Use of frozen biologic material for combined light and electron microscopy

A simple and rapid method that enables the use of unfixed frozen material for light and electron microscopic purposes is described. At the light microscopic (LM) level, unfixed cryostat sections were used for enzyme histochemistry. When electron microscopic (EM) inspection was needed, tissue blocks, which were stored at -80 degrees C, were fixed at 4 degrees C and prepared for EM according to standard procedures. Ultrastructural analysis of this material demonstrated that most morphologic aspects of normal (human pancreas and rat liver) and pathologic (human pancreatic adenocarcinoma and rat colon carcinoma metastases in liver) tissue were rather well retained. Cryostat sectioning at -25 degrees C did not appear to have damaging effects on the morphology. The method was applied to correlate enzyme histochemical (LM) data with ultrastructural (EM) aspects of mineralization of stroma in explants of human pancreatic adenocarcinoma grown in nude mice and of nonparenchymal cells around metastases of colon carcinoma in rat liver.