Fig. 8.

Hypomyelination then demyelination in the taiep rat result from microtubule accumulation in oligodendrocytes. a) Sagittal sections of the brain of control and taiep rats at 1, 6 and 12 months show that the taiep rat has myelin at 1 month though less than control but myelin is gradually lost throughout the brain and brainstem. The spinal cord area of the taiep cord at 6 months (b) is less than control (a). This is most obvious in the dorsal column where by 12 months the fasciculus gracilis (asterisk) and corticospinal tract (arrowhead) have no obvious myelin (d). At 4 months, the ventral column of the taiep spinal cord (e) contains non-myelinated and hypomyelinated axons compared to controls (f). EM of the 4 month taiep spinal cord shows accumulation of microtubules in the cytoplasm of an OL (g) that are forming arrays, aligned with smooth ER (h). Processes of OLs contained densely packed microtubules (i). Accumulation of microtubules leads to failure of transport of certain proteins such as MAG that accumulate around the cell body of OLs in the taiep cerebellum (k) not seen in controls (j). Myelin is gradually lost in the optic nerve of taiep from 3 months (l), 6 months (m) and 12 months (n). Occasional examples of myelin breakdown are seen (o) and rare degenerating axons (p). Scale bar: 20 μm (e, f), 100 μm (j, k).

Panel a, reproduced from O'Connor et al. (2000), MCN, 16, 396; b–d, reproduced from Lunn et al. (1995), Microsc. Res. Tech., 32, 183; o, reproduced from Duncan et al. (1992), J. Neurocytol, 21, 870. All with permission.