Medical Dictionary

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ataractic (at-a-rak′tik)
1. Having a calming or tranquilizing effect. 2. A tranquilizer. SYN: ataraxic. [G. ataraktos, calm]

ataraxia (at-a-rak′se-a)
Calmness and peace of mind; tranquility. [G. a- priv. + taraktos, disturbed, + -ia]

ataraxic (at-a-rak′sik)
SYN: ataractic.

atavism (at′a-vizm)
The appearance in an individual of characteristics presumed to have been present in some remote ancestor; reversion to an earlier biologic type, a throwback. [L. atavus, a remote ancestor]

atavistic (at-a-vis′tik)
Relating to atavism.

ataxia (a-tak′se-a)
An inability to coordinate muscle activity during voluntary movement; most often due to disorders of the cerebellum or the posterior columns of the spinal cord; may involve the limbs, head, or trunk. SYN: ataxy, incoordination. [G. a-prov. + taxis, order] acute a. generalized a. of abrupt onset, most often caused by drug intoxications, poisonings, or vestibular neuronitis. Briquet a. weakening of the muscle sense and increased sensibility of the skin, in hysteria. SYN: hysterical a.. Bruns a. difficulty in initiation of movement of the feet when they are in contact with the ground; a condition related to a frontal lobe lesion. cerebellar a. loss of muscle coordination caused by disorders of the cerebellum. chronic a. persistent a., most often caused by hereditary cerebellar or metabolic disorders. a. cordis SYN: atrial fibrillation. Friedreich a. [MIM*229300] a neurologic disorder characterized by a., dysarthria, scoliosis, high-arched foot or pes cavus and paralysis of the muscles, especially of the lower extremities; onset usually in childhood or youth with sclerosis of the posterior and lateral columns of the spinal cord; autosomal recessive inheritance, caused by mutation involving trinucleotide repeat expansion in Friedreich a. gene (FRDA) on chromosome 9q. SYN: hereditary spinal a., heredotaxia. gluten a. a. resultant from immunologic damage to cerebellulm, posterior spinal columns, and periperal nerves in gluten-senstive individuals hereditary cerebellar a. 1. a disease of later childhood and early adult life, marked by ataxic gait, hesitating and explosive speech, nystagmus, and sometimes optic neuritis. It probably comprises several distinct conditions with diverse patterns of inheritance. 2. collective term for a number of hereditary disorders in which cerebellar signs are the most prominent finding. hereditary spinal a. [MIM*229300] SYN: Friedreich a.. hysterical a. SYN: Briquet a.. kinetic a. SYN: motor a.. Leyden a. SYN: pseudotabes. locomotor a. the severe gait a. seen with tabetic neurosyphylis. Patients walk with the feet wide apart, slapping them clumsily to the floor with each step, and depend on visual cues to maintain balance. SEE ALSO: tabetic neurosyphilis. Marie a. obsolete term for a variety of non-Friedreich hereditary ataxias. motor a. a. developing upon attempting to perform coordinated muscular movements. SYN: kinetic a.. optic a. an inability to guide the hand toward an object using visual information; seen in Balint syndrome. respiratory a. SYN: Biot respiration. sensory a. an a. due to impairment of position sense caused by lesions located at some point along the central or peripheral sensory pathways. spinal a. a. due to spinal cord disease, as in tabes dorsalis. spinocerebellar a. the most common hereditary a., with onset in middle to late childhood, manifested as limb a., nystagmus, kyphoscoliosis, and pes cavus; the major pathologic changes are found in the posterior columns of the spinal cord; most often autosomal recessive inheritance. static a. inability to preserve equilibrium while standing, due to loss of myesthesia; present during the resting state. a. telangiectasia, a.-telangiectasia a slowly progressive multisystem disorder with the following manifestations: a. appearing with the onset of walking; telangiectases of the conjunctiva and skin of the face, neck, and ears; athetosis and nystagmus; and recurrent infections of the respiratory system caused by immunoglobulin deficiencies. Due to an autosomal recessive trait, with major pathologic changes involving the cerebellar cortex, posterior columns, spinocerebellar tracks, anterior horn cells, dorsal roots, and peripheral nerves. A high percentage of the patients have an IgA deficiency concomitant with decreased T-helper cell function. There are numerous chromosome breaks and α-fetoprotein levels in the sera are usually elevated; caused by several mutations in PI3′kinase gene. SYN: a. telangiectasia syndrome, Louis-Bar syndrome. vasomotor a. a form of autonomic a. causing irregularity in the peripheral circulation, marked by alternations of pallor and suffusion, due to spasm of the smaller blood vessels. vestibulocerebellar a. a. due to disease of the central vestibular system or its cerebellar components, manifested clinically by an unsteady gait, nystagmus, and incoordination of arm and leg movements.

ataxiadynamia (a-tak′se-a-di-nam′e-a)
Muscular weakness combined with incoordination.

ataxiagram (a-tak′se-a-gram)
The recording made by an ataxiagraph.

ataxiagraph (a-tak′se-a-graf)
An instrument for measuring the degree and direction of the swaying of the body and head in static ataxia, with the individual's eyes closed. SYN: ataxiameter.

ataxiameter (a-tak′se-a-me′ter)
SYN: ataxiagraph.

ataxiaphasia (a-tak′se-a-fa′ze-a)
Inability to form connected sentences, although single words may perhaps be used intelligibly. [G. a- priv. + taxis, order, + phasis, an affirmation, speech]

ataxia-telangiectasia
See ataxia telangiectasia.

ataxic (a-tak′sik)
Relating to, marked by, or suffering from ataxia.

ataxiophobia (a-tak′se-o-fo′be-a)
Morbid dread of disorder or untidiness. [G. a- priv. + taxis, order, + phobos, fear]

ataxy (a-tak′se)
SYN: ataxia.

-ate
Termination used as a replacement for “-ic acid” when the acid is neutralized ( e.g., sodium acetate) or esterified ( e.g., ethyl acetate).

atelectasis (at-e-lek′ta-sis)
Decreased or absent air in the entire or part of a lung, with resulting loss of lung volume. Loss of lung volume itself. SEE ALSO: pulmonary collapse. [G. ateles, incomplete, + ektasis, extension] adhesive a. alveolar collapse in the presence of patent airways, especially when surfactant is inactivated or absent, especially in respiratory distress syndrome of the newborn, acute radiation pneumonitis, or viral pneumonia. SYN: microatelectasis, nonobstructive a.. cicatrization a. 1. the decrease in air per unit lung volume due to fibrosis, causing decreased lung compliance, and increased tissue. 2. a. due to scarring or pulmonary fibrosis. a. of the middle ear reduction in the volume of the middle ear because of eustachian tube obstruction followed by absorption of the oxygen in the middle ear and subsequent retraction of the tympanic membrane medially. nonobstructive a. SYN: adhesive a.. passive a. the pulmonary collapse that occurs due to a space-occupying intrathoracic process such as pneumothorax or hydrothorax. SYN: relaxation a.. patchy a. decreased aeration and collapse of multiple small areas of lung. platelike a. SYN: subsegmental a.. primary a. nonexpansion of the lungs after birth, found in all stillborn infants and in liveborn infants who die before respiration is established. relaxation a. SYN: passive a.. resorption a. the slow partial collapse of a lobe that occurs when communication between alveoli and trachea is obstructed. rounded a. an area of atelectatic lung caused by parenchymal infolding due to pleural fibrosis, most often from asbestos exposure; appears as a masslike opacity and can be mistaken for lung cancer; may be associated with a comet tail sign; high level of contrast enhancement on dynamic computed tomography aids diagnosis. SYN: folded-lung syndrome. secondary a. pulmonary collapse at any age, but particularly of infants, due to hyaline membrane disease or elastic recoil of the lungs while dying from other causes. segmental a. partial collapse of one or more individual pulmonary segments. subsegmental a. collapse of the portion of the lung distal to an obstructed subsegmental bronchus, manifested as a linear opacity on a chest radiograph. See Fleischner lines, under line. SYN: platelike a..

atelectatic (at-e-lek-tat′ik)
Relating to atelectasis.

atelia (a-te′le-a)
SYN: ateliosis.

ateliosis (a-te′le-o′sis)
Incomplete development of the body or any of its parts, as in infantilism and dwarfism. SYN: atelia. [G. ateles, incomplete, + -osis, condition]

ateliotic (a-te-le-ot′ik)
Marked by ateliosis.

atelopidtoxin (a-tel-op′id-tok′sin)
A potent poison from the skin of the golden arrow frog (Atelopus zeteki) of Central and South America.

atenolol (a-ten′o-lol)
A relatively cardioselective β-adrenergic blocking agent used primarily in the treatment of angina pectoris and hypertension; it possesses lower lipid solubility than other members of this class and hence apparently less central nervous system side effects.

athelia (a-the-le-a)
Congenital absence of the nipples. [G. a- priv. + thele, nipple]

atherectomy (ath-e-rek′to-me)
Any removal by surgery or specialized catheterization of an atheroma in the coronary or any other artery. coronary a. instrumental removal, via catheter, of atheromas in coronary arteries. directional a. removal of coronary atherometer with instrumented catheter.

athermancy (a-ther′man-se)
Impermeability to heat. [G. athermantos, not heated, fr. a- priv. + thermaino, to heat, fr. therme, heat]

athermanous (a-ther′ma-nus)
Absorbing radiant heat; not permeable to heat rays.

athermosystaltic (a-ther′mo-sis-tal′tik)
Not contracted or constricted by ordinary variations of temperature; said of certain tissues. [G. a- priv. + thermos, hot, + systaltikos, constringent]

athero-
Gruel-like, soft, pasty materials; atheroma, atheromatous. [G. athere, gruel, porridge]

atheroembolism (ath′er-o-em′bo-lizm)
Cholesterol embolism, with or without calcific matter, originating from an atheroma of the aorta or other diseased artery.

atherogenesis (ath′er-o-jen′e-sis)
Formation of atheroma, important in the pathogenesis of arteriosclerosis.

atherogenic (ath-er-o-jen′ik)
Having the capacity to initiate, increase, or accelerate the process of atherogenesis.

atheroma (ath-er-o′ma)
The lipid deposits in the intima of arteries, producing a yellow swelling on the endothelial surface; a characteristic of atherosclerosis. SYN: atherosis. [G. athere, gruel, + -oma, tumor]

atheromatous (ath-er-o′ma-tus)
Relating to or affected by atheroma.

atherosclerosis (ath′er-o-skler-o′sis)
Arteriosclerosis characterized by irregularly distributed lipid deposits in the intima of large and medium-sized arteries, causing narrowing of arterial lumens and proceeding eventually to fibrosis and calcification; lesions are usually focal and progress slowly and intermittently. Limitation of blood flow accounts for most clinical manifestations, which vary with the distribution and severity of lesions. In lower animals, a. of swine and fowl closely resemble human a.. SYN: nodular sclerosis. [G. athere, gruel, + sclerosis] A., the most common form of arteriosclerosis, is a complex process that begins with the appearance of cholesterol-laden macrophages (foam cells) in the intima of an artery. Smooth muscle cells respond to the presence of lipid by proliferating, under the influence of platelet factors. A plaque forms at the site, consisting of smooth muscle cells, leukocytes, and further deposition of lipid; in time the plaque becomes fibrotic and may calcify. Expansion of an atherosclerotic plaque leads to gradually increasing obstruction of the artery and ischemia of tissues supplied by it. Ulceration, thrombosis, or embolization of a plaque, or intimal hemorrhage and dissection, can cause more acute and severe impairment of blood flow, with the risk of infarction. These are the principal mechanisms of coronary artery disease (arteriosclerotic heart disease with or without heart failure, angina pectoris, myocardial infarction), peripheral vascular disease (particularly occlusive disease of the lower extremity causing intermittent claudication or gangrene), and stroke (cerebral infarction due to occlusion of carotid or intracranial arteries). Independent risk factors for a. are male sex, advancing age, the postmenopausal state, a family history of a., cigarette smoking, hypertension, diabetes mellitus, elevated plasma LDL cholesterol, elevated plasma homocysteine, overweight, and a sedentary life-style. Mounting evidence suggests that elevation of plasma levels of triglycerides, fasting insulin, fibrinogen, apolipoproteins A and B, and lipoprotein (a) are also independent risk factors. The diagnosis of a. is usually based on history and physical examination and confirmed by angiography, Doppler ultrasonography, and other imaging techniques. Treatment is largely mechanical: balloon stretching, laser ablation, or surgical removal of plaques, and various bypass and grafting procedures. The prevention of a. is a major objective of modern medicine. Preventive measures include regular vigorous exercise, a diet low in fat and cholesterol, maintenance of a healthful weight, avoidance of tobacco, and use of pharmacologic agents as indicated (e.g., rigorous control of hypertension and diabetes mellitus, reduction of elevated cholesterol, estrogen replacement therapy after menopause). See free radical; low-fat diet.

atherosclerotic (ath′er-o-skler-ot′ik)
Relating to or characterized by atherosclerosis.

atherosis (ath-er-o′sis)
SYN: atheroma.

atherothrombosis (ath′er-o-throm-bo′sis)
Thrombus formation in an atheromatous vessel.

atherothrombotic (ath′er-o-throm-bot′ik)
Denoting, characteristic of, or caused by atherothrombosis.

athetoid (ath′e-toyd)
Resembling athetosis.

athetosic, athetotic (ath-e-to′sik, -tot′ik)
Pertaining to, or marked by, athetosis.

athetosis (ath-e-to′sis)
A condition in which there is a constant succession of slow, writhing, involuntary movements of flexion, extension, pronation, and supination of the fingers and hands, and sometimes of the toes and feet. Usually caused by an extrapyramidal lesion. SYN: extrapyramidal cerebral palsy, Hammond disease. [G. athetos, without position or place] double a. a type of cerebral palsy manifested predominantly as bilateral involuntary movements, beginning at about the age of 3 years, and preceded by generalized hypotonia and delayed motor development. Due to various causes, including kernicterus and birth hypoxia. SYN: congenital choreoathetosis, double congenital a., Vogt syndrome. double congenital a. SYN: double a.. posthemiplegic a. a unilateral a. involving hemiplegic limbs, usually seen in children. SYN: posthemiplegic chorea.

aThr
Abbreviation for allothreonines. See allothreonines.

athrepsia, athrepsy (a-threp′se-a, ath′rep-se)
1. Obsolete term for marasmus. 2. As used by Ehrlich, immunity to transplanted neoplastic cells due to a lack of nourishment in the sense of a deficiency of supposed substances required for the development of such cells. SYN: atrepsy. [G. a- priv. + threpsis, nourishment]

athrocytosis (ath′ro-si-to′sis)
The capacity of cells to absorb and retain electronegative colloids, as shown by macrophages and at the apical surface of proximal convoluted tubule cells of the kidney. [G. athro, gathered together, + kytos, cell, + -osis, condition]

athrombia (a-throm′be-a) [MIM*209050]
A hereditary bleeding disorder characterized by prolonged bleeding time, decreased platelet adhesion and aggregation but normal plasma clotting and clot retraction, normal platelet count with platelet factor 3 availability; probably autosomal recessive inheritance. [G. a- priv. + thrombin]

athymia (a-thi′me-a)
1. Absence of affect or emotivity; morbid impassivity. 2. Congenital absence of the thymus gland, often with associated immunodeficiency. SYN: athymism. [G. a- priv. + thymos, mind, also thymus]

athymism (a-thi′mizm)
SYN: athymia (2) .

athyrea (a-thi′re-a)
1. SYN: hypothyroidism. 2. SYN: athyroidism.

athyroidism (a-thi′royd-izm)
Congenital absence of the thyroid gland or suppression or absence of its hormonal secretion. See hypothyroidism. SYN: athyrea (2) , athyrosis.

athyrosis (a-thi-ro′sis)
SYN: athyroidism.

athyrotic (a-thi-rot′ik)
Relating to athyroidism.

ATL
Abbreviation for adult T-cell leukemia or adult T-cell lymphoma.

atlantad (at-lan′tad)
In a direction toward the atlas.

atlantal (at-lan′tal)
Relating to the atlas. SYN: atloid.

atlanto-, atlo-
The atlas (the vertebra that supports the skull). [G. Atlas, Atlantos, Atlas, the mythical Titan who supported the dome of the sky on his shoulders]

atlantoaxial (at-lan′to-ak′se-al)
Pertaining to the atlas and the axis; denoting the joint between the first two cervical vertebrae. SYN: atlantoepistrophic, atloaxoid.

atlantodidymus (at-lan′to-did′e-mus)
Conjoined twins with two heads on one neck and a single body. SYN: atlodidymus. [atlanto- + G. didymos, twin]

atlantoepistrophic (at-lan′to-ep′i-strof′ik)
SYN: atlantoaxial.

atlanto-occipital (at-lan′to-ok-sip′i-tal)
Relating to the atlas and the occipital bone. SYN: atlo-occipital.

atlanto-odontoid (at-lan′to-o-don′toyd)
Relating to the atlas and the dens of the axis.

atlas (at′las) [TA]
First cervical vertebra, articulating with the occipital bone and rotating around the dens of the axis. SYN: vertebra C1&star, first cervical vertebra. [G. A., in Greek mythology a Titan who supported the heavens on his shoulders]

atlo-
See atlanto-.

atloaxoid (at-lo-ak′soyd)
SYN: atlantoaxial.

atlodidymus (at-lo-did′e-mus)
SYN: atlantodidymus.

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