Fig. 2. Defects in secretory differentiation, but not vascular expansion, at day 15 of pregnancy. (A,B) Paraffin wax-embedded sections prepared from wild-type (A) or Hif1a^–/– (B) glands isolated at day 15 of pregnancy stained with Hematoxylin and Eosin. Scale bar: 50 µm. Note the striking block in differentiation in the Hif1a^–/– glands (B). (C,D) Patterning of the vasculature in relationship to the mammary epithelium after lectin (green) and phalloidin (red) staining in wild-type (C) and Hif1a^–/– glands (D).