The technique shown demonstrates staining of which substance group?

• A. Both carboxylated and sulfated mucosubstances
• B. The basement membrane
• C. Aldehydes
• D. Kidney

Answer: (A)

The key idea is that this staining method targets acidic mucosubstances, which are glycosaminoglycans with negative charges from carboxyl and sulfate groups. The dye used is cationic and binds to those negative sites, so tissues rich in these mucosubstances take up the stain.

At the staining conditions used, both carboxylated and sulfated mucosubstances are stained, making this method able to reveal a broad range of acidic mucopolysaccharides. Neutral mucosubstances wouldn’t take up the dye under these conditions, so the result specifically highlights the acidic group-containing mucosubstances.

So, the technique is best described as staining both carboxylated and sulfated mucosubstances. It isn’t about staining aldehyde groups or identifying a tissue like the basement membrane or an organ such as the kidney, but about the chemical class of mucosubstances themselves.