Campion D R, Richardson R L, Kraeling R R, Reagan J O
Growth. 1978 Jun;42(2):189-204.
The effect of upper motor neuron regulation on skeletal muscle development was studied in the fetal pig. A region of the spinal cord at the level of the upper cervical vertebrae was destroyed by cauterization at 45 days of gestation in four pig fetuses. Five fetuses with intact spinal cords served as controls. Innervation and enzyme activities in the longissimus muscle, the ultrastructure and quantitation of satellite cells in the sartorius muscle, and plasma composition were evaluated at 110 days of gestation. The terminal innervation ratios were similar (P greater than 0.05) for muscles from control and cauterized fetuses. Endplate morphology was also similar. Therefore, innervation of newly formed primary fibers is not controlled by upper motor neurons after 45 days of gestation. Mean values for body weight, percentage of muscle dry weight, percentage of myofibers with myonuclei and plasma levels of protein, glucose, triglycerides, lactate, and creatine phosphokinase activity were similar (P greater than 0.05) between the two groups of fetuses. All but one muscle fiber examined was of the secondary fiber type. These observations suggest that the physiological maturity of the muscle was not appreciably altered even though glucose-6-phosphate dehydrogenase activity was higher (P greater than 0.05) and total phosphorylase activity was lower (P greater than 0.05) in the spinal cauterized fetuses than in the control group. The percentage of satellite cells was lower when based on the number of myofibers observed (P greater than 0.005) or on the number of nuclei contained within the basal lamina (P greater than 0.001) in the muscle of the spinal cauterized fetuses than in the control fetuses. The cytoplasm of satellite cells from the muscles of control fetuses was rich in organelles indicative of metabolic and mitotic activity whereas a paucity of such organelles was observed in the satellite cells of cauterized fetuses. Since the percentage of myofibers that had myonuclei was similar (P greater than 0.05) for the control and cauterized fetuses, it appeared that the myonuclear population was maintained by direct incorporation of the parent satellite cell.
在胎猪中研究了上运动神经元调节对骨骼肌发育的影响。在妊娠45天时，对4头猪胎儿的上颈椎水平脊髓区域进行烧灼破坏。5头脊髓完整的胎儿作为对照。在妊娠110天时，评估了最长肌的神经支配和酶活性、缝匠肌卫星细胞的超微结构和定量以及血浆成分。对照和烧灼胎儿肌肉的终末神经支配率相似（P>0.05）。终板形态也相似。因此，妊娠45天后，新形成的初级纤维的神经支配不受上运动神经元的控制。两组胎儿的体重平均值、肌肉干重百分比、有肌核的肌纤维百分比以及血浆中蛋白质、葡萄糖、甘油三酯、乳酸和肌酸磷酸激酶活性水平相似（P>0.05）。除一根肌纤维外，所有检查的肌纤维均为次级纤维类型。这些观察结果表明，尽管脊髓烧灼胎儿的葡萄糖-6-磷酸脱氢酶活性较高（P>0.05）且总磷酸化酶活性较低（P>0.05），但肌肉的生理成熟度并未明显改变。基于观察到的肌纤维数量（P>0.005）或基膜内所含核数量（P>0.001），脊髓烧灼胎儿肌肉中的卫星细胞百分比低于对照胎儿。对照胎儿肌肉中的卫星细胞胞质富含指示代谢和有丝分裂活性的细胞器，而在烧灼胎儿的卫星细胞中观察到此类细胞器较少。由于对照和烧灼胎儿中有肌核的肌纤维百分比相似（P>0.05），似乎肌核群体是通过亲代卫星细胞的直接并入来维持的。
