1) Michelson, Russell and Harman (1955) first called attention to the existence of a primary myopathy in an inbred strain of laboratory mice. The need for an experimental model of this type had been recognized by workers in the field for some time and this new mutant soon became the experimental animal for choice in many laboratories. Previous investigations on non-human forms usually had to depend on situations simulating muscular dystrophy as induced by such agencies as nutritional deficiencies, myotoxins and denervation. The presence of a naturally occurring disease on a hereditary basis in a laboratory mammal has provided a significant impetus, to myopathic research.
2) Muscular dystrophy as referred to here arose as an apparently spon-taneous mutation in the breeding stocks of inbred strain 129mice at the Roscoe B.Jackson Memorial Laboratory. Bar Harbor, Maine. Inheritance of the trait conformed to the pattern of an autosomal recessive gene. Three genetic types may occur in litters of dystrophic stock i.e., affected animals (dydy), non-affected heterozygous carriers(Dydy) and non-affected homozygous normals(DyDy).
Histological and histochemical study have been done with Jax. 129 strain dystrophic mice every 12 weeks aged from 5 weeks to 53 weeks. i.e., Sacrificed at 5, 17, 29, 41 and 53 weeks.
As the mice aged the total number of muscle fibers was diminished gradually compared to control mice, because of fregmentation, necrosis, and fatty replacement.
The size end plate of myoneural junction in Jax. 129strain mice was increased compared to control mice. But the marginal structure of the end plate was obscured compared to the control mice. The Summary of histology of Jax-129 strain mice is as follows:
A. Variation in muscle fiber size.
B. Increase in connective tissue.
C. Nuclear alternation (migration of nuclei to center of the cell) D. Necrosis and Regeneration of muscle fiber.
E. Progressive decrease of total number of muscle fiber.
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