Search Results (6)

Seasonal reproduction is a survival strategy by which animals adapt to environmental changes to improve their fitness. Males are often characterized by a significantly reduced testicular volume, indicating that they are in an immature state. Although many hormones, including gonadotropins, have played a role in testicular development and spermatogenesis, research on other hormones is insufficient. The anti-Müllerian hormone (AMH), which is a hormone responsible for inducing the regression of Müllerian ducts involved in male sex differentiation, was discovered in 1953. Disorders in AMH secretion are the main biomarkers of gonadal dysplasia, indicating that it may play a crucial role in reproduction regulation. A recent study has found that the AMH protein is expressed at a high level during the non-breeding period of seasonal reproduction in animals, implying that it may play a role in restricting breeding activities. In this review, we summarize the research progress on the AMH gene expression, regulatory factors of the gene’s expression, and its role in reproductive regulation. Using males as an example, we combined testicular regression and the regulatory pathway of seasonal reproduction and attempted to identify the potential relationship between AMH and seasonal reproduction, to broaden the physiological function of AMH in reproductive suppression, and to provide new ideas for understanding the regulatory pathway of seasonal reproduction. Full article

Testicular regression occurs during the non-breeding season in many mammals. This affects spermatogenesis, resulting in decreased or arrested activity. Both lead to a decrease or cessation in sperm production. In recent years, the cellular mechanisms that lead to infertility in males in non-reproductive periods have been studied in very different species of mammals. At the start of the present century, the main mechanism involved was considered as an increase in the apoptotic activity of germ cells during the regression period. The loss of spermatogonia and spermatocytes causes not only a decrease in spermatogenesis, but an arrest of the seminiferous epithelium activity at the end of regression. Recently, in some mammal species, it was found that apoptosis is the usual mechanism involved in epithelium activity arrest, although it is firstly atrophied by massive desquamation of the germ cells that are released from their binding with the Sertoli cells, and which are shed into the lumen of the seminiferous tubule. In other species, it has been shown that not only germ cell apoptosis, but also Sertoli cell apoptosis, including decreased proliferative activity, spermatophagy or autophagy, are involved in testicular regression. Furthermore, the most recent studies indicate that there are multiple patterns of seminiferous epithelium regression in seasonally breeding animals, which may not only be used by different species, but also by the same ones to reproduce in the best conditions, ensuring their survival. In conclusion, at this time, it is not possible to consider the existence of a paradigmatic cellular mechanism in the involution of the seminiferous epithelium applicable to all male mammals with seasonal reproduction, rather the existence of several mechanisms which participate to a greater or lesser extent in each of the species that have been studied to date. Full article

The present study was designed to elucidate a relationship between lymphoid organs and reproductive activity in male Japanese quails (Coturnix japonica) bred in a temperate region of Pakistan (30.3753° N, 69.3451° E) in response to photoperiodic changes. The research focused primarily on the relative morphological changes in primary (thymus and bursa of Fabricius) and secondary (spleen) lymphoid organs with respect to seasonal variations in the histomorphometry of testicular tissue. For this purpose, a comparable number of clinically healthy Japanese quails were exsanguinated during active (April–May), regressive (September–October) and inactive (January–February) reproductive phases. Following an extensive gross measurement of lymphoid and reproductive organs, a histomorphometric analysis was performed on sampled tissues by employing ImageJ^® software. Blood was collected for hormonal and leukocytic analysis. One-way ANOVA was used for statistical comparison. Testes had the highest parenchymal development in the active phase (80.66 ± 21.22 µm) and the lowest in the inactive phase (27.80 ± 7.22 µm). Conversely, a percentage change was evident in the sizes of primary (bursa: 61.5%, thymus: 46.9%) and secondary (spleen: 23.9%) lymphoid organs during inactive and active reproductive phases. This study demonstrated that a physiological trade-off is imperative between immune and reproductive systems for optimum survivability and reproductive performance. Full article

The quail Coturnix coturnix is a seasonal breeding species, with the annual reproductive cycle of its testes comprising an activation phase and a regression phase. Our previous results have proven that the testicular levels of both 17β-estradiol (E₂) and androgens are higher during the reproductive period compared to the non-reproductive period, which led us to hypothesize that estrogens and androgens may act synergistically to initiate spermatogenesis. The present study was, therefore, aimed to investigate the estrogen responsive system in quail testis in relation to the reproduction seasonality, with a focus on the molecular pathways elicited in both active and regressive quail testes. Western blotting and immunohistochemistry analysis revealed that the expression of ERα, which is the predominant form of estrogen receptors in quail testis, was correlated with E₂ concentration, suggesting that increased levels of E₂-induced ERα could play a key role in the resumption of spermatogenesis during the reproductive period, when both PCNA and SYCP3, the mitotic and meiotic markers, respectively, were also increased. In the reproductive period we also found the activation of the ERK1/2 and Akt-1 kinase pathways and an increase in second messengers cAMP and cGMP levels. In the non-reproductive phase, when the E2/ERα levels were low, the inactivation of ERK1/2 and Akt-1 pathways favored apoptotic events due to an increase in the levels of Bax and cytochrome C, with a consequent regression of the gonad. Full article

Most mammalian species of the temperate zones of the Earth reproduce seasonally, existing a non-breeding period in which the gonads of both sexes undergo functional regression. It is widely accepted that photoperiod is the principal environmental cue controlling these seasonal changes, although several exceptions have been described in other mammalian species in which breeding depends on cues such as food or water availability. We studied the circannual reproductive cycle in males of the Mediterranean pine vole, Microtus duodecimcostatus, in the Southeastern Iberian Peninsula. Morphological, hormonal, functional, molecular and transcriptomic analyses were performed. As reported for populations of other species from the same geographic area, male voles captured in wastelands underwent seasonal testis regression in summer whereas, surprisingly, those living either in close poplar plantations or in our animal house reproduced throughout the year, showing that it is the microenvironment of a particular vole subpopulation what determines its reproductive status and that these animals are pure opportunistic, photoperiod-independent breeders. In addition, we show that several molecular pathways, including MAPK, are deregulated and that the testicular “immune privilege” is lost in the inactive testes, providing novel mechanisms linking seasonal testosterone reduction and testis regression. Full article

Apoptosis is a crucial process in spermatogenesis, responsible for the elimination of abnormal sperm cells and testicular regression out of breeding season. The aim of this study was to assess if the expression of apoptosis-related genes in testicular tissue of domestic cats differed: (1) between normozoospermic and teratozoospermic donors, and (2) between reproductive and non-reproductive season. The expression of genes: BCL2L1, BCL2, BAX, BAD, FAS, FASLG, and caspases (CASP3, CASP8, CASP9, and CASP10) was analyzed by qRT-PCR in testicular tissue samples. During non-reproductive season significantly higher expression of two anti-apoptotic genes (BCL2L1 and BCL2) was observed. Additionally, there was a significant higher expression of CASP10 in teratozoospermic cats during non-reproductive than during reproductive season. No differences were noted between normozoospermic and teratozoospermic groups. Upregulation of some genes during the non-reproductive season indicates engagement of apoptotic mechanisms in the seasonal changes of semen quality in cats, however further studies on protein levels and analysis of changes on distinct testicular germinal layers are required. At the same time, teratozoospermia in the general population of cats seems to be not connected with dysregulation of apoptosis in the testes. Full article