462 research outputs found
Consumption of submerged aquatic macrophytes by rudd (scardinius erythrophthalmus L.) in New Zealand
In experiments in New Zealand, rudd (Scardinius erythrophthalmus L.) of 108â277mm fork length (FL) ate a wide range of native and introduced submerged aquatic macrophytes in captivity and in the field. Rudd consumed the native charophytes Chara globularis Thuill., Chara fibrosa Ag. ex Bruz., and Nitella spp., the native macrophytes Potamogeton ochreatus Raoul. and Myriophyllum propinquum A. Cunn., and the introduced macrophytes Elodea canadensis Michx., Egeria densa Planch., Lagarosiphon major L., and Ceratophyllum demersum L. Rudd consistently consumed the Nitella spp. and Potamogeton ochreatus before Ceratophyllum demersum. From the results of experiments in tanks and in the field, we found the order of highest to lowest palatability was: Nitella spp. > Potamogeton ochreatus > Elodea canadensis> Chara globularis = Chara fibrosa> Egeria densa = Lagarosiphon major > Myriophyllum propinquum > Ceratophyllum demersum. The order of consumption was subject to some variation with season, especially for Egeria densa, Lagarosiphon major, and Myriophyllum propinquum. Rudd
consumed up to 20% of their body weight per day of Egeria densa in spring, and 22% of their body weight per day of Nitella spp. in summer. Consumption rates were considerably lower in winter than in summer. The results of our field trial suggested that the order of consumption also applies in the field and that rudd are having a profound impact on vulnerable native aquatic plant communities in New Zealand. Nitella spp. and Potamogeton ochreatus are likely to be selectively eaten, and herbivory by rudd might prevent the re-establishment of these species in
restoration efforts
Exploration of Drug Therapies for Post-Traumatic Elbow Joint Contracture
This semester I worked in the Musculoskeletal Soft Tissue Laboratory to explore the potential drug therapies for post-traumatic joint contracture (PTJC), or arthrofibrosis, in the elbow following a traumatic joint injury. To simulate the potential effects of these drugs in the elbow post-injury, this study utilized an in-vitro model using collagen gels and NIH-3T3 cells to mimick the contraction of capsule tissue in the elbow and the cells thought to contribute to disease progression in the capsule, namely fibroblasts and myofibroblasts. The first part of the study tested the effects of two drugs, losartan and simvastatin, on decreasing contraction. The standard testing procedure required that the gels be seeded with cells, then administered the appropriate drug concentration and mixture, and then observed for a period of six days. Once we narrowed down the drug formulations to a few possible candidates, we considered the issues related to timing of treatment and pharmacokinetics of these drugs if administered into the human elbow; more specifically, we wanted to understand how factors like drug clearance, or the treatment of PTJC after its onset, would affect the drugâs effectiveness. To this end, the second part of the study looked at how exposure time of the drug to the cells affected the drugâs function; more specifically, the impact of both time delay and a shorter exposure period on the performance of the drugs were explored. It quickly became apparent through these studies that simvastatin could halt contraction, but did nothing to reverse it. The third and final part of the study tested the ability of the hormone relaxing on decreasing contraction. By the end of the semester, we determined that,within the construct of our experimental set-up and parameters, simvastatin was the only promising candidate for treatment of PTJC
Design Thinking Accelerated Leadership: Transforming Self, Transforming Community
Higher education institutions are continually seeking to recruit nontraditional adult students yet struggle at the same time to meet their needs effectively. The following case study offers strategies to address this situation by documenting the pedagogical design and initial outcomes of an interdisciplinary, nineteen-month leadership-themed liberal studies undergraduate degree completion program at Grand Valley State University. As an innovative, accelerated, hybrid cohort model, it incorporates a wide range of high-impact practices focused on developing the skills leaders use and employers require. The curriculum integrates practices from motivational and experiential learning, community-based learning, and design thinking to scaffold students\u27 learning across their courses. The program thereby encourages students to wrestle with the complexity of social issues in their communities and develop the skills and virtues necessary for addressing those problems. As a case study, this article is particularly relevant for educators and administrators hoping to uncover a means for catalyzing innovative co-participatory engagement projects that engage with the needs of the surrounding community in a format supportive of nontraditional learners
Real-Time Maps of Fluid Flow Fields in Porous Biomaterials
Mechanical forces such as fluid shear have been shown to enhance cell growth
and differentiation, but knowledge of their mechanistic effect on cells is
limited because the local flow patterns and associated metrics are not
precisely known. Here we present real-time, noninvasive measures of local
hydrodynamics in 3D biomaterials based on nuclear magnetic resonance. Microflow
maps were further used to derive pressure, shear and fluid permeability fields.
Finally, remodeling of collagen gels in response to precise fluid flow
parameters was correlated with structural changes. It is anticipated that
accurate flow maps within 3D matrices will be a critical step towards
understanding cell behavior in response to controlled flow dynamics.Comment: 23 pages, 4 figure
Different mixed astrocyte populations derived from embryonic stem cells have variable neuronal growth support capacities
Using Videography to Quantify Landscape-Level Availability of Habitat for Grazers: An Example with Emperor Geese in Western Alaska
We present a videography approach to estimating large-scale availability of grazing lawns, an important food resource used by broods of emperor geese (Chen canagica) on the Yukon-Kuskokwim Delta, Alaska. Sampling was conducted in 1999, 2003, and 2004 at six locations that encompassed ~40% of the North American population of breeding emperor geese. We conducted ground truthing in 2003 and 2004 to estimate how accurately grazing lawn was classified. Overall, classification accuracy for grazing lawn and non-grazing lawn habitat was greater than 91%. Availability of grazing lawns was stable among years, but varied both among and within locations. Some locations have up to three times as much available grazing lawn, which in combination with densities of geese, likely represents dramatic variation in per capita food availability. Our results suggest that videography is a useful way to sample quickly across a large region and accurately identify fine-scale habitats. We present its use for estimating the availability of a preferred food resource for emperor geese, but the method could be applied to many other cases.Nous prĂ©sentons une mĂ©thode vidĂ©ographique pour Ă©valuer, Ă grande Ă©chelle, la disponibilitĂ© des pĂąturages, une importante ressource alimentaire pour les couvĂ©es dâoies empereurs (Chen canagica) du delta Yukon-Kuskokwim, en Alaska. Des Ă©chantillonnages ont Ă©tĂ© effectuĂ©s en 1999, 2003 et 2004 Ă six emplacements visant environ 40 % de la population nord-amĂ©ricaine dâoies empereurs nicheuses. Nous avons rĂ©alisĂ© des vĂ©rifications au sol en 2003 et en 2004 dans le but dâestimer dans quelle mesure les pĂąturages Ă©taient bien classĂ©s. Dans lâensemble, lâexactitude du classement des habitats destinĂ©s au pĂąturage et de ceux qui ne sont pas destinĂ©s au pĂąturage dĂ©passait les 91 %. La disponibilitĂ© des pĂąturages Ă©tait stable au fil des ans, mais variait dâun emplacement Ă lâautre et au sein de ceux-ci. Certains emplacements ont trois fois plus de pĂąturages disponibles que dâautres. Cela, alliĂ© aux densitĂ©s dâoies, reprĂ©sente vraisemblablement des Ă©carts remarquables pour ce qui est de la disponibilitĂ© de nourriture par tĂȘte. Nos rĂ©sultats laissent supposer que la vidĂ©ographie reprĂ©sente une bonne maniĂšre de faire des Ă©chantillonnages rapides dans de grandes rĂ©gions et de repĂ©rer avec prĂ©vision les habitats Ă petite Ă©chelle. Nous prĂ©sentons lâemploi de cette mĂ©thode pour Ă©valuer la disponibilitĂ© dâune source alimentaire prĂ©fĂ©rĂ©e de lâoie empereur, mĂ©thode qui pourrait ĂȘtre employĂ©e dans bien dâautres cas
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Weight gain among treatment-naĂŻve persons with HIV starting integrase inhibitors compared to non-nucleoside reverse transcriptase inhibitors or protease inhibitors in a large observational cohort in the United States and Canada.
IntroductionWeight gain following antiretroviral therapy (ART) initiation is common, potentially predisposing some persons with HIV (PWH) to cardio-metabolic disease. We assessed relationships between ART drug class and weight change among treatment-naĂŻve PWH initiating ART in the North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD).MethodsAdult, treatment-naĂŻve PWH in NA-ACCORD initiating integrase strand transfer inhibitor (INSTI), protease inhibitor (PI) or non-nucleoside reverse-transcriptase inhibitor (NNRTI)-based ART on/after 1 January 2007 were followed through 31 December 2016. Multivariate linear mixed effects models estimated weight up to five years after ART initiation, adjusting for age, sex, race, cohort site, HIV acquisition mode, treatment year, and baseline weight, plasma HIV-1 RNA level and CD4+ cell count. Due to shorter follow-up for PWH receiving newer INSTI drugs, weights for specific INSTIs were estimated at two years. Secondary analyses using logistic regression and all covariates from primary analyses assessed factors associated with >10% weight gain at two and five years.ResultsAmong 22,972 participants, 87% were male, and 41% were white. 49% started NNRTI-, 31% started PI- and 20% started INSTI-based regimens (1624 raltegravir (RAL), 2085 elvitegravir (EVG) and 929 dolutegravir (DTG)). PWH starting INSTI-based regimens had mean estimated five-year weight change of +5.9kg, compared to +3.7kg for NNRTI and +5.5kg for PI. Among PWH starting INSTI drugs, mean estimated two-year weight change was +7.2kg for DTG, +5.8kg for RAL and +4.1kg for EVG. Women, persons with lower baseline CD4+ cell counts, and those initiating INSTI-based regimens had higher odds of >10% body weight increase at two years (adjusted odds ratio = 1.37, 95% confidence interval: 1.20 to 1.56 vs. NNRTI).ConclusionsPWH initiating INSTI-based regimens gained, on average, more weight compared to NNRTI-based regimens. This phenomenon may reflect heterogeneous effects of ART agents on body weight regulation that require further exploration
Effects of impurity scattering on electron-phonon resonances in semiconductor superlattice high-field transport
A non-equilibrium Green's function method is applied to model high-field
quantum transport and electron-phonon resonances in semiconductor
superlattices. The field-dependent density of states for elastic (impurity)
scattering is found non-perturbatively in an approach which can be applied to
both high and low electric fields. I-V curves, and specifically electron-phonon
resonances, are calculated by treating the inelastic (LO phonon) scattering
perturbatively. Calculations show how strong impurity scattering suppresses the
electron-phonon resonance peaks in I-V curves, and their detailed sensitivity
to the size, strength and concentration of impurities.Comment: 7 figures, 1 tabl
Recon 2.2: from reconstruction to model of human metabolism.
IntroductionThe human genome-scale metabolic reconstruction details all known metabolic reactions occurring in humans, and thereby holds substantial promise for studying complex diseases and phenotypes. Capturing the whole human metabolic reconstruction is an on-going task and since the last community effort generated a consensus reconstruction, several updates have been developed.ObjectivesWe report a new consensus version, Recon 2.2, which integrates various alternative versions with significant additional updates. In addition to re-establishing a consensus reconstruction, further key objectives included providing more comprehensive annotation of metabolites and genes, ensuring full mass and charge balance in all reactions, and developing a model that correctly predicts ATP production on a range of carbon sources.MethodsRecon 2.2 has been developed through a combination of manual curation and automated error checking. Specific and significant manual updates include a respecification of fatty acid metabolism, oxidative phosphorylation and a coupling of the electron transport chain to ATP synthase activity. All metabolites have definitive chemical formulae and charges specified, and these are used to ensure full mass and charge reaction balancing through an automated linear programming approach. Additionally, improved integration with transcriptomics and proteomics data has been facilitated with the updated curation of relationships between genes, proteins and reactions.ResultsRecon 2.2 now represents the most predictive model of human metabolism to date as demonstrated here. Extensive manual curation has increased the reconstruction size to 5324 metabolites, 7785 reactions and 1675 associated genes, which now are mapped to a single standard. The focus upon mass and charge balancing of all reactions, along with better representation of energy generation, has produced a flux model that correctly predicts ATP yield on different carbon sources.ConclusionThrough these updates we have achieved the most complete and best annotated consensus human metabolic reconstruction available, thereby increasing the ability of this resource to provide novel insights into normal and disease states in human. The model is freely available from the Biomodels database (http://identifiers.org/biomodels.db/MODEL1603150001)
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