stationary cultures of human fibroblasts were exposed to various doses of carcinogens ( uv-light at 254 nm , n-acetoxy-acetyl-aminofluorene , ethyl-methane sulfonate , n-methylnitro-nitrosoguanidine , mitomycin c and 4-nitroquinoline-n-oxide ) at different time-intervals before preparing crude cellular extracts and assaying for ligase activity .
C0016030
fibroblasts
C0007634
cellular