Inhibition of masculine differentiation in male offspring of rabbits actively immunised against testosterone before pregnancy

Birth order, birth interval, and deviant sexual preferences among sex offenders

We investigated whether birth order and birth interval are associated with phallometric responding among 168 sex offenders. Based on the immunoreactivity hypothesis, we predicted that a larger number of older brothers and a shorter birth interval between the offenders and their next older brothers would be associated with more deviant responding. Results showed that a larger number of older brothers (but not older sisters, younger brothers, or younger sisters) was associated with more deviant responding on the Most Deviant Index, a general measure of sexual deviance. A larger number of older brothers was associated with arousal to nonsexual violence against women and children, but contrary to expectation, the same association was also found for the number of younger brothers. A short birth interval with the next older brother was associated with greater relative arousal to nonsexual violence, but the correlation with the Most Deviant Index did not reach statistical significance. Overall, results were consistent with the main predictions, but the effects of birth order and birth interval were mostly restricted to arousal to nonsexual violence. Birth order and birth interval were not associated with pedophilic interests or gender preferences.

Role of 5 alpha-reductase in health and disease

The mechanism of androgen action varies in different tissues, but in the majority of androgen target tissues either testosterone or 5 alpha-dihydrotestosterone (DHT) binds to a specific androgen receptor to form a complex that can regulate gene expression. Testosterone is metabolized to DHT by the enzyme 5 alpha-reductase. The autosomal recessive genetic disorder of 5 alpha-reductase deficiency has clearly shown that the requirement for DHT formation varies with different tissues. In this syndrome genetic males contain normal male internal structures including testes, but exhibit ambiguous or female external genitalia at birth; at puberty they undergo partial virilization which includes development of a male gender identity even if brought up as females. Their development suggests that testosterone itself is able to stimulate psychosexual behaviour, development of the embryonic wolffian duct, muscle development, voice deepening, spermatogenesis, and axillary and pubic hair growth; DHT seems to be essential for prostate development and growth, the development of the external genitalia and male patterns of facial and body hair growth or male-pattern baldness. How different hormones operate to regulate genes via the same receptor is currently unknown, but appears to involve cell-specific factors. The 5-alpha-reductase enzyme has proved difficult to isolate biochemically, but recently at least two human isoenzymes have been identified using molecular biological methods. All the various 5 alpha-reductase-deficient kindreds have been shown to have mutations in 5 alpha-reductase 2, the predominant form in the prostate. The biological role of 5 alpha-reductase 1 has not yet been ascertained, but at present it cannot be ruled out that some of the actions ascribed to testosterone are indeed in cells producing DHT via this enzyme. The activity of 5 alpha-reductase is also implicated in benign prostatic hypertrophy, hirsutism and possibly male-pattern baldness; recent evidence discounts the role of 5 alpha reductase 2 in sebaceous glands and acne. Specific inhibitors of both enzymes are now available and finasteride, a 5 alpha-reductase 2 inhibitor, has been used successfully in clinical trials of benign prostatic hypertrophy. Knowledge of 5 alpha-reductase is expanding dramatically at the moment with the application of molecular biological methods. The advent of antibodies to the isoenzymes should herald further understanding of their biological and clinical roles.

Sexual differentiation of copulatory behaviour in the male chick requires gonadal steroids

1. Embryonic injections of 0.3 mg/egg of tamoxifen (TAM), 0.2 mg/egg CI-628 (both antioestrogens), 0.5 mg/egg (ATD (aromatisation inhibitor), or antibodies to oestradiol (E), all suppressed male copulatory activity (MCA) in young male chicks. 2. Embryonic injections with either flutamide (F, androgen antagonist) or high dose of antibodies to testosterone (T) only slightly suppressed MCA. 3. TAM had no effect on embryonic plasma LH levels, 24 and 48 h after injection. 4. It seems that at the embryonic stage oestradiol is required for the normal differentiation of MCA.

Developmental and hormonal regulation of cholesterol side chain cleavage cytochrome P-450 in the fetal rabbit testis

Male sexual differentiation is dependent upon the induction of testosterone synthesis by the fetal testis at a critical phase of development. In the rabbit, testosterone synthesis by the fetal testis is initiated after 17.5-18 days of gestation, reaches peak values by day 21 and subsequently declines. In the present study, we analyzed the specific activity and concentration of immunoreactive cholesterol side chain cleavage cytochrome P-450 (cytochrome P-450scc) in the fetal rabbit testis during development to assess its possible role as a key regulatory enzyme in fetal testicular steroidogenesis. The effects of human chorionic gonadotropin (hCG) and dibutyryl cyclic AMP on the specific activity and synthesis of cytochrome P-450scc in fetal rabbit testes in vitro also were evaluated. We observed that changes in cholesterol side chain cleavage activity paralleled the induction of testosterone synthesis; the specific activity of this enzyme which was approximately equal to 0.25 pmol min-1 mg-1 protein in testes from 19-day fetal rabbits was increased approximately equal to 10-fold in testes of 21-day fetuses and thereafter declined dramatically. Immunoreactive cytochrome P-450scc, which was first detectable in gonads of 19-day fetal rabbits, was induced markedly in 21-day fetal testes, reached maximum levels on day 24 and declined slightly thereafter. Incubation of testes from 19- and 21-day gestational age fetal rabbits with hCG or dibutyryl cyclic AMP for 24 h resulted in an induction of testosterone synthesis, cholesterol side chain cleavage activity and synthesis of cytochrome P-450scc. These findings are suggestive that androgen synthesis by the fetal Leydig cell is mediated by an induction of the synthesis and specific activity of cytochrome P-450scc. In addition, these data support the hypothesis that the developmental changes in the synthesis of cytochrome P-450scc are regulated by fetal gonadotropin and are mediated by cyclic AMP.

Persistence of müllerian ducts in male rabbits passively immunized against bovine anti-müllerian hormone during fetal life

A female rabbit was immunized against purified bovine AMH and mated. Booster injections were given at Day 8 of pregnancy to ensure a high titer of anti-AMH antibodies at the time the rabbit fetal testis begins to produce AMH. In three consecutive litters, the immunized female produced a total of 12 males, 9 of which had persistent Müllerian duct derivatives. No other significant abnormalities were detected in these animals, which were compared to the offspring of a control saline-injected female. In particular, testicular morphology was normal in most animals, and serum FSH levels did not differ from controls. This experimental model lends no support to the hypothesis that AMH controls extra-Müllerian events of male sex differentiation, nor that of the existence of a regulatory mechanism for synthesis of AMH by Sertoli cells, but it does not definitely exclude these possibilities, inasmuch as our tentative conclusions are based upon study of only one immunized female.

[Hormonal principles in normal and pathologic somatic sexual development]

Normal sexual development is the consequence of three sequential interrelated processes: establishment of genetic, gonadal and somatic sex. It is the terminal phase of sexual differentiation--the translation of gonadal into somatic sex, which is governed by the presence or absence of both testosterone and Müllerian-inhibiting hormone and of dihydrotestosterone, which is formed in its respective target tissues. Thus, despite a testis, somatic male sexual differentiation will proceed to a normal male phenotype only if all three hormones are synthesized and act during a critical period of uterine development. Many clinically distinct syndromes are the results of abnormalities in the synthesis or action of the above-mentioned hormones; these syndromes are described in detail. In contrast to male somatic differentiation, female somatic development is independent of these hormones.

Neuroendocrine mechanisms and the aetiology of male and female homosexuality

Theories on the classification and aetiology of male homosexuality are reviewed, particularly recent hypotheses on the role of prenatal hormonal influences on brain sexual differentiation and subsequent sexual object choice in the male. Female as well as male brain sexual differentiation may be hormonally determined, and so primary homosexuality in both sexes may be due to abnormalities in foetal exposure to hormones, leading first to physical mis-differentiation and later to homosexual behaviour in genetically and phenotypically normal men and women.

Peripheral concentrations of gonadotropins and progestins during pregnancy in rabbits after active immunization against testosterone

The effects of active immunization of female rabbits against testosterone on various endocrine parameters during pregnancy were examined. Peripheral blood samples were obtained from immunized rabbits at timed intervals after mating up to the 29th day of pregnancy, when the rabbits were killed and various tissues were analyzed. Progesterone concentrations were higher in testosterone-immunized rabbits (TIR) than in controls during pregnancy. Luteinizing hormone (LH) and follicle-stimulating hormone concentrations were not significantly different in controls and TIR during pregnancy. Both progestins and gonadotropins showed the expected coitus-induced increases, but LH levels were higher in TIR. The binding of testosterone in fetal plasma and amniotic fluid was higher in TIR than in controls. Weights of fetuses and litter size were not significantly different in TIR and controls. These data suggest that testosterone may play a role during pregnancy in the rabbit.

Immunization of female rabbits against testosterone stimulates testosterone accumulation by isolated ovarian follicles

Ovarian follicles isolated from female rabbits after active immunization against testosterone-3-oxime bovine serum albumin produced more testosterone than similar follicles from controls.