Fig 1: Muscle fibres and related myosin heavy chains in the upper lip vermilion at different ages. (A) Representative low-magnification images of MT-stained sections of the upper lip vermilion at 33 (young) and 66 (old) years old. Bar = 1000 µm; dotted line, analysed regions as the rounded knob-like tip of OOM; red, muscle fibres; blue, collagenous fibres. (B) High-magnification images of muscle fibre in the rounded knob-like tip of the OOM in upper lip vermilion from 27 (young) and 78 (old) years old. Bar = 500 µm; red, muscle fibres; blue, collagenous fibres. (C) Plots of areas occupied by muscle fibres against age. n = 15. *P < 0.05 (Pearson's correlation test). (D) Representative images of immunofluorescence for myosin heavy chain proteins at 27 (young) and 78 (old) years old. Green indicates immunolabelled signal by antibodies specifically targeting MYH1, MYH2, MYH4 and MYH7, respectively. Bar = 20 µm.