Observations on the production of frozen-dried thin sections for electron microscopy using unfixed fresh liver, fast-frozen without cryoprotectants.

Thin sections of unfixed liver, fast-frozen without cryoprotectants, have been cut using conditions under which momentary thawing of the sections is unlikely to occur. A transfer stage which facilitates this procedure is described. Sections show hole damage probably due to ice-crystal formation during the freezing process and have well defined edges, but despite hole damage, some morphological features of the cell are discernible. Presumptive mitochondria appear smaller in frozen sections than in conventional Araldite sections. Sections devoid of hole damage have indistinct edges and are presumed to have undergone transient thawing. Carbon coating of freeze-dried sections to exclude atmospheric moisture during transference of sections to the electron microscope (EM) appear unnecessary as regards preservation of morphological structure. The results are discussed in relation to the limitations of the method and the potential value of the technique.