K E Y w ORDS. Medium-and high-voltage EM, nucleolus, Ag-NOR, bas-relief.
S U M M A R YTilted thick sections (one-half to several micrometres) of biological specimens observed with medium-to high-voltage electron microscopes are extremely useful for the study of the three-dimensional (3-D) structure of organelles.If high resolution in 3-D visualization and 3-D reconstruction is needed, many images corresponding to various angles of rotation and tilt must be recorded. This necessitates very time-consuming work-including eventual photographic processing-before good positioning of the object is defined.We have developed software which permits very rapid and precise determination of the tilt-axis, the registration of tilted views, 3-D measurements and 3-D visualization. Images are digitized either from negative films or directly with a camera fitted to the microscope. The application of the software is performed in minutes and allows for a rapid check of the quality of the tilt-series and of the features of interest of the object.Application of the software to the study of the 3-D structure of active components of the nucleolus stained with silver is shown.