Biomaterial Database

The site of action of calcium in producing contraction in striated muscle. 1969

J M Gillis

1. Contraction of glycerinated crab myofibrils, suspended in a relaxing medium containing Mg-ATP and EGTA, was induced by iontophoretic application of Ca ions through a micropipette. Contraction was observed by phase-contrast microscopy.2. The large size of the sarcomere (10-15 mu) in the crab Cancer allowed applications of Ca ions at several discrete points along a single sarcomere.3. The threshold iontophoretic current needed to produce just visible contraction was measured for each position of the micropipette along the sarcomere. It was always lowest at the A-I junction.4. When Ca was delivered to the I band, the threshold current increased with the distance of the pipette from the A-I junction. Along the A band, the results depended on the sarcomere length: for short sarcomere lengths, the threshold current remained roughly constant over a large part of the A band; for long sarcomeres, it increased with the distance from the A-I junction in the same manner as in the case of the I band.5. As Ca reached the fibril by diffusion from the micropipette, the influence of the diffusion path on the threshold current was investigated.6. The length of the region of overlap of the thick and thin filaments in the A band was estimated by electron microscopy.7. The results demonstrate that, in order to produce contraction, Ca has to reach the region of overlap of the myofilaments.

UI	MeSH Term	Description	Entries
D007094	Imides	Organic compounds containing two acyl groups bound to NITROGEN.	Imide
D007478	Iontophoresis	Therapeutic introduction of ions of soluble salts into tissues by means of electric current. In medical literature it is commonly used to indicate the process of increasing the penetration of drugs into surface tissues by the application of electric current. It has nothing to do with ION EXCHANGE; AIR IONIZATION nor PHONOPHORESIS, none of which requires current.	Iontophoreses
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
D008858	Microscopy, Phase-Contrast	A form of interference microscopy in which variations of the refracting index in the object are converted into variations of intensity in the image. This is achieved by the action of a phase plate.	Phase-Contrast Microscopy,Microscopies, Phase-Contrast,Microscopy, Phase Contrast,Phase Contrast Microscopy,Phase-Contrast Microscopies
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
D009210	Myofibrils	The long cylindrical contractile organelles of STRIATED MUSCLE cells composed of ACTIN FILAMENTS; MYOSIN filaments; and other proteins organized in arrays of repeating units called SARCOMERES .	Myofilaments,Myofibril,Myofilament
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
D003445	Crustacea	A large subphylum of mostly marine ARTHROPODS containing over 42,000 species. They include familiar arthropods such as lobsters (NEPHROPIDAE), crabs (BRACHYURA), shrimp (PENAEIDAE), and barnacles (THORACICA).	Ostracoda,Ostracods,Crustaceas,Ostracod,Ostracodas
D004058	Diffusion	The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially FACILITATED DIFFUSION, is a major mechanism of BIOLOGICAL TRANSPORT.	Diffusions