Degeneration of SNc neurons in human PD. A-C. Hematoxylin-eosin (H&E) staining shows that SNc neuron degeneration is characterized by chromatolysis (A), nuclear condensation (B), and severe soma attrition (C). D. Pigmented SNc neurons accumulate DNA double-strand breaks (arrow, brown staining). E. SNc neurons accumulate cleaved caspase-3 immunoreactivity (arrows, brown staining). F. SNc neurons can form Lewy bodies (arrow). Scale bars: A, 20 μm (same for B-D, F); E, 45 μm.