Histochemical identification of sialylated glycans in Xenopus laevis testis

Abstract

Carbohydrate chains of glycoprotein and glycosphingolipids are highly diverse molecules involved in many cell functions, including cell recognition, adhesion and signalling. Sialylated glycans are of special interest because the terminal position of sialic acid (NeuAc) in glycans linked by different ways to subterminal monosaccharides has been shown to be involved in several biological processes, as occurs with gangliosides, which have been reported as being essential in spermatogenesis in mammals. Some glycan-binding proteins, the lectins, which specifically recognize glycan sequences, have been extensively used to characterize tissue and cell carbohydrates by means of cytochemical techniques. The aim of the present work was to determine the presence of NeuAc by means of histochemical techniques in the testis of Xenopus laevis, an animal model widely used in cell and molecular biology research. However, considering that some NeuAc-binding lectins are capable of binding to N-acetylglucosamine (GlcNAc), other GlcNAc-binding lectins were also assayed. The results showed that NeuAc is mainly expressed in the interstitium, and only a weak labelling in the male germ cells was observed. Most NeuAc was located in O-linked oligosaccharides, but some masked NeuAc in N-glycans were identified in primary and secondary spermatogonia and spermatocytes. By contrast, GlcNAc was widely expressed in all germ cell types. Deglycosylative pre-treatments suggest that both N-and O-glycans and/or glycolipids could be responsible for this labelling. In addition, GlcNAc in O-linked oligosaccharides has been identified in spermatogonial cells. The acrosome of spermatids was always negative. Variations of glycan expression have been found in different cell types, suggesting that glycosylation is modified during spermatogenetic development.

Microvascular anatomy of testes in the adult pipid frog, Xenopus laevis Daudin: A scanning electron microscopic study of vascular corrosion casts

“…Xenopus laevis increasingly serves as an in-vitro and in-vivo model for the screening of Endocrine Disruptor Chemicals (EDCs) that affect hypophysis and thyroid glands as well as gonads, and as a model animal species to study reproductive toxicity of phytoestrogens (Cong et al, 2006). For these reasons, gonadal histomorphology (Cevasco et al, 2008;Kalt, 1976) and histochemistry (Valbuena et al, 2012(Valbuena et al, , 2010Valbuena, Alonso, Diaz Flores, et al, 2011;Valbuena, Alonso, Madrid, & Diaz Flores, and Saez, 2011b) are well documented in adult Xenopus. However, only one of the above-mentioned studies has paid attention to the testicular blood vessels (Cevasco et al, 2008).…”

“…Anatomy, morphology, fine structure, histochemistry and endocrine regulation of the anuran testes have been studied in great detail (e.g., Lofts, ; Duellman & Trueb, ; Valbuena, Madrid, Hernandez, & Saez, ; Valbuena, Alonso, Diaz Flores, Madrid, & Saez, ; Valbuena et al, ; Villagra, Ramos, Cisint, Crespo, & Fernandez, ). However, little is known on the vascular anatomy of the anuran testes.…”

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

“…15,30 The results obtained with lectin histochemistry could be interpreted taking into account that the specificity of a lectin is affected by (1) the linkage of the labeled sugar, 15,17,18 (2) the protein backbone of the glycoprotein, 31 and (3) the neighboring glycans, so the removal of O-linked glycans can modify the affinity for N-glycans or viceversa 22 or can unmask carbohydrates which were previously inaccessible to the lectin. 21 In this work, we have used 17 selected lectins which recognize the most frequent carbohydrate moieties in mammalian glycoproteins, that is, Fuc, GalNAc, Gal, NeuAc, GlcNAc, and Man, to identify the glycan composition of parietal cells in rat gastric glands.…”

“… Decreasing specificity is indicated by one or more “greater than” symbols. 18–22 Abbreviations: Fuc, fucose; Gal, galactose; GalNAc, N-acetylgalactosamine; NeuAc, sialic acid; GlcNAc, N-acetylglucosamine; Man, mannose; Glc, glucose. a AAL is sometimes abbreviated as AAA but then could be confused with the lectin from fresh water eel ( Anguilla anguilla ), which is usually abbreviated as AAA. b MAH is also abbreviated as MAA-II, MAA-2, and MAL-II. MAH should not be confused with MAL ( Maackia amurensis leukoagglutinin, also abbreviated as MAM, MAL-I, and MAA-I) or MAA (an undefined mixture of MAL and MAH). …”

“… Decreasing specificity is indicated by one or more “greater than” symbols. 18–22 Abbreviations: Fuc, fucose; Gal, galactose; GalNAc, N-acetylgalactosamine; NeuAc, sialic acid; GlcNAc, N-acetylglucosamine; Man, mannose; Glc, glucose. …”