P4.2 gene expression in E10.5 embryos. Bright-field and dark-field views are displayed of hybridization of sagittal sections of embryos at E10.5 days with the P4.2 antisense riboprobe (A and B). Higher-power views of the heart (C and D) or liver (E and F) region are also shown. P4.2 hybridization signal was observed in the erythroid cells in the sinusoids and vessels of the liver (representatives are marked with arrowheads). (A, C, and E) Bright-field illumination; (B, D, and F) dark-field illumination. H, heart; L, liver. Micrographs were taken with a 10× (A and B) or 20× (C, D, E, and F) objective.