Immunohistochemical detection of caspase-3 in placental tissue in different stages of pregnancy (days 16, 19 and 21). Caspase 3 was detected using a polyclonal antibody (Santa Cruz Biotechnology, diluted 1:100) followed by incubation with biotinylated anti-goat antibody (1:500) and reaction with DAB in the presence of H2O2. The arrows indicate the cytoplasmic immunostaining of caspase-3 in trophoblastic cells. The tissue section contains cytotrophoblastic cells (c), trophoblastic giant cells (gc) and vesicular glycogen cells (v). Groups: C – control rats, corresponding to images A, B and C on the 16th, 19th and 21st day, respectively, W – tumour-bearing rats, corresponding to images D, E and F on the 16th, 19th and 21st day, respectively, and A – rats injected with ascitic fluid, corresponding to images G, H and I on the 16th, 19th and 21st day, respectively. Image J is a negative control. Magnification – 40×. Horizontal bar = 10 μm.