Difference between the E1 and E2 conformations of gastric H+/K+-ATPase in a multilamellar lipid film system. Characterization by fluorescence and ATR-FTIR spectroscopy under a continuous buffer flow.

A liquid flow cell was used for an attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) study of conformational changes taking place in the gastric H+/K+-ATPase. Shifting from E1 to E2 form is induced by replacing Na+ by K+ ions. Introducing ions through a flow passing over a protein multilayer film induced the conformational change without cell manipulations. Measurement sensitivity was thereby improved by about one order of magnitude. The detection threshold allowed the possibility to detect a change affecting five amino acids out of the 1324 that compose the H+/K+-ATPase molecule. It appeared that fewer than five amino-acid residues undergo a conformational change upon replacing Na+ by K+ ions in the medium. Evidence that conformational changes occur in an identical system was brought by monitoring the fluorescence of fluorescein isothiocyanate-labeled H+/K+-ATPase in similar conditions. Our data suggest that essentially the tertiary structure of the protein is modified.     

Dexamethasone acts as a negative regulator of epidermal growth factor receptor synthesis in fetal rat lung cells

125I-Epidermal growth factor (EGF) binding capacity in fetal rat lung cells is decreased by approximately 50% following 24-h dexamethasone treatment. Ligand binding assays identified an average of 30,000 receptors per cell in untreated FRL cells, while analysis of dexamethasone treated cells showed a decrease to about 16,000 receptors per cell. No substantial changes in receptor affinities were detected. Immunoprecipitation of 35S-methionine-labeled EGF receptor protein demonstrated a 50% decrease in total EGF receptor protein after 24-h dexamethasone treatment. Brief pulse labeling with 35S-methionine showed that the reduction in total EGF receptor protein content was due to a decrease in EGF receptor synthesis. Receptor synthesis declined about 25% after 1 h of dexamethasone treatment and at 3 h, EGF receptor synthesis was maximally decreased to nearly 50% that of cells not exposed to dexamethasone. Dexamethasone treatment was also effective in reducing EGF receptor synthesis in cells pretreated with retinoic acid, an agent which enhances receptor synthesis. These data are the first to document a dexamethasone-induced decrease in EGF receptor synthesis. Furthermore, these findings may provide a plausible mechanism by which dexamethasone could regulate EGF responsiveness.     

INFLAM – INFLAMmation in Brain and Vessels with Iron Nanoparticles and Cell Trafficking: A Multiscale Approach of Tissue Microenvironment,Iron Nanostructure and Iron Biotransformation

Background

Inflammation is a share process in atherosclerosis and stroke and is thought to be a key player in the evolution of these diseases. Ten years ago, inflammation imaging with magnetic resonance imaging (MRI) was considered very promising for both pre-clinical and clinical studies of atherosclerosis and stroke.

Evidence for ongoing introduction of non-native earthworms in the Washington,DC metropolitan area

Earthworm introductions and invasions are ongoing, with significant consequences for ecological characteristics and function where populations of invasive species reach high densities. In North America the influx of people, goods and materials to coastal cities has long been recognized to be related to introduction and establishment of many different invasive organisms. We conducted surveys for soil invertebrates in the Washington, DC area along the Potomac River corridor to examine the influence of historic soil profile disrupting disturbances on the composition of soil invertebrate communities. Here we report three earthworm taxa that either (1) had never been previously reported in North America (Lumbricidae: Helodrilus oculatus), (2) had never been reported from “wild” caught samples in forested soils (Lumbricidae: Eisenia fetida), or (3) represented a notable range expansion for an introduced species (Lumbricidae: Murchieona muldali). All three species reported here have attributes that give reason for concern over their expansion into North American soils, not least of which is their potential for competitive interactions with the remaining native earthworm species.