Fig. 8. Working hypothesis to explain the cellular basis of the results obtained. Myogenic stem cells (red nuclei) are derived from a pleuripotent stem cell (yellow nuclei) population at an earlier stage in ontogeny. The myogenic stem cells are assumed to undergo an asymmetric division to regenerate the stem cell and produce a daughter cell (orange) capable of a limited number of further divisions before terminal differentiation. Relative to ambient winter photoperiod (illustrated in A), the cells committed to differentiation (orange) undergo more divisions and/or have a shorter cell cycle time than similar cells in the continuous light treatment (illustrated in B), resulting in a higher standing population of c-met immuno-positive cells (see Fig. 7), a higher content of myonuclei (see Fig. 6) and a higher fibre number (Fig. 2).

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