Alterations in the bovine bronchoalveolar lavage proteome induced by dexamethasone

Stressors such as transportation, weaning and co-mingling increase susceptibility to bacterial pneumonia in cattle and are associated with elevated levels of endogenous glucocorticoids. To determine the effect of glucocorticoids on the proteins expressed in the fluid lining the respiratory tract, bronchoalveolar lavage (BAL) was performed on cattle treated with dexamethasone or saline and proteins were resolved by two-dimensional electrophoresis (2-DE). Significant changes in expression were observed for 9 of the 363 detected spots, and the identities of these proteins were determined by mass spectrometry. Consistent with the initiation of an acute phase response, the expression of alpha-1-acid glycoprotein (orosomucoid) and alpha-1-antitrypsin was increased and alpha-2-HS-glycoprotein (fetuin) was decreased in the BAL fluid of dexamethasone-treated cattle. In addition, dexamethasone induced the expression of two hydrophobic ligand-binding proteins, adipocyte-fatty acid binding protein and odorant binding protein (OBP), as well as the proteins alpha-enolase, cofilin-1 and immunoglobulin J chain. OBP mRNA expression in bronchial biopsies was quantified by real-time RT-PCR and the 6-fold higher levels of expression observed in dexamethasone- versus saline-treated animals correlated with the changes observed in OBP protein level. These findings demonstrate glucocorticoid-dependent changes in the protein composition of the epithelial lining fluid of the respiratory tract, identifying proteins potentially integral to respiratory disease susceptibility.     

Involvement of mammalian Mus81 in genome integrity and tumor suppression

Mus81-Eme1 endonuclease has been implicated in the rescue of stalled replication forks and the resolution of meiotic recombination intermediates in yeast. We used gene targeting to study the physiological requirements of Mus81 in mammals. Mus81-/- mice are viable and fertile, which indicates that mammalian Mus81 is not essential for recombination processes associated with meiosis. Mus81-deficient mice and cells were hypersensitive to the DNA cross-linking agent mitomycin C but not to gamma-irradiation. Remarkably, both homozygous Mus81-/- and heterozygous Mus81+/- mice exhibited a similar susceptibility to spontaneous chromosomal damage and a profound and equivalent predisposition to lymphomas and other cancers. These studies demonstrate a critical role for the proper biallelic expression of the mammalian Mus81 in the maintenance of genomic integrity and tumor suppression.     

Autocatalytic oxidation of lead crystallite surfaces

Growth of an ultrathin lead oxide layer causes massive changes in the shape of lead crystallites. The dynamics of this process was investigated with time-lapsed scanning tunneling microscopy. Pure lead crystallites proved extremely resistant to oxidation. Once nucleated by surface impurities, monolayer films of lead oxide grew readily on lead (111) microfacets in an autocatalytic process. The anisotropic growth of orthorhombic lead oxide films (massicot structure) was most rapid along the direction of weakest lead-oxygen bonding, which suggests that the growth edge autocatalyzes oxygen dissociation by providing proximal sites for oxygen dissociation and attachment.     

Lipid-like material as the source of the uncharacterized organic carbon in the ocean?

The composition and formation mechanisms of the uncharacterized fraction of oceanic particulate organic carbon (POC) are not well understood. We isolated biologically important compound classes and the acid-insoluble fraction, a proxy of the uncharacterized fraction, from sinking POC in the deep Northeast Pacific and measured carbon isotope ratios to constrain the source(s) of the uncharacterized fraction. Stable carbon and radiocarbon isotope signatures of the acid-insoluble fraction were similar to those of the lipid fraction, implying that the acid-insoluble fraction might be composed of selectively accumulated lipid-like macromolecules.     

Radar soundings of the subsurface of Mars

The martian subsurface has been probed to kilometer depths by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument aboard the Mars Express orbiter. Signals penetrate the polar layered deposits, probably imaging the base of the deposits. Data from the northern lowlands of Chryse Planitia have revealed a shallowly buried quasi-circular structure about 250 kilometers in diameter that is interpreted to be an impact basin. In addition, a planar reflector associated with the basin structure may indicate the presence of a low-loss deposit that is more than 1 kilometer thick.     

Improved learning in a large-enrollment physics class

We compared the amounts of learning achieved using two different instructional approaches under controlled conditions. We measured the learning of a specific set of topics and objectives when taught by 3 hours of traditional lecture given by an experienced highly rated instructor and 3 hours of instruction given by a trained but inexperienced instructor using instruction based on research in cognitive psychology and physics education. The comparison was made between two large sections (N = 267 and N = 271) of an introductory undergraduate physics course. We found increased student attendance, higher engagement, and more than twice the learning in the section taught using research-based instruction.     

Resolution of lung inflammation by CD44

Successful repair after tissue injury and inflammation requires resolution of the inflammatory response and removal of extracellular matrix breakdown products. We have examined whether the cell-surface adhesion molecule and hyaluronan receptor CD44 plays a role in resolving lung inflammation. CD44-deficient mice succumb to unremitting inflammation following noninfectious lung injury, characterized by impaired clearance of apoptotic neutrophils, persistent accumulation of hyaluronan fragments at the site of tissue injury, and impaired activation of transforming growth factor-beta1. This phenotype was partially reversed by reconstitution with CD44+ cells, thus demonstrating a critical role for this receptor in resolving lung inflammation.     

Kilimanjaro ice core records: evidence of holocene climate change in tropical Africa

Six ice cores from Kilimanjaro provide an approximately 11.7-thousand-year record of Holocene climate and environmental variability for eastern equatorial Africa, including three periods of abrupt climate change: approximately 8.3, approximately 5.2, and approximately 4 thousand years ago (ka). The latter is coincident with the "First Dark Age," the period of the greatest historically recorded drought in tropical Africa. Variable deposition of F- and Na+ during the African Humid Period suggests rapidly fluctuating lake levels between approximately 11.7 and 4 ka. Over the 20th century, the areal extent of Kilimanjaro's ice fields has decreased approximately 80%, and if current climatological conditions persist, the remaining ice fields are likely to disappear between 2015 and 2020.