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Search Results: 1 - 10 of 194859 matches for " Bruce D Whitaker "
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Characterization of a calcium/calmodulin-regulated SR/CAMTA gene family during tomato fruit development and ripening
Tianbao Yang, Hui Peng, Bruce D Whitaker, William S Conway
BMC Plant Biology , 2012, DOI: 10.1186/1471-2229-12-19
Abstract: Previous studies have shown that calcium/calmodulin-regulated SR/CAMTAs are important for modulation of disease resistance, cold sensitivity and wounding response in vegetative tissues. To study the possible roles of this gene family in fruit development and ripening, we cloned seven SR/CAMTAs, designated as SlSRs, from tomato, a model fruit-bearing crop. All seven genes encode polypeptides with a conserved DNA-binding domain and a calmodulin-binding site. Calmodulin specifically binds to the putative targeting site in a calcium-dependent manner. All SlSRs were highly yet differentially expressed during fruit development and ripening. Most notably, the expression of SlSR2 was scarcely detected at the mature green and breaker stages, two critical stages of fruit development and ripening; and SlSR3L and SlSR4 were expressed exclusively in fruit tissues. During the developmental span from 10 to 50 days post anthesis, the expression profiles of all seven SlSRs were dramatically altered in ripening mutant rin compared with wildtype fruit. By contrast, only minor alterations were noted for ripening mutant nor and Nr fruit. In addition, ethylene treatment of mature green wildtype fruit transiently stimulated expression of all SlSRs within one to two hours.This study indicates that SlSR expression is influenced by both the Rin-mediated developmental network and ethylene signaling. The results suggest that calcium signaling is involved in the regulation of fruit development and ripening through calcium/calmodulin/SlSR interactions.Fleshy fruits, a significant part of the human diet, provide fiber, minerals and various nutraceuticals, and promote human health. Fruit quality and postharvest shelf life are dependent upon the control of ripening. Fruit ripening is a complex, genetically programmed process. Classically, fruits are grouped into two ripening types, climacteric and non-climacteric. The ripening of climacteric fruits such as tomato and apple, usually is triggered by
Survival of Adult Songbirds in Boreal Forest Landscapes Fragmented by Clearcuts and Natural Openings
Darroch M. Whitaker,Philip D. Taylor,Ian G. Warkentin
Avian Conservation and Ecology , 2008,
Abstract: There exists little information on demographic responses of boreal songbirds to logging. We conducted a 4-yr (2003-2006) songbird mark-recapture study in western Newfoundland, where land cover is a naturally heterogeneous mosaic of productive spruce-fir forest, stunted taiga, and openings such as bogs, fens, and riparian zones. We compared apparent survival and rate of transience for adults of 14 species between areas having forests fragmented primarily by either natural openings or 3-7 yr-old clearcuts. Data were collected on three landscape pairs, with birds being marked on three 4-6 ha netting sites on each landscape (total = 18 netting sites). Survival rates were estimated using multi-strata mark-recapture models with landscape types specified as model strata. Landscape type was retained in the best model for only two species, Ruby-crowned Kinglet and Yellow-rumped Warbler, in both cases indicating lower apparent survival in landscapes having clearcuts. Though parameter estimates suggested lower survival in clearcut landscapes for several species, meta-analysis across all species detected no general difference between landscape types. Further, we did not detect any relation between landscape differences in survival and a species' habitat affinity, migratory strategy, or the proportion of transients in its population. Although sensitivity to logging was limited, we observed high interspecific variation in rates of breeding season apparent survival (48% [Dark-eyed Junco] to 100% [several species]), overwinter apparent survival (0.3% [Ruby-crowned Kinglet] to 86.5% [Gray Jay]), and transience (≈0% [several species] to 61% [Ruby-crowned Kinglet in clearcut landscapes]). For Lincoln's and White-throated Sparrows, over-winter apparent survival was >2× higher for males than females, and rate of transience was > 8× higher for White-throated Sparrow males than females. Moderately male-biased sex ratios suggested that both lower mortality and higher site fidelity contributed to higher apparent survival of males. Overall, variability in our estimates of survival was too great to be explained by mortality alone, suggesting a large influence of landscape-scale movement by adults, e.g., breeding dispersal, extra-territorial forays, and transience, on the dynamics of boreal songbird populations. These movement patterns may also confer resilience to localized disturbance in boreal landscapes.
Systematic review of the clinical effect of glucocorticoids on nonhematologic malignancy
Bruce D Keith
BMC Cancer , 2008, DOI: 10.1186/1471-2407-8-84
Abstract: A systematic review of clinical studies of glucocorticoid therapy in patients with nonhematologic malignancy was undertaken. Only studies having endpoints of tumor response or tumor control or survival were included. PubMed, EMBASE, the Cochrane Register/Databases, conference proceedings (ASCO, AACR, ASTRO/ASTR, ESMO, ECCO) and other resources were used. Data was extracted using a standard form. There was quality assessment of each study. There was a narrative synthesis of information, with presentation of results in tables. Where appropriate, meta-analyses were performed using data from published reports and a fixed effect model.Fifty four randomized controlled trials (RCTs), one meta-analysis, four phase l/ll trials and four case series met the eligibility criteria. Clinical trials of glucocorticoid monotherapy in breast and prostate cancer showed modest response rates. In advanced breast cancer meta-analyses, the addition of glucocorticoids to either chemotherapy or other endocrine therapy resulted in increased response rate, but not increased survival. In GI cancer, there was one RCT each of glucocorticoids vs. supportive care and chemotherapy +/- glucocorticoids; glucocorticoid effect was neutral. The only RCT found of chemotherapy +/- glucocorticoids, in which the glucocorticoid arm did worse, was in lung cancer. In glucocorticoid monotherapy, meta-analysis found that continuous high dose glucocorticoids had a detrimental effect on survival. The only other evidence, for a detrimental effect of glucocorticoid monotherapy, was in one of the two trials in lung cancer.Glucocorticoid monotherapy has some benefit in breast and prostate cancer. In advanced breast cancer, the addition of glucocorticoids to other therapy does not change the long term outcome. In GI cancer, glucocorticoids most likely have a neutral effect. High dose continuous glucocorticoids have a detrimental effect in nonhematologic malignancy. Glucocorticoid therapy might have a deleterious impact
Salmon, Science, and Reciprocity on the Northwest Coast
D. Bruce Johnsen
Ecology and Society , 2009,
Abstract: Severe depletion of many genetically distinct Pacific salmon populations has spawned a contentious debate over causation and the efficacy of proposed solutions. No doubt the precipitating factor was overharvesting of the commons beginning along the Northwest Coast around 1860. Yet, for millenia before that, a relatively dense population of Indian tribes managed salmon stocks that have since been characterized as “superabundant.” This study investigates how they avoided a tragedy of the commons, where in recent history, commercial ocean fishers guided by scientifically informed regulators, have repeatedly failed. Unlike commercial fishers, the tribes enjoyed exclusive rights to terminal fisheries enforced through rigorous reciprocity relations. The available evidence is compelling that they actively husbanded their salmon stocks for sustained abundance.
Using Short-Term Concentration Measures and Intelligence in Rehabilitation Settings
Bruce D. Kirkcaldy
The Scientific World Journal , 2006, DOI: 10.1100/tsw.2006.233
Abstract:
Within-district resource allocation and the marginal costs of providing equal educational opportunity: Evidence from Texas and Ohio.
Bruce D. Baker
Education Policy Analysis Archives , 2009,
Abstract: This study explores within-district fiscal resource allocation across elementary schools in Texas and Ohio large city school districts and in their surrounding metropolitan areas. Specifically, I ask whether districts widely reported as achieving greater resource equity through adoption of Weighted Student Funding (WSF) have in fact done so. I compare Houston Independent School District (a WSF district) to other large Texas cities and Cincinnati (also using WSF) to other large Ohio cities. Using a conventional expenditure function approach, I evaluate the sensitivity of elementary school budgets to special education populations, poverty rates, and school size. Next, I estimate two-stage least squares cost functions across schools to evaluate the relative costs of achieving average outcomes with respect to varied poverty rates within and across school districts within metropolitan areas. I use these estimates to evaluate whether urban core schools on average spend sufficient resources to compete with neighboring schools in other districts in the same Core Based Statistical Area. I find first that widely reported WSF success stories provide no more predictable funding with respect to student needs than other large urban districts in the same state. I also find that in some cases, resource levels in urban core elementary schools are relatively insufficient for competing with schools in neighboring districts to achieve comparable outcomes.
Resolvin D1 and Resolvin E1 Promote the Resolution of Allergic Airway Inflammation via Shared and Distinct Molecular Counter-Regulatory Pathways
Bruce D. Levy
Frontiers in Immunology , 2012, DOI: 10.3389/fimmu.2012.00390
Abstract: Resolvins are generated from omega-3 fatty acids during inflammatory responses in the lung. These natural mediators interact with specific receptors to decrease lung inflammation and promote its resolution in healthy tissues. There are several lung diseases of chronic inflammation that fail to resolve, most notable asthma. This common disorder has a lifetime prevalence of nearly 10% and is characterized, in part, by chronic, non-resolving inflammation of the airway. Pro-resolving mediators are generated during asthma; however, their biosynthesis is decreased in severe and uncontrolled asthma, suggesting that the chronic, adaptive inflammation in asthmatic airways may result from a resolution defect. This article focuses on recent insights into the cellular and molecular mechanisms for resolvins that limit adaptive immune responses in healthy airways.
Nonlinear polarisation and dissipative correspondence between low frequency fluid and gyrofluid equations
Bruce D. Scott
Physics , 2007, DOI: 10.1063/1.2783993
Abstract: The correspondence between gyrofluid and low frequency fluid equations is examined. The lowest order conservative effects in ExB advection, parallel dynamics, and curvature match trivially. The principal concerns are polarisation fluxes, and dissipative parallel viscosity and parallel heat fluxes. The emergence of the polarisation heat flux in the fluid model and its contribution to the energy theorem is reviewed. It is shown that gyroviscosity and the polarisation fluxes are matched by the finite gyroradius corrections to advection in the long wavelength limit, provided that the differences between gyrocenter and particle representations is taken into account. The dissipative parallel viscosity is matched by the residual thermal anisotropy in the gyrofluid model in the collision dominated limit. The dissipative parallel heat flux is matched by the gyrofluid parallel heat flux variables in the collision dominated limit. Hence, the gyrofluid equations are a complete superset of the low frequency fluid equations.
Derivation via free energy conservation constraints of gyrofluid equations with finite-gyroradius electromagnetic nonlinearities
Bruce D. Scott
Physics , 2007,
Abstract: The derivation of electromagnetic gyrofluid equations is made systematic by using the Hermite polynomial form of the underlying delta-f gyrokinetic distribution function. The gyrokinetic free-energy functional is explicitly used to set up the model. The gyrofluid free energy follows directly. The interaction term in the gyrokinetic Lagrangian is used to obtain the gyrofluid counterpart, from which the polarisation equation follows. One closure rule is decided for taking moments over the kinetic gyroaveraging operator. These steps fix the rest of the derivation of the conservative part of the gyrofluid equations. Dissipation is then added in a form to obtain positive definite dissipation and to obtain the collisional fluid equations in their appropriate limit. Existing results are recovered, with the addition of a completely consistent model for finite gyroradius effects in the nonlinearities responsible for magnetic reconnection.
Drift Wave versus Interchange Turbulence in Tokamak Geometry: Linear versus Nonlinear Mode Structure
Bruce D. Scott
Physics , 2002,
Abstract: The competition between drift wave and interchange physics in general E-cross-B drift turbulence is studied with computations in three dimensional tokamak flux tube geometry. For a given set of background scales, the parameter space can be covered by the plasma beta and drift wave collisionality. At large enough plasma beta the turbulence breaks out into ideal ballooning modes and saturates only by depleting the free energy in the background pressure gradient. At high collisionality it finds a more gradual transition to resistive ballooning. At moderate beta and collisionality it retains drift wave character, qualitatively identical to simple two dimensional slab models. The underlying cause is the nonlinear vorticity advection through which the self sustained drift wave turbulence supersedes the linear instabilities, scattering them apart before they can grow, imposing its own physical character on the dynamics. This vorticity advection catalyses the gradient drive, while saturation occurs solely through turbulent mixing of pressure disturbances. This situation persists in the whole of tokamak edge parameter space. Both simplified isothermal models and complete warm ion models are treated.
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