200 research outputs found
Associations between epigenetic aging and childhood peer victimization, depression, and suicidal ideation in adolescence and adulthood: A study of two population-based samples
Background: Prior studies indicate that peer victimization (including bullying) is associated with higher risk for depression and suicidal ideation across the life course. However, molecular mechanisms underlying these associations remain unclear. This two-cohort study proposes to test whether epigenetic aging and pace of aging, as well as a DNA methylation marker of responsive to glucocorticoids, are associated to childhood peer victimization and later depressive symptoms, or suicidal ideation. Methods: Cohort 1: Epigenome-wide DNA methylation (EPIC array) was measured in saliva collected when participants were 10.47 years (standard deviation = 0.35) in a subsample of the Quebec Longitudinal Study of Child Development (QLSCD, n = 149 participants), with self-reported peer victimization at 6-8 years, depressive symptoms (mean symptoms, and dichotomized top 30% symptoms) and suicidal ideation at 15-17 years. Cohort 2: Epigenome-wide DNA methylation (EPIC array) was measured in blood collected from participants aged 45.13 years (standard deviation = 0.37) in a subsample of the 1958 British Birth cohort (1958BBC, n = 238 participants) with information on mother-reported peer victimization at 7-11 years, self-reported depressive symptoms at 50 years, and suicidal ideation at 45 years. Five epigenetic indices were derived: three indicators of epigenetic aging [Horvath's pan-tissue (Horvath1), Horvath's Skin-and-Blood (Horvath2), Pediatric-Buccal-Epigenetic age (PedBE)], pace of aging (DunedinPACE), and stress response reactivity (Epistress). Results: Peer victimization was not associated with the epigenetic indices in either cohort. In the QLSCD, higher PedBE epigenetic aging and a slower pace of aging as measured by DunedinPACE predicted higher depressive symptoms scores. In contrast, neither the Horvath1, or Horvath2 epigenetic age estimates, nor the Epistress score were associated with depressive symptoms in either cohort, and none of the epigenetic indices predicted suicidal ideation. Conclusion: The findings are consistent with epigenome-wide and candidate gene studies suggesting that these epigenetic indices did not relate to peer victimization, challenging the hypothesis that cumulative epigenetic aging indices could translate vulnerability to depressive symptoms and suicidal ideation following peer victimization. Since some indices of epigenetic aging and pace of aging signaled higher risk for depressive symptoms, future studies should pursue this investigation to further evaluate the robustness and generalization of these preliminary findings
Pulsational Mapping of Calcium Across the Surface of a White Dwarf
We constrain the distribution of calcium across the surface of the white
dwarf star G29-38 by combining time series spectroscopy from Gemini-North with
global time series photometry from the Whole Earth Telescope. G29-38 is
actively accreting metals from a known debris disk. Since the metals sink
significantly faster than they mix across the surface, any inhomogeneity in the
accretion process will appear as an inhomogeneity of the metals on the surface
of the star. We measure the flux amplitudes and the calcium equivalent width
amplitudes for two large pulsations excited on G29-38 in 2008. The ratio of
these amplitudes best fits a model for polar accretion of calcium and rules out
equatorial accretion.Comment: Accepted to the Astrophysical Journal. 16 pages, 10 figures
Know Your Neighborhood: A Detailed Model Atmosphere Analysis of Nearby White Dwarfs
We present improved atmospheric parameters of nearby white dwarfs lying
within 20 pc of the Sun. The aim of the current study is to obtain the best
statistical model of the least-biased sample of the white dwarf population. A
homogeneous analysis of the local population is performed combining detailed
spectroscopic and photometric analyses based on improved model atmosphere
calculations for various spectral types including DA, DB, DC, DQ, and DZ stars.
The spectroscopic technique is applied to all stars in our sample for which
optical spectra are available. Photometric energy distributions, when
available, are also combined to trigonometric parallax measurements to derive
effective temperatures, stellar radii, as well as atmospheric compositions. A
revised catalog of white dwarfs in the solar neighborhood is presented. We
provide, for the first time, a comprehensive analysis of the mass distribution
and the chemical distribution of white dwarf stars in a volume-limited sample.Comment: 104 pages, 22 figures, 2 tables, accepted for publication in the
Astrophysical Journal Supplemen
Spectral modeling of gaseous metal disks around DAZ white dwarfs
We report on our attempt for the first non-LTE modeling of gaseous metal
disks around single DAZ white dwarfs recently discovered by Gaensicke et al.
and thought to originate from a disrupted asteroid. We assume a Keplerian
rotating viscous disk ring composed of calcium and hydrogen and compute the
detailed vertical structure and emergent spectrum. We find that the observed
infrared CaII emission triplet can be modeled with a hydrogen-deficient gas
ring located at R=1.2 R_sun, inside of the tidal disruption radius, with Teff
about 6000 K and a low surface mass density of about 0.3 g/cm**2. A disk having
this density and reaching from the central white dwarf out to R=1.2 R_sun would
have a total mass of 7 10**21 g, corresponding to an asteroid with about 160 km
diameter.Comment: Proceedings, 16th European White Dwarf Workshop, Barcelona, 200
Searches for Gravitational Waves from Binary Neutron Stars: A Review
A new generation of observatories is looking for gravitational waves. These
waves, emitted by highly relativistic systems, will open a new window for ob-
servation of the cosmos when they are detected. Among the most promising
sources of gravitational waves for these observatories are compact binaries in
the final min- utes before coalescence. In this article, we review in brief
interferometric searches for gravitational waves emitted by neutron star
binaries, including the theory, instru- mentation and methods. No detections
have been made to date. However, the best direct observational limits on
coalescence rates have been set, and instrumentation and analysis methods
continue to be refined toward the ultimate goal of defining the new field of
gravitational wave astronomy.Comment: 30 pages, 5 Figures, to appear in "Short-Period Binary Stars:
Observations, Analyses, and Results", Ed.s Eugene F. Milone, Denis A. Leahy,
David W. Hobil
Monkey-based Research on Human Disease: The Implications of Genetic Differences
Assertions that the use of monkeys to investigate human diseases is valid scientifically are frequently based on a reported 90–93% genetic similarity between the species. Critical analyses of the relevance of monkey studies to human biology, however, indicate that this genetic similarity does not result in sufficient physiological similarity for monkeys to constitute good models for research, and that monkey data do not translate well to progress in clinical practice for humans. Salient examples include the failure of new drugs in clinical trials, the highly different infectivity and pathology of SIV/HIV, and poor extrapolation of research on Alzheimer’s disease, Parkinson’s disease and stroke. The major molecular differences underlying these inter-species phenotypic disparities have been revealed by comparative genomics and molecular biology — there are key differences in all aspects of gene expression and protein function, from chromosome and chromatin structure to post-translational modification. The collective effects of these differences are striking, extensive and widespread, and they show that the superficial similarity between human and monkey genetic sequences is of little benefit for biomedical research. The extrapolation of biomedical data from monkeys to humans is therefore highly unreliable, and the use of monkeys must be considered of questionable value, particularly given the breadth and potential of alternative methods of enquiry that are currently available to scientists
A dearth of small particles in the transiting material around the white dwarfWD 1145+017
White dwarf WD 1145+017 is orbited by several clouds of dust, possibly
emanating from actively disintegrating bodies. These dust clouds reveal
themselves through deep, broad, and evolving transits in the star's light
curve. Here, we report two epochs of multi-wavelength photometric observations
of WD 1145+017, including several filters in the optical, K and
4.5 m bands in 2016 and 2017. The observed transit depths are different at
these wavelengths. However, after correcting for excess dust emission at
K and 4.5 m, we find the transit depths for the white dwarf
itself are the same at all wavelengths, at least to within the observational
uncertainties of 5%-10%. From this surprising result, and under the
assumption of low optical depth dust clouds, we conclude that there is a
deficit of small particles (with radii 1.5 m) in the
transiting material. We propose a model wherein only large particles can
survive the high equilibrium temperature environment corresponding to 4.5 hr
orbital periods around WD 1145+017, while small particles sublimate rapidly. In
addition, we evaluate dust models that are permitted by our measurements of
infrared emission
Understanding the Cool DA White Dwarf, G29-38
The white dwarfs are promising laboratories for the study of cosmochronology
and stellar evolution. Through observations of the pulsating white dwarfs, we
can measure their internal structures and compositions, critical to
understanding post main sequence evolution, along with their cooling rates,
allowing us to calibrate their ages directly. The most important set of white
dwarf variables to measure are the oldest of the pulsators, the cool DAVs,
which have not previously been explored through asteroseismology due to their
complexity and instability. Through a time-series photometry data set spanning
ten years, we explore the pulsation spectrum of the cool DAV, G29-38 and find
an underlying structure of 19 (not including multiplet components) normal-mode,
probably l=1 pulsations amidst an abundance of time variability and linear
combination modes. Modelling results are incomplete, but we suggest possible
starting directions and discuss probable values for the stellar mass and
hydrogen layer size. For the first time, we have made sense out of the
complicated power spectra of a large-amplitude DA pulsator. We have shown its
seemingly erratic set of observed frequencies can be understood in terms of a
recurring set of normal-mode pulsations and their linear combinations. With
this result, we have opened the interior secrets of the DAVs to future
asteroseismological modelling, thereby joining the rest of the known white
dwarf pulsators.Comment: 29 pages including 5 figures To appear in ApJ 1 Mar 9
Maternal depression is associated with DNA methylation changes in cord blood T lymphocytes and adult hippocampi
Depression affects 10-15% of pregnant women and has been associated with preterm delivery and later developmental, behavioural and learning disabilities. We tested the hypothesis that maternal depression is associated with DNA methylation alterations in maternal T lymphocytes, neonatal cord blood T lymphocytes and adult offspring hippocampi. Genome-wide DNA methylation of CD3+ T lymphocytes isolated from 38 antepartum maternal and 44 neonatal cord blood samples were analyzed using Illumina Methylation 450 K microarrays. Previously obtained methylation data sets using methylated DNA immunoprecipitation and array-hybridization of 62 postmortem hippocampal samples of adult males were re-analyzed to test associations with history of maternal depression. We found 145 (false discovery rate (FDR) q<0.05) and 2520 (FDR q<0.1) differentially methylated CG-sites in cord blood T lymphocytes of neonates from the maternal depression group as compared with the control group. However, no significant DNA methylation differences were detected in the antepartum maternal T lymphocytes of our preliminary data set. We also detected 294 differentially methylated probes (FDR q<0.1) in hippocampal samples associated with history of maternal depression. We observed a significant overlap (P=0.002) of 33 genes with changes in DNA methylation in T lymphocytes of neonates and brains of adult offspring. Many of these genes are involved in immune system functions. Our results show that DNA methylation changes in offspring associated with maternal depression are detectable at birth in the immune system and persist to adulthood in the brain. This is consistent with the hypothesis that system-wide epigenetic changes are involved in life-long responses to maternal depression in the offspring. © 2015 Translational Psychiatry
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