Use of the fluorochrome propidium iodide for the identification of Xenopus germ plasm during immunofluorescence studies.

Addition of 0.5 microgram/ml of the red fluorescent dye propidium iodide to the penultimate wash of Xenopus early embryo serial sections during immunofluorescence studies causes germ plasm to fluoresce brightly. Germ plasm can be accurately and speedily identified in the serial sections. The use of this dye is a marked improvement over previous methods of germ plasm identification in unstained sections. Studies involving screening for germ-plasm-specific antibodies are greatly facilitated by staining germ plasm red with propidium iodide and searching for green colabelling by fluoresceinated antibodies.