Mucosal epithelium

The in vitro system we have been using to study the transepithelial transport is cultured Madin-Darby canine kidney (MDCK) epithelial cells (11). When cultured on microporous polycarbonate filters (Transwell, Costar, Cambridge, MA), MDCK cells will develop into monolayers mimicking the mucosal epithelium (11). When these cells reach confluence, tight junctions will be established between the cells, and free diffusion of solutes across the cell monolayer will be markedly inhibited. Tight junction formation can be monitored by measuring the transepithelial electrical resistance (TEER) across the cell monolayers. In Figure 1, MDCK cells were seeded at 2 X 104 cells per well in Transwells (0.4 p pore size) as described previously. TEER and 14C-sucrose transport were measured daily. To determine 14C-sucrose... 

Wright, K.A., Weidman, E. and Hong, H. (1987) The distribution of cells killed by Trichinella spiralis in the mucosal epithelium of two strains of mice. Journal of Parasitology 73, 935-939. 

Recently, more importance is given to the link between the integrity of the mucosal epithelium on one side and the immune system on the... 

Cultured nasal cells are reliable models for drug transport and metabolism studies, since they are known to express important biological features (e.g. tight junctions, mucin secretion, cilia, and various transporters), resembling those found in vivo systems. Moreover, easy control of experimental conditions as well as separation of the permeation step from the subsequent absorption cascade is also possible. A relatively simple primary culture condition using human nasal epithelial cells for in vitro drug transport studies has been established and applied in transport and metabolism studies of drugs. It is known that the culture condition and/or selection of culture media are critical in the recapitulation of well-differentiation features of in vivo nasal mucosal epithelium [46],... 

Oral rehydration solution (g/L of boiled water NaQ 3.5, glucose 20, NaHCOs 2.5, KQ 1.5). Oral administration of glucose-containing salt solutions enables fluids to be absorbed because toxins do not impair the cotransport of Na+ and glucose (as well as of H2O) through the mucosal epithelium. In this manner, although frequent discharge of stool is not prevented, dehydration is successfully corrected. 

Astringents such as tannic acid (home remedy black tea) or metal salts precipitate surface proteins and are thought to help seal the mucosal epithelium. Protein denaturation must not include cellular proteins, for this would mean cell death. Although astringents induce constipation (cf AP salts, p. 166), a therapeutic effect in diarrhea is doubtful. 

The major antibody isotype in external secretions is sIgA, and the total amount of IgA synthesized is twice the amount of IgG produced daily in humans. IgA cells represent up to 80% of the entire mucosal lymphoid cell population. sIgA in mucosal secretions results from polymeric IgA transported across mucosal epithelium via binding to the pIgRreceptor (also known as the secretory component). The receptor is eventually cleaved and results in an IgAipIgR complex, referred to as sIgA (Figure 7.2) (Rojas and Apodaca, 2002). 

Microcarrier particles Can encapsulate antigen and be carried across the mucosal epithelium Biodegradable microspheres, liposomes, vims-hke particles, stimulating complexes (ISCOMM... 

Mucosal adjuvants Bind to M cells and GMl ganglioside receptors on mucosal epithelium CT toxin... 

The iron is transferred by the mucosal epithelium to the body and is bound to plasma transferrin in the ferric state. In the plasma, iron takes part in a dynamic transferrin-iron equilibrium and is distributed into vascular and interstitial extravascular compartment. 50 to 60% of transferrin is extravascular. The plasma iron pool in adults is about 3 mg and has an estimated turnover of 20 to 30 mg per 24 hours. Daily and obligatory losses of iron in healthy men are about 1 mg in healthy menstruating women these average 2 mg and in either case are compensated by a net absorption of 1 to 2 mg from the intestine, which enters the mobile pool of transferrin iron. 

Parsons, D.S. (1975). Multimembrane systems membrane function and energetics in intestinal mucosal epithelium (Parsons, D.S., Ed.), pp. 172-192. In Biological Membranes. Clarendon Press, Oxford, UK. 

Cortez, M., Silva, M. R., Neira, I., Ferreira, D., Sasso, G. R. S., Luquetti, A. O., Rassi, A., and Yoshida, N. (2006). Trypanosoma cruzi surface molecule gp90 downregulates invasion of gastric mucosal epithelium in orally infected mice. Microbes Infect. 8(1), 36-44. 

Jacob, J., Santos, C., Carino, G., et al. An in-vitro bioassay for quantification of bioadhesion of polymer microspheres to mucosal epithelium. Proceed. Int. Symp. Control. Rel. Bioact. Mater. 22 312—313, 1995. 

Gollnick, H.P.M. and Siebenwirth, C., /S-Carotene plasma levels and content in oral mucosal epithelium is skin type associated, Skin Pharmacol. Appl. Skin Physiol., 15, 360, 2002. 

The concept that the scolex of adult cestodes is generally non-penetrative has been shown not to hold for species such as Echinococcus granulosus and E. multilocularis, where the scolex penetrates the crypts of Lieberkiihn and, occasionally, even the lamina propria (Fig. 9.5) often resulting in a complete breakdown of the mucosal epithelium. These species can be regarded as both tissue and lumenal parasites. That the scolex contact is close is reflected in the fact that anti-Echinococcus antibodies appear in dog sera 14 days post-infection (p.i.) (368). It is likely, however, that in many cestodes the scolex contact is more superficial and breakdown of the mucosa may not occur, especially in those species which undergo diurnal migration - see Chapter 9. 

The permeability of the oral mucosal epithelium is intermediate between that of the skin epithelium, which is highly specialized for a barrier function (see Section 8.1) and the gut, which is highly specialized for an absorptive function. Within the oral cavity, the buccal mucosa is less permeable than the sublingual mucosa. 

In terms of oral delivery, under normal conditions, only negligible amounts of proteins are absorbed intact through the gastrointestinal (GI) tract [70,71]. Ingested proteins are naturally fragmented into amino acids and short peptides by various enzymes present in the gut [72]. These proteolytic enzymes are found both in the lumen and in the mucosal epithelium therefore, although proteins can be protected from the luminal enzymes by common encapsulated methods, they are still susceptible to degradation at the absorption site by various mucosal enzymes located in the intestinal walls. 

Diarrhoea associated with deranged motility. In order for nutrients and water to be efficiently absorbed, the intestinal contents must be adequately exposed to the mucosal epithelium and retained long enough to allow absorption. Disorders in motility that accelerate transit time can decrease absorption, resulting in diarrhoea. Alterations in intestinal motility (usually increased propulsion) are observed in many types of diarrhoea. What is not usually clear, and is very difficult to demonstrate, is whether primary alterations in motility are the cause of diarrhoea or simply an effect. 

It is unclear whether any mammalian genes are activated under Cu dehciency. The likely candidates for mammalian genes induced by Cu dehciency are those involved in intestinal Cu ion absorption, since stringent control of absorption and excretion of dietary copper across the mucosal epithelium is known (Linder, 1991 Linder and Hazegh-Azam,... 

Acute infection is typically initiated in the mucosal epithelium, and then HSV-1 establishes latency in sensory neurons located in trigeminal ganglia (TG) or sacral dorsal root ganglia. Despite a vigorous immune response during acute infection, latency is established. As many as 20-30% of sensory neurons are latently infected (reviewed in Tones, 1998, 2003). As a consequence of primary infection, HSV-1 genomic DNA is also present in the central nervous system (CNS) of a significant proportion of the adult human population (Fraser et al., 1981). 

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