Looping of chick embryo hearts in vitro.

Heart rudiments were removed from chick embryos at times earlier than any previously reported, and cultured in vitro, in order to test the widely reported view that looping is an intrinsic process. This view is based on experiments that are inadequately reported in certain key details. An organ culture technique was employed which combined ease of observation with good nutrient and mechanical support for the explants. A total of 23 hearts from stages before the onset of looping were examined. Hearts from as early as the six-somite stage looped normally in these experimental conditions. The view that heart looping is an intrinsic phenomenon is therefore confirmed.