Effect of age on mitochondrial genome and cytochrome c content and citrate synthase activity. (a) Age-specific mitochondrial genome content of wild-type and daf-2(e1370) animals. Three mitochondrial genes were quantified; the results were normalized to obtain the relative mitochondrial genome content per strain and age cohort. The error bars indicate ± standard error of mean for three mitochondrial genes and three replicate ageing cohorts. (b) Western blots showing age-related changes of cytochrome c abundance in crude worm extract and isolated mitochondria. Results from one representative experiment are shown. The numeric values below each spot denote the abundance of cytochrome c in that spot normalized to the corresponding spot from 1-day-old wild-type (WT) adults. (c-d) Activity levels of citrate synthase in crude worm extract (indicated as 'W') and in isolated mitochondria (indicated as 'M'). Left panel: WT versus daf-2(e1370), right panel: WT versus daf-16(mgDf50). Data represent means ± standard error of mean (bars) for at least three replicate cultures; *, P < 0.05, **, P < 0.01, ***, P < 0.001.