The intestinal glycocalyx constitutes a glycosilated milieu, reactive with gut microflora and protects the gut form intestinal infections. The contents of the glycocalyx layer are in dynamic balance between biosynthesis of new glycans and removal of existing constituents. The fine structure of the glycocalyx was recently revealed to some extend. The aim of our work was to study the structure and localization of the components of intestinal glycocalyx in mice. For that purpose we used lectins

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... eled with fluorescent dye or with biotin (Lotus tetragonolobus, Ulex europaeus, Triticum vulgaris). We used fluorescent and transmission electron microscopy to trace the localization of N-acetyl--glucosamine oligomeres and of -L-fucosyl residues on the microvillus glycocalyx. N-acetyl--glucosamine oligomeres were abundant in all microvillus surfaces. -L-fucosyl residues were not detectable in the glycocalyx of duodenum, jejunum or ileum of adult mice by fluorescent microscopy but localized using the confocal state of art technique. INTRODUCTION The intestinal glycocalyx is comprised of protein-and lipid-bound oligosaccharides and polysaccharides attached to membrane-associated proteins and lipids covering the apical surface of enterocytes. It constitutes a significant barrier to transvascular exchange of water and solutes, and a binding site for different enzymes, growth factors and microorganisms [7, 12]. It has been suggested that the fine structure of that porous layer is composed of a matrix of molecules which are arranged in a regular pattern [14]. The fine structure of the glycocalyx could be revealed by electron microscopy. Many recent studies prove that glycosaminoglycans like hyaluronan (HA), heparan sulfate (HS) and chondroitin sulfate (CS) are found in different level of sulfation ,depending on the physiological micro-environment, and are linked to transmembare proteoglycans [12, 15]. Moreover the contents of the glycocalyx layer are in dynamic balance between biosynthesis of new glycans and removal of existing constituents [8]. It has been shown in previous studies that glycocalyx is an important factor for gut colonization. Breastfed children receive different glycans with milk and a preponderance of Bifidobacterium bifidum and lactobacillae in their intestines was noted. In contrast, not breastfed infants had microbiota more typical of adults. That causes the gut contents of breastfed infants to be more acidic, which can inhibit colonization by many pathogens [9]. Oligosaccharides in human milk are indigestible by the infant gut and therefore are not used as a nutrient. Their probable function is to protect the gut form pathogens. Mass spectrometry analysis proved that many milk oligosaccharides could contain components with structural homology to cell surface glycans. Therefore they are able to inhibit binding of pathogens to cell surface receptors in the mucosa and protect the infant from disease [10]. It is obvious that the saccharide "barrier" is crucial to the biology of the cell. It specifically modulates its interactions with small molecules, macromolecules, other cells, and with the extracellular environment. The aim of our work was to study the structure and localization of the components of intestinal glycocalyx in adult mice. For that purpose we used lectins that were stained with fluorescent dye or with biotin.