Fig. 10. Vitellin (VT) proteolysis after calcium incubation. (A) SDS-PAGE showing VT proteolysis after calcium incubation. Yolk granules (YGs) were extracted from day 0 and day 3 eggs and incubated in Ringer saline containing 1 mmol l^-1 ATP and 1 mmol l^-1 PPi. For experimental groups 23 mmol l^-1 Ca²⁺ was added. (Lane 1) Day-0 YGs after incubation with EGTA; (lane 2) day-0 YGs after incubation with calcium; (lane 3) day-3 YGs after incubation with EGTA; (lane 4) day-3 YGs after incubation with calcium. (B) Cathepsin D activities tested in all samples used in A. AU, arbitrary units.