Electron dense chains and clusters in human platelets.

Human platelets contain dense organelles that serve as storage sites for adenine nucleotides and serotonin. They also contain calcium and phosphate responsible for the opacity of dense bodies in the electron microscope. The present study has shown that there are also bead-like structures and clusters of beads that are electron opaque when viewed by the whole mount technique. Their origin and function are not known. However, their presence might interfere with the accuracy of imaging techniques currently being used to measure the number and volume of dense bodies in patients with platelet storage pool deficiency.