A STUDY OF AREA AND THICKNESS COMPRESSION OF PARAFFIN SECTIONS

This study was carefully designed to determine the section compression of paraffin embedded sections. Two sections (one with thickness 5 µm and one 10 µm set by microtome) were cut from each of 2 sets of 12 testicular tissue (adult rats) blocks and stained with hematoxylin. Using scanned images, the area and the vertical (along the sectioning direction) and horizontal diameters of the block face were measured and compared with those of the unstained, stained or coverslipped section. Using the coverslipped section, the vertical and horizontal diameters of round spermatid nuclear profiles and the actual thickness of section were measured with light microscopy. Overall, the area of the coverslipped section was reduced by 5.5%-8.6% (on average) in comparison with that of the block face, with 69.5%-84.4% of the reduction being contributed by section compression in the process of section cutting, mounting and drying. The vertical (linear) compression of section, the primary cause of section area compression, was 5.9%-8.9%. The vertical compression of nuclear profiles was 1.5%-2.3% in 2 sets of sections and 5.2%-5.7% in other sections, indicating a non-uniform compression of structures within some sections depending on procedures of section drying. The measured mean thickness of sections decreased by 3.1%-5.0%.