ULTRASTRUCTURAL-STUDY OF ENSHEATHING CELLS IN EARLY DEVELOPMENT OF OLFACTORY AXONS

Ultrastructural observations in the grey short-tailed opossum (Monodel phis domestica) and rat revealed that ensheathing cells were intimatel y related to the early formation of olfactory axons. Whilst the axons were still in the olfactory epithelium, they were enveloped by ensheat hing cell processes which formed a cradle-like structure on the basal side of the epithelium. Continued downgrowth of the axons towards the lamina propria resulted in an evagination with the ensheathing cell pr ocess or cell body in direct contact with the basal lamina. Subsequent ly the basal lamina became fragmented, and the newly formed olfactory nerve emerged from the olfactory epithelium. As the olfactory nerve gr ew, it was observed that the ensheathing cell process always extended ahead of the axons while axon terminals moving ahead of ensheathing ce lls were never observed. The findings in this study suggest strongly t hat ensheathing, cells play a role in regulating and promoting olfacto ry axon growth.