Development of Cathodoluminescence Electron Microscope (CEM) and its Application to the Medical and Biological Fields.

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In 1984, the intensities of cathodoluminescence (CL) emitting from fluorochromes, dyes, metals, biological substances and other materials were examined under an Akashi scanning electron microscope (SEM) ISI-DS130 equipped with a simple CL detector. Some salts of rare earth metals and some substances related to vitamin A (Vit A) metabolism and steroid hormone biosynthesis were proved to emit strong CL.In 1985, the bottom stage of DS130 was modified with a half ellipsoidal mirror, photomultiplier tube (PMT) and monochrometer, so that precise CL images and CL spectra were able to obtain. CL images and spectra of Ito cells of Vit A loaded rat liver and zona fasciculata cells of rat adrenal cortex were observed and analyzed by means of the simple cryo-SEM method as a specimen preparation method for CL observation. They showed strong CL from their lipid droplets.In 1986, the top stage of DS130 was remodeled into a color CL electron microscope (a color CEM). A newly shaped mirror, combining three half ellipsoidal mirrors, was induced, so that the detected CL photons could be amplified in red, green and blue zones separately. The specimen holder was totally changed in order to maintain the specimen temperature down to the liquid nitrogen temperature. Color CL images and CL spectra analysis of biological materials were turned out to be a useful method of identifying the unknown substances and displaying them in situ. Vit A esters were proved to emit CL from the lipid droplets of Ito cells under the color CEM.