Which technique would look almost identical to the technique in the image?

• A. Schmorl technique for reducing substances
• B. PAS
• C. Alcian blue pH 2.5
• D. Colloidal iron

Answer: (D)

Acidic mucopolysaccharides in tissue sections can be highlighted by different stains that end up producing very similar blue deposits. Alcian blue at pH 2.5 binds to sulfated and carboxylated glycosaminoglycans, giving a blue color where acidic mucins are present. Colloidal iron also targets these same negatively charged mucosubstances, resulting in a comparable blue staining pattern in the same locations. Because they both light up the same chemical groups, their appearances are nearly indistinguishable on the slide, which is why colloidal iron would look almost identical to the image you’re comparing it to. Other stains, like those for reducing substances or neutral polysaccharides, produce different colors or patterns, so they wouldn’t match as closely.