Electron microscopy of mitochondria in wild type, APP23, and APP48 mice. a-b: Electron microscopy showed predominantly non-altered mitochondria in nerve cell somata of wild type (WT) (a) and APP23 mice (b). c: More altered mitochondria in the nerve cell somata were observed in frontocentral neurons of 18-month-old APP48 mice. Mitochondrial alteration was characterized by a loss of mitochondrial christae although the double membrane architecture and at least single christa structures (arrow) were preserved. d-f: The percentage of altered mitochondria in the nerve cell somata of 18-month-old APP48 mice was higher than in 15-18-month-old wild type and APP23 mice (d). The volume density of altered mitochondria in the frontocentral nerve cell somata of 18-month-old APP48 mice was increased in comparison to 15-18-month-old wild type and APP23 mice (e). At 3 months of age such differences in the presence of altered mitochondria were not observed. The total mitochondrial volume density, i.e. altered and non-altered mitochondria together, did not differ among the investigated mouse lines in both age groups (f). g-i: In CA1 there were no obvious changes in the percentage and volume density of altered mitochondria in the nerve cell somata. *p < 0.05, **p < 0.01 (Further statistical analysis: Additional file
2). Means and standard errors are depicted in d-f. Calibration bar in c is valid for: a-c = 150 nm.