Fig. 2. Expression pattern of NOS isoforms during three stages of vascular development. Conceptuses were excised from timed pregnant matings at 8.0 dpc (A,D), 8.5 dpc (B,E) and 9.5 dpc (C,F), which correspond with the blood island formation, primary capillary plexus and vessel maturation stages, respectively. Immunofluorescence for eNOS (A-C) and iNOS (D-F) was performed (red, NOS; blue, DAPI). Images of single blood islands or vessels stained with NOS were captured at 40x magnification and merged with DAPI images. En, endoderm; Me, mesoderm/endothelium (n4).