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Isotope tracer

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https://www.readbyqxmd.com/read/29351616/deficient-glucagon-response-to-hypoglycemia-during-a-mixed-meal-in-total-pancreatectomy-islet-autotransplantation-recipients
#1
L D Bogachus, M D Bellin, A Vella, R P Robertson
Context: Total pancreatectomy and intrahepatic islet autotransplantation (TP/IAT) is performed to alleviate severe abdominal pain, avoid narcotic use, maintain islet function, and avoid diabetes in patients with chronic pancreatitis. However, many TP/IAT recipients complain of post-prandial hypoglycemia. Objective: This study was designed to discover mechanisms of this problem. Design: Participants consumed a triple-isotope mixed meal. Setting: Hospital research unit...
January 17, 2018: Journal of Clinical Endocrinology and Metabolism
https://www.readbyqxmd.com/read/29351488/measurement-of-postprandial-glucose-fluxes-in-response-to-acute-and-chronic-endurance-exercise-in-healthy-humans
#2
Dale J Morrison, Greg M Kowalski, Eleonora Grespan, Andrea Mari, Clinton R Bruce, Glenn D Wadley
The effect of endurance exercise on enhancing insulin sensitivity and glucose flux has been well established with techniques such as the hyperinsulinemic clamp. Although informative, such techniques do not emulate the physiological postprandial state, and it remains unclear how exercise improves postprandial glycaemia. Accordingly, combining mixed meal tolerance testing and the triple-stable isotope glucose tracer approach, glucose fluxes (rates of meal glucose appearance (Ra), disposal (Rd) and endogenous glucose production (EGP)) were determined following acute endurance exercise (1h cycling; ~70% VO2max) and 4 weeks of endurance training (cycling 5d/wk)...
December 19, 2017: American Journal of Physiology. Endocrinology and Metabolism
https://www.readbyqxmd.com/read/29341238/temporal-trends-in-a-biomagnifying-contaminant-application-of-amino-acid-compound-specific-stable-nitrogen-isotope-analysis-to-the-interpretation-of-bird-mercury-levels
#3
Craig E Hebert, Brian N Popp
Temporal trends in levels of biomagnifying contaminants, such as mercury (Hg), in top predators can provide insights into changes in contaminant bioavailability through time. However, interpreting contaminant temporal trends in predators can be confounded by temporal changes in their diets which, in turn, could affect organism trophic position and exposure to biomagnifying contaminants. To address this issue, bulk stable nitrogen isotope analysis, i.e. analysis of whole tissue, is widely incorporated into contaminant monitoring programs for the estimation of organism trophic position...
January 17, 2018: Environmental Toxicology and Chemistry
https://www.readbyqxmd.com/read/29333721/carbohydrate-dose-influences-liver-and-muscle-glycogen-oxidation-and-performance-during-prolonged-exercise
#4
Andy J King, John P O'Hara, Douglas J Morrison, Tom Preston, Roderick F G J King
This study investigated the effect of carbohydrate (CHO) dose and composition on fuel selection during exercise, specifically exogenous and endogenous (liver and muscle) CHO oxidation. Ten trained males cycled in a double-blind randomized order on 5 occasions at 77% V˙O2max for 2 h, followed by a 30-min time-trial (TT) while ingesting either 60 g·h-1 (LG) or 75 g·h-113 C-glucose (HG), 90 g·h-1 (LGF) or 112.5 g·h-113 C-glucose-13 C-fructose ([2:1] HGF) or placebo. CHO doses met or exceed reported intestinal transporter saturation for glucose and fructose...
January 2018: Physiological Reports
https://www.readbyqxmd.com/read/29325415/recrystallization-of-manganite-%C3%AE-mnooh-and-implications-for-trace-element-cycling
#5
Tobias Hens, Joël Brugger, Susan Cumberland, Barbara Etschmann, Andrew J Frierdich
The recrystallization of Mn(III,IV) oxides is catalyzed by aqueous Mn(II) (Mn(II)aq) during (bio)geochemical Mn redox cycling. It is poorly understood how trace metals associated with Mn oxides (e.g., Ni) are cycled during such recrystallization. Here, we use X-ray absorption spectroscopy (XAS) to examine the speciation of Ni associated with manganite (γ-Mn(III)OOH) suspensions in the presence or absence of Mn(II)aq under variable pH conditions (pH 5.5 and 7.5). In a second set of experiments, we used a 62Ni isotope tracer to quantify the amount of dissolved Ni that exchanges with Ni incorporated in the manganite crystal structure during reactions in 1 mM Mn(II)aq and in Mn(II)-free solutions...
January 11, 2018: Environmental Science & Technology
https://www.readbyqxmd.com/read/29315909/seeking-excellence-an-evaluation-of-235-international-laboratories-conducting-water-isotope-analyses-by-isotope-ratio-and-laser-absorption-spectrometer
#6
L I Wassenaar, S Terzer-Wassmuth, C Douence, L Araguas-Araguas, P K Aggarwal, T B Coplen
RATIONALE: Water stable isotope ratios (δ2 H and δ18 O values) are widely used tracers in environmental studies; hence, accurate and precise assays are required for providing sound scientific information. We tested the analytical performance of 235 international laboratories conducting water isotope analyses using dual-inlet and continuous-flow isotope ratio mass spectrometers and laser spectrometers through a water isotope inter-comparison test. METHODS: Eight test water samples were distributed by the IAEA to international stable isotope laboratories...
January 5, 2018: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/29313551/fate-of-nitrogen-in-overlying-water-with-biochar-addition-to-sediment-in-planted-ditches
#7
Qianding Cheng, Hongguang Cheng, Lu Lu, Xiao Pu, Zhenzhen Wu, Haixu Sun
Best management practice (BMP) in drainage ditch systems is of high concern due to its importance in intercepting and removing pollution. Biochar has recently become an interesting option for agricultural pollution elimination, but knowledge is still limited on the fate of nitrogen (N) in drainage ditch systems with biochar added into the sediment. This isotope tracer study examined the effects of biochar addition into the sediment on the fate of inorganic N (15N-NO3- and 15N-NH4+) in sediment microcosms through a 93 day incubation experiment...
January 9, 2018: Environmental Science. Processes & Impacts
https://www.readbyqxmd.com/read/29305946/a-whole-grain-diet-reduces-peripheral-insulin-resistance-and-improves-glucose-kinetics-in-obese-adults-a-randomized-controlled-trial
#8
Steven K Malin, Emily L Kullman, Amanda R Scelsi, Jacob M Haus, Julianne Filion, Mangesh R Pagadala, Jean-Philippe Godin, Sunil Kochhar, Alastair B Ross, John P Kirwan
BACKGROUND: Whole-grain intake is associated with lower risk of type 2 diabetes but mechanisms are unclear. PURPOSE: We tested the hypothesis that a WG diet reduces insulin resistance and improves glucose use in individuals at risk for type 2 diabetes compared with an isocaloric-matched refined-grain diet. METHODS: A double-blind, randomized, controlled, crossover trial of 14 moderately obese adults (Age, 38±2 yrs.; BMI, 34.0±1.1kg/m2). Insulin resistance and glucose metabolism was assessed using an oral glucose tolerance test combined with isotopic tracers of [6,6-2H2]-glucose and [U-13C]-glucose, and indirect calorimetry...
January 3, 2018: Metabolism: Clinical and Experimental
https://www.readbyqxmd.com/read/29301367/metabolic-responses-to-carbohydrate-ingestion-during-exercise-associations-between-carbohydrate-dose-and-endurance-performance
#9
Michael L Newell, Gareth A Wallis, Angus M Hunter, Kevin D Tipton, Stuart D R Galloway
Carbohydrate (CHO) ingestion during exercise lasting less than three hours improves endurance exercise performance but there is still debate about the optimal dose. We utilised stable isotopes and blood metabolite profiles to further examine metabolic responses to CHO (glucose only) ingestion in the 20-64 g·h-1 range, and to determine the association with performance outcome. In a double-blind, randomized cross-over design, male cyclists (n = 20, mean ± SD, age 34 ± 10 years, mass 75.8 ± 9 kg, peak power output 394 ± 36 W, VO2max 62 ± 9 mL·kg-1·min-1) completed four main experimental trials...
January 3, 2018: Nutrients
https://www.readbyqxmd.com/read/29300826/from-rhizoids-to-roots-experimental-evidence-of-mutualism-between-liverworts-and-ascomycete-fungi
#10
Jill Kowal, Silvia Pressel, Jeffrey G Duckett, Martin I Bidartondo, Katie J Field
Background and Aims: The rhizoids of leafy liverworts (Jungermanniales, Marchantiophyta) are commonly colonized by the ascomycete fungus Pezoloma ericae. These associations are hypothesized to be functionally analogous to the ericoid mycorrhizas (ErMs) formed by P. ericae with the roots of Ericaceae plants in terms of bi-directional phosphorus for carbon exchange; however, this remains unproven. Here, we test whether associations between the leafy liverwort Cephalozia bicuspidata and P...
January 2, 2018: Annals of Botany
https://www.readbyqxmd.com/read/29298140/improving-marine-ecosystem-models-with-biochemical-tracers
#11
Heidi R Pethybridge, C Anela Choy, Jeffrey J Polovina, Elizabeth A Fulton
Empirical data on food web dynamics and predator-prey interactions underpin ecosystem models, which are increasingly used to support strategic management of marine resources. These data have traditionally derived from stomach content analysis, but new and complementary forms of ecological data are increasingly available from biochemical tracer techniques. Extensive opportunities exist to improve the empirical robustness of ecosystem models through the incorporation of biochemical tracer data and derived indices, an area that is rapidly expanding because of advances in analytical developments and sophisticated statistical techniques...
January 3, 2018: Annual Review of Marine Science
https://www.readbyqxmd.com/read/29295620/high-initial-sputter-rate-found-for-vaccinia-virions-using-isotopic-labeling-nanosims-and-afm
#12
Sean Damien Gates, Richard C Condit, Nissin Moussatche, Benjamin J Stewart, Alexander J Malkin, Peter K Weber
High lateral resolution secondary ion mass spectrometry (SIMS) has the potential to provide functional and depth resolved information from small biological structures, such as viral particles (virions) and phage, but sputter rate and sensitivity are not characterized at shallow depths relevant to these structures. Here we combine stable isotope labeling of the DNA of vaccinia virions with correlated SIMS imaging depth profiling and atomic force microscopy (AFM) to develop a non-linear, non-equilibrium sputter rate model for the virions and validate the model based on reconstructing the location of the DNA within individual virions...
January 3, 2018: Analytical Chemistry
https://www.readbyqxmd.com/read/29285548/preclinical-evaluation-of-an-18f-trifluoroborate-methionine-derivative-for-glioma-imaging
#13
Xiangyu Yang, Zhibo Liu, Huimin Zhang, Zhu Li, Jeeva P Munasinghe, Gang Niu, Gaojun Teng, Xiaoyuan Chen
PURPOSE: 11C-methionine (MET) is one of the most commonly used amino acid tracers for PET imaging of brain tumors. In this study, we report an 18F-labeled boron-derived methionine analogue, denoted as 18F-B-MET, as a potential substitute of 11C-MET for glioma PET imaging. METHODS: 19F-B-MET was synthesized from readily available chemicals according to our previous publication. For kit development, 19F-B-MET was aliquoted in quantities of 10 nmol for on-demand one-step labeling...
December 29, 2017: European Journal of Nuclear Medicine and Molecular Imaging
https://www.readbyqxmd.com/read/29277601/an-isotope-dilution-model-for-partitioning-of-phenylalanine-and-tyrosine-uptake-by-the-liver-of-lactating-dairy-cows
#14
L A Crompton, L L McKnight, C K Reynolds, J A N Mills, J L Ellis, M D Hanigan, J Dijkstra, B J Bequette, A Bannink, J France
An isotope dilution model to describe the partitioning of phenylalanine (PHE) and tyrosine (TYR) in the bovine liver was developed. The model comprises four intracellular and six extracellular pools and various flows connecting these pools and external blood. Conservation of mass principles were applied to generate the fundamental equations describing the behaviour of the system in the steady state. The model was applied to datasets from multi-catheterised dairy cattle during a constant infusion of [1-13C] phenylalanine and [2,3,5,6-2H] tyrosine tracers...
December 22, 2017: Journal of Theoretical Biology
https://www.readbyqxmd.com/read/29276427/quantitative-imaging-of-deuterated-metabolic-tracers-in-biological-tissues-with-nanoscale-secondary-ion-mass-spectrometry
#15
Christelle Guillermier, J Collin Poczatek, Walter R Taylor, Matthew L Steinhauser
In the field of secondary ion mass spectrometry at nanometer scale (NanoSIMS), configuration of parallel detectors to routinely measure isotope ratios in sub-100 nm domains brings classical stable isotope tracer studies from the whole tissue level down to the suborganelle level. Over the past decade, the marriage of stable isotope tracers with NanoSIMS has been applied to a range of fundamental biological questions that were largely inaccessible by other means. Although multiplexed measurement of different stable isotope tracers is feasible, in practice there remains a gap in the current analytical capacity to efficiently measure stable isotopes commonly utilized in tracer studies...
November 2017: International Journal of Mass Spectrometry
https://www.readbyqxmd.com/read/29274994/zn-isotopes-fractionation-during-slags-weathering-one-source-of-contamination-multiple-isotopic-signatures
#16
Nang-Htay Yin, Eric D van Hullebusch, Marc Benedetti, Piet N L Lens, Yann Sivry
During the chemical weathering of lead blast furnace (LBF) and imperial smelting furnace (ISF) slags, possible Zn isotopes fractionation was studied as a function of pH, atmosphere (open air vs nitrogen), and time. Bulk LBF and ISF displayed heavier signatures compared to Johnson Matthey Company (JMC) Zn standard solution (i.e. 0.13 ± 0.06‰ and 0.78 ± 0.13‰ for LBF and ISF, resp). The Zn signatures vary greatly by changes in solution pH; heavier signatures at low pH and lighter signature at high pH...
December 12, 2017: Chemosphere
https://www.readbyqxmd.com/read/29260858/a-methodology-for-the-validation-of-isotopic-analyses-by-mass-spectrometry-in-stable-isotope-labelling-experiments
#17
Maud Heuillet, Floriant Bellvert, Edern Cahoreau, Fabien Letisse, Pierre Millard, Jean-Charles Portais
Stable-isotope labeling experiments (ILEs) are widely used to investigate the topology and operation of metabolic networks. The quality of isotopic data collected in ILEs is of utmost importance to guarantee the reliability of biological interpretations, but current evaluation approaches are limited due to the lack of a suitable reference material and relevant evaluation criteria. In this work, we present a complete methodology to evaluate mass spectrometry (MS) methods used for quantitative isotopic studies of metabolism...
December 20, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/29249311/determination-of-gas-recovery-efficiency-at-two-danish-landfills-by-performing-downwind-methane-measurements-and-stable-carbon-isotopic-analysis
#18
Ehsan F Aghdam, Anders M Fredenslund, Jeffrey Chanton, Peter Kjeldsen, Charlotte Scheutz
In this study, the total methane (CH4) generation rate and gas recovery efficiency at two Danish landfills were determined by field measurements. The landfills are located close to each other and are connected to the same gas collection system. The tracer gas dispersion method was used for quantification of CH4 emissions from the landfills, while the CH4 oxidation efficiency in the landfill cover layers was determined by stable carbon isotopic technique. The total CH4 generation rate was estimated by a first-order decay model (Afvalzorg) and was compared with the total CH4 generation rate determined by field measurements...
December 14, 2017: Waste Management
https://www.readbyqxmd.com/read/29248595/quantification-of-11b-hydroxysteroid-dehydrogenase-1-kinetics-and-pharmacodynamic-effects-of-inhibitors-in-brain-using-mass-spectrometry-imaging-and-stable-isotope-tracers-in-mice
#19
D F Cobice, D E W Livingstone, A McBride, C L MacKay, B R Walker, S P Webster, R Andrew
11β-Hydroxysteroid dehydrogenase 1 (11β-HSD1; EC 1.1.1.146) generates active glucocorticoid hormones. Small molecule inhibitors have been developed to target 11β-HSD1 for the treatment of dementia; these must enter brain subregions, such as the hippocampus, to be effective. We previously reported mass spectrometry imaging measurement of murine tissue steroids, and deuterated steroid tracer infusion quantification of 11 β -HSD1 turnover in humans. Here, these tools are combined to assess tissue pharmacokinetics and pharmacodynamics of an 11 β -HSD1 inhibitor that accesses the brain...
December 14, 2017: Biochemical Pharmacology
https://www.readbyqxmd.com/read/29247455/synthesis-and-evaluation-of-an-18-f-labeled-trifluoroborate-derivative-of-2-nitroimidazole-for-imaging-tumor-hypoxia-with-positron-emission-tomography
#20
Paulo Sérgio Gonçalves Nunes, Zhengxing Zhang, Hsiou-Ting Kuo, Chengcheng Zhang, Julie Rousseau, Etienne Rousseau, Joseph Lau, Daniel Kwon, Ivone Carvalho, François Bénard, Kuo-Shyan Lin
2-Nitroimidazole-based hypoxia imaging tracers such as 18 F-FMISO are normally imaged at late time points (several hours post-injection) due to their slow clearance from background tissues. Here we investigated if a hydrophilic zwitterion-based ammoniomethyl-trifluoroborate derivative of 2-nitroimidazole, 18 F-AmBF3 -Bu-2NI, could have the potential to image tumor hypoxia at earlier time points. AmBF3 -Bu-2NI was prepared in four steps. 18 F labeling was conducted via 18 F-19 F isotope exchange reaction, and 18 F-AmBF3 -Bu-2NI was obtained in 14...
December 16, 2017: Journal of Labelled Compounds & Radiopharmaceuticals
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