PERIODIC THERMAL STRESS: OPTIMAL SPACING PREDICTED BY A SIMPLE SET-BACK MODEL OF CELL DIVISION SYNCHRONIZATION

Digital computer simulations have been used to make quantitative predictions based on a simple set-back model of cell division synchronization. According to the model appropriate thermal stress reverses progress within a segment of the division cycle called the set-back interval. In the simulations normally distributed cell-to-cell variations in division cycling rate between periodic thermal shocks were produced with the Monte Carlo method.
The simulations have shown that reasonably good synchronization with the single shock per division strategy requires a relatively long set-back interval and small cell-to-cell variations in rate of progress through the division cycle. The simulations have shown that the degree of synchrony produced by such periodic shocks is highly dependent on the time interval between shocks—with a series of as many as seven shocks inappropriately spaced producing less synchrony than a single shock! The optimal time interval between successive thermal shocks was found approximately equal to the mode division cycle time at synchrony equilibrium multiplied by 1 plus half the fraction of the division cycle occupied by the set-back interval. Position of the set-back interval within the division cycle had little effect on synchrony at the end of the final shock.