DILUTED AND UNDILUTED MERCOX SEVERELY DESTROY UNFIXED ENDOTHELIAL, CELLS - A LIGHT AND ELECTRON-MICROSCOPIC STUDY USING CULTURED ENDOTHELIAL-CELLS AND TADPOLE TAIL FIN VESSELS

Mercer is a methylmethacrylate-based resin which is widely used for va scular corrosion casting with subsequent scanning electron microscopic analysis. In the present study the effect of undiluted and diluted Me rcer (4 + 1; volume + volume; Mercer: monomeric methylmethacrylate (MM A); 0.02 g catalyst MA/ml Mercer) and methyl-methacrylate with and wit hout catalyst MA (0.625 g/10 ml MMA) on fixed and unfixed endothelial cells was studied. Light microscopy (LM) of cultured capillary endothe lial cells (ECs), which were replicated with diluted or undiluted Merc er shows degranulation and membrane perturbation of ECs, while no morp hological changes occur in glutaraldehyde-prefixed ECs. Scanning elect ron microscopy (SEM) of replicas (= resin blocks) polymerized on prefi xed ECs reveals unchanged ECs and replicas show many details. Unfixed ECs are destroyed and replicas reveal aberrant features. Transmission electron microscopy (TEM) of prefixed and unfixed ECs (cultured endoth elial cells, endothelial cells of perfusion prefixed and of unfixed ta dpole tail fin vessels) substantiates LM and SEM findings. Prefixed EC s resist Mercer without fine structural changes, while unfixed cells u ndergo destruction. It is recommended to fix vessels prior to casting. Extravasations in microvessels are considered to be caused by focal c hemical destruction of endothelial cells.