Fig. 5. Increased heterogeneity of TRF length under chronic oxidative stress. (A) FISH of a (CCCTAA)3 telomeric probe to metaphase chromosomes from HUVEC of the indicated replicative ages after long term culture under pro-oxidant (t-BHP) or normal conditions. Photographs were taken using a 100x objective and identical exposure times. Note the bright telomeres (arrows) and the greater heterogeneity of signals in the t-BHP treated sample. (B) Box and whiskers plots for the relative telomere fluorescence intensities of ten representative metaphase spreads each of control and t-BHP-treated HUVEC cultures at 20-25 CPD. Boxes represent the spread of telomere signals between the 25th and 75th percentile, while bars show the range between the weakest and strongest telomere spot fluorescence. The horizontal line within the box represents the median. (C) Cumulative frequency distributions of all telomere signals from the metaphases shown in B.