Studies on the pathogenesis of organophosphate-induced delayed neuropathy in the chicken

The purpose of this study was to explore the pathogenesis of the lesion in organophosphate induced delayed neuropathy (OPIDN) using biochemical, morphologic and immunocytochemical techniques in both aggregating and dissociated embryonic avian brain culture system and a kinesin-driven microtubule (MT) motility assay.; Dissociated embryonic avian brain cultures were exposed to a single dose of either the neuropathic OP phenyl saligenin phosphate (PSP) or the non-neuropathic paraoxon (10{dollar}sp{lcub}-3{rcub}{dollar} M to 10{dollar}sp{lcub}-6{rcub}{dollar} M). The cultures were subsequently examined immunocytochemically at postexposure intervals up to 5 days. Immunostaining of neurofilament (NF)-68Kd was abolished with only PSP at 10{dollar}sp{lcub}-3{rcub}{dollar} M and 10{dollar}sp{lcub}-4{rcub}{dollar} M suggesting specific neuronal cytotoxicity. In neurons identified by a double labeling procedure, there was aggregation of kinesin in only the PSP exposed cultures. F-actin filaments were fragmented after exposure to PSP and PO, but no difference between PSP and PO was detected.; The results suggest that this structural alteration in the distribution of kinesin may reflect a specific target of neuropathic OPs which may result in functional impairment of kinesin-driven fast axonal anterograde transport in neuronal processes.; Secondly, the effect of neuropathic and non-neuropathic organophosphates (OPs) and acrylamide on an in vitro kinesin-driven microtubule (MT) motility assay was compared. We compared separately the effect of two neuropathic OPs (diisopropylfluorophosphate (DFP) and PSP) and a non-neuropathic OP (PO) as well as acrylamide each at a concentration of 10{dollar}sp{lcub}-2{rcub}{dollar} M. Our results demonstrated that none of these compounds significantly affected kinesin-driven MT motility in vitro compared to the standard controls. Thus this assay system was not able to discriminate between the neuropathic and non-neuropathic effect of these OPs.; Thirdly, the oxygen consumption and ultrastructural changes in embryonic chicken brain aggregates were studied after exposure to single doses of DFP or PO for up to 12 days following exposure. There was a significant decrease (p {dollar}<{dollar} 0.05) of oxygen consumption rates in DFP and PO exposed cultures compared to the control cultures. The oxygen consumption rate in the DFP group was significantly lower than that in the PO group. Also, prolonged inhibition of oxygen consumption up to 12 days postexposure was seen in the DFP, but not in PO group. Ultrastructural alterations in mitochondria of neurons in exposed cultures paralleled the decrease in oxygen consumption.