Axon swelling

Delisle, M. B. and Carpenter, S. Neurofibrillary axonal swellings and amyotrophic lateral sclerosis. J. Neurol. Sci. 63 241-250, 1984. 

Whether neurofilament cross-linking is related to the neurofilament accumulation, axonal swellings, and ultimate axonal degeneration observed in -hexane neurotoxicity or is incidental remains to be elucidated (Graham et al. 1995). Since the maintenance of the axon depends on transport of cellular components from the neuronal cell body, the effect of 2,5-hexanedione on axonal transport has been investigated. If... 

Clinical signs of peripheral neuropathy similar to those seen in human occupational exposures to w-hexane can be produced in rats via the inhalation and oral routes, but not in other test species (Altenkirch et al. 1982 De Martino et al. 1987 Dunnick et al. 1989 Frontali et al. 1981 Huang et al. 1989 IRDC 1981 Krasavage etal. 1980 NTP 1991 Schaumburg and Spencer 1976 Takeuchi etal. 1980). Paranodal axonal swelling in mice (Dunnick et al. 1989 NTP 1991) and leg weakness in chickens (Abou-Donia et al. 1985) can be produced with inhalation exposure to -hexane, but these conditions do not progress to the severe neurotoxicity observed in humans and rats. The molecular mechanism... 

Animals continually exposed to concentrations between 100 and 600 ppm developed signs of peripheral neuropathy after 4-8 weeks in cats, the conduction velocity of the ulnar nerve was less than one-half of normal after exposure for 7-9 weeks. In these animals, histologic examination revealed focal denudation of myelin from nerve fibers with or without axonal swelling. In rats and monkeys, adverse effects on neurophysiological indicators of nervous system integrity were found with 9-month exposures to 100 ppm, 6 hours/day, 5 days/week. MBK neuropathies, however, occurred only after 4-month exposure at 1000 ppm. Four months of intermittent respiratory exposure of rats to 13 00 ppm caused severe symmetric weakness in the hind limbs. ... 

These clinical observations were accompanied or preceded by morphological changes in the peripheral nerves, including an increase in the number of neurofilaments in the nerve fibers, axonal swelling, and inpouchings and thinning of the myelin sheath. It is also important to note that... 

Examination of the affected nerves in these test species indicated that demyelination and axonal swelling were generally associated with the observed clinical effects. A significant finding was that in rats that became paralyzed as a result of 2-hexanone exposure at 225 ppm for 9.5 weeks or to 400... 

Neurofilaments. Neurofilaments are presumed to be the target site for several neurotoxicants of environmental significance. Exposure to certain toxicants induces focal accumulations of neurofilaments within neurons and their processes. Accumulation may be within the cell body, or in proximal, middle, or distal regions of the axon. Within myelinated axons, these accumulations of neurofilaments generally occur at multiple, paranodal sites and produce axonal swellings. This common feature of multifocal accumulations of neurofilaments suggests that these toxicants share a common mechanism of action. 

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