Fig. 1. Terminal deoxynucleotide transferase-mediated dUTP nick-end labelling (TUNEL) assay. DNA fragmentation was evaluated by performing the TUNEL assay in decondensed mice sperm that were previously preincubated with endosulfan AI or the control conditions. A: The negative control was performed by omitting the “enzyme” solution [under green fluorescence (A), phase contrast (A′), and merge (A′′)]. B: A DNase-treated sample was used as the positive control [green fluorescence, 100% of positive cells (B), phase contrast (B′), and merge (B′′)]. C: Intact sperm with intense fluorescence considered as positive (arrow). D: Moderately (M) and grossly (G) decondensed sperm with positive staining (arrows). Only complete spermatozoa were considered in the evaluation of TUNEL; sperm heads without tails were not counted for this purpose (A′, A′′, arrowhead).