Winchester P K, Gonyea W J
Department of Cell Biology and Neuroscience, University of Texas Southwestern Medical Center, Dallas 75235.
Dev Biol. 1992 Jun;151(2):459-72. doi: 10.1016/0012-1606(92)90185-j.
In the avian stretch model, the application of a weight overload to the humerus induces enlargement of the anterior latissimus dorsi (ALD) muscle and an increase in muscle fiber number which is accompanied by satellite cell activation. Myofiber injury may be an important stimulus to muscle fiber hyperplasia; therefore, light and electron microscopic evaluation was undertaken to determine if myofiber injury occurs in the stretch-enlarged ALD muscle of the adult quail. Autoradiographic studies were used to determine the terminal differentiation of labeled myogenic cells. A weight equal to 10% of body mass was attached to one wing of 27 adult quail and 3 birds were euthanized at 9 intervals of stretch, from 1 to 30 days. Birds were injected with tritiated thymidine at intervals ranging from 1 hr to 3 days prior to euthanization. Labeled nuclei were detected by light microscopic examination and identified by electron microscopy of a serial section. Three regions of the muscle were examined for disorganization of contractile elements, presence of cytoplasmic vacuoles, and/or phagocytic cell infiltration. The percentage of fibers exhibiting one or more of these criterion was significantly greater in the stretched ALD by Days 5 and 7 and declined at Day 10, reaching near control values by Day 14. Myofiber necrosis and phagocytic cell infiltration were only observed in the middle and distal regions of the stretched ALD muscle. Traditional signs of regeneration and repair were observed, including clusters of labeled myoblast-like cells and myotube formation within an existing basal lamina. New myotube formation with labeled central nuclei was also noted in the interstitial space, outside of basal lamina of persisting fibers. Labeled myonuclei were observed in the stretched fibers. These results demonstrate that chronic stretch produces regional injury and fiber degeneration and resultant regeneration in the ALD muscle of the adult quail. This may be an important stimulus for new fiber formation in this model.
在禽类拉伸模型中，对肱骨施加重量过载会导致背阔肌前部（ALD）肌肉增大以及肌纤维数量增加，同时伴有卫星细胞激活。肌纤维损伤可能是肌纤维增生的重要刺激因素；因此，进行了光镜和电镜评估，以确定成年鹌鹑拉伸增大的ALD肌肉中是否发生肌纤维损伤。放射自显影研究用于确定标记的成肌细胞的终末分化。将相当于体重10%的重物附着在27只成年鹌鹑的一侧翅膀上，并在1至30天的9个拉伸间隔期对3只鸟实施安乐死。在安乐死之前，每隔1小时至3天给鸟注射氚标记的胸腺嘧啶核苷。通过光镜检查检测标记的细胞核，并通过连续切片的电镜进行鉴定。检查肌肉的三个区域，观察收缩元件的紊乱情况、细胞质空泡的存在以及/或者吞噬细胞浸润情况。到第5天和第7天时，拉伸的ALD肌肉中表现出一种或多种这些标准的纤维百分比显著更高，在第10天下降，到第14天接近对照值。仅在拉伸的ALD肌肉的中部和远端区域观察到肌纤维坏死和吞噬细胞浸润。观察到了再生和修复的传统迹象，包括标记的成肌细胞样细胞簇以及在现有基膜内形成肌管。在持续存在的纤维基膜之外的间质空间中也注意到了带有标记中央核的新肌管形成。在拉伸的纤维中观察到了标记的肌核。这些结果表明，慢性拉伸会在成年鹌鹑的ALD肌肉中产生局部损伤和纤维变性以及由此导致的再生。在该模型中，这可能是新纤维形成的重要刺激因素。
