Possibilities For The Study Of Blood Platelets Using Soft X-Ray Microscopy

Two imaging techniques, soft x-ray contact microscopy using a stationary source and transmission electronmicroscopy (TEM) were used in parallel for the study of human blood platelets. Thin sections of fixed cell preparations on EM grids were examined by the two methods and images of the same individual cells could be compared. Not all electrondense structures could be seen in contact x-ray images. However, other structures in the same cells, not identified by TEM, could be seen in soft x-ray contact pictures. In addition, whole cell mounts of intact platelet microtubules were examined by the two techniques. These electrondense structures were not photondense and disappeared in the x-ray pictures. Whole cell mounts of partially activated human platelets were also examined in parallel, by the use of the scanning electron microscope (SEM). In the x-ray images, a new platelet cytoskeleton could be seen in the partially activated cells. This was made of radial, filamentous structures departing from a centralized and retracted bunch of platelet organelles and, at times, extending into pseudopods outside the cell perimeter. The gas puff Z pinch method was also used in the study of live and partially activated human platelets. An image of multiple craters and undulating cell cords, in addition to a polarized and contracted bunch of platelet organelles, could be seen, while few pseudopods were seen extending beyond the cell perimeter. Some individual platelet granules could be identified in the cell craters, others were seen in the medium, outside the cell. A tear in the cell surface structure could also be identified. The latter was interpreted as a possible portal for the partial extrusion of platelet granules during platelet activation.