ULTRASTRUCTURE OF NORMAL REGENERATION AND LOSS OF REGENERATIVE CAPACITY FOLLOWING TEFLON BLOCKAGE IN GOLDFISH SPINAL CORD

Although the spinal cord of goldfish normally regenerates, 30 or more days of blockage by Teflon inserts will result in the loss of this regenerative capacity. The following studies were undertaken to investigate the ultrastructure of normal regeneration and the loss of regenerative capacity following Teflon blockage. The spinal cords of 13 normal and 27 cord-transected goldfish were examined with the electron microscope. Cord-transected goldfish were killed 1 day to 3 months postoperatively. In 15 additional goldfish the spinal cords were transected and Teflon sheet placed between the severed stumps for 1-3 months, after which time it is known the spinal cord will not regenerate following Teflon removal. The spinal cords were immersed in buffered 1% osmic acid and prepared for electron microscopy. In the absence of Teflon, regenerating axons were repelte with smooth endoplasmic reticulum and mitochondria. The majority of axons had regenerated across the site of lesion by day 30 and synapsed in the first segment of the caudal spinal cord stump. Dendrites regenerated in neurite fascicles along with axons. After blockage by Teflon, the nerve fiber tips grew into juxtaposition in zones subjacent to a glialependymal scar. These axons possessed multibulbous processes at the tip which usually formed axoaxonic and axodendritic synapses. Retransection (five goldfish) of the spinal cord one segment rostral to the Teflon block resulted in the degeneration of approximately 50% of all the synapses in the synaptic zone subjacent to the glial-ependymal scar. © 1969.