Key result
Intramuscular temperature gradients in Manduca sexta flight muscles enable cross-bridges to store and elastically return energy during muscle lengthening and shortening.
May inform cardiac muscle energetics; leaves open relevance to human myocardial performance.
Muscles not only generate force. They may act as springs, providing energy storage to drive locomotion. Although extensible myofilaments are implicated as sites of energy storage, we show that intramuscular temperature gradients may enable molecular motors (cross-bridges) to store elastic strain energy. By using time-resolved small-angle x-ray diffraction paired with in situ measurements of mechanical energy exchange in flight muscles of Manduca sexta, we produced high-speed movies of x-ray equatorial reflections, indicating cross-bridge association with myofilaments. A temperature gradient within the flight muscle leads to lower cross-bridge cycling in the cooler regions. Those cross-bridges could elastically return energy at the extrema of muscle lengthening and shortening, helping drive cyclic wing motions. These results suggest that cross-bridges can perform functions other than contraction, acting as molecular links for elastic energy storage.
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George et al. (2013) studied Flight muscle mechanics in Manduca sexta. Intramuscular temperature gradients was evaluated on Mechanical energy exchange and cross-bridge association with myofilaments. Intramuscular temperature gradients in Manduca sexta flight muscles enable cross-bridges to store and elastically return energy during muscle lengthening and shortening.
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