encoding th...

In the literature of the Roman Era, a case of macrosomia and genital ambiguity in a newborn is described. Textual evidence concerning this case of androgynism and its symbolism is provided in the present study. Medical interpretation of such cases covers the entire spectrum of differential diagnosis of macrosomia concurrent with genital ambiguity. Female pseudohermaphroditism may be excluded fr...

OBJECTIVE These three studies examined the hypothesis that prenatal exposure to sex hormones influences twins' risk for eating disorders based on co-twin sex, such that individuals with a female co-twin would be more likely than individuals with a male co-twin to meet diagnostic criteria for an eating disorder. METHODS Male and female twins from the United States (N=2607), Norway (N=2796) and...