712 research outputs found
Mutation analysis using the restriction site mutation (RSM) assay
The restriction site mutation RSM assay see Steingrimsdottir et al. H. Steingrimsdottir, D. Beare, J. Cole, J.F.M. Leal, Ž. Ž w
T. Kostic, J. Lopez-Barea, G. Dorado, A.R. Lehmann, Development of new molecular procedures for the detection of
genetic alteration in man, Mutat. Res. 353 1996 pp. 109–121 for a review has been developed as a genotypic mutation Ž . x .
detection system capable of identifying mutations occurring in restriction enzyme sites of genomic DNA. Here we will
report the steps taken to overcome some of the initial problems of the assay, namely the lack of quantitative data and limited
sensitivity, the aim being to achieve a methodology suitable for the study of low dose chemical exposures. Quantitative data
was achieved in the RSM assay by the inclusion of an internal standard molecule in the PCR amplification stage, thus
allowing the calculation of both spontaneous and induced mutation frequencies. The sensitivity of the assay was increased
through the discovery that intron sequences of genomic DNA accumulated more mutations in vivo compared to the exons,
presumably due to differential selective pressure within genes G.J.S. Jenkins, I.deG. Mitchell, J.M. Parry, Enhanced w
restriction site mutation RSM analysis of 1,2-dimethylhydrazine-induced mutations, using endogenous Ž . p53 intron
sequences, Mutagenesis 12 1997 pp. 117–123 . This increased sensitivity was examined by applying the RSM assay to Ž . x
analyse the persistence of N-ethyl-N-nitrosourea ENU -induced mutations in mice testes. Germ line mutations were sought Ž .
in testes DNA 3, 10 and 100 days after ENU treatment. Mutations were detected in exons and especially intron regions, the
intron mutations were more persistent, still being detected 100 days post-chemical treatment. Assignment of these mutations
as ENU induced was complicated in some cases where the spontaneous mutation level was high. This theme of mutation
persistence was further investigated by studying the presence of 4-nitroquinoline-1-oxide 4-NQO -induced DNA mutations Ž .
in vitro. This study also analysed the relationship between DNA adduct formation and DNA mutation induction by the
concurrent RSM analysis and 32P post-labelling analysis of 4-NQO treated human fibroblasts. The results demonstrated that
early DNA mutations detected 4 days post-treatment by the RSM assay were probably ex vivo mutations induced by Taq
polymerase misincorporation of 4-NQO adducted DNA, due to the maximum levels of 4-NQO adducts being present at this
time point. A later mutational peak, after the adduct level had declined, was assumed to be due to DNA sequence changes
produced in the fibroblasts by the in vivo processing of DNA adducts
SALT observations of the Chromospheric Activity of Transiting Planet Hosts: Mass Loss and Star Planet Interactions
We measured the chromospheric activity of the four hot Jupiter hosts WASP-43, WASP-51/HAT-P-30, WASP-72 & WASP-103 to search for anomalous values caused by the close-in companions. The Mount Wilson Ca II H&K S-index was calculated for each star using observations taken with the Robert Stobie Spectrograph at the Southern African Large Telescope. The activity level of WASP-43 is anomalously high relative to its age and falls among the highest values of all known main sequence stars. We found marginal evidence that the activity of WASP-103 is also higher than expected from the system age. We suggest that for WASP-43 and WASP-103 star-planet interactions (SPI) may enhance the Ca II H&K core emission. The activity levels of WASP-51/HAT-P-30 and WASP-72 are anomalously low, with the latter falling below the basal envelope for both main sequence and evolved stars. This can be attributed to circumstellar absorption due to planetary mass loss, though absorption in the ISM may contribute. A quarter of known short period planet hosts exhibit anomalously low activity levels, including systems with hot Jupiters and low mass companions. Since SPI can elevate and absorption can suppress the observed chromospheric activity of stars with close-in planets, their Ca II H&K activity levels are an unreliable age indicator. Systems where the activity is depressed by absorption from planetary mass loss are key targets for examining planet compositions through transmission spectroscopy
VIP enhances TRH-stimulated prolactin secretion of pituitary tumours Studies with 31P NMR
AbstractIntravenous thyrotrophin releasing hormone (TRH) caused a 6.5-fold increase in plasma prolactin (PRL) in rats carrying implanted pituitary tumours. Vasoactive intestinal polypeptide (VIP) had no effect, but TRH given after VIP raised TRH stimulated secretion 13-fold above basal. 31P NMR spectroscopy showed that VIP caused a decrease in high energy metabolites (depleted phosphocreatine, elevated inorganic phosphate and lowered intracellular pH). TRH alone caused a similar but smaller effect; given after VIP, it caused no detectable depletion. We suggest that the changes in high energy metabolite cencentrations reflect increased cellular energy consumption consistent with a priming process (stage 1) in PRL secretion, followed by hormone release (stage 2). VIP induces stage 1 whereas RTH induced both stages
Benchmark low-mass objects in Moving Groups
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.In order to compile a sample of ultracool dwarfs that will serve as benchmarks for testing theoretical formation and evolutionary models, we selected low-mass cool (>M7) objects that are potentially members of five known young Moving Groups in the solar neighbourhood. We have studied the kinematics of the sample, finding that 49 targets belong to the young disk area, from which 36 are kinematic member of one of the five moving groups under study. Some of the identified low-mass members have been spectroscopically characterised (T-eff, log g) and confirmed as young members through a detailed study of age indicators
Velocity correlations in dense granular gases
We report the statistical properties of spherical steel particles rolling on
an inclined surface being driven by an oscillating wall. Strong dissipation
occurs due to collisions between the particles and rolling and can be tuned by
changing the number density. The velocities of the particles are observed to be
correlated over large distances comparable to the system size. The distribution
of velocities deviates strongly from a Gaussian. The degree of the deviation,
as measured by the kurtosis of the distribution, is observed to be as much as
four times the value corresponding to a Gaussian, signaling a significant
breakdown of the assumption of negligible velocity correlations in a granular
system.Comment: 4 pages, 4 Figure
Granular clustering in a hydrodynamic simulation
We present a numerical simulation of a granular material using hydrodynamic
equations. We show that, in the absence of external forces, such a system
phase-separates into high density and low density regions. We show that this
separation is dependent on the inelasticity of collisions, and comment on the
mechanism for this clustering behavior. Our results are compatible with the
granular clustering seen in experiments and molecular dynamic simulations of
inelastic hard disks.Comment: 4 pages, 5 figure
Ab-initio density-functional lattice-dynamics studies of ice
We present the results of first-principles computational studies of the dynamical properties of hexagonal ice using both the ab-initio pseudopotential method and the full-potential augmented plane-wave method. Properties obtained using both the generalized gradient approximation (GGA) and the meta-GGA in density-functional theory are compared. The lattice-dynamical properties of the structures are obtained using a finite-difference evaluation of the dynamical matrix and force-constant matrix from atomic forces. Phonon dispersion is evaluated by the direct determination of the force-constant matrix in supercells derived from the primitive molecule unit cells with the assumption that force constants are zero beyond the second molecular nearest neighbors. The k-dependent phonon frequencies are then obtained from the force-constant matrix and dispersion relations, and the Brillouin-zone integrated density of states is evaluated. The importance of phonon dispersion in the various regions of the phonon spectra is then assessed and compared to existing neutron-scattering data. Frozen-phonon calculations are used to compare phonon frequencies evaluated in both the GGA and meta-GGA
Symmetry-breaking instability in a prototypical driven granular gas
Symmetry-breaking instability of a laterally uniform granular cluster (strip
state) in a prototypical driven granular gas is investigated. The system
consists of smooth hard disks in a two-dimensional box, colliding inelastically
with each other and driven, at zero gravity, by a "thermal" wall. The limit of
nearly elastic particle collisions is considered, and granular hydrodynamics
with the Jenkins-Richman constitutive relations is employed. The hydrodynamic
problem is completely described by two scaled parameters and the aspect ratio
of the box. Marginal stability analysis predicts a spontaneous symmetry
breaking instability of the strip state, similar to that predicted recently for
a different set of constitutive relations. If the system is big enough, the
marginal stability curve becomes independent of the details of the boundary
condition at the driving wall. In this regime, the density perturbation is
exponentially localized at the elastic wall opposite to the thermal wall. The
short- and long-wavelength asymptotics of the marginal stability curves are
obtained analytically in the dilute limit. The physics of the symmetry-breaking
instability is discussed.Comment: 11 pages, 14 figure
Contributions from SUSY-FCNC couplings to the interpretation of the HyperCP events for the decay \Sigma^+ \to p \mu^+ \mu^-
The observation of three events for the decay
with a dimuon invariant mass of MeV by the HyperCP collaboration
imply that a new particle X may be needed to explain the observed dimuon
invariant mass distribution. We show that there are regions in the SUSY-FCNC
parameter space where the in the NMSSM can be used to explain the
HyperCP events without contradicting all the existing constraints from the
measurements of the kaon decays, and the constraints from the
mixing are automatically satisfied once the constraints from kaon decays are
satisfied.Comment: 18 pages, 7 figure
Determination of atomic abundances of solar-type stars
We discuss the results of abundance determinations of the solar-type stars HD 1835 and HD 10700 using our new procedure. This procedure has the advantage of automated pipeline usage for large amounts of spectroscopic data, with minimal user input. It is based on the spectral synthesis method, where the best values are found with our own
developed minimization technique. We reduce the number of free parameters in minimization space using the fit to the observed atomic iron lines. We calibrated our procedure using fits to the observed solar spectrum. Then we determined abundances in two solar-type stars, namely the metal-deficient star HD 10700 and the metal-rich star HD 1835. We found good agreement with previously published results. Thus, we aim to use this procedure for the abundance determination of solar-type stars, particularly planet hosting stars, where the knowledge of abundances is crucial for our understanding of their evolution and formation processes
- …