(BQ) Part 2 book “Muscle contraction and cell motility” has contents: Stiffness of contracting human muscle measured with supersonic shear imaging, essential myosin light chains regulate myosin function and muscle contraction, the catch state of molluscan smooth muscle, and other contents. | Chapter 8 Stiffness of Contracting Human Muscle Measured with Supersonic Shear Imaging Kazushige Sasakia and Naokata Ishiib aFaculty of Human Sciences and Design, Japan Women’s University, Tokyo 112-8681, Japan bDepartment of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan sasakik@, ishii@ Recently, an ultrasound-based elastographic technique called supersonic shear imaging (SSI) has been developed and used to measure stiffness (shear modulus) of in vivo muscles. This review describes the theoretical background of SSI, summarizes some basic observations on the shear modulus of contracting human muscles, and presents the latest experimental findings. It is well documented that the muscle shear modulus increases with increasing intensity of contraction. A linear association has been found between the muscle shear modulus and motor unit activity assessed with surface electromyography. Moreover, we have demonstrated both the length-dependent changes in shear Muscle Contraction and Cell Motility: Fundamentals and Developments Edited by Haruo Sugi Copyright © 2017 Pan Stanford Publishing Pte. Ltd. ISBN 978-981-4745-16-1 (Hardcover), 978-981-4745-17-8 (eBook) 210 Stiffness of Contracting Human Muscle Measured with Supersonic Shear Imaging modulus and the association of shear modulus with contractile force, even when the motor unit activity is controlled by direct electric stimulation of muscle. These findings provide strong evidence that the muscle shear modulus measured with SSI can be a useful indicator of muscle activation level or contractile force in a variety of conditions. While the structures and mechanisms determining muscle stiffness in vivo are not fully understood, the result of our pilot study suggests that the shear modulus of contracting muscle may reflect both the single-fiber stiffness (cross-bridge kinetics) and the motor unit recruitment,
