Lefaucheur L, Edom F, Ecolan P, Butler-Browne G S
Station de Recherches Porcines, INRA, St. Gilles, France.
Dev Dyn. 1995 May;203(1):27-41. doi: 10.1002/aja.1002030104.
The aim of this study was to analyze the temporal sequence of expression of the myosin isoforms in the populations of muscle fibers in the pig and to bring more information on the origin of the strikingly different pattern of fiber composition and distribution between the deep medial red (oxido-glycolytic) and superficial white (glycolytic) portions of semitendinosus (ST) muscle. Muscle samples were taken from 49-, 55-, 75-, 90-, 103-, and 113- (birth) day-old fetuses, from 6-, 11-, 21-, 35-, 50-, and 80-day-old piglets, and from a 3-year-old pig. Our results confirm the sequential formation of primary and secondary generation fibers. The use of immunohistochemistry and heterologous monoclonal antibodies (mAb) directed against specific myosin heavy chain (MHC) isoforms revealed a different pattern of gene expression between the two portions of the ST muscle for both generations of fibers. By 75 days of gestation (dg), primary myotubes from the deep medial portion stained positively for the anti-slow MHC mAb and negatively for the adult anti-fast MHC, whereas the opposite was observed in the superficial portion. Secondary fibers never expressed slow MHC until late gestation. Instead, they expressed an adult fast MHC isoform as soon as they formed in the deep medial portion and later on in the superficial portion. From late gestation to the first 3 postnatal weeks, slow MHC began to be expressed in a subpopulation of secondary fibers. These fibers were in the direct vicinity of primary myotubes in the deep medial portion, whereas their location could not be established in the superficial portion. The remaining secondary fibers matured to type IIA in the direct vicinity of these type I fibers and to type IIB at the periphery of the islets. In both portions of the muscle, a subpopulation of secondary fibers, the first ones to express slow MHC, also transitorily expressed a MHC that was identical or closely related to the alpha-cardiac MHC during the early postnatal period. A third generation of small diameter fibers was observed shortly after birth and reacted with the anti-fetal MHC mAb; their destiny remains to be established.(ABSTRACT TRUNCATED AT 400 WORDS)
本研究的目的是分析猪肌纤维群体中肌球蛋白同工型的表达时间顺序，并获取更多关于半腱肌（ST）深层内侧红色（氧化 - 糖酵解型）和表层白色（糖酵解型）部分纤维组成和分布显著不同模式起源的信息。肌肉样本取自49日龄、55日龄、75日龄、90日龄、103日龄和113日龄（出生）的胎儿，6日龄、11日龄、21日龄、35日龄、50日龄和80日龄的仔猪，以及一头3岁的猪。我们的结果证实了初级和次级纤维的顺序形成。使用免疫组织化学和针对特定肌球蛋白重链（MHC）同工型的异源单克隆抗体（mAb）显示，两代纤维在ST肌的两部分之间存在不同的基因表达模式。到妊娠75天（dg）时，深层内侧部分的初级肌管抗慢MHC mAb染色呈阳性，而成人抗快MHC染色呈阴性，而在表层部分观察到相反的情况。次级纤维直到妊娠后期才表达慢MHC。相反，它们在深层内侧部分形成后立即表达成人快MHC同工型，随后在表层部分也开始表达。从妊娠后期到出生后的前三周，慢MHC开始在次级纤维的一个亚群中表达。这些纤维在深层内侧部分紧邻初级肌管，而在表层部分其位置无法确定。其余的次级纤维在这些I型纤维紧邻处成熟为IIA型，在胰岛周边成熟为IIB型。在肌肉的两部分中，次级纤维的一个亚群，即最早表达慢MHC的亚群，在出生后早期也短暂表达一种与α - 心脏MHC相同或密切相关的MHC。出生后不久观察到第三代小直径纤维，它们与抗胎儿MHC mAb发生反应；它们的命运尚待确定。（摘要截断于400字）
