199 research outputs found
Co-regulation of primary mouse hepatocyte viability and function by oxygen and matrix
No full textAlthough oxygen and extracellular matrix cues both influence differentiation state and metabolic function of primary rat and human hepatocytes, relatively little is known about how these factors together regulate behaviors of primary mouse hepatocytes in culture. To determine the effects of pericellular oxygen tension on hepatocellular function, we employed two methods of altering oxygen concentration in the local cellular microenvironment of cells cultured in the presence or absence of an extracellular matrix (Matrigel) supplement. By systematically altering medium depth and gas phase oxygen tension, we created multiple oxygen regimes (hypoxic, normoxic, and hyperoxic) and measured the local oxygen concentrations in the pericellular environment using custom-designed oxygen microprobes. From these measurements of oxygen concentrations, we derived values of oxygen consumption rates under a spectrum of environmental contexts, thus providing the first reported estimates of these values for primary mouse hepatocytes. Oxygen tension and matrix microenvironment were found to synergistically regulate hepatocellular survival and function as assessed using quantitative image analysis for cells stained with vital dyes, and assessment of secretion of albumin. Hepatocellular viability was affected only at strongly hypoxic conditions. Surprisingly, albumin secretion rates were greatest at a moderately supra-physiological oxygen concentration, and this effect was mitigated at still greater supra-physiological concentrations. Matrigel enhanced the effects of oxygen on retention of function. This study underscores the importance of carefully controlling cell density, medium depth, and gas phase oxygen, as the effects of these parameters on local pericellular oxygen tension and subsequent hepatocellular function are profound.National Institutes of Health (U.S.) (Grant P50-GM068762-08)National Institutes of Health (U.S.) (Grant R01-EB010246-04)National Institutes of Health (U.S.) (Grant R01-ES015241)National Institutes of Health (U.S.) (Grant P30-ES002109
Challenges in Using Cultured Primary Rodent Hepatocytes or Cell Lines to Study Hepatic HDL Receptor SR-BI Regulation by Its Cytoplasmic Adaptor PDZK1
No full textBackground:
PDZK1 is a four PDZ-domain containing cytoplasmic protein that binds to a variety of membrane proteins via their C-termini and can influence the abundance, localization and/or function of its target proteins. One of these targets in hepatocytes in vivo is the HDL receptor SR-BI. Normal hepatic expression of SR-BI protein requires PDZK1 - <5% of normal hepatic SR-BI is seen in the livers of PDZK1 knockout mice. Progress has been made in identifying features of PDZK1 required to control hepatic SR-BI in vivo using hepatic expression of wild-type and mutant forms of PDZK1 in wild-type and PDZK1 KO transgenic mice. Such in vivo studies are time consuming and expensive, and cannot readily be used to explore many features of the underlying molecular and cellular mechanisms.
Methodology/Principal Findings:
Here we have explored the potential to use either primary rodent hepatocytes in culture using 2D collagen gels with newly developed optimized conditions or PDZK1/SR-BI co-transfected cultured cell lines (COS, HEK293) for such studies. SR-BI and PDZK1 protein and mRNA expression levels fell rapidly in primary hepatocyte cultures, indicating this system does not adequately mimic hepatocytes in vivo for analysis of the PDZK1 dependence of SR-BI. Although PDZK1 did alter SR-BI protein expression in the cell lines, its influence was independent of SR-BI’s C-terminus, and thus is not likely to occur via the same mechanism as that which occurs in hepatocytes in vivo.
Conclusions/Significance:
Caution must be exercised in using primary hepatocytes or cultured cell lines when studying the mechanism underlying the regulation of hepatic SR-BI by PDZK1. It may be possible to use SR-BI and PDZK1 expression as sensitive markers for the in vivo-like state of hepatocytes to further improve primary hepatocyte cell culture conditions.National Institutes of Health (U.S.) (Grant HL052212)National Institutes of Health (U.S.) (Grant HL066105)National Institutes of Health (U.S.) (Grant ES015241)National Institutes of Health (U.S.) (Grant GM068762
Fe nano-particle coatings for high temperature wear resistance
No full textOxidational wear continues to present an economic challenge for the replacement of components subject to high temperature fretting and sliding contacts in applications such as gas turbine engines. At elevated temperatures, low friction oxide ‘glaze’ layers can form and act as an interface between the contact and the substrate material. Whilst desirable, the glaze is formed from wear debris and often consumes the underlying substrate material. In order to induce rapid formation of low friction oxide layers without a severe ‘running-in’ period, nano particles of Fe in the range 5-10nm were deposited on ground flat ended pin and plate 080M40 substrates using a terminated gas condensation PVD process, to a thickness of 600nm. Coatings were tested in a reciprocating geometry at a fixed stroke length of 0.4mm, frequency of 31Hz and 40N normal load (1MPa contact stress) and at ambient, 300°C and 540°C. At ambient temperature the coated surfaces exhibited higher friction but lower wear compared to the uncoated substrates, whereas at elevated temperatures, the coated surfaces exhibited slightly lower steady state dynamic friction coefficients, and minimal changes in wear depth after a short incubation period. SEM of the worn surfaces indicated that hard oxide plateaus were responsible for the load bearing contact area at elevated temperatures. Cross sectional FIB, TEM and SIMS confirmed that at elevated temperatures, the nano-particle coating induced rapid formation of a nano-crystalline porous surface oxide film of mixed composition which protected the substrate from severe wear during the running-in period
User-centred car design and the role of feedback in driving
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A survey of car manufacturers reveals an impressive list of upcoming technologies, the combined effect of which is likely to have a profound impact upon feedback to the driver. Feedback is information that the situation provides back to the driver and is specified with reference to content, source, and timing. Feedback quality is achieved when the information requirements of the task, derived from a new task analysis of driving, are matched to the sources, content, and timing of feedback provided by the environment and the vehicle. An exploratory on-road study begins by observing that better quality feedback is
implicated in increasing driver's situational awareness (even though drivers have little self awareness of this fact), and optimising mental workload. The exploratory level of analysis builds into the experimental, whereby a highly controlled simulator study replicates and builds upon these findings. Feedback is again seen to positively influence situational awareness, where changes in driver's confidence ratings as to the presence or absence of feedback information in the simulation were observed, according to the modality of feedback presented. This was achieved with a probe recall paradigm, and using psychophysical techniques as a
useful extension to the Situational awareness Global Assessment Technique
(SAGAI). Similarly, an analysis of mental workload via the NASA TLX self report
questionnaire demonstrates that a combination of visual, steering force feedback and auditory feedback gives rise to lower mental workload, lower driver frustration, and lower, though possibly more realistic self ratings of performance. This knowledge can be discussed with reference to a feedback framework of driving that provides the theoretical backdrop to the key psychological variables implicated in driving task performance. Overall, the findings contribute to knowledge in terms of new and imaginative ways of designing future vehicle technologies in order to maximise safety, efficiency, and enjoyment.This research is funded by the Hamilton Research Studentship
Becoming a teacher : an ethnographic study
No full textThis ethnographic study of the professional studies year
of a Bachelor of Education course in a College of Higher
Education aims to understand teacher education as a process of
professional socialisation. The study starts from the
recognition that our present understanding of the process of
teacher socialisation is limited - theoretically, conceptually
and empirically - despite considerable recent developments in
the sociological understanding of school and classroom processes.
By taking an interactionist/ethnographic approach to the study
of the process of becoming a teacher, attention is drawn to the
negotiated character of professional socialisation, and the
similarities and differences in student teachers' experiences
and perceptions of what it is to be a teacher. The study is
concerned with the social processes and experiences of teacher
education the subjective perceptions, feelings, interests
and understandings of individuals and their creative and
strategic adaptations in response to perceived circumstances.
The study finds student teachers actively constructing
perspectives, strategies and identities as potential teachers,
a process involving conflicts and contradictions, taking
place within a social context which imposes constraints on
individual action Conceptualising the professional socialisation
process as a critical phase of 'survival' in which
student teachers must learn to cope, the study documents the
necessity for strategic negotiation, accommodation and
resistance to ensure success in the teacher education course.
The particular difficulties of initial encounters with pupils
and student teacher's relationships with teachers on school
experience are discussed. The study also examines the power
relations involved in teacher education, particularly those
concerning the 'hidden pedagogy' of control and its relation
to assessments of teacher competence
A new look at the pathogenesis of asthma
No full textAsthma is an inflammatory disorder of the conducting airways that has strong association with allergic sensitization. The disease is characterized by a polarized Th-2 (T-helper-2)-type T-cell response, but in general targeting this component of the disease with selective therapies has been disappointing and most therapy still relies on bronchodilators and corticosteroids rather than treating underlying disease mechanisms. With the disappointing outcomes of targeting individual Th-2 cytokines or manipulating T-cells, the time has come to re-evaluate the direction of research in this disease. A case is made that asthma has its origins in the airways themselves involving defective structural and functional behaviour of the epithelium in relation to environmental insults. Specifically, a defect in barrier function and an impaired innate immune response to viral infection may provide the substrate upon which allergic sensitization takes place. Once sensitized, the repeated allergen exposure will lead to disease persistence. These mechanisms could also be used to explain airway wall remodelling and the susceptibility of the asthmatic lung to exacerbations provoked by respiratory viruses, air pollution episodes and exposure to biologically active allergens. Variable activation of this epithelial-mesenchymal trophic unit could also lead to the emergence of different asthma phenotypes and a more targeted approach to the treatment of these. It also raises the possibility of developing treatments that increase the lung's resistance to the inhaled environment rather than concentrating all efforts on trying to suppress inflammation once it has become established.<br/
Second Harmonic Generation Microscopy As A Powerful Diagnostic Imaging Modality For Human Ovarian Cancer
No full textIn this study we showed that second-harmonic generation (SHG) microscopy combined with precise methods for images evaluation can be used to detect structural changes in the human ovarian stroma. Using a set of scoring methods (alignment of collagen fibers, anisotropy, and correlation), we found significant differences in the distribution and organization of collagen fibers in the stroma component of serous, mucinous, endometrioid and mixed ovarian tumors as compared with normal ovary tissue. This methodology was capable to differentiate between cancerous and healthy tissue, with clear cut distinction between normal, benign, borderline, and malignant tumors of serous type. Our results indicated that the combination of different image-analysis approaches presented here represent a powerful tool to investigate collagen organization and extracellular matrix remodeling in ovarian tumors © 2014 WILEY-VCH Verlag GmbH & Co. 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Interrogating Participatory Catchment Organisations:cases from Canada, New Zealand, Scotland and the Scottish–English Borderlands
No full textCatchment management in the developed world is undergoing a fundamental reconfiguration in which top-down governance is being challenged by local organisations promoting collaborative decisionmaking. Local, participation-based organisations are emerging as mediators of relations between governments and publics. These organisations, defined here as participatory catchment organisations (PCOs), are emergent at a time when developed world catchment management is itself undergoing substantial change. Through in-depth engagement with four PCOs, and using six case studies, we identify the principles associated with successful problem resolution. The findings illustrate the importance of PCOs as two-way bridges between publics and governments. We identify three principles shared by these organisations that show how, through participatory approaches founded on trust, complicated problems can be resolved in ways that do not unduly punish groups or individuals. In conclusion, we identify four questions that highlight the need to consider the practicality of evolving relations amongst governments, publics, and the organisations that have come to mediate catchment management. The file displayed is the pre-peer reviewed version of the following article: Cook, B. R., Atkinson, M., Chalmers, H., Comins, L., Cooksley, S., Deans, N., Fazey, I., Fenemor, A., Kesby, M., Litke, S., Marshall, D. and Spray, C. (2013), Interrogating participatory catchment organisations: cases from Canada, New Zealand, Scotland and the Scottish–English Borderlands. The Geographical Journal, 179: 234–247. doi: 10.1111/j.1475-4959.2012.00492.x, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4959.2012.00492.x/abstract</p
A review of residential water conservation tool performance and influences on implementation effectiveness.
No full textThere has been sparse coverage of advances in the application of Demand-Side
Management (DSM) in the academic press in recent years. At the same time a
number of important DSM studies have been reported on by non-academic
institutions, and there is therefore a need for a comprehensive, up to date
review of the impacts of DSM tools and the factors which influence their
effectiveness. This paper aims to begin to address this apparent lack of
coverage with a review of residential DSM tools using recent reports of DSM
campaigns in the western (developed) world collected from a range of sources.
The aims are, to understand the potential for residential DSM tools to save
water in different types of household under varying conditions and, identify
influences on implementation effectiveness. The current review will be of
interest to, among others, water company professionals, policy makers,
regulators and environmental agencies
A taxonomy of virtual worlds usage in education
No full textVirtual worlds are an important tool in modern education practices as well as providing socialisation, entertainment and a laboratory for collaborative work. This paper focuses on the uses of virtual worlds for education and synthesises over 100 published academic papers, reports and educational websites from around the world. A taxonomy is then derived from these papers, delineating current theoretical and practical work on virtual world usage, specifically in the field of education. The taxonomy identifies rich veins of current research and practice in associated educational theory and in simulated worlds or environments, yet it also demonstrates the paucity of work in important areas such as evaluation, grading and accessibility.Peer reviewe
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