46 research outputs found
On the origin of the Norwegian lemming.
The Pleistocene glacial cycles resulted in significant changes in species distributions, and it has been discussed whether this caused increased rates of population divergence and speciation. One species that is likely to have evolved during the Pleistocene is the Norwegian lemming (Lemmus lemmus). However, the origin of this species, both in terms of when and from what ancestral taxon it evolved, has been difficult to ascertain. Here, we use ancient DNA recovered from lemming remains from a series of Late Pleistocene and Holocene sites to explore the species' evolutionary history. The results revealed considerable genetic differentiation between glacial and contemporary samples. Moreover, the analyses provided strong support for a divergence time prior to the Last Glacial Maximum (LGM), therefore likely ruling out a postglacial colonization of Scandinavia. Consequently, it appears that the Norwegian lemming evolved from a small population that survived the LGM in an ice-free Scandinavian refugium
A Fluorescent Glycolipid-Binding Peptide Probe Traces Cholesterol Dependent Microdomain-Derived Trafficking Pathways
10.1371/journal.pone.0002933PLoS ONE38
Electrocardiogram Pattern Recognition and Analysis Based on Artificial Neural Networks and Support Vector Machines: A Review
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Interacting effects of change in climate, human population, land use, and water use on biodiversity and ecosystem services
Human population growth and resource use, mediated by changes in climate, land use, and water use, increasingly impact biodiversity and ecosystem services provision. However, impacts of these drivers on biodiversity and ecosystem services are rarely analyzed simultaneously and remain largely unknown. An emerging question is how science can improve the understanding of change in biodiversity and ecosystem service delivery and of potential feedback mechanisms of adaptive governance. We analyzed past and future change in drivers in south-central Sweden. We used the analysis to identify main research challenges and outline important research tasks. Since the 19th century, our study area has experienced substantial and interlinked changes; a 1.6°C temperature increase, rapid population growth, urbanization, and massive changes in land use and water use. Considerable future changes are also projected until the mid-21st century. However, little is known about the impacts on biodiversity and ecosystem services so far, and this in turn hampers future projections of such effects. Therefore, we urge scientists to explore interdisciplinary approaches designed to investigate
change in multiple drivers, underlying mechanisms, and interactions over time, including assessment and analysis of matching-scale data from several disciplines. Such a perspective is needed for science to contribute to adaptive governance by constantly improving the understanding of linked change complexities and their impacts
A new free-floating planet in the Upper Scorpius association
We report on a deep photometric survey covering an area of 1.17 deg in
the young Upper Scorpius stellar association using VIMOS and UKIDSS
data taking several years apart. The search for the least massive population of
Upper Scorpius (5-10 Myr, 145 pc) is performed on the basis of various
optical and infrared color-color and color-magnitude diagrams, including WISE
photometry, in the magnitude interval =14.5-19 mag (completeness), which
corresponds to substellar masses from 0.028 through 0.004 M at the age
and distance of Upper Scorpius. We also present the proper motion analysis of
the photometric candidates, finding that two objects successfully pass all
photometric and astrometric criteria for membership in the young stellar
association. One of them, UScoJ155150.2213457, is a new discovery. We
obtained low resolution, near-infrared spectroscopy (450, 0.85--2.35
m) of this new finding using the FIRE instrument. We confirmed its
low-gravity atmosphere expected for an Upper Scorpius member (weak alkaline
lines, strong VO absorption, peaked -band pseudocontinuum). By comparison
with spectroscopic standards, we derive a spectral type of L61, and
estimate a mass of 0.008-0.010 M for UScoJ155150.2213457.
The colors and spectral slope of this object resemble those of other young,
cool members of Upper Scorpius and Orionis (3 Myr) and field,
high gravity dwarfs of related classification in contrast with the very red
indices of field, low gravity, L-type dwarfs of intermediate age.
UScoJ155150.2213457, which does not show infrared flux excesses up to 4.5
m, becomes one of the least massive and latest type objects known in the
entire Upper Scorpius stellar association.Comment: 12 pages, 8 figures. Accepted for publication in A&
Distinct Lipid Rafts in Subdomains from Human Placental Apical Syncytiotrophoblast Membranes
Rifampicin-Independent Interactions between the Pregnane X Receptor Ligand Binding Domain and Peptide Fragments of Coactivator and Corepressor Proteins
[Image: see text] The pregnane X receptor (PXR), a member of the nuclear receptor superfamily, regulates the expression of drug-metabolizing enzymes in a ligand-dependent manner. The conventional view of nuclear receptor action is that ligand binding enhances the receptor’s affinity for coactivator proteins, while decreasing its affinity for corepressors. To date, however, no known rigorous biophysical studies have been conducted to investigate the interaction among PXR, its coregulators, and ligands. In this work, steady-state total internal reflection fluorescence microscopy (TIRFM) and total internal reflection with fluorescence recovery after photobleaching were used to measure the thermodynamics and kinetics of the interaction between the PXR ligand binding domain and a peptide fragment of the steroid receptor coactivator-1 (SRC-1) in the presence and absence of the established PXR agonist, rifampicin. Equilibrium dissociation and dissociation rate constants of ~5 μM and ~2 s(−1), respectively, were obtained in the presence and absence of rifampicin, indicating that the ligand does not enhance the affinity of the PXR and SRC-1 fragments. Additionally, TIRFM was used to examine the interaction between PXR and a peptide fragment of the corepressor protein, the silencing mediator for retinoid and thyroid receptors (SMRT). An equilibrium dissociation constant of ~70 μM was obtained for SMRT in the presence and absence of rifampicin. These results strongly suggest that the mechanism of ligand-dependent activation in PXR differs significantly from that seen in many other nuclear receptors