Studies in lipid histochemistry. I. Criticism of performic and peracetic acid-schiff reactions

Region-specific variation in the properties of skeletal adipocytes reveals regulated and constitutive marrow adipose tissues

Marrow adipose tissue (MAT) accumulates in diverse clinical conditions but remains poorly understood. Here we show region-specific variation in MAT adipocyte development, regulation, size, lipid composition, gene expression and genetic determinants. Early MAT formation in mice is conserved, whereas later development is strain dependent. Proximal, but not distal tibial, MAT is lost with 21-day cold exposure. Rat MAT adipocytes from distal sites have an increased proportion of monounsaturated fatty acids and expression of Scd1/Scd2, Cebpa and Cebpb. Humans also have increased distal marrow fat unsaturation. We define proximal 'regulated' MAT (rMAT) as single adipocytes interspersed with active haematopoiesis, whereas distal 'constitutive' MAT (cMAT) has low haematopoiesis, contains larger adipocytes, develops earlier and remains preserved upon systemic challenges. Loss of rMAT occurs in mice with congenital generalized lipodystrophy type 4, whereas both rMAT and cMAT are preserved in mice with congenital generalized lipodystrophy type 3. Consideration of these MAT subpopulations may be important for future studies linking MAT to bone biology, haematopoiesis and whole-body metabolism.

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.

A technique to tocopherol (vitamin E) histochemical detection

A technique to detect tocopherol histochemically was proposed in basis on the following schedule: 1. toluidine blue and Schiff reagent negativity before a suitable oxidation; 2. performic acid-toluidine blue and performic acid-Schiff reagent positivity after fixing in formalin-CaCl2; 3. performic acid-toluidine blue and performic acid-Schiff reagent negativity after fixing in formalin-HgCl2; 4. ferric ferricyanide reaction positivity not influenced by the formalin-HgCl2 blockade. This technique tested on filter paper strips loaded with several lipids, steroids, vitamins, proteins, amino acids and ribonucleic acid shows that it is specific to tocopherols among the tested substances. Used on tissue sections this technique appears as very suitable to histochemical purposes.

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.