Ultrastructure of the cuneate nucleus in the streptozotocin-induced diabetic rat

This study describes the ultrastructural changes in the cuneate nucleus of the streptozotocin-induced diabetic rats at 3, 6, 9, and 12 months post-induction. At 3 and 6 months, post-diabetes, a marked atrophy was observed in the myelinated axons. The atrophic axons showed delamination of myelin sheath, tightly arranged lamellar whorls, vesicular elements and degenerating debris within the electron-lucent axoplasm. At 9 and 12 months post-diabetes, a variety of dystrophic and degenerating axonal profiles and dendrites were seen in neuropil. The dystrophic axonal profiles containing tubulovesicular elements, slit-like clefts, vacuoles, swollen mitochondria, membranous and multigranular bodies appeared to be hypertrophied. The degenerating axon terminals contained swollen mitochondria and clustered spherical agranular vesicles in their electron-dense granular axoplasm. The degenerating dendrites were identified by the presence of swollen mitochondria, dilated ER in the electron-dense cytoplasm and they often formed the synaptic glomeruli with central axon terminals. Macrophages containing lipid bodies and electron-dense elements in their cytoplasm were in the process of phagocytosis. In all the time intervals studied, the somata appeared to be normal and the number of dystrophic and degenerating axonal profiles in the cuneate nucleus of diabetic rats was significantly increased in comparison with age-matched saline injected control rats.