PSEN1 and Alzheimer disease: While dark microglia were previously observed near Aβ plaques and dystrophic neurites among the ventral hippocampus CA1 of APP-PS1 mice [64, 65], their relationship to AD hallmarks (Aβ plaques, dystrophic neurites), other elements of the CNS parenchyma, and their ultrastructural markers [i.e., dilated ER, altered mitochondria] remained to be quantitively analyzed.