Coping with a challenging environment: effects of seasonal variability and reproductive status on glucocorticoid concentrations of female baboons (Papio cynocephalus).

Environmental stressors impact physiology and behavior in many species of animals. These effects are partly mediated through changing concentrations of glucocorticoids, which also vary with reproductive state and social conditions. Prior research has focused largely on seasonal breeders, but the close temporal linkage between season and reproductive state in these species hinders ability to disentangle environmental effects from those of the animal's reproductive status. Here we assessed the effects of environmental challenges on the fecal glucocorticoid (fGC) levels of non-seasonal breeders, female baboons (Papio cynocephalus) of Amboseli, Kenya. Amboseli is characterized by a long dry season, during which food and water become scarce, and by extreme temperatures above 40 degrees C in the shade during some months of the year. We found that after accounting for female reproductive status and individual variability, females exhibited higher fGC levels during the dry season than during the wet season. Further, during the wet season, fGC levels were higher in months of high average daily maximum temperatures. During the dry season, fGC levels were elevated both in hotter months and in months during which the baboons spent a relatively high proportion of time feeding. In spite of these stressors, female baboons reproduce during all months of the year in Amboseli, unlike most other mammals in this environment. This may be attributable to their extreme adaptability, specifically their diversified diet, and their ability to modify their behavior, including their activity profiles.

Persistence of maternal effects in baboons: Mother's dominance rank at son's conception predicts stress hormone levels in subadult males.

Dominance status and reproductive experience are maternal characteristics that affect offspring traits in diverse taxa, including some cercopithecine primates. Maternal effects of this sort are widespread and are sources of variability in offspring fitness. We tested the hypothesis that maternal dominance rank and reproductive experience as well as a male's own age and dominance rank predicted chronic fecal glucocorticoid (fGC) concentrations in 17 subadult wild male baboons, Papio cynocephalus (median age 6.5 years), in the Amboseli basin, Kenya. Among these variables, maternal dominance rank at a subadult male's conception was the sole significant predictor of the male's fGC and accounted for 42% of fGC variance; sons of lower ranking mothers had higher fGC than did those of high-ranking mothers. This result is striking because subadult male baboons are approximately 4-6 years past the period of infant dependence on their mothers, and are larger than and dominant to all adult females. In addition, many males of this age have survived their mothers' death. Consequently, the influence of maternal dominance rank persisted well beyond the stage at which direct maternal influence on sons is likely. Persistence of these major maternal influences from the perinatal period may signal organizational effects of mothers on sons' HPA axis. Although short-term, acute, elevations in GC are part of adaptive responses to challenges such as predators and other emergencies, chronically elevated GC are often associated with stress-related pathologies and, thereby, adverse effects on fitness components.

Mechanisms of sexual selection: sexual swellings and estrogen concentrations as fertility indicators and cues for male consort decisions in wild baboons.

Male mate-guarding episodes ('consortships'), are taxonomically widespread, yet costly to individual males. Consequently, males should bias consortships toward females with whom the probability of conception is high. We combined data on consortships with visual scoring of sexual swellings and assays of fecal estrogen concentrations (fE) in a wild population of baboons (Papio cynocephalus) to test the hypotheses that sexual swellings are reliable indicators of (1) within-cycle timing of ovulation, (2) differences in conception probability among females that differ in maturational stage, and (3) conceptive versus non-conceptive cycles of parous females. We also evaluated whether adult males might rely on swellings or other estrogen-dependent signals (e.g., fE) for mate-guarding decisions. We found that sexual swellings reflected conception probability within and among cycles. Adult males limited their consortships to the turgescent phase of cycles, and consorted more with adult females than with newly cycling adolescents. The highest ranking (alpha) males discriminated more than did males of other ranks; they (1) limited their consortships to the 5-day peri-ovulatory period, (2) consorted more with adult than with adolescent females, and (3) consorted more with adult females on conceptive cycles than on non-conceptive cycles, all to a greater extent than did males of other ranks. Male mate choice based on sexual swellings and other estrogenic cues of fertility may result in sexual selection on these female traits and enhance dominance-based reproductive skew in males. Alpha males are the least constrained in their mating behavior and can best take advantage of these cues to mate selectively.

In vitro study of the effects of khat (Catha edulis Forsk) extract on isolated mouse interstitial cells.

Isolated mouse interstitial cells were incubated with different concentrations of khat (Catha edulis) extract (0.06 mg/ml, 0.6 mg/ml, 6 mg/ml, 30 mg/ml and 60 mg/ml) and cell viability as well as testosterone concentration measured at 30 min intervals over a 3h incubation period. High concentrations of khat extract (30 mg/ml and 60 mg/ml) significantly inhibited testosterone production while low concentrations (0.06 mg/ml, 0.6 mg/ml and 6 mg/ml) significantly stimulated (P<0.05) testosterone production by mouse interstitial cells. Similarly, at concentrations of 30 mg/ml and 60 mg/ml, there was a significant decrease in interstitial cell viability, whereas at 0.06 mg/ml, 0.6 mg/ml and 6 mg/ml there was no significant decrease. There was only a weak correlation (r=0.39) between testosterone production and viable interstitial cells. We postulate that khat extract at high concentrations may cause reproductive function impairment in the user but at low concentrations, may enhance testosterone production with accompanying effects on reproductive functions in male mice.

The endocrinology of pregnancy and fetal loss in wild baboons.

An impressive body of research has focused on the mechanisms by which the steroid estrogens (E), progestins (P), and glucocorticoids (GC) ensure successful pregnancy. With the advance of non-invasive techniques to measure steroids in urine and feces, steroid hormones are routinely monitored to detect pregnancy in wild mammalian species, but hormone data on fetal loss have been sparse. Here, we examine fecal steroid hormones from five groups of wild yellow baboons (Papio cynocephalus) in the Amboseli basin of Kenya to compare the hormones of successful pregnancies to those ending in fetal loss or stillbirth. Using a combination of longitudinal and cross-sectional data, we analyzed three steroid hormones (E, P, GC) and related metabolites from 5 years of fecal samples across 188 pregnancies. Our results document the course of steroid hormone concentrations across successful baboon pregnancy in the wild and demonstrate that fecal estrogens predicted impending fetal loss starting 2 months before the externally observed loss. By also considering an additional 450 pregnancies for which we did not have hormonal data, we determined that the probability for fetal loss for Amboseli baboons was 13.9%, and that fetal mortality occurred throughout gestation (91 losses occurred in 656 pregnancies; rates were the same for pregnancies with and without hormonal data). These results demonstrate that our longstanding method for early detection of pregnancies based on observation of external indicators closely matches hormonal identification of pregnancy in wild baboons.

Khat (Catha edulis) up-regulates testosterone and decreases prolactin and cortisol levels in the baboon.

The potential effect of Khat (Catha edulis, Celastraceae) on fertility in humans has not been elucidated. In this study, we used the olive baboon (Papio anubis, Cercopithecidae) to determine the effects of oral administration of khat on circulating hormones. In order to establish baseline hormonal levels, five male baboons were bled once a week for 1 month. The same baboons were then fed with crude khat juice extract once a week over a period of 2 months, and the effects on serum levels of cortisol, testosterone and prolactin determined using enzyme immunoassay (EIA) and radioimmunoassay (RIA). Subsequently, sampling was repeated for a further 1 month to determine the residual effect of khat. The results showed that khat administration causes a significant increase in the mean levels of testosterone while prolactin and cortisol levels were reduced. These effects were also evident 1 month post treatment and indicate khat may exert a transient effect on male fertility by interfering with the hormonal profiles.

Influence of age of mice on the susceptibility to murine schistosomiasis infection.

Intensity of human schistosomiasis infection increases with age, a peak being attained at early puberty. Hormones could be involved in the age-related changes in susceptibility to schistosomiasis. Male BALB / c mice were infected with Schistosoma mansoni either before or after puberty and worm numbers, cellular immune responses, hormonal levels and pathology analysed. Pre-puberty infected mice had a significantly higher number of adult worms (p < 0.05), more severe granulomas, higher mortality rate and higher proliferative responses as compared to post-puberty infected mice. Levels of the hormones were lower in the pre-puberty infected mice as compared to the post-puberty group early in the infection. Plasma levels of testosterone and luteinizing hormones decreased significantly (p < 0.05) in infected mice when compared to controls. Susceptibility to S. mansoni in male BALB / c mice seems to be influenced by levels of testosterone and luteinizing hormone at infection. Albeit, an infection with S. mansoni seems to lower the hormonal levels.

Coming of age: steroid hormones of wild immature baboons (Papio cynocephalus).

Large gaps exist in our knowledge about common patterns and variability in the endocrinology of immature nonhuman primates, and even normal hormonal profiles during that life stage are lacking for wild populations. In the present study we present steroid profiles for a wild population of baboons (Papio cynocephalus) from infancy through reproductive maturation, obtained by noninvasive fecal analyses. Fecal concentrations of glucocorticoid (fGC) and testosterone (fT) metabolites for males, and of fGC, estrogen (fE), and progestin (fP) metabolites for females were measured by radioimmunoassay (RIA). In males, infancy was characterized by high and declining levels of fGC and fT, whereas steroid concentrations were low during the juvenile years. During the months immediately prior to testicular enlargement, fT (but not fGC) concentration tended to increase. Males that matured early consistently had higher fT and fGC concentrations than those that matured late, but not significantly so at any age. Individual differences in fT concentrations were stable across ages, and average individual fT and fGC concentrations were positively correlated. For females, high and declining levels of fE characterized infancy, and values increased again after 3.5 years of age, as some females reached menarche by that age. Both fP and fGC were relatively low and constant throughout infancy and the juvenile period. During the months immediately prior to menarche, fGC concentration significantly decreased, while no changes were observed for fE levels. fP exhibited a complicated pattern of decrease that was subsequently followed by a more modest and nonsignificant increase as menarche approached. Early- (EM) and late-maturing (LM) females differed only in fP concentration; the higher fP concentrations in EM females reached significance at 4-4.5 years of age. Maternal rank at offspring conception did not predict concentrations of any hormone for either sex. Our results demonstrate the presence of individual endocrine variability, which could have important consequences for the timing of sexual maturation and subsequently for individual reproductive success. Further evaluation of the factors that affect hormone concentrations during the juvenile and adolescent periods should lead to a better understanding of mechanisms of life-history variability.

Progesterone, estradiol and their receptors in leiomyomata and the adjacent normal myometria of black Kenyan women.

The contents of progesterone and oestrogen, and their respective receptors in uterine leiomyomata and adjacent normal myometrial tissue in indigenous black women in Kenya were studied. A random selection of twenty women undergoing hysterectomy for uterine fibroids at Kenyatta National Hospital was used for the studies. The myometria contained higher levels of E(2 ) (181% : P < 0.001); and P(4 ) (240.6 % : P < 0.001); as compared to the leiomyomata. On the other hand uterine leiomyomata contained significantly higher levels of ER (147.6% : P < 0.001); and PR (178.7% : P < 0.001 ); than normal myometria. These findings differ slightly from those reported in black women in developed countries, but support the proposal that manipulation of sex steroids may be useful in the treatment and management of uterine leiomyomata.