Comment about the paper M. Elleder and Z. Lojda. Studies in lipid histochemistry. I. Criticism of performic and peracetic reactions. Vol. 24, 7-20 (1970)

Histochemical studies of the colonic epithelial glycoproteins of the normal rabbit

Two general classes of glycoproteins have been identified in the colonic epithelial cells of New Zealand white rabbits. Each is associated with an ultrastructurally distinct secretory cell. The first of these classes is found in cells, termed vesiculated columnar cells, characterized by electron-translucent vesicles, a small rough endoplasmic reticulum-Golgi complex and prominent microvilli. The glycoproteins of the vesiculated cells contain abundant O-sulphate ester, sialic acids with ester substituents at positions C-8 or C-9 (or with two or three side chain substituents) and neutral sugars with vicinal diols whose periodate oxidation is prevented by an O-acyl ester substituent(s). The second class of glycoproteins occurs in goblet cells characterized by electron-dense vesicles, an abundant rough endoplasmic reticulum, a well-developed Golgi apparatus and few, if any, microvilli. Goblet cells along the entire length of the crypts contain neutral sugars with periodate-oxidisable vicinal diols and a ferriferricyanide-reactive component. Cells in the upper halves of the crypts also contain components that are sulphated, Schiff-reactive and acid-fast. In the lower halves of the crypts, the goblet cells contain smaller quantities of the above components plus sialic acids, some of which possibly have an O-acyl substituent located at position C-8 or C-9 (or which have two or three side chain O-acyl substituents). It is suggested that the function of the glycoproteins from the vesiculated columnar cells is protective and that from the goblet cells is lubricative.

Identification of tocopherol (vitamin E) in the skin and its histochemical detection

The epidermis upper layer reacts positively to the performic acid-toluidine blue and the performic acid-Schiff; such reactions were inhibited by a previous formalin-HgCl2 fixation. The substance accounted for that reactivity could be extracted from skin histological sections by means of the chloroform-methanol-HCl effect. If this same solvent was used on human skin shaven horny layer powder it was able to extract protein-lipid complex that displays the tocopherol histochemical reactivity. Since this complex was subjected to the KOH hydrolysis, an hexane-soluble lipid moiety could be isolated from the hexane-insoluble protein moiety. The isolated lipid moiety react as does the tocopherol histochemically, in opposite to the protein moiety that react negatively to the performic acid-toluidine blue and the performic acid-Schiff reactions. By using thin layer chromatography it was possible to isolate from the lipid moiety two substances identified as alpha-tocopherol and cholesterol in basis of its chromatographic properties, the first being the sole responsible by the performic acid-toluidine blue and performic acid-Schiff reactivity of the lipid moiety. From the other fractions isolated from the horny layer powder, either the lipid or the protein ones do not show positive performic acid-toluidine blue or performic acid-Schiff reaction. It was deduced, in basis of these findings that the positivity of such reactions on the epidermis upper layer keeps a close correlation with the alpha-tocopherol, contained by the protein-lipid complex. The ethylenic double bonds from lipids and the S-S group from protein could not be taken as responsible by them. On the other hand, the peracetic acid-toluidine blue reaction shows a proper histochemical meaning, since it is able to detect free cholesterol.