Biomaterial Database

The effect of temperature on the asymmetrical charge movement in squid giant axons. 1979

J E Kimura, and H Meves

1. Asymmetrical displacement currents ('gating currents') have been recorded in intracellularly perfused squid giant axons by averaging the currents associated with depolarizing and hyperpolarizing voltage pulses. The effect of temperature on 'gating currents' was studied and compared with the effect of temperature on Na currents. 2. Increasing the temperature in seven steps from 0 to 15 degrees C increased the area under the on- and off-response (Qon, Qoff). The average Q10 values for Qon and Qoff (measured with depolarizing pulses to 0 to 20 mV) were 1.41 and 1.62, respectively. 3. The on- and the off-response were described mathematically by the sum of two exponentials. The first component of the on-response, Qon 1, represented 80% or more of the total charge movement associated with 2.5 msec pulses; the Q10 of Qon 1 was similar to that of total Qon. The first component of the off-response, Qoff 1, represented 50--70% of total Qoff; its Q10 was smaller than that of total Qoff. 4. The temperature dependence of the rate constants (tauon 1)-1 and (tauoff 1)-1 was stronger at temperatures below 6--8 degrees C (Q10 = 3.1--6.4) than at higher temperatures (Q10 = 2.0--3.3). In an Arrhenius plot two lines of different slope were required to fit the data. 5. The effect of increasing the temperature on the Q vs. V curve can be described as an increase of Qmax or, alternatively, as a shift of the curve to more negative potentials. 6. Increasing the temperature from 0 to 15 degrees C increased the peak of the Na current (recorded in sea water with a fifth of the normal Na concentration), increased the rate constants taum-1 and tauh-1 and shifted the m3infinity and hinfinity curves to more positive potentials. 7. The Q10 of the rate constant taum-1 varied between 2.04 and 2.61 and was independent of temperature. In an Arrhenius plot the values for taum-1 could be fitted by a single line. 8. The results support the view that 'gating current' does not simply reflect changes of the Na activation variable m. The increase of Qon, Qoff with increasing temperature may be attributed to an increase in membrane fluidity. The possibility that those charges which become mobile at higher temperatures may not be related to gating is considered.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008564	Membrane Potentials	The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization).	Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D001369	Axons	Nerve fibers that are capable of rapidly conducting impulses away from the neuron cell body.	Axon
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures
D049832	Decapodiformes	A superorder of CEPHALOPODS comprised of squid, cuttlefish, and their relatives. Their distinguishing feature is the modification of their fourth pair of arms into tentacles, resulting in 10 limbs.	Cuttlefish,Illex,Sepiidae,Squid,Todarodes,Cuttlefishs,Decapodiforme,Illices,Squids,Todarode
D066298	In Vitro Techniques	Methods to study reactions or processes taking place in an artificial environment outside the living organism.	In Vitro Test,In Vitro Testing,In Vitro Tests,In Vitro as Topic,In Vitro,In Vitro Technique,In Vitro Testings,Technique, In Vitro,Techniques, In Vitro,Test, In Vitro,Testing, In Vitro,Testings, In Vitro,Tests, In Vitro,Vitro Testing, In