Figure 2.

EM sections documenting the advanced stages of differentiation achieved by nascent SMFs in control cultured chick myotubes. Fig. 2 A is of a day 4 myotube, and Fig. 2 A′ is of a day 10 myotube. In ultrastructural details, day 10 SMFs are virtually indistinguishable from those in newly hatched chickens (Takekura et al. 1993). This advanced degree of maturation of SMFs, SR, T-system, etc., has not been described in cultured myotubes prepared from immortalized myogenic cell lines and is pertinent to the findings in this report (see below). Bar, 1 μm.