Complex I activity and levels are up-regulated between P12 and P24 in muscle and nerve. (A, B) Bar chart (Mean ± SEM) showing Complex I (NADH dehydrogenase) activity in P12 and P24 sciatic nerve (A) and lumbrical muscle (B). NADH dehydrogenase activity was measured kinetically over 60 min and the rate was determined as change in optical density over time, and expressed normalized to P12 (n = 3 biological replicates, 5 mice per group; ** P < 0.05 by Mann Whitney U test). (C) Image showing example western blot using antibodies against Complex I subunit on muscle from P12 and P24 mice, with Ponceau S staining showing total protein as a loading control. (D) Bar chart (Mean ± SEM) showing quantification of western blot against Complex I. Data expressed normalized to loading control and relative to levels at P12. (N = 3 biological replicates, 5 mice per time point, * P < 0.05 by Mann Whitney U test).