Sister chromatid exchanges and cell cycle kinetics in Alzheimer's disease.

Six female outpatients with Alzheimer's disease (AD) along with four female controls of a similar age range were analyzed for sister chromatid exchangers (SCEs), cell cycle kinetics, and sensitivity to mutagens, in lymphocyte cultures. The mean level of SCEs for the AD patients was 11.40 SCEs/metaphase, while that for the controls was 9.12. The difference between the two groups was significant as shown by the Wilcoxon rank-sum test (p = 0.05). Cell cycle was 50% longer both in the AD patients (31.7 hr) and aged controls (31.5 hr) than in normal young adults (21.76 hr). Mitomycin-C (MMC) decreased the mitotic index in AD patients by 35% and in controls by only 12%. MMC also increased the cell cycle duration in AD patients by a greater extent (20%) than it did in the controls (13.5%), and AD cells were more sensitive to the toxic effects of bromodeoxyuridine. What appeared to be chromosomes with prematurely divided centromeres were also observed in AD cells.