“…Placental tissue was immersed in Perl solution for 20 minutes to detect early infarcted tissue. 7 Standard avidin-biotin-peroxidase complex immunohistochemical staining, using 3,3'-diaminobenzidine as a chromogen, was conducted with antibodies to a smooth muscle actin (monoclonal, 1A4 clone, dilution 1:2; DakoCytomation, Carpinteria, CA), desmin (monoclonal, D33 clone, dilution 1:100; DakoCytomation), Ki-67 antigen (monoclonal, MIB-1 clone, dilution 1:50; DakoCytomation), and the vascular endothelial growth factor (VEGF) receptor, Flk-1 (monoclonal, A-3 clone, dilution 1:300; Santa Cruz Biotechnology, Santa Cruz, CA) in 4 cases (3, 5, 6, and 8) with appropriate control samples. Samples from a normal placenta at 36 weeks' gestation also were stained for comparison.…”