CELL-DIVISION AND DEOXYRIBONUCLEIC-ACID (DNA) SYNTHESIS IN CULTURES OF STIMULATED LYMPHOCYTES

  • 1 January 1976
    • journal article
    • research article
    • Vol. 31  (2) , 195-204
Abstract
The responses of [murine] lymphocytes cultured with various stimulants [concanavalin A, phytohemagglutinin, mixed lymphocyte culture with allogeneic speen cells] were analyzed with respect to DNA synthesis and cell division. Autoradiographic labeling with [3H]thymidine indicated that similar proportions of cells incorporated this labeled precursor for DNA synthesis during short and long periods of exposure to this specific precursor for DNA synthesis. Changes in labeling index (LI) after pulsing these cells with [3H]thymidine showed that exchange of labeled material, which could not be chased out with unlabeled thymidine, was responsible for the increases of LI seen. Failure to prevent this increase with excess unlabeled thymidine indicated that direct incorporation of [3H]thymidine did not account for this exchange. Using hydroxyurea and colcemid arrest to analyze cell cycle events in these cultures, it was shown that approximately 70% of the responding cells in cultures of stimulated lymphocytes, while actively synthesizing DNA, were not in cell cycle for division. DNA turnover, involving synthesis and exchange of newly synthesized material, possibly DNA, apparently occurred in these cells.