Organophosphorous neuropathy. II. A fine-structural study of the early stages of axonal degeneration.

The early stages in the evolution of axonal degeneration in organophosphorous neuropathy have been studied by electron microscopy of single nerve fibers. Two young adult cats were given a single, intraperitoneal injection of di-isopropylfluorophosphate (DFP). Eighteen and 20 days later, respectively, after intracardiac perfusion with glutaraldehyde, single nerve fibers were teased from the cats' left recurrent laryngeal nerves. Four nerve fibers in progressive stages of axonal degeneration, were subserially sectioned and studied in the electron microscope. Unique, mid-internodal nerve fiber varicosities preceded an axonal degeneration which was initially focal and nonterminal. The varicosities were associated ultrastructurally with intra-axonal and/or intramyelinic vacuoles. Accumulations of axonal agranular reticulum were found in all four fibers but were associated with less than one half the varicosities. It appeared, both by light and electron microscopy, that the nerve fiber varicosities progressed to the focal, nonterminal axonal degeneration.