"mdx" mouse myopathy: histopathological, morphometric and histochemical observations on young mice.

Histopathological examination of tibialis anterior (TA) and lateral gastrocnemius (LG) muscles from "mdx" mice sometimes revealed lesions of calcification and the close proximity of degenerative lesions with regenerative changes. Morphometric examinations showed that the TA was more severely affected than the LG in mice of all age groups. The soleus muscle was less severely affected than the TA in very young mice, but appeared to be affected almost as severely as the TA in older mice. Type 1 myofibres were more acid-labile in the mdx mice than in control mice and all three major fibre types degenerated and subsequently regenerated in young mdx mice. The aetiological significance of the above findings is unknown at present.