New insight on the role of melatonin receptors in reproductive processes of seasonal breeders on the example of mature male European bison (Bison bonasus, Linnaeus 1758).

Melatonin receptors (MT1 and MT2) were shown to regulate proper functioning of reproductive system, especially in seasonally breeding animals. European bison is a unique endangered seasonal breeder and knowledge of the molecular mechanisms of its reproduction is crucial for the survival of the species. The aim of this study was to assess gene expression, protein synthesis and immunohistochemical localization of MT1 and MT2 receptors in testicular and spermatic cord vessels tissues collected in pre-rut (June) and post-rut (December) seasons from adult male European bisons in Bialowieza National Park. We confirmed the highest expression of MT1 and MT2 mRNA and protein levels in testis in December, while in spermatic cord gene expression was also highest in December, but protein amounts were comparable in both analyzed periods. Furthermore, immunohistochemical staining revealed the same amount of both receptors in arteries and veins of spermatic cord in both periods and increased amounts in December in Leydig, Sertoli and germ cells. The high level of testicular melatonin in December confirms the inhibition of spermatogenesis and increased anti-oxidant and anti-inflammatory protection. In spermatic cord vessels, it may prevent from age-related changes due to the overexploitation and ensure a constant temperature regardless of changing environmental conditions. This knowledge can contribute to finding a solution of problems associated with male infertility in general and also further explore the mechanisms regulating the proper functions of the male reproductive system.

Retinal venous blood carbon monoxide response to bright light in male pigs: A preliminary study.

The physical mechanism by which light is absorbed in the eye and has antidepressant and energizing effects in Seasonal Affective Disorder and other forms of psychiatric major depression is of scientific interest. This study was designed to explore one specific aspect of a proposed humoral phototransduction mechanism, namely that carbon monoxide (CO) levels increase in retinal venous blood in response to bright light. Eleven mature male pigs approximately six months of age were kept for 7days in darkness and fasted for 12h prior to surgery. Following mild sedation, anesthesia was induced. Silastic catheters were inserted into the dorsal nasal vein through the angular vein of the eye to reach the ophthalmic sinus, from which venous blood outflowing from the eye area was collected. The animals were exposed to 5000lx of fluorescent-generated white light. CO levels in the blood were analyzed by gas chromatography before and after 80min of light exposure. At baseline, mean CO levels in the retinal venous blood were 0.43±0.05(SE)nmol/ml. After bright light, mean CO levels increased to 0.54±0.06nmol/ml (two-tailed t-test p<0.05). This study provides preliminary mammalian evidence that acute bright light exposure raises carbon monoxide levels in ophthalmic venous blood.

Retrograde and destination transfer of sex steroid hormones in the spermatic cord vessels of the mature boar (Sus scrofa) in short-daylight and long-daylight periods, as well as vernal and autumnal equinox.

The aim of this study was to examine the seasonal changes in concentration of steroid hormones in the spermatic cord vessels of the mature boar. Cytochrome P450 aromatase (P450arom) was also localized in the arteries and veins of the spermatic cord. Arterial blood was collected from the common carotid artery and from two branches of the testicular artery supplying the testis and epididymis to determine progesterone (P4), androstenedione (A2), testosterone (T2) and estradiol (E2) plasma concentrations. The greatest concentration of P4 was found in testicular artery during December (P<0.001), when compared with other periods and vessels. In contrast, the greatest A2 concentration was observed in the epididymal artery during the same season (P<0.001). Greater T2 concentrations were found in both testis and epididymal arteries than in common artery in March (P<0.001, P<0.001; respectively) and in September (P<0.01, P<0.001; respectively). The E2 concentration was weakly affected by seasonal periods, but greater E2 concentrations were found within vessels in the testis and epididymis than in the common artery. The P450arom was immunolocalized in all layers of the arteries and veins of the testicular spermatic cord. The intensity of P450arom staining was greater in December than in June (P<0.001). There were greater steroid concentrations in arterial vessels during December in comparison to June and this may explain the summer infertility in boars and may be related to the local retrograde and destination transfer into the spermatic cord area. The P450arom gene expression in this area seems to be involved in the conversion of T2 into E2 to enrich the testes and epididymis.