Quantitative electron microscopic observations on the non-neuronal cells and lipid droplets in the posterior funiculus of the cat after dorsal rhizotomy.

Adult cats were subjected to unilateral dorsal L6, L7, and S1 rhizotomies. After survival times of 1-1,552 days the different glial cell types, the perivascular cells, and the lipid droplet content of each cell type were studied quantitatively at the ultrastructural level in sections from the posterior funiculus at the L1 level. The number of astrocytes did not appear to change during the degeneration process. From 105 days postoperatively (p.o.), a marked reduction in the oligodendroglial cell population was observed. The number of microglial cells increased from 5 days p.o. onward. A large increase was observed particularly between 20 and 160 days p.o. The occurrence of pericytes was unchanged during the degeneration but the number of non-pericytic perivascular cells/blood vessel was increased from 10 days p.o. onward. The number of lipid droplets in the microglial cells increased early during the degeneration period. Subsequently an increase in lipid droplet number was observed in the astrocytes and somewhat later also in the non-pericytic perivascular cells. These findings have been interpreted to reflect a redistribution of lipid droplet material from the degenerating white matter to cells in the perivascular space during the observed time period.