Fig. 4. Effect of IBMX and forskolin on sperm incorporation into the oocytes. (A) Control fertilized oocyte after 30 minutes (metaphase I of meiosis) showing alignment of maternal chromosomes (mc) and a decondensed male pronuleus (mp). (B) Control fertilized oocyte 60 minutes (metaphase II of meiosis) after the addition of sperm, showing a polar body (pb), maternal chromosomes (mc) and a decondensed male pronucleus (mp). (C) Oocytes 30 minutes after insemination in the presence of IBMX (65 µM) and forskolin (60 µM), showing an intact germinal vesicle (gv) and undecondensed sperm heads (sh) at the periphery of the oocyte. (D) Similarly treated oocytes 60 minutes after insemination, still showing intact germinal vesicles and the absence of any male pronucleus in their cytoplasm.