|Medical Dictionary - Dictionary of Medicine and Human Biology|
One of the microtubules, about 24 nm in diameter, occurring in the cell body, dendrites, axon, and some synaptic endings of neurons.
A fixed or standardized vaccine virus of definite strength, obtained by continued passage through the brain of rabbits; old way to prepare rabies vaccine.
neurovaricosis, neurovaricosity (noor′o-var-i-ko′sis, -var-i-kos′i-te)
A condition marked by multiple swellings along the course of a nerve. [neuro- + L. varix, varicosis]
Relating to both nervous and vascular systems; relating to the nerves supplying the walls of the blood vessels, the vasomotor nerves.
Vaccine virus modified by means of passage into and growth in nervous tissue.
Referring to the innervation of the internal organs by the autonomic (visceral motor) nervous system. SYN: neurosplanchnic, neurovegetative. [neuro- + L. viscera, the internal organs]
neurula, pl .neurulae (noor′oo-la, -le)
Stage in embryonic development in which the prominent processes are the formation of the neural plate and the plate's closure to form the neural tube. [neur- + L. -ulus, small one]
Formation of the neural plate and its closure to form the neural tube. [see neurula]
Edmund von, Austrian physician, 1852–1912. See N. granules, under granule.
1. Exhibiting no positive properties; indifferent. 2. In chemistry, neither acid nor alkaline, i.e., [OH−] = [H+]. 3. Having the same number of positive and negative charges. [L. neutralis, fr. neuter, neither]
1. The change in reaction of a solution from acid or alkaline to neutral by the addition of just a sufficient amount of an alkaline or of an acid substance, respectively. 2. The rendering ineffective of any action, process, or potential. viral n. the elimination of viral infectivity as with specific antibodies.
To effect neutralization.
neutral red [C.I. 50040]
Used as an indicator (red at pH 6.8, yellow at 8.0), as a vital dye to stain granules and vacuoles in living cells, in testing the secretion of acid by the stomach (given with a test meal), and in general histologic staining. SYN: toluylene red.
Neutral. [L. neutralis, fr. neuter, neither]
A malocclusion in which there is a normal anteroposterior relationship between the maxilla and mandible; in Angle classification, a Class I malocclusion. SYN: neutral occlusion (2) . [neutro- + occlusion]
An electrically neutral particle in the nuclei of all atoms (except hydrogen-1) with a mass slightly larger than that of a proton; in isolation, it has a half-life of about 10.3 minutes. [L. neuter, neither] epithermal n. a n. having an energy in the range immediately above the thermal range, i.e., having an energy between a few hundredths and approximately 100 ev.
The presence of abnormally small numbers of neutrophils in the circulating blood. SYN: neutrophilic leukopenia, neutrophilopenia. [neutrophil + G. penia, poverty] cyclic n. SYN: periodic n.. periodic n. n. recurring at regular intervals (14–45 days), in association with various types of infectious diseases, e.g., stomatitis, cutaneous ulcers, furuncles, arthritis, and others. SYN: cyclic n..
neutrophil, neutrophile (noo′tro-fil, -fil)
1. A mature white blood cell in the granulocytic series, formed by myelopoietic tissue of the bone marrow (sometimes also in extramedullary sites), and released into the circulating blood, where they normally represent 54–65% of the total number of leukocytes. When stained with the usual Romanovsky type of dyes, neutrophils are characterized by 1) a nucleus that is dark purple-blue, lobated (three to five distinct lobes joined by thin strands of chromatin), and with a rather coarse network of fairly dense chromatin; and 2) a cytoplasm that is faintly pink (sharply contrasted with the nucleus) and contains numerous fine pink or violet-pink granules, i.e., not acidophilic or basophilic (as in eosinophils or basophils). The precursors of neutrophils, in order of increasing maturity, are: myeloblasts, promyelocytes, myelocytes, metamyelocytes, and band forms. Although the terms neutrophilic leukocytes and neutrophilic granulocytes include younger cells in which neutrophilic granules are recognized, the two expressions are frequently used as synonyms for neutrophils, which are mature forms unless otherwise indicated by a modifying term, such as immature n.. SEE ALSO: leukocyte, leukocytosis. 2. Any cell or tissue that manifests no special affinity for acid or basic dyes, i.e., the cytoplasm stains approximately equally with either type of dye. [neutro- + G. philos, fond] band n. SYN: band cell. hypersegmented n. an aged and degenerated n. in which there may be 6 to 10 lobes in the nucleus. immature n. a young n.; the term is usually used with reference to stab neutrophils (or other “juvenile” neutrophils), neutrophilic granulocytes in which the nucleus is indented but not distinctly segmented. juvenile n. any cell of the granulocytic series in which the neutrophilic granules are recognizable and the nucleus is indented (the first phase of segmentation). mature n. SYN: segmented n.. segmented n. a fully matured n. that has at least 2 (and as many as 5) distinct lobes in the nucleus and manifests active ameboid motion. SYN: mature n.. stab n. SYN: band cell.
An increase of neutrophilic leukocytes in blood or tissues; also frequently used synonymously with leukocytosis, inasmuch as the latter is generally the result of an increased number of neutrophilic granulocytes in the circulating blood (or in the tissues, or both). N. is usually absolute, i.e., there is an increase in the total number of leukocytes as well as an increased percentage of neutrophils; in some instances, n. may be relative ( i.e., there is an increased percentage of neutrophils), but the total number of all types of leukocytes may be within the normal range. SYN: neutrophilic leukocytosis.
1. Pertaining to or characterized by neutrophils, such as an exudate in which the predominant cells are n. granulocytes. 2. Characterized by a lack of affinity for acid or basic dyes, i.e., staining approximately equally with either type. SYN: neutrophilous.
SYN: neutropenia. [neutrophil + G. penia, poverty]
SYN: neutrophilic (2) .
A phenomenon in which neutrophilic leukocytes are stimulated by a substance in such a manner that they are either attracted, and move toward it (positive n.), or they are repelled, and move away from it (negative n.); in some instances, there is no effect (sometimes called indifferent n.). [neutrophil + G. taxis, arrangement]
Plural of nevus. [L.]
SYN: nevus cell.
Resembling a nevus. [L. naevus, mole (nevus), + G. eidos, resemblance]
SYN: juvenile xanthogranuloma. [nevus + G. xanthos, yellow, + endothelioma]
nevus, pl .nevi (ne′vus, -vi)
1. A circumscribed malformation of the skin, especially if colored by hyperpigmentation or increased vascularity; a n. may be predominantly epidermal, adnexal, melanocytic, vascular, or mesodermal, or a compound overgrowth of these tissues. 2. A benign localized overgrowth of melanin-forming cells of the skin present at birth or appearing early in life. SYN: mole (1) . [L. naevus, mole, birthmark] acquired n. a melanocytic n. that is not visible at birth, but appears in childhood or adult life. n. anemicus a functional developmental defect in vascular filling characterized by pale, round or oval, flat lesions, indistinguishable from surrounding normal skin on diascopy. n. araneus SYN: spider angioma. balloon cell n. a n. in which many of the cells are large, with clear cytoplasm. basal cell n. [MIM*109400] a hereditary disease noted in infancy or adolescence, characterized by lesions of the eyelids, nose, cheeks, neck, and axillae, appearing as uneroded flesh-colored papules, some becoming pedunculated, and histologically indistinguishable from basal cell epithelioma; also noted are punctate keratotic lesions of the palms and soles; the lesions usually remain benign, but in some cases ulceration and invasion occur and are evidence of malignant change; autosomal dominant inheritance; caused by mutation in the human PTCH, the homolog of the “patched gene” of Drosophila. PTCH is found on chromosome 9q22. bathing trunk n. a large hairy congenital pigmented n. with a predilection for the entire lower trunk; malignant melanoma may develop in childhood. SYN: giant pigmented n.. Becker n. a n. first seen as an irregular pigmentation of the shoulders, upper chest, or scapular area, gradually enlarging irregularly and becoming thickened and hairy. SYN: pigmented hair epidermal n.. blue n. a dark blue or blue-black n. covered by smooth skin and formed by heavily pigmented spindle-shaped or dendritic melanocytes in the reticular dermis. blue rubber-bleb nevi a syndrome characterized by erectile, easily compressible, thin-walled hemangiomatous nodules, present at birth, widely distributed in the skin and the alimentary canal and sometimes in other tissues; lesions in the gut may perforate or cause hemorrhage, and the patient may be anemic from continual bleeding. capillary n. capillary hemangioma of the skin. n. cavernosus SYN: cavernous angioma. cellular blue n. a large, acquired blue n. in which melanocytes are often clear and large, alternating with pigmented spindle cells and which may expand deeply into the subcutis; malignant change is very rare. n. comedonicus congenital or childhood linear keratinous cystic invaginations of the epidermis, with failure of development of normal pilosebaceous follicles. compound n. a n. in which there are nests of melanocytes in the epidermal-dermal junction and in the dermis. congenital n. a melanocytic n. that is visible at birth, is often larger than an acquired n., and more frequently involves deeper structures. Congenital n. larger than 20.0 cm in diameter, termed giant congenital nevi, have a 6–12% lifetime risk of developing melanoma. SEE ALSO: bathing trunk n.. dysplastic n. a n. exceeding 5 mm in diameter, with irregular, indistinct, or notched borders and mixed tan-to-black and pink-to-red color. Microscopically these are basally nested and scattered intraepidermal melanocytes with hyperchromatic nuclei larger than those of basal keratinocytes. If multiple and associated with a family history of melanoma, these nevi have a high risk of malignant change, but isolated dysplastic nevi in the absence of a family history of melanoma are less frequently premalignant. SEE ALSO: malignant mole syndrome. See dysplastic n. syndrome. epithelioid cell n. SYN: Spitz n.. faun tail n. a circumscribed growth of hair of the lumbosacral area, associated with diastematomyelia. n. flammeus, flame n. a large congenital vascular malformation n. having a purplish color; it is usually found on the head and neck and persists throughout life. SEE ALSO: Sturge-Weber syndrome. SYN: port-wine stain. giant pigmented n. SYN: bathing trunk n.. halo n. a benign, sometimes multiple, melanocytic n. in which involution occurs with a central brown mole surrounded by a uniformly depigmented zone or halo. SYN: leukoderma acquisitum centrifugum, Sutton n.. inflammatory linear verrucous epidermal n. rare pruritic confluent scaly erythematous papules in linear array, usually appearing in early childhood on a limb and resolving before adulthood. intradermal n. a n. in which nests of melanocytes are found in the dermis, but not at the epidermal-dermal junction; benign pigmented nevi in adults are most commonly intradermal. Ito n. pigmentation of skin innervated by lateral branches of the supraclavicular nerve and the lateral cutaneous nerve of the arm, due to scattered, heavily pigmented, dendritic melanocytes in the dermis. Jadassohn n. SYN: n. sebaceus. junction n. a n. consisting of nests of melanocytes in the basal cell zone, at the junction of the epidermis and dermis, appearing as a slightly raised, small, flat, nonhairy pigmented (brown or black) tumor. linear epidermal n. SYN: n. unius lateris. n. lymphaticus a cutaneous lymphangioma. nape n. a pale vascular birthmark found on the nape of the neck in 25–50% of normal persons. oral epithelial n. SYN: white sponge n.. Ota n. SYN: oculodermal melanosis. n. papillomatosus a prominent wartlike mole. pigmented hair epidermal n. SYN: Becker n.. n. pigmentosus a benign pigmented melanocytic proliferation; raised or level with the skin, present at birth or arising early in life. SYN: mole (2) . n. pilosus a mole covered with an abundant growth of hair. SYN: hairy mole. n. sebaceus congenital papillary acanthosis of the epidermis, with hyperplasia of sebaceous glands developing at puberty and presence of apocrine glands in nonapocrine areas of the skin (commonly the scalp). A variety of epithelial tumors may arise from a n. sebaceus in adult life, most commonly basal cell carcinoma. SYN: Jadassohn n.. spider n. SYN: spider angioma. n. spilus a form of (flat) n. pigmentosus. SYN: spilus. spindle cell n. SYN: Spitz n.. Spitz n. a benign, slightly pigmented or red superficial small skin tumor composed of spindle-shaped, epithelioid, and multinucleated cells that may appear atypical; most common in children, but also appearing in adults. SYN: benign juvenile melanoma, epithelioid cell n., spindle cell n.. strawberry n. a small n. vascularis (capillary hemangioma) resembling a strawberry in size, shape, and color; it usually disappears spontaneously in early childhood. See capillary hemangioma. SYN: strawberry birthmark. Sutton n. SYN: halo n.. n. unius lateris a congenital systematized linear n. limited to one side of the body or to portions of the extremities on one side; lesions are often extensive, forming wave-like bands on the trunk and spiraling streaks on the extremities. SYN: linear epidermal n.. Unna n. capillary stain on nape of neck; persistent form of n. flammeus nuchae. SYN: erythema nuchae. n. vascularis, n. vasculosus SYN: capillary hemangioma. n. venosus a n. formed of a patch of dilated venules. verrucous n. a skin-colored or darker wartlike, often linear lesion appearing at birth or early in childhood and occurring in various sizes and locations, single or multiple. white sponge n. [MIM*193900] an autosomal dominant condition of the oral cavity characterized by soft, white or opalescent, thickened, and corrugated folds of mucous membrane; other mucosal sites are occasionally involved simultaneously; caused by mutation in either the mucosal keratin gene K4 on chromosome 12 or keratin-13 gene on 17. SYN: familial white folded dysplasia, oral epithelial n.. woolly hair n. [MIM*194300] a circumscribed patch of fine, curly hair in an otherwise normal scalp appearing during childhood and enlarging for a period of 2–3 years; autosomal dominant inheritance. There is another, mostly sporadic form that may be autosomal recessive [MIM*278150].
The trihydrate of magnesium hydrogen phosphate; found in some renal calculi. Cf.:bobierrite, struvite. [J. Cosmo Newberry, Australian mineralogist, + -ite]
SYN: neonatal, neonate.
See under fixative.
Sir Isaac, English physicist, 1642–1727. See n., newtonian aberration, Newtonian constant of gravitation, newtonian flow, newtonian viscosity, N. disk, N. law.
newton (N) (noo′ton)
Derived unit of force in the SI system, expressed as meters-kilograms per second squared (m&chmpnt;kg s−2); equivalent to 105 dynes in the CGS system. [I. N.]
A unit of the MKS system, expressed as energy expended, or work done, by a force of 1 N acting through a distance of 1 m; equal to 1 J = 107 ergs.
Proteins that bridge adjacent microtubule doublets of the axoneme of cilia and flagella. [L. nexus, a binding, fr. necto, to bind + -in]
nexus, pl .nexus (nek′sus)
SYN: gap junction. [L. interconnection]
C., French pathologist, *1922. See N. syndrome, N. type of thymic alymphoplasia.
Abbreviation for National Formulary.
Abbreviation for nanogram.
Abbreviation for nerve growth factor.
Abbreviation for non-Hodgkin lymphoma.
Abbreviation for National Health Service (England).
Symbol for nickel.
SYN: nicotinic acid.
A monoamine oxidase inhibitor used in the treatment of depressive disorders.
In dentistry, the portion of a condensing instrument that comes into contact with the restorative material being condensed; its end, the face, is smooth or serrated.
A calcium channel blocker of the dihydropyridine series; used as an antihypertensive and antianginal agent.
niche (nitch, nesh)
1. In contrast radiography, an eroded or ulcerated area, especially gastrointestinal or vascular, which can be detected when it fills with contrast medium. 2. An ecologic term for the position occupied by a species in a biotic community, particularly its relationships to various other competitor, predator, prey, and parasite species. [Fr.] enamel n. SYN: enamel crypt. Haudek n. an archaic term for the radiographic appearance in profile of contrast material filling a gastric ulcer in the wall of the stomach.
In molecular biology, a hydrolytic cleavage of a phosphodiester bond in one strand of a double-stranded polynucleic acid. Cf.:cut.
nickel (Ni) (nik′l)
A metallic bioelement, atomic no. 28, atomic wt. 58.6934, closely resembling cobalt and often associated with it. Protects ribosome structure against heat denaturation. A deficiency of n. causes changes in the ultrastructure of the liver. It is a cofactor in a number of enzymes ( e.g., urease). [abbrev. fr. Ger. kupfer-n., name of copper-colored ore from which n. was first obtained; n., the Ger. word for a dwarfish imp] Raney n. See Raney N..
A nickel-containing protein found in human sera.
See under test.
Localized constrictions in retinal blood vessels. arteriovenous n. constriction of a retinal vein at an artery-vein crossing.
A teniacide effective against intestinal cestodes.
A peripheral vasodilator.
William, Scottish physicist, 1768–1851. See N. prism.
Joseph, French physician, *1878. See N.-Favre disease.
Charles J.H., French microbiologist and Nobel laureate, 1866–1936. See N. stain for capsules.
The biologically active amide of nicotinic acid, used in the prevention and treatment of pellagra. SYN: niacinamide, nicotinic acid amide.
nicotinamide adenine dinucleotide (NAD, NAD+, NADH)
Ribosylnicotinamide 5′-phosphate (NMN) and adenosine 5′-phosphate (AMP) linked by phosphoanhydride linkage between the two phosphoric groups; binds as a coenzyme to proteins, serves in respiratory metabolism (hydrogen acceptor and donor) through alternate oxidation and reduction (NAD+ &rrl; NADH). See also entries under NAD+ and NADP+.
nicotinamide adenine dinucleotide phosphate (NADP, NADP+, NADPH)
A coenzyme of many oxidases (dehydrogenases), in which the reaction NADP+ + 2H &rrl; NADPH + H+ takes place; the third phosphoric group esterifies the 2′-hydroxyl of the adenosine moiety of NAD+.
nicotinamide mononucleotide (NMN)
A condensation product of nicotinamide and ribose 5-phosphate, linking the N of nicotinamide to the (β) C-1 of the ribose; in NAD+, the ring is linked by the 5′-phosphoryl residue of the ribose moiety to the 5′-phosphoryl residue of AMP; a precursor in the synthesis of NAD+.
Salt or ester of nicotinic acid; some nicotinates are used in ointments as rubefacients.
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