title: High-resolution analysis of barrier function.
abstract: High-resolution analysis of epithelial barrier function adds substantial information to that provided by conventional transepithelial electrical resistance (TER) measurements. This chapter describes three high-resolution techniques. First, two variants of impedance spectroscopy are delineated. One-path impedance spectroscopy discriminates vertically between serial pathways, namely resistances of the epithelial cell layer and of subepithelial tissues. As a typical application, measurements on human sigmoid colon biopsies from patients suffering from Crohn's disease are reported. Two-path impedance spectroscopy allows to discriminate between trans- and paracellular resistance, and the general principle of this technique is outlined. Second, the conductance scanning technique is presented, which discriminates horizontally between optically distinct parallel pathways over a wide range of spatial resolutions. Using this technique, it was shown that occludin--in contrast to the then prevailing opinion--is not irreplaceable to barrier function. Third, three-dimensional confocal fluorescence imaging for depicting transepithelial transport processes is introduced. Using this method the transepithelial translocation of bacteria which generate focal leaks was discovered.
authors.affiliation: Institute of Clinical Physiology, Charité, Berlin, Germany. michael.fromm@charite.de
authors.forename: Michael
authors.initials: M
authors.lastname: Fromm
authors.forename: Susanne M
authors.initials: SM
authors.lastname: Krug
authors.forename: Sebastian
authors.initials: S
authors.lastname: Zeissig
authors.forename: Jan F
authors.initials: JF
authors.lastname: Richter
authors.forename: Rita
authors.initials: R
authors.lastname: Rosenthal
authors.forename: Jörg-Dieter
authors.initials: JD
authors.lastname: Schulzke
authors.forename: Dorothee
authors.initials: D
authors.lastname: Günzel
mesh_terms: D000818:Animals; D002460:Cell Line; D002463:Cell Membrane Permeability; D012809:Colon, Sigmoid / Q000378:metabolism; D004553:Electric Conductivity; D017097:Electric Impedance; D004847:Epithelial Cells / Q000502:physiology*; D006460:Hemolysin Proteins / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018613:Microscopy, Confocal; D062793:Occludin
chemical_list: D006460:Hemolysin Proteins; D008565:Membrane Proteins; C568985:OCLN protein, human; D062793:Occludin; C568986:Ocln protein, mouse