861 research outputs found
Preliminary Evidence of Increased Hippocampal Myelin Content in Veterans with Posttraumatic Stress Disorder.
Recent findings suggest the formation of myelin in the central nervous system by oligodendrocytes is a continuous process that can be modified with experience. For example, a recent study showed that immobilization stress increased oligodendrogensis in the dentate gyrus of adult rat hippocampus. Because changes in myelination represents an adaptive form of brain plasticity that has a greater reach in the adult brain than other forms of plasticity (e.g., neurogenesis), the objective of this "proof of concept" study was to examine whether there are differences in myelination in the hippocampi of humans with and without post-traumatic stress disorder (PTSD). We used the ratio of T1-weighted/T2-weighted magnetic resonance image (MRI) intensity to estimate the degree of hippocampal myelination in 19 male veterans with PTSD and 19 matched trauma-exposed male veterans without PTSD (mean age: 43 ± 12 years). We found that veterans with PTSD had significantly more hippocampal myelin than trauma-exposed controls. There was also found a positive correlation between estimates of hippocampal myelination and PTSD and depressive symptom severity. To our knowledge, this is the first study to examine hippocampal myelination in humans with PTSD. These results provide preliminary evidence for stress-induced hippocampal myelin formation as a potential mechanism underlying the brain abnormalities associated with vulnerability to stress
Unique growth pattern of human mammary epithelial cells induced by polymeric nanoparticles.
Due to their unique properties, engineered nanoparticles (NPs) have found broad use in industry, technology, and medicine, including as a vehicle for drug delivery. However, the understanding of NPs' interaction with different types of mammalian cells lags significantly behind their increasing adoption in drug delivery. In this study, we show unique responses of human epithelial breast cells when exposed to polymeric Eudragit® RS NPs (ENPs) for 1-3 days. Cells displayed dose-dependent increases in metabolic activity and growth, but lower proliferation rates, than control cells, as evidenced in tetrazolium salt (WST-1) and 5-bromo-2'-deoxyuridine (BrdU) assays, respectively. Those effects did not affect cell death or mitochondrial fragmentation. We attribute the increase in metabolic activity and growth of cells culture with ENPs to three factors: (1) high affinity of proteins present in the serum for ENPs, (2) adhesion of ENPs to cells, and (3) activation of proliferation and growth pathways. The proteins and genes responsible for stimulating cell adhesion and growth were identified by mass spectrometry and Microarray analyses. We demonstrate a novel property of ENPs, which act to increase cell metabolic activity and growth and organize epithelial cells in the epithelium as determined by Microarray analysis
The Stellar Parameters and Evolutionary State of the Primary in the d'-Symbiotic System StH\alpha190
We report on a high-resolution, spectroscopic stellar parameter and abundance
analysis of a d' symbiotic star: the yellow component of StH\alpha190. This
star has recently been discovered, and confirmed here, to be a rapidly rotating
(vsini=100 km/s) subgiant, or giant, that exhibits radial-velocity variations
of probably at least 40 km/s, indicating the presence of a companion (a white
dwarf star). It is found that the cool stellar component has Teff=5300K and log
g=3.0. The iron and calcium abundances are close to solar, however, barium is
overabundant, relative to Fe and Ca, by about +0.5 dex. The barium enhancement
reflects mass-transfer of s-process enriched material when the current white
dwarf was an asymptotic giant branch (AGB) star. The past and future evolution
of this binary system depends critically on its current orbital period, which
is not yet known. Concerted and frequent radial-velocity measurements are
needed to provide crucial physical constraints to this d' symbiotic system.Comment: 9 pages, 1 table, 3 figures. In press to Astrophysical Journal
Letter
The Rigidly Rotating Magnetosphere of Sigma Ori E
We attempt to characterize the observed variability of the magnetic
helium-strong star sigma Ori E in terms of a recently developed rigidly
rotating magnetosphere model. This model predicts the accumulation of
circumstellar plasma in two co-rotating clouds, situated in magnetohydrostatic
equilibrium at the intersection between magnetic and rotational equators. We
find that the model can reproduce well the periodic modulations observed in the
star's light curve, H alpha emission-line profile, and longitudinal field
strength, confirming that it furnishes an essentially correct, quantitative
description of the star's magnetically controlled circumstellar environment.Comment: 4 pages, 3 figures, accepted by Ap
On the photometric variability of blue supergiants in NGC 300 and its impact on the Flux-weighted Gravity-Luminosity Relationship
We present a study of the photometric variability of spectroscopically
confirmed supergiants in NGC 300, comprising 28 epochs extending over a period
of five months. We find 15 clearly photometrically variable blue supergiants in
a sample of nearly 70 such stars, showing maximum light amplitudes ranging from
0.08 to 0.23 magnitudes in the V band, and one variable red supergiant. We show
their light curves, and determine semi-periods for two A2 Ia stars. Assuming
that the observed changes correspond to similar variations in the bolometric
luminosity, we test for the influence of this variability on the Flux-weighted
Gravity--Luminosity Relationship and find a negligible effect, showing that the
calibration of this relationship, which has the potential to measure
extragalactic distances at the Cepheid accuracy level, is not affected by the
stellar photometric variability in any significant way.Comment: 9 pages, 3 figures, 3 tables. Accepted for publication in the
Astrophysical Journa
Wind structure of late B supergiants I. Multi-line analyses of near-surface and wind structure in HD 199 478 (B8 Iae)
We provide a quantitative analysis of time-variable phenomena in the
photospheric, near-star, and outflow regions of the late-B supergiant (SG) HD
199478. The analysis is based primarily on optical spectroscopic datasets
secured between 1999 and 2000 from the Bulgarian NAO, Tartu, and Ritter
Observatories. The temporal behaviour of HD 199478 is characterised by three
key empirical properties: (i) systematic central velocity shifts in the
photospheric absorption lines, including C II and He I, over a characteristic
time-scale of abou 20 days; (ii) extremely strong, variable H alpha emission
with no clear modulation signal, and (iii) the occurrence in 2000 of a (rare)
high-velocity absorption (HVA) event in H alpha, which evolved over about 60
days, showing the clear signature of mass infall and outflows. In these
properties HD 199478 resembles few other late-B SGs with peculiar emission and
HVAs in H alpha (HD 91619, HD 34085, HD 96919). Non-LTE line synthesis
modelling is conducted using FASTWIND for these late-B SGs to constrain and
compare their fundamental parameters within the context of extreme behaviour in
the H alpha lines. Our analysis indicate that at the cooler temperature edge of
B SGs, there are objects whose wind properties, as traced by H alpha, are
inconsistent with the predictions of the smooth, spherically symmetric wind
approximation. This discordance is still not fully understood and may highlight
the role of a non-spherical, disk-like, geometry, which may result from
magnetically-driven equatorial compression of the gas. Ordered dipole magnetic
fields may also lead to confined plasma held above the stellar surface, which
ultimately gives rise to transient HVA events.Comment: 12 pages. To be published in Astronomy and AStrophysic
Evolution of the polarization of the optical afterglow of the gamma-ray burst GRB 030329
We report 31 polarimetric observations of the afterglow of GRB 030329 with
high signal-to-noise and high sampling frequency. We establish the polarization
light curve, detect sustained polarization at the percent level, and find
significant variability of polarization degree and angle. The data imply that
the afterglow magnetic field has small coherence length and is mostly random,
probably generated by turbulence.Comment: Nature 426 (13. Nov. 2003), 2 figure
The most rapidly rotating He-strong emission line star: HR7355
Using archival spectroscopic and photometric data, we searched for massive
stars with Balmer-emission consistent with magnetically confined circumstellar
material. HR 7355 is a formerly unknown He-strong star showing Balmer emission.
At V=6.02 mag, it is one of the brightest objects simultaneously showing
anomalous helium absorption and hydrogen emission. Among similar objects, only
sigma Ori E has so far been subjected to any systematic analysis of the
circumstellar material responsible for the emission. We argue that the
double-wave photometric period of 0.52d corresponds to the rotation period. In
tandem with the high projected equatorial velocity, v sin i=320 km/s, this
short period suggests that HR 7355 is the most rapidly rotating He-strong star
known to date; a class that was hitherto expected to host stars with slow to
moderate rotation only.Comment: 4 pages with 2 figures. Accepted for publication as Research Note by
Astronomy and Astrophysic
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