3,251 research outputs found

    No evidence for a culturable bacterial tetrodotoxin producer in Pleurobranchaea maculata (Gastropoda: Pleurobranchidae) and Stylochoplana sp. (Platyhelminthes: Polycladida)

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    Tetrodotoxin (TTX) is a potent neurotoxin found in the tissues of many taxonomically diverse organisms. Its origin has been the topic of much debate, with suggestions including endogenous production, acquisition through diet, and symbiotic bacterial synthesis. Bacterial production of TTX has been reported in isolates from marine biota, but at lower than expected concentrations. In this study, 102 strains were isolated from Pleurobranchaea maculata (Opisthobranchia) and Stylochoplana sp. (Platyhelminthes). Tetrodotoxin production was tested utilizing a recently developed sensitive method to detect the C9 base of TTX via liquid chromatography—mass spectrometry. Bacterial strains were characterized by sequencing a region of the 16S ribosomal RNA gene. To account for the possibility that TTX is produced by a consortium of bacteria, a series of experiments using marine broth spiked with various P. maculata tissues were undertaken. Sixteen unique strains from P. maculata and one from Stylochoplana sp. were isolated, representing eight different genera; Pseudomonadales, Actinomycetales, Oceanospirillales, Thiotrichales, Rhodobacterales, Sphingomonadales, Bacillales, and Vibrionales. Molecular fingerprinting of bacterial communities from broth experiments showed little change over the first four days. No C9 base or TTX was detected in isolates or broth experiments (past day 0), suggesting a culturable microbial source of TTX in P. maculata and Stylochoplana sp. is unlikely

    The BBC: Guardian of Public Understanding

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    The British Broadcasting Corporation (BBC) is a long-standing institution with a worldwide reputation as the maker and supplier of trustworthy news embedded in programmes aimed at serving the public not commoditising it. This chapter describes the BBC’s institutional DNA and explains how its birth characteristics informed its institutional trajectory over the decades. The chapter discusses the internal principles and the particular ‘craft’ that has made this a true British institution that has become equally revered outside Britain’s borders. It analyses how the BBC survived institutional crises to reach a moment in history where the very idea underlying this venerable but agile institution has come under fire

    Investigating diet as the source of tetrodotoxin in Pleurobranchaea maculata

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    The origin of tetrodotoxin (TTX) is highly debated; researchers have postulated either an endogenous or exogenous source with the host accumulating TTX symbiotically or via food chain transmission. The aim of this study was to determine whether the grey side-gilled sea slug (Pleurobranchaea maculata) could obtain TTX from a dietary source, and to attempt to identify this source through environmental surveys. Eighteen non-toxic P. maculata were maintained in aquariums and twelve were fed a TTX-containing diet. Three P. maculata were harvested after 1 h, 24 h, 17 days and 39 days and TTX concentrations in their stomach, gonad, mantle and remaining tissue/fluids determined using liquid chromatography-mass spectrometry. Tetrodotoxin was detected in all organs/tissue after 1 h with an average uptake of 32%. This decreased throughout the experiment (21%, 15% and 9%, respectively). Benthic surveys at sites with dense populations of toxic P. maculata detected very low or no TTX in other organisms. This study demonstrates that P. maculata can accumulate TTX through their diet. However, based on the absence of an identifiable TTX source in the environment, in concert with the extremely high TTX concentrations and short life spans of P. maculata, it is unlikely to be the sole TTX source for this species

    B799: Field Appraisal of Resource Management Systems Farms Crop Yield and Quality Relationships with Soil Erosion

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    This document presents objectives and preliminary results of the Field Appraisal of Resource Management Systems (FARMS) study. This study assumes that estimates of soil erosion using the Universal Soil Loss Equation (USLE) represent long-term rather than short- term effects. The FARMS study randomly sampled 2400 plots over a three year period, 1980-82, for: crop management, soils, conservation practices and management, crop yields, soil chemistry, and sociological data. This report presents analyses from the 800 plots sampled in 1980. Statistics of rill and sheet soil erosion, as estimated by the Universal Soil Loss Equation (USLE), are presented. Data are presented for each of the factors in the USLE, for potato yields and quality, for yield of other field crops, and for soil nutrient analyses. A significant response of yield to erosion was found when the dataset was limited to the most commonly found soil, Caribou (144 plots). Data analyses including potato yields for all varieties and soils (429 plots) do not show any relation to predicted erosion. Regression analysis predicts that for each ton increase in soil erosion per acre per year up to 12 tons, a decrease of 2.3 hundred- weight of potatoes per acre will occur. The cover and management factor (C) was found to be the most important variable in the USLE in predicting potato yield decreases. With each increase of 0.1 C, the predicted yield decrease amounted to 17 hundredweight gross for potatoes, and 20 hundredweight decrease for US-1 potatoes per acre.https://digitalcommons.library.umaine.edu/aes_bulletin/1113/thumbnail.jp

    Are Audience Response Systems Worth the Cost? Comparing Question-Driven Teaching Strategies for Emergency Medical Technician Education

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    Purpose: As Emergency Medical Technician educators develop curricula to meet new national educational standards, effective teaching strategies validated for course content and unique student demographics are warranted. Three methods for answering multiple choice questions presented during lectures were compared: a) Audience Response System (ARS, clickers), b) hand-raising-with-eyes-closed (no-cost option), and c) passive response (no-cost option). The purpose was to determine if using the ARS resulted in improved exam scores. Method: 113 Emergency Medical Technician (EMT) students participated in this cross-over, block randomized, controlled trial, which was incorporated into their Cardiac Emergencies and Pulmonary Emergencies course lectures. Students took pretests, immediate post-tests, and delayed post-tests composed of multiple choice questions that targeted either lower or higher order thinking. Results: For both lectures, there were significant improvements on all immediate post-test scores compared to all pretest scores (p Conclusions: In this cohort, incorporation of no-cost question-driven teaching strategies into lectures was as effective as an ARS at encouraging significant, immediate and sustained improvements in answering multiple choice questions

    Increased fluxes of shelf-derived materials to the central Arctic Ocean

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    © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Science Advances 4 (2018): eaao1302, doi:10.1126/sciadv.aao1302.Rising temperatures in the Arctic Ocean region are responsible for changes such as reduced ice cover, permafrost thawing, and increased river discharge, which, together, alter nutrient and carbon cycles over the vast Arctic continental shelf. We show that the concentration of radium-228, sourced to seawater through sediment-water exchange processes, has increased substantially in surface waters of the central Arctic Ocean over the past decade. A mass balance model for 228Ra suggests that this increase is due to an intensification of shelf-derived material inputs to the central basin, a source that would also carry elevated concentrations of dissolved organic carbon and nutrients. Therefore, we suggest that significant changes in the nutrient, carbon, and trace metal balances of the Arctic Ocean are underway, with the potential to affect biological productivity and species assemblages in Arctic surface waters.This work was funded by NSF awards OCE-1458305 to M.A.C. and OCE-1458424 to W.S.M. The Mackenzie River sampling was supported by a Graduate Student Research Award from the North Pacific Research Board to L.E.K. L.E.K. also acknowledges support from a National Defense Science and Engineering Graduate Fellowship. I.G.R. acknowledges funding by the contributors to the U.S. Interagency Arctic Buoy Program, which include the U.S. Coast Guard, the Department of Energy, NASA, the U.S. Navy, the National Oceanic and Atmospheric Administration, and NSF
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