Axoplasmic incorporation of amino acids in myelinated fibers of the cat.

Incorporation of amino acids into the axoplasm of nerve fibers of the cat was studied with radioautography. The dorsal funiculus of the spinal cord, or the sciatic nerve, was exposed to tritiated leucine, lysine, and proline; the tissue was processed 1 h later or the following day. In all instances, a radioautographic response of widely varying intensity was observed over the axoplasm; this response could not be adscribed to emissions originating from axonal mitochondria or myelin. The axoplasmic response ranged to as much as 56% compared with that over nearby glial cytoplasm and was often conspicuously greater than that over the surrounding myelin. We interpret our findings as axoplasmic synthesis of proteins. This finding has implications in the maintenance of the neuron.