Transmission electron microscope images showing the ultrastructural properties of splenocytes from mice treated with atrazine (2-chloro-4-ethytlamino-6-isopropylamine-1,3,5-triazine; ATR). (a) Control group. Splenocytes showing normal phenotype (magnification ×10,000). (b) The 200 mg/kg ATR group. Splenocytes exhibiting chromatin margination and condensation into dense granules or blocks (filled triangles), as well as mitochondrial vacuolization (arrow) (magnification ×5,000). (c) The 400 mg/kg ATR group. Splenocytes exhibiting apoptotic morphology including chromatin margination, mitochondrial vacuolization (arrow) and formation of apoptotic bodies (filled triangles) (magnification ×15,000).