On the He II Emission In Eta Carinae and the Origin of Its Spectroscopic Events

We describe and analyze Hubble Space Telescope (HST) observations of transient emission near 4680 {\AA} in Eta Car, reported earlier by Steiner & Damineli (2004). If, as seems probable, this is He II $\lambda$4687, then it is a unique clue to Eta Car's 5.5-year cycle. According to our analysis, several aspects of this feature support a mass-ejection model of the observed spectroscopic events, and not an eclipse model. The He II emission appeared in early 2003, grew to a brief maximum during the 2003.5 spectroscopic event, and then abruptly disappeared. It did not appear in any other HST spectra before or after the event. The peak brightness was larger than previously reported, and is difficult to explain even if one allows for an uncertainty factor of order 3. The stellar wind must provide a temporary larger-than-normal energy supply, and we describe a special form of radiative amplification that may also be needed. These characteristics are consistent with a class of mass-ejection or wind-disturbance scenarios, which have implications for the physical structure and stability of Eta Car.Comment: 47 pages (including all appendices, tabs, & figs), 9 figures, 3 tables; submitted to Astrophysical Journal (2005 March 29), accepted for publication in Ap

Perlecan-Induced Suppression of Smooth Muscle Cell Proliferation Is Mediated Through Increased Activity of the Tumor Suppressor PTEN

We were interested in the elucidation of the interaction between the heparan sulfate proteoglycan, perlecan, and PTEN in the regulation of vascular smooth muscle cell (SMC) growth. We verified serum-stimulated DNA synthesis, and Akt and FAK phosphorylation were significantly reduced in SMCs overexpressing wild-type PTEN. Our previous studies showed perlecan is a potent inhibitor of serum-stimulated SMC growth. We report in the present study, compared with SMCs plated on fibronectin, serum-stimulated SMCs plated on perlecan exhibited increased PTEN activity, decreased FAK and Akt activities, and high levels of p27, consistent with SMC growth arrest. Adenoviral-mediated overexpression of constitutively active Akt reversed perlecan-induced SMC growth arrest while morpholino antisense-mediated loss of endogenous PTEN resulted in increased growth and phosphorylation of FAK and Akt of SMCs on perlecan. Immunohistochemical and Western analyses of balloon-injured rat carotid artery tissues showed a transient increase in phosphoPTEN (inactive) after injury, correlating to high rates of neointimal cell replication; phosphoPTEN was largely limited to actively replicating SMCs. Similarly, in the developing rat aorta, we found increased PTEN activity associated with increased perlecan deposition and decreased SMC replication rates. However, significantly decreased PTEN activity was detected in aortas of perlecan-deficient mouse embryos, consistent with SMC hyperplasia observed in these animals, compared with E17.5 heterozygous controls that produce abundant amounts of perlecan at this developmental time point. Our data show PTEN is a potent endogenously produced inhibitor of SMC growth and increased PTEN activity mediates perlecan-induced suppression of SMC proliferation.Costell Rossello, M.Mercedes, [email protected]

Similarity of Recombinant Human Perlecan Domain 1 by Alternative Expression Systems Bioactive Heterogenous Recombinant Human Perlecan D1

<p>Abstract</p> <p>Background</p> <p>Heparan sulfate glycosaminoglycans are diverse components of certain proteoglycans and are known to interact with growth factors as a co-receptor necessary to induce signalling and growth factor activity. In this report we characterize heterogeneously glycosylated recombinant human perlecan domain 1 (HSPG2 abbreviated as rhPln.D1) synthesized in either HEK 293 cells or HUVECs by transient gene delivery using either adenoviral or expression plasmid technology.</p> <p>Results</p> <p>By SDS-PAGE analysis following anion exchange chromatography, the recombinant proteoglycans appeared to possess glycosaminoglycan chains ranging, in total, from 6 kDa to >90 kDa per recombinant. Immunoblot analysis of enzyme-digested high M_rrhPln.D1 demonstrated that the rhPln.D1 was synthesized as either a chondroitin sulfate or heparan sulfate proteoglycan, in an approximately 2:1 ratio, with negligible hybrids. Secondary structure analysis suggested helices and sheets in both recombinant species. rhPln.D1 demonstrated binding to rhFGF-2 with an apparent k_Dof 2 ± 0.2 nM with almost complete susceptibility to digestion by heparinase III in ligand blot analysis but not to chondroitinase digestion. Additionally, we demonstrate HS-mediated binding of both rhPln.D1 species to several other GFs. Finally, we corroborate the augmentation of FGF-mediated cell activation by rhPln.D1 and demonstrate mitogenic signalling through the FGFR1c receptor.</p> <p>Conclusions</p> <p>With importance especially to the emerging field of DNA-based therapeutics, we have shown here that proteoglycan synthesis, in different cell lines where GAG profiles typically differ, can be directed by recombinant technology to produce populations of bioactive recombinants with highly similar GAG profiles.</p

Biodiversity of CS-proteoglycan sulphation motifs: chemical messenger recognition modules with roles in information transfer, control of cellular behaviour and tissue morphogenesis

Chondroitin sulphate glycosaminoglycan chains on cell and ECM proteoglycans can no longer be regarded as merely hydrodynamic space fillers. Overwhelming evidence over recent years indicates that sulphation motif sequences within the chondroitin sulphate chain structure are a source of significant biological information to cells and their surrounding environment. Chondroitin sulphate sulphation motifs have been shown to interact with a wide variety of bioactive molecules e.g. cytokines, growth factors, chemokines, morphogenetic proteins, enzymes and enzyme inhibitors, as well as structural components within the extracellular milieu. They are therefore capable of modulating a panoply of signalling pathways thus controlling diverse cellular behaviours including proliferation, differentiation, migration and matrix synthesis. Consequently, through these motifs, chondroitin sulphate proteoglycans play significant roles in the maintenance of tissue homeostasis, morphogenesis, development, growth and disease. Here we review (i) the biodiversity of chondroitin sulphate proteoglycans and their sulphation motif sequences and (ii) the current understanding of the signalling roles they play in regulating cellular behaviour during tissue development, growth, disease and repai

A massive cluster of Red Supergiants at the base of the Scutum-Crux arm

We report on the unprecedented Red Supergiant (RSG) population of a massive young cluster, located at the base of the Scutum-Crux Galactic arm. We identify candidate cluster RSGs based on {\it 2MASS} photometry and medium resolution spectroscopy. With follow-up high-resolution spectroscopy, we use CO-bandhead equivalent width and high-precision radial velocity measurements to identify a core grouping of 26 physically-associated RSGs -- the largest such cluster known to-date. Using the stars' velocity dispersion, and their inferred luminosities in conjuction with evolutionary models, we argue that the cluster has an initial mass of $\sim$40,000\msun, and is therefore among the most massive in the galaxy. Further, the cluster is only a few hundred parsecs away from the cluster of 14 RSGs recently reported by Figer et al (2006). These two RSG clusters represent 20% of all known RSGs in the Galaxy, and now offer the unique opportunity to study the pre-supernova evolution of massive stars, and the Blue- to Red-Supergiant ratio at uniform metallicity. We use GLIMPSE, MIPSGAL and MAGPIS survey data to identify several objects in the field of the larger cluster which seem to be indicative of recent region-wide starburst activity at the point where the Scutum-Crux arm intercepts the Galactic bulge. Future abundance studies of these clusters will therefore permit the study of the chemical evolution and metallicity gradient of the Galaxy in the region where the disk meets the bulge.Comment: 49 pages, 22 figures. Accepted for publication in ApJ. Version with hi-res figures can be found at http://www.cis.rit.edu/~bxdpci/RSGC2.pd

Illumination in symbiotic binary stars: Non-LTE photoionization models. II. Wind case

We describe a non-LTE photoionization code to calculate the wind structure and emergent spectrum of a red giant wind illuminated by the hot component of a symbiotic binary system. We consider spherically symmetric winds with several different velocity and temperature laws and derive predicted line fluxes as a function of the red giant mass loss rate, \mdot. Our models generally match observations of the symbiotic stars EG And and AG Peg for \mdot about 10^{-8} \msunyr to 10^{-7} \msunyr. The optically thick cross- section of the red giant wind as viewed from the hot component is a crucial parameter in these models. Winds with cross-sections of 2--3 red giant radii reproduce the observed fluxes, because the wind density is then high, about 10^9 cm^{-3}. Our models favor winds with acceleration regions that either lie far from the red giant photosphere or extend for 2--3 red giant radii.Comment: 51 pages, LaTeX including three tables, requires 15 Encapsulated Postscript figures, to appear in Ap

The Mira Distance to M101 and a 4% Measurement of H0

The giant spiral galaxy M101 is host to the nearest recent Type Ia Supernova (SN 2011fe) and thus has been extensively monitored in the near-infrared to study the late-time lightcurve of the supernova. Leveraging this existing baseline of observations, we derive the first Mira-based distance to M101 by discovering and classifying a sample of 211 Miras with periods ranging from 240 to 400 days in the supernova field. Combined with new HST WFC3/IR channel observations, our dataset totals 11 epochs of F110W (HST $YJ$) and 13 epochs of F160W (HST $H$) data spanning $\sim$2900 days. We adopt absolute calibrations of the Mira Period-Luminosity Relation based on geometric distances to the Large Magellanic Cloud and the water megamaser host galaxy NGC 4258, and find $\mu_{\rm M101} =$ 29.10 $\pm$ 0.06 mag. This distance is in 1$\sigma$ agreement with most other recent Cepheid and Tip of the Red Giant Branch distance measurements to M101. Including the previous Mira-SNIa host, NGC 1559 and SN 2005df, we determine the fiducial SN Ia peak luminosity, $M^0_B = -19.27 \pm 0.09$ mag. With the Hubble diagram of SNe Ia, we derive $H_0 = 72.37 \pm 2.97$ km s$^{-1}$Mpc$^{-1}$, a $4.1\%$ measurement of $H_0$ using Miras. We find excellent agreement with recent Cepheid distance ladder measurements of $H_0$ and confirm previous indications that the local universe value of $H_0$ is higher than the early-universe value at $\sim$ $95\%$ confidence. Currently, the Mira-based $H_0$ measurement is still dominated by the statistical uncertainty in the SN Ia peak magnitude.Comment: 22 pages, 11 figures, accepted to Ap

The UV Scattering Halo of the Central Source Associated with Eta Carinae

We have made an extensive study of the UV spectrum of Eta Carinae, and find that we do not directly observe the star and its wind in the UV. Because of dust along our line of sight, the UV light that we observe arises from bound-bound scattering at large impact parameters. We obtain a reasonable fit to the UV spectrum by using only the flux that originates outside 0.033". This explains why we can still observe the primary star in the UV despite the large optical extinction -- it is due to the presence of an intrinsic coronagraph in the Eta Carinae system, and to the extension of the UV emitting region. It is not due to peculiar dust properties alone. We have computed the spectrum of the purported companion star, and show that it could only be directly detected in the UV spectrum preferentially in the Far Ultraviolet Spectroscopic Explorer (FUSE) spectral region (912-1175 Ang.). However, we find no direct evidence for a companion star, with the properties indicated by X-ray studies and studies of the Weigelt blobs, in UV spectra. This might be due to reprocessing of the companion's light by the dense stellar wind of the primary. Broad FeII and [FeII] emission lines, which form in the stellar wind, are detected in spectra taken in the SE lobe, 0.2" from the central star. The wind spectrum shows some similarities to the spectra of the B & D Weigelt blobs, but also shows some marked differences in that high excitation lines, and lines pumped by Ly-alpha, are not seen. The detection of the broad lines lends support to our interpretation of the UV spectrum, and to our model for Eta Carinae.Comment: To appear in ApJ. 57 pages with 18 figure

Secular Changes in Eta Carinae's Wind 1998-2011

Stellar wind-emission features in the spectrum of eta Carinae have decreased by factors of 1.5-3 relative to the continuum within the last 10 years. We investigate a large data set from several instruments (STIS, GMOS, UVES) obtained between 1998 and 2011 and we analyze the progression of spectral changes in the direct view of the star, in the reflected polar-on spectra at FOS4, and at the Weigelt knots. We find that the spectral changes occurred gradually on a time scale of about 10 years and that they are dependent on the viewing angle. The line strengths declined most in our direct view of the star. About a decade ago, broad stellar wind-emission features were much stronger in our line-of-sight view of the star than at FOS4. After the 2009 event, the wind-emission line strengths are now very similar at both locations. High-excitation He I and N II absorption lines in direct view of the star strengthened gradually. The terminal velocity of Balmer P Cyg absorption lines now appears to be less latitude-dependent and the absorption strength may have weakened at FOS4. Latitude-dependent alterations in the mass-loss rate and the ionization structure of eta Carinae's wind are likely explanations for the observed spectral changes.Comment: 42 pages, 12 figures, 2 table