The mass-to-light ratio of rich star clusters

We point out a strong time-evolution of the mass-to-light conversion factor eta commonly used to estimate masses of unresolved star clusters from observed cluster spectro-photometric measures. We present a series of gas-dynamical models coupled with the Cambridge stellar evolution tracks to compute line-of-sight velocity dispersions and half-light radii weighted by the luminosity. We explore a range of initial conditions, varying in turn the cluster mass and/or density, and the stellar population's IMF. We find that eta, and hence the estimated cluster mass, may increase by factors as large as 3 over time-scales of 50 million years. We apply these results to an hypothetic cluster mass distribution function (d.f.) and show that the d.f. shape may be strongly affected at the low-mass end by this effect. Fitting truncated isothermal (Michie-King) models to the projected light profile leads to over-estimates of the concentration parameter c of delta c ~ 0.3 compared to the same functional fit applied to the projected mass density.Comment: 6 pages, 2 figures, to appear in the proceedings of the "Young massive star clusters", Granada, Spain, September 200

The dopamine D1 receptor is expressed and induces CREB phosphorylation and MUC5AC expression in human airway epithelium

Background Dopamine receptors comprise two subgroups, Gs protein-coupled “D1-like” receptors (D1, D5) and Gi-coupled “D2-like” receptors (D2, D3, D4). In airways, both dopamine D1 and D2 receptors are expressed on airway smooth muscle and regulate airway smooth muscle force. However, functional expression of the dopamine D1 receptor has never been identified on airway epithelium. Activation of Gs-coupled receptors stimulate adenylyl cyclase leading to cyclic AMP (cAMP) production, which is known to induce mucus overproduction through the cAMP response element binding protein (CREB) in airway epithelial cells. We questioned whether the dopamine D1 receptor is expressed on airway epithelium, and whether it promotes CREB phosphorylation and MUC5AC expression. Methods We evaluated the protein expression of the dopamine D1 receptor on native human airway epithelium and three sources of cultured human airway epithelial cells including primary cultured airway epithelial cells, the bronchial epithelial cell line (16HBE14o-), and the pulmonary mucoepidermoid carcinoma cell line (NCI-H292) using immunohistochemistry and immunoblotting. To characterize the stimulation of cAMP through the dopamine D1 receptor, 16HBE14o- cells and NCI-H292 cells were treated with dopamine or the dopamine D1 receptor agonists (SKF38393 or A68930) before cAMP measurements. The phosphorylation of CREB by A68930 in both 16HBE14o- and NCI-H292 cells was measured by immunoblot. The effect of dopamine or A68930 on the expression of MUC5AC mRNA and protein in NCI-H292 cells was evaluated by real-time PCR and immunofluorescence staining, respectively. Results The dopamine D1 receptor protein was detected in native human airway epithelium and three sources of cultured human airway epithelial cells. Dopamine or the dopamine D1-like receptor agonists stimulated cAMP production in 16HBE14o- cells and NCI-H292 cells, which was reversed by the selective dopamine D1-like receptor antagonists (SCH23390 or SCH39166). A68930 significantly increased phosphorylation of CREB in both 16HBE14o- and NCI-H292 cells, which was attenuated by the inhibitors of PKA (H89) and MEK (U0126). Expression of MUC5AC mRNA and protein were also increased by either dopamine or A68930 in NCI-H292 cells. Conclusions These results suggest that the activation of the dopamine D1 receptor on human airway epithelium could induce mucus overproduction, which could worsen airway obstructive symptoms

Valproate, thalidomide and ethyl alcohol alter the migration of HTR-8/SVneo cells

BACKGROUND: Valproate, thalidomide and alcohol (ethanol) exposure during the first trimester of pregnancy is known to cause several developmental disorders. All these teratogens are known to pass the placental barrier and interfere directly with the normal development of the fetus. However, these teratogens also alter the formation and function of the placenta itself which may in turn affect the proper nourishment and development of the fetus. Optimum development of the placenta requires adequate invasion of trophoblast into the maternal uterine tissues. Changes in the migratory behavior of trophoblast by maternal exposure to these teratogens during placentogenesis may therefore alter the structure and function of the placenta. METHODS: In the present study, the effects of sodium valproate, thalidomide and alcohol on the migration of human first trimester trophoblast cell line (HTR-8/SVneo) were examined in vitro. Cells were cultured in the wells of 48-well culture plates as mono or multilayers. Circular patches of cells were removed from the center of the wells by suction, and the migration of cells into the wound was studied using microscopy. Effects of low and high concentrations of valproate, thalidomide and alcohol were examined on the healing of wounds and on the migration rate of cells by determining the wound areas at 0, 3, 6, 12, 24 and 48 h. Effects of drugs and alcohol on the proliferation and the expression levels of integrin subunits beta1 and alpha5 in cells were examined. RESULTS: The migration rates of trophoblast differed between wounds created in mono and multilayers of cells. Exposure to teratogens altered the migration of trophoblast into mono and multilayer wounds. The effects of valproate, thalidomide and alcohol on the proliferation of cells during the rapid migratory phase were mild. Drug exposure caused significant changes in the expression levels of beta1 and alpha5 integrin subunits. CONCLUSION: Results suggest that exposure to valproate, thalidomide or alcohol during the first trimester of pregnancy may change the ultrastructure of the placenta by altering the migration of trophoblast cells and this effect may be mediated by drug- or alcohol-induced changes in the expression levels of beta1 and alpha5 integrin subunits

Relativistic Dynamics and Extreme Mass Ratio Inspirals

It is now well-established that a dark, compact object (DCO), very likely a massive black hole (MBH) of around four million solar masses is lurking at the centre of the Milky Way. While a consensus is emerging about the origin and growth of supermassive black holes (with masses larger than a billion solar masses), MBHs with smaller masses, such as the one in our galactic centre, remain understudied and enigmatic. The key to understanding these holes - how some of them grow by orders of magnitude in mass - lies in understanding the dynamics of the stars in the galactic neighbourhood. Stars interact with the central MBH primarily through their gradual inspiral due to the emission of gravitational radiation. Also stars produce gases which will subsequently be accreted by the MBH through collisions and disruptions brought about by the strong central tidal field. Such processes can contribute significantly to the mass of the MBH and progress in understanding them requires theoretical work in preparation for future gravitational radiation millihertz missions and X-ray observatories. In particular, a unique probe of these regions is the gravitational radiation that is emitted by some compact stars very close to the black holes and which could be surveyed by a millihertz gravitational wave interferometer scrutinizing the range of masses fundamental to understanding the origin and growth of supermassive black holes. By extracting the information carried by the gravitational radiation, we can determine the mass and spin of the central MBH with unprecedented precision and we can determine how the holes "eat" stars that happen to be near them.Comment: Update from the first version, 151 pages, accepted for publication @ Living Reviews in Relativit

Relativistic Binaries in Globular Clusters

Galactic globular clusters are old, dense star systems typically containing 10\super{4}--10\super{7} stars. As an old population of stars, globular clusters contain many collapsed and degenerate objects. As a dense population of stars, globular clusters are the scene of many interesting close dynamical interactions between stars. These dynamical interactions can alter the evolution of individual stars and can produce tight binary systems containing one or two compact objects. In this review, we discuss theoretical models of globular cluster evolution and binary evolution, techniques for simulating this evolution that leads to relativistic binaries, and current and possible future observational evidence for this population. Our discussion of globular cluster evolution will focus on the processes that boost the production of hard binary systems and the subsequent interaction of these binaries that can alter the properties of both bodies and can lead to exotic objects. Direct {\it N}-body integrations and Fokker--Planck simulations of the evolution of globular clusters that incorporate tidal interactions and lead to predictions of relativistic binary populations are also discussed. We discuss the current observational evidence for cataclysmic variables, millisecond pulsars, and low-mass X-ray binaries as well as possible future detection of relativistic binaries with gravitational radiation.Comment: 88 pages, 13 figures. Submitted update of Living Reviews articl

A MODEST review

We present an account of the state of the art in the fields explored by the research community invested in 'Modeling and Observing DEnse STellar systems'. For this purpose, we take as a basis the activities of the MODEST-17 conference, which was held at Charles University, Prague, in September 2017. Reviewed topics include recent advances in fundamental stellar dynamics, numerical methods for the solution of the gravitational N-body problem, formation and evolution of young and old star clusters and galactic nuclei, their elusive stellar populations, planetary systems, and exotic compact objects, with timely attention to black holes of different classes of mass and their role as sources of gravitational waves. Such a breadth of topics reflects the growing role played by collisional stellar dynamics in numerous areas of modern astrophysics. Indeed, in the next decade, many revolutionary instruments will enable the derivation of positions and velocities of individual stars in the Milky Way and its satellites and will detect signals from a range of astrophysical sources in different portions of the electromagnetic and gravitational spectrum, with an unprecedented sensitivity. On the one hand, this wealth of data will allow us to address a number of long-standing open questions in star cluster studies; on the other hand, many unexpected properties of these systems will come to light, stimulating further progress of our understanding of their formation and evolution.Comment: 42 pages; accepted for publication in 'Computational Astrophysics and Cosmology'. We are much grateful to the organisers of the MODEST-17 conference (Charles University, Prague, September 2017). We acknowledge the input provided by all MODEST-17 participants, and, more generally, by the members of the MODEST communit

SMOKE AND VIRAL-INFECTION CAUSE CILIA LOSS DETECTABLE BY BRONCHOALVEOLAR LAVAGE CYTOLOGY AND DYNEIN ELISA

The purpose of this study was to quantitate cilia loss following airway epithelial cell injury. Two models of airway injury were used: (1) Ex vivo acute cigarette smoke exposure model: Bovine lungs, obtained directly after slaughter, were ventilated with air or cigarette smoke for 5 min followed immediately by bronchoalveolar lavage (BAL). The bronchi were examined histologically and bronchial and alveolar fractions of BAL fluid were examined for cell counts, cell differentials, and cilia dynein concentrations using a specific 13S dynein ELISA. Smoke exposure resulted in a marked loss of ciliated cells from the bronchial luminal surface (2,364 +/- 351 versus 11,090 +/- 542 ciliated cells/mm2; p = 0.0001), a comparable increase in ciliated cells in the bronchial BAL fraction (0.90 x 10(6) cells/mm3 versus 0.15 x 10(6) cells/mm3; p = 0.0003) and a significant increase in bronchial fluid dynein concentrations (24.5 +/- 6.0 micrograms/ml versus 8.9 +/- 2.2 micrograms/ml; p = 0.03) compared with that in air-exposed lungs. The dynein concentrations strongly correlated with the absolute number of ciliated cells recovered in the bronchial lavage (r = 0.80; p < 0.0001). (2) In vivo viral infection model: Healthy cattle underwent bronchoscopy 3 days before and 7 days after inoculation with bovine respiratory syncytial virus (BRSV). BAL fluid was examined as in the first model. Following BRSV inoculation, airway exfoliation of ciliated cells and squamous metaplasia were observed histologically, bronchial ciliated cell counts doubled (0.011 +/- 0.003 x 10(6) cells/mm3 versus 0.026 +/- 0.006 x 10(6) cells/mm3; p = 0.002) and bronchial dynein concentrations increased threefold (2.2 +/- 1.0 micrograms/ml versus 7.2 +/- 1.9 micrograms/ml; p = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS