A cryoembedding method for cutting ultrathin cryosections from small frozen specimens

A technique is described which allows one to embed small frozen specimens for easy sectioning in a cryoultramicrotome. n-Heptane is recommended as a cryoembedding medium due to its suitable melting point (182.4K), high vapour pressure, chemical inertia, and good sectioning properties when solid. Freeze dried cryosections of cultured muscle cells, slime moulds, insect antennae and unicellular algaee are presented as examples. There is no evidence that the preparation disturbs the distribution of soluble elements in the specimen, since X-ray spectra of muscle cells exposed to heptane do not differ from those of samples not exposed.