Figure 1: Expression of activated caspases (Casp) 3 and 9 in postnatal day 3 (PND3) gonocytes and PND8 spermatogonia. Activated caspases were visualized by immunocytochemical and immunohistochemical analyses. (a) PND3 gonocytes were either fixed after cell isolation (day 0) or cultured for 3 days with or without retinoic acid (10−6 M) and collected on cytospin slides after fixation. Bottom panel: immunohistochemical analyses of Casp3 and 9 in PND3 testes. (b) Immunocytochemical analysis of PND8 spermatogonia at day 0. Bottom panel: immunohistochemical analyses of Casp3 and 9 in PND8 testes. Representative pictures are shown. Scale = 20 μm. Arrows: germ cells. Arrowheads: apoptotic (cleaved-caspase positive) cells.