Accumulation of amorphous materials and membrane bound inclusions.
A, regions of the cell characterized by accumulation of degenerating mitochondria and vacuolization (open arrows) also contained accumulations of amorphous electron-dense material (asterisks). B and C, the electron-dense material was granular in appearance and was observed either with (C, arrowhead) or without (C, asterisk) a membrane envelope. In certain MCK-βAPP fibers, stack-like aggregations of the SR membranes were also observed (wavy arrows). Bars, A, 1 μm; B and C, 0.5 μm.