Figure 1.

Hypoxia affects cardiac morphogenesis. Embryos were exposed to hypoxia (10% O2) or room air (21% O2) for 6 h followed by recovery in room air until stage 11. Embryos were then stained for myosin heavy chain protein with MF 20 antibody (A,C,E,G,I). (A,B) Control embryos (room air oxygen) developed normally with rightward looping heart tubes. Examples of hypoxia-induced malformations include: (C,D) a butterfly shaped beating heart with smaller somites, (E,F) cardia bifida, (G,H) incompletely looped heart, (I,J) swollen heart tube with severely thickened somites. All embryos are shown as ventral views with anterior embryonic end at the top. Arrow points to developing heart tube.