Small Animal Muscle Dynamometry System

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Request: We are requesting $ 121,330 for the purchase of a world-unique small animal muscle testing system, that will allow for the simultaneous and instantaneous measurement of muscle force, fascicle length, and changes in individual sarcomere lengths in skeletal muscles of small animals (mice, frogs, rats), while controlling all activation parameters. The system is a combination of multi-photon and second harmonic generation microscopy and a mechanical tester for small skeletal muscles. We already have a cutting-edge multi-photon excitation microscope powered by two femto-second pulsed lasers that allow for second harmonic generation microscopy. This system was purchased with a recent Canada Foundation for Innovation grant for approximately $ CDN 1.2 million. The microscope system allows for deep tissue penetration and accurate identification of the anisotropic bands (A-bands or myosin filament region) of individual sarcomeres, thus allowing for instantaneous measurements of individual sarcomere lengths, sarcomere velocities and sarcomere length non-uniformities during dynamic muscle contractions. With this RTI application, we would like to expand this system to include a mechanical testing system for skeletal muscles from small animals for full description of the mechanics of muscle contraction while measuring simultaneously the sarcomere dynamics. Such a system cannot be purchased commercially, and we propose to buy the required system components and build the system in house. The uniqueness of the system lies in the fact that we will be able to visualize single sarcomeres along strings of serial sarcomeres in an entire muscle during contraction, and quantify instantaneous sarcomere lengths, sarcomere length non-uniformities, and dynamic interactions of individual sarcomeres in an entire muscle, thus providing relevant and currently inaccessible information to muscle physiologists and biomechanists. ***Once finalized, this equipment system will allow us to address some fundamental questions in muscle mechanics, including the relationship between sarcomere length non-uniformities and basic muscle properties, such as the isometric force-length relationship, residual force enhancement following eccentric contraction, and instabilities of sarcomere length and force on the descending limb of the force-length relationship. Although some of these ideas have been contemplated for decades, the proposed system will be the first to allow for systematic evaluation of sarcomere lengths non-uniformities and skeletal muscle properties and function.***We have conceived this idea in consultation with local and international colleagues who are eager to collaborate with us, and send us students for specific projects, once this system has been fully implemented, tested and validated. Pilot results using static, steady- state, and passive muscles using second harmonic generation microscopy, have provided encouraging results. **