Fig. 3. Cortical granule translocation is linked to meiotic maturation. Immunolabeling cortical granules of a control cell (A) that has matured in vitro shows that nearly all of its cortical granules have translocated to the cortex. Its pronucleus, which is indicative of meiotic maturation, is evident as a uniform, 12 µm sphere, labeled with Hoechst (B). Cells inhibited from maturation by cAMP (C) or roscovitine (E) show prominent germinal vesicles with dispersed chromatin (D,F, respectively) and no translocation of cortical granules. A cell that did mature in the presence of dbcAMP (even though only a small percentage do, see Fig. 2) shows a normal looking cortical granule translocation (G) and a pronucleus (H). Scale bar: 25 µm. (I) Cortical granule translocation was quantitated by measuring immunolabeled cortical granules in eggs and oocytes cultured in vitro. Even though during some treatments a small percentage of the oocytes mature (see Fig. 2), those that do mature show translocation indistinguishable from control, whereas oocytes that have not matured by these same treatments also have no demonstrable translocation, indistinguishable from an oocyte freshly isolated from the ovary. None of the experimental treatments differ from the control at the P>0.05 confidence level by Student’s t-test analysis.