Functional Histology of Skeletal Muscle, Development and the Endocrine Function in Domestic Animals

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1. Studies on the skeletal muscle development and the meat quality of Japanese Black steers (Part I)(1) Biceps femoral muscle is the largest skeletal muscle and acts mainly as the locomotion of the hind leg. But, the functional activity of the proximal part muscle may be changed to maintain the posture and support the heavy body weight.(2) The muscle fibers were enzyme-histochemically distinguished into three types (alphaR, betaR and alphaW) in the biceps femoral muscle. The percentage of type betaR fibers was higher in the proximal part than that in the middle and distal part muscles. The percentage of type alphaW fibers was the highest in the distal part muscle.(3) Among the distal part, the percentage of type alphaR fibers was higher in the profound subpart than in the superficial subpart, while that of type alphaW fibers exhibited a converse tendency. These differencies will support the previous physiological properties which is the locomotion or the maitenance of posture.(4) Thoracic longissimus muscle is very important for the estimation of meat quality (Beef Marbling Score). The percentage of type betaR fibers in this muscle was larger than that of other breeds. It is suggested that increase of the percentage of type betaR fibers was resulted to obtain the good meat quality.(5) Histological properties of biopsy materials taken from longissimus and biceps femoral muscles of Japanese Black steers were observed. In the longissimusu muscle, histological volume score of fatty tissue was related significantly to Beef Marbling Score. This result was indicated that BMS could be estimated from the early observation of the perimysium deposits in the longissimus muscle.2. Studies on the growth and the endocrine controls of swine, chicken and Tokara native goat skeletal muscles will be reported later as part II.