Sarcomere length fluctuations and flow in capillary endothelial cells.

Tensile force within non-muscle tissue cells is generated in actomyosin stress fibers, which are composed of contractile units called sarcomeres. The number of sarcomeres and sarcomere lengths dynamically change in the cell but the mechanisms by which these processes occur are not understood. Using live cell imaging of labeled sarcomeres, we show that sarcomere lengths continually fluctuate, with a fluctuation relaxation time of about 20 min.