FIGURE 3. Survival of V79 cells in multicellular clusters as function of initial ¹³¹I activity per labeled cell. Data are shown for experiments where 100% (), 10% (), or 1% () of cells in multicellular cluster were labeled with ¹³¹IdU. Clusters were maintained at 10.5°C for 72 h and then survival fraction was determined compared with that of cells from control clusters (0% labeled). Data from 3 independent experiments are plotted for each labeling condition. Least-squares fits of data are shown for each labeling condition.