Fig. 2.

Morphological changes in the muscles of Rpt3^−/− mice. (A) Hematoxylin and eosin (HE) staining shows a general decrease in myofiber size along with the presence of central nuclei, basophilic inclusions and vacuolated fibers in the gastrocnemius of Rpt3^−/− mice at 4 weeks of age. Modified trichrome Gomori (mTG) staining revealed several basophilic inclusions in the myofibers and monocellular infiltrations in the interstitial perimysial space in Rpt3^−/− mice. NADH staining suggested that the myofibrils were disorganized in Rpt3^−/− mice. Acid phosphatase staining revealed mononuclear cell infiltrations around muscle fibers in Rpt3^−/− mice. Scale bar: 50 µm. (B) Quantification of the cross-sectional area of the myofibers in the gastrocnemius of Rpt3^−/− mice and Rpt3^+/+ mice (n = 5). P<0.05 (Student's t-test). (C) Immunohistochemistry using myosin heavy chain slow (MyHCs) and fast (MyHCf) in the gastrocnemius of Rpt3^−/− and Rpt3^+/+ mice. The diameter of the MyHCf-positive fibers in Rpt3^−/− mice was smaller; however, the same was not observed for the MyHCs-positive fibers. Red, laminin; green, MyHCf or MyHCs. Scale bar: 50 µm. (D) Quantitative data are also shown from the gastrocnemius of Rpt3^−/− and Rpt3^+/+ mice (n = 200 for each fiber type). (E) The percentage of slow-twitch fibers was increased in the gastrocnemius of Rpt3^−/− and Rpt3^+/+ mice (n = 5). Quantitative data show the mean+s.e.m.; *P<0.05 (Student's t-test). (F–I) Electron microscopy findings in the tibialis anterior muscles. Axial (F,G) and longitudinal (H,I) sections from 6-week-old Rpt3^+/+ mice (F) and Rpt3^−/− mice (G–I). The myofibrils were smaller and the interstitial space was wider in the Rpt3^−/− mice. Sarcoplasmic reticulum dilation, filamentous structures and vacuolated structures were observed (H,I). Scale bars: 500 nm.