| natural dyes | Dye's obtained from animals or plants; examples include carmine, obtained from cochineal in the dried female insect Dactylopius cacti of Central America, and haematoxylin, extracted from the bark of the logwood tree Haematoxylon campechianum in the Caribbean area. (05 Mar 2000) |
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| natural focus of infection | An ecosystem in which an infectious agent normally persists in nature; e.g., yellow fever virus in a jungle monkey-Haemagogus mosquito ecosystem. (05 Mar 2000) |
| natural haemolysin | Haemolysin occurring in the plasma of an animal of one species, e.g., a dog, which fixes complement with the red blood cells of some other species, e.g., a rabbit, thereby causing haemolysis of the cells of the rabbit, although the dog was not previously exposed to antigenic stimulation with such cells. (05 Mar 2000) |
| natural history | A former branch of knowledge embracing the study, description, and classification of natural objects (as animals, plants, and minerals) and thus including the modern sciences of zoology, botany, and mineralogy insofar as they existed at that time. In the 17th, 18th, and 19th centuries it was much used for the generalised pursuit of certain areas of science. (webster, 3d ed; from dr. James h. Cassedy, nlm history of medicine division) (12 Dec 1998) |
| natural immunity | This includes local barriers to infection such as skin, stomach acid, mucous, the cough reflex, enzymes in tears and saliva and skin oils. (27 Sep 1997) |
| 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) |
| 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 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 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) |
| natural selection | The hypothesis that genotype environment interactions occurring at the phenotypic level lead to differential reproductive success of individuals and hence to modification of the gene pool of a population. (18 Nov 1997) |
| naturalism | 1. A state of nature; conformity to nature. 2. <psychology> The doctrine of those who deny a supernatural agency in the miracles and revelations recorded in the Bible, and in spiritual influences; also, any system of philosophy which refers the phenomena of nature to a blind force or forces acting necessarily or according to fixed laws, excluding origination or direction by one intelligent will. Origin: Cf. F. Naturalisme. Source: Websters Dictionary (01 Mar 1998) |
Synonyms :
Synonyms : Childbirth, Natural
Synonyms : Natural Disaster, Tornado, Disaster, Natural, Disasters, Natural, Droughts, Earthquake, Flood, Hurricane
Synonyms : Rhythm Method of Family Planning, Rhythm Method of Family Planning, Calendar, Rhythm Method of Family Planning, Cervical Mucus, Rhythm Method of Family Planning, Temperature, Symptothermal Method of Family Planning, Abstinence, Periodic
Synonyms : History, Natural
| natural childbirth |
The natural childbirth technique attempts to minimize medical intervention, particularly anaesthetics, during childbirth. Proponents advocate that anaesthetics may increase the likelihood of complications, because labor may be slowed or the woman may not be able to adequately direct her body to push properly during final delivery. ...
출처: en.wikipedia.org/wiki/Natural_childbirth
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| natural selection |
Natural selection is a process by which biological populations are altered over time, as a result of the propagation of heritable traits that affect the capacity of individual organisms to survive and reproduce. It is one of several mechanisms that give rise to the evolution of biological species (other mechanisms include genetic drift and gene flow. ...
출처: en.wikipedia.org/wiki/Natural_selection
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| National Institute on Aging |
Information Center PO Box 8057 Gaithersburg, MD 20898-8057 800-222-2225 (M - F / 9 - 5 EST)
출처: www.geocities.com/HotSprings/8741/define.html
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| natural killer cell |
NK cell. A type of white blood cell that contains granules with enzymes that can kill tumor cells or microbial cells. Also called a large granular lymphocyte.
출처: www.stjude.org/glossary
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| natural selection |
Evolutionary change based on the differential reproductive success of individuals within a species.
출처: highered.mcgraw-hill.com/sites/0072549238/student_...
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| NAT | authorized by law and limiting work or official business |
|---|---|
| NAT | the total value of all income in a nation (wages and profits and interest and rents and pension payments) during a given period (usually 1 yr) |
| NAT | social insurance program in Britain |
| NAT | agency of the United States government charged with mediating disputes between management and labor |
| NAT | a man who is a respected leader in national or international affairs |
| NAT | memorial consisting of a structure or natural landmark of historic interest |
| NAT | a tract of land declared by the national government to be public property |
| NAT | an agency of the Interior Department responsible for the National Parks |
| NAT | a committee in the executive branch of government that advises the president on foreign and military and national security |
| NAT | a form of socialism featuring racism and expansionism |
| NAT | relating to a form of socialism |
| NAT | a government's policy controlling foreign trade |