Study of Golgi-impregnated material using the confocal tandem scanning reflected light microscope

The tandem scanning reflected-light microscope (TSM) is a real-time, direct-view confocal microscope. Only those points in the specimen situated in the focal plane contribute information to the image. A Tracor Northern TMS with piezo-electric control of the objective lens was used to generate 3-D images from Golgi-impregnated hamster cerebral cortex. Stereoscopic pairs of images were recorded as 35-mm colour film transparencies by photographing while automatically through-focusing along inclined axes. Transferring the image via a TV camera to the computer, stereo-pairs were obtained by oblique through-focusing and summing, displaying maximum intensity data in each line of sight. Pseudocolour topographic displays were generated by assigning the pixel value in a zeta map image as the focal depth at which the back-scattered light signal was maximal. The TSM was also modified so that a conventional transmitted-light image with a large depth of field could be obtained simultaneously as the very shallow depth of field confocal back-scattered-light image seen at any focus level. The conventional image is a silhouette of the impregnated neurons: the top surface of the cell is not visible and the relationships of processes that cross over cell bodies cannot be discerned. TSM gives a high-contrast image. The Golgi precipitate over the neuronal surface is resolved as globular or ovoid, coloured particles. The smaller particles also cover the dendritic spines. All the confocal range (extended focus) image display methods satisfactorily demonstrated the 3-D arrangement of cell bodies and processes in the chosen volume.