Examination of injected specimens by confocal laser scanning microscopy and scanning electron microscopy

Although corrosion casts commonly examined by scanning electron microscopy (SEM) offer good insights into the general arrangement of the microvasculature of certain organs, no information can be obtained from such specimens on special morphological data or dynamic events. Thus, most investigators are obliged to make their interpretations of cast structures only on the basis of indirect criteria. A synopsis, which considers the most important data in that respect, is given for the blood and lymphatic microvessels. Moreover, a methodological approach is introduced, based on the application of fluorescent resin, which allows the examination of cast structures in uncorroded specimens together with the surrounding tissue by confocal laser scanning microscopy (CLSM). When two differently stained resins are injected at different sites, e.g., Mercox-fluorescent yellow into an artery and Mercox-rhodamine into the interstice, blood vessels and lymphatics can be well distinguished. In lymph nodes, the system of lymphoid spaces and that of intranodal sinuses can be separately represented with the same technique. Applications and advantages of the CLSM method, which is a useful tool for an extended interpretation of corrosion casts in SEM, are shown in cast specimens from tongue, skin, and liver in rats. In this study, both corroded and uncorroded specimens were considered. In addition, a new approach is demonstrated which combines casting technique and fluorescence microscopy with investigations carried out under experimental conditions. This allows the examination of microvascular casts together with labelled cells in liver and spleen in a state of phagocytosis.