 This study will try to determine what causes toxic side effects of stem cell transplantation, such as increased blood pressure, increased heart rate, decreased kidney function and abnormal heart rhythms. Stem cells are used to treat various diseases, including cancer, aplastic anemia and sickle cell disease. The cells may be given fresh to the patient or they may be preserved first with a chemical called DMSO and frozen for later use. Some stem cell transplant procedures include infusion of red blood cells along with the stem cells. This study will examine whether side effects of stem cell transplants are associated with the DMSO preservative in frozen cells or with hemoglobin a protein released from defrosted red blood cells or neither of these factors. 