| anemia | <haematology> Too few red blood cells in the bloodstream, resulting in insufficient oxygen to tissues and organs. Origin: Gr. Haima = blood (16 Dec 1997) |
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| anaemia, megaloblastic | Anaemia characterised by the presence of megaloblasts in the bone marrow. (12 Dec 1998) |
| megaloblastic | <haematology> A large abnormal red blood cell appearing in the blood in pernicious anaemia. (18 Nov 1997) |
| megaloblastic anaemia | Any anaemia in which there is a predominant number of megaloblastic erythroblasts, and relatively few normoblasts, among the hyperplastic erythroid cells in the bone marrow (as in pernicious anaemia). (05 Mar 2000) |
| absolute refractory period | The period following excitation when no response is possible regardless of the intensity of the stimulus. (05 Mar 2000) |
| anaemia, refractory | Anaemia (a shortage of red blood cells) unresponsive to treatment. (12 Dec 1998) |
| anaemia, refractory, with excess of blasts | Chronic refractory anaemia with granulocytopenia, and/or thrombocytopenia. Myeloblasts and progranulocytes constitute 5 to 40 percent of the nucleated marrow cells. (12 Dec 1998) |
| refractory | Not readily yielding to treatment. Origin: L. Refractorius (18 Nov 1997) |
| refractory anaemia | <haematology> A form of myelodysplasia which primarily affects the red cell production by the bone marrow. In some cases the developing red cells show an internal ring of iron granules. These cells are called sideroblasts. Refractory anaemia and refractory anaemia with sideroblasts are the most common forms of myelodysplasia. Origin: Gr. Haima = blood (13 Nov 1997) |
| refractory anaemia with excess blasts | <haematology> A form of myelodysplasia characterised by the build up of immature white blood cells (blasts) in the bone marrow. If the immature cells are particularly numerous it may indicate a chance of transformation to acute leukaemia and the condition is called refractory anaemia with excess blasts in transformation (RAEBt). Acronym: RAEB (13 Nov 1997) |
| refractory cast | A cast made of material that will withstand the high temperatures of metal casting or soldering without disintegrating. Synonym: investment cast. (05 Mar 2000) |
| refractory flask | A metal tube in which a refractory mold is made for casting metal dental restorations or appliances. Synonym: casting flask, casting ring. (05 Mar 2000) |
| refractory lining | A lining, usually of ceramic, capable of resisting and maintaining high temperatures. (05 Dec 1998) |
| refractory period | <neurology, physiology> most commonly used in reference to the interval (typically 1ms) after the passage of an action potential during which an axon is incapable of responding to another. This is caused by inactivation of the sodium channels after opening. The maximum frequency at which neurons can fire is thus limited to a few hundred Hertz. An analogous refractory period occurs in individuals of Dictyostelium discoideum, which are insensitive to extracellular cyclic AMP immediately after a pulse of cAMP has been secreted. The term can be applied to any system where a similar insensitive period follows stimulation. (18 Nov 1997) |
| refractory period of electronic pacemaker | The time required to restore full sensitivity after detecting cardiac activity or delivering a pacing impulse. (05 Mar 2000) |