PMID: 591919Dec 1, 1977

Mechanical control of the rising phase of contraction of frog skeletal and cardiac muscle

The Journal of General Physiology
E Bozler

Abstract

The effect of shortening on contractile activity was studied in experiments in which shortening during the rising phase of an isotonic contraction was suddenly stopped. At the same muscle length and the same time after stimulation the rise in tension was much faster, if preceded by shortening, than during an isometric contraction, demonstrating an increase in contractile activity. In this experiment the rate of tension rise determined in various phases of contraction was proportional to the rate of isotonic shortening at the same time after stimulation. Therefore, the time course of the isotonic rising phase could be derived from the tension rise after shortening. The rate of isotonic shortening was found to be unrelated to the tension generated at various lengths and to correspond closely to the activation process induced by shortening. The length response explains differences between isotonic and isometric contractions with regard to energy release (Fenn effect) and time relations. These results extend previous work which showed that shortening during later phases of a twitch prolongs, while lengthening abbreviates contraction. Thus the length responses, which have been called shortening activation and lengthening deactivatio...Continue Reading

References

Mar 1, 1975·The Journal of General Physiology·E Bozler
Feb 1, 1976·Circulation Research·F J Julian, R L Moss
Aug 1, 1972·The Journal of General Physiology·K L Briden, N R Alpert
Sep 1, 1972·The Journal of General Physiology·E Bozler
Nov 1, 1973·The Journal of General Physiology·E Bozler, J F Delahayes
Jan 1, 1970·The Journal of General Physiology·S Winegrad

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