Home About us Contact
|
Home About us Contact | ||
|
|
||
Likely Role (likely + role)
Selected AbstractsAgriculture's Likely Role in Meeting Canada's Kyoto Commitments,CANADIAN JOURNAL OF AGRICULTURAL ECONOMICS, Issue 4 2005Alfons Weersink Voluntary adoption of beneficial management practices will be the primary means by which farmers cut net greenhouse gas (GHG) emissions. The offset system will not be a major driver due to (a) the relatively low prices likely to be offered by large final emitters facing an emission cap, (b) discounts applied to those prices for temporary sequestration, (c) the transaction costs and risk premiums associated with signing carbon contracts, and (d) the low elasticity of supply of CO2 abatement. Although Canadian farmers are likely to participate to only a limited extent in the carbon-offset market, many will find it profitable to adopt one or more of the BMPs for reducing net GHG emissions. Canadian agriculture is likely to contribute significantly to net emission reductions by voluntarily sequestering carbon due to the adoption of zero till in the last decade, and possibly by cutting fertilizer levels in the next decade. The contribution will be mainly a response to meeting personal economic objectives rather than being induced by direct incentives through the offset program. L'adoption volontaire de pratiques de gestion bénéfiques (PGB) sera le principal moyen dont les producteurs disposeront pour diminuer les émissions de gaz à effet de serre (GES). Le système de compensation des GES ne constituera pas un facteur de motivation important pour les raisons suivantes: a) les faibles prix qu'offriront probablement les grands émetteurs finaux confrontés à un plafond d'émissions; b) les escomptes appliqués à ces prix pour la séquestration temporaire; c) les coûts de transaction et les primes de risque associés à la conclusion de contrats de réduction des émissions de carbone; d) la faible élasticité de l'offre de réduction du CO2. Bien que la participation des producteurs canadiens au marché de contrepartie de la fixation du carbone sera probablement limitée, de nombreux producteurs trouveront qu'il est rentable d'adopter une ou plusieurs PGB pour réduire l'émission nette de GES. L'apport de l'agriculture canadienne à la réduction nette des émissions sera probablement important compte tenu de la séquestration volontaire du carbone découlant de l'adoption du semis direct au cours de la dernière décennie et de la diminution probable des concentrations de fertilisants au cours de la prochaine décennie. L'apport sera principalement liéà l'atteinte d'objectifs économiques personnels plutôt qu'aux incitatifs directs du programme de contrepartie de la fixation du carbone. [source] The replication fork trap and termination of chromosome replicationMOLECULAR MICROBIOLOGY, Issue 6 2008Iain G. Duggin Summary Bacteria that have a circular chromosome with a bidirectional DNA replication origin are thought to utilize a ,replication fork trap' to control termination of replication. The fork trap is an arrangement of replication pause sites that ensures that the two replication forks fuse within the terminus region of the chromosome, approximately opposite the origin on the circular map. However, the biological significance of the replication fork trap has been mysterious, as its inactivation has no obvious consequence. Here we review the research that led to the replication fork trap theory, and we aim to integrate several recent findings that contribute towards an understanding of the physiological roles of the replication fork trap. Likely roles include the prevention of over-replication, and the optimization of post-replicative mechanisms of chromosome segregation, such as that involving FtsK in Escherichia coli. [source] Structural dynamics and robustness of food websECOLOGY LETTERS, Issue 7 2010Phillip P. A. Staniczenko Ecology Letters (2010) 13: 891,899 Abstract Food web structure plays an important role when determining robustness to cascading secondary extinctions. However, existing food web models do not take into account likely changes in trophic interactions (,rewiring') following species loss. We investigated structural dynamics in 12 empirically documented food webs by simulating primary species loss using three realistic removal criteria, and measured robustness in terms of subsequent secondary extinctions. In our model, novel trophic interactions can be established between predators and food items not previously consumed following the loss of competing predator species. By considering the increase in robustness conferred through rewiring, we identify a new category of species , overlap species , which promote robustness as shown by comparing simulations incorporating structural dynamics to those with static topologies. The fraction of overlap species in a food web is highly correlated with this increase in robustness; whereas species richness and connectance are uncorrelated with increased robustness. Our findings underline the importance of compensatory mechanisms that may buffer ecosystems against environmental change, and highlight the likely role of particular species that are expected to facilitate this buffering. [source] A likely role for anoxygenic photosynthetic microbes in the formation of ancient stromatolitesGEOBIOLOGY, Issue 2 2007T. BOSAK ABSTRACT Although cyanobacteria are the dominant primary producers in modern stromatolites and other microbialites, the oldest stromatolites pre-date geochemical evidence for oxygenic photosynthesis and cyanobacteria in the rock record. As a step towards the development of laboratory models of stromatolite growth, we tested the potential of a metabolically ancient anoxygenic photosynthetic bacterium to build stromatolites. This organism, Rhodopseudomonas palustris, stimulates the precipitation of calcite in solutions already highly saturated with respect to calcium carbonate, and greatly facilitates the incorporation of carbonate grains into proto-lamina (i.e. crusts). The appreciable stimulation of the growth of proto-lamina by a nonfilamentous anoxygenic microbe suggests that similar microbes may have played a greater role in the formation of Archean stromatolites than previously assumed. [source] Mammalian sperm quality and aromatase expressionMICROSCOPY RESEARCH AND TECHNIQUE, Issue 8 2009Serge Carreau Abstract In most mammalian species the aromatase is encoded by a single gene (cyp19), which contains 18 exons, 9 of them being translated. In adult rats, together with Leydig cells germ cells represent an additional source of estrogens. The amount of P450arom transcript is threefold higher in pachytene spermatocytes compared to younger cells (spermatogonia-preleptotene spermatocyte) or round spermatids; conversely, aromatase activity is more intense in haploid cells. In man besides Leydig cells, we have shown the presence of a biologically active aromatase and of estrogen receptors (ER, and ERß) in immature germ cells and ejaculated spermatozoa. Concerning aromatase, a 30% decrease of the amount of mRNA is observed in immotile compared to motile sperm fraction from the same sample; moreover, the aromatase activity is diminished. We have amplified aromatase mRNA by RT-real time PCR in spermatozoa from asthenospermic, teratospermic, and asthenoteratospermic men and recorded respectively 44, 52, and 67% decreases of the amount of transcripts as compared to controls. Statistical analyses between the sperm morphology and the aromatase/GAPDH ratio have revealed a high degree of correlation (r = ,0.64) with the percentage of abnormal spermatozoa (especially microcephaly and acrosome malformations). Alterations of sperm number and motility have been described in men genetically deficient in aromatase, which together with our data, suggest a likely role for aromatase/estrogens in the acquisition of sperm motility. Therefore besides gonadotrophins and testosterone, estrogens produced locally should be considered as a physiologically relevant hormone involved in the regulation of mammalian spermatogenesis. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc. [source] ACTH and adrenocortical gap junctionsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 3 2003Sandra A. Murray Abstract Since the initial identification of gap junctions in the adrenal gland, it has been proposed that a system involving direct cell,cell communication might be involved in adrenal cortical functions. Gap junction channels do, in fact, provide pathways for direct intercellular exchange of small molecules (<1,000 Da), many of which have the potential to influence a wide range of cellular activities. Gap junctions are composed of proteins called connexin which, in the adrenal cortex, have proven to be remarkably consistent in both type and zonal distribution with connexin 43 (Cx43) as the predominant component in mammalian adrenal glands thus far evaluated. Only the inner two zones of the cortex (zonae fasciculata and reticularis) exhibit significant amounts of Cx43 and functional coupling. Adrenocorticotropin (ACTH) has been shown to increase Cx43 protein in vivo and in vitro, and a strong correlation has been noted between the presence of gap junctions and certain adrenal cortical functions, especially steroidogenic capacity and cell proliferation. This review summarizes evidence of the Cx43 expression in adrenal cortical cells and the likely role of Cx43 in steroidogenesis and cell proliferation. It is concluded that control of gap junction expression in the adrenal gland is hormonally dependent and is functionally linked to adrenal gland zonation. Microsc. Res. Tech. 61:240,246, 2003. © 2003 Wiley-Liss, Inc. [source] Physical and psychological health of first and second generation Turkish immigrants in Germany,AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 4 2010Ashwin A. Kotwal Recent studies in Germany suggest that first generation Turkish immigrants have lower mortality rates compared to native Germans. Conversely, studies examining morbidity, though not national in scope, have demonstrated that first generation Turks may have poorer health than native Germans. Additionally, little is known about the health of the emerging second generation Turkish population in Germany. To evaluate the discrepancy between mortality and morbidity trends and contribute to a better understanding of second generation Turkish immigrant health, this paper uses a nationally-representative dataset, including the 2005 German Gender and Generations Study (GGS) (n = 10,017) and the 2006 GGS Turkish supplement (n = 4,045), to assess three health outcomes: chronic illness, self-assessed health, and feelings of emptiness. The paper investigates whether sex, age, socioeconomic status, emotional support, or duration of residence in Germany predict these dimensions of health. Results establish clear health status differences between Turks and native Germans. Surprisingly, both first and second generation Turks tend to have lower chronic illness rates and rate their health as better than Germans at younger ages, but the advantage diminishes among higher age strata for the first generation. Feelings of emptiness results generally indicate an increased susceptibility to psychological problems for both generations of Turks. Controlling for socioeconomic status and age reduces these health differences modestly, pointing to their likely role as mediators. The relatively higher risks for all three health outcomes among Turkish females of both generations compared to their German counterparts suggest that female Turkish immigrants and their female offspring may be particularly vulnerable. Am. J. Hum. Biol. 2010. © 2010 Wiley-Liss, Inc. [source] Annotation: Tourette syndrome: a relentless drumbeat , driven by misguided brain oscillationsTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 6 2006James F. Leckman Objective:, This annotation reviews recent evidence that points to the likely role of aberrant neural oscillations in the pathogenesis of Tourette syndrome (TS). Methods:, The available anatomic and electrophysiological findings in TS are reviewed in the context of an emerging picture of the crucial role that neural oscillations play in maintaining normal central nervous system (CNS) function. Results:, Neurons form behavior-dependent oscillating networks of various sizes and frequencies that bias input selection and facilitate synaptic plasticity, mechanisms that cooperatively support temporal representation as well as the transfer and long-term consolidation of information. Coherent network activity is likely to modulate sensorimotor gating as well as focused motor actions. When these networks are dysrhythmic, there may be a loss of control of sensory information and motor action. The known electrophysiological effects of medications and surgical interventions used to treat TS likely have an ameliorative effect on these aberrant oscillations. Similarly, a strong case can be made that successful behavioral treatments involve the willful training regions of the prefrontal cortex to engage in tic suppression and the performance of competing motor responses to unwanted sensory urges such that these prefrontal regions become effective modulators of aberrant thalamocortical rhythms. Conclusions:, A deeper understanding of neural oscillations may illuminate the complex, challenging, enigmatic, internal world that is TS. [source] Redox Reactions and Electron Transfer Across the Red Cell MembraneIUBMB LIFE, Issue 7 2003Eleanor Kennett Abstract Plasma membrane electron transport systems appear to be ubiquitous. These systems are implicated in hormone signal transduction, cell growth and differentiation events as well as protection from oxidative stress. The red blood cell is constantly exposed to oxidative stress; protection against the reactive species generated during this process may be the main role of its membrane electron transport systems. Membrane redox activity has been studied for over three-quarters of a century, and yet many questions remain regarding its identity and likely roles: are electron transfers by distinct and specific mechanisms; what are the physiological donors and acceptors; and how do these systems affect metabolism? Current evidence suggests that the human erythrocyte membrane contains a number of distinct electron transfer systems, some of which, at least, involve membrane proteins, and NADH or ascorbate as electron donors. The activity of these systems appears to be closely related to the metabolic state of the cell, suggesting that mediation of reducing equivalents across the plasma membrane allows redox buffering of each environment, intra- and extracellular, by the other. We have decided to study this from a new perspective, NMR spectroscopy the area of our own technical expertise, hence this review is slanted towards this more recent analysis. IUBMB Life, 55: 375-385, 2003 [source] | ||||||||||