Freeze-etching of unglycerinated tissue dispersions by application of the oil emulsion technique.

The oil emulsion technique has been applied to rat brain and liver tissue for freeze-etching preparation without antifreeze pretreatment. It has been demonstrated that the dispersed tissue exhibits a high degree of vitrification throughout the mostly globular fragments up to at least 30 micrometer in diameter. Signs of insignificant ice crystal formation of 50 nm and less could only rarely be detected. Although the dispersion process seriously affects the tissue organization as a whole, most cellular organelles and the plasma membrane show satisfactory preservation of structure. In larger tissue drops, a local overall structural preservation of the original cellular organization is recognizable. The results obtained demonstrate the applicability of this method to various biological objects for realizing sufficient cryofixation in the absence of cryoprotectants.