Neuropil and nuclear aggregates in cortex and striatum. Micrographs of coronal sections through the top layer (layer III, top panel) and the bottom layers (layers V/VI, middle panel) of insular cortex from adult HD brain of grade 1 (A, D, G), grade 4 (B, E, H), or juvenile HD brain (C, F). In the cortex of the grade 1 HD brain, neuropil aggregates are more frequent in layers V/VI than in layer III. More nuclear aggregates (arrowheads) are present in grade 4 and juvenile HD brain. Layer III from grade 4 adult HD brain has more aggregates than from grade 1. In the striatum, EM48-immunoreactive aggregates are present in grade 1 (G) and grade 4 (H), but at a much lower density than in cortex. Aggregates were absent in controls (I). Arrowheads indicate intranuclear aggregates. Scale bar, 50 μm.