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Search Results: 1 - 10 of 402202 matches for " Georgina M. Ellison "
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c-kitpos GATA-4 High Rat Cardiac Stem Cells Foster Adult Cardiomyocyte Survival through IGF-1 Paracrine Signalling
Nanako Kawaguchi,Andrew J. Smith,Cheryl D. Waring,Md Kamrul Hasan,Shinka Miyamoto,Rumiko Matsuoka,Georgina M. Ellison
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0014297
Abstract: Resident c-kit positive (c-kitpos) cardiac stem cells (CSCs) could be considered the most appropriate cell type for myocardial regeneration therapies. However, much is still unknown regarding their biological properties and potential.
Cardiosphere-Derived Cells Improve Function in the Infarcted Rat Heart for at Least 16 Weeks – an MRI Study
Carolyn A. Carr, Daniel J. Stuckey, Jun Jie Tan, Suat Cheng Tan, Renata S. M. Gomes, Patrizia Camelliti, Elisa Messina, Alessandro Giacomello, Georgina M. Ellison, Kieran Clarke
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0025669
Abstract: Aims Endogenous cardiac progenitor cells, expanded from explants via cardiosphere formation, present a promising cell source to prevent heart failure following myocardial infarction. Here we used cine-magnetic resonance imaging (MRI) to track administered cardiosphere-derived cells (CDCs) and to measure changes in cardiac function over four months in the infarcted rat heart. Methods and Results CDCs, cultured from neonatal rat heart, comprised a heterogeneous population including cells expressing the mesenchymal markers CD90 and CD105, the stem cell marker c-kit and the pluripotency markers Sox2, Oct3/4 and Klf-4. CDCs (2×106) expressing green fluorescent protein (GFP+) were labelled with fluorescent micron-sized particles of iron oxide (MPIO). Labelled cells were administered to the infarcted rat hearts (n = 7) by intramyocardial injection immediately following reperfusion, then by systemic infusion (4×106) 2 days later. A control group (n = 7) was administered cell medium. MR hypointensities caused by the MPIOs were detected at all times and GFP+ cells containing MPIO particles were identified in tissue slices at 16 weeks. At two days after infarction, cardiac function was similar between groups. By 6 weeks, ejection fractions in control hearts had significantly decreased (47±2%), but this was not evident in CDC-treated hearts (56±3%). The significantly higher ejection fractions in the CDC-treated group were maintained for a further 10 weeks. In addition, CDC-treated rat hearts had significantly increased capillary density in the peri-infarct region and lower infarct sizes. MPIO-labelled cells also expressed cardiac troponin I, von Willebrand factor and smooth muscle actin, suggesting their differentiation along the cardiomyocyte lineage and the formation of new blood vessels. Conclusions CDCs were retained in the infarcted rat heart for 16 weeks and improved cardiac function.
MicroRNA-1 Downregulation Increases Connexin 43 Displacement and Induces Ventricular Tachyarrhythmias in Rodent Hypertrophic Hearts
Antonio Curcio, Daniele Torella, Claudio Iaconetti, Eugenia Pasceri, Jolanda Sabatino, Sabato Sorrentino, Salvatore Giampà, Mariella Micieli, Alberto Polimeni, Beverley J. Henning, Angelo Leone, Daniele Catalucci, Georgina M. Ellison, Gianluigi Condorelli, Ciro Indolfi
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0070158
Abstract: Downregulation of the muscle-specific microRNA-1 (miR-1) mediates the induction of pathologic cardiac hypertrophy. Dysfunction of the gap junction protein connexin 43 (Cx43), an established miR-1 target, during cardiac hypertrophy leads to ventricular tachyarrhythmias (VT). However, it is still unknown whether miR-1 and Cx43 are interconnected in the pro-arrhythmic context of hypertrophy. Thus, in this study we investigated whether a reduction in the extent of cardiac hypertrophy could limit the pathological electrical remodeling of Cx43 and the onset of VT by modulating miR-1 levels. Wistar male rats underwent mechanical constriction of the ascending aorta to induce pathologic left ventricular hypertrophy (LVH) and afterwards were randomly assigned to receive 10mg/kg valsartan, VAL (LVH+VAL) delivered in the drinking water or placebo (LVH) for 12 weeks. Sham surgery was performed for control groups. Programmed ventricular stimulation reproducibly induced VT in LVH compared to LVH+VAL group. When compared to sham controls, rats from LVH group showed a significant decrease of miR-1 and an increase of Cx43 expression and its ERK1/2-dependent phosphorylation, which displaces Cx43 from the gap junction. Interestingly, VAL administration to rats with aortic banding significantly reduced cardiac hypertrophy and prevented miR-1 down-regulation and Cx43 up-regulation and phosphorylation. Gain- and loss-of-function experiments in neonatal cardiomyocytes (NCMs) in vitro confirmed that Cx43 is a direct target of miR-1. Accordingly, in vitro angiotensin II stimulation reduced miR-1 levels and increased Cx43 expression and phosphorylation compared to un-stimulated NCMs. Finally, in vivo miR-1 cardiac overexpression by an adenoviral vector intra-myocardial injection reduced Cx43 expression and phosphorylation in mice with isoproterenol-induced LVH. In conclusion, miR-1 regulates Cx43 expression and activity in hypertrophic cardiomyocytes in vitro and in vivo. Treatment of pressure overload-induced myocyte hypertrophy reduces the risk of life-threatening VT by normalizing miR-1 expression levels with the consequent stabilization of Cx43 expression and activity within the gap junction.
Experiments Are Revealing a Foundation Species: A Case Study of Eastern Hemlock (Tsuga canadensis)
Aaron M. Ellison
Advances in Ecology , 2014, DOI: 10.1155/2014/456904
Abstract: Foundation species are species that create and define particular ecosystems; control in large measure the distribution and abundance of associated flora and fauna; and modulate core ecosystem processes, such as energy flux and biogeochemical cycles. However, whether a particular species plays a foundational role in a system is not simply asserted. Rather, it is a hypothesis to be tested, and such tests are best done with large-scale, long-term manipulative experiments. The utility of such experiments is illustrated through a review of the Harvard Forest Hemlock Removal Experiment (HF-HeRE), a multidecadal, multihectare experiment designed to test the foundational role of eastern hemlock, Tsuga canadensis, in eastern North American forests. Experimental removal of T. canadensis has revealed that after 10 years, this species has pronounced, long-term effects on associated flora and fauna, but shorter-term effects on energy flux and nutrient cycles. We hypothesize that on century-long scales, slower changes in soil microbial associates will further alter ecosystem processes in T. canadensis stands. HF-HeRE may indeed continue for >100 years, but at such time scales, episodic disturbances and changes in regional climate and land cover can be expected to interact in novel ways with these forests and their foundation species.
The Limits to Sustainability Science: Ecological Constraints or Endless Innovation?
Georgina M. Mace
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1001343
Abstract:
The Limits to Sustainability Science: Ecological Constraints or Endless Innovation?
Georgina M. Mace
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.1001343
Abstract:
Food-Web Models Predict Species Abundances in Response to Habitat Change
Nicholas J. Gotelli,Aaron M. Ellison
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0040324
Abstract: Plant and animal population sizes inevitably change following habitat loss, but the mechanisms underlying these changes are poorly understood. We experimentally altered habitat volume and eliminated top trophic levels of the food web of invertebrates that inhabit rain-filled leaves of the carnivorous pitcher plant Sarracenia purpurea. Path models that incorporated food-web structure better predicted population sizes of food-web constituents than did simple keystone species models, models that included only autecological responses to habitat volume, or models including both food-web structure and habitat volume. These results provide the first experimental confirmation that trophic structure can determine species abundances in the face of habitat loss.
The relation between career anchors, occupational types and job satisfaction of midcareer employees
J. A. Ellison,A. M. G. Schreuder
South African Journal of Industrial Psychology , 2000, DOI: 10.4102/sajip.v26i2.700
Abstract: The objective of this research was to determine the value of the career anchor model in career decision-making. Career models that can provide the individual with greater self-insight can serve as an important guide when making career choices in todays turbulent working environment. Two hundred and ninety-five midcareer employees (managerial and non-managerial) completed questionnaires to determine their career anchor, occupation type and levels of general, intrinsic and extrinsic job satisfaction. The differences in job satisfaction between employees with a fit between career anchor and occupational type and those with no such fit were compared. It was found that respondents with a fit had a significantly higher level of general and intrinsic job satisfaction than those with no such fit. It is therefore suggested that the career anchor construct could probably serve as a useful tool for midcareer employees to make career choices. Opsomming Die doel van hierdie ondersoek was om die waarde van die loopbaanankermodel in loopbaanbesluitneming te bepaal. Loopbaanmodelle wat individue van groter insig kan voorsien kan as n belangrike riglyn in vandag se turbulente werksomgewing dien. Tweehonderd vyf-en-negentig middelloopbaan-werknemers (bestuur en nie-bestuur) het vraelyste voltooi om hulle loopbaanankers, beroepstipe en vlakke van algemene, intrinsieke en ekstrinsieke werkstevredenheid te bepaal. Die verskille in werkstevredenheid tussen werknemers met n passing tussen loopbaananker en beroepstipe en die sender n sodanige passing, is vergelyk. Daar is bevind dat respondente met n passing 'n beduidende hoer vlak van algemene en intrinsieke werkstevredenheid het as die sender so 'n passing. Daar word derhalwe voorgestel dat die loopbaanankermodel waarskynlik as n nuttige instrument by middelloopbaan-werknemers gebruik kan word om loopbaanbesluite te neem.
Food-Web Models Predict Species Abundances in Response to Habitat Change
Nicholas J Gotelli ,Aaron M Ellison
PLOS Biology , 2006, DOI: 10.1371/journal.pbio.0040324
Abstract: Plant and animal population sizes inevitably change following habitat loss, but the mechanisms underlying these changes are poorly understood. We experimentally altered habitat volume and eliminated top trophic levels of the food web of invertebrates that inhabit rain-filled leaves of the carnivorous pitcher plant Sarracenia purpurea. Path models that incorporated food-web structure better predicted population sizes of food-web constituents than did simple keystone species models, models that included only autecological responses to habitat volume, or models including both food-web structure and habitat volume. These results provide the first experimental confirmation that trophic structure can determine species abundances in the face of habitat loss.
The importance of household composition in epidemiological analyses of sleep: Evidence from the Understanding Society longitudinal panel survey  [PDF]
Helen Fowler, George T. H. Ellison, Eleanor M. Scott, Graham R. Law
Open Journal of Epidemiology (OJEpi) , 2014, DOI: 10.4236/ojepi.2014.41009
Abstract: Aims: To establish the relationship between household composition and sleep, we: 1) used latent class analysis (LCA) to classify households; 2) examined the reliability and stability of household composition classes over time; 3) conducted multinomial logistic regression analyses to determine the relationship between household class and the self-reported sleep duration and quality of adults. Methods: Data were sourced from Waves 1 and 2 of the United Kingdom “Understanding Society” (USoc) longitudinal panel survey. LCA was used to classify household composition as a categorical latent construct using data on the number and ages of household occupants and the number of rooms used for sleeping. The Bayesian Information Criterion assessed model fit and identified the optimum number of latent classes. Multi-nomial logistic regression was used to investigate cross-sectional relationships between the household classes and self-reported sleep duration and quality amongst adults, after adjustment for confounders. Results: Household composition was best defined by 7 latent classes in data from Wave 1 of USoc. This finding was confirmed in Wave 2. Compared to the reference class (households with no children and no overcrowding), there was a higher risk of short sleep (≤5 hours) versus 7-8 hours sleep for latent household composition classes that included children (RR: 1.56; 95% CI: 1.29-1.89) and for those with both children and overcrowding (RR: 1.57; 95% CI: 1.31-1.88). Similarly the risk of “very bad” versus “fairly good” quality sleep was significantly higher in those household classes with overcrowding, particularly those with extended (RR: 1.75; 95% CI: 1.34-2.29) and large (RR: 1.51; 95% CI: 1.21-1.87) households. Conclusion: These analyses of a recent, nationally representative cohort from the UK, demonstrated that latent household composition classes are reliable over time; and that these latent household composition classes are important correlates of self-reported sleep amongst adult occupants. We showed that household composition is an important contextual variable to consider in most epidemiological studies of sleep.
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