70 research outputs found
The regulation of animal behavior by cellular stress responses
Cellular stress responses exist to detect the effects of stress on cells, and to activate protective mechanisms that promote resilience. As well as acting at the cellular level, stress response pathways can also regulate whole organism responses to stress. One way in which animals facilitate their survival in stressful environments is through behavioral adaptation; this review considers the evidence that activation of cellular stress responses plays an important role in mediating the changes to behavior that promote organismal survival upon stress
Investigation of Single Air Bubble Dynamics and the Effect of Nanoparticles in Rectangular Minichannels
Bubble dynamics and understanding related mechanisms based on force analysis are necessary for better understanding two-phase flow phenomena in small channels. To address this subject, experiments were conducted with injected single air bubbles into rectangular minichannels containing flows of pure water, pure ethanol and TiO2-nanoparticle-based nanofluids, which had a nanoparticle mass fraction of 0.005 wt% for both water and ethanol base fluids. For a range of fluid flow rates, bubble movement and temperature profiles were captured along the channel using high-speed and infrared (IR) cameras, respectively. Upon heating, when using nanofluids, deposition of TiO2 nanoparticles occurred. The results in the channels with cross sectional dimensions of 2 mm × 4 mm and heated length of 7 cm were compared with their counterparts on plain surfaces. Heat fluxes were applied by means of a tantalum film heater on the outer surface of the channel. Bubble dynamics and forces acting on the bubbles were quantitatively analyzed in relation to the fluid type, heat flux, flow rate and deposition. This study highlights the effects of TiO2-nanoparticles (dispersed in two different base fluids) on single-bubble dynamics in minichannels. The nanoparticle deposition was found to have a retarding effect on the bubble movement and led to a more elliptical shape rather than a spherical bubble shape. The bubble behavior is comprehensively assessed in the light of the visualization data and acting forces
Neuronal XBP-1 Activates Intestinal Lysosomes to Improve Proteostasis in C. elegans
The unfolded protein response of the endoplasmic reticulum (UPRER) is a crucial mediator of secretory pathway homeostasis. Expression of the spliced and active form of the UPRER transcription factor XBP-1, XBP-1s, in the nervous system triggers activation of the UPRER in the intestine of Caenorhabditis elegans (C. elegans) through release of a secreted signal, leading to increased longevity. We find that expression of XBP-1s in the neurons or intestine of the worm strikingly improves proteostasis in multiple tissues, through increased clearance of toxic proteins. To identify the mechanisms behind this enhanced proteostasis, we conducted intestine-specific RNA-seq analysis to identify genes upregulated in the intestine when XBP-1s is expressed in neurons. This revealed that neuronal XBP-1s increases the expression of genes involved in lysosome function. Lysosomes in the intestine of animals expressing neuronal XBP-1s are more acidic, and lysosomal protease activity is higher. Moreover, intestinal lysosome function is necessary for enhanced lifespan and proteostasis. These findings suggest that activation of the UPRER in the intestine through neuronal signaling can increase the activity of lysosomes, leading to extended longevity and improved proteostasis across tissues
Distorted cyclotron line profile in Cep X-4 as observed by NuSTAR
We present spectral analysis of NuSTAR and Swift observations of Cep X-4
during its outburst in 2014. We observed the source once during the peak of the
outburst and once during the decay, finding good agreement in the spectral
shape between the observations. We describe the continuum using a powerlaw with
a Fermi-Dirac cutoff at high energies. Cep X-4 has a very strong cyclotron
resonant scattering feature (CRSF) around 30 keV. A simple absorption-like line
with a Gaussian optical depth or a pseudo-Lorentzian profile both fail to
describe the shape of the CRSF accurately, leaving significant deviations at
the red side of the line. We characterize this asymmetry with a second
absorption feature around 19 keV. The line energy of the CRSF, which is not
influenced by the addition of this feature, shows a small but significant
positive luminosity dependence. With luminosities between (1-6)e36 erg/s, Cep
X-4 is below the theoretical limit where such a correlation is expected. This
behavior is similar to Vela X-1 and we discuss parallels between the two
systems.Comment: 6 pages, 4 figure, accepted for publication in ApJ letter
Soft X-ray emission lines in the X-ray binary Swift J1858.6-0814 observed with XMM-Newton-RGS: disc atmosphere or wind?
We find soft X-ray emission lines from the X-ray binary Swift J1858.6-0814 in
data from XMM-Newton-RGS: N VII, O VII and O VIII, as well as notable residuals
short of a detection at Ne IX and other higher ionisation transitions. These
could be associated with the disc atmosphere, as in accretion disc corona
sources, or with a wind, as has been detected in Swift J1858.6-0814 in emission
lines at optical wavelengths. Indeed, the N VII line is redshifted, consistent
with being the emitting component of a P-Cygni profile. We find that the
emitting plasma has an ionisation parameter and a
density cm. From this, we infer that the emitting
plasma must be within cm of the ionising source,
for a neutron star, and from the
line width that it is at least away
( cm). We compare this with known classes of
emission line regions in other X-ray binaries and active galactic nuclei.Comment: 10 pages, 7 figures, MNRAS accepte
Identifications of Five INTEGRAL Sources via Optical Spectroscopy
The International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is discovering
hundreds of new hard X-ray sources, many of which remain unidentified. We
report on optical spectroscopy of five such sources for which X-ray
observations at lower energies (~0.5-10 keV) and higher angular resolutions
than INTEGRAL have allowed for unique optical counterparts to be located. We
find that IGR J16426+6536 and IGR J22292+6647 are Type 1 Seyfert active
galactic nuclei (with IGR J16426+6536 further classified as a Seyfert 1.5)
which have redshifts of z=0.323 and z=0.113, respectively. IGR J18308-1232 is
identified as a cataclysmic variable (CV), and we confirm a previous
identification of IGR J19267+1325 as a magnetic CV. IGR J18214-1318 is
identified as an obscured high mass X-ray binary (HMXB), which are systems
thought to have a compact object embedded in the stellar wind of a massive
star. We combine Chandra fluxes with distances based on the optical
observations to calculate X-ray luminosities of the HMXB and CVs, finding
L_(0.3-10 keV)=5e36 erg s^-1 for IGR J18214-1318, L_(0.3-10 keV)=1.3e32 erg
s^-1 for IGR J18308-1232, and L_(0.3-10 keV)=6.7e32 erg s^-1 for IGR
J19267+1325.Comment: 8 pages, 5 figures, accepted for publication by Ap
Tyramine acts downstream of neuronal XBP-1s to coordinate inter-tissue UPRER activation and behavior in C. elegans
In C. elegans, expression of the UPRER transcription factor xbp-1s in neurons cell non-autonomously activates the UPRER in the intestine, leading to enhanced proteostasis and lifespan. To better understand this signaling pathway, we isolated neurons from animals expressing neuronal xbp-1s for transcriptomic analysis, revealing a striking remodeling of transcripts involved in neuronal signaling. We then identified signaling molecules required for cell non-autonomous intestinal UPRER activation, including the biogenic amine tyramine. Expression of xbp-1s in just two pairs of neurons that synthesize tyramine, the RIM and RIC interneurons, induced intestinal UPRER activation and extended longevity, and exposure to stress led to splicing and activation of xbp-1 in these neurons. In addition, we found that neuronal xbp-1s modulates feeding behavior and reproduction, dependent upon tyramine synthesis. XBP-1s therefore remodels neuronal signaling to coordinately modulate intestinal physiology and stress-responsive behavior, functioning as a global regulator of organismal responses to stress
TMS-induced inhibition of the left premotor cortex modulates illusory social perception
Communicative actions from one person are used to predict another person’s response. However, in some cases, these predictions can outweigh the processing of sensory information and lead to illusory social perception such as seeing two people interact, although only one is present (i.e., seeing a Bayesian ghost). We applied either inhibitory brain stimulation over the left premotor cortex (i.e., real TMS) or sham TMS. Then, participants indicated the presence or absence of a masked agent that followed a communicative or individual gesture of another agent. As expected, participants had more false alarms in the communicative (i.e., Bayesian ghosts) than individual condition in the sham TMS session and this difference between conditions vanished after real TMS. In contrast to our hypothesis, the number of false alarms increased (rather than decreased) after real TMS. These pre-registered findings confirm the significance of the premotor cortex for social action predictions and illusory social perception
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