  A model of telomere dynamics is proposed and examined. Our model, which
extends a previously introduced two-compartment model that incorporates stem
cells as progenitors of new cells, imposes the Hayflick Limit, the maximum
number of cell divisions that are possible. This new model leads to cell
populations for which the average telomere length is not necessarily a
monotonically decreasing function of time, in contrast to previously published
models. We provide a phase diagram indicating where such results would be
expected. In addition, qualitatively different results are obtained for the
evolution of the total cell population. Last, in comparison to available
leukocyte baboon data, this new model is shown to provide a better fit to
biological data.
