Fig. (5) Quantitative assessment of TUNEL (a) and PNCA assay (b) representing the ratio of positive stained cells over total cell number (%). (a) TUNEL assay. The 13-cis-RA significantly induced apoptotic cell death (more TUNEL-positive cells) in LNP, MNP and MxP of 13-cis-RA treated embryos compared to DMSO treated embryos. A significant reduction of TUNEL-positive cells was observed in FA-RA-treated embryos compared to those of the 13-cis-RA-treated embryos. (b): PCNA staining. The 13-cis-RA treated embryos revealed significantly decreased cell proliferation (less PCNA-positive cells) in midfacial processes compared to that of DMSO-treated embryos. Midfacial processes of FA-RA treated embryos showed significantly higher an increased cell proliferation than that of 13-cis-RA -treated embryos. Note: *p < 0.05 vs. DMSO; **p < 0.05 vs. RA.