Từ điển y khoa
Thuật ngữ y khoa chuẩn hóa theo MeSH, ICD-11, SNOMED CT.
62,341 terms indexed
Cholestadiene derivatives containing a hydroxy group anywhere in the molecule.
Derivatives of the saturated steroid cholestane with methyl groups at C-18 and C-19 and an iso-octyl side chain at C-17.
An NAPH-dependent cytochrome P450 enzyme that catalyzes the oxidation of the side chain of sterol intermediates such as the 27-hydroxylation of 5-beta-cholestane-3-alpha,7-alpha,12-alpha-triol.
A cholesterol derivative found in human feces, gallstones, eggs, and other biological matter.
Cholestanes substituted in any position with one or more hydroxy groups. They are found in feces and bile. In contrast to bile acids and salts, they are not reabsorbed.
CHOLESTANES substituted with any number of keto groups.
Impairment of bile flow due to obstruction in small bile ducts (INTRAHEPATIC CHOLESTASIS) or obstruction in large bile ducts (EXTRAHEPATIC CHOLESTASIS).
Impairment of bile flow in the large BILE DUCTS by mechanical obstruction or stricture due to benign or malignant processes.
Impairment of bile flow due to injury to the HEPATOCYTES; BILE CANALICULI; or the intrahepatic bile ducts (BILE DUCTS, INTRAHEPATIC).
A non-neoplastic mass of keratin-producing squamous EPITHELIUM, frequently occurring in the MENINGES; bones of the skull, and most commonly in the MIDDLE EAR and MASTOID region. Cholesteatoma can be congenital or acquired. Cholesteatoma is not a tumor nor is it associated with high CHOLESTEROL.
Congenital forms of cholesteatoma are rare (2% to 5% of cases) and may be associated with other conditions such as BRANCHIOOTORENAL SYNDROME (OMIM: 113650). However, there is little evidence that congenital cholesteatoma itself is hereditary. OMIM: 604183
A mass of KERATIN-producing squamous EPITHELIUM that resembles an inverted (suck-in) bag of skin in the MIDDLE EAR. It arises from the eardrum (TYMPANIC MEMBRANE) and grows into the MIDDLE EAR causing erosion of EAR OSSICLES and MASTOID that contains the INNER EAR.
Steroids with methyl groups at C-10 and C-13 and a branched 8-carbon chain at C-17. Members include compounds with any degree of unsaturation; however, CHOLESTADIENES is available for derivatives containing two double bonds.
An oxidoreductase that catalyzes the conversion of 3-oxo-delta4 steroids into their corresponding 5alpha form. It plays an important role in the conversion of TESTOSTERONE into DIHYDROTESTOSTERONE and PROGESTERONE into DIHYDROPROGESTERONE.
CHOLESTENES with one or more double bonds and substituted by any number of keto groups.
The principal sterol of all higher animals, distributed in body tissues, especially the brain and spinal cord, and in animal fats and oils.
A membrane-bound cytochrome P450 enzyme that catalyzes the 7-alpha-hydroxylation of CHOLESTEROL in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP7, converts cholesterol to 7-alpha-hydroxycholesterol which is the first and rate-limiting step in the synthesis of BILE ACIDS.
An autosomal recessive disorder caused by mutations in the gene for acid lipase (STEROL ESTERASE). It is characterized by the accumulation of neutral lipids, particularly CHOLESTEROL ESTERS in leukocytes, fibroblasts, and hepatocytes.
Proteins that bind to and transfer CHOLESTEROL ESTERS between LIPOPROTEINS such as LOW-DENSITY LIPOPROTEINS and HIGH-DENSITY LIPOPROTEINS.
Fatty acid esters of cholesterol which constitute about two-thirds of the cholesterol in the plasma. The accumulation of cholesterol esters in the arterial intima is a characteristic feature of atherosclerosis.
An enzyme that catalyzes the oxidation of cholesterol in the presence of molecular oxygen to 4-cholesten-3-one and hydrogen peroxide. The enzyme is not specific for cholesterol, but will also oxidize other 3-hydroxysteroids. EC 1.1.3.6.
A mitochondrial cytochrome P450 enzyme that catalyzes the side-chain cleavage of C27 cholesterol to C21 pregnenolone in the presence of molecular oxygen and NADPH-FERRIHEMOPROTEIN REDUCTASE. This enzyme, encoded by CYP11A1 gene, catalyzes the breakage between C20 and C22 which is the initial and rate-limiting step in the biosynthesis of various gonadal and adrenal steroid hormones.
Cholesterol present in food, especially in animal products.
Cholesterol which is contained in or bound to high-density lipoproteins (HDL), including CHOLESTEROL ESTERS and free cholesterol.
Cholesterol which is contained in or bound to low density lipoproteins (LDL), including CHOLESTEROL ESTERS and free cholesterol.
Cholesterol which is contained in or bound to very low density lipoproteins (VLDL). High circulating levels of VLDL cholesterol are found in HYPERLIPOPROTEINEMIA TYPE IIB. The cholesterol on the VLDL is eventually delivered by LOW-DENSITY LIPOPROTEINS to the tissues after the catabolism of VLDL to INTERMEDIATE-DENSITY LIPOPROTEINS, then to LDL.
PROM
A strongly basic anion exchange resin whose main constituent is polystyrene trimethylbenzylammonium Cl(-) anion.
A major primary bile acid produced in the liver and usually conjugated with glycine or taurine. It facilitates fat absorption and cholesterol excretion.
The 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholanic acid family of bile acids in man, usually conjugated with glycine or taurine. They act as detergents to solubilize fats for intestinal absorption, are reabsorbed by the small intestine, and are used as cholagogues and choleretics.
A basic constituent of lecithin that is found in many plants and animal organs. It is important as a precursor of acetylcholine, as a methyl donor in various metabolic processes, and in lipid metabolism.
A condition produced by a deficiency of CHOLINE in animals. Choline is known as a lipotropic agent because it has been shown to promote the transport of excess fat from the liver under certain conditions in laboratory animals. Combined deficiency of choline (included in the B vitamin complex) and all other methyl group donors causes liver cirrhosis in some animals. Unlike compounds normally considered as vitamins, choline does not serve as a cofactor in enzymatic reactions. (From Saunders Dictionary and Encyclopedia of Laboratory Medicine and Technology, 1984)
An enzyme bound to the inner mitochondrial membrane that catalyzes the oxidation of CHOLINE to BETAINE.
An enzyme that is active in the first step of choline phosphoglyceride (lecithin) biosynthesis by catalyzing the phosphorylation of choline to phosphorylcholine in the presence of ATP. Ethanolamine and its methyl and ethyl derivatives can also act as acceptors. EC 2.7.1.32.
An enzyme that catalyzes the formation of acetylcholine from acetyl-CoA and choline. EC 2.3.1.6.
An enzyme that catalyzes the transfer of cytidylate (CMP) to choline phosphate to form CDPcholine. It is the rate-limiting enzyme in the choline pathway for the biosynthesis of phosphatidylcholine. Its activity is increased by glucocorticoids. EC 2.7.7.15.
Any drug used for its actions on cholinergic systems. Included here are agonists and antagonists, drugs that affect the life cycle of ACETYLCHOLINE, and drugs that affect the survival of cholinergic neurons. The term cholinergic agents is sometimes still used in the narrower sense of MUSCARINIC AGONISTS, although most modern texts discourage that usage.
Drugs that bind to and activate cholinergic receptors.
Drugs that bind to but do not activate CHOLINERGIC RECEPTORS, thereby blocking the actions of ACETYLCHOLINE or cholinergic agonists.
Nerve fibers liberating acetylcholine at the synapse after an impulse.
Neurons whose primary neurotransmitter is ACETYLCHOLINE.
Drugs that inhibit cholinesterases. The neurotransmitter ACETYLCHOLINE is rapidly hydrolyzed, and thereby inactivated, by cholinesterases. When cholinesterases are inhibited, the action of endogenously released acetylcholine at cholinergic synapses is potentiated. Cholinesterase inhibitors are widely used clinically for their potentiation of cholinergic inputs to the gastrointestinal tract and urinary bladder, the eye, and skeletal muscles; they are also used for their effects on the heart and the central nervous system.
Drugs used to reverse the inactivation of cholinesterase caused by organophosphates or sulfonates. They are an important component of therapy in agricultural, industrial, and military poisonings by organophosphates and sulfonates.
An enzyme from the sulfuric ester hydrolase class that breaks down one of the products of the chondroitin lyase II reaction. EC 3.1.6.9.
A usually benign tumor composed of cells which arise from chondroblasts or their precursors and which tend to differentiate into cartilage cells. It occurs primarily in the epiphyses of adolescents. It is relatively rare and represents less than 2% of all primary bone tumors. The peak incidence is in the second decade of life; it is about twice as common in males as in females. (From Dorland, 27th ed; Holland et al., Cancer Medicine, 3d ed, p1846)
Presence of CALCIUM PYROPHOSPHATE in the connective tissues such as the cartilaginous structures of joints. When accompanied by GOUT-like symptoms, it is referred to as pseudogout.