Recent star formation in clusters of galaxies: extreme compact starbursts in A539 and A634

We report on the detection of two Halpha-emitting extreme compact objects from deep images of the Abell 634 and Abell 539 clusters of galaxies at z ~ 0.03. Follow up long slit spectroscopy of these two unresolved sources revealed that they are members of their respective clusters showing HII type spectra. The luminosity and the extreme equivalent width of Halpha+[NII] measured for these sources, together with their very compact appearance, has raised the question about the origin of these intense starbursts in the cluster environment. We propose the compact starburst in Abell 539 resulted from the compression of the interstellar gas of a dwarf galaxy when entering the cluster core; while the starburst galaxy in Abell 634 is likely to be the result of a galaxy-galaxy interaction, illustrating the preprocessing of galaxies during their infall towards the central regions of clusters. The contribution of these compact star-forming dwarf galaxies to the star formation history of galaxy clusters is discussed, as well as a possible link with the recently discovered early-type ultra-compact dwarf galaxies. We note that these extreme objects will be rarely detected in normal magnitude-limited optical or NIR surveys, mainly due to their low stellar masses (of the order of 10^6 solar masses), whereas they will easily show up in dedicated Halpha surveys given the high equivalent width of their emission lines.Comment: Accepted for publication in the Astronomical Journal. 31 pages, 10 fig

Expansion of CD8+CD57+ T Cells in an Immunocompetent Patient with Acute Toxoplasmosis

CD57+ T cells increase in several viral infections like cytomegalovirus, herpesvirus, parvovirus, HIV and hepatitis C virus and are associated with several clinical conditions related to immune dysfunction and ageing. We report for the first time an expansion of CD8+ CD57+ T cells in a young patient with an acute infection with Toxoplasma gondii. Our report supports the concept that CD8+ CD57+ T cells could be important in the control of chronic phase of intracellular microorganisms and that the high numbers of these cells may reflect the continuing survey of the immune system, searching for parasite proliferation in the tissues

The Luminosity Function of Galaxies in the Hercules Cluster

We have imaged $\sim$ 1 deg$^{2}$ in the V-band in the direction of the Hercules Cluster (Abell 2151). The data are used to compute for the first time the luminosity function (LF) of galaxies in the cluster down to the dwarf regime (M$_{lim}$ $\sim$ -13.85). The global LF is well described by a Schechter function (\cite{schechter76}) with best-fit parameters $\alpha$ = -1.30 $\pm$ 0.06 and M$_V$$^*$ = -21.25 $\pm$ 0.25. The radial dependence of the LF has also been studied, finding that it turns out to be almost constant within the errors even further away than the virial radius. Given the presence of significant substructure within the cluster, we have analized the LFs in different regions. While two of the subclusters present LFs consistent with each other and with the global one, the southernmost one exhibits a somewhat steeper faint-end slope.Comment: 3 pages, to appear in Proc. of IAU Colloq. 195: "Outskirts of Galaxy Clusters: Intense Life in the Suburbs

proMetalloproteinase-10 is associated with brain damage and clinical outcome in acute ischemic stroke

BACKGROUND: Matrix metalloproteinases (MMPs) mediate tissue injury during stroke but also neurovascular remodeling and we have shown that MMP-10 is involved in atherothrombosis. OBJECTIVE: The purpose of this study was to examine the relationship between proMMP-10 and clinical outcome, assessing inflammatory and proteolytic markers, in patients with acute ischemic stroke. METHODS: We prospectively studied 76 patients with ischemic stroke treated with tPA within the first 3 h from symptom onset, compared with 202 non-tPA-treated ischemic stroke patients and 83 asymptomatic subjects. Stroke severity was assessed with the National Institutes of Health Stroke Scale (NIHSS). Hemorrhagic transformation (HT) and severe brain edema were diagnosed by cranial CT. Good functional outcome was defined as a modified Rankin scale score </= 2 at 90 days. Serum levels of MMP-9, proMMP-10, TIMP-1, tumor necrosis factor-alpha (TNFalpha), interleukin-6 and cellular fibronectin were measured at admission. The effect of TNFalpha on endothelial proMMP-10 was assessed in vitro. RESULTS: Serum proMMP-10 concentration in ischemic stroke patients, non-treated or treated with t-PA, which was higher than age-matched healthy subjects (P < 0.0001), was independently associated with higher infarct volume, severe brain edema, neurological deterioration and poor functional outcome at 3 months (all P < 0.05), but not with HT. proMMP-10 levels were also independently and positively associated with circulating levels of TNFalpha (P < 0.0001), which induced its endothelial expression in vitro, both mRNA and protein. MMP-9, however, was only associated with HT and severe edema (all P < 0.05). CONCLUSIONS: Increased serum proMMP-10 after acute ischemic stroke, associated with TNFalpha, is a new marker of brain damage and poor outcome

The r'-band luminosity function of Abell1367: a comparison with Coma

We made a large (approximately 1degr x 1degr) r'-band imaging survey of the central regions of the two nearby clusters of galaxies, Abell1367 and Coma. The data, presented as a catalog, are used to construct the r'-band luminosity function (LF) of galaxies in these two clusters, by subtracting the Yasuda et al. (2001) galaxy counts from our cluster counts. Our Coma luminosity function is consistent with previous determinations, i.e. providing a faint end slope alpha = -1.47_-0.09^+0.08, significantly steeper than the one we find for Abell1367 (alpha = -1.07_-0.16^+0.20). The counts in Abell1367 show a relative minimum at r' ~ 19, followed by a steep increase faintward. The difference between the two clusters appears significant, given the consistency of the experimental conditions in the two clusters. Whereas for Coma we find a significant increase of the slope of the LF outwards, no such effect is found for Abell1367.Comment: 12 pages, 8 figures, accepted for publication in A&

Ultraviolet dust attenuation in spiral galaxies: the role of age-dependent extinction and the initial mass function

We analyse the attenuation properties of a sample of ultraviolet (UV) selected galaxies, with the use of the spectrophotometric model GRASIL. In particular, we focus on the relation between dust attenuation and the reddening in the UV spectral region. We show that a realistic modelling of geometrical distribution of dust and the different population of stars can explain the UV reddening of normal spiral galaxies also with a standard Milky Way dust. Our results clearly underline that it is fundamental to take into account that younger stars suffer a higher attenuation than older stars (the age-dependent extinction) because stars are born in more-than-average dusty environments. In this work, we also find that the concentration of young stars on the galactic plane of spirals has a relevant impact on the expected UV colours, impact that has not been explored before this paper. Finally, we discuss the role of the initial mass function (IMF) in shaping the relation between UV reddening and dust attenuation, and we show that a Kroupa IMF is more consistent with observed data than the classical Salpeter IMF

Association of sepsis-related mortality with early increase of TIMP-1/MMP-9 ratio

Objective: Higher circulating levels of tissue inhibitor of matrix metalloproteinases (TIMP)-1 at the time of severe sepsis diagnosis have been reported in nonsurviving than in surviving patients. However, the following questions remain unanswered: 1) Does TIMP-1/MMP-9 ratio differ throughout the first week of intensive care between surviving and nonsurviving patients? 2) Is there an association between TIMP-1/MMP-9 ratio and sepsis severity and mortality during such period? 3) Could TIMP-1/MMP-9 ratio during the first week be used as an early biomarker of sepsis outcome? 4) Is there an association between TIMP-1/MMP-9 ratio and coagulation state and circulating cytokine levels during the first week of intensive care in these patients? The present study sought to answer these questions. Methods: Multicenter, observational and prospective study carried out in six Spanish Intensive Care Units (ICUs) of 295 patients with severe sepsis. Were measured circulating levels of TIMP-1, MMP-9, tumour necrosis factor (TNF)-alpha, interleukin (IL)-10 and plasminogen activator inhibitor (PAI)-1 at day 1, 4 and 8. End-point was 30-day mortality. Results: We found higher TIMP-1/MMP-9 ratio during the first week in non-surviving (n = 98) than in surviving patients (n = 197) (p, 0.01). Logistic regression analyses showed that TIMP-1/MMP-9 ratio at days 1, 4 and 8 was associated with mortality. Receiver operating characteristic (ROC) curves showed that TIMP-1/MMP-9 ratio at days 1, 4 and 8 could predict mortality. There was an association between TIMP-1/MMP-9 ratio and TNF-alpha, IL-10, PAI-1 and lactic acid levels, SOFA score and platelet count at days 1, 4 and 8. Conclusions: The novel findings of our study were that non-surviving septic patients showed persistently higher TIMP-1/ MMP-9 ratio than survivors ones during the first week, which was associated with severity, coagulation state, circulating cytokine levels and mortality; thus representing a new biomarker of sepsis outcome

Ripples and tails in the compact group of galaxies Hickson 54

HCG 54 has been classified as a compact galaxy group by Hickson, but its nature is uncertain because of its unusual properties. We present here a study of HCG~54 based on deep optical images and spectroscopy as well as high spatial and spectral resolution HI observations obtained at the VLA. Both optical and radio data indicate clearly that HCG~54 is a product of a recent merger involving at least two galaxies. Our optical images have revealed a blue elongated structure associated with HCG 54a embedded in a rounder and redder stellar envelope. Several ripples or shells whose center is located near HCG 54a and b are also detected. These observed features are similar to those found in the numerical simulations of tidal interactions involving two equal mass disk galaxies. This system is embedded in an HI cloud 12 kpc in diameter, and a 20 kpc HI tidal tail emerges from its western edge. Both the HI distribution and kinematics are consistent with a recent history of a deeply penetrating interaction or a merger. Based on the analysis of our new data we propose that HCG 54 is the remnant of a merger in an advanced stage, whose main body is what has been called HCG 54a, while HCG 54b marks the location of a strong starburst induced by the interaction, as evidenced by the Wolf Rayet stellar population that we detect. Optical spectra of HCG 54c and d show HII region features and are interpreted as tidal debris of the collision undergoing active star formation.Comment: Accepted for publication in A&