On the presence of peripheral-like nervous and connective tissue within irradiated spinal cord.

Abstract

AbstractCells with elongated nuclei resembling those of fibroblasts and/or Schwann cells had been noted previously in x‐irradiated portions of rat spinal cords. The present experiment was undertaken to determine the identity and fates of these cells. For this experiment, a 5 mm length of lumbosacral spinal cord was irradiated (4000 R) in three‐day‐old Holtzman rats. Groups of these rats and their litter mate controls were killed at intervals from 11 through 60 days following irradiation. Most of the spinal cords were prepared for light microscopic examination; a few were prepared for ultrastructural studies. Light microscopic examination revealed that the cells in question became observable near the dorsal roots within and immediately caudal to the irradiated area in a few rats as early as 15 days post‐irradiation and in all rats by 19 days following irradiation. The number of cells increased rapidly and in some cases filled the dorsal funiculi. Axons that were intermingled with these cells usually became myelinated approximately 25 days post‐irradiation. The myelin that formed on these axons resembled peripheral rather than central myelin. Reticular fibers were also abundant in the cell aggregations. The ultrastructural studies confirmed these observations. The data indicate that these cells were involved in formation of peripheral‐like nervous tissue within the spinal cord of all irradiated rats.