Fig. 1. The effect of Hsp/Hsc70 on nuclear envelope breakdown (NEB) in fertilized sea urchin eggs. Fertilized sea urchin eggs were incubated in varying concentrations of Hsc70 and Hsc/Hsp70 ranging from 0.1–10 µg ml^–1, in artificial sea water (ASW) (control) or in 1 µg ml^–1 of bovine serum albumin (BSA) or ovalbumin, and the times to NEB and cleavage were observed. Eggs exposed to Hsp/Hsc70 reached NEB earlier than eggs incubated in ASW, ovalbumin or BSA. There were no significant differences in the time to NEB between untreated control eggs and BSA- and ovalbumin-treated eggs. The difference between Hsc/Hsp70-treated and control, BSA and ovalbumin-treated eggs was statistically significant at all concentrations, as indicated by the asterisks (P<0.05). Values are means ± s.e.m. N=6 replicate experiments in which at least 100 eggs were observed.