Analysis of the samples The fixed samples are decalcified in 10% EDTA, hydrated through graded concentrations of ethanol and finally placed in Araldite. They can then be cut with a bonemicrotome (Reichert Ultracut E Microtome, Vienna, Austria) and further prepared for light microscopic and ultrastructural analysis. Staining with methylene blue (0.1% aqueous solution) will be done on sections of 0.5 um. These sections will be viewed with a light microscope and digitized at a high resolution Mirax Scan (Carl Zeiss Micro-Imaging GmbH, Germany). The images will be evaluated by an expert at a magnification of 20x, 40x and 100x on a 30inch LCD screen with custom software (Mirax Viewer 1.1, Göttingen, Germany). For the analysis of the ultrastructural features, the investigators will make ultrathin sections (0.06μm) and on plates coated with 0.7% formvar places, contrasted with uranyl acetate and lead citrate. These sections are EM208S analyzed with a transmission electron microscope (Philips, Eindhoven, The Netherlands) at 80 kV.