An electron microscopic study on differences in the fine structures of motor endplate in red, white and intermediate muscle fibers of rat intercostal muscle. A preliminary study.

An electron microscopic study on the fine structural differences of motor endplates among the red, white and intermediate muscle fibers of the rat intercostal muscles was made and the following results were obtained. 1. In the motor endplate of the red fiber, the junctional folds were poorly developed and their number was small. 2. In the motor endplate of the white fiber, the junctional folds were well developed and their number was far more numerous than those in the red fiber. 3. The fine structure of the motor endplate of the intermediate fiber was of an intermediate character between the red and white fiber. ∗PMID: 4236512 [PubMed indexed for MEDLINE] Copyright c ©OKAYAMA UNIVERSITY MEDICAL SCHOOL Acta Mcd. Okayama 21, 327-338 (1967) AN ELECT:RON MICROSCOPIC STUDY ON DIFFERENCES IN THE FINE STRUCTURES OF MOTOR ENDPLATE IN RED, WHITE AND INTERMEDIATE MUSCLE FIBERS OF RAT INTERCOSTAL MUSCLE. A PRELIMINARY STUDY Takuro OGATA, Tsutomu HONDO and Takashi SEITO Department of Surgery, Okayama Universiry Medical School, Okayama, Japan (Director: Prof. S. Tanaka) Received for publication, October 2, 1967 In the previous histochemical study1 on the mouse motor endplate, it was shown that different type of striated muscle fibers had a motor endplate of different structure; namely, the motor endplate of the red muscle fiber was small and compact, while that of the white muscle fiber large and complicated. The motor endplate of the intermediate fiber was intermediate in size and structure between that of the red and white fiber. In this preliminary study, fine structural differences of the motor endplate in red, white and intermediate muscle fibers of the rat intercostal muscle were observed by electron microscopy. MATERIALS AND METHODS Male Wistar rats weighing 200-300 g, of 100 days old were used. Thin strips of the intercostal muscle were fixed in 1% osmium tetroxide buffered to pH 7.4 with veronal acetate, rapidly dehydrated, and embedded in epon. Ultrathin sections were cut on a Porter.Blum ultramicrotome MT-I, stained with uranyl acetate and lead hydroxide, and then examined with a Hitachi model HU-1IA. Thicker sections (about 2.0 fl.) were stained with toluidine blue and examined with the light microscope.