Figure 9.

Light micrographs of 1-μm sections of developing hearts from a representative cultured normoglycemic 9.5 day p.c embryo culture (A and C), a representative cultured hyperglycemic 9.5 day p.c. embryo culture (B and D), a representative embryo at 9.5 days p.c. harvested from a control, normoglycemic mother, and a representative affected embryo at 9.5 days p.c. harvested from a hyperglycemic mother. Although the development of the epicardium, myocardium, and endocardium appears normal in all instances (A, B, E, and F), upon further examination of the hearts we noted a failure of endocardial cushion development in the embryos cultured in hyperglycemic media (20 mmol/L d-glucose, B and D) and in the affected embryos harvested from hyperglycemic mothers (F and H). Specifically, as illustrated in D and H, there is a failure of migration of endocardial cells overlying putative cushion areas into the cardiac jelly (CJ). Compare normal cushion development at this stage of development (C and C inset and G and G inset, which illustrate this migration (arrows)) to the arrest of cushion development (D and D inset and H and H inset, which illustrate a failure of migration of endocardial cells into the cardiac jelly (CJ)). Scale bars, 100 μm. Experiments were performed five times with separate litters.