Three-dimensional viewing of internal cell structure.

3T3 and HeLa cells, grown as a monolayer, have been rapidly frozen by propane jet as a fresh preparation, without pretreatment. In some experiments the frozen cells were fractured at -170 degrees C, thawed into fixative and viewed by high-resolution SEM after critical-point drying. In other experiments the frozen cells were thawed into fixative unfractured. These preparations were refrozen in 15% methanol, fractured and deep-etched for replication and TEM study. The technique used in this work appears to give rapid rewarming from -170 degrees C to 0 degree C with little evidence of ice crystal growth. The cells fractured before thawing, examined by SEM, show extensive extraction of both nucleus and cytoplasm with deep views of nuclear chromatin, and of cytoplasmic organelles caught amongst rather distorted filaments of the cytoskeleton. Initial fixation for the SEM work was light (0.3% glutaraldehyde for 10 mins) so that structure is seen as it would be retained for antibody labelling.