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An antinuclear antibody directed against small nuclear ribonucleoproteins (snRNPs), that is highly specific, but has poor sensitivity for systemic lupus erythematosus (SLE). Presence of anti-Sm antibodies are associated with central nervous system, kidney, lung and cardiac involvement in SLE, but are not indicative of disease activity.
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Proteins released into blood when heart muscle is injured; the central laboratory marker in suspected heart attack.
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A cardiac glycoside. Digoxin inhibits the sodium potassium adenosine triphosphatase (ATPase) pump, thereby increasing intracellular calcium and enhancing cardiac contractility. This agent also acts directly on the atrioventricular node to suppress conduction, thereby slowing conduction velocity. Apparently due to its effects on intracellular calcium concentrations, digoxin induces apoptosis of tumor cells via a pathway involving mitochondrial cytochrome c and caspases 8 and 3. (NCI04)
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A natural alkaloid derivative of xanthine isolated from the plants Camellia sinensis and Coffea arabica. Theophylline appears to inhibit phosphodiesterase and prostaglandin production, regulate calcium flux and intracellular calcium distribution, and antagonize adenosine. Physiologically, this agent relaxes bronchial smooth muscle, produces vasodilation (except in cerebral vessels), stimulates the CNS, stimulates cardiac muscle, induces diuresis, and increases gastric acid secretion; it may also suppress inflammation and improve contractility of the diaphragm. (NCI04)
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Troponin I, troponin T, and troponin C are the three closely associated subunits of the troponin complex of thin filaments in muscle. The complex serves as a calcium-sensitive switch that regulates muscle contraction. In the absence of calcium, Troponin I binds actin, inhibits actomyosin ATPase activity, and inhibits F-actin-myosin interactions. The troponin I gene family comprises three isoforms: skeletal TNI-fast, skeletal TNI-slow, and TNI-cardiac. (from OMIM 191044, 191043, 191042 and NCI)
Indicators
Troponin I, troponin T, and troponin C are the three closely associated subunits of the troponin complex of thin filaments in muscle. The complex serves as a calcium-sensitive switch that regulates muscle contraction. Troponin T binds tropomyosin to the troponin complex and inhibits F-actin-myosin interactions. The troponin T gene family comprises three isoforms: slow skeletal (TNNT1), cardiac (TNNT2) and fast skeletal (TNNT3). Because it is not normally found in blood, cardiac troponin-T in serum is a sensitive indicator of myocardial cell injury.