Fig. 4. Oocytes with reduced levels of CPEB undergo parthenogenetic activation. (A) This MI oocyte displayed two spindles and appeared to be undergoing asymmetric division with the cleavage furrow oriented longitudinally near of the spindle poles. (B) This four-cell embryo was enclosed in an abnormal follicle that apparently contained a polar body. The follicle contained undifferentiated and possibly apoptotic squamous granulosa cells (arrow). (C) This parthenote resided in an immature follicle (stage 5a-5b) and was detached from the cumulus granulosa cells. (D) This 7-8-cell parthenote resided in a 5a stage follicle; note the mitotic spindle in the bottom blastomere (arrow). (E,F) Multicell parthenotes enclosed in abnormal follicles (stage 4 to 5a); notice abnormally compacted granulosa cells. (G,H) Oocytes in stage 4-5b follicles with fragmented or multiple nuclei and nucleoli. (I) This irregularly shaped overgrown oocyte contains a number of structures in the cytoplasm that resemble nucleoli (empty arrowheads); notice two polar bodies. Scale bar: 20 µm. pb, polar bodies.