[Ultrastructural changes in the rat cerebellar cortex in the remote periods after exposure to accelerated carbon...

The cerebellar cortex of rats irradiated with carbon ion fluxes of 320 Mev/nuclon and 60Co gamma-radiation was examined by light and electron microscopy 1, 3 or 6 months after exposure. Carbon ions induced the greatest pathomorphological changes. A month after exposure the changes were diffuse and reversible while 3 and, especially, 6 months after irradiation they were focal disorders, a large portion of which being irreversible. 3 and 6 months after exposure some structures of the cerebellar cortex showed destructive while others exhibited reparative changes. Structural disorders in various nerve and glial cells were of different type. Disorders of the Purkinje cells were of the dark type and those of adjacent Bergmann glial cells of the light type. In the granular layer, neurons showed light type changes and adjacent oligodendrocytes, a densely packed karyo- and cytoplasm and a higher osmiophilia. It can be assumed that the above changes are to maintain disordered neuronal functions, including cell interactions. Study of time course variations in the neuronal and glial ultrastructure of the cerebellar cortex of irradiated animals shows an increase of destructive changes with time. This investigation has demonstrated that CNS cells may be damaged long after exposure even to small fluxes of heavy charged particles.