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Comment
. 2016 Jul 1;311(1):C158-9.
doi: 10.1152/ajpcell.00373.2015.

Letter to the editor: Comments on Cornachione et al. (2016): "The increase in non-cross-bridge forces after stretch of activated striated muscle is related to titin isoforms"

Walter Herzog  1
Affiliations
Comment

Letter to the editor: Comments on Cornachione et al. (2016): "The increase in non-cross-bridge forces after stretch of activated striated muscle is related to titin isoforms"

Walter Herzog. Am J Physiol Cell Physiol. .
No abstract available

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Figures

Fig. 1.
Fig. 1.
Isometric reference force-time trace from a rabbit soleus myofibril contracting at an average sarcomere length of 3.0 μm (black line) and corresponding experimental contraction of that same myofibril starting with an isometric contraction at an average sarcomere length of 2.8 μm, then stretched to 3.0 μm and held isometrically at 3.0 μm (red line). The active force for the red trace at arrow 1 should be ∼14% greater than that for the black trace but it is only about half of the expected value. The total residual force enhancement (arrow 4) should be greater than the passive force enhancement (arrow 3), whereas it is clearly smaller. Together, these results suggest that the active force in the experimental (red trace) is ∼50% lower than expected compared with the black trace. The reasons for this inconsistency are not known but are likely associated with damage to the myofibril, incomplete activation, or deviation from the experimental protocol described in the methods section. [From Cornachione et al. (1).]
Fig. 2.
Fig. 2.
Isometric force-time trace of a rabbit cardiac myofibril at an average sarcomere length of 2.0 μm (black line), and corresponding experimental contraction of that same myofibril starting with an isometric contraction at an average sarcomere length of 1.8 μm, then stretched to 2.0 μm, and held isometrically at that final length (red line). Note the substantial passive force enhancement (arrow 1), indicating that cardiac myofibrils are predicted to exhibit residual force enhancement and static tension. The apparent lack of residual force enhancement (arrow 2), is inconsistent as the total force enhancement should be at least as large as the passive force enhancement (3, 4, 5). [From Cornachione et al. (1).]
See this image and copyright information in PMC

Comment in

Comment on

References

    1. Cornachione AS, Leite F, Bagni MA, Rassier DE. The increase in non-cross-bridge forces after stretch of activated striated muscle is related to titin isoforms. Am J Physiol Cell Physiol 310: C19–C26, 2016. - PMC - PubMed
    1. Gordon AM, Huxley AF, Julian FJ. The variation in isometric tension with sarcomere length in vertebrate muscle fibres. J Physiol 184: 170–192, 1966. - PMC - PubMed
    1. Herzog W, Leonard TR. Force enhancement following stretching of skeletal muscle: a new mechanism. J Exp Biol 205: 1275–1283, 2002. - PubMed
    1. Rassier DE, Herzog W. Effects of shortening on the stretch-induced force enhancement in single skeletal muscle fibers. J Biomech 37: 1305–1312, 2004. - PubMed
    1. Rassier DE, Herzog W, Wakeling JM, Syme D. Stretch-induced, steady-state force enhancement in single skeletal muscle fibers exceeds the isometric force at optimal fibre length. J Biomech 36: 1309–1316, 2003. - PubMed

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