Histochemistry and isomyosins of tail musculature in Xenopus.

The main bulk of the larval tail in Xenopus laevis is composed of thick muscle fibres which are succinate dehydrogenase (SDH) negative and show strong positive ATPase activity only at alkaline preincubation (pH 10.4). The thin muscle fibres (which cover the surface of the myotomes and extend to the tail tip) show positive SDH activity as well as strong positive ATPase activity after both alkaline and acid preincubations (pH 10.4, 4.5, 4.4, and 4.3). The pattern of myosin isoenzymes does not change in the tail muscle in the course of development of Xenopus: the same three bands of larval isomyosins were found in all the examined developmental stages: 40, 47, 50 and 56. However, the larval bands were distinct from three bands of myosin isoforms in the musculus longissimus dorsi (MLD) and musculus gastrocnemius (MG) of the metamorphosed Xenopus.