[The role of the ubiquitin proteasome system and PP2A in spermatogenesis].

The ubiquitin proteasome system (UPS) plays an important role in cell degradation, and is involved in many biological processes such as cell cycle regulation, immune response, DNA damage repair, and signal transduction. It also acts a crucial part in spermatogenesis by selectively degrading proteins and regulating such processes as DNA repair and protamine histone replacement. PP2A, as an essential serine/threonine phosphatase, participates in a variety of life activities. Studies have shown the involvement of UPS in the ubiquitination regulation of PP2A and that of PP2A in several stages of meiosis. This review updates the roles of UPS and PP2A in spermatogenesis.

Short communication: Chemical structure, concentration, and pH are key factors influencing antimicrobial activity of conjugated bile acids against lactobacilli.

Effects of chemical structure, concentration, and pH on antimicrobial activity of conjugated bile acids were investigated in 4 strains of lactobacilli. Considerable differences were observed in the antimicrobial activity between the 6 human conjugated bile acids, including glycocholic acid, taurocholic acid, glycodeoxycholic acid, taurodeoxycholic acid, glycochenodeoxycholic acid, and taurochenodeoxycholic acid. Glycodeoxycholic acid and glycochenodeoxycholic acid generally showed significantly higher antimicrobial activity against the lactobacilli, but glycocholic acid and taurocholic acid exhibited the significantly lower antimicrobial activity. Glycochenodeoxycholic acid was selected for further analysis, and the results showed its antimicrobial activity was concentration-dependent, and there was a significantly negative linear correlation (R2 > 0.98) between bile-antimicrobial index and logarithmic concentration of the bile acid for each strain of lactobacilli. Additionally, the antimicrobial activity of glycochenodeoxycholic acid was also observed to be pH-dependent, and it was significantly enhanced with the decreasing pH, with the result that all the strains of lactobacilli were unable to grow at pH 5.0. In conclusion, chemical structure, concentration, and pH are key factors influencing antimicrobial activity of conjugated bile acids against lactobacilli. This study provides theoretical guidance and technology support for developing a scientific method for evaluating the bile tolerance ability of potentially probiotic strains of lactobacilli.