Subsequently, a modified Davidson’s fixative (mDF) was developed and applied. An earlier study speculated that mDF was regarded as an alternative of BF to fix testes for later histopathologic examination [22]. Another study then found that mDF caused less shrinkage of the seminferous tubules, superior morphologic detail and excellent immunohistochemistry (IHC) staining in testes when compared to BF [20]. Thus, the Society of Toxicologic Pathology (STP) has recommended the use of mDF to fix animal testes for reproductive toxicological studies since 2002 [23]. Nevertheless, another study showed that excessive false TUNEL-positive cells were observed in mDF-fixed rodent testes when fixed at room temperature [24]. It had been reported that the harshness of the fixative might resulted in false TUNEL-positive cells [25]. Therefore, the optimization of fixatives and fixation procedures is essential for precision and specificity of TUNEL assay.