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Definitions for: Nucleus
[n] a part of the cell containing DNA and RNA and responsible for growth and reproduction
[n] any histologically identifiable mass of neural cell bodies in the brain or spinal cord
[n] a small group of indispensable persons or things; "five periodicals make up the core of their publishing program"
[n] the positively charged dense center of an atom
[n] (astronomy) the center of the head of a comet; consists of small solid particles of ice and frozen gas that vaporizes on approaching the sun to form the coma and tail
Webster (1913) Definition: Nu"cle*us, n.; pl. E. Nucleuses, L. Nuclei. [L., a
kernel, dim. fr. nux, nucis, nut. Cf. Newel post.]
1. A kernel; hence, a central mass or point about which
matter is gathered, or to which accretion is made; the
central or material portion; -- used both literally and
figuratively.
It must contain within itself a nucleus of truth.
--I. Taylor.
2. (Astron.) The body or the head of a comet.
3. (Bot.)
(a) An incipient ovule of soft cellular tissue.
(b) A whole seed, as contained within the seed coats.
4. (Biol.) A body, usually spheroidal, in a cell or a
protozoan, distinguished from the surrounding protoplasm
by a difference in refrangibility and in behavior towards
chemical reagents. It is more or less protoplasmic, and
consists of a clear fluid (achromatin) through which
extends a network of fibers (chromatin) in which may be
suspended a second rounded body, the nucleolus (see
Nucleoplasm). See Cell division, under Division.
Note: The nucleus is sometimes termed the endoplast or
endoblast, and in the protozoa is supposed to be
concerned in the female part of the reproductive
process. See Karyokinesis.
5. (Zo["o]l.)
(a) The tip, or earliest part, of a univalve or bivalve
shell.
(b) The central part around which additional growths are
added, as of an operculum.
(c) A visceral mass, containing the stomach and other
organs, in Tunicata and some mollusks.
Synonyms: cell nucleus, core, core group, karyon
See Also: achromatin, atom, cadre, cell, cell organ, center, centre, chromatin, chromosome, comet, karyoplasm, midpoint, neural structure, nucleole, nucleolus, nucleon, nucleoplasm, organelle, pronucleus, set
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