Medical Dictionary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

deferent (def′er-ent)
Carrying away. [L. deferens, pres. p. of defero, to carry away]

deferential (def-er-en′shal)
Relating to the ductus deferens.

deferentitis (def′er-en-ti′tis)
Inflammation of the ductus deferens. SYN: vasitis.

deferoxamine mesylate (de-fer-ok′sa-men)
Chelate used in the treatment of iron poisoning. SYN: desferrioxamine mesylate.

defervescence (def-er-ves′ens)
Falling of an elevated temperature; abatement of fever. [L. de-fervesco, to cease boiling, fr. de- neg. + fervesco, to begin to boil]

defibrillation (de-fib-ri-la′shun)
The arrest of fibrillation of the cardiac muscle (atrial or ventricular) with restoration of the normal rhythm, if successful.

defibrillator (de-fib′ri-la-ter)
1. Any agent or measure, e.g., an electric shock, that arrests fibrillation of the ventricular muscle and restores the normal beat. 2. The machine designed to administer a defibrillating electric shock. external d. a d. that delivers its defibrillating shock through the unopened chest wall.

defibrination (de-fi-bri-na′shun)
Removal of fibrin from the blood, usually by means of constant agitation while the blood is collected in a container with glass beads or chips.

deficiency (de-fish′en-se)
An insufficient quantity of some substance (as in dietary d. or hemoglobin d. in marrow aplasia); organization (as in mental d.); activity (as in enzyme d. or reduced oxygen-carrying capacity of the blood), etc., of which the amount present is of normal quality. SEE ALSO: d. disease. [L. deficio, to fail, fr. facio, to do] adult lactase d. onset of lactase d., with resulting milk intolerance and malabsorption, in adulthood. Inherited forms may not be manifested until adulthood; any process that damages the intestinal lining cells can cause lactase d. in adults. antitrypsin d. d. of α1-antitrypsin, a serum protease inhibitor (PI), is associated with emphysema and/or liver cirrhosis. By isoelectric focusing, numerous variants have been identified, with different levels of normal activity; autosomal recessive inheritance, caused by mutation in the P1 gene on chromosomal 14q. α1-antitrypsin d. absence of a serum proteinase inhibitor that may cause relapsing nodular nonsuppurative panniculitis. arch length d. the difference between the available circumference of the dental arch and that required to accommodate the succedaneous teeth in proper alignment. arginosuccinate lyase d. SYN: argininosuccinic aciduria. arylsulfatase A d. SYN: metachromatic leukodystrophy. arylsulfatase B d. SYN: Maroteaux-Lamy syndrome. biotinidase d. a rare, autosomal recessive disease causing loss of excessive biotin; clinical manifestations may be absent, but extreme manifestations include seizures, alopecia, dermatitis, hypotonia, optic atrophy, ataxia, developmental delay, hearing deficits, and occasionally immunodeficiency; trait has a prevalence of 1 in 60,000. carnitine d. a condition associated with many disorders of fatty acid oxidation. Fatty acids are linked to carnitine as they are transported across the inner mitochondrial membrane; errors in this process lead to problems with energy production; patients may experience episodes of hypoglycemia or metabolic acidosis and may have cardiomyopathy or skeletal muscle weakness. debrancher d. SYN: brancher glycogen storage disease. familial high density lipoprotein d. SYN: analphalipoproteinemia. fructokinase d. SYN: essential fructosuria. galactokinase d. [MIM*230200] an inborn error of metabolism due to congenital d. of galactokinase (GALK), resulting in increased blood galactose concentration (galactosemia), cataracts, hepatomegaly, and mental d.; autosomal recessive inheritance, caused by mutation in the GALK gene on 17q. Galactose epimerase d. [MIM*230350] and galactose-1-phosphate uridyl transferase d. [MIM*230400] produce much the same clinical picture. glucose-6-phosphate dehydrogenase d. a d. of glucose-6-phosphate dehydrogenase, an enzyme important for maintaining cellular concentrations of reduced nucleotides. An X-linked disorder with various polymorphic forms, it can cause a variety of anemias including favism, primaquine sensitivity and other drug sensitivity anemias, anemia of the newborn, and chronic nonspherocytic hemolytic anemia. glucosephosphate isomerase d. [MIM*172400] an enzyme d. characterized by chronic nonspherocytic hemolytic anemia; autosomal recessive inheritance. SYN: phosphohexose isomerase d.. β-d-glucuronidase d. a rare d. of β-d-glucuronidase; an autosomal recessive disorder with several allelic forms, characterized by abnormal mucopolysaccharide metabolism leading to progressive mental deterioration, splenic and hepatic enlargement, and dysostosis multiplex. SYN: mucopolysaccharidase. glutathione synthetase d. an inborn error of metabolism associated with massive urinary excretion of 5-oxyproline, elevated levels of 5-oxyproline in the blood and cerebrospinal fluid, severe metabolic acidosis, tendency toward hemolysis, and defective central nervous systems function. Glutathione synthetase d. has been reported as a generalized condition or with a d. restricted to erythrocytes. 11-hydroxylase d. a type of congenital adrenal hyperplasia, with multiple manifestations, including hypertensive types and salt-wasting varieties. 21-hydroxylase d. one form of congenital adrenal hyperplasia, with variable presentations, including simple virilizing, salt-wasting, or nonclassic types. hypoxanthine guanine phosphoribosyltransferase d. a sex-linked inherited metabolic disorder; complete d. results in Lesch-Nyhan syndrome; incomplete d. is associated with acute gouty arthritis and renal stones. immune d. SYN: immunodeficiency. immunity d. SYN: immunodeficiency. immunologic d. SYN: immunodeficiency. LCAT d. a rare condition characterized by corneal opacities, hemolytic anemia, proteinuria, renal insufficiency, and premature atherosclerosis, and very low levels of lecithin cholesterol acyltransferase (LCAT) activity; results in accumulation of unesterfied cholesterol in plasma and tissues. leukocyte adhesion d. (LAD) an inherited disorder (autosomal recessive) in which there is a defective CD18 adherence complex that disturbs chemotaxis. It is characterized by recurrent bacterial pyogenic infections and impaired wound healing. long-chain 3-hydroxyacyl-CoA dehydrogenase d. a fatty acid oxidation disorder; patients may experience episodes of acute hypoketotic hypoglycemia (similar to that found in MCAD d.), cardiomyopathy, muscle weakness, and liver abnormalities. long-chain/very long-chain acyl-CoA dehydrogenase d. a disorder of fatty acid oxidation in patients who lack the enzyme very long chain acyl-CoA dehydrogenase; sometimes manifested as weakness, hypotonia, cardiomyopathy, rhabdomyolysis, and episodes of hypoglycemia during fasting. luteal phase d. SYN: luteal phase defect. medium-chain acyl-CoA dehydrogenase d. the most common fatty acid oxidation disorder, presenting as acute episodes triggered by prolonged fasting for more than 12–16 hours, with hypoglycemia, vomiting, and lethargy, which may progress to seizures, coma, or cardiopulmonary collapse, usually presenting before age 3. mental d. SYN: mental retardation. muscle phosphorylase d. type V glycogen storage disease, affecting muscle, caused by d. of muscle phosphorylase. phosphohexose isomerase d. SYN: glucosephosphate isomerase d.. placental sulfatase d. an enzyme defect in the placenta which results in failure of conversion of 16α-hydroxydehydroepiandrosterone to estriol; women with this condition rarely enter into spontaneous labor. primary carnitine d. a rare defect in carnitine metabolism due to a defect in carnitine transport; patients may present with hypoketotic hypoglycemia and develop cardiomyopathy or skeletal muscle weakness. proximal femoral focal d. (PFFD) a congenital defect in which variable portions of the upper end of the femur are reduced or absent. pseudocholinesterase d. [MIM*177400] an autosomal dominant disorder manifested by exaggerated responses to drugs ordinarily hydrolyzed by serum pseudocholinesterase ( e.g., succinylcholine); believed to entail production of a variant enzyme that is less active than the normal enzyme in hydrolyzing appropriate substrates, but also abnormally resistant to the effects of anticholinesterases, caused by mutation in the pseudocholinesterase E1 gene (CHE1) on 3q. pyruvate kinase d. [MIM*266200] a disorder in which there is a d. of pyruvate kinase in red blood cells; characterized by hemolytic anemia varying in degree from one patient to another; autosomal recessive inheritance, caused by mutation in the pyruvate kinase liver and red blood cell gene (PKLR) on chromosome 1q. riboflavin d. ariboflavinosis. secondary antibody d. SYN: secondary immunodeficiency. short-chain acyl-CoA dehydrogenase d. a disorder of fatty acid oxidation; patients may have chronic acidosis, failure to thrive, muscle weakness, and developmental delay. taste d. [MIM*171200] reduced or absent ability to detect a bitter taste in a group of compounds of which phenylthiocarbamide is the prototype, due to the homozygous state of a common allele. SEE ALSO: phenylthiourea.

deficit (def′i-sit)
The result of consuming or using something faster than it is being replenished or replaced. [L. deficio, to fail] base d. a decrease in the total concentration of blood buffer base, indicative of metabolic acidosis or compensated respiratory alkalosis. oxygen d. the difference between oxygen uptake of the body during early stages of exercise and during a similar duration in a steady state of exercise; sometimes considered as the formation of the oxygen debt. pulse d. 1. the absence of palpable pulse waves in a peripheral artery for one or more heart beats, as is often seen in atrial fibrillation; 2. the number of such missing pulse waves (usually expressed as heart rate minus pulse rate per minute). sleep d. a lack of sleep time or a relative lack of one of the stages of sleep as determined by a sleep study.

definition (def′i-nish′un)
In optics, the power of a lens to give a distinct image. SEE ALSO: resolving power. [L. de-finio, pp. -finitus, to bound, fr. finis, limit]

deflection (de-flek′shun)
1. A moving to one side. 2. In the electrocardiogram, a deviation of the curve from the isoelectric base line; any wave or complex of the electrocardiogram. [L. de-flecto, pp. -flexus, to bend aside] intrinsic d. with the electrode in direct contact with the muscle fiber, a rapid downward d. from the peak of latest positivity, signifying that the activation front has reached the subjacent muscle. intrinsicoid d. the abrupt downstroke from latest positivity when the electrode is placed not directly on the muscle but at a distance, as in the unipolar chest leads in clinical electrocardiography.

deflexion (de′fleks-shun)
Term used to describe the position of the fetal head in relation to the maternal pelvis in which the head is descending in a nonflexed or extended attitude. [de- + L. flexio, a bending, fr. flecto, pp. flexum, to bend]

deflorescence (de-flo-res′ens)
Disappearance of the eruption in scarlet fever or other exanthemas. [L. de-floresco, to fade, wither, fr. flos (flor-), flower]

defluoridation (de-flor′i-da′shun)
Removal of excess fluorides from a community water supply.

defluvium (de-floo′ve-um)
SYN: defluxion. [L., fr. de-fluo, pp. -fluxus, to flow down]

defluxion (de-fluk′shun)
1. A falling down or out, as of the hair. SEE ALSO: effluvium. 2. A flowing down or discharge of fluid. SYN: defluvium. [L. defluxio, de-fluo, pp. -fluxus, to flow down]

deformability (de-form′a-bil′i-te)
The ability of cells, such as erythrocytes, to change shape as they pass through narrow spaces, such as the microvasculature.

deformation (de-for-ma′shun)
1. Deviation of form from the normal; specifically, an alteration in shape and/or structure of a previously normally formed part. It occurs after organogenesis and often involves the musculoskeletal system ( e.g., clubfoot). 2. In rheology, the change in the physical shape of a mass by applied stress. [L. de-formo, pp. -atus, to deform, fr. forma, form]

deforming (de-form′ing)
Causing a deviation from the normal form.

deformity (de-for′mi-te)
A permanent structural deviation from the normal shape, size, or alignment, resulting in disfigurement; may be congenital or acquired. SEE ALSO: deformation (1) . Åkerlund d. indentation (incisura) with niche of duodenal cap as demonstrated radiographically. Arnold-Chiari d. [MIM*207950] SYN: Arnold-Chiari malformation. bell clapper d. a testis and epididymis free of the usual posterior attachment of the tunica vaginalis such that the tunic inserts high on the spermatic cord leaving the gonad more likely to undergo torsion. boutonnière d. flexion of the proximal interphalangeal joint with hyperextension of the distal interphalangeal joint of the finger, caused by separation of the extensor hood and protrusion of the head of the proximal phalanx through the resulting “buttonhole”; can result from degeneration (rheumatoid arthritis) or trauma. contracture d. d. of a limb without discernable primary changes of bone. Erlenmeyer flask d. a d. at the distal end of the femur caused by a failure of the shaft of the bone to develop to its normal tubular shape, with the result that the bone is wide for a much longer distance up the shaft than normal; encountered in Gaucher disease. [resemblance to an E. flask] gunstock d. a form of cubitus varus resulting from supracondylar or condylar fracture at the elbow in which the axis of the extended forearm is not continuous with that of the arm but is displaced toward midline. Haglund d. SYN: Haglund disease. J-sella d. pear-shaped or J-shaped d. of sella turcica caused by increased pressure on growing sphenoid bone; noted in the mucopolysaccharide storage diseases. keyhole d. mucosal ectropion at the posterior edge of the anus following sphincterotomy at that location. lobster-claw d. See ectrodactyly. Madelung d. a distal radioulnar subluxation due to a relative deficiency of axial growth of the medial side of the distal radius, which, as a consequence, is abnormally inclined proximally and ulnarwards. SYN: carpus curvus. mermaid malformation SYN: sirenomelia. parachute d. SYN: parachute mitral valve. reduction d. congenital absence or attenuation of one or more body parts; usually of the limbs or limb components. silver-fork d. the d. resembling the curve of the back of a fork seen in Colles (distal radius) fracture. Sprengel d. congenital elevation of the scapula. SYN: scapula elevata. swan-neck d. hyperextension of the proximal interphalangeal joint with flexion of the distal interphalangeal joint of the finger. torsional d. in orthopedics, a d. caused by an abnormal rotation of a portion of an extremity with relationship to the long axis of the entire extremity. whistling d. d. caused by insufficient tissue in the lower border of a repaired cleft lip, giving the appearance of whistling. Whitehead d. circumferential mucosal ectropion at the anus following Whitehead operation.

defurfuration (de-fer-fer-a′shun)
The shedding of the epidermis in the form of fine scales. SYN: branny desquamation. [L. de, away from, + furfur, bran]

deganglionate (de-gang′gle-on-at)
To deprive of ganglia.

degeneracy (de-jen′er-a-se)
1. A condition marked by deterioration of mental, physical, or moral processes. 2. The fact that several different triplet codons encode the same amino acid. [L. de, from, + genus, (gener-), race]

degenerate
1. (de-jen′er-at)To pass to a lower level of mental, physical, or moral state; to fall below the normal or acceptable type or state. 2. (de-jen′e-rat)Below the normal or acceptable; that which has passed to a lower level.

degeneratio (de-jen-er-a′she-o)
SYN: degeneration. [L. degenero, pp. -atus, fr. de, from, + genus, race]

degeneration (de-jen-er-a′shun)
1. Deterioration; passing from a higher to a lower level or type. 2. A worsening of mental, physical, or moral qualities. 3. A retrogressive pathologic change in cells or tissues, in consequence of which their functions are often impaired or destroyed; sometimes reversible; in the early stages, necrosis results. SYN: retrograde metamorphosis. SYN: degeneratio. [L. degeneratio] adipose d. SYN: fatty d.. adiposogenital d. SYN: adiposogenital dystrophy. age-related macular d. a common macular d. beginning with drusen of the macula and pigment disruption and sometimes leading to severe loss of central vision. amyloid d. infiltration of amyloid between cells and fibers of tissues and organs. SYN: waxy d. (1) . angiolithic d. calcareous d. of the walls of the blood vessels. ascending d. 1. retrograde d. of an injured nerve fiber; i.e., toward the nerve cell of the fiber; 2. spinal cord d. that begins in one region and then progresses cephalad. atheromatous d. focal accumulation of lipid material (atheroma) in the intima and subintimal portion of arteries, eventually resulting in fibrous thickening or calcification. axon d. SYN: axonal d.. axonal d. a type of peripheral nerve fiber response to insult, wherein axon death and subsequent breakdown occurs, with secondary breakdown of the myelin sheath associated; caused by focal injury to peripheral nerve fibers; often referred to as wallerian d.. SYN: axon d.. ballooning d. an obsolete term for cells that are infected with certain viruses, resulting in conspicuous swelling of the cell and cytoplasmic vacuolation. basophilic d. blue staining of connective tissues when hematoxylin-eosin stain is used; found in such conditions as solar elastosis. calcareous d. in a precise sense, not a degenerative process per se, but the deposition of insoluble calcium salts in tissue that has degenerated and become necrotic, as in dystrophic calcification. carneous d. SYN: red d.. caseous d. SYN: caseous necrosis. colloid d. a d. similar to mucoid d., in which the material is inspissated. cone d. SYN: cone dystrophy. corticobasal d. a rare, progressive disease involving both cerebral cortex and extrapyramidal structures; clinically manifest as disturbances of voluntary movements and rigidity; pathologic characteristics include d. of the cerebral cortex with balloon neurons and d. of the substantia nigra. Crooke hyaline d. SYN: Crooke hyaline change. descending d. 1. wallerian d. of an injured nerve fiber; i.e., d. distal to the lesion; 2. d. caudal to the level of a spinal cord lesion. disciform d. foveal or parafoveal subretinal neovascularization with retinal separation and hemorrhage leading finally to a circular mass of fibrous tissue with marked loss of visual acuity. SYN: disciform macular d.. disciform macular d. SYN: disciform d.. ectatic marginal d. of cornea SYN: pellucid marginal corneal d.. elastoid d. 1. SYN: elastosis (2) . 2. hyaline d. of the elastic tissue of the arterial wall, seen during involution of the uterus. elastotic d. SYN: elastosis (2) . familial pseudoinflammatory macular d. [MIM*136900] macular d. that occurs during the fifth decade of life, with sudden development of a central scotoma in one eye followed rapidly by a similar lesion in the opposite eye; autosomal dominant inheritance. SYN: Sorsby macular d.. fascicular d. d. restricted to certain fascicles of nerves or muscles. fatty d. abnormal formation of microscopically visible droplets of fat in the cytoplasm of cells, as a result of injury. SYN: adipose d., steatosis (2) . fibrinoid d., fibrinous d. a process resulting in poorly defined, deeply acidophilic, homogeneous refractile deposits with some staining reactions that resemble fibrin, occurring in connective tissue, blood vessel walls, and other sites. fibrous d. not a d. per se, but rather a reparative process; cells and foci of tissue previously affected with degenerative processes, and necrosis, are replaced by cellular fibrous tissue. granular d. SYN: cloudy swelling. granulovacuolar d. d. of hippocampal brain cells in elderly persons, characterized by basophilic granules surrounded by a clear zone in hippocampal neurons; occurs more frequently in Alzheimer disease. gray d. d. of the white substance of the spinal cord, the fibers of which lose their myelin sheaths and become darker in color. hepatolenticular d. SYN: Wilson disease (1) . hyaline d. a group of several degenerative processes that affect various cells and tissues, resulting in the formation of rounded masses (“droplets”) or relatively broad bands of substances that are homogeneous, translucent, refractile, and moderately to deeply acidophilic; may occur in the collagen of old fibrous tissue, smooth muscle of arterioles or the uterus, and as droplets in parenchymal cells. hyaloideoretinal d. [MIM*143200] progressive liquefaction and destruction of the vitreous humor with grayish-white preretinal membranes, myopia, cataract, retinal detachment, and hyper- and hypopigmentation; autosomal dominant inheritance. SYN: Wagner disease, Wagner syndrome. hydropic d. SYN: cloudy swelling. infantile neuronal d. degenerative disorder of infants with widespread neuronal loss in thalamus, cerebellum, pons, and spinal cord, resembling infantile muscular atrophy. liquefaction d. 1. necrosis with softening, as in ischemic brain tissue; 2. dissolution of the basal epidermal layer by necrosis of scattered cells with vacuolization, observed in lichen planus, lupus erythematosus, and other dermatologic conditions. macular d. any ocular d. affecting predominately the posterior fundus, but most commonly age-related macular d.. Mönckeberg d. SYN: Mönckeberg arteriosclerosis. mucinoid d. a term including both mucoid and colloid d., the essential cellular changes in both being similar, the only difference being that, in colloid d., the substance is firmer and more inspissated than in mucoid d., in which it is thin and jellylike. mucoid d. a conversion of any of the connective tissues into a gelatinous or mucoid substance. SYN: myxoid d., myxomatous d., myxomatosis (1) . mucoid medial d. SYN: cystic medial necrosis. myelinic d. formation of myelin figures in the cytoplasm of cells, possibly by degradation or hydration of lipoprotein of self-digested organelles. myopic d. association of crescent of the optic disk, atrophy of the choroid and macular pigment, subretinal neovascularization, hemorrhage, and pigment proliferation in pathologic myopia. myxoid d., myxomatous d. SYN: mucoid d.. neurofibrillary d. formation of coarse, argentophilic, intracytoplasmic fibers, often in complex tangles within intracranial nerve cells. SEE ALSO: Alzheimer disease. Nissl d. d. of the cell body occurring after transection of the axon; characterized by dispersion of the granular endoplasmic reticulum, swelling of the soma, and an eccentric position of the nucleus of the cell. olivopontocerebellar d. SYN: olivopontocerebellar atrophy. parenchymatous d. SYN: cloudy swelling. pellucid marginal corneal d. bilateral opacification and vascularization of the periphery of the cornea, progressing to formation of a gutter and ectasia. SYN: ectatic marginal d. of cornea. primary neuronal d. SYN: Alzheimer disease. primary pigmentary d. of retina SYN: tapetoretinal d.. primary progressive cerebellar d. a familial ataxic condition related to cerebellar d.. pseudotubular d. obsolete term for a form of d. observed in adrenal glands, especially those of patients with febrile infectious disease; the shrunken, lipid-depleted cells of the zona fasciculata (and sometimes the zona glomerulosa) are arranged in a circular pattern about spaces that may be empty or partly filled with fibrin, necrotic cells, or amorphous material. red d. obsolete term for necrosis, with staining by hemoglobin, which may occur in uterine myomas, especially during pregnancy; marked by softening and a red color resembling partly cooked meat. SYN: carneous d.. reticular d. severe epidermal edema resulting in multilocular bullae. retrograde d. retrograde cell d. with chromatolysis of Nissl bodies and peripheral displacement of the nucleus of the cell of origin of a nerve fiber injured or sectioned. Salzmann nodular corneal d. large and prominent nodules of a solid, opaque material that stands out from the surface of the cornea; occurs occasionally in persons previously affected by phlyctenular keratitis. senile d. the process of involution occurring in old age. snail track d. circumferential line of fine white dots in the peripheral retina associated with atrophic retinal holes. Sorsby macular d. SYN: familial pseudoinflammatory macular d.. spheroidal d. SYN: climatic keratopathy. spongy d. of infancy SYN: Canavan disease. subacute combined d. of the spinal cord a subacute or chronic disorder of the spinal cord, such as that occurring in certain patients with vitamin B12 deficiency, characterized by a slight to moderate degree of gliosis in association with spongiform d. of the posterior and lateral columns. SYN: combined sclerosis, combined system disease, funicular myelitis (2) , Putnam-Dana syndrome, vitamin B12 neuropathy. tapetoretinal d. [MIM*272600] a hereditary disorder of the retina mainly affecting photoreceptors and retinal pigment epithelium; this may be a manifestation of Friedreich ataxia, Refsum disease, and abetalipoproteinemia. SYN: primary pigmentary d. of retina. Terrien marginal d. a form of pellucid marginal corneal d.. transsynaptic d. an atrophy of nerve cells following damage to the axons that make synaptic connection with them; noted especially in the lateral geniculate body. SYN: transneuronal atrophy, transsynaptic chromatolysis. Türck d. d. of a nerve fiber and its sheath distal to the point of injury or section of the axon; usually applied to d. within the central nervous system. vacuolar d. formation of nonlipid vacuoles in cytoplasm, most frequently due to accumulation of water by cloudy swelling. vitelliform d. [MIM*153700] SYN: Best disease. SYN: vitelliruptive d.. vitelliruptive d. SYN: vitelliform d.. wallerian d. the degenerative changes the distal segment of a peripheral nerve fiber (axon and myelin) undergoes when its continuity with its cell body is interrupted by a focal lesion. waxy d. 1. SYN: amyloid d.. 2. SYN: Zenker d.. xerotic d. scarring of the conjunctiva associated with keratinized epithelium. Zenker d. obsolete term for a form of severe hyaline d. or necrosis in skeletal muscle, occurring in severe infections. SYN: waxy d. (2) .

degenerative (de-jen′er-a-tiv)
Relating to degeneration.

degloving (de-glov′ing)
1. Intraoral surgical exposure of the anterior mandible used in various orthognathic surgical operations such as genioplasty or mandibular alveolar surgery. 2. Intraoral exposure of the midfacial skeleton used in various operations on the nose and paranasal sinuses particularly for excision of neoplasms. 3. See d. injury.

deglut.
Abbreviation for L. deglutiatur, swallow.

deglutition (de-gloo-tish′un)
The act of swallowing. [L. de-glutio, to swallow]

deglutitive (de-gloo′ti-tiv)
Relating to deglutition.

Degos
Robert, French dermatologist, *1904. See D. disease, D. syndrome, Kohlmeier-D. syndrome.

degradation (deg-ra-da′shun)
The change of a chemical compound into a less complex compound. [L. degradatus, degrade]

degranulation (de-gran-u-la′shun)
Disappearance or loss of cytoplasmic granules (lysosomes) from a cell.

degree (de-gre′)
1. One of the divisions on the scale of a measuring instrument such as a thermometer, barometer, etc. See Comparative Temperature Scales appendix. See scale. 2. The 360th part of the circumference of a circle. 3. A position or rank within a graded series. 4. A measure of damage to tissue. [Fr. degré; L. gradus, a step] degrees of freedom in statistics, the number of independent comparisons that can be made between the members of a sample ( e.g., subjects, test items and scores, trials, conditions); in a contingency table it is one less than the number of row categories multiplied by one less than the number of column categories.

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

dehalogenase (de-hal′o-jen-as)
Any enzyme (EC subclass 3.8) removing halogen atoms from organic halides.

Dehio
Karl K., Russian physician, 1851–1927. See D. test.

dehiscence (de-his′ens)
A bursting open, splitting, or gaping along natural or sutured lines. [L. dehisco, to split apart or open] iris d. a defect of the eye characterized by multiple holes in the iris. root d. a loss of the buccal or lingual bone overlaying the root portion of a tooth, leaving that area covered by soft tissue only. wound d. disruption of apposed surfaces of a wound.

dehumanization (de-hu′man-i-za′shun)
Loss of human characteristics; brutalization by either mental or physical means; stripping one of self-esteem. [de- + humanus, human, fr. homo, man]

dehydrase (de-hi′dras)
Former name for dehydratase.

dehydratase (de-hi′dra-tas)
A subclass (EC 4.2.1.x) of lyases (hydro-lyases) that remove H and OH as H2O from a substrate, leaving a double bond, or add a group to a double bond by the elimination of water from two substances to form a third; synthase is sometimes used when the synthetic aspect of the reaction is emphasized. Some trivial names of enzymes in this subclass bear the generic term hydratase, emphasizing the reverse reaction.

dehydrate (de-hi′drat)
1. To extract water from. 2. To lose water. [L. de, from + G. hydor (hydr-), water]

dehydration (de-hi-dra′shun)
1. Deprivation of water. SYN: anhydration. 2. Reduction of water content. 3. SYN: exsiccation (2) . 4. SYN: desiccation. absolute d. actual water deficit as measured by a difference from the normal or from a given water content. relative d. water deficit relative to content of solutes contributing effective osmotic pressure; a state of increased effective osmotic pressure of body fluids. voluntary d. that physiologic lag or deficit that results when sensations of thirst are not strong enough to bring about complete replacement of water loss, as in rapid sweating.

dehydro-
Prefix used in the names of those chemical compounds that differ from other and more familiar compounds in the absence of two hydrogen atoms; e.g., dehydroascorbic acid, which resembles ascorbic acid in all structural features except for its lack of two hydrogen atoms that are present in the ascorbic acid molecule. In systematic nomenclature, didehydro- is preferred as being more exact.

dehydroacetic acid (de-hi′dro-a-se′tik)
An antimicrobial agent used as a preservative in cosmetics.

dehydrobilirubin (de-hi′dro-bil-e-roo′bin)
SYN: biliverdin.

dehydrocholate (de-hi-dro-ko′lat)
A salt or ester of dehydrocholic acid.

7-dehydrocholesterol (de-hi′dro-ko-les′ter-ol)
A zoosterol in skin and other animal tissues that upon activation by ultraviolet light becomes antirachitic and is then referred to as cholecalciferol (vitamin D3). SYN: provitamin D3.

24-dehydrocholesterol
SYN: desmosterol.

dehydrocholic acid (de-hi-dro-kol′ik)
Has a stimulating effect upon the secretion of bile by the liver (choleretic), and improves the absorption of essential food materials in states associated with deficient bile formation.

11-dehydrocorticosterone (de-hi′dro-kor-ti-ko-s′ter-on)
Principally, a metabolite of corticosterone, found in the adrenal cortex.

dehydroemetine (de-hi-dro-em′e-ten)
A synthetic derivative of emetine; used in the treatment of intestinal amebiasis. d. resinate a derivative of emetine.

dehydroepiandrosterone
Steroid agent related to male hormones that have been advocated as able to prevent physiologic consequences of aging, without studies that show benefit or safety.

dehydro-3-epiandrosterone (DHEA) (de-hi′dro-ep-e-an-dros′ter-on)
a steroid secreted chiefly by the adrenal cortex, but also by the testis; it is the principal precursor of urinary 17-ketosteroids. Weakly androgenic itself, it is metabolized to delta-5 androstenediol, a hormone with both androgenic and estrogenic effects, and is one of the precursors of testosterone. Serum levels are elevated in adrenal virilism. It may function as a neurotransmitter. SYN: androstenolone, dehydroisoandrosterone.DHEA secretion begins during fetal life, reaches a peak in the 3rd decade, and declines steadily thereafter; the level at age 80 is only 10–20% of the peak level. This decline has been speculatively associated with the changes of aging. Commercial formulations of DHEA are marketed as dietary supplements, although this substance is neither a nutrient nor a component of the human food chain. Available from health food stores in 10-, 25-, and 50-mg capsules, DHEA has been promoted for the prevention of degenerative diseases including atherosclerosis, Alzheimer dementia, and parkinsonism, and other effects of aging. None of the alleged benefits have been demonstrated in large, randomized clinical trials. Long-term administration to postmenopausal women has been associated with insulin resistance, hypertension, and reduction of LDL cholesterol. An analysis of 16 preparations of DHEA by high-performance liquid chromatography showed a variation in content from 0–150% of the labeled strength; only 7 products fell between the expected 90–110% of labeled strength.

dehydrogenase (de-hi′dro-jen-as)
Class name for those enzymes that oxidize substrates by catalyzing removal of hydrogen from metabolites (hydrogen donors) and transferring it to other substances (hydrogen acceptors), which are thus reduced; most of the oxidative enzymes (oxidoreductases, EC class 1) perform their oxidations in this manner. aerobic d. an enzyme (usually a metalloflavoenzyme) catalyzing the transfer of hydrogen from some metabolite to oxygen, forming hydrogen peroxide in the process; e.g., xanthine oxidase and others in several sub-subclasses ( e.g., EC 1.1.3, 1.2.3, 1.7.3, 1.8.3, 1.10.3). anaerobic d. an enzyme (usually a pyridinoenzyme) catalyzing the transfer of hydrogen from some metabolite to some acceptor molecule ( e.g., NAD+, cytochrome) other than oxygen; e.g., lactate dehydrogenases, isocitrate dehydrogenases, and others in EC class 1, excluding those listed under aerobic d.. α-keto acid d. See α-keto acid d.. Robison ester d. SYN: glucose-6-phosphate d..

dehydrogenate (de-hi′dro-jen-at)
To subject to dehydrogenation.

dehydrogenation (de-hi′dro-jen-a′shun)
Removal of a pair of hydrogen atoms from a compound by the action of enzymes (dehydrogenases) or other catalysts.

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