Stx1B-induced phosphatidylinositol-4,5 bisphosphate hydrolysis. (A) Confocal fluorescence images of cells expressing GFP-PH-PLCδ before (0 seconds) and after (50 and 300 seconds) treatment with 1 U/mL thrombin, 5nM Stx1B, 5nM Stx2B, or with thrombin after pretreatment with Stx2B for 300 seconds. Images were prepared with Photoshop CS4 (Adobe Systems). (B) Time course of cytoplasmic fluorescence changes relative to t = 0 (F/F0; data are means ± SE; *P < .01, ⁺P < .05 relative to the initial condition).