Comparison of preparation methods for the evaluation of nerve axons.

We have conducted a study to compare various preparation methods, including a certain number of new methods, to find which ones are best suited to the morphological evaluation of nerve fibers in the pyramidal tract of the human medulla oblongata. Our main concern was to find fixation and staining methods that would minimize errors, especially regarding the tissue shrinkage ratio and the ease of staining. From the two fixation methods we examined, the most satisfactory was the secondary chromic acid fixation (which gave the best overall results when followed by nitrocellulose embedding), as it gives the lowest shrinkage ratio with the narrowest range (10 +/- 0%). Among the ten staining methods we tested, we found that the most suitable for morphological evaluation were the discriminative staining methods (Luxol fast blue-Periodic acid-Schiff-Hematoxylin stain, Masson-Goldner-Goto method and modified Hematoxylin-Eosin stain) and the silver impregnation methods (Luxol fast blue-Silver impregnation and Luxol fast blue-Silver impregnation-Periodic acid-Schiff-Hematoxylin).