Signs of microglial dysfunction. A, Langhans type giant cell consisting of fused microglia in the brainstem of a SOD1G93A rat, as shown by lectin histochemistry (brown color). Note the characteristic arrangement of nuclei along periphery. B, nidus of bacilli in another section from the same animal, possibly a reflection of impaired bactericidal activity of microglia. Cresyl violet stain. Scale bar = 20 μm.