Cell division, DNA replication and nucleotide metabolism. A: cell proliferation was assessed by immunocytochemical detection of proliferating cell nuclear antigen (PCNA). Data (labeling index) are shown as mean ± SEM (n = 5). Different letters indicate significant differences (p ≤ 0.05). B: expression changes (mean log-ER ± SE) of eight genes (Cdc45, cell division control protein 42 homolog, anti-silencing function 1B, ribonucleoside-diphosphate reductase large subunit, cold inducible RNA binding protein-1 and 2, chromosome segregation 1-like protein, chromosome-associated kinesin KIF4A) analyzed with microarrays.