| natriuresis | <physiology> The excretion of abnormal amounts of sodium in the urine. Origin: L. Natrium = sodium, Gr. Ouresis = a making water (18 Nov 1997) |
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| natriuretic | <endocrinology> Of a substance or hormone, causing natriuresis (elimination of extra sodium in the urine). See: atrial natriuretic peptide. (18 Nov 1997) |
| natriuretic hormone | <chemical> A low-molecular weight substance, possibly from the hypothalamus, which is released due to plasma volume expansion. It causes natriuresis in part by inhibiting sodium potassium atpase. The development of hypertension may be the consequence of an abnormality in volume regulation induced by a defect in the renal response to the natriuretic effect of the natriuretic hormone. Do not confuse with atrial natriuretic factor or cardionatrin which is a different, well characterised hormone. Chemical name: Natriuretic factor (12 Dec 1998) |
| natrolite | <chemical> A zeolite occuring in groups of glassy acicular crystals, and in masses which often have a radiated structure. It is a hydrous silicate of alumina and soda. Origin: Natron: cf. F. Natrolithe. Source: Websters Dictionary (01 Mar 1998) |
| natron | <chemical> Native sodium carbonate. Alternative forms: anatron. Origin: F, fr. Sp. Natron, Ar. Natrun, nitrun. Cf. Niter, Anatron. Source: Websters Dictionary (01 Mar 1998) |
| natronobacterium | A genus of rod-shaped, extremely halophilic halobacteriaceae which grows in alkaline conditions. They are strictly aerobic and some strains are motile. Natronobacterium is found in soda lakes, alkaline salterns, and soda soils. (12 Dec 1998) |
| natronococcus | A genus of coccoid, extremely halophilic halobacteriaceae which grows in alkaline conditions. They are nonmotile and strictly aerobic and are found in soda lakes, alkaline salterns, and soda soils. (12 Dec 1998) |
| natterjack | <zoology> A European toad (Bufo calamita), having a yellow line along its back. Source: Websters Dictionary (01 Mar 1998) |
| nattokinase | <enzyme> Isolated from the japanese soybean cheese natto; mw: 20,000; pi=8.6 Pharmacological action: fibrinolytic agents Registry number: EC 3.4.21.- (26 Jun 1999) |
| natural | 1. Fixed or determined by nature; pertaining to the constitution of a thing; belonging to native character; according to nature; essential; characteristic; not artifical, foreign, assumed, put on, or acquired; as, the natural growth of animals or plants; the natural motion of a gravitating body; natural strength or disposition; the natural heat of the body; natural colour. "With strong natural sense, and rare force of will." (Macaulay) 2. Conformed to the order, laws, or actual facts, of nature; consonant to the methods of nature; according to the stated course of things, or in accordance with the laws which govern events, feelings, etc.; not exceptional or violent; legitimate; normal; regular; as, the natural consequence of crime; a natural death. "What can be more natural than the circumstances in the behavior of those women who had lost their husbands on this fatal day?" (Addison) 3. Having to do with existing system to things; dealing with, or derived from, the creation, or the world of matter and mind, as known by man; within the scope of human reason or experience; not supernatural; as, a natural law; natural science; history, theology. "I call that natural religion which men might know . By the mere principles of reason, improved by consideration and experience, without the help of revelation." (Bp. Wilkins) 4. Conformed to truth or reality; as: Springing from true sentiment; not artifical or exaggerated; said of action, delivery, etc.; as, a natural gesture, tone, etc. Resembling the object imitated; true to nature; according to the life; said of anything copied or imitated; as, a portrait is natural. 5. Having the character or sentiments properly belonging to one's position; not unnatural in feelings. "To leave his wife, to leave his babes, . He wants the natural touch." (Shak) 6. Connected by the ties of consanguinity. "Natural friends." 7. Begotten without the sanction of law; born out of wedlock; illegitimate; bastard; as, a natural child. 8. Of or pertaining to the lower or animal nature, as contrasted with the higher or moral powers, or that which is spiritual; being in a state of nature; unregenerate. "The natural man receiveth not the things of the Spirit of God." (1 Cor. Ii. 14) 9. <mathematics> Belonging to, to be taken in, or referred to, some system, in which the base is 1; said or certain functions or numbers; as, natural numbers, those commencing at 1; natural sines, cosines, etc, those taken in arcs whose radii are 1. 10. Produced by natural organs, as those of the human throat, in distinction from instrumental music. Of or pertaining to a key which has neither a flat nor a sharp for its signature, as the key of C major. Applied to an air or modulation of harmony which moves by easy and smooth transitions, digressing but little from the original key. Natural day, the space of twenty-four hours. Natural fats, Natural gas, etc. See Fat, Gas. Etc. Natural Harmony, a classification based upon real affinities, as shown in the structure of all parts of the organisms, and by their embryology. "It should be borne in mind that the natural system of botany is natural only in the constitution of its genera, tribes, orders, etc, and in its grand divisions." (Gray) Natural theology, or Natural religion, that part of theological science which treats of those evidences of the existence and attributes of the Supreme Being which are exhibited in nature; distinguished from revealed religion. See Quotation under Natural. Natural vowel, the vowel sound heard in urn, furl, sir, her, etc.; so called as being uttered in the easiest open position of the mouth organs. See Neutral vowel. Synonym: See Native. Origin: OE. Naturel, F. Naturel, fr. L. Naturalis, fr. Natura. See Nature. Source: Websters Dictionary (01 Mar 1998) |
| natural antibody | Antibody demonstrable in the serum or plasma of various persons or animals not known to have been stimulated by specific antigen, either artificially or as the result of naturally occurring contact. Synonym: natural antibody. (05 Mar 2000) |
| natural childbirth | Psychophysical relaxation techniques that are used to facilitate childbirth. (12 Dec 1998) |
| natural classification | <zoology> Classification based on inferences concerning the phylogenetic relationships of animals. (09 Jan 1998) |
| natural dentition | See: dentition. (05 Mar 2000) |
| natural disasters | Sudden calamitous events producing great material damage, loss, and distress. They are the result of natural phenomena such as earthquakes, floods, etc. (12 Dec 1998) |