P aneth cells , originally described by Schwalbe (1872) and later by Paneth (1888), are normally located at the base of the crypts of Lieberkühn in the small intestine of many mammals, except carnivores. They are easily recognized by a large number of eosinophilic granules located in the supranuclear portion of the cell. Electron microscopic studies (Satoh et al. 1990;Staley and Trier 1965;Hally 1958) have revealed the structural complexity of Paneth granules. These granules are characterized in several species, including rat and human, by an electron-lucent peripheral halo of variable thickness surrounding a large electron-dense core (Satoh et al. 1990).The functions of the Paneth cells have not been clearly established. However, it has been demonstrated that Paneth cells produce and secrete antibacterial agents (lysozyme, cryptidin, and immunoglobulin A), hydrolases, lipases, and growth factors and modulators (Desai et al. 1991;Quellette and Lualdi 1990;Saito et al. 1988;Lechene de la Porte et al. 1986;Poulsen et al. 1986;Senegas-Balas et al. 1984;Erlandsen et al. 1974 Erlandsen et al. , 1976Erlandsen and Parsons, 1973). The granules also contain a zinc-binding protein (Sawada et al. 1994). It has been suggested that goblet and Paneth cells share a common pathway of development (Kedinger et al. 1988;Lopez-Lewellyn and Erlandsen 1980;Lopez-Lewellyn 1979).Lectins are proteins or glycoproteins that bind specifically to carbohydrate groups (Goldstein and Hayes, 1978). They have been widely used in combination with enzymes for in situ characterization of the

We examined the distribution and pattern of reactivity of a panel of 16 lectins in the digestive gland of the bivalve mollusc Mytilus galloprovincialis at the light-microscopic level. Various chemical treatments were applied in combination with lectins to differentiate between N- and O-linked oligosaccharides. Several control reactions were carried out, including replacement of lectins by buffer and incubation with their specific competitive inhibitors. Some lectins reacted selectively with particular cell types, thus revealing a cell-specific glycoconjugate distribution pattern which is possibly related to the metabolic role of each cell type in the digestive gland. Glycoconjugates containing glucosamine, mannose, and sulfated galactose were associated with the endolysosomal system of digestive cells. These glycoconjugates were also found in small vesicles randomly distributed in the cytoplasm of adipogranular cells in the connective tissue. However galactosamine residues appeared to be associated mainly with basophilic cells. Fucose residues did not exhibit a cell-specific distribution and appeared in small amounts homogeneously distributed throughout the digestive gland tissue. Conventional histochemical reactions for carbohydrate detection revealed moderate amounts of periodic-acid-Schiff-positive, neutral carbohydrates widely distributed in digestive and connective tissues. Among the acid carbohydrates, most cell types contained complex sulfated carbohydrates, but not carboxylated ones; this agreed well with the complete lack of sialic acid residues in all cell types studied, as observed by lectin histochemistry.

SUMMARYThe oligosaccharides of the mucous gastric glycoproteins are involved in the protection of the gastric mucosa and are altered in different diseases. Therefore, it is important to know their composition in health, to better determine the alterations induced by the disease. Moreover, analysis of the molecular composition of the fundic gland cells has been previously used to obtain new insights into the origin of the different cell types. The aim of the present study was the localization in the subcellular structures of the fucose residues of the oligosaccharides in human fundic glands. For this, lectin cytochemical methods were used at the light and electron microscopic levels. They were combined with enzymatic and chemical treatments to characterize the nature of the oligosaccharide chains containing the fucose residues. The presence of this carbohydrate belonging to N-or O-linked oligosaccharides has been demonstrated in the secretory granules of the surface, gastric pit, mucous neck, and transitional cells of the fundic mucosa, and in the intracellular canaliculi and tubulovesicular system of the parietal cells. These fucose residues were added in the trans-Golgi regions to the elongating chains. The term "mucosal defense" refers to the factors that permit the gastric mucosa to withstand frequent exposure to substances with a wide range of properties including, e.g., pH, osmolarity, and detergent properties. The first level of defense consists of the factors secreted into the lumen, including acid, bicarbonate, mucus, immunoglobulins, and other antibacterial substances (Wallace and Granger 1996). Mucous secretions form a barrier that traps bicarbonate secreted by the epithelium and stops acid retrodiffusion from the gastric lumen. Moreover, bacteria become trapped in the mucus and are eventually excreted in the feces (Wallace and Granger 1996).

Brain edema in gliomas is an epiphenomenon related to blood-brain-barrier (BBB) breakdown in which endothelial nitric oxide synthase (eNOS) plays a key role. When induced by vascular endothelial growth factor (VEGF), eNOS synthesizes nitric oxide that increases vascular permeability. We investigated the relationship between eNOS, VEGF and BBB dysfunction in experimental gliomas.Tumors were produced in Sprague-Dawley rats by transplacentary administration of Ethylnitrosourea (ENU). Immunoexpression of eNOS and VEGF(165) was studied to identify locations of vascular permeability. BBB permeability was evaluated using gadolinium and intravital dyes and BBB integrity by endothelial barrier antigen (EBA), glucose transporter-1 (GluT-1) and occludin immunostaining. Low grade gliomas displayed constitutive eNOS expression in endothelial cells and in VEGF-positive astrocytes surrounding vessels. Malignant gliomas overexpressed eNOS in aberrant vessels and displayed numerous adjacent reactive astrocytes positive for VEGF. Huge dilated vessels inside tumors and glomeruloid vessels on the periphery of the tumor showed strong immunopositivity for eNOS and a lack of occludin and EBA staining in several vascular sections. BBB dysfunction on these aberrant vessels caused increased permeability as shown by Gadolinium contrast enhancement and intravital dye extravasation.These findings support the central role of eNOS in intra- and peritumoral edema in ENU-induced gliomas.