| primary rays | Cosmic ray's in the form in which they first strike the atmosphere, X-ray's generated at the focal spot of the tube. Synonym: direct rays. (05 Mar 2000) |
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| primary reaction | <dermatology> The cutaneous and sometimes systemic reactions associated with vaccination with smallpox vaccine. (18 Nov 1997) |
| primary refractory anaemia | Any of a group of anaemic conditions in which there is persistent, frequently advanced anaemia that is not successfully treated by any means except blood transfusions, and that is not associated with another primary disease. (05 Mar 2000) |
| primary reinforcement | Satisfaction of physiological needs or drives, such as that supplied by food or sleep. (05 Mar 2000) |
| primary rejection | A rejection occurring more than seven days after transplantation, mainly from a cellular immune response. (05 Mar 2000) |
| primary renal calculus | A calculus formed in an apparently healthy urinary tract, usually composed of oxalates, urates, or cystine. (05 Mar 2000) |
| primary renal tubular acidosis | A metabolic defect in the mechanism of urinary acidification that may be either the transient type, with onset in infancy, or the persistent type, with onset in childhood or adult years; both types are familial. (05 Mar 2000) |
| primary reninism | Overproduction of renin by juxtaglomerular cells in the absence of a stimulus (such as decreased renal perfusion); leads to hyperaldosteronism, hypertension, hypokalaemia, and oedema. (05 Mar 2000) |
| primary sclerosing cholangitis | <radiology> Idiopathic, associated with IBD (50%), usually UC, M more than F, peak age 20-30 years of age, chronic inflammation and fibrosis of all bile ducts, stricture, obstruction, abscess (string of beads), intramural pseudo-diverticula, cholangiocarcinoma (10%!!), dilatation proximal to stricture may signal carcinoma Differential diagnosis: cholangiocarcinomarcinoma (diffuse form), primary biliary cirrhosis (PBC), AIDS-related cholangitis (? due to CMV) (12 Dec 1998) |
| primary screw-worm | An obligatory screw-worm that can penetrate normal tissues and feed as a primary invader. The important myiasis flies of man that serve as p. Screw-worm's are Cochliomyia hominivorax, Chrysomyia bezziana, and Wohlfahrtia magnifica. (05 Mar 2000) |
| primary senile dementia | <disease> A progressive, neurodegenerative disease characterised by loss of function and death of nerve cells in several areas of the brain leading to loss of cognitive function such as memory and language. The cause of nerve cell death is unknown but the cells are recognised by the appearance of unusual helical protein filaments in the nerve cells (neurofibrillary tangles) and by degeneration in cortical regions of brain, especially frontal and temporal lobes. Alzheimer's disease is the most common cause of dementia. (22 May 1997) |
| primary sequestrum | A completely detached sequestrum. (05 Mar 2000) |
| primary sex characters | The sex glands, testes or ovaries, and the accessory sex organs. (05 Mar 2000) |
| primary shock | Shock mainly nervous in nature, from pain, anxiety, etc., which ensues almost immediately upon the receipt of a severe injury. (05 Mar 2000) |
| primary skin graft | A skin graft transferred immediately after the creation of a raw area. (05 Mar 2000) |