| passive clot | A clot formed in an aneurysmal sac consequent to the cessation or slowing of circulation through the aneurysm. (05 Mar 2000) |
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| passive congestion | Congestion caused by obstruction or slowing of the venous drainage, resulting in partial stagnation of blood in the capillaries and venules. (05 Mar 2000) |
| passive cutaneous anaphylaxis | An evanescent cutaneous reaction occurring when antibody is injected into a local area on the skin and antigen is subsequently injected intravenously along with a dye. The dye makes the rapidly occurring capillary dilatation and increased vascular permeability readily visible by leakage into the reaction site. Pca is a sensitive reaction for detecting very small quantities of antibodies and is also a method for studying the mechanisms of immediate hypersensitivity. (12 Dec 1998) |
| passive cutaneous anaphylaxis test | An animal is injected intradermally with antibody (usually IgE) and subsequently challenged intravenously with a mixture of antigen and Evans blue dye 24-48 hours later. A dark blue area indicates a positive reaction due to the leakage of the dye at the site of antigen-antibody reactions. (05 Mar 2000) |
| passive diffusion | See: facilitated transport. (05 Mar 2000) |
| passive duction | A manoeuver to determine whether a mechanical obstruction is present in the eye; with forceps grasping an eye muscle, an attempt is made to passively move the eyeball in the direction of restricted rotation. Synonym: passive duction. (05 Mar 2000) |
| passive eruption | The apparent continued eruption of the teeth, actually the result of regression of the gingivae and crestal bone. Polymorphous light eruption, a common pruritic papular eruption appearing in a few hours and lasting up to several days on skin exposed to shortwave ultraviolet light; subepidermal oedema and deep perivascular lymphocytic infiltration is seen microscopically. Eruption sequestrum, spicule of bone overlying the central occlusal fossa of an erupting permanent molar. Serum eruption, urticaria seen in serum sickness. Surgical eruption, the uncovering of an unerupted tooth to permit its further eruption into the oral cavity by surgically removing overlying soft tissue, bone, and sometimes teeth. (05 Mar 2000) |
| passive haemagglutination | A kind of passive agglutination in which erythrocytes, usually modified by mild treatment with tannic acid or other chemicals, are used to adsorb soluble antigen onto their surface, and which then agglutinate in the presence of antiserum specific for the adsorbed antigen. Synonym: indirect haemagglutination test. (05 Mar 2000) |
| passive hyperaemia | Hyperaemia due to an obstruction in the flow of blood from the affected part, the venous radicles becoming distended. Synonym: venous hyperaemia. (05 Mar 2000) |
| passive immunity | <immunology> Immunity acquired by the transfer from another animal of antibody or sensitised lymphocytes. Passive transfer of antibody from mother to offspring is important for immune defense during the perinatal period. (18 Nov 1997) |
| passive immunization | The production of passive immunity. (05 Mar 2000) |
| passive immunotherapy | <immunology> A process in which individuals with advanced disease (who have low levels of HIV antibody production) are infused with plasma rich in HIV antibodies or an immunoglobulin concentrate (HIV Ig) from such plasma. The plasma is obtained from asymptomatic HIV-positive individuals with high levels of HIV antibodies. (09 Oct 1997) |
| passive incontinence | Dribbling of urine by reason of inability of the bladder to empty itself and of consequent overdistention. See: overflow incontinence. (05 Mar 2000) |
| passive learning | Learning without a direct attempt. Synonym: passive learning. (05 Mar 2000) |
| passive length-tension curve | The relationship between passive tension and preload (rest length) for a muscle at rest. (05 Mar 2000) |