Application of ultrasound for tissue fixation: Combined use with microwave to enhance the effect of chemical fixation

Microwave (MW) has the advantage of accelerating infiltration of fixatives into tissue blocks, but the disadvantage of causing the temperature of the fixatives and tissue blocks to rise. We tried to minimize the temperature elevation during MW irradiation by applying ultrasound (US) in combination with MW oven furnishing US generator. US was uneffective in reducing the rise of temperature, however, it was able to enhance the rapid tissue fixation. Electron microscopic examination showed that the fine structure of organs, such as liver, pancreas, submandibular gland, small intestine, and kidney, was well preserved. Characteristically, the matrix of mitochondria appeared electron-dense, and the marginal zone of zymogen granules in the pancreas was more electron-opaque than the core of the granule. The immunoreactivity of zymogen granules to anti-amylase antibody was strong. The deformation or disorder of cell structure due to the thermal effect and cavitation that can be caused by US was not seen. US can be useful for histologic and immunohistochemical study.