3,304 research outputs found
A powerful and efficient set test for genetic markers that handles confounders
Approaches for testing sets of variants, such as a set of rare or common
variants within a gene or pathway, for association with complex traits are
important. In particular, set tests allow for aggregation of weak signal within
a set, can capture interplay among variants, and reduce the burden of multiple
hypothesis testing. Until now, these approaches did not address confounding by
family relatedness and population structure, a problem that is becoming more
important as larger data sets are used to increase power.
Results: We introduce a new approach for set tests that handles confounders.
Our model is based on the linear mixed model and uses two random effects-one to
capture the set association signal and one to capture confounders. We also
introduce a computational speedup for two-random-effects models that makes this
approach feasible even for extremely large cohorts. Using this model with both
the likelihood ratio test and score test, we find that the former yields more
power while controlling type I error. Application of our approach to richly
structured GAW14 data demonstrates that our method successfully corrects for
population structure and family relatedness, while application of our method to
a 15,000 individual Crohn's disease case-control cohort demonstrates that it
additionally recovers genes not recoverable by univariate analysis.
Availability: A Python-based library implementing our approach is available
at http://mscompbio.codeplex.comComment: * denotes equal contribution
Isostructural Phase Transition of TiN Under High Pressure
In situ high-pressure energy dispersive x-ray diffraction experiments on
polycrystalline powder TiN with NaCl-type structure have been conducted with
the pressure up to 30.1 GPa by using the diamond anvil cell instrument with
synchrotron radiation at room tempearture. The experimental results suggested
that an isostructural phase transition might exist at about 7 GPa as revealed
by the discontinuity of V/V0 with pressure.Comment: submitte
Doppler Parameters in Renal Transplant Dysfunction
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135678/1/jum2011302169.pd
Single-layer graphene on silicon nitride micromembrane resonators
Due to their exceptional mechanical and optical properties, dielectric
silicon nitride (SiN) micromembrane resonators have become the centerpiece of
many optomechanical experiments. Efficient capacitive coupling of the membrane
to an electrical system would facilitate exciting hybrid optoelectromechanical
devices. However, capacitive coupling of such dielectric membranes is rather
weak. Here we add a single layer of graphene on SiN micromembranes and compare
electromechanical coupling and mechanical properties to bare dielectric
membranes and to membranes metallized with an aluminium layer. The
electrostatic coupling of graphene coated membranes is found to be equal to a
perfectly conductive membrane. Our results show that a single layer of graphene
substantially enhances the electromechanical capacitive coupling without
significantly adding mass, decreasing the superior mechanical quality factor or
affecting the optical properties of SiN micromembrane resonators
Acoustic detection of microbubble formation induced by enhanced optical breakdown of silver/dendrimer nanocomposites
We utilize a real-time acoustic technique, based on pulse-echo measurements to detect formation of microbubbles in an aqueous solution of a silver/dendrimer nanocomposite (DNC). Wave-field plots of successive recordings illustrate the generation and behavior of bubbles created by the optical breakdown process. A significant threshold reduction is achieved with DNC particles compared to its host dendrimer, enabling a diverse field of low-threshold breakdown applications. © 2003 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70570/2/APPLAB-82-6-994-1.pd
Dynamic expression of cytokine and transcription factor genes during experimental Fasciola gigantica infection in buffaloes
Background
Determining the mechanisms involved in the immune-pathogenesis of the tropical liver fluke, Fasciola gigantica, is crucial to the development of any effective therapeutic intervention. Here, we examined the differential gene expression of cytokines and transcription factors in the liver of F. gigantica-infected buffaloes, over the course of infection.
Methods
Water buffaloes (swamp type) were infected orally with 500 F. gigantica encysted metacercariae. Liver tissue samples were collected 3, 10, 28, 42, 70 and 98 days post-infection (dpi). Levels of gene expression of nine cytokines (IFN-γ, TGF-β, IL-1β, IL-4, IL-6, IL-10, IL-12B, IL-13 and IL-17A) and four transcription factors (T-bet, GATA-3, Foxp3 and ROR-γτ) were determined using quantitative real-time PCR (qRT-PCR). We evaluated any correlation between gene expression of these immune-regulatory factors and the severity of liver pathology.
Results
Histopathological examination revealed that cellular infiltration, hemorrhage and fibrosis without calcification in the liver parenchyma of infected buffaloes, increased over the course of infection. This progressive pathology was attributed to dysregulated and excessive inflammatory responses induced by infection. The early infection phase (3–10 dpi) was marked by a generalized immunosuppression and elevated TGF-β expression in order to facilitate parasite colonization. A mixed Th1/Th2 immune response was dominant from 28 to 70 dpi, to promote parasite survival while minimizing host tissue damage. During late infection (98 dpi), the response was biased towards Th1/Treg in order to inhibit the host’s Th2 protective response and promote chronic infection. Both IL-10 and IL-17A and the Th17/Treg balance, played key roles in mediating the inflammatory and immunoregulatory mechanisms in the liver during chronic fasciolosis.
Conclusions
Our data showed distinct CD4+ T helper (Th) polarization and cytokine dysregulation in response to F. gigantica infection in water buffaloes over the course of infection. Characterizing the temporal expression profiles for host immune genes during infection should provide important information for defining how F. gigantica adapts and survives in the liver of buffaloes and how host immune responses influence F. gigantica pathogenicity
Generation of cloned transgenic pigs rich in omega-3 fatty acids
Meat products are generally low in omega-3 (n-3) fatty acids, which are beneficial to human health. We describe the generation of cloned pigs that express a humanized Caenorhabditis elegans gene, fat-1, encoding an n-3 fatty acid desaturase. The hfat-1 transgenic pigs produce high levels of n-3 fatty acids from n-6 analogs, and their tissues have a significantly reduced ratio of n-6/n-3 fatty acids (P < 0.001). © 2006 Nature Publishing Group
Quantum Algebras Associated With Bell States
The antisymmetric solution of the braided Yang--Baxter equation called the
Bell matrix becomes interesting in quantum information theory because it can
generate all Bell states from product states. In this paper, we study the
quantum algebra through the FRT construction of the Bell matrix. In its four
dimensional representations via the coproduct of its two dimensional
representations, we find algebraic structures including a composition series
and a direct sum of its two dimensional representations to characterize this
quantum algebra. We also present the quantum algebra using the FRT construction
of Yang--Baxterization of the Bell matrix.Comment: v1: 15 pages, 2 figures, latex; v2: 18 pages, 2 figures, latex,
references and notes adde
The splicing factor SR2 is an important virulence factor of Toxoplasma gondii
Serine/arginine-rich (SR) proteins are key factors with important roles in constitutive and alternative splicing (AS) of pre-mRNAs. However, the role of SR splicing factors in the pathogenicity of T. gondii remains largely unexplored. Here, we investigated the role of splicing factor SR2, a homolog of Plasmodium falciparum SR1, in the pathogenicity of T. gondii. We functionally characterized the predicted SR2 in T. gondii by gene knockout and studied its subcellular localization by endogenous protein HA tagging using CRISPR-Cas9 gene editing. The results showed that SR2 was localized in the nucleus and expressed in the tachyzoite and bradyzoite stages. In vitro studies including plaque formation, invasion, intracellular replication, egress and bradyzoite differentiation assays showed that deletion of SR2 in type I RH strain and type II Pru strains had no significant effect on the parasite growth and bradyzoite differentiation (p > 0.05). Interestingly, the disruption of SR2 in RH type I (p < 0.0001) and Pru type II (p < 0.05) strains resulted in varying degrees of attenuated virulence. In addition, disruption of SR2 in type II Pru strain significantly reduced brain cyst burden by ~80% (p < 0.0001). Collectively, these results suggest that splicing factor SR2 is important for the pathogenicity of T. gondii, providing a new target for the control and treatment of toxoplasmosis
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