IF and EM analysis of EDL fibers from control, denervated, and reinnervated rats. A, C and E) Representative IF images showing fibers double immuno-labeled with RyR1 and TOM20 antibodies marking the position of CRUs and mitochondria, respectively. B, D and F) Representative EM images showing the disposition of mitochondria in EDL fibers from control, denervated, and reinnervated rats. In B and F black arrows point to mitochondria properly positioned at the I band, while in D empty arrows point to mitochondria forming longitudinal columns between myofibrils. G-L) Quantitative analysis of mitochondrial n./area, volume, disposition, and association with CRUs. Data are shown as mean ± SEM; n = number of fibers analyzed; *p < 0.05 as evaluated by one-way ANOVA followed by post-hoc Tuckey test. Scale bars: A, C and E, 5 μm (insets 2 μm); B, D and F, 1 μm.