Electron Probe Microanalysis of the Dense Bodies of Human Blood Platelets

Abstract

Air-dried spreads of human blood platelets were prepared by incubating a drop of fresh blood from finger tips on collodion membrane covered copper grid for 4min at 37°C. The blood was blotted with filter paper and dried in the air at room temperature. Under the electron microscope various substructures were observable in the attenuated cytoplasm of platelets without any treatment, i.e., fixation, embedding or staining. The granulomere of platelets revealed dense bodies of 200-300nm diameter and smaller dense granules (about 50nm). Larger ovoid bodies with dense granules presumably corresponded to mitochondria and lysosomes. In the hyalomere there were vacuoles partly connected with surface of the platelet by a canalicule.
Using an energy dispersive type X-ray microanalyzer attached to a scanning transmission electron microscope, electron probe analysis detected high levels of calcium and phosphorus and an appreciable amount of chlorine in the dense bodies of platelets. The three elements were also detected in the smaller dense granule.
This technique offers some advantages for microanalytic study of the chemical components of cell organelles including the simplicity of the procedure, disuse of liquids in specimen preparation which were possibly causing substance escape, and avoidance of cryosections usually causing ice crystal artifacts.