Partial demyelination of cat spinal cord after X-irradiation and surgical interference.

Following 4000 rad of X-irradiation and transplantation of sciatic nerve over the dorsal columns, extensive partial demyelination occurred in some animals. This dose of radiation inhibits remyelination so this phenomenon could be studied knowing that remylination was absent. Partial demyelination was characterized by translocation of myelin to form large myelin ovoids which remained associated with the remaining thinned myelin sheath: nodal widening, involvement of one paranode only, transition from thin to thick myelin along an internode, enlargement and disorientated oligodendrocyte tongues were also features of this change. It is concluded that partial demyelination results when oligodendrocytes have to function in a sub-optimal environment.