Fig. 4

Expression of iNOS in mdx muscles. (A) Histogram of repartition of iNOS-positive fibers in the quadriceps muscle of mdx mouse. No iNOS-positive fiber was observed before 4 weeks. Standard deviations bars are not indicated on the histogram because standard deviations were very small. (B) Transverse cryostat sections (10 µm-thick) of a Tibialis Anterior (TA, first row, left column), Soleus (SOL, first row, right column), Extensor Digitorum Longus (EDL, second row, left column) and diaphragm (DIA, second row, right column) muscles from 42 days-old mdx mouse immunostained by anti-iNOS antibody. All the muscles had iNOS-positive muscle fibers. Control 1 (third row, left column) represents immunostaining of mdx TA muscle where the primary antibody has been substituted by a non-immune IgG. Control 2 (third row, right column) is a section of a C57BL10 mouse TA muscle immunostained for iNOS. Same results concerning the controls were observed in other muscles (EDL, DIA, SOL) of mdx and C57BL10 mice. (C) Transverse cryostat sections (10 εm-thick) of a quadriceps muscle from mdx mouse stained for HE (upper row, left column), NADPH-d reactivity (upper row, right column), immunostained by anti-iNOS antibody and stained for Evans blue (lower row, right column) and immunostained for d-MHC and stained for Evans blue (lower row, left column). Necrotic fibers (indicated by double arrows) were NADPH-d negative and the NADPH-d staining was more intense in small-sized centronucleated muscle fibers (single arrows). Evans blue stained degenerating muscle fibers. An immunostaining for iNOS was observed in the small sized fibers, as well as partly in degenerating fibers. Small-sized centronucleated muscle fibers were immunostained by anti d-MHC antibody.