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Changing Environment (changing + environment)
Selected AbstractsReal-time deadlock-free navigation for multiple mobile robotsELECTRICAL ENGINEERING IN JAPAN, Issue 3 2008Harunori Gakuhari Abstract This paper proposes a practicable navigation method for multiple mobile robots in a realistic environment. In the past, many navigation methods have been developed. However, they were often limited to a single robot and sometimes assumed robots with special mobility such as holonomic ones. From the viewpoint of practical applications it is indispensable that the number of robots is arbitrary and a general shape and mobility for them is allowed. In this study, deadlock-free navigation for nonholonomic mobile robots in a practical environment is given. In the proposed scheme, states of the environment and robots are fed back in real time, and global path planning is cyclically executed. This enables an adaptation to a changing environment and reliable, deadlock-free navigation for multiple robots. The real-time online path planning is performed by an efficient A* search in Configuration Spaces representing the robots and environment. The proposed method is tested in several simulations which represent typical complicated navigation situations. As a result, the effectiveness of the method is verified. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(3): 27, 36, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20714 [source] Spectro-temporal sound density-dependent long-term adaptation in cat primary auditory cortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2008Boris Gourévitch Abstract Sensory systems use adaptive strategies to code for the changing environment on different time scales. Short-term adaptation (up to 100 ms) reflects mostly synaptic suppression mechanisms after response to a stimulus. Long-term adaptation (up to a few seconds) is reflected in the habituation of neuronal responses to constant stimuli. Very long-term adaptation (several weeks) can lead to plastic changes in the cortex, most often facilitated during early development, by stimulus relevance or by behavioral states such as attention. In this study, we show that long-term adaptation with a time course of tens of minutes is detectable in anesthetized adult cat auditory cortex after a few minutes of listening to random-frequency tone pips. After the initial post-onset suppression, a slow recovery of the neuronal response strength to tones at or near their best frequency was observed for low-rate random sounds (four pips per octave per second) during stimulation. The firing rate at the end of stimulation (15 min) reached levels close to that observed during the initial onset response. The effect, visible for both spikes and, to a smaller extent, local field potentials, decreased with increasing spectro-temporal density of the sound. The spectro-temporal density of sound may therefore be of particular relevance in cortical processing. Our findings suggest that low stimulus rates may produce a specific acoustic environment that shapes the primary auditory cortex through very different processing than for spectro-temporally more dense and complex sounds. [source] Opposing effects of amygdala and orbital prefrontal cortex lesions on the extinction of instrumental responding in macaque monkeysEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2005Alicia Izquierdo Abstract Extinction is a well-known behavioural phenomenon that allows organisms to respond flexibly to a changing environment. Although recent work implicates the amygdala and orbital prefrontal cortex (PFo) in extinction of Pavlovian conditioned fear and aversion, much less is known about the neural bases of instrumental extinction. To explore the contribution of the macaque amygdala to flexible responding in the face of changing reward contingency, we tested the effects of selective, excitotoxic lesions of the amygdala on extinction of an instrumental response. For comparison, we evaluated the effects of ablation of PFo on the same task. Amygdala lesions facilitated the extinction of instrumental responses, whereas lesions of PFo had the opposite effect. [source] Detecting the change of customer behavior based on decision tree analysisEXPERT SYSTEMS, Issue 4 2005Jae Kyeong Kim Abstract: Understanding and adapting to changes in customer behavior is an important aspect for survival in a continuously changing environment. This paper develops a methodology based on decision tree analysis to detect the change in classified customer segments automatically between two data sets collected over time. We first define three types of changes as the emerging pattern, the unexpected change and the added/perished rule. Then, similarity and difference measures are developed for rule matching to detect all types of change. Finally, the degree of change is developed to evaluate the amount of change. Our suggested methodology based on decision tree analysis in the change detection problem can be used in more structured situations in which the manager has a specific research question and it also detects the change of classification criteria in a dynamically changing environment. A Korean Internet shopping mall case is evaluated to represent the performance of our suggested methodology, and practical business implications for this methodology are also provided. We believe that the change detection problem and the suggested methodology will become increasingly important as more data mining applications are implemented. [source] Global constraints on rural fishing communities: whose resilience is it anyway?FISH AND FISHERIES, Issue 1 2007Martin D Robards Abstract Sustaining natural resources is regarded as an important component of ecological resilience and commonly assumed to be of similar importance to social and economic vitality for resource-dependent communities. However, communities may be prevented from benefiting from healthy local resources due to constrained economic or political opportunities. In the case of Alaskan wild salmon, the fisheries are in crisis due to declining economic revenues driven by the proliferation of reliable and increasingly high-quality products from fish farms around the world. This stands in contrast with many of the world's wild-capture fisheries where diminished biological abundance has led to fishery collapse. Furthermore, increasing efficiency of salmon farm production, globalization, and dynamic consumer preferences, suggests that the wild salmon industry will continue to be challenged by the adaptability, price and quality of farmed salmon. Conventional responses to reduced revenues by the wild-capture industry have been to increase economic efficiency through implementing a range of entry entitlement and quota allocation schemes. However, while these mechanisms may improve economic efficiency at a broad scale, they may not benefit local community interests, and in Alaska have precipitated declines in local ownership of the fishery. To be viable, economic efficiency remains a relevant consideration, but in a directionally changing environment (biological, social or economic), communities unable to procure livelihoods from their local resources (through access or value) are likely to seek alternative economic opportunities. The adopted strategies, although logical for communities seeking viability through transformation in a changing world, may not be conducive to resilience of a ,fishing community' or the sustainability of their wild fish resources. We use a theoretically grounded systems approach and data from Alaska's Bristol Bay salmon fishery to demonstrate feedbacks between global preferences towards salmon and the trade-offs inherent when managing for the resilience of wild salmon populations and human communities at different scales. [source] Neural correlates of exemplar novelty processing under different spatial attention conditionsHUMAN BRAIN MAPPING, Issue 11 2009Christian Michael Stoppel Abstract The detection of novel events and their identification is a basic prerequisite in a rapidly changing environment. Recently, the processing of novelty has been shown to rely on the hippocampus and to be associated with activity in reward-related areas. The present study investigated the influence of spatial attention on neural processing of novel relative to frequently presented standard and target stimuli. Never-before-seen Mandelbrot-fractals absent of semantic content were employed as stimulus material. Consistent with current theories, novelty activated a widespread network of brain areas including the hippocampus. No activity, however, could be observed in reward-related areas with the novel stimuli absent of a semantic meaning employed here. In the perceptual part of the novelty-processing network a region in the lingual gyrus was found to specifically process novel events when they occurred outside the focus of spatial attention. These findings indicate that the initial detection of unexpected novel events generally occurs in specialized perceptual areas within the ventral visual stream, whereas activation of reward-related areas appears to be restricted to events that do possess a semantic content indicative of the biological relevance of the stimulus. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Spatial assessment of hydrologic alteration across the Pearl River Delta, China, and possible underlying causesHYDROLOGICAL PROCESSES, Issue 11 2009Qiang Zhang Abstract The alterations of the water level across the Pearl River Delta (PRD) were investigated using a ,range of variability approach' (RVA) based on monthly water level datasets extracted from 17 gauging stations. A mapping method was used to illustrate the spatial patterns in the degrees of alteration of water levels. The results indicated that more stations showing moderate and high alterations in monthly mean maximum and minimum water levels when compared with monthly maximum and minimum water levels. River channels characterized by higher alterations of water levels were observed mainly in the regions north of 22° 30,N. Alterations of water levels across the PRD were a consequence of various influencing factors. However, changed hypsography due to extensive and intensive human activities, particularly the large-scale dredging and excavation of the river sand, may be taken as one of the major causes for the substantial hydrologic alteration. This study indicated that the river channels characterized by altered water levels are mostly those characterized by highly and moderately intensive sand dredging. The changed ratio of the streamflow between Makou and Sanshui stations, the major upstream flow control stations, also influenced the water level alterations of the Pearl River delta. The results of this study will be of great significance in water resources management and better human mitigation of the natural hazards due to the altered water level under the changing environment. Copyright © 2009 John Wiley & Sons, Ltd. [source] Water problems and hydrological research in the Yellow River and the Huai and Hai River basins of ChinaHYDROLOGICAL PROCESSES, Issue 12 2004Changming Liu Abstract This paper deals with hydrological research in regard to the water resources crisis in the vulnerable areas found in the northern part of China. This area includes three main river basins, namely the basins of the Yellow (Huang) River, the Hai River and the Huai River. Several water problems are becoming very severe. Among them, two are the most critical: the Yellow River has been drained dry in the main course of its lower reaches and along its major tributaries, and the groundwater table has rapidly declined in the floodplains of the three rivers' downstream areas. To counter the problems, particularly the critical issues mentioned above, hydrological research, which serves as the basis of water development and management, has been carried out in the last two decades. This paper addresses three basic scientific problems in North China, namely: (a) water consumption and the capacity for saving water; (b) the changes in hydrological processes and water resources caused by natural change and human activities; and (c) the ability to supply water resources and water safety in terms of both quantity and quality within a changing environment. However, opportunities and challenges for ameliorating the problems exist, and new ideas and methodology to solve the problems have been proposed, such as the interface process study on the interactions in the soil,root interface, the plant,atmosphere interface, the soil,atmosphere interface, and the interface of soil water and groundwater. In order to manage water resources in a sustainable manner, the study of water resources' renewal ability as affected by natural change and human activity is addressed from the viewpoint of both water quantity and quality, and their integration. To reduce the vulnerability of water resources in regional water management, a paradigm of sustainable water resources utilization is also proposed, using water,heat balance, water,salt balance, water,sediment balance, and water supply,demand balance. This approach may help reveal the basic problems and point to possible approaches to solving the water problems in North China in the 21st century. Copyright © 2004 John Wiley & Sons, Ltd. [source] Transitional Spaces: Mapping Physical ChangeINTERNATIONAL JOURNAL OF ART & DESIGN EDUCATION, Issue 2 2007Juliet Sprake Museums and buildings are both considered immutable by the majority of people who use them. A small team from Goldsmiths College, the V&A+RIBA Architecture Partnership and Pimlico School set out to challenge this preconception. The Victoria & Albert museum was taken as a case study to investigate how buildings are a physical manifestation of an institute, and how their physical presence records the way the museum has to respond to outside criteria, from government funding strategies to cultural trends. This article puts forward the argument that a museum building as a subject is a constantly changing environment, through which young learners can develop their historical imagination and critical abilities. It describes the process and findings from a project carried out with students from Pimlico School, who were asked to find and respond to evidence in the fabric of the V&A museum buildings of the substantial physical changes that it is currently undergoing. By choosing specific sites, the students put together a series of PDA-based threads to describe and archive different narratives about the museum at the moment of their mapping. These are made for future visitors to see, hear and compare the museum environment they are experiencing with the one that the students recorded. [source] A tree-based approach to matchmaking algorithms for resource discoveryINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 5 2008Md. Rafiqul Islam One of the essential operations in a distributed computing is resource discovery. A resource discovery service provides mechanisms to identify the set of resources capable of satisfying the requirements of a job from a large collection of resources. The matchmaking framework provides a reasonable solution to resource management in a distributed environment; it is composed of four important components as classified advertisement (classad), matchmaker protocol, matchmaking algorithm and claiming protocols. Most of the time required to find a resource depends on the performance of the matchmaking algorithms. A distributed environment introduces a large set of heterogeneous resources which is always changing. The matchmaking algorithms should incorporate with this highly changing environment. In this paper we proposed a fast and efficient searching method for matchmaking algorithms which also deals with resource heterogeneity. The proposed approach reduces the searching time to a linear function from a cubic function proposed by R. Raman, M. Livny, and M. Solomon. We discuss briefly the working principles of the method and compare the experimental results of the proposed matchmaking algorithm with those of the existing algorithm. Copyright © 2008 John Wiley & Sons, Ltd. [source] Trends in wound care , our changing environmentINTERNATIONAL WOUND JOURNAL, Issue 3 2006Dr Douglas Queen Editor No abstract is available for this article. [source] Sexual vs. asexual reproduction in an ecosystem engineer: the massive coral Montastraea annularisJOURNAL OF ANIMAL ECOLOGY, Issue 2 2007NICOLA L. FOSTER Summary 1Long-lived sedentary organisms with a massive morphology are often assumed to utilize a storage effect whereby the persistence of a small group of adults can maintain the population when sexual recruitment fails. However, employing storage effects could prove catastrophic if, under changing climatic conditions, the time period between favourable conditions becomes so prolonged that the population cannot be sustained solely be sexual recruitment. When a species has multiple reproductive options, a rapidly changing environment may favour alternative asexual means of propagation. 2Here, we revisit the importance of asexual dispersal in a massive coral subject to severe climate-induced disturbance. Montastraea annularis is a major framework-builder of Caribbean coral reefs but its survival is threatened by the increasing cover of macroalgae that prevents settlement of coral larvae. 3To estimate levels of asexual recruitment within populations of M. annularis, samples from three sites in Honduras were genotyped using four, polymorphic microsatellite loci. 4A total of 114 unique genets were identified with 8% consisting of two or more colonies and an exceptionally large genet at the third site comprising 14 colonies. 5At least 70% of multicolony genets observed were formed by physical breakage, consistent with storm damage. 6Our results reveal that long-lived massive corals can propagate using asexual methods even though sexual strategies predominate. [source] Herbivore and neighbour effects on tundra plants depend on species identity, nutrient availability and local environmental conditionsJOURNAL OF ECOLOGY, Issue 1 2008Anu Eskelinen Summary 1I performed a factorial transplant experiment to test the roles of plant,plant interactions, herbivory by mammal grazers and resource availability for plant performance in two contrasting habitat types in a mountain tundra environment. 2Three perennial dicot herbs, Solidago virgaurea, Erigeron uniflorus and Saussurea alpina, were used as target plants to study the effects of neighbour removal and grazer exclusion, and nutrient enrichment and liming on plant growth, survival and reproductive success. These treatments were replicated in two contrasting habitat types, infertile acidic and fertile non-acidic tundra heaths. 3The effects of plant,plant interactions on Saussurea varied from facilitation in infertile acidic habitats to competition in fertile non-acidic habitats and in nutrient-enriched conditions, while the overall performance of Saussurea was strongly negatively influenced by the presence of grazers, the effects being greater when plants were fertilized and in fertile non-acidic heaths. Erigeron performed better under nutrient-enriched conditions than in unfertilized plots, when neighbours had been removed. Solidago was negatively affected by grazing and this impact was greater in nutrient-enriched plots and in non-acidic heaths than in acidic heaths and for unfertilized controls. There were no interactions between neighbour removal and herbivory in any of the three species, indicating that these processes operated independently. 4Grazer-preferred tall plants are strongly limited by consumption by mammal herbivores in nutrient-enriched conditions and in inherently fertile habitats. By contrast, arctic,alpine specialists and species of low stature experience increased competition with neighbouring vegetation in fertile habitats and in enriched nutrient conditions. 5Synthesis. Overall, the results suggest that the strength and directions of plant,plant and plant,herbivore interactions depend on plant species identity and are modified by soil edaphic factors to govern vegetation processes in tundra plant communities. These findings have important implications for understanding the forces structuring vegetation in barren tundra ecosystems under a changing environment. [source] Muscle precursor cells isolated from aged rats exhibit an increased tumor necrosis factor-, responseAGING CELL, Issue 1 2009Simon J. Lees Summary Improving muscle precursor cell (MPC, muscle-specific stem cells) function during aging has been implicated as a key therapeutic target for improving age-related skeletal muscle loss. MPC dysfunction during aging can be attributed to both the aging MPC population and the changing environment in skeletal muscle. Previous reports have identified elevated levels of tumor necrosis factor-, (TNF-,) in aging, both circulating and locally in skeletal muscle. The purpose of the present study was to determine if age-related differences exist between TNF-,-induced nuclear factor-kappa B (NF-,B) activation and expression of apoptotic gene targets. MPCs isolated from 32-month-old animals exhibited an increased NF-,B activation in response to 1, 5, and 20 ng mL,1 TNF-,, compared to MPCs isolated from 3-month-old animals. No age differences were observed in the rapid canonical signaling events leading to NF-,B activation or in the increase in mRNA levels for TNF receptor 1, TNF receptor 2, TNF receptor-associated factor 2 (TRAF2), or Fas (CD95) observed after 2 h of TNF-, stimulation. Interestingly, mRNA levels for TRAF2 and the cell death-inducing receptor, Fas (CD95), were persistently upregulated in response to 24 h TNF-, treatment in MPCs isolated from 32-month-old animals, compared to 3-month-old animals. Our data indicate that age-related differences may exist in the regulatory mechanisms responsible for NF-,B inactivation, which may have an effect on TNF-,-induced apoptotic signaling. These findings improve our understanding of the interaction between aged MPCs and the changing environment associated with age, which is critical for the development of potential clinical interventions aimed at improving MPC function with age. [source] Forecasting with leading indicators revisitedJOURNAL OF FORECASTING, Issue 8 2003Ruey S. Tsay Abstract Transfer function or distributed lag models are commonly used in forecasting. The stability of a constant-coefficient transfer function model, however, may become an issue for many economic variables due in part to the recent advance in technology and improvement in efficiency in data collection and processing. In this paper, we propose a simple functional-coefficient transfer function model that can accommodate the changing environment. A likelihood ratio statistic is used to test the stability of a traditional transfer function model. We investigate the performance of the test statistic in the finite sample case via simulation. Using some well-known examples, we demonstrate clearly that the proposed functional-coefficient model can substantially improve the accuracy of out-of-sample forecasts. In particular, our simple modification results in a 25% reduction in the mean squared errors of out-of-sample one-step-ahead forecasts for the gas-furnace data of Box and Jenkins. Copyright © 2003 John Wiley & Sons, Ltd. [source] Diacylglycerol kinases in the regulation of dendritic spinesJOURNAL OF NEUROCHEMISTRY, Issue 3 2010Karam Kim J. Neurochem. (2010) 112, 577,587. Abstract Diacylglycerol (DAG) is an important lipid-signaling molecule that binds and activates various downstream effectors. Tight control over the production and removal of DAG is important in maintaining the dynamic responses of the DAG signaling system to a changing environment. Diacylglycerol kinases (DGKs) are enzymes that convert DAG to phosphatidic acid (PA). This conversion terminates DAG signaling and, at the same time, initiates additional signaling events downstream of PA, which also acts as a lipid-signaling molecule. However, little is known about how (or if) DGKs are targeted to specific subcellular sites or how DGKs tightly regulate local DAG and PA signaling. Dendritic spines are tiny protrusions on neuronal dendrites that receive the majority of excitatory synaptic inputs. They are also the sites where DAG molecules are produced through activation of postsynaptic receptors, including metabotropic glutamate receptors and NMDA receptors. Accumulating evidence indicates that synaptic levels of DAG and PA are important determinants of dendritic spine stability and that the DGK, isoform at excitatory postsynaptic sites is critically involved in spine maintenance. In addition, DGK, appears to form a multi-protein complex with functionally related proteins to organize efficient DAG and PA signaling pathways at excitatory synapses. [source] Clinical supervision for mental health nurses in Northern Ireland: formulating best practice guidelinesJOURNAL OF PSYCHIATRIC & MENTAL HEALTH NURSING, Issue 5 2007F. RICE rmn msc Nurses work in a constantly challenging and changing environment. Within this context, there is a continuing need for support. Such support will help increase morale, decrease strain and burnout, and encourage self-awareness and self-expression. Clinical supervision address all these issues and enhances the quality of care for patients. While clinical supervision is a policy imperative in Northern Ireland, it was clear that there were problems in its implementation in mental health nursing. The aim of this project was to explore ways to make clinical supervision available to all mental health nurses and to improve and evaluate their contribution to patient care. The research team undertook a comprehensive literature review and a baseline survey of relevant stakeholders. Results represent the outcome of the group work. They will assist healthcare providers to develop local policies and procedures on clinical supervision for practising mental health nurses. [source] Legislative Issues Impacting On The Practice Of The South African Nurse PractitionerJOURNAL OF THE AMERICAN ACADEMY OF NURSE PRACTITIONERS, Issue 1 2002Nelouise Geyer Purpose To present an overview of the impact of the nurse practitioner (NP) on the South African health care arena and describe the legislative framework for NP practice. Data Sources Statutes and laws of the government of South Africa; published professional guidelines; authors' experiences. Conclusions The key challenges for NPs in South Africa lie in lobbying for enabling legislation, obtaining access to education and training opportunities, and managing risks within the rapidly changing environment. Implications for Practice Some aspects of the NP's accountability and responsibilities have as yet not been adequately addressed in the current legislative framework and will certainly increase the risk for malpractice. South African NPs will have to establish partnerships with important role players, not only in South Africa, but also internationally, to ensure that an enabling environment for quality health services is created. [source] Molecular ecology of global changeMOLECULAR ECOLOGY, Issue 19 2007THORSTEN B. H. REUSCH Abstract Global environmental change is altering the selection regime for all biota. The key selective factors are altered mean, variance and seasonality of climatic variables and increase in CO2 concentration itself. We review recent studies that document rapid evolution to global climate change at the phenotypic and genetic level, as a response to shifts in these factors. Among the traits that have changed are photoperiod responses, stress tolerance and traits associated with enhanced dispersal. The genetic basis of two traits with a critical role under climate change, stress tolerance and photoperiod behaviour, is beginning to be understood for model organisms, providing a starting point for candidate gene approaches in targeted nonmodel species. Most studies that have documented evolutionary change are correlative, while selection experiments that manipulate relevant variables are rare. The latter are particularly valuable for prediction because they provide insight into heritable change to simulated future conditions. An important gap is that experimental selection regimes have mostly been testing one variable at a time, while synergistic interactions are likely under global change. The expanding toolbox available to molecular ecologists holds great promise for identifying the genetic basis of many more traits relevant to fitness under global change. Such knowledge, in turn, will significantly advance predictions on global change effects because presence and polymorphism of critical genes can be directly assessed. Moreover, knowledge of the genetic architecture of trait correlations will provide the necessary framework for understanding limits to phenotypic evolution; in particular as lack of critical gene polymorphism or entire pathways, metabolic costs of tolerance and linkage or pleiotropy causing negative trait correlations. Synergism among stressor impacts on organismal function may be causally related to conflict among transcriptomic syndromes specific to stressor types. Because adaptation to changing environment is always contingent upon the spatial distribution of genetic variation, high-resolution estimates of gene flow and hybridization should be used to inform predictions of evolutionary rates. [source] Small non-coding RNAs, co-ordinators of adaptation processes in Escherichia coli: the RpoS paradigmMOLECULAR MICROBIOLOGY, Issue 4 2003F. Repoila Summary Adaptation to the changing environment requires both the integration of external signals and the co-ordination of internal responses. Around 50 non-coding small RNAs (sRNAs) have been described in Escherichia coli; the levels of many of these vary with changing environmental conditions. This suggests that they play a role in cell adaptation. In this review, we use the regulation of RpoS (,38) translation as a paradigm of sRNA-mediated response to environmental conditions; rpoS is currently the only known gene regulated post-transcriptionally by at least three sRNAs. DsrA and RprA stimulate RpoS translation in response to low temperature and cell surface stress, respectively, whereas OxyS represses RpoS translation in response to oxidative shock. However, in addition to regulating RpoS translation, DsrA represses the translation of HNS (a global regulator of gene expression), whereas OxyS represses the translation of FhlA (a transcriptional activator), allowing the cell to co-ordinate different pathways involved in cell adaptation. Environmental cues affect the synthesis and stability of specific sRNAs, resulting in specific sRNA-dependent translational control. [source] Introduction to "In Focus: Global Change and Adaptation in Local Places"AMERICAN ANTHROPOLOGIST, Issue 3 2009Donald R. Nelson ABSTRACT In recognition of unavoidable changes that human actions are producing in our environment, the term adaptation has become ubiquitous in the environmental and climate-change literature. Human adaptation is a field with a significant history in anthropology, yet anthropological contributions to the burgeoning field of climate change remain limited. This "In Focus" section presents studies of local adaptations to climate variation and change. Each is concerned with current environmental challenges and future environmental change, and each study is placed within a wider context that includes processes of globalization and integration into market economies, formal and informal institutions, and disasters. These studies highlight the challenges involved in understanding complex adaptations under conditions of stress. They also illustrate how anthropologists engage the larger climate-change and human-adaptation discussions and enhance our ability to respond to the challenges of a changing environment. [source] The role of cell-specific circadian clocks in metabolism and diseaseOBESITY REVIEWS, Issue 2009M. S. Bray Summary Biological rhythms are an integral component of essentially all aspects of life. These rhythms are controlled in part by circadian clocks, transcriptionally based mechanisms that synchronize the organism to its changing environment. The central circadian clock is located within the suprachiasmatic nucleus of the brain, while peripheral clocks are located within virtually all cells outside of the suprachiasmatic nucleus. Although our understanding of central clock structure and function is well advanced, the role of peripheral clocks in whole body energy metabolism is just beginning to be elucidated. Both central and peripheral circadian clocks likely regulate many physiological functions, including insulin sensitivity, endocrine regulation, energy homeostasis, satiety signalling, cellular proliferation and cardiovascular function. Widely varying phenotypes have been reported following global genetic disruption of the clock mechanism in mice, with phenotype dependent on both the clock component targeted and genetic background. The inconsistency in phenotypes associated with clock disruption may be due, in part, to cell-specific effects of the circadian clocks. To address this question, many laboratories have begun generating animal models of cell type-specific clock disruption. In this review, we summarize the existing literature on tissue-specific models of circadian clock disruption and provide a focus for future research in this area. [source] Consequences of sequential attack for resistance to herbivores when plants have specific induced responsesOIKOS, Issue 8 2007D. V. Viswanathan Plants in nature are attacked sequentially by herbivores, and theory predicts that herbivore-specific responses allow plants to tailor their defenses. We present a novel field test of this hypothesis, and find that specific responses of Solanum dulcamara lead to season-long consequences for two naturally colonizing herbivores, irrespective of the second herbivore to attack plants. This result indicates that responses induced by the initial herbivore made plants less responsive to subsequent attack. We show that initial herbivory by flea beetles and tortoise beetles induce distinct plant chemical responses. Initial herbivory by flea beetles lowered the occurrence of conspecifics and tortoise beetles relative to controls. Conversely, initial herbivory by tortoise beetles did not influence future herbivory. Remarkably, the experimentally imposed second herbivore to feed on plants did not modify consequences (induced resistance or lack thereof) of the first attacker. Induction of plant chemical responses was consistent with these ecological effects; i.e. the second herbivore did not modify the plant's initial induced response. Thus, canalization of the plant resistance phenotype may constrain defensive responses in a rapidly changing environment. [source] Temperature Effects on Survival and DNA Repair in Four Freshwater Cladoceran Daphnia Species Exposed to UV RadiationPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2009Sandra J. Connelly The biological responses of four freshwater daphniid species, Daphnia middendorffiana, D. pulicaria, D. pulex and D. parvula, to a single acute dose of ultraviolet B radiation (UVB) were compared. In addition to survival, we compared the induction of DNA damage (i.e. cyclobutane pyrimidine dimers) between species as well as the ability to repair this damage in the presence or absence of photoreactivating light. All four species showed high levels of shielding against DNA damage when compared to damage induced in purified DNA dosimeters at the same time and dose. Significant variation in survival was observed between species depending on temperature and light conditions. Contrary to our expectations, all species showed significantly higher survival and light-dependent DNA damage removal rates at 10°C compared to 20°C, suggesting that the enhanced rate of photoenzymatic repair (PER) at the lower temperature contributed significantly to the recovery of these organisms from UVB. PER was highly effective in promoting survival of three of the four species at 10°C, but at 20°C it was only partially effective in two species, and ineffective in two others. None of the species showed significant dark repair at 20°C and only D. pulicaria showed a significant capacity at 10°C. Two species, D. middendorffiana and D. pulex, showed some short-term survival at 10°C in absence of PER despite their inability to repair any appreciable amount of DNA damage in the dark. All species died rapidly at 20°C in absence of PER, as predicted from complete or near-absence of nucleotide excision repair (NER). Overall, the protective effects of tissue structure and pigmentation were similar in all Daphnia species tested and greatly mitigated the absorption of UVB by DNA and its damaging effects. Surprisingly, the visibly melanotic D. middendorffiana was not better shielded from DNA damage than the three non-melanotic species, and in fact suffered the highest damage rates. Melanin content in this species was not temperature dependent under the experimental growth conditions, and so did not contribute to temperature-dependent responses. It is evident that different species within the same genus have developed diverse biological responses to UVB. Our data strongly suggest that DNA damage is lethal to Daphnia and that photoenzymatic repair is the primary mechanism for removing these lesions. In the absence of light, few species are capable of removing any DNA damage. Surprisingly, the single species in which significant excision repair was detected did so only at reduced temperature. This temperature-dependence of excision repair is striking and may reflect adaptations of certain organisms to stress in a complex and changing environment. [source] Fetal signaling through placental structure and endocrine function: Illustrations and implications from a nonhuman primate modelAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 6 2009Julienne N. Rutherford The placenta is a transmitter of fetal need and fetal quality, interfacing directly with maternal physiology and ecology. Plasticity of placental structure and function across the developmental timeframe of gestation may serve as an important tool by which a fetus calibrates its growth to shifting maternal ecology and resource availability, and thereby signals its quality and adaptability to a changing environment. Signals of this quality may be conveyed by the size of the placental interface, an important marker of fetal access to maternal resources, or by production of placental insulin-like growth factor-II, a driver of fetoplacental growth. Litter size variation in the common marmoset monkey offers the opportunity to explore intrauterine resource allocation and placental plasticity in an important nonhuman primate model. Triplet marmosets are born at lower birth weights and have poorer postnatal outcomes and survivorship than do twins; triplet placentas differ in placental efficiency, microscopic morphology, and endocrine function. Through placental plasticity, triplet fetuses are able to adjust functional access to maternal resources in a way that allows pregnancy to proceed. However, the costs of such mechanisms may relate to reduced fetal growth and altered postnatal outcomes, with the potential to lead to adverse adult health consequences, suggesting an important link between the placenta itself and the developmental origins of health and disease. Am. J. Hum. Biol. 2009. © 2009 Wiley-Liss, Inc. [source] Comparative Effectiveness Research and Evidence-Based Health Policy: Experience from Four CountriesTHE MILBANK QUARTERLY, Issue 2 2009KALIPSO CHALKIDOU Context: The discussion about improving the efficiency, quality, and long-term sustainability of the U.S. health care system is increasingly focusing on the need to provide better evidence for decision making through comparative effectiveness research (CER). In recent years, several other countries have established agencies to evaluate health technologies and broader management strategies to inform health care policy decisions. This article reviews experiences from Britain, France, Australia, and Germany. Methods: This article draws on the experience of senior technical and administrative staff in setting up and running the CER entities studied. Besides reviewing the agencies' websites, legal framework documents, and informal interviews with key stakeholders, this analysis was informed by a workshop bringing together U.S. and international experts. Findings: This article builds a matrix of features identified from the international models studied that offer insights into near-term decisions about the location, design, and function of a U.S.-based CER entity. While each country has developed a CER capacity unique to its health system, elements such as the inclusiveness of relevant stakeholders, transparency in operation, independence of the central government and other interests, and adaptability to a changing environment are prerequisites for these entities' successful operation. Conclusions: While the CER entities evolved separately and have different responsibilities, they have adopted a set of core structural, technical, and procedural principles, including mechanisms for engaging with stakeholders, governance and oversight arrangements, and explicit methodologies for analyzing evidence, to ensure a high-quality product that is relevant to their system. [source] The Ca2+ -dependent protein kinase CPK3 is required for MAPK-independent salt-stress acclimation in ArabidopsisTHE PLANT JOURNAL, Issue 3 2010Norbert Mehlmer Summary Plants use different signalling pathways to respond to external stimuli. Intracellular signalling via calcium-dependent protein kinases (CDPKs) or mitogen-activated protein kinases (MAPKs) present two major pathways that are widely used to react to a changing environment. Both CDPK and MAPK pathways are known to be involved in the signalling of abiotic and biotic stresses in animal, yeast and plant cells. Here, we show the essential function of the CDPK CPK3 (At4g23650) for salt stress acclimation in Arabidopsis thaliana, and test crosstalk between CPK3 and the major salt-stress activated MAPKs MPK4 and MPK6 in the salt stress response. CPK3 kinase activity was induced by salt and other stresses after transient overexpression in Arabidopsis protoplasts, but endogenous CPK3 appeared to be constitutively active in roots and leaves in a strictly Ca2+ -dependent manner. cpk3 mutants show a salt-sensitive phenotype comparable with mutants in MAPK pathways. In contrast to animal cells, where crosstalk between Ca2+ and MAPK signalling is well established, CPK3 seems to act independently of those pathways. Salt-induced transcriptional induction of known salt stress-regulated and MAPK-dependent marker genes was not altered, whereas post-translational protein phosphorylation patterns from roots of wild type and cpk3 plants revealed clear differences. A significant portion of CPK3 was found to be associated with the plasma membrane and the vacuole, both depending on its N -terminal myristoylation. An initial proteomic study led to the identification of 28 potential CPK3 targets, predominantly membrane-associated proteins. [source] Adapting wheat cultivars to resource conserving farming practices and human nutritional needsANNALS OF APPLIED BIOLOGY, Issue 4 2005R M TRETHOWAN Summary As farmers increasingly adopt resource conserving farming practices, there is a need for wheat cultivars that better adapt to the changing environment and the nutritional needs of people, particularly those living in developing countries. Improved adaptation to zero and minimum tillage, better water use efficiency, improved root health, durable resistance to foliar diseases and enhanced nutritional value of the grain are key selection criteria for plant breeders. Significant responses to selection for these constraints have been achieved at the International Maize and Wheat Improvement Center (CIMMYT), by selecting segregating populations and advanced lines in carefully managed tillage, moisture deficit and heat stressed environments, that correlate with key spring wheat growing environments globally. Root health has been improved through a combination of marker assisted selection and disease bioassays, and the nutritional value of wheat grain has been enhanced using genetic variation for high Fe and Zn grain content found among tetraploid wheat ancestral species. [source] Ensuring a graduated integrated progression of learning in a changing environmentANZ JOURNAL OF SURGERY, Issue 3 2009W. E. G. Thomas Abstract Surgical training is under threat in the changing environment of today. In the past, training consisted of an apprenticeship, which is no longer feasible or practical within the time limitation imposed on trainees currently, and so a new and innovative approach is required to train the surgeons of tomorrow. There is therefore a need for an explicit curriculum that ensures a graduated and integrated progression of learning in which both trainees and trainers are aware of what is required for each stage in training and for each surgical specialty. Such a curriculum has now been developed in the UK. [source] The brain's calendar: neural mechanisms of seasonal timingBIOLOGICAL REVIEWS, Issue 1 2004Michel A. Hofman ABSTRACT The suprachiasmatic nucleus (SCN) of the hypothalamus is the principal component of the mammalian biological clock, the neural timing system that generates and coordinates a broad spectrum of physiological, endocrine and behavioural circadian rhythms. The pacemaker of the SCN oscillates with a near 24 h period and is entrained to the diurnal light-dark cycle. Consistent with its role in circadian timing, investigations in rodents and non-human primates furthermore suggest that the SCN is the locus of the brain's endogenous calendar, enabling organisms to anticipate seasonal environmental changes. The present review focuses on the neuronal organization and dynamic properties of the biological clock and the means by which it is synchronized with the environmental lighting conditions. It is shown that the functional activity of the biological clock is entrained to the seasonal photic cycle and that photoperiod (day length) may act as an effective zeitgeber. Furthermore, new insights are presented, based on electrophysiological and molecular studies, that the mammalian circadian timing system consists of coupled oscillators and that the clock genes of these oscillators may also function as calendar genes. In summary, there are now strong indications that the neuronal changes and adaptations in mammals that occur in response to a seasonally changing environment are driven by an endogenous circadian clock located in the SCN, and that this neural calendar is reset by the seasonal fluctuations in photoperiod. [source] | ||||||||||||||||||||||||||||||||||||||||