Sialoglycoderivatives of bovine submandibular gland identified in situ by histochemical techniques combined with lectins

Histochemical analyses of glycoconjugates and antimicrobial substances in goat labial glands

Saliva is known to protect the oral cavity and contains glycoproteins and antimicrobial substances. The distribution of these salivary secretions was studied in the labial glands of the Japanese miniature (Shiba) goat using lectin histochemical and immunohistochemical methods. The mucous acinar cells of the labial glands exhibited glycoconjugates with different saccharide residues, such as GalNAcα1-3GalNAc, Galβ1-4GalNAc, β-D-GlcNAc and sialic acid linked to α2-6Gal/GalNAc. Furthermore, α-D-Man, α-L-Fuc, α-D-GalNAc, β-D-Gal and sialic acid residues were present, in particular, in the serous demilunar cells. Antimicrobial substances (lysozyme, IgA, lactoferrin and β-defensin) were shown to be mainly immunolocalized in the serous demilunes and duct cells. The results obtained are discussed with regard to the functional role of labial glands. The secretory compounds demonstrated may play an important role in the maintenance of oral health with regard to saliva.

Equine mandibular gland: in situ characterisation of sialoderivatives

REASONS FOR PERFORMING STUDY

Sialic acids modulate the metabolite transport across membranes and may be involved in protection against pathogenic agents. The presence of sialoderivatives in the equine mandibular gland requires further study.

OBJECTIVE

To biochemically visualise in situ the presence of sialoderivatives, by means of mild and strong periodate oxidation and alcoholic saponification, combined with lectin histochemistry and sialidase digestion in order to hypothesise roles for detached sialoderivatives.

METHODS

Mandibular glands were removed from 8 mature horses of both sexes and subjected to histochemical procedures, including periodate oxidation, saponfication and lectin staining. Controls were based upon the omission of peroxidase-conjugated lectins and respective enzyme-free buffers.

RESULTS

The reactivities of PNA and RCA I lectins were affected by sialidase treatment, whether preceded by saponification or not, showing that the dimer N-acetyl-sialic acid-beta-Gal was linked (1-3)GalNAc and (1-4)GlcNAc. In acinar cells the sequence sialic acid-beta-Gal(1-3)GalNAc showed sialic residues acetylated at C4 only and at C4 and C7 and/or C8 and/or C9(alpha2-6Gal) in both sexes, while in female mandibular gland also C4 and C9(alpha2-3Gal) acetylated residues were present. Sialic acid linked to beta-Gal(1-4)GlcNAc was prevalently C4 and C7 and/or C8 and/or C9(alpha2-6Gal and alpha2-3Gal) acetylated, whereas only a minor quantity showed acetyl groups at C7 and/or C8 and/or C9(alpha2-6Gal) in the acinar cells of both sexes.

CONCLUSIONS

The great variety of sialic acid residues expressed by equine mandibular gland could assume an important role in the defensive mechanisms towards pathogen agents and, compared with those of cattle, probably represents an example of molecular species-specificity related to different alimentary habits.

Histochemical localization of complex carbohydrates in the nasolabial glands of the Japanese deer (Cervus nippon yakushimae)

The localization of complex glycoconjugates in the nasolabial glands of the Japanese deer (C. nippon yakushimae) was studied using various histochemical methods, including lectin histochemistry, viewed using both light and electron microscopy. The secretory epithelium and luminal secretion of the deer nasolabial glands exhibited neutral and acidic glycoconjugates with different saccharide residues (alpha-D-mannose, alpha-N-acetyl-D-galactosamine, beta-D-galactose, beta-N-acetyl-D-glucosamine and sialic acid). Additionally, O-acetylated sialic acids were detectable in the glandular acini. The results obtained are discussed with regard to the specific functions of the glandular secretion, which may particularly improve water retention on the skin surface and protect against physical damage as well as microbial contamination. Furthermore, our results support the view of a salivary nature of this gland type.

Mucoadhesion dependence of pharmaceutical polymers on mucosa characteristics

Well known mucoadhesive polymers such as Carbopol 974P and Pharmacoat 606 and three different mucosas (sublingual, oesophageal and duodenal bovine) were used to verify how the mucoadhesive properties of materials may depend on the mucosa characteristics and if a polymer may reveal more mucoadhesive than another and vice versa by changing the type of interacting mucosa. So, tablets of Carbopol 974P and Pharmacoat 606 were prepared and their mucoadhesion on the three mucosas was set in terms of maximum load and work of detachment, using a texture analyzer. At the same time, mucosas were characterized by immunohistochemical techniques and lectin histochemistry. Results obtained from the Tensile test analyses show that the adhesive power of the two polymers is different in the three mucosas. Particularly, in the sublingual mucosa, Carbopol was more mucoadhesive than Pharmacoat. On the contrary, Pharmacoat was more mucoadhesive than Carbopol in duodenal mucosa. The significantly different behavior of polymers was correlated with the desquamation layer thickness and the differential sialic acid and fucose exposition in the targeted mucosas.

Sialoglycoconjugate expression in acinar cells of rat developing submandibular gland

Direct and indirect staining procedures were developed to characterize sialoglycoconjugates in developing rat submandibular gland. Lectin histochemistry, with and without prior sialidase digestion, combined with differential oxidation and deacetylation procedures was performed in situ. This allowed the expression of sialic acids to be followed during acinar cell development. It was found that terminal periodate-labile sialic acids linked to beta-galactose occurred early. In contrast, the terminal disaccharide sialic acid-N-acetylgalactosamine was only detectable at the adult stage and so was considered to be a good marker of the full maturity of this gland. The developing acinar cells were mainly characterized by C4-acetylated sialic acids belonging to short side-chains. Dimorphic expression of sialoglycoconjugate components was evident by postnatal day 44.

Characterisation of sugar residues in glycoconjugates of pig mandibular gland by traditional and lectin histochemistry

Sugar residues are important components of salivary gland secretion. Traditional histochemical methods and lectin histochemistry were used to characterise glycoconjugates present in the mandibular gland of normal adult pigs. Acinar cells contained abundant quantities of glycoconjugates with the terminal trisaccharide sialic acid - (alpha 2-->3, 6) galactosyl (beta 1-->3) N -acetylgalactosamine. Mandibular acinar cells also contained alpha and beta N -acetylgalactosamine and N -acetylglucosamine residues, whereas the demilunar cells contained glycoconjugates with fucose, mannose and N -acetylglucosamine residues. In the duct system a range of sugar residues were localised throughout the cell cytoplasm or limited to the apical surface. These results provide new knowledge concerning the structure of salivary glycoconjugates in normal adult pig and a basis for future pathological studies.

Histochemical study of lectin binding in the major salivary glands of adult fallow-deer (Dama dama L.)

The sugar residues in glycoconjugates present in the parotid and mandibular glands of the adult fallow-deer were detected and characterized by using a battery of eight different lectin-horseradish peroxidase conjugates. In some cases a treatment with sialidase preceded the lectin staining. Parotid secretory cells produced glycoconjugates with N-acetylgalactosamine, N-acetylglucosamine and mannose residues. Mucous acinar cells were the most reactive sites of the mandibular gland and contained conspicuous quantities of oligosaccharides with terminal sialic acid radicals. Galactosil-(beta 1-->3)N-acetylgalactosamine was the most abundant penultimate sugar linked to N-acetylneuraminic acid. Mandibular mucous cells also presented N-acetylglucosamine and sialylated components with the terminal dimer sialic acid-N-acetylgalactosamine. Demilunar cells contained glycoconjugates with fucose and mannose residues. The apical surface of duct cells was stained by all the lectins.

Sialic acids in the chicken anterior lingual glands detected by lectins combined with enzymatic degradation and oxidizing agents

The chicken anterior lingual glands contain a large amount of sialoglycoconjugates. This study is aimed at discriminating between them, on the basis of the degree of acetylation and the acceptor sugars, by means of lectins combined with neuraminidase digestion and treatment with oxidizing and deacetylating agents. In the anteromedial part of lingual glands, only low concentrations of periodate-labile sialic acid having alpha 2-3,6-galactose and alpha 2-6-N-acetylgalactosamine acceptor sugars were present. Mostly, C7 and/or C8 acetylated sialic acids occurred, while C9 acetylated sialic acid linked alpha 2-3-galactose and alpha 2-6-N-acetylgalactosamine were restricted to some cells. In the anterolateral part, sialic acid linked alpha 2-6-N-acetylgalactosamine was not acetylated, while sialoderivatives alpha 2-3 linked to galactose were mainly C9 acetylated.

Glycoconjugates in the mandibular salivary gland of adult dogs revealed by lectin histochemistry

The glycosidic residues in the mandibular glands of five adult dogs were studied by using seven different lectin-horseradish peroxidase conjugates. In some cases a treatment with sialidase preceded the lectin staining. The mucous acinar cells contained oligosaccharides with alpha- and beta-N-acetylgalactosamine, N-acetylglucosamine and fucose residues, whereas the demilunar cells contained glycoconjugates rich in sialic acid linked to the penultimate disaccharide galactosyl-(beta 1-->3) N-acetylgalactosamine.

Localization of glycoconjugates in dog parotid gland by lectin histochemistry

Parotid glands from adult dogs were stained with a battery of seven horseradish peroxidase-conjugated lectins (PNA, UEA, LTA, DBA, SBA, WGA and ConA). In some cases (PNA and DBA) neuraminidase digestion was followed by lectin staining. Acinar cells contained conspicuous quantities of oligosaccharides with terminal sialic acid radicals. Galactosil-(beta 1-->3) N-acetylgalactosamine was the most abundant penultimate sugar linked to N-acetylneuraminic acid. Sialylated components having the terminal dimer sialic acid-N-acetylgalactosamine were found in the acinar cells. Secretory cells presented a heterogeneous distribution of glycoconjugates with terminal fucose and beta-N-acetylgalactosamine. Fucose, N-acetylglucosamine and alpha-N-acetylgalactosamine were present on the apical cytoplasm and surface of the striated and interlobular duct cells. This glycosidic composition was unaffected by extensive selective breeding. The role of abundant amounts of sialic acid radicals in the oral mucosa was considered.

Lectin histochemical study of bovine lingual glands

Bovine lingual glands consist of mucous acini capped by demilunes. Information on the chemical structure of their secretory glycoconjugates was obtained by means of a battery of peroxidase-conjugated lectins with affinity for specific terminal sugars. Sialidase procedures followed by lectin staining were also used to visualize the sugar sequences. Stored secretions in mucous acinar cells contained fucose, N-acetylglucosamine, alpha and beta-N-acetylgalactosamine as terminal sugar residues and beta-galactose as penultimate sugar in a heterogeneous distribution. Demilunar cells failed to react with any of the lectins examined except that of Dolichos biflorus.

Basic and lectin histochemistry for studying glycoconjugates in the lingual salivary glands of the Japanese quail (Coturnix coturnix japonica)

Traditional non-lectin staining methods and lectin histochemistry combined with specific exoglycosidase digestion were used to investigate the histological structure of these glands and to visualize the occurrence and composition of salivary glycoconjugates. The quail lingual glands comprise the anterior lingual gland, with rostral and caudal portions that differ in morphology and histochemical staining, and the posterior lingual gland devoid of regional differences. Carbohydrate histochemistry further differentiated the secretory structures by revealing a heterogeneous cell population of tubules within the rostral and caudal portions of the anterior gland, and a rather homogeneous staining of the tubuloalveolar elements in the rostral portion of the anterior lingual gland and in the posterior gland. Tubuloalveolar secretory cells mainly produced sulphate-containing molecules. In addition, sialoglycoconjugates were present in both anterior and posterior lingual glands, whereas fucoglycoconjugates were visualized only in the anterior gland.

Determination in situ of neutral and acidic fucose-containing oligosaccharides in the bovine submandibular gland

Lectins conjugated to horseradish peroxidase in combination with selected exoglycosidase digestion procedures were used to localize fucoglycoconjugates in the bovine submandibular gland. In particular, sequential treatments were employed to determine the distribution of neutral and acidic fucose-containing oligosaccharides that were previously shown to be present by biochemical techniques. Information was obtained on the distribution of the acidic oligosaccharide A-1a, alpha-Fuc(1-->2)-beta-Gal-(1-->4)-beta-GlcNAc-(1-->3)-[alpha-NeuAc-(2--> 6)]-GalNAc-ol, which was sequenced in situ and localized in acinar cells.