Fig. 4. Distribution of velocities of actin filament sliding over myosin at baseline ( A ) and with 2 mm 2,3-butanedione 2-monoxime (BDM) ( B ). Individual frame-to-frame velocities from tracked filaments are plotted in a frequency histogram. Each histogram contains data from 150 filaments taken from five separate assays. Temperature, 30°C. Additional information regarding this is available on the Anesthesiology Web site at http://www.anesthesiology.org.