“…Cross sections (10 μm) of the middle part of frozen placentas from 0 ppm and 40 ppm ZEAtreated groups were collected on the same slides for immunofluorescence. The sections were fixed in 4% paraformaldehyde for 15 min, and blocked with 3% hydrogen peroxide in methanol for 10 min at 25°C, and 10% goat serum in 1x phosphate buffered saline (PBS) for 1 hour at 25°C, incubated with rabbit anti-proliferating cell nuclear antigen (PCNA (D3H8P)1:250, 13110XP, Cell Signaling Technology, Danvers, MA, USA) overnight [35,38,39]. On the second day, the slides were incubated with goat anti-rabbit secondary antibody (Alexa Fluor 288, 1:200, A-11034, ThermoFisher, Rockford, IL, USA).…”