Figure 1.

A senescent phenotype in aged myofibres. (a) Representative images of H&E‐stained cryosections of gastrocnemius muscle from C57Bl6 mice at 8 (left) and 32 (right) months of age. Scale bar 50 μm. Arrows indicate centrally nucleated fibres (CNF). (b) Frequency distributions of myofibre cross‐sectional areas in adult and old mice. Averages are different with p < 0.001 (Mann–Whitney U test). (c) Representative p21 immunofluorescence images. Red: p21, blue: DAPI, green autofluorescence. Arrows indicate examples of positive nuclei. Bar equals 15 μm. (d) Frequencies of p21‐positive nuclei in adult and old muscles. (e) Immuno‐FISH staining for telomeres (red) and γH2AX (green). Signal co‐localization (TAF) is marked by an arrow. Scale bar 2 μm. (f) Frequencies of TAF‐positive nuclei. (g) lamin B1 immunofluorescence. Red: lamin B1, blue: DAPI. Bar equals 20 μm. (h) Normalized pixel‐to‐pixel variation of laminar LB1 fluorescence intensity. (i) HMGB1 immunofluorescence (red). Blue: DAPI. Arrows indicate examples of HMBG1‐negative nuclei. Scale bar 20 μm. (j) Frequencies of HMGB1‐positive nuclei. (k) SBB plus Nuclear Fast Red‐stained cryosections. SBB‐positive fibres appear dark (examples indicated by arrows). Scale bar 50 μm. (l) Frequencies of SBB‐positive fibres. All data are mean ± SD, three animals/group. *p < 0.05