En bloc optical sectioning of resin‐embedded specimens using a confocal laser scanning microscope

Reconstruction of 3D structures of specimens embedded for light or electron microscopy is usually achieved by cutting serial sections through the tissues, then assembling the images from each section to reconstruct the original structure or feature. This is both time-consuming and destructive, and may lead to areas of particular interest being missed. This paper describes a method of examining specimens which have been fixed in glutaraldehyde and embedded in epoxy resin, by utilising the autofluorescence preserved or enhanced by aldehyde fixation, and by using a confocal laser scanning microscope to section optically such specimens in the block down to a depth of about 200 &mgr;m. In this way, the accurate estimation of the depth of particular features could be used to facilitate subsequent sectioning at the light microscope or electron microscope level for more detailed studies, and 3D images of tissues/structures within the block could be easily prepared if required.