Publication Cover
Inhalation Toxicology
International Forum for Respiratory Research
Volume 18, 2006 - Issue 1
117
Views
11
CrossRef citations to date
0
Altmetric
Research Article

Atrophy of Large Myelinated Motor Axons and Declining Muscle Grip Strength Following Mercury Vapor Inhalation in Mice

Pages 57-69 | Received 28 May 2005, Accepted 07 Jul 2005, Published online: 06 Oct 2008
 

Abstract

The effects of acute mercury vapor (Hg0) exposure on the peripheral motor system have not been previously addressed in the literature. Early case studies report that acute exposure in humans can cause symptoms resembling motor neuron disease (MND). Mercury granules can be histochemically demonstrated in the cytoplasm of murine motor neurons following Hg0 exposure, suggesting it is transported from the neuromuscular junction (NMJ) to the cell body by retrograde axonal transport mechanisms. We considered the hypothesis that morphological damage to the peripheral motor axonal cytoskeleton possibly involving neurofilaments (NFs) follows Hg0 exposure. Eight-week-old wild type (Wt) 129S/v mice were exposed to 500 μg/m3 of Hg0 for 4 h in an experimental vapor exposure chamber. Forelimb grip strength (FGS) was measured over 4-wk intervals prior to removal of the murine phrenic nerves (MPN) 7 mo postexposure. Autometallography of 7- μm-thick spinal-cord sections from Hg0-exposed mice confirmed the presence of mercury deposits in ventral horn motor neurons. The morphology of the myelinated motor axons was assessed by computer-assisted image analysis of 1- μm-thick resin cross sections of the MPN. The group exposed to Hg0 showed a significant reduction in the mean axon caliber, p < .0001. Gaussian spectral analysis of axon diameter distribution showed atrophy principally to large myelinated fibers, a subpopulation of axons that is also affected in MND. This atrophic change was also accompanied by an increased irregularity in axon shape. FGS initially increased with age until 20 wk and then progressively decreased after 22 wk to 36 wk. In conclusion, Hg0 exposure appears to reduce axon diameter, suggesting axon caliber-determining cytoskeletal components such as neurofilaments may be damaged by heavy metal-induced oxidative stress mechanisms, resulting in functional changes to motor units.

Log in via your institution

Log in to Taylor & Francis Online

PDF download + Online access

  • 48 hours access to article PDF & online version
  • Article PDF can be downloaded
  • Article PDF can be printed
USD 65.00 Add to cart

Issue Purchase

  • 30 days online access to complete issue
  • Article PDFs can be downloaded
  • Article PDFs can be printed
USD 389.00 Add to cart

* Local tax will be added as applicable

Related Research

People also read lists articles that other readers of this article have read.

Recommended articles lists articles that we recommend and is powered by our AI driven recommendation engine.

Cited by lists all citing articles based on Crossref citations.
Articles with the Crossref icon will open in a new tab.