A rapid rise in cell variants during the senescence of populations of human fibroblasts.

An attempt has been made to measure the frequency of mutations throughout the lifespan of human fibroblast strain MRC-5. A novel procedure has been used which involves staining individual cells for high levels of glucose-6-phosphate dehydrogenase. Evidence is presented that this phenotype is due to mutation. The frequency of variants was scored from passage 16 until the final phase of senescence (passage 60). There is an exponential increase of stained cells throughout this period. The results are in agreement with the general error theory, which proposes that aging is due to a breakdown in the fidelity of information transfer between macromolecules.