Distribution of Ganglioside GM1 in l-α-Dipalmitoylphosphatidylcholine/Cholesterol Monolayers: A Model for Lipid Rafts1

AbstractThe distribution of low concentrations of ganglioside GM1 in l-α-dipalmitoylphosphatidylcholine (DPPC) and DPPC/cholesterol monolayers supported on mica has been studied using atomic force microscopy (AFM). The monolayers studied correspond to a pure gel phase and a mixture of liquid-expanded (LE) and liquid-condensed (LC) phases for DPPC and to a single homogeneous liquid-ordered phase for 2:1 DPPC/cholesterol. The addition of 2.5–5% GM1 to phase-separated DPPC monolayers resulted in small round ganglioside-rich microdomains in the center and at the edges of the LC domains. Higher amounts of GM1 (10%) give numerous filaments in the center of the LC domains and larger patches at the edges. A gel phase DPPC monolayer containing GM1 showed large domains containing a network of GM1-rich filaments. The addition of GM1 to a liquid-ordered 2:1 DPPC/cholesterol monolayer gives small, round domains that vary in size from 50 to 150nm for a range of surface pressures. Larger amounts of GM1 lead to coalescence of the small, round domains to give longer filaments that cover 30–40% of the monolayer surface for 10mol % GM1. The results indicate that biologically relevant GM1 concentrations lead to submicron-sized domains in a cholesterol-rich liquid-ordered phase that is analogous to that found in detergent-insoluble membrane fractions, and are thought to be important in membrane microdomains or rafts. This demonstrates that AFM studies of model monolayers and bilayers provide a powerful method for the direct detection of microdomains that are too small for study with most other techniques

Contagion and learning in business networks

The purpose of this study is to examine network learning through the application of contagion theories. The transmission of knowledge, sharing of resources, and facilitation of learning through contagion has interested both business-to-business and economic geography researchers. This study responds to calls in both research traditions for research into knowledge and learning at the level of an interfirm network. More specifically, it focuses on developing an understanding of how the contagion of knowledge and ideas and the co-ordination of activities within a network tales place. We achieve this by drawing upon research in both network relationships dynamics and learning processes to investigate the causal mechanisms that drive contagion. We focus on two types of contagion: contagion by cohesion (i.e. the presences and closeness of direct contact with others in the network), and contagion by structural equivalence (i.e. where influence is related to the structural patterns of relationships in the network). We also identify two key mechanisms that act as a barrier to such contagion: isolation and immunity. We explore the implications of these findings for network learning opportunities, specifically learning-by-doing, learning-by-using, and learning-by-interacting

Contingent factors affecting network learning

To increase understanding of the impact of individuals on organizational learning processes, this paper explores the impact of individual cognition and action on the absorptive capacity process of the wider network. In particular this study shows how contingent factors such as social integration mechanisms and power relationships influence how network members engage in, and benefit from, learning. The use of cognitive consistency and sensemaking theory enables examination of how these contingent factors influence the learning processes of two construction industry design teams embedded within more permanent home-organizational structures. A number of practical ways arise by which firms can facilitate organizational learning through their interactions with network partners. Enhancement of learning in and between organizations occurs when members are cognizant of the means by which they connect within a network to create shared meanings, and the way in which they forge ties and share expertise in the learning process they engage in

Involving customers in innovation: knowledgeability and agency as process variables

Purpose: Recent research places an increased emphasis on the inclusion of the customer in value creation, learning, and innovation processes yet there remains a gap in our understanding of just how such customer involvement may work. This paper seeks to address this gap by examining two aspects of customer involvement; their knowledgeability and their agency. In addition, we explore three boundaries (semantic, syntactic, and pragmatic) across which relationship development occurs and which mayfacilitate and/or inhibit value co-creation, collaborative learning, and innovation processes. Design/methodology/approach: We utilised three case studies. Two were large scale construction projects in the UK, and one was a global professional accounting firm in the USA. Findings: Customers may become frustrated if not allowed to exercise their agency. However, their involvement can create tensions for suppliers who may have to become more tolerant of divergent goals. In respect of knowledgeability, we found that constraint satisfaction is important in allowing customers to reconcile their personal knowledge schema with that of the collective schema. However, we also noted that customer knowledgeability brings with it challenges for suppliers, who must find ways to add value for such customers. Research implications: We pose a number of further questions relating to the agency and knowledgeability of customers and their inclusion in value co-creation, collaborative learning, and innovation processes. We also highlight the need for guidance in identifying and minimising the barriers to crossing semantic, syntactic and pragmatic boundaries between customers and suppliers. Originality/value: We make an important contribution to research in the field in that we investigate how the inclusion of the customer in business networksalters current assumptions and practices

Cholesterol Tuning of BK Ethanol Response Is Enantioselective, and Is a Function of Accompanying Lipids

In the search to uncover ethanol's molecular mechanisms, the calcium and voltage activated, large conductance potassium channel (BK) has emerged as an important molecule. We examine how cholesterol content in bilayers of 1,2-dioleoyl-3-phosphatidylethanolamine (DOPE)/sphingomyelin (SPM) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylethanolamine (POPE)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylserine (POPS) affect the function and ethanol sensitivity of BK. In addition, we examine how manipulation of cholesterol in biological membranes modulates ethanol's actions on BK. We report that cholesterol levels regulate the change in BK channel open probability elicited by 50 mM ethanol. Low levels of cholesterol (<20%, molar ratio) supports ethanol activation, while high levels of cholesterol leads to ethanol inhibition of BK. To determine if cholesterol affects BK and its sensitivity to ethanol through a direct cholesterol-protein interaction or via an indirect action on the lipid bilayer, we used the synthetic enantiomer of cholesterol (ent-CHS). We found that 20% and 40% ent-CHS had little effect on the ethanol sensitivity of BK, when compared with the same concentration of nat-CHS. We accessed the effects of ent-CHS and nat-CHS on the molecular organization of DOPE/SPM monolayers at the air/water interface. The isotherm data showed that ent-CHS condensed DOPE/SPM monolayer equivalently to nat-CHS at a 20% concentration, but slightly less at a 40% concentration. Atomic force microscopy (AFM) images of DOPE/SPM membranes in the presence of ent-CHS or nat-CHS prepared with LB technique or vesicle deposition showed no significant difference in topographies, supporting the interpretation that the differences in actions of nat-CHS and ent-CHS on BK channel are not likely from a generalized action on bilayers. We conclude that membrane cholesterol influences ethanol's modulation of BK in a complex manner, including an interaction with the channel protein. Finally, our results suggest that an understanding of membrane protein function and modulation is impossible unless protein and surrounding lipid are considered as a functional unit

Engineered Nanomaterials and Human Health: Part 2. Applications and Nanotoxicology (IUPAC Technical Report) (Review)

Research on engineered nanomaterials (ENM) has progressed rapidly from the very early stages of studying their unique, size-dependent physicochemical properties and commercial exploration to the development of products that influence our everyday lives. We have previously reviewed various methods for synthesis, surface functionalization, and analytical characterization of ENM in a publication titled \u27Engineered Nanomaterials: Preparation, Functionalization and Characterization\u27. In this second, inter-linked document, we first provide an overview of important applications of ENM in products relevant to human healthcare and consumer goods, such as food, textiles, and cosmetics. We then highlight the challenges for the design and development of new ENM for bio-applications, particularly in the rapidly developing nanomedicine sector. The second part of this document is dedicated to nanotoxicology studies of ENM in consumer products. We describe the various biological targets where toxicity may occur, summarize the four nanotoxicology principles, and discuss the need for careful consideration of the biodistribution, degradation, and elimination routes of nanosized materials before they can be safely used. Finally, we review expert opinions on the risk, regulation, and ethical aspects of using engineered nanomaterials in applications that may have direct or indirect impact on human health or our environment

Physical and physiologic determinants of rock climbing

Purpose: Rock climbing performance relies on many characteristics. Here, we identified the physical and physiologic determinants of peak performance in rock climbing across the range from lower-grade to elite. Methods: 44 male and 33 female climbers with onsight maximal climbing grades 5a-8a and 5a-7b+, respectively, were tested for physical, physiologic and psychologic characteristics (independent variables) that were correlated and modelled by multiple regression and principal component analysis to identify the determinants of rock climbing ability. Results: In males, 23 of 47 variables correlated with climbing ability (p&lt;0.05, Pearson’s correlation coefficients 0.773-0.340), including shoulder endurance, hand and finger strength, shoulder power-endurance, hip flexibility, lower-arm grip strength, shoulder power, upper-arm strength, core-body endurance, upper-body aerobic endurance, hamstrings and lower-back flexibility, aerobic endurance, and open-hand finger strength. In females, 10 of 47 variables correlated with climbing ability (p&lt;0.05, Pearson’s correlation coefficients 0.742-0.482): shoulder endurance and power, lower-arm grip strength, balance, aerobic endurance, and arm span. Principal component analysis and univariate multiple regression identified the main explanatory variables. In both sexes, shoulder power and endurance measured as maximum pull-ups, average arm crank power, and bent-arm hang, emerged as the main determinants (p&lt;0.01; adjusted R2=0.77 in males and 0.62 in females). In males, finger pincer (p=0.07) and grip strength also had trends (p=0.09) toward significant effects. Finally, in test-of-principle training studies, we trained to increase main determinants 42-67%; this improved climbing ability 2-3 grades. Conclusions: Shoulder power and endurance majorly determines maximal climbing. Finger, hand and arm strength, core-body endurance, aerobic endurance, flexibility and balance are important secondary determinants

On my watch : a review of the environmental education literature with particular reference to South Africa, and South African teenagers

Thesis (MPhil)--Stellenbosch University, 2015.ENGLISH ABSTRACT: About half a million students matriculate from South African high schools each year, with limited environmental education and an underdeveloped capacity to live sustainable lives. This does not seem to be the case in some other parts of the world, where many high school students appear to be receiving education that is relevant to the socio-ecological crisis. The rationale of this thesis was to understand this phenomenon and explore what could be done to improve the situation for South African teenagers. This was a desktop study based upon systematic literature review methodology. The primary research objectives were to describe the local context of the study, explore emerging environmental education theoretical themes and detail a number of practical initiatives from around the world. The research process culminated in the fourth objective, which was to consolidate the work into key learnings for South Africa, with particular reference to South African teenagers. A backdrop to environmental education was provided that included a discussion on the global socio-ecological crisis, development and sustainable development in South Africa. The definition and use of the term “environmental education” was justified. In this instance, it is an inclusive definition that incorporates eco-literacy, ecological learning and education for sustainability. In addition to this, a brief comparative history of sustainable development and environmental education has been tabulated. Key theoretical themes in environmental education cluster around the centrality of place. Six themes are presented, namely space and place, trans-national education and third-culture kids, claims of transformation, principles of environmental education, institutional innovation, and the sustainability researcher. Three kinds of practical initiatives emerged in the literature review. These are “green fields” environmental education (brand new institutions), “moving train” environmental education (adaption of existing organisations) and “plug-in” environmental education. Eight initiatives are described, providing examples for all three of these groups. The key learnings for environmental education in South Africa and South African teenagers conclude this thesis. Among other key learnings, the value of the radical perspective is presented, as well as the benefit of perceiving environmental education through different lenses, including a historical one. The link between environmental education and food is explored. It is suggested that the theory and praxis of place-based education exerts a gravitational pull on many aspects of this work. It seems that place-based education provides a “holding space” for environmental education in South Africa, and a starting point for future research or practical application.AFRIKAANSE OPSOMMING: Ongeveer ’n halfmiljoen studente matrikuleer jaarliks aan Suid-Afrikaanse hoërskole. Hierdie leerders beskik oor beperkte omgewingsopvoeding en ’n onderontwikkelde vermoë om volhoubare lewens te lei. Dít blyk nie die geval te wees in ander wêrelddele nie, waar baie hoërskoolleerders oënskynlik onderrig ontvang wat met die sosio-ekologiese krisis verband hou. Die beweegrede vir hierdie tesis was om hierdie verskynsel te verstaan en te bepaal wat gedoen kan word om die stand van sake vir Suid-Afrikaanse tieners te verbeter. Die navorsing het bestaan uit ’n lessenaarstudie op grond van ’n stelselmatige literatuuroorsig. Die hoofnavorsingsdoelwitte was om die plaaslike konteks van die studie te beskryf, ontluikende teoretiese temas op omgewingsopvoedkundige gebied te verken, en ’n aantal praktiese inisiatiewe van oor die hele wêreld te beskryf. Die navorsingsproses het uitgeloop op die vierde doelwit, naamlik om die studieresultate in kernlesse vir Suid-Afrika, bepaald met verwysing na Suid-Afrikaanse tieners, te verwerk. Eerstens word die agtergrond van omgewingsopvoeding geskets, wat onder meer bestaan uit ’n bespreking van die wêreldwye sosio-ekologiese krisis sowel as ontwikkeling en volhoubare ontwikkeling in Suid-Afrika. Die omskrywing en gebruik van die term ‘omgewingsopvoeding’ word ook geregverdig. In hierdie geval word die term inklusief gebruik om ook na eko-geletterdheid, ekologiese leer en onderwys vir volhoubaarheid te verwys. Daarbenewens bied die studie ’n bondige vergelykende geskiedenis van volhoubare ontwikkeling en omgewingsopvoeding in tabelvorm. Die vernaamste teoretiese temas op omgewingsopvoedkundige gebied draai om die kernrol van plek. Ses temas word aangebied, naamlik ruimte en plek, transnasionale onderwys en derdekultuurkinders, bewerings van transformasie, beginsels van omgewingsopvoeding, institusionele innovasie, en die volhoubaarheidsnavorser. Drie soorte praktiese inisiatiewe het uit die literatuuroorsig na vore getree, naamlik “braakland”-omgewingsopvoeding (splinternuwe instellings), “bewegende trein”-omgewingsopvoeding (aanpassing van bestaande organisasies) en “inprop”-omgewingsopvoeding. Agt inisiatiewe word beskryf, wat voorbeelde van ál drie hierdie groepe bied. Die tesis bied ten slotte die belangrikste lesse vir omgewingsopvoeding in Suid-Afrika en vir Suid-Afrikaanse tieners aan. Dit sluit onder andere in die waarde van die radikale perspektief, sowel as die voordeel daarvan om omgewingsopvoeding deur verskillende lense, waaronder ’n historiese een, te beskou. Die koppeling tussen omgewingsopvoeding en voedsel word verken. Die studie kom tot die gevolgtrekking dat die teorie en praktyk van plekgebaseerde onderwys ’n soort ‘beweegruimte’ vir omgewingsopvoeding in Suid-Afrika, sowel as ’n wegspringplek vir toekomstige navorsing of praktiese toepassing, bied

Acellular oxidative potential assay for screening of amorphous silica nanoparticles.

Rapid acellular screening of amorphous silica nanoforms of different sizes and surface modifications for their oxidative potential

Tri6 Is a Global Transcription Regulator in the Phytopathogen Fusarium graminearum

In F. graminearum, the transcriptional regulator Tri6 is encoded within the trichothecene gene cluster and regulates genes involved in the biosynthesis of the secondary metabolite deoxynivalenol (DON). The Tri6 protein with its Cys2His2 zinc-finger may also conform to the class of global transcription regulators. This class of global transcriptional regulators mediate various environmental cues and generally responds to the demands of cellular metabolism. To address this issue directly, we sought to find gene targets of Tri6 in F. graminearum grown in optimal nutrient conditions. Chromatin immunoprecipitation followed by Illumina sequencing (ChIP-Seq) revealed that in addition to identifying six genes within the trichothecene gene cluster, Tri1, Tri3, Tri6, Tri7, Tri12 and Tri14, the ChIP-Seq also identified 192 additional targets potentially regulated by Tri6. Functional classification revealed that, among the annotated genes, ∼40% are associated with cellular metabolism and transport and the rest of the target genes fall into the category of signal transduction and gene expression regulation. ChIP-Seq data also revealed Tri6 has the highest affinity toward its own promoter, suggesting that this gene could be subject to self-regulation. Electro mobility shift assays (EMSA) performed on the promoter of Tri6 with purified Tri6 protein identified a minimum binding motif of GTGA repeats as a consensus sequence. Finally, expression profiling of F. graminearum grown under nitrogen-limiting conditions revealed that 49 out of 198 target genes are differentially regulated by Tri6. The identification of potential new targets together with deciphering novel binding sites for Tri6, casts new light into the role of this transcriptional regulator in the overall growth and development of F. graminearum