| First Author | Harris JB | Year | 1982 |
| Journal | J Physiol | Volume | 326 |
| Pages | 50P-51P (Abstr) | Mgi Jnum | J:24907 |
| Mgi Id | MGI:72623 | Citation | Harris JB, et al. (1982) Motor end-plate disease and the mutant Jolter (medjo) mouse. J Physiol 326:50P-51P (Abstr) |
| abstractText | Full text of Abstract: Motor end-plate disease and the mutant Jolter (medjo) mouse. By J.B. HARRIS and SANDRA POLLARD. Muscular Dystrophy Laboratories, Newcastle General Hospital, Newcastle upon Tyne. The mouse with motor end-plate disease (med) is of particular interest because it exhibits a functional denervation of skeletal muscle (Duchen & Stefani, 1971). The life-span of the animal is approximately 23 days and so it was of interest to learn of a mutant called Jolter. Allelism tests have shown Jolter (medjo) to be allelic with med but Jolter mice enjoy a normal life-span. Our observations suggest that the expression of the disease in the two mutants is qualitatively different. Normal med and medjo mice were killed by cervical dislocation. Biceps brachii and extensor digitorum longus (EDL) muscles were isolated and some electrophysiological properties of individual muscle fibres were recorded using standard intracellular techniques. Normal and medjo muscle fibres generated action potentials following indirect stimulation. In med muscles (aged 15-17 days) neuromuscular transmission was seen in only 12% of fibres of the short head of biceps (SH biceps), 72% of long head of biceps and 73% of EDL: these proportions fell to 0%, 33% and 40% respectively by 20-24 days. M.e.p.p.s could be recorded from 94% of the inexcitable fibres. The mean values for resting membrane potential, and the maximum rate of rise (dV/dt) and overshoot of directly elicited action potentials were reduced in med muscle fibres but were indistinguishable from normal in medjo muscle fibres. The quantum contents of e.p.p.s were also indistinguishable from normal in medjo muscles. Muscles from med mice, especially SH biceps, exhibited a large proportion of small atrophied muscle fibres characteristic of denervation. No muscles from medjo were affected. No abnormalities in the axons, or the ventral or dorsal roots were detected in any animal. In conclusion, the peripheral nerves and skeletal musculature of medjo mice are indistinguishable from normal in all respects. In contrast, the muscles from the med mouse exhibit, electrophysiologically and morphologically, a functional denervation of skeletal muscle. Our findings illustrate major qualitative differences in the expression of allelic forms of a genetic defect. REFERENCE: Duchen, L.W. & Stefani, E. (1971). J. Physiol. 212, 538-548. |
