The morphology of carbon disulfide neurotoxicity.

The morphology of carbon disulfide induced peripheral neuropathy was studied in rats exposed to three concentrations of carbon disulfide by inhalation for 90 days. Rats exposed to 800 ppm developed neurofilamentous axonal swellings in the distal portions of long fibers, including the dorsal ascending sensory and corticospinal tracts of the spinal cord. In peripheral nerve the predominant effect was seen at the level of the posterior tibial nerve. Teased fiber preparations of the muscular branch of the posterior tibial nerve showed numerous paranodal and internodal swellings as well as Wallerian degeneration. Ultrastructurally the swellings were characterized by neurofilament accumulations, decreased numbers of microtubules and thin myelin. Other features included segregation of axoplasmic organelles and cytoskeletal components, intrusion of Schwann cell processes into the axoplasm, Schwann cells with increased cytoplasmic contents, and Schwann cell proliferation around many swollen and demyelinated axons. These features draw important parallels between the morphology of carbon disulfide neuropathy and the neurofilamentous neuropathies induced by hexacarbons and beta,beta' iminodipropionitrile (IDPN).