Fig. 4. Low levels of Cdk1-cyclin B activity do not explain persistent Ca²⁺ oscillations after extrusion of the second polar body. To inhibit cyclin synthesis after polar body extrusion, cycloheximide (CHX) was added to eggs 90 minutes after fertilization. In the presence of CHX, Ca²⁺ transients were generated as in controls (Ai). The time that the Ca²⁺ oscillations stop relative to Pn formation is shown in Aii (n=17). Note that the distribution is similar to that shown for controls in Fig. 1Bii (see also Table 1). (B) Cdk1-cyclin B activity was measured in groups of 50 unfertilized eggs and in eggs 3 hours after fertilization that had extruded a second polar body and 6 hours after fertilization when they had formed pronuclei. Data are from two experiments, each with two replicates. No significant difference in Cdk1-cyclin B activity is seen before and after Pn formation.