Histology of highly-stretched beef muscle. IV. Evidence for movement of gap filaments through the Z-line, using the N2-line and M-line as markers

Locker, R.H.; Leet, N.G.

Journal of Ultrastructure Research 56(1): 31-38


ISSN/ISBN: 0022-5320
PMID: 985886
DOI: 10.1016/s0022-5320(76)80138-4
Accession: 068539376

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In heavily loaded rigor muscle, breaks or stretch zones often occur on one side of the Z-line. The N2-line in the opposite intact I-band is dragged toward the Z-line. This is considered to be evidence for its attachment to filaments, other than actin, running through the Z-line. These are probably the gap filaments. Further evidence in this direction was obtained from single fibers, overstretched in the prerigor state. In some sarcomeres the M-line was off-center in the same direction in consecutive sarcomeres, indicating connections between A-bands. Other evidence from muscle cooked under stretch, in which gap filaments are clearly visible, supports the attachment of the N2-line to the gap filaments.