The elastimeter method was applied to the single muscle fiber of the frog semitendinosus to obtain the elastic moduli of the sarcolemma and myoplasm, as well as their relative contributions to resting fiber tension at different extensions. A bleb which was sucked into a flat-mouthed pipette at the fiber surface separated into an external sarcolemmal membrane and a thick inner myoplasmic region. Measurements showed that the sarcolemma does not contribute to intact fiber tension at sarcomere lengths below 3 µ. It was estimated that the sarcolemma contributed on the order of 10% to intact fiber tension at sarcomere lengths between 3 and 3.75 µ, and more so with further extension. Between these sarcomere lengths, the sarcolemma can be linearly extended and has a longitudinal elastic modulus of 5 x 106 dyne/cm2 (assuming a thickness of 0.1 µ). Resistance to deformation of the inner bleb region is due to myoplasmic elasticity. The myoplasmic elastic modulus was estimated by use of a model and was used to predict a fiber length-tension curve which agreed approximately with observations.
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1 May 1972
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May 01 1972
Mechanical Properties of the Sarcolemma and Myoplasm in Frog Muscle as a Function of Sarcomere Length
Stanley I. Rapoport
Stanley I. Rapoport
From the Laboratory of Neurophysiology, National Institute of Mental Health, Bethesda, Maryland 20014
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Stanley I. Rapoport
From the Laboratory of Neurophysiology, National Institute of Mental Health, Bethesda, Maryland 20014
Received:
August 30 1971
Online ISSN: 1540-7748
Print ISSN: 0022-1295
Copyright © 1972 by The Rockefeller University Press
1972
J Gen Physiol (1972) 59 (5): 559–585.
Article history
Received:
August 30 1971
Citation
Stanley I. Rapoport; Mechanical Properties of the Sarcolemma and Myoplasm in Frog Muscle as a Function of Sarcomere Length . J Gen Physiol 1 May 1972; 59 (5): 559–585. doi: https://doi.org/10.1085/jgp.59.5.559
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