THE FLUORESCENT MICROSCOPIC LOCALIZATION OF THIAMINE IN NERVOUS TISSUE

A new fluorescent microscopic technique for visualizing thiamine in nervous tissue is described. Freeze dried sections are exposed to the vapors of cyanogen bromide and ammonia to convert thiamine to its fluorescent derivative thiochrome. The specificity of the procedure is ensured by utilizing monochromatic light for activation and a narrow band filter for emission and by scanning fluorescence after exposing the preparation to ultraviolet light at 365 mµ to destroy the thiochrome fluorescence. With this technique it has been shown that, with every preparation of nervous tissue that has been examined, thiamine is present only in membranes and not in axoplasm. This finding is discussed in relation to a suggested role of the vitamin in ion transport.