An Electron Microscopic Observation of Rat Peritoneal Cells Processed by Rapid Freezing and Freeze-Substitution Fixation

The ultrastnicture of rat peritoneal free cells processed by rapid freezing followed by freeze-substitution fixation was compared with that of routinely prepared materials. The present cryoftxation preserved well the fine structural features of the cells, which were similar in general to those of conventional sections but different in several aspects. Macrophages provided numerous folds and invagjnations of the plasma membrane, and a labyrinthine system of smooth-surfaced cisterns which was open to the cell surface was developed in the peripheral cytoplasm. A number of primary lysosomes contained in macrophages appeared to have a less-dense, homogeneous interior, in contrast to a finely granulated, dense appearance in conventional sections. No peculiar differences in cytology of lymphocytes were noticed, but the intracytoplasmic filaments were more clearly detected in frozen materials. Eosinophils contained specific granules which showed variety in the morphology of their contents. Mast cell granules which were bounded with a well-defined limiting membrane appeared to be filled with less-dense, homogeneous materials, in contrast to a finely granulated, dense interior as seen in conventional sections. Their contents were positive with the periodic acidthiosemicarbazide-sUver proteinate (PA-TSC-SP) reaction. © 1982 Oxford University Press. All rights reserved.