9,670 research outputs found

    P metabolism and transport in AM fungi

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    The arbuscular mycorrhizal symbiosis is mutualistic, based on reciprocal transfer of P from the fungus to the plant and carbon from the plant to the fungus. Thus P is a most important 'currency' in the symbiosis. After absorbing P from the soil solution, the fungi first incorporate it into the cytosolic pool, and the excess P is transferred to the vacuoles. The vacuolar P pool probably plays a central role in P supply to the plant. The main forms of inorganic P in fungal vacuoles are orthophosphate and polyphosphate, but organic P molecules may also be present. Long distance translocation of P from the site of uptake in the external mycelium to the site of transfer to the plant is probably achieved via transfer of vacuolar components. This transport would be mediated either by protoplasmic streaming or the motile tubular vacuole-like system. The site of release of P into the interfacial apoplast and thence to the plant is most probably the fungal arbuscules. The biochemical and biophysical processes involved in P metabolism and transfer between cellular compartments in the symbiosis are currently not well understood. Some recent investigations of substrate specificities of phosphatase-type enzymes in AM fungi and other eukaryotic microorganisms, however, have shed new light on earlier results and permit the construction of a hypothetical scheme of P-flow, including possible regulatory factors. Steps in this scheme are experimentally testable and should stimulate future researc

    Using NCLB to Improve Student Achievement: An Action Guide for Community and Parent Leaders

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    This guide addresses the various provisions of the No Child Left Behind Act of 2001 (called NCLB, or the act). Included are specific rights, roles, and responsibilities that offer parents and community leaders opportunities to send the no-nonsense message that unequal educational opportunities will no longer be tolerated in their public schools.The guide highlights ways NCLB can be used to strengthen the public's voice in education, and to increase community and parental involvement in school-level and district-level operations and decisions:Identifies major areas of NCLB that require or provide for community and/or parental involvement in Title I (Improving the Academic Achievement of the Disadvantaged) and Title II (Preparing, Training, and Recruiting High-Quality Teachers and Principals) of the actProvides general information on the scope and requirements for each major area of community and parental engagementBreaks down legislative language into understandable terms and recommends actions that can be taken by parents and/or the community as a result of their rights under the actProvides a formatted and easily reproduced training tool for parent/teacher meetings and town meetingsIdentifies areas in the act that are silent about community and/or parental engagement, but where PEN believes openings in the law allow parents and/or the community to exercise leadership and take initiativ

    Unraveling the Influence of Arbuscular Mycorrhizal Colonization on Arsenic Tolerance in Medicago: Glomus mosseae is More Effective than G. intraradices, Associated with Lower Expression of Root Epidermal Pi Transporter Genes

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    We used medic (Medicago truncatula) to investigate effects of inoculation with two arbuscular mycorrhizal (AM) fungi and application of arsenate (AsV) and phosphate (Pi) on mechanisms underlying increased tolerance (in terms of growth) of AM plants to AsV. We tested the hypotheses that (1) inoculation with AM fungi results in down-regulation of MtPht1;1 and MtPht1;2 genes (encoding high-affinity Pi and AsV uptake systems in the direct root epidermal pathway) and up-regulation of the AM-induced MtPht1;4 (responsible for transfer of Pi from the arbuscular interface to cortical cells), and (2) these changes are involved in decreased As uptake relative to P uptake and hence increased As tolerance. We also measured expression of MtMT4, a Pi starvation-inducible gene, other genes encoding Pi uptake systems (MtPht 1;5 and MtPht1;6) and arsenate reductase (MtACR) and phytochelatin synthase (MtPCS), to gain insights into broader aspects of P transfers in AM plants and possible detoxification mechanisms. Medic responded slightly to AM colonization in terms of growth in the absence of As, but positively in terms of P uptake. Both growth and P responses in AM plants were positive when As was applied, indicating As tolerance relative to non-mycorrhizal (NM) plants. All AM plants showed high expression of MtPT4 and those inoculated with Glomus mosseae showed higher selectivity against As (shown by P/As molar ratios) and much lower expression of MtPht1;1 (and to some extent MtPht1;2) than Glomus intraradices-inoculated or NM plants. Results are consistent with increased P/As selectivity in AM plants (particularly those inoculated with G. mosseae) as a consequence of high P uptake but little or no As uptake via the AM pathway. However, the extent to which selectivity is dependent on down-regulation of direct Pi and AsV uptake through epidermal cells is still not clear. Marked up-regulation of a PCS gene and an ACR gene in AM plants may also be involved and requires further investigation

    Effects of individual differences and job characteristics on the psychological health of Italian nurses

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    The Demand Resources and Individual Effects Model (DRIVE Model) is a transactional model that integrates Demands- Control-Support and Effort-Reward Imbalance models emphasising the role of individual (Coping Strategies; Overcommitment) and job characteristics (Job Demands, Social Support, Decision Latitude, Skill Discretion, Effort, Rewards) in the work-related stress process. The present study aimed to test the DRIVE Model in a sample of 450 Italian nurses and to compare findings with those of a study conducted in a sample of UK nurses. A questionnaire composed of Ways of Coping Checklist-Revised (WCCL-R); Job Content Questionnaire (JCQ); ERI Test; Hospital Anxiety and Depression Scale (HADS) was used. Data supported the application of the DRIVE Model to the Italian context, showing significant associations of the individual characteristics of Problem-focused, Seek Advice and Wishful Thinking coping strategies and the job characteristics of Job Demands, Skill Discretion, Decision Latitude, and Effort with perceived levels of Anxiety and Depression. Effort represented the best predictor for psychological health conditions among Italian nurses, and Social Support significantly moderated the effects of Job Demands on perceived levels of Anxiety. The comparison study showed significant differences in the risk profiles of Italian and UK nurses. Findings were discussed in order to define focused interventions to promote nurses’ wellbeing

    Queen control of a key life-history event in a eusocial insect

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    In eusocial insects, inclusive fitness theory predicts potential queen–worker conflict over the timing of events in colony life history. Whether queens or workers control the timing of these events is poorly understood. In the bumble-bee Bombus terrestris, queens exhibit a ‘switch point’ in which they switch from laying diploid eggs yielding females (workers and new queens) to laying haploid eggs yielding males. By rearing foundress queens whose worker offspring were removed as pupae and sexing their eggs using microsatellite genotyping, we found that queens kept in the complete absence of adult workers still exhibit a switch point. Moreover, the timing of their switch points relative to the start of egg-laying did not differ significantly from that of queens allowed to produce normal colonies. The finding that bumble-bee queens can express the switch point in the absence of workers experimentally demonstrates queen control of a key life-history event in eusocial insects. In addition, we found no evidence that workers affect the timing of the switch point either directly or indirectly via providing cues to queens, suggesting that workers do not fully express their interests in queen–worker conflicts over colony life history

    Forecast analysis of the incidence of tuberculosis in the province of Quebec

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    BACKGROUND: While the overall population prevalence of tuberculosis in Quebec has been declining for many years, tuberculosis is still disproportionately more prevalent among the immigrant and Inuit communities. As such, the aim of this study was to forecast the incidence of tuberculosis in the Province of Quebec over time in order to examine the possible impact of future preventative and treatment programs geared to reducing such disparities. METHODS: A compartmental differential equation based on a Susceptible Exposed Latent Infectious Recovered (SELIR) model was simulated using the Euler method using Visual Basic for Applications in Excel. Demographic parameters were obtained from census data for the Province of Quebec and the model was fitted to past epidemiological data to extrapolate future values over the period 2015 to 2030. RESULTS: The trend of declining tuberculosis rates will continue in the general population, falling by 42% by 2030. The incidence among immigrants will decrease but never vanish, and may increase in the future. Among the Inuit, the incidence is expected to increase, reaching a maximum and then stabilizing, although if re-infection is taken into account it may continue to increase. Tuberculosis among non-indigenous Canadian born persons will continue to decline, with the disease almost eradicated in that group in the mid 21st century. CONCLUSIONS: While the incidence of tuberculosis in the Province of Quebec is expected to decrease overall, certain populations will remain at risk
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