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Search Results: 1 - 10 of 306235 matches for " Christopher J. Graves "
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Transmission of a Gammabaculovirus within Cohorts of Balsam Fir Sawfly (Neodiprion abietis) Larvae
Roger Graves,Dan T. Quiring,Christopher J. Lucarotti
Insects , 2012, DOI: 10.3390/insects3040989
Abstract: Nucleopolyhedroviruses (NPV: Gammabaculovirus: Baculoviridae) of diprionid sawflies (Diprionidae: Hymenoptera) are highly host specific and only infect the midgut epithelium. While still alive, infected sawfly larvae excrete NPV-laden diarrhea that contaminates food sources. The diarrhea can then be consumed by conspecific larvae, resulting in rapid horizontal transmission of the virus. To better understand the efficacy of Gammabaculovirus-based biological control products, the horizontal spread of such a virus (NeabNPV) within cohorts of balsam fir sawfly ( Neodiprion abietis) larvae was studied by introducing NeabNPV-treated larvae into single-cohort groups at densities similar to those observed during the increasing (field study) and peak (laboratory study) phases of an outbreak. In field studies (~200 N. abietis larvae/m 2 of balsam fir ( Abies balsamea) foliage), NeabNPV-induced mortality increased positively in a density-dependent manner, from 23% (in control groups) to 51% with the addition of one first-instar NeabNPV-treated larva, to 84% with 10 first–instar-treated larvae. Mortality was 60% and 63% when one or 10 NeabNPV-treated third-instar larva(e), respectively, were introduced into groups. Slightly higher levels of NeabNPV-induced mortality occurring when NeabNPV-treated larvae were introduced into first- rather than third-instar cohorts suggests that early instars are more susceptible to the virus. In the laboratory (~1330 N. abietis larvae/ m 2 of foliage), NeabNPV-caused mortality increased from 20% in control groups to over 80% with the introduction of one, five or 10 NeabNPV-treated larvae into treatment groups of first-instar larvae.
Spread of a Gammabaculovirus within Larval Populations of Its Natural Balsam Fir Sawfly (Neodiprion abietis) Host Following Its Aerial Application
Roger Graves,Christopher J. Lucarotti,Dan T. Quiring
Insects , 2012, DOI: 10.3390/insects3040912
Abstract: Field trials and assessments of the balsam fir sawfly ( Neodiprion abietis) nucleopolyhedrovirus (NeabNPV: Baculoviridae, Gammabaculovirus) against its natural host were conducted in July and August 2002 near Corner Brook, Newfoundland and Labrador, Canada, in naturally regenerated, precommercially thinned stands dominated by balsam fir ( Abies balsamea). Two experimental blocks, each with its own untreated control, were established. The purpose of the Island Pond block was to examine the spread of NeabNPV from a 313-ha aerial treatment block out into adjacent populations of balsam fir sawflies. The purpose of the Old Man’s Pond block (2,093 ha) was to determine whether NeabNPV could disperse into populations of balsam fir sawflies within a 200-m zone between spray swaths. NeabNPV was applied to treatment blocks by a Cessna 188B AgTruck aircraft equipped with MicronAir AU4000 rotary atomizers at an application rate equivalent to 1 × 10 9 NeabNPV occlusion bodies/ha in 2.5 L of 20% aqueous molasses. At Island Pond, NeabNPV infection increased with time following the spray, especially for individuals close to the treatment block, and infection rate decreased to a measured distance of 400 m from the treatment block. At Old Man’s Pond, NeabNPV infection rose higher (80% vs. 15%) and sawfly densities declined more (84% vs. 60%) in the area between spray swaths than in the control block.
Natural Selection Promotes Antigenic Evolvability
Christopher J. Graves,Vera I. D. Ros,Brian Stevenson,Paul D. Sniegowski,Dustin Brisson
PLOS Pathogens , 2013, DOI: 10.1371/journal.ppat.1003766
Abstract: The hypothesis that evolvability - the capacity to evolve by natural selection - is itself the object of natural selection is highly intriguing but remains controversial due in large part to a paucity of direct experimental evidence. The antigenic variation mechanisms of microbial pathogens provide an experimentally tractable system to test whether natural selection has favored mechanisms that increase evolvability. Many antigenic variation systems consist of paralogous unexpressed ‘cassettes’ that recombine into an expression site to rapidly alter the expressed protein. Importantly, the magnitude of antigenic change is a function of the genetic diversity among the unexpressed cassettes. Thus, evidence that selection favors among-cassette diversity is direct evidence that natural selection promotes antigenic evolvability. We used the Lyme disease bacterium, Borrelia burgdorferi, as a model to test the prediction that natural selection favors amino acid diversity among unexpressed vls cassettes and thereby promotes evolvability in a primary surface antigen, VlsE. The hypothesis that diversity among vls cassettes is favored by natural selection was supported in each B. burgdorferi strain analyzed using both classical (dN/dS ratios) and Bayesian population genetic analyses of genetic sequence data. This hypothesis was also supported by the conservation of highly mutable tandem-repeat structures across B. burgdorferi strains despite a near complete absence of sequence conservation. Diversification among vls cassettes due to natural selection and mutable repeat structures promotes long-term antigenic evolvability of VlsE. These findings provide a direct demonstration that molecular mechanisms that enhance evolvability of surface antigens are an evolutionary adaptation. The molecular evolutionary processes identified here can serve as a model for the evolution of antigenic evolvability in many pathogens which utilize similar strategies to establish chronic infections.
Circulating Tumor Cells in Breast Cancer Patients: An Evolving Role in Patient Prognosis and Disease Progression
Holly Graves,Brian J. Czerniecki
Pathology Research International , 2011, DOI: 10.4061/2011/621090
Abstract: In this paper, we examine the role of circulating tumor cells (CTCs) in breast cancer. CTCs are tumor cells present in the peripheral blood. They are found in many different carcinomas but are not present in patients with benign disease. Recent advances in theories regarding metastasis support the role of early release of tumor cells in the neoplastic process. Furthermore, it has been found that phenotypic variation exists between the primary tumor and CTCs. Of particular interest is the incongruency found between primary tumor and CTC HER2 status in both metastatic and early breast cancer. Overall, CTCs have been shown to be a poor prognostic marker in metastatic breast cancer. CTCs in early breast cancer are not as well studied, however, several studies suggest that the presence of CTCs in early breast cancer may also suggest a poorer prognosis. Studies are currently underway looking at the use of CTC level monitoring in order to guide changes in therapy. 1. Introduction Breast cancer is one of the most common cancers affecting women. It is estimated that one in eight women will develop an invasive breast cancer at some point during her lifetime. In 2010, according to the American Cancer Society, approximately 207, 090 new cases of invasive breast cancer will be diagnosed and 39, 840 women will die from metastatic disease. In this era of molecular medicine, novel approaches are needed in the management of breast cancer. In the last several decades, circulating tumor cells (CTCs) have emerged as a unique target for understanding disease progression, prognosis, and treatment in breast cancer pathogenesis. CTCs are tumor cells present in the peripheral blood. They are found in many different carcinomas but are not present in patients with benign disease [1]. Much of the research involving CTCs stems from studies involving disseminated tumor cells (DTCs). DTCs are tumor cells present in the bone marrow. Briefly, several studies have shown that patients with DTCs at the time of diagnosis have larger tumors, higher histologic grade, and a higher incidence of lymph-node metastasis, distance metastasis, and cancer-related death versus those patients without DTCs [2, 3]. Furthermore, detection of DTCs after systemic treatment is associated with increased risk of recurrence and decreased disease-free survival as well as decreased breast cancer-specific survival [4, 5]. Though DTCs have been more thoroughly studied, there are several studies that have documented a correlation between the occurrence of DTCs and CTCs in both primary and metastatic breast cancer
Eye disorders in patients with multiple sclerosis: natural history and management
Jennifer Graves, Laura J Balcer
Clinical Ophthalmology , 2010, DOI: http://dx.doi.org/10.2147/OPTH.S6383
Abstract: isorders in patients with multiple sclerosis: natural history and management Review (5969) Total Article Views Authors: Jennifer Graves, Laura J Balcer Published Date December 2010 Volume 2010:4 Pages 1409 - 1422 DOI: http://dx.doi.org/10.2147/OPTH.S6383 Jennifer Graves, Laura J Balcer Department of Neurology, University of Pennsylvania, Philadelphia, PA, USA Abstract: Multiple sclerosis (MS) is a demyelinating disease of the central nervous system and leading cause of disability in young adults. Vision impairment is a common component of disability for this population of patients. Injury to the optic nerve, brainstem, and cerebellum leads to characteristic syndromes affecting both the afferent and efferent visual pathways. The objective of this review is to summarize the spectrum of eye disorders in patients with MS, their natural history, and current strategies for diagnosis and management. We emphasize the most common disorders including optic neuritis and internuclear ophthalmoparesis and include new techniques, such as optical coherence tomography, which promise to better our understanding of MS and its effects on the visual system.
A Correction to the Standard Galactic Reddening Map: Passive Galaxies as Standard Crayons
J. E. G. Peek,Genevieve J. Graves
Physics , 2010, DOI: 10.1088/0004-637X/719/1/415
Abstract: We present corrections to the Schlegel, Finkbeiner, Davis (SFD98) reddening maps over the Sloan Digital Sky Survey northern Galactic cap area. To find these corrections, we employ what we dub the "standard crayon" method, in which we use passively evolving galaxies as color standards by which to measure deviations from the reddening map. We select these passively evolving galaxies spectroscopically, using limits on the H alpha and O II equivalent widths to remove all star-forming galaxies from the SDSS main galaxy catalog. We find that by correcting for known reddening, redshift, color-magnitude relation, and variation of color with environmental density, we can reduce the scatter in color to below 3% in the bulk of the 151,637 galaxies we select. Using these galaxies we construct maps of the deviation from the SFD98 reddening map at 4.5 degree resolution, with 1-sigma error of ~ 1.5 millimagnitudes E(B-V). We find that the SFD98 maps are largely accurate with most of the map having deviations below 3 millimagnitudes E(B-V), though some regions do deviate from SFD98 by as much as 50%. The maximum deviation found is 45 millimagnitudes in E(B-V), and spatial structure of the deviation is strongly correlated with the observed dust temperature, such that SFD98 underpredicts reddening in regions of low dust temperature. Our maps of these deviations, as well as their errors, are made available to the scientific community as supplemental correction to SFD98 at http://www.peekandgraves2010.com.
Early-Type Galaxy Star Formation Histories in Different Environments
Patrick J. Fitzpatrick,Genevieve J. Graves
Physics , 2014, DOI: 10.1093/mnras/stu2509
Abstract: We use very high-S/N stacked spectra of $\sim$29,000 nearby quiescent early-type galaxies (ETGs) from the Sloan Digital Sky Survey (SDSS) to investigate variations in their star formation histories (SFHs) with environment at fixed position along and perpendicular to the Fundamental Plane (FP). We define three classifications of local group environment based on the `identities' of galaxies within their dark matter halos: central `Brightest Group Galaxies' (BGGs); Satellites; and Isolateds (those `most massive' in a dark matter halo with no Satellites). We find that the SFHs of quiescent ETGs are almost entirely determined by their structural parameters $\sigma$ and $\Delta I_e$. Any variation with local group environment at fixed structure is only slight: Satellites have the oldest stellar populations, 0.02 dex older than BGGs and 0.04 dex older than Isolateds; BGGs have the highest Fe-enrichments, 0.01 dex higher than Isolateds and 0.02 dex higher than Satellites; there are no differences in Mg-enhancement between BGGs, Isolateds, and Satellites. Our observation that, to zeroth-order, the SFHs of quiescent ETGs are fully captured by their structures places important qualitative constraints on the degree to which late-time evolutionary processes (those which occur after a galaxy's initial formation and main star-forming lifetime) can alter their SFHs/structures.
Marsupials and monotremes sort genome treasures from junk
Matthew J Wakefield, Jennifer AM Graves
Genome Biology , 2005, DOI: 10.1186/gb-2005-6-5-218
Abstract: Sequencing of a variety of mammalian and other vertebrate genomes is now proceeding apace, and one major goal of this work is to interpret the massive amounts of data from the Human Genome Project by aligning sequence and distinguishing conserved elements from the background of variable sequence ('phylogenetic footprinting'). Sequence data from mammals that are more or less closely related to humans (chimpanzee, mouse, dog) and more distantly related vertebrates (birds, fish) span 450 million years of evolution. But there is still an awkward gap, precisely in the region of the tree from which genomic data are most needed: species that are not so close that sequence comparison gives false-positive signals and not so far that the sequences are unalignable. Marsupials and monotremes, the earliest groups of mammals to diverge, fill this gap (Figure 1). All mammals produce milk and suckle their young, but marsupials and monotremes are distinguished from eutherian ('placental') mammals by differences in reproduction. Marsupials such as kangaroos and wallabies give birth to highly underdeveloped young and much of their development occurs while suckling in the pouch (including of the hindlimbs, eyes, gonads and a significant portion of the brain). Monotremes such as platypus lay eggs that are incubated in a burrow, where the young hatch and suckle from milk patches until they mature.In a recent landmark paper in Proceedings of the National Academy of Sciences USA, Margulies et al. [1] present the sequencing and comparative analysis of a 1.9 megabase (Mb) region from three marsupials (the North American opossum Didelphis virginiana, the Brazilian opossum Monodelphis domestica and the tammar wallaby Macropus eugenii) and a monotreme (the platypus Ornythorhynchus anatinus). Although previous studies [2] have clearly demonstrated the utility of marsupial sequences in comparative analysis, Margulies et al. [1] have analyzed a significantly larger region, looked at multiple marsu
Dissecting the Red Sequence - III. Mass-to-Light Variations in 3D Fundamental Plane Space
Genevieve J. Graves,S. M. Faber
Physics , 2010, DOI: 10.1088/0004-637X/717/2/803
Abstract: The Fundamental Plane has finite thickness and is tilted from the virial relation, indicating that dynamical mass-to-light ratios (Mdyn/L) vary among early type galaxies. We use a sample of 16,000 quiescent galaxies from the Sloan Digital Sky Survey to map out variations in Mdyn/L through the 3D Fundamental Plane space defined by velocity dispersion (sigma), effective radius (R_e), and effective surface brightness. We consider contributions to Mdyn/L variation due to stellar population effects, IMF variations, and variations in the dark matter fraction within one R_e. Along the FP, we find that the stellar population contribution scales as M*/L ~ f(sigma), while the dark matter and/or IMF contribution scales as Mdyn/M* ~ g(Mdyn). The two contributions to the tilt of the FP rotate the plane around different axes in the 3D space, with dark matter/IMF variations likely dominating. Through the thickness of the FP, we find that Mdyn/L variations must be dominated either by IMF variations or by real differences in dark matter fraction with R_e. Thus the finite thickness of the FP is due to variations in the stellar mass surface density within R_e, not the fading of passive stellar populations. These structural variations are correlated with galaxy star formation histories such that galaxies with higher Mdyn/M* at a given sigma have higher [Mg/Fe], lower metallicities, and older mean stellar ages. It is difficult to explain the observed correlations by allowing the IMF to vary, suggesting difference in dark matter fraction dominate. These can be produced by variations in the "conversion efficiency" of baryons into stars or by the redistribution of stars and dark matter through dissipational merging. A model in which some galaxies experience low conversion efficiencies due to premature truncation of star formation provides a natural explanation for the observed trends.
Oscillation Frequency Dependence of Non-Classical Rotation Inertia of Solid $^4$He
Y. Aoki,J. C. Graves,H. Kojima
Physics , 2007, DOI: 10.1103/PhysRevLett.99.015301
Abstract: The non-classical rotational inertia fraction of the identical cylindrical solid $^4$He below 300 mK is studied at 496 and 1173 Hz by a double resonance torsional oscillator. Below 35 mK, the fraction is the same at sufficiently low rim velocities. Above 35 mK, the fraction is greater for the higher than the lower mode. The dissipation peak of the lower mode occurs at a temperature $\sim$ 4 mK lower than that of the higher mode. The drive dependence of the two modes shows that the reduction of the fraction is characterized by critical velocity, \textit{not} amplitude nor acceleration.
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