V. Pedini

Histology and Ultrastructure of the Gut of the Tilapia (Tilapia spp.), a Hybrid Teleost

The morphology of the intestine has been studied in a species of warm water fish, Tilapia spp., a hybrid teleost of notable economic importance. Light and electron microscope results show that the intestine is a relatively undifferentiated muscular tube lined with a simple columnar epithelium interspersed with goblet cells. The proximal region has a greater surface area, manifested by elongated mucosal ridges. The enterocytes are covered apically with uniform microvilli and exhibit the typical ultrastructural features of pinocytosis, namely extensive invaginations of the luminal plasma membrane and massive accumulation of vesicles in the apical cytoplasm. The distal intestine mucosa is thinner and less elaborately folded and consists of columnar cells with shorter and sparser microvilli. Their supranuclear cytoplasm contains abundant clear vacuoles. Numerous endocrine cells can also be seen. Regional cellular ultrastructural features are correlated with digestive functions.

Carbohydrate histochemistry of the alimentary canal of the shi drum, Umbrina cirrosa L.

Histochemical staining techniques, which differentiate the main categories of carbohydrates, were applied to sections from different segments of the alimentary canal of the shi drum Umbrina cirrosa L. to study patterns of distribution of epithelial glycoconjugates. In the oesophagus, mucous cells contained sulphomucins, together with a small amount of sialomucins. Stomach epithelial cells secreted neutral and acidic glycoconjugates, while gastric glands only produced small quantities of sialomucins. Goblet cells showed the presence of sialo and sulphomucins in the pyloric caeca, whereas intestinal mucous cells secreted sulphated glycoconjugates. This work serves as a baseline for further studies on carbohydrate composition of the mucosa of the shi drum digestive system.

Ultrastructural Study on the Stomach of Tilapia spp (Teleostei)

An ultrastructural study has been made of gastric mucosa of a teleostean fish, Tilapia spp. The cytological features of the surface mucous cells, mucous neck cells, glandular cells and endocrine cells are described. The surface mucous cells, identified by their superficial localization, are characterized by apical granules. The mucous neck cells are distinguished by the appearance of their mucous granules and their localization between surface mucous cells and glandular cells. The gastric glands contain only one form of cell whose fine structure is similar to cells that secrete hydrochloric acid.

Immunohistochemical identification and localization of orexin A and orexin type 2 receptor in the horse gastrointestinal tract.

The aim of the present study was to investigate the presence and the distribution of cells containing orexin A and orexin type 2 receptor in the horse stomach and gut, by means of immunohistochemical techniques. Orexin A was identified in the stomach fundic and pyloric regions and in the duodenum. In the same stomach regions, a large subset of orexin A-positive cells also showed orexin type 2 receptor-like immunoreactivity. Moreover, in the duodenum, many of them, seemed to store serotonin. Characteristically, enteric neurons or ganglia also displayed orexin A and, sometimes, orexin type 2 receptor immunoreaction. Orexin A and orexin type 2 receptor immunoreactivity was also found in the nerve fibers in the enteric submucosal layer. Our results, together with data present in the literature, could contribute to the understanding of complex mechanisms regulating the horse gut functionality that are depending very likely on the consequence of the co-operation of both a central and a peripheral control.

The Endocrine Cells in the Gastro‐enteric Tract of Adult Fallow Deer (Dama dama L.)

Endocrine cells were detected in the gastro‐enteric tract of the fallow deer by means of immunohistochemical procedures, using antibodies against serotonin, somatostatin, gastrin, glucagon and cholecystokinin. The number of cells positive for each antiserum in each region was evaluated. Serotonin‐containing enterochromaffin (Ec) cells were present in every region investigated and were most numerous in the proximal duodenum. Cells positive for somatostatin were present in all the regions studied, with the exception of the colon, and were especially numerous in the proper gastric‐gland region. Cells that were stained by the anti‐gastrin antibody were very numerous in the pyloric‐gland region but only rare in the duodenum. Glucagon‐immunoreactive cells were only detected in the large intestine and their frequency was always less than 10/0.5 mm2. Cholecystokinin‐containing cells were scarce and restricted to the pyloric‐gland region and duodenum.

Serotonin-Containing Cells in the Horse Gastrointestinal Tract

The presence and distribution of serotonin‐containing cells in the gastroenteric tract of horses have been investigated. The enterochromaffin (EC) cells have been identified using immunostaining procedures at both light and electron microscopic level. The EC cells were very numerous in the pyloric gland region, were only few in the duodenum but were absolutely lacking from the more distal portions of the intestine.

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.

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.

Carbohydrate histochemistry of lamb duodenum

In order to elucidate the carbohydrate profile of the mucosa of lamb duodenum, conventional histochemical methods and a panel of 7 labelled lectins were used. In some cases, treatment with sialidase preceeded lectin staining. Carbohydrate histochemistry revealed the presence of sugar residues in the brush border of enterocytes, goblet cells and duodenal glands. All sites contained neutral and acid glycoconjugates. The presence of sulphomucins in goblet and duodenal gland cells was age-dependent. Enterocytes and duodenal gland cells contained abundant amounts of oligosaccharides with terminal sialic acid-galactosyl(beta1 --> 3)N-acetylgalactosamine, whereas goblet cells contained the penultimate N-acetylgalactosamine residue linked to sialic acid. These findings were not age-dependent, whereas scarce amounts of fucose were found in all sites especially in young animals. The findings obtained in the present study serve as a basis for future pathological studies in lamb and sheep.

Complex Carbohydrate Histochemistry and Ultracytochemistry of the Sheep Lacrimal Gland

The chemical content of the secretion of the sheep lacrimal gland was analysed at the light and electron microscope levels by applying histochemical techniques and an ultrastructural histochemical method (periodic acid, thiocarbohydrazide and silver proteinate). Mucosubstance histochemistry demonstrated acidic glycoconjugates, mainly sulphated, in the mucous and seromucous glandular cells and in the apical portion of the cells lining the terminal ducts. Moreover, secretory granules, stained with PA‐TCH‐SP, showed a different localization of the reaction product. The presence of lysozyme was also found in the glandular serous cells. These histochemical studies demonstrate that the secretion of sheep lacrimal glands is mixed, having serous, mucous and seromucous components, and that an excellent correlation exists between the secretory granule substructure and glycoprotein localization.