Adult Testosterone Levels Research Articles

Relationships among Musical Aptitude, Digit Ratio and Testosterone in Men and Women

Circulating adult testosterone levels, digit ratio (length of the second finger relative to the fourth finger), and directional asymmetry in digit ratio are considered sexually dimorphic traits in humans. These have been related to spatial abilities in men and women, and because similar brain structures appear to be involved in both spatial and musical abilities, neuroendocrine function may be related to musical as well as spatial cognition. To evaluate relationships among testosterone and musical ability in men and women, saliva samples were collected, testosterone concentrations assessed, and digit ratios calculated using standardized protocols in a sample of university students (N = 61), including both music and non-music majors. Results of Spearman correlations suggest that digit ratio and testosterone levels are statistically related to musical aptitude and performance only within the female sample: A) those females with greater self-reported history of exposure to music (p = 0.016) and instrument proficiency (p = 0.040) scored higher on the Advanced Measures of Music Audiation test, B) those females with higher left hand digit ratio (and perhaps lower fetal testosterone levels) were more highly ranked (p = 0.007) in the orchestra, C) female music students exhibited a trend (p = 0.082) towards higher testosterone levels compared to female non-music students, and D) female music students with higher rank in the orchestra/band had higher testosterone levels (p = 0.003) than lower ranked students. None of these relationships were significant in the male sample, although a lack of statistical power may be one cause. The effects of testosterone are likely a small part of a poorly understood system of biological and environmental stimuli that contribute to musical aptitude. Hormones may play some role in modulating the phenotype of musical ability, and this may be the case for females more so than males.

Chromosome Y Regulates Survival Following Murine Coxsackievirus B3 Infection

Coxsackievirus B3 (CVB3) contributes to the development of myocarditis, an inflammatory heart disease that predominates in males, and infection is a cause of unexpected death in young individuals. Although gonadal hormones contribute significantly to sex differences, sex chromosomes may also influence disease. Increasing evidence indicates that Chromosome Y (ChrY) genetic variants can impact biological functions unrelated to sexual differentiation. Using C57BL/6J (B6)-ChrY consomic mice, we show that genetic variation in ChrY has a direct effect on the survival of CVB3-infected animals. This effect is not due to potential Sry-mediated differences in prenatal testosterone exposure or to differences in adult testosterone levels. Furthermore, we show that ChrY polymorphism influences the percentage of natural killer T cells in B6-ChrY consomic strains but does not underlie CVB3-induced mortality. These data underscore the importance of investigating not only the hormonal regulation but also ChrY genetic regulation of cardiovascular disease and other male-dominant, sexually dimorphic diseases and phenotypes.

Second to fourth digit ratio, adult testosterone level and testosterone deficiency

The ratio of the second and fourth finger lengths (2D/4D) is related to intrauterine exposure to testosterone. The relationship between 2D/4D and adult hormonal pattern is controversial. The aim of our study was to determine if there was a relationship between adult serum testosterone levels and the 2D/4D ratio. We prospectively recruited 204 consecutive patients referred for transrectal prostate biopsy between January 2008 and June 2009. The same physician performed clinical examinations, 2D/4D measurements and the transrectal biopsy in all cases. Cut-off points of 231 and 346 ng/dL testosterone (8 and 12 nmol/L) were used. 2D/4D determination was done with a vernier calliper on the left hand. The hormonal profile (testosterone and sexual hormone binding globulin) of the patients was determined between 7.00 am and 11.00 am. Age, weight, height, body mass index, toxic habits, digital rectal examination, prostate-specific antigen and 2D and 4D measurements were recorded prospectively. The mean age was 67 ± 7 years and the mean testosterone level was 413 ± 18 ng/dL (14.33 ± 0.62 nmol/L). The percentages of patients with testosterone <231 ng/dL (8 nmol/L) and testosterone <346 ng/dL (12 nmol/L) were 6.1 and 30.6 respectively. Univariate analysis showed that low 2D/4D ratios were related to higher levels of testosterone (B=-741.98; β=-0.165, P= 0.045) and also with low prevalence of biochemical hypogonadism (testosterone <346 ng/dL). Mean 2D/4D ratio in patients with testosterone >346 ng/dL was lower than in patients with testosterone <346 ng/dL (2D/4D 0.97 ± 0.037 vs 0.99 ± 0.043 depending on their hormonal status, P= 0.05). High 2D/4D ratio was associated with low testosterone serum levels (P= 0.046). The 2D/4D ratio is related to adult testosterone levels and the presence of testosterone deficiency syndrome. Patients with high 2D/4D ratios have lower testosterone levels and higher risk of testosterone deficiency syndrome.

Quantitative measurement of salivary testosterone in Korean adults by stable isotope-dilution liquid chromatographyelectrospray-tandem mass spectrometry

Salivary testosterone levels in Korean adults were quantitatively measured for the first time by liquid chromatography-electrospray-tandem mass spectrometry (LC ESI MS/MS). Salivary testosterone was separated on a multiple reaction monitoring (MRM) chromatogram within 7 min. The LC ESI MS/MS assay was validated over the linearity range of 0.01-2.00 ng/ml (r=0.99987) using testosterone-d(3) as an internal standard. The lower limit of quantification (LOQ) was 0.01 ng/ml. The intra- and inter-assay precisions were 1.54% to 4.09% and 0.96% to 4.29%, respectively. The mean recovery was 93.32% (range 88.43-98.05%). The validated assay was then applied to measure the salivary testosterone levels of Korean adults. In men, the salivary testosterone level collected between 9:00-11:00 am was approximately 2.8 times higher than that in women (P < 0.0001). Salivary testosterone levels in both sexes negatively correlated with age. The present assay would also be useful in measuring salivary testosterone levels in clinical laboratories.

Social influences on plasma testosterone levels in morphine withdrawn adolescent mice and their drug-naïve cage-mates

Opioid administration in males results in opioid-induced androgen deficiency which persists throughout the treatment. In adults, this quickly reverses once opioid administration is suspended. However, less is known about the duration of the effect following drug discontinuation in adolescents. Given the significant implications to sexual maturation in adolescent males, this study examined plasma testosterone levels in both morphine withdrawn mice and their drug-naïve (saline-injected) cage-mates as compared to drug-naïve mice housed physically and visually separate from the morphine-treated mice ('saline only'). Consistent with the literature, plasma testosterone levels in morphine withdrawn adults were reduced on withdrawal day 1 (WD1) and returned to baseline levels by WD9. No significant effects were observed in their saline cage-mates. In the adolescents, no significant differences were observed on WD1 between the morphine withdrawn mice, their saline cage-mates, and the saline only mice - all of which had significantly lower plasma testosterone levels than adults. By WD9, testosterone levels in the saline only adolescent mice had reached adult levels. Notably, plasma testosterone levels were reduced in both the morphine withdrawn adolescent mice and their saline cage-mates, as compared to saline only mice. The effect was not a drug effect per se, given that reduced plasma testosterone levels were not observed in individually housed morphine withdrawn mice. Moreover, our results also suggest that these social effects are not solely explained by stress. These results have numerous implications to the short term and long term health of both adolescents requiring pain management and of adolescent drug addicts.

Testosterone related to age and life-history stages in male baboons and geladas

Despite significant advances in our knowledge of how testosterone mediates life-history trade-offs, this research has primarily focused on seasonal taxa. We know comparatively little about the relationship between testosterone and life-history stages for non-seasonally breeding species. Here we examine testosterone profiles across the life span of males from three non-seasonally breeding primates: yellow baboons (Papio cynocephalus or P. hamadryas cynocephalus), chacma baboons (Papio ursinus or P. h. ursinus), and geladas (Theropithecus gelada). First, we predict that testosterone profiles will track the reproductive profiles of each taxon across their respective breeding years. Second, we evaluate age-related changes in testosterone to determine whether several life-history transitions are associated with these changes. Subjects include males (>2.5 years) from wild populations of each taxon from whom we had fecal samples for hormone determination. Although testosterone profiles across taxa were broadly similar, considerable variability was found in the timing of two major changes: (1) the attainment of adult levels of testosterone and (2) the decline in testosterone after the period of maximum production. Attainment of adult testosterone levels was delayed by 1 year in chacmas compared with yellows and geladas. With respect to the decline in testosterone, geladas and chacmas exhibited a significant drop after 3 years of maximum production, while yellows declined so gradually that no significant annual drop was ever detected. For both yellows and chacmas, increases in testosterone production preceded elevations in social dominance rank. We discuss these differences in the context of ecological and behavioral differences exhibited by these taxa.

169. SERTOLI CELL-SPECIFIC DISRUPTION OF THE ANDROGEN RECEPTOR DNA-BINDING DOMAIN REVEALS DIFFERENTIAL TEMPORAL CONTROL OF DISTINCT ANDROGEN-REGULATED GENES

Androgen receptor (AR) actions are vital for spermatogenesis. However, in postnatal development male germ cells do not express AR, highlighting its key role in testicular somatic cells. We recently used a Cre-loxP strategy to determine the in vivo requirement of AR DNA-binding in Sertoli cell (SC) function. Transgenic (Tg) mice with Cre expression targeted by SC-specific AMH or Abp promoters were crossed with floxed-Ar (Arflox) mice for Cre-loxP inframe deletion of Ar exon 3, which encodes a zinc finger essential for the DNA-binding domain (DBD). SC-specific mutated ARΔex3 (SCARΔex3) produced infertile AMH.SCARΔex3 and Abp.SCARΔex3 males. Testes from adult homozygous TgCre(+/+) AMH.SCARΔex3 or Abp.SCARΔex3 males were 30% of normal size and exhibited meiotic arrest, whereas testes from hemizygous TgCre(+/–) Abp.SCARΔex3 males were larger (47% normal) with more postmeiotic germ cell development. Despite marked Leydig cell hypertrophy, testicular expression of the adult Leydig marker Hsd3b6 (RT-PCR) and normal intratesticular testosterone levels (LC-MS/MS) in SCARΔex3 males indicated the presence of morphologically distinct but functional adult Leydig cells. SC-specific mutated AR Δex3 was predicted to disrupt classical AR-regulated pathways via loss of direct DNA interaction. Androgen-repressed testicular Ngfr expression (known to be via non-classical AR pathways) was not upregulated in SCARΔex3 testes, suggesting maintenance of a non-classical mechanism independent of AR-DBD. In contrast, SC-specific Rhox5 and Eppin transcription, regulated by divergent or classical androgen-response elements respectively, were both decreased in postnatal SCARΔex3 vs. control testes, demonstrating SC-specific AR function as early as postnatal day 5. However, Rhox5 expression declined dose-dependently, whereas Eppin expression increased, in adult TgCre(+/−) and TgCre(+/+) SCARΔex3 testes, revealing differential temporal control for distinct AR-regulated transcripts. Thus, our SCARΔex3 paradigm displayed dose-dependent TgCre-disruption of meiotic competence and post-meiotic development as well as gene expression, and represents a unique model to selectively differentiate AR-regulated genes.

Maternal 2nd to 4th digit ratio does not predict lifetime offspring sex ratio at birth

The low ratio of second-to-fourth digit length (2D:4D) of parents, a putative indicator of high prenatal and even adult testosterone levels, has been suggested to predict a male-biased secondary offspring sex ratio. We investigated this question in 244 contemporary postreproductive Finnish women. Information on the lifetime offspring birth sex ratio of women was collected by questionnaires and the 2D:4D of both their hands were measured from scanned photographs. We found no evidence that the right hand 2D:4D, the left hand 2D:4D, the mean of the right and the left hand 2D:4D, or the difference between the right and the left hand 2D:4D was related to offspring sex ratio at birth among these women. Our results thus do not support the suggestion that offspring birth sex ratio is related to 2D:4D in women.

Involvement of testicular growth factors in fetal Leydig cell aggregation after exposure to phthalate in utero

Exposures to di-(2-ethylhexyl) phthalate (DEHP) have been shown to be associated with decreased adult testosterone (T) levels and increased Leydig cell numbers. As yet, little is known about DEHP effects in utero on fetal Leydig cells (FLC). The present study investigated effects of DEHP on FLC function. Pregnant Long-Evans female rats received vehicle (corn oil) or DEHP at 10, 100, or 750 mg/kg by oral gavage from gestational day (GD)2-20. At GD21, T production, FLC numbers and distribution, and testicular gene expression were examined. The percentage of FLC clusters containing 6-30 cells increased in all treatment groups, with 29 +/- 2% in control vs. 37 +/- 3, 35 +/- 3, and 56 +/- 4% in rats receiving 10, 100, and 750 mg/kg DEHP, respectively. In contrast, FLC numbers were 33% and 39% lower than control after exposures to 100 and 750 mg/kg DEHP, respectively. At these doses, mRNA levels of leukemia inhibitory factor (LIF) increased. LIF was found to induce cell aggregation in FLCs in vitro, consistent with the hypothesis that DEHP induced FLC aggregation. Testicular T levels were doubled by the 10 mg/kg dose and halved at 750 mg/kg. The mRNA levels of IGF-1 and c-Kit ligand (KITL) were induced by 10 mg/kg DEHP. These results, taken together, indicate that fetal exposures to DEHP have effects on FLC number, distribution, and most importantly, steroidogenic capacity and suggest that abnormal expressions of IGF1, KITL, and LIF genes may contribute to the reproductive toxicity of phthalates.

In Utero Exposure to Di-(2-ethylhexyl) Phthalate Exerts Both Short-Term and Long-Lasting Suppressive Effects on Testosterone Production in the Rat1

We examined the effects of fetal exposure to a wide range of di-(2-ethylhexyl) phthalate (DEHP) doses on fetal, neonatal, and adult testosterone production. Pregnant rats were administered DEHP from Gestational Day (GD) 14 to the day of parturition (Postnatal Day 0). Exposure to between 234 and 1250 mg/kg/day of DEHP resulted in increases in the absolute volumes of Leydig cells per adult testis. Despite this, adult serum testosterone levels were reduced significantly compared to those of controls at all DEHP doses. Organ cultures of testes from GD20 rats exposed in utero to DEHP showed dose-dependent reductions in basal testosterone production. Surprisingly, however, no significant effect of DEHP was found on hCG-induced testosterone production by GD20 testes, suggesting that the inhibition of basal steroidogenesis resulted from the alteration of molecular events upstream of the steroidogenic enzymes. Reduced fetal and adult testosterone production in response to in utero DEHP exposure appeared to be unrelated to changes in testosterone metabolism. In view of the DEHP-induced reductions in adult testosterone levels, a decrease in the expression of steroidogenesis-related genes was anticipated. Surprisingly, however, significant increases were seen in the expression of Cyp11a1, Cy17a1, Star, and Tspo transcripts, suggesting that decreased testosterone production after birth could not be explained by decreases in steroidogenic enzymes as seen at GD20. These changes may reflect an increased number of Leydig cells in adult testes exposed in utero to DEHP rather than increased gene expression in individual Leydig cells, but this remains uncertain. Taken together, these results demonstrate that in utero DEHP exposure exerts both short-term and long-lasting effects on testicular steroidogenesis that might involve distinct molecular targets in fetal and adult Leydig cells.

Reversal of Idiopathic Hypogonadotropic Hypogonadism

Idiopathic hypogonadotropic hypogonadism, which may be associated with anosmia (the Kallmann syndrome) or with a normal sense of smell, is a treatable form of male infertility caused by a congenital defect in the secretion or action of gonadotropin-releasing hormone (GnRH). Patients have absent or incomplete sexual maturation by the age of 18. Idiopathic hypogonadotropic hypogonadism was previously thought to require lifelong therapy. We describe 15 men in whom reversal of idiopathic hypogonadotropic hypogonadism was sustained after discontinuation of hormonal therapy. We defined the sustained reversal of idiopathic hypogonadotropic hypogonadism as the presence of normal adult testosterone levels after hormonal therapy was discontinued. Ten sustained reversals were identified retrospectively. Five sustained reversals were identified prospectively among 50 men with idiopathic hypogonadotropic hypogonadism after a mean (+/-SD) duration of treatment interruption of 6+/-3 weeks. Of the 15 men who had a sustained reversal, 4 had anosmia. At initial evaluation, 6 men had absent puberty, 9 had partial puberty, and all had abnormal secretion of GnRH-induced luteinizing hormone. All 15 men had received previous hormonal therapy to induce virilization, fertility, or both. Among those whose hypogonadism was reversed, the mean serum level of endogenous testosterone increased from 55+/-29 ng per deciliter (1.9+/-1.0 nmol per liter) to 386+/-91 ng per deciliter (13.4+/-3.2 nmol per liter, P<0.001), the luteinizing hormone level increased from 2.7+/-2.0 to 8.5+/-4.6 IU per liter (P<0.001), the level of follicle-stimulating hormone increased from 2.5+/-1.7 to 9.5+/-12.2 IU per liter (P<0.01), and testicular volume increased from 8+/-5 to 16+/-7 ml (P<0.001). Pulsatile luteinizing hormone secretion and spermatogenesis were documented. Sustained reversal of normosmic idiopathic hypogonadotropic hypogonadism and the Kallmann syndrome was noted after discontinuation of treatment in about 10% of patients with either absent or partial puberty. Therefore, brief discontinuation of hormonal therapy to assess reversibility of hypogonadotropic hypogonadism is reasonable. (ClinicalTrials.gov number, NCT00392756 [ClinicalTrials.gov].).

Glucocorticoid hormone levels increase with group size and parasite load in cliff swallows

Animals often cope with adverse events by releasing glucocorticoid hormones, which in turn promote increased energy assimilation. In captive animals, crowding also leads to increased glucocorticoid activity, probably because of increased levels of social competition. We investigated how group size and ectoparasite infestations affected endogenous levels of the glucocorticoid hormone, corticosterone, in colonial cliff swallows, Petrochelidon pyrrhonota, in southwestern Nebraska, U.S.A. Parasites were removed from some colonies by fumigating nests. Baseline levels of corticosterone in breeding adults varied significantly with whether parasites were present, colony size (measured by total number of active nests at a site) and nesting stage. Across all analyses, birds from fumigated colonies averaged significantly lower baseline levels of corticosterone. These levels in adults increased with colony size at nonfumigated sites, especially during the period when nestlings were being fed, but no relation or the opposite one was found for birds in fumigated colonies. Baseline corticosterone levels were unrelated to sex, age, body weight or testosterone levels in adults. Corticosterone concentrations tended to increase during a bad-weather event when food was scarce. Patterns in nestling and recently fledged juveniles were consistent with those in adults. The increased baseline levels of corticosterone in birds of larger colonies appear related to the larger number of parasites there. Higher levels of corticosterone probably facilitate increased allocation of time and energy to foraging and greater energy assimilation during challenging events such as bad weather, parasitism by blood-feeding bugs in large colonies and the period when young are becoming independent of their parents.

Diagnosis of hypogonadism in the aging male

The diagnosis of hypoandrogenism in the aging male is still difficult, since the symptomatology is aspecific and multifactorial, and it is unknown whether the androgen requirements of elderly men are thesame as those of young men. Indeed, there are arguments for decreased (increased androgen feed-back sensitivity) as well as for increased (decreased concentration of androgen receptors) requirements inelderly men. In the absence of a reliable, clinically useful, parameter of androgen activity, we have to rely on plasma androgen level, an indirect parameter. In the absence of convincing arguments foraltered requirements with age, we consider that the normal range of (free) testosterone levels in young adults is also valid for elderly men, the lower normal limit being 11 nmol/l for total testosteroneand 0.225 nmol/l for free testosterone. There are indirect, suggestive clinical arguments for accepting these limit values. The diagnosis of hypoandrogenism in elderly males requires both the presence ofclinical symptoms and decreased (free) testosterone levels. The best methods for determining free or bioavailable testosterone, are equilibrium dialysis and ammonium sulfate precipitation, respectively.They are, however, time-consuming techniques which are not easily automated. Calculation of the free androgen index (testosterone/sex hormone binding globulin (SHBG)) is not a valid method for male serum.Calculation of free testosterone from total testosterone, SHBG and albumin concentration, yields values that are in good agreement with values obtained by dialysis or ammonium sulfate precipitation. Severalconditions should, however, be fulfilled: reliable methods for the determination of testosterone and SHBG, SHBG measurement in serum and not in plasma, use of fresh serum (not repeatedly frozen and thawed),absence of (exogenous) steroids competing for binding sites on SHBG and blood samples taken between 08.00 and 10.00 in the fasting state. Under these conditions an excellent correlation with dialysis andbioavailable testosterone (ammonium sulfate precipitation) is generally obtained.

Antihormonal treatment during early development affects sexual function and behavior in male rats

The effects of early applied antihormones on different behavioral and physiological aspects of sexuality were investigated in male Wistar rats. Animals were pre- and perinatally treated with flutamide in a preliminary experiment, and postnatally treated with flutamide or tamoxifen in a second trial. The precopulatory and copulatory behavior patterns of each male in the presence of an estrus-induced female were video recorded and analyzed. Genital development was estimated by weight of the testes, seminal vesicle, prostate and preputial gland. Total testosterone levels were determined by RIA. Male precopulatory behavior was not diminished by treatment suggesting the independence of androgen and estrogen levels during the perinatal critical period. Postnatal flutamide treatment led to decreased testosterone levels in adults. In contrast, copulatory behavior and sexual development were impaired in all the treatment groups. The heterotypical behavior and socio-sexual interactions also observed were affected by the prenatal presence of flutamide.

Peripuberal sexual development of pantaneiro stallions

Pantaneiro horses are a breed native to flood plains of Brazil, where they thrive with little human interference. The aims of this study were to characterize age-associated changes in testicular size, serum testosterone and sexual behavior and to determine age at puberty as well as to evaluate daily sperm production in the Pantaneiro stallion. After weaning the males were kept in bachelor groups away from the females, in a separated area in the natural environment of flood plains. Infantile period ended at approximately 14.4 mo of age. Sexual interest and breeding capability first appeared between the ages of 15.6 to 27.5 mo. The transition from prepuberal to postpuberal histological stage, occurred at approximately 27.8 mo of age. All animals were in the postpuberal period at 38.5 mo of age. Daily sperm production estimated with testicle homogenate, at 38.5 mo of age was low (1.4603 ± 0.48X10 9 sperm) and serum testosterone levels were similar to adult levels by 27.8 mo. In conclusion the 2 y old Pantaneiro stallions showed full sexual behavior and had adult testosterone levels, but at this age, the stage of development of the seminiferous epithelium was variable and the efficiency of sperm production was still low.

Adult testosterone levels have little or no influence on dominance in men

There is substantial evidence that psychological factors influence human testosterone levels, but little support if any for an influence of circulating testosterone on dominance in men. Persistent interest in testosterone as an explanation of behaviors such as dominance and aggression might reflect the influence of cognitive schemas regarding race and sex rather than empirical evidence.

The role of glia in the neuroendocrine hypothalamus: possible implications in hormone secretion.

Recent evidence indicates that glia may play a significant role in the link between the endocrine and nervous systems. Gonadal steroids modulate astroglia morphology, differentiation and gene expression in different brain areas. Hormonal effects on glia may have important consequences for neuronal development, metabolism and activity, for the formation and plasticity of synaptic connections, and for the modulation of hypothalamic hormone release. Perinatal and adult testosterone levels modulate the expression of the specific astroglia cytoskeletal marker glial fibrillary acidic protein in the arcuate nucleus of the rat hypothalamus. These changes parallel hormonal effects on the expression of growth hormone-releasing hormone (GHRH) and the number of GHRH neurones in the arcuate nucleus. The effects of testosterone and its metabolite oestradiol on hypothalamic neurones may be dependent on the release by hypothalamic astroglia of insulin-like growth factor I, a molecule involved in the control of growth hormone secretion.

Climate, trophic factors, and breeding patterns of the Nile grass rat (Arvicanthis niloticus solatus): a 5-year study in the Sahelian region of Burkina Faso (formerly Upper Volta)

From 1984 to 1989, five populations of the Nile grass rat, Arvicanthis niloticus solatus, living in five different habitats of the Sahelian region were studied in northern Burkina Faso (Oursi, 14°N). The following were investigated: (i) seasonal variations in the percentages of sexually active males and females and the percentage of the population less than 6 weeks old, and (ii) seasonal variations in testis and seminal vesicle masses and plasma testosterone levels in adults. Both the large form of A. niloticus occupying habitats with stable trophic resources and the small form of the species occupying habitats with fluctuating resources showed seasonal breeding, mainly in the dry season, in contrast with what we have observed elsewhere in other species in this region. In dry years with normal rainfall (rains between June and September), breeding occurred from mid-October to mid-July in habitats with constant trophic resources and from mid-October to mid-April in habitats with fluctuating resources. In 1986, a year with exceptional rainfall (additional rains in January), breeding was continuous in habitats where this climatic disturbance caused a reappearance of primary production and there was a population outbreak of A. n. solatus. Relationships between (i) breeding cycles, (ii) long-day periods, which have a gonadoinhibitory effect, (iii) seasonal variations in relative humidity and temperature, and (iv) dietary characteristics of A. n. solatus suggest that this subspecies is capable of breeding throughout the year. This is due to its adaptable dietary habits, which allow it to take advantage of resources that are either constant (insects, harvest wastes, and the water-rich bark of certain woody plants) or seasonal (rain-dependent herbaceous plants and farm vegetables). The end of breeding appears to be related to the relative timing of the stimulatory effect of certain foods and the inhibitory effects of photoperiod, temperature, and humidity. Under this hypothesis, the gonadoinhibitory effect of long days was masked in 1986 by an earlier stimulatory effect related to the reappearance of vegetation following the exceptionally heavy rainfall in January.

Dermatoglyphic asymmetry and testosterone levels in normal males

Dermatoglyphic prints and salivary samples were taken on a sample of 39 adult males. A statistical relationship between dermatoglyphic asymmetry and adult testosterone levels as measured in saliva was examined for seven dermatoglyphic variables by means of correlation, regression, and analysis of covariance, controlling for age and stature when necessary. The first two types of analyses indicated a significant effect of testosterone level upon the asymmetry of three dermatoglyphic variables: a-b ridge count, palmar pattern intensity, and the combined pattern intensity of palm and digits. Analysis of covariance, which examined the effect of testosterone level as a categorical variable, while holding age or stature constant, demonstrated the asymmetry of five variables to be significantly affected by testosterone level: radial digital count, digital pattern intensity, palmar pattern intensity, total digital ridge count, and the combined palmar and digital intensity. Although there is as yet only associational evidence linking levels of prenatal and secondary testosterone, the results of the present study lend support to the hypothesis that prenatal testosterone levels may have a significant effect on the development of dermatoglyphics.

Prenatal stress reduces fertility of male offspring in mice, without affecting their adult testosterone levels

The male offspring of mice stressed by crowding during the final third of pregnancy showed reductions in sexual behavior and fertility. When paired with receptive females, their latencies to mount and to achieve intromission and ejaculation were greater than controls, and 30% of them failed to ejaculate in the 100-min test. When housed continuously for 4 days with females, 31% of them failed to impregnate their partners, compared with 4% of controls. The sexual receptivity of the untreated females paired with prenatally stressed males was not affected. Resting testosterone levels of prenatally stressed males did not differ from those of controls, and the pattern of rise and fall of testosterone during a 60-min interaction with a female showed only minor differences. The results suggest a central, rather than peripheral, mediation of the behavioral effects of prenatal Stress.