|Medical Dictionary - Dictionary of Medicine and Human Biology|
Pertaining to the synaptic relationship of an axon with a dendrite of another neuron. See synapse.
SYN: axifugal. [axo- + L. fugio, to flee]
A device for recording scales or axes of predetermined magnitude on kymographic records. [axo- + G. grapho, to write]
The plasma membrane of the axon. SYN: Mauthner sheath. [axo- + G. lemma, husk]
Destruction or dissolution of a nerve axon. [axo- + G. lysis, dissolution]
The single process of a nerve cell that under normal conditions conducts nervous impulses away from the cell body and its remaining processes (dendrites). It is a relatively even filamentous process varying in thickness from about 0.25 to more than 10 μm. In contrast to dendrites, which rarely exceed 1.5 mm in length, Axons can extend great distances from the parent cell body (some axons of the pyramidal tract are 40–50 cm long). Axons 0.5 μm thick or over are generally enveloped by a segmented myelin sheath provided by oligodendroglia cells (in brain and spinal cord) or Schwann cells (in peripheral nerves). Like dendrites and nerve cell bodies, Axons contain a large number of neurofibrils. With some exceptions, nerve cells synaptically transmit impulses to other nerve cells or to effector cells (muscle cells, gland cells) exclusively by way of the synaptic terminals of their a.. [G. a., axis]
Pertaining to an axon.
1. The central thread running in the axis of the chromosome. 2. SYN: axial filament. 3. The distinctive array of microtubules in the core of eukaryotic cilia and flagella comprising a central pair surrounded by a sheaf of nine doublet microtubules. [axo- + G. nema, a thread]
The recording of electrical changes in axons. SYN: electroaxonography.
A disorder affecting primarily the axons of peripheral nerve fibers (although secondary demyelination occurs), in contrast to one that affects only myelin (myelinopathy).
Interruption of the axons of a nerve followed by complete degeneration of the peripheral segment, without severance of the supporting structures of the nerve; such a lesion may result from pinching, crushing, or prolonged pressure. SEE ALSO: neurapraxia, neurotmesis. [axon + G. tmesis, a cutting]
Extending in a direction toward an axon. [axo- + L. peto, to seek]
Neuroplasm of the axon. SYN: axioplasm.
axopodium, pl .axopodia (ak-so-po′de-um, -a)
A permanent pseudopodium containing a stiff axial filament of differentiated protoplasm. SYN: axiopodium. [Mod. L., fr. L. axis + G. podion, dim. of pous (pod-), foot]
Relating to the synaptic relationship of an axon with a nerve cell body. See synapse. [axo- + G. soma, body]
An elongate supporting rod or tubule that runs the length of certain flagellate protozoans, frequently projecting out of the posterior end. Single or multiple, filamentous or rigid, they vary with the species but serve as an endoskeletal framework and may function in locomotion as well. [axo- + G. stylos, pillar]
Incision or transection of an axon. [axo- + G. tome, to cut]
G., Italian neurologist, 1878–1943. See A. index, A. quotient.
L., Argentinian physician, 1861–1918. See A. disease, A. syndrome.
James Ernest, U.S. gynecologist, *1910. See A. brush.
An antimalarial; an effective schizontocide in acute falciparum infection.
azacyclonol hydrochloride (a′za-si′klo-nol)
A structural isomer of pipradol hydrochloride partially antagonistic to its actions, used with varying results in the treatment of hallucinations and confusion.
Guanine with N for C in position 8; a guanine antagonist that has been used in the treatment of acute leukemia. SYN: guanazolo, triazologuanine.
azamethonium bromide (a′za-me-tho′ne-um)
A ganglionic blocking agent.
A tranquilizing agent.
azapetine phosphate (a-zap′e-ten)
A potent adrenergic (α-receptor) blocking agent similar in action and uses to those of tolazoline; used in the treatment of peripheral vascular diseases.
Anxiolytics acting through agonist action at serotonin 1-A receptors.
An antipsoriatic agent no longer used because of a high incidence of severe adverse reactions.
O-Diazoacetyl-lserine;an antibiotic inhibitor of purine synthesis; a glutamine analog; mutagenic and antitumorogenic. It retards the growth of transplantable animal neoplasms.
A class of antianxiety agents not chemically or pharmacologically related to other classes of sedative and anxiolytic drugs; e.g., buspirone hydrochloride.
azatadine maleate (a-zat′a-den)
An antihistamine with anticholinergic and antiserotonin properties.
A derivative of 6-mercaptopurine, used as a cytotoxic and immunosuppressive agent in organ transplantation and in the treatment of autoimmune diseases such as hemolytic anemias, systemic lupus erythematosus, rheumatoid arthritis and leukemias.
Thymine with N for C in position 6; an antimetabolite of thymine.
6-azauridine (AZUR) (az-aw′ri-den)
Uridine with N for C in position 6; a triazine analogue of uridine and an antimetabolite with selectivity for human neoplastic leukocytes; produces partial remissions in certain acute leukemias of adults.
A mixture of two or more liquids that boils without a change in proportion of the substances either in the liquid or the vapor phase; e.g., 95% ethanol (actually 94.9% by volume, the rest being water). [G. a- priv. + zeo, to boil, + tropos, a turning] halothane-ether a. an azeotropic mixture in the proportions halothane 68 to diethyl ether 32, by volume, that combines the advantages of each anesthetic yet is non-flammable.
Denoting or characteristic of an azeotrope.
A compound that contains the monovalent &cbond;N3 group.
azidothymidine (AZT) (az′i-do-thi′mi-den)
azlocillin sodium (az-lo-sil′in)
An extended spectrum penicillin used in treatment of infections caused by Pseudomonas aeruginosa, Escherichia coli, and Haemophilus influenzae.
Prefix denoting the presence in a molecule of the group &tbond;C–N&dbond;N–C&tbond;. Cf.:diazo-. [Fr. azote, name for nitrogen proposed by AL Lavoisier (1743–1794)]
The red-violet pigment formed by the condensation of diazotized sulfanilic acid with bilirubin in the van den Bergh reaction.
A series of azo dyes used in preparing tissue stains.
azocarmine B, azocarmine G (az-o-kar′min) [C.I. 50090, C.I. 50085]
Red acid dyes, the former more soluble in water, useful in Heidenhain azan stain.
azoic (a-zo′ik, a-)
Containing no living things; without organic life. [G. a- priv. + zoikos, relating to an animal]
azolitmin (az-o-lit′min) [old C.I. 1242]
A purplish red coloring matter obtained from natural litmus or synthesized by oxidizing orcinol in the presence of ammonia, lime, and potash; used as a broad indicator of pH (red at 4.5, blue at 8.3).
Absence of living spermatozoa in the semen; failure of spermatogenesis. SEE ALSO: aspermia. [G. a- priv. + zoon, animal, + sperma, seed]
SYN: amidonaphthol red.
Any of the modified proteins produced by treatment with diazonium derivatives of various aromatic amines; used to elicit antibody formation and demonstrate antibody specificity.
A reddish derivative, soluble in water, less toxic but less effective than sulfanilamide; it owes its antibacterial activity to the sulfanilamide released.
An abnormal increase in concentration of urea and other nitrogenous substances in the blood plasma. SEE ALSO: uremia. [azo- (azote) + G. haima, blood] nonrenal a., prerenal a. nitrogen retention resulting from something other than primary renal disease.
Relating to azotemia.
Rarely used term for fever resulting from uremia. [azote + G. therme, heat]
An increased elimination of urea in the urine. [azo- (azote) + G. ouron, urine]
azovan blue (az′o-van)
SYN: Evans blue.
Abbreviation for azidothymidine.
A synthetic bactericidal monolactam antibiotic with a wide spectrum of activity against Gram-negative aerobic pathogens.
SYN: pinta. [Sp. blue]
Abbreviation for 6-azauridine.
A term for a group of metachromatic basic blue methylthionine or phenothiazine dyes; used as biologic stains, especially in blood and nuclear stains. a. A [C.I. 52005] asymmetric dimethylthionine chloride;a blue dye used as a component of MacNeal tetrachrome blood stain and of Romanowsky-type blood stains; also used as a stain for mucins, nucleic acids, and mast cell granules; gives a metachromatic violet to red color to highly acidic substances in tissues. a. B [C.I. 52010] trimethylthionine chloride;a blue dye used like a. A; also as a. B bromide to give metachromatic staining of RNA and DNA. a. C [C.I. 52002] monomethylthione chloride;a blue-violet thiazin dye used in the metachromatic staining of mucins and cartilage. a. I a mixture of a. A and B. SYN: methylene a.. a. II a mixture of a. I and methylene blue; the eosinate, a. II-eosin, is the principal ingredient of Giemsa stain.
A complex of azure A and carbacrylic resin; used as an indicator for the detection of gastric achlorhydria without intubation. SYN: quinine carbacrylic resin.
azurophil, azurophile (azh′u-ro-fil, -fil)
Staining readily with an azure dye, denoting especially the hyperchromatin and reddish purple granules of certain blood cells. [azure + G. philos, fond]
A condition in which the blood contains cells having azurophil granulations.
Radiographic demonstration of the azygos venous system after injection of contrast medium. [azygos + G. gramma, a writing]
Radiography of the azygos venous system after injection of contrast medium.
1. An unpaired (azygous) anatomical structure. 2. SYN: a. vein. [G. a- priv. + zygon, a yoke] a. continuation (of the inferior vena cava) a congenital anomaly in which the infrahepatic portion of the vena cava fails to form, and venous drainage of the lower body is maintained through a persistent right supracardinal vein, which becomes a large a. vein.
azygous (az′i-gus, a-zi′gus)
Unpaired;single. [G. azygos]
A conjugate of chloral and glucose used as an anesthetic in laboratory animals; it does not depress cardiovascular reflexes as much as most other anesthetic agents.
The 5β enantiomer of α-allocortol;a reduction product of cortisone, present in the urine, differing from cortisone in that the three keto groups are reduced to hydroxyls.
The 5β enantiomer of α-allocortolone; a reduction product of cortisone, present in the urine, differing from cortisone in that two of the keto groups (at positions 3 and 20) are reduced to hydroxyls.
An enzyme with action similar to that of isoamylase; it cleaves 1,6-α-glucosidic linkages in pullalan, amylopectin, and glycogen, and in α- and β-amylase limit-dextrins of amylopectin and glycogen. Cf.:isoamylase. SYN: limit dextrinase (1) , pullulanase, R enzyme.
An active form of vitamin D formed in the proximal convoluted tubules of the kidney. A deficiency of the receptor for a. results in all of the features of a vitamin D3 deficiency.
A straight open-chain hydrocarbon built up of three isoprene units; one of the four isomeric forms occurs in the natural coating of apples.
SYN: fludrocortisone acetate.
9α-fluorohydrocortisone acetate (flor′o-hi-dro-kor′ti-son)
SYN: fludrocortisone acetate.
An enzyme that catalyzes the hydrolysis of an an α-l-fucoside, producing an alcohol and l-fucose; a deficiency of the lysosomal enzyme will result in fucosidosis.
An enzyme catalyzing the hydrolysis of α-d-galactosides to release free d-galactose. A deficiency of type A α-d-galactosidase is associated with Fabry disease. SYN: melibiase.
Amylo-(1,4→1,6)-transglucosylase or transglucosidase;an enzyme in muscle and in plants (Q enzyme) that cleaves α-1,4 linkages in glycogen or starch, transferring the fragments into α-1,6 linkages, creating branches in the polysaccharide molecules; in plants, it converts amylose to amylopectin; this enzyme is deficient in individuals with glycogen storage disease type IV. SYN: α-glucan-branching glycosyltransferase, amylo-1,4:1,6-glucantransferase, amylo-(1,4→1,6)-transglucosidase, amylo-(1,4→1,6)-transglucosylase, branching enzyme.
SYN: 1,4-α-d-glucan-branching enzyme.
A glucosyltransferase that transfers an α-glucosyl residue in a 1,4-α-glucan to the primary hydroxyl group of glucose in a 1,4-α-glucan. SEE ALSO: 1,4-α-d-glucan-branching enzyme. SYN: oligoglucan-branching glycosyltransferase.
Dextrin transglycosylase or glycosyltransferase;a 4-glycosyltransferase converting maltodextrins into amylose and glucose by transferring parts of 1,4-glucan chains to new 4-positions on glucose or other 1,4-glucans. SYN: amylomaltase, D enzyme, dextrin glycosyltransferase, dextrin transglycosylase, disproportionating enzyme.
Maltase; a glucohydrolase removing terminal nonreducing 1,4-linked α-glucose residues by hydrolysis, yielding α-glucose; a deficiency of the lysosomal enzyme is associated with glycogen storage disease type II. There are at least five isozymes of maltase. SYN: glucoinvertase.
First intermediate in the conversion of cholesterol to the bile acids; formed in the principal rate-limiting step of bile acid biosynthesis.
SYN: activated acetaldehyde.
A catabolite of progesterone; found in the urine of pregnant women.
A steroid hormone with medical use similar to that of progesterone. The acetate is an orally effective derivative, useful in conditions in which parenterally administered progesterone or the caproate is indicated; it possesses some androgenic potency and may cause virilizing changes in a female fetus. The caproate or hexanoate has essentially the same actions and uses as progesterone, but is more potent and has a longer duration of action. A precursor of the androgens, estrogens, and adrenocortical hormones.
An enzyme that hydrolyzes terminal desulfated α-l-iduronic acid residues of dermatan sulfate and of heparan sulfate; a deficiency of this enzyme is associated with Hurler syndrome and Scheie syndrome.
Formerly, the enzyme system converting pyruvate (a 2-oxoacid) to acetyl-CoA and CO2, with reduction of NAD+ to NADH and the participation of lipoamide and thiamin pyrophosphate; now known to involve at least three enzymes in succession: pyruvate dehydrogenase, dihydrolipoamide acetyltransferase, and dihydrolipoamide dehydrogenase. Cf.:pyruvate dehydrogenase (lipoamide).
α-ketoglutaramic acid (ke′to-gloo-tar-ik)
A metabolite of glutamine formed by the action of glutamine aminotransferase; elevated in certain cases of hepatocoma. SYN: 2-oxoglutaric acid.
A salt or ester of α-ketoglutaric acid. α-ketoglutarate dehydrogenase an enzyme that catalyzes the oxidative decarboxylation of 2-ketoglutaric acid to succinyldihydrolipoate; the succinyl group is later transferred to CoA and the reduced lipoate is oxidized by NAD+; a complex that is a part of the tricarboxylic acid cycle. SYN: 2-oxoglutarate dehydrogenase, α-ketoglutarate dehydrogenase complex.
α-ketosuccinamic acid (ke′to-suk-si-nam′ik)
The transamination product of asparagine; acted upon by ω-amidase.
SYN: active pyruvate.
α-naphthylthiourea (ANTU) (naf′thil-thi′o-u-re′a)
A derivative of thiourea; a highly toxic antithyroid agent, especially to small mammals, causing pulmonary edema, fatty degeneration of the liver, and low body temperature; used as a rat poison.
A glycoprotein that contains neuraminic acid and that during electrophoresis migrates with the α2 portion of serum proteins. SEE ALSO: C1 esterase inhibitor.
α-phenoxyethylpenicillin potassium (fe-nok′se-eth′il-pen-i-sil′in)
SYN: phenethicillin potassium.
α-phenoxypropylpenicillin potassium (fe′nok-se-pro′pil-pen-i-sil′in)
The benzimidazole nucleoside in vitamin B12.
A fungal toxin that acts on the large subunit of rRNA and inactivates the ribosome.
Symbol for α-tocopherol.
5,7,8-Trimethyltocol;a light yellow, viscous, odorless, oily liquid that deteriorates on exposure to light, is obtained from wheat germ oil or by synthesis, biologically exhibits the most vitamin E activity of the α-tocopherols, and is an antioxidant retarding rancidity by interfering with the autoxidation of fats. Prepared from natural phytol, it is called 2-ambo-α-tocopherol; from synthetic phytol, all-rac-α-tocopherol or synt-α-tocopherol; also available are d-α-tocopheryl acetate, dl-α-tocopheryl acetate, d-α-tocopheryl acid succinate, and d-α-tocopheryl acetate concentrate. One of several forms of vitamin E. SYN: vitamin E (1) .
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