Meiotic block with roscovitine improves competence of porcine oocytes by fine-tuning activities of different cyclin-dependent kinases.

Successful use of oocytes from small follicles (SFs) is of great importance for animal embryo production and human in vitro fertilization with reduced hormone-related side effects. How in vitro meiotic arrest maintenance (MAM) increases the competence of oocytes is not clear. In this study, pig oocytes recovered from SF of 1-2 mm and medium-follicles (MF) of 3-6 mm in diameter from abattoir ovaries were treated by various MAM treatments to improve their competence. The results showed that 25 µM roscovitine or 1 mM db-cAMP efficiently blocked germinal vesicle breakdown in both SF and MF oocytes suggesting a similar cyclin-dependent kinase (CDK) 1 level between the two oocyte groups. MAM with 15- and 25-µM roscovitine alone or with 1-mM db-cAMP improved competence of SF and MF oocytes, respectively, with a promoted chromatin configuration transition from surrounded nucleoli (SN) to re-decondensation (RDC) pattern that supported substantial gene transcription. However, MAM with db-cAMP alone or with higher concentrations of roscovitine did not improve oocyte competence, could not support an SN-to-RDC transition, and/or evoked a premature chromatin condensation (PMC) that suppressed gene transcription. Both CDK2 and CDK5 contents were higher (p < .05) in MF than in SF oocytes. It is concluded that the competence of pig oocytes, particularly that of SF oocytes can be improved by MAM using a proper roscovitine concentration that promotes gene transcription by inhibiting CDK5 while letting CDK2 off to prevent PMC.

[Studies on combined release behaviors of versatile mini-tablets in capsule systems and fittings of their mathematical model].

AIM: To prepare nifedipine (NP) rapid release mini-tablet, sustained release mini-tablets, pulsed release mini-tablets and delayed-onset sustained release mini-tablets and develop multiplied pulsed drug delivery system (DDS), site-specific DDS, zero-order DDS and quick/slow DDS by various ways. METHODS: Velocity-time (v-t) equation of each mini-tablet was deduced by non-linear least square model fit. The difference of combinations in v-t profiles between theoretical value and test value was compared. RESULTS: According to the v-t equations, the combined release behaviors were observed directly from v-t profiles and the test values coincided with the theoretical profiles. CONCLUSION: The programmed DDS, which consist of a variety of mini-tablets with different dosages and combinations in capsules, could be predicted by summing up the v-t equation of each tablet.