Azure B Bromide Staining of Regenerating Muscle

Abstract

Paraffin sections of regenerating muscle fibers color intensely blue or purple with the metachromatic stain azure B bromide. These darkly stained fibers show excellent cellular detail in cytoplasm as well as nuclei. They contrast conspicuously with the pale blue of adjacent normal muscle. Differential staining of nucleic acids is the principle on which this technic is based. With stain dissolved in water at a pH of 4.0, the ribonucleic acid (RNA) stains purple and deoxyribonucleic acid (DNA) stains blue-green. Early work with azure B bromide was done by Flax and Himes. They and Lash and associates demonstrated that treatment of sections with ribonuclease (RNAse) before staining eliminated the purple color. This stain has been used very satisfactorily in our laboratory for a study of the basophilia of regenerating muscle, the pathology of human muscular dystrophy, and the inflammatory disorders of muscle. We have obtained good results from it also with regenerating diaphragm and rectus abdominis muscle of rats which had been inoculated intraperitoneally with the myotoxic substance plasmocid.* 8 ' Procedures for using azure B bromide are not, to our knowledge, generally included in current histologic technic books, nor do they seem to be well known. It is the purpose of the present paper to call attention to some of the literature on this subject, to describe briefly the technic of using azure B bromide, and to emphasize that it is probably not strictly accurate to refer to this stain simply as azure B, as has been done in some previous publications. •