Figure 1.
Computer image analysis of individual replication sites. Replication sites were single labeled for 5 min with BrdU in unsynchronized 3T3 fibroblast cells. (A) Confocal image of replication sites in 3T3 cells in a typical 0.5-μm midplane section. (B) Contours of replication sites in the optical section shown in A after the spot based segmentation method. 495 RS were counted. (C) Contours of replication sites for A using the threshold based segmentation method. 189 RS were counted. Yellow arrow indicates one cluster of weak RS that were imaged well in B but missed in C. Yellow arrowheads indicate closely spaced RS that were imaged as individual RS in B, but grouped into a single contour in C. Bar, 5 μm.