Effects of tri-ortho-cresyl-phosphate on spinal ganglia and peripheral nerves of chicken

Aberrant activation of CDK5 is involved in the pathogenesis of OPIDN

Exposure to triorthocresyl phosphate (TOCP) may result in a late neurological complication, i.e. organophosphate-induced delayed neuropathy (OPIDN). The aim of this study was to examine changes in levels of cyclin-dependent kinase 5 (CDK5) and of its activator, p35/p25, in the spinal cord of hens treated by TOCP. After exposure to a single dose of TOCP, groups of adult hens were examined in 3, 5, 7, 9, 14, and 18 days after exposure. CDK5, p35/p25 expression and distribution in the lumbar spinal cord were evaluated by immunohistochemistry and Western blotting. The hens showed signs of OPIDN around day 9 after exposure. The number of p (phosphorylated) -CDK5 and p35 positive cells increased significantly. Co-localization and mislocalization of p-CDK5 and p35/p25 was identified and became evident in neurons around the 9th day. Meanwhile, CDK5, p-CDK5, p35, p25 protein levels and p25/p35 ratio were increased, and peaked around the 9th day, then decreased. Some hens' unilateral common peroneal was treated by roscovitine 3 days after TOCP exposure. Axonal transport of these nerves was faster than of their opposite side and of those simply treated by TOCP. These findings indicate aberrant activation of CDK5 may be involved in the pathogenesis of OPIDN.

Neural development and neurodegeneration: two faces of neuropathy target esterase

Neuropathy target esterase (NTE) is an integral membrane protein in vertebrate neurons. Recent evidence suggests that NTE plays an important role in neural development, possibly via involvement in a signalling pathway between neurons and glial cells. NTE is a member of a novel protein family, represented in organisms from bacteria to man. NTE comprises an N-terminal regulatory domain (with some sequence similarity to cyclic nucleotide-binding proteins) and a C-terminal catalytic domain: the latter has three predicted transmembrane segments and requires membrane-association for activity. In vitro, NTE potently catalyses hydrolysis of phenyl valerate: however, its physiological substrate is likely to be a metabolite of a much longer chain carboxylic acid, possibly associated with cell membranes. NTE was discovered originally as the primary target for those organophosphorus esters (OPs) which cause a delayed neuropathy with degeneration of long axons in peripheral nerves and spinal cord. Paradoxically, NTE's catalytic activity appears redundant in adult vertebrates. Neuropathic OPs react covalently with NTE in a rapid two-step process which not only inhibits catalytic activity but also leaves a negatively-charged OP group attached to the active site serine. The latter event is proposed to induce a toxic gain of function in NTE. OP-modified NTE somehow engenders a "chemical transection of the axon". In turn, this leads to calcium entry, elevation of axonal calpain activity and Wallerian-type degeneration. The net damage to peripheral nerve axons is a balance between ongoing degenerative and repair processes: the latter involve serine hydrolases which can be inhibited by the same OPs used to modify NTE.

Ultrastructure of 6-aminonicotinamide (6-AN)-induced lesions in the central nervous system of rats. III. Alterations of the spinal gray matter lesion with aging

Following a single i.p. injection of 6-AN (10 mg/kg), the anterior horn cells of 20- and 25-month-old rats increased more in size and recovered slower from chromatolytic changes than those of 3-month-old rats. Neurofilamentous hyperplasia of the perikarya was more prominent in aged rats; proliferated neurofilaments were arranged in thick parallel bundles. In the acute stage, reactive and degenerative changes of glial and mesenchymal elements were more conspicuous in 3-month-old rats; however, they disappeared by day 14 with prominent proliferation of hypertrophic astrocytes. The older rats showed less intensity and slower progression of these changes; sponginess and swelling of the astrocytic cytoplasm were still observed at day 14. Our results suggest that these age-dependent changes in the response to neurotoxins are not only induced on the neuron without mitotic phenomena after birth, but also on neuroglial cells. Furthermore, an alteration or reduction in the support of the neuron augments its intensified and delayed susceptibility to neurotoxins.

Changes in the ultrastructure of satellite cells of slow loris in tricresylphosphate poisoning

Toxic reaction of satellite cells from posterior root ganglia of slow loris in TCP poisoning is described. The satellite cells in experimental animals show a marked increase in the rough ER, Golgi complex, microvesicles and filaments. Furthermore there is also an increase in the number of dense bodies and mitochondrial density in these cells. The significance of these changes are discussed and it is concluded that in TCP poisoning not only the neurons but the supporting cells are also affected.