402 research outputs found
Modulation of the glyoxalase system in the aging model Podospora anserina : effects on growth and lifespan
The eukaryotic glyoxalase system consists of two enzymatic components, glyoxalase I (lactoylglutathionelyase) and glyoxalase II (hydroxyacylglutathione hydrolase). These enzymes are dedicated to the removal of toxic alpha-oxoaldehydes like methylglyoxal (MG). MG is formed as a by-product of glycolysis and MG toxicity results from its damaging capability leading to modifications of proteins, lipids and nucleic acids. An efficient removal of MG appears to be essential to ensure cellular functionality and viability. Here we study the effects of the genetic modulation of genes encoding the components of the glyoxalase system in the filamentous ascomycete and aging model Podospora anserina. Overexpression of PaGlo1 leads to a lifespan reduction on glucose rich medium, probably due to depletion of reduced glutathione. Deletion of PaGlo1 leads to hypersensitivity against MG added to the growth medium. A beneficial effect on lifespan is observed when both PaGlo1 and PaGlo2 are overexpressed and the corresponding strains are grown on media containing increased glucose concentrations. Notably, the double mutant has a ‘healthy’ phenotype without physiological impairments. Moreover, PaGlo1/PaGlo2_OEx strains are not long-lived on media containing standard glucose concentrations suggesting a tight correlation between the efficiency and capacity to remove MG within the cell, the level of available glucose and lifespan. Overall, our results identify the up-regulation of both components of the glyoxalase system as an effective intervention to increase lifespan in P. anserina. Key words: Podospora anserina, aging, lifespan, glycation, glucose, methylglyoxal, advanced glycation end product
Wavelet-based methodology for [15O]-H20 PET brain activation assessment
[Abstract] AMI International Conference 2003, September 21-27, Madrid, Spain: "High Resolution Molecular Imaging: from Basic Science to Clinical Applications"Statistical parametric mapping (SPM) is a voxel-byvoxel analysis method commonly used for the detection of brain activation patterns. An alternative approach is the use of multiscale information by means of wavelet analysis. In this study, we have compared the detection of brain activations using conventional SPM and a statistical wavelet analysis in a set of realistic simulated [15O]-H20 positron emission tomography (PET) phantomsPublicad
The Far-Infrared Background Correlation with CMB Lensing
The intervening large--scale structure distorts cosmic microwave background
(CMB) anisotropies via gravitational lensing. The same large--scale structure,
traced by dusty star--forming galaxies, also induces anisotropies in the
far--infrared background (FIRB). We investigate the resulting inter--dependence
of the FIRB and CMB with a halo model for the FIRB. In particular, we calculate
the cross--correlation between the lensing potential and the FIRB. The lensing
potential can be quadratically estimated from CMB temperature and/or
polarization maps. We show that the cross--correlation can be measured with
high signal--to--noise with data from the Planck Surveyor. We discuss how such
a measurement can be used to understand the nature of FIRB sources and their
relation to the distribution of dark matter.Comment: 9 pages, 5 figures, submitted to Ap
SPM analysis of FDG rat PET scans
[Abstract] AMI Annual Conference 2002, October 23 - 27, San Diego, CaliforniaPublicad
Inhomogeneity correction of magnetic resonance images by minimization of intensity overlapping
Proceeding of: IEEE 2003 International Conference on Image Processing (ICIP), Barcelona, Spain, 14-17 Sept. 2003This work presents a new algorithm (NIC; Non uniform Intensity Correclion) for the correction of intensity inhomogeneities in magnetic resonance images. The algorithm has been validated by means of realistic phantom images and a set of 24 real images. Evaluation using previously proposed phantom images for inhomogeneity correction algorithms allowed us to obtain results fully comparable to the previous literature on the topic. This new algorithm was also compared, using a real image dataset, to other widely used methods which are
freely available in the Internet (N3, SPM'99 and SPM2).
Standard quality criteria have been used for determining the goodness of the different methods. The new algorithm showed better results removing the intensity inhomogeneities and did not produce degradation when used on images free from this artifact
The extragalactic background and its fluctuations in the far-infrared wavelengths
A Cosmic Far-InfraRed Background (CFIRB) has long been predicted that would
traces the intial phases of galaxy formation. It has been first detected by
Puget et al.(1996) using COBE data and has been later confirmed by several
recent studies (Fixsen et al. 1998, Hauser et al. 1998, Lagache et al. 1999).
We will present a new determination of the CFIRB that uses for the first time,
in addition to COBE data, two independent gas tracers: the HI survey of
Leiden/Dwingeloo (hartmann, 1998) and the WHAM H survey (Reynolds et
al 1998). We will see that the CFIRB above 100 micron is now very well
constrained. The next step is to see if we can detect its fluctuations. To
search for the CFIRB fluctuations, we have used the FIRBACK observations.
FIRBACK is a deep cosmological survey conducted at 170 micron with ISOPHOT
(Dole et al., 2000). We show that the emission of unresolved extra-galactic
sources clearly dominates, at arcminute scales, the background fluctuations in
the lowest galactic emission regions. This is the first detection of the CFIRB
fluctuations.Comment: To appear in "ISO Surveys of a Dusty Universe", Workshop at Ringberg
Castle, November 8 - 12, 199
Detection of rat brain activation using statistical parametric mapping analysis in FDG-PET studies
[Abstract] AMI International Conference 2003, September 21 - 27, Madrid, Spain: High Resolution Molecular Imaging: from Basic Science to Clinical ApplicationsStatistical parametric mapping (SPM) is an analysis technique long been used in clinical research to detect subtle activity changes in brain; it is an excellent exploratory tool as it does not require a priori assumptions about the expected brain region activations.
Research in animal imaging may also take benefit from this technique, if properly adapted to the new scenario. This is the case of brain activation studies in murine models using PET tracers and dedicated imaging devices. This work proposes the use of an SPM methodology adapted to the analysis of 2-deoxy-2-[18F] fluoro-D-Glucose (FDG) positron emission tomography (PET) scans of rat brains. Advantages over conventional region of interest (ROI) based analysis were assessed in an experiment addressing the detection of brain activation in of rats which underwent three different visual stimulation paradigmsPublicad
FIRBACK Source Counts and Cosmological Implications
FIRBACK is a one of the deepest surveys performed at 170 microns with ISOPHOT
onboard ISO, and is aimed at the study of cosmic far infrared background
sources. About 300 galaxies are detected in an area of four square degrees, and
source counts present a strong slope of 2.2 on an integral "logN-logS" plot,
which cannot be due to cosmological evolution if no K-correction is present.
The resolved sources account for less than 10% of the Cosmic Infrared
Background at 170 microns. In order to understand the nature of the sources
contributing to the CIB, and to explain deep source counts at other
wavelengths, we have developed a phenomenological model, which constrains in a
simple way the luminosity function evolution with redshift, and fits all the
existing deep source counts from the mid-infrared to the submillimetre range.
Images, materials and papers available on the FIRBACK web:
http://wwwfirback.ias.u-psud.fr wwwfirback.ias.u-psud.frComment: proceedings of "ISO Surveys of a Dusty Universe", eds. D. Lemke, M.
Stickel, K. Wilke, Ringberg, 8-12 Nov 1999, to appear in Springer 'Lecture
Notes of Physics'. 8 pages, 7 eps figures, .sty include
An 850 Micron SCUBA Survey of the HDF-N GOODS Region
The Hubble Deep Field-North (HDF-N) is one of the best studied extragalactic
fields, and ultra-deep optical, radio, X-ray, and mid-infrared wide-field
images are available for this area. Here we present an 850 um survey around the
HDF-N, covering most of the area imaged by the Advanced Camera for Surveys as a
part of the Great Observatories Origins Deep Survey. Our map has 0.4-4 mJy
sensitivities (1 sigma) over an area ~110 arcmin^2 and there are 45 sources
detected at >3 sigma. After correcting the effects of noise, confusion,
incompleteness, and the Eddington bias using Monte Carlo simulations, we find
that the detected 850 m sources with fluxes greater than 2 mJy have a
surface density of 3200^+1900_-1000 deg^-2 and account for about 24% to 34% of
the far-infrared extragalactic background light. Using the deep radio
interferometric image and the deep X-ray image, we are able to accurately
locate ~60% of the bright submillimeter (submm) sources. In addition, by
assuming the Arp 220 spectral energy distribution in the submm and radio, we
estimate millimetric redshifts for the radio detected submm sources, and
redshift lower limits for the ones not detected in the radio. Using the
millimetric redshifts of the radio identified sources and spectroscopic and
optical photometric redshifts for galaxies around the submm positions, we find
a median redshift of 2.0 for 11 possibly identified sources, or a lower limit
of 2.4 for the median redshift of our 4 sigma sample.Comment: 27 pages, 8 figures, ApJ accepte
Far Infrared Source Counts at 70 and 160 microns in Spitzer Deep Surveys
We derive galaxy source counts at 70 and 160 microns using the Multiband
Imaging Photometer for Spitzer (MIPS) to map the Chandra Deep Field South
(CDFS) and other fields. At 70 microns, our observations extend upwards about 2
orders of magnitude in flux density from a threshold of 15 mJy, and at 160
microns they extend about an order of magnitude upward from 50 mJy. The counts
are consistent with previous observations on the bright end. Significant
evolution is detected at the faint end of the counts in both bands, by factors
of 2-3 over no-evolution models. This evolution agrees well with models that
indicate most ofthe faint galaxies lie at redshifts between 0.7 and 0.9. The
new Spitzer data already resolve about 23% of the Cosmic Far Infrared
Background at 70 microns and about 7% at 160 microns.Comment: Small modifications to match printed version. Models in Differential
Counts plots were changed. MIPS Source Counts are available at:
http://lully.as.arizona.edu/GTODeep/Counts/ . Accepted for Publication in
ApJS Special Issue on Spitze
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