Ultrastructural morphology of neuronal death following reversible focal ischemia in the rat.

Electron microscopy and terminal deoxynucleotidyl transferase (TdT) mediated dUTP-biotin nick end-labelling (TUNEL) were used to illustrate the different stages and subcellular alterations of cell degeneration that occur in the striatum of the rat after transient focal ischemia. Degenerating neurons exhibited different morphological types: apoptosis Type 1 (aggregation of dense masses of chromatin beneath the 'intact' nuclear membrane) and Type 2 (high cytoplasmic vacuolization), and necrosis. These profiles were localized in different part of the striatum. Type 1 was found in the head of the caudate putamen, Type 2 in the middle part of the striatum and necrosis in the striatal core. These ultrastructural results demonstrated that apoptosis occurs in neurons following focal ischemia in the striatal penumbra. In contrast, necrosis can be observed in the ischemic core, the region maximally affected by the ischemia. Finally, the presence of astrocytes throughout both the penumbra and ischemic core displaying numerous cytoplasmic vacuoles suggested an activation of glial cells.