| HAT medium | <cell biology, cell culture> A selective growth medium for animal tissue cells that contains Hypoxanthine, the folate antagonist Aminopterin (or amethopterin) and Thymine. Used for selection of hybrid somatic cell lines, as in the production of monoclonal antibodies. In HAT medium, cells are forced to use these exogenous bases, via the salvage pathways, as their sole source of purines and pyrimidines. Parental cells lacking enzymes such as HGPRT or TK can be eliminated whilst hybrids grow. (18 Nov 1997) |
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| hatch | <ornithology> To produce young; said of eggs; to come forth from the egg; said of the young of birds, fishes, insects, etc. 1. To cross with lines in a peculiar manne in drawing and engraving. See Hatching. "Shall win this sword, silvered and hatched." (Chapman) "Those hatching strokes of the pencil." (Dryden) 2. To cross; to spot; to stain; to steep. "His weapon hatched in blood." (Beau. & Fl) Origin: F. Hacher to chop, hack. See Hash. 1. A door with an opening over it; a half door, sometimes set with spikes on the upper edge. "In at the window, or else o'er the hatch." (Shak) 2. A frame or weir in a river, for catching fish. 3. A flood gate; a a sluice gate. 4. A bedstead. 5. An opening in the deck of a vessel or floor of a warehouse which serves as a passageway or hoistway; a hatchway; also; a cover or door, or one of the covers used in closing such an opening. 6. <chemical> An opening into, or in search of, a mine. Booby hatch, Buttery hatch, Companion hatch, etc. See Booby, Buttery, etc. To batten down the hatches, to lay tarpaulins over them, and secure them with battens. To be under hatches, to be confined below in a vessel; to be under arrest, or in slavery, distress, etc. Origin: OE. Hacche, AS. Haec, cf. Haca the bar of a door, D. Hek gate, Sw. Hack coop, rack, Dan. Hekke manger, rack. Prob. Akin to E. Hook, and first used of something made of pieces fastened together. Cf. Heck, Hack a frame. Source: Websters Dictionary (01 Mar 1998) |
| Hatch Slack Kortshak pathway | <biochemistry> Metabolic pathway responsible for primary carbon dioxide fixation in C4 plant photosynthesis. The enzymes that are found in mesophyll chloroplasts include PEP carboxylase, that adds carbon dioxide to phosphoenolpyruvate to give the 4 carbon compound, oxaloacetate. Four carbon compounds are transferred to bundle sheath chloroplasts, where the carbon dioxide is liberated and re fixed by the Calvin Benson cycle. The Hatch Slack Kortshak pathway permits efficient photosynthesis under conditions of high light intensity and low carbon dioxide concentration, avoiding the nonproductive effects of photorespiration. Acronym: HSK pathway (15 Nov 1997) |
| hatch-boat | A vessel whose deck consists almost wholly of movable hatches; used mostly in the fisheries. Source: Websters Dictionary (01 Mar 1998) |
| hatchery | A house for hatching fish, etc. Source: Websters Dictionary (01 Mar 1998) |
| hatchet | 1. A small ax with a short handle, to be used with one hand. 2. Specifically, a tomahawk. "Buried was the bloody hatchet." (Longfellow) Hatchet face, a thin, sharp face, like the edge of a hatchet; hence: Hatchet-faced, sharp-visaged. To bury the hatchet, to make peace or become reconciled. To take up the hatchet, to make or declare war. The last two phrases are derived from the practice of the American Indians. Origin: F. Hachette, dim. Of hache . See 1st Hatch, Hash. Source: Websters Dictionary (01 Mar 1998) |
| hatchet excavator | See: hatchet. (05 Mar 2000) |
| hatchettite | <chemical> Mineral t low; a waxy or spermaceti-like substance, commonly of a greenish yellow colour. Origin: Named after the discoverer, Charles Hatchett. Source: Websters Dictionary (01 Mar 1998) |
| hatching | A mode of execution in engraving, drawing, and miniature painting, in which shading is produced by lines crossing each other at angles more or less acute. Synonym: crosshatching. See: 1st Hatch. Source: Websters Dictionary (01 Mar 1998) |
| hate | 1. To have a great aversion to, with a strong desire that evil should befall the person toward whom the feeling is directed; to dislike intensely; to detest; as, to hate one's enemies; to hate hypocrisy. "Whosoever hateth his brother is a murderer." (1 John III. 15) 2. To be very unwilling; followed by an infinitive, or a substantive clause with that; as, to hate to get into debt; to hate that anything should be wasted. "I hate that he should linger here." (Tennyson) 3. To love less, relatively. Synonym: To Hate, Abhor, Detest, Abominate, Loathe. Hate is the generic word, and implies that one is inflamed with extreme dislike. We abhor what is deeply repugnant to our sensibilities or feelings. We detest what contradicts so utterly our principles and moral sentiments that we feel bound to lift up our voice against it. What we abominate does equal violence to our moral and religious sentiments. What we loathe is offensive to our own nature, and excites unmingled disgust. Our Savior is said to have hated the deeds of the Nicolaitanes; his language shows that he loathed the lukewarmness of the Laodiceans; he detested the hypocrisy of the scribes and Pharisees; he abhorred the suggestions of the tempter in the wilderness. Origin: OE. Haten, hatien, AS. Hatian; akin to OS. Hatan, hatn to be hostile to, D. Haten to hate, OHG. Hazzn, hazzn, G. Hassen, Icel. & Sw. Hata, Dan. Hade, Goth. Hatan, hatian. Cf. Hate, Heinous. Source: Websters Dictionary (01 Mar 1998) |
| hateful | 1. Manifesting hate or hatred; malignant; malevolent. "And worse than death, to view with hateful eyes His rival's conquest." (Dryden) 2. Exciting or deserving great dislike, aversion, or disgust; odious. "Unhappy, wretched, hateful day!" (Shak) Synonym: Odious, detestable, abominable, execrable, loathsome, abhorrent, repugnant, malevolent. Hate"fully, Hate"fulness. Source: Websters Dictionary (01 Mar 1998) |
| hatred | Strong aversion; intense dislike; hate; an affection of the mind awakened by something regarded as evil. Synonym: Odium, ill will, enmity, hate, animosity, malevolence, rancor, malignity, detestation, loathing, abhorrence, repugnance, antipathy. See Odium. Origin: OE. Hatred, hatreden. See Hate, and cf. Kindred. Source: Websters Dictionary (01 Mar 1998) |
| hatstand | A stand of wood or iron, with hooks or pegs upon which to hang hats, etc. Source: Websters Dictionary (01 Mar 1998) |
| hatteria | <zoology> A New Zealand lizard, which, in anatomical character, differs widely from all other existing lizards. It is the only living representative of the order Rhynchocephala, of which many Mesozoic fossil species are known. Synonym: Sphenodon, and Tuatera. (01 Mar 1998) |
| panama hat | A fine plaited hat, made in Central America of the young leaves of a plant (Carludovica palmata). Source: Websters Dictionary (01 Mar 1998) |
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| Mexican hat cell | An erythrocyte in target cell anaemia, with a dark centre surrounded by a light band that again is encircled by a darker ring; it thus resembles a shooting target; such cell's also appear after splenectomy. A cell lysed by cytotoxic T lymphocytes, as in graft rejection. Synonym: Mexican hat cell. (05 Mar 2000) |
| Mexican hat corpuscle | An erythrocyte in target cell anaemia, with a dark centre surrounded by a light band that again is encircled by a darker ring; it thus resembles a shooting target; such cell's also appear after splenectomy. A cell lysed by cytotoxic T lymphocytes, as in graft rejection. Synonym: Mexican hat cell. (05 Mar 2000) |
| derby hat fracture | Regular cranial concavity in infants; may or may not be associated with fracture Synonym: dishpan fracture. (05 Mar 2000) |