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Isotope tracer

Wei Xiong, Luis H Reyes, William E Michener, Pin-Ching Maness, Katherine J Chou
Cellulose and hemicellulose are the most abundant components in plant biomass. A preferred Consolidated Bioprocessing (CBP) system is one which can directly convert both cellulose and hemicellulose into target products without adding the costly hydrolytic enzyme cocktail. In this work, the thermophilic, cellulolytic, and anaerobic bacterium, Clostridium thermocellum DSM 1313, was engineered to grow on xylose in addition to cellulose. Both xylA (encoding for xylose isomerase) and xylB (encoding for xylulokinase) genes from the thermophilic anaerobic bacterium Thermoanaerobacter ethanolicus were introduced to enable xylose utilization while still retaining its inherent ability to grow on 6-carbon substrates...
March 14, 2018: Biotechnology and Bioengineering
Laurentiu M Pop, Andrea Mari, Tong-Jin Zhao, Lori Mitchell, Shawn Burgess, Xilong Li, Beverley Adams-Huet, Ildiko Lingvay
AIM: To investigate the physiological mechanisms leading to rapid improvement in diabetes after Roux-en-Y Gastric Bypass (RYGB). In particular, the roles of concurrent peri-operative dietary restrictions, which may also alter glucose metabolism, have not been completely elucidated. MATERIALS AND METHODS: To assess the differential contributions of diet and surgery to the mechanisms leading to the rapid improvement in diabetes after RYGB we enrolled ten patients with type 2 diabetes scheduled to undergo RYGB...
March 13, 2018: Diabetes, Obesity & Metabolism
Sonja Cerar, Kim Mezga, Gorazd Žibret, Janko Urbanc, Marko Komac
Groundwater is the most important source of drinking water in the world. Therefore, information on the quality and quantity is important, as is new information related to the characteristics of the aquifer and the recharge area. In the present study we focused on the isotope composition of oxygen (δ18 O) in groundwater, which is a natural tracer and provides a better understanding of the water cycle, in terms of origin, dynamics and interaction. The groundwater δ18 O at 83 locations over the entire Slovenian territory was studied...
March 9, 2018: Science of the Total Environment
Helena Banning, Monika Stelling, Stephan König, Ronny Schoenberg, Thomas Neumann
Selenium (Se) is an important micronutrient but also a strong toxin with a narrow tolerance range for many organisms. As such, a globally heterogeneous Se distribution in soils is responsible for various disease patterns (i.e. Se excess and deficiency) and environmental problems, whereby plants play a key role for the Se entrance into the biosphere. Selenium isotope variations were proved to be a powerful tracer for redox processes and are therefore promising for the exploration of the species dependent Se metabolism in plants and the Se cycling within the Critical Zone...
2018: PloS One
Ying Chen, Olga Berejnaia, Jinqi Liu, Sheng-Ping Wang, Natalie A Daurio, Wu Yin, Rafael Mayoral, Aleksandr Petrov, Takhar Kasumov, Guo-Fang Zhang, Stephen F Previs, David E Kelley, David G McLaren
Numerous studies have implicated dyslipidemia as a key factor in mediating insulin resistance. Ceramides have received special attention since their levels are inversely associated with normal insulin signaling and positively associated with factors that are involved in cardiometabolic disease. Despite the growing literature surrounding ceramide biology, there are limited data regarding the activity of ceramide synthesis and turnover in vivo. Herein, we demonstrate the ability to measure ceramide kinetics by coupling the administration of [2 H]water with LC-MS/MS analyses...
March 6, 2018: American Journal of Physiology. Endocrinology and Metabolism
Julien Farlin, Piotr Małoszewski
The use of the annual cycles of stable isotopes to estimate the parameters of transit time distribution functions has been recently criticised by Kirchner who showed that if the catchment is heterogeneous the mean residence time calculated from the damping of the amplitude of the input signal is often underestimated by large factors. We modify Kirchner's initial analysis and show that the estimation bias is a function of the degree of heterogeneity. In low heterogeneity cases corresponding to permeable aquifers, the transit time distribution of a simple exponential model developed assuming a homogeneous medium deviates only slightly from the true transit time distribution, and thus estimated and true mean transit times are close...
March 6, 2018: Ground Water
David V Bekaert, Michael W Broadley, Frédéric Delarue, Guillaume Avice, Francois Robert, Bernard Marty
Understanding the composition of the Archean atmosphere is vital for unraveling the origin of volatiles and the environmental conditions that led to the development of life. The isotopic composition of xenon in the Archean atmosphere has evolved through time by mass-dependent fractionation from a precursor comprising cometary and solar/chondritic contributions (referred to as U-Xe). Evaluating the composition of the Archean atmosphere is challenging because limited amounts of atmospheric gas are trapped within minerals during their formation...
February 2018: Science Advances
Fatema Bhinderwala, Samantha Lonergan, Jade Woods, Chunyi Zhou, Paul D Fey, Robert Powers
Isotopically labeling a metabolite and tracing its metabolic fate has provided invaluable insights about the role of metabolism in human diseases in addition to a variety of other issues.13 C-labeled metabolite tracers or unlabeled1 H-based NMR experiments are currently the most common application of NMR to metabolomics studies. Unfortunately, the coverage of the metabolome has been consequently limited to the most abundant carbon-containing metabolites. To expand the coverage of the metabolome and enhance the impact of metabolomics studies, we present a protocol for15 N-labeled metabolite tracer experiments that may also be combined with routine13 C-tracer experiments to simultaneously detect both15 N- and13 C-labeled metabolites in metabolic samples...
March 5, 2018: Analytical Chemistry
Thomas Brendan Smith, Kamlesh Patel, Haydn Munford, Andrew Peet, Daniel A Tennant, Mark Jeeves, Christian Ludwig
Tracing the fate of stable isotopically-enriched nutrients is a sophisticated method of describing and quantifying the activity of metabolic pathways. Nuclear Magnetic Resonance (NMR) offers high resolution data, yet is under-utilised due to length of time required to collect the data, quantification requiring multiple samples and complicated analysis. Here we present two techniques, quantitative spectral filters and enhancement of the splitting due to J-coupling in1 H,13 C-HSQC NMR spectra, which allow the rapid collection of NMR data in a quantitative manner on a single sample...
2018: Wellcome Open Research
Eszter Boros, Omar R Pinkhasov, Peter Caravan
Background: Current analytical methods for characterizing pharmacokinetic and metabolic properties of positron emission tomography (PET) and single photon emission computed tomography (SPECT) probes are limited. Alternative methods to study tracer metabolism are needed. The study objective was to assess the potential of high performance liquid chromatography - inductively coupled plasma - mass spectrometry (HPLC-ICP-MS) for quantification of molecular probe metabolism and pharmacokinetics using stable isotopes...
2018: EJNMMI Radiopharm Chem
Yonggang Yang, Tingting Guo, Wentao Jiao
There is less research on the hydrological system and its destruction processes mechanism in the mining areas, especially combined application of isotope technology and chemical signals, which is a key scientific problem that need to be solved. This study takes Jinci spring area in Shanxi as a case study. It is based on the data of hydrology and mining condition from 1954 to 2015, combining monitoring experiments, O18 , D, S34 and N15 tracing, chemical and model simulation. This study investigates the hydrological regularity and impacts of mining activities on water quantity and quality, and reveals the destruction process of hydrological system...
March 1, 2018: Environmental Pollution
Laura Freije-Carrelo, Laura Alonso Sobrado, Mariella Moldovan, Jorge Ruiz Encinar, Jose Ignacio Garcia-Alonso
Dissolved inorganic carbon (DIC) is one of the most important parameters to be measured in seawaters for climate change studies. Its quantitative assessment requires analytical methodologies with overall uncertainties around 0.05% RSD for clear evaluation of temporal trends. Herein, two alternative Isotope Dilution Mass Spectrometry (IDMS) methodologies (on-line and species-specific) using an Isotope Ratio Mass Spectrometer (IRMS) and two calculation procedures for each methodology have been compared. As a result, a new method for the determination of DIC in seawaters, based on species-specific IDMS with Isotope Pattern Deconvolution calculation, was developed and validated...
March 2, 2018: Analytical Chemistry
Lishan Zheng, Xiaoyang Yang, Senchao Lai, Hong Ren, Siyao Yue, Yingyi Zhang, Xin Huang, Yuanguan Gao, Yele Sun, Zifa Wang, Pingqing Fu
Fine particles (PM2.5 ) samples, collected at Weizhou Island over the Gulf of Tonkin on a daytime and nighttime basis in the spring of 2015, were analyzed for primary and secondary organic tracers, together with organic carbon (OC), elemental carbon (EC), and stable carbon isotopic composition (δ13 C) of total carbon (TC). Five organic compound classes, including saccharides, lignin/resin products, fatty acids, biogenic SOA tracers and phthalic acids, were quantified by gas chromatography/mass spectrometry (GC/MS)...
February 26, 2018: Environmental Pollution
Surya N Mulukutla, Jean W Hsu, Ruchi Gaba, Kurt M Bohren, Anu Guthikonda, Dinakar Iyer, Nadim J Ajami, Joseph F Petrosino, Christiane S Hampe, Nalini Ram, Farook Jahoor, Ashok Balasubramanyam
Background: A-β + ketosis-prone diabetes (KPD) is a subset of type 2 diabetes in which patients have severe but reversible β cell dysfunction of unknown etiology. Plasma metabolomic analysis indicates that abnormal arginine metabolism may be involved. Objective: The objective of this study was to determine the relation between gut microbiome and arginine metabolism and the relation between arginine availability and β cell function in KPD patients compared with control participants...
February 1, 2018: Journal of Nutrition
Cao Thi Thuy Hai, Nakamura Takashi, Saiki Makoto, Ta Thi Thao, Toyama Tadashi, Nishida Kei
RATIONALE: The isotopic tracer technique is widely used to identify the sources and fate of nitrogen (N) in order to understand the N cycle and contamination in water environments. The stable isotope ratio of ammonium is expected to greatly enhance the tracing analysis by combining it with the traditional nitrate isotope ratio. Diffusion followed by gas-phase trapping is the most commonly applied method for ammonium isotope ratio measurement. Although dissolved organic nitrogen (DON) is abundant in natural water and its breakdown in the diffusion procedure has been reported, the interference of DON with the measurement of ammonium isotope ratios has not been fully examined...
February 27, 2018: Rapid Communications in Mass Spectrometry: RCM
Joshua D Bryant, Shannon R Sweeney, Enrique Sentandreu, Minhye Shin, Helene Ipas, Blerta Xhemalce, Jessica Momb, Stefano Tiziani, Dean R Appling
One-carbon (1C) metabolism is a universal folate-dependent pathway essential for de novo purine and thymidylate synthesis, amino acid interconversion, universal methyl-donor production, and regeneration of redox cofactors. Homozygous deletion of the 1C pathway gene Mthfd1l encoding methylenetetrahydrofolate dehydrogenase (NADP+ dependent) 1-like, which catalyzes mitochondrial formate production from 10-formyltetrahydrofolate, results in 100% penetrant embryonic neural tube defects (NTDs), underscoring the central role of mitochondrially derived formate in embryonic development and providing a mechanistic link between folate and NTDs...
February 26, 2018: Journal of Biological Chemistry
Søren Reitelseder, Kasper Dideriksen, Jakob Agergaard, Nikolaj M Malmgaard-Clausen, Rasmus L Bechshoeft, Rasmus K Petersen, Anja Serena, Ulla R Mikkelsen, Lars Holm
PURPOSE: The responsiveness of older individuals' skeletal muscle to anabolic strategies may be impaired. However, direct comparisons within the same experimental setting are sparse. The aim of this study was to assess the resting and post-resistance exercise muscle protein synthesis rates in response to two types of milk protein and carbohydrate using a unilateral exercise leg model. METHODS: Twenty-seven older (69 ± 1 year, mean ± SE) men were randomly assigned one of three groups: Whey hydrolysate (WH), caseinate (CAS), or carbohydrate (CHO)...
February 22, 2018: European Journal of Nutrition
Bo Meng, Yanbin Li, Wenbin Cui, Ping Jiang, Guangliang Liu, Yongmin Wang, Jennifer H Richards, Xinbin Feng, Yong Cai
The role of macrophytes in the biogeochemical cycle of mercury (Hg) in the Florida Everglades is poorly understood. Stable isotope tracer techniques were employed to investigate Hg uptake by sawgrass (Cladium jamaicense) from soil and from the atmosphere pathways, and the fate of Hg after absorption. Our results suggest that soil spiked 201Hg2+was rapidly taken up by roots and transported to aboveground parts. The spiked 201Hg that was transported to the aboveground parts was trapped; no release of the spiked 201Hg from the leaf to the air was detected...
February 21, 2018: Environmental Science & Technology
Noah Edward Jemison, Alyssa Shiel, Thomas M Johnson, Craig Lundstrom, Philip E Long, Kenneth H Williams
Biostimulation to induce reduction of soluble U(VI) to relatively immobile U(IV) is an effective strategy for decreasing aqueous U(VI) concentrations in contaminated groundwater systems. If oxidation of U(IV) occurs following the biostimulation phase, U(VI) concentrations increase, challenging the long-term effectiveness of this technique. However, detecting U(IV) oxidation through dissolved U concentrations alone can prove difficult in locations with few groundwater wells to track the addition of U to a mass of groundwater...
February 21, 2018: Environmental Science & Technology
I Hoffman, B Lewis, P Chan
Using a recently published global data set of22 Na and7 Be from the global monitoring network of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO), atmospheric circulation and stratosphere-troposphere interactions are examined. Cosmogenic22 Na has a half-life well-suited to environmental processes with durations from several months to a decade. Combined with corresponding7 Be observations, these two cosmogenic isotopes form a useful environmental tracer and new radiochronometer to study physical interactions of air masses in the stratosphere and troposphere...
February 16, 2018: Journal of Environmental Radioactivity
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