614 research outputs found

    Cellular elemental content of individual phytoplankton cells collected during US GEOTRACES North Atlantic Transect cruises in the Subtropical western and eastern North Atlantic Ocean during Oct and Nov, 2010 and Nov. 2011.

    Get PDF
    Dataset: GT10-11 - cellular element quotasPhytoplankton contribute significantly to global C cycling and serve as the base of ocean food webs. Phytoplankton require trace metals for growth and also mediate the vertical distributions of many metals in the ocean. This dataset provides direct measurements of metal quotas in phytoplankton from across the North Atlantic Ocean, known to be subjected to aeolian Saharan inputs and anthropogenic inputs from North America and Europe. Bulk particulate material and individual phytoplankton cells were collected from the upper water column (<150 m) as part of the US GEOTRACES North Atlantic Zonal Transect cruises (KN199-4, KN199-5, KN204-1A,B). The cruise tracks spanned several ocean biomes and geochemical regions. Chemical leaches (to extract biogenic and otherwise labile particulate phases) are combined together with synchrotron X-ray fluorescence (SXRF) analyses of individual micro and nanophytoplankton to discern spatial trends across the basin. Individual phytoplankton cells were analyzed for elemental content using SXRF (Synchrotron radiation X-Ray Fluorescence). Carbon was calculated from biovolume using the relationships of Menden-Deuer & Lessard (2000).NSF Ocean Sciences (NSF OCE) OCE-092828

    Research on ICT in K-12 schools e A review of experimental and survey-based studies in computers & education 2011 to 2015

    Get PDF
    International audienceWhat is the role of a journal? Is it to follow the research or lead it? For the former, it is to serve as an archival record of the scholarship in a field. It can serve to permit the research community to engage with each other via the written record. But, for the latter, it can serve the research community by pointing out gaps in the research based on the archival record. This review is intended to do just that

    Element quotas of individual Synechococcus cells collected during Bermuda Atlantic Time-series Study (BATS) cruises aboard the R/V Atlantic Explorer between dates 2012-07-11 and 2013-10-13

    Get PDF
    Dataset: Cellular element quotas: Si in Synechococcus cellsThese data include element quotas of individual Synechococcus cells collected during Bermuda Atlantic Time-series Study (BATS) cruises. The three cruises (AE1218,AE1228, and AE1322) were all aboard the R/V Atlantic Explorer between dates 2012-07-11 and 2013-10-13 around Bermuda. Instruments used were a CTD profiler, and a Synchrotron X-ray Fluorescence Microprobe (SXRF). Understanding the accumulation of silicon by marine picocyanobacteria of the genus Synechococcus has the potential to drive a major paradigm shift in our understanding of biogenic silica cycling in the ocean. These data assess the contribution of Synechococcus to total biogenic silica and were collected by Dr. Benjamin Twining of the Bigelow Laboratory for Ocean Sciences as part of the project Understanding the Role of Picocyanobacteria in the Marine Silicate Cycle. For a complete list of measurements, refer to the supplemental document 'Field_names.pdf', and a full dataset description is included in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: http://www.bco-dmo.org/dataset/644840NSF Ocean Sciences (NSF OCE) OCE-1131139, NSF Ocean Sciences (NSF OCE) OCE-1335012, NSF Ocean Sciences (NSF OCE) OCE-113104

    Aversive Stimuli Drive Drug Seeking in a State of Low Dopamine Tone

    Get PDF
    Background Stressors negatively impact emotional state and drive drug seeking, in part, by modulating the activity of the mesolimbic dopamine system. Unfortunately, the rapid regulation of dopamine signaling by the aversive stimuli that cause drug seeking is not well characterized. In a series of experiments, we scrutinized the subsecond regulation of dopamine signaling by the aversive stimulus, quinine, and tested its ability to cause cocaine seeking. Additionally, we examined the midbrain regulation of both dopamine signaling and cocaine seeking by the stress-sensitive peptide, corticotropin releasing factor (CRF). Methods Combining fast-scan cyclic voltammetry with behavioral pharmacology, we examined the effect of intraoral quinine administration on nucleus accumbens dopamine signaling and hedonic expression in 21 male Sprague-Dawley rats. We tested the role of CRF in modulating aversion-induced changes in dopamine concentration and cocaine seeking by bilaterally infusing the CRF antagonist, CP-376395, into the ventral tegmental area (VTA). Results We found that quinine rapidly reduced dopamine signaling on two distinct time scales. We determined that CRF acted in the VTA to mediate this reduction on only one of these time scales. Further, we found that the reduction of dopamine tone and quinine-induced cocaine seeking were eliminated by blocking the actions of CRF in the VTA during the experience of the aversive stimulus. Conclusions These data demonstrate that stress-induced drug seeking can occur in a terminal environment of low dopamine tone that is dependent on a CRF-induced decrease in midbrain dopamine activity

    Variations in Synechococcus Cell Quotas of Phosphorus, Sulfur, Manganese, Iron, Nickel, and Zinc within Mesoscale Eddies in the Sargasso Sea

    Get PDF
    The quotas of P, S, Mn, Fe, Ni, and Zn in individual Synechococcus cells collected from the surface and deep chlorophyll maximum (DCM) layer of three mesoscale eddies in the Sargasso Sea were measured using synchrotron X-ray fluorescence microscopy. Cells in a mode-water eddy had significantly higher P (57 +/- 10 amol) and Mn (28 +/- 7 zmol) cell quotas than cells collected from a cyclone (22 +/- 2 amol and 10 +/- 1 zmol, respectively) or anticyclone (25 +/- 3 amol and 18 +/- 3 zmol, respectively). Conversely, Ni and Zn quotas were significantly higher in the cells from the anticyclone (92 +/- 19 and 561 +/- 150 zmol, respectively) than in cells from the cyclonic (25 +/- 4 and 35 +/- 7 zmol, respectively) or mode-water (30 +/- 9 and 21 +/- 8 zmol, respectively) eddies. These changes may reflect biochemical responses (e. g., production of urease and alkaline phosphatase) to gradients in inorganic N and P supplies. Cellular quotas of Fe (111 +/- 17 zmol in the cyclone) and S (52 +/- 6 amol in the cyclone) did not vary significantly among eddies despite two-to threefold higher dissolved and particulate Fe concentrations in the anticylone. Cells collected from 10-m depth contained approximately 80% more Ni and S than cells collected from the DCM, potentially reflecting cell responses to heightened oxidative stress. Depth-related trends varied by eddy for the other elements. Cellular P and Zn varied significantly during repeated samplings of the cyclone, with quotas of both elements dropping as bulk chlorophyll biomass in the DCM increased. These data demonstrate the dynamic responses of phytoplankton elemental composition to physical and chemical environmental gradients

    The Unique Biogeochemical Signature of the Marine Diazotroph Trichodesmium

    Get PDF
    The elemental composition of phytoplankton can depart from canonical Redfield values under conditions of nutrient limitation or production (e.g., N fixation). Similarly, the trace metal metallome of phytoplankton may be expected to vary as a function of both ambient nutrient concentrations and the biochemical processes of the cell. Diazotrophs such as the colonial cyanobacteria Trichodesmium are likely to have unique metal signatures due to their cell physiology. We present metal (Fe, V, Zn, Ni, Mo, Mn, Cu, Cd) quotas for Trichodesmium collected from the Sargasso Sea which highlight the unique metallome of this organism. The element concentrations of bulk colonies and trichomes sections were analyzed by ICP-MS and synchrotron x-ray fluorescence, respectively. The cells were characterized by low P contents but enrichment in V, Fe, Mo, Ni, and Zn in comparison to other phytoplankton. Vanadium was the most abundant metal in Trichodesmium, and the V quota was up to fourfold higher than the corresponding Fe quota. The stoichiometry of 600C:101N:1P (mol mol−1) reflects P-limiting conditions. Iron and V were enriched in contiguous cells of 10 and 50% of Trichodesmium trichomes, respectively. The distribution of Ni differed from other elements, with the highest concentration in the transverse walls between attached cells. We hypothesize that the enrichments of V, Fe, Mo, and Ni are linked to the biochemical requirements for N fixation either directly through enrichment in the N-fixing enzyme nitrogenase or indirectly by the expression of enzymes responsible for the removal of reactive oxygen species. Unintentional uptake of V via P pathways may also be occurring. Overall, the cellular content of trace metals and macronutrients differs significantly from the (extended) Redfield ratio. The Trichodesmium metallome is an example of how physiology and environmental conditions can cause significant deviations from the idealized stoichiometry
    corecore