Seasonal and social correlates of fecal testosterone and cortisol levels in wild male muriquis (Brachyteles arachnoides).

Seasonal and social influences on fecal androgen and glucocorticoid excretion in wild male long-tailed macaques (Macaca fascicularis).

The aim of this study was to examine effects of seasonal and social factors on male androgen excretion in a seasonally breeding primate living in multimale-multifemale groups. By combining detailed behavioural observations (>2,500 h) on 3 groups of redfronted lemurs living in Kirindy Forest/Madagascar with non-invasive hormone analysis of >800 faecal samples collected concomitantly from the same animals, we tested predictions on: (1) the effect of social status on immunoreactive testosterone (iT) excretion; (2) seasonal variation of iT across reproductive periods; and (3) the relationship between aggression and iT excretion. The study lasted 14 months, covering two mating and one birth season. The results revealed that males fall into two distinct social classes, with one dominant male and several subordinate males in each group. In contrast to our prediction, the behavioural differences between these two classes were not reflected by differences in androgen levels, making physiological suppression of testicular function an unlikely mechanism of male reproductive competition. As expected for a seasonally breeding animal, iT values were elevated during the mating season. Androgen levels tracked the increase in the rate of reproductive aggression during the mating season as predicted by the challenge hypothesis. An increase in aggression due to spontaneous social instability outside the mating season, however, was not linked to a parallel rise of iT. Furthermore, the highest iT levels were obtained during the birth season, which may be part of a male strategy to remain aggressive during this period of high infanticide risk. These findings suggest that redfronted lemurs do not respond with increases in androgens to short-term challenges and that high androgen levels instead correlate with longer-lasting and predictable situations, such as the mating and birth seasons.

Seasonal variation and social correlates of androgen excretion in male redfronted lemurs (Eulemur fulvus rufus)

An import role for gonadal steroid hormones, particularly testosterone, in mediating aggressive behavior is well‐established across vertebrate taxa. Due to the emphasis placed on testosterone much less is know regarding the potential role of other steroid and peptide hormones in the regulation of aggression. The idea that any single hormone mediates aggression, however, is overly simplistic. In fact, research over the last two decades or more have has suggested that aggression in a complex behavior that is regulated by a wide range of hormones in addition to testosterone. This chapter reviews several novel neuroendocrine mechanisms that have been recently identified as being implicated in the regulation of aggressive behavior. Specific focus is placed on studies conducted in rodents, birds and primates, as the majority of research in this area has focused on these groups of animals. List of Abbreviations: ACTH, adrenocorticotropic hormone; ADHD, attention deficit hyperactivity disorder; AE, androstenedione; ALLO, allopregnanolone; AR, androgen receptor; Aromatase, cytochrome P450 aromatase; AVP, arginine vasopressin; AVT, arginine vasotocin; BERKO, estrogen receptor b knock‐ out; BNST, bed nucleus of the stria terminalis; CNS, central nervous system; CORT, cortisol; 5a‐DHT, 5a‐dihydrotestosterone; DHEA‐S, dehydroepiandrosterone sulfate; DHEA, dehydroepiandrosterone; E1, estrone; E2, 17b‐estradiol; ER, estrogen receptor; ERKO, estrogen receptor knock‐out; GABA, gamma‐ aminobutyric acid; 17b‐HSD, 17b‐hydroxysteroid dehydrogenase; 3b‐HSD, 3b‐hydroxysteroid dehydrogenase/isomerase; HP, hippocampus; HPA, hypothalamo‐pituitary‐adrenal; LD, light:dark; LH, luteinizing hormone; MPOA, medial preoptic area; N, nidopallium; NCM, caudomedial nidopallium; P450c17, cytochrome P450 17a‐hydroxylase/C17,20 lyase; P450scc, cytochrome P450 side chain cleavage; POA, preoptic areaPREG, pregnenolone; PROG, progesterone; RA, robust nucleus of the arcopallium; STI, simulated territorial intrusion; T, testosterone; Tn, nucleus taeniae of the amygdala; TP, testosterone propionate; VMN, ventromedial nucleus

Novel mechanisms underlying neuroendocrine regulation of aggression: A synthesis of rodent, avian, and primate studies

Salinomycin is used as an antibiotic in animal husbandry. Its implication in cancer therapy has recently been proposed. Present study evaluated the toxic effects of Salinomycin on male reproductive system of mice. Doses of 1, 3 or 5 mg/kg of Salinomycin were administered daily for 28 days. Half of the mice were sacrificed after 24 h of the last treatment and other half were sacrificed 28 days after withdrawal of treatment. Effects of SAL on body and reproductive organ weights were studied. Histoarchitecture of testis and epididymis was evaluated along with ultrastructural changes in Leydig cells. Serum and testicular testosterone and luteinizing hormones were estimated. Superoxide dismutase, reduced glutathione, lipid peroxidation, catalase and lactate dehydrogenase activities were measured. Spermatozoa count, morphology, motility and fertility were evaluated. Expression patterns of steroidogenic acute regulatory protein (StAR) and cytochrome P450 side chain cleavage proteins (CYP11A1) were assessed by Western blotting. Salinomycin treatment was lethal to few mice and retarded body growth in others with decreased weight of testes and seminal vesicles in a dose dependent manner. Seminiferous tubules in testes were disrupted and the epithelium of epididymis showed frequent occurrence of vacuolization and necrosis. Leydig cells showed hypertrophied cytoplasm with shrunken nuclei, condensed mitochondria, proliferated endoplasmic reticulum and increased number of lipid droplets. Salinomycin decreased motility and spermatozoa count with increased number of abnormal spermatozoa leading to infertility. The testosterone and luteinizing hormone levels were decreased in testis but increased in serum at higher doses. Depletion of superoxide dismutase and reduced glutathione with increased lipid peroxidation in both testis and epididymis indicated generation of oxidative stress. Suppressed expression of StAR and CYP11A1 proteins indicates inhibition of steroidogenesis. Spermatogenesis was however observed in testis 28 days after Salinomycin withdrawal. The results indicate reversible dose-dependent adverse effects of Salinomycin on male reproductive system of mice.

Dose-Dependent Adverse Effects of Salinomycin on Male Reproductive Organs and Fertility in Mice

The reproductive exocrine and endocrine profiles in male langurs are reported with an emphasis on seasonality. The animals showed positive response to electroejaculation throughout the year. The sperm concentration varied between 10-383 x 10(6)/ejaculation with wide fluctuations all through the year. No appreciable changes in the motility and percent live sperm were observed throughout the year. The levels of seminal fructose and magnesium remained unchanged throughout the year, while acid phosphatase showed wide fluctuations. Citric acid showed elevation during February and March and LDH showed elevated levels during April and May. The annual range of serum testosterone was 6-34 nMol/l with a peak during July. Cortisol ranged between 575-1587 nMol/l and prolactin ranged between 107-900 mU/l. Wide fluctuations were observed in hormonal levels. No seasonality was exhibited in the seminiferous tubule diameter, nuclear diameter of Sertoli cells and Leydig cells, and the cholesterol, glycogen, and sialic acid contents of testis. None of the parameters studied have shown any correlation with season. The results suggest that the male langurs lack seasonality in their reproductive exocrine and endocrine profiles and thus could be used as model for research in human reproduction.

B. Manivannan

Papers

Reproductive exocrine and endocrine profiles and their seasonality in male langur monkeys (Presbytis entellus entellus).