Lectin histochemistry on mucous substances of the taste buds and adjacent epithelia of different vertebrates

Summary In the present study carbohydrate residues in taste buds (TBs) and adjacent epithelial formations of a teleostean fish, a frog and the rabbit were detected by means of lectin histochemistry. Biotinylated lectins fromPisum sativum (PSA),Arachis hypogaea (PNA),Dolichos biflorus (DBA),Triticum vulgaris (WGA and succinylated WGA),Glycine max (SBA) andUlex europaeus (UEA I) have been applied. The lectins were bound to an avidin-biotin-peroxidase-complex (ABC) and visualized by diaminobenzidine/ H₂O₂. Most intensive reactivity was observed at the taste dise cells of the frog with DBA, S-WGA and SBA. PNA did not bind to the TBs of any of the animals tested. As shown in SBA preparations, sialic acid is present in a nonacylated and an acylated form in the mucosa of the frog's tongue. The TBs of the fish possess all the sugars we looked for except for the disaccharided-galactose-(1–3)--d-N-acetyl-galactosamine (Gal/GalNAc) and sialic acid. The TBs of the rabbit contain GalNAc, as detected with DBA, but not with SBA; and fucose (Fuc), mannose (Man) andN-acetyl-glucosamine (GlcNAc). As revealed by preincubation of the tissue sections with neuraminidase in TB cells of the rabbit, sialic acid masks Gal/GalNAc and GalNAc. These lectin-binding characteristics show that in the TBs of some selected representatives which belong to different vertebrate classes exist different mucous substances. These substances possess different binding characteristics to specific sugars, and this is possibly of particular interest to chemoreception phenomena.Dedicated to Professor Dr. T.H. Schiebler on the occasion of his 65th birthday.Parts of this investigation were presented at the 81. Versammlung der Anatomischen Gesellschaft, March 9–14, 1986 at Lübeck (Witt and Reutter 1986), and at the VII th Congress of the Europaen Chemoreception Research Organization, September 22–26, 1986, at Davos (Reutter and Witt 1987).Supported by the Deutsche Forschungsgemeinschaft (Re 225/9-1)     

Localization of penultimate carbohydrate residues in zona pellucida and acrosomes by means of lectin cytochemistry and enzymatic treatments

Lectins from peanuts (PNA) and soy beans (SBA) bind terminal residues of galactose (Gal) and N-acetyl-galactosamine (GalNAc) respectively. Galactose oxidase oxidizes the hydroxyl group at C-6 of terminal Gal and GalNAc blocking the binding of PNA and SBA. Binding of these lectins to sugar residues is also severely limited by the existence of terminal residues of sialic acid. In the present study, lectin cytochemistry in combination with enzymatic treatments and quantitative analysis has been applied at light and electron microscopical levels to develop a simple methodology allowing the in situ discrimination between penultimate and terminal Gal/GalNAc residues. The areas selected for the demonstration of the method included rat zona pellucida and acrosomes of rat spermatids, which contain abundant glycoproteins with terminal Gal/GalNAc residues. Zona pellucida was labelled by LFA, PNA and SBA. After galactose oxidase treatment, terminal Gal/GalNAc residues are oxidized, and reactivity to PNA/SBA is abolished. The sequential application of galactose oxidase, neuraminidase and PNA/ SBA has the following effects: (i) oxidation of terminal Gal/GalNAc residues; (ii) elimination of terminal sialic acid residues rendering accessible to the lectins preterminal Gal/GalNAc residues; and (iii) binding of the lectins to the sugar residues. Acrosomes were reactive to PNA and SBA. No LFA reactivity was detected, thus indicating the absence of terminal sialic acid residues. Therefore, no labelling was observed after both galactose oxidase--PNA/SBA and galactose oxidase--neuraminidase--PNA/SBA sequences. In conclusion, the combined application of galactose oxidase, neuraminidase and PNA/SBA cytochemistry is a useful technique for the demonstration of penultimate carbohydrate residues with affinity for these lectins. This revised version was published online in November 2006 with corrections to the Cover Date.     

Comparative lectin histochemistry on taste buds in foliate, circumvallate and fungiform papillae of the rabbit tongue.

Taste buds (TB) in the foliate, circumvallate and fungiform papillae of the rabbit tongue were examined with lectin histochemistry by means of light (LM) and electron (EM) microscopy. Biotin- and gold-labeled lectins were used for the detection of carbohydrate residues in TB cells and subcutaneous salivary glands. At the LM level, the lectins of soybean (SBA) and peanut (PNA) react with material of the foliate and circumvallate taste pores only after pretreatment of the section with neuraminidase. This indicates that the terminal trisaccharide sequences are as follows: Sialic acid-Gal-GalNAc in O-glycosylated glycoproteins or Sialic acid-Gal-GlcNAc in N-glycosylated glycoproteins. In fungi-form taste buds the lectins of Dolichos biflorus (DBA) and Helix pomatia (HPA), also specific to GalNAc residues, are reactive without preincubation with neuraminidase. Wheat germ agglutinin (WGA), specific to GlcNAc, reacts with TBs of all papillae; and the lectin from Ulex europaeus (UEA I), specific to fucose, binds to individual TB cells. The presence of sialic acid may protect mucus or other glycoproteins in TB cells and inside the taste pore from premature enzymatic degradation. In a post-embedding EM procedure on LR-White-embedded tissue sections, only gold-labeled HPA was found to bind especially on membrane surfaces of the microvilli which protrude into the taste pore; however HPA did not bind to the electron-dense mucus inside the taste pore. The mucus situated in the trough and at the top of the adjacent epithelial cells also is strongly HPA-positive, but is of different origin and composition than that found in the taste pore. These results demonstrate distinct carbohydrate histochemical differences between fungiform and circumvallate/foliate taste buds. The different configuration of galactosyl residues and the occurrence of mannose in circumvallate and foliate TBs leads to the suggestion that the lectin reactivities of TBs are not only due to the presence of mucins, but also to N-linked glycoproteins, possibly with a hormone-like paraneuronal function. A possible relationship to v. Ebner glands in these papillae is discussed.     

Light microscopic characterization of glycoconjugates in secretory cells of the carp (Cyprinus carpio) gill epithelium

Secretory products of granular and mucous cells in the gill epithelium of the carp, Cyprinus carpio, were distinguished by their cytochemical reactions with peroxidase-labelled lectins and with the galactose oxidase (GO)-Schiff reagents. Secretory products of granular cells reacted with lectins from Triticum vulgaris (WGA), Arachis hypogaea (PNA), Dolichos biflorus (DBA), Glycine max (SAB), and Lotus tetragonolobus (LTA). They also reacted with GO-Schiff reagents. After sialic acid cleavage with HCl, new binding sites for DBA and SBA appeared, suggesting the terminal sequence sialic acid-N-acetylgalactosamine (SA-GalNAc) for the secretion of this cell type. In mucous cells, binding sites for WGA, DBA, and SBA and, after acid hydrolysis, binding sites for PNA and a positive GO-Schiff reaction were detected. The terminal trisaccharide sialic acid-galactose (beta 1-3)-N-acetylgalactosamine (SA-Gal-GalNAc) is proposed for the secretion of mucous cells. These cytochemical differences are discussed in light of the involvement of both cell types in fish mucus elaboration.     

Comparative lectin histochemistry on taste buds in foliate,circumvallate and fungiform papillae of the rabbit tongue

Summary Taste buds (TB) in the foliate, circumvallate and fungiform papillae of the rabbit tongue were examined with lectin histochemistry by means of light (LM) and electron (EM) microscopy. Biotin- and gold-labeled lectins were used for the detection of carbohydrate residues in TB cells and subcutaneous salivary glands. At the LM level, the lectins of soybean (SBA) and peanut (PNA) react with material of the foliate and circumvallate taste pores only after pretreatment of the section with neuraminidase. This indicates that the terminal trisaccharide sequences are as follows: Sialic acid-Gal-GalNAc in O-glycosylated glycoproteins or Sialic acid-Gal-GlcNAc in N-glycosylated glycoproteins. In fungiform taste buds the lectins of Dolichos biflorus (DBA) and Helix pomatia (HPA), also specific to GalNAc residues, are reactive without preincubation with neuraminidase. Wheat germ agglutinin (WGA), specific to GlcNAc, reacts with TBs of all papillae; and the lectin from Ulex europaeus (UEA I), specific to fucose, binds to individual TB cells. The presence of sialic acid may protect mucus or other glycoproteins in TB cells and inside the taste pore from premature enzymatic degradation. In a post-embedding EM procedure on LR-White-embedded tissue sections, only gold-labeled HPA was found to bind especially on membrane surfaces of the microvilli which protrude into the taste pore; however HPA did not bind to the electron-dense mucus inside the taste pore. The mucus situated in the trough and at the top of the adjacent epithelial cells also is strongly HPA-positive, but is of different origin and composition than that found in the taste pore. These results demonstrate distinct carbohydrate histochemical differences between fungiform and circumvallate/foliate taste buds. The different configuration of galactosyl residues and the occurrence of mannose in circumvallate and foliate TBs leads to the suggestion that the lectin reactivities of TBs are not only due to the presence of mucins, but also to N-linked glycoproteins, possibly with a hormone-like, paraneuronal function. A possible relationship to v. Ebner glands in these papillae is discussed.     

Light microscopic characterization of glycoconjugates in secretory cells of the carp (Cyprinus carpio) gill epithelium

Summary Secretory products of granular and mucous cells in the gill epithelium of the carp, Cyprinus carpio, were distinguished by their cytochemical reactions with peroxidase-labelled lectins and with the galactose oxidase (GO)-Schiff reagents. Secretory products of granular cells reacted with lectins from Triticum vulgaris (WGA), Arachis hypogaea (PNA), Dolichos biflorus (DBA), Glycine max (SAB), and Lotus tetragonolobus (LTA). They also reacted with GO-Schiff reagents. After sialic acid cleavage with HCl, new binding sites for DBA and SBA appeared, suggesting the terminal sequence sialic acid-N-acetylgalactosamine (SA-GalNAc) for the secretion of this cell type. In mucous cells, binding sites for WGA, DBA, and SBA and, after acid hydrolysis, binding sites for PNA and a positive GO-Schiff reaction were detected. The terminal trisaccharide sialic acid-galactose (1-3)-N-acetylgalactosamine (SA-Gal-GalNAc) is proposed for the secretion of mucuous cells. These cytochemical differences are discussed in light of the involvement of both cell types in fish mucus elaboration.     

Eosinophilic globule cells in mouse MFH-like sarcomas: lectin histochemistry.

Lectin binding patterns in ten mouse malignant fibrous histiocytoma (MFH)-like sarcomas containing eosinophilic globule (EG) cells and in granular metrial gland (GMG) cells of mouse placenta were stained with nine lectins (Con A, LCA, WGA, DBA, SBA, e-PHA, PNA, RCA-I and UEA-I) by an avidin-biotin-peroxidase-complex method. EG cells stained strongly with DBA, SBA and PNA which are specific for N-acetyl-D-galactosamine and/or D-galactose. DBA and SBA bound throughout the cytoplasm including the globules; PNA reacted preferentially at the cell surface. There was no evidence that these three lectins were reactive for immature EG cells. WGA, RCA-I and e-PHA also gave a slightly to moderately positive reaction to globules of EG cells. The results indicate that the globules contain abundant O-linked sequences of sugars, but also a few N-linked residues. MFH tumor cells showed a variable degree of binding with Con A, RCA-I, and WGA, but did not react with DBA, SBA and PNA. On the other hand, GMG cells exhibited specific affinities for DBA, SBA and PNA with staining patterns similar to those of EG cells. These findings suggest that EG and GMG cells may be of the same cellular lineage.     

Lectin-binding pattern of neuroepithelial and respiratory epithelial cells in the mouse nasal cavity

Summary Sections from the nasal cavity of 12-day-old Swiss albino mice (NMRI strain) were subjected to lectin histochemistry. A panel of biotinylated lectins (Con A, WGA, s-WGA, PNA, SBA, DBA and UEA I) and a horseradish peroxidase-conjugated lectin (GSA II) showed marked differences in binding to the respiratory and the neuroepithelial cells. SBA (affinity for galactose andN-acetylgalactosamine), PNA (galactose) and WGA (sialic acids andN-acetylglucosamine) labelled the receptor neurons in the olfactory and vomeronasal epithelium. DBA (N-acetylgalactosamine) labelled a subgroup of about 5% of the olfactory receptor neurons, but most neurons in the vomeronasal organ. UEA I (fucose) and s-WGA (N-acetylglucosamine) intensely labelled the entire nerve cell population in the vomeronasal organ, but in the olfactory epithelium the labelling with these lectins was stratified. In the respiratory epithelium the ciliated cells were labelled with WGA and s-WGA, while the secretory cells bound most of the lectins. Thus different sugars are exposed on the surface of the different types of epithelia in the nasal cavity, providing a basis for selectivity in microbial attacks on these areas.     

Distribution of lectin receptors in postimplantation mouse embryos at 6-8 days gestation

We have examined the pattern of binding of eleven lectins--BSL-II, WGA, LPA, Con A, DBA, SBA, LTA, UEA-I, MPA, PNA, and RCA-I, with specificity for a range of saccharides, to postimplantation mouse embryos from 6 to 8 days of gestation. The lectins were used to stain sections of ethanol-fixed paraffin-embedded and formaldehyde-fixed gelatin-embedded embryonic material. Our observations reveal a complex pattern of lectin binding to both cell surfaces and cytoplasm. Many of the lectins bind particularly to the outer surface of visceral endoderm (e.g., DBA, WGA, SBA, and RCA-I) and to the surface of the proamniotic cavity (e.g., RCA-I, PNA, and WGA). In the newly formed mesenchyme of primitive-streak-stage embryos, galactose and N-Ac-neuraminic acid are present but lectins with specificity for other sugars either did not bind to the cells or bound only in small amounts.     

Characterization of carbohydrates of adult Echinococcus granulosus by lectin-binding analysis

The identification of lectin-binding structures in adult worms of Echinococcus granulosus was carried out by lectin fluorescence; the distribution of carbohydrates in parasite glycoconjugates was also studied by lectin blotting. The lectins with the most ample recognition pattern were ConA, WGA, and PNA. ConA showed widespread reactivity in tegument and parenchyma components, including the reproductive system, suggesting that mannose is a highly expressed component of the adult glycans. Although reproductive structures appeared to be rich in N-acetyl-D-glucosamine (GlcNAc)-N-acetyl neuraminic acid (NeuAc) and galactose (Gal) as demonstrated by their strong reactivity with WGA and PNA, respectively, some differences were observed in their labeling patterns. This was very clear in the case of the vagina, which only reacted with WGA. Furthermore, WGA and ConA both had reactivity with the excretory canals. RCA, the other Gal binding lectin used, only reacted with the tegument, suggesting that widespread PNA reactivity with the reproductive system is related to the presence of the D-Gal-beta-(1,3)D-GalNAc terminal structure. UEA I failed to bind to any parasite tissues as determined by lectin fluorescence, whereas DBA and SBA showed a very faint staining of the tegument. However, in transferred glycans, N-acetyl-D-galactosamine (GalNAc) and fucose (Fuc) containing glycoproteins were distinctly detected.     

短额负蝗卵子发生过程中糖复合物的动态分布

以生物素标记的凝集素(UEA-I、SBA、PNA)为探针,利用凝集素组织化学方法对短额负蝗(Atracto-morphasinensis)卵子发生过程中滤泡细胞和卵母细胞内糖复合物的分布进行了定位研究。结果表明,在卵子发生的各期滤泡细胞和卵母细胞中没有UEA-I受体的表达,SBA和PNA受体以不同的分布模式呈阶段性表达。两者首次出现于卵母细胞生长期,随后PNA受体消失,SBA受体大量表达;在卵黄形成期前期SBA受体和重新出现的PNA受体表达于卵黄颗粒形成部位,卵黄形成期后期两者均为阴性表达;成熟卵子中两种受体又以不同程度重新出现于卵黄膜。两种受体在滤泡细胞内均大量表达。提示,N-乙酰半乳糖胺和半乳糖-β-(1,3)半乳糖胺复合物的修饰和变化与卵母细胞的发育、卵黄物质的形成及滤泡细胞的增殖分化密切相关,卵黄膜上的糖复合物可能与精卵识别有关。     

Lectinhistochemical demonstration of galactose- and N-acetyl-D-galactosamine residues in cells of the rat anterior pituitary

Lectins are a useful tool for identification of differently glycosylated hypophyseal hormones, prohormones and glycoconjugates without hormone function. Beta-D-galactose and beta-N-acetyl-D-galactosamine (GalNAc) containing glycoconjugates were identified by light microscopy with biotinylated lectins in immunocytochemically localized cells of the anterior pituitary of the rat. Galactose, histochemically detectable by the peanut lectin (PNA), was found at penultimate position of the carbohydrate chain after removal of sialic acid. Galactose containing cells correspond to gonadotrophs and thyrotrophs located mainly in medioanterior regions of the pituitary. The lectins from the soybean (SBA) and horse gram (DBA) both specific for GalNAc residues, are bound to round and also polygonal cells corresponding again to gonadotrophs and thyrotrophs.     

Enzymatic degradation and quantitative lectin labeling for characterizing glycoconjugates which act as lectin acceptors in cat submandibular gland

Sites of binding of eight different lectins (LTA, UEA I, WGA, SBA, DBA, CON A, PNA, RCA I) to cat submandibular gland were studied after exposure of tissue sections to sialidase, alpha-fucosidase, beta-galactosidase, alpha-mannosidase, beta-N-acetylglucosaminidase. All lectins were affected by enzymatic predigestion and the labeling of individual lectins was highly dependent upon the glycosidase used to pretreat the sections. Glycoconjugates of demilunar, acinar and ductal cells exhibited a different composition of terminal sequences. For example, fucose proved to form the disaccharide fucose-galactose in demilunar and acinar cells, whereas it was present with the sequence fucose-N-acetyl-D-glucosamine in striated duct cells. Sialic acid participated both to the terminal sequence sialic acid-galactose and sialic acid-N-acetyl-D-galactosamine either in demilunar or in ductal cells. Lectin labeling combined with glycosidase digestion was also helpful in verifying the influence of neighbouring oligosaccharides on the affinity of lectins for the respective sugars.     

Carbohydrate patterns of the pure cholinergic synapse of Torpedo electric organ: a cytochemical and immunocytochemical electron microscopic approach.

Using post-embedding gold staining techniques, we investigated the ultrastructural distribution of terminal sugars and carbohydrate chains located at the pure cholinergic electric organ tissue of Torpedo marmorata. Neither alpha-N-acetylgalactosamine (GalNAc)-specific lectins (DBA, SBA, HPA) nor monoclonal antibodies (MAb) recognizing Tn (Gal-NAc alpha-O-Ser/Thr; MAb Cu-1) and sialyl-Tn epitopes (NeuAc alpha 2,6GalNAc alpha-O-Ser/Thr; MAb B72.3 and OSM-10) were capable of labeling any of the synaptic structures. The absence of gold labeling was likewise noted with UEA-I (L-fucose) and with PNA (T-antigen, Gal beta 1,3GalNAc alpha). After neuraminidase pre-treatment of ultra-thin sections, PNA labeling was rendered evident, indicating the presence of neuraminic acid-masked T-antigen. Certain synaptic vesicles were labeled for neuraminic acid (LFA) and for N-acetyllactosamine (DSA), whereas others were not labeled at all. Gold labeling with LFA, RCA-I (beta-galactose), and DSA in the membrane infoldings of the dorsal face of the electrocyte was visualized. As noted above, the PNA reaction was revealed only after pre-treatment with neuraminidase. Dorsal (non-synaptic) basal lamina were reactive with DSA, whereas the synaptic portion was likewise labeled with LFA and RCA-I. Finally, RCA-I labeling was noted in the Schwann cell nucleus. Comparisons between these results and those described at the neuromuscular junction were made.     

Lectin histochemistry of rabbit nephron

In order to investigate the usefulness of lectin histochemistry to detail nephronal segmentation we used 12 different biotinylated lectins (Con-A, DBA, GS-I, LCA, PNA, PWN, RCA-I, RCA-II, SWGA, SBA, UEA-I, and WGA) and Avidin-Biotin-Peroxidase (ABC) system on formalin-fixed and paraffin-embedded rabbit kidney sections. Each lectin, except UEA-I which did not stain any nephron structure, shows a different staining pattern along the nephron. Con-A, LCA, and RCA-I display a diffuse staining, while BS-I, RCA-II, SWGA, PWN, DBA, SBA and PNA are selective markers for specific nephron tracts. Furthermore, it is possible, according to the WGA binding pattern, to differentiate the convoluted part of the proximal tubule into two parts, named Segment A and Segment B. Lectin histochemistry on formalin-fixed and paraffin-embedded rabbit kidney sections displays a specific binding pattern along the rabbit nephron and shows interesting morphofunctional correlations.     

Glycoconjugates in normal human kidney. A histochemical study using 13 biotinylated lectins

The avidin-biotin-peroxidase complex technique was used with 13 lectins to study the glycoconjugates of normal human renal tissue. The evaluated lectins included Triticum vulgaris (WGA), Concanavalin ensiformis (ConA), Phaseolus vulgaris leukoagglutinin and erythroagglutinin (PHA-L and PHA-E), Lens culinaris (LCA), Pisum sativum (PSA), Dolichos biflorus (DBA), Glycine max (SBA), Arachis hypogaea (PNA), Sophora japonica (SJA), Bandeiraea simplicifolia I (BSL-I), Ulex europaeus I (UEA-I) and Ricinus communis I (RCA-I). Characteristic and reproducible staining patterns were observed. WGA and ConA stained all tubules; PHA-L, PHA-E, LCA, PSA stained predominantly proximal tubules; DBA, SBA, PNA, SJA and BSL-I stained predominantly distal portions of nephrons. In glomeruli, WGA and PHA-L stained predominantly visceral epithelial cells; ConA stained predominantly basement membranes and UEA-I stained exclusively endothelial cells. UEA-I also stained endothelial cells of other blood vessels and medullary collecting ducts. Sialidase treatment before staining caused marked changes of the binding patterns of several lectins including a focal loss of glomerular and tubular staining by WGA; an acquired staining of endothelium by PNA and SBA; and of glomeruli by PNA, SBA, PHA-E, LCA, PSA and RCA-I. The known saccharide specificities and binding patterns of the lectins employed in this study allowed some conclusions about the nature and the distribution of the sugar residues in the oligosaccharide chains of renal glycoconjugates. The technique used in this report may be applicable to other studies such as evaluation of normal renal maturation, classification of renal cysts and pathogenesis of nephrotic syndrome. The observations herein reported may serve as a reference for these studies.     

Lectin binding to rat spermatogenic cells: Effects of different fixation methods and proteolytic enzyme treatment

Summary The binding of a panel of eight different fluorescein-conjugated lectins to rat spermatogenic cells was investigated. Particular attention was paid to the effects of different fixation methods and proteolytic enzyme digestion on the staining pattern.Concanavalin A (Con A), wheatgerm agglutinin (WGA), succinylated WGA (s-WGA) and agglutinin from gorse (UEA I) stained the cytoplasm of most germ cells as well as the spermatid acrosome. In contrast, peanut agglutinin (PNA), castor bean agglutinin (RCAI) and soy bean agglutinin (SBA) mainly stained the acrosome. The staining pattern varied depending on the fixation method used. PNA was particularly sensitive to formalin fixation, while SBA, DBA and UEA I showed decreased binding and Con A, WGA, s-WGA and RCA I were insensitive to this type of fixation. Pepsin treatment of the sections before lectin staining caused marked changes in the staining pattern; staining with PNA in formalin-fixed tissue sections was particularly improved but there was also enhanced staining with SBA and horse gram agglutinin (DBA). On the other hand, in Bouin- and particularly in acetone-fixed tissue sections, pepsin treatment decreased the staining with several of the lectins, for example WGA and UEA I.     

Carbohydrate composition of human megakaryocyte membranes in culture: identification using binding of seven lectins

Seven tetramethylrhodamine B isothiocyanate- (TRITC) labeled lectins: lens culinaris (LCH), ulex europeus-1 (UEA-1), lycopersicon esculentum (LEA), wheat germ agglutinin (WGA), dolichos biflorus (DBA), soybean agglutinin (SBA) and erythrina cristagalli (ECA) were applied on cultured human megakaryocytes (Megs) detected by immunofluorescence. All stages of Megs (from lymphocyte-like Megs to mature Megs) and platelets were labeled by LCH, LEA, UEA-1 and WGA. ECA binds to platelets but only to some Megs. DBA did not bind to platelets but did bind to some Megs, irrespective of stage. SBA binds to all stages of Megs, but did not bind to platelets. These results indicate the presence of mannose, glucose (LCH), sialic acid (WGA), and glucosamine (UEA-1, LEA, WGA) on the surface of all cells of the Meg lineage, a variable presence of galactosamine (DBA, SBA, ECA), and a discrepancy in the presence of some galactosamine compounds between platelets and Megs (DBA, SBA).     

GalNAc moieties in O-linked oligosaccharides of the primordial germ cells of Xenopus embryos

Glycoconjugates could play a role in cell adhesion and migration mechanisms, including the locomotive movements of the primordial germ cells (PGCs) during the development of the embryo. In the present work, we have studied by lectin histochemistry the presence of N-acetylgalactosamine (GalNAc) in the glycans of the Xenopus PGCs, as a first approach to identifying their glycoconjugates which could be involved in the migration mechanism. The PGCs were negative for three of the GalNAc-binding lectins employed (from soybean, SBA; from lima bean, LBA; and from snail, HPA). However, when sialic acid (NeuAc) was previously removed by acid hydrolysis, SBA and HPA, but not LBA, labeled the PGCs, except if the staining was combined with the beta-elimination procedure. This suggests the presence of GalNAc alpha(1,3)-linked to galactose (Gal) in O-linked oligosaccharides, in a subterminal position to NeuAc. As the PGCs were always negative for LBA, the absence of fucose alpha(1,2)-linked to subterminal Gal is suggested. With the lectin from horse gram (DBA), the PGCs were stained, although beta-elimination turned the cells negative and acid hydrolysis increased the labeling, suggesting that GalNAc(alpha)(1,3)GalNAc was in O-linked glycans in terminal and subterminal to NeuAc position.     

Lectin histochemistry of human skeletal muscle

Biotinyl derivatives of seven plant lectins-concanavalin A (Con A), peanut agglutinin (PNA), Ricinus communis agglutinin I (RCA I), Ulex europeus agglutinin I (UEA I), soybean agglutinin (SBA), Dolichos biflorus agglutinin (DBA), and wheat germ agglutinin (WGA)-were bound to cryostat sections of biopsied normal human muscle and visualized with avidin-horseradish peroxidase conjugates. A distinct staining pattern was observed with each lectin. The most general staining was observed with Con A, RCA I, and WGA, which permitted strong visualization of the plasmalemma-basement membrane unit, tubular profiles in the interior of muscle fibers, blood vessels, and connective tissue. PNA gave virtually no intracellular staining, while SBA and UEA I selectively stained blood vessels. DBA was unique in providing good visualization of myonuclei. In each case, lectin staining could be blocked by appropriate sugar inhibitors. Neuraminidase pretreatment of the cryostat sections altered the pattern of staining by all lectins except UEA I and Con A; staining with RCA I became stronger and that with WGA became less intense, while staining with PNA, SBA and DBA became stronger and more generalized, resembling that of RCA I. These effects of neuraminidase pretreatment are in conformity with the known structure of the oligosaccharide chains of membrane glycoproteins and specificities of the lectins involved.