214 research outputs found

    Corrigendum to "A culture-based calibration of benthic foraminiferal paleotemperature proxies: ή18O and Mg/Ca results" published in Biogeosciences, 7, 1335–1347, 2010

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    © The Author(s), 2011. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 8 (2011): 1521, doi:10.5194/bg-8-1521-2011

    A culture-based calibration of benthic foraminiferal paleotemperature proxies : ÎŽ18O and Mg/Ca results

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    © The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 7 (2010): 1335-1347, doi:10.5194/bg-7-1335-2010Benthic foraminifera were cultured for five months at four temperatures (4, 7, 14 and 21 °C) to establish the temperature dependence of foraminiferal calcite ÎŽ18O and Mg/Ca. Two Bulimina species (B. aculeata and B. marginata) were most successful in terms of calcification, adding chambers at all four temperatures and reproducing at 7 and 14 °C. Foraminiferal ÎŽ18O values displayed ontogenetic variations, with lower values in younger individuals. The ÎŽ18O values of adult specimens decreased with increasing temperature in all but the 4 °C treatment, exhibiting a relationship consistent with previous ÎŽ18O paleotemperature calibration studies. Foraminiferal Mg/Ca values, determined by laser ablation inductively coupled plasma mass spectrometry, were broadly consistent with previous Mg/Ca calibration studies, but extremely high values in the 4 °C treatment and higher than predicted values at two of the other three temperatures make it challenging to interpret these results.Funding was provided by US NSF OCE-0647899 to DCM and JMB, and by the Swedish Research Council (grant no 621-2005-4265), the Lamm Foundation, and the Engkvist Foundation to HLF. A Fulbright fellowship to HLF together with traveling grants from Gšoteborg University, the Crafoord Foundation, and the Royal Physiographic Society in Lund enabled HLF’s Postdoc stay and subsequent visits to WHOI

    Pre‐ and postoperative 68Ga‐DOTATOC positron emission tomography for hormone‐secreting pituitary neuroendocrine tumors

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    Objectives: Somatostatin receptors (SSTRs) are potential targets for detecting pituitary neuroendocrine tumours (PitNETs) that can be visualized effectively with 68Ga-labelled PET tracers. With this study, we have evaluated the diagnostic properties of such a tracer, 68Ga-DOTATOC, in patients with hormone-producing PitNETs before and after surgery. Design/Methods: This prospective case-control study presents preoperative positron emission tomography (PET) and histopathological data in 18 patients with somatotroph (n = 8), corticotroph (n = 7) and thyrotroph (n = 3) PitNETs. Patients were scanned pre- and postoperatively with 68Ga-DOTATOC PET. For the postoperative part of the study, patients with gonadotroph tumours (n = 7) were also included. Fifteen pituitary healthy controls underwent the same protocol once. The maximum standard uptake value (SUVmax) was analysed in manually outlined regions around the tumour in patients and around the pituitary gland in controls. specimens were collected during surgery in subjects for assessment of adenohypophyseal tumour cell type and the SSTR expression. Results: Thyrotroph tumours showed higher uptake (median SUVmax 41.1; IQR 37.4-60.0) and corticotroph tumours lower uptake (SUVmax 6.8; 2.6-9.3) than normal pituitary gland (SUVmax 13.8; 12.1-15.5). The uptake in somatotroph tumours (SUVmax 15.9; 11.6-19.7) was similar to the uptake in the pituitary gland. There was a strong correlation between SUVmax and SSTR2 expression (r = .75 (P 13.8. Conclusions: 68Ga-DOTATOC PET can be used to detect thyrotroph tumours in the pre- and postoperative imaging assessment. Corticotroph tumours had a significantly lower uptake compared to the pituitary gland but without a distinct increased tumour uptake the clinical postoperative value is limited

    Technical Note : Towards resolving in situ, centimeter-scale location and timing of biomineralization in calcareous meiobenthos – the calcein–osmotic pump method

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    © The Author(s), 2015. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Biogeosciences 12 (2015): 5515-5522, doi:10.5194/bg-12-5515-2015.Insights into oceanographic environmental conditions such as paleoproductivity, deep-water temperatures, salinity, ice volumes, and nutrient cycling have all been obtained from geochemical analyses of biomineralized carbonate of marine organisms. However, we cannot fully understand geochemical proxy incorporation and the fidelity of such in species until we better understand fundamental aspects of their ecology such as where and when these (micro)organisms calcify. Here, we present an innovative method using osmotic pumps and the fluorescent marker calcein to help identify where and when calcareous meiofauna calcify in situ. Method development initially involved juvenile quahogs (Mercenaria mercenaria); subsequent method refinement involved a neritic benthic foraminiferal community. Future applications of this method will allow determining the in situ growth rate in calcareous organisms and provide insights about microhabitats where paleoceanographically relevant benthic foraminifera actually calcify.This research was funded by WHOI’s Ocean Life Institute, WHOI’s Ocean and Climate Change Institute, by a Gori Fellowship (to F. Mezzo), The Investment in Science Fund at WHOI (to J. M. Bernhard) and the Robert W. Morse Chair for Excellence in Oceanography (to J. M. Bernhard). Ship time was provided by US NSF grant OCE-1219948 to J. M. Bernhard

    Lower 68 Ga-DOTATOC Uptake in Non-Functioning Pituitary Neuroendocrine Tumors Compared to Normal Pituitary Gland - a Proof-of-Concept Study

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    OBJECTIVES: 68 Ga-DOTATOC PET targets somatostatin receptors (SSTRs) and is well established for the detection of SSTR-expressing tumors, such as gastrointestinal neuroendocrine tumors. Pituitary adenomas, recently designated as pituitary neuroendocrine tumors (PitNETs), also express SSTRs, but there has been no previous evaluations of 68 Ga-DOTATOC PET in PitNET patients. The aim of this pilot study was to evaluate the diagnostic properties of 68 Ga-DOTATOC PET in the most common PitNET, i.e. non-functioning (NF)-PitNET. DESIGN/METHODS: NF-PitNET patients (n = 9) and controls (n = 13) were examined preoperatively with 68 Ga-DOTATOC PET for 45 min after tracer injection in dynamic list mode. Tumor specimens were collected during surgery in patients. MRI and PET images were co-registered using PMOD software. The maximum standard uptake value (SUVmax ) was analyzed in manually outlined regions of interest (ROC) around the tumor in patients and around the pituitary gland in controls. Immunohistochemical analyses were conducted on tumor specimens for assessment of tumor cell type and SSTR expression. RESULTS: Median SUVmax (IQR) was lower in patients than in controls (3.9 [3.4-8.5] vs 14.1 [12.5-15.9]; P < .01]. In ROC analysis, the area under the curve was 0.87 (P < .01) for SUVmax , with 78% sensitivity and 92% specificity. Immunohistochemical analysis showed NF-PitNETs were of gonadotroph (n = 7) and corticotroph (n = 2) origin. SSTR expression was high for SSTR3, low-to-moderate for SSTR2, and low for SSTR1 and SSTR5. CONCLUSIONS: This proof-of-concept study shows that 68 Ga-DOTATOC PET can be used to differentiate between normal pituitary tissue and NF-PitNET

    Holocene Hydrographic Variations From the Baltic‐North Sea Transitional Area (IODP Site M0059)

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    Deoxygenation affects many continental shelf seas across the world today and results in increasing areas of hypoxia (dissolved oxygen concentration ([O2]) <1.4 ml/L). The Baltic Sea is increasingly affected by deoxygenation. Deoxygenation correlates with other environmental variables such as changing water temperature and salinity and is directly linked to ongoing global climate change. To place the ongoing environmental changes into a larger context and to further understand the complex Baltic Sea history and its impact on North Atlantic climate, we investigated a high accumulation-rate brackish-marine sediment core from the Little Belt (Site M0059), Danish Straits, NW Europe, retrieved during the Integrated Ocean Drilling Program (IODP) Expedition 347. We combined benthic foraminiferal geochemistry, faunal assemblages, and pore water stable isotopes to reconstruct seawater conditions (e.g., oxygenation, temperature, and salinity) over the past 7.7 thousand years (ka). Bottom water salinity in the Little Belt reconstructed from modeled pore water oxygen isotope data increased between 7.7 and 7.5 ka BP as a consequence of the transition from freshwater to brackish-marine conditions. Salinity decreased gradually (from 30 to 24) from 4.1 to ~2.5 ka BP. By using the trace elemental composition (Mg/Ca, Mn/Ca, and Ba/Ca) and stable carbon and oxygen isotopes of foraminiferal species Elphidium selseyensis and E. clavatum, we identified that generally warming and hypoxia occurred between about 7.5 and 3.3 ka BP, approximately coinciding in time with the Holocene Thermal Maximum (HTM). These changes of bottom water conditions were coupled to the North Atlantic Oscillation (NAO) and relative sea level change

    Anthropogenic and climatic impacts on a coastal environment in the Baltic Sea over the last 1000 years

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    Coastal environments have experienced large ecological changes as a result of human activities over the last 100-200 years. To understand the severity and potential consequences of such changes, paleoenvironmental records provide important contextual information. The Baltic Sea coastal zone is naturally a vulnerable system and subject to significant human-induced impacts. To put the recent environmental degradation in the Baltic coastal zone into a long-term perspective, and to assess the natural and anthropogenic drivers of environmental change, we present sedimentary records covering the last 1000 years obtained from a coastal inlet (Gasfjarden) and a nearby lake (Lake Storsjon) in Sweden. We investigate the links between a pollen-based land cover reconstruction from Lake Storsjon and paleoenvironmental variables from Gasfjarden itself, including diatom assemblages, organic carbon (C) and nitrogen (N) contents, stable C and N isotopic ratios, and biogenic silica contents. The Lake Storsjon record shows that regional land use was characterized by small-scale agricultural activity between 900 and 1400 CE, which slightly intensified between 1400 and 1800 CE. Substantial expansion of cropland was observed between 1800 and 1950 CE, before afforestation between 1950 and 2010 CE. From the Gasfjarden record, prior to 1800 CE, relatively minor changes in the diatom and geochemical proxies were found. The onset of cultural eutrophication in Gasfjarden can be traced to the 1800s and intensified land use is identified as the main driver. Anthropogenic activities in the 20th century have caused unprecedented ecosystem changes in the coastal inlet, as reflected in the diatom composition and geochemical proxies. (c) 2018 Elsevier Ltd. All rights reserved.Peer reviewe

    Ecological speciation in European whitefish is driven by a large-gaped predator

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    Lake-dwelling fish that form species pairs/flocks characterized by body size divergence are important model systems for speciation research. Although several sources of divergent selection have been identified in these systems, their importance for driving the speciation process remains elusive. A major problem is that in retrospect, we cannot distinguish selection pressures that initiated divergence from those acting later in the process. To address this issue, we studied the initial stages of speciation in European whitefish (Coregonus lavaretus) using data from 358 populations of varying age (26-10,000 years). We find that whitefish speciation is driven by a large-growing predator, the northern pike (Esox lucius). Pike initiates divergence by causing a largely plastic differentiation into benthic giants and pelagic dwarfs: ecotypes that will subsequently develop partial reproductive isolation and heritable differences in gill raker number. Using an eco-evolutionary model, we demonstrate how pike's habitat specificity and large gape size are critical for imposing a between-habitat trade-off, causing prey to mature in a safer place or at a safer size. Thereby, we propose a novel mechanism for how predators may cause dwarf/giant speciation in lake-dwelling fish species.Peer reviewe

    On the Convergence of Kergin and Hakopian Interpolants at Leja Sequences for the Disk

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    We prove that Kergin interpolation polynomials and Hakopian interpolation polynomials at the points of a Leja sequence for the unit disk DD of a sufficiently smooth function ff in a neighbourhood of DD converge uniformly to ff on DD. Moreover, when ff is C∞C^\infty on DD, all the derivatives of the interpolation polynomials converge uniformly to the corresponding derivatives of ff

    Acute interaction between hydrocortisone and insulin alters the plasma metabolome in humans

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    With the aim of identifying biomarkers of glucocorticoid action and their relationship with biomarkers of insulin action, metabolomic profiling was carried out in plasma samples from twenty healthy men who were administered either a low or medium dose insulin infusion (n = 10 each group). In addition, all subjects were given metyrapone (to inhibit adrenal cortisol secretion) +/-hydrocortisone (HC) in a randomised crossover design to produce low, medium and high glucocorticoid levels. The clearest effects of insulin were to reduce plasma levels of the branched chain amino acids (BCAs) leucine/isoleucine and their deaminated metabolites, and lowered free fatty acids and acylcarnitines. The highest dose of hydrocortisone increased plasma BCAs in both insulin groups but increased free fatty acids only in the high insulin group, however hydrocortisone did not affect the levels of acyl carnitines in either group. The clearest interaction between HC and insulin was that hydrocortisone produced an elevation in levels of BCAs and their metabolites which were lowered by insulin. The direct modulation of BCAs by glucocorticoids and insulin may provide the basis for improved in vivo monitoring of glucocorticoid and insulin action
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