ISSN:
1432-1017
Keywords:
Insect-fibrillar muscle
;
Cross bridge kinetics
;
Actin-Myosin interaction
;
Length dependent activation of muscle
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract Stretch induced activation and release induced deactivation of single glycerol-extracted insect flight muscle fibres were investigated. The results are interpreted to indicate that the muscle length controls the number of acting cross bridges, whereas their attachment-detachment kinetics in mainly determined by the state of strain of the cross bridges. It is concluded that the net detachment rate of the cross bridges is enhanced if the muscle is released thereby “unloading” the cross bridges. This behaviour of the unloaded cross bridge is a basic postulation of most of the molecular muscle contraction models. 1. The delayed tension rise induced by stretches of different amplitudes could be restored to the level before the stretch by a release to the initial length. 2. The delayed tension decrease induced by a release of moderate (up to δL=1.5% L i)amplitude is quantitatively restored within the delayed increase induced by the restretch to the initial length. 3. Stiffness, which decreased during the delayed tension drop after release, is restored during a delayed stiffness increase effected by a restretch to the initial length. 4. The rate and the extent of the stiffness drop after release increased with increasing amplitude of the release and with increasing temperature. 5. After the deactivation, i.e., after tension and stiffness achieved a new steady level after the release, the attached cross bridges are already in the same state of strain as they were before the release. This finding is interpreted to indicate that within the deactivation phase all cross bridges attached prior the release are replaced by cross bridges attached after the release. 6. The rate of tension and stiffness decay after release does not depend on the absolute muscle length but on the amplitude of the release which induced the deactivation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00539176
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