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Medical Dictionary - Dictionary of Medicine and Human Biology


Medical Dictionary


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lyophobe (li′o-fob)
A substance that is lyophobic.

lyophobic (li-o-fo′bik)
1. In colloid chemistry, denoting a dispersed phase having but slight affinity for the dispersion medium; when the dispersed phase is l., the colloid is usually an irreversible one. 2. Denoting a lack of preference or rejection of the solvent. [lyo- + G. phobos, fear]

lyosorption (li-o-sorp′shun)
Adsorption of a liquid on a solid surface.

lyotropic (li-o-trop′ik)
SYN: lyophilic. [lyo- + G. trope, a turning]

lypressin (li′pres-in)
Vasopressin-containing lysine in position 8; an antidiuretic and vasopressor hormone. SYN: 8-lysine vasopressin.

lyra (li′ra)
A lyre-shaped structure. [L. and G. lyre] l. davidis, lyre of David obsolete terms for commissura fornicis. l. uterina SYN: palmate folds of cervical canal, under fold.

Lys
Symbol for lysine or lysyl.

lys-
See lyso-.

lysate (li′sat)
Material produced by the destructive process of lysis.

lyse (liz)
To break up, to disintegrate, to effect lysis. SYN: lyze.

lysemia (li-se′me-a)
Disintegration or dissolution of red blood cells and the occurrence of hemoglobin in the circulating plasma and in the urine. [lyso- + G. haima, blood]

lysergamide (li-serj′a-mid)
SYN: lysergic acid amide.

lysergic acid (li-ser′jik)
The d-isomer is a cleavage product of alkaline hydrolysis of ergot alkaloids; occurs as shiny crystals, slightly soluble in water; a psychotomimetic. l. amide a psychotomimetic agent present in Rivea corymbosa and Ipomoea tricolor; possesses less hallucinogenic potency than does l. diethylamide. SYN: ergine, lysergamide. l. diethylamide (LSD) peripherally, a serotonin antagonist; 1 to 2 μg per kg induces hallucinatory states of a visual rather than auditory nature; its use may precipitate psychoses; it has been occasionally used in the treatment of chronic alcoholism and psychotic disorders. SYN: lysergide. l. monoethylamide a psychotomimetic agent present in Rivea corymbosa and Ipomoea tricolor; possesses less hallucinatory potency than does l. diethylamide.

lysergide (li-ser′jid)
SYN: lysergic acid diethylamide.

lysergol (li-sur-jol)
A semisynthetic ergot alkaloid.

lysin (li′sin)
1. A specific complement-fixing antibody that acts destructively on cells and tissues; the various types are designated in accordance with the form of antigen that stimulates the production of the l., e.g., hemolysin, bacteriolysin. 2. Any substance that causes lysis.

lysine (K, Lys) (li′sen)
2,6-Diaminohexanoic acid;the l-isomer is a nutritionally essential α-amino acid of mammals found in many proteins; distinguished by an ε-amino group. l. decarboxylase an enzyme that catalyzes the decarboxylation of l-l., with the production of cadaverine and CO2.

lysinemia (li-si-ne′me-a)
See hyperlysinemia.

8-lysine vasopressin
SYN: lypressin.

lysinium (li-sin′e-um)
The cation form of lysine, either l. (+1) or l. (+2).

lysinogen (li-sin′o-jen)
An antigen that stimulates the formation of a specific lysin.

lysinogenic (li′si-no-jen′ik)
Having the property of a lysinogen.

lysinuria (li-si-noo′re-a)
The presence of lysine in the urine.

lysis (li′sis)
1. Destruction of red blood cells, bacteria, and other structures by a specific lysin, usually referred to by the structure destroyed ( e.g., hemolysis, bacteriolysis, nephrolysis); may be due to a direct toxin or an immune mechanism, such as antibody reacting with antigen on the surface of a target cell, usually by binding and activation of a series of proteins in the blood with enzymatic activity (complement system). 2. Gradual subsidence of the symptoms of an acute disease, a form of the recovery process, as distinguished from crisis. [G. dissolution or loosening] bystander l. complement-mediated l. of nearby cells in the vicinity of a complement activation site.

lyso-, lys-
Lysis, dissolution. SEE ALSO: lyo-. [G. lysis, a loosening]

lysocephalin (li-so-sef′a-lin)
A lysophosphatidic acid esterified with serine or ethanolamine, i.e., a lysophosphatidylserine or -ethanolamine; analogous to lysolecithin.

lysogen (li′so-jen)
1. That which is capable of inducing lysis. 2. A bacterium in the state of lysogeny. 3. Any antigen that stimulates lysin production. [lysin + G. -gen, producing]

lysogenesis (li-so-jen′e-sis)
The production of lysins.

lysogenic (li-so-jen′ik)
1. Causing or having the power to cause lysis, as the action of certain antibodies and chemical substances. 2. Pertaining to bacteria in the state of lysogeny.

lysogenicity (li′so-je-nis′i-te)
The property of being lysogenic.

lysogenization (li′so-je-ni-za′shun, li-soj′e-ni-za′shun)
The process by which a bacterium becomes lysogenic.

lysogeny (li-soj′e-ne)
The phenomenon by which a bacterium is infected by a temperate bacteriophage whose DNA is integrated into the bacterial genome and replicates along with the bacterial DNA but remains latent or unexpressed; triggering of the lytic cycle may occur spontaneously or by certain agents and will result in the production of bacteriophage and lysis of the bacterial cell.

lysokinase (li-so-ki′nas)
Term for activator agents ( e.g., streptokinase, urokinase, staphylokinase) that produce plasmin by indirect or multiple-stage action on plasminogen.

lysolecithin (li-so-les′i-thin)
A lysophosphatidylcholine; capable of lysing erythrocytes. l.-lecithin acyltransferase (LLAT) an enzyme that catalyzes the reversible reaction of l. and another phospholipid ( E.G., phosphatidylethanolamine) to form lecithin and lysophosphatidylethanolamine; a major route in the restructuring of lecithin.

lysolecithinase (li-so-les′i-thin-as)
SYN: lysophospholipase.

lysophosphatidic acid (li′so-fos′fa-tid′ik)
A phosphatidic acid in which only one of the two hydroxyl groups of the glycerophosphate is esterified; most commonly, when carbon-1 of the glycerol moiety is esterified ( e.g., 1-acylglycerol-3-phosphate). l. acyltransferase, 1-acylglycerol-3-phosphate acyltransferase 1-acylglycerol-3-phosphate acyltransferase.

lysophosphatidylcholine (li′so-fos′fa-ti′dil-ko′len)
A phosphatidylcholine in which a fatty acid has been removed from the C2 position of the glycerol group.

lysophosphatidylserine (li′so-fos′fa-ti′dil-ser′en)
Phosphatidylserine from which one fatty acid residue has been removed from the glycerol moiety, typically at carbon-2. Cf.:lysophosphatidic acid.

lysophospholipase (li′so-fos′fo-lip′as)
A hydrolase removing the single acyl group from a lysolecithin, producing glycerophosphocholine and the free fatty acid anion. SYN: lecithinase B, lysolecithinase, phospholipase B (1) .

lysosome (li′so-som)
A cytoplasmic membrane-bound vesicle measuring 5-8 nm (primary l.) and containing a wide variety of glycoprotein hydrolytic enzymes active at an acid pH; serves to digest exogenous material, such as bacteria, as well as effete organelles of the cells. [lyso- + G. soma, body] definitive lysosomes SYN: secondary lysosomes. primary lysosomes lysosomes produced at the Golgi apparatus where hydrolytic enzymes are incorporated; they fuse with phagosomes or pinosomes to become secondary lysosomes. secondary lysosomes lysosomes in which lysis takes place, owing to the activity of hydrolytic enzymes; they are believed to eventually become residual bodies. SYN: definitive lysosomes, digestive vacuole.

lysostaphin (li-so-staf′in)
A peptidase enzyme produced by certain strains of staphylococcus microorganisms with antibacterial activity against staphylococci.

lysotype (li′so-typ)
A type within a bacterial species determined by its reaction to specific phages. [lyso + type]

lysozyme (li′so-zim)
An enzyme hydrolyzing 1,4-β links between N-acetylmuramic acid and N-acetyl-d-glucosamine, and thus destructive to cell walls of certain bacteria; present in tears and some other body fluids, in egg white, and in some plant tissues; used in the prevention of caries and in the treatment of infant formulas. SYN: mucopeptide glycohydrolase, muramidase.

Lyssavirus (lis′a-vi-rus)
A genus of viruses (family Rhabdoviridae) that includes the rabies virus group. Australian bat L. a species that has caused a fatal rabieslike disease in a woman in Australia. European bat L. two species (1 & 2) causing rabieslike diseases in humans in Europe; transmitted by bite of insectivorous bats.

lysyl (K) (li′sil)
The univalent radical of lysine. l. hydroxylase an enzyme that acts on specific l. residues in certain proteins ( E.G., collagens) with α-ketoglutarate and O2 to produce δ-hydroxylysyl residues, succinate, and CO2; this enzyme, which requires Fe2+ and ascorbate, is deficient in Ehlers-Danlos syndrome type VI. SYN: l. 2-oxoglutarate dioxygenase. l. oxidase an enzyme, which requires Cu2+ and O2, that oxidizes certain l. residues in collagen to allysyl residues and hydroxylysyl residues to hydroxyallysyl residues; this is a required step for the cross-linking (via aldol condensations and Amadori rearrangements) of collagen strands; a lower activity of this enzyme is associated with occipital horn syndrome. l. 2-oxoglutarate dioxygenase SYN: l. hydroxylase.

lysyl-bradykinin (li′sil-brad-e-ki′nin)
SYN: kallidin.

Lythoglyphopsis (lith-o-glif-op′-sis)
A genus of amphibious freshwater operculate snails of the family Hydrobiidae (subfamily Hydrobiinae; subclass Prosobranchiata). In the Mekong River delta, L. aperta serves as an intermediate host of the blood fluke, Schistosoma mekongi.

lytic (lit′ik)
Pertaining to lysis; used colloq. as an abbreviation for osteolytic.

lyxitol (lik′si-tol)
A pentitol (reduced lyxose) occurring in lyxoflavin.

lyxoflavin (lik-so-fla′vin)
A compound similar to riboflavin except that d-lyxitol is present in place of the d-ribitol group; present in small quantity in cardiac muscle.

lyxose (lik′sos)
An aldopentose; d-l. is epimeric with both d-arabinose and d-xylose; l-l. is epimeric with d-ribose.

lyxulose (liks′u-los)
The 2-keto derivative of lyxose.

lyze (liz)
SYN: lyse.

l-rhamnose (Rha) (ram′nos)
A methylpentose present in a number of plant glycosides, found in free form in poison sumac, in lipopolysaccharides of Enterobacteriaceae, and in rutinose (a disaccharide). SYN: isodulcit.

l-sorbose (sor′bos)
A very sweet reducing, but not fermentable, 2-ketohexose obtained from the berries of the mountain ash, Sorbus aucuparia (family Rosaceae), and from sorbitol by fermentation with Acetobacter suboxydans; l-sorbose is epimeric with d-fructose and is used in the manufacture of vitamin C. SYN: sorbin, sorbinose, sorbitose.

l-stercobilinogen (ster′ko-bi-lin′o-jen)
Reduction product of l-urobilinogen, precursor of l-stercobilin in the final stages of bilirubin metabolism; excreted in feces, wherein it is oxidized to stercobilin. SEE ALSO: bilirubinoids.

l-xylulosuria (zi′loo-lo-soo′re-a)
SYN: essential pentosuria.




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