Fig. 5.

Ablation by laser-irradiation eliminates muscle pioneers without affecting surrounding muscle cells. Side views of two whole-mount embryos at 24 h labeled with 4D9 (A) or zn-5 (B) mAbs. The asterisksmark experimental segments in which muscle pioneers were ablated, andarrows point to muscle pioneers in adjacent segments.C, Transverse section of embryo at 24 h labeled with F59. The asterisk marks experimental segment in which muscle pioneers were ablated, and the arrow points to muscle pioneers on the contralateral side. Except for the absence of muscle pioneers, the slow muscle cells on the experimental side appear normal. Because slow muscle cells have not been observed to divide (Devoto et al., 1996), this suggests that ablation of muscle pioneers has no effect on neighboring muscle cells. Scale bars: A, B, 25 μm; C, 20 μm.