Commercial Porcine Gastric Mucin Preparations, also Used as Artificial Saliva, are a Rich Source for the Lectin TFF2: In Vitro Binding Studies

Mucous gels (mucus) cover internal body surfaces. The secretory mucins MUC5AC and MUC6 and the protective peptide TFF2 are characteristic constituents of gastric mucus; TFF2 is co-secreted with MUC6. Herein, we investigated two commercial mucin preparations by FPLC and proteomics, because they are model systems for studying the rheology of gastric mucins. One preparation is also used as a saliva substitute, for example, after radiation therapy. We show that both preparations contain TFF2 (≈0.6 to 1.1 %, w/w). The majority of TFF2 is strongly bound noncovalently to mucin in a manner that is resistant to boiling in SDS. First overlay assays with ¹²⁵ I-labeled porcine TFF2 revealed that mucin binding is modulated by Ca²⁺ and can be blocked by the lectin GSA-II and the antibody HIK1083, both recognizing the peripheral GlcNAcα1→4Galβ1→R moiety of MUC6. TFF2 binding was also inhibited in the presence of Me-β-Gal but less so by the α anomer. TFF2 may play a role in the oligomerization and secretion of MUC6, the rheology of gastric mucus, and the adherence of gastric microbiota. TFF2 in artificial saliva may be of benefit. TFF2 might also interact with the sugar moiety of various receptors.

Morphological study of the gastrointestinal tract of Larimichthys crocea (Acanthopterygii: Perciformes)

The present study aimed to investigate the macroscopic and histological structure of the gastrointestinal tract (GIT) of Larimichthyscrocea (Richardson, 1846). It consists of esophagus, stomach regions, pyloric caeca, intestinal regions, and rectum. Sixteen tubular light yellowish pyloric caeca of similar sizes were observed in all individuals. The digestive wall consists of mucosa, submucosa, muscularis, and adventitia. No major differences appeared in the structure of the tunica, epithelial cell types, connective tissues and musculature glands of L.crocea GIT. The mucosal epithelia in the oesophagus has longitudinal branched folds with frontward and hindmost zones. The gastric tunica mucosa has a characteristic folded structure and can be divided into three regions. The intestinal tunica mucosa is characterized by villi structures and numerous mucus-secreting cells. Mucus-secreting goblet cells were strongly positive to AB at pH 2.5 in the oesophagus (excluding gastro-oesophageal junction) and intestine mucosal regions, which indicates an abundance of carboxylate mucins. The surface epithelia of the gastric mucosa is PAS-positive and AB-negative. SEM examination revealed that cells in the epithelium of the esophagus have an unbroken apical layer and goblet cells. The intestinal coefficient (IC) of L.crocea was 0.80 ± 0.21, consistent with a carnivorous or omnivorous habit. Our study adds the knowledge of the digestive system of L.crocea and might be useful in the management of L.crocea stocks.

Cytochemical characterization of glycoconjugates in the apocrine glands of the equine scrotal skin

Cytochemistry of glycoconjugates in the apocrine glands in the scrotal skin of the horse was studied using cytochemical methods for electron microscopy, particularly lectin cytochemistry. The secretory cells possessed a variable number of secretory vesicles, a well-developed Golgi apparatus, and abundant cisternae of the rough endoplasmic reticulum. Additionally, the basolateral plasma membrane formed numerous interdigitating folds. Glycoconjugates with vicinal diol groupings were present predominantly in the secretory vesicles, the Golgi apparatus, the surface coat of the plasma membrane, and the majority of the intracellular membranes. With lectin cytochemistry, the secretory vesicles of the glandular cells exhibited glycoproteins with different terminal sugars (alpha-D-mannose, beta-D-galactose beta-N-acetyl-D-glucosamine, and sialic acid). Several sugars were distinctly prominent in the surface coat of the plasma membrane of the secretory cells. The cytochemical properties of the complex glycoconjugates found are discussed in relation to the specific functions of the glandular secretions. These glands may have an important role in not only thermoregulation but protection of the scrotal skin, a specific body region.

Pharmaceutical applications of mucoadhesion for the non-oral routes

The adhesion of pharmaceutical formulations to the mucosal tissue offers the possibility of creating an intimate and prolonged contact at the site of administration. This prolonged residence time can result in enhanced absorption and, in combination with a controlled release of the drug, also improved patient compliance by reducing the frequency of administration. During the almost 30 years over which mucoadhesion has been studied, a considerable amount of knowledge has been gained, and much has been learned about the different mechanisms occurring at the formulation-mucus interface and the properties that affect these mechanisms. The in-vivo performance of a dosage form not only depends on the mechanisms occurring at the interface, but also on the properties of the total mucoadhesive complex: the dosage form, the mucosa and the interface between them. A wide variety of methods are used for studying mucoadhesion; some rather similar to the in-vivo situation and some mimicking the interface alone. In this review, the mucus surface, the methods used for the study of mucoadhesion, the different mechanisms involved in mucoadhesion and theories underpinning them have been described. The complexity of mucoadhesion when trying to systemize the subject will also be discussed. The last part of the review describes the buccal, nasal, ocular, vaginal and rectal routes and provides examples of what can be achieved in-vivo when using mucoadhesive formulations.

Ultracytochemical Demonstration of Glycoproteins in the Eccrine Glands of the Digital Pads of the North American Raccoon (Procyon lotor)

In the eccrine glands of the digital pads of the North American raccoon (Procyon lotor), ultrastructural localization of glycoproteins with various saccharide residues was studied using preferably lectin cytochemical methods. Secretory granules observed in the dark cells exhibited glycoproteins with different terminal sugars (alpha-D-mannose, beta-D-galactose, beta-N-acetyl-D-glucosamine and sialic acid). The cytoplasm of the clear cells contained numerous glycogen particles. Several sugars were also detectable in the surface coat of the plasma membrane of the secretory cells. The results obtained could be helpful in understanding secretion production and cell related secretion functions of the eccrine glands of the raccoon digital foot pads.

Lectin and proteoglycan histochemistry of feline pacinian corpuscles

We studied carbohydrate residues of glycoproteins and proteoglycans (PGs) in peritoneal Pacinian corpuscles of five adult cats. Terminal monosaccharides of glycoproteins and related polysaccharides were identified by lectin histochemistry and the PGs and glycosaminoglycans (GAGs) by specific antibodies. The most intensive lectin staining reactions indicated an abundance of glycoconjugates with terminal mannose (Man) or sialic acid residues, but no complex-type oligosaccharides were detected within the corpuscles. Terminal fucose (Fuc) and galactose (Gal) residues typical for O-linked mucin-type glycoproteins generally associated with high water binding capacity were also absent. Antibodies against unsulfated chondroitin (C-0-S), chondroitin-4-sulfate (C-4-S), and decorin showed positive reactions in the interfibrillar spaces between the lamellae, around collagen fibers, and around the lamellae of the perineural capsule, especially in the outer parts known to contain Type II collagen. Biglycan showed a preference for the innermost part of the perineural capsule (intermediate layer), known to contain Type V collagen. Collagen V and biglycan are both linked to growth processes. Hyaluronic acid (HA), chondroitin-6-sulfate (C-6-S) chains, and a chondroitin sulfate proteoglycan (CSPG) were co-localized in the terminal glia. The study of carbohydrates with high water binding capacity may contribute to our understanding of the high viscoelasticity of Pacinian corpuscles.