Beating Heart Muscle Cells (video) Gladstone Institutes Loading video... Caption The video shows beating heart muscle cells, or cardiomyoctes, at day 10 of differentiation. Credit Jeff Alexander Usage Restrictions Please contact Gladstone Press Relations for reprint permissions. 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.