| let-down reflex | <neurology, paediatrics> An involuntary reflex during breast feeding which causes the milk to flow freely. See: milk-ejection reflex (22 Sep 2002) |
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| lethal | Deadly, fatal. Origin: L. Lethalis, from lethum = death (18 Nov 1997) |
| lethal coefficient | <microbiology> That concentration of disinfectant that kills bacteria at 20-25캜 in the shortest period of time. (05 Mar 2000) |
| lethal dose | <pharmacology> The amount, or dosage, of a toxin necessary to cause death. (16 Mar 1998) |
| lethal dose 50 | <pharmacology> The amount, or dosage, of a toxin necessary to kill 50% of the experimental subjects. (16 Mar 1998) |
| lethal dwarfism | Dwarfism leading to intrauterine or neonatal death. (05 Mar 2000) |
| lethal equivalent | A combination of selective effects that on average have the same impact on the composition of the gene pool as one death; e.g., two carriers at 50% risk of dying would be the lethal equivalent of one carrier at 100% risk, in the population genetics of recessive traits lethal equivalent is expressed as twice the sum of the expected number of deaths ascribable to the genetic load. Expression used of the genetic load of recessive genes in heterozygous state that if in homozygous state would cause death or carry a risk of death. The expected number of deaths from all such genes is expressed in lethal equivalent. (05 Mar 2000) |
| lethal factor | A disorder that prevents effective reproduction by those affected; e.g., Klinefelter syndrome. (05 Mar 2000) |
| lethal gene | A gene that produces a genotype that leads to death of the organism before reproduction is possible or that precludes reproduction; for a recessive gene the homozygous or hemizygous state is lethal. (05 Mar 2000) |
| lethal midline granuloma | Destruction of the nasal septum, hard palate, lateral nasal walls, paranasal sinuses, skin of the face, orbit and nasopharynx by an inflammatory infiltrate with atypical lymphocytic and histiocytic cells; presumably a form of lymphoma in most cases. An obsolete term for polymorphic reticulosis. Synonym: granuloma gangrenescens, malignant granuloma, midline malignant reticulosis granuloma. (05 Mar 2000) |
| lethal mutation | <genetics, molecular biology> Mutation that eventually results in the death of an organism carrying the mutation. (18 Nov 1997) |
| lethality | The quality or state of being lethal. (05 Mar 2000) |
| lethality rate | <statistics> The proportion of deaths in a population or to a specific number of the population. (18 Nov 1997) |
| lethargic hypnosis | The deep sleep following major hypnosis. Synonym: trance coma. (05 Mar 2000) |
| lethargy | <symptom> Abnormal drowsiness or stupor, a condition of indifference. Origin: Gr. Lethargia = drowsiness (18 Nov 1997) |
| reflex, let down | The let down reflex of the mother is an involuntary reflex during breastfeeding which causes the milk to flow freely. (12 Dec 1998) |
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| milk let-down reflex | Release of milk from the breast following tactile stimulation of the nipple; the afferent path is postulated to exist from the nipple to the hypothalamus; the efferent limb is represented by the neurohypophysial release of oxytocin into the systemic circulation; contraction of myoepithelial elements within the breast, caused by oxytocin, moves milk into the collecting ducts and toward the nipple. Synonym: let-down reflex, milk let-down reflex. (05 Mar 2000) |
| eya-let | Formerly, one of the administrative divisions or provinces of the Ottoman Empire; now called a vilayet. Origin: Turk,fr. Ar.iyalah. Source: Websters Dictionary (01 Mar 1998) |