Stickland N C, Handel S E
Department of Anatomy, Royal Veterinary College, London.
J Anat. 1986 Aug;147:181-9.
M. semitendinosus and m. trapezius (portion) were removed from eight miniature pigs ranging from 21 to 160 days of age and eight age-control as well as eight weight-control commercial Large White pigs. Complete transverse frozen sections were obtained for each muscle sample and stained for various enzyme activities including myosin adenosine triphosphatase activity which enabled the identification of 'metabolic bundles'. This in turn enabled conclusions to be made about the prenatal development of the muscle in terms of primary and secondary myofibres. The Large White pigs contained 173% more muscle fibres in m. semitendinosus than did the miniature pigs. Primary myofibre number was found to be about four times more important than secondary to primary myofibre ratios in determining myofibre number in the two breeds of pigs. Both primary myofibre number and secondary to primary myofibre ratios were, however, significantly greater in Large White than in miniature pigs. When the age- and weight-control Large Whites were compared with the miniature pigs it was found that at any given live weight the miniature pigs had thicker myofibres whereas at the same age there was no significant difference. The total area of m. semitendinosus occupied by slow myofibres was about three times greater in the Large White pigs; the functional aspects of this are discussed. It was concluded that genetically smaller animals develop fewer muscle fibres in their muscles by a different mechanism to that exhibited by animals which are smaller due to nutritional deprivation in utero.
从8只年龄在21至160天的小型猪、8只年龄对照以及8只体重对照的商用大白猪身上取下半腱肌和斜方肌（部分）。对每个肌肉样本获取完整的横向冰冻切片，并对包括肌球蛋白三磷酸腺苷酶活性在内的各种酶活性进行染色，这有助于识别“代谢束”。这反过来又能就肌肉在初级和次级肌纤维方面的产前发育得出结论。大白猪半腱肌中的肌纤维数量比小型猪多173%。在确定这两个品种猪的肌纤维数量时，发现初级肌纤维数量比次级与初级肌纤维比例重要约四倍。然而，大白猪的初级肌纤维数量和次级与初级肌纤维比例均显著高于小型猪。当将年龄和体重对照的大白猪与小型猪进行比较时发现，在任何给定的活体重下，小型猪的肌纤维更粗，而在相同年龄时则没有显著差异。大白猪中慢肌纤维占据的半腱肌总面积约大三倍；对此的功能方面进行了讨论。得出的结论是，基因上较小的动物其肌肉中发育的肌纤维较少，其机制与因子宫内营养剥夺而较小的动物所表现出的机制不同。
