Prolamellar bodies (PLBs) were isolated from etioplasts of Cucurbita moschata Durch var.melonaeformis Makino, and their fractured planes were observed at high magnification with a high-resolution scanning electron microscope (SEM) to elucidate the paracrystalline structure of the PLB. Thus, we obtained a standard method of preparation of biological specimens. A good preparation should provide a high quality SEM image which will reveal fine structures of the specimens even at high magnification. In this experiment, the specimens were fixed with osmium tetroxide, conductlvely stained with uranyl acetate, dehydrated with alcohol series, rapidly frozen in liquid Freon, and freeze-fractured in liquid nitrogen. It was proved that the specimens correctly retained their fine structures, and this suggested that very thin, high quality platinum-carbon coating (2 nm in thickness) by rotary evaporation with the electron beam gun provide the best high-resolution contrast for the fractured specimens. Through these procedures, the three-dimensional structure of the PLBS could be observed precisely at high magnification using a high-resolution SEM.
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Yamada et al. (1983) studied this question.