Contrast of biological cryosections in scanning transmission electron microscopy

Abstract

SUMMARY Ultrathin (70–100 nm thick) frozen‐hydrated cryosections of yeast cells were studied by scanning transmission electron microscopy (STEM). Generally, the contrast is very poor in brightfield and increases slightly by use of the darkfield signal in imaging. The contrast can either be enhanced by selective staining before cryofixation or by mass loss caused either by freeze‐drying or by radiation damage. Partial freeze‐drying by superficial ice sublimation seems to be the most efficient method to increase the contrast in cryosections in the frozen‐hydrated state. The highest contrast in cryosections is achieved after complete freeze‐drying.

A survey of ultra‐rapid cryofixation methods with particular emphasis on applications to freeze‐fracturing, freeze‐etching, and freeze‐substitution

“…Griffiths (1984) states that tungsten-coated glass knives are better for cryosectioning than diamond knives. Nevertheless, cytochemistry (Christensen and Komorowski, 1985;Griffiths, 1984;Griffiths et al, 1984;various papers in Cuello (1983) and in Polak and Varndell(l984)) and microprobe analysis (Gupta and Hall, 1984;Hohling and Kreft-ing, 1984;Kellenberger and Chiu, 1982;Steinbrecht and Zierold, 1984;Zierold, 1982aZierold, , b, 1983Zierold, , 1985 are now more or less routinely carried out with that technique. A number of cytochemical probes, especially ones conjugated to protein A-gold and immunoglobulin-gold, have successfully been applied to cryosections, and this is the case for the subcellular localization of intracellular as well as for membrane-bound antigens and receptors.…”