Histochemical demonstration of asparagine-linked oligosaccharides in glycoproteins of human placenta and umbilical cord tissues by means of almond glycopeptidase digestion

Lectin binding in the umbilical cord in altered glycemia

OBJECTIVE

Content and distribution of the oligosaccharides in the umbilical cord from pregnancies with altered glycemia were investigated.

STUDY DESIGN

A prospective cohort study was conducted in the Florence Policlinic of Careggi, Italy. Samples of cord from physiological pregnancies (n=20), from pregnancies with minor degree of glucose intolerance (n=20) and from pregnancies with gestational diabetes mellitus (GDM) treated with insulin (n=20) were collected. Eleven lectins were used (ConA, WGA, PNA, SBA, DBA, LTA, UEA I, OOA, GSL II, MAL II and SNA) in combination with chemical and enzymatic treatments.

RESULTS

Increase of N-acetyl-d-glucosamine and a loss of sialic acid in the umbilical cord of the cases with minor degree of glucose intolerance with respect to the other study groups was observed. d-Galactose(beta1-->3)-N-acetyl-d-galactosamine, N-acetyl-d-galactosamine and l-fucose were in less amount in both the pathological groups with respect to the control one.

CONCLUSION

The increase of some glycoconjugates carbohydrates and the loss of others in the umbilical cord from pregnancies with minor degree of glucose intolerance might be related to its morphofunctional alterations in a not diabetic altered glycemia. Moreover, the treatment with insulin in the GDM might play a role in restoring partially the normal glycosilation in the cord components in the attempt to renew some their functions.

Localization of blood-group-related linear poly-N-acetyllactosamine structure in different human tissues by Griffonia simplicifolia agglutinin-II staining following endo-beta-galactosidase digestion

Endo-beta-galactosidase from Escherichia freundii cleaves polylactosaminyl structures as follows: R-GlcNAc beta I-3Gal beta I-4GlcNac beta I-R' + H2O-->R-GlcNAc beta I-3Gal + GlcNAc beta I-R'. By staining with Griffonia simplicifolia agglutinin-II following the enzyme digestion, the distribution of R-GlcNAc beta I-3Gal beta I-4GlcNAc can be demonstrated in tissue sections. This carbohydrate chain is one of the backbone structures carrying the blood-group-related antigens and, thus, localization of this structure may provide detailed information about the distribution of variants with different backbone structures. Various formalin-fixed, paraffin-embedded tissue sections were stained by Griffonia simplicifolia agglutinin-II with or without prior enzyme digestion and the reactivity of the agglutinin imparted by enzyme digestion was studied in the following tissues and cells: pancreatic acinar cells, gastric surface mucosae, duct cells and mucous cells of salivary glands and tracheal glands, surface epithelium of trachea, goblet cells of large intestine, columnar epithelium of uterine cervical glands, distal and collecting tubules of kidney, certain cells of anterior lobe and colloid of middle lobe of pituitary glands, epithelial reticular cells and Hassall's corpuscles of thymus and Kupffer cells of liver. In gastric surface mucosae, the reactivity of the agglutinin appeared in non-secretor individuals but not in the secretor individuals, and in mucous cells of salivary and tracheal glands the reactivity appeared in Le(a- b-) non-secretor individuals but not in Le(a + b-) non-secretor or secretor individuals.(ABSTRACT TRUNCATED AT 250 WORDS)

Histochemical and cytochemical localization of blood group antigens

The oligosaccharide structures of blood group antigens are not the primary gene products; they are constructed in a stepwise manner by adding particular sugar to precursor oligosaccharides via several glycosyltransferases coded for by different blood group genes (Watkins 1966, 1978, 1980). Consequently, final profiles of antigens expressed in each cell type are influenced by many different factors such as the intrinsic composition of glycosyltransferase species which are defined by the genotype of the individuals, relative activity or amount of these enzymes (repression, derepression or induction of the enzymes), competition between enzymes with overlapping substrate specificity, the organization of the enzymes in membranes, utilizability of precursors and specific substrate sugars, and the activity level of degradating enzymes. Changes in the antigen profiles during maturation, differentiation and malignant transformation are thought to be intimately related to the variability of these factors. Although great importance attaches to histo- and cytochemical information on the distribution and levels of glycosyltransferases and messenger RNA corresponding to the relevant enzyme, detailed and precise localization of the blood group antigens and their variants is the base line for analyzing these complex factors. On the basis of individual genotype and histochemical findings about the antigen distribution and the interrelationship between cells and cellular components producing different antigenic structures (cellular and subcellular mosaicism), we can deduce precursor oligosaccharide levels as well as the status of gene activation and its primary product, glycosyltransferases. Thus, these findings are a prerequisite for further analysis at the molecular genetic level. As emphasized in this article, lectin staining or immunostaining methods with MAbs combined with glycosidase digestion procedures are powerful tools for in situ analysis of carbohydrate structures in histochemical systems. Although in some cases valuable results have been obtained by applying the technique, our knowledge concerning the distribution of complex carbohydrate structures is still far from satisfactory. Along with well defined MAbs and lectins, the key to developing our methods further is successful introduction of glycosidases, in particular, endoglycosidases since these reagents are indispensable for analyzing the inner core structures and glycoconjugate species of the blood group antigens. Application of these techniques at the ultrastructural level is an alluring possibility, even though many difficulties must be overcome. Although their functional roles have not yet been determined, a diverse array of macromolecules is known to be decorated with blood group-related antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Identification of extra-villous trophoblast cells in human decidua using an apparently unique murine monoclonal antibody to trophoblast

Murine monoclonal antibodies were raised to human first trimester trophoblast cells. Eleven antibodies reacted with first trimester trophoblast, tested by immunoperoxidase staining on frozen sections, but only one had apparent specificity for trophoblast after examining reactivities with a panel of other cells and tissues. This antibody, designated FD0161G, bound selectively to syncytiotrophoblast and non-villous trophoblast in first trimester and term placentae. Villous cytotrophoblast was negative. This was clearly demonstrated on freeze-dried, paraffin embedded tissue sections which have superior architecture to frozen sections. FD0161G reacted with extra-villous trophoblast cells in human decidua which are also delineated by a monoclonal anti-cytokeratin antibody. Unlike the latter, however, FD0161G did not react with decidual glands. Thus FD0161G could be used as a specific probe for extra-villous trophoblast in decidual tissue.

The histochemistry of asparagine-linked oligosaccharides of glycoproteins in mammalian and avian tissues as studied by digestion with almond glycopeptidase

In a series of mammalian and avian tissues, asparagine-linked oligosaccharides of glycoproteins have been localized histochemically by means of combined periodic acid-Schiff (PAS) and almond glycopeptidase digestion procedures. According to the present results, the particular saccharide residues were found to be localized primarily in glycoproteins of connective and muscular tissue elements but were hardly visualizable or absent in glycoproteins of epithelial tissue elements. In view of the substrate specificity of almond glycopeptidase and the known staining selectivity of the PAS reaction, the majority of connective and muscular tissue elements are thought to be the main sites where plasma types of glycoproteins are involved.

Effects of digestion with N-oligosaccharide glycopeptidase upon certain lectin-peroxidase-diaminobenzidine reactions of glycoproteins in mammalian and avian tissues

To determine the histochemical localization of asparagine-linked oligosaccharides of glycoproteins in a series of different mammalian and avian tissues, the effects of digestion with N-oligosaccharide glycopeptidase upon certain lectin-peroxidase-diaminobenzidine reactions of the histological structures involved have been studied by light microscopy. Throughout the tissues examined, asparagine-linked oligosaccharides of glycoproteins were localized mainly in histological structures of connective and muscular tissues, but were hardly or not visualized in those of epithelial tissues. These results appear to lead to the concept that connective and muscular tissues represent the main sites where plasma types of glycoproteins are involved in mammalian and avian species.