Immunohistochemical study of phosphorylated neurofilaments during the evolution of organophosphorus ester-induced delayed neuropathy (OPIDN)

Organophosphorus ester-induced delayed neuropathy (OPIDN) is manifest by de layed degeneration of distal levels of long myelinated fibers following an appropriate neurotoxic exposure. We investigated the dynamics of cytoskelet al changes during nerve fiber degeneration in this condition, focusing on t he immunohistochemistry of axonal phosphorylated neurofilaments. OPIDN was produced in 5-month-old White Leghorn hens using a single 2.5 mg/kg intramu scular dose of phenyl saligenin phosphate. Hens were sacrificed on days 4, 7, 9, 15, and 20, and the tibial nerve branch to the gastrocnemius muscle w as studied by light microscopy and immunohistochemistry (using the SMI 31 m onoclonal primary antibody to phosphorylated neurofilaments). At post-dosin g days 9, 15, and 20 various stages of OPIDN lesions were noted, including axonal swelling and myelinated nerve fiber degeneration. These were associa ted with intra-axonal cytoskeletal lysis, manifest by loss of immunolabeled phosphorylated neurofilaments, a process consistent with proteolysis. Aggr egations of excess axonal phosphorylated neurofilaments were not observed. (C) 1999 Intox Press, Inc.