4,539 research outputs found
Glutamate induces autophagy via the two-pore channels in neural cells
NAADP (nicotinic acid adenine dinucleotide phosphate) has been proposed as a second messenger for glutamate in neuronal and glial cells via the activation of the lysosomal Ca2+ channels TPC1 and TPC2. However, the activities of glutamate that are mediated by NAADP remain unclear. In this study, we evaluated the effect of glutamate on autophagy in astrocytes at physiological, non-toxic concentration. We found that glutamate induces autophagy at similar extent as NAADP. By contrast, the NAADP antagonist NED-19 or SiRNA-mediated inhibition of TPC1/2 decreases autophagy induced by glutamate, confirming a role for NAADP in this pathway. The involvement of TPC1/2 in glutamate-induced autophagy was also confirmed in SHSY5Y neuroblastoma cells. Finally, we show that glutamate leads to a NAADP-dependent activation of AMPK, which is required for autophagy induction, while mTOR activity is not affected by this treatment. Taken together, our results indicate that glutamate stimulates autophagy via NAADP/TPC/AMPK axis, providing new insights of how Ca2+ signalling glutamate-mediated can control the cell metabolism in the central nervous system
On a functional satisfying a weak Palais-Smale condition
In this paper we study a quasilinear elliptic problem whose functional
satisfies a weak version of the well known Palais-Smale condition. An existence
result is proved under general assumptions on the nonlinearities.Comment: 18 page
Low temperature specific heat of La_{3}Pd_{4}Ge_{4} with U_{3}Ni_{4}Si_{4}-type structure
Low temperature specific heat has been investigated in a novel ternary
superconductor La_{3}Pd_{4}Ge_{4} with an U_{3}Ni_{4}Si_{4}-type structure
consisting of the alternating BaAl_{4} (ThCr_{2}Si_{2})- and AlB-type
layers. A comparative study with the related ThCr_{2}Si_{2}-type superconductor
LaPd_{2}Ge_{2}, one of the layers in La_{3}Pd_{4}Ge_{4}, is also presented.
From the normal state specific heat, the Sommerfeld coefficient mJ/mol K^2 and the Debye temperature = 256 K are derived
for the La_{3}Pd_{4}Ge_{4}, while those for the LaPd_{2}Ge_{2} are mJ/mol K^2 and = 291 K. The La_{3}Pd_{4}Ge_{4} has
moderately high electronic density of state at the Fermi level. Electronic
contribution on the specific heat, , in each compound is well
described by the BCS behavior, suggesting that both of the La_{3}Pd_{4}Ge_{4}
and the LaPd_{2}Ge_{2} have fully opened isotropic gap in the superconducting
state
Site-site memory equation approach in study of density/pressure dependence of translational diffusion coefficient and rotational relaxation time of polar molecular solutions: acetonitrile in water, methanol in water, and methanol in acetonitrile
We present results of theoretical study and numerical calculation of the
dynamics of molecular liquids based on combination of the memory equation
formalism and the reference interaction site model - RISM. Memory equations for
the site-site intermediate scattering functions are studied in the
mode-coupling approximation for the first order memory kernels, while
equilibrium properties such as site-site static structure factors are deduced
from RISM. The results include the temperature-density(pressure) dependence of
translational diffusion coefficients D and orientational relaxation times t for
acetonitrile in water, methanol in water and methanol in acetonitrile, all in
the limit of infinite dilution. Calculations are performed over the range of
temperatures and densities employing the SPC/E model for water and optimized
site-site potentials for acetonitrile and methanol. The theory is able to
reproduce qualitatively all main features of temperature and density
dependences of D and t observed in real and computer experiments. In
particular, anomalous behavior, i.e. the increase in mobility with density, is
observed for D and t of methanol in water, while acetonitrile in water and
methanol in acetonitrile do not show deviations from the ordinary behavior. The
variety exhibited by the different solute-solvent systems in the density
dependence of the mobility is interpreted in terms of the two competing origins
of friction, which interplay with each other as density increases: the
collisional and dielectric frictions which, respectively, increase and decrease
with increasing density.Comment: 13 pages, 8 eps-figures, 3 tables, RevTeX4-forma
Future Detection of Supernova Neutrino Burst and Explosion Mechanism
Future detection of a supernova neutrino burst by large underground detectors
would give important information for the explosion mechanism of collapse-driven
supernovae. We studied the statistical analysis for the future detection of a
nearby supernova by using a numerical supernova model and realistic Monte-Carlo
simulations of detection by the Super-Kamiokande detector. We mainly discuss
the detectability of the signatures of the delayed explosion mechanism in the
time evolution of the \anue luminosity and spectrum. For a supernova at 10
kpc away from the Earth, we find that not only the signature is clearly
discernible, but also the deviation of energy spectrum from the Fermi-Dirac
(FD) distribution can be observed. The deviation from the FD distribution
would, if observed, provide a test for the standard picture of neutrino
emission from collapse-driven supernovae. For the = 50 kpc case, the
signature of the delayed explosion is still observable, but statistical
fluctuation is too large to detect the deviation from the FD distribution. We
also propose a method for statistical reconstruction of the time evolution of
\anue luminosity and spectrum from data, by which we can get a smoother time
evolution and smaller statistical errors than a simple, time-binning analysis.
This method is useful especially when the available number of events is
relatively small, e.g., a supernova in the LMC or SMC. Neutronization burst of
's produces about 5 scattering events when = 10 kpc and this signal
is difficult to distinguish from \anue p events.Comment: 28 pages including all figures. Accepted by Astrophys.
Phenomenological interaction between current quarks
We construct a phenomenological model which describes the dynamical chiral
symmetry breaking (DCSB) of QCD vacuum and reproduces meson spectra. Quark
condensates, the pion decay constant, and meson spectra are well reproduced by
phenomenological interaction which consists of a linear confining potential, a
Coulombic potential, and the 't Hooft determinant interaction. In this model,
the 't Hooft determinant interaction plays a important role not to only
\eta,\eta' mass difference, but other meson masses through DCSB.Comment: 18 pages, LaTe
A Dirac-Hartree-Bogoliubov approximation for finite nuclei
We develop a complete Dirac-Hartree-Fock-Bogoliubov approximation to the
ground state wave function and energy of finite nuclei. We apply it to
spin-zero proton-proton and neutron-neutron pairing within the
Dirac-Hartree-Bogoliubov approximation (we neglect the Fock term), using a
zero-range approximation to the relativistic pairing tensor. We study the
effects of the pairing on the properties of the even-even nuclei of the
isotopic chains of Ca, Ni and Sn (spherical) and Kr and Sr (deformed), as well
as the =28 isotonic chain, and compare our results with experimental data
and with other recent calculations.Comment: 43 pages, RevTex, 13 figure
A Common Explanation for the Atmospheric, Solar-Neutrino and Double Beta Decay Anomalies
We make a number of small changes, including correcting an error in our
heavy-neutrino decay rate. None of our analysis is changed, either in substance
or detail.Comment: 25 pages, 6 Figures, McGill-93/1
Functionalized up conversion rare earth nanoparticles for bio imaging of cancer cells
In recent yearsupconversion nanoparticles (UCNPs)have being investigated due to their potential applications in biomedicine such as fluorescent biolabels, among many others. The luminescence of this kind of NP's are effectively activatedby near infrared radiation (NIR) and upconvertto luminescence in the visible region. Besides, their luminescence is not faded as compared with organic dyes and fluorescent proteins. In this study, UCNPs made of Y2O3:Yb3+, Er3+ (1%, 10% mol) and Gd2O3:Yb3+, Er3+ (1%, 10% mol) were functionalized with aminosilanes and folic acid (UCNP-NH2-FA) and characterized with transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and luminescence measurements. Moreover, cytotoxicity was analyzed via colorimetric assays MTT (methy-134 thiazolyltetrazolium) in two cancer cell lines: cervical adenocarcinoma cells (HeLa) and breast cancer cells MB-MDA-231. It is found that the functionalized UCNPs were non-cytotoxic in all cancer cell lines. Confocal images revealed that UCNP-NH2-FA conjugates as a target to attract cells with overexpressed folate receptor (FR). The UCNPs offer a great potential to be used as bio labels because their fluorescence was clearly localized into cell cytoplasm
Primordial helium recombination. I. Feedback, line transfer, and continuum opacity
Precision measurements of the cosmic microwave background temperature anisotropy on scales ℓ>500 will be available in the near future. Successful interpretation of these data is dependent on a detailed understanding of the damping tail and cosmological recombination of both hydrogen and helium. This paper and two companion papers are devoted to a precise calculation of helium recombination. We discuss several aspects of the standard recombination picture, and then include feedback, radiative transfer in He i lines with partial redistribution, and continuum opacity from H i photoionization. In agreement with past calculations, we find that He ii recombination proceeds in Saha equilibrium, whereas He i recombination is delayed relative to Saha due to the low rates connecting excited states of He i to the ground state. However, we find that at z<2200 the continuum absorption by the rapidly increasing H i population becomes effective at destroying photons in the He i 21Po-11S line, causing He i recombination to finish around z≃1800, much earlier than previously estimated
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