Biomaterial Database

Excitation-contraction coupling in amphioxus muscle cells. 1971

S Hagiwara, and M P Henkart, and Y Kidokoro

1. Excitation-contraction coupling was studied in myotomal muscles of amphioxus, Branchiostoma californiense.2. The action potential of a muscle cell produces a twitch with a rise time of 30-40 msec at 11 degrees C and its Q(10) is about 2.2.3. The twitch increases in amplitude with increasing external Ca concentration and is abolished in Ca-free saline (1 mM-EGTA and 55.7 mM-MgCl(2)); the twitch amplitude is suppressed by Co or La ions.4. Caffeine at concentrations above 1 mM in the external saline causes a prolongation of the action potential and a contracture which lasts several minutes.5. After exposure to caffeine the responsiveness of the muscle to subsequent applications of caffeine recovers in normal saline in 20-30 minutes but not in Ca-free saline.6. The amplitude of the caffeine contracture is independent of the external Ca concentration and is unaltered after the twitch is eliminated in Ca-free saline.7. After exposure to caffeine a full-sized twitch can be obtained before the responsiveness to caffeine shows any significant recovery.8. It is concluded that the twitch is produced by the Ca influx resulting from the increased permeability of the muscle cell membrane to Ca during the action potential and that the Ca mobilized by caffeine is not necessary to the initiation of the twitch.9. Electronmicroscopy shows the existence of sarcoplasmic reticulum.

UI	MeSH Term	Description	Entries
D007094	Imides	Organic compounds containing two acyl groups bound to NITROGEN.	Imide
D007811	Lanthanum	The prototypical element in the rare earth family of metals. It has the atomic symbol La, atomic number 57, and atomic weight 138.91. Lanthanide ion is used in experimental biology as a calcium antagonist; lanthanum oxide improves the optical properties of glass.
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D008854	Microscopy, Electron	Microscopy using an electron beam, instead of light, to visualize the sample, thereby allowing much greater magnification. The interactions of ELECTRONS with specimens are used to provide information about the fine structure of that specimen. In TRANSMISSION ELECTRON MICROSCOPY the reactions of the electrons that are transmitted through the specimen are imaged. In SCANNING ELECTRON MICROSCOPY an electron beam falls at a non-normal angle on the specimen and the image is derived from the reactions occurring above the plane of the specimen.	Electron Microscopy
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
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
D002463	Cell Membrane Permeability	A quality of cell membranes which permits the passage of solvents and solutes into and out of cells.	Permeability, Cell Membrane
D002816	Chordata, Nonvertebrate	A portion of the animal phylum Chordata comprised of the subphyla CEPHALOCHORDATA; UROCHORDATA, and HYPEROTRETI, but not including the Vertebrata (VERTEBRATES). It includes nonvertebrate animals having a NOTOCHORD during some developmental stage.	Invertebrate Chordate,Chordatas, Nonvertebrate,Chordate, Invertebrate,Chordates, Invertebrate,Invertebrate Chordates,Nonvertebrate Chordata,Nonvertebrate Chordatas