Cardiac looping in experimental conditions: Effects of extraembryonic forces

The chick embryo is a popular experimental model used to study the mechanisms of cardiac looping. To facilitate oxygen transport, researchers typically culture the embryo on the surface of the medium. Such preparations, however, expose the embryo and the heart to surface tension that is not present in ovo. This study investigates the influence that surface and extraembryonic membrane tensions have on looping morphology. To eliminate surface tension, we developed a technique in which the embryo is cultured under a thin layer of fluid. To eliminate membrane tension, the membrane was removed. Our results show that both tensions can affect looping, with surface tension potentially having a much greater effect. Moreover, we show that surface tension can alter results in one classic looping experiment. (C) 2002 Wiley-Liss, Inc.