N-Glycans in Xenopus laevis testis characterised by lectin histochemistry

Different Glycoconjugate Content in Mucus Secreting Cells of the Rat Fundic Gastric Glands

The fundic glands of the stomach contain two types of mucous cells: surface mucous cells (SMCs) located at the surface of the stomach and the pits, and mucous neck cells (MNCs) situated in the neck of the glands. They produce mucins, highly glycosylated proteins. Very little is known about the glycan composition of these mucins and of gastric secretion in general. We used several lectins combined with deglycosylation pretreatments to analyze the glycan composition of SMCs and MNCs. The results showed the presence of terminal sialic acid and subterminal Gal and GalNAc, which is consistent with previous knowledge about glycosylation in mucins. Our results also support previous reports that showed a different expression of mucins in the SMCs, depending on their superficial or deep location in the pit. Some lectins labeled only the perinuclear region of the SMCs, but not the apical region, where the secretory granules are stored. This suggests that the lectins are labeling sugar residues that are accessible to lectins during the first steps of glycan synthesis, which occurs in the endoplasmic reticulum and Golgi apparatus. Our results indicate that SMCs and MNCs produce a mucus secretion with a different glycoconjugate composition. The secretion is more varied in SMCs. As our results coincide with what we know about glycosylation of mucins, we can conclude that most of the glycans detected belong to mucins, and the differences in glycosylation observed in each cell type may be due, mainly, to the different secreted mucins. Anat Rec, 301:2128-2144, 2018. © 2018 Wiley Periodicals, Inc.

Transdifferentiation of mucous neck cells into chief cells in fundic gastric glands shown by GNA lectin histochemistry

The epithelium of the gastric mucosa and its glands in the corpus of rat stomach contains mucous surface cells (MSCs), parietal cells, mucous neck cells (MNCs), zymogenic or chief cells (ZCs), several types of enteroendocrine cells, and intermediate cells with characteristics between MNCs and ZCs also called transitional or prezymogenic cells (pre-ZCs). The aim of our work was to analyze the expression of Mannose (Man) in the rat gastric glands by means of Galanthus nivalis lectin (GNA) histochemistry to identify the differences between MNC, pre-ZCs and ZCs and to establish the relationships between these cells. Most of the cytoplasm of MNCs was negative for GNA histochemistry. Intensity of GNA labeling in the gastric gland showed a graduation from pre-ZCs (weak labeling) to ZCs (moderate labeling). Labeling of ZCs was stronger at the perinuclear and apical cytoplasm. In the last years, strong evidence has been reported supporting that ZCs differentiate from MNCs. Our work also supports the origin of ZCs from MNCs, because the GNA labeling graduation might be due to oligosaccharides which are not expressed in MNCs, start to express in pre-ZCs and are more abundant in ZCs, indicating that differentiation from MNCs to ZCs is a process in which glycans with Man moieties are synthesized.

Characterization by Lectin Histochemistry of Two Subpopulations of Parietal Cells in the Rat Gastric Glands

Parietal cells undergo a differentiation process while they move from the isthmus toward the pits and the base region of the gastric gland. The aim of this work was to analyze the rat gastric glands by lectin histochemistry to show the glycans expressed by upper (young) and lower (old) parietal cells. We used lectins recognizing the most frequent sugar moieties in mammals. Each lectin was assayed alone and in combination with several deglycosylation pretreatments: (1) β-elimination, which removes O-linked oligosaccharides; (2) incubation with Peptide-N-glycosidase F, to remove N-linked glycans; (3) acid hydrolysis, which removes terminal sialic acid moieties; (4) methylation-saponification, to remove sulfate groups from sugar residues; and (5) glucose oxidase, a technique carried out with the lectin concanavalin A to convert glucose into gluconic acid. The lectins from Helix pomatia, Dolichos biflorus (DBA), Glycine max (soybean), Maclura pomifera, Arachis hypogaea (peanut), Bandeiraea simplicifolia (lectin I-B₄), and Datura stramonium showed a different glycan expression in the parietal cells throughout the gastric gland. This difference supports that parietal cells undergo a maturation/degeneration process while the cells descend along the gland. The role of DBA as a marker of parietal cells previously reported should be taken with caution because these cells showed different reactivity for the lectin, ranging from negative to strong labeling.