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Search Results: 1 - 10 of 169940 matches for " Amy E. Maas "
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Energetic Plasticity Underlies a Variable Response to Ocean Acidification in the Pteropod, Limacina helicina antarctica
Brad A. Seibel, Amy E. Maas, Heidi M. Dierssen
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0030464
Abstract: Ocean acidification, caused by elevated seawater carbon dioxide levels, may have a deleterious impact on energetic processes in animals. Here we show that high PCO2 can suppress metabolism, measured as oxygen consumption, in the pteropod, L. helicina forma antarctica, by ~20%. The rates measured at 180–380 μatm (MO2 = 1.25 M?0.25, p = 0.007) were significantly higher (ANCOVA, p = 0.004) than those measured at elevated target CO2 levels in 2007 (789–1000 μatm, = 0.78 M?0.32, p = 0.0008; Fig. 1). However, we further demonstrate metabolic plasticity in response to regional phytoplankton concentration and that the response to CO2 is dependent on the baseline level of metabolism. We hypothesize that reduced regional Chl a levels in 2008 suppressed metabolism and masked the effect of ocean acidification. This effect of food limitation was not, we postulate, merely a result of gut clearance and specific dynamic action, but rather represents a sustained metabolic response to regional conditions. Thus, pteropod populations may be compromised by climate change, both directly via CO2-induced metabolic suppression, and indirectly via quantitative and qualitative changes to the phytoplankton community. Without the context provided by long-term observations (four seasons) and a multi-faceted laboratory analysis of the parameters affecting energetics, the complex response of polar pteropods to ocean acidification may be masked or misinterpreted.
Reexamination of the Species Assignment of Diacavolinia Pteropods Using DNA Barcoding
Amy E. Maas, Leocadio Blanco-Bercial, Gareth L. Lawson
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0053889
Abstract: Thecosome pteropods (Mollusca, Gastropoda) are an ecologically important, diverse, and ubiquitous group of holoplanktonic animals that are the focus of intense research interest due to their external aragonite shell and vulnerability to ocean acidification. Characterizing the response of these animals to low pH and other environmental stressors has been hampered by continued uncertainty in their taxonomic identification. An example of this confusion in species assignment is found in the genus Diacavolinia. All members of this genus were originally indentified as a single species, Cavolinia longirostris, but over the past fifty years the taxonomy has been revisited multiple times; currently the genus comprises 22 different species. This study examines five species of Diacavolinia, including four sampled in the Northeast Atlantic (78 individuals) and one from the Eastern tropical North Pacific (15 individuals). Diacavolina were identified to species based on morphological characteristics according to the current taxonomy, photographed, and then used to determine the sequence of the “DNA barcoding” region of the cytochrome c oxidase subunit I (COI). Specimens from the Atlantic, despite distinct differences in shell morphology, showed polyphyly and a genetic divergence of <3% (K2P distance) whereas the Pacific and Atlantic samples were more distant (~19%). Comparisons of Diacavolinia spp. with other Cavolinia spp. reveal larger distances (~24%). These results indicate that specimens from the Atlantic comprise a single monophyletic species and suggest possible species-level divergence between Atlantic and Pacific populations. The findings support the maintenance of Diacavolinia as a separate genus, yet emphasize the inadequacy of our current taxonomic understanding of pteropods. They highlight the need for accurate species identifications to support estimates of biodiversity, range extent and natural exposure of these planktonic calcifiers to environmental variability; furthermore, the apparent variation of the pteropods shell may have implications for our understanding of the species’ sensitivity to ocean acidification.
Performance and Optimization of a Small Hybrid Solar-Thermal Collector  [PDF]
Amy Lebar, Heather E. Dillon
Smart Grid and Renewable Energy (SGRE) , 2018, DOI: 10.4236/sgre.2018.912016
Abstract: A hybrid solar collector was designed to investigate the effects of combining two different solar collector techniques on the overall collector’s effectiveness. While most solar collectors focus only on one solar collection method, the small hybrid system uses a flat plate collector in conjunction with five evacuated tubes to absorb the most energy possible from both direct and diffuse solar radiation. Data was collected over four months while the system operated at different flow rates and with various levels of available insolation from the sun to evaluate the performance of the solar collector. To understand the relative contribution of the flat plate collector and the evacuated tubes, temperature differences across each part of the system were measured. The results indicate the average first law efficiency of the hybrid system is 43.3%, significantly higher than the performance of the flat plate alone. An exergy analysis was performed for this system to assess the performance of the flat plate system by itself. Results of the second law analysis were comparable to the exergetic efficiencies of other experimental collectors, around 4%. Though the efficiencies were in the expected range, they reveal that further improvements to the system are possible.
Motivational Priming Predicts How Noxious Unconditioned Stimuli Influence Affective Reactions to Emotional Pictures  [PDF]
Amy E. Williams, Jamie L. Rhudy
Psychology (PSYCH) , 2012, DOI: 10.4236/psych.2012.310133
Abstract: Motivational priming theory (MPT) and preparedness theory generate competing hypotheses about the impact of an aversive US on responses to an affective foreground. MPT predicts the aversive US will facilitate negative emotional reactions to unpleasant pictures and inhibit positive emotional reactions to pleasant pictures. Preparedness theory predicts an aversive US will increase negative emotional reactions to unpleasant pictures, but will not impact responses to pleasant pictures. The present study (N = 125) compared these competing hypotheses by assessing how noxious shocks and non-noxious noises influence responses to emotional pictures. Following each picture, participants rated how the picture made them feel using the Self Assessment Manikin. Results supported MPT - noxious USs, but not non-noxious USs, facilitated negative emotional reactions to unpleasant pictures and inhibited positive emotional reactions to pleasant pictures.
Pink1 and parkin demonstrate multifaceted roles when co-expressed with Foxo  [PDF]
Amy M. Todd, Brian E. Staveley
Advances in Parkinson's Disease (APD) , 2013, DOI: 10.4236/apd.2013.21002
Abstract: Pink1 has been linked to both autosomal recessive and sporadic forms of Parkinson disease. The Pink1 protein is thought to be involved in mitochondrial protection by interacting with parkin to prevent oxidative damage, maintain mitochondrial integrity and regulate mitophagy. Pink1 and parkin have been linked to components of the insulin receptor (INR) pathway, including PTEN, Akt and Foxo, but their effects in the INR pathway have been largely overlooked. To further investigate the roles of Pink1/parkin, we have performed co-expression studies to determine the effects Pink1 and parkin on the Foxo-induced phenotype of developmental defects in the Drosophila eye. We examined directed expression of Pink1, parkin, Pink1 or parkin mutants, and Pink1 or parkin interfering RNAs (RNAi) with the overexpression of Foxo in the developing eye of Drosophila. Our findings show that reduction of Pink1 suppresses the effects of Foxo overexpression, where co-overexpression with Pink1 or parkin increases the severity of the phenotype. This suggests that Pink1 and parkin are able to increase the pro-apoptotic effects of Foxo. Contrary to the view that Pink1 and parkin act exclusively as protective proteins in the cell, it is likely that the Pink1/parkin pathway is involved in aspects of cell fate decisions other than degrading toxic proteins and maintaining mitochondrial integrity.
Pink1 Rescues Gal4-Induced Developmental Defects in the Drosophila Eye  [PDF]
Amy M. Todd, Brian E. Staveley
Advances in Parkinson's Disease (APD) , 2015, DOI: 10.4236/apd.2015.43006
Abstract: Parkinson disease pathology often includes the presence of ubiquitin-positive, α-synuclein-enriched inclusions in the remaining neurons. Pink1 (also identified as PARK6) encodes a serinethreonine kinase involved in mitochondrial protection that works with parkin to ubiquitinate various proteins, promoting mitophagy. The parkin protein works to tag cystolic proteins for degradation, and previous work in our laboratory has shown the ability of parkin to rescue a Gal4-induced phenotype. To further investigate the role of Pink1 in protection against toxic proteins, we have performed expression studies to determine the effects of increases and decreases in Pink1 on the Gal4-induced phenotype consisting of developmental defects in the Drosophila eye. Our results show that Pink1 is able to rescue the Gal4-induced phenotype, highlighting a protective role for Pink1 against toxic proteins. When expressing low levels of Gal4, reductions in Pink1 or parkin are not able to induce a phenotype. This suggests that Pink1 or parkin may counter Gal4 effects despite reductions, or that the effects of low level Gal4 may be alleviated by an alternative mechanism. Moreover, the Pink1 mechanism of action during differing types of cell stress, including degradation of toxic proteins, warrants further investigation.
Dimensions of Prym varieties
Amy E. Ksir
International Journal of Mathematics and Mathematical Sciences , 2001, DOI: 10.1155/s016117120101153x
Abstract: Given a tame Galois branched cover of curves π:X→Y with any finite Galois group G whose representations are rational, we compute the dimension of the (generalized) Prym variety Prymρ(X) corresponding to any irreducible representation ρ of G. This formula can be applied to the study of algebraic integrable systems using Lax pairs, in particular systems associated with Seiberg-Witten theory. However, the formula is much more general and its computation and proof are entirely algebraic.
A rational route to probing membrane proteins
Amy E Keating
Genome Biology , 2007, DOI: 10.1186/gb-2007-8-5-214
Abstract: Membrane proteins constitute around 20-30% of most proteomes. They carry out numerous critical functions and are significantly over-represented as drug targets compared with soluble proteins. However, membrane proteins present a host of practical challenges that have limited our understanding of their structure-function relationships. Methods that are standard for investigating the interactions among soluble proteins, such as phage display, yeast two-hybrid analysis, or any experiment that requires specific antibodies, are difficult or impossible to apply to transmembrane regions of membrane proteins. This makes it hard to probe the effects of specifically inhibiting or activating proteins that reside within the membrane. New reagents and approaches for deciphering membrane protein function could significantly advance our understanding.Given the difficulties of experimentally selecting probes specific for membrane proteins, the rational design of such molecules is appealing. In particular, computational protein design holds promise for providing micro-scale tools appropriate for manipulating the molecular world. Successes in designing protein sequences that adopt desired folds, specifically recognize small molecules or catalyze reactions have raised hopes that rational design may provide a route to useful reagents and therapeutics [1-7]. The obstacles that confront the field are significant, however. In particular, the challenge of designing proteins or peptides to bind tightly and specifically to native protein targets is largely unmet, although this is arguably one of the areas where the impact of protein design could be greatest. Two big problems confront protein engineers. One is the vast sequence/structure space in which possible solutions lie (the 'search problem'). The other is the physics of molecular recognition, which is complex and has proved difficult to capture in computational methods that are fast enough to use for design (the 'energy problem').There
Amy E. Gregory
International Journal of English Studies (IJES) , 2007, DOI: 10.6018/ijes.7.1.48861
Abstract: This study deals with the discourse function of the Spanish subjunctive mood. Traditional approaches focus on its semantics, invoking the notions of volition, doubt, negation, and emotion while maintaining the importance of the clause's subordinate status and change of subject from matrix verb to subordinate verb. Notwithstanding, thirty years of linguistic research on the Spanish mood contrast have given rise to the descriptors ± assertion: indicative is +assertive while subjunctive is -assertive. Although these descriptors are appropriate, viewing the subjunctive mood as a discourse cohesive device makes apparent the true nature of the mood contrast. Anaphoric, exophoric, and cataphoric features of languages refer to antecedents, elements of the physical context, or foreshadowed events/information, respectively. This article proposes a mechanism by which Spanish subjunctive clauses fulfill all three functions, circumscribing the Spanish mood contrast within the language's deictic system, and suggests avenues for future research.
Synergistic Action of Gentamicin and Bacteriophage in a Continuous Culture Population of Staphylococcus aureus
Amy E. Kirby
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0051017
Abstract: With the increasing frequency of antibiotic resistance and the decreasing frequency of new antibiotics entering the market, interest has returned to developing bacteriophage as a therapeutic agent. Acceptance of phage therapy, however, is limited by the unknown pharmacodynamics of a replicating agent, as well as the potential for the evolution of resistant bacteria. One way to overcome some of these limitations is to incorporate phage and antibiotics into a dual therapy regimen; however, this increases the complexity of the pharmacodynamics. The aim of this study is to develop an experimental system to evaluate the pharmacodynamics of dual phage-drug therapy. A continuous culture system for Staphylococcus aureus is used to simulate the pharmacokinetics of periodic antibiotic dosing alone and in combination with lytic phage. A computer model representation of the system allows further evaluation of the conditions governing the observed pharmacodynamics. The results of this experimental/modeling approach suggest that dual therapy can be more efficacious than single therapies, particularly if there is an overlap in the physiological pathways targeted by the individual agents. In this case, treatment with gentamicin induces a population of cells with a strong aggregation phenotype. These aggregators also have an increased ability to form biofilm, which is a well-known, non-genetic mechanism of drug resistance. However, the aggregators are also more susceptible than the parental strain to the action of the phage. Thus, dual treatment with gentamicin and phage resulted in lower final cell densities than either treatment alone. Unlike in the phage-only treatment, phage-resistant isolates were not detected in the dual treatment.
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