Background-The mechanism of iron absorption by the intestine and its transfer to the main iron storage site, the liver, is poorly understood. Recently an iron carrier was cloned and named DMT1 (divalent metal transporter 1). Aims-To determine the level of DMT1 gene expression and protein distribution in duodenum and liver. Methods-A DMT1 cRNA and antibody were produced and used in in situ hybridisation and immunohistochemistry, respectively, in rats in which the iron stores were altered by feeding diets with normal, low, and high iron content. Results-Duodenal DMT1 mRNA was low in crypts and increased at the crypt-villus junction in iron deficient and control rats; it fell in the iron loaded state. Staining for DMT1 protein was not detected in crypts. In villus enterocytes, protein staining was localised to the microvillus membrane in iron deficiency, in the cytoplasm and to a lesser extent in the membrane in controls, and entirely in the cytoplasm of iron loaded animals. Liver DMT1 mRNA was distributed evenly across hepatocytes. DMT1 protein staining was observed on hepatocyte plasma membranes, with highest values in the iron loaded state, lower values in control animals, and none after iron depletion. Conclusions-Results are consistent with a role for DMT1 in the transmembrane transport of non-transferrin bound iron from the intestinal lumen and from the portal blood. (Gut 2000;46:270-276)

A systematic review of studies that investigated the association of antibiotics with hospital-acquired Clostridium difficile-associated diarrhoea (CDAD) was undertaken to summarize the strength of the evidence for this relationship. The results from the studies identified were considered after critically reviewing the design and conduct of each study. Although the majority of studies found an association with various antibiotics, antibiotic classes or components of antibiotic administration, most were limited in their ability to establish a causal relationship by the use of incorrect control groups, the presence of bias, inadequate control of confounding and small sample sizes. The limitations identified in this review prevented the pooling of results in a meta-analysis. Two studies of reasonable quality suggested an association between clindamycin, cephalosporins, penicillins and CDAD. Well-designed studies grounded in epidemiological principles are needed to identify true risk factors for CDAD and to provide reliable estimates of the strength of association.

Serosal pathologies including malignant mesothelioma (MM) can show features of osseous and/or cartilaginous differentiation although the mechanism for its formation is unknown. Mesothelial cells have the capacity to differentiate into cells with myofibroblast, smooth muscle and endothelial cell characteristics. Whether they can differentiate into other cell types is unclear. This study tests the hypothesis that mesothelial cells can differentiate into cell lineages of the embryonic mesoderm including osteoblasts and adipocytes. To examine this, a functional assay of bone formation and an adipogenic assay were performed in vitro with primary rat and human mesothelial cells maintained in osteogenic or adipogenic medium (AM) for 0–26 days. Mesothelial cells expressed increasing levels of alkaline phosphatase, an early marker of the osteoblast phenotype, and formed mineralized bone-like nodules. Mesothelial cells also accumulated lipid indicative of a mature adipocyte phenotype when cultured in AM. All cells expressed several key osteoblast and adipocyte markers, including osteoblast-specific runt-related transcription factor 2, and demonstrated changes in mRNA expression consistent with epithelial-to-mesenchymal transition. In conclusion, these studies confirm that mesothelial cells have the capacity to differentiate into osteoblast- and adipocyte-like cells, providing definitive evidence of their multipotential nature. These data strongly support mesothelial cell differentiation as the potential source of different tissue types in MM tumours and other serosal pathologies, and add support for the use of mesothelial cells in regenerative therapies.

Background: Absorption of non-haeme iron occurs mainly in the duodenum. It involves the divalent metal transporter 1 (DMT1) in the uptake of ferrous Fe(II) iron and the basolateral transporter ferroportin/ IREG-1/MTP-1/SLC40A1 in its release. Whether ferroportin functions in this process at other sites in the enterocyte is unknown. In this study the effect of a blocking antibody to ferroportin on the uptake and release of iron was evaluated in enterocyte-like cells (IEC-6 and Caco-2) and in freshly isolated duodenal enterocytes from rats. Methods: Uptake of 1 mM Fe(II) and its release by cells was studied in the presence of the antibody. Ferroportin expression was determined by western blot analysis of duodenal mucosa enriched microvillus membranes, Caco-2 cells, IEC-6 cells, and freshly isolated enterocytes. Immunofluorescent detection of ferroporitn was performed on frozen sections of duodenum from rats with variations in body iron stores. Results: Ferroportin was expressed in all cell types. In these cells, the antibody significantly reduced (p,0.05) uptake of Fe(II) by 40-50% but had no effect on the release of iron. In Caco-2 cells, Fe(II) uptake was reduced only when the antibody was in contact with the apical membrane. Ferroportin protein was enriched in microvillus membrane preparations. In enterocytes from iron deficient rats, ferroportin was expressed along the brush border where it colocalised with lactase. Ferroportin was seen in the basal cytoplasm and along the basolateral membranes. Iron loading markedly reduced intracellular expression of ferroportin. In Caco-2 cells, ferroportin also localised to the microvillus and lateral and basal membranes. Conclusions: In addition to release, ferroportin functions in the uptake of iron at the apical membrane, possibly by modulating the activity of DMT1.

Regulation of iron absorption, which is the primary mechanism for maintaining body iron stores, occurs primarily in the proximal small intestine. Recent identification of proteins that are involved in iron absorption such as the uptake transporter-divalent metal transporter (DMT1), the basolateral transporter, IREG1, and the ferroxidase-hephaestin provide new opportunities to study this process. We evaluated the rat intestinal cell line, IEC-6, as a model of intestinal iron transport. This involved measuring the expression of DMT1 and IREG1 by Western blot analysis and confocal microscopy, and hephaestin by protein-dependent copper oxidase activity. DMT1 and IREG1 were expressed in IEC-6 cells. The uptake of 1 micromol/L ferrous iron [Fe(II)]:ascorbate and its efflux also was associated with the expression of DMT1 under different levels of iron loading. The expression of DMT1 changed inversely with iron levels as did the uptake of Fe(II). However, with different levels of cellular iron, IREG1 expression remained constant, as did the release of iron from the cells, suggesting that they could be related. Ceruloplasmin and apotransferrin did not enhance the rate or extent of iron release. Copper oxidase activity, considered to indicate hephaestin activity, was detected only intracellularly. Confocal microscopy showed DMT1 and IREG1 on the cell membrane of IEC-6 cells at 4 degrees C but at intracellular locations at 37 degrees C, indicating that these proteins can function at the cell membrane and intracellularly. In terms of iron absorption, IEC-6 cells have a villous enterocyte phenotype and are regulated by iron stores as occurs in vivo; therefore, they represent an appropriate cell model with which to study this process.