Division of Radiooncology, Deutsches Krebsforschungszentrum, 69120 Heidelberg, Germany
Apart from tissue processing by cryo-techniques, fixation is usually followed by dehydration and some kind of embedment to allow mechanical support for the sectioning process. Other possibilities of dehydration include procedures of freeze-drying and freeze-substitution. Specimens are commonly infiltrated and embedded in a stable medium as for example in paraffin for light microscopy or a resin for electron microscopy. Three main types of resins may be used for plastic embedding of specimens: methacrylate esters, polyester resin, and epoxy resins. The introduction of water-miscible resins of low solvent power was a significant progress in cell research. Polar and low-temperature embedding procedures offer the advantage to reduce denaturation and conformational changes which are generally associated with nonpolar dehydration and with conventional resin curing. Several Lowicryl® embedding media are in use since the 1980s which were designed for a wide range of embedding conditions. These resins consist of highly cross-linked acrylate-methacrylate media with the outstanding feature of low viscosity at low temperature (CARLEMALM E et al. 1980).