Lectin staining of microglia in the brainstem (level of cranial nerve VII) in wildtype animals (A) and in late symptomatic/end stage animals (B-H). Cresyl violet counterstain. A, microglia show normal ramified morphology. B, a large lectin-positive aggregate of fused microglia is evident in severely vacuolated brainstem tissue. Note enlarged perineuronal spaces to the right. C, string-like microglial fusions extend over long distances. D, breakage of neuronal process, probably a dendrite, from cell body within markedly vacuolated space (arrows). E, two multinucleated microglial giant cells are seen below a neuron with broken off process (arrow). F, large multinucleated giant cell displaying vacuolization is present amidst numerous microglial cytoplasmic fragments. G, multinucleated giant cell of the Langhans type displaying characteristic peripheral arrangement of nuclei. H, rounded lectin-positive microglial cell (arrow) within vacuolated space displays nuclear fragmentation indicative of apoptosis. Scale bars: 20 μm (A-H).