Sex differences in adrenal cortex beta-catenin immunolocalisation of the Saharan gerbil, Libyan jird (Meriones libycus, Lichtenstein, 1823).

BACKGROUND: The adrenal cortex provides adequate steroidogenic responses to environmental changes. However, in desert rodents, the adrenocortical activity varies according to several factors especially sex, age, and seasonal variations. Herein, we examined the sex differences in the adrenal cortex activity and explored the involvement of sex hormones in the regulation of this function in Libyan jird Meriones libycus. MATERIALS AND METHODS: Twenty-four adult male and female animals weighing 109-110 g were captured in the breeding season and equally assigned into control and gonadectomised groups. Animal euthanasia was performed 50 days after the gonadectomy. Adrenal gland was processed for structural and immunohistochemistry study of b-catenin, whereas plasma was used for cortisol assay. RESULTS: The results showed that female adrenal gland weight was heavier than male and gonadectomy reduced this dimorphism. The adrenal cortex thickness was greater in the female than in the male, mainly due to significant development of the zona fasciculata. Females presented higher cell density in fasciculata and reticularis zones. The plasma cortisol was higher in females than in males. The immunolocalisation of beta-catenin showed that the expression was particularly glomerular in both sexes. However, in the female, the immunostaining was present in the zona reticularis while it was absent in the control male. Orchiectomy reduced zona glomerulosa cell density and induced hypertrophy of zona reticularis characterised by strong beta-catenin immunoreactivity. CONCLUSIONS: Results indicated that sex hormones had a major role in the regulation of the Saharan gerbil's adrenal homeostasis by modulating beta-catenin signalling. Androgens seem to inhibit the Wnt-beta-catenin pathway and oestrogens are activators of the adrenal inner zones.

Apoptosis in epididymis of sand rat Psammomys obesus, Cretzschmar, 1828: Effects of seasonal variations, castration and efferent duct ligation.

The aim of this study was to visualize apoptosis throughout the reproductive cycle and after castration, castration then treatment with testosterone, and ligation of efferent ducts. The sand rat, Psammomysobesus, Cretzschmar 1828, is a diurnal rodent belonging to the family Gerbillidae. Its breeding cycle is seasonal with reproduction in autumn, winter and early spring and a short resting period from late spring to early summer. Five groups of males were studied: (1) animals captured during the breeding season; (2) animals captured during the resting season; (3) animals castrated and kept 30 days; (4) animals castrated, kept 30 days, and then treated with testosterone for 15 days; (5) animals subjected to the ligation of efferent ducts and kept 30 days. Epididymis were removed and the presence of apoptotic cells was explored using the "Apostain" immunohistochemical method. Histological results showed cell and tissue remodeling. During the breeding season, a positive apoptotic signal was observed mainly in smooth muscle cells of caput and cauda epididymis. This signal persisted throughout the resting season. The orchiectomy induced apoptosis in almost of epithelial and connective cells. However, this intense cell death was not reversed by treatment with testosterone. In animals that experienced efferent duct ligation, principal cells and smooth muscle cells showed a positive signal for apoptosis. Our results converge to qualify the sand rat epididymis as an excellent model for the study of apoptosis and argue for continued cell death, at least independent of circulating testosterone levels.

Expression of adenosine 5'-monophosphate-Activated protein kinase (AMPK) in ovine testis (Ovis aries): In vivo regulation by nutritional state.

In the present study, we identified AMPK and investigated its potential role in steroidogenesis in vivo in the ovine testis in response to variation in nutritional status (fed control vs. restricted). We performed immunoblotting to show that both active and non-active forms of AMPK exist in ovine testis and liver. In testis, we confirmed these results by immunohistochemistry. We found a correlation between ATP (Adenosine-Triphosphate) levels and the expression of AMPK in liver. Also, low and high caloric diets induce isoform-dependent AMPK expression, with an increase in α2, ß1ß2 and γ1 activity levels. Although the restricted group exhibited an increase in lipid balance, only the triglyceride and HC-VLDL (Cholesterol-Very low density lipoprotein) fractions showed significant differences between groups, suggesting an adaptive mechanism. Moreover, the relatively low rate of non-esterified fatty acid released into the circulation implies re-esterification to compensate for the physiological need. In the fed control group, AMPK activates the production of testosterone in Leydig cells; this is, in turn, associated with an increase in the expression of 3ß-HSD (3 beta hydroxy steroid deshydrogenase), p450scc (Cholesterol side-chain cleavage enzyme) and StAR (Steroidogenic acute regulatory protein) proteins induced by decreased MAPK ERK½ (Extracellular signal-regulated kinase -Mitogen-activated protein kinase) phosphorylation. In contrast, in the restricted group, testosterone secretion was reduced but intracellular cholesterol concentration was not. Furthermore, the combination of high levels of lipoproteins and emergence of the p38 MAP kinase pathway suggest the involvement of pro-inflammatory cytokines, as confirmed by transcriptional repression of the StAR protein. Taken together, these results suggest that AMPK expression is tissue dependent.

Seasonal effects on plasma cortisol concentrations in the Bedouin buck: circadian studies and response to ACTH.

Our work aims at the exploration of cortisol secretion in the Bedouin goat, native to the Algerian Sahara desert, to understand the mechanisms of adaptation to extreme hot climates. In the present study, diurnal and seasonal variations of cortisol concentrations were measured in basal conditions, as well as the response to ACTH stimulation tests across seasons in bucks. The plasma concentrations of cortisol showed no diurnal cycle but a large variation across seasons. The highest levels occurred in summer and winter when the environmental conditions are at their extreme levels. The rectal temperature showed nychthemeral and seasonal variations, and BW was also different across seasons with highest values in summer and lowest in winter. The results obtained after administration of two doses (2 or 10 µg/kg BW) of synthetic ACTH to three different age groups (kids, adults and elderly animals) showed a strong increase in plasma cortisol concentrations under all conditions with maximum levels achieved between 15 and 120 min. The analysis of the area under the cortisol curve showed no significant difference between the responses to the two doses of ACTH and between age groups, but showed seasonal variations with the lowest response in autumn than in other seasons. We conclude that season significantly affects secretion of cortisol in both basal state and under ACTH stimulation. However, the variation of adrenal reactivity to ACTH is not sufficient to explain seasonal differences, and in particular the summer peak in basal circulating cortisol concentrations. Further research should focus on the respective contribution of environmental factors (such as day length, temperature, humidity) and the mechanisms involved in cortisol regulation.

Seasonal expression of KiSS-1 and the pituitary gonadotropins LHß and FSHß in adult male Libyan jird (Meriones libycus).

The molecular mechanisms operating on a seasonal time-scale and regulating functions such as reproduction are poorly understood in animals living in desert environments. Kisspeptin, the product of the KiSS-1 gene, plays a critical role in control of the hypothalamic-pituitary-gonad axis that orchestrates the reproductive system in vertebrates. We report a sequence analysis of KiSS-1 and the pituitary luteinising hormone-beta (LHß) and follicle-stimulating hormone-beta (FSHß) in the Libyan jird (Meriones libycus), a seasonal breeding rodent that is sexually active during spring and quiescent in fall. We also assessed gene expression by quantitative real-time reverse transcription-polymerase chain reaction during the non-breeding and breeding seasons. The KiSS-1 cDNA sequence analysis showed high homology between M. libycus and all other rodents (94%) and humans (92%). KiSS-1 expression was higher during the breeding season than that during the non-breeding season. In contrast, LHß and FSHß expression levels were higher during the non-breeding season in autumn and varied in an opposite manner with testicular, seminal vesicle weights and plasma testosterone levels. Our results extend the role for KiSS-1 in activating the HPG axis in this desert rodent in its natural biotope by relaying environmental cues as in other seasonal non-desert rodent models.

Ovarian function of the Algerian wild Libyan jird, Meriones libycus during seasonal reproductive cycle: histological and immunohistochemical expression.

Meriones libycus (Libyan jird), a nocturnal Saharan rodent, is characterized by a seasonal reproductive cycle with a short active phase (spring and early summer) and a long resting period (late summer, autumn, winter). Histological and immunohistochemical techniques were performed in order to study the seasonal variations in mature ovaries. During the breeding season, the ovary showed a continuous cyclical activity, the various stages of folliculogenesis from primordial to preovulatory follicles were observed; broken follicles and corpora lutea were also observed. During sexual quiescence, the ovarian cycle was interrupted; anovulation was observed without any corpus luteum. Non mature antral follicles entered the atretic process. Steroid and steroidogenic enzyme activities were studied using indirect immunohistochemistry. 17ß-estradiol, progesterone, testosterone hormones and P450 aromatase (P450 arom) were detected in the different components of the ovary and in various stages of healthy and atretic follicles during the seasonal reproductive cycle. Our results indicate that during ovarian folliculogenesis in breeding season steroids hormone and P450 arom present important activities. In comparison with the resting period, steroidogenesis and steroidogenic enzyme activity became less pronounced in the healthy preantral follicle; it seemed that steroid biosynthesis was reduced and could be involved in the stimulation and maintenance of the ovarian structural integrity in early follicle development. In conclusion, the histological and immunohistochemical seasonal variations of ovaries in Meriones libycus support the hypothesis that seasonal fluctuations are indirectly involved in regulating reproduction, inducing significant changes in both ovarian morphology and its hormonal function.

Pregnancy-associated glycoprotein and progesterone concentrations during pregnancy failure in Bedouin goat from the southwest of Algeria.

Thirteen female Bedouin goats living in arid land of Algeria Sahara desert were used in this study. These goats were pregnant but they sustained an abortion because of unidentified causes. None of the goats showed any signs of general disease. Plasma concentrations of caprine pregnancy-associated glycoproteins (cPAGs) and progesterone (P4) were determined during pregnancy using radioimmunoassay. The cPAGs concentration was undetectable (<0.8 ng/ml) throughout the first 2 weeks of gestation. From week 3 after mating, cPAGs concentration was detectable with significant individual variations (p < 0.05) reaching a maximum secretion (436.1 ng/ml). Throughout gestation, cPAGs concentration remained relatively constant but decreased few days before abortion, on an average of 9.2 ± 1.2 days (n = 11), except for two females where the concentrations decreased later (1-2 days before abortion). One or two peaks of cPAGs concentrations (in 4/13 and in 9/13 females, respectively) have been measured few weeks before abortion (77-124 days after mating), when a decline of cPAGs was detected. The P4 concentration increased after mating, and was high from the first week till the end of pregnancy. The P4 concentration (9.1 ± 0.9 ng/ml) decreased rapidly (<0.5 ng/ml) after 4 ± 0.7 days (n = 6) or 9.4 ± 1.6 days (n = 7) before abortion. A positive relationship (p < 0.01) was found between P4 and cPAGs concentrations during gestation. Results indicate that cPAGs and P4 measurements can be used for monitoring gestation and for abortion prediction.

Seasonal changes in plasma concentrations of gonadotropins and in the responsiveness of the pituitary and testis to GnRH in a desert rodent, the sand rat (Psammomys obesus).

The male sand rat (Psammomys obesus), captured alive in the Sahara desert in the area of Béni-Abbès (Algeria), exhibited seasonal changes in plasma concentrations of LH, characterized by an increase in early summer. Administration of a standard dose of GnRH (200 ng/100 g body weight) failed to elicit significant season-dependent changes in LH release, whereas the increase in plasma testosterone was maximum in June-July and quite small between November and March-April. The present results suggest that the summer seasonal onset of the testicular endocrine activity of the sand rat is due to increases both in LH release and in testis sensitivity to gonadotropin.

Seasonal changes in plasma testosterone concentrations in response to administration of hCG in a desert rodent, the sand rat (Psammomys obesus).

In adult male sand rats inhabiting the Béni-Abbès area (Algeria), testicular endocrine activity increased in early summer (June-July), was highest in autumn-winter and decreased throughout spring. Testosterone secretion by the testis of the sand rat was stimulated (by 10-60-fold) throughout the year by exogenously administered hCG (25 i.u.). However, the response exhibited annual changes mainly characterized by a marked increase in early summer (June-July); the response to hCG was depressed in autumn and became minimal in winter and in early spring. The results strongly suggest that the summer onset of testicular endocrine activity is, at least in part, due to an increase in the testis sensitivity to LH.

Seasonal changes in testicular contents and plasma concentrations of androgens in the desert gerbil (Gerbillus gerbillus).

Gerbils were caught in the Béni-Abbès area (Algeria). Testicular endocrine activity was highest in spring (testicular wt 298 +/- 10 mg; seminal vesicle wt 603 +/- 62 mg; testicular testosterone and androstenedione content 9.2 +/- 1.7 and 0.5 +/- 0.1 ng/testis; plasma testosterone 832 +/- 200 pg/ml). Values decreased in summer, were lowest in late summer and in autumn (84 +/- 17 mg; 40 +/- 14 mg; 0.20 +/- 0.06 and 0.02 +/- 0.01 ng/testis; 228 +/- 54 pg/ml, respectively) and increased again in winter (December-January). The onset of testicular endocrine activity was concomitant with the lowest temperatures and the shortest photoperiod; it increased when temperatures and daylength were increasing and began to decline when temperatures and photoperiod were still maximal. These seasonal changes in the endocrine activity of the testis of the gerbil differ from those of the sand rat inhabiting the same area.

Seasonal changes in testicular contents of testosterone and androstenedione and in the metabolic clearance rate of testosterone in the sand rat (Psammomys obesus).

Adult male sand rats (Psammomys obesus) were caught in the Béni-Abbès area. The highest testicular contents of androgens (ng/testis) were observed in autumn and in winter (testosterone: 7.6 +/- 1.1; androstenedione: 0.76 +/- 0.11) and the lowest in early summer (June) (testosterone: 1.5 +/- 0.3; androstenedione: 0.20 +/- 0.05). Values had increased by late July. Annual variations of the testosterone metabolic clearance rate (litres/24 h/100 g body wt) were similar to those of testicular androgens; values were high in winter (6.7 +/- 0.7) and lowest in June (3.2 +/- 0.3). The onset of testicular endocrine activity in sand rats was concomitant both with the highest temperatures and the start of reduction in photoperiod; its regression occurred when temperature and photoperiod were increasing.