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digitalis (dĭjˌĭtălˈĭs), any of several chemically similar drugs used primarily to increase the force and rate of heart contractions, especially in damaged heart muscle. The effects of the drug were known as early as 1500 B.C.; it was later obtained from the foxglove plant, Digitalis purpurea, and from fuchsia (see figwort). It was used in the 19th cent. to treat dropsy (edema). Digitalislike substances are found in a wide variety of plants and animals, including the poisons of some toad species. Foxglove remains the main source for the drug used medically today.

Chemically, digitalis is composed of a sugar (glycoside), a steroid, and a cyclic ester known as a lactone; the pharmacological activity varies according to differences, occurring naturally or introduced synthetically, in the steroid or sugar portions. Common preparations include digitalis, digitoxin, and digoxin, all from foxglove, and ouabain from Strophanthus gratus, the ouabaio tree; these vary both in solubility and in rapidity and duration of effect.

Digitalis slows the pulse and slows the conduction of nerve impulses in the heart. By increasing the amount of calcium available to the heart muscle, it improves the force of each heartbeat and increases the amount of blood pumped. It is used in the treatment of congestive heart failure and cardiac arrhythmias. The mechanism by which it acts to enhance heart muscle contraction is not definitely known. Toxic effects include nausea, vomiting, and visual disturbances.

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(organic chemistry)
C29H44O12·8H2O White crystals that melt with decomposition at 190°C, soluble in water and ethanol; used in medicine.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
The study, which enrolled its first patient in July, is titled Preop Digifab in CABG to Reduce Ouabain Levels and Prevent AKI.
Actions of bufalin and cinobufalin, two bufadienolides respectively more active and less active than ouabain, on ouabain binding and 86Rb uptake by human erythrocytes.
According to the study, the ouabain compound does not affect the cells in testicles that create sperm, so the men would be able to generate new, healthy sperm down the road.
Expectedly, omeprazole (34.5 [micro]g/ mL), but not ouabain (72.8 [micro]g/mL), inhibited the in vitro [H.sup.+]/[K.sup.+]-ATPase activity by 37.54%, when compared to vehicle (1.38 [+ or -] 0.05 [micro]mol iP/mg/min).
Ouabain is known to act by inhibiting Na?ATPase leading to strong inotropic effects on the heart [163].
Inhibition of[Na.sup.+]/[K.sup.+]/ATPase by ouabain was associated with failure of constitution of an efficient trophectoderm tight junctional seal that is required for expansion of the blastocyst cavity and hatching (17).
Cardiac glycosides are found in a diverse group of plants including Digitalis purpurea and Digitalis lanata (Foxgloves), Nerium oleander (Common oleander), Thevetia peruviana (yellow oleander), Convallaria majalis (Lily of the valley), Urginea maritime and Urginea indica (Squill), Strophanthus gratus (ouabain), Apocynum cannabinum (Dogbane), and Cheiranthus cheiri (Wallflower) has resulted in cardiac glycoside poisoning.
Generally, stem cells reside within a special microenvironment or 'niche', which provides factors that regulate the proliferation and differentiation of the stem cell population.23 SSCs expand in the presence of feeder layer cells such as mouse embryonic fibroblast (MEF) cells, Sandos Inbred Mouse (SIM) mouse embryo-derived Thioguanine and Ouabain resistant cells (STO cells) and human embryonic cell- derived fibroblast-like cells (hEFs).24 However, use of xenogeneic orallogeneic feeder cells for culturing human SSCs is associated with risks such as pathogen transmission and viral infection.
Dietary sodium alters airway function by elevating systemic levels of endogenous ouabain that in turn inhibit the Na[sup]+/K[sup]+ pump.
Cardiac glycosides such as ouabain and proscillaridin were among the most potent compounds in the screen.
Assays were performed with or without 1 mmol Ouabain, a specific inhibitor of [Na.sup.+]-[K.sup.+]-ATPase.