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PubMed1997

Masculine sexual behavior is disrupted in male and female mice lacking a functional estrogen receptor alpha gene.

Masculine sexual behavior is regulated by testosterone (T). However, T can be metabolized to form estrogens or other androgens, which then activate their own receptors. We used knockout mice lacking a functional estrogen receptor alpha (ER alpha) gene to test the hypothesis that, following aromatization, T acts via the ER alpha to activate normal masculine sexual behavior. After gonadectomy and T replacement, wild-type (WT) male and female mice displayed masculine behavior. However, given the same T treatment, little masculine behavior was displayed by mice of either sex that lack a normal copy of the ER alpha gene. In particular, the latency to display masculine sex behavior and the number of mount attempts per trial were significantly reduced in the ER alpha- mice compared to WT littermates (P < 0.05). In addition, we found that in both sexes, ER alpha- mice have a smaller cluster of androgen receptor immunoreactivity in the bed nucleus of the stria terminalis. Using adult ER alpha- mice we were unable to determine whether these genotypic differences are due to organizational or activational effects. However, it is clear that the ER alpha plays a key role in the expression of masculine sexual behavior and in the regulation of androgen receptors in a neuronal cell population involved in the display of motivated behaviors.

Animals↗
PubMed1991

Neonatal testosterone masculinizes sexual behavior without affecting the morphology of the dorsal preoptic/anterior hypothalamic area of female ferrets.

We examined whether testosterone (T) administered to female ferrets neonatally--a treatment known to enhance masculine coital capacity--induces formation of the sexually dimorphic male nucleus in the dorsal preoptic/anterior hypothalamic area (MN-POA/AH), and/or sensitizes dorsal POA/AH neurons to the stimulatory effect of later androgen treatment on somal dimensions. In males, the MN-POA/AH was present in all subjects, and exposure to androgen following castration at postnatal day 56 (P56) increased both MN-POA/AH volume as well as mean somal areas of MN-POA/AH neurons relative to oil-treated controls. Females given androgen from P5 to P20 and for one month beginning after ovariectomy on P56 failed to develop the MN-POA/AH, but displayed high levels of masculine sexual behavior. Somal areas of dorsal POA/AH neurons in females that received either T or a control neonatally did not increase following androgen treatment at P56. Thus, the correlation that exists between somal enlargement of dorsal POA/AH neurons and masculine sexual behavior in androgen-treated males is not found in behaviorally masculinized females. Masculine coital ability does not appear related to aspects of dorsal POA/AH morphology, supporting data from a previous study in which lesions of the MN-POA/AH caused negligible deficits in masculine sexual behavior of adult male ferrets.

Animals↗
PubMed1990

Antiestrogens fail to prevent the masculine ontogeny of the zebra finch song system.

Early treatment with the antiestrogen, tamoxifen, fails to block the ontogeny of the male zebra finch song system which is hypothesized to occur as a result of early estradiol action. In Experiment 1, two other antiestrogens, LY117018 or CI628, or vehicle was administered daily to zebra finch chicks for the first 20 days after hatching at which time the males were castrated. Comparisons of experimental and control brains at 60 days revealed that neither antiestrogen prevented the masculinization of the song system in males. Rather, both compounds increased (hypermasculinized) neuronal soma area in male MAN (magnocellular nucleus of the anterior neostriatum), DLRA (dorsolateral portion of the robust nucleus of the archistriatum), and in HVc (caudal nucleus of the ventral hyperstriatum). In females both compounds masculinized by increasing neuronal soma area in HVc and inducing the formation of Area X. Experiment 2 showed that neither LY117018 nor CI628 was effective in preventing the masculinization of the song system typical of 25-day-old males when administered daily from hatching until sacrifice. Rather, both compounds masculinized females by inducing the formation of Area X, and LY117018 increased RA volume. LY117018 hypermasculinized males by increasing HVc volume and size of neuronal somata in MAN, HVc, and DLRA. CI628 also hypermasculinized males by increasing RA volume and neuronal soma size in HVc and RA. The failure of the present compounds to block masculinization of the song system and the paradox of hypermasculinization by antiestrogens are discussed with reference to the estradiol-masculinization hypothesis.

Animals↗
PubMed1993

Further characterization of the testosterone inducible protein fraction from the mouse fetal male reproductive tract inducing masculine differentiation in vitro.

Recently, we identified a protein fraction with phospholipase A2 (PLA2) stimulatory activity (named as PLSP in previous publications) from the fetal male reproductive tract which induced masculine differentiation of the Wolffian duct in vitro. The role of the PLA2-stimulatory activity of this protein was not clear from the past investigations and the present study was designed to elucidate its role. PLSP as expected stimulated snake venom PLA2 and it induced masculinization not only in male explant but also in female explants in a dose-dependent manner in the absence of gonads. However, neither its PLA2-stimulatory activity nor its masculinizing activity was affected after passing it through a PLA2-Sepharose column (a compound expected to eliminate any PLA2 binding component) suggesting that the PLA2-stimulatory activity of PLSP was not at the level of PLA2 enzyme. To investigate whether modulation of the PLA2 substrate by PLSP played a role in producing PLA2-stimulatory activity, we determined the effect of increasing amounts of unlabeled substrate on the PLA2-stimulatory activity induced by PLSP. However, no change in the PLA2-stimulatory activity of PLSP by unlabeled substrate was noticed suggesting against this possibility. The PLA2-stimulatory activity of PLSP, however, was found completely abolished when it was subjected to extensive dialysis, while its protein composition and masculinizing activity remained unaffected. Thus, it appears that PLA2-stimulatory activity of PLSP is associated with a small compound co-purified with masculinizing protein of PLSP and this activity plays no role in inducing masculinization by PLSP.

Animals↗
PubMed2004

Steroid hormone masculinization of neural structure in rats: a tale of two nuclei.

We review the mechanisms by which steroid hormones masculinize two different regions of the central nervous system (CNS) in rats. Although in both cases, androgens induce a male phenotype, the detailed mechanisms are remarkably different in the two models. In the spinal nucleus of the bulbocavernosus (SNB), testosterone must be present during the perinatal period to spare motoneurons and their target muscles from cell death. This masculinization of the SNB system is through activation of androgen receptors, because XY rats with a defective gene for the androgen receptor fail to develop a masculine SNB system. Interestingly, the motoneurons are spared by androgen, even though they themselves do not possess androgen receptors during the critical period for their survival. Thus, steroids can act on one part of the body to secondarily masculinize the CNS. In the posterodorsal aspect of the medial amygdala (MePD), testosterone can induce masculine development even in adulthood, indicating that there is no critical period for steroids to affect sexual differentiation of this system. In the case of the MePD, both estrogen receptors and androgen receptors appear to mediate testosterone's masculinizing influence on neural structure. The extended neural plasticity of the MePD may reflect annual "reorganization" of the brain in the seasonally breeding ancestors of laboratory rats.

Amygdala↗
PubMed2002

Monoaminergic and cholinergic stimulation of masculine sexual behavior in neonatally demasculinized male rats.

Sexual behavior during adulthood largely depends upon hormonal events that take place around birth. Administration of the antiestrogen Tamoxifen (Tx) to males immediately after birth induces a marked decrease of masculine sexual behavior during adulthood. On the other hand, it is well known that masculine sexual behavior can be stimulated by the administration of drugs acting specifically on the monoaminergic or the cholinergic systems. This study was performed to analyze if masculine sexual behavior can be pharmacologically stimulated in adult male rats neonatally demasculinized by the administration of Tx. Neonatal administration of Tx induced clear impairments of masculine sexual behavior during adulthood. Administration of oxotremorine (OXO), 8-OH-DPAT (8-hydroxy-2(di-n-propylaminotetraline)), yohimbine (YH), and apomorphine (APO), drugs that normally elicit a stimulation of masculine sexual behavior were unable to fully restore it in demasculinized males. Only slight improvements of some behavioral parameters were observed with 8-OH-DPAT and YH. OXO seems to induce a worsening of sexual behavior impairments. Results obtained with APO were not significantly different from saline controls. Data suggest that neonatal treatment with Tx induces permanent impairments of the neural circuitry regulating masculine sexual behavior not only limited to morphological changes but also functional alterations of the neurotransmitter systems.

Adrenergic alpha-Antagonists↗
PubMed2005

Body image concerns of gay men: the roles of minority stress and conformity to masculine norms.

The authors hypothesized that gay men's experiences of minority stress and their conformity to masculine norms would be associated with increased body image dissatisfaction and masculine body ideal distress. For this cross-sectional study, 357 gay males completed a Web-based survey, and 2 multiple regression analyses indicated that minority stress factors (i.e., internalized homophobia, expected stigma for being gay, and experiences of physical attack) were associated with body image dissatisfaction and masculine body ideal distress, accounting for 5% and 13% of the variance, respectively. Gay men's conformity to masculine norms was not associated with body image dissatisfaction but did uniquely explain an additional 3% of variance in masculine body ideal distress scores. The utility of the minority stress model, how traditional masculinity may contribute to gender-related presenting concerns, suggestions for developing and evaluating remedial and preventive interventions, limitations, and future research issues are discussed.

Adolescent↗
PubMedDate not supplied

An exploratory study of constructions of masculinity, sexuality and HIV/AIDS in Namibia, Southern Africa.

The goal of the current study was to explore notions of masculinity and their linkages to HIV/AIDS among Owambo men and women in Namibia, where an estimated one-fifth of 15-49 year-olds have acquired HIV. Thirteen open-ended interviews and three focus groups were conducted with 50 male and female participants aged 19-50 in rural and urban Namibia. Qualitative analysis revealed six central themes: the evolving meanings of masculinity, power dynamics between men and women, women as active agents, the tension between formal and informal education and HIV transmission, alcohol and masculinity, and the blending of masculinity and explanations of HIV and AIDS. The findings suggest both direct and indirect linkages between notions of masculinity and AIDS, and highlight the need for prevention efforts that focus on providing alternative avenues for attaining culturally recognized markers of masculinity.

Adolescent↗
PubMed2002

Transient masculinization in the fossa, Cryptoprocta ferox (Carnivora, Viverridae).

In at least 9 mammalian species, females are masculinized throughout life, but the benefits of this remain unclear despite decades of thorough study, in particular of the spotted hyaena (Crocuta crocuta) in which the phenomenon has been associated with a high fitness cost. Through examination of wild and captive fossas (Cryptoprocta ferox, Viverridae), androgen assays, and DNA typing for confirmation of gender, we made the first discovery of transient masculinization of a female mammal. Juvenile female fossas exhibited an enlarged, spinescent clitoris supported by an os clitoridis and a pigmented secretion on the underpart fur that in adults was confined to males. These features appeared to diminish with age. The majority of adult females lacked them, and os clitoridis length was inversely related to head-body length. No evidence was found to link this masculinization to elevated female androgen levels. Circulating concentrations of testosterone and androstenedione, but not dihydrotestosterone, were significantly lower in females than in males. No significant differences in testosterone, androstenedione, or dihydrotestosterone levels were found between juvenile (masculinized) and adult (nonmasculinized) females. There are several possible physiological mechanisms for this masculinization. None of the hypotheses so far proposed to explain the evolutionary basis of female masculinization in mammals are applicable to our findings. We present 2 new hypotheses for testing and development.

Aging↗
PubMed1994

Masculinity, femininity, and marital satisfaction: an examination of theoretical models.

This study sought to investigate the relationship between masculinity, femininity, and marital satisfaction. A number of polynomial multiple regression analyses were performed in an effort to determine the validity of six theoretical models linking sex roles to marital satisfaction. These are the femininity model, masculinity model, sex-typed model, additive androgynous model, interactive androgynous model, and curvilinear model. The sample was composed of 117 couples who completed the Bem Sex-Role Inventory (Bem, 1974) and the Dyadic Adjustment Scale (Spanier, 1976). For men, the results showed that marital satisfaction was related to (a) their self-described levels of femininity and masculinity, (b) the level of self-described femininity of their wives, and (c) the presence of feminine qualities as well as a limited optimal level of masculine qualities which they perceived in their wives. For women, marital satisfaction was associated with (a) the number of self-described feminine qualities and (b) the level of masculinity, as well as an optimal level of femininity, which they perceived in their husbands. Furthermore, small actual-ideal discrepancies in levels of masculinity and femininity ascribed to partners constituted reliable predictors of marital satisfaction for both men and women.

Adult↗
PubMed1989

The role of prostaglandins in masculine differentiation: modulation of prostaglandin levels in the differentiating genital tract of the fetal mouse.

The present study was designed to test the hypothesis that the stimulation of arachidonic acid prostaglandins (PG) mediates the masculinizing effects of testosterone in the fetal mouse. We examined a number of situations in which masculine organization was either induced or inhibited by external agents and determined whether PG levels in the fetal genital tracts were altered in a manner coincident with those situations. We show here that both PGE2 and 6-keto-PGF1 alpha levels in the male fetal genital tracts increased with the advancement of masculine differentiation. PG levels in males (1.2 +/- 0.3 pg PGE2 and 0.1 +/- 0.03 pg 6-keto-PGF1 alpha on day 14 of gestation) increased to 2.1 +/- 0.3 pg PGE2 and 1.2 +/- 0.3 PG 6-keto-PGF1 alpha on day 18 of gestation. The PG levels in the male genital tract were significantly higher than the PG levels in the female genital tract throughout the period of sexual differentiation. Before this period, however, such as on day 14 of gestation (when male and female fetuses have identical genital tracts) we found no difference in their PG levels. Moreover, administration of testosterone (40 mg/kg) during the critical period of masculine differentiation (days 13-17 of gestation) significantly increased PG levels (approximately 2-fold) of female fetuses. Furthermore, we found that cyproterone acetate (20 mg/kg), an inhibitor of masculine differentiation, on days 13-17 of gestation deceased PG levels in male fetuses. In addition, administration of PG synthesis inhibitors, namely indomethacin (1 mg/kg) and aspirin (100 mg/kg), inhibited both resting and androgen-inducible PG levels in male and female fetuses. Considering these results together, it may be concluded that PGs have a critical role in the masculinizing action of fetal testosterone.

6-Ketoprostaglandin F1 alpha↗
PubMed2004

Accessing the multitude within: a psychoanalytic perspective on the transformation of masculinity at mid-life.

This paper reflects upon the essential components of male identity that commonly are reworked in middle age. The author argues that healthy masculine gender identity involves an ongoing, plastic process of destabilization and reconstruction at various pivotal developmental stages, particularly during middle adulthood. In essence, a man's mature transformation of his sense of masculinity results when finite concepts of gender identity are superseded by an awareness of the complexity of one's multiple, early and diverse gender identifications. A clinical case provides insight into how psychoanalytic treatment can contribute to a new experience of masculinity. The case illustrates how a maturing man, meeting an altered sense of identity in mid-life, relies less on gender splitting and more on reuniting previously antithetical intrapsychic elements. Why this more pluralistic, polythreaded masculinity frequently must wait until mid-life is further clarified. Specific importance is attached to the early development of male gender identity as it is founded on the boy's unique struggles in separating from his mother. The foundation for male gender identity formation is reconsidered as the author questions the 'dis-identification' model while explicating how the boy's striving for narcissistic completion shapes the gendered masculine ego ideal. Classically termed 'phallicism' is understood both to facilitate and obstruct a man's adult development, while the concept of 'genitality' is augmented by the postclassical notion of 'interiority'. At mid-life, 'phallic' ego ideals (resting on omnipotence, desires for narcissistic completion and gender splitting) are transformed into more realistic, 'genital' ego ideals (synthesizing autonomy and connection). The achievement of a mature, less sharply gendered 'masculine' ego ideal (revitalizing the foreclosed dimensions of both the early maternal and paternal imagos) occurs as the balance of forces shifts in the direction of true genitality rather than defensive phallicism.

Adult↗
PubMed1985

Effects of intracranial androgen on the development of masculine ultrasonic vocalizations in the Mongolian gerbil (Meriones unguiculatus).

The effects of testosterone propionate (TP) on brain mechanisms involved in the sexual differentiation of ultrasonic vocalizations were examined in Mongolian gerbils (Meriones unguiculatus). Treatment of neonatal females with TP fully masculinized the rate of emission of the upsweep precopulatory ultrasound during adult sexual interactions with oestrous females. Intracranial implantation of small crystals of TP mixed with cholesterol (65 ng) into females 1-15 h after birth also masculinized the upsweep vocalization emitted in adulthood. Implants of TP positioned in the hypothalamic area had a significantly greater masculinizing effect than TP implants outside this region, or pure cholesterol implants. Two other sexually dimorphic vocalizations, the modulated (mainly precopulatory) and unmodulated (mainly copulatory) calls were masculinized by systemic TP, but intracranial TP had no significant masculinizing action on these calls. Genital structures of females which received neonatal injections of TP were strongly virilized in that their clitorides were lengthened and male-type cornified spines were present on the glans. Females which had received intracranial implants of TP were not virilized peripherally in adulthood. We conclude that testosterone or its metabolites have a direct hypothalamic effect on the development of masculine upsweep vocalizations. Because other vocalizations were insensitive to intracranial TP, the underlying neural tissues may have different thresholds of response to androgen.

Animals↗
PubMed1978

Effects of subliminal stimulation on masculinity-femininity ratings of a male model.

The effects of subliminal stimulation on masculinity-femininity ratings of a male model were tested for 100 male undergraduates, randomly divided into four groups and individually shown a slide of a male model. One group received no further stimulation. A second group received a subliminal flash of white light across the image of the model; a third group was presented with the subliminal message "masculine," while a fourth group was presented with the subliminal message "feminine." Subjects were asked to rate the model on a six-point scale of masculinity-femininity. The differences in ratings among groups were not significant, indicating that subliminal stimulation did not influence masculinity-femininity value-norm-anchor judgments. There were no significant differences in the reported perception of additional stimuli or the tendency to be relaxed among the four groups. However, subjects who received the "masculine" message and reported that they were more relaxed did tend to rate the model higher in masculinity.

Gender Identity↗
PubMed1983

Hormonal control of a developing neuromuscular system. II. Sensitive periods for the androgen-induced masculinization of the rat spinal nucleus of the bulbocavernosus.

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 before birth also masculinizes the number of SNB neurons in females. SNB soma size is significantly masculinized, i.e., enlarged, by administration of androgen prenatally or as late as 7 to 11 days after birth, even though this late postnatal treatment has no effect on the number of SNB cells. Following TP treatment in adulthood, the androgenized females did not display the postural correlates of male copulatory behavior more often than did control females. From these results we infer the following. (1) Androgens act both before and after birth to influence the sexually dimorphic development of the SNB system. (2) There are different sensitive periods for the masculinization of SNB neuronal number and neuronal size, indicating that these two dimorphic characteristics of the SNB are masculinized by somewhat independent mechanisms. (3) TP and DHTP may act via separate mechanisms to alter the number of SNB neurons. (4) Aromatized metabolites of testosterone are not necessary for masculinization of the SNB system. (5) Virilization of the SNB system does not ensure the masculinization of the traditionally defined measures of male copulatory behavior in rodents.

Aging↗
PubMed1982

Masculinization of the female rat spinal cord following a single neonatal injection of testosterone propionate but not estradiol benzoate.

We previously reported that a motor nucleus of the rat spinal cord, the spinal nucleus of the bulbocavernosus (SNB), has more and larger neurons in males than females. The SNB is significantly masculinized in adult female rats receiving 1 mg of testosterone propionate (TP) on the second day of life, compared to that of their oil treated sisters. This masculinization consists of more neurons in the region of the SNB. These results are consistent with the hypothesis that the action of androgens during the early perinatal period is responsible for the sexually dimorphic development of the SNB. Neonatal TP caused no detected masculinization, i.e. enlargement of the size of individual neurons in this region in females. Male rats given TP on day 2 had significantly smaller testes and smaller SNB somas in adulthood than oil treated males. In female rats given 100 micrograms of estradiol benzoate (EB) on day 2, the SNB was not masculinized in either number of size when observed in adulthood. The lack of a masculinizing effect of EB suggests that the aromatization of testosterone to estradiol is not sufficient for this dimorphic development.

Animals↗
PubMed1990

Role of septum and preoptic area in regulating masculine and feminine sexual behavior in male rats.

The effects of septal or preoptic lesions on both masculine and feminine sexual behaviors were examined in castrated adult male rats. Three weeks after brain surgery, animals were implanted with Silastic tubes containing testosterone (T) and observations of masculine sexual behavior were carried out four times every 5 days. T tubes were removed immediately after the end of the masculine behavioral tests. Two weeks later, animals implanted with Silastic tubes containing estradiol-17 beta(E2) were subjected to three feminine sexual behavioral tests at 5-day intervals. The bilateral lateral septal lesion (LSL) and the medial preoptic lesion (MPOL) effectively suppressed the performance of mounts, intromissions, and ejaculations, whereas the medial septal lesion (MSL), the dorsolateral preoptic lesion (DPOL), and the sham operation did not show any significant suppression of these behaviors. In the feminine sexual behavioral tests, intact and sham-operated control males showed only a low lordotic activity. However, the performance of the lordosis reflex was markedly facilitated by LSL or DPOL, while the lordotic activity of MSL and MPOL males was not significantly different from that of control males. These results suggest that the lateral septum exerts not only a facilitatory influence on masculine sexual behavior but also an inhibitory influence on feminine sexual behavior in male rats. On the other hand, the medial preoptic area may play a critical role in regulating masculine sexual behavior in male rats.

Animals↗
PubMed1990

Relationship between masculinity and feminity in drinking in alcohol-related behavior in a general population sample.

The relationship between gender-related personality traits, on one hand and drinking, permissiveness towards drinking, and social as well as personal problems associated to drinking on the other, was studied in a general population sample from the City of Morelia, Mexico. Four gender-related traits scales were used for measuring assertive and aggressive masculinity and affective and submissive feminity, in addition to a standardized questionnaire for assessing drinking and other associated behavior. Some of the main results showed that people with high scores in affective feminity were less willing to allow drinking. Men who adopted a submissive feminine role and women with high masculine aggressive scores were more permissive as regards drinking. Among men, assertive masculine and affective feminine traits were more characteristic among those who drank than among abtainers. Drinking among women was related to liberal attitudes towards drinking and to aggressive masculinity. As regards the number of drinks consumed per month, assertive masculinity and liberal attitudes among men and affective feminity and liberal attitudes among women predicted the number of drinks. Affective feminity was negatively related to drinking. Regarding drinking-associated problems, frequency of drunkenness and submissive feminity among males predicted greater personal and social problems. Among women, drunkenness frequency and number of drinks were the most significant predictors. Contrary to what has been found in other countries, gender was a better drinking predictor than gender-related personality traits.

Adolescent↗