The AB/PAS method
was used to stain for acidic glyconjugates (staining blue) and periodate
reactive vicinal diols (staining purple), as well as visualising cells that
contain a mixture of both (staining violet). The HID/AB sequence was
used to differentiate the acidic glycoconjugates, i.e. those that are
sulphated and stain a brownish-black colour fromthose that are carboxylated,
non-sulphated and stain blue.