Imprinted <i>Grb10,</i> encoding growth factor receptor bound protein 10, regulates fetal growth independently of the insulin-like growth factor type 1 receptor (<i>Igf1r</i>) and insulin receptor (<i>Insr</i>) genes

BackgroundOptimal size at birth dictates perinatal survival and long-term risk of developing common disorders such as obesity, type 2 diabetes and cardiovascular disease. The imprinted Grb10 gene encodes a signalling adaptor protein capable of inhibiting receptor tyrosine kinases, including the insulin receptor (Insr) and insulin-like growth factor type 1 receptor (Igf1r). Grb10 restricts fetal growth such that Grb10 knockout (KO) mice are at birth some 25-35% larger than wild type. Using a mouse genetic approach, we test the widely held assumption that Grb10 influences growth through interaction with Igf1r, which has a highly conserved growth promoting role.ResultsShould Grb10 interact with Igf1r to regulate growth Grb10:Igf1r double mutant mice should be indistinguishable from Igf1r KO single mutants, which are around half normal size at birth. Instead, Grb10:Igf1r double mutants were intermediate in size between Grb10 KO and Igf1r KO single mutants, indicating additive effects of the two signalling proteins having opposite actions in separate pathways. Some organs examined followed a similar pattern, though Grb10 KO neonates exhibited sparing of the brain and kidneys, whereas the influence of Igf1r extended to all organs. An interaction between Grb10 and Insr was similarly investigated. While there was no general evidence for a major interaction for fetal growth regulation, the liver was an exception. The liver in Grb10 KO mutants was disproportionately overgrown with evidence of excess lipid storage in hepatocytes, whereas Grb10:Insr double mutants were indistinguishable from Insr single mutants or wild types.ConclusionsGrb10 acts largely independently of Igf1r or Insr to control fetal growth and has a more variable influence on individual organs. Only the disproportionate overgrowth and excess lipid storage seen in the Grb10 KO neonatal liver can be explained through an interaction between Grb10 and the Insr. Our findings are important for understanding how positive and negative influences on fetal growth dictate size and tissue proportions at birth

A Near-Infrared Study of the Stellar Cluster: [DBS2003] 45

We present a multi-wavelength photometric and spectroscopic study of a newly discovered candidate cluster [DBS2003] 45. Our H, Ks photometry confirms that [DBS2003] 45 is a cluster. An average visual extinction Av 7.1+/-0.5 is needed to fit the cluster sequence with a model isochrone. Low resolution spectroscopy indicates that half a dozen early B and at least one late O type giant stars are present in the cluster. We estimate the age of the cluster to be between 5 and 8 Myr based on spectroscopic analysis. Assuming an age of 6 Myr, we fit the observed mass function with a power law, N(M) M^(-Gamma), and find an index Gamma 1.27+/-0.15, which is consistent with the Salpeter value. We estimate the total cluster mass is around 1000 solar masses by integrating the derived mass function between 0.5 and 45 solar masses. Both mid-infrared and radio wavelength observations show that a bubble filled with ionized gas is associated with the cluster. The total ionizing photon flux estimated from radio continuum measurements is consistent with the number of hot stars we detected. Infrared bright point sources along the rim of the bubble suggest that there is triggered star formation at the periphery of the HII region.Comment: 12 pages, 10 figures, 2 tables. Accepted by ApJ, a typo in the Abstract correcte

Detailed analysis of paternal knockout <i>Grb10 </i>mice suggests effects on stability of social behavior, rather than social dominance

Imprinted genes are highly expressed in monoaminergic regions of the midbrain and their functions in this area are thought to have an impact on mammalian social behaviors. One such imprinted gene is Grb10, of which the paternal allele is generally recognized as mediating social dominance behavior. However, there has been no detailed study of social dominance in Grb10 +/p mice. Moreover, the original study examined tube‐test behavior in isolated mice 10 months of age. Isolation testing favors more territorial and aggressive behaviors, and does not address social dominance strategies employed in group housing contexts. Furthermore, isolation stress impacts midbrain function and dominance related behavior, often through alterations in monoaminergic signaling. Thus, we undertook a systematic study of Grb10 +/p social rank and dominance behavior within the cage group, using a number of convergent behavioral tests. We examined both male and female mice to account for sex differences and tested cohorts aged 2, 6 and 10 months to examine any developments related to age. We found group‐housed Grb10 +/p mice do not show evidence of enhanced social dominance, but cages containing Grb10 +/p and wild‐type mice lacked the normal correlation between three different measures of social rank. Moreover, a separate study indicated isolation stress induced inconsistent changes in tube test behavior. Taken together, these data suggest future research on Grb10 +/p mice should focus on the stability of social behaviors, rather than dominance per se

On the central ionizing star of G23.96+0.15 and near-IR spectral classification of O stars

Aims: A near-infrared study of the main ionizing star of the ultracompact HII region G23.96+0.15 (IRAS 18317-0757) is presented, along with a re-evaluation of the distance to this source, and a re-assessment of H- and K-band classification diagnostics for O dwarfs; Methods: We have obtained near-IR VLT/ISAAC imaging and spectroscopy of G23.96+0.15, plus archival imaging from UKIRT/UFTI. A spectroscopic analysis was carried out using a non-LTE model atmosphere code; Results: A quantitative H- and K-band classification scheme for O dwarfs is provided, from which we establish an O7.5V spectral subtype for the central star of G23.96+0.15. We estimate an effective temperature of Teff ~ 38 kK from a spectral analysis; Conclusions: A spectroscopic distance of 2.5 kpc is obtained for G23.96+0.15, substantially lower than the kinematic distance of 4.7 kpc, in common with recent studies of other Milky way HII regions. Such discrepancies would be alleviated if sources are unresolved binaries or clusters.Comment: 5 pages, 3 figures, accepted for Astronomy & Astrophysic

Subaru and Gemini High Spatial Resolution Infrared 18 Micron Imaging Observations of Nearby Luminous Infrared Galaxies

We present the results of a ground-based, high spatial resolution infrared 18 micron imaging study of nearby luminous infrared galaxies (LIRGs), using the Subaru 8.2-m and Gemini South 8.1-m telescopes. The diffraction-limited images routinely achieved with these telescopes in the Q-band (17-23 micron) allow us to investigate the detailed spatial distribution of infrared emission in these LIRGs. We then investigate whether the emission surface brightnesses are modest, as observed in starbursts, or are so high that luminous active galactic nuclei (AGNs; high emission surface brightness energy sources) are indicated. The sample consists of 18 luminous buried AGN candidates and starburst-classified LIRGs identified in earlier infrared spectroscopy. We find that the infrared 18 micron emission from the buried AGN candidates is generally compact, and the estimated emission surface brightnesses are high, sometimes exceeding the maximum value observed in and theoretically predicted for a starburst phenomenon. The starburst-classified LIRGs usually display spatially extended 18 micron emission and the estimated emission surface brightnesses are modest, within the range sustained by a starburst phenomenon. The general agreement between infrared spectroscopic and imaging energy diagnostic methods suggests that both are useful tools for understanding the hidden energy sources of the dusty LIRG population.Comment: 17 pages, 3 figures, accepted for publication in AJ (No. 141, 2011 May issue). Higher resolution version is available at http://optik2.mtk.nao.ac.jp/~imanishi/Paper/20um/20um.pd

Follow-Up Near-infrared Spectroscopy of Ultraluminous Infrared Galaxies observed by ISO

We present low resolution near-infrared spectroscopy of an unbiased sample of 24 ultraluminous infrared galaxies (ULIRGs), selected from samples previously observed spectroscopically in the mid-infrared with the Infrared Space Observatory (ISO). Qualitatively, the near-infrared spectra resemble those of starbursts. Only in one ULIRG, IRAS 04114-5117E, do we find spectroscopic evidence for AGN activity. The spectroscopic classification in the near-infrared is in very good agreement with the mid-infrared one. For a subset of our sample for which extinction corrections can be derived from Pa-alpha and Br-gamma, we find rather high Pa-alpha luminosities, in accordance with the powering source of these galaxies being star formation.[Fe] emission is strong in ULIRGs and may be linked to starburst and superwind activity. Additionally, our sample includes two unusual objects. The first, IRAS F00183-7111, exhibits extreme [Fe] emission and the second, IRAS F23578-5307, is according to our knowledge one of the most luminous infrared galaxies in H2 rotation-vibration emission.Comment: Accepted for publication in A&A (12 pages, 4 figures). See http://www.mpia-hd.mpg.de/homes/dannerb/ for a version with higher quality figure

Results from a Near Infrared Search for Emission-line Stars in the Inner Galaxy: Spectra of New Wolf-Rayet Stars

We present follow-up spectroscopy of emission line candidates detected on near-infrared narrow band images in the inner Galaxy (Homeier et al. 2003). The filters are optimized for the detection of Wolf-Rayet stars and other objects which exhibit emission--lines in the 2 $\mu$m region. Approximately three square degrees along the Galactic plane have been analyzed in seven narrow--filters (four emission--lines and three continuum). We have discovered 4 new Wolf-Rayet stars and present coordinates, finding charts, and K-band spectra.Comment: To appear in Astronomy & Astrophysic

The properties of quasar hosts at the peak of the quasar activity

We present near-infrared imaging obtained with ESO VLT/ISAAC of a sample of 16 low luminosity radio-quiet quasars at the epoch around the peak of the quasar activity (2 < z < 3), aimed at investigating their host galaxies. For 11 quasars, we are able to detect the host galaxies and derive their properties, while for the other five quasars, upper limits to the host luminosity are estimated. The luminosities of the host galaxies of radio-quiet quasars at high redshift are in the range of those of massive inactive elliptical galaxies. This work complements our previous systematic study of quasar hosts aimed to trace the cosmological luminosity evolution of the host galaxies up to z ~2 and extends our pilot study of a few luminous quasars at z > 2. The luminosity trend with cosmic epoch resembles that observed for massive inactive galaxies, suggesting a similar star formation history. In particular, both quasar host galaxies and massive inactive galaxies appear mostly assembled already at the peak age of the quasar activity. This result is of key importance for testing the models of joint formation and evolution of galaxies and their active nuclei.Comment: 27 pages, 8 figures, 2 tables. Accepted for publication in Ap

GLIMPSE-CO1: the most massive intermediate-age stellar cluster in the Galaxy

The stellar cluster GLIMPSE-C01 is a dense stellar system located in the Galactic Plane. Though often referred to in the literature as an old globular cluster traversing the Galactic disk, previous observations do not rule out that it is an intermediate age (less than a few Gyr) disk-borne cluster. Here, we present high-resolution near-infrared spectroscopy of over 50 stars in the cluster. We find an average radial velocity is consistent with being part of the disk, and determine the cluster's dynamical mass to be (8 \pm 3)x10^4 Msun. Analysis of the cluster's M/L ratio, the location of the Red Clump, and an extremely high stellar density, all suggest an age of 400-800Myr for GLIMPSE-C01, much lower than for a typical globular cluster. This evidence therefore leads us to conclude that GLIMPSE-C01 is part of the disk population, and is the most massive Galactic intermediate-age cluster discovered to date.Comment: 10 pages, 9 figures, accepted for publication in MNRA