Histochemical analysis of glycoconjugate secretion in the alimentary canal of Anguilla anguilla L

Mucus cells in the digestive tract in prenatal platyfish larvae (Poeciliidae, Teleostei)

The appearance and histochemical properties of mucus cells in various parts of digestive tract in prenatal larvae of platyfish (Xiphophorus maculatus), a stomachless teleost, are described and compared. Such cells occurred regularly throughout the entire epithelial cell layer in mouth, pharynx, oesophagus and intestine in 6 mm long larvae i.e. approximately 1 week before delivery, but were very scarce in 4 mm long larvae. The mucin in these cells was strongly stained by alcian blue at pH 2.5 and weakly coloured by this dye at pH 1.0. It displayed a clean blue colour after high iron diamine followed by alcian blue (pH 2.5), except in some very few cells which displayed a purple-brown colour after this treatment. The mucus cells displayed various colours between purple-blue and magenta when the alcian blue (pH 2.5) was followed by periodic acid-Schiff (PAS) solution; the magenta-coloured cells were mainly confined to oesophagus. Together these findings suggest that the mucin in the digestive tract of prenatal platyfish consists mainly of non-sulphated, carboxylated glycoconjugates. The observations from the present lectin histochemistry suggest that the amount of galactosamine and glucosamine in this mucin varies much from cell to cell. Also, the various colours after PAS suggest a significant cellular heterogeneity in the mucus cell population. This may reflect different stages in development and maturation or a true and permanent cellular heterogeneity, suggesting that this mucus is able to play a number of important roles even a week before the larvae start to feed and digest.

Carbohydrate patterns in the digestive tract of Sparus aurata L. and Psetta maxima (L.) (Teleostei) parasitized by Enteromyxum leei and E. scophthalmi (Myxozoa)

The influence of Enteromyxum spp. infections on the carbohydrate patterns of the digestive tract of gilthead sea bream (GSB) Sparus aurata L. and turbot (TB) Psetta maxima (L.) has been studied. Histochemical stainings to differentiate the types of mucins and lectin-binding assays to detect terminal carbohydrate residues were applied to histological sections of GSB and TB uninfected or infected by Enteromyxum leei and E. scophthalmi, respectively. The number of intestinal GC decreased in severely infected fish in both parasitoses, though changes in mucin patterns were limited to the decrease in the staining intensity for acidic mucins in infected GSB. The TB stomach and intestine lacked histochemically detectable acidic mucins, or sialic acid detectable by SNA, in contrast with their abundance in GSB. Glucose/mannose, fucose and GlcNAc residues were less abundant in both infected hosts with respect to uninfected fish. In contrast, D-Gal and D-GalNAc moieties (detectable by BSL I) increased in most parts of E. scophthalmi-infected TB while decreasing (oesophagus) or remaining unchanged (intestine) in E. leei-infected GSB. The decreasing in the expression of acidic mucins and of sialic acid detectable by SNA in E. leei-infected GSB is remarkable. Differences in the carbohydrate patterns between both hosts could aid to explain the differences in the severity of both enteromyxoses. In addition, the changes induced by Enteromyxum spp. infections in the digestive tract of GSB and TB suggest a role of terminal carbohydrate residues in the parasite-host interaction.

Histochemical study on the intestine goblet cells in cichlid and poecilid species (Teleostei)

Histochemical properties of intestine goblet cells in firemouth cichlid, zebra mbuna, freshwater angelfish and platyfish are described. Goblet cells occurred regularly in the epithelial cell layer throughout the entire intestine, they were strongly coloured by alcian blue at pH 2.5. This colour got gradually weaker when the pH was reduced, but still after alcian blue at pH 0.2 these cells displayed a distinct blue colour. When the goblet cells were treated with periodic acid-Schiff (PAS), they displayed a strong purple-magenta colour. The findings that a number of goblet cells displayed various colours between blue and purple-magenta when acidic alcian blue was followed by PAS, and between blue and red-brown when acidic alcian blue was followed by neutral red, may reflect different ages or stages of development and differentiation for these cells. However, such results may also suggest a true cellular heterogeneity in the present population of goblet cells, reflecting that the intestine mucus layer has a number of roles in teleosts like lubrication, protection, immunological defence, digestion and absorption. In the ferritin injected specimens of firemouth cichlid and platyfish, a number of macrophage-like cells in intestine wall displayed Prussian blue precipitations in tissue treated with acid ferrocyanide, suggesting that these cells play a cleansing role in the intestinal wall. No ferritin uptake was seen in the intestine goblet cells and eosinophilic granule cells.

Histology and mucin histochemistry of the digestive tract of yellow catfish, Pelteobagrus fulvidraco

The histology and characteristics of mucins secreted by epithelial mucous cells of the digestive tract in yellow catfish, Pelteobagrus fulvidraco were investigated using light microscope and transmission electron microscope. The digestive tract was divided into a pharynx, oesophagus, U-shaped stomach (with a cardiac, fundic and pyloric part) and intestine, composed of anterior intestine, middle intestine and posterior intestine, which consisted of a mucosa (epithelial layer), lamina propria-submucosa, muscularis and serosa. A large number of isolated longitudinal striated muscular bundles were present in the lamina propria-submucosa of pharynx. Goblet cells were observed throughout the digestive tract, except in the stomach. In the cardiac and fundic stomach, a plenty of gastric glands were observed, whereas they were absent in the pyloric part. Numerous mitochondria and endoplasmic reticulum were observed in the columnar epithelial cells of the intestine, especially of the anterior part. The epithelial mucous cells contained neutral or other two mixtures of acid and neutral mucins, the first being the most common. The neutral mucin was the only type of mucins in the stomach, anterior intestine and middle intestine. The results of this study will be helpful for understanding the digestive physiology and diagnosing some gastrointestinal diseases in yellow catfish.

Histochemical analysis of glycoproteins in the secretory cells in the gill epithelium of a catfish, Rita rita (Siluriformes, Bagridae)

Glycoproteins (GPs) were visualised histochemically in the secretory cells - the mucous goblet cells (the type A and the type B), the serous goblet cells, the club cells and the epithelial cells in the gill epithelium of Rita rita. The type A mucous goblet cells, the type B mucous goblet cells and the epithelial cells elaborate GPs with oxidizable vicinal diols and GPs with sialic acid residue without O-acyl substitution. In addition, GPs with O-sulphate esters are elaborated by the type A and GPs with O-acyl sugars by the type B mucous goblet cells. GPs are absent in the serous goblet cells and are with oxidizable vicinal diols in low moieties in the club cells. The analysis of the results elucidates interesting differences in the composition and concentration of GPs in the mucus elaborated by the epithelium of the gill arches and the gill rakers; and the gill filaments and the secondary lamellae indicating the potential importance of the glycoproteins at these locations. GPs elaborated on the surfaces of the gill arches and the gill rakers could be associated to assist in feeding activities and on the surfaces of the gill filaments and the secondary lamellae in the respiratory activity.

Glycoconjugates in the mucosa of the digestive tract of Cynoscion guatucupa: a histochemical study

This study addresses the histomorphology, the histochemistry and the distribution of glycoconjugates (GCs) in the mucosa of the digestive tract of the weakfish Cynoscion guatucupa. The histological characterization of the buccopharyngeal cavity and the esophagus revealed that they are lined by a stratified epithelium where the mucosa is thrown into longitudinal folds. The stomach is lined with a simple columnar secretory epithelium with tubular glands. GCs were analyzed using a range of histochemical methods. They were identified as oxidizable vicinal diols; sialic acids and some of their chain variants, C7, C8 or C9; sialic acid residues with O-acyl substitution at C8 or C9; carboxyl groups and sulfate groups. Sugar residues in the oligosaccharide side chains of the GCs were investigated using seven biotinylated lectins. Mucous cells from the contents of the buccopharyngeal cavity, esophagus and stomach evidenced neutral, sulphated and sialylated GCs. The latter were substituted mainly in C8. A moderately strong lectin labeling was observed in mucous cells of the three organs studied. Nonetheless, the apical edge of the gastric gland cells showed a strong positive labeling. The presence of different classes of GCs has been associated with different functions, such as lubrication, protection, inhibition of microorganisms proliferation and ionic regulation.

Characterization of a population of unique granular lymphocytes in a bitch deciduoma, using a panel of histo- and immunohistochemical markers

The ovaries and uterus were collected after ovariohysterectomy from a 16-month-old Labrador bitch in diestrus that never mated. Discrete swellings were found in the uterine horns, with the macroscopic appearance of normal early pregnancy. At histologic examination, the endometrium, devoid of any conceptus and chorion, showed a marked proliferation, on the basis of which a diagnosis of deciduoma was made. A remarkable population of stromal eosinophilic granular lymphocytes was present, especially in the axis of the endometrial folds. Periodic acid-Schiff and Dolichos biflorus-lectin histochemical reaction and a panel of 10 immunohistochemical markers were used to characterize eosinophilic granular cells. Our findings allowed us to compare these granular cells with the granulated decidual cells, whose presence was until now described only in primates, rodents, or a few other epitheliochorial species. On the basis of our results, the importance of eosinophilic granular cells in a decidualization process is hypothesized to occur also in the bitch.

Histochemical characterization of glycoproteins in the buccal epithelium of the catfish, Rita rita

Glycoproteins (GPs) elaborated by the buccal epithelium of the catfish, Rita rita, were analysed by a range of histochemical methods. These included methods for the characterization and simultaneous visualization of GPs with oxidizable vicinal diols, with O-acyl sugars, with O-sulphate esters and with sialic acid residues with and without O-acyl substitution at C7, C8 or C9. GPs elaborated at the surface of the buccal epithelium are primarily from two sources, the epithelial cells and the mucous goblet cells. They include GPs with O-sulphate esters, GPs with sialic acid residues without O-acyl substitution and GPs with oxidizable vicinal diols. Different classes of GPs have been associated with specific functions and are discussed in relation to their physiological significance, with special reference to their roles in lubrication, alteration in viscosity, trapping of food particles, buffering of fluids at the epithelial surface, prevention of proteoloytic damage to the epithelium, antimicrobial activity and defence against pathogens. The epithelium shows specialized modifications in the form of the buccal glands. These have been considered to increase the secretory surface that allows profuse secretion of mucus in a very short period of time. The secretions of these glands have been associated with multiple functions similar to those of saliva.

Glycoconjugate histochemistry of the digestive tract of Triturus carnifex (Amphibia, Caudata)

In this study, the variety of sugar residues in the gut glycoconjugates of Triturus carnifex (Amphibia, Caudata) are investigated by carbohydrate conventional histochemistry and lectin histochemistry. The oesophageal surface mucous cells contained acidic glycoconjugates, with residues of GalNAc, Gal beta1,3 GalNAc and (GlcNAc beta1,4)(n) oligomers. The gastric surface cells mainly produced neutral glycoproteins with residues of fucose, Gal beta1-3 GalNAc, Gal-alphaGal, and (GlcNAc beta1,4)(n) oligomers in N- and O-linked glycans, as the glandular mucous neck cells, with residues of mannose/glucose, GalNAc, Gal beta1,3 GalNAc, (GlcNAc beta1,4)(n)oligomers and fucose linked alpha1,6 or terminal alpha1,3 or alpha1,4 in O-linked glycans. The oxynticopeptic tubulo-vesicular system contained neutral glycoproteins with N- and O-linked glycans with residues of Gal-alphaGal, Gal beta1-3 GalNAc and (GlcNAc beta1,4)(n)oligomers; Fuc linked alpha1,2 to Gal, alpha1,3 to GlcNAc in (poly)lactosamine chains and alpha1,6 to GlcNAc in N-linked glycans. Most of these glycoproteins probably corresponds to the H(+)K(+)-ATPase beta-subunit. The intestinal goblet cells contained acidic glycoconjugates, with residues of GalNAc, mannose/ glucose, (GlcNAc beta1,4)(n)oligomers and fucose linked alpha1,2 to Gal in O-linked oligosaccharides. The different composition of the mucus in the digestive tracts may be correlated with its different functions. In fact the presence of abundant sulphation of glycoconjugates, mainly in the oesophagus and intestine, probably confers resistance to bacterial enzymatic degradation of the mucus barrier.