Figure 4. Chromosome- and chromatid-type aberrations measured by solid-stained chromosome analysis at day 3, 12 and 20 post exposure to either tumour necrosis factor (TNF) or X-rays at the indicated doses. Data are presented as the mean aberrations per cell. Day 3 data were pooled from five separate experiments, while days 12 and 20 were pooled from three separate experiments. The asterisks denote the p-value 0.05 compared with corresponding negative controls by chi-squared analysis for day 3 and Fisher's exact test for days 12 and 20.