Spatial Distribution of Cells in Mitotic and DNA-Synthetic Phases of the Cell Cycle in Hamster Cheek Pouch Epithelium

The spatial distributions of dividing and DNA-synthesizing cells in sections of cheek pouch epithelium of Chinese hamsters were subjected to four statistical tests for ran-domness. The results were consistent with, and provided statistical support for, the ob-servation that localized regions of high mitotic and labeling indices occur in this tissue, separated by broad zones of low activity. Many investigators have observed that mi-totic figures in germinal layers of epithelial tissues are not randomly distributed, but appear in "growth waves," ' "clusters,"2 or "nests."3 Statistical analyses of these ap-parently nonrandom spatial distributions have been rare; extensive, laborious sam-pling methods and calculations are re-quired. Frequency distributions of mitotic indices from samples of an arbitrarily pre-selected length of oral epithelium,4 or area of epidermis5 were not significantly different from Poisson distributions. By analyzing the frequency distributions of numbers of interphase cells between successive mitotic figures and numbers of nonlabeled cells between successive cells labeled with triti-ated thymidine, Cameron, Gosslee, and Pilgrim6 have provided statistical support for nonrandomness in the spatial distribu-This paper was presented at the 44th annual meetin