Protein precipitation is another simple pretreatment technique. The protein content of human body fluids and tissues is considerable, from about 6% by weight in plasma to greater than 50% by weight in liver and other organs. Numerous reagents have been developed to precipitate protein; two that are commonly used in drug analysis are trichloroacetic acid (10-15% in water) and tungstic acid (10% sodium tungstate in water and used in conjunction with 3n sulfuric acid). Once proteins have been precipitated, separation of aqueous and solid protein must occur by filtration or centrifugation.
René Leriche (FR) described a constellation of symptoms in male patients, which became known as Leriche syndrome or aortoiliac occlusive disease . The syndrome consists of the following triad: (a) absent or diminished femoral pulses; (b) intermittent claudication with pallor, coldness and diffuse muscle atrophy of both the lower extremities; and (c) impotence. Leriche believed that segmental atherosclerosis caused this syndrome and proposed that restoration of the blood supply could be curative. He suggested in the 1920s that resection of the obliterated segment and repair with a vascular graft would be the ideal treatment for this syndrome ( 2029 , 2030 ).