Histochemical studies on the histogenesis of rat lateral pterygoid muscle
Katsura, S.; Ishizuka, H.; Matsumoto, H.
Cellular and Molecular Biology 29(5): 405-413
1983
ISSN/ISBN: 0145-5680 PMID: 6627303 Document Number: 207907
The cellular differentiation and histogenesis of the architecture of the lateral pterygoid muscle of rats were studied by histochemical staining for succinic dehydrogenase (sd). From day 18 of gestation to day 16 after birth development of 2 kinds of muscle fibers could be distinguished: fibers with fine formazan particles diffusely distributed in the sarcoplasm (ss) and fibers with large formazan particles diffusely distributed in the sarcoplasm (sl). After day 16, some muscle fibers showed marked progress of cellular differentiation and became similar to adult fiber types. After day 23, most muscle fibers could be classified into 3 types: type A, type B and type C according to Stein and Padykula. Until day 1 after birth the muscle was composed mainly of isolated muscle fibers. Thus regions with high (region A) and low (region B) Psl values were distinguishable. By day 3 after birth the organization of the primordial muscle structure observed in cross-sections became similar to that of adult muscle and region A had higher average Psl values. Thereafter, the Psl values of each muscle region increased, especially from day 12-16 in region A and from day 14-16 in region B. On day 23 after birth the distribution pattern of Pbc and Pc values in cross-sections became similar to that in young adult muscles. The distribution pattern and the ranges of Psl, Pbc and Pc values of primary fasciculi in each region showed significant changes during postnatal development.