Chapter 4. X-Ray Diffraction Studies on Cardiac Muscle
- Ruth Porter and
- David W. Fitzsimons
Published Online: 30 MAY 2008
Copyright © 1974 Ciba Foundation
Ciba Foundation Symposium 24 - Physiological Basis of Starling's Law of the Heart
How to Cite
Matsubara, I. and Millman, B. M. (1974) X-Ray Diffraction Studies on Cardiac Muscle, in Ciba Foundation Symposium 24 - Physiological Basis of Starling's Law of the Heart (eds R. Porter and D. W. Fitzsimons), John Wiley & Sons, Ltd, Chichester, UK. doi: 10.1002/9780470720066.ch4
- Published Online: 30 MAY 2008
- Published Print: 1 JAN 1974
Print ISBN: 9789021940250
Online ISBN: 9780470720066
- cardiac muscle;
- x-ray diffraction;
- vertebrate heart muscle;
- electron microscopy
Light and X-ray diffraction patterns were obtained from trabecular and papillary muscles of cat heart in the living resting state and in rigor. Equatorial X-ray patterns showed two pairs of reflections which may be classified as the 1,0 and 1,1 reflections from a hexagonal array of myofilaments. In the living resting state, the 1,0 reflection was stronger than the 1,l reflection, whereas in rigor the 1,l reflection was as strong as the 1,0 reflection. These changes in intensity were similar to those found in vertebrate skeletal muscle and suggest that the mechanism of cross-bridge attachment to actin is similar in both muscles.
The meridional X-ray pattern from living resting heart muscle was characterized by myosin-related reflections, which included off-meridional layer-lines associated with projections (cross-bridges) from the thick filaments. This pattern was similar to that from resting, vertebrate, skeletal muscle except that the layer-lines were weaker. This weakness indicated that the projections are less-well ordered in heart muscle than in skeletal muscle.
The pattern from heart muscle in rigor showed strong reflections related to those from actin but weak reflections associated with myosin and this pattern was essentially the same as that from vertebrate skeletal muscle in rigor. The greater intensity of actin reflections indicated that the cross-bridges are attached to actin in the rigor state.