Proliferating cells leave the blastema within 6 hours of dividing. Regenerating fins were treated with BrdU and harvested immediately (A,B,C), following a 2 hour chase in fresh water (D,E,F), or following a 6 hour chase in fresh water (G,H,I). Harvested fins were processed for cx43 in situ hybridization (left panels) and BrdU detection (middle panels). Rightward panels show overlap of bright field and fluorescence. Brackets indicate the cx43-positive domain, revealing that the majority of BrdU-labeled cells overlap with cx43. By the 6 hour chase, very few BrdU positive cells remain in the cx43-positive region.