Transmission electron microscopy of purified platelets. Platelet-rich plasma was prepared and a platelet pellet was fixed with glutaraldehyde. After osmium staining, platelet samples were viewed by electron microscopy. Shown are representative sections from GP Ibβ^WT and GP Ibβ^Null platelets. A black bar in each panel represents 500 nm. Platelet areas and α-granule areas were quantified from 41 randomly selected sections and the results are presented in Table 2. Images were obtained using a Jeol JEM-1010 transmission electron microscope (Jeol, Croissysur-seine, France) at 80 kV. Quantitation of surface areas was calculated using Metamorph software (Universal Imaging, Paris, France).