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Complex Process (complex + process)
Selected AbstractsHow to optimize patch testing with diphenylmethane diisocyanateCONTACT DERMATITIS, Issue 3 2007Malin Frick-Engfeldt We have previously shown that patch test preparations of polymeric diphenylmethane diisocyanate (PMDI) are more stable than preparations of diphenylmethane-4,4'-diisocyanate (4,4'-MDI). This study was conducted to (i) investigate whether PMDIs yield as many positive reactions as 4,4'-MDI, (ii) study concurrent reactions to 4,4'-MDI and 4,4'-diaminodiphenylmethane (4,4'-MDA), and (iii) follow the course of positive reactions during 4 weeks. It was shown that PMDIs detect as many positive reactions as 4,4'-MDI. Thus, they are better patch test agents being more stable than preparations of 4,4'-MDI. We recommend that PMDIs with a monomer content of at least 35% is used in 2.0% petrolatum (pet.) (i.e. monomer patch test concentration approximately 0.7%). It was shown that reactions to 4,4'-MDI and PMDIs appear late and we recommend readings on both day (D) 3/4 and D7. 4,4'-MDA was shown to be a good marker for 4,4'-MDI and patch testing with 4,4'-MDA in 0.25% pet. can be used instead of PMDI. Concomitant reactions to 4,4'-MDI and 4,4'-MDA are probably not caused by conversion of 4,4'-MDI into 4,4'-MDA by reaction with water. Another explanation is a path of reactions leading to ureas and MDI conjugates with skin constituents, which are hydrolysed into 4,4'-MDA. This complex process depends upon several factors and might explain why positive MDI reactions appear after D7. [source] Vulnerability, Control and Oil Palm in Sarawak: Globalization and a New Era?DEVELOPMENT AND CHANGE, Issue 2 2002Fadzilah Majid Cooke In the post logging era, Sarawak is being restructured to make way for large-scale oil palm plantations. In this restructuring, the vulnerabilities of particular areas are being used in a wider battle to control production, particularly for export. Native customary lands, considered ,unproductive' or ,idle' by officials, are the target of oil palm plantation development under a new land development programme called Konsep Baru (New Concept). This article looks at the contradictions generated by the complex process of laying claims to ,idle' native customary land and focuses on Dayak organizing initiatives in northern Sarawak, Malaysia. [source] Risky Business: Economic Uncertainty, Market Reforms and Female Livelihoods in Northeast GhanaDEVELOPMENT AND CHANGE, Issue 5 2000Brenda Chalfin This article examines the implications of economic uncertainty for rural markets and the livelihoods of female traders. It does so through a case study of a community in northern Ghana caught in the throes of a structural adjustment-driven privatization initiative. In order to fully comprehend the nature of the economic uncertainties in which rural economic actors are enmeshed and the manner in which they resist, engage or engender these conditions, two theoretical lenses are interposed. One, focusing on structural dissolution and an overall process of rural, and especially female, disempowerment, is drawn from recent approaches to African political economy. The other, gleaned from the field of economic anthropology, attends to the agency and knowledge of rural entrepreneurs in the face of unstable and imperfect market conditions. By bringing together these different analytic traditions, the critical significance of uncertainty within the complex process of rural economic transformation and reproduction becomes evident. Rather than functioning as a diagnostic of economic crisis and insecurity, uncertainty can be a strategic resource integral to the constitution of markets, livelihoods and economic coalitions. Such a perspective, privileging the institutional potentials of local social practice, makes apparent the forceful role played by female traders in the structuring of rural marketing systems even in the face of externally-induced and sometimes dramatic shifts in material conditions. [source] Preimplantation development of mouse: A view from cellular behaviorDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 3 2010Toshihiko Fujimori A mature animal body contains a variety of different cell types, and these cells are distributed in a well-organized fashion along the body axes. One of the major questions in developmental biology is how cells acquire different characteristics. In addition, it is important to understand how the embryo forms the body axes and how cells are allocated along these axes during development. Among mammalian species, the molecular mechanisms that regulate embryonic development have been well analyzed and characterized in mice. Here, mouse preimplantation embryonic development is briefly summarized and our current understanding of this complex process based on recent observations is reviewed. [source] Identification of candidate secreted factors involved in trigeminal placode inductionDEVELOPMENTAL DYNAMICS, Issue 10 2007Kathryn L. McCabe Abstract Cranial ectodermal placodes are critical for normal development of the peripheral nervous system of the head. However, many aspects of the molecular and tissue interactions involved in their induction have yet to be elucidated. The trigeminal placode is induced by an unidentified secreted factor(s) from the dorsal neural tube. To determine candidates that may be involved in this induction process, we have performed reverse transcriptase-polymerase chain reaction (RT-PCR) and whole-mount in situ hybridization to screen for receptors expressed by uninduced presumptive trigeminal level ectoderm. We have found that receptors for fibroblast growth factors, insulin-like growth factors, platelet-derived growth factors, Sonic hedgehog, the transforming growth factor-beta superfamily, and Wnts all are expressed in patterns consistent with a role in trigeminal placode formation. This RT-PCR screen for candidate receptors expressed in presumptive trigeminal ectoderm is the first systematic screen to identify potential interactions underlying induction of the trigeminal placode and represents a critical step for understanding this complex process. Developmental Dynamics 236:2925,2935, 2007. © 2007 Wiley-Liss, Inc. [source] Contribution of mesothelium-derived cells to liver sinusoids in avian embryosDEVELOPMENTAL DYNAMICS, Issue 3 2004J.M. Pérez-Pomares Abstract The developing liver is vascularized through a complex process of vasculogenesis that leads to the differentiation of the sinusoids. The main structural elements of the sinusoidal wall are endothelial and stellate (Ito) cells. We have studied the differentiation of the hepatic sinusoids in avian embryos through confocal colocalization of differentiation markers, in ovo direct labeling of the liver mesothelium, induced invasion of the developing chick liver by quail proepicardial cells, and in vitro culture of chimeric aggregates. Our results show that liver mesothelial cells give rise to mesenchymal cells which intermingle between the growing hepatoblast cords and become incorporated to the sinusoidal wall, contributing to both endothelial and stellate cell populations. We have also shown that the proepicardium, a mesothelial tissue anatomically continuous with liver mesothelium, is able to form sinusoid-like vessels into the hepatic primordium as well as in cultured aggregates of hepatoblasts. Thus, both intrinsic or extrinsic mesothelium-derived cells have the developmental potential to contribute to the establishment of liver sinusoids. Developmental Dynamics 229:465,474, 2004. © 2004 Wiley-Liss, Inc. [source] The role of BDNF and its receptors in depression and antidepressant drug action: Reactivation of developmental plasticityDEVELOPMENTAL NEUROBIOLOGY, Issue 5 2010Eero Castrén Abstract Recent evidence suggests that neuronal plasticity plays an important role in the recovery from depression. Antidepressant drugs and electroconvulsive shock treatment increase the expression of several molecules, which are associated with neuronal plasticity, in particular the neurotrophin BDNF and its receptor TrkB. Furthermore, these treatments increase neurogenesis and synaptic numbers in several brain areas. Conversely, depression, at least in its severe form, is associated with reduced volumes of the hippocampus and prefrontal cortex and in at least some cases these neurodegenerative signs can be attenuated by successful treatment. Such observations suggest a central role for neuronal plasticity in depression and the antidepressant effect, and also implicate BDNF signaling as a mediator of this plasticity. The antidepressant fluoxetine can reactivate developmental-like neuronal plasticity in the adult visual cortex, which, under appropriate environmental guidance, leads to the rewiring of a developmentally dysfunctional neural network. These observations suggest that the simple form of the neurotrophic hypothesis of depression, namely, that deficient levels of neurotrophic support underlies mood disorders and increases in these neurotrophic factors to normal levels brings about mood recovery, may not sufficiently explain the complex process of recovery from depression. This review discusses recent data on the role of BDNF and its receptors in depression and the antidepressant response and suggests a model whereby the effects of antidepressant treatments could be explained by a reactivation of activity-dependent and BDNF-mediated cortical plasticity, which in turn leads to the adjustment of neuronal networks to better adapt to environmental challenges. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 2010 [source] ,-cell development: the role of intercellular signalsDIABETES OBESITY & METABOLISM, Issue 2008R. Scharfmann Understanding in detail how pancreatic endocrine cells develop is important for many reasons. From a scientific point of view, elucidation of such a complex process is a major challenge. From a more applied point of view, this may help us to better understand and treat specific forms of diabetes. Although a variety of therapeutic approaches are well validated, no cure for diabetes is available. Many arguments indicate that the development of new strategies to cure diabetic patients will require precise understanding of the way ,-cells form during development. This is obvious for a future cell therapy using ,-cells produced from embryonic stem cells. This also holds true for therapeutic approaches based on regenerative medicine. In this review, we summarize our current knowledge concerning pancreatic development and focus on the role of extracellular signals implicated in ,-cell development from pancreatic progenitors. [source] Synthesis of pattern and process in biodiversity conservation assessment: a flexible whole-landscape modelling frameworkDIVERSITY AND DISTRIBUTIONS, Issue 3 2010Simon Ferrier Abstract Aim, To describe a general modelling framework for integrating multiple pattern- and process-related factors into biodiversity conservation assessments across whole landscapes. Location, New South Wales (Australia), and world-wide. Methods, The framework allows for a rich array of alternatives to the target-based model traditionally underpinning systematic conservation planning and consists of three broad modelling components. The first component models the future state (condition) of habitat across a landscape as a function of present state, current and projected pressures acting on this state, and any proposed, or implemented, management interventions. The second component uses this spatially explicit prediction of future habitat state to model the level of persistence expected for each of a set of surrogate biodiversity entities. The third component then integrates these individual expectations to estimate the overall level of persistence expected for biodiversity as a whole. Results, Options are explored for tailoring implementation of the framework to suit planning processes varying markedly in purpose, and in availability of data, time, funding and expertise. The framework allows considerable flexibility in the nature of employed biodiversity surrogates (species-level, discrete or continuous community-level) and spatial data structures (polygonal planning units, or fine-scaled raster), the level of sophistication with which each of the three modelling components is implemented (from simple target-based assessment to complex process-based modelling approaches), and the forms of higher-level analysis supported (e.g. optimal plan development, priority mapping, interactive scenario evaluation). Main conclusions, The described framework provides a logical, and highly flexible, foundation for integrating disparate pattern- and process-related factors into conservation assessments in dynamic, multiple-use landscapes. [source] Targeting the development of resveratrol as a chemopreventive agent,DRUG DEVELOPMENT RESEARCH, Issue 6 2010Nian-Guang Li Abstract Tumor development consists of several separate, but closely linked, stages: tumor initiation, promotion, and progression. This long and complex process provides opportunities for intervention both in preventing cancer initiation and in treating the neoplasm during its premalignant stages. Resveratrol, a polyphenolic compound found in many plant species, including grapes, peanuts, and various herbs, has recently been investigated intensely for its cancer chemopreventive property. The present work is an overview of the chemopreventive mechanisms of resveratrol in anti-initiation, anti-promotion, and anti-progression. These, together with the low toxicity of resveratrol, suggest promise for novel chemopreventive agents. However, the low bioavailability and rapid clearance of resveratrol from the circulation require the design of new resveratrol-like chemopreventive agents, the structural modifications and the structure,activity relationship of which are also discussed in this review. Drug Dev Res 71:335,350, 2010. © 2010 Wiley-Liss, Inc. [source] Dating the Gesta martyrum: a manuscript-based approachEARLY MEDIEVAL EUROPE, Issue 3 2000Clare Pilsworth The gesta martyrum are an anonymous and disparate group of texts celebrating saints venerated in early medieval Rome as having been martyred in that city. This paper investigates the problems involved in placing these texts in their early medieval contexts. Since the beginning of the twentieth century, when scholarship moved away from attempts to identify a core of authentic ancient tradition in these early medieval narratives, most work on the corpus has concentrated on dating the composition of the accounts of individual martyrs. Given the sparsity of absolute chronological markers through references or citations in other written sources, this has inevitably rested on circumstantial evidence and the reconstruction of probable contexts for the redaction of specific works. This paper argues that much new light can be shed on the development of the cult of Roman martyrs if we shift the focus of our investigation from the origin and composition of the Urtexts to the surviving manuscript witnesses , all bar one eighth century or later , and the complex process of transmission which they document. The earliest copies of gesta martyrum, in both legendaries and other manuscripts, reveal surprisingly diverse contexts of transmission. Detailed investigation of Vienna National bibliothek 357, which Dufourcq argued contains a copy of a collection of martyr-narratives available to Gregory the Great, shows that in fact this manuscript sheds light on interest in Roman martyrs north of the Alps in the late Carolingian period, and the networks of contact and communication through which information about the Roman martyrs was transmitted across time and space. [source] Challenges and recovery actions for the widespread, threatened Grey-headed Flying-fox: A review from a New South Wales policy perspectiveECOLOGICAL MANAGEMENT & RESTORATION, Issue 2009Kylie McClelland Summary The challenges of managing and conserving threatened species that have a widespread distribution operate at several levels and recovery of these species is a complex process. This paper provides an overview of how science is informing the management and conservation of the Grey-headed Flying-fox (Pteropus poliocephalus) in New South Wales. It outlines a series of research projects and activities the Department of Environment and Climate Change (New South Wales) has led or been involved in since the Grey-headed Flying-fox was listed as threatened in New South Wales in May 2001. This includes investigation of the species' distribution and abundance; its roosting and foraging habitat requirements; assessment of horticultural damage and the mitigation techniques used; public attitudes towards the species; and development of policies and plans to guide the species' conservation and management. Conservation gains for threatened species can be achieved through a sustained, focused programme of management, coordinated by dedicated individuals and informed by the available science. Scientists, policy-makers and the general community must continue to strive together for the recovery of widespread, threatened species. [source] The spatial spread of invasions: new developments in theory and evidenceECOLOGY LETTERS, Issue 1 2005Alan Hastings Abstract We review and synthesize recent developments in the study of the spread of invasive species, emphasizing both empirical and theoretical approaches. Recent theoretical work has shown that invasive species spread is a much more complex process than the classical models suggested, as long range dispersal events can have a large influence on the rate of range expansion through time. Empirical work goes even further, emphasizing the role of spatial heterogeneity, temporal variability, other species, and evolution. As in some of the classic work on spread, the study of range expansion of invasive species provides unique opportunities to use differences between theory and data to determine the important underlying processes that control spread rates. [source] Trust, Transactions, and Information Technologies in the U.S. Logistics IndustryECONOMIC GEOGRAPHY, Issue 2 2007Yuko Aoyama Abstract: How does information technology (IT) alter the organizational dynamics in an industry? In this article, we examine changes in competition and interfirm relations in the U.S. logistics industry, particularly whether "trust-based" interfirm relationships are being substituted by "competition-based" relationships and the rationale for outsourcing. We also examine how new IT tools and outsourcing interact and how logistics contracts, the size of firms, and knowledge lead to integration or disintegration within the industry. The results of our research demonstrate that while the use of IT tools is widespread, traditional trust-based relationships exhibit a considerable resilience in the logistics industry. The industry is also undergoing a complex process of restructuring in response to technological change, on the one hand, and the persistence of geographic and functional specialization, on the other hand. The industry's focus on the delivery of high-quality services, coupled with excess capacity in the industry in the past few years, has contributed to these contradictory trends. As a result, elimination of the middleman has not been as widely observed as expected. [source] The Role of Human Capital in Technological EntrepreneurshipENTREPRENEURSHIP THEORY AND PRACTICE, Issue 6 2007Mike Wright This special issue addresses the role that the human capital characteristics of individuals and teams play in the complex process of technological entrepreneurship. In this article, we position the special issue on human capital and technology-based entrepreneurship within the literatures concerning academic entrepreneurship, technology transfer and innovation, and corporate spin-offs. We summarize the articles in the special issue and also outline a research agenda at the firm, entrepreneurial team, and individual entrepreneur levels. Finally, we discuss managerial and policy implications. [source] Biofilm formation and cellulose expression among diverse environmental Pseudomonas isolatesENVIRONMENTAL MICROBIOLOGY, Issue 11 2006Susanne Ude Summary The ability to form biofilms is seen as an increasingly important colonization strategy among both pathogenic and environmental bacteria. A survey of 185 plant-associated, phytopathogenic, soil and river Pseudomonas isolates resulted in 76% producing biofilms at the air,liquid (A,L) interface after selection in static microcosms. Considerable variation in biofilm phenotype was observed, including waxy aggregations, viscous and floccular masses, and physically cohesive biofilms with continuously varying strengths over 1500-fold. Calcofluor epifluorescent microscopy identified cellulose as the matrix component in biofilms produced by Pseudomonas asplenii, Pseudomonas corrugata, Pseudomonas fluorescens, Pseudomonas marginalis, Pseudomonas putida, Pseudomonas savastanoi and Pseudomonas syringae isolates. Cellulose expression and biofilm formation could be induced by the constitutively active WspR19 mutant of the cyclic-di-GMP-associated, GGDEF domain-containing response regulator involved in the P. fluorescens SBW25 wrinkly spreader phenotype and cellular aggregation in Pseudomonas aeruginosa PA01. WspR19 could also induce P. putida KT2440, which otherwise did not produce a biofilm or express cellulose, as well as Escherichia coli K12 and Salmonella typhimurium LT2, both of which express cellulose yet lack WspR homologues. Statistical analysis of biofilm parameters suggest that biofilm development is a more complex process than that simply described by the production of attachment and matrix components and bacterial growth. This complexity was also seen in multivariate analysis as a species-ecological habitat effect, underscoring the fact that in vitro biofilms are abstractions of those surface and volume colonization processes used by bacteria in their natural environments. [source] Elucidating the factors influencing the biodegradation of cylindrospermopsin in drinking water sourcesENVIRONMENTAL TOXICOLOGY, Issue 3 2008Maree J. Smith Abstract The cyanotoxin cylindrospermopsin (CYN) is produced by several species of cyanobacteria and can be persistent in drinking waters supplies, which is of major concern to water authorities because of its potential to severely compromise human health. Consequently, there is a need to fully understand the persistence of CYN in water supplies, in particular, to determine whether this toxin is readily degraded by endemic aquatic organisms. This study provides insights into the environmental factors that can influence the biodegradation of this toxin in Australian drinking water supplies. Biodegradation of CYN was only evident in water supplies that had a history of toxic Cylindrospermopsis raciborskii blooms. In addition, lag periods were evident prior to the onset of biodegradation; however, repeated exposure of the endemic organisms to CYN resulted in substantial decreases in the lag periods. Furthermore, the concentration of CYN was shown to influence biodegradation with a near linear relationship (R2 of 0.9549) existing between the biodegradation rate and the initial CYN concentration. Temperature was also shown to affect the biodegradation of CYN, which is important since CYN is now being detected in more temperate climates. The presence of copper-based algicides inhibited CYN degradation, which has significant implications since copper-based algicides are commonly used to control cyanobacterial growth in water bodies. The results from this study indicate that the biodegradation of CYN in natural water bodies is a complex process that can be influenced by many environmental factors, some of which include CYN concentration, temperature, and the presence of copper-based algicides. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Tricks of Festival: Children, Enculturation, and American HalloweenETHOS, Issue 2 2005CINDY DELL CLARK The American children's ritual, Halloween, involves an emergent, active and complex process rather than unidirectional socialization of children by adults. Inversions of meaning are prominent in Halloween through: 1) adult support for inverted, anti-normative themes, and 2) a turnabout by which children gain ascendance through costumed trick-or-treating. Based on interviews with six and seven year old children and their parents, as well as participant observation at Halloween events, Halloween's inversions had different interpretations for adults compared to children. For example the degree and quality of fear associated with Halloween varied between elders and children. Following the traumatic events of September 11, 2001, adult-rendered meanings of Halloween were shown to be unfixed and subject to modification. These findings raise critical questions about simplistic notions of socialization and cultural reduplication. [source] Expression of Sox11 in adult neurogenic niches suggests a stage-specific role in adult neurogenesisEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2009Anja Haslinger Abstract In the mammalian brain, neural stem and progenitor cells in the subventricular zone of the lateral ventricles and the subgranular zone of the dentate gyrus generate new neurons throughout adulthood. The generation of new functional neurons is a complex process that is tightly controlled by extrinsic signals and that is characterized by stage-specific gene expression programs and cell biological processes. The transcription factors regulating such stage-specific developmental steps in adult neurogenesis are largely unknown. Here we report that Sox11, a member of the group C Sox transcription factor family, is prominently expressed in the neurogenic areas of the adult brain. Further analysis revealed that Sox11 expression is strictly confined to doublecortin-expressing neuronally committed precursors and immature neurons but that Sox11 is not expressed in non-committed Sox2-expressing precursor cells and mature neurons of the adult neurogenic lineage. Finally, overexpression of Sox11 promotes the generation of doublecortin-positive immature neurons from adult neural stem cells in vitro. These data indicate that Sox11 is involved in the transcriptional regulation of specific gene expression programs in adult neurogenesis at the stage of the immature neuron. [source] Activation of class I metabotropic glutamate receptors limits dendritic growth of Purkinje cells in organotypic slice culturesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006Alexandra Sirzen-Zelenskaya Abstract The development of the dendritic tree of a neuron is a complex process which is thought to be regulated strongly by signals from afferent fibers. We showed previously that the blockade of glutamatergic excitatory neurotransmission has little effect on Purkinje cell dendritic development. We have now studied the effects of glutamate receptor agonists on the development of Purkinje cell dendrites in mouse organotypic slice cultures. The activation of N -methyl- d -aspartate receptors had no major effect on Purkinje cell dendrites and the activation of (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid receptors was strongly excitotoxic so that no analysis of its effects on dendritic development was possible. The activation of metabotropic glutamate receptors led to a very strong inhibition of dendritic growth, resulting in Purkinje cells with very small stubby dendrites. This effect was specific for the activation of class I metabotropic glutamate receptors and could not be reduced by blocking synaptic transmission in the cultures, indicating that it was mediated by receptors present on Purkinje cells. Pharmacological experiments suggest that the signaling pathway involved does not require activation of phospholipase C or protein kinase C. The inhibition of dendritic growth by activation of class I metabotropic glutamate receptor could be a useful negative feedback mechanism for limiting the size of the dendritic tree of Purkinje cells after the establishment of a sufficient number of parallel fiber contacts. This developmental mechanism could protect Purkinje cells from excitotoxic death through excessive release of glutamate from an overload of parallel fiber contacts. [source] Offer and demand: proliferation and survival of neurons in the dentate gyrusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2005Konrad Lehmann Abstract The proliferation and survival of new cells in the dentate gyrus of mammals is a complex process that is subject to numerous influences, presenting a confusing picture. We suggest regarding these processes on the level of small networks, which can be simulated in silico and which illustrate in a nutshell the influences that proliferating cells exert on plasticity and the conditions they require for survival. Beyond the insights gained by this consideration, we review the available literature on factors that regulate cell proliferation and neurogenesis in the dentate gyrus in vivo. It turns out that the rate of cell proliferation and excitatory afferents via the perforant path interactively determine cell survival, such that the best network stability is achieved when either of the two is increased whereas concurrent activation of the two factors lowers cell survival rates. Consequently, the mitotic activity is regulated by systemic parameters in compliance with the hippocampal network's requirements. The resulting neurogenesis, in contrast, depends on local factors, i.e. the activity flow within the network. In the process of cell differentiation and survival, each cell's spectrum of afferent and efferent connections decides whether it will integrate into the network or undergo apoptosis, and it is the current neuronal activity which determines the synaptic spectrum. We believe that this framework will help explain the biology of dentate cell proliferation and provide a basis for future research hypotheses. [source] Effect of monovalent cations and G-quadruplex structures on the outcome of intramolecular homologous recombinationFEBS JOURNAL, Issue 11 2009Paula Barros Homologous recombination is a very important cellular process, as it provides a major pathway for the repair of DNA double-strand breaks. This complex process is affected by many factors within cells. Here, we have studied the effect of monovalent cations (K+, Na+, and NH4+) on the outcome of recombination events, as their presence affects the biochemical activities of the proteins involved in recombination as well as the structure of DNA. For this purpose, we used an in vitro recombination system that includes a protein nuclear extract, as a source of recombination machinery, and two plasmids as substrates for intramolecular homologous recombination, each with two copies of different alleles of the human minisatellite MsH43. We found that the presence of monovalent cations induced a decrease in the recombination frequency, accompanied by an increase in the fidelity of the recombination. Moreover, there is an emerging consensus that secondary structures of DNA have the potential to induce genomic instability. Therefore, we analyzed the effect of the sequences capable of forming G-quadruplex on the production of recombinant molecules, taking advantage of the capacity of some MsH43 alleles to generate these kinds of structure in the presence of K+. We observed that the MsH43 recombinants containing duplications, generated in the presence of K+, did not include the repeats located towards the 5,-side of the G-quadruplex motif, suggesting that this structure may be involved in the recombination events leading to duplications. Our results provide new insights into the molecular mechanisms underlying the recombination of repetitive sequences. [source] Bacterial quorum sensing and nitrogen cycling in rhizosphere soilFEMS MICROBIOLOGY ECOLOGY, Issue 2 2008Kristen M. DeAngelis Abstract Plant photosynthate fuels carbon-limited microbial growth and activity, resulting in increased rhizosphere nitrogen (N) mineralization. Most soil organic nitrogen is macromolecular (chitin, protein, nucleotides); enzymatic depolymerization is likely rate limiting for plant nitrogen accumulation. Analyzing Avena (wild oat) planted in microcosms containing sieved field soil, we observed increased rhizosphere chitinase and protease-specific activities, bacterial cell densities, and dissolved organic nitrogen (DON) compared with bulk soil. Low-molecular-weight (MW) DON (<3000 Da) was undetectable in bulk soil but comprised 15% of rhizosphere DON. Extracellular enzyme production in many bacteria requires quorum sensing (QS), cell-density-dependent group behavior. Because proteobacteria are considered major rhizosphere colonizers, we assayed the proteobacterial QS signals N -acyl-homoserine lactones (AHLs), which were significantly increased in the rhizosphere. To investigate the linkage between soil signaling and nitrogen cycling, we characterized 533 bacterial isolates from Avena rhizosphere: 24% had chitinase or protease activity and AHL production; disruption of QS in seven of eight isolates disrupted enzyme activity. Many Alphaproteobacteria were newly found with QS-controlled extracellular enzyme activity. Enhanced specific activities of nitrogen-cycling enzymes accompanied by bacterial density-dependent behaviors in rhizosphere soil gives rise to the hypothesis that QS could be a control point in the complex process of rhizosphere nitrogen mineralization. [source] Splitting of the fission yeast septumFEMS YEAST RESEARCH, Issue 6 2007Matthias Sipiczki Abstract In cell-walled organisms, a cross wall (septum) is produced during cytokinesis, which then splits in certain organisms to allow the daughter cells to separate. The formation and the subsequent cleavage of the septum require wall synthesis and wall degradation, which need to be strictly coordinated in order to prevent cell lysis. The dividing fission yeast (Schizosaccharomyces) cell produces a three-layered septum in which the middle layer and a narrow band of the adjacent cell wall can be degraded without threatening the integrity of the separating daughter cells. This spatially very precise process requires the activity of the Agn1p 1,3-,-glucanase and the Eng1p 1,3-,-glucanase, which are localized to the septum by a complex mechanism involving the formation of a septin ring and the directed activity of the exocyst system. The Sep1p-Ace2p transcription-factor cascade regulates the expression of many genes producing proteins for this complex process. Recent advances in research into the molecular mechanisms of separation and its regulation are discussed in this review. [source] Interaction between wind-induced seiches and convective cooling governs algal distribution in a canyon-shaped reservoirFRESHWATER BIOLOGY, Issue 7 2007RAFAEL MARCÉ Summary 1. Wind is considered the dominant factor controlling phytoplankton distribution in lentic environments. In canyon-shaped reservoirs, wind tends to blow along the main axis generating internal seiches and advective water movements that jointly with biological features of algae can produce a heterogeneous phytoplankton distribution. Turbulence generated by wind stress and convection will also affect the vertical distribution of algae, depending on their sinking properties. 2. We investigated the vertical and horizontal distribution of phytoplankton during the stratification period in Sau Reservoir (NE Spain). Sites along the main reservoir axis were sampled every 4 h for 3 days, and profiles of chlorophyll- a and temperature were made using a fluorescent FluoroProbe, which can discriminate among the main algal groups. Convective and wind shear velocity scales, and energy dissipation were calculated from meteorological data, and simulation experiments were performed to describe non-measured processes, like vertical advection and sinking velocity of phytoplankton. 3. Wind direction changed from day to night, producing a diel thermocline oscillation and an internal seiche. Energy dissipation was moderate during the night, and mainly attributed to convective cooling. During the day the energy dissipation was entirely attributed to wind shear, but values indicated low turbulence intensity. 4. The epilimnetic algal community was mainly composed of diatoms and chlorophytes. Chlorophytes showed a homogeneous distribution on the horizontal and vertical planes. Diatom horizontal pattern was also homogeneous, because the horizontal advective velocities generated by wind forcing were not high enough to develop phytoplankton gradients along the reservoir. 5. Diatom vertical distribution was heterogeneous in space and time. Different processes dominated in different regions of the reservoir, due to the interaction between seiching and the daily cycle of convective-mediated turbulence. As the meteorological forcing followed a clear daily pattern, we found very different diatom sedimentation dynamics between day and night. Remarkably, these dynamics were asynchronous in the extremes of the seiche, implying that under the same meteorological forcing a diatom population can show contrasting sedimentation dynamics at small spatial scales (approximately 103 m). This finding should be taken into account when interpreting paleolimnological records from different locations in a lake. 6. Vertical distribution of non-motile algae is a complex process including turbulence, vertical and horizontal advection, variations in the depth of the mixing layer and the intrinsic sinking properties of the organisms. Thus, simplistic interpretations considering only one of these factors should be regarded with caution. The results of this work also suggest that diatoms can persist in stratified water because of a synergistic effect between seiching and convective turbulence. [source] Dealing with Timing and Synchronization in Opportunities for Joint Activity ParticipationGEOGRAPHICAL ANALYSIS, Issue 3 2010Tijs Neutens The ability of people to access opportunities offered by the built environment is circumscribed by various sets of space,time constraints, including the requirements to meet other persons at particular times and places to undertake activities together. While models of space,time accessibility recognize that joint activities may constrain the performance of activities in space and time, their specifications do not explicitly acknowledge the opportunities that individuals of a group have for joint activity participation. Therefore, this article focuses on joint activity participation and argues that collective activity decisions are the outcome of a complex process involving various aspects of timing, synchronization, and social hierarchy. The utility-theoretic model proposed here quantifies the extent to which opportunities can be jointly accessed by a particular group of people within a specific time period. Central to the approach are three key variables: the attractiveness of an opportunity, the time available for activity participation, and the travel time to an activity location. Because of the multiperson character of joint activities, the determination of these variables is subject to individual preferences, privileges, and power differentials within a group. Specific attention is given to how time-of-day and synchronization effects influence the opportunities accessible to a group of individuals. The impact of these factors on joint accessibility is illustrated by a real-world example of an everyday rendezvous scenario. The outcomes of a simulation exercise suggest that time-of-day and synchronization effects significantly affect the benefits that can be gained from opportunities for joint activities. La capacidad de acceso a las oportunidades que los entornos construidos (como las ciudades) ofrecen a las personas, está limitada por un conjunto diverso de restricciones espacio-temporales. Entre ellas se incluyen los requisitos para coincidir y encontrarse con otras personas en determinados momentos y lugares con el fin de realizar actividades conjuntas. Los modelos de accesibilidad comunes reconocen que las actividades conjuntas pueden limitar el ejercicio de actividades en el espacio y el tiempo. Sin embargo, sus especificaciones no reconocen explícitamente las oportunidades disponibles a todos los individuos de un grupo para participar de una actividad conjunta. Es en este contexto y dadas las limitaciones descritas que este artículo se centra en la participación de individuos en actividades conjuntas y propone el argumento que la toma de decisiones relacionadas con dichas actividades son el resultado de un proceso complejo que involucra varios aspectos de temporización (programación temporal), sincronización, y jerarquía social. El modelo teórico de utilidad que se propone aquí cuantifica el grado en que las oportunidades pueden ser evaluadas en forma conjunta por un grupo de personas particular dentro de un período de tiempo específico. El marco general propuesto por los autores se basa en tres variables fundamentales: el atractivo de una oportunidad, el tiempo disponible para la participación de la actividad, y el tiempo de desplazamiento al lugar donde se lleva a cabo actividad. Debido al carácter particular de estas actividades (que involucran múltiples participantes), la determinación de estas variables está sujeta a preferencias individuales, a privilegios y a diferencias de poder dentro de un grupo. El presente estudio además presta atención especial a la forma en la que la hora del día y los efectos de sincronización pueden influenciar la disponibilidad de oportunidades para un grupo determinado de individuos. El impacto de estos factores sobre la accesibilidad agregada de actividades conjuntas es ejemplificado por los autores mediante un caso del mundo real que utiliza escenarios de encuentros diarios entre personas. Los resultados de este ejercicio de simulación sugieren que los efectos de la hora del día y la sincronización afectan significativamente los beneficios que se pueden obtener a partir las oportunidades disponibles para acceder a y realizar actividades conjuntas. [source] Network, exposure and rhetoric: Italian occupational fields and heterogeneity in constructing the globalized selfGLOBAL NETWORKS, Issue 4 2003Massimiliano Monaci Drawing on the findings of a broad inter-university research programme conducted in Italy, in this article we explore how individuals' transnational networks combine with other dimensions of their social experience in the production of a self-perception of their own ,global identity'. In particular, attention is focused on the structures and social spaces of everyday life in five crucial occupations (corporate managers, financial services workers, artists, media professionals and schoolteachers) where people's professional action is performed simultaneously along local and global axes. Within these groups the globalized self does not merely reflect individuals' engagement in transnational networks, but is also the outcome of a complex process including two added dimensions of social life in the job setting: (1) the degree and type of non-filtered exposure to pressures stemming from the global environment, which both constrain and enable subjective practices of coping with change and ambiguity; and (2) the degree and type of competence in the rhetorics of globalization, namely the level of access to well-known repertoires of interpretive resources for making sense of global trends. This analysis is consistent with social science conceptualizations arguing for a more nuanced understanding of globalization. In this light, not only is globalization a multidimensional process but it also produces a variety of responses and meanings by differently positioned actors. [source] Beyond Kyoto: Climate Change Policy in Multilevel Governance SystemsGOVERNANCE, Issue 3 2007BARRY G. RABE Climate change policy has commonly been framed as a matter of international governance for which global policy strategies can be readily employed. The decade of experience following the 1997 signing of the Kyoto Protocol suggests a far more complex process involving a wide range of policy options and varied engagement by multiple levels of governance systems. The respective experiences of the United States and Canada suggest that formal engagement in the international realm of policy is not a good indicator of domestic policy development or emissions reductions. The different contexts of intergovernmental relations, varied resources available to subnational governments for policy development and implementation, and role of subnational leaders in policy formation have emerged as important factors in explaining national differences between these North American neighbors. Consequently, climate change increasingly presents itself as a challenge not only of international relations but also of multilevel governance, thereby creating considerable opportunity to learn from domestic policy experimentation. [source] Finding Meaning in Memory: A Methodological Critique of Collective Memory StudiesHISTORY AND THEORY, Issue 2 2002Wolf Kansteiner The memory wave in the humanities has contributed to the impressive revival of cultural history, but the success of memory studies has not been accompanied by significant conceptual and methodological advances in the research of collective memory processes. Most studies on memory focus on the representation of specific events within particular chronological, geographical, and media settings without reflecting on the audiences of the representations in question. As a result, the wealth of new insights into past and present historical cultures cannot be linked conclusively to specific social collectives and their historical consciousness. This methodological problem is even enhanced by the metaphorical use of psychological and neurological terminology, which misrepresents the social dynamics of collective memory as an effect and extension of individual, autobiographical memory. Some of these shortcomings can be addressed through the extensive contextualization of specific strategies of representation, which links facts of representation with facts of reception. As a result, the history of collective memory would be recast as a complex process of cultural production and consumption that acknowledges the persistence of cultural traditions as well as the ingenuity of memory makers and the subversive interests of memory consumers. The negotiations among these three different historical agents create the rules of engagement in the competitive arena of memory politics, and the reconstruction of these negotiations helps us distinguish among the abundance of failed collective memory initiatives on the one hand and the few cases of successful collective memory construction on the other. For this purpose, collective memory studies should adopt the methods of communication and media studies, especially with regard to media reception, and continue to use a wide range of interpretive tools from traditional historiography to poststructural approaches. From the perspective of collective memory studies, these two traditions are closely related and mutually beneficial, rather than mutually exclusive, ways of analyzing historical cultures. [source] A novel mutation in the GATA4 gene in patients with Tetralogy of Fallot,,HUMAN MUTATION, Issue 3 2006Georges Nemer Abstract In vertebrates, heart formation which integrates different structures and cell types is a complex process that involves a network of genes regulated by transcription factors. Proper spatiotemporal expression of these factors ensure the highly needed tight control of each step in organogenesis. A mistake at any step from cell-commitment to valve formation will have a major impact on heart morphogenesis and function leading to congenital heart disease (CHD). Cardiac abnormalities occur with an incidence of one per 100 live births and represent 25% of all congenital malformations. As an alternative approach to linkage-analysis of familial cases of CHD, we started screening familial and sporadic cases of CHDs in a highly consanguineous population for mutations in genes encoding cardiac-enriched transcription factors. The evolutionarily conserved role of these proteins in cardiac development suggested a role in CHD. In this study, we report a mutation in the gene encoding GATA4, one of the earliest markers of heart development. This mutation was found in two out of 26 patients with Tetralogy of Fallot (TOF), and in none of the 94 patients with different phenotypes included in the study, nor in 223 healthy individuals. The heterozygous mutation results in an amino acid substitution in the first zinc finger of GATA4 that reduced its transcriptional activation of downstream target genes, without affecting GATA4 ability to bind DNA, nor its interaction with ZFPM2. © 2006 Wiley-Liss, Inc. [source] | |||||||||||||||||||||||||||||||||||||||||||