Early ultrastructural studies on local acid phosphatase activity in rat sciatic nerve after nerve crush.

Rat sciatic nerve was crushed at mid thigh level. 30 minutes up to 24 hours after the lesion, the nerve was excised, fixed, stained for acid phosphatase activity, and embedded in araldite. The nerve was cut lengthwise over a distance of 6 mm proximally and distally to the lesion and examined by electron microscopy. Not more than 30 minutes after damage fundamental changes were found to take place, with little difference between the proximal and the distal "stump". Changes affect the axon itself, the axolemma and the Schwann cell. In the axoplasm, structures not existent in normal axons became visible during the first hour. Acid phosphatase activity appeared in the endoplasmatic reticulum, vesicles and cisterns, along the axolemma, and in the Schwann cell. Enzyme filled vesicles were released from the Schwann cell into the axoplasm. Mitochondria were found in increasing numbers in the axoplasm next to the lesion, being mainly small and round in shape and prominent where various organelles and enzymes had accumulated. It is concluded that the axon itself is capable of enzyme activation and organelle production, and that there is a complex interaction between the Schwann cell and the axoplasm after nerve crush.