Figure 2. TUNEL assay. The negative control was performed by omitting the “enzyme” solution (phase contrast (A´) under green fluorescence (A) and A” dark field + fluorescence). A DNAse-treated sample was used as a positive control (B, green fluorescence – 100% of positive cells, B´ phase contrast and B” dark field + fluorescence). Only complete spermatozoa (arrow) were considered in the evaluation of TUNEL; sperm heads without tails were not counted for this purpose (Fig C, arrowhead).