Histochemical Studies on the Zinc in the Islets of Langerhans of the Pancreas

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Histochemical test for Zinc was first reported by Okamoto and his coworkers in 1944 with use of diphenylthiocarbazide and dithizone. Since then a number of other reports of various methods came in attention but all of these were based on the identical principle. Mager's method is one emphasis placed on a specificity for Zinc only when freshly frozen section. was made of the Islets of Langerhans of pancreatic tissue, but admitted negative result almost always if alcohol fixation of the tissue would be followed by sectioning in paraffin embedding.
These findings have been reportedly true with the results obtained by applying the method of Amann and Wolff to the fresh frozen section. A positive test, however, can ce obtained by Okamoto et al or Maeda et al method using alcohol fixed, paraffin section. Timm, also, had succeeded to obtain positive test even with alcohol fixation and paraffin sectioning with application of magnesium dithizonate.
Okamoto at the same time stated that the reaction for Zinc was hardly obtainable if ammonium chloride or ammonium carbonate solutions was employed as a medium in differentiating the other metals which would present reaction resembling Zinc.
In our investigation, nevertheless, we have reached a conclusion that it is always possible to obtain a positive test when freshly frozen section were tried. Present experiment was carried out to seek possible explanation if any for the nature of difference in reaction between fresh section specimen and paraffin section one after alcohol fixation.