Unsaturated 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholines (unsaturated platelet-activating factor): aggregation of human platelets after incubation with indomethacin, creatinephosphate/creatinephosphokinase, xylocain and hirudine, and serotonin release after incubation with indomethacin.