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PubMed2000

Perinatal exposure to estradiol masculinizes aspects of sexually dimorphic behavior and morphology in gray short-tailed opossums (Monodelphis domestica).

The effects on adult sexually dimorphic behavior of perinatal exposure to estrogen were examined by treating male and female gray opossums with estradiol (EST), an estrogen receptor antagonist (tamoxifen:TX) or oil control (OIL) during the first week of life, a time period corresponding in this marsupial to late gestation in rodent species. Following gonadectomy and replacement therapy with testosterone in adulthood, males showed more scent-marking behavior than females and EST animals showed more scent marking than TX or OIL animals. Also, phalluses were longer and body weight was higher in males than in females and in EST-treated animals than in TX-treated animals; OIL animals were intermediate in these morphological measures. EST animals of both sexes showed less female-typical screeching threat behavior than OIL or TX animals. Because these hormone manipulations were conducted on the "fetus" directly in this marsupial (rather than via the maternal circulation as in previously studied eutherian species), these findings provide unique confirming evidence for masculinization of aspects of behavior and morphology by early exposure to estradiol in mammals.

Aging↗
PubMed2002

Oral estrogen masculinizes female zebra finch song system.

It is well established that parenteral treatment of female zebra finch chicks with estradiol masculinizes their song control nuclei and that as adults they are capable of song. Concern over the widespread use of putative environmental estrogens caused us to ask whether oral exposure to estrogens (a natural route of exposure) could produce similar effects. We dosed chicks orally with estradiol benzoate (EB; 1, 10, 100, and 1000 nmol/g of body mass per day, days 5-11 posthatch), the non-ionic surfactant octylphenol (100 and 1000 nmol/g), or the pesticides methoxychlor (100 and 1000 nmol/g) and dicofol (100 nmol/g) and measured their song control nuclei as adults. EB treatment produced increases in song nuclei comparable to that induced by parenteral administration of estrogens. This is the first study of which we are aware to use an oral route of administration, which simulates the natural process of parent birds feeding their nestlings. We conclude that oral exposure to estradiol alters song control nuclei and we report in a related paper (Millam et al., 2001) that such exposure severely disrupts reproductive performance. Although we detected no influence of xenobiotics on induction of song control nuclei the possibility remains that oral exposure to xenoestrogens in high enough doses could affect development.

Animals↗
PubMed1984

Increase of steroid-producing cells in interrenal tissue and masculinization of gonads after long-term treatment of juvenile rainbow trout with cyanoketone.

Cyanoketone administered via the food (0.1, 0.2 and 2 mg/g) for 8 weeks from the first feeding (day 46 after fertilization) or via the aquarium water (3 and 30 mg/100 l) for 4 weeks from day 41 does not influence the activity of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) in the interstitial cells of the gonads or interrenal cells of juvenile trout in vivo. However, the number of 3 beta-HSD-positive interrenal cells was strongly increased by administration of the highest dose of cyanoketone via both routes. These high doses furthermore affect the sex ratio in favor of males. It is concluded that interrenal tissue is responsible for the masculinizing effect of cyanoketone via increased production of androgens and/or corticosteroids. Cyanoketone at concentrations of 0.01 to 100 micrograms/ml causes a dose-response inhibition of 3 beta-HSD activity in the interrenal cells, when the substance is administered to an incubation medium for demonstration of this enzyme in tissue sections. The controversial in-vivo and in-vitro effects of cyanoketone on 3 beta-HSD activity are discussed.

3-Hydroxysteroid Dehydrogenases↗
PubMed1978

Loss of rRNA genes during a phenotypic, masculinizing mutation in Allomyces arbuscla.

Saturation hybridization of 3H rRNA from Allomyces arbuscula Bali wild-type to homologous DNA and to DNA preparations from Allomyces arbuscula Bali X-ray induced male mutant and an interspecific male hybrid (Allomyces arbuscula X Allomyces macrogynus Emerson and Wilson) has shown approximately 50--60% reduction in the cistrons coding for rRNA in the masculinized strains.

Chytridiomycota↗
PubMed2006

Gender role and relationship norms among young adults in South Africa: measuring the context of masculinity and HIV risk.

In the global literature on HIV/AIDS, much attention has been paid to the role of gender inequalities in facilitating the transmission of HIV. For women, gender inequality may be manifested in sexual coercion, reduced negotiating power and partnering with older men, all practices that heighten risk for HIV. Less attention, however, has been paid to how men's relationship behaviors may place them at risk for HIV. Using six culturally specific psychometric scales developed in South Africa, this study examined men's and women's gender role and relationship norms, attitudes and beliefs in the context of ongoing partnerships. These measures were then examined in relation to four sexual risk behaviors: frequency of condom use (with primary or secondary partners) and number of partners (last 3 months and lifetime). Participants were 101 male and 199 female young adults aged, 18-24, recruited from a secondary school in northern KwaZulu/Natal province. Associations between gender and relationship scale scores and sexual risk outcomes yielded both expected and contradictory findings. For men, more frequent condom use was associated with higher levels of partner attachment (hyper-romanticism) but also with stronger approval of relationship violence and dominant behavior. In contrast, for women, more frequent condom use was correlated with a lower endorsement of relationship violence. Men with lower relationship power scores had fewer sexual partners in the preceding 3 months, while women with more egalitarian sexual scripts reported more sexual partners, as did those with higher hyper-romanticism scores. In logistic regression analysis, more egalitarian relationship norms among men were predictive of less consistent condom use, as were higher relationship power scores for women. These findings are discussed in relation to previous research on gender, heterosexual interactions and masculinity in this area, as well as the implications for HIV prevention programs.

Adolescent↗
PubMed2006

Phenomenologies of the akratic self: masculinity, regrets, and HIV among men on methadone.

This study explores the motivational bargaining processes that constitute an "act" of heterosexual HIV risk-taking by focusing on the narrative viewpoint of two men in methadone maintenance treatment programs in the Harlem section of New York City. These men reported sexual episodes with complex motivational "event grammars" that were analyzed using qualitative methods. Building on the concept of akrasia (failure to convert intentions into action), I argue that HIV risky heterosex results from temporal displacements of instrumental rationality by two other equally relevant orientations of sexual action, namely, affectual and normative. I conclude that sexual risk occurs in the context of emotions and normative presentations of the masculine self. Consequently, a man's risk of loosing footing or consistent face vis-à-vis his female sex partner, and not the risks of HIV, becomes a priority of the sexual interaction. Sexuality is at its core social and, hence, subject to more powerful forces than personal safety or behaviorist reward.

Adult↗
PubMed1984

Spinal monoaminergic modulation of masculine copulatory behavior in the rat.

The sexual behavior of male rats receiving infusions of 5-HT, dopamine and noradrenaline intrathecally in the spinal cord of intracerebroventricularly (i.c.v.) in the lateral ventricle was observed. Intrathecal infusions of 5-HT and noradrenaline inhibited penile insertions and ejaculation, noradrenaline being the more potent of the amines. Dopamine was without effect. I.c.v. amine infusions impaired to various extents the masculine mating pattern, primarily by interfering with the males' tendency to approach the females. The facilitation of mating seen after intrathecal administration of the aminotetraline, 8-OH-DPAT, was more pronounced than that observed following its i.c.v. infusion.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1986

Testosterone implants into the amygdala during the neonatal period masculinize the social play of juvenile female rats.

The masculinization of social play behavior in the rat is dependent upon the actions of androgens during the neonatal period. The amygdala, a major androgen-target region in the rat limbic brain, appears to be a critical site for this androgenic effect. We tested this hypothesis by implanting testosterone-bearing cannulae into the amygdala of female rat pups on Day 1 of life; the implants were removed on Day 8 of life. The animals were then observed daily between Days 26 and 40 of life and the frequency of play-fighting was recorded. Testosterone-implanted females, like normal males, engaged in significantly more play-fighting than did control females (implanted with cholesterol-bearing cannulae). We have also presented data indicating that the testosterone diffusion from the cannulae was, for the most part, restricted to the amygdala. Thus, testosterone implanted into the amygdala mimicked the effects previously reported for systemic testosterone injections, supporting the idea that the amygdala is a critical region for the actions of androgens on the sexual differentiation of social play behavior in the rat.

Amygdala↗
PubMed1980

Stimulating effects of lisuride on masculine sexual behavior of rats.

Treatment of adult male rats with lisuride, an ergot derivative, resulted in selective changes in the masculine mating pattern. A dose-dependent decrease was found in the number of intromissions preceding ejaculation and in the ejaculatory latency. No other components of the mating pattern showed any significant alteration. Further, castrated sexually inexperienced rats treated with lisuride displayed a dose-dependent increase in complete heterosexual behavior.

Animals↗
PubMed1987

Structure of the right testis of sexually mature genetically female fowl experimentally masculinized during embryonic life and submitted to a posthatching left castration.

Posthatching left castration of genetically female fowl, Gallus domesticus, preceded, during embryonic life, by a masculinizing treatment associating a testis graft and an antiestrogen resulted in the development of the right rudimentary gonad into a testis. Examined after the sexual maturity, the right testis of most treated animals was entirely composed of seminiferous tubules possessing a spermatogenic cell complement. Spermiogenesis proceeded to the stage of spermatozoon in 4 out of 17 treated animals and was almost as well organized as in a normal cock testis in 3 of them. Testis development appeared then as clearly improved, compared to that described previously in only left-castrated, with or without treatment with an antiestrogen, or only sex-reversed female fowl. The possible mechanism of this improvement is discussed.

Animals↗
PubMed1983

Reproductive success, postpartum maternal behavior, and masculine sexual behavior of neonatally androgenized female hamsters.

Sex differences in maternal behavior induced by pup stimulation (sensitization) have been reported for rats and hamsters and may be affected by the presence or absence of perinatal androgen treatment. Postpartum maternal behavior and litter survival in golden hamsters treated with testosterone propionate (TP) as neonates were studied. A high dose of TP (300 micrograms)1 eliminated feminine reproductive capacity when given on Day 2 or 4 postpartum and had no discernible effect on Day 12. Treatment on Days 6, 8, or 10 resulted in treatment day-dependent deficiencies in reproductive success which fell short of sterility in most females. These deficiencies included low birth weight, weight gain, and higher litter losses than controls. However, the maternal behavior of TP dams, as measured by retrieval and crouching, appeared to be normal. The disparity between delivery and successful rearing of normal-weight young may include uterine incompetence, lactation deficiency, and hypercannibalism. Behavioral masculinization was a more sensitive index of neonatal androgen action than any aspect of defeminization, but the two phenomena were dissociated in individuals.

Animals↗
PubMed1983

Neural correlates of frog calling. Masculinization by androgens.

Neural correlates of mating calling can be recorded from isolated brainstems of male, Northern leopard frogs after the circuits for this behavior have been triggered by electrical stimulation of the preoptic area. Correlates can be evoked reliably and by a stimulus of low amplitude. However, such correlates can be evoked only rarely from female brainstems, and then only by a much larger stimulus. The sensitivity to triggering in female brainstems can be masculinized by previous treatment of the intact frog with testosterone propionate or dihydrotestosterone, but not by estradiol benzoate. This suggests that the action of the androgens is direct and does not require aromatization to estrogens. Comparisons with other studies suggest that the androgen effect may be mainly on posterior parts of the calling circuits (i.e., call pattern generator or motoneurons), rather than on the preoptic area trigger of the generator.

Androgens↗
PubMed1994

Prenatal androgen blockade with flutamide inhibits masculinization of the genitofemoral nerve and testicular descent.

Prenatal androgen blockade with the antiandrogen flutamide inhibits the inguinoscrotal phase of testicular descent. The evidence suggests that androgens may act indirectly via the sexually dimorphic genitofemoral nerve (GFN) to control this phase. Rats were exposed to flutamide on gestational days 16 through 19. Seven-day-old rats were subjected to retrograde fluorescent labelling of the GFN combined with immunohistochemistry for calcitonin gene-related peptide (CGRP), a neurotransmitter found in the GFN. Fluorescent-labelled and CGRP-immunoreactive neurons in the GFN spinal nucleus were quantified. Sexual dimorphism of the GFN nucleus was absent in the flutamide-treated rats but obviously present in control rats. Furthermore, control male nuclei had 24% more CGRP-immunoreactive neurons and 12% more fluorescent-labelled neurons than did flutamide-treated male nuclei. This study shows that prenatal androgen blockade with flutamide inhibits masculinization of the GFN, with significant reduction of its CGRP content. This supports the proposal that androgens act via the GFN, with CGRP as the second messenger, to control inguinoscrotal testicular descent.

Animals↗
PubMed1988

Steroid metabolism in testes of patients with incomplete masculinization due to androgen insensitivity or 17 beta-hydroxysteroid dehydrogenase deficiency and normally differentiated males.

For purposes of establishing suitable controls in studies of patients with a suspected enzyme deficiency, activities of enzymes involved in the biosynthesis of testosterone were compared in testes of patients with androgen insensitivity syndrome (AIS) and normally differentiated males with carcinoma of the prostate (Ca prostate) or testis (Ca testis). Activities of 17,20-desmolase and of 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) were higher in the testes of pre-, peri- or postpubertal patients with AIS than in elderly men (58-80 yr) with Ca prostate. Activities of 17 beta-HSD (reductive direction) and 3 beta-HSD tended to be higher in peri- or postpubertal than in prepubertal patients with AIS. Activity of 3 beta-HSD was low in the patient with Ca testis. In a peripubertal (12 yr) patient with incomplete masculinization due to a severe deficiency of 17 beta-HSD, reductive activity of 17 beta-HSD was very low compared with that of patients with Ca prostate, Ca testis or AIS. In contrast, in testes from the younger sibling (4 yr), in whom the deficiency of 17 beta-HSD was less severe, 17 beta-HSD reduction of dehydroepiandrosterone was as high as that of men with Ca prostate, yet deficient in comparison with that of more closely age-matched patients with AIS. This emphasizes the desirability of using age-matched tissue for control purposes in enzyme studies.

17-Hydroxysteroid Dehydrogenases↗
PubMed1983

Successful pregnancy following surgery for a masculinizing adrenocortical carcinoma.

A 16-year-old girl with a masculinizing adrenal carcinoma treated surgically is presented. Following surgery a full clinical and steroid remission has been achieved, without any adjuvant chemotherapy. In the 7th year after the surgical treatment the patient became pregnant. Pregnancy and labour were uncomplicated. The patient continues in complete remission, and her son has been noted to have normal development at 21 mth of age.

Adolescent↗
PubMed1990

Differences in feminine and masculine characteristics in women as a function of handedness: support for the Geschwind/Galaburda theory of brain organization.

The Geschwind/Galaburda testosterone theory successfully predicted differences in feminine sex role identification and behavior between women with anomalous dominance and standard dominance. The women with anomalous dominance (consisting of left-handed and ambidextrous as well as right-handed women with first-degree non-right-handed relatives) were compared to women with standard dominance (right-handed women with all right-handed first-degree relatives) on the Bem Test of Sex Role Identity and a tomboy scale. Across three samples, handedness classifications were related to both tomboy characteristics and sex role identification. In addition, the study showed that the anomalous dominance women had a higher masculine sex role identification as compared to the college normative sample for the Bem, while the standard dominance women had a higher feminine identification than the normative sample.

Adolescent↗
PubMed1988

Hormonal restoration of masculine sexual behavior in long-term castrated B6D2F1 mice.

In contrast to the facilitative effects reported for other rodents, testosterone treatment at the time of castration previously was reported to inhibit masculine sexual behavior in male B6D2F1 mice. Males of this genotype vary in their behavioral response to castration. Some castrates retain sexual behaviors for many weeks after surgery, whereas others do not. In the present study, we sought to determine the effects of exogenous steroid hormone treatment on castrated B6D2F1 mice that had ceased to show copulatory behavior. Testosterone propionate and estradiol benzoate restored copulatory behavior to precastration levels in B6D2F1 males that did not retain sexual behaviors after castration.

Animals↗
PubMed1989

Environmental influences on masculine sexual behavior in mice.

Retention of masculine copulatory behaviors following castration varies among B6D2F1 male mice. In the present study, we examined the effect of test environment and the amount of behavioral testing after castration, on retention of copulatory responses in castrated B6D2F1 male mice. Results showed that weekly behavioral testing after castration was not necessary for the retention of ejaculatory reflexes. However, the test environment had a major effect. Following castration, 26% of the males completely stopped showing ejaculatory responses when tested in the test arenas. When these males were tested in their home cages, 75% achieved at least one ejaculatory response in four home cage tests. Castrated males that continued to copulate in the test arena situation also achieved ejaculatory reflexes in their home cages. These results indicate that for some B6D2F1 males, the retention of sexual behaviors after castration is influenced by environmental factors.

Animals↗