Abstract
Studies of myelination after transplantation of mature oligodendrocytes to cerebellar cultures in which oligodendrocyte maturation and myelination had been irreversibly inhibited by exposure to cytosine arabinoside were reviewed. Transplanted oligodendrocytes were derived from three sources, including cerebellar explants treated with kainic acid, dissociated oligodendrocyte cultures, and optic nerve fragments. Oligodendrocytes from all sources migrated into the host explants and myelinated appropriate axons. The time of appearance of myelin and the percentage of host cultures myelinated differed for the three sources of oligodendrocytes, however. Myelin was visible earliest and in the highest percentage of host explants transplanted with cultured dissociated oligodendrocytes, which were presumably the most free to migrate into the host tissue, and latest and in the lowest percentage of host cultures transplanted with optic nerve, from which oligodendrocytes were presumably least free to migrate. Some myelin-like membranes unassociated with axons appeared in cerebellar cultures transplanted with cultured dissociated oligodendrocytes, and not in cerebellar explants transplanted with oligodendrocytes from other sources. The formation of such myelin-like membranes was interpreted as a manifestation of oligodendrocyte hyperreactivity induced by culture in isolation.