| Popis: |
The serine/cysteine protease inhibitor phenylmethylsulfonyl fluoride (PMSF) has been used both to promote and to protect against neuropathic events of organophosphorus-induced delayed neuropathy (OPIDN) in hens (Veronesi and Padilla, 1985; Pope and Padilla, 1990; Lotti et al., 1991; Pope et al., 1993; Randall et al., 1997). This study is the first to expand upon this work by using high resolution microscopy provided by epoxy resin embedding and thin sectioning to evaluate neuropathological manifestations of promotion and protection, and to correlate them with associated clinical modifications. To evaluate dose-related effects of OPIDN, single phenyl saligenin phosphate (PSP) dosages of 0.5, 1.0, or 2.5 mg/kg were administered to adult hens. PMSF (90 mg/kg) was given either 4 hours after (for promotion) or 12 hours prior to (for protection) PSP administration. Clinical signs and pathologic changes in the biventer cervicis nerve, which is uniquely sensitive to OPIDN (El-Fawal et al., 1988), were monitored. PSP alone, 2.5 mg/kg, caused severe OPIDN (terminal clinical score 7.5 +/- 1.0 [0-8 scale]; neuropathology score 2.7 +/- 0.3 [0-4 scale, based on myelinated fiber degeneration]). PMSF given 12 hours prior to PSP gave complete protection (clinical and neuropathology scores of 0; p0.0001 compared to PSP alone). Signs and lesions of OPIDN were absent following 0.5 mg/kg PSP alone, but PMSF given 4 hours after PSP potentiated its neurotoxic effects (all hens had clinical scores of 4.0 and the average neuropathology score was 3.5 +/- 0.3; p0.0001 compared to PSP alone). Although quantitative differences were noted, qualitative differences among nerves from hens with OPIDN were not evident, either with light or electron microscopy. At the time of sacrifice, there was a statistically linear relationship (r2 = 0.76) between the clinical scores on the last day of observation and the neuropathology scores (p0.0001). This study demonstrates that the degree of peripheral nerve myelinated fiber degeneration correlates with clinical deficits in PMSF-induced potentiation of and protection against OPIDN. |
