320 research outputs found
Attenuated Virulence and Biofilm Formation in Staphylococcus aureus following Sublethal Exposure to Triclosan
Sub-effective exposure of Staphylococcus aureus to the biocide triclosan can reportedly induce a small colony variant (SCV) phenotype in Staphylococcus aureus. S. aureus SCVs are characterised by slow growth rates, reduced pigmentation and lowered antimicrobial susceptibility. Whilst they may exhibit enhanced intracellular survival, there are conflicting reports regarding their pathogenicity. The current study reports the characteristics of a SCV-like strain of S. aureus, created by repeated passage on sub-lethal triclosan concentrations. S. aureus ATCC 6538 (P0) was serially exposed ten times to concentration gradients of triclosan to generate strain P10. This strain was then further passaged ten times on triclosan-free medium (designated x10). The minimum inhibitory and bactericidal concentrations of triclosan for P0, P10 and x10 were determined and growth rates measured in biofilm and planktonic culture. Haemolysin, DNAse and coagulase activities were measured and virulence determined using a Galleria mellonella pathogenicity model. Strain P10 exhibited decreased susceptibility to triclosan and characteristics of a SCV phenotype, including considerably reduced growth rate and the formation of pinpoint colonies. However, this strain also had delayed coagulase production, impaired haemolysis (p<0.01), was defective in biofilm formation and DNAase activity, and displayed significantly attenuated virulence. Colony size, haemolysis, coagulase activity and virulence were only partially restored in strain x10, whereas planktonic growth rate was fully restored. However, x10 was at least as defective in biofilm formation and DNAse production as P10. These data suggest that although repeated exposure to triclosan may result in a SCV-like phenotype, this is not necessarily associated with increased virulence, and adapted bacteria may exhibit other functional deficiencies
THE INFLUENCE OF PEER EDUCATORS IN A FIRST-YEAR SEMINAR ON FRESHMAN PREPARATION FOR COLLEGIATE CHALLENGES: A QUALITATIVE INVESTIGATION OF OBSERVATIONAL LEARNING
Most high school students have not spent deliberate time preparing for their transition to college.
Knowing this, institutions have developed a first-year seminar geared toward transitional issues
inherent to a specific institution. While the research on these programs illustrates their utility,
there appears to be an opportunity to further their success by incorporating peers as educators in
the classroom. Bandura (1986) saw the potential of observational learning through peer
modeling, though few researchers have studied first-year seminars from this theoretical
perspective. Through a postpositivistic philosophical paradigm, this exploratory qualitative
study utilized a phenomenological design to investigate two research questions: what are the
academic and social challenges freshmen face in the transition to a small, private, highly
selective, STEM-focused institution and how does the presence of sophomore peer educators in a
first-year seminar influence freshman preparation for those fall quarter challenges. A total of 41
freshmen participated in the study. Data were collected through student journals and focus group
interviews. The results of this study confirm that the transition to this specific type of institution
is just as complex as the transition to other types of institutions, with students reporting similar
academic and social challenges as found in the literature. However, their emphasis was on the
core (i.e., academic) rather than the periphery (i.e., social) of the collegiate experience. The
application of modeling, however, was not strong enough to determine whether observational
learning influenced these transitional challenges
Gaseous Tidal Debris found in the NGC 3783 Group
We have conducted wide-field HI mapping of a ~5.5 x 5.5 degree region
surrounding the NGC 3783 galaxy group, to an HI mass limit of ~4 x 10^8 Msun.
The observations were made using the multibeam system on the Parkes 64-m
radiotelescope, as part of the Galaxy Evolution Multiwavelength Study (GEMS).
We find twelve HI detections in our Parkes data, four more than catalogued in
HIPASS. We find two new group members, and discover an isolated region of HI
gas with an HI mass of ~4 x 10^8 Msun, without a visible corresponding optical
counterpart. We discuss the likelihood of this HI region being a low surface
brightness galaxy, primordial gas, or a remnant of tidal debris. For the NGC
3783 group we derive a mean recession velocity of 2903 km/s, and a velocity
dispersion of 190 km/s. The galaxy NGC 3783 is the nearest galaxy to the
luminosity weighted centre of the group, and is at the group mean velocity.
From the X-ray and dynamical state of this galaxy group, this group appears
to be in the early stages of its evolution.Comment: 12 pages, MNRAS accepted: full resolution paper available at
http://astronomy.swin.edu.au/~vkilborn/MF1350rv.pd
Using two commercial kits for detection of Toxoplasma in lightly infected swine
Toxoplasma is a zoonotic parasite that infects most mammals including swine. Illness is generally serious in immunocompromised hosts and abortion or congenital defects can occur if women are infected during pregnancy. An important route of infection for people is ingestion of undercooked meat containing Toxoplasma cysts
Southern GEMS groups II: HI distribution, mass functions and HI deficient galaxies
We investigate the neutral hydrogen (HI) content of sixteen groups for which
we have multi-wavelength data including X-ray observations. Wide-field imaging
of the groups was obtained with the 20-cm multibeam system on the 64-m Parkes
telescope. We have detected ten previously uncatalogued HI sources, one of
which has no visible optical counterpart. We examine the HI properties of the
groups, compared to their X-ray characteristics, finding that those groups with
a higher X-ray temperature and luminosity contain less HI per galaxy. The HI
content of a group depends on its morphological make-up, with those groups
dominated by early-type galaxies containing the least total HI. We determined
the expected HI for the spiral galaxies in the groups, and found that a number
of the galaxies were HI deficient. The HI deficient spirals were found both in
groups with and without a hot intra-group medium. The HI deficient galaxies
were not necessarily found at the centre of the groups, however, we did find
that two thirds of HI deficient galaxies were found within about 1 Mpc from the
group centre, indicating that the group environment is affecting the gas-loss
from these galaxies. We determined the HI mass function for a composite sample
of 15 groups, and found that it is significantly flatter than the field HI mass
function. We also find a lack of high HI-mass galaxies in groups. One possible
cause of this effect is the tidal stripping of HI gas from spiral galaxies as
they are pre-processed in groups.Comment: accepted for publication in MNRAS, 26 pages, 13 Figures, 2 Appendice
Systematic review and network meta-analysis on the efficacy of evolocumab and other therapies for the management of lipid levels in hyperlipidemia
Background: The proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors evolocumab and alirocumab substantially reduce low‐density lipoprotein cholesterol (LDL‐C) when added to statin therapy in patients who need additional LDL‐C reduction.
Methods and Results: We conducted a systematic review and network meta‐analysis of randomized trials of lipid‐lowering therapies from database inception through August 2016 (45 058 records retrieved). We found 69 trials of lipid‐lowering therapies that enrolled patients requiring further LDL‐C reduction while on maximally tolerated medium‐ or high‐intensity statin, of which 15 could be relevant for inclusion in LDL‐C reduction networks with evolocumab, alirocumab, ezetimibe, and placebo as treatment arms. PCSK9 inhibitors significantly reduced LDL‐C by 54% to 74% versus placebo and 26% to 46% versus ezetimibe. There were significant treatment differences for evolocumab 140 mg every 2 weeks at the mean of weeks 10 and 12 versus placebo (−74.1%; 95% credible interval −79.81% to −68.58%), alirocumab 75 mg (−20.03%; 95% credible interval −27.32% to −12.96%), and alirocumab 150 mg (−13.63%; 95% credible interval −22.43% to −5.33%) at ≥12 weeks. Treatment differences were similar in direction and magnitude for PCSK9 inhibitor monthly dosing. Adverse events were similar between PCSK9 inhibitors and control. Rates of adverse events were similar between PCSK9 inhibitors versus placebo or ezetimibe.
Conclusions: PCSK9 inhibitors added to medium‐ to high‐intensity statin therapy significantly reduce LDL‐C in patients requiring further LDL‐C reduction. The network meta‐analysis showed a significant treatment difference in LDL‐C reduction for evolocumab versus alirocumab
Ischemic preconditioning in the liver is independent of regulatory T cell activity
Ischemic preconditioning (IPC) protects organs from ischemia reperfusion injury (IRI) through unknown mechanisms. Effector T cell populations have been implicated in the pathogenesis of IRI, and T regulatory cells (Treg) have become a putative therapeutic target, with suggested involvement in IPC. We explored the role of Treg in hepatic IRI and IPC in detail. IPC significantly reduced injury following ischemia reperfusion insults. Treg were mobilized rapidly to the circulation and liver after IRI, but IPC did not further increase Treg numbers, nor was it associated with modulation of circulating pro-inflammatory chemokine or cytokine profiles. We used two techniques to deplete Treg from mice prior to IRI. Neither Treg depleted FoxP3.LuciDTR mice, nor wildtyoe mice depleted of Tregs with PC61, were more susceptible to IRI compared with controls. Despite successful enrichment of Treg in the liver, by adoptive transfer of both iTreg and nTreg or by in vivo expansion of Treg with IL-2/anti-IL-2 complexes, no protection against IRI was observed.We have explored the role of Treg in IRI and IPC using a variety of techniques to deplete and enrich them within both the liver and systemically. This work represents an important negative finding that Treg are not implicated in IPC and are unlikely to have translational potential in hepatic IRI
Does the virial mass drive the intra-cluster light? The relationship between the ICL and M from VEGAS
In this Letter we revisit the relationship between the fraction of the
intra-cluster light (ICL) and both the virial mass and the fraction of Early
Type Galaxies in the host halo. This is based on a statistically significant
and homogeneous sample of 22 groups and clusters of galaxies in the local
Universe (), obtained with the VST Early-type GAlaxy Survey
(VEGAS). Taking advantage of the long integration time and large area of the
VEGAS images, we are able to map the galaxy outskirts and ICL down to
29-30 mag/arcsec and out to hundreds of kpc. With this data-set, we
have expanded the sample of ICL measurements, doubling the previous measures
available from the literature for z 0.05. The main result of this work
is the lack of any significant trend between the fraction of ICL and the virial
mass of the host environment, covering a wide range of virial masses (
), in agreement with some
theoretical studies. Since the new data points are all derived with the same
methodology and from the same observational setup, and all have comparable
depth, the large observed scatter indicates an intrinsic variation in the ICL
fraction.On the other hand, there is a weak relation between the fraction of
ICL and the fraction of Early Type Galaxies in the host halo, where a larger
fraction of ICL is found in groups and clusters of galaxies dominated by
earlier morphological types, indicating a connection between the ICL and the
dynamical state of the host system.Comment: Letter to the editor, accepted for publication in A&A. 8 pages, 3
figure
The early-type galaxies NGC 1407 and NGC 1400 - I: spatially resolved radial kinematics and surface photometry
This is the first paper of a series focused on investigating the star
formation and evolutionary history of the two early-type galaxies NGC 1407 and
NGC 1400. They are the two brightest galaxies of the NGC 1407 (or Eridanus-A)
group, one of the 60 groups studied as part of the Group Evolution
Multi-wavelength Study (GEMS). Here we present new high signal-to-noise
long-slit spectroscopic data obtained at the ESO 3.6m telescope and
high-resolution multi-band imaging data from the HST/ACS and wide-field imaging
from Subaru Suprime-Cam. We spatially resolved integrated spectra out to 0.6
(NGC 1407) and 1.3 (NGC 1400) effective radii. The radial profiles of the
kinematic parameters v(rot), sigma, h3 and h4 are measured. The surface
brightness profiles are fitted to different galaxy light models and the colour
distributions analysed. The multi-band images are modelled to derive isophotal
shape parameters and residual galaxy images. The parameters from the surface
brightness profile fitting are used to estimate the mass of the possible
central supermassive black hole in NGC 1407. The galaxies are found to be
rotationally supported and to have a flat core in the surface brightness
profiles. Elliptical isophotes are observed at all radii and no fine structures
are detected in the residual galaxy images. From our results we can also
discard a possible interaction between NGC 1400, NGC 1407 and the group
intergalactic medium. We estimate a mass of 1.03x10^9 M(sun) for the
supermassive black hole in NGC 1407 galaxy.Comment: 11 pages, 6 tables, 6 figures, Accepted for publication in MNRA
The early-type galaxies NGC 1407 and NGC 1400 - II: star formation and chemical evolutionary history
We present a possible star formation and chemical evolutionary history for
two early-type galaxies NGC 1407 and NGC 1400. They are the two brightest
galaxies of the NGC 1407 (or Eridanus-A) group, one of the 60 groups studied as
part of the Group Evolution Multi-wavelength Study (GEMS). Our analysis is
based on new high signal-to-noise spatially resolved integrated spectra
obtained at the ESO 3.6m telescope, out to 0.6 (NGC 1407) and 1.3 (NGC 1400)
effective radii. Using Lick/IDS indices we estimate luminosity-weighted ages,
metallicities and -element abundance ratios. Colour radial
distributions from HST/ACS and Subaru Suprime-Cam multi-band wide-field imaging
are compared to colours predicted from spectroscopically determinated ages and
metallicities using single stellar population models. The galaxies formed over
half of their mass in a single short-lived burst of star formation (> 100
M(sun)/year) at redshift z>5. This likely involved an outside-in mechanism with
supernova-driven galactic winds, as suggested by the flatness of the
alpha-element radial profiles and the strong negative metallicity gradients.
Our results support the predictions of the revised version of the monolithic
collapse model for galaxy formation and evolution. We speculate that, since
formation the galaxies have evolved quiescently and that we are witnessing the
first infall of NGC 1400 in the group.Comment: 14 pages, 9 tables, 6 figures, Accepted for publication in MNRA
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