The historical and current research literature is reviewed with special attention to the role of the satellite cell in the reconstitution of skeletal muscle following damage. Implications for the clinical management of trauma patients are stressed in the light of this new knowledge. At the end of the 18th century, it was known that gross damage to muscle resulted in a fibrous cicatrix. In the early and mid-19th century, European observers noted microscopic changes in damaged skeletal muscles which they interpreted as regenerati~n.'~."' In his work on enteric fever, Zenker1I3 described toxic waxy fiber degeneration surrounded by spindle-shaped cells which he believed gave rise to ribbon-like formations and new muscle fibers (cf the fine illustrations by Bischoff'* shown at the 1978 Conference on Muscle Regeneration at Rockefeller University). Ideas originating with 19th century European pathologists have been confirmed by recent research, including budding and new fiber formation from the ends of old striated fibers and the role of the sarcolemmal tube and the cells it contains.IoR Myogenic cells came from the endomysial sheath and underwent nuclear division, and then cell fusion formed transitory ribbon-like elements which became muscle fibers. Muscle nuclei in mitosis had survived the injury. There was a great difference in outcome depending on whether the sarcolemma was destroyed (bad result) or was preserved (good result). These are opinions selected with the hindsight of a century of further research. There MUSCLE

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Autoradiographic experiments using 3H-thymidine were designed to analyse cell proliferation which occurs in skeletal muscle after denervation and after tenotomy. In mouse tibialis anterior and tongue muscles during the first 24 h after denervation or tenotomy labelling levels were low and did not differ significantly from sham operated control muscles. By 48 h after denervation and tenotomy of tibialis anterior muscles, increased levels of labelling occurred in both muscle and connective tissue nuclei. Daily pulse labelling for 7 days after denervation produced a labelling level which was 8 times that of sham operated controls, 25--30% of the total nuclear population being labelled. Denervated muscles had twice the level of labelling compared to tenotomised muscles. These results provide conclusive evidence that both denervation and tenotomy stimulate cell proliferation in skeletal muscle and it is suggested that the increased numbers of labelled muscle nuclei are likely to be the result of mitotic activity in muscle satellite cells.

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