Cell nucleus

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Cell nucleus

The largest of the membrane-bounded organelles which characterize eukaryotic cells; it is thought of as the control center since it contains the bulk of the cell's genetic information in the form of deoxyribonucleic acid (DNA). The nucleus has two major functions: (1) It is the site of synthesis of ribonucleic acid (RNA), which in turn directs the formation of the protein molecules on which all life depends; and (2) in any cell preparing for division, the nucleus precisely duplicates its DNA for later distribution to cell progeny. See Deoxyribonucleic acid (DNA), Eukaryotae, Ribonucleic acid (RNA)

The diameter of nuclei ranges from 1 micrometer in intracellular parasites and yeast cells to several millimeters in some insect sperm. Spherical or ellipsoidal nuclei are found in most cell types, although occasionally spindle-shaped, lobulated, disc-shaped, or cup-shaped nuclei may be observed. Although nuclear size and shape are somewhat consistent features of a particular cell type, these features are more variable in cancer cells. In addition, tumor cell nuclei are characterized by indentation, furrowing, elongation, and budding.

The nucleus is bounded by a double membrane (the nuclear envelope) and contains several major components: chromatin, which is composed of DNA and chromosomal proteins; the nucleolus, which is the site of ribosomal RNA (rRNA) synthesis; and nucleoplasmic fibrils and granules, some of which are involved in the processing and transport of messenger RNA out of the nucleus (see illustration). The constituents of the nucleus are contained within a framework referred to as the nuclear matrix.

Transmission electron micrograph of a thin section of a rat liver cell nucleusenlarge picture
Transmission electron micrograph of a thin section of a rat liver cell nucleus
References in periodicals archive ?
To prepare a monolayer cytocentrifuge slide, which is optimal for nucleated cell identification, use the nucleated cell count (not the RBC count) to determine the saline dilution for the cytocentrifuge preparation.
Although metal phosphonate possesses excellent nucleating effect on PLLA, which has attracted a great deal of interest, the lower toughness of nucleated PLLA compared with non-nucleated PLLA and the high cost of metal phosphonate would restrict its applications.
A body fluid specimen has a nucleated cell count of 853/[mm.
WINSCAN(TM) automatically scans slides made from peripheral blood and locates and stores color images of the nucleated red blood cells in the sample.
By incorporating lysing of red blood cells into the body fluids analysis procedure, the iQ200 can provide a quantitative result for red blood cells and nucleated cells.
p] are the crystallization peak temperature of PLLA nucleated and non-nucleated with a nucleator.
Basell has two new grades of Metocene mPP homopolymers for injection molding, both of which are nucleated and have very narrow molecular-weight distribution.
It is through reduction in the free-energy barrier to nucleation that quiescent crystallization of nucleated polymers is facilitated (7), but after the application of a strong shear, it is not clear whether the nucleation pathway is still influenced by the nucleating agent.
nucleated LLDPE films demonstrated a 30% increase in MD tear and a 20% improvement in stiffness compared with typical LLDPE/LDPE blends, while maintaining dart impact.
The optimum thermoforming conditions for thin-gauge polypropylene sheet are determined, and the processing characteristics of a nucleated grade and an unnucleated grade are compared.
The first of these dyes penetrates membranes, entering and staining the DNA of all nucleated cells.
It is said to have the optical performance of highly clarified randora copolymers plus the stiffness (217,500 psi) of a nucleated PP homopolymer.