Dynamic Model (IMAGE) University of Pennsylvania Caption Researchers at the University of Pennsylvania, Brown University and ETH Zurich have used a series of experiments to develop a dynamic model of the stresses that stretch growing tissue. This model is the first to take into account the complicated feedback effects of cells' molecular motors, which can respond to external stress by pulling harder on their environment, eventually tearing the tissue apart. When cells in developing tissue pull on each other in these dogbone-shaped wells, they first break in the long middle section. Credit University of Pennsylvania Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.