Fig. 4. Different muscle types of E18.5 embryos stained with the anti-slow MHC antibody show a reduction in primary and secondary myotubes in ß1D1D ki/ki embryos (B,E,H,K) compared to wild-type littermates (A,D,G,J). Transverse sections of body wall (A,B), cleidomastoideus (D,E) and lower hindlimb (G,H) muscles. J and K are higher magnifications of EDL muscles in G and H. (C,F,I,L) Graphical representation of the differences in myotube number between wild-type and ß1D1D ki/ki E18.5 muscles. (C) Total, secondary and primary myotube numbers/mm² in intercostal/serratus dorsalis muscles. (F) Total, secondary and primary myotube numbers in red area of cleidomastoideus muscle. (I) Total number of primary myotubes in lower hindlimb represents the sum of myotubes in TA, EDL, and P group. (L) Total, secondary and primary myotubes in EDL muscle. Bars represent means ± s.d.; **P0.01. EDL, extensor digitorum longus; f, fibula; FDF, flexor digitorum fibularis; I, intercostal; LS, latissimus dorsi/serratus dorsalis; P, peroneus group (including: PB, peroneus brevis; PD, peroneus digiti; PL, peroneus longus); r, rib; ra, red area of cleidomastoideus; SOL, soleus; t, tibia; TA, tibialis anterior; wa, white area of cleidomastoideus. Scale bars: 200 µm.