Ultraviolet Microscopy of Pancreatic Acinar Nuclei Fixed in Potassium Permanganate

The fixation of rat pancreas in potassium permanganate according to Luft (1) imparts a brown coloration and a strong ultraviolet absorption to the cytoplasm of the exocrine cells, but only a weak one to the nuclei. Within the latter an even paler zone surrounding the nucleoli can be observed. After the removal of the stain by means of oxalic acid, ultraviolet microscopy and the Feulgen technic reveal that the distribution of D N A within the nucleus is complementary to that of the staining caused by the KMnO4 fixation. Small pieces of rat pancreas were fixed, within a few minutes after the death of the animal, in 0.6 per cent potassium permanganate in veronalacetate buffer at pH 7.2 for 1 hour at 0°C., washed in 30 per cent ethyl alcohol, dehydrated, and embedded in methacrylate, which was polymerized in ultraviolet light (2). Other specimens were prepared from the same material by freeze-drying and direct embedding in methacrylate (3). Sections were cut at 1 > on a modified rocking microtome equipped with a glass knife and observed without the methacrylate having been removed (4). Ultraviolet microphotography was performed with " O l d Delft" reflecting optics at condenser and objective numerical apertures of 0.65 and 0.85, respectively. The light was provided by a monochromator built for ultraviolet microscopy (5),