Autoradiographic analysis of normal trophoblastic proliferation

Abstract

Analysis of the cell cycle has been made possible by the introduction of high resolution autoradiographic techniques with tritiated thymidine, a specific DNA precursor. This article reports a study of the cell cycle of normal early trophoblast. Placental tissue, made available by therapeutic abortion, was maintained in organ culture. The tissue was exposed to tritiated thymidine for variable periods of time and autoradiographs were prepared by the dipping method of Messier and Leblond. By using grain counts, timing of labeled mitosis, and the appearance of label in various cells, the typical cell cycle for trophoblast was formulated. The duration of DNA synthesis was approximately 5 1/2 hours. G1, phase was 7 hours and G2 was 2 hours. The generation time was 15 hours and turnover time 3 to 4 days. Analysis of the cell cycle has been made possible by the introduction of high resolution autoradiographic techniques with tritiated thymidine, a specific DNA precursor. This article reports a study of the cell cycle of normal early trophoblast. Placental tissue, made available by therapeutic abortion, was maintained in organ culture. The tissue was exposed to tritiated thymidine for variable periods of time and autoradiographs were prepared by the dipping method of Messier and Leblond. By using grain counts, timing of labeled mitosis, and the appearance of label in various cells, the typical cell cycle for trophoblast was formulated. The duration of DNA synthesis was approximately 5 1/2 hours. G1, phase was 7 hours and G2 was 2 hours. The generation time was 15 hours and turnover time 3 to 4 days.