Reduced erythropoiesis in blood islands of VAD embryos.

Normal (A-C) or VAD (D-F) quail embryos were stained witho-dianisidine to identify (dark stained) globin-expressing cells at stages 9 (A, D), 11 (B, E), or 12 (C, F). Views are ventral, and the anterior portion is at the top; H indicates the head of each embryo. By stage 12, blood can be seen intra-embryonically in the normal embryo. Arrows (A, D) indicate the differences in the globin-expressing caudo-lateral domains. VAD embryos show significantly reduced staining, particularly limited to the extreme caudo-lateral regions by stage 12. Original magnification × 32.