(A) Immunofluorescence analysis of the old APPPS1 slice in co-culture using antibody 6E10 to detect amyloid plaques (green) and Thiazine Red (TR, red) to visualize fibrillar amyloid cores. At 7 DIV, the majority of amyloid plaques contain 6E10 and TR positive dense core surrounded by 6E10 positive halo of diffuse Aβ. In contrast, at 14 DIV, the majority of amyloid plaques are core-only plaques co-stained with 6E10 and TR without detectable 6E10 positive halo. Lower panels are higher magnification images of boxed regions. Scale bars: 50 µm. 