Iron accumulation in zi/zi rat oligodendrocytes. Accumulating iron was stained using the enhanced Perls' method.A-D, Coronal sections of midbrain. Iron was present within the entire midbrain region in zi/zi rats (B). With increasing age (8 months), iron accumulation became prominent in the substantia nigra (D). E, F, Higher magnifications of the substantia nigra region shown in C and D, respectively. In zi/zi rats, iron was present in axon bundles and in oligodendrocytic cell bodies and processes (F,inset). G-L, Iron staining of coronal sections of the cerebellum, counterstained with methyl-green. Iron accumulation was initially detected in the cerebellar white matter at 4 weeks (4w) of age (G, H). I, J, Higher magnifications of the white matter, shown in the rectangular areas in G and H, respectively. K, L, Iron deposition increased with age (8 months) within the cerebellar white matter areas in zi/zi rats. M, High-power view of iron-containing cells in the zi/zi substantia nigra. Arrow indicates an iron-accumulating cell that had the morphology of a small and oval cell body with a few short processes, representing an oligodendrocyte. n represents a large neuronal cell stained with cresyl-violet. N, High power view of the zi/zi cerebellar white matter, showing the cytosolic accumulation of iron (brown) in the interfascicular oligodendrocytes. O, P, Electron microscopic photomicrographs of Perls' DAB iron staining of the aged zi/zi substantia nigra (8 months), showing iron deposits in cytoplasm of oligodendrocytes (O, arrows). The processes of these iron-laden oligodendrocytes frequently encompassed the axon (P, asterisk). Scale bars: 1 mm (A-D); 100 μm (E, F, I, J); 500 μm (G, H, K, L); 5 μm (M, N); 1 μm (O); 200 nm (P).