Muscle proteins in the chick myotome examined by the immunofluorescent method

Abstract

ABSTRACT This work was undertaken to examine by the immunofluorescent antibody technique at which stage of development of the chick embryo the first muscle proteins are formed. In addition the spatial interrelationship of presumptive myoblasts, myoblasts and myotubes was studied. Chick embryos ranging in age from 52 h to 5 days were fixed in Carnoy and transverse sections cut at 3 – 4 μ .The indirect fluorescent method (sandwich technique) was applied using fluor-scent goat gamma-globulin and myosin antiserum. When the specificity of the myosin antiserum was tested by the immuno-electrophoretic technique, antibodies against myosin as well as against actin, adenylic acid deaminase and some other fractions were detected. Consequently, the fluorescent reactions found in the embryo do not specifically indicate the prescence of myosin, but rather that of muscle proteins. The first fluorescent reaction over the myotome was found at stages 17–18, and was restricted to a few cells on the lateral side of the central myotome region. From here the reaction spread rapidly to other cells on the lateral side in a ventral and dorsal direction. Simultaneously with the increase in thickness of the myotome, the fluorescent reaction spread in a medial direction. The cells of the myotome, particularly those in the most dorsal portion, did not begin to show fluorescense until the adjacent dermatome cells had lost their epithelial structure. At stages 24 – 26 the lateral side of the myotome is formed by myotubes with fluorescent myofibrils. In a medial direction are found subsequently heavily fluorescent spindle cells, either in bundles or as individual cells, which in turn are followed by irregular cells either slightly or not at all fluorescent. The latter cells sometimes showed DNA synthesis. Hence, the differentiation from presumptive myoblast to myoblast and from myoblast to myotube proceeds from lateral to medial.