The use of ruthenium and p-phenylenediamine to stain cartilage simultaneously for light and electron microscopy.

p-Phenylenediamine was incorporated during the dehydration of cartilage blocks fixed with ruthenium red, glutaraldehyde and osmium. The addition of p-phenylenediamine permitted the visualization by light microscopy of cellular detail not obtained with ruthenium red alone. Ruthenium red is a widely used method for retaining and localizing proteoglycan for electron microscopy but its inability to produce sufficient density within the cells for light microscopy prevented simultaneous visualization by these two modes. The addition of p-phenylenediamine staining overcame this shortcoming without interfering with the ultrastructural detail and both stains can also be used before the making of radioautographs.