There is evidence that red blood cells produce NO, which normally causes arteries to relax and increase blood supply. The investigators will try to determine the nature of NO in red blood cells and whether the amount of this substance is altered because of different blood processing and storage techniques. It is their thought that "aged" red blood cells have less NO that naturally relaxes our arteries and further changes the blood supply. This study is designed to determine the most ideal way of storing and processing blood.