Spitzer Mid-Infrared Spectroscopy of 70um-Selected Distant Luminous Infrared Galaxies

We present mid-infrared spectroscopy obtained with the Spitzer Space Telescope of a sample of 11 optically faint, infrared luminous galaxies selected from a Spitzer MIPS 70um imaging survey of the NDWFS Bootes field. These are the first Spitzer IRS spectra presented of distant 70um-selected sources. All the galaxies lie at redshifts 0.3<z<1.3 and have very large infrared luminosities of L_IR~ 0.1-17 x 10^12 solar luminosities. Seven of the galaxies exhibit strong emission features attributed to polycyclic aromatic hydrocarbons (PAHs). The average IRS spectrum of these sources is characteristic of classical starburst galaxies, but with much larger infrared luminosities. The PAH luminosities of L(7.7) ~ 0.4 - 7 x 10^11 solar luminosities imply star formation rates of ~ 40 - 720 solar masses per year. Four of the galaxies show deep 9.7um silicate absorption features and no significant PAH emission features (6.2um equivalent widths < 0.03um). The large infrared luminosities and low f70/f24 flux density ratios suggests that these sources have AGN as the dominant origin of their large mid-infrared luminosities, although deeply embedded but luminous starbursts cannot be ruled out. If the absorbed sources are AGN-dominated, a significant fraction of all far-infrared bright, optically faint sources may be dominated by AGN.Comment: 8 Pages, ApJ accepte

Novel HIV-1 Recombinant Forms in Antenatal Cohort, Montreal, Quebec, Canada

Near full-length genomes of 4 unclassified HIV-1 variants infecting patients enrolled in an antenatal cohort in Canada were obtained by sequencing. All 4 variants showed original recombination profiles, including A1/A2/J, A1/D, and A1/G/J/CRF11_cpx structures. Identification of these variants highlights the growing prevalence of unique recombinant forms of HIV-1 in North America

The Evolution of the Star Formation Rate of Galaxies at 0.0 < z < 1.2

We present the 24 micron rest-frame luminosity function (LF) of star-forming galaxies in the redshift range 0.0 < z < 0.6 constructed from 4047 spectroscopic redshifts from the AGN and Galaxy Evolution Survey of 24 micron selected sources in the Bootes field of the NOAO Deep Wide-Field Survey. This sample provides the best available combination of large area (9 deg^2), depth, and statistically complete spectroscopic observations, allowing us to probe the evolution of the 24 micron LF of galaxies at low and intermediate redshifts while minimizing the effects of cosmic variance. In order to use the observed 24 micron luminosity as a tracer for star formation, active galactic nuclei (AGNs) that could contribute significantly at 24 micron are identified and excluded from our star-forming galaxy sample based on their mid-IR spectral energy distributions or the detection of X-ray emission. The evolution of the 24 micron LF of star-forming galaxies for redshifts of z < 0.65 is consistent with a pure luminosity evolution where the characteristic 24 micron luminosity evolves as (1+z)^(3.8+/-0.3). We extend our evolutionary study to encompass 0.0 < z < 1.2 by combining our data with that of the Far-Infrared Deep Extragalactic Legacy Survey. Over this entire redshift range the evolution of the characteristic 24 micron luminosity is described by a slightly shallower power law of (1+z)^(3.4+/-0.2). We find a local star formation rate density of (1.09+/-0.21) x 10^-2 Msun/yr/Mpc^-3, and that it evolves as (1+z)^(3.5+/-0.2) over 0.0 < z < 1.2. These estimates are in good agreement with the rates using optical and UV fluxes corrected for the effects of intrinsic extinction in the observed sources. This agreement confirms that star formation at z <~ 1.2 is robustly traced by 24 micron observations and that it largely occurs in obscured regions of galaxies. (Abridged)Comment: ApJ, in press, 16 pages 9 figure

P2X7 receptor: Death or life?

The P2X7 plasma membrane receptor is an intriguing molecule that is endowed with the ability to kill cells, as well as to activate many responses and even stimulate proliferation. Here, the authors give an overview on the multiplicity and complexity of P2X7-mediated responses, discussing recent information on this receptor. Particular attention has been paid to early and late signs of apoptosis and necrosis linked to activation of the receptor and to the emerging field of P2X7 function in carcinogenesis

Inhibition of HIV-1 infection of peripheral blood mononuclear cells by a monoclonal antibody that binds to phosphoinositides and induces secretion of β-chemokines

A murine IgG mAb, WR321, selected for the ability to bind to phosphatidylinositol-4-phosphate and phosphatidylinositol-4, 5-bisphosphate, but an inability to bind to any of 17 other lipids, including phosphatidylinositol, was examined as a probe for studying interactions of HIV-1 with primary human peripheral blood mononuclear cells. The WR321 mAb broadly neutralized CCR5-tropic strains of HIV-1 to prevent infection of the cells. The mAb also exhibited direct interaction with cells in the culture, resulting in secretion of chemokines that interfered with the interaction of HIV-1 virions with CCR5, the coreceptor for HIV-1 on the susceptible cells, leading to inhibition of infection by HIV-1. Phosphoinositides that are recognized by WR321 do not exist on the external surface of cells, but are concentrated on the inner surface (cytoplasmic leaflet) of the plasma membrane. Murine anti-phosphoinositide mAbs similar to WR321 have previously been directly microinjected into a variety of cultured cells, resulting in important changes in the functions of the cells. The present results suggest that binding of a mAb to phosphoinositides, resulting in secretion of β-chemokines into the culture medium and neutralization of infection by CCR5-tropic HIV-1 of nearby susceptible cells, occurred by uptake and binding of the mAb at an intracellular location in the cultured cells that then led to secretion of HIV-1-inhibitory β-chemokines