3,742 research outputs found
Identifying QTLs Associated and Marker-Assisted Selection for Salinity Tolerance at the Seedling, Vegetative and Reproductive Stages in Rice (Oryza Sativa L.)
Salinity affects rice growth in all growth stages, with the seedling and reproductive stages being the most sensitive. Genetically improving salt tolerance of rice is an important objective of rice breeding programs. Hence, mapping quantitative trait loci (QTL) will be useful for marker-assisted selection in rice breeding programs. An advanced backcross population (BC2F2) was developed with the parents included OM5629 as a donor of salt tolerance and OM7347 as a recurrent parent with good quality traits and drought tolerance. Molecular markers associated with both qualitative and quantitative trait loci (QTL) salt tolerance were identified by using 416 polymorphic SSR markers. QTLs, associated with stress tolerance at EC = 15 dS/m at seedling stage, detected from the BC2F2 population of OM7347/OM5629, were located on chromosomes 1 and 3. Three QTLs were identified at the intervals of RM3252-S1-1 - RM10694, RM3740-RM5336 and RM11125-RM9 with genetic distance of 4.4, 4.5 and 18 cM on chromosome 1, respectively. Two QTLs at the intervals of RM3867-RM6959 and RM6876-RM4425 with genetic distance of 4.5 and 18.0 cM on chromosome 3, respectively. One QTL on chromosome 5 was detected at the interval of RM874 - RM10359, it was associated with salt stress tolerance under EC = 8dS/m at vegetative stage. Three QTLs at the regions of RM1324-RM2412, RM1185-RM24, and RM1282-RM2560 on chromosome 1, and one QTL of RM453-RM511 on chromosome 12, were related to salt tolerance under EC = 8dS/m at reproductive stage. Two tightly linked markers as RM3252-S1-1 and RM3867, were exhibited their effectiveness in identification of salt tolerance genotypes in BC3F6 population of OMCS2000/ Pokkali. The identification of new QTLs associated with salt tolerance will provide important information for the functional analysis of rice salinity stress
Phenotypic Screening of Drought-Tolerant Lines for Brown Planthopper, Blast and Phytic Acid Content Assay of Rice (Oryza sativa L.)
Advanced drought tolerant lines were analysed for blast disease, brown planthopper (BPH), and phytic acid content. Thirsty lines of BC2F4 derived from OMCS2000/ IR75499-73-1 were used to screen for BPH and blast resistance. Three good resistant lines were screened against blast (45, 54, and 310) under greenhouse condition. As eight lines were identified to be resistant to BPH. The results further reveal that BC2F4-45 was the best line resistant to both BPH and blast disease. These lines will be useful in reducing grain phytic acid and improving the nutritional value of rice grain. Based on an assay for high phosphate germination stage of rice, the lowest content was found in the I5 variety (line 45). Hence, this line provides the urgent objective for breeders in cultivars of these crops to genetically enhance a healthy and functional diet. These characters will then need to be incorporated into high yield under drought stress with others such as disease and insect resistance
Regulation of Anthrax Toxin-Specific Antibody Titers by Natural Killer T Cell-Derived IL-4 and IFNγ
Activation of Natural Killer-like T cells (NKT) with the CD1d ligand α-GC leads to enhanced production of anthrax toxin protective Ag (PA)-neutralizing Abs, yet the underlying mechanism for this adjuvant effect is not known. In the current study we examined the role of Th1 and Th2 type responses in NKT-mediated enhancement of antibody responses to PA. First, the contribution of IL-4 and IFNγ to the production of PA-specific toxin-neutralizing Abs was examined. By immunizing C57Bl/6 controls IL-4−/− mice and IFNγ−/− mice and performing passive serum transfer experiments, it was observed that sera containing PA-specific IgG1, IgG2b and IgG2c neutralized toxin in vitro and conferred protection in vivo. Sera containing IgG2b and IgG2c neutralized toxin in vitro but were not sufficient for protection in vivo. Sera containing IgG1 and IgG2b neutralized toxin in vitro and conferred protection in vivo. IgG1 therefore emerged as a good correlate of protection. Next, C57Bl/6 mice were immunized with PA alone or PA plus a Th2-skewing α-GC derivative known as OCH. Neutralizing PA-specific IgG1 responses were modestly enhanced by OCH in C57Bl/6 mice. Conversely, IgG2b and IgG2c were considerably enhanced in PA/OCH-immunized IL-4−/− mice but did not confer protection. Finally, bone marrow chimeras were generated such that NKT cells were unable to express IL-4 or IFNγ. NKT-derived IL-4 was required for OCH-enhanced primary IgG1 responses but not recall responses. NKT-derived IL-4 and IFNγ also influenced primary and recall IgG2b and IgG2c titers. These data suggest targeted skewing of the Th2 response by α-GC derivatives can be exploited to optimize anthrax vaccination
Effects of exemestane and letrozole therapy on plasma concentrations of estrogens in a randomized trial of postmenopausal women with breast cancer
PURPOSE:
Inter-individual differences in estrogen concentrations during treatment with aromatase inhibitors (AIs) may contribute to therapeutic response and toxicity. The aim of this study was to determine plasma concentrations of estradiol (E2), estrone (E1), and estrone sulfate (E1S) in a large cohort of AI-treated breast cancer patients.
METHODS:
In a randomized, multicenter trial of postmenopausal women with early-stage breast cancer starting treatment with letrozole (n = 241) or exemestane (n = 228), plasma estrogen concentrations at baseline and after 3 months were quantitated using a sensitive mass spectrometry-based assay. Concentrations and suppression below the lower limit of quantification (LLOQ) were compared between estrogens and between drugs.
RESULTS:
The ranges of baseline estrogen concentrations were <LLOQ-361 pg/mL for E2, <LLOQ-190 pg/mL for E1, and 8.3-4060 pg/mL for E1S. For E2, the frequency of suppression below the LLOQ was not statistically significantly different between AIs (exemestane: 89.0%, letrozole: 86.9%, p = 0.51). However, patients on letrozole were more likely to achieve suppression below the LLOQ of both E1 (exemestane: 80.1%, letrozole: 90.1%, p = 0.005) and E1S (exemestane: 17.4%, letrozole: 54.9%, p = 4.34e-15). After 3 months of AI therapy, the ranges of estrogen concentrations were <LLOQ-63.8 pg/mL, <LLOQ-36.7 pg/mL, and <LLOQ-1090 pg/mL for E2, E1, and E1S, respectively. During treatment, 16 patients had an increased concentration compared to the baseline concentration of at least one estrogen.
CONCLUSIONS:
Letrozole had greater suppression of plasma E1 and E1S than exemestane, though the response was highly variable among patients. Additional research is required to examine the clinical relevance of differential estrogen suppression
A Search for Very High-Energy Gamma Rays from the Missing Link Binary Pulsar J1023+0038 with VERITAS
The binary millisecond radio pulsar PSR J1023+0038 exhibits many
characteristics similar to the gamma-ray binary system PSR B1259--63/LS 2883,
making it an ideal candidate for the study of high-energy non-thermal emission.
It has been the subject of multi-wavelength campaigns following the
disappearance of the pulsed radio emission in 2013 June, which revealed the
appearance of an accretion disk around the neutron star. We present the results
of very high-energy gamma-ray observations carried out by VERITAS before and
after this change of state. Searches for steady and pulsed emission of both
data sets yield no significant gamma-ray signal above 100 GeV, and upper limits
are given for both a steady and pulsed gamma-ray flux. These upper limits are
used to constrain the magnetic field strength in the shock region of the PSR
J1023+0038 system. Assuming that very high-energy gamma rays are produced via
an inverse-Compton mechanism in the shock region, we constrain the shock
magnetic field to be greater than 2 G before the disappearance of the
radio pulsar and greater than 10 G afterwards.Comment: 7 pages, 3 figures, accepted for publication in Ap
Very-High-Energy -Ray Observations of the Blazar 1ES 2344+514 with VERITAS
We present very-high-energy -ray observations of the BL Lac object
1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array
System (VERITAS) between 2007 and 2015. 1ES 2344+514 is detected with a
statistical significance above background of in hours
(livetime) of observations, making this the most comprehensive very-high-energy
study of 1ES 2344+514 to date. Using these observations the temporal properties
of 1ES 2344+514 are studied on short and long times scales. We fit a constant
flux model to nightly- and seasonally-binned light curves and apply a
fractional variability test, to determine the stability of the source on
different timescales. We reject the constant-flux model for the 2007-2008 and
2014-2015 nightly-binned light curves and for the long-term seasonally-binned
light curve at the level. The spectra of the time-averaged emission
before and after correction for attenuation by the extragalactic background
light are obtained. The observed time-averaged spectrum above 200 GeV is
satisfactorily fitted () by a power-law function with
index and extends to at least 8
TeV. The extragalactic-background-light-deabsorbed spectrum is adequately fit
() by a power-law function with index while an F-test indicates that the power-law with
exponential cutoff function provides a marginally-better fit ( =
) at the 2.1 level. The source location is found to be
consistent with the published radio location and its spatial extent is
consistent with a point source.Comment: 7 pages, 2 figures. Published in Monthly Notices of the Royal
Astronomical Societ
Probing New Physics Models of Neutrinoless Double Beta Decay with SuperNEMO
The possibility to probe new physics scenarios of light Majorana neutrino
exchange and right-handed currents at the planned next generation neutrinoless
double beta decay experiment SuperNEMO is discussed. Its ability to study
different isotopes and track the outgoing electrons provides the means to
discriminate different underlying mechanisms for the neutrinoless double beta
decay by measuring the decay half-life and the electron angular and energy
distributions.Comment: 17 pages, 14 figures, to be published in E.P.J.
Single-molecule experiments in biological physics: methods and applications
I review single-molecule experiments (SME) in biological physics. Recent
technological developments have provided the tools to design and build
scientific instruments of high enough sensitivity and precision to manipulate
and visualize individual molecules and measure microscopic forces. Using SME it
is possible to: manipulate molecules one at a time and measure distributions
describing molecular properties; characterize the kinetics of biomolecular
reactions and; detect molecular intermediates. SME provide the additional
information about thermodynamics and kinetics of biomolecular processes. This
complements information obtained in traditional bulk assays. In SME it is also
possible to measure small energies and detect large Brownian deviations in
biomolecular reactions, thereby offering new methods and systems to scrutinize
the basic foundations of statistical mechanics. This review is written at a
very introductory level emphasizing the importance of SME to scientists
interested in knowing the common playground of ideas and the interdisciplinary
topics accessible by these techniques. The review discusses SME from an
experimental perspective, first exposing the most common experimental
methodologies and later presenting various molecular systems where such
techniques have been applied. I briefly discuss experimental techniques such as
atomic-force microscopy (AFM), laser optical tweezers (LOT), magnetic tweezers
(MT), biomembrane force probe (BFP) and single-molecule fluorescence (SMF). I
then present several applications of SME to the study of nucleic acids (DNA,
RNA and DNA condensation), proteins (protein-protein interactions, protein
folding and molecular motors). Finally, I discuss applications of SME to the
study of the nonequilibrium thermodynamics of small systems and the
experimental verification of fluctuation theorems. I conclude with a discussion
of open questions and future perspectives.Comment: Latex, 60 pages, 12 figures, Topical Review for J. Phys. C (Cond.
Matt
Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils
The development of BiPo detectors is dedicated to the measurement of
extremely high radiopurity in Tl and Bi for the SuperNEMO
double beta decay source foils. A modular prototype, called BiPo-1, with 0.8
of sensitive surface area, has been running in the Modane Underground
Laboratory since February, 2008. The goal of BiPo-1 is to measure the different
components of the background and in particular the surface radiopurity of the
plastic scintillators that make up the detector. The first phase of data
collection has been dedicated to the measurement of the radiopurity in
Tl. After more than one year of background measurement, a surface
activity of the scintillators of (Tl) 1.5
Bq/m is reported here. Given this level of background, a larger BiPo
detector having 12 m of active surface area, is able to qualify the
radiopurity of the SuperNEMO selenium double beta decay foils with the required
sensitivity of (Tl) 2 Bq/kg (90% C.L.) with a six
month measurement.Comment: 24 pages, submitted to N.I.M.
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