Search

Copyright of Revista Lasallista de Investigación is the property of Corporacion Universitaria Lasallista and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Counteracting calpain: During fibrosis, myofibroblasts produce extracellular matrix that accumulates and impairs tissue function. Kim et al. found that transforming growth factor–β induced translation of calpain 9, a cysteine protease, which mediated myofibroblast differentiation. Mice lacking calpain 9 were protected from experimentally induced fibrosis in the heart, lung, and liver. The authors identified a common calpain 9 loss-of-function mutation in people that was not associated with markers of intolerance. This study suggests that targeting calpain 9 could have therapeutic potential for inhibiting fibrosis. Fibrosis is a common pathologic outcome of chronic disease resulting in the replacement of normal tissue parenchyma with a collagen-rich extracellular matrix produced by myofibroblasts. Although the progenitor cell types and cellular programs giving rise to myofibroblasts through mesenchymal transition can vary between tissues and diseases, their contribution to fibrosis initiation, maintenance, and progression is thought to be pervasive. Here, we showed that the ability of transforming growth factor–β (TGFβ) to efficiently induce myofibroblast differentiation of cultured epithelial cells, endothelial cells, or quiescent fibroblasts is dependent on the induced expression and activity of dimeric calpains, a family of non-lysosomal cysteine proteases that regulate a variety of cellular events through posttranslational modification of diverse substrates. siRNA-based gene silencing demonstrated that TGFβ-induced mesenchymal transition of a murine breast epithelial cell line was dependent on induction of expression of calpain 9 (CAPN9), an isoform previously thought to be restricted to the gastrointestinal tract. Mice lacking functional CAPN9 owing to biallelic targeting of Capn9 were viable and fertile but showed overt protection from bleomycin-induced lung fibrosis, carbon tetrachloride–induced liver fibrosis, and angiotensin II–induced cardiac fibrosis and dysfunction. A predicted loss-of-function allele of CAPN9 is common in Southeast Asia, with the frequency of homozygosity matching the prediction of Hardy-Weinberg equilibrium. Together with the highly spatially restricted pattern of CAPN9 expression under physiologic circumstances and the heartiness of the murine knockout, these data provide a strong signature for tolerance of therapeutic strategies for fibrosis aimed at CAPN9 antagonism. [ABSTRACT FROM AUTHOR]

Copyright of Revista Kavilando is the property of Kavilando and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Thoracic aortic aneurysms (TAA) are permanent and localized dilations of the aorta that predispose patients to a life-threatening risk of aortic dissection or rupture. The identification of pathogenic variants that cause hereditary forms of TAA has delineated fundamental molecular processes required to maintain aortic homeostasis. Vascular smooth muscle cells (VSMCs) elaborate and remodel the extracellular matrix (ECM) in response to mechanical and biochemical cues from their environment. Causal variants for hereditary forms of aneurysm compromise the function of gene products involved in the transmission or interpretation of these signals, initiating processes that eventually lead to degeneration and mechanical failure of the vessel. These include mutations that interfere with transduction of stimuli from the matrix to the actin–myosin cytoskeleton through integrins, and those that impair signaling pathways activated by transforming growth factor-β (TGF-β). In this review, we summarize the features of the healthy aortic wall, the major pathways involved in the modulation of VSMC phenotypes, and the basic molecular functions impaired by TAA-associated mutations. We also discuss how the heterogeneity and balance of adaptive and maladaptive responses to the initial genetic insult might contribute to disease. [ABSTRACT FROM AUTHOR]

We present a variability study of the lowest-luminosity Seyfert 1 nucleus of the galaxy NGC 4395 based on photometric monitoring campaigns in 2017 and 2018. Using 22 ground-based and space telescopes, we monitored NGC 4395 with a ∼5-minute cadence during a period of 10 days and obtained light curves in the ultraviolet (UV), V, J, H, and K/Ks bands, as well as narrowband Hα. The rms variability is ∼0.13 mag in the Swift UVM2 and V filter light curves, decreasing down to ∼0.01 mag in the K filter. After correcting for the continuum contribution to the Hα narrow band, we measured the time lag of the Hα emission line with respect to the V-band continuum as – minutes in 2017 and – minutes in 2018, depending on assumptions about the continuum variability amplitude in the Hα narrow band. We obtained no reliable measurements for the continuum-to-continuum lag between UV and V bands and among near-IR bands, owing to the large flux uncertainty of UV observations and the limited time baseline. We determined the active galactic nucleus (AGN) monochromatic luminosity at 5100 Å, , after subtracting the contribution of the nuclear star cluster. While the optical luminosity of NGC 4395 is two orders of magnitude lower than that of other reverberation-mapped AGNs, NGC 4395 follows the size–luminosity relation, albeit with an offset of 0.48 dex (≥2.5σ) from the previous best-fit relation of Bentz et al. [ABSTRACT FROM AUTHOR]

The high-energy emission from nearby, star-forming galaxies is dominated by X-ray binaries, where a neutron star or black hole is accreting mass from either a low-mass (≲3 M⊙) or high-mass (≳8 M⊙) star. Donor stars with intermediate masses ≈3–7 M⊙ are also possible, but rarer in our Galaxy. Since it is not possible to separate low-, intermediate-, and high-mass X-ray binaries (LMXBs, IMXBs, and HMXBs) from their X-ray properties alone, we use optical images of M101 taken with the Hubble Space Telescope to directly constrain the masses of donor stars in X-ray binaries down to ≈3 M⊙. For X-ray binaries that still live within their parent star cluster, the age of the cluster provides strong constraints on the mass of the donor and hence type of binary. We present the classification, on a source-by-source basis, of 140 X-ray point sources in the nearby spiral galaxy M101 (D = 6.4 ± 0.2 Mpc). We find that, overall, HMXBs appear to follow the spiral arms, while LMXBs dominate the bulge region as expected, but also appear to form an inter-arm disk population. The X-ray luminosity functions for HMXBs and LMXBs are well fit by a power-law distribution, dN/dLX ∝ Lα, with α = −1.71 ± 0.06 (HMXBs) and α = −1.96 ± 0.08 (LMXBs), and the brightest sources are consistent with the expectations from sampling statistics without requiring a physical cutoff. Overall, our results for HMXB and LMXB populations agree well with the specific star formation rate map presented for M101 recently by Lehmer and collaborators. [ABSTRACT FROM AUTHOR]

Active galactic nuclei (AGNs) show a correlation between the size of the broad line region and the monochromatic continuum luminosity at 5100 Å, allowing black hole mass estimation based on single-epoch spectra. However, the validity of the correlation is yet to be clearly tested for high-luminosity AGNs. We present the first reverberation mapping results of the Seoul National University AGN Monitoring Project (SAMP), which is designed to focus on luminous AGNs for probing the high end of the size–luminosity relation. We report time lag measurements of two AGNs, namely, 2MASS J10261389+5237510 and SDSS J161911.24+501109.2, using the light curves obtained over an ∼1000 days period with an average cadence of 10 and 20 days, respectively, for photometry and spectroscopy monitoring. Based on a cross-correlation analysis and Hβ line width measurements, we determine the Hβ lag as and days in the observed frame, and black hole mass as and , respectively, for 2MASS J1026 and SDSS J1619. [ABSTRACT FROM AUTHOR]

Protection from pregnancy-associated aortic dissection is achieved by decreasing oxytocin-induced ERK signaling in a mouse model of Marfan syndrome. Dissecting a risk of Marfan syndrome: Marfan syndrome is an autosomal dominant connective tissue disorder associated with manifestations in multiple organ systems. The aorta is a key site affected by this syndrome, and female patients are at risk for aortic dissection associated with pregnancy and childbirth. Traditionally, this risk has been ascribed to labor-induced stress, but Habashi et al. noted that aortic dissection often occurs relatively late postpartum, prompting them to examine possible additional explanations. Using mouse models of Marfan syndrome, the researchers discovered that oxytocin, the hormone involved in milk letdown, plays a key role in aortic dissection, and identified several potential approaches for preventing this complication. Women with Marfan syndrome (MFS) are at high risk for pregnancy-associated aortic dissection. Pathogenic models that singularly invoke hemodynamic stress are difficult to reconcile with predominant postnatal occurrence of aortic tear, often occurring weeks to months after delivery. In consideration of events that peak at term, are sustained after delivery, and might synergize with previously defined signaling pathways implicated in aneurysm progression, we examined the hormone oxytocin, which initiates uterine contraction and milk letdown for the duration of lactation through phosphorylation of extracellular signal–regulated kinase (ERK). In a mouse model of MFS that shows highly penetrant postnatal aortic dissection, risk was strongly attenuated by preventing lactation or use of an oxytocin receptor antagonist. Survival correlated inversely with the extent of ERK activation in the aortic wall, and strong protection was observed upon attenuation of ERK phosphorylation using an inhibitor of ERK kinase (MEK) or the U.S. Food and Drug Administration–approved medication hydralazine, offering potential therapeutic strategies for pregnancy-associated vascular catastrophe in the setting of MFS. [ABSTRACT FROM AUTHOR]

We characterize the incidence and intensity of low-level supermassive black hole activity within the Fornax cluster, through X-ray observations of the nuclei of 29 quiescent early-type galaxies. Using the Chandra X-ray Telescope, we target 17 galaxies from the Hubble Space Telescope Fornax Cluster Survey, down to a uniform (3σ) limiting X-ray luminosity threshold of 5 · 1038 erg s−1, which we combine with deeper, archival observations for an additional 12 galaxies. A nuclear X-ray point source is detected in 11 out of 29 targets. After accounting for the low-mass X-ray binary contamination to the nuclear X-ray signal, the X-ray active fraction is measured at 26.6% ± 9.6%. The results from this analysis are compared to similar investigations targeting quiescent early types in the Virgo cluster, as well as the field. After correcting for the different mass distributions, the measured Fornax active fraction is less than the field fraction, at more than 3σ, confirming that the funneling of gas to the nuclear regions of cluster members is inhibited compared to those galaxies in the field. At the same time, we find no statistically significant difference between Fornax and Virgo galaxies, with only marginal evidence for a lower active fraction in Fornax (1σ); if real, owing to Fornax's higher galaxy number density, this could indicate that galaxy–galaxy interactions are more effective at gas removal than galaxy-gas effects. [ABSTRACT FROM AUTHOR]

We report on the results of optical, near-infrared (NIR), and mid-infrared observations of the black hole X-ray binary candidate (BHB) MAXI J1535–571 during its 2017/2018 outburst. During the first part of the outburst (MJD 58004–58012), the source shows an optical–NIR spectrum that is consistent with an optically thin synchrotron power law from a jet. After MJD 58015, however, the source faded considerably, the drop in flux being much more evident at lower frequencies. Before the fading, we measure a dereddened flux density of ≳100 mJy in the mid-infrared, making MAXI J1535–571 one of the brightest mid-infrared BHBs known so far. A significant softening of the X-ray spectrum is evident contemporaneous with the infrared fade. We interpret it as being due to the suppression of the jet emission, similar to the accretion–ejection coupling seen in other BHBs. However, MAXI J1535–571 did not transition smoothly to the soft state, instead showing X-ray hardness deviations associated with infrared flaring. We also present the first mid-IR variability study of a BHB on minute timescales, with a fractional rms variability of the light curves of ∼15%–22%, which is similar to that expected from the internal shock jet model, and much higher than the optical fractional rms (≲7%). These results represent an excellent case of multiwavelength jet spectral timing and demonstrate how rich, multiwavelength time-resolved data of X-ray binaries over accretion state transitions can help in refining models of the disk–jet connection and jet launching in these systems. [ABSTRACT FROM AUTHOR]

RGG 118 (SDSS 1523+1145) is a nearby (z = 0.0243), dwarf disk galaxy () that is found to host an active ∼50,000 solar mass black hole at its core. RGG 118 is one of a growing collective sample of dwarf galaxies known to contain active galactic nuclei (AGNs)—a group that, until recently, contained only a handful of objects. Here, we report on new Hubble Space Telescope Wide Field Camera 3 UVIS and IR imaging of RGG 118, with the main goal of analyzing its structure. Using 2D parametric modeling, we find that the morphology of RGG 118 is best described by an outer spiral disk, an inner component consistent with a pseudobulge, and a central point-spread function (PSF). The luminosity of the PSF is consistent with the central point source that is being dominated by the AGN. We measure the luminosity and the mass of the “pseudobulge” and confirm that the central black hole in RGG 118 is under-massive, with respect to the and relations. This result is consistent with a picture in which black holes in disk-dominated galaxies grow primarily through secular processes. [ABSTRACT FROM AUTHOR]

Motivated by theoretical expectations that nuclear star clusters (NSCs) in galactic centers may provide a favorable environment for supermassive black holes to form and/or efficiently grow, we set out to measure the fraction of nearby nucleated galaxies that also host an active galactic nucleus. We targeted a distance-limited sample of 98 objects with the Chandra X-ray Telescope, down to a uniform X-ray luminosity threshold of ∼1038 erg s−1. The sample is composed of 47 late-types and 51 early-types, enabling us to further investigate the active fraction as a function of galactic morphology. After correcting for contamination to the nuclear X-ray signal from bright X-ray binaries, we measure an active fraction (1σ C.L.) across the whole sample, in agreement with previous estimates based on a heterogeneous combination of optical, X-ray, and radio diagnostics, by Seth et al. After accounting for the different stellar mass distributions in our samples, we find no statistically significant difference in the active fraction of early- versus late-type nucleated galaxies, with and , respectively. For the early-type nucleated galaxies, we are able to carry out a controlled comparison with a parent sample of non-nucleated galaxies covering the same stellar mass range, again finding no statistically significant difference in the active fraction. Taken at face value, our findings suggest that the presence of an NSC does not facilitate or enhance accretion-powered emission from a nuclear supermassive black hole. This is true even for late-type nucleated galaxies, home to bluer NSCs and arguably larger gas reservoirs. [ABSTRACT FROM AUTHOR]

To investigate active galactic nucleus (AGN) outflows as a tracer of AGN feedback on star formation, we perform integral-field spectroscopy of 20 type 2 AGNs at z < 0.1, which are luminous AGNs with [O iii] luminosity > 10 erg s−1 that exhibit strong outflow signatures in the [O iii] kinematics. By decomposing the emission-line profile, we obtain the maps of the narrow and broad components of the [O iii] and Hα lines, respectively. The broad components in both [O iii] and Hα represent the nongravitational kinematics, that is, gas outflows, while the narrow components, especially in Hα, represent the gravitational kinematics, that is, the rotational disk. By using the integrated spectra within the flux-weighted size of the narrow-line region, we estimate the energetics of the gas outflows. The ionized gas mass is 1.0–38.5, and the mean mass outflow rate is 4.6 ± 4.3 M⊙ yr−1, which is a factor of ∼260 higher than the mean mass accretion rate of 0.02 ± 0.01 yr−1. The mean energy injection rate of the sample is 0.8% ± 0.6% of the AGN bolometric luminosity , while the momentum flux is (5.4 ± 3.6) × on average, except for the two most kinematically energetic AGNs with low , which are possibly due to the dynamical timescale of the outflows. The estimated outflow energetics are consistent with the theoretical expectations for energy-conserving outflows from AGNs, yet we find no supporting evidence of instantaneous quenching of star formation due to the outflows. [ABSTRACT FROM AUTHOR]

We present new Chandra X-ray Observatory and Hubble Space Telescope observations of eight optically selected broad-line active galactic nucleus (AGN) candidates in nearby dwarf galaxies (z < 0.055). Including archival Chandra observations of three additional sources, our sample contains all 10 galaxies from Reines et al. (2013) with both broad Hα emission and narrow-line AGN ratios (six AGNs, four composites), as well as one low-metallicity dwarf galaxy with broad Hα and narrow-line ratios characteristic of star formation. All 11 galaxies are detected in X-rays. Nuclear X-ray luminosities range from L0.5–7keV ≈ 5 × 1039 to 1 × 1042 ergs−1. In all cases except for the star-forming galaxy, the nuclear X-ray luminosities are significantly higher than would be expected from X-ray binaries, providing strong confirmation that AGNs and composite dwarf galaxies do indeed host actively accreting black holes (BHs). Using our estimated BH masses (which range from ∼7 × 104 to 1 × 106M⊙), we find inferred Eddington fractions ranging from ∼0.1% to 50%, i.e., comparable to massive broad-line quasars at higher redshift. We use the HST imaging to determine the ratio of UV to X-ray emission for these AGNs, finding that they appear to be less X-ray luminous with respect to their UV emission than more massive quasars (i.e., αOX values an average of 0.36 lower than expected based on the relation between αOX and 2500 Å luminosity). Finally, we discuss our results in the context of different accretion models onto nuclear BHs. [ABSTRACT FROM AUTHOR]

We use time-domain optical spectroscopy to distinguish between broad emission lines powered by accreting black holes (BHs) and stellar processes (i.e., supernovae) for 16 galaxies identified as active galactic nucleus (AGN) candidates by Reines et al (2013). Our study is primarily focused on those objects with narrow emission line ratios dominated by star formation, for which the origin of the broad Hα emission was unclear. Based on follow-up spectroscopy, we find that the broad Hα emission has faded or was ambiguous for all of the star-forming objects (14/16), over baselines ranging from 5–14 years, suggesting a transient stellar process was responsible for the broad emission in previous Sloan Digital Sky Survey observations. For the two objects in our follow-up sample with narrow-line AGN signatures (RGG 9 and RGG 119), we find persistent broad Hα emission consistent with an AGN origin. Additionally, we use high spectral resolution observations to measure stellar velocity dispersions for 15 objects in the Reines et al. (2013) sample, all with narrow-line ratios indicating the presence of an AGN. Stellar masses range from to M⊙, and we measure in the range of . These correspond to some of the lowest-mass galaxies with optical signatures of AGN activity. We show that RGG 119, the one object that has both a measured and persistent broad Hα emission, falls near the extrapolation of the relation to the low-mass end. [ABSTRACT FROM AUTHOR]

We present new Chandra X-ray observations of seven low-mass black holes () accreting at low-bolometric Eddington ratios between . We compare the X-ray properties of these seven low-mass active galactic nuclei (AGNs) to a total of 73 other low-mass AGNs in the literature with published Chandra observations (with Eddington ratios extending from ). We do not find any statistical differences between the low and high Eddington ratio low-mass AGNs in the distributions of their X-ray to ultraviolet luminosity ratios (), or in their X-ray spectral shapes. Furthermore, the distribution of low- AGNs displays an X-ray weak tail that is also observed within high- objects. Our results indicate that between , there is no systematic change in the structure of the accretion flow for active galaxies hosting black holes. We examine the accuracy of current bolometric luminosity estimates for our low- objects with new Chandra observations, and it is plausible that their Eddington ratios could be underestimated by up to an order of magnitude. If so, then in analogy with weak emission line quasars, we suggest that accretion from a geometrically thick, radiatively inefficient “slim disk” could explain their diverse properties in . Alternatively, if current Eddington ratios are correct (or overestimated), then the X-ray weak tail would imply that there is diversity in disk/corona couplings among individual low-mass objects. Finally, we conclude by noting that the distribution for low-mass black holes may have favorable consequences for the epoch of cosmic reionization being driven by AGN. [ABSTRACT FROM AUTHOR]

Over the past 15 yr, examples of exotic radio-quiet quasars with intrinsically weak or absent broad emission line regions (BELRs) have emerged from large-scale spectroscopic sky surveys. Here, we present spectroscopy of seven such weak emission line quasars (WLQs) at moderate redshifts (z = 1.4–1.7) using the X-shooter spectrograph, which provides simultaneous optical and near-infrared spectroscopy covering the rest-frame ultraviolet (UV) through optical. These new observations effectively double the number of WLQs with spectroscopy in the optical rest-frame, and they allow us to compare the strengths of (weak) high-ionization emission lines (e.g., C iv) to low-ionization lines (e.g., Mg ii, Hβ, Hα) in individual objects. We detect broad Hβ and Hα emission in all objects, and these lines are generally toward the weaker end of the distribution expected for typical quasars (e.g., Hβ has rest-frame equivalent widths ranging from 15–40 Å). However, these low-ionization lines are not exceptionally weak, as is the case for high-ionization lines in WLQs. The X-shooter spectra also display relatively strong optical Fe ii emission, Hβ FWHM ≲ 4000 km s−1, and significant C iv blueshifts (≈1000–5500 km s−1) relative to the systemic redshift; two spectra also show elevated UV Fe ii emission, and an outflowing component to their (weak) Mg ii emission lines. These properties suggest that WLQs are exotic versions of “wind-dominated” quasars. Their BELRs either have unusual high-ionization components, or their BELRs are in an atypical photoionization state because of an unusually soft continuum. [ABSTRACT FROM AUTHOR]

We present a sample of hard X-ray-selected candidate black holes (BHs) in 19 dwarf galaxies. BH candidates are identified by cross-matching a parent sample of ∼44,000 local dwarf galaxies ( , ) with the Chandra Source Catalog and subsequently analyzing the original X-ray data products for matched sources. Of the 19 dwarf galaxies in our sample, eight have X-ray detections reported here for the first time. We find a total of 43 point-like hard X-ray sources with individual luminosities erg s−1. Hard X-ray luminosities in this range can be attained by stellar-mass X-ray binaries (XRBs) and by massive BHs accreting at low Eddington ratio. We place an upper limit of 53% (10/19) on the fraction of galaxies in our sample hosting a detectable hard X-ray source consistent with the optical nucleus, although the galaxy center is poorly defined in many of our objects. We also find that 42% (8/19) of the galaxies in our sample exhibit statistically significant enhanced hard X-ray emission relative to the expected galaxy-wide contribution from low-mass and high-mass XRBs, based on the star formation rate relation defined by more massive and luminous systems. For the majority of these X-ray-enhanced dwarf galaxies, the excess emission is consistent with (but not necessarily due to) a nuclear X-ray source. Follow-up observations are necessary to distinguish between stellar-mass XRBs and active galactic nuclei powered by more massive BHs. In any case, our results support the notion that X-ray-emitting BHs in low-mass dwarf galaxies may have had an appreciable impact on reionization in the early universe. [ABSTRACT FROM AUTHOR]