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K A Edman

Publications and source records attributed to K A Edman.

69 records · Page 4Linked to original sources
PubMed1972

Changes in sarcomere length during isometric tension development in frog skeletal muscle.

1. Changes in sarcomere length during isometric contraction of isolated semitendinosus muscle fibres from the frog were studied using laser diffraction techniques. Movements of the first-order diffraction line relative to the zero-order reference were recorded from a screen on continuously moving film. Sarcomere length changes of 50 A could be resolved in this way.2. Following a latent period of approximately 12 msec after the stimulus of a single skeletal muscle fibre at 1-2 degrees C, there appeared to be a simultaneous onset of tension development and sarcomere shortening. Provided that the fibre was uniformly excited along its length, different regions shortened together by approximately the same amount. The extent of the shortening was a function of the total compliance of the tendons and tension measuring device.3. During the plateau of a smooth tetanus no fluctuations of first-order line width or zero- to first-order line spacing were detectable at any point examined along the preparation. This finding provides evidence that, in a functionally intact fibre, no synchronous oscillations of the sarcomeres, at least no length changes exceeding 50 A, occur during a fused tetanus. Furthermore, the fact that the first-order line did not increase in width as the preparation went from rest to full activity indicates that contraction proceeds without appreciable change in distribution of sarcomere lengths.4. The sarcomere movements during relaxation differed along the length of the fibre. As the tension declined smoothly, sarcomeres in some parts of the fibre underwent further shortening, while the end sarcomeres near the tendons and in one or two regions in the middle segment of the fibre were further extended. These data indicate that the duration of the mechanical activity differs in different regions along the length of the fibre. The pattern of relaxation, i.e. the behaviour of the sarcomeres in different fibre segments, is unique to any particular fibre.

Animals↗
PubMed1969

Laser diffraction studies on single skeletal muscle fibers.

Sarcomere movements during isometric tetanic contractions were resolved to 50 angstroms by diffraction techniques. After a latent period that followed the first stimulus, all sarcomeres shortened simultaneously and uniformly. Oscillations in length and tension in synchrony with the stimuli occurred during an incomplete tetanus. However, no oscillations in length were detected during the plateau of a tetanus.

Animals↗
PubMed1966

The relation between sarcomere length and active tension in isolated semitendinosus fibres of the frog.

1. The relation between sarcomere length and tetanic tension at various states of shortening was investigated in single frog semitendinosus fibres that were subjected to different degrees of prestretch (2.45-3.0 mu).2. The capacity to produce tension changed in a characteristic way during shortening, the tension output at each length being determined by the actual sarcomere spacing without reference to the striation spacing at the onset of contraction.3. The capacity to shorten against a given load was independent of the initial striation spacing, provided the load was not great enough to cause fatigue of the fibre.4. The findings strongly suggest that the functionally relevant structure of the contractile system of the intact muscle cell is always in the same state at a given sarcomere length independent of how the previous length change has been achieved, by passive extension at rest or by active shortening from a prestretched position. This probably means that contraction involves a structural change of the contractile system, which, at least in so far as it is of relevance to function, is a true reversal of the change produced by passive extension of the resting fibre. These aspects of the contractile behaviour of the intact muscle fibre are in full accord with the concepts of the sliding-filament hypothesis of muscular contraction.

Animals↗
PubMedDate not supplied

The instantaneous force-velocity relationship as an index of the contractile state in cardiac muscle.

The instantaneous force-velocity curve of mammalian myocardium has a hyperbolic shape like that of skeletal muscle. Similar to the situation in single skeletal muscle fibres maximum speed of shortening and maximum contractile force in myocardium are altered in parallel as the state of activity is changed. Various inotropic interventions affect the force-velocity relation in the same way as occurs when the activity is altered during the course of the contraction. These findings support the view that activator-calcium governs both the number of active crossbridges between the A and I filaments during tension development and the rate of turnover of the myosin bridges during shortening at zero load.

Animals↗