Oxygen Regulates Vascular Endothelial Growth Factor-Mediated Vasculogenesis and Tubulogenesis

AbstractTo determine whether low oxygen is a stimulus for endothelial cell differentiation and vascular development in the kidney, we examined the effect of low oxygen on rat metanephric organ culture, a model known to recapitulate nephrogenesis in the absence of vessels. After 6 days in culture in standard (20% O2) or low oxygen (1–3% O2) conditions, metanephric kidney growth and morphology were assessed by DNA measurement, and light and electron microscopy. DNA content was higher in 3% O2-treated explants (2.5 ± 0.17 μg/kidney,n= 9) than in 20% O2explants (1.5 ± 0.09 μg/kidney,n= 9),P< 0.05. Low oxygen induced proliferation of tubular epithelial cells, resulting in enhanced number of tubules of similar size. Endothelial cells forming capillaries were localized in 3% O2explants by light and electron microscopy and by immunocytochemistry using endothelial cell markers. Flt-1, Flk-1, and ACE-containing cells were detected in 3% O2-treated explants, whereas 20% O2explants were virtually negative. VEGF mRNA levels were 10-fold higher in 3% O2-treated explants than in 20% O2-treated explants. Addition of anti-VEGF antibodies to 3% O2-treated explants prevented low oxygen-induced growth and endothelial cell differentiation and proliferation. Our data indicate that low oxygen stimulates growth by cell proliferation and induces tubulogenesis, endothelial cell differentiation, and vasculogenesis in metanephric kidneys in culture. Upregulation of VEGF expression by low oxygen and prevention of low oxygen-induced tubulogenesis and vasculogenesis by anti-VEGF antibodies indicate that these changes were mediated by VEGF. These data suggest that low oxygen is the stimulus to initiate renal vascularization

A self-consistent model of Galactic stellar and dust infrared emission and the abundance of polycyclic aromatic hydrocarbons

We present a self-consistent three-dimensional Monte-Carlo radiative transfer model of the stellar and dust emission in the Milky-Way, and have computed synthetic observations of the 3.6 to 100 microns emission in the Galactic mid-plane. In order to compare the model to observations, we use the GLIMPSE, MIPSGAL, and IRAS surveys to construct total emission spectra, as well as longitude and latitude profiles for the emission. The distribution of stars and dust is taken from the SKY model, and the dust emissivities includes an approximation of the emission from polycyclic aromatic hydrocarbons in addition to thermal emission. The model emission is in broad agreement with the observations, but a few modifications are needed to obtain a good fit. Firstly, by adjusting the model to include two major and two minor spiral arms rather than four equal spiral arms, the fit to the longitude profiles for |l|>30 degrees can be improved. Secondly, introducing a deficit in the dust distribution in the inner Galaxy results in a better fit to the shape of the IRAS longitude profiles at 60 and 100 microns. With these modifications, the model fits the observed profiles well, although it systematically under-estimates the 5.8 and 8.0 microns fluxes. One way to resolve this discrepancy is to increase the abundance of PAH molecules by 50% compared to the original model, although we note that changes to the dust distribution or radiation field may provide alternative solutions. Finally, we use the model to quantify which stellar populations contribute the most to the heating of different dust types, and which stellar populations and dust types contribute the most to the emission at different wavelengths.Comment: Published in A&A. This version has been revised (compared to the published version) to include additional references to previous work. Scripts to reproduce the results in this paper can be found as supplementary material on the A&A site, or at https://github.com/hyperion-rt/paper-galaxy-rt-mode

Comparison of K+K^+ and e−e^- Quasielastic Scattering

We formulate $K^+$-nucleus quasielastic scattering in a manner which closely parallels standard treatments of $e^-$-nucleus quasielastic scattering. For $K^+$ scattering, new responses involving scalar contributions appear in addition to the Coulomb (or longitudinal) and transverse $(e,e')$ responses which are of vector character. We compute these responses using both nuclear matter and finite nucleus versions of the Relativistic Hartree Approximation to Quantum Hadrodynamics including RPA correlations. Overall agreement with measured $(e,e')$ responses and new $K^+$ quasielastic scattering data for $^{40}$Ca at |\qs|=500 MeV/c is good. Strong RPA quenching is essential for agreement with the Coulomb response. This quenching is notably less for the $K^+$ cross section even though the new scalar contributions are even more strongly quenched than the vector contributions. We show that this ``differential quenching'' alters sensitive cancellations in the expression for the $K^+$ cross section so that it is reduced much less than the individual responses. We emphasize the role of the purely relativistic distinction between vector and scalar contributions in obtaining an accurate and consistent description of the $(e,e')$ and $K^+$ data within the framework of our nuclear structure model.Comment: 26 pages, 5 uuencoded figures appended to end of this fil

Coordinating domestic legislation and international agreements to conserve migratory species: a case study from Australia

Migratory movements of animals frequently span political borders and the need for international collaboration in the conservation of migratory species is well recognized. There is, however, less appreciation of the need for coordinated protection within nations. We explore consequences of multilevel governance for top-down implementation of international agreements, drawing on examples from Australia and with reference to the United States and European Union. Coherent implementation of legislation and policy for migratory species can be challenging in federal jurisdictions where environmental law making can be split across multiple levels of governance and local and federal priorities may not necessarily be aligned. As a result of these challenges, for example, two-thirds of Australian migratory birds remain unprotected under national legislation. In Australia and elsewhere, coordinated protection of migratory species can be implemented within the current framework of conservation law and policy by actions such as designating national migration areas, negotiating nationally coordinated agreements or listings of migratory species and pursuing new bilateral agreements with key countries along migratory routes.Claire A. Runge, Eduardo Gallo-Cajiao, Mark J. Carey, Stephen T. Garnett, Richard A. Fuller, Phillipa C. McCormac

The choline transporter Slc44a2 controls platelet activation and thrombosis by regulating mitochondrial function

Genetic factors contribute to the risk of thrombotic diseases. Recent genome wide association studies have identified genetic loci including SLC44A2 which may regulate thrombosis. Here we show that Slc44a2 controls platelet activation and thrombosis by regulating mitochondrial energetics. We find that Slc44a2 null mice (Slc44a2(KO)) have increased bleeding times and delayed thrombosis compared to wild-type (Slc44a2(WT)) controls. Platelets from Slc44a2(KO) mice have impaired activation in response to thrombin. We discover that Slc44a2 mediates choline transport into mitochondria, where choline metabolism leads to an increase in mitochondrial oxygen consumption and ATP production. Platelets lacking Slc44a2 contain less ATP at rest, release less ATP when activated, and have an activation defect that can be rescued by exogenous ADP. Taken together, our data suggest that mitochondria require choline for maximum function, demonstrate the importance of mitochondrial metabolism to platelet activation, and reveal a mechanism by which Slc44a2 influences thrombosis

A Rigorous Geometric Derivation of the Chiral Anomaly in Curved Backgrounds

We discuss the chiral anomaly for a Weyl field in a curved background and show that a novel index theorem for the Lorentzian Dirac operator can be applied to describe the gravitational chiral anomaly. A formula for the total charge generated by the gravitational and gauge field background is derived directly in Lorentzian signature and in a mathematically rigorous manner. It contains a term identical to the integrand in the Atiyah–Singer index theorem and another term involving the η -invariant of the Cauchy hypersurfaces

Prospects for Studies of Stellar Evolution and Stellar Death in the JWST Era

I review the prospects for studies of the advanced evolutionary stages of low-, intermediate- and high-mass stars by the JWST and concurrent facilities, with particular emphasis on how they may help elucidate the dominant contributors to the interstellar dust component of galaxies. Observations extending from the mid-infrared to the submillimeter can help quantify the heavy element and dust species inputs to galaxies from AGB stars. JWST's MIRI mid-infrared instrument will be so sensitive that observations of the dust emission from individual intergalactic AGB stars and planetary nebulae in the Virgo Cluster will be feasible. The Herschel Space Observatory will enable the last largely unexplored spectral region, the far-IR to the submillimeter, to be surveyed for new lines and dust features, while SOFIA will cover the wavelength gap between JWST and Herschel, a spectral region containing important fine structure lines, together with key water-ice and crystalline silicate bands. Spitzer has significantly increased the number of Type II supernovae that have been surveyed for early-epoch dust formation but reliable quantification of the dust contributions from massive star supernovae of Type II, Type Ib and Type Ic to low- and high-redshift galaxies should come from JWST MIRI observations, which will be able to probe a volume over 1000 times larger than Spitzer.Comment: 24 pages, 19 figures. To appear in `Astrophysics in the Next Decade: JWST and Concurrent Facilities' (JWST Conference Proceedings), edited by H. A. Thronson, M. Stiavelli and A. G. G. M. Tielens; Springer Series: Astrophysics and Space Science Proceeding

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics

Proximity effect at superconducting Sn-Bi2Se3 interface

We have investigated the conductance spectra of Sn-Bi2Se3 interface junctions down to 250 mK and in different magnetic fields. A number of conductance anomalies were observed below the superconducting transition temperature of Sn, including a small gap different from that of Sn, and a zero-bias conductance peak growing up at lower temperatures. We discussed the possible origins of the smaller gap and the zero-bias conductance peak. These phenomena support that a proximity-effect-induced chiral superconducting phase is formed at the interface between the superconducting Sn and the strong spin-orbit coupling material Bi2Se3.Comment: 7 pages, 8 figure

Centrality Dependence of the High p_T Charged Hadron Suppression in Au+Au collisions at sqrt(s_NN) = 130 GeV

PHENIX has measured the centrality dependence of charged hadron p_T spectra from central Au+Au collisions at sqrt(s_NN)=130 GeV. The truncated mean p_T decreases with centrality for p_T > 2 GeV/c, indicating an apparent reduction of the contribution from hard scattering to high p_T hadron production. For central collisions the yield at high p_T is shown to be suppressed compared to binary nucleon-nucleon collision scaling of p+p data. This suppression is monotonically increasing with centrality, but most of the change occurs below 30% centrality, i.e. for collisions with less than about 140 participating nucleons. The observed p_T and centrality dependence is consistent with the particle production predicted by models including hard scattering and subsequent energy loss of the scattered partons in the dense matter created in the collisions.Comment: 7 pages text, LaTeX, 6 figures, 2 tables, 307 authors, resubmitted to Phys. Lett. B. Revised to address referee concerns. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are publicly available at http://www.phenix.bnl.gov/phenix/WWW/run/phenix/papers.htm