Figure 3. Nicotine exposure increases apoptosis in cultured fetal ovaries. (A) TUNEL-stained ovarian tissues cultured in vitro for 4 days. (B) Percentages of TUNEL positive cells in ovary tissue sections. All experiments were repeated at least three times. Results are presented as mean ± SD. (*) and (**) indicate significant (P < 0.05) and highly significant (P < 0.01) difference, respectively.