Fig. 7. The interaction of bovine pituitary extract and E14 retinal conditioned medium depended on the developmental stage of the RPE. Strand number (A,C,E) and depth (B,D,F) were determined for RPE that was isolated from E7 (A, B), E10 (C,D) and E14 (E,F) embryos and cultured with SF2 medium in the basal chamber and either SF3 () or rcSF3 () in the apical chamber. In E7 cultures, rcSF3 had minimal effects on strand number, but increased depth in some regions to create a bimodal distribution. In the E10 and E14 cultures, the effect of rcSF3 was to create a more homogeneous junction that was similar to those of E14 RPE in vivo. Notably, the E14 cultures in rcSF3 had the highest TER, but as in vivo (Fig. 2), had fewer strands and reduced depth.