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Search Results: 1 - 10 of 461361 matches for " Sharyn A. Endow "
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Anastral spindle assembly and γ-tubulin in Drosophila oocytes
Sharyn A Endow, Mark A Hallen
BMC Cell Biology , 2011, DOI: 10.1186/1471-2121-12-1
Abstract: We show, for the first time, using a bright GFP fusion protein and live imaging, that the Drosophila maternally-expressed γTub37C is present at low levels in oocyte meiosis I spindles. Despite this, we find that formation of bipolar meiosis I spindles does not require functional γTub37C, extending previous findings by others. Fluorescence photobleaching assays show rapid recovery of γTub37C in the meiosis I spindle, similar to the cytoplasm, indicating weak binding by γTub37C to spindles, and fits of a new, potentially more accurate model for fluorescence recovery yield kinetic parameters consistent with transient, diffusional binding.The FRAP results, together with its mutant effects late in meiosis I, indicate that γTub37C may perform a role subsequent to metaphase I, rather than nucleating microtubules for meiosis I spindle formation. Weak binding to the meiosis I spindle could stabilize pre-existing microtubules or position γ-tubulin for function during meiosis II spindle assembly, which follows rapidly upon oocyte activation and completion of the meiosis I division.Anastral spindles assemble without centrosomes by a pathway that is still not fully understood. In particular, the mechanism by which microtubule nucleation occurs has not been well defined. Although chromatin has been shown to play an essential role [1], the involvement of the microtubule nucleator, γ-tubulin, is still an open question. γ-Tubulin localizes to centrosomes and other microtubule organizing centers in mitosis and is essential for nucleating microtubules in organisms as diverse as yeast, Drosophila, Xenopus, humans, and higher plants [2-5]. γ-Tubulin is also found on spindle microtubules, where it has been proposed to nucleate microtubules for spindle maintenance by functioning in a chromatin-mediated nucleation pathway that augments the dominant pathway of nucleation by centrosomes [6,7].γ-Tubulin is present in cells as a large ring complex, γTuRC, comprising 12-13 γ-tubulin molecules a
Altered Nucleotide-Microtubule Coupling and Increased Mechanical Output by a Kinesin Mutant
Hong-Lei Liu, Mark A. Hallen, Sharyn A. Endow
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0047148
Abstract: Kinesin motors hydrolyze ATP to produce force and do work in the cell – how the motors do this is not fully understood, but is thought to depend on the coupling of ATP hydrolysis to microtubule binding by the motor. Transmittal of conformational changes from the microtubule- to the nucleotide-binding site has been proposed to involve the central β-sheet, which could undergo large structural changes important for force production. We show here that mutation of an invariant residue in loop L7 of the central β-sheet of the Drosophila kinesin-14 Ncd motor alters both nucleotide and microtubule binding, although the mutated residue is not present in either site. Mutants show weak-ADP/tight-microtubule binding, instead of tight-ADP/weak-microtubule binding like wild type – they hydrolyze ATP faster than wild type, move faster in motility assays, and assemble long spindles with greatly elongated poles, which are also produced by simulations of assembly with tighter microtubule binding and faster sliding. The mutated residue acts like a mechanochemical coupling element – it transmits changes between the microtubule-binding and active sites, and can switch the state of the motor, increasing mechanical output by the motor. One possibility, based on our findings, is that movements by the residue and the loop that contains it could bend or distort the central β-sheet, mediating free energy changes that lead to force production.
A kinesin motor in a force-producing conformation
Elisabeth Heuston, C Eric Bronner, F Jon Kull, Sharyn A Endow
BMC Structural Biology , 2010, DOI: 10.1186/1472-6807-10-19
Abstract: Here we show that mutation of a single residue in the kinesin-14 Ncd causes the motor to release ADP and hydrolyze ATP faster than wild type, but move more slowly along microtubules in gliding assays, uncoupling nucleotide hydrolysis from force generation. A crystal structure of the motor shows a large rotation of the stalk, a conformation representing a force-producing stroke of Ncd. Three C-terminal residues of Ncd, visible for the first time, interact with the central β-sheet and dock onto the motor core, forming a structure resembling the kinesin-1 neck linker, which has been proposed to be the primary force-generating mechanical element of kinesin-1.Force generation by minus-end Ncd involves docking of the C-terminus, which forms a structure resembling the kinesin-1 neck linker. The mechanism by which the plus- and minus-end motors produce force to move to opposite ends of the microtubule appears to involve the same conformational changes, but distinct structural linkers. Unstable ADP binding may destabilize the motor-ADP state, triggering Ncd stalk rotation and C-terminus docking, producing a working stroke of the motor.Motor proteins of the kinesin family hydrolyze ATP and use the energy released by nucleotide hydrolysis to move along microtubules, performing essential roles in transport, division and other cellular processes. The mechanism by which motors produce force to move on microtubules is not fully understood and remains an outstanding problem in the field. A prevailing hypothesis is that the motor undergoes a conformational change that, under load, produces strain. The strain is relieved by a force-producing movement that displaces the motor relative to the microtubule [1]. Coupling of steps of ATP hydrolysis to the force-producing structural changes of the motor is thought to drive motor movement along microtubules.Progress in understanding the motor mechanism has come from the discovery of the kinesin-14 motors. The motors in this kinesin group bin
Is There an Association between Social Connectedness, Social Identity, Alcohol Consumption and Mental Health among Young University Students?  [PDF]
Kristen Hunt, Sharyn Burns
Open Journal of Preventive Medicine (OJPM) , 2017, DOI: 10.4236/ojpm.2017.76009
Abstract: Social connectedness has been identified as a protective factor for a range of health issues however the literature is not conclusive. The high prevalence of hazardous alcohol consumption and mental health problems among university students along with the potential for the university as a setting for health promotion prompted this study. The study aims to explore the association between levels of alcohol consumption, mental health, social connectedness and social identity among university students. Online data were collected from a random sample of university undergraduate students (n = 2506) aged 18 - 24 years old. Outcomes were measured using the Alcohol Use Disorders Identification Test (AUDIT), the Kessler Psychological Distress Scale, Social Connectedness Scale, Social Identity Scale and measures of paid employment and study (hours), and participation in sports and other clubs. The majority of students had consumed alcohol in the last 12 months (87%). Of these students 38% reported to drink at hazardous levels (AUDIT ≥ 8). When all factors were considered: gender, living arrangements, being a domestic student, hours spent at work, participation in university and community sport, higher levels of psychological distress, higher levels of social connectedness, and lower levels of social identity were significant predictors of hazardous alcohol consumption. The finding highlights the need for the inclusion of integrated, multi-strategy health promotion interventions on campus. Further exploration of the associations between social connectedness and social identity as influences of health behaviors will better inform the development of targeted strategies for specific groups.
Vector–valued functional calculus for a convolution algebra of distributions on cone
O. V. Lopushansky,S. V. Sharyn,A. V. Solomko
Matematychni Studii , 2011,
Abstract: For {the} Fourier image $widehat{D}'_Gamma$ of {the} algebra $D'_Gamma$ of the distributions with supports on {a}cone $Gamma$ the functional calculus for generators of$n$--parametric $(C_o)$--semigroups of operators is determined. {For this purpose, we consider construction of the dual pair} $langlewidehat{D}'_Gamma,,widehat{D}_Gamma angle$, {and provide some examples with respect to the formula of operator calculus.}
Gender Inequality as Cultural Diversity
Sharyn Jones,Loretta A. Cormier,Lisa R. Baker
Antrocom : Online Journal of Anthropology , 2011,
Abstract: We describe an anthropological and interdisciplinary field school, primary involving female undergraduates. Our field program was conducted in 2009 and 2010 on a remote island in Fijian archipelago, in the context of a patriarchal society where gender avoidance is practiced. We had two broad objectives for this program: to conduct research on the understanding of cultural and marine biological resources; and to evaluate the effectiveness of the field experience in promoting anthropological and scientific learning principles. We summarize qualitative and quantitative outcomes of the educational evaluation of the student learning experience. We also discuss educational aims and the unique gender-associated challenges of conducting this program in a patriarchal cultural setting.
The many faces of Crohn’s Disease: Latest concepts in etiology  [PDF]
Jordana Campbell, Thomas J. Borody, Sharyn Leis
Open Journal of Internal Medicine (OJIM) , 2012, DOI: 10.4236/ojim.2012.22020
Abstract: The notion that Crohn’s Disease (CD) occurs as a result of an aberrant reaction to the commensal microbiota in genetically susceptible hosts is widely regarded by physicians and scientists as fact. Yet although it is undisputed that Crohn’s Disease is immune-mediated, an aberrant reaction to one’s own native flora is far from proven. The aim of the current review is to present a summary of the known infectious causes of Crohn’s Disease, whilst highlighting the limitations of using outdated methods to attempt to classify the disease as a single entity. We propose a re-classification of Crohn’s Disease, and suggest that the disease is best conceptualized as a syndrome, an “umbrella-like” term comprising a group of diseases with varying infective etiologies, which clinically, endoscopically and histologically are indistinguishable from CD.
Factors influencing the consumption of seafood among young children in Perth: a qualitative study
Alexandra McManus, Sharyn K Burns, Peter A Howat, Lisa Cooper, Lynda Fielder
BMC Public Health , 2007, DOI: 10.1186/1471-2458-7-119
Abstract: Purposive sampling techniques were used to select and recruit mothers of children aged between four and six years from within the Perth metropolitan area. A total of seven focus groups were conducted. Thematic content analysis was employed to code data generated and to extract major themes.Findings indicated that all children of study participants had tried fish and seafood products, with some being exposed to a wide variety from an early age. Across focus groups, several dominant factors were apparent in influencing the frequency and type of seafood purchased and consumed. Perceived cost, freshness, availability/accessibility, and the level of confidence to prepare a meal to suit all family members were significant determinants of whether seafood featured regularly on the household menu. The influence of others in the family (particularly the husband or partner) also tended to impact upon the likelihood of serving fish and seafood, and the types of products mothers were willing to serve.Findings from this qualitative study indicate that interventions seeking to promote seafood (particularly fish) as an integral part of a healthy diet should address existing negative attitudes and beliefs around the storage and preparation of seafood. The influence of dominant male influences within the family unit should also be considered. Strategies directed at parents and children should include experimental 'hands-on' components to encourage experimentation, particularly focussing on ease of preparation and the variety of lower cost seafood available.Establishing regular fish consumption as a healthy, cost effective option for families has the potential to impact upon their short and long-term health [1,2]. It also compliments the existing nutritional messages that relate to fruit and vegetables as essential to a healthy diet. Furthermore, the significant increase in cardiovascular diseases, overweight and obesity in childhood and adolescence facilitates the promotion of regula
Developing a Dynamic Microsimulation Model of the Australian Health System: A Means to Explore Impacts of Obesity over the Next 50 Years
Sharyn Lymer,Laurie Brown
Epidemiology Research International , 2012, DOI: 10.1155/2012/132392
Abstract: Health of the ageing population has the potential to place considerable pressure on future government spending. Further, the impacts of the obesity epidemic have the potential to place additional pressure on government health budgets. In response to such fiscal concerns in Australia, a dynamic microsimulation model, APPSIM, has been developed at the National Centre for Social and Economic Modelling (NATSEM). The health module was developed to allow consideration of health behaviours within the context of an ageing population and the resultant health profile of the population. Also included in the modelling is the associated use of health services and their costs. All health variables used were imputed onto the 2001 basefile derived from the 1 percent unit record file of the 2001 Australian census. Transition equations of these variables were estimated to allow projections over time. In this paper, the model has been used to look at the impacts of obesity on the Australian population health profile and associated health expenditure. In the scenario, removal of obesity from the population leads to a simulated population with a better health profile but showed only marginal changes in relative health expenditure. 1. Introduction It is well known that the Australian population is ageing and that across all age groups there is rising levels of obesity. In 1971, 8 percent of the Australian population was aged 65 years and over: by 2010, this had increased to almost 14 percent [1]. Official projections indicate that by 2050 some 23 percent of the Australian population will be aged 65 years and over [2]. An ageing population places increased pressure on government spending through increased demand for health care, aged care, and pensions. Health care spending has been steadily growing, from $Au 42 billion in 1996-1997 to $Au 103 billion in 2006-2007 [3]. Projections estimate continued rises in health expenditure from 3.7 percent of GDP in 2009/10 to 7.0 percent of GDP in 2046/47 [2]. Beyond the number or proportion of the aged population, the impacts on future health expenditure will be moderated by the health experience of the aged population. Possibilities of morbidity compression [4], expansion [5], dynamic equilibrium [6], or some cyclic effect between compression and expansion of morbidity [7] will impact the possible demand for health services. The relationship between health and longevity may be effected by the severity of disease not being as great due to slower progression of disease [8]. Further, issues such as new technology, medications, and changes
CRITIQUING AUSTRALIA’S KNOWLEDGE STRATEGY: HOW CAN WE BETTER POSITION OURSELVES IN A GLOBAL COMMUNITY?
Sharyn Renshaw,Girija Krishnaswamy
Lex et Scientia , 2008,
Abstract: This paper will provide critical analysis of Australia’ knowledge strategy, conducted from the perspective that driving a national knowledge strategy is the predominant responsibility of government for reasons of impartiality. As such critique will be focused upon the actionsundertaken by the Australian government to position the nation as a Knowledge-based Economy (KBE) competitively within the global community. It will be argued that to qualify for the title of “knowledge nation” the country needs to perform well across a composite range of factors. Examination of composite strategies will be conducted within a model of Knowledge Development, categorising the government’s knowledge sourcing, abstraction, conversion, diffusion and refinement strategies. The paper will conclude with recommendations for improving Australia’s position within the global knowledge economy and consequently within the global information community.
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