Non-anemic Ccbe1−/− embryos survive to late gestation with normal cardiovascular function. (A) E17–18 Ccbe1−/− embryos that did not appear pale were selected for studies of lung function. The hematocrits of non-pale Ccbe1−/− embryos were not reduced compared with littermate controls. Quantitative data are represented as mean and SEM from 8 control and 5 Ccbe1−/− embryos from 3 independent litters (P = 0.40). (B) Gross appearance of Ccbe1−/− and control littermate embryos at E18.5. Representative images are shown from 81 control and 20 Ccbe1−/− E18.5 embryos examined from 15 litters. Bars, 5 mm. (C) Cardiac size and structure of Ccbe1−/− and control littermate embryos are shown at E18.5 by H-E staining. Images are representative of 5 control and 5 Ccbe1−/− embryos examined from 3 independent litters. Bars, 1,000 µm. (D) Cardiac ejection fraction and fractional shortening of E18.5 Ccbe1−/− and littermate control embryos determined by transuterine ultrasound. Quantitative data for ejection fraction and fractional shortening are represented as mean and SEM from 7 control and 4 Ccbe1−/− embryos examined from 3 independent litters (P = 0.2 and P = 0.14 for ejection fraction and fractional shortening, respectively).