This is a platelet transfusion study. The primary purpose of this study is to determine if Biotin, vitamin B7 is an effective way to label platelets in survival and recovery studies. This study involves using a radioactive material as well as Biotin added to platelets to track platelets in the blood. The platelets will be collected using an apheresis procedure, labeled with biotin, and stored for 3 days. After the storage period, a radioactive material will be added to a small amount of the stored biotin-treated platelets. The radiolabeled platelets will be given back to donor and follow-up blood draws will be done to see how many of the platelets are circulating.