Epithelial barrier, Disruption

Ethical concerns over the use of animals may be addressed by the use of ex vivo or in vitro cell culture models such as this. In addition comeal cell culture combined with objectively quantifiable assays for comeal epithelial barrier disruption and transactivation of stress-related genes may reduce the high variability associated to the subjectively scored Draize Test. 

Comeal organ culture combined with objectively quantifiable assays for comeal epithelial barrier disruption reduces the high variability associated to the subjectively scored Draize Test. The FITC-Dextran retention has been studied as a quantitative evaluation of the comeal epithelial barrier (Lopez et al. 1991) following chemical exposure of bcnzal konium chloride (BAC), Polyquad, and Thimerosal. Sodium dodecyl sulfate (SDS) has also been tested for disruption of the tight junctions via FITC-Dextran retention assay. However, as an objective outcome measure for ocular toxicity, the scoring system is not yet quantitatively comparable for assessment of ocular irritancy to multiple test products. This limitation is similar to surface biotinylation assays. As fluorometry is utilized more extensively in varied laboratories with numerous test chemicals a standardized scoring system can be elicited similar to the familiar Draize Test. 

Permeation enhancers in general disrupt the integrity of the epithelial barrier, and have been said to act in the following ways [10,13,15] (Figure 10.1) ... 

Jepson, M.A., Colares-Buzato, C.B., Clark, M.A., Hirst, B.H., and Simmons, N.L. 1995. Rapid disruption of epithelial barrier function by Salmonella typhimurium is associated with structural modification of intercellular junctions. Infect Immun 63 356-359. 

The method allows visualization of the epithelial barrier and penetration of small molecules into cell layers indicating disruption of tight junctions (Saitou et al. 1998). Slides are examined under the fluorescent microscope for bound biotin and rhodamine staining in deeper epithelial and stromal layers. Staining indicates penetration of biotin molecules into the tissue through disrupted tight junction barriers (Xu et al. 2004). Recovery from disruption is tracked on day 0,1,2,3, and 4. 

This test uses the ex vivo model of comeal organ culture previously discussed combined with Fluorescein Isothiocyanate-Dextran Retention technique. Chemical insult may interfere with the comeal epithelial barrier function by disturbing the integrity of tight junctions. Disruption of tight junctions would... 

With these pathological features of ARDS in mind, hypotheses about the pathogenesis of ARDS must account for the accumulation of PMN and macrophages in the airspaces, the disruption of the endothelial and the epithelial barriers, and the initiation and propagation of repair processes that lead to sustained abnormalities of lung function. 

Propionibacterium acnes, commonly isolated from the skin, is the most frequently found anaerobe. Factors and conditions such as blepharitis, dry eye syndrome, meibomian gland dysfunction, and contact lens use may influence the composition of the normal flora or cause disruption to normal epithelial microbial barriers, either of which can lead to disease in susceptible patients. Although immunocompromised individuals may harbor Candida albicans, fungi are considered opportunistic pathogens. Little evidence supports the existence of any indigenous fungi in the normal conjunctival flora. 

PSA is one of the most widely used cancer biomarkers. It is a chymotryp-sin-like serine protease that is produced by epithelial cells of the prostate gland and secreted into the prostatic fluid. Prostate-cancer invasion disrupts the epithelial membrane barrier leading to elevated serum levels of PSA. Detection of PSA in blood can therefore be useful in the diagnosis of prostate abnormalities and for evaluation of prostate cancer therapy efficacy [21]. Two different forms of PSA are immunologically detectable the free form (MW 34 kDa) and a complex with a-l-antichymotrypsin (MW 96 kDa). Diagnostic assays developed for detection of PSA (e.g., enzyme-linked immunosorbent assays) detect total PSA concentrations down to 0.1 ngmL [22,23]. 

The infant immune system is not fnlly mature at birth it has deficits in the ability to prevent invasion of pathogens and to respond to antigens. Of particular concern in the context of ingredients new to infant formulas is the increased permeability of the gut mucosal barrier in the presence of inflammation or infection or if the integrity of the epithelial cell layer is disrupted. The increased permeability allows macromolecules to be absorbed, which stimulates allergic responses to food proteins. 

---