N-Cadherin extracellular repeat 4 mediates epithelial to mesenchymal transition and increased motility.

E- and N-cadherin are members of the classical cadherin family of proteins. E-cadherin plays an important role in maintaining the normal phenotype of epithelial cells. Previous studies from our laboratory and other laboratories have shown that inappropriate expression of N-cadherin by tumor cells derived from epithelial tissue results in conversion of the cell to a more fibroblast-like cell, with increased motility and invasion. Our present study was designed to determine which domains of N-cadherin make it different from E-cadherin, with respect to altering cellular behavior, such as which domains are responsible for the epithelial to mesenchymal transition and increased cell motility and invasion. To address this question, we constructed chimeric cadherins comprised of selected domains of E- and N-cadherin. The chimeras were transfected into epithelial cells to determine their effect on cell morphology and cellular behavior. We found that a 69-amino acid portion of EC-4 of N-cadherin was necessary and sufficient to promote both an epithelial to mesenchymal transition in squamous epithelial cells and increased cell motility. Here, we show that different cadherin family members promote different cellular behaviors. In addition, we identify a novel activity that can be ascribed to the extracellular domain of N-cadherin.

Clinical and laboratory evaluation of a closed enteral feeding system under cyclic feeding conditions: a microbial and cost evaluation.

Cyclic feeding schedules are now commonly used in conjunction with closed enteral feeding systems. Some manufacturers and clinicians have speculated that closed system cyclic feeding may promote formula contamination via retrograde movement of bacteria during the "no-flow" periods. Using both laboratory and clinical settings, our study evaluated whether retrograde bacterial movement under "no-flow" conditions results in contamination of closed system feeding containers. The clinical phase was conducted with 57 closed system feeding containers used to feed nursing home residents. In both laboratory and clinical testing there was no evidence of container contamination at 36-48 h, nor was there evidence of retrograde movement of bacteria beyond the drip chamber. Formula waste and costs were also analyzed using several 24- or 36-h hang time scenarios. Provided the appropriate container size is used, potential cost savings between $67 to $135 per patient per month may be achieved with the 36-h hang time scenarios. Retrograde movement of bacteria does not appear to be a source of closed system feeding container contamination in systems that incorporate a drip chamber. Using the appropriate size feeding container and systems with at least a 36-h hang time will result in significant cost savings.

Cross-talk between adherens junctions and desmosomes depends on plakoglobin.

Squamous epithelial cells have both adherens junctions and desmosomes. The ability of these cells to organize the desmosomal proteins into a functional structure depends upon their ability first to organize an adherens junction. Since the adherens junction and the desmosome are separate structures with different molecular make up, it is not immediately obvious why formation of an adherens junction is a prerequisite for the formation of a desmosome. The adherens junction is composed of a transmembrane classical cadherin (E-cadherin and/or P-cadherin in squamous epithelial cells) linked to either beta-catenin or plakoglobin, which is linked to alpha-catenin, which is linked to the actin cytoskeleton. The desmosome is composed of transmembrane proteins of the broad cadherin family (desmogleins and desmocollins) that are linked to the intermediate filament cytoskeleton, presumably through plakoglobin and desmoplakin. To begin to study the role of adherens junctions in the assembly of desmosomes, we produced an epithelial cell line that does not express classical cadherins and hence is unable to organize desmosomes, even though it retains the requisite desmosomal components. Transfection of E-cadherin and/or P-cadherin into this cell line did not restore the ability to organize desmosomes; however, overexpression of plakoglobin, along with E-cadherin, did permit desmosome organization. These data suggest that plakoglobin, which is the only known common component to both adherens junctions and desmosomes, must be linked to E-cadherin in the adherens junction before the cell can begin to assemble desmosomal components at regions of cell-cell contact. Although adherens junctions can form in the absence of plakoglobin, making use only of beta-catenin, such junctions cannot support the formation of desmosomes. Thus, we speculate that plakoglobin plays a signaling role in desmosome organization.