In the Hotchkiss-McManus modification of the PAS technique, aldehydes are formed by which reagent?

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Multiple Choice

In the Hotchkiss-McManus modification of the PAS technique, aldehydes are formed by which reagent?

Explanation:
In this modification of PAS, the key step is creating aldehyde groups by oxidizing carbohydrate-rich structures with periodic acid. Periodic acid cleaves vicinal diols in sugars and related molecules to generate aldehydes, which then react with Schiff reagent to produce the characteristic magenta color. This makes aldehyde formation the essential trigger for the PAS signal. Sodium borohydride would reduce aldehydes rather than create them, so it wouldn’t serve this purpose. Glutaraldehyde and formalin are fixatives—they preserve tissue structure but don’t provide the aldehyde-forming oxidation step used in this PAS modification.

In this modification of PAS, the key step is creating aldehyde groups by oxidizing carbohydrate-rich structures with periodic acid. Periodic acid cleaves vicinal diols in sugars and related molecules to generate aldehydes, which then react with Schiff reagent to produce the characteristic magenta color. This makes aldehyde formation the essential trigger for the PAS signal.

Sodium borohydride would reduce aldehydes rather than create them, so it wouldn’t serve this purpose. Glutaraldehyde and formalin are fixatives—they preserve tissue structure but don’t provide the aldehyde-forming oxidation step used in this PAS modification.

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