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Using CHARA and VLTI near-infrared spectro-interferometry with hectometric baseline lengths (up to 330 m) and with high spectral resolution (up to λ/Δλ, = 12,000), we studied the gas distribution and kinematics around two classical Be stars. The combination of high spatial and spectral resolution achieved allows us to constrain the gas velocity field on scales of a few stellar radii and to obtain, for the first time in optical interferometry, a dynamical mass estimate using the position-velocity analysis technique known from radio astronomy. For our first target star, β Canis Minoris, we model the H + K-band continuum and Brγ-line geometry with a near-critical rotating stellar photosphere and a geometrically thin equatorial disk. Testing different disk rotation laws, we find that the disk is in Keplerian rotation (v(r) ∝ r-0.5±0.1) and derive the disk position angle (140° ± 1°.7), inclination (38°.5 + 1°), and the mass of the central star (3.5 ± 0.2 M⊙). As a second target star, we observed the prototypical Be star ζ Tauri and spatially resolved the Bry emission as well as nine transitions from the hydrogen Pfund series (Pf 14-22). Comparing the spatial origin of the different line transitions, we find that the Brackett (Brγ), Pfund (Pf 14-17), and Balmer (Hot) lines originate from different stellocentric radii (Rcont < RPf < RBrγ, ~ RHα), which we can reproduce with an LTE line radiative transfer computation. Discussing different disk-formation scenarios, we conclude that our constraints are inconsistent with wind compression models predicting a strong outflowing velocity component, but support viscous decretion disk models, where the Keplerian-rotating disk is replenished with material from the near-critical rotating star. [ABSTRACT FROM AUTHOR]

In 2005 we obtained very precise interferometric measurements of the pole-on rapid rotator Vega (A0 V) with the longest baselines of the Center for High Angular Angular Resolution (CHARA) Array and the Fiber Linked Unit for Optical Recombination (FLUOR). For the analysis of these data, we developed a code for mapping sophisticated PHOENIX model atmospheres on to the surface of rotationally distorted stars described by a Roche-von Zeipel formalism. Given a set of input parameters for a star or binary pair, this code predicts the interferometric visibility, spectral energy distribution and high-resolution line spectrum expected for the system. For the gravity-darkened Vega, our model provides a very good match to the K-band interferometric data, a good match to the spectral energy distribution – except below 160 nm – and a rather poor match to weak lines in the high dispersion spectrum where the model appears overly gravity darkened. In 2006, we used the CHARA Array and FLUOR to obtain high precision measurements of the massive, non-eclipsing, double-line spectroscopic binary Spica, a 4-day period system where both components are gravity darkened rapid rotators. These data supplement recent data obtained with the Sydney University Stellar Interferometer (SUSI). Our study follows the classic 1971 study by Herbison-Evans et al. who resolved Spica as a binary with the Narrabri Stellar Intensity Interferometer (NSII). We will report on our progress modeling the new interferometric and archival spectroscopic data, with the goal towards better constraining the apsidal constant. [ABSTRACT FROM PUBLISHER]

We present the results of an all sky survey for binary systems among the massive stars that we made with the HST Fine Guidance Sensors. The sample of 225 stars is comprised mainly of Galactic O- and B-type stars and Luminous Blue Variables, plus a few luminous stars in the LMC. The FGS TRANS mode observations are sensitive to detection of companions with an angular separation of 0.01-1 arcsec and brighter than Δm = 5 mag. The FGS observations resolved 52 binary and 6 triple star systems and detected partially resolved binaries in 7 additional targets, yielding a companion detection frequency of 29%. We also gathered literature results on the numbers of close spectroscopic binaries and wider astrometric binaries among the sample. These results confirm the high multiplicity fraction. The period distribution is essentially flat in increments of logP, although there remains an observational gap in detections for periods of years and decades. [ABSTRACT FROM AUTHOR]

We present the first high angular resolution observations in the near-infrared H band (1.6µm) of the luminous blue variable star P Cygni. We obtained six-telescope interferometric observations with the CHARA Array and the MIRC beam combiner. These show that the spatial flux distribution is larger than expected for the stellar photosphere. A two-component model for the star (uniform disk) plus a halo (two-dimensional Gaussian) yieldsan excellent fit of the observations, and we suggest that the halo corresponds to flux emitted from the base ofthe stellar wind. This wind component contributes about 45% of the H-band flux and has an angular FWHM =0.96 mas, compared to the predicted stellar diameter of 0.41 mas. We show several images reconstructed from the interferometric visibilities and closure phases, and they indicate a generally spherical geometry for the wind. We also obtained near-infrared spectrophotometry of P Cygni from which we derive the flux excess comparedto a purely photospheric spectral energy distribution. The H-band flux excess matches that from the wind flux fraction derived from the two-component fits to the interferometry. We find evidence of significant near-infrared flux variability over the period from 2006 to 2010 that appears similar to the variations in the Ha emission flux from the wind. [ABSTRACT FROM AUTHOR]

A classical nova occurs when material accreting onto the surface of a white dwarf in a close binary system ignites in a thermonuclear runaway. Complex structures observed in the ejecta at late stages could result from interactions with the companion during the common-envelope phase. Alternatively, the explosion could be intrinsically bipolar, resulting from a localized ignition on the surface of the white dwarf or as a consequence of rotational distortion. Studying the structure of novae during the earliest phases is challenging because of the high spatial resolution needed to measure their small sizes. Here we report near-infrared interferometric measurements of the angular size of Nova Delphini 2013, starting one day after the explosion and continuing with extensive time coverage during the first 43 days. Changes in the apparent expansion rate can be explained by an explosion model consisting of an optically thick core surrounded by a diffuse envelope. The optical depth of the ejected material changes as it expands. We detect an ellipticity in the light distribution, suggesting a prolate or bipolar structure that develops as early as the second day. Combining the angular expansion rate with radial velocity measurements, we derive a geometric distance to the nova of 4.54 ± 0.59 kiloparsecs from the Sun. [ABSTRACT FROM AUTHOR]

We explored whether a functionally blocking anti-C5 monoclonal antibody (mAb) combined with T- and B-cell immunosuppression can successfully prevent antibody-mediated (AMR) and cell-mediated rejection (CMR) in presensitized murine recipients of life-supporting kidney allografts. To mimic the urgent clinical features of AMR experienced by presensitized patients, we designed a murine model in which BALB/c recipients were presensitized with fully MHC-mismatched C3H donor skin grafts one week prior to C3H kidney transplantation. Presensitized recipients demonstrated high levels of circulating and intragraft antidonor antibodies and terminal complement activity, rejecting grafts within 8.5 +/- 1.3 days. Graft rejection was predominantly by AMR, characterized by interstitial hemorrhage, edema and glomerular/tubular necrosis, but also demonstrated moderate cellular infiltration, suggesting CMR involvement. Subtherapeutic treatment with cyclosporine (CsA) and LF15-0195 (LF) did not significantly delay rejection. Significantly, however, the addition of anti-C5 mAb to this CsA/LF regimen prevented terminal complement activity and inhibited both AMR and CMR, enabling indefinite (>100 days) kidney graft survival despite the persistence of antidonor antibodies. Long-term surviving kidney grafts expressed the protective proteins Bcl-x(S/L) and A-20 and demonstrated normal histology, suggestive of graft accommodation or tolerance. Thus, C5 blockade combined with routine immunosuppression offers a promising approach to prevent graft loss in presensitized patients.

Complement plays a significant role in mediating endothelial injury following oxidative stress. We have previously demonstrated that the lectin complement pathway (LCP), which is initiated by deposition of the mannose-binding lectin (MBL), is largely responsible for activating complement on endothelial cells following periods of oxidative stress. Identifying functional inhibitors that block MBL binding will be useful in characterizing the role of the LCP in disease models. The human cytokeratin peptide SFGSGFGGGY has been identified as a molecular mimic of N-acetyl-D-glucosamine (GlcNAc), a known ligand of MBL. Thus, we hypothesized that this peptide would specifically bind to MBL and functionally inhibit the LCP on endothelial cells following oxidative stress. Using a BIAcore 3000 optical biosensor, competition experiments were performed to demonstrate that the peptide SFGSGFGGGY inhibits binding of purified recombinant human MBL to GlcNAc in a concentration-dependent manner. Solution affinity data generated by BIAcore indicate this peptide binds to MBL with an affinity (K(D)) of 5 x 10(-5) mol/L. Pretreatment of human serum (30%) with the GlcNAc-mimicking peptide (10-50 microg/ml) significantly attenuated MBL and C3 deposition on human endothelial cells subjected to oxidative stress in a dose-dependent manner, as demonstrated by cell surface ELISA and confocal microscopy. Additionally, this decapeptide sequence attenuated complement-dependent VCAM-1 expression following oxidative stress. These data indicate that a short peptide sequence that mimics GlcNAc can specifically bind to MBL and functionally inhibit the proinflammatory action of the LCP on oxidatively stressed endothelial cells.

Muscle-specific kinase (MuSK) is part of the receptor complex that is involved in the agrin-induced formation of the neuromuscular junction. In the rodent, prominent mRNA expression of MuSK is restricted to skeletal muscle while the expression of agrin can also be detected in brain and certain nonneuronal tissues. The recent identification of Xenopus MuSK reveals that MuSK can be detected in tissues other than skeletal muscle, such as the neural tube, eye vesicles, and spleen. In this study, we describe the cloning and characterization of the chicken ortholog of MuSK and demonstrate that the regulation of MuSK expression in muscle is conserved from avian to rodent. Abundant mRNA expression of MuSK can be detected in early embryonic chick muscle and is up-regulated after nerve injury. More importantly, we also demonstrate that, in the chicken, MuSK mRNA is expressed during development in brain and liver, suggesting possible novel functions for MuSK. Furthermore, the regulatory profile of MuSK expression in chick muscle closely parallels that observed for acetylcholine receptor, in terms of both mRNA expression and protein localization. Finally, studies with paralyzed chicken muscle as well as with cultured chick myotubes demonstrate the dependence of MuSK on both electrical activity and trophic factors., (Copyright 2000 Academic Press.)

While a number of growth factors have been described that are highly specific for particular cell lineages, neither a factor nor a receptor uniquely specific to the skeletal muscle lineage has previously been described. Here we identify a receptor tyrosine kinase (RTK) specific to skeletal muscle, which we term "MuSK" for muscle-specific kinase. MuSK is expressed at low levels in proliferating myoblasts and is induced upon differentiation and fusion. In the embryo, it is specifically expressed in early myotomes and developing muscle. MuSK is then dramatically down-regulated in mature muscle, where it remains prominent only at the neuromuscular junction; MuSK is thus the only known RTK that localizes to the neuromuscular junction. Strikingly, MuSK expression is dramatically induced throughout the adult myofiber after denervation, block of electrical activity, or physical immobilization. In humans, MuSK maps to chromosome 9q31.3-32, which overlaps with the region reported to contain the Fukuyama muscular dystrophy mutation. Identification of MuSK introduces a novel receptor-factor system that seems sure to play an important and selective role in many aspects of skeletal muscle development and function.