| AE | above-elbow [amputation]; acrodermatitis enteropathica; activation energy; adult erythrocyte; advers... |
|---|---|
| ARAM | antigen recognition activation motif |
| CMNA | complement-mediated neutrophil activation |
| HIPA | heparin-induced platelet activation |
| INAA | instrumental neutron activation analysis |
| trans-activation (genetics) | Increased rate of gene expression directed by either viral or cellular proteins. These regulatory factors (diffusible gene products) act in trans -- that is, act on homologous or heterologous molecules of DNA. (cis-acting factors act only on homologous molecules.) (12 Dec 1998) |
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| energy of activation | Energy that must be added to that already possessed by a molecule or molecules in order to initiate a reaction; usually expressed in the Arrhenius equation relating a rate constant to absolute temperature. (05 Mar 2000) |
| enzyme activation | Conversion of an inactive form of an enzyme to one possessing metabolic activity. It includes 1) activation by ions (activators); 2) activation by cofactors (coenzymes); and 3) conversion of an enzyme precursor (proenzyme or zymogen) to an active enzyme. (12 Dec 1998) |
| juxtacrine activation | Activation of target cells by membrane anchored growth factors, also used for activation of leucocytes by PAF bound to endothelial cell surface. (18 Nov 1997) |
| feedback activation | The activation of an enzyme by an end product of a biochemical pathway in which that enzyme plays a part. For example, the activation of factors VIII and V by thrombin during blood clotting. (05 Mar 2000) |
| feed-forward activation | The activation of an enzyme by a precursor of the substrate of that enzyme. (05 Mar 2000) |
| upstream activation site | A DNA sequence that regulates transcription like an enhancer but does notwork if its located downstream from a promoter. (09 Oct 1997) |
| low-activation materials | <radiobiology> In fission reactors, one is forced to deal with the radioactive byproducts of the fission process, but in fusion reactors one generally has a choice of what materials to expose to neutrons produced by the fusion process. A major problem for fusion reactors is developing materials (such as for the reactor vacuum vessel structure) which can be exposed to high levels of neutron bombardment without becoming permanently radioactive. Candidate structural materials which have relatively low induced radiactivation (generally relative to stainless steel) are known as low-activation materials, these include titanium, vanadium, and silicon-carbide. (09 Oct 1997) |
| lymphocyte activation | <haematology> The change in morphology and behaviour of lymphocytes exposed to a mitogen or to an antigen to which they have been primed. The result is the production of lymphoblasts, cells that are actively engaged in protein synthesis and that divide to form effector populations. Should not be confused with transformation of the type associated with oncogenic viruses and activation is therefore perhaps a better term. (18 Nov 1997) |
| rapid eye movement sleep | REM sleep, that state of deep sleep in which rapid eye movements, alert EEG pattern, and dreaming occur; several central and autonomic functions are distinctive during this state. (05 Mar 2000) |
| paradoxical sleep | A deep sleep, with a brain wave pattern more like that of waking states than of other states of sleep, which occurs during rapid eye movement sleep. (05 Mar 2000) |
| paroxysmal sleep | <neurology> A disorder of sleep associated with excessive daytime sleepiness, involuntary daytime sleep episodes, disturbed nocturnal sleep and cataplexy. Narcolepsy affects over 100,000 people in the United States and appears to have a genetic basis. Symptoms usually begin in the patients twenties. Treatment often includes the use of amphetamines and-or tricyclic antidepressants. (27 Sep 1997) |
| REM stage sleep | <physiology> A stage of deep sleep that is accompanied by rapid eye movement and muscle paralysis. Vivid dreams can be recalled in over 80% of patients who awake from REM stage sleep. (27 Sep 1997) |
| central sleep apnoea | <neurology> A form of sleep apnoea which from the lack of neurologic stimulation to breathe. (12 Jan 1998) |
| mixed sleep apnoea | <chest medicine> A form of sleep apnoea where there is exists a combination of obstructive and central sleep apnoea syndromes. (13 Nov 1997) |