Fig. 2. Expression of slow (A–E) and fast (F–J) myosin heavy chain (MyHC) in trout embryo. (A) Stage 16 embryo (approximately 45 somites), lateral view. (B) Stage 15 embryo (35 somites), transverse section within a rostral somite pair. The label is restricted to the medial domain of the somite. (C) Stage 16 embryo, transverse section within a rostral somite pair. The slow-MyHC-positive cells have begun to move dorsally and ventrally. (D) Stage 17 embryo (50 somites), horizontal section. The slow-MyHC-positive cells progressively reach the lateral surface of the myotome. (E) Stage 22 embryo, transverse section. The slow-MyHC-positive cells are present in the outermost domains of the myotome. (F) Stage 14 embryo (30 somites), lateral view. The fast MyHC label is observed in the most rostral somites. (G) Stage 17 embryo, lateral view. The label progresses caudally as somites form. (H) Stage 16 embryo, dorsal view. The label is initially confined to medial cells in caudal somites (arrowhead) and spreads laterally as the somite matures rostrally. (I) Stage 15 embryo, transverse section within a somite of the trunk. The label is restricted to the medial domain of the somite. (J) Stage 17 embryo, horizontal section. The label fills most of the medial bulk of the somite. s, somite; n, notochord. Scale bars: A, 300µm; B,C,D,J, 25µm; E, 14µm; F, 250µm; G, 350µm; H, 200µm; I, 30µm.
