Fig. 6. H⁺-PPase specific activity levels in different yolk granule (YG) fractions at days 0 and 3 of development. Membrane fractions were separated from LYGs and SYGs and assayed for H⁺-PPase activity. (A) H⁺-PPase activity levels during days 0 and 3 of embryogenesis. White bars, day 0 activity; gray bars day 3 activity. EH, total egg homogenate activity. Values are means ± s.e.m. of 3 different experiments. (B) H⁺-PPase specific activity levels in day 0 LYGs with and without Ca²⁺. ^*Statistically significant difference (P<0.05, t-test). (C-F) To determine the location of the H⁺-PPase, YGs were also incubated with Acridine Orange in the presence of PPi during day 0 (C,D) and day 3 (E,F) of embryogenesis. Arrows indicate acidic SYGs and arrowheads indicate acidic LYGs. (C,E) DIC images; (D,F) corresponding fluorescence images. Scale bars, 25 µm.