Cymarine: A cardiotonic cardiac glycoside found in STROPHANTHUS. The aglycone is STROPHANTHIN.Lubricants: Compounds that provide LUBRICATION between surfaces in order to reduce FRICTION.Lubrication: The application of LUBRICANTS to diminish FRICTION between two surfaces.Viscosity: The resistance that a gaseous or liquid system offers to flow when it is subjected to shear stress. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Blood Viscosity: The internal resistance of the BLOOD to shear forces. The in vitro measure of whole blood viscosity is of limited clinical utility because it bears little relationship to the actual viscosity within the circulation, but an increase in the viscosity of circulating blood can contribute to morbidity in patients suffering from disorders such as SICKLE CELL ANEMIA and POLYCYTHEMIA.Ships: Large vessels propelled by power or sail used for transportation on rivers, seas, oceans, or other navigable waters. Boats are smaller vessels propelled by oars, paddles, sail, or power; they may or may not have a deck.Friction: Surface resistance to the relative motion of one body against the rubbing, sliding, rolling, or flowing of another with which it is in contact.Methylcellulose: Methylester of cellulose. Methylcellulose is used as an emulsifying and suspending agent in cosmetics, pharmaceutics and the chemical industry. It is used therapeutically as a bulk laxative.Cardenolides: C(23)-steroids with methyl groups at C-10 and C-13 and a five-membered lactone at C-17. They are aglycone constituents of CARDIAC GLYCOSIDES and must have at least one double bond in the molecule. The class includes cardadienolides and cardatrienolides. Members include DIGITOXIN and DIGOXIN and their derivatives and the STROPHANTHINS.Cardiac Glycosides: Cyclopentanophenanthrenes with a 5- or 6-membered lactone ring attached at the 17-position and SUGARS attached at the 3-position. Plants they come from have long been used in congestive heart failure. They increase the force of cardiac contraction without significantly affecting other parameters, but are very toxic at larger doses. Their mechanism of action usually involves inhibition of the NA(+)-K(+)-EXCHANGING ATPASE and they are often used in cell biological studies for that purpose.Cardanolides: The aglycone constituents of CARDIAC GLYCOSIDES. The ring structure is basically a cyclopentanoperhydrophenanthrene nucleus attached to a lactone ring at the C-17 position.Digitoxin: A cardiac glycoside sometimes used in place of DIGOXIN. It has a longer half-life than digoxin; toxic effects, which are similar to those of digoxin, are longer lasting. (From Martindale, The Extra Pharmacopoeia, 30th ed, p665)Acetyldigoxins: Alpha- or beta-acetyl derivatives of DIGOXIN or lanatoside C from Digitalis lanata. They are better absorbed and longer acting than digoxin and are used in congestive heart failure.Acetyldigitoxins: Cardioactive derivatives of lanatoside A or of DIGITOXIN. They are used for fast digitalization in congestive heart failure.Glycosides: Any compound that contains a constituent sugar, in which the hydroxyl group attached to the first carbon is substituted by an alcoholic, phenolic, or other group. They are named specifically for the sugar contained, such as glucoside (glucose), pentoside (pentose), fructoside (fructose), etc. Upon hydrolysis, a sugar and nonsugar component (aglycone) are formed. (From Dorland, 28th ed; From Miall's Dictionary of Chemistry, 5th ed)Atrial Flutter: Rapid, irregular atrial contractions caused by a block of electrical impulse conduction in the right atrium and a reentrant wave front traveling up the inter-atrial septum and down the right atrial free wall or vice versa. Unlike ATRIAL FIBRILLATION which is caused by abnormal impulse generation, typical atrial flutter is caused by abnormal impulse conduction. As in atrial fibrillation, patients with atrial flutter cannot effectively pump blood into the lower chambers of the heart (HEART VENTRICLES).Atrial Fibrillation: Abnormal cardiac rhythm that is characterized by rapid, uncoordinated firing of electrical impulses in the upper chambers of the heart (HEART ATRIA). In such case, blood cannot be effectively pumped into the lower chambers of the heart (HEART VENTRICLES). It is caused by abnormal impulse generation.Equipment Safety: Freedom of equipment from actual or potential hazards.Quality Indicators, Health Care: Norms, criteria, standards, and other direct qualitative and quantitative measures used in determining the quality of health care.Device Approval: Process that is gone through in order for a device to receive approval by a government regulatory agency. This includes any required preclinical or clinical testing, review, submission, and evaluation of the applications and test results, and post-marketing surveillance. It is not restricted to FDA.Writing: The act or practice of literary composition, the occupation of writer, or producing or engaging in literary work as a profession.Catheter Ablation: Removal of tissue with electrical current delivered via electrodes positioned at the distal end of a catheter. Energy sources are commonly direct current (DC-shock) or alternating current at radiofrequencies (usually 750 kHz). The technique is used most often to ablate the AV junction and/or accessory pathways in order to interrupt AV conduction and produce AV block in the treatment of various tachyarrhythmias.Apocynum: A plant genus of the family APOCYNACEAE. On rare occasions it is called Milkweed, but should not be confused with true Milkweed (ASCLEPIAS).Periosteum: Thin outer membrane that surrounds a bone. It contains CONNECTIVE TISSUE, CAPILLARIES, nerves, and a number of cell types.British Columbia: A province of Canada on the Pacific coast. Its capital is Victoria. The name given in 1858 derives from the Columbia River which was named by the American captain Robert Gray for his ship Columbia which in turn was named for Columbus. (From Webster's New Geographical Dictionary, 1988, p178 & Room, Brewer's Dictionary of Names, 1992, p81-2)WyomingSulfolobales: An order of CRENARCHAEOTA consisting of aerobic or facultatively aerobic, chemolithotrophic cocci which are extreme thermoacidophiles. They lack peptidoglycan in their cell walls.Digoxin: A cardiotonic glycoside obtained mainly from Digitalis lanata; it consists of three sugars and the aglycone DIGOXIGENIN. Digoxin has positive inotropic and negative chronotropic activity. It is used to control ventricular rate in ATRIAL FIBRILLATION and in the management of congestive heart failure with atrial fibrillation. Its use in congestive heart failure and sinus rhythm is less certain. The margin between toxic and therapeutic doses is small. (From Martindale, The Extra Pharmacopoeia, 30th ed, p666)Plant Bark: The outer layer of the woody parts of plants.

Increase in dissociation rate constants of cardiotonic steroid-brain (Na+ + K+)-ATPase complexes by reduction of the unsaturated lactone. (1/2)

Several cardiotonic steroids have been modified by reduction of the unsaturated lactone and their interactions with the sodium- and potassium-activated ATPase ((Na+ + K+)-ATPase) have been investigated. Reduction of the unsaturated lactone results in a decrease in binding affinity due primarily to an increase in the dissociation rate constant concomitant with a decrease in the activation free energy of dissociation. This decrease in activation free energy is about 2 to 4 kcal, which is approximately equal to the energy of one hydrogen bond. It is suggested that the increase in dissociation rate due to reduction of the unsaturated lactone may make possible the use of these compounds as affinity ligands for purification of the (Na+ + K+)-ATPase or an ouabain-binding fragment.  (+info)

Photoaffinity labeling of (Na+K+)-ATPase with [125I]iodoazidocymarin. (2/2)

A radioiodinated, photoactive cardiac glycoside derivative, 4'-(3-iodo-4-azidobenzene sulfonyl)cymarin (IAC) was synthesized and used to label (Na+K+)-ATPase in crude membrane fractions. In the dark, IAC inhibited the activity of (Na+K+)-ATPase in electroplax microsomes from Electrophorus electricus with the same I50 as cymarin. [125I]IAC binding, in the presence of Mg2+ and Pi, was specific, of high affinity (KD = 0.4 microM), and reversible (k-1 = 0.11 min-1) at 30 degrees C. At 0 degree C, the complex was stable for at least 3 h, thus permitting washing before photolysis. Analysis of [125]IAC photolabeled electroplax microsomes by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) (7-14%) showed that most of the incorporated radioactivity was associated with the alpha (Mr = 98,000) and beta (Mr = 44,000) subunits of the (Na+K+)-ATPase (ratio of alpha to beta labeling = 2.5). A higher molecular weight peptide (100,000), similar in molecular weight to the brain alpha(+) subunit, and two lower molecular weight peptides (12,000-15,000), which may be proteolipid, were also labeled. Two-dimensional gel electrophoresis (isoelectric focusing then SDS-PAGE, 10%) resolved the beta subunit into 12 labeled peptides ranging in pI from 4.3 to 5.5. When (Na+K+)-ATPase in synaptosomes from monkey brain cortex was photolabeled and analyzed by SDS-PAGE (7-14%), specific labeling of the alpha(+), alpha, and beta subunits could be detected (ratio of alpha(+) plus alpha to beta labeling = 35). The results show that [125I]IAC is a sensitive probe of the cardiac glycoside binding site of (Na+K+)-ATPase and can be used to detect the presence of the alpha(+) subunit in crude membrane fractions from various sources.  (+info)