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Jaffe & Créton | Calcium Waves |
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Jaffe & Créton | Calcium Waves |
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4/27/00: A manuscript with following summary is being revised for the Journal of Theoretical Biology. Your e-mailed comments would be appreciated
The Conduction Velocities of Calcium Action Potentials are Highly Conserved
LIONEL F. JAFFE ( ljaffe@mbl.edu )
SUMMARY
Calcium waves are a major signalling mechanism within living systems. They have been put into four classes based upon their velocities which vary from a nanometer/sec to nearly 100 cm/sec. The two best understood groups are 1. Fast calcium waves which move at 10-30 microns/sec in fully active systems and are propagated by a reaction-diffusion mechanism and 2. Slow calcium waves which move at 1-3 microns/sec and are thought to be mechanically propagated. Here I extend this scheme to calcium action potentials. These are here called ultrafast calcium waves and prove to move at about 15-40 cm/sec whereever the velocity is limited by intracellular mechanisms. Such waves are of course electrically rather than chemically or mechanically propagated.
The supporting data were critically compiled from published observations of the velocities of calcium action potentials in the syncitial trabecular reticulum of a sponge, in jellyfish and tunicate epithelia, in neurons within systems that range from jellyfish and sea urchins up to rat brains, in muscles within organisms that range from Ascaris to crabs and man and in the trap lobes of insectivorous plants. All of these waves move at about 15-40 cm/sec at 20 degrees C with no demonstrable relationship to cell width. This narrow, 2-3 fold range contrasts sharply with that of the better known sodium action potentials whose velocities vary by a thousand-fold in different systems and rise with cell width. Finally, the possible evolutionary basis of this remarkable conservation of velocity is discussed.
Spring has sprung,
Lionel