Fig. 4From: Collaborative study of thresholds for mutagens: proposal of a typical protocol for detection of hormetic responses in cytotoxicity testsRe-examination of cell number and expression time. HeLa S3 cells (2000 cells per well) were plated and treated with MMC 48 h after plating. OD-450 was measured 9, 11, and 13 h after MMC treatment. Data show OD-450 ratios (Mean ± SD)Back to article page