Three-dimensional structures of canine senile plaques

In this study, the three-dimensional structures of two types of canine seni le plaques (SP), diffuse plaques (DP) and mature plaques (MP), were compare d using a confocal laser scanning microscope. The three-dimensional observa tion revealed that canine DP were uneven nebula-like assemblies of amyloid- beta (A beta), while MP were comparatively uniform assemblies of membrane-l ike or fibrous A beta materials with some differences among subtypes (primi tive, classic and compact). We also noticed the presence of areas with low- density A beta deposition inside DP and MP, indicating degradation of A bet a. Double staining for A beta and other SP constituents was also conducted. Amyloid precursor protein (APP) was mainly deposited as rough granules aro und A beta assemblies in DP and both inside and around A beta assemblies in MR The pattern of ubiquitin deposition was quite similar to that of APP. G lial fibrillary acidic protein-positive astroglial projections were found a round and inside A beta assemblies in both types of SP, but were more promi nent in MP than DP. DP were often invaded by neurofilament-positive neurona l processes (neurites), while no such neurites were observed inside MP. Dys trophic neurites were, however, frequently detected around MP. These result s clearly showed that canine DP and MP have completely different three-dime nsional structures, consistent with different processes of DP and MP format ion.