Fig. 2. SSPN-Tg mice display muscle pathology. (A) Transverse cryosections of quadriceps (Quad), tibialis anterior (TA), soleus (Sol), and diaphragm (Diaph) muscles from non-Tg and phenotypic SSPN-Tg (line 37.5) mice were stained with Hematoxylin and Eosin. SSPN-Tg muscle exhibits a greater variation in fiber diameter in comparison to non-Tgs. Pathological features were not observed in non-phenotypic SSPN-Tg muscle (data not shown). Bar, 20 µm. (B) Central nucleation (%) was quantified for quadriceps and tibialis anterior muscles isolated from 4-week-old phenotypic SSPN-Tg mice and non-Tg littermate controls. SSPN-Tg mice display between 17- and 20-fold more fibers with centrally placed nuclei compared to non-Tgs. Values are means and s.e.m. of total fibers counted. ^*P0.05. (C) DNA fragmentation was analyzed by TdT-dUTP labeling. Apoptotic myonuceli (red, arrows) were present only in phenotypic SSPN-Tg mice and were never observed in non-Tg or non-phenotypic SSPN-Tg. Both apoptotic nuclei shown lie within the same myofiber outlined with -DG (green). Bar, 50 µm. (D) Quadriceps muscle from non-Tg and phenotypic SSPN-Tg mice was stained with antibodies to collagen III and collagen IV. Small areas of fibrosis in the SSPN-Tg muscle are denoted with an asterisk. Bar, 20 µm.