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Search Results: 1 - 10 of 229524 matches for " Mark L Wilson "
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Isomorphism in expanding families of indistinguishable groups
Mark L. Lewis,James B. Wilson
Mathematics , 2010, DOI: 10.1515/gcc-2012-0008
Abstract: For every odd prime $p$ and every integer $n\geq 12$ there is a Heisenberg group of order $p^{5n/4+O(1)}$ that has $p^{n^2/24+O(n)}$ pairwise nonisomorphic quotients of order $p^{n}$. Yet, these quotients are virtually indistinguishable. They have isomorphic character tables, every conjugacy class of a non-central element has the same size, and every element has order at most $p$. They are also directly and centrally indecomposable and of the same indecomposability type. The recognized portions of their automorphism groups are isomorphic, represented isomorphically on their abelianizations, and of small index in their full automorphism groups. Nevertheless, there is a polynomial-time algorithm to test for isomorphisms between these groups.
Allostery without conformation change: modelling protein dynamics at multiple scales
Tom C B McLeish,Thomas L Rogers,Mark R Wilson
Quantitative Biology , 2013, DOI: 10.1088/1478-3975/10/5/056004
Abstract: The original ideas of Cooper and Dryden, that allosteric signalling can be induced between distant binding sites on proteins without any change in mean structural conformation, has proved to be a remarkably prescient insight into the rich structure of protein dynamics. It represents an alternative to the celebrated Monod-Wyman-Changeux mechanism and proposes that modulation of the amplitude of thermal fluctuations around a mean structure, rather than shifts in the structure itself, give rise to allostery in ligand binding. In a complementary approach to experiments on real proteins, here we take a theoretical route to identify the necessary structural components of this mechanism. By reviewing and extending an approach that moves from very coarse-grained to more detailed models, we show that, a fundamental requirement for a body supporting fluctuation-induced allostery is a strongly inhomogeneous elastic modulus. This requirement is reflected in many real proteins, where a good approximation of the elastic structure maps strongly coherent domains onto rigid blocks connected by more flexible interface regions.
Molecular Signals and Skeletal Muscle Adaptation to Exercise
Mark Wilson
International Journal of Applied Exercise Physiology , 2013,
Abstract: The phenotypic plasticity of skeletal muscle affords a considerable degree of adaptability not seen in other bodily tissues. The mechanical properties of skeletal muscle are highly dependent on loading conditions. The extent of skeletal muscle plasticity is distinctly highlighted by a loss of muscle mass, or atrophy, after a period of reduced weight-bearing activity, for example during periods of extended bed rest, space flight and in spinal cord injury. On the other hand, increased mechanical loading, or resistance training, induces muscle growth, or hypertrophy. Endurance exercise performance is also dependent on the adaptability of skeletal muscle, especially muscles that contribute to posture, locomotion and the mechanics of breathing. However, the molecular pathways governing skeletal muscle adaptations are yet to be satisfactorily delineated and require further investigation. Researchers in the areas of exercise physiology, physiotherapy and sports medicine are endeavoring to translate experimental knowledge into effective, innovative treatments and regimens in order to improve physical performance and health in both elite athletes and the general community. The efficacy of the translation of molecular biological paradigms in experimental exercise physiology has long been underappreciated. Indeed, molecular biology tools can now be used to answer questions regarding skeletal muscle adaptation in response to exercise and provide new frameworks to improve physical performance. Furthermore, transgenic animal models, knockout animal models and in vivo studies provide tools to test questions concerned with how exercise initiates adaptive changes in gene expression. In light of these perceived deficiencies, an attempt is made here to elucidate the molecular mechanisms of skeletal muscle adaptation to exercise. An examination will be made of the functional capacity of skeletal muscle to respond to a variety of exercise conditions, namely endurance and resistance exercise training. Through the critical evaluation of relevant scientific literature, it is hoped that an overview of the current status of this important area of exercise physiology is achieved.
Assembly of the Complex between Archaeal RNase P Proteins RPP30 and Pop5
Brandon L. Crowe,Christopher J. Bohlen,Ross C. Wilson,Venkat Gopalan,Mark P. Foster
Archaea , 2011, DOI: 10.1155/2011/891531
Abstract: RNase P is a highly conserved ribonucleoprotein enzyme that represents a model complex for understanding macromolecular RNA-protein interactions. Archaeal RNase P consists of one RNA and up to five proteins (Pop5, RPP30, RPP21, RPP29, and RPP38/L7Ae). Four of these proteins function in pairs (Pop5-RPP30 and RPP21–RPP29). We have used nuclear magnetic resonance (NMR) spectroscopy and isothermal titration calorimetry (ITC) to characterize the interaction between Pop5 and RPP30 from the hyperthermophilic archaeon Pyrococcus furiosus (Pfu). NMR backbone resonance assignments of free RPP30 (25 kDa) indicate that the protein is well structured in solution, with a secondary structure matching that observed in a closely related crystal structure. Chemical shift perturbations upon the addition of Pop5 (14 kDa) reveal its binding surface on RPP30. ITC experiments confirm a net 1 : 1 stoichiometry for this tight protein-protein interaction and exhibit complex isotherms, indicative of higher-order binding. Indeed, light scattering and size exclusion chromatography data reveal the complex to exist as a 78 kDa heterotetramer with two copies each of Pop5 and RPP30. These results will inform future efforts to elucidate the functional role of the Pop5-RPP30 complex in RNase P assembly and catalysis.
Social Exclusion Modifies Climate and Deforestation Impacts on a Vector-Borne Disease
Luis Fernando Chaves ,Justin M. Cohen,Mercedes Pascual,Mark L. Wilson
PLOS Neglected Tropical Diseases , 2008, DOI: 10.1371/journal.pntd.0000176
Abstract: Background The emergence of American Cutaneous Leishmaniasis (ACL) has been associated with changes in the relationship between people and forests, leading to the view that forest ecosystems increase infection risk and subsequent proposal that deforestation could reduce re-emergence of this disease. Methodology/Principal Findings We analyzed county-level incidence rates of ACL in Costa Rica (1996–2000) as a function of social and environmental variables relevant to transmission ecology with statistical models that incorporate breakpoints. Once social marginality was taken into account, the effect of living close to a forest on infection risk was small, and diminished exponentially above a breakpoint. Forest cover was associated with the modulation of temporal effects of El Ni?o Southern Oscillation (ENSO) at small spatial scales, revealing an additional complex interplay of environmental forces and disease patterns. Conclusions/Significance Social factors, which previously have not been evaluated rigorously together with environmental and climatic factors, appear to play a critical role that may ultimately determine disease risk.
Early Interferon-γ Production in Human Lymphocyte Subsets in Response to Nontyphoidal Salmonella Demonstrates Inherent Capacity in Innate Cells
Tonney S. Nyirenda,Anna E. Seeley,Wilson L. Mandala,Mark T. Drayson,Calman A. MacLennan
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013667
Abstract: Nontyphoidal Salmonellae frequently cause life-threatening bacteremia in sub-Saharan Africa. Young children and HIV-infected adults are particularly susceptible. High case-fatality rates and increasing antibiotic resistance require new approaches to the management of this disease. Impaired cellular immunity caused by defects in the T helper 1 pathway lead to intracellular disease with Salmonella that can be countered by IFNγ administration. This report identifies the lymphocyte subsets that produce IFNγ early in Salmonella infection.
A Plant DJ-1 Homolog Is Essential for Arabidopsis thaliana Chloroplast Development
Jiusheng Lin, Tara J. Nazarenus, Jeanine L. Frey, Xinwen Liang, Mark A. Wilson, Julie M. Stone
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0023731
Abstract: Protein superfamilies can exhibit considerable diversification of function among their members in various organisms. The DJ-1 superfamily is composed of proteins that are principally involved in stress response and are widely distributed in all kingdoms of life. The model flowering plant Arabidopsis thaliana contains three close homologs of animal DJ-1, all of which are tandem duplications of the DJ-1 domain. Consequently, the plant DJ-1 homologs are likely pseudo-dimeric proteins composed of a single polypeptide chain. We report that one A. thaliana DJ-1 homolog (AtDJ1C) is the first DJ-1 homolog in any organism that is required for viability. Homozygous disruption of the AtDJ1C gene results in non-viable, albino seedlings that can be complemented by expression of wild-type or epitope-tagged AtDJ1C. The plastids from these dj1c plants lack thylakoid membranes and granal stacks, indicating that AtDJ1C is required for proper chloroplast development. AtDJ1C is expressed early in leaf development when chloroplasts mature, but is downregulated in older tissue, consistent with a proposed role in plastid development. In addition to its plant-specific function, AtDJ1C is an atypical member of the DJ-1 superfamily that lacks a conserved cysteine residue that is required for the functions of most other superfamily members. The essential role for AtDJ1C in chloroplast maturation expands the known functional diversity of the DJ-1 superfamily and provides the first evidence of a role for specialized DJ-1-like proteins in eukaryotic development.
Family leadership styles and adolescent dietary and physical activity behaviors: a cross-sectional study
Katie L Morton, Alexandra H Wilson, Lisa S Perlmutter, Mark R Beauchamp
International Journal of Behavioral Nutrition and Physical Activity , 2012, DOI: 10.1186/1479-5868-9-48
Abstract: 857 adolescents (aged 13–15, mean age?=?14.70 yrs) completed measures of transformational parenting behaviors, healthful dietary intake and leisure-time physical activity. Regression analyses were conducted to examine relationships between family transformational leadership and adolescent health outcomes. A further ‘extreme group analysis’ was conducted by clustering families based on quartile splits. A MANCOVA (controlling for child gender) was conducted to examine differences between families displaying (a) HIGH levels of transformational parenting (consistent HIGH TP), (b) LOW levels of transformational parenting (consistent LOW TP), and (c) inconsistent levels of transformational parenting (inconsistent HIGH-LOW TP).Results revealed that adolescents’ perceptions of family transformational parenting were associated with both healthy dietary intake and physical activity. Adolescents who perceived their families to display the highest levels of transformational parenting (HIGH TP group) displayed greater healthy eating and physical activity behaviors than adolescents who perceived their families to display the lowest levels of transformational parenting behaviors (LOW TP group). Adolescents who perceived their families to display inconsistent levels of transformational parenting behaviors (HIGH-LOW TP group) displayed the same levels of healthy eating behaviors as those adolescents from the LOW TP group. For physical activity behaviors, adolescents who perceived their families to display inconsistent levels of transformational parenting behaviors (HIGH-LOW TP group) did not differ in terms of physical activity than those in either the HIGH TP or LOW TP group.Family transformational parenting behaviors were positively associated with both healthful dietary intake and leisure-time physical activity levels amongst adolescents. The findings suggest that transformational leadership theory is a useful framework for understanding the relationship between family leadership
Distance to health services influences insecticide-treated net possession and use among six to 59 month-old children in Malawi
Peter S Larson, Don P Mathanga, Carl H Campbell, Mark L Wilson
Malaria Journal , 2012, DOI: 10.1186/1475-2875-11-18
Abstract: A household malaria survey undertaken in eight districts of Malawi during 2007 was used to characterize ITN possession and use. The location of each respondent's household was geocoded as was those of Ministry of Health (MoH) HFs and other health centres. Euclidean distance from each household to the nearest HF was calculated. Patterns of net possession and use were determined through descriptive methods. The authors then analysed the significance of distance and ITN possession/use through standard statistical tests, including logistic regression.Median distance to HFs was greater among households that did not possess ITNs and did not use an ITN the previous evening. Descriptive statistical methods confirmed a pattern of decreasing ITN possession and use with increasing distance from HFs. Logistic regression showed the same statistically significant association of distance to HFs, even when controlling for age and gender of the child, ratio of nets to children in household, community net possession and use, and household material wealth.Strategies that exclusively distribute ITNs through HFs are likely to be less effective in increasing possession and use in communities that are more distant from those health services. Health providers should look towards community-based distribution services that take ITNs directly to community members to more effectively scale up ITN possession and regular use aimed at protecting children from malaria.Insecticide-treated mosquito nets (ITNs) have reduced all-cause childhood deaths by 15-20% according to diverse research evidence [1-7]. ITN programme evaluations have also demonstrated substantial impacts against malaria [8-10]. Greater coverage has produced enhanced reduction in malaria morbidity and mortality, even more so among those within a close proximity of households with treated nets [11]. Given these benefits, as well as the low cost, safety and ease of ITN implementation, national malaria programmes are now scaling up ITN
Malaria hotspot areas in a highland Kenya site are consistent in epidemic and non-epidemic years and are associated with ecological factors
Kacey C Ernst, Samson O Adoka, Dickens O Kowuor, Mark L Wilson, Chandy C John
Malaria Journal , 2006, DOI: 10.1186/1475-2875-5-78
Abstract: To address this issue, spatial distribution of malaria incidence and the relationship of ecological factors to malaria incidence were assessed in the highland area of Kipsamoite, Kenya, from 2001–2004.Clustering of disease in a single geographic "hotspot" area occurred in epidemic and non-epidemic years, with a 2.6 to 3.2-fold increased risk of malaria inside the hotspot, as compared to outside the area (P < 0.001, all 4 years). Altitude and proximity to the forest were independently associated with increased malaria risk in all years, including epidemic and non-epidemic years.In this highland area, areas of high malaria risk are consistent in epidemic and non-epidemic years and are associated with specific ecological risk factors. Ongoing interventions in areas of ecological risk factors could be a cost-effective method of significantly reducing malaria incidence and blunting or preventing epidemics, even in the absence of malaria early warning systems. Further studies should be conducted to see if these findings hold true in varied highland settings.It has been estimated that 34 million individuals in highland areas of East Africa are at risk for malaria [1] and malaria in these highland areas has been responsible for numerous deaths [2]. However, the levels of variation in malaria risk within these highland areas are not well described and only a few studies have investigated risk factors for malaria there [3-5]. Previous studies have demonstrated that malaria cases aggregate from the household to the countrywide level [3,6,7]. The determinants of such clustering are likely due to shared anthropogenic and environmental variables, as well as factors related to contagion such as population density and human interactions [8,9]. Brooker et al demonstrated that there was spatial clustering of malaria cases in children during an epidemic in a single year in highland area of Kenya [3]. However, without data from multiple years, it is difficult to discern if clusters of
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