Medical Dictionary

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notencephalocele (no-ten-sef′a-lo-sel)
Malformation in the occipital portion of the cranium with protrusion of brain substance. [G. notos, back, + enkephalos, brain, + kele, hernia]

Nothnagel
C.W. Hermann, Austrian physician, 1841–1905. See N. syndrome.

notochord (no′to-kord)
1. In primitive vertebrates, the primary axial supporting structure of the body, derived from the notochordal or head process of the early embryo; an important organizer for determining the final form of the nervous system and related structures. 2. In embryos, the axial fibrocellular cord about which the vertebral primordia develop; vestiges of it persist in the adult as the nuclei pulposi of the intervertebral discs. SYN: chorda dorsalis. [G. notos, back, + chorde, cord, string]

notochordal (no-to-kor′dal)
Relating to the notochord.

Notoedres cati (no-to-ed′rez ka′ti)
Sarcoptic mange mite of cats.

noumenal (noo′men-al)
Intellectually, not sensuously or emotionally, intuitional; relating to the object of pure thought divorced from all concepts of time or space. [G. nooumenos, perceived, fr. noeo, to perceive, think]

nourishment (ner′ish-ment)
A substance used to feed or to sustain life and growth of an organism. SYN: aliment (1) .

nous (noos, nows)
A word originally used by Anaxagoras to mean an all-knowing, all-pervading spirit or force; in later Greek philosophy it came to mean simply mind, reason, or intellect. [G. mind, reason]

novobiocin (no-vo-bi′o-sin)
An antibiotic antibacterial substance produced by fermentation from cultures of Streptomyces niveus or S. spheroides, effective against penicillin-resistant Staphylococcus and Proteus; also available as n. calcium and n. sodium. SYN: streptonivicin.

Novy
Frederick George, U.S. bacteriologist, 1864–1957. See N. and MacNeal blood agar.

noxa (nok′sa)
Anything that exerts a harmful influence, such as trauma, poison, etc. [L. injury, fr. noceo, to injure]

noxious (nok′shus)
Injurious; harmful. [L. noxius, injurious, fr. noceo, to injure]

noxythiolin (nok-se-thi′o-lin)
An antibacterial and antifungal agent.

Np
1. Symbol for neptunium. 2. Abbreviation for neper.

NPC
Abbreviation for Niemann-Pick C1 disease.

NPN
Abbreviation for nonprotein nitrogen.

NPO, n.p.o.
Abbreviation for L. non per os or nil per os, nothing by mouth.

Nps
Abbreviation for nitrophenylsulfenyl.

NREM
Abbreviation for nonrapid eye movement.

nRNA
Abbreviation for nuclear RNA.

NSAID
Abbreviation for nonsteroidal anti-inflammatory drugs, under drug; e.g., aspirin, ibuprofen.

NSF
Abbreviation for National Science Foundation.

NSILA
Abbreviation for nonsuppressible insulinlike activity.

NTMI
Abbreviation for nontransmural myocardial infarction.

NTNG
Abbreviation for nontoxic nodular goiter.

NTP
Abbreviation for nucleoside 5′-triphosphate.

nu (noo)
Thirteenth letter of the Greek alphabet, &n.; (q.v.).

nubecula (noo-bek′u-la)
A faint cloud or cloudiness. [L. dim. of nubes, cloud]

Nuc
Abbreviation for nucleoside.

nucha (noo′ka)
The back of the neck. SYN: nape. [Fr. nuque]

nuchal (noo′kal)
Relating to the nucha.

Nuck
Anton, Dutch anatomist, 1650–1692. See N. diverticulum, N. hydrocele, canal of N..

nucl-
See nucleo-.

nuclear (noo′kle-er)
Relating to a nucleus, either cellular or atomic; in the latter sense, usually referring to radiation emanating from atomic nuclei (α, β, or γ) or to atomic fission.

Nuclear Regulatory Commission
The U.S. federal commission supervising the use of radioactive by-product material for commercial and medical purposes; successor to the Atomic Energy Commission along with the U.S. Department of Energy.

nuclease (noo′kle-as)
General term for enzymes that catalyze the hydrolysis of nucleic acid into nucleotides or oligonucleotides by cleaving phosphodiester linkages. For nucleases not listed below, see the specific term. Cf.:exonuclease, endonuclease. azotobacter n. endonuclease (Serratia marcescens). micrococcal n. SYN: micrococcal endonuclease. mung bean n. endonuclease S1 (Aspergillus).

nucleate (noo′kle-at)
A salt of a nucleic acid.

nucleated (noo′kle-a-ted)
Provided with a nucleus, a characteristic of all true cells.

nucleation (noo-kle-a′shun)
Process of forming a nidus (4). heterogeneous n. n. about a nidus composed of material other than that precipitating. homogeneous n. n. about a nidus composed of material identical with that precipitating.

nuclei (noo′kle-i)
Plural of nucleus.

nucleic acid (noo-kle′ik, -kla′ik)
A family of macromolecules, of molecular masses ranging upward from 25,000, found in the chromosomes, nucleoli, mitochondria, and cytoplasm of all cells, and in viruses; in complexes with proteins, they are called nucleoproteins. On hydrolysis they yield purines, pyrimidines, phosphoric acid, and a pentose, either d-ribose or d-deoxyribose; from the last, the nucleic acids derive their more specific names, ribonucleic acid and deoxyribonucleic acid. Nucleic acids are linear ( i.e., unbranched) chains of nucleotides in which the 5′-phosphoric group of each one is esterified with the 3′-hydroxyl of the adjoining nucleotide. infectious n. viral n. that can infect cells and bring about the production of viruses.

nucleiform (noo′kle-i-form)
Shaped like or having the appearance of a nucleus. SYN: nucleoid (1) .

nucleo-, nucl-
Nucleus, nuclear. SEE ALSO: karyo-, caryo-. [L. nucleus]

nucleocapsid (noo′kle-o-kap′sid)
See virion.

nucleochylema (noo-kle-o-ki-le′ma)
SYN: karyolymph. [nucleo- + G. chylos, juice]

nucleochyme (noo′kle-o-kim)
SYN: karyolymph.

nucleofilaments (noo′kle-o-fil′-a-ments)
A filamentary form of chromosome formed in low ionic strength solutions; fibers are about 100 Å wide and have a string-of-beads appearance.

nucleohistone (noo′kle-o-his′ton)
A complex of histone and deoxyribonucleic acid, the form in which the latter is usually found in the nuclei of cells; n. may be viewed as a salt between the basic protein and the acidic nucleic acid.

nucleoid (noo′kle-oyd)
1. SYN: nucleiform. 2. A nuclear inclusion body. 3. SYN: nucleus (2) . [nucleo- + G. eidos, resemblance] Lavdovsky n. SYN: astrosphere.

nucleolar (noo-kle′o-lar)
Relating to a nucleolus.

nucleoli (noo-kle′o-li)
Plural of nucleolus.

nucleoliform (noo-kle′o-le-form)
Resembling a nucleolus. SYN: nucleoloid.

nucleoloid (noo-kle′o-loyd)
SYN: nucleoliform. [nucleolus + G. eidos, resemblance]

nucleolonema (noo-kle′o-lo-ne′ma)
The irregular network or rows of fine ribonucleoprotein granules or microfilaments forming most of the nucleolus. [nucleolus + G. nema, thread]

nucleolus, pl .nucleoli (noo-kle′o-lus, -li)
1. A small rounded mass within the cell nucleus where ribonucleoprotein is produced; it is usually single, but there may be several accessory nucleoli besides the principal one. The n. is composed of a meshwork (nucleolonema) of microfilaments and granules and the pars amorpha, now shown to have microfilaments also. 2. A more or less central body in the vesicular nucleus of certain protozoa in which an endosome is lacking but one or more Feulgen-positive (DNA+) nucleoli are present; characteristic of certain sporozoans, flagellates, opalinids, dinoflagellates, and radiolarians among the Protozoa. The chromatin material is distributed throughout the nucleus rather than peripherally, as in the endosome type of nucleus of Entamoeba. [L. dim of nucleus, a nut, kernel] chromatin n. SYN: karyosome. false n. SYN: karyosome.

nucleomicrosome (noo′kle-o-mi′kro-som)
SYN: karyomicrosome.

nucleon (noo′kle-on)
1. One of the subatomic particles of the atomic nucleus; i.e., either a proton or a neutron. 2. Slang term for specialist in nuclear medicine. [nucleus + -on]

Nucleophaga (noo-kle-of′a-ga)
A microsporan parasite of amebae that destroys the nucleus of its host. [nucleo- + G. phago, to eat]

nucleophil, nucleophile (noo′kle-o-fil, -fil)
1. The electron pair donor atom in a chemical reaction in which a pair of electrons is picked up by an electrophil; any reagent or substance that is attracted to a region of low electron density. 2. Relating to a n.. SYN: nucleophilic (1) . [nucleo- + G. philos, fond]

nucleophilic (noo′kle-o-fil′ik)
1. SYN: nucleophil (2) . 2. A reaction involving a nucleophile.

nucleophosphatases (noo′kle-o-fos′fa-tas-ez)
SYN: nucleotidases.

nucleoplasm (noo′kle-o-plazm)
The protoplasm of the nucleus of a cell.

nucleoplasmin (noo′kle-plas′min)
Contents of resting (interphase) nucleus. [nucleo- + plasma + -in]

nucleoprotein (noo′kle-o-pro′ten)
A complex of protein and nucleic acid, the form in which essentially all nucleic acids exist in nature; chromosomes and viruses are largely n..

nucleoreticulum (noo′kle-o-re-tik′u-lum)
The intranuclear network of chromatin or linin. [nucleo- + L. reticulum, dim. of rete, net]

nucleorrhexis (noo′kle-o-rek′sis)
Fragmentation of a cell nucleus. [nucleo- + G. rhexis, rupture]

nucleosidases (noo′kle-o-si′das-ez)
Enzymes (particularly EC subgroup 3.2.2) that catalyze the hydrolysis or phosphorolysis of nucleosides, releasing the purine or pyrimidine base.

nucleoside (Nuc, N) (noo′kle-o-sid)
A compound of a sugar (usually ribose or deoxyribose) with a purine or pyrimidine base by way of an N-glycosyl link. n. bisphosphate a n. that carries two independent ( i.e., not linked to each other) phosphoric residues. Cf.:n. diphosphate. n. diphosphate (NDP) the pyrophosphoric ester of a n., i.e., a n. in which the H of one of the ribose hydroxyls (usually the 5′) is replaced by a pyrophosphoric (diphosphoric) radical; e.g., adenosine 5′-diphosphate. Cf.:n. bisphosphate. n. monophosphate a nucleotide containing only one phosphoryl group, e.g., AMP. n. triphosphate a n. in which the H of one of the ribose hydroxyls (usually the 5′) is replaced by a triphosphoric group, –PO(OH)–O–PO(OH)–O–PO(OH)2 or the corresponding conjugate base; e.g., adenosine triphosphate.

nucleoside diphosphate kinase
A phosphotransferase reversibly catalyzing the transfer of one phosphoryl group from ATP to a nucleoside diphosphate to yield a nucleoside triphosphate and ADP.

nucleoside diphosphate sugars
Nucleoside diphosphates linked through the 5′-diphosphoric group with simple or complex carbohydrates; e.g., GDPmannose, UDPglucose (UDPG), dTDPglucosamine.

nucleoskeleton (nook′le-o-skel′e-ton)
Proteins forming a fibrillar substructure of the nuclear matrix to which DNA is bound.

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