Guest guest Posted July 12, 2007 Report Share Posted July 12, 2007 Muscle Nerve. 2007 Jul;36(1):81-6. Axonal degeneration in the Trembler-j mouse demonstrated by stimulated single-fiber electromyography. Meekins GD, GT, Emery MJ, Weiss MD. Department of Neurology, University of Washington Medical Center, Box 356115, 1959 NE Pacific Street, Seattle, Washington 98195, USA. The Trembler-j (Tr-j) mouse is a naturally occurring mutant with a point mutation in the peripheral myelin protein-22 gene causing severe peripheral nerve demyelination. It is a genetically homologous murine model for Charcot-Marie-Tooth disease type 1A (CMT 1A). Our prior pilot studies using stimulated single-fiber needle electromyograpy (SSFEMG) showed increased jitter in 60-day-old Tr-j mice compared to age-matched, wildtype animals. The aim of this study was to better elucidate the etiology of increased jitter in Tr- j mice and test the following hypotheses: (1) the increased jitter in Tr-j mice is due to turnover of endplates secondary to axonal degeneration with reinnervation and not to conduction block secondary to demyelination of motor nerve axons; and (2) aging Tr-j mice demonstrate increased jitter and fiber density compared with younger mutant mice due to progressive motor axon loss. SSFEMG studies performed on 60- and 140-day-old mice indicated that average mean consecutive difference (MCD) and fiber density estimates (FDE) were significantly increased in Tr-j mice at both ages compared to age-matched wildtypes. FDE also increased substantially in older mutant mice. Intraperitoneal neostigmine injections produced significant reductions in average MCD in Tr-j mice, suggesting that impaired neuromuscular transmission is an early pathologic feature in these mice and likely reflects distal axonal degeneration. Our findings corroborate our prior pilot study, although in a much larger number of animals across a wider age span. Our study also indicates that SSFEMG, performed in a serial fashion, is a useful, noninvasive method of detecting progressive axon loss in this murine model of CMT 1A. This technique may be a valuable tool to study the affects of genetic or pharmaceutical interventions in murine models of peripheral neuropathy. Quote Link to comment Share on other sites More sharing options...
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