Control of Contractility in Spirostomum by Dissociated Calcium Ions
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TLDR
The evidence shows that calcium release from an interval compartment is directly associated with the onset of contraction in Spirostomum, and that the removal of calcium, through some internal sequestering mechanism, signals relaxation.Abstract:
The freshwater protozoan, Spirostomum ambiguum, exhibits generalized contraction when electrically stimulated with a DC pulse. Light and electron microscopic studies show a subcortical filamentous network, believed responsible for generating contractile tension, in association with vesicles which were shown to accumulate calcium oxalate precipitates. Organisms microinjected with the calcium-sensitive, bioluminescent protein, aequorin, emit light when stimulated to contract. Analyses of cinefilm records of electrically induced contraction indicate that contraction may occur up to 25 msec after the onset of stimulation at a point when the calcium-aequorin light emission is at a peak. The evidence shows that calcium release from an interval compartment is directly associated with the onset of contraction in Spirostomum, and that the removal of calcium, through some internal sequestering mechanism, signals relaxation.read more
Citations
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Aequorin luminescence: relation of light emission to calcium concentration--a calcium-independent component.
TL;DR: Light emission from the calcium-sensitive bioluminescent protein aequorin was measured at calcium ion concentrations of 10(-9) to 10(-2) molar and the complete relation is well described by a two-state model involving three calcium-binding sites.
References
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Journal ArticleDOI
Extraction, Purification and Properties of Aequorin, a Bioluminescent Protein from the Luminous Hydromedusan, Aequorea
Journal ArticleDOI
The action of various cations on muscle protoplasm
Book ChapterDOI
Energized Calcium Transport and Relaxing Factors
TL;DR: The energized calcium transport is described and the relaxing factors are discussed and the behavior of actomyosin in vitro and its correlation to in vivo contraction and relaxation of actonomyosin is discussed.
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