Satellite cells in the latissimus dorsi of the rat

This study was carried out with the aid of the electron microscope to determine the frequency of satellite cells in mammalian skeletal muscle fibre. 10 normal adult male albino rats were used and specimens from the latissimus dorsi muscle were removed, processed and prepared for electron microscope examination. Satellite cells were first identified by their location, shape and organelles. Counts were then carried out on 72 electron microscope fields at X 8,000 magnification from both longitudinal and transverse sections. The total number of nuclei was counted first, then the nuclei of satellite cells were identified and recorded. It has been found that satellite cell nuclei accounted for only 4.5% of all the nuclei seen. The rest being myonuclei within the muscle fibre. This surprisingly small number of satellite cells leaves the question of their role in muscle regeneration and that of the origin of the large numbers of 'myoblasts' that appear in the early stages of muscle repair after injury yet to be answered.