| critical point drying | <procedure> A method for preparing specimens for the scanning electron microscope that avoids the problems of shrinkage caused by normal drying procedures. Water in the specimen is replaced by an intermediate fluid, for example liquid carbon dioxide, avoiding setting up a liquid/gas interface and then the second fluid is allowed to vaporise by raising the temperature above the critical point, the temperature at which the liquid state no longer occurs. (18 Nov 1997) |
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| freeze-drying | <technique> Method commonly adopted to produce a dry and stable form of biological material that has not been seriously denatured. By freezing the specimen, often with liquid nitrogen and then subliming water from the specimen under vacuum, proteins are left in reasonably native form and can usually be rehydrated to an active state. Since the freeze dried material will store without refrigeration for long periods, it is a convenient method for holding back up or reference material or for the distribution of antibiotics, vaccines etc. Synonym: lyophilization. (18 Sep 2002) |
| adrenergic blocking agent | A compound that selectively blocks or inhibits responses to sympathetic adrenergic nerve activity (sympatholytic agent) and to epinephrine, norepinephrine, and other adrenergic amines (adrenolytic agent); two distinct classes exist, alpha-and beta-adrenergic receptor blocking agent's. (05 Mar 2000) |
| adrenergic neuronal blocking agent | A drug that prevents the release of norepinephrine from sympathetic nerve terminals; it does not inhibit the responses of the adrenergic receptors to circulating epinephrine, norepinephrine, and other adrenergic amines. (05 Mar 2000) |
| agent | <pharmacology> Any power, principle or substance capable of producing an effect, whether physical, chemical or biological. Origin: L. Agens = acting (18 Nov 1997) |
| agent, antihypertensive | As the name suggests, a drug aimed at reducing high blood pressure (hypertension). (12 Dec 1998) |
| agent, anti-infective | Something capable of acting against infection, by inhibiting the spread of an infectious agent or by killing the infectious agent outright. (12 Dec 1998) |
| Agent Orange | An herbicide and defoliant, consisting of (2,4,5-trichlorophenoxy)acetic acid, (2,4-dichlorophenoxy)acetic acid, and dioxin, that was widely used in the Vietnam War; it has been shown to possess residual post-exposure carcinogenic and teratogenic properties in humans. (05 Mar 2000) |
| agent, tocolytic | A medication that can inhibit labour, slow down or halt the contractions of the uterus. Tocolytic agents are widely used today to treat premature labour and permit pregnancy to procede and so let the foetus gain in size and maturity before being born. (12 Dec 1998) |
| alkylating agent | <oncology, pharmacology> A reagent that places an alkyl group, for example propyl in place of a nucleophilic group in a molecule. Alkylating reagents include a number of cytotoxic drugs some of which react fairly specifically with N7 of the purine ring and lead to depurination of DNA, for example the agent ethyl ethanesulphonic acid and thus to mutagenesis. The drugs interaction with DNAand prevents the division of the cells. Examples of drugs include: busulphan, chlorambucil, cyclophosphamide, melphalan. (29 Sep 1997) |
| alpha-adrenergic blocking agent | An agent that competitively blocks alpha-adrenergic receptors; used in the treatment of hypertension. Synonym: alpha-blocker. (05 Mar 2000) |
| antianxiety agent | A functional category of drugs useful in the treatment of anxiety and able to reduce anxiety at doses which do not cause excessive sedation (e.g., diazepam). Synonym: anxiolytic, minor tranquilliser. (05 Mar 2000) |
| antidiabetic agent | A substance that helps a person with diabetes control the level of glucose (sugar) in the blood so that the body works as it should. See: insulin. (09 Oct 1997) |
| antifibrinolytic agent | Agents that prevent fibrinolysis or lysis of a blood clot or thrombus. Several endogenous antiplasmins are known. The drugs are used to control massive haemorrhage and in other coagulation disorders. (12 Dec 1998) |
| antifoam agent | A chemical that reduces the surface tension of foams that form on thesurface of broths in fermentors because of aeration or agitation. Stearyldecanol, octal decanol, vegetable oils, silicones, sulphonates, andpolypropylene glycol are typically used, though they can cause problems inrefining the broth later on. (09 Oct 1997) |