Mercury staining in mouse spinal cord and brain after exposure to mercury. (A) After Hg0 exposure, all large spinal motor neurons in the cervical spinal cord contain HgAMG grains. No glial staining is seen. (B) After Hg0 exposure, all large hypoglossal motor neurons contain HgAMG grains. No glial staining is seen. (C) After Hg0 exposure, dense HgAMG grains are seen in subependymal astrocytes near the ventricle (V), but no locus ceruleus neurons (outlined) contain mercury. (D) After mercuric chloride exposure, no mercury staining is present in layer 5 somatomotor neurons in the frontal lobe, or in surrounding glial cells. Hematoxylin-HgAMG, bar = 50 μm.