Thiosemicarbazide-ferricyanide reduction for the histochemical demonstration of aldehydes in tissue sections

Abstract

Aldehydes produced from carbohydrates by oxidation or acid hydrolysis may be visualized by application of aqueous thiosemicarbazide followed by Schmorl's ferricyanide reduction. The thiosemicarbazide reacts with the aldehydes by its hydrazine group, while its thiocarbamyl group remains active. The thiocarbamyl moiety is a strong reducing group that converts ferricyanide to ferrocyanide in Schmorl's reaction. The ferrocyanide is trapped immediately by the ferric salt, which deposits Prussian blue at the site of the aldehydes thereby demonstrating the location of the original substance.

Key words::

• aldehyde
• carbohydrate
• DNA
• Feulgen
• hydrolysis
• PAS
• Prussian blue
• Schmorl
• thiosemicarbazide

Acknowledgments

I should like to thank Allen Smith, Professor of Anatomy in the School of Podiatric Medicine at Barry University, Miami Shores, FL and Colleen Forster, Scientist at the Academic Health Center, University of Minnesota, both of whom were kind enough to prepare some stained slides. Thanks also to the members of Histonet who provided paraffin blocks of fungal tissue when I began to develop this method.

Declaration of interest statement: The author reports no conflict of interest. The author alone is responsible for the content and writing of this paper.