| NAM | N-acetylmuramic acid; natural actomyosin |
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| Nat | native; natural |
| NCMC | natural cell-mediated cytotoxicity |
| ND | Doctor of Naturopathy; nasal deformity; natural death; Naval Dispensary; neonatal death; neoplastic ... |
| NK | Commission on [Anatomical] Nomenclature [Ger. Nomenklatur Kommission]; natural killer [cell]; neurok... |
| natural killer cell | <haematology, immunology> A certain type of white blood cell that attacks tumour cells and infected body cells by binding to a tumour cell and releasing lethal chemicals. Natural killer cells are thought to play a key role in cancer prevention by killing abnormal cells before they multiply and grow. (16 Dec 1997) |
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| natural killer cells | Large granular lymphocytes which do not express markers of either T or B-cell lineage. These cells do possess Fc receptors for IgG and can kill target cells using antibody-dependent cell-mediated cytotoxicity. NK cells can also use perforin to kill cells in the absence of antibody. Killing may occur without previous sensitization. Synonym: NK cells. (05 Mar 2000) |
| natural killer cell stimulating factor | <cytokine> A 75 kD heterodimeric cytokine composed of disulfide-bonded 40 kD and 35 kD subunits that was originally identified by its ability to induce cytotoxic effector cells in synergy with less than optimal concentrations of interleukin-2. It is released by macrophages in response to infection and promotes the activation of cell-mediated immunity. Specifically, IL-12 triggers the maturation of Thl CD4 cells, specific cytotoxic T-lymphocyte responses and an increase in the activity of NK cells and consequently, it is the initiator of cell-mediated immunity. It enhances the lytic activity of NK cells, induces interferon production, stimulates the proliferation of activated T-cells and NK cells. Is secreted by human B lymphoblastoid cells (NC 37). May play a role in controlling immunoglobulin isotype selection as it also inhibits IgE synthesis (even in the presence of anti-IFN monoclonal antibody) and as a growth factor for activated CD4+ and CD8+ T-cells independently of interleukin-2, and for CD56+ NK cells but not resting peripheral blood mononuclear cells or resting or activated tonsillar B-cells. It is likely that interleukin 12 has a major role in protective immunity against viruses and is under study as an immunotherapy in HIV infection. Formerly referred to as cytotoxic lymphocyte maturation factor. Acronym: IL-12 (12 Dec 1998) |
| natural language processing | Computer processing of a language with rules that reflect and describe current usage rather than prescribed usage. (12 Dec 1998) |
| natural mutation | A mutation which occurs by itself without first being affected by a mutagen, for example during the process of DNA replication. Spontaneous mutations arise at a remarkably constant rate. The rate that spontaneous mutations arise has been used as an evolutionary clock to estimate how closely related two (or more) separate species are to each other. (09 Oct 1997) |
| natural passive immunity | Immunity conferred by the mother on the foetus or newborn. (14 Nov 1997) |
| natural pigment | A naturally occurring coloured compound; absorbs light in the visible range of the electromagnetic spectrum. Compare: structural colour. Synonym: biochrome. (05 Mar 2000) |
| natural products | Naturally occurring compounds that are end products of secondary metabolism; often, they are unique compounds for particular organisms or classes of organisms. (05 Mar 2000) |
| immunity, natural | The capacity of a normal organism to remain unaffected by microorganisms and their toxins. It results from non-specific mechanisms such as genetic endowment, naturally occurring antiviral and bactericidal substances, phagocytosis, and constitutional factors such as body temperature, oxygen tension, and age. (12 Dec 1998) |
| killer cells, natural | Cells responsible for spontaneous cytotoxicity of a variety of tumour cells without prior immunization. These natural killer cells are found in non-immune humans and experimental animals and are thought by some to be the same as killer cells (killing by antibody-dependent cell cytotoxicity), but they can also kill in the absence of antibody. (12 Dec 1998) |
| natural selection |
the process whereby members of a species who have more surviving offspring than others pass their traits on to the next generation, whereas the less favored do not do so to the same degree.
출처: farahsouth.cgu.edu/dictionary/
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| natural selection |
The differential survival and reproduction of organisms with genetic characteristics that enable them to better utilize environmental resources
출처: www.accessexcellence.org/AE/AEPC/WWC/1994/glossary...
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| natural selection |
The process by which new species evolve when influenced by selective pressure (Martin et al, 2000). Natural selection occurs when the natural factors of environmental resistance tend to eliminate those members of a population that are least well adapted to cope and thus, in effect, select those best adapted for survival and reproduction (Nebel et al, 1998).
출처: www.med.uwo.ca/ecosystemhealth/education/glossary....
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| natural selection |
the resulting survival and reproduction of organisms due to the varying effects of environmental forces on genetically different members of a population; results in the preservation of favorable adaptations.
출처: www.pen.k12.va.us/VDOE/LFB/glossary/n_o.html
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| natural selection |
central thesis of the biologist Charles Darwin which suggests that within every population of living organisms there are random variations which have different survival value. Those which aid survival (or enhance reproductive capacity) are 'selected' by being genetically transmitted to succeeding generations.
출처: www.filosofia.net/materiales/rec/glosaen.htm
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