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Medical Dictionary - Dictionary of Medicine and Human Biology

Medical Dictionary


Baron Georges L.C.F.D. de la, French scientist, 1769–1832. See C. ducts, under duct, C. veins, under vein.

Abbreviation for coefficient of variation; cardiovascular; closing volume.

Abbreviation for cerebrovascular accident.

Abbreviation for central venous pressure.

Abbreviation for phosgene oxime.

Abbreviation for concentration × time. See AUC.

See cyano-.

cyanalcohols (si-an-al′ko-holz)
SYN: cyanohydrins.

cyanamide (si-an′i-mid)
An irritating and caustic water-soluble substance, H2NCN or HN&dbond;C&dbond;NH; often used in referring to calcium c..

cyanate (si′an-at)
The radical &cbond;O&cbond;C&tbond;N or ion (CNO)−.

cyanemia (si-a-ne′me-a)
Obsolete term for cyanosis. [cyan- + G. haima, blood]

cyanide (si′an-id)
1. The radical –CN or ion (CN)−. The ion is extremely poisonous, forming hydrocyanic acid in water, it has the odor of almond oil; inhibits respiratory proteins (cytochromes) at the cellular level. 2. A salt of HCN or a cyano-containing molecule. c. methemoglobin SYN: cyanmethemoglobin.

cyanidenon (si-a-nid′e-non)
SYN: luteolin.

cyanidol (si′an-i-dol)
SYN: catechin.

cyanmethemoglobin (si′an-met-he′mo-glo-bin)
A relatively nontoxic compound of cyanide with methemoglobin, which is formed when methylene blue is administered in cases of cyanide poisoning. SYN: cyanide methemoglobin.

cyano-, cyan-
1. Combining form meaning blue. 2. Chemical prefix frequently used in naming compounds that contain the cyanide group, CN. [G. kyanos, a dark blue substance]

Cyanobacteria (si′a-no-bak-ter′e-a)
A division of the kingdom Prokaryotae consisting of unicellular or filamentous bacteria that are either nonmotile or possess a gliding motility, reproduce by binary fission, and perform photosynthesis with the production of oxygen. These blue-green bacteria were formerly referred to as blue-green algae. SYN: Cyanophyceae.

cyanochroic, cyanochrous (si-an-o-kro′ik, si-an-ok′rus)
SYN: cyanotic. [cyano- + G. chroia, color]

cyanocobalamin (si′an-o-ko-bal′a-min)
A complex of cyanide and cobalamin, as in vitamin B12, in which a cyanide group has filled the sixth coordinate position of the cobalt atom. radioactive c. cyano[57Co]cobalamin, cyano[58Co]cobalamin, or cyano[60Co]cobalamin produced by the growth of certain microorganisms on a medium containing cobalt-57, cobalt-58, or cobalt-60; used in the investigation of the absorption and metabolism of c. (vitamin B12).

cyanogen (si-an′o-jen)
1. A compound of two cyano radicals, NC&cbond;CN. 2. Highly toxic compounds (general formula X&cbond;CN, where X is a halogen) that are used in chemical syntheses and as tissue preservatives. An example is c. bromide. c. chloride CNCl;a highly volatile liquid; a systemic poison used as a warning agent in fumigation with hydrogen cyanide.

cyanogenic (si′an-o-jen′ik)
Capable of producing hydrocyanic acid; said of plants such as sorghum, Johnson grass, arrowgrass, and wild cherry which may cause cyanide poisoning in herbivorous animals.

cyanohydrins (si′an-o-hi′drinz)
R&cbond;CHOH&cbond;CN;addition compounds of HCN and aldehydes. SYN: cyanalcohols.

cyanophil, cyanophile (si′an-o-fil, -fil)
A cell or element that is differentially colored blue by a staining procedure. [cyano- + G. philos, fond]

cyanophilous (si-a-nof′i-lus)
Readily stainable with a blue dye.

Cyanophyceae (si′a-no-fi′se-e)
SYN: Cyanobacteria. [cyano- + G. phykos, seaweed]

cyanopia (si-a-no′pe-a)
SYN: cyanopsia.

cyanopsia (si-a-nop′se-a)
A condition in which all objects appear blue; may temporarily follow cataract extraction. SYN: blue vision, cyanopia. [cyano- + G. opsis, vision]

cyanosed (si′a-nost)
SYN: cyanotic.

cyanosis (si-a-no′sis)
A dark bluish or purplish discoloration of the skin and mucous membrane due to deficient oxygenation of the blood, evident when reduced hemoglobin in the blood exceeds 5 g/100 ml. [G. dark blue color, fr. kyanos, blue substance] compression c. c. accompanied by edema and petechial hemorrhages over the head, neck, and upper part of the chest, as a venous reflex resulting from severe compression of the thorax or abdomen; the conjunctiva and retinas are similarly affected. enterogenous c. apparent c. caused by the absorption of nitrites or other toxic materials from the intestine with the formation of methemoglobin or sulfhemoglobin; the skin color change is due to the chocolate color of methemoglobin. false c. c. due to the presence of an abnormal pigment, such as methemoglobin, in the blood, and not resulting from a deficiency of oxygen. hereditary methemoglobinemic c. SYN: congenital methemoglobinemia. late c. c. due to right to left shunt in congenital heart disease appearing only after cardiac failure. SYN: cyanose tardive, tardive c.. c. retinae venous congestion of the retina. shunt c. any blue color of the entire skin or a region of the skin or mucous membrane due to a right to left shunt permitting unoxygenated blood to reach the left side of the circulation. tardive c. SYN: late c.. toxic c. c. due to methemoglobin formation resulting from the action of certain drugs, e.g., nitrites.

cyanotic (si-a-not′ik)
Relating to or marked by cyanosis. SYN: cyanochroic, cyanochrous, cyanosed.

cyanuria (si-a-noo′re-a)
The presence of blue urine. [cyano- + G. ouron, urine]

cyanuric acid (si-a-noor′ik)
A cyclic product formed by heating urea; used industrially and as an herbicide.

Cyathostoma (si-a-thos′to-ma)
A genus of gapeworms of poultry in the nematode family Syngamidae, so called because of the gaping habit of fowl infected by these worms in their upper respiratory tract. [G. kyathos, cup, cup-shaped, + stoma, mouth] C. bronchialis a species found in wild geese and domestic ducks, geese, and swans; occurs in the larynx, trachea, and bronchi and causes distress and symptoms similar to those produced by the chicken gapeworm, Syngamus trachea; its life cycle is thought to be similar to that of Syngamus trachea.

Cyathostomum (si-a-thos′to-mum)
A genus of strongyle nematodes (family Cyasthostomidae, formerly part of the family Strongylidae); it includes many of the small strongyles of horses formerly placed in the genus Trichonema, which have been variously divided into a number of genera and subgenera. [see Cyathostoma]

cybernetics (si-ber-net′iks)
1. The comparative study of computers and the human nervous system, with intent to explain the functioning of the brain. 2. The science of control and communication in both living and nonliving systems; characteristically, control is governed by feedback, that is, by communication within the system concerning the difference between the actual and the desired result, action then being modified so as to minimize this difference. SEE ALSO: feedback. [G. kybernetica, things pertaining to control or piloting]

cybrid (si′brid)
A cell with cytoplasm from two different cells as a result of cell hybridization. [cell + hybrid]

See cyclo-.

cyclamate (si′kla-mat)
A salt or ester of cyclamic acid; the calcium and sodium are noncaloric artificial sweetening agents.

cyclamic acid (si-klam′ik)
A sweetening agent, usually used as sodium or calcium cyclamate. SYN: cyclohexanesulfamic acid, cyclohexylsulfamic acid.

cyclamide (si′kla-mid)
SYN: glycyclamide.

cyclandelate (si-klan′de-lat)
An antispasmodic similar in action to papaverine; used for obliterative vascular diseases and vasospastic conditions.

cyclarthrodial (si-klar-thro′de-al)
Relating to a cyclarthrosis.

cyclarthrosis (si-klar-thro′sis)
A joint capable of rotation. [cyclo- + G. arthrosis, articulation]

cyclase (si′klas)
Descriptive name applied to an enzyme that forms a cyclic compound; e.g., adenylate c..

cycle (si′kl)
1. A recurrent series of events. 2. A recurring period of time. 3. One successive compression and rarefaction of a wave, as of a sound wave. [G. kyklos, circle] anovulatory c. a sexual c. in which no ovum is discharged. brain wave c. the complete upward and downward excursion of a single wave, complex, or impulse as seen on an electroencephalogram. carbon dioxide c., carbon c. the circulation of carbon as CO2 from the expired air of animals and decaying organic matter to plant life where it is synthesized (through photosynthesis) to carbohydrate material, from which, as a result of catabolic processes in all life, it is again ultimately released to the atmosphere as CO2. cardiac c. the complete round of cardiac systole and diastole with the intervals between, or commencing with, any event in the heart's action to the moment when that same event is repeated. cell c. the periodic biochemical and structural events occurring during proliferation of cells such as in tissue culture; the c. is divided into phases called: G0, Gap1 (G1), synthesis (S1), Gap2 (G2), and mitosis (M). The period runs from one division to the next. SYN: mitotic c.. chewing c. a complete course of movement of the mandible during a single masticatory stroke. citric acid c. SYN: tricarboxylic acid c.. Cori c. the phases in the metabolism of carbohydrate: 1) glycogenolysis in the liver; 2) passage of glucose into the circulation; 3) deposition of glucose in the muscles as glycogen; 4) glycogenolysis during muscular activity and conversion to lactate, which is converted to glycogen in the liver. Also called the lactic acid c.. dicarboxylic acid c. 1. that portion of the tricarboxylic acid c. involving the dicarboxylic acids (succinic, fumaric, malic, and oxaloacetic acids); 2. a cyclic scheme in which certain steps of the tricarboxylic acid c. are used with the glyoxylate c.; important in the utilization of glyoxylic acid in microorganisms. endogenous c. the portion of a parasitic life c. occurring within the host. erythrocytic c. that pathogenic portion of the vertebrate phase of the life c. of malarial organisms that takes place in the red blood cells. estrous c. the series of physiologic uterine, ovarian, and other changes that occur in higher animals, consisting of proestrus, estrus, postestrus, and anestrus or diestrus. exoerythrocytic c. that nonpathogenic portion of the vertebrate phase of the life c. of malarial organisms that takes place in liver cells, outside of the blood cells. exogenous c. the portion of a parasitic life c. occurring outside the host. fatty acid oxidation c. a series of reactions involving acyl-coenzyme A compounds, whereby these undergo beta oxidation and thioclastic cleavage, with the formation of acetyl-coenzyme A; the major pathway of fatty acid catabolism in living tissue. forced c. a cardiac c. (atrial or ventricular) that is cut short by a forced beat. futile c. a c. of phosphorylation and dephosphorylation catalyzed by two enzymes which normally function in two different metabolic pathways; the net effect is the hydrolysis of ATP and the generation of heat; E.G., the futile c. from the unregulated action of 6-phosphofructokinase and fructose-1,6-bisphosphatase in muscle; such cycles may have important roles in heat production, in the fine tuning of the regulation of certain pathways and may be a factor in malignant hyperthermia. SYN: substrate c.. γ-glutamyl c. a proposed pathway for the glutathione-dependent transport of certain amino acids (most notably l-cystine, l-methionine, and l-glutamine) and dipeptides into certain cells; this c. requires the formation of γ-glutamyl amino acids and γ-glutamyl dipeptides as well as a protein for the translocation of these di- and triisopeptides into the cells. glycine-succinate c. a series of metabolic steps in which glycine is condensed with succinyl-CoA and is then oxidized to CO2 and H2O with regeneration of the succinyl-CoA; important in the synthesis of δ-aminolevulinic acid and in the metabolism of red blood cells. SYN: Shemin c.. glyoxylic acid c. a catabolic c. in plants and microorganisms like that of the tricarboxylic acid c. in animals; its key reaction is the condensation of acetyl-CoA with glyoxylic acid to malic acid (analogous to the condensation of acetyl-CoA and oxaloacetic acid to form citric acid in the tricarboxylic acid c.). SYN: Krebs-Kornberg c.. gonadotrophic c. (go′nad-o-trof′ik) one complete round of ovarian development in the insect vector from the time when the blood meal is taken to the time when the fully developed eggs are laid. hair c. the cyclical phases of growth (anagen), regression (catagen), and quiescence (telogen) in the life of a hair. heterogonic life c. free-living stage of life c. of an organism ( e.g., Strongyloides stercoralis) that also has a parasitic stage. homogonic life c. parasitic stage of life c. of an organism ( e.g., Strongyloides stercoralis) that also has a free-living stage. Krebs c. SYN: tricarboxylic acid c.. Krebs-Henseleit c., Krebs ornithine c., Krebs urea c. SYN: urea c.. Krebs-Kornberg c. SYN: glyoxylic acid c.. life c. the entire life history of a living organism. masticating cycles the patterns of mandibular movements formed during the chewing of food. menstrual c. the period in which an ovum matures, is ovulated, and enters the uterine lumen via the fallopian tubes; ovarian hormonal secretions effect endometrial changes such that, if fertilization occurs, nidation will be possible; in the absence of fertilization, ovarian secretions wane, the endometrium sloughs, and menstruation begins; this c. lasts an average of 28 days, with day 1 of the c. designated as that day on which menstrual flow begins. mitotic c. SYN: cell c.. nitrogen c. the series of events in which the nitrogen of the atmosphere is fixed, thus made available for plant and animal life, and is then returned to the atmosphere: nitrifying bacteria convert N2 and O2 to NO2− and NO3−, the latter being absorbed by plants and converted to protein; if plants decay, the nitrogen is in part given up to the atmosphere and the remainder is converted by microorganisms to ammonia, nitrites, and nitrates; if the plants are eaten, the animals' excreta or bacterial decay return the nitrogen to the soil and air. ornithine c. SYN: urea c.. ovarian c. the normal sex c. which includes development of an ovarian (graafian) follicle, rupture of the follicle with discharge of the ovum, and formation and regression of a corpus luteum. pentose phosphate c. SYN: pentose phosphate pathway. reproductive c. the c. which begins with conception and extends through gestation and parturition. restored c. an atrial or ventricular cardiac c. that follows the returning c. and resumes the normal rhythm. returning c. an atrial or ventricular cardiac c. that begins with an extrasystole or a forced beat. Ross c. the life c. of the malaria parasite. Shemin c. SYN: glycine-succinate c.. substrate c. SYN: futile c.. succinic acid c. a series of oxidation reduction reactions in which succinic acid and other acids containing four-carbon atoms (fumaric, malic, oxaloacetic) take part in the oxidation of pyruvic acid as part of the tricarboxylic acid c.. SEE ALSO: dicarboxylic acid c.. tricarboxylic acid c. together with oxidative phosphorylation, the main source of energy in the mammalian body and the end toward which carbohydrate, fat, and protein metabolism are directed; a series of reactions, beginning and ending with oxaloacetic acid, during the course of which a two-carbon fragment is completely oxidized to carbon dioxide and water with the production of 12 high-energy phosphate bonds. So called because the first four substances involved (citric acid, cis-aconitic acid, isocitric acid, and oxalosuccinic acid) are all tricarboxylic acids; from oxalosuccinate, the others are, in order, α-ketoglutarate, succinate, fumarate, l-malate, and oxaloacetate, which condenses with acetyl-CoA (from fatty acid degradation) to form citrate (citric acid) again. SYN: citric acid c., Krebs c.. urea c. the sequence of chemical reactions, occurring primarily in the liver, that results in the production of urea; the key reaction is the hydrolysis of l-arginine by arginase to l-ornithine and urea; l-ornithine is then converted to l-citrulline by a carbamoylation reaction, then to l-argininosuccinate by an amination reaction involving l-aspartic acid, and finally there is a lyase-dependent step that generates arginine and fumarate. SYN: Krebs-Henseleit c., Krebs ornithine c., Krebs urea c., ornithine c.. visual c. the transformation of carotenoids involved in the bleaching and regeneration of the visual pigment.

cyclectomy (si-klek′to-me, sik-lek′to-me)
Excision of a portion of the ciliary body. SYN: ciliectomy. [cyclo- + G. ektome, excision]

cyclencephaly, cyclencephalia (si-klen-sef′a-le, -se-fa′le-a)
Condition in a malformed fetus characterized by poor development and a varying degree of fusion of the two cerebral hemispheres. SYN: cyclocephaly, cyclocephalia. [cyclo- + G. enkephalos, brain]

cycles per second (cps)
The number of successive compressions and rarefactions per second of a sound wave. The preferred designation for this unit of frequency is hertz.

cyclic (si′klik, sik′lik)
1. Pertaining to, or characteristic of, a cycle; occurring periodically, denoting the course of the symptoms in certain diseases or disorders. 2. In chemistry, continuous, without end, as in a ring; denoting a c. compound.

cyclic AMP
SYN: adenosine 3′,5′-cyclic monophosphate.

3′,5′-cyclic AMP synthetase
SYN: adenylate cyclase.

cyclic GMP
SYN: cyclic guanosine 3′,5′-monophosphate.

cyclin D
Protein involved in progression to cell division.

cyclitis (si-kli′tis)
Inflammation of the ciliary body. [G. kyklos, circle (ciliary body), + -itis, inflammation] Fuchs heterochromic c. SYN: Fuchs syndrome. heterochromic c. a chronic inflammatory c. in which the iris of the affected eye becomes atrophic. plastic c. inflammation of the ciliary body, and usually of the entire uveal tract, with a fibrinous exudation into the anterior and vitreous chambers. purulent c. suppurative inflammation of the ciliary body.

cyclizine hydrochloride (si′kli-zen)
An H1 antihistamine agent useful in the prevention and relief of motion sickness and symptoms caused by vestibular disorders.

cyclizine lactate
An agent with the same use and action as the hydrochloride.

cyclo-, cycl-
1. Combining forms relating to a circle or cycle; or denoting an association with the ciliary body. 2. In chemistry, a combining form indicating a continuous molecule, without end, or the formation of such a structure between two parts of a molecule. [G. kyklos, circle]

cyclobenzaprine hydrochloride (si-klo-ben′za-pren)
A centrally acting skeletal muscle relaxant used to relieve acute muscular spasms.

cyclocephaly, cyclocephalia (si-klo-sef′a-le, -se-fa′le-a)
SYN: cyclencephaly. [cyclo- + G. kephale, head]

cyclochoroiditis (si′klo-ko-roy-di′tis)
Inflammation of the ciliary body and the choroid.

cyclocryotherapy (si′klo-kri′o-thar′a-pe)
Transscleral freezing of the ciliary body in the treatment of glaucoma.

cyclocumarol (si-klo-ku′ma-rol)
4-Hydroxycoumarin anticoagulant No. 63; a synthetic anticoagulant compound, related to bishydroxycoumarin.

cyclodestructive (si′klo-dis-truk′tiv)
Relating to a procedure designed to damage the ciliary body in order to diminish the production of aqueous fluid in patients with glaucoma. See cyclocryotherapy, cyclodiathermy, cyclophotocoagulation.

cyclodialysis (si′klo-di-al′i-sis)
Establishment of a communication between the anterior chamber and the suprachoroidal space in order to reduce intraocular pressure in glaucoma. [cyclo- + G. dialysis, separation]


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