Immunohistochemical detection of cleaved PARP in placental tissue at different stages of pregnancy (days 16, 19 and 21). Cleaved PARP was detected using a polyclonal antibody (Santa Cruz; diluted 1:100) followed by incubation with a biotinylated anti-goat antibody (1:500) and reaction with DAB in the presence of H2O2. The tissue sections are from the placental junctional zone, which contains cytotrophoblastic cells (c) and trophoblastic giant cells (gc). The arrows indicate nuclei with immunostaining for cleaved PARP. 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 – 100×. Horizontal bar = 100 μm.