761 research outputs found
Analysis of autophagy and inflammasome regulation in neuronal cells and monocytes infected with Chlamydia Pneumoniae: Implications for Alzheimerâs disease
Objectives: Our laboratory has been studying the role of infection with the obligate intracellular bacterium Chlamydia pneumoniae in sporadic late-onset Alzheimer disease (LOAD). This infection may be a trigger for the pathology observed in LOAD as a function of initiating changes in gene regulation following entry of the organism into the brain. As such, we are analyzing how this infection can promote changes in autophagy and inflammasome gene regulation as both have been shown to be altered in LOAD. Methods: Human SKNMC neuronal cells and THP1 monocytes were infected in vitro for 24-72 hrs with a laboratory strain of Chlamydia pneumoniae followed by RNA extraction, cDNA synthesis and analysis using Real-Time PCR microarrays for autophagy and inflammasome genes. Results: Gene expression for autophagy and inflammasome pathways was altered dramatically following infection. Genes encoding for co-regulation of autophagy, apoptosis, and the cell cycle that were significantly changed included: BCL2L1, FAS, PIK3CG, APP, and TP53. In addition, ATG3, and GABARAP, genes encoding for protein transport & ubiquitination and autophagic vacuole formation were significantly deregulated. Of the inflammasome genes, 4 NOD-like receptor genes were significantly up-regulated. IL-1beta, AIM2, CCL2, and CCL7 genes were all dramatically up-regulated in monocytes during the 72 hrs of infection. Conclusions: Our data suggest that Chlamydia pneumoniae-infected human SKNMC neuronal cells and THP1 monocytes exhibit specific changes in gene regulation for both autophagy and inflammasome pathways. These gene changes appear to correlate with pathologic changes previously reported in AD and further support the contention that infection with Chlamydia pneumoniae plays a role in LOAD pathogenesis
Diamonds on the Hat: Globular Clusters in The Sombrero Galaxy (M104)
Images from the HST ACS are used to carry out a new photometric study of the
globular clusters (GCs) in M104, the Sombrero galaxy. The primary focus of our
study is the characteristic distribution function of linear sizes (SDF) of the
GCs. We measure the effective radii for 652 clusters with PSF-convolved King
and Wilson dynamical model fits. The SDF is remarkably similar to those
measured for other large galaxies of all types, adding strong support to the
view that it is a "universal" feature of globular cluster systems.
We develop a more general interpretation of the size distribution function
for globular clusters, proposing that the shape of the SDF that we see today
for GCs is strongly influenced by the early rapid mass loss during their star
forming stage, coupled with stochastic differences from cluster to cluster in
the star formation efficiency (SFE) and their initial sizes. We find that the
observed SDF shape can be accurately predicted by a simple model in which the
protocluster clouds had characteristic sizes of pc and SFEs of
. The colors and luminosities of the M104 clusters show the
clearly defined classic bimodal form. The blue sequence exhibits a
mass/metallicity relation (MMR), following a scaling of heavy-element abundance
with luminosity of very similar to what has been found in most
giant elliptical galaxies. A quantitative self-enrichment model provides a good
first-order match to the data for the same initial SFE and protocluster size
that were required to explain the SDF. We also discuss various forms of the
globular cluster Fundamental Plane (FP) of structural parameters, and show that
useful tests of it can be extended to galaxies beyond the Local Group.Comment: In press for MNRA
Inclination-Independent Galaxy Classification
We present a new method to classify galaxies from large surveys like the
Sloan Digital Sky Survey using inclination-corrected concentration,
inclination-corrected location on the color-magnitude diagram, and apparent
axis ratio. Explicitly accounting for inclination tightens the distribution of
each of these parameters and enables simple boundaries to be drawn that
delineate three different galaxy populations: Early-type galaxies, which are
red, highly concentrated, and round; Late-type galaxies, which are blue, have
low concentrations, and are disk dominated; and Intermediate-type galaxies,
which are red, have intermediate concentrations, and have disks. We have
validated our method by comparing to visual classifications of high-quality
imaging data from the Millennium Galaxy Catalogue. The inclination correction
is crucial to unveiling the previously unrecognized Intermediate class.
Intermediate-type galaxies, roughly corresponding to lenticulars and early
spirals, lie on the red sequence. The red sequence is therefore composed of two
distinct morphological types, suggesting that there are two distinct mechanisms
for transiting to the red sequence. We propose that Intermediate-type galaxies
are those that have lost their cold gas via strangulation, while Early-type
galaxies are those that have experienced a major merger that either consumed
their cold gas, or whose merger progenitors were already devoid of cold gas
(the ``dry merger'' scenario).Comment: Accepted for publication in ApJ. 7 pages in emulateap
CP violation and modular symmetries
We reconsider the origin of CP violation in fundamental theory. Existing
string models of spontaneous CP violation make ambiguous predictions, due to
the arbitrariness of CP transformation and the apparent non-invariance of the
results under duality. We find an unambiguous modular CP invariance condition,
applicable to predictive models of spontaneous CP violation, which circumvents
these problems; it strongly constrains CP violation by heterotic string moduli.
The dilaton is also evaluated as a source of CP violation, but is likely
experimentally excluded. We consider the prospects for explaining CP violation
in strongly-coupled strings and brane worlds.Comment: 6 pages, REVTeX 4b5+amssymb. 2 references added, substantially the
same as published versio
The history of stellar metallicity in a simulated disc galaxy
We explore the chemical distribution of stars in a simulated galaxy. Using simulations of the same initial conditions but with two different feedback schemes (McMaster Unbiased Galaxy Simulations â MUGS â and Making Galaxies in a Cosmological Context â MaGICC), we examine the features of the ageâmetallicity relation (AMR), and the three-dimensional ageâ [Fe/H]â[O/Fe] distribution, both for the galaxy as a whole and decomposed into disc, bulge, halo and satellites. The MUGS simulation, which uses traditional supernova feedback, is replete with chemical substructure. This substructure is absent from the MaGICC simulation, which includes early feedback from stellar winds, a modified initial mass function and more efficient feedback. The reduced amount of substructure is due to the almost complete lack of satellites in MaGICC. We identify a significant separation between the bulge and disc AMRs, where the bulge is considerably more metal-rich with a smaller spread in metallicity at any given time than the disc. Our results suggest, however, that identifying the substructure in observations will require exquisite age resolution, of the order of 0.25 Gyr. Certain satellites show exotic features in the AMR, even forming a âsawtoothâ shape of increasing metallicity followed by sharp declines which correspond to pericentric passages. This fact, along with the large spread in stellar age at a given metallicity, compromises the use of metallicity as an age indicator, although alpha abundance provides a more robust clock at early times. This may also impact algorithms that are used to reconstruct star formation histories from resolved stellar populations, which frequently assume a monotonically increasing AMR
Neutrino scattering off pair-breaking and collective excitations in superfluid neutron matter and in color-flavor locked quark matter
We calculate the correlation functions needed to describe the linear response
of superfluid matter, and go on to calculate the differential cross section for
neutral-current neutrino scattering in superfluid neutron matter and in
color-flavor locked quark matter (CFL). We report the first calculation of
scattering rates that includes neutrino interactions with both pair-breaking
excitations and low-lying collective excitations (Goldstone modes). Our results
apply both above and below the critical temperature, allowing use in
simulations of neutrino transport in supernovae and neutron stars.Comment: 22 pages, 9 figure
Globular Cluster Systems in Brightest Cluster Galaxies. III: Beyond Bimodality
We present new deep photometry of the rich globular cluster (GC) systems
around the Brightest Cluster Galaxies UGC 9799 (Abell 2052) and UGC 10143
(Abell 2147), obtained with the HST ACS and WFC3 cameras. For comparison, we
also present new reductions of similar HST/ACS data for the Coma supergiants
NGC 4874 and 4889. All four of these galaxies have huge cluster populations (to
the radial limits of our data, comprising from 12000 to 23000 clusters per
galaxy). The metallicity distribution functions (MDFs) of the GCs can still be
matched by a bimodal-Gaussian form where the metal-rich and metal-poor modes
are separated by ~0.8 dex, but the internal dispersions of each mode are so
large that the total MDF becomes very broad and nearly continuous from [Fe/H] =
-2.4 to Solar. There are, however, significant differences between galaxies in
the relative numbers of \emph{metal-rich} clusters, suggesting that they
underwent significantly different histories of mergers with massive, gas-rich
halos. Lastly, the proportion of metal-poor GCs rises especially rapidly
outside projected radii R > 4 R_eff, suggesting the importance of accreted
dwarf satellites in the outer halo. Comprehensive models for the formation of
GCs as part of the hierarchical formation of their parent galaxies will be
needed to trace the systematic change in structure of the MDF with galaxy mass,
from the distinctly bimodal form in smaller galaxies up to the broad continuum
that we see in the very largest systems.Comment: In press for Astrophysical Journa
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