Biomaterial Database

Comparison of birefringence signals and calcium transients in voltage-clamped cut skeletal muscle fibres of the frog. 1983

L Kovács, and R A Schümperli, and G Szücs

The characteristic features of birefringence and calcium transients were compared in voltage-clamped cut skeletal muscle fibres: Birefringence signals were measured by introducing crossed polarizers above and below the fibres (+/- 45 degrees to the fibre axis) and using light of 790 nm. Calcium transients were monitored by the metallochromic indicator dye, Antipyrylazo III recording the changes in fibre absorbance at 720 nm. The dye entered the myoplasmic space by diffusion through the cut end. The early large birefringence signals, related to excitation-contraction coupling had a time course similar to that of calcium transients. The two signals had superimposable onset but the change in optical retardation peaked later and declined more slowly than the calcium signal. Using depolarizing pulses with increasing amplitudes both transients showed the same voltage dependence in the rate of rise, the time-to-peak and the peak amplitude. Birefringence signals recorded at different voltages along the strength-duration curve for contraction threshold had the same amplitudes and similar time constants for the falling phase comparable to the properties of the calcium transients. After applying dantrolene sodium both signals were reduced to the same extent. A shift in the contraction threshold was found towards more positive membrane potential values. The birefringence and calcium transients recorded at the new contraction threshold during the dantrolene treatment showed nearly the same size and time course as threshold transients obtained before the treatment. A subthreshold concentration of caffeine increased the peak amplitude of birefringence signals at a given voltage and decreased the latency of the signals. Birefringence transients at the new contraction threshold under caffeine were smaller than controls. Both effects are very similar to the changes in calcium transients due to caffeine treatment as previously reported. Consequently the voltage-dependent properties of birefringence and calcium transients and their responses to caffeine and dantrolene treatment are nearly the same. These results support the view that the changes in optical retardation of the fibres reflect calcium bound to some sarcoplasmic binding site rather than a potential change of the sarcoplasmic reticulum.

UI	MeSH Term	Description	Entries
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
D009119	Muscle Contraction	A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.	Inotropism,Muscular Contraction,Contraction, Muscle,Contraction, Muscular,Contractions, Muscle,Contractions, Muscular,Inotropisms,Muscle Contractions,Muscular Contractions
D009132	Muscles	Contractile tissue that produces movement in animals.	Muscle Tissue,Muscle,Muscle Tissues,Tissue, Muscle,Tissues, Muscle
D011893	Rana esculenta	An edible species of the family Ranidae, occurring in Europe and used extensively in biomedical research. Commonly referred to as "edible frog".	Pelophylax esculentus
D001718	Birefringence	The property of nonisotropic media, such as crystals, whereby a single incident beam of light traverses the medium as two beams, each plane-polarized, the planes being at right angles to each other. (Cline et al., Dictionary of Visual Science, 4th ed)	Birefraction,Double Refraction,Birefractions,Birefringences,Double Refractions,Refraction, Double,Refractions, Double
D002110	Caffeine	A methylxanthine naturally occurring in some beverages and also used as a pharmacological agent. Caffeine's most notable pharmacological effect is as a central nervous system stimulant, increasing alertness and producing agitation. It also relaxes SMOOTH MUSCLE, stimulates CARDIAC MUSCLE, stimulates DIURESIS, and appears to be useful in the treatment of some types of headache. Several cellular actions of caffeine have been observed, but it is not entirely clear how each contributes to its pharmacological profile. Among the most important are inhibition of cyclic nucleotide PHOSPHODIESTERASES, antagonism of ADENOSINE RECEPTORS, and modulation of intracellular calcium handling.	1,3,7-Trimethylxanthine,Caffedrine,Coffeinum N,Coffeinum Purrum,Dexitac,Durvitan,No Doz,Percoffedrinol N,Percutaféine,Quick-Pep,Vivarin,Quick Pep,QuickPep
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D003620	Dantrolene	Skeletal muscle relaxant that acts by interfering with excitation-contraction coupling in the muscle fiber. It is used in spasticity and other neuromuscular abnormalities. Although the mechanism of action is probably not central, dantrolene is usually grouped with the central muscle relaxants.	Dantrium,Dantrolene Sodium,Sodium, Dantrolene
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
D013997	Time Factors	Elements of limited time intervals, contributing to particular results or situations.	Time Series,Factor, Time,Time Factor