Effect of Aβ wild type and G37L ADDL exposure on tau hyperphosphorylation. A. - D. Representative epifluorescence images of cultured embryonic hippocampal neurons that were exposed for 18 hr to vehicle (A), 500 nM Aβ G37L ADDLs (B), 500 nM Aβ scrambled ADDLs (C), or 500 nM Aβ wild type ADDLs (D), then fixed and probed with anti-phospho tau monoclonal antibody PHF-1. Note strong increase in PHF-1 staining only in neurons treated with Aβ wild type ADDLs. E. Quantification of PHF-1 staining. Exposure to Aβ wild type produced significant increases in PHF-1 staining relative to control at 4 hr (204% ± 13; p = 0.0023; n = 5) and 18 hr (416% ± 48; p = 0.0041; n = 5); none of the other treatments significantly increased PHF-1 staining (Student's T-test, * P < 0.005).