Fig. 2. Soluble signal from retinal cells inhibits postnatal proliferation. (A) Experimental protocol (see text). Cells were cultured in the presence of 5 million retinal cells for 12 hours, BrdU was added for the final 2 hours of progenitor cell culture (B,D) and the final 6 hours of glial cell culture (C,E). (B-E) Example fields of nestin⁺ (red) BrdU-labeled (green) progenitor cells (B,D), and CRALBP⁺ (red) BrdU-labeled (green) Müller glia (C,E), under control conditions (no added cells: B,C) or with the addition of 5 million dissociated retinal cells (D,E). (F) Quantification of BrdU⁺/nestin⁺ cells shows a significant reduction in proliferation with 5 million added cells (15±2.2%) compared with control (24.9±2.4%). (G) Quantification of BrdU⁺/CRALBP⁺ cells shows significant inhibition of glial proliferation with addition of 5 million cells (23.0±2.8%) compared with control treated cells (44.3±2.3%). ^*P<0.02, pairwise comparison (Student's t-test).