Histochemical Demonstration of Carbohydrates

Oldest of all the histochemical tests is the iodine reaction 60) with starch, applied to plant histology in the early nineteenth century by Caventon and Raspail. For almost all purposes, it has been replaced by methods that give better color and contrast, and more permanent preparations. Still, the iodine reaction is used in a modem histochemical method for phos-phorylase (54)- 

More than seventy-five years ago, it was discovered that amyloid was colored red by a basic dye that is normally blue. Soon, it was learned that metachromasia, or the property of causing a change in the color of a pure dye when bound, is shown by many but not all mucinous substances when stained with any one of a number of thiazine dyes. Metachromatic 

A more critical approach to histochemical problems was heralded by the publication of Lison s Histochemie Animale in 1936 (55). Some of Lison s original studies dealt with the meaning of metachromasia, the effects of fixatives on glycogen, and other topics of carbohydrate histochemistry. Other milestones in histochemistry were the alkaline phosphatase method of Gomori (57) and the periodic acid - Schiff method for carbohydrates developed by McManus (55), Lillie 59), and Hotchkiss (50). The technical performance and fruitful results of these two methods did much to show the possibilities of histochemistry in histology and pathology. 

The formation of insoluble aldehydes from vicinal glycols or their amino derivatives by oxidants that include periodic acid, chromic acid (55), lead tetraacetate, 49) and many others is well known and widely used in histologic studies. (See Chapter VI for further information about these oxidants.) Although Schiff s leucofuchsin 49) is almost always used for the coloration of the insoluble aldehydes produced by oxidation, other indicators can be used (50). The requisite vicinal glycol groupings are usually plentiful in carbohydrates but are not always present and are not limited to carbohydrates. 

Histochemie animale/ Gauthier-Villars, Paris, 1936. 

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