Sex reversal in female Betta splendens as a function of testosterone manipulation and social influence.

In Experiment 1, female Betta given daily injections of testosterone (T) for 9 weeks acquired anatomical features characteristic of males as indicated by changes in fin length, body coloration, and gonadal morphology. These findings suggested that a potential for sex reversal exists in females of this species. In Experiment 2 we measured changes in aggressive behavior during testosterone-induced anatomical changes. Aggression decreased toward females and increased toward males as treatment with T progressed. The final displays of aggressive behavior and anatomical characteristics of fish injected with T resembled those of typical males. In Experiment 3, female Betta primed with T injections for 3 or 6 weeks and permitted to interact socially with females continued to display characteristics of sex reversal after T supplementation ceased. Sex reversal in isolated fish injected with T for 3 or 6 weeks was not sustained, and fish receiving only the control vehicle showed negligible change in both the isolated and community conditions. We discuss the results in terms of similarities with the sex change process found in isolated communities of coral reef fish. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex differences in anxiety behavior in rats: role of gonadal hormones

These experiments examined the role of gonadal hormones at both the organizational and activational time periods on sex differences in plus-maze behavior. In the first experiment, adult female Long-Evans rats were found to spend more time on the open arms of the plus maze than adult males, indicating less anxious behavior. In the second experiment, male and female subjects received a neonatal treatment (chemical castration with flutamide or tamoxifen, vehicle injection, or no injection) and a prepubertal treatment (gonadectomy, sham surgery, or no surgery). Adult females receiving either neonatal tamoxifen or prepubertal ovariectomy spent less time on the open arms than control females, but females who received both treatments were the most defeminized subjects. Males were not affected by the absence of gonadal hormones at either time period. These experiment indicate that female gonadal hormones play an important role both organizationally and activationally in plus-maze behavior. The role of the GABA receptor complex in mediating this effect is discussed. Knowledge of sex differences in plus-maze behavior may help to make this maze a more useful tool in investigating anxiety behavior in rats.     

Overexpression of transforming growth factor !a in transgenic mice alters nonreproductive, sex-related behavioral differences: Interaction with gonadal hormones.

Sexually dimorphic differences in voluntary sodium intake, locomotor activity, immobility in the swim test, and aggressive behavior were found to be altered in transgenic CD-1 mice that overexpressed transforming growth factor α (TGFα). In contrast to nontransgenic CD-1 mice, immobility in the swim test was longer and sodium intake higher in the male TGFα mice than in the female TGFα mice. These findings indicate that the male TGFα mice exhibited feminization of some behaviors. Furthermore, the male TGFα mice were highly aggressive. Castration reversed the behavioral effects in the adult male transgenic mice, but ovariectomy did not reverse the behavioral effects in the adult female transgenic mice. Thus, the feminizing effect of TGFα on some nonreproductive behaviors and increased aggressive behavior in male mice may be mediated through an interaction between this growth factor and gonadal hormones. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Another hamster paradox: more males carry pups and fewer kill and cannibalize young than do females

The response of virgin male and female golden hamsters to young was studied. In contrast to most species, males are more likely to carry pups than are females. All males carried pups, but approximately 50% of females cannibalized the young. The females that did not cannibalize the pups carried them with less hesitation and after shorter latencies than did the males. The response of females to young was not correlated with the aggressiveness displayed toward adult males during separate tests. Tests with gonadectomized females indicated that the maintenance of pup-killing behavior is not dependent on concurrent gonadal hormones. Progesterone injections did not significantly increase pup killing in males that had previously carried young. Speculations on the adaptive significance of the male and female hamster's response to pups are presented.     

Elicitation of male mouse (Mus musculus) ultrasonic vocalizations: I. Urinary cues.

18 experiments on a total of 223 DBA/2J, AKD2F1/J, and hybrid mice, plus additional social-experience mice, examined the physical characteristics and physiological modulation of the ultrasound-eliciting property of female urine. The following results were found: An excitatory factor exists in female urine, and male urine is essentially neutral with regard to ultrasound elicitation. The ultrasound-eliciting factor is relatively nonvolatile and heat resistant, although extreme heat will destroy its activity. Ovarian and adrenal hormones appear relatively unimportant. Exogenous androgen suppresses female urinary ultrasound-eliciting activity. Castration of males did not improve the ability of their adult urine to elicit ultrasounds, nor did administration of androgen to neonatal females suppress the ability of their adult urine to elicit ultrasounds. Hypophysectomy eliminates the ultrasound-eliciting properties of female urine, which suggests that the dimorphism in ultrasound elicitation may be regulated by pituitary hormones. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Genetic studies in NZB mice. IV. The effect of sex hormones on the spontaneous production of anti-T cell autoantibodies

Hybrid NZB X NZW or NZB X DBA/2 females have markedly accelerated development of autoimmunity when compared with their respective male littermates. This difference is attributable to the ability of male sex hormones to retard the expression of autoimmunity. In contrast to the sex differences in expression of autoimmunity in F1 mice, parental NZB males and females have only minor differences in disease expression. We have been investigating the basis for the difference in anti-T cell antibody production between NZB and F1 mice. In this study, the appearance of antibodies cytotoxic for T cells (NTA) was studied in NZB and DBA/2 mice and in their F1 hybrids and backcross progeny. A major sex difference in NTA production was observed in the F1 hybrids; females produced more NTA than did males. Castration of males led to a marked increase in NTA production. Furthermore, the NTA production of castrated male and female F1 mice was significantly suppressed by administration of testosterone in Silastic capsules. In contrast to the studies in F1 mice, we found little difference between intact male and female parental NZB mice at any age studied. Furthermore, NZB mice of both sexes who were given androgen-containing capsules at 2 weeks of age failed to demonstrate a decrease in NTA production. This result suggested an androgen insensitivity in NZB mice with regard to NTA production. This insensitivity, which appears to be a recessive trait, may help to explain why NZB mice do not manifest the sex differences in disease expression observed in the F1 hybrids.     

The effect of the lipid A analog E5531 on phospholipid membrane properties

The orphan nuclear receptor steroidogenic factor 1 (SF-1) was initially isolated as a key regulator of the cytochrome P450 steroid hydroxylases in adrenocortical and gonadal cells. Subsequent analyses of SF-1 knockout mice have expanded considerably our understanding of the roles that SF-1 plays in endocrine development. These SF-1 knockout mice lacked adrenal glands and gonads, with consequent male-to-female sex reversal of their internal and external genitalia. Thus, SF-1 is essential for the embryonic survival of the primary steroidogenic organs. They further exhibited impaired gonadotrope function and agenesis of the ventromedial hypothalamic nucleus, establishing that SF-1 contributes to reproductive function at all three levels of the hypothalamic-pituitary-gonadal axis. This report reviews experiments that have defined these critical roles of SF-1 in endocrine development, and highlights areas of ongoing investigation.     

Sex differences in investigatory and grooming behaviors of laboratory rats (Rattus norvegicus) following exposure to novelty.

Prior research suggested that during exposure to novel stimuli, rodent investigation and self-grooming behaviors may be sexually dimorphic and interact with ambient illumination. To test this notion we compared the behavior of adult male and female groups of Long-Evans hooded rats in normal room lighting (860 lx) and in very dim, red light (0.2 lx) following exposure to a novel juvenile conspecific. Illuminance level had little or no effect, but investigatory and subsequent self-grooming behaviors of males were substantially greater than those of females, and females engaged in greater ambulatory activity than did males. In a second experiment adult males and females were exposed to a novel inanimate object. No reliable sex differences were observed. We conclude that social novelty, as provided by exposure to a juvenile conspecific, stimulates greater investigation and postinvestigatory self-grooming than exposure to a novel inanimate object and that exposure to novel conspecifics presents a useful method for the investigation of sex differences, gonadal hormone effects, and interactions of hormones with neurotransmitter systems governing motor control systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gonadal hormones influence the emergence of cortical function in nonhuman primates.

The role of gonadal hormones in the maturation of the orbital prefrontal cortex (ORB) was studied in normal male and female rhesus monkeys, monkeys given ORB lesions at 50 days of age, and female monkeys given androgen at different ages. Monkeys were tested on an object discrimination reversal task at 75 days of age. Gender influenced the performance of monkeys on the task during normal development and after ORB lesions. Normal males made fewer errors than did normal females. Females treated with androgen performed similarly to normal male monkeys. ORB lesions produced deficits in male monkeys and in females given androgen during late prenatal or early postnatal life, but not in normal females. These findings suggest that gonadal hormones may play an inductive role in the differentiation of higher cortical function in nonhuman primates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gender differences in the activities of aspirin-esterases in rat tissues

The activities of aspirin (acetylsalicylic acid)-esterases were measured in several tissues (liver, kidney, adrenal glands, brain and serum) from adult male and female Wistar rats. In males, both aspirin-esterase I (assayed at pH 5.5) and II (assayed at pH 7.4) activities were higher in liver homogenates when compared to females (aspirin-esterase I: males 48.9 +/- 4.8 (N = 8) and females 29.3 +/- 4.2 (N = 8) nmol of salicylic acid formed min-1 mg protein-1; aspirin-esterase II: males 41.4 +/- 4.1 (N = 8) and females 26.1 +/- 4.5 (N = 8) nmol of salicylic acid formed min-1 mg protein-1, P < 0.001). In serum, enzyme activity was higher in females than in males (aspirin-esterase I: males 0.85 +/- 0.06 (N = 6) and females 1.18 +/- 0.11 (N = 6) nmol of salicylic acid formed min-1 mg protein-1, aspirin-esterase II: males 1.03 +/- 0.13 (N = 6) and females 1.34 +/- 0.11 (N = 6) nmol of salicylic acid formed min-1 mg protein-1, P < 0.001). In the other tissues assayed, no statistically significant difference between males and females was found. There were no statistically significant differences when the enzymes were assayed in different phases of the estrous cycle in liver and serum. These results show that the differences in aspirin-esterase activity observed between males and females are not due to the estrous cycle. The gender difference obtained in our study may indicate an involvement of gonadal hormones in the control of the hydrolysis of aspirin. This possibility is currently under investigation.     

Dominance in intermale encounters and subsequent sexual success in mice.

In Exp I, when previously isolated male CD-1 mice (n?=?26) were paired and given a female, they fought before beginning to mount, and the more aggressive male ejaculated somewhat more frequently. Males housed together (n?=?26) for several days showed little aggression when jointly given a female, but those that were more aggressive in the home cage clearly ejaculated more frequently. In Exp II, with 144 Ss, males were paired for 4 days after a period of isolation. More aggressive males showed more ejaculations when subsequently tested individually with females, but not when pair members conjointly encountered females. In Exp III, 60 males were paired for several weeks before encountering females. In cases in which home cage dominance was constant, the more aggressive males ejaculated more frequently both when tested individually and when tested as pairs. Findings indicate that success in reproductive behavior in mice is contingent on dominance in intermale aggressive encounters. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of sex hormones on protein and collagen content of the temporomandibular joint disc of the rat

PURPOSE: The effect of sex hormones on the protein and collagen content of the temporomandibular joint (TMJ) disc of adult male and female rats. MATERIALS AND METHODS: One hundred forty-four Wistar rats were assigned to 14 groups of 12 each. Two groups, one female and one male, served as a control and received no treatment, and two other groups (one female and one male) received a sham gonadectomy and placebo hormone. The remaining 10 groups (five males and five females) received either orchiectomy or ovariectomy, followed by administration of estrogen, progesterone, combined estrogen and progesterone, or testosterone. The total protein and collagen content of the TMJ disc were determined using the calorimetric hydroxyproline method. RESULTS: The collagen content of TMJ discs of control males was statistically greater than the collagen content of the control female rats. This difference disappeared after ovariectomy of females and orchiectomy of males. Also, there was a general trend for a decrease in collagen and protein content to be produced by estrogen, progesterone, and by estrogen combined with progesterone in castrated male and female rats, and by orchiectomy of male rats. There was also a trend toward an increase in collagen and protein content after ovariectomy in female rats and administration of testosterone to castrated male and female rats. However, the only statistically significant effect of the drugs tested was that of estrogen combined with progesterone in ovariectomized female rats (a lowering effect on the total protein) and of estrogen alone in orchiectomized male rats (a lowering effect on the collagen content). CONCLUSION: Steroid sex hormones have an effect on the collagen and protein content of the TMJ disc of the rat as indicated by the difference in the values between control males and females and by the disappearance of this difference on castration of both male and female animals. This was also manifested by the significant effect of estradiol on collagen content of castrated males, by the effect of estrogen combined with progesterone on the protein content of castrated females.     

Aggression in male mice lacking functional estrogen receptor α.

Estrogen receptor alpha knockout (ERαKO) male mice fail to display sexual behavior. The authors hypothesized that ERαKOs require higher testosterone (T) concentrations than wild-type (WT) males to exhibit copulatory behavior. Increasing T stimulated sexual behavior and preference for females in WT males but failed to do so in ERαKOs. However, T did induce female-directed aggression in ERαKOs. In aggression tests, WT residents selectively attacked T-treated male intruders. ERαKO residents attacked female, T-treated male, and estrogen-treated male intruders equally. Increased access to olfactory cues prior to direct contact reduced overall aggression in ERαKO versus WT males but did not cause ERαKOs to differentially attack male and female opponents. Results suggest that ERα is essential for normal social behavior, perhaps via processing of chemoinvestigatory cues, which are required to discriminate males from females. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social play soliciting by male and female juvenile rats: Effects of neonatal androgenization and sex of cagemates.

Investigated the behavior of male and female Long-Evans hooded rats during individual exposure to nonplayful juvenile social stimuli in a novel test of play-soliciting behavior in 2 experiments examining hormonal and experiential determinants of sex differences. In Exp I, using 36 female and 18 male Ss, neonatally androgenized females engaged in play soliciting at a level equal to that of male controls and greater than that of nonandrogenized female controls. In Exp II, 52 males and 32 females were reared in unisexual and bisexual groups in order to compare long-term sex-related social experience effects on juvenile play soliciting. Males exposed only to other young males engaged in greater play soliciting than males exposed to both sexes; females, in contrast, were unaffected by sex of cagemates. Within rearing conditions, however, males engaged in greater play soliciting than females. The combined results suggest that perinatal gonadal androgen exposure effects on social play are prepotent and contribute essentially to sex differences in the initiation of social play behavior. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Open-field and avoidance behavior after neostriatal lesions in male and female rats.

The behavioral effects of lesions of the anterodorsal or posteroventral parts of the caudate-putamen were studied in 2 experiments with a total of 115 male and 101 female adult albino Holtzman rats that were gonadectomized or left untreated prior to brain surgery. Anterodorsal (ADC) lesions consistently impaired acquisition of 1-way avoidance behavior and tended to interfere with the development of a 2-way avoidance response; comparable effects were observed in gonadectomized and intact Ss of both sexes. By contrast, ADC lesions increased activity in the open field only in intact females and increased rearing only in ovariectomized females. Posteroventral caudate (PVC) lesions caused transient aphagia and adipsia in both sexes but did not consistently affect open-field activity or the acquisition of 1-way avoidance responses by either sex. These lesions profoundly impaired acquisition of shuttle box avoidance responses by intact males. By contrast, castrated males and intact and ovariectomized females with PVC lesions avoided normally in the shuttle box. Results suggest that localization of behavioral functions within the striatum differs with the sex of the S, in part because of activational effects of gonadal hormones. (37 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serum sex hormones are altered in patients with chronic temporal lobe epilepsy receiving anticonvulsant medication

PURPOSE: To evaluate the changes in serum sex hormones of gonadal or adrenal origin, the gonadotropic hormones, and sex hormone-binding globulin (SHBG) in men and women with chronic temporal lobe epilepsy (TLE), who are undergoing monotherapy with carbamazepine or receiving carbamazepine in combination with other anticonvulsant drugs. METHODS: Gonadal hormones (estradiol, testosterone, free testosterone, and inhibin B), adrenal hormones [cortisol, dehydroepiandrosterone sulfate (DHEAS), androstenedione, and 17alpha-hydroxyprogesterone], and gonadotropic hormones (luteinizing hormone [LH] and follicle-stimulating hormone [FSH]) were measured in 22 women and 26 men with TLE. The study also measured prolactin; human growth hormone and its major mediator, insulin-like growth factor-I; thyroid hormones (free thyroxine and free triiodothyronine); thyroid-stimulating hormone (TSH); and SHBG. The results were compared with those obtained from 60 healthy women and 106 healthy men. RESULTS: In the female patients, TSH, DHEAS, follicular-phase LH, and luteal-phase estradiol were significantly lower than in the control groups, with prolactin and SHBG significantly higher. In the male patients, DHEAS, 17alpha-hydroxyprogesterone, free testosterone, inhibin B, and the testosterone/LH ratio were significantly lower than in the control group, with LH, FSH, and SHBG significantly higher. Increased FSH in 31% of the men indicates an impairment of spermatogenesis; lowered inhibin B in 12% indicates an impaired Sertoli's cell function; and the decreased testosterone/LH ratio in 50% indicates an impaired Leydig's cell function. CONCLUSIONS: The case patients had endocrine disorders, mainly concerning the gonadotropic and gonadal functions in both sexes; the adrenal function, with lowered DHEAS levels in both sexes; and lowered 17alpha-hydroxyprogesterone levels in the men. SHBG levels were increased in patients taking anticonvulsant medications.     

Testosterone and persistence of social investigation in laboratory rats.

In 5 experiments 92 mature male and 44 mature female Long-Evans rats were individually exposed in their home cages to sexually immature conspecifics. A prominent sex difference was observed in duration of social investigation prior to a criterion of neglect. When pups were 5 days of age, no sex difference was observed, but when pups were 8 days of age and older, mature males consistently investigated them for significantly longer intervals than did mature females. Furthermore, intact males investigated prepuberal conspecifics for significantly longer intervals than did castrated males, castrated females, or intact females; none of the latter 3 groups differed significantly from each other. Following testosterone treatment, castrated males investigated unfamiliar, prepuberal conspecifics for a significantly longer duration than did untreated castrated control Ss. Combined results support the conclusion that gonadal testosterone effects a greater perseveration of social investigation in males. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sex-related differences in spatial divided attention and motor impulsivity in rats.

The acquisition and performance of a self-paced test of spatial divided attention linked with frontal cortex function were assessed in postpubertal (> 60 days) normal or gonadectomized male and female rats. Males were more accurate at detecting relatively brief visual stimuli than females, but this difference was eliminated by increasing the target stimulus duration, indicating an attentional basis for this effect. Premature errors were, however, greater in males than in females, suggesting greater impulsivity in males. Subsequent experiments in gonadectomized rats suggest that circulating hormones influence attention and impulsivity, but not necessarily sex differences. These results demonstrate a double dissociation between components of impulse control and divided attention in male and female rats and may have implications for sex differences in disorders of attention and cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A kinematic analysis of sex-typical movement patterns used during evasive dodging to protect a food item: The role of testicular hormones.

Feeding rats dodge laterally away from a conspecific attempting to steal their food. Dodges by female and male rats differ in their composition of movement. Females pivot around a point more posterior on the longitudinal axis than do males, producing a greater amount of movement of the snout in relation to the pelvis. This experiment examined the role of testicular hormones on these sex-typical movement patterns. Castration at weaning (21 days) does not affect the male-typical pattern. Neonatal testicular hormone manipulation, however, does alter sex-typical patterns of movements. Whereas castration neonatally makes male rats more female-like, injections of neonatal female rats with testosterone propionate make them more male-like. These findings suggest that the organization of sex-typical patterns of dodging involves perinatal action of gonadal hormones. Results are discussed in relation to anatomy, neural structure, and the role of gonadal hormones during development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of female hormonal condition on body weight of male partners: Dependence on testicular factors.

Four experiments explored the short-term effects of female estrous condition or gonadal hormones on body weight (BW) of male guinea pigs. The BW of male Ss and their ovulating female partners initialy showed a significant periovular suppression relative to those of female cagemates that were not ovulating at that time. Similar effects in male rats have been hypothesized to result from postcopulatory increases in circulating testosterone (TTT) and the conversion of that TTT to estradiol (ED). To evaluate the role of the guinea pig testes in this phenomenon, intact and castrated males were housed with ovariectomized females. Female estrus, induced by injecting the females with ED and progesterone, resulted in an immediate decline in BW of the intact male partners, but the BW of castrated male partners was unaffected. Additional tests evaluated the direct effects of ED and TTT on BW of males. Injections of up to 1 mg per day of TTT propionate were insufficient to produce short-term suppression of BW in either intact or castrated males. However, treatment of the males with ED readily reduced their BW. Overall, results are not consistent with the hypothesis that short-term reductions in BW of mated males result from immediate postcopulatory increases in circulating TTT. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)