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Search Results: 1 - 10 of 402763 matches for " Sheila M. Walsh "
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Ecosystem-Scale Effects of Nutrients and Fishing on Coral Reefs
Sheila M. Walsh
Journal of Marine Biology , 2011, DOI: 10.1155/2011/187248
Abstract: Nutrient pollution and fishing are the primary local causes of coral reef decline but their ecosystem-scale effects are poorly understood. Results from small-scale manipulative experiments of herbivores and nutrients suggest prioritizing management of fishing over nutrient pollution because herbivores can control macroalgae and turf in the presence of nutrients. However, ecological theory suggests that the opposite occurs at large scales. Moreover, it is unclear whether fishing decreases herbivores because fishing of predators may result in an increase in herbivores. To investigate this paradox, data on the fish and benthic communities, fishing, and nutrients were collected on Kiritimati, Kiribati. Oceanographic conditions and a population resettlement program created a natural experiment to compare sites with different levels of fishing and nutrients. Contrary to theory, herbivores controlled macroalgae in the presence of nutrients at large spatial scales, and herbivores had greater effects on macroalgae when nutrients were higher. In addition, fishing did not increase herbivores. These results suggest that protecting herbivores may have greater relative benefits than reducing nutrient pollution, especially on polluted reefs. Reallocating fishing effort from herbivores to invertivores or planktivores may be one way to protect herbivores and indirectly maintain coral dominance on reefs impacted by fishing and nutrient pollution. 1. Introduction Fishing [1–7] and nutrient pollution [8, 9] or both [10–14] are cited as the most important local causes of coral reef decline. It is difficult, however, to evaluate local fishing and nutrient effects independently because these factors are almost always confounded and large-scale experiments are infeasible. Results from theoretical and small-scale experimental studies (typically <1?m2, four from 50 to 250?m2 [14]) suggest prioritizing management of herbivore populations because herbivores can control the effect of nutrients on macroalgal and turf abundance and nutrient enrichment alone is not sufficient to cause a phase shift from coral to macroalgal and/or turf algal dominance [11, 14, 15]. In order to apply these results and implement ecosystem-based management, information is needed on (1) how fishing and nutrients interactively affect the fish and benthic communities, (2) the mechanisms by which fishing (rather than cages that exclude fish) and nutrients are linked to shifts to macroalgal and turf algal dominance, and (3) whether herbivores can control macroalgae and turf algae when nutrient enrichment
Local Stressors Reduce Coral Resilience to Bleaching
Jessica E. Carilli, Richard D. Norris, Bryan A. Black, Sheila M. Walsh, Melanie McField
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006324
Abstract: Coral bleaching, during which corals lose their symbiotic dinoflagellates, typically corresponds with periods of intense heat stress, and appears to be increasing in frequency and geographic extent as the climate warms. A fundamental question in coral reef ecology is whether chronic local stress reduces coral resistance and resilience from episodic stress such as bleaching, or alternatively promotes acclimatization, potentially increasing resistance and resilience. Here we show that following a major bleaching event, Montastraea faveolata coral growth rates at sites with higher local anthropogenic stressors remained suppressed for at least 8 years, while coral growth rates at sites with lower stress recovered in 2–3 years. Instead of promoting acclimatization, our data indicate that background stress reduces coral fitness and resilience to episodic events. We also suggest that reducing chronic stress through local coral reef management efforts may increase coral resilience to global climate change.
Predator-Induced Demographic Shifts in Coral Reef Fish Assemblages
Benjamin I. Ruttenberg,Scott L. Hamilton,Sheila M. Walsh,Mary K. Donovan,Alan Friedlander,Edward DeMartini,Enric Sala,Stuart A. Sandin
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0021062
Abstract: In recent years, it has become apparent that human impacts have altered community structure in coastal and marine ecosystems worldwide. Of these, fishing is one of the most pervasive, and a growing body of work suggests that fishing can have strong effects on the ecology of target species, especially top predators. However, the effects of removing top predators on lower trophic groups of prey fishes are less clear, particularly in highly diverse and trophically complex coral reef ecosystems. We examined patterns of abundance, size structure, and age-based demography through surveys and collection-based studies of five fish species from a variety of trophic levels at Kiritimati and Palmyra, two nearby atolls in the Northern Line Islands. These islands have similar biogeography and oceanography, and yet Kiritimati has ~10,000 people with extensive local fishing while Palmyra is a US National Wildlife Refuge with no permanent human population, no fishing, and an intact predator fauna. Surveys indicated that top predators were relatively larger and more abundant at unfished Palmyra, while prey functional groups were relatively smaller but showed no clear trends in abundance as would be expected from classic trophic cascades. Through detailed analyses of focal species, we found that size and longevity of a top predator were lower at fished Kiritimati than at unfished Palmyra. Demographic patterns also shifted dramatically for 4 of 5 fish species in lower trophic groups, opposite in direction to the top predator, including decreases in average size and longevity at Palmyra relative to Kiritimati. Overall, these results suggest that fishing may alter community structure in complex and non-intuitive ways, and that indirect demographic effects should be considered more broadly in ecosystem-based management.
Expression of the Flp proteins by Haemophilus ducreyi is necessary for virulence in human volunteers
Diane M Janowicz, Sean A Cooney, Jessica Walsh, Beth Baker, Barry P Katz, Kate R Fortney, Beth W Zwickl, Sheila Ellinger, Robert S Munson
BMC Microbiology , 2011, DOI: 10.1186/1471-2180-11-208
Abstract: We constructed 35000HPΔflp1-3, a deletion mutant that lacks expression of all three Flp proteins but has an intact tad secretion system. 35000HPΔflp1-3 was impaired in its ability to form microcolonies and to attach to HFF in vitro when compared to its parent (35000HP). Complementation of the mutant with flp1-3 in trans restored the parental phenotype. To test whether expression of Flp1-3 was necessary for virulence in humans, ten healthy adult volunteers were experimentally infected with a fixed dose of 35000HP (ranging from 54 to 67 CFU) on one arm and three doses of 35000HPΔflp1-3 (ranging from 63 to 961 CFU) on the other arm. The overall papule formation rate for the parent was 80% (95% confidence interval, CI, 55.2%-99.9%) and for the mutant was 70.0% (95% CI, 50.5%-89.5%) (P = 0.52). Mutant papules were significantly smaller (mean, 11.2 mm2) than were parent papules (21.8 mm2) 24 h after inoculation (P = 0.018). The overall pustule formation rates were 46.7% (95% CI 23.7-69.7%) at 30 parent sites and 6.7% (95% CI, 0.1-19.1%) at 30 mutant sites (P = 0.001).These data suggest that production and secretion of the Flp proteins contributes to microcolony formation and attachment to HFF cells in vitro. Expression of flp1-3 is also necessary for H. ducreyi to initiate disease and progress to pustule formation in humans. Future studies will focus on how Flp proteins contribute to microcolony formation and attachment in vivo.The tad (tight adherence) locus is present in many Gram-positive and Gram-negative bacteria as well as the Archaea and likely represents an ancient subtype of type IV secretion systems that was horizontally transferred to many bacterial species early in the course of evolution. The tad genes are located on a mobile genomic island coined "the widespread colonization island" by Figurski and coworkers [1]. The functions of the tad locus gene products have been best described for Aggregatibacter (formerly Actinobacillus) actinomycetemcomitans, where th
The anti-inflammatory effects of levocetirizine - are they clinically relevant or just an interesting additional effect?
Garry M Walsh
Allergy, Asthma & Clinical Immunology , 2009, DOI: 10.1186/1710-1492-5-14
Abstract: The effects of histamine are exerted through three well defined classical G protein coupled histamine receptor subtypes termed H1R, H2R, and H3R [1] and the more recently described H4R [2]. Histamine signalling through H1R is responsible for the majority of the immediate manifestations of allergic disease. Levocetirizine (Xyzal?) is the single R-isomer of the racemic mixture piperazine H1R-antagonist cetirizine dihydrochloride in a once-daily 5mg formulation. The parent compound cetirizine (Zyrtec), a once-daily 10 mg formulation, is also an effective treatment for allergic disease being the most-widely used second-generation antihistamine worldwide. Levocetirizine is a selective, potent, oral histamine H1R antagonist that is licensed in Europe as tablets and oral solution for use in adults and children over 2 years of age for the symptomatic treatment of allergic rhinitis (including persistent allergic rhinitis) and chronic idiopathic urticaria. More recently, levocetirizine tablets under the trade name Xyzal have been approved by the Food and Drug Administration for use in adults and children over 6 years of age in the United States.Levocetirizine is a potent antihistamine as demonstrated by its ability to inhibit cutaneous histamine-induced itching and the wheal and flare reaction [3-5]. The histamine-induced wheal and flare model in human skin is a widely-used reproducible and standardized methodology that gives an objective measure of the effectiveness of antihistamines in human subjects, together with any differences in onset and duration of action. The majority of these studies found levocetirizine to be the most potent of the antihistamines tested [5], including the parent compound cetirizine [6]. Large, well designed controlled clinical trials have demonstrated the efficacy of levocetirizine in adults with allergic rhinitis and chronic idiopathic urticaria [7,8], while well conducted studies have demonstrated levocetirizine to be safe and effective in young
Introductory Editorial (Journal of Cell Death)
Garry M. Walsh
Journal of Cell Death , 2012,
Grand challenges in cell death and survival: apoptosis vs. necroptosis
Craig M. Walsh
Frontiers in Cell and Developmental Biology , 2014, DOI: 10.3389/fcell.2014.00003
Antagonism of cytokine-induced eosinophil accumulation in asthma
Garry M. Walsh
Frontiers in Pharmacology , 2012, DOI: 10.3389/fphar.2012.00197
Non-uniqueness in conformal formulations of the Einstein constraints
D. M. Walsh
Physics , 2006, DOI: 10.1088/0264-9381/24/8/002
Abstract: Standard methods in non-linear analysis are used to show that there exists a parabolic branching of solutions of the Lichnerowicz-York equation with an unscaled source. We also apply these methods to the extended conformal thin sandwich formulation and show that if the linearised system develops a kernel solution for sufficiently large initial data then we obtain parabolic solution curves for the conformal factor, lapse and shift identical to those found numerically by Pfeiffer and York. The implications of these results for constrained evolutions are discussed.
On the stability of solutions of the Lichnerowicz-York equation
Darragh M Walsh
Physics , 2012, DOI: 10.1088/0264-9381/30/6/065007
Abstract: We study the stability of solution branches for the Lichnerowicz-York equation at moment of time symmetry with constant unscaled energy density. We prove that the weak-field lower branch of solutions is stable whilst the upper branch of strong-field solutions is unstable. The existence of unstable solutions is interesting since a theorem by Sattinger proves that the sub-super solution monotone iteration method only gives stable solutions.
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