HOW THICK ARE THE PARAFFIN-EMBEDDED TISSUE-SECTIONS ROUTINELY PREPARED IN LABORATORY - A MORPHOMETRIC STUDY USING A CONFOCAL LASER-SCANNINGMICROSCOPE

In order to evaluate the differences between cut and measured thicknes ses of formalin-fixed, paraffin-embedded tissue sections, formalin-fix ed, paraffin-embedded blocks of liver tissue were prepared from four m ale Wistar rats, The sections were cut at preselected thicknesses of 3 , 6, 9, 12, 15 and 18 mu m, and observed under confocal laser scanning microscopy. The maximum and minimum section thicknesses were measured using a vertically cut section image constructed by the software inco rporated in the microscope, The surface of the section was not smooth but showed fine undulations in addition to a slight inclination, The m ean and range of the section thicknesses measured were 4.3 +/- 1.3, 7. 0 +/- 1.7, 9.8 +/- 2.1, 12.0 +/- 2.6, 14.1 +/- 3.0, and 17.7 +/- 3.8 m u m for the preselected cut thicknesses of 3, 6, 9, 12, 15 and 18 mu m . It is stressed that the evaluated parameters of the section (volume or surface densities) include standard errors of up to 10% caused by t he differences between the cut and real thicknesses.