Fig. 2. Plasma membrane PtdIns(4,5)P₂ increases at fertilization. MII oocytes were fertilized on the stage of the microscope and GFP fluorescence (in arbitrary units; PM, plasma membrane; C, cytoplasm) and Fura-red fluorescence (F/F) were continuously recorded at a rate of 1 frame every 7 seconds (A) or 10 seconds (B). Note the translocation of PH-GFP from the cytoplasm to the plasma membrane. The increase in PM/C ratio indicates an increase in plasma membrane PtdIns(4,5)P₂. The white and black arrowheads indicate the position for measurement of the peak change in PM/C and value of PM/C at the end of the first Ca²⁺ transient, respectively. This data is displayed in Table 1 as the PM/C(peak) and PM/C(end) and used to compare the different properties of the increase in PtdIns(4,5)P₂.