Pancreatic progenitor-derived hepatocytes are viable and functional in a 3D high density bioreactor culture system.

The rat pancreatic progenitor cell line B-13 is of interest for research on drug metabolism and toxicity since the cells trans-differentiate into functional hepatocyte-like cells (B-13/H) when treated with glucocorticoids. In this study we investigated the trans-differentiation and liver-specific functions of B-13/H cells in a three-dimensional (3D) multi-compartment bioreactor, which has already been successfully used for primary liver cell culture. Undifferentiated B-13 cells were inoculated into the bioreactor system and exposed to dexamethasone to promote hepatic trans-differentiation (B-13/HT). In a second approach, pre-differentiated B-13 cells were cultured in bioreactors for 15 days to evaluate the maintenance of liver-typical functions (B-13/HP). During trans-differentiation of B-13 cells into hepatocyte-like cells in the 3D bioreactor system (approach B-13/HT), an increase in glucose metabolism and in liver-specific functions (urea and albumin synthesis; cytochrome P450 [CYP] enzyme activity) was observed, whereas amylase - characteristic for exocrine pancreas and undifferentiated B-13 cells - decreased over time. In bioreactors with pre-differentiated cells (approach B-13/HP), the above liver-specific functions were maintained over the whole culture period. Results were confirmed by gene expression and protein analysis showing increased expression of carbamoyl-phosphate synthase 1 (CPS-1), albumin, CYP2E1, CYP2C11 and CYP3A1 with simultaneous loss of amylase. Immunohistochemical studies showed the formation of 3D structures with expression of liver-specific markers, including albumin, cytokeratin (CK) 18, CCAAT/enhancer-binding protein beta (CEBP-ß), CYP2E1 and multidrug resistance protein 2 (MRP2). In conclusion, successful culture and trans-differentiation of B-13 cells in the 3D bioreactor was demonstrated. The requirement for only one hormone and simple culture conditions to generate liver-like cells makes this cell type useful for in vitro research using 3D high-density culture systems.

Increased phosphorylated extracellular signal-regulated kinase immunoreactivity associated with proliferative and morphologic lung alterations after chrysotile asbestos inhalation in mice.

Activation of extracellular signal-regulated kinases (ERK) has been associated with the advent of asbestos-associated apoptosis and proliferation in mesothelial and alveolar epithelial cells and may be linked to the development of pulmonary fibrosis. The objective of studies here was to characterize the development of inflammation, cellular proliferation, and fibrosis in asbestos-exposed C57Bl/6 mice in relationship to patterns of ERK phosphorylation. Inflammation occurred after 10 and 20 days of asbestos exposure as evidenced by increases in total protein and neutrophils in bronchoalveolar lavage fluid. Increases in cell proliferation were observed at 30 days in bronchiolar epithelia and at 4, 14, and 30 days in the alveolar compartment of the lung. Trichrome-positive focal lesions of pulmonary fibrosis developed at 30 days in the absence of elevations in lung hydroxyproline or procollagen mRNA levels. Striking increases in ERK phosphorylation were observed within pulmonary epithelial cells at sites of developing fibrotic lesions after 14 and 30 days of inhalation. In addition to characterizing a murine inhalation model of asbestosis, we provide the first evidence showing activation of ERK signaling within lung epithelium in vivo, following inhalation of asbestos fibers.

Antibiotic resistance in the hospital setting: extent of the problem and possible solutions.

The advent of effective antimicrobial agents has been justifiably hailed as one of the most significant medical advances. However, as experience with older agents has grown and as newer compounds have been added to the clinician's armamentarium, certain disadvantages associated with the use of antimicrobials have become increasingly apparent. Toxicity and cost are among the disadvantages, but drug resistance is probably the major adverse consequence of widespread antimicrobial use. This article reviews the extent, mechanisms, and consequences of antimicrobial resistance--particularly in the hospital environment--and offers strategies for minimizing both its emergence and its spread.

The enterococcus: "putting the bug in our ears".

High-level resistance to gentamicin among clinical isolates of enterococci has been found with increasing frequency in recent years. In this issue, Zervos and colleagues report findings from a prospective study in which they assessed the frequency of colonization and infection with such organisms at a university medical center, demonstrating probable person-to-person spread. Their findings suggest that hospitals should conduct systematic screening for enterococci with high-level resistance to gentamicin, that antimicrobial treatment habits be modified to limit the emergence of such organisms, and that rigorous infection control be practiced to minimize their spread. These observations are particularly timely because it has become clear that enterococci are extremely versatile pathogens which are both well suited for survival and capable of causing serious illness, especially in hospitalized patients treated with some of the newer broad-spectrum antibiotic agents. Enterococci with high-level resistance to gentamicin are also of growing concern because their resistance to many antibiotic agents severely limits the clinician's options for treatment.