The response of the atrium to direct mechanical wounding in the adult heart of the newt, Notophthalmus viridescens. An electron-microscopic and autoradiographic study.
Wound repair and proliferation were examined in the injured newt atrium with light- and electron-microscopic techniques including autoradiography. Hearts were injured by removing a piece approximately 0.5 mm2 of the atrial wall. The five-day wound was an endothelial and mesothelial-lined blood clot bordered by a 150-micron necrotic zone. Repair progressed from the periphery inward with areas of macrophage activity replaced by fibroblasts and connective tissue. The wound at 25 days consisted of a scar with few myocytes. There was no difference in the proliferative behavior between the right and left atria. Proliferative cells were localized to a 500-micron reactive zone surrounding the wound. The maximum mesothelial cell thymidine-labeling index of 20.5% and mitotic index of 1.4% were seen 5 days after injury. The peak connective tissue cell thymidine-labeling index of 10.2% and mitotic index of 0.4% were seen 10 days after wounding. The peak thymidine-labeling index of 9.8% for myocardial cells was recorded 10 days after injury with a mitotic index of 0.2%. Proliferation returned to control levels by 25 days post-injury. Electron microscopy demonstrated that myocytes engaged in DNA synthesis were indistinguishable from control myocytes. Z-band material was not observed in mitotic myocytes, but myofilaments and junctions were present.
D000818:Animals; D001345:Autoradiography; D006335:Heart Injuries / Q000378:metabolism / Q000503:physiopathology*; D008854:Microscopy, Electron; D008940:Mitotic Index; D009673:Notophthalmus viridescens / Q000502:physiology*; D012455:Salamandridae / Q000502:physiology*; D013936:Thymidine / Q000378:metabolism; D014945:Wound Healing
D013936:Thymidine