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Medical Dictionary


guanazolo (gwahn-a-zol′o)
SYN: 8-azaguanine.

guanethidine sulfate (gwahn-eth′i-den)
A potent antihypertensive agent. It appears to interfere with the release of the chemical mediator (norepinephrine) at the sympathetic neuroeffector junction; it does not produce ganglionic or parasympathetic blockade with recommended doses. In ophthalmology, it is used topically for the treatment of glaucoma and to counteract eyelid retraction in Graves disease.

guanfacine (gwan′fa-sen)
An antihypertensive agent which is an α2-adrenergic agonist acting in the central nervous system to reduce the output of the sympathetic nervous system; resembles clonidine in its pharmacologic profile.

guanidine (gwahn′i-den, -din)
A strongly basic compound, usually found (in some plants and lower animals) as the hydrochloride; a constituent of creatine and arginine; administered as a cholinergic striated muscle stimulant.

guanidinium (gwahn′i-din-e-um)
Referring to a guanidine moiety in a molecule ( E.G., in arginine).

guanidinoacetate (gwahn′i-din-o-as-e-tat)
An intermediate in creatine biosynthesis.

guanidinoacetate N-methyltransferase
The enzyme catalyzing the transfer of a methyl group from S-adenosyl-l-methionine (“active methionine”) to guanidinoacetate (glycocyamine), forming creatine and S-adenosyl-l-homocysteine.

guanine (Gua, G) (gwahn′en, -in)
2-Amino-6-oxypurine;one of the two major purines (the other being adenine) occurring in all nucleic acids. g. aminase SYN: g. deaminase. g. deaminase a deaminase of the liver that catalyzes the hydrolysis of g. into xanthine and ammonia; the first step in purine degradation. SYN: guanase, g. aminase. g. deoxyribonucleotide SYN: deoxyguanylic acid. g. ribonucleotide SYN: guanylic acid.

guanochlor sulfate (gwahn′o-klor)
Used as an α-adrenergic blocking agent for the treatment of essential hypertension.

guanosine (G, Guo) (gwahn′o-sen, -sin)
9-β-d-Ribosylguanine (guanine combined through its N-9 with the C-1 of β-d-ribose); a major constituent of RNA and of guanine nucleotides. SYN: 9-β-d-ribofuranosylguanine. cyclic g. 3′,5′-monophosphate (cGMP) an analog of cAMP; a second messenger for atrial natriuretic factor. SYN: cyclic GMP.

guanosine 5′-diphosphate (GDP)
Guanosine esterified at its 5′ position with diphosphoric acid; bound tightly in microtubules.

guanosine 5′-monophosphate
SYN: guanylic acid.

guanosine 5′-triphosphate (GTP)
An immediate precursor of guanine nucleotides in RNA; similar to ATP; has a crucial role in microtubule formation. GTP cyclohydrolase an enzyme that catalyzes the reaction of GTP and H2O forming formate and a precursor of tetrahydrobiopterin; a deficiency of this enzyme will result in one form of malignant hyperphenylalaninemia.

guanoxan sulfate (gwahn-ok′san)
An antihypertensive agent.

guanyl (gwahn′il)
The radical of guanine. g. cyclase SYN: guanylate cyclase.

guanylate cyclase (gwahn′i-lat)
Analogous to adenylate (adenylyl) cyclase, but cyclizing guanosine 5′-triphosphate to guanosine 3′:5′-cyclic monophosphate and also producing pyrophosphate; activated by nitric oxide. SYN: guanyl cyclase, guanylyl cyclase.

guanylic acid (GMP) (gwa-nil′ik)
A major component of ribonucleic acids. SYN: guanine ribonucleotide, guanosine 5′-monophosphate. g. reductase (GMP reductase) an enzyme that catalyzes the reaction of GMP with NADPH, producing IMP, NH3, and NADP+; a part of the purine salvage pathway. g. synthetase (GMP synthetase) an enzyme catalyzing the reaction of l-glutamine, XMP, and ATP to produce GMP, l-glutamate, AMP, and pyrophosphate; a key step in purine biosynthesis.

guanyloribonuclease (gwahn′i-lo-ri-bo-noo′kle-as)
SYN: RNase T1. See entries under ribonuclease.

guanylyl (gwahn′i-lil)
The radical of guanylic acid. g. cyclase SYN: guanylate cyclase.

guarana (gwah-rah-nah′)
A dried paste of the crushed seeds of Paullinia cupana (family Sapindaceae), a vine extensively cultivated in Brazil. It contains guaranine (caffeine), saponin, a volatile oil, and paullinitannic acid. Has been used for the relief of headache. [Native Brazilian word]

guaranine (gwahr′a-nen)
SYN: caffeine.

guarding (gard′ing)
A spasm of muscles to minimize motion or agitation of sites affected by injury or disease. abdominal g. a spasm of abdominal wall muscles, detected on palpation, to protect inflamed abdominal viscera from pressure; usually a result of inflammation of the parietal peritoneal surface as in appendicitis, diverticulitis, or generalized peritonitis. involuntary g. abdominal muscle spasm, caused by retroperitoneal inflammation, which cannot be willfully suppressed. voluntary g. abdominal muscle spasm that can be willfully suppressed.

Giuseppi, Italian physician, 1856–1918. See G. bodies, under body.

gubernaculum (goo′ber-nak′u-lum) [TA]
A fibrous cord connecting two structures. A mesenchymal column of tissue that connects the fetal testis to the developing scrotum; it appears to play a role in testicular descent. SYN: g. testis. [L. a helm] g. dentis a connective tissue band uniting the tooth sac with the gum. Hunter g. obsolete term for g. testis. g. testis SYN: g..

Adolphe, French physician, 1821–1879. See G. line, G. paralysis, G. syndrome, Millard-G. syndrome.

Bernhard A. von, German neurologist, 1824–1886. See G. commissure, G. ganglion, G. tegmental nuclei, under nucleus.

Arthur Ernest, U.S. anesthesiologist, 1883–1956. See G. airway.

Guéneau de Mussy
Noël F.O., French physician, 1813–1885. See G. point.

Camille, French bacteriologist, 1872–1961. See bacille Calmette-G., bacillus Calmette-G. vaccine, Calmette test, Calmette-G. bacillus, Calmette-G. vaccine.

Alphonse F.M., French surgeon, 1816–1895. See G. fold, G. fracture, G. glands, under gland, G. sinus, G. valve.

guidance (gi′dans)
1. The act of guiding. 2. A guide. condylar g. the mechanical device on an articulator which is intended to produce g. in articulator movement, similar to those produced by the paths of the condyles in the temporomandibular joints. SEE ALSO: condylar g. inclination. SYN: condylar guide. incisal g. the influence on mandibular movements caused by the contacting surfaces of the mandibular and maxillary anterior teeth during eccentric excursions. SYN: incisal path.

guide (gid)
1. To lead in a set course. 2. Any device or instrument by which another is led into its proper course, e.g., a grooved director, a catheter g.. [M.E., fr. O.Fr. guier, to show the way, fr. Germanic] anterior g. SYN: incisal g.. catheter g. a flexible metallic wire or thin sound over which a catheter is passed to advance it into its proper position, as in a blood vessel or the urethra. SEE ALSO: stylet. condylar g. SYN: condylar guidance. incisal g. in dentistry, that part of an articulator on which the anterior g. pin rests to maintain the vertical dimension of occlusion and the incisal g. angle as established by the incisal guidance; may be adjustable, with a superior surface that may be changed to provide variations in the incisal g. angle, or customized, being individually formed in plastic to allow other than straight line incisal guidance in eccentric movements. SYN: anterior g.. mold g. a g. used to specify the shape of artificial teeth, or of an artificial tooth.

guideline (gid′lin)
A marking in the form of a line that serves as a guide or reference. clasp g. SYN: survey line. clinical practice guidelines a formal statement about a defined task or function in clinical practice, such as desirable diagnostic tests or the optimal treatment regimen for a specific diagnosis; generally based on the best available evidence, e.g., randomized controlled trials that have been assessed by a Cochrane collaborating group. SEE ALSO: Cochrane collaboration. Cummer g. SYN: survey line. practice guidelines recommendations developed by groups of clinicians for delivery of care based on various indications. SYN: practice parameters.

guidewire (gid′wir)
A wire or spring used as a guide for placement of a larger device or prosthesis, such as a catheter or intramedullary pin.

Georges, French neurologist, 1876–1961. See G.-Barré reflex, G.-Barré syndrome, Landry-G.-Barré syndrome.

guillotine (gil′o-ten, ge′o-ten)
An instrument in the shape of a metal ring through which runs a sliding knifeblade, used in excising a tonsil. [Fr. an instrument for execution by decapitation]

guinea green B (gin′e) [C.I. 42085]
An acid diaminotriphenylmethane dye, used as an indicator for H-ion determinations (changing at pH 6.0 from magenta to green) and as a fiber cytoplasmic stain in certain Masson trichrome staining procedures.

guinea pig (gin′e)
SYN: Cavia porcellus.

C., Norwegian chemist, 1862–1902. See G.-Waage law.

gullet (gul′et)
SYN: throat (1) . [L. gula, throat]

Allvar, Swedish ophthalmologist and Nobel laureate, 1862–1930. See biomicroscope.

gulose (goo′los)
One of the eight pairs (d and l) of aldoses; d-g. is an epimer of d-galactose.

gum (gum)
1. The dried exuded sap from a number of trees and shrubs, forming an amorphous brittle mass; it usually forms a mucilaginous solution in water and is often used as a suspending agent in liquid preparations of insoluble drugs. [L. gummi] 2. gingiva. [A.S. goma, jaw] 3. Water-soluble glycans, often containing uronic acids, found in many plants. g. arabic SYN: acacia. SEE ALSO: arabin. Bassora g. a g. from Iran and Turkey, resembling tragacanth, acacia, and the gummy exudate of cherry and plum trees; used in making storax. g. benjamin, g. benzoin SYN: benzoin. British g. a form of dextrin. eucalyptus g. a dried gummy exudation from Eucalyptus rostrata and other species of Eucalyptus (family Myrtaceae); used as an astringent (in gargles and troches) and as an antidiarrheal agent. SYN: red g.. ghatti g. SYN: Indian g.. guaiac g. SYN: guaiac. guar g. the ground endosperms of Cyamopsis tetragonolobus; used in pharmaceutical jelly formulations. Indian g. an exudation from Anogeisus latifolia (family Combrettaceae); the mucilage is used as a substitute for acacia mucilage. SYN: ghatti g.. karaya g. SYN: sterculia g.. locust g. SYN: algaroba. g. opium SYN: opium. red g. SYN: eucalyptus g.. senegal g. the g. of Acacia senegal. See acacia. starch g. SYN: dextrin. sterculia g. the dried gummy exudation from Sterculia urens, S. villosa, S. tragacantha, or other species of Sterculia, or from Cochlospermum gossypium or other species of Cochlospermum (family Bixaceae); used as a hydrophilic laxative and in the manufacture of lotions and pastes. SYN: karaya g.. wheat g. SYN: gluten.

gumboil (gum′boyl)
SYN: gingival abscess.

gumma, pl .gummatagummas (gum′a, a-ta, -z)
An infectious granuloma that is characteristic of tertiary syphilis, but does not always develop, and that may be solitary (as large as 8–10 cm in diameter) or multiple and diffusely scattered (1 mm or less in diameter). Gummas are characterized by an irregular central portion that is firm, sometimes partially hyalinized, and consisting of coagulative necrosis in which “ghosts” of structures may be recognized; a poorly defined middle zone of epithelioid cells, with occasional multinucleated giant cells; and a peripheral zone of fibroblasts and numerous capillaries, with infiltrated lymphocytes and plasma cells. As gummas become older, an irregular scar or rounded fibrous nodule persists. SYN: syphiloma. [L. gummi, gum, fr. G. kommi]

Ferdinand A., German physician, 1864–1941. See Klein-G. shadow nuclei, under nucleus, G. shadows, under shadow.

Robert Marcus, British ophthalmologist, 1850–1909. See G. phenomenon, G. dots, under dot, G. sign, G. syndrome, Marcus G. pupil.

Jan W., Dutch chemist, 1827–1901. See G. reaction.

Thomas B., U.S. dentist, 1813–1889. See G. splint.

Justus W., German anatomist, 1714–1815. See G. ligament.

Alfred, German physician, *1861. See G. reagent, G. test.

Symbol for guanosine.

gurney (gur′ne)
A stretcher or cot with wheels used to transport patients. [Sir Goldsworthy G., British physician and inventor, 1793–1875]

gusher (gush′er)
An abundant flow of fluid. perilymphatic g. abnormal flow of perilymph when the footplate of the stapes is perforated; occurs in X-linked mixed deafness (DFN 3) due to a mutation of the POU3F4 gene and in other conditions.

Carl, German surgeon, 1842–1903. See G. suture.

gustation (gus-ta′shun)
1. The act of tasting. 2. The sense of taste. [L. gustatio, fr. gusto, pp. -atus, to taste]

gustatory (gus′ta-tor-e)
Relating to gustation, or taste.

gustducin (gust-dus-in)
A protein messenger in taste buds that is activated in response to sweet tastes; g. is a G-protein α-subunit. [L. gustus, taste, + duco, to lead, induce, + -in]

gut (gut)
1. SYN: intestine. 2. Embryonic digestive tube. 3. Abbreviated term for catgut. SEE ALSO: suture. [A.S.] blind g. SYN: cecum (1) . postanal g. an extension of the hindgut caudal to the point at which the anal opening is formed. SYN: postcloacal g., tailgut. postcloacal g. SYN: postanal g.. preoral g. SYN: Seessel pocket. primitive g. a flat sheet of intraembryonic endoderm that will change into a tubular g. due to the folding of embryonic body—head, tail and lateral body folds. SYN: archenteron, celenteron, endodermal canal, subgerminal cavity.

George J., English ophthalmologist, 1785–1856. See G. muscle.

Robert, U.S. pediatrician, 1916–1995. See G. test.

Carl, German physician, *1872. See Michaelis-G. body.

gutta (gt.) , pl .guttae (gtt.) (gut′a, -e)
1. A drop. 2. A rubber-like polyterpene found in g.-percha. Cf.:chicle, g.-percha. [L.] g. serena former term for blindness of unknown etiology; the “serena” suggested that the anterior segment of the eye was clear and tranquil, that there was no visible cause for the blindness, no corneal scar, no inflammation, no cataract. Thus, g. serena became the code word for blindness due to some unfathomable posterior cause, some damage to retina, optic nerve, or brain. This was the name given to John Milton's blindness. With the opthalmoscope, in 1851, the diagnosis of g. serena suddenly became old-fashioned and inadequate.

Plural of gutta. [L.]

gutta-percha (gut′a-per′cha)
The coagulated, purified, dried, milky juice of trees of the genera Palaguium and Payena (family Sapotaceae); used as a filling material in dentistry, and in the manufacture of splints and electrical insulators; a solution is used as a substitute for collodion, as a protective, and to seal incised wounds. Cf.:chicle, gutta. [Malay gatah, gum, + percha, the name of a tree]

Abbreviation for L. guttatim, drop by drop.


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