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PubMed1981

Glycoconjugates in salivary glands of rats during postnatal development.

In the salivary glands of young rats in different experimental conditions, we have found glycoconjugates containing hexosamines, hexoses, fucose and sialic acid in lower percentages than those found in adult rats. In the submandibular gland, the presence of sialic acid can be demonstrated only after the second week, whereas in the sublingual gland sialic acid is present in an amount roughly equal to half of what has been found in adult animals. The appearance of sialic acid in the submandibular gland is due to the development of the animals and not, as we had initially surmised to their diet.

Animals↗
PubMed1994

Sialylation of terminal saccharides of glycoconjugates expressed by murine molar tooth germs developing in vitro and in vivo.

During development of the mammalian tooth germ the pattern of terminal saccharides of glycoconjugates changes, with many structures losing lectin reactivity in a consistent pattern. This study investigated whether the epitopes are lost or become masked by terminal sialylation, using a combination of neuraminidase treatment of sections and sialic acid-reactive lectins. The results suggested that most of the terminal galactosamine and fucose sites in the epithelial enamel organ were removed during morphogenesis. Conversely, during condensation of the dental mesenchyme, masked peanut agglutinin (PNA)-reactive galactose epitopes appeared. During differentiation and organisation of the mesenchyme into odontoblasts and a subodontoblastic layer the PNA-reactive sites became masked again. These regions also specifically expressed sialylated glucosamine. However, at the proliferating epithelial cervical loop galactose sites appeared to be masked. This was more pronounced during in vitro development when abnormal expression of PNA-reactive sites was found at the cervical loop. Additionally, fucosylated sites persisted in the enamel organ, further indicating that the expression of terminal saccharides was disrupted during development in the organ culture system. These data suggest that loss of terminal galactose and galactosamine is related to differentiation of the cells. However, whether this loss occurs by removal or sialic acid masking is not dependent either on the origin of the cells or the epitope being lost.

Animals↗
PubMed1995

Carcinoembryonic antigen and other glycoconjugates act as ligands for galectin-3 in human colon carcinoma cells.

Galectin-1 and galectin-3, galactoside-binding lectins with molecular weights of M(r) 14,500 and 31,000, respectively, are expressed in normal and malignant cells and have been implicated in regulation of cell growth, adhesion, and metastasis. We analyzed the expression of galectins in 21 cultured human colon carcinoma cell lines by immunoblotting. Galectin-1 was detected in only 7, whereas galectin-3 was found in 20 of the cell lines. KM12 cells, which express only galectin-3, were used to isolate this lectin by affinity chromatography, and the purified lectin was used to identify complementary glycoconjugates by blotting. Galectin-3 was shown to bind to human laminin, carcinoembryonic antigen, and lysosome-associated membrane glycoproteins, which are involved in cell adhesion. Galectin-3 was localized on the KM12 cell surface and colocalized with carcinoembryonic antigen. Several endogenous glycoproteins and cell surface proteins of molecular weights in the range M(r) 58,000 to > 200,000, including carcinoembryonic antigen and lysosome-associated membrane glycoproteins, were identified as galectin-3 ligands by coimmunoprecipitation with and affinity chromatography on immobilized galectin-3. These data demonstrate that galectin-3 interacts with several adhesion molecules and suggest that this lectin may have a role in human colon carcinoma cell adhesion.

Antigens, CD↗
PubMed1997

Remodeling of glycoconjugates on CD44 enhances cell adhesion to hyaluronate, tumor growth and metastasis in B16 melanoma cells expressing beta1,4-N-acetylglucosaminyltransferase III.

Beta1-4 N-acetylglucosaminyltransferase III (GnT-III) synthesizes bisecting N-acetylglucosamine structures on asparagine-linked oligosaccharides. Using B16-hm mouse melanoma cells stably expressing GnT-III activity as positive transfectants, the effect of bisecting N-acetylglucosamine on the function of CD44 was analyzed in association with adhesion to hyaluronate and tumor spread in mice. Transfection of GnT-III caused increased affinity of immunoprecipitated CD44 to erythro-agglutinating phytohemagglutinin, that preferentially recognizes bisecting N-acetylglucosamine, without affecting the surface CD44 amount, indicating an increase in bisecting N-acetylglucosamine residues on CD44 in positive transfectants. CD44-mediated adhesion to immobilized hyaluronate and the binding of fluorescence-labeled hyaluronate to the cell surface were increased in positive transfectants. The enhanced adhesion in positive transfectants was suppressed by the treatment with beta-N-acetylhexosaminidase, indicating that N-acetylglucosamine residues were responsible for the enhanced adhesion. Positive transfectants showed promoted CD44-mediated tumor growth and metastatic development in the spleen after subcutaneous inoculation into mice. These results indicate that glycosylation of CD44 due to GnT-III causes enhanced adhesion to hyaluronate, local tumor growth and metastatic growth in spleen, suggesting that the CD44-mediated adhesion and tumor spread can be modified through introduction of a glycosyltransferase gene.

Acetylglucosamine↗
PubMed2001

Wedgelike glycodendrimers as inhibitors of binding of mammalian galectins to glycoproteins, lactose maxiclusters, and cell surface glycoconjugates.

Galectins are mammalian carbohydrate-binding proteins that are involved in cell-cell and cell-matrix adhesion, cell migration, and growth regulation with relevance to inflammation and tumor spread. These important functions account for the interest to design suitable low molecular weight inhibitors that match the distinct modes of presentation of the carbohydrate recognition domains of the different galectin subfamilies. Using 3,5-di-(2-aminoethoxy)benzoic acid as the branching unit, wedgelike glycodendrimers with two, four, and eight lactose moieties (G1-G3) were synthesized. They were tested in solid-phase competition assays with lactose maxiclusters and various N-glycan branching profiles (miniclusters) as the matrix and also in cell assays. Prototype galectins-1 and -7, chimera-type galectin-3, a plant (AB)(2) toxin, and a lactose-binding immunoglobulin G fraction from human serum were the carbohydrate-binding targets. Potent inhibition and remarkable cluster effects were seen for the homodimeric galectin-1, especially in combination with biantennary N-glycans as the matrix. Remarkably, for the tetravalent G2 glycodendrimer, the inhibitory potency of each lactose unit reached a maximum value of 1667 relative to free lactose. In haemagglutination experiments as a model for cell adhesion, galectin-3 was markedly sensitive to increased sugar valency and a relative potency per lactose of 150 was reached. The spatial orientation of the carbohydrate recognition domains of the endogenous lectins and the branching pattern of the carbohydrates of the glycoprotein matrices used are both important factors in the design and synthesis of glycodendrimers with galectin-selective properties.

Animals↗
PubMed2002

Towards a synthetic glycoconjugate vaccine against Neisseria meningitidis A.

Albumin conjugates of synthetic fragments of the capsular polysaccharide of the Gram-negative bacterium Neisseria meningitidis serogroup A were prepared. The fragments include monosaccharides 1 [alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)] and 2 [6-O-P(O)(O(-))(2)-alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)], disaccharide 3 [alpha-D-ManpNAc-[1-->O-P(O)(O(-))-->6]-alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)], and trisaccharide 4 [alpha-D-ManpNAc-[1-->O-P(O)(O(-))-->6]-alpha-D-ManpNAc-[1-->O-P(O)(O(-))-->6]-alpha-D-ManpNAc-(1-->O)-(CH(2))(2)NH(2)]. Two monosaccharide blocks were employed as key intermediates. The reducing-end mannose unit featured the NHAc group at C-2, and contained the aminoethyl spacer as the aglycon for the final bioconjugation. The interresidual phosphodiester linkages were fashioned from an anomerically positioned H-phosphonate group in a 2-azido-mannose building block. The spacer-linked saccharides 1-4 were N-acylated with hepta-4,6-dienoic acid and the resulting conjugated diene-equipped saccharides were subjected to Diels-Alder-type addition with maleimidobutyryl-group functionalized human serum albumin to form covalent conjugates containing up to 26 saccharide haptens per albumin molecule. Complete (1)H, (13)C, and (31)P NMR assignments for 1-4 are given. Antigenicity of the neoglycoconjugates containing 1-4 was demonstrated by a double immunodiffusion assay which indicated that a fragment as small as a monosaccharide is recognized by a polyclonal meningococcus group A antiserum and that the O-acetyl group(s) present in the natural capsular material is not essential for antigenicity.

Carbohydrate Sequence↗
PubMed1988

Glycoconjugate histochemistry of the rat fundic gland using Griffonia simplicifolia agglutinin-II during the development.

The development and maturation of fundic glands of Wistar rats were studied using Griffonia simplicifolia agglutinin-II (GSA-II) histochemistry at the light microscopic and electron microscopic levels. In adult rats, mucous neck cells and cells intermediate between mucous neck cells and chief cells were specifically labeled with GSA-II, whereas other fundic gland cells were virtually negative. Ontogenetic studies revealed that GSA-II positive cells appeared at the bottom of the gland by 21 days of gestation. With differentiation and aging, the elongation of the fundic gland continued, and the labeling intensity of the mucous neck cells increased by 3 weeks after birth. Cells intermediate between mucous neck cells and chief cells were discernible from 3 days after birth. Typical mucous neck cells appeared at 3 weeks after birth, when their labeling intensity with colloidal gold (CG) particles approximated that of adults. On the other hand, the reactive cell population gradually moved from the bottom toward the middle portion of the gland. Finally, the reactive cells were localized at the neck portion of the fundic gland. These results suggest that GSA-II is a valuable marker for studying mucous neck cells and both their precursor cells and their derivatives.

Acetylglucosamine↗
PubMed1991

Glycoconjugate histochemistry of Xenopus laevis fundic gland with special reference to mucous neck cells during development.

Mucous neck cells (MNCs) of the fundic gland are phylogenetically thought to have first appeared in amphibians. We studied the origin and differentiation of MNCs in fundic glands of Xenopus laevis. By means of lectin histochemical methods using Griffonia simplicifolia agglutinin-II (GSA-II), MNCs were detected specifically in fundic glands of adult X. laevis. Mucous granules of MNCs were labeled by GSA-II-colloidal gold (CG) staining. Other cells such as surface mucous cells (SMCs), oxynticopeptic cells (OPCs), and endocrine cells did not react to GSA-II. Ulex europaeus agglutinin-I specifically stained OPCs, but not MNCs and SMCs. During the morphogenetic period of the stomach in metamorphosing larvae, GSA-II reactive cells randomly appeared in various portions of the underdeveloped fundic glands and then rapidly localized in the neck portion. At this time, newly appearing mucous granules of MNC type were labeled by GSA-II-CG. Two types of cells intermediate to MNCs and SMCs and intermediate to MNCs and OPCs were observed in the larval gastric region. Cells intermediate to MNCs and OPCs were also found in adults. In these cells, mucous granules of MNC type were labeled by GSA-II-CG, but mucous granules of SMC type and zymogen-like granules did not react to GSA-II. These observations suggest that GSA-II is a useful marker in studying the differentiation of MNCs and their precursors regardless of species differentiation.

Animals↗
PubMed1991

Changes in glycoconjugate expression during early chick embryo development: a lectin-binding study.

A selection of lectins was used to investigate developmentally regulated changes in the distribution of cell surface oligosaccharides during the gastrulation and neurulation stages of early chick embryo development. Lectins from three specificity classes were used: glucose/mannose specificity (concanavalin A [Con A], Lens culinaris agglutinin [LCA], Pisum sativum agglutinin [PSA]); N-acetylglucosamine specificity (Lycopersicon esculentum agglutinin [LEA], wheat germ agglutinin [WGA], succinylated WGA [sWGA]); N-acetylgalactosamine/galactose specificity (Dolichos biflorus agglutinin [DBA], soybean agglutinin [SBA], Sophora japonica agglutinin [SJA], Bandeiraea (Griffonia) simplicifolia lectin I [BSL I], peanut agglutinin [PNA], Artocarpus integrifolia lectin [Jacalin], Ricinus communis agglutinin-1 [RCA-1], Erythrina cristagalli lectin [ECL]). At gastrulation stages, patterns of lectin binding could be distinguished in the epiblast, mesoderm, and endoderm cell layers. The primitive streak failed to bind any of the lectins, but LEA and WGA bound to the epiblast in regions lateral to the streak, indicating the loss of some glucosamine residues medially in preparation for the ingression movements of gastrulation. Several lectins showed marked binding to the mesoderm cells after their passage through the primitive streak; these were LCA, PSA, WGA, sWGA, BSL, and most particularly PNA. Therefore, the epithelial-mesenchymal transformation from epiblast to mesoderm at the primitive streak is accompanied by cell surface oligosaccharide changes in the epiblast and mesoderm that involve all classes of lectins including the PNA-binding sequence Gal beta 1-3GalNAc. Ultrastructurally, PNA was shown to bind extracellularly to matrix fibrils. Jacalin, having the same sugar specificity as PNA, but binding to serine/threonine linked chains rather than asparagine linked chains showed no binding to the mesoderm.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Heterogenous distribution of glycoconjugates in the kidney of dogfish Scyliorhinus caniculus (L.) with reference to changes in the glycosylation pattern during ontogenetic development of the nephron.

Eight fluorochrome-coupled lectins with different sugar specificities were applied to cryosections of dogfish kidney. Despite profound differences in renal architecture between elasmobranch fish and other vertebrates, the sequence of nephron segments as revealed by the lectin-binding pattern was rather similar to that of tetrapodes. Wheat germ agglutinin (WGA) bound to cell membranes of epithelial cells of glomeruli, proximal and distal tubules, their basement membranes, the collecting tubule, and epithelial cells. Among other broadly binding lectins were Ricinus communis agglutinin I (RCA-I), soybean agglutinin (SBA), peanut agglutinin (PNA), Lycopersicon esculentum agglutinin (LEA), and Jacalin, all of which marked proximal as well as distal portions of the renal tubule. Dolichos biflorus agglutinin (DBA) did not react with any renal structure. Ulex europaeus agglutinin I (UEA-I), which indicates the presence of alpha-L-fucose, very strongly and specifically marked single epithelial cells of the early distal nephron, all epithelial cells of the late distal tubule, the beginning of the collecting tubule in the mesial tissue zone, and single cells in the end portion of the collecting tubule in the lateral bundles. Binding of UEA-I to receptors of distal nephron cells could be useful for the identification of these cells in functional studies employing teased tubule and/or isolated cell preparations. Binding of UEA-I to dogfish kidney structures resembles staining with UEA-I conjugates of late distal tubules and collecting tubules in the kidneys of frog and other, higher vertebrates. Epithelial cells of early developmental stages showed, very rarely, binding sites for most lectin-fluorochrome conjugates. A large number of lectin binding sites was observed in the extracellular matrix of fibroblast layers surrounding the early anlage and the S-shaped body. Lectin binding sites of the nephron epithelia appeared in a sequential manner in the next stages of development of the nephron. Ontogenetic and phylogenetic aspects of the merging region between nephron proper (late distal tubule) and collecting system (collecting tubule) are discussed.

Animals↗
PubMed1995

Hydrolytically stable cellulose-derivative coatings for capillary electrophoresis of peptides, proteins and glycoconjugates.

A method for the preparation of versatile, hydrolytically stable coatings of fused silica capillaries is described. First, the HNO3-pretreated silica surface is reacted with 7-oct-1-enyltrimethoxysilane to form a stable self-assembled alkylsilane monolayer. Secondly, the copolymer of hydroxypropylcellulose and 2-hydroxyethyl methacrylate is statically coated onto a hydrophobized wall. This allows the formation of a highly crosslinked copolymer layer which is tightly bound to the wall surface. Hydrolytical stability in the pH range of 2-10 for several weeks has been demonstrated. The coating generates a low electroosmotic flow at alkaline pH, which can be easily masked by using special buffers. The versatility of this column technology is documented by separations of peptides, glycoproteins and derivatized oligosaccharides.

Capillary Action↗
PubMed2005

Sheathless reverse-polarity capillary electrophoresis-electrospray-mass spectrometry for analysis of underivatized glycoconjugates.

We report on the development of a novel methodology to extend the limits of capillary electrophoresis-electrospray ionization-mass spectrometry (CE-ESI-MS) general applicability. A sheathless on-line CE-ESI-MS setup was optimized on standard monosaccharide mixture to operate in reverse polarity and negative ion mode for MS detection without pressure to assist the sample migration, coating of the capillaries, and/or sample derivatization. This approach was further applied for screening of a complex glycopeptide mixture obtained from the urine of a patient diagnosed with N-acetylhexosaminidase deficiency, known as Schindler's disease. The potential of this methodology in terms of high sensitivity, separation efficiency, resolution, and reproducibility is demonstrated. In combination with the high quality of MS data, a new, significantly improved insight into the sample heterogeneity is possible.

Carbohydrate Sequence↗
PubMed1995

Structural effect of galactose residue in synthetic glycoconjugates on interaction with rat hepatocytes.

N-p-Vinylbenzyl-O-beta-D-galactopyranosyl-(1,4)-D-gluconamide++ + (PVLA) has been used as an asialoglycoprotein model polymer. Rat hepatocytes expressing asialoglycoprotein receptors are capable of binding to hydrophobic plastic dishes coated with PVLA. PVLA, water-soluble polystyrene derivatives bearing galactose residues preferentially adsorb to plastic plates made of polystyrene rather than those of poly(methyl methacrylate). Hence, we modified chitosan beads with linear chains composed of a long alkyl or phenyl moiety to study the effect of structural variations of adsorbed PVLA, and investigated the extent of hepatocyte attachment to the hydrophobic beads coated with PVLA. The attachment was independent of the amount of immobilized PVLA; rather, it was dependent on the hydrophobicity of the beads with PVLA. To simplify the surface of the hydrophobic beads with PVLA, galactopyranoses were covalently linked to chitosan beads via hydrophobic spacer arms, and hepatocyte attachment was compared among the prepared beads. The beads with spacer arms containing phenylalanine and a phthalic moiety showed increased hepatocyte attachment, which was elicited by galactose residues on the beads. These results suggest that rotational restriction or stiffness and hydrophobicity due to the phenyl moiety are essential to enhance the specificity of terminal galactose in PVLA. This analysis contributes to the design and optimization of an artificial ligand for cellular receptors recognizing sugar moieties.

Animals↗
PubMed1988

Differential localization of glycoconjugates having affinity for concanavalin A on the surface of the sperm head in the testis, the epididymis, and the ejaculate of the ram.

The localization of Con A receptors on the surface of the head of ram spermatozoa originating from the rete testis, from three regions of the epididymis, or from the ejaculate was investigated using a gold-Con A labelling technique. Electron microscopic observation revealed three major localizations, each being characteristic of the origin of the spermatozoa: periacrosomal in the rete testis, postacrosomal in the epididymis, on the entire surface of the sperm head in the ejaculate.

Animals↗
PubMed1999

Expression of serum amyloid A3 mRNA by inflammatory macrophages exposed to membrane glycoconjugates from Trypanosoma cruzi.

Differential display reverse transcriptase-polymerase chain reaction (PCR) was used to identify genes expressed by murine macrophages exposed to glycosylphosphatidylinositol-anchored mucin-like glycoproteins isolated from Trypanosoma cruzi trypomastigotes. Among the different PCR product bands identified in the differential display gel, one showed high homology with the serum amyloid A3 protein (SAA3). Northern blot assays showed augmentation of SAA3 mRNA expression by inflammatory macrophages exposed to live trypomastigotes or parasite glycolipids, as compared to unstimulated macrophages. Our results also showed the expression of SAA3 mRNA, in liver and heart from animals in the acute phase of Chagas disease. It is important that expression of SAA3 mRNA was closely associated with tissue parasitism and presence of inflammatory cells. Together, our findings indicate the possible involvement of SAA3 protein on immunopathology of Chagas disease and establish a new infectious disease model to study the pathophysiological role of this acute-phase protein.

Animals↗
PubMed2003

Surface glycoconjugates in the olfactory system of Ambystoma mexicanum.

Lectin binding histochemistry was performed on the olfactory system of neotenic and metamorphosed Ambystoma mexicanum to investigate the distribution and density of defined carbohydrate residues on the cell surface glycoproteins of the olfactory and vomeronasal receptor cells and their terminals in the olfactory bulbs. The lectin binding patterns indicate that the main olfactory system possesses a high density of N-acetyl-galactosamine and N-acetyl-glucosamine residues, while the vomeronasal system contains a high density of N-acetyl-galactosamine and galactose moieties and a moderate density of N-acetyl-glucosamine. The presence of specific glycoproteins, whose terminal sugars are detected by lectin binding, might be related to the chemoreception and transduction of the odorous message into a nervous signal or to the histogenesis and development of the olfactory system. In fact, the olfactory and vomeronasal receptor cells are neurons that undergo a continuous cycle of proliferation not only during development but also in mature animals.

Acetylgalactosamine↗