Trans epithelial electrical resistance

Just recently a series of other quaternized chitosan derivatives have been synthesized and characterized, namely, A,A-dimethyl, A-ethyl chitosan (DMEC) (Bayat et al. 2006), A-methyl, A,A-diethyl chitosan (DEMC) (Avadi et al. 2004) and A,A,A-triethyl chitosan (TEC) (Avadi et al. 2003). In a comprehensive study (Sadeghi et al. 2008a, b) the four quaternized derivatives of chitosan, trimethyl chitosan (TMC), diethylmethyl chitosan (DEMC), triethyl chitosan (TEC) and dimethylethyl chitosan (DMEC) with degree of substitution of approximately 50% were synthesized and their effect on the permeability of insulin across intestinal Caco-2 monolayers was studied and compared with chitosan both in free-soluble form and in nanoparticulate systems. Trans-epithelial electrical resistance (TEER) studies revealed that all four chitosan derivatives in free-soluble forms were able to decrease the TEER value in the following order TMC>DEMC>TEC = DMEC>chitosan, indicating their... 

Concentrations of compound to be used in omic investigations would ideally cause no measurable change in cell viability, i.e., LC0 or NOAEL, and induce cellular stress, as indicated by an appropriate stress marker such as supernatant lactate [55] or a functional endpoint such as trans-epithelial electrical resistance (TEER) for epithelial cells [56]. This concentration can be defined as the point of departure of decreased viability in the dose range finding experiments, i.e., the highest possible LC0. 

It is often possible to address function more specifically in in vitro assays, where functional parameters are usually very sensitive readouts of adverse effects. For example trans-epithelial electrical resistance (TEER) is a very sensitive marker of epithelial disturbances. TEER measures the barrier function of the entire mono-layer and is utilized to study functional disturbances of many epithelial/endothelial cell types including blood-brain barrier, pulmonary, renal, and gastrointestinal cells. Its sensitivity lies in the fact that only a small proportion of cell death has a very large impact on barrier function. Additionally, cell stress can interfere with the arrangement and population of tight junction proteins [16] thus, TEER can in certain conditions measure functional disturbances in the absence of cell death [13]. Also since TEER can be measured noninvasively, it is nondestructive and can be used to monitor the effects of treatment over days and weeks [13, 17]. For excitable cells, electrical activity has also been proven to be an extremely sensitive parameter of adverse drug reactions and microelectrode arrays have been employed successfully to monitor neurotoxicity in vitro [18]. Also, for contractile cells, such as cardiomyocytes, the use of impedance measurements to measure the effects of compounds on spontaneous contraction has been demonstrated to be a very sensitive functional monitoring parameter in vitro [19, 20], Admittedly, none of the aforementioned techniques are true biomarkers per se however, such measurements illustrate the fact that in vitro techniques allow certain possibilities that are not practically tenable in the whole body. 

Commane DM, Short CT, Silvi S, Cresci A, Hughes RM, Rowland IR. Effects of fermentation products of pro- and prebiotics on trans-epithelial electrical resistance in an in vitro model of the colon. Nutr Cancer. 2005 51 102-109. 

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