Fig. 5. Analysis of S₁ and S₂ myosin heavy chain (MHC) and tropomyosin (Tm) expression in single fibers from the superficial flexor and extensor muscles by RT-PCR. (A) Individual reactions were run for S₁ and S₂ MHC primers and then products were combined and separated on the same gel. Plasmids containing either the S₁ or S₂ MHC cDNA were used as controls. (B) Same analysis as in A, but using the S₁ and S₂ Tm primers. All of the fibers, with the exception of the second extensor in A, expressed both the S₁ and S₂ isoforms of MHC and Tm. (Inverse images of ethidium bromide-stained agarose gels.)