Chromosome changes revealed by the Q-band staining method during cell senescence of WI-38.

Abstract

used to initiate separate aging experiments which were carried out serially over a three year period. In order to detect subtle, progressive changes in banding associated with cell age, we examined the chromosome constitution of WI-38 during early (passage 27) , middle (passages 27-40), and late (passage 40) phases of FL at weekly intervals. A total of 140 cells of high quality were randomly sampled during FL from experiments I and IV: 20 from early; 54 from middle; and 66 from late phase. The quinacrine mustard (QM) staining method (6, 7) was employed in this study. This technique permits the analysis of longitudinal differentiation along chromosome arms and allows the identification of each homologous chromosome pair. Moreover, this method reveals alterations in chromosome structure with a greater degree of discrimination than conventional chromosome staining procedures. Cultures were tested for pleuropneumonia-like organisms (PPLO) periodically by the Baltimore Biological Laboratories. No infections were detected. Results. Our observations revealed no detectable alteration in the banding pattern of diploid chromosome sets during FL. This indicates that in the majority of cells no progressive change in chromosome structure occurs during the so-called aging process. Nevertheless, it is known from earlier studies that generally a small proportion of cells in normal cultures undergo chromosomal rearrangement, even during the early in vitro period (3). We have used the QM technique to obtain greater insight into the nature, origin and fate of such chromosomal alterations. In this report, we have selected three chromosome modifications which are particularly instructive.