Histological studies of normal and mutant mouse embryo hearts (a glycogen content study)

Mutant tail-short (Ts/+) embryos are developmentally retarded compared with normal +/+ litter mates. The development of the heart of Ts/+ embryos is severely affected if the tail-short gene is transferred to a new genetic (50% A/Gr) background. The aim of the present study was to investigate the glycogen content of the sinus muscle, the cushion and the atrial and ventricular walls of the heart. In normal embryos the sinus muscle is well developed by the 15th day post coitum (d.p.c.) and is crowded with glycogen granules. In Ts/+ mutant embryos, on the other hand, the development of this muscle is retarded and it contains only a little, diffusely distributed glycogen. The atrial and ventricular walls of embryos with a normal heart are well trabeculated and contain a large quantity of glycogen granules, while in mutant embryos they are less well trabeculated and contain only a little glycogen in a diffuse of finely granular form.