Skeletal muscle is a stable tissue composed of parallel arrays of contractile muscle fibres, each consisting of a syncytium of many hundreds or thousands of post-mitotic nuclei. Increase or decease in muscle size and strength can, in principle, reflect changes in the sizes or numbers of muscle fibres that may or may not be accompanied by changes in the numbers of muscle nuclei. These options can be distinguished by careful morphometric analysis of the muscle.

Growth repair and replacement of skeletal muscle fibres is sustained by a population of mononucleated muscle precursor cells called satellite cells that characteristically reside between the plasma membrane of the fibre and the overlying basement membrane. On activation by excessive work, or by damage to the muscle, the satellite cells proliferate rapidly and fuse both with one another and with the fibres or their surviving residua to achieve repair or growth. A proportion of these cells remain unfused as satellite cells, ready for future bouts of activation. In recent years, a number of markers have become available that permit detailed study of satellite cells. We have developed the use of isolated muscle fibres as a means of determining the numbers of satellite cells and their proliferative and myogenic potentials in muscles of mice of different ages and genotypes. These methods are widely applicable as descriptive and investigative tools in the analysis of the capacity of muscle for regeneration and growth.

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