Figure 4

Effect of the radiation dose on the conditioning of the medium. Cultures of cells were irradiated with various doses of X-rays and 50 000 cells were incubated for 96 h. CMX was tested as described in Figure 1, with the difference that the cloning efficiency was used to calculate the surviving cell population. Cells were given fresh medium (closed circles) or the conditioned media from nonirradiated cells (open triangles), respectively, from cells that were irradiated with 2, 4, 6 or 8 Gy.