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Significant Questions (significant + question)
Selected AbstractsResponses of tree fine roots to temperatureNEW PHYTOLOGIST, Issue 1 2000KURT S. PREGITZER Soil temperature can influence the functioning of roots in many ways. If soil moisture and nutrient availability are adequate, rates of root length extension and root mortality increase with increasing soil temperature, at least up to an optimal temperature for root growth, which seems to vary among taxa. Root growth and root mortality are highly seasonal in perennial plants, with a flush of growth in spring and significant mortality in the fall. At present we do not understand whether root growth phenology responds to the same temperature cues that are known to control shoot growth. We also do not understand whether the flush of root growth in the spring depends on the utilization of stored nonstructural carbohydrates, or if it is fueled by current photosynthate. Root respiration increases exponentially with temperature, but Q10 values range widely from c. 1.5 to > 3.0. Significant questions yet to be resolved are: whether rates of root respiration acclimate to soil temperature, and what mechanisms control acclimation if it occurs. Limited data suggest that fine roots depend heavily on the import of new carbon (C) from the canopy during the growing season. We hypothesize that root growth and root respiration are tightly linked to whole-canopy assimilation through complex source,sink relationships within the plant. Our understanding of how the whole plant responds to dynamic changes in soil temperature, moisture and nutrient availability is poor, even though it is well known that multiple growth-limiting resources change simultaneously through time during a typical growing season. We review the interactions between soil temperature and other growth-limiting factors to illustrate how simple generalizations about temperature and root functioning can be misleading. [source] Interferon-alpha regulates the dynamic balance between human activated regulatory and effector T cells: implications for antiviral and autoimmune responsesIMMUNOLOGY, Issue 1 2010Amit Golding Summary An adequate effector response against pathogens and its subsequent inactivation after pathogen clearance are critical for the maintenance of immune homeostasis. This process involves an initial phase of T-cell effector (Teff) activation followed by the expansion of regulatory T cells (Tregs), a unique cell population that limits Teff functions. However, significant questions remain unanswered about the mechanisms that regulate the balance between these cell populations. Using an in vitro system to mimic T-cell activation in human peripheral blood mononuclear cells (PBMC), we analysed the patterns of Treg and Teff activation, with special attention to the role of type I interferon (IFN-I). Interestingly, we found that IFN-,, either exogenously added or endogenously induced, suppressed the generation of CD4+ FoxP3HI IFN-,Neg activated Tregs (aTregs) while simultaneously promoting propagation of CD4+ FoxP3Low/Neg IFN-,Pos activated Teffs (aTeffs). We also showed that IFN-,-mediated inhibition of interleukin (IL)-2 production may play an essential role in IFN-,-induced suppression of aTregs. In order to test our findings in a disease state with chronically elevated IFN-,, we investigated systemic lupus erythematosus (SLE). Plasma from patients with SLE was found to contain IFN-I activity that suppressed aTreg generation. Furthermore, anti-CD3 activated SLE PBMCs exhibited preferential expansion of aTeffs with a very limited increase in aTreg numbers. Together, these observations support a model whereby a transient production of IFN-, (such as is seen in an early antiviral response) may promote CD4 effector functions by delaying aTreg generation, but a chronic elevation of IFN-, may tip the aTeff:aTreg balance towards aTeffs and autoimmunity. [source] Behaviour and ecology of the western corn rootworm (Diabrotica virgifera virgifera LeConte)AGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2009Joseph L. Spencer Abstract 1,The western corn rootworm (WCR) is a historic pest with a legacy of resistance and behavioural plasticity. Its behaviour and nutritional ecology are important to rootworm management. The success of the most effective and environmentally benign rootworm management method, annual crop rotation, was based on an understanding of rootworm behaviour and host,plant relationships. Enthusiastic adoption of crop rotation, provided excellent rootworm management, but also selected for behavioural resistance to this cultural control. 2,Though well-studied, significant gaps in WCR biology remain. Understanding the topics reviewed here (mating behaviour, nutritional ecology, larval and adult movement, oviposition, alternate host use, and chemical ecology) is a starting point for adapting integrated pest management and insect resistance management (IRM) to an expanding WCR threat. A presentation of significant questions and areas in need of further study follow each topic. 3,The expansion of WCR populations into Europe exposes this pest to new environmental and regulatory conditions that may influence its behaviour and ecology. Reviewing the state of current knowledge provides a starting point of reference for researchers and pest management decision-makers in North America and Europe. 4,The trend toward increasing adoption of transgenic maize will place an increasing premium on understanding WCR behaviour. IRM plans designed to promote sustainable deployment of transgenic hybrids are grounded on assumptions about WCR movement, mating and ovipositional behaviour. Preserving the utility of new and old management options will continue to depend on a thorough understanding of WCR biology, even as the ecological circumstances and geography of WCR problems become more complex. [source] Global Englishes, Rip Slyme, and performativityJOURNAL OF SOCIOLINGUISTICS, Issue 4 2003Alastair Pennycook In this article I suggest that while recent sociolinguistic work focusing on crossing, styling the Other or language boundaries is raising significant questions concerning how we relate language, identity and popular culture, these insights have largely passed by the sociolinguistics of world Englishes. This latter work is still caught between arguments about homogeneity and heterogeneity, between arguments based on liberal accommodationism, linguistic imperialism or linguistic hybridity that do not allow for sufficiently complex understandings of what is currently happening with global Englishes. Focusing particularly on rap music, I suggest that we need, at the very least, a critical understanding of globalization, a focus on popular cultural flows, and a way of taking up performance and performativity in relationship to identity and culture. [source] Examining the potential of nurse practitioners from a critical social justice perspectiveNURSING INQUIRY, Issue 2 2008Annette J. Browne Nurse practitioners (NPs) are increasingly called on to provide high-quality health-care particularly for people who face significant barriers to accessing services. Although discourses of social justice have become relatively common in nursing and health services literature, critical analyses of how NP roles articulate with social justice issues have received less attention. In this study, we examine the role of NPs from a critical social justice perspective. A critical social justice lens raises morally significant questions, for example, why certain individuals and groups bear a disproportionate burden of illness and suffering; what social conditions contribute to disparities in health and social status; and what social mandate NPs ought to develop in response to these realities. In our analysis, we draw on lessons learned from the initial Canadian experience with the introduction of NPs in the 1970s to consider the renewed and burgeoning interest in NPs in Canada, Australia and elsewhere. As we argue, a critical social justice perspective (in addition to the biomedical foci of NP practice) will be essential to sustaining long-term, socially responsive NP roles and achieving greater equity in health and health-care. [source] | ||||||||||