Cryo-ultramicrotomy of islets of Langerhans. Some observations on the fine structure of mammalian islets in frozen sections.

A procedure is described for the preparation of ultrathin frozen sections of glutaraldehydefixed or unfixed islets of Langerhans by cryo-ultramicrotomy. Freezing of the tissue was accomplished by direct immersion of isolated islets in liquid nitrogen. Sectioning was performed at a specimen temperature of —80 °C and a knife temperature of —40 °C, the ribbon of sections being collected on a trough containing 60 % dimethyl sulphoxide. Staining was accomplished with 4 % silicotungstic acid and sections were protected from drying artifacts by rinsing with 0-5 % polyethylene glycol. Even in tissue not subjected to prior glutaraldehyde fixation, most of the structural features of A and B cells were well preserved in frozen sections, which were obtained in a number and quality which should render them suitable for ultrastructural, cytochemical or radioautographic studies.