Fatty acid composition of RBC membrane (thin liquid chromatography) 5 mls of blood will be centrifuged at 4000 rpm for 10 min at 5 o C, removal of plasma and buffy coat; addition of 5 ml cold saline + EDTA (NaCl 0.9% containing 1 mM EDTA) and mix; centrifuge at 3000 rpm for 10 min at 5oC; repeat; flushing of erythrocytes with N2; storage at -70o C (Revco). Lipid extraction will be performed by homogenization of the cells in hexane/ isopropanol (3 :2 vol./vol.) containing 5 mg/100 ml butylated hydroxytoluene as an antioxidant and 5 mg/100 ml heneicosanoic acid (21 :0) as an internal standard. Fatty acid analysis: fatty acids will be converted to methyl esters by heating with BF3 in methanol, and the methyl esters separated on a HP 5890 Series II Gas Chromatograph containing a flame ionization detector. Peak areas will be integrated and plotted with the aid of the Varian Star Integrator computer package (Varian Star Workstation, 1990, Varian Associates, Inc.). Individual fatty acid methyl esters will be identified by comparing retention times with authentic standards. Values will be expressed as wt.% of total identified fatty acids (16).