Morphological and biochemical decidualization of St-T1b cells. A) The left panel shows phase contrast microphotographs of untreated (control) or decidualized St-T1b cells after 7 d treatment with 8-Br-cAMP (magnification, 100×). Right panel: St-T1b cells and primary ESC were left untreated or exposed to 8-Br-cAMP for 4 d before staining with FITC-phalloidin to visualize the cytoskeleton (200×). B) St-T1b cells and ESC were cultured for 1, 3, or 7 d in the absence or presence of 8-Br-cAMP. Induction of transcripts for decidualization markers dPRL and IGFBP-1 was demonstrated by RT-PCR; GAPDH mRNA was amplified for normalization.