553 research outputs found
A Mutation in Amino Acid Permease AAP6 Reduces the Amino Acid Content of the Arabidopsis Sieve Elements but Leaves Aphid Herbivores Unaffected.
The aim of this study was to investigate the role of the amino acid permease gene AAP6 in regulating phloem amino
acid composition and then to determine the effects of this altered diet on aphid performance. A genotype of
Arabidopsis thaliana (L.) was produced in which the function of the amino acid permease gene AAP6 (At5g49630)
was abolished. Plants homozygous for the insertionally inactivated AAP6 gene had a significantly larger mean
rosette width than the wild type and a greater number of cauline leaves. Seeds from the aap6 mutant were also
significantly larger than those from the wild-type plants. Sieve element (SE) sap was collected by aphid stylectomy
and the amino acids derivatized, separated, and quantified using Capillary Electrophoresis with Laser Induced
Fluorescence (CE-LIF). In spite of the large variation across samples, the total amino acid concentration of SE sap of the aap6 mutant plants was significantly lower than that of the wild-type plants. The concentrations of lysine,
phenylalanine, leucine, and aspartic acid were all significantly lower in concentration in the aap6 mutant plants compared with wild-type plants. This is the first direct demonstration of a physiological role for an amino acid transporter in regulating SE composition in vivo. The amino acid availability in sieve element sap is thought to be the major limiting factor for aphid growth and reproduction. Despite the changes in their diet, the aphid Myzus persicae(Sulzer) displayed only small changes in feeding behaviour on mutant plants when measured using the Electronic Penetration Graph (EPG) technique. Salivation by the aphid into the SE (E1 phase) was increased on mutant plants but there was no significant effect on other feeding EPG behaviours, or in the rate of honeydew production.
Consistent with the small effect on aphid feeding behaviour, there was only a small effect of reduced sieve element amino acid concentration on aphid reproduction. The data are discussed in relation to the regulation of phloem
composition and the role of phloem amino acids in regulating aphid performance
Hadron Spectrum with Wilson fermions
We present results of a high statistics study of the quenched spectrum using
Wilson fermions at on lattices. We calculate the
masses of mesons and baryons composed of both degenerate and non-degenerate
quarks. Using non-degenerate quark combinations allows us to study baryon mass
splittings in detail. We find significant deviations from the lowest order
chiral expansion, deviations that are consistent with the expectations of
quenched chiral perturbation theory. We find that there is a
systematic error in the extracted value of , depending on the meson mass
ratio used to set its value. Using the largest estimate of we find that
the extrapolated octet mass-splittings are in agreement with the experimental
values, as is , while the decuplet splittings are 30% smaller
than experiment. Combining our results with data from the GF11 collaboration we
find considerable ambiguity in the extrapolation to the continuum limit. Our
preferred values are and , suggesting that the quenched approximation is good to only . We also analyze the discretization errors in heavy quark
masses.Comment: 52 pages. Tex. Modified "axis" source for figures also included.
Needs macro packages lanlmac and epsf. Uses hyperbasics if available.
Significant number of typographical errors correcte
Quenched chiral logarithms in lattice QCD with exact chiral symmetry
We examine quenched chiral logarithms in lattice QCD with overlap Dirac
quark. For 100 gauge configurations generated with the Wilson gauge action at on the lattice, we compute quenched quark
propagators for 12 bare quark masses. The pion decay constant is extracted from
the pion propagator, and from which the lattice spacing is determined to be
0.147 fm. The presence of quenched chiral logarithm in the pion mass is
confirmed, and its coefficient is determined to be , in agreement with the theoretical estimate in quenched chiral perturbation
theory. Further, we obtain the topological susceptibility of these 100 gauge
configurations by measuring the index of the overlap Dirac operator. Using a
formula due to exact chiral symmetry, we obtain the mass in quenched
chiral perturbation theory, Mev, and an estimate
of , which is in good agreement with that
determined from the pion mass.Comment: 24 pages, 6 EPS figures; v2: some clarifications added, to appear in
Physical Review
Extensive sequence-influenced DNA methylation polymorphism in the human genome
Background: Epigenetic polymorphisms are a potential source of human diversity, but their frequency and relationship to genetic polymorphisms are unclear. DNA methylation, an epigenetic mark that is a covalent modification of the DNA itself, plays an important role in the regulation of gene expression. Most studies of DNA methylation in mammalian cells have focused on CpG methylation present in CpG islands (areas of concentrated CpGs often found near promoters), but there are also interesting patterns of CpG methylation found outside of CpG islands. Results: We compared DNA methylation patterns on both alleles between many pairs (and larger groups) of related and unrelated individuals. Direct observation and simulation experiments revealed that around 10% of common single nucleotide polymorphisms (SNPs) reside in regions with differences in the propensity for local DNA methylation between the two alleles. We further showed that for the most common form of SNP, a polymorphism at a CpG dinucleotide, the presence of the CpG at the SNP positively affected local DNA methylation in cis. Conclusions: Taken together with the known effect of DNA methylation on mutation rate, our results suggest an interesting interdependence between genetics and epigenetics underlying diversity in the human genome
Antitumor activity and safety of the PARP inhibitor rucaparib in patients with high grade ovarian carcinoma and a germline or somatic BRCA1 or BRCA2 mutation: integrated analysis of data from Study 10 and ARIEL2
Objective:
An integrated analysis was undertaken to characterize the antitumor activity and safety profile of the oral poly(ADP-ribose) polymerase inhibitor rucaparib in patients with relapsed high-grade ovarian carcinoma (HGOC).
Methods:
Eligible patients from Study 10 (NCT01482715) and ARIEL2 (NCT01891344) who received a starting dose of oral rucaparib 600 mg twice daily (BID) with or without food were included in these analyses. The integrated efficacy population included patients with HGOC and a deleterious germline or somatic BRCA1 or BRCA2 (BRCA1/2) mutation who received at least two prior chemotherapies and were sensitive, resistant, or refractory to platinum-based chemotherapy. The primary endpoint was investigator-assessed confirmed objective response rate (ORR). Secondary endpoints included duration of response (DOR) and progression-free survival (PFS). The integrated safety population included patients with HGOC who received at least one dose of rucaparib 600 mg BID, irrespective of BRCA1/2 mutation status and prior treatments.
Results:
In the efficacy population (n = 106), ORR was 53.8% (95% confidence interval [CI], 43.8–63.5); 8.5% and 45.3% of patients achieved complete and partial responses, respectively. Median DOR was 9.2 months (95% CI, 6.6–11.6). In the safety population (n = 377), the most frequent treatment-emergent adverse events (AEs) were nausea, asthenia/fatigue, vomiting, and anemia/hemoglobin decreased. The most common grade ≥ 3 treatment-emergent AE was anemia/hemoglobin decreased. Treatment-emergent AEs led to treatment interruption, dose reduction, and treatment discontinuation in 58.6%, 45.9%, and 9.8% of patients, respectively. No treatment-related deaths occurred.
Conclusions:
Rucaparib has antitumor activity in advanced BRCA1/2-mutated HGOC and a manageable safety profile
Universal Scaling of the Chiral Condensate in Finite-Volume Gauge Theories
We confront exact analytical predictions for the finite-volume scaling of the
chiral condensate with data from quenched lattice gauge theory simulations.
Using staggered fermions in both the fundamental and adjoint representations,
and gauge groups SU(2) and SU(3), we are able to test simultaneously all of the
three chiral universality classes. With overlap fermions we also test the
predictions for gauge field sectors of non-zero topological charge. Excellent
agreement is found in most cases, and the deviations are understood in the
others.Comment: Expanded discussion of overlap fermion results. 17 pages revtex, 7
postscript figure
Low-lying fermion modes, topology and light hadrons in quenched QCD
We explore the properties of low lying eigenmodes of fermions in the quenched
approximation of lattice QCD. The fermion action is a recently proposed overlap
action and has exact chiral symmetry. We find that chiral zero-eigenvalue modes
are localized in space and their positions correlate strongly with the
locations (as defined through the density of pure gauge observables) of
instantons of the appropriate charge. Nonchiral modes are also localized with
peaks which are strongly correlated with the positions of both charges of
instantons. These correlations slowly die away as the fermion eigenvalue rises.
Correlators made of quark propagators restricted to these modes closely
reproduce ordinary hadron correlators at small quark mass in many channels. Our
results are in qualitative agreement with the expectations of instanton liquid
models.Comment: 21 pages, Revtex, 21 postscript figures. COLO-HEP-45
Failure to obtain adequate anaesthesia associated with a bifid mandibular canal: a case report
The document attached has been archived with permission from the Australian Dental Association. An external link to the publisher’s copy is included.The inferior alveolar nerve (IAN) block is the most common method for obtaining mandibular anaesthesia in dental practice but it is estimated to have a success rate of only 80 to 85 per cent. Causes of failure include problems with operator technique and anatomical variation between individuals. This case report involves a patient who received IAN blocks on two separate occasions that resulted in only partial anaesthesia of the ipsilateral side of the mandible. Radiographic assessment disclosed the presence of bifid mandibular canals that were present bilaterally and that may have affected the outcomes of the local anaesthetic procedures. Previous studies of bifid mandibular canals are reviewed and suggestions provided that should enable clinicians to differentially diagnose, and then manage, cases where IAN blocks result in inadequate mandibular anaesthesia.K Lew, G Townsen
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