This in vivo study employs p27-deficient mice to investigate the significance of p27 for the metabolism of D-type cyclins in differentiated cells. The absence of p27 results in decreased levels of cyclins D2 and/or D3 in some organs. As demonstrated on Leydig cells of testis, such dependency is only restricted to certain cell types including terminally differentiated ones, and the absence of p27 in these cells can interfere with their differentiation. The decrease of cyclin D caused by the absence of p27 equals the amount of cyclin D physically associated with p27 in non-mutant animals. The data indicate that it is the proportion of p27-associated cyclin D that determines the response to p27 deficiency. Cells in which the level of D-type cyclin is dependent on p27 do not up-regulate the activity of their CDK2 and CDK4 upon loss of p27, and these cells have a negligible amount of p27 bound to CDK2 and/or cyclin A/E under normal conditions. Together, the findings suggest the existence of a dual role for p27, one being a classical regulation of cell cycle via inhibition of cyclin-dependent kinases (CDK), and the other being participation in the establishment and/or maintenance of differentiated status that is realized in conjunction with D-type cyclins.

Damage to the genetic component of spermatozoa seems to play the main role in a majority of cases where current approaches fail to reveal the specific cause of male infertility. In this study, we compared semen quality in men assigned to two defined groups: men from couples with unexplained infertility - idiopathic infertility (A) and young men with no experiences of infertility (B). All samples were examined by standard ejaculate analysis and sperm chromatin structure assay (SCSA). Sperm chromatin damage was significantly higher in men from group A than in those from group B. Similar results were obtained by comparison of men from group A (all men were normozoospermic) with normozoospermic men from group B. According to these results, we can suppose that chromatin disorders may be the causal factor of subfertility or infertility in some of these men. No evidence for a strong association between chromatin disorders and standard parameters of ejaculates was found. We failed to confirm a relationship between smoking and sperm quality in men from any of the investigated groups. SCSA is a method that facilitates the identification of infertile men who otherwise show normal semen variables.

Analysis of sperm parameters is very important for predicting the outcome of assisted reproductive techniques and is necessary for determination of fertility potential of males tested for artificial insemination. In our study we have determined the level of bull and boar sperm DNA damage by Sperm Chromatin Structure Assay (SCSA). This test is based on increased susceptibility of altered DNA (strand breaks) in sperm nuclear chromatinto in situ denaturation measured by flow cytometry after staining with acridine orange (AO). Sperm chromatin damage was quantified by percentages of spermatozoa with detectable DNA Fragmentation Index – DFI divided into moderate (m-DFI) and high (h-DFI) DFI. Percentage of immature cells (HDS; cells with High DNA Stainability) was also evaluated. We measured sperm SCSA parameters in a total of 37 bulls in two groups from different localities and 68 boar samples from one locality. Significantly higher percentage of spermatozoa with detectable DFI was detected in six bulls (16.2%) and a significantly higher percentage of immature cell forms (HDS) was found in other six bulls (16.2%) among all tested bulls. The mean percentages of spermatozoa with h-DFI and HDS of bulls from the second group were statistically higher than those from the first group (P < 0.01). Five boars (7.4%) of all tested boars had significantly higher percentage of spermatozoa with DFI and 18 boars (26.5%) had significantly higher percentage of sperm with HDS compared to the other boars. Both percentages of spermatozoa with DFI and HDS were significantly higher in one boar compared to the others. Boars had significantly higher percentages of spermatozoa with h-DFI and HDS (P < 0.0001) in comparison to bulls. For individual bulls, the highest percentages of spermatozoa with DFI and HDS were 20.8% and 3.5%, respectively while for boars these were 17.6% and 10.2%, respectively. No significant correlations were found between percentages of spermatozoa with DFI and HDS. This sensitive procedure seems to be convenient as additional method for semen quality detection in farm animals before their exploitation in breeding.

The testosterone production by Leydig cells of mice adversely affected with nutritional or social factors and exposed to chronic stress was studied in vitro. Both basal and gonadotrophin stimulated testosterone production were highly significantly decreased (P < 0.01) as in groups given the hypothyreotics or potassium nitrate alone as in combination with stress. Stimulated in vitro testosterone production was not significantly changed in groups fed with synthetic diets, however, in mice given modified diets and exposed to stress decreased responsivity of Leydig cells stimulated by gonadotrophin was found. Basal and stimulated testosterone production in vitro in most of gonadotrophin concentrations was non-significantly lower in mice affected only by stress when compared with undisturbed controls. In isolated male mice the basal testosterone production was significantly (P < 0.05) decreased and gonadotrophin stimulated production highly significantly (P < 0.01) decreased when compared with group caged males. The testosterone production was most severely suppressed in aggressive individuals. Serum testosterone levels were detected in all animals, corticosterone, T3and T4 in selected groups of mice. We can conclude that the testosterone production was adversely affected by nutritional factors, and the impact was more profound when exerted together with chronic stress. The adverse effect of individual caging of male mice was also proved.