Abstract
Fibrils from the indirect flight muscle of Drosophila melanogaster which have been teased into a solution containing 0.1 M KCl, 2 mM EDTA, 4 mM MgCl2, and 2.5 mM ATP at pH 7.0 can be made to shorten to 10 per cent of their initial length by reducing the level of ATP at a pH of about 8 or by briefly treating the fibrils with trypsin before lowering the level of ATP. Fibrils shortened in either of these ways, when dehydrated and immersed in nitrobenzene, display a strong positively birefringent band at the level of the Z band. In the trypsin-treated fibrils the width of this Z band increases as the fibril shortens. The data obtained are in agreement with the view that the positively birefringent Z band results from the interdigitation of A filaments in adjacent sarcomeres. With shortening to about 35 per cent of the initial length, the cytological pattern suggests that the A filaments of alternate as well as of adjacent A regions interdigitate.
Full Text
The Full Text of this article is available as a PDF (562.5 KB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- ASHLEY C. A., PORTER K. R., PHILPOTT D. E., HASS G. M. Observations by electron microscopy on contraction of skeletal myofibrils induced with adenosinetriphosphate. J Exp Med. 1951 Jul 1;94(1):9–20. doi: 10.1084/jem.94.1.9. [DOI] [PMC free article] [PubMed] [Google Scholar]
- GILEV V. P. A study of myofibril sarcomere structure during contraction. J Cell Biol. 1962 Jan;12:135–147. doi: 10.1083/jcb.12.1.135. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HANSON J. Studies on the cross-striation of the indirect flight myofibrils of the blowfly Calliphora. J Biophys Biochem Cytol. 1956 Nov 25;2(6):691–710. doi: 10.1083/jcb.2.6.691. [DOI] [PMC free article] [PubMed] [Google Scholar]
- SJOSTRAND F. S., ANDERSSON-CEDERGREN E. The ultrastructure of the skeletal muscle myofilaments at various states of shortening. J Ultrastruct Res. 1957 Nov;1(1):74–108. doi: 10.1016/s0022-5320(57)80014-8. [DOI] [PubMed] [Google Scholar]