Apoptosis, cleaved caspase-3 expression and cell proliferation in in-phase and out-of-phase endometrium. Histological sections were assessed for apoptosis by TUNEL (A-C) and immunostained for cleaved caspase-3 (D-F) and PCNA (G-I). Negative control sections were incubated in absence of TdT for apoptosis detection (A) and with an immunoglobulin of the same immunoglobulin class and concentration as the primary antibody for cleaved caspase-3 (D) and PCNA expression (G). Out-of-phase endometrium shows higher levels of apoptotic cells (C) and cleaved caspase-3 positive cells (F) and decreased levels of cell proliferation (I) compared to in-phase endometrium (B, E, and H respectively). Magnification: 400X.