| react | 1. To return an impulse or impression; to resist the action of another body by an opposite force; as, every body reacts on the body that impels it from its natural state. 2. To act upon each other; to exercise a reciprocal or a reverse effect, as two or more chemical agents; to act in opposition. Source: Websters Dictionary (01 Mar 1998) |
|---|---|
| reactance | The weakening of an alternating electric current by passage through a coil of wire or a condenser. Synonym: inductive resistance. (05 Mar 2000) |
| reactant | A substance taking part in a chemical reaction. Acute phase reactants, A group of proteins that are produced and/or released in increased concentrations during the acute phase reaction, including fibrinogen; C-reactive protein; complement proteins B, C3, C4; a2-acid glycoprotein, serum amyloid A, proteinase inhibitors, etc. (05 Mar 2000) |
| reaction | Standard method for identifying Clostridium perfringens. When grown on agar containg egg yolk, an opalescent halo is formed around colonies that produce _ toxin (lecithinase). (18 Nov 1997) |
| reaction centre | <plant biology> The site in the chloroplast that receives the energy trapped by chlorophyll and accessory pigments and initiates the electron transfer process. A photosynthetic complex containing chlorophyll (or bacteriochlorophyll) and other components, within which occurs the initial electron transfer reactions of photophosphorylation. (09 Oct 1997) |
| reaction formation | In psychoanalysis, a postulated defense mechanism in which attitudes and behaviours that are adopted are the opposites of that which the individual would ordinarily be expected to express and actually feel at an unconscious level. (05 Mar 2000) |
| reaction intermediate | <biochemistry> Any biomolecule which iscreated and destroyed during the course of of a particular reaction pathway. (09 Oct 1997) |
| reaction of degeneration | The electrical reaction in a degenerated nerve and the muscles supplied by it; characterised by absence of response to both galvanic and faradic stimulus in the nerve and to faradic stimulus in the muscles; the muscles may still respond to galvanic stimulation, but the cathodal closing contraction is greater than the anodal closing contraction, the reverse of normal. (05 Mar 2000) |
| reaction of identity | See: gel diffusion precipitin tests in two dimensions. (05 Mar 2000) |
| reaction of nonidentity | See: gel diffusion precipitin tests in two dimensions. (05 Mar 2000) |
| reaction of partial identity | See: gel diffusion precipitin tests in two dimensions. (05 Mar 2000) |
| reaction quotient | <chemistry> A constant represented by the symbol Q which is defined as the product of the concentrations of the products, each raised to the power that corresponds to its coefficient in the balanced equation, divided by the product of the concentrations of reactants, each raised to the power that corresponds to its coefficient in the balanced equation (see the equation in the equations page). at equilibrium conditions Q=K, the equilibrium constant. (09 Jan 1998) |
| reaction time | The time from the onset of a stimulus until the organism responds. (12 Dec 1998) |
| reaction, allergic | A reaction that occurs when the immune system attacks a usually harmless substance (an allergen) that gains access to the body. The immune system calls upon a protective substance called immunoglobulin e (IgE) to fight these invading allergic substances ( allergens). Even though everyone has some IgE, an allergic person has an unusually large army of these IgE defenders -in fact, too many for their own good. This army of IgE antibodies attacks and engages the invading army of allergic substances of allergens. As is often the case in war, innocent bystanders are affected by this battle. These innocent bystanders are special cells called mast cells. These cells are frequently injured during the warring of the IgE antibodies and the allergic substances. When a mast cell is injured, it releases a variety of strong chemicals including histamine into the tissues and blood that frequently cause allergic reactions. These chemicals are very irritating and cause itching, swelling, and fluid leaking from cells. These allergic chemicals can cause muscle spasm and can lead to lung and throat tightening as is found in asthma and loss of voice. (12 Dec 1998) |
| reactivate | 1. To render active again. 2. In particular, of an inactivated immune serum to which normal serum (complement) is added. (05 Mar 2000) |