Lectin binding patterns in rat nasal-associated lymphoid tissue (NALT) and the influence of various types of lectin on particle uptake in NALT. (57/567)

We investigated the binding of four types of lectin to follicle-associated epithelium overlying the nasal-associated lymphoid tissue (NALT) of rats in order to identify M-cell specific surface markers and to determine the influence of lectin administration to NALT on the uptake of a particulate antigen. The NALT tissues were incubated with a panel of four types of lectin conjugated to horseradish peroxidase (HRP). Ulex europaeus-1 (UEA-1) and Dolichos biflorus (DBA) lectin stained the surface of M-cells and goblet cells. Uniform staining by Triticum vulgaris (WGA) was detected in the M-cells, ciliated cells and goblet cells. In contrast, staining of Griffonia simplicifolia I isolectin-B4 (GSI-B4) was almost exclusively M-cell specific. The administration of M-cell specific lectin (GS I-B4) to NALT suppressed the uptake of baker's yeast particles administered later, whereas the non-specific one (UEA-1) had no influence on the uptake. These results indicate that GS I-B4 is a useful marker for the identification of rat NALT M-cells and that such a specific expression of surface glycoconjugates by M-cells may permit the targeting of vaccines and drugs to the antigen sampling sites of the nose. It also appears possible to block the uptake of pathogens by an administration of M-cell specific lectin to NALT.  (+info)

The role of phosphomannose isomerase in Leishmania mexicana glycoconjugate synthesis and virulence. (58/567)

Phosphomannose isomerase (PMI) catalyzes the reversible interconversion of fructose 6-phosphate and mannose 6-phosphate, which is the first step in the biosynthesis of activated mannose donors required for the biosynthesis of various glycoconjugates. Leishmania species synthesize copious amounts of mannose-containing glycolipids and glycoproteins, which are involved in virulence of these parasitic protozoa. To investigate the role of PMI for parasite glycoconjugate synthesis, we have cloned the PMI gene (lmexpmi) from Leishmania mexicana, generated gene deletion mutants (Delta lmexpmi), and analyzed their phenotype. Delta lmexpmi mutants lack completely the high PMI activity found in wild type parasites, but are, in contrast to fungi, able to grow in media deficient for free mannose. The mutants are unable to synthesize phosphoglycan repeats [-6-Gal beta 1-4Man alpha 1-PO(4)-] and mannose-containing glycoinositolphospholipids, and the surface expression of the glycosylphosphatidylinositol-anchored dominant surface glycoprotein leishmanolysin is strongly decreased, unless the parasite growth medium is supplemented with mannose. The Delta lmexpmi mutant is attenuated in infections of macrophages in vitro and of mice, suggesting that PMI may be a target for anti-Leishmania drug development. L. mexicana Delta lmexpmi provides the first conditional mannose-controlled system for parasite glycoconjugate assembly with potential applications for the investigation of their biosynthesis, intracellular sorting, and function.  (+info)

Complex carbohydrate synthesis tools for glycobiologists: enzyme-based approach and programmable one-pot strategies. (59/567)

The ultimate goal in complex carbohydrate synthesis is to develop synthetic tools which are simple and easily accessible to glycobiologists. This review will describe methods which have the potential to reach this goal, with particular focus on enzymatic and computer-based one-pot approaches for the preparation of complex carbohydrates and glycoconjugates.  (+info)

Heterogeneous distribution of plasma membrane glycoconjugates in pancreatic acinar cells. (60/567)

Flow-cytometric studies of lectin binding to individual acinar cells have been carried out in order to analyse the distribution of membrane glycoconjugates in cells from different areas of the pancreas: duodenal lobule (head) and splenic lobule (body and tail). The following fluoresceinated lectins were used: wheat germ agglutinin (WGA), Tetragonolobus purpureus agglutinin (TP) and concanavalin A (Con A), which specifically bind to N-acetyl D-glucosamine and sialic acid, L-fucose and D-mannose, respectively. In both pancreatic areas, two cell populations (R1 and R2) were identified according to the forward scatter (size). On the basis of their glycoconjugate pattern, R1 cells displayed higher density of WGA and TP receptors than R2 cells throughout the pancreas. Although no difference in size was found between the cells from duodenal and splenic lobules, N-acetyl D-glucosamine and/or sialic acid and L-fucose residues were more abundant in plasma membrane cell glycoconjugates from the duodenal lobule. The results provide evidence for biochemical heterogeneity among individual pancreatic cells according to the distribution of plasma membrane glycoconjugates.  (+info)

Assessment of lectin-binding analysis for in situ detection of glycoconjugates in biofilm systems. (61/567)

An assessment of lectin-binding analysis for the characterization of extracellular glycoconjugates as part of the extracellular polymeric substances in environmental microbial communities was performed using fully hydrated river biofilms. The applicability of the method was evaluated for single, dual and triple staining with a panel of fluor-conjugated lectins. It was shown that lectin-binding analysis was able to stain glycoconjugates within biofilm communities. Lectin staining also demonstrated spatial heterogeneity within the biofilm matrix. Furthermore, the application of two or even three lectins was possible if suitable combinations were selected. The lectin-binding analysis can be combined with general nucleic acid stains to collect both nucleic acid and glycoconjugate signals. The effects of incubation time, lectin concentration, fluor labelling, carbohydrate inhibition, order of addition and lectin interactions were studied. An incubation time of 20 min was found to be sufficient for completion of lectin binding. It was not possible to ascertain saturating concentration for individual lectins, therefore a standard concentration was used for the assay. Carbohydrate inhibition tests indicated that fluorescein isothiocyanate (FITC)-conjugated lectins had more specific binding characteristics than tetramethyl rhodamine isothiocyanate (TRITC)- or cyanine dye (CY5)-labelled lectins. The order of addition and the nature of the fluor conjugate were also found to influence the binding pattern of the lectins. Therefore the selection of a panel of lectins for investigating the EPS matrix must be based on a full evaluation of their behaviour in the biofilm system to be studied. Despite this necessity, lectin-binding analysis represents a valuable tool to examine the glycoconjugate distribution in fully hydrated biofilms. Thereby, chemical heterogeneities within extracellular biofilm locations can be identified in order to examine the role (e.g. sorption properties, microenvironments, cell-extracellular polymeric substance interactions) of the extracellular polymeric substances in environmental biofilm systems.  (+info)

Sulfated glycoconjugates are powerful modulators of bovine sperm adhesion and release from the oviductal epithelium in vitro. (62/567)

The mechanisms of sperm adhesion and release within the mammalian oviduct are still poorly understood. In this in vitro study, a previously developed adhesion assay was used to analyze the effects of heparin, N-desulfated heparin, fucoidan, dextran sulfate, and dextran on bovine sperm-oviductal cell adhesion and release. Results showed that 1) all sulfated glycoconjugates were powerful inhibitors of sperm binding to oviductal monolayers in a dose-dependent manner, whereas N-desulfated heparin and dextran had no effect; 2) sperm pretreatment with heparin and fucoidan markedly inhibited adhesion; 3) treatment of oviductal monolayers with heparinase I, II, or sodium chlorate (an inhibitor of sulfation) had no effect on sperm adhesion; 4) sulfated glycoconjugates were also powerful and quick inducers of sperm release from oviductal monolayers; and 5) addition of sulfated glycoconjugates to the cocultures caused a sudden increase of bound-sperm flagellar beat frequencies, followed by a release of highly motile sperm. In conclusion, these data support the hypothesis that sulfated glycoconjugates may act as signals that induce sperm release and migration from the oviductal reservoir.  (+info)

Origin of enzootic intranasal tumor in the goat (Capra hircus): a glycohistochemical approach. (63/567)

Enzootic intranasal tumor (EIT) appears glandular in type and has recently been classified as an adenocarcinoma of low malignancy. The aim of this study was to characterize the secretion of surface glycoconjugates (GCs) in EIT and in normal respiratory and olfactory mucosae of the goat by means of conventional and lectin histochemistry, in order to shed light on the histogenesis of EIT. Morphologic and ultrastructural investigations showed two growth types of EIT: i.e., tubular and papillary patterns. Conventional histochemistry revealed the presence of neutral and carboxylated GCs in the olfactory glands and in the tubular part of EIT, as well neutral and sulphated GCs in the respiratory glands and in the papillary part of EIT, suggesting that the papillary pattern tumor arises from the respiratory glands, whereas the tubular portion of EIT arises from the olfactory glands. Lectin histochemistry gave further information on the expressed GCs.  (+info)

GPI-anchored proteins and glycoconjugates segregate into lipid rafts in Kinetoplastida. (64/567)

The plasma membranes of the divergent eukaryotic parasites, Leishmania and Trypanosoma, are highly specialised, with a thick coat of glycoconjugates and glycoproteins playing a central role in virulence. Unusually, the majority of these surface macro-molecules are attached to the plasma membrane via a glycosylphosphatidylinositol (GPI) anchor. In mammalian cells and yeast, many GPI-anchored molecules associate with sphingolipid and cholesterol-rich detergent-resistant membranes, known as lipid rafts. Here we show that GPI-anchored parasite macro-molecules (but not the dual acylated Leishmania surface protein (hydrophilic acylated surface protein) or a subset of the GPI-anchored glycoinositol phospholipid glycolipids) are enriched in a sphingolipid/sterol-rich fraction resistant to cold detergent extraction. This observation is consistent with the presence of functional lipid rafts in these ancient, highly polarised organisms.  (+info)