Stable Isotope Techniques Research Articles

Abstract 394: Ldl-cholesterol, ApoB100 Kinetics and Atherosclerosis in Ldlr-deficient Yucatan Minipigs: A New Model for Familial Hypercholesterolemia

Lack of animal models with human-like lipoprotein metabolism and pathology has hampered translational research in atherosclerosis. Recently, a model of familial hypercholesterolemia was developed in Yucatan miniature pigs, in which the LDL receptor (LDLR) was deleted through gene targeting of exon 4. The objective of the present study was to determine the plasma lipoprotein response to a high fat diet and the kinetics of apolipoprotein (apo) B metabolism in LDLR-deficient miniature pigs. LDLR+/+ (n=5), LDLR+/- pigs (n=6) and LDLR-/- pigs (n=5) were fed a diet containing 34% kcal from fat and 0.2% cholesterol (C). At 6 weeks, the kinetics of plasma apoB100 (fasting) were measured using stable isotopic techniques and multi-compartmental modeling. In chow-fed pigs, LDL-C was 0.8mM, 1.3mM and 14mM in LDLR+/+, LDLR+/- and LDLR-/- pigs, respectively. On diet for 6 weeks, LDL-C increased 1.3-fold (to 1.09mM), 1.7-fold (to 2.3mM) and 1.2-fold (to 15.8mM) in LDLR+/+, LDLR+/- and LDLR-/- pigs, respectively. The effect of genotype or diet on plasma TG and HDL-C was modest. Compared to LDLR+/+ pigs, VLDL apoB100 pool sizes increased 1.4-fold in LDLR+/- and 1.7-fold in LDLR-/- pigs, due primarily to a decrease in fractional catabolic rates (FCR) of 18% and 63%, respectively. Compared to LDL+/+ pigs, LDL apoB100 pool sizes increased 2.2-fold and 14-fold in LDLR+/- and LDLR-/-, respectively, which was due to both 1.5-fold and 2-fold increases in production rates and 24% and 85% decreases in FCR, respectively. At 23 weeks, raised lesion area in the abdominal aorta was 3.3% in LDLR+/- pigs and 48.5% in LDLR-/- pigs. In the left anterior descending coronary artery, lesion area was 14.7x10 3 μm 2 in LDLR+/- pigs and 656x10 3 μm 2 in LDLR-/- pigs. This model should prove useful for translational research in lipoprotein metabolism and atherosclerosis.

Dietary glutamine, glutamic acid and nucleotide supplementation accelerate carbon turnover (δ13C) on stomach of weaned piglets.

The use of stable isotope analysis as a tool for characterization of carbon turnover (δ13C) in piglet's tissues by tracing its feeding system has drawn attention. Thus, this study aimed at evaluating the influence of dietary glutamine, glutamic acid and nucleotides supplementation on carbon turnover in fundic-stomach region of weaned piglets at an average age of 21 days. The diets consisted of additive-free diet – control (C); 1% glutamine (G); 1% glutamic acid (GA) and 1% nucleotides (Nu). At weaning day (day 0: baseline), 3 piglets were slaughtered to quantify the δ13C of stomach. The remaining 120 piglets were blocked by weight and sex, randomly assigned to pens with 3 piglets slaughtered per treatment at days 1, 2, 4, 5, 7, 9, 13, 20, 27 and 49 after weaning in order to verify the fundic-stomach isotopic composition by treatments. Samples were analyzed in terms of 13C/12C ratio by mass spectrometry and converted to relative isotopic enrichment values (δ13C ‰) used to plot the first order exponential curves over time using OriginPro 8.0 software. The inclusion of glutamine, glutamate and nucleotides in piglet's diets has accelerated the carbon turnover in stomach during the post-weaning period, demonstrating also that glutamate has guaranteed fastest 13C incorporation rate on fundic-stomach region and pH-lowering. Besides that, stable isotopes technique (δ13C) has proved to be an important methodology to determine the time-scales at which piglets shift among diets with different isotopic values, characterizing the trophic effects of additives and the phenotypic flexibility of stomach.

Elucidating the Origin of Milk Products on the Chinese Market Using Multi Element Stable Isotope Technique

Preference for foreign milk products is the cause of the economically motivated adulteration of milk products on the Chinese market. The present study was done to ascertain the feasibility of utilizing δ2 H, δ18O and δ15N stable isotope techniques in elucidating the geographical origin of milk products on the Chinese market. 42 milk samples from the United States of America, Canada, Southern China, Northern China, Australia and New Zealand were analyzed. An isotope ratio mass spectrometer with a combination of a high-temperature conversion elemental analyzer, Thermo-Fisher was used. Statistical analysis was performed using one-way ANOVA. The study revealed that both δ2 H and δ18O had a wide range of mean values: 13.86 to 22.25‰ and -82.86 to -28.5‰, respectively. There was a significant difference in the δ2 H (n=7; F=20880, P=7.876E-43) and δ18O (n=7; F=1399.0; P=9.215E-29) composition of the milk samples from the different regions. It was observed that δ2 H and δ18O composition is helpful in elucidating milk products from different regions on the Chinese market (P<0.05). The range of the mean δ15N values of the milk samples was very close, 3.06 to 5.61‰, indicating a possible limitation in employing δ15N isotopic technique. The nitrogen stable isotope could not provide a clear distinction for the milk products because δ15N of an animal reflects that of the diet. Hence in cases of similar diet, it may not be possible to provide a distinction between the animals using this technique.

Influence of rice straw on priming of soil C for dissolved organic C and CH4 production

We investigated the priming effect (PE) of plant residue on soil organic carbon (SOC) to release substrates for methane (CH4) production. Carbon-13-labeled rice straws were anaerobically incubated with paddy soils with a range of SOC contents (2%, 6% and 15%) for 32 days. Stable isotope techniques were used to partition the production of dissolved organic carbon (DOC) and CH4 into their sources, and the PE was quantified. Straw addition resulted in up to a 3-fold increase in the release of DOC from SOC with the largest magnitudes found in the 15% SOC soils, where the priming of DOC production was associated with the reduction of Fe3+ to Fe2+. In straw-amended soils, SOC was always the dominant source of DOC. Nonetheless, the primed DOC production did not result in a proportional increase of CH4 production. The contribution of SOC to CH4 production increased 30 to 50% with residue addition, depending on SOC content. However, more than 52% of the total CH4 production was straw-derived. The straw-induced priming of CH4 from SOC sources was positively correlated to the degree of residue decomposition, while the priming efficiency of straw on CH4 production was seemingly negated by the existence of various electron acceptors. Our results suggest that field residue incorporation will exacerbate the role of rice paddies as significant sources of atmospheric CH4, and likely DOC as well.

Late Quaternary relative humidity changes from Mt. Kilimanjaro, based on a coupled 2H-18O biomarker paleohygrometer approach

Abstract Our understanding of African paleoclimate/hydrological history is mainly based on lake level and lake sediment studies. It improved during the last decade thanks to emerging stable isotope techniques such as compound-specific deuterium analysis of sedimentary leaf wax biomarkers (δ2Hleaf-wax). Here we present the results from a multi-proxy biomarker study carried out on a ∼100 ka loess-like paleosol sequence preserved in the Maundi crater at ∼2780 m a.s.l. on the southeastern slopes of Mt. Kilimanjaro in equatorial East Africa. The Maundi stable isotope records established for hemicellulose-derived sugars, lignin- and pectin-derived methoxyl groups, leaf wax-derived fatty acid and n-alkane biomarkers (δ18Osugars, δ2Hmethoxyl groups, δ2Hfatty-acids and δ2Hn-alkanes, respectively) reveal similar patterns, but also some distinct differences are obvious. The periods from ∼70 to 60 ka, the Last Glacial Maximum (LGM) and the Younger Dryas (YD) are characterized by more positive δ values, whereas during the Holocene, and around 30, 39, and 56 ka BP more negative δ values are determined. The application of a ‘coupled δ2Hn-alkane-δ18Osugar paleohygrometer’ approach allows us to derive information about Late Quaternary changes of air relative humidity at the Maundi study site. Reconstructed changes of mean day-time relative humidity (RHD) are in good agreement with pollen results from the study area. Apart from the overall regional moisture availability, the intensification versus weakening of the trade wind inversion, which affects the diurnal montane atmospheric circulation on the slopes of Mt. Kilimanjaro, is suggested as a local factor which may contribute to the observed variability of RHD at Maundi study site. The combined usage of δ2Hn-alkanes and δ18Osugars allowed us to reconstruct δ2H/δ18O of source water utilized by plants in the study area, which is directly linked to local precipitation. The results of this reconstruction caution against a straightforward interpretation of δ2Hleaf-wax and δ18Osugars records as proxies for isotopic composition of local precipitation because variable and primarily RH-dependent isotopic evaporative enrichment of leaf water can mask changes of δ2Hprec/δ18Oprec in the past. The biomarker-based δ2H/δ18Osource-water records derived for the Maundi site revealed a discernible link with the reconstructed RHD record; lower RHD values were generally observed during periods characterized by more negative δ2H/δ18Osource-water values, indicating a reverse relationship with the expected precipitation amount. This indicates that the empirical relationship between amount of rainfall and its isotopic composition, observed nowadays on monthly timescale in the East African region, might not be valid on millennial time scale.

Raman microspectroscopy, surface-enhanced Raman scattering microspectroscopy, and stable-isotope Raman microspectroscopy for biofilm characterization.

Biofilms represent the predominant form of microbial life on our planet. These aggregates of microorganisms, which are embedded in a matrix formed by extracellular polymeric substances, may colonize nearly all interfaces. Detailed knowledge of microorganisms enclosed in biofilms as well as of the chemical composition, structure, and functions of the complex biofilm matrix and their changes at different stages of the biofilm formation and under various physical and chemical conditions is relevant in different fields. Important research topics include the development and improvement of antibiotics and medical devices and the optimization of biocides, antifouling strategies, and biological wastewater treatment. Raman microspectroscopy is a capable and nondestructive tool that can provide detailed two-dimensional and three-dimensional chemical information about biofilm constituents with the spatial resolution of an optical microscope and without interference from water. However, the sensitivity of Raman microspectroscopy is rather limited, which hampers the applicability of Raman microspectroscopy especially at low biomass concentrations. Fortunately, the resonance Raman effect as well as surface-enhanced Raman scattering can help to overcome this drawback. Furthermore, the combination of Raman microspectroscopy with other microscopic techniques, mass spectrometry techniques, or particularly with stable-isotope techniques can provide comprehensive information on monospecies and multispecies biofilms. Here, an overview of different Raman microspectroscopic techniques, including resonance Raman microspectroscopy and surface-enhanced Raman scattering microspectroscopy, for in situ detection, visualization, identification, and chemical characterization of biofilms is given, and the main feasibilities and limitations of these techniques in biofilm research are presented. Future possibilities of and challenges for Raman microspectroscopy alone and in combination with other analytical techniques for characterization of complex biofilm matrices are discussed in a critical review. Graphical Abstract Applicability of Raman microspectroscopy for biofilm analysis.

Using stable isotope techniques in nutrition assessments and tracking of global targets post-2015

Stable isotopes are non-radioactive, safe and are applied for various purposes in human health assessment in trace amounts that minimally disturb normal physiology. The International Atomic Energy Agency supports the use of stable isotope techniques to design and evaluate interventions addressing malnutrition in all its forms with focus on infant and young child feeding; maternal and adolescent nutrition; diet quality; prevention and control of non-communicable diseases; healthy ageing and gut function. These techniques can be used to objectively measure: (1) amount of human milk consumed and whether an infant is exclusively breastfed; (2) body composition in the context of re-feeding programmes for moderate and severe acute malnutrition and as an indicator of the risk for obesity; (3) bioavailability and bioconversion of pro-vitamin A and vitamin A body stores following vitamin A intervention programmes; (4) absorption and retention of iron, zinc and protein; (5) total energy expenditure for validation of physical activity measurement and dietary assessment tools and (6) diagnosis of Helicobacter pylori. Stable isotope techniques will be invaluable in the tracking of global targets on exclusive breast-feeding childhood obesity and anaemia among women. Efforts are underway to make nuclear techniques more affordable, field-friendly and less invasive, and to develop less sophisticated but precise equipment. Advocacy for the wide adoption of the techniques is needed.

Analysis and prediction of gas recovery from abandoned underground coal mines in China

Mine closures will be especially widespread in eastern China. However, Because of relatively high residual coal-bed methane content, the abandoned coal mine methane (ACMM) reserves of China are huge, and from a greenhouse gas control perspective it is preferable that they be developed and utilized, rather than allowed to vent to the atmosphere. The exploitation and development of ACMM in China is still in its infancy, with theory and practice undergoing rapid development. Four factors are particularly influential on design of ACMM recovery strategies. The first factor is what may be termed the "enrichment space", which reflects the final state of the strata after completion of longwall extraction and subsequent strata settlement, and is here defined as the region between the outer, limit of stress relief and the limit of the extracted panels. Quantitative analysis of the components of gas mixtures recovered from the enrichment space can be tracked using stable carbon isotope techniques. The second factor is the permeability field surrounding the abandoned mine voids. The thick mudstones that commonly overlie the coal seams serve to confine the water and gas within the enrichment space and old mine voids. The geometry of these confining layers can be confirmed by seismic reflection or other geophysical methods, which can reveal the extent of the zone affected by fracture development. On this basis, models of methane movement in abandoned mines can be constrained, allowing valuable predictions of availability of ACMM resources under different mining and post-closure drainage conditions.

Elucidating the Origin of Milk Products on the Chinese Market Using Hydrogen and Oxygen Stable Isotope Technique

Preference for foreign milk products is the cause of the economically motivated adulteration of milk products on the Chinese market. 42 milk samples from the United States of America, Canada, Southern China, Northern China, Australia and New Zealand were analyzed using δ2H and δ18O stable isotope technique to differentiate the origin of milk products. An isotope ratio mass spectrometer with a combination of a high-temperature conversion elemental analyzer, Thermo-Fisher was used. Statistical analysis was performed using one-way ANOVA. The study revealed δ2H and δ18O had a wide range of mean values: 13.86 to 22.25‰ and -82.86 to -28.5‰, respectively. There was a significant difference in the δ2H (n=7; F=20880, P=7.876E-43) and δ18O (n=7; F=1399.0; P=9.215E-29) composition of the milk samples from the different regions. It was observed that δ2H and δ18O composition is helpful in elucidating milk products from different regions on the Chinese market (P<0.05).

Stable isotopic evolutions of ground ice in permafrost of the Hoh Xil regions on the Qinghai-Tibet Plateau

Climatic warming-induced permafrost (ground ice) thaw is expected to considerably alter hydro−geomorphology and the water cycle on the Qinghai-Tibet Plateau (QTP). A unique feature of permafrost is the substantial enrichment of ground ice, which can be used to directly indicate the past climate and hydrological cycle. However, essential characteristics of ground ice on the QTP are not yet understood. The stable isotope technique was used to investigate the formation processes and initial source of water in the ground ice in a borehole of Zhuonaihu (ZNH) lake at the Hoh Xil permafrost regions in the hinterland of the QTP. Variability in water migration, replenishment of water, and climatic conditions (freezing rate) have created a complex isotopic stratigraphy and ice growth history. The δD−δ18O relationship of ground ice samples showed similar characteristics to a local meteoric water line of regional precipitation on QTP, and the D-excess−δD relations of ground ice reveal different features from those of precipitation and freezing condition. The near−surface ground ice (0–3 m) was enriched in δ18O and δD which was formed from freezing of active layer water suffering evaporation, and deep layer ground ice (>3 m) was depleted in these isotopes. Stable isotope results were indicative of past−precipitation origin of ground ice between 2.5 and 5.5 m. Ground ice between depths of 5.5 and 10 m was formed under unstable freezing conditions. However, ice from 10 to 16 m was formed by freezing segregation of liquid water. Comparison of the results with other five boreholes indicates that differences in lithology, source water, and climatic conditions were responsible for the significant deviations in ground ice isotopes. This research provides an insight into the fundamental formation processes related to ground ice in the QTP, which will provide important guidance for future studies of permafrost hydrology.

Detection of corn oil in adulterated olive and soybean oil by carbon stable isotope analysis

The production of olive oil and soybean oil is expensive and time-consuming, and the products have high commercial value. These make the products highly susceptible to economically motivated adulteration, especially on the Chinese market. The study was performed to elucidate the possible detection of varying adulteration levels of corn oil in olive and soybean oil using the carbon isotope technique. An elemental analyzer, which was connected to an isotope ratio mass spectrometer and operated in the continuous flow mode was utilized. Statistical analysis was performed using descriptive statistics and one-way ANOVA. The results showed that the samples of olive and soybean oil had lower δ13C values relative to corn oil samples irrespective of the origin of production. The standard error (SE) of the mean on δ13C value of olive oil, soybean and corn oil was −29.26 ± 0.14; −28.90 ± 0.35 and −15.84 ± 0.08‰, respectively. The difference in δ13C values of both olive oil and soybean oil adulterated with corn oil samples at different adulteration content (25, 50, 75, and 95%) were statistically significant (p 0.97 for both products. Therefore, the carbon stable isotope technique is a good tool for detecting both complete and partial substitution of pure olive oil and soybean oil with corn oil.

Mining the isotopic complexity of nitrous oxide: a review of challenges and opportunities

Nitrous oxide (N2O) is an important focus of international greenhouse gas accounting agreements and mitigation of emissions will likely depend on understanding the mechanisms of its formation and reduction. Consequently, applications of stable isotope techniques to understand N2O cycling are proliferating and recent advances in technology are enabling (1) increases in the frequency of isotope analyses and (2) analyses not previously possible. The two isotopes of N and 3 isotopes of O combine to form a total of 12 possible isotopic molecules of N2O. Consequently, this remarkably simple molecule contains a wealth of isotopic information in the form of bulk (δ15N, δ18O), position dependent (site preference), mass independent (Δ17O) and multiply-substituted or clumped isotope compositions. With recent developments in high-mass resolution double sector instruments all 12 isotopic molecules will likely be resolved in the near future. Advances in spectroscopic instruments hold the promise of substantial increases in sample throughput; however, spectroscopic analyses require corrections due to interferences from other gases and frequent and accurate calibration. Mass spectrometric approaches require mass overlap corrections that are not uniform between research groups and interlaboratory comparisons remain imprecise. The continued lack of attention to calibration by both funding agencies and investigators can only perpetuate disagreement between laboratories in reported isotope values for N2O that, in turn, will compromise global assessments of N2O sources and sinks based on isotope ratios. This review discusses the challenges and opportunities offered by the isotopic complexity of N2O.

24-Hour protein, arginine and citrulline metabolism in fed critically ill children – A stable isotope tracer study

The reference method to study protein and arginine metabolism in critically ill children is measuring plasma amino acid appearances with stable isotopes during a short (4-8h) time period and extrapolate results to 24-h. However, 24-hmeasurements may be variable due to critical illness related factors and a circadian rhythm could be present. Since only short duration stable isotope studies in critically ill children have been conducted before, the aim of this study was to investigate 24-happearance of specific amino acids representing protein and arginine metabolism, with stable isotope techniques in continuously fed critically ill children. In eight critically ill children, admitted to the pediatric (n=4) or cardiovascular (n=4) intensive care unit, aged 0-10 years, receiving continuous (par)enteral nutrition with protein intake 1.0-3.7g/kg/day, a 24-hstable isotope tracer protocol was carried out. L-[ring-2H5]-phenylalanine, L-[3,3-2H2]-tyrosine, L-[5,5,5-2H3]-leucine, L-[guanido-15N2]-arginine and L-[5-13C-3,3,4,4-2H4]-citrulline were infused intravenously and L-[15N]-phenylalanine and L-[1-13C]leucine enterally. Arterial blood was sampled every hour. Coefficients of variation, representing intra-individual variability, of the amino acid appearances of phenylalanine, tyrosine, leucine, arginine and citrulline were high, on average 14-19% for intravenous tracers and 23-26% for enteral tracers. No evident circadian rhythm was present. The pattern and overall 24-hlevel of whole body protein balance differed per individual. In continuously fed stable critically ill children, the amino acid appearances of phenylalanine, tyrosine, leucine, arginine and citrulline show high variability. This should be kept in mind when performing stable isotope studies in this population. There was no apparent circadian rhythm. NCT01511354 on clinicaltrials.gov.

Assessment of tissue development in fattening quails using the stable isotope technique.

We aimed to study the behaviour of tissue renewal in blood, pectoral muscle and keel of fattening quails during their growth and adulthood through carbon-13 turnover using the stable isotope technique. Three hundred male European quails were randomly subjected to six treatments. Diets fed to animals were initially based on corn and soybean meal and were replaced at 0, 7, 14, 21, 28 and 35days of age with diets of rice grits and soybean meal. These diets have distinct isotopic signals and over time it changes; the tissue will incorporate dietary signal, and then, we can measure the return time for each tissue in each age. Treatments were T1 (0 to 21days), T2 (7 to 35days), T3 (14 to 42days), T4 (21 to 56days), T5 (28 to 63days) and T6 (35 to 70days). Carbon-13 turnover in tissues of the birds at the above-mentioned time periods was calculated using the first-order exponential function. The values of half-lives were 2.6, 3.6, 5.4, 6.3, 9.0 and 9.8days for blood and 2.0, 1.7, 4.8, 6.7, 6.9 and 6.6days for pectoral muscle in treatments T1, T2, T3, T4, T5 and T6 respectively. The half-lives for the keel in treatments T2, T3, T4, T5 and T6 were 2.0, 5.4, 7.7, 8.9 and 15days respectively. Thus, half-life in sampled tissues generally increased with age of birds. Initially, the tissue half-lives are influenced by growth, and at the end of the growth cycle, the breast muscle tissue was the most metabolically active in either periods, followed by blood and the keel. All tissues showed a sigmoidal growth curve, which can be confirmed by half-life as a function of age.

Mechanisms responsible for high N2O emissions from subarctic permafrost peatlands studied via stable isotope techniques

AbstractRecent field studies have shown that there are habitats in the subarctic tundra emitting N2O at exceptionally high rates. In this study, stable isotope techniques were applied to characterize the processes responsible for these high N2O emissions which have been found from bare peat surfaces in permafrost peatlands. The results include the first data on the nitrogen and oxygen isotopic composition of N2O emitted from arctic tundra. The emission‐weighted average δ15Nbulk value for N2O of −13.0‰ ± 2.0‰ (mean ± SD; n = 8) from the bare peat surfaces falls within the range of the emission‐weighted average values from other natural ecosystems but is distinct from those for managed/agricultural ecosystems. This implies that if in the future, a smaller rate in the overall decreasing trend of δ15Nbulk N2O tropospheric isotopic composition is found, it cannot be attributed only to agricultural N2O emission reductions from mitigation actions but also to soils in natural ecosystems that may be emitting more N2O to the atmosphere due to warmer conditions. The site preference (SP) values from emitted N2O range from −30‰ to 58‰, indicating a temporal shift of microbial production and consumption of N2O during the sampling period. Soil emission SP data suggest that the N2O emission in subarctic tundra are more likely to be produced by nitrifier denitrification in the drier study year, but due to variable published SP values for N2O production processes in soils, this interpretation has to be taken with caution. According to SP values at depth, denitrification was the main N2O production pathway. To better address the usefulness of SP in partitioning microbial mechanisms in soils, further studies in soils mesocosms are required.

Dietary glutamine, glutamic acid and nucleotides increase the carbon turnover (δ13C) on the intestinal mucosa of weaned piglets

This study aimed at evaluating the influence of dietary glutamine, glutamic acid and nucleotides on duodenal and jejunal carbon turnover, and on mucosa morphometry of piglets weaned at an age of 21 days. The diets were: additive-free diet – control (C); 1% of glutamine (G); 1% of glutamic acid (GA); and 1% of nucleotides (N). In intestinal mucosa morphometry trial, 65 animals were used. At day 0 (baseline), five animals were slaughtered to determine the villus height (VH), crypt depth (CD), VH : CD ratio and villi density (VD). The remaining 60 animals were allocated into a randomized block design with 4×3 factorial arrangement (four diets: C – control, G – glutamine, GA – glutamic acid and N – nucleotides; three slaughter ages: 7, 14 and 21 days post-weaning) with five piglets slaughtered per treatment. In carbon turnover trial, 123 animals were used. At day 0 (baseline), three animals were slaughtered to quantify the δ13C half-life (T50%) and the 99% carbon substitution (T99%) on intestinal mucosa. The remaining 120 animals were blocked by three weight categories (light, medium and heavy) and, randomly assigned to pen with the same four diets from the previous trial with one piglet slaughtered per weight category per treatment at days 1, 2, 4, 5, 7, 9, 13, 20, 27 and 49 after weaning. Morphometric analyses have yielded no consistent results regarding the action of the evaluated additives, and few reproducible age-related effects. The N diets determined lower T50% values (5.18 days) and T99% (17.21 days) than G and C diets (T50%=7.29, 7.58 days and T99%=24.22, 25.17 days, respectively) in the duodenal mucosa. In jejunum, the N, GA and G diets determined the lowest T50% means (4.9, 6.2 and 6.7 days, respectively) and T99% means (15.34, 21.10 and 21.84 days, respectively) in comparison with C diets (T50%=7.44 and T99%=24.72 days). The inclusion of the additives in the diets of piglets accelerated the carbon turnover in piglets during the post-weaning period. The stable isotopes technique (δ13C) is an important methodology in studies of additives with trophic effects on the intestinal mucosa of the piglets.

Editorial introductions

Editorial introductions

采用稳定碳同位素法分析白羊草在不同干旱胁迫下的水分利用效率

PDF HTML阅读 XML下载 导出引用 引用提醒 采用稳定碳同位素法分析白羊草在不同干旱胁迫下的水分利用效率 DOI: 10.5846/stxb201601180112 作者: 作者单位: 西安理工大学,西安理工大学,西安理工大学,西安理工大学,西安理工大学,西安理工大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（41330858）；国家自然科学基金（41471226，41271290）；校级基金（310-252071506） Effects of drought stress on Bothriochloa ischaemum water-use efficiency based on stable carbon isotope Author: Affiliation: Xi’an University of Technology,Xi’an University of Technology,Xi’an University of Technology,Xi’an University of Technology,Xi’an University of Technology,Xi’an University of Technology Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:本研究以黄土高原乡土草种白羊草（Bothriochloa ischaemum （L.）Keng.）为研究对象，采用盆栽控制实验，比较白羊草在3个水分处理（CK80%FC、MS60%FC和SS 40%FC）下的生物量积累和分配模式、瞬时水分利用效率（WUE）、不同部位（新叶、老叶、茎、细根、粗根）的稳定碳同位素组成（δ13C）和碳同位素分辨率（Δ13C）及其相互关系，以及干旱胁迫下影响水分利用效率的主导环境因子。结果表明：1）重度干旱胁迫显著降低植物整体生物量，显著增加根冠比和细根生物量比例；2）随着干旱胁迫加剧，白羊草各器官的δ13C均呈上升趋势，Δ13C呈减小趋势，SS处理不同器官δ13C和Δ13C没有显著差异，CK和MS处理的各器官δ13C均值表现分别为细根 > 粗根 > 老叶 > 新叶 > 茎、细根 > 新叶 > 老叶 > 粗根 > 茎，CK和MS处理Δ13C的值总体呈根 < 叶 < 茎。3）新叶的δ13CNL和Δ13CNL与WUE的相关系数均最大，说明利用稳定碳同位素方法测定白羊草水分利用效率具有可行性。4）不同水分处理的WUE的主导影响因子不同，CK、MS、SS水分处理WUE分别受到叶面温度、大气水汽压亏缺和空气温度的影响最大。为采用稳定碳同位素方法指示白羊草水分利用效率可行性及阐明植物的胁迫响应机制提供理论依据。 Abstract:Owing to low precipitation and high inter-annual variability, the Loess hilly and valley region experiences frequent drought, which significantly affects plant growth. Studying the response mechanism of plants to water stress is important with respect to improving water-use efficiency (WUE) in this arid and semi-arid area. In the present research, Bothriochloa ischaemum (L.) Keng., a typical native species in the Loess hilly-gully region, was selected to investigate biomass accumulation and allocation, instantaneous WUE, stable carbon isotope composition (δ13C), and stable carbon isotope discrimination (Δ13C) in different organs under three water regimes: control [CK, 80% field capacity (FC)], mild water stress (MS, 60% FC), and severe stress (SS, 40% FC). Photosynthetic parameters of B. ischaemum were measured at 09:00-11:00 on sunny windless days (Aug 3, 10, and 13,2014), using a portable photosynthesis determination system (Li-6400; Li-Cor, USA). On Nov 11, when the experiment ended, the new leaf, old leaf, stem, fine root, and coarse root parts of seedlings were sampled carefully and weighed (with accuracy 0.001 g) after drying at 65℃. The root-to-shoot ratio was then calculated as the ratio of the belowground dry biomass to aboveground dry biomass. The δ13C of different plant parts was measured using a CCIA-36d-EP Carbon isotope ratio mass spectrometer (Los Gatos Research, USA). The Δ13C of different plant parts was calculated based on δ13C and the carbon isotope ratio of atmospheric CO2. Many environmental factors that might affect WUE were analyzed to explore the response mechanisms of B. ischaemum under drought conditions. The following results were obtained. (1) The total biomass of B. ischaemum was significantly decreased under the SS condition, whereas the root-to-shoot ratio and fine root biomass were significantly increased under this water regime. (2) The δ13C and Δ13C in different plant parts showed different trends. Drought stress led to an increase in the δ13C value and decrease in the Δ13C value. There was no significant difference in the δ13C and Δ13C of different plant parts under the SS condition. The δ13C values under CK and MS conditions were in the order of fine root > coarse root > old leaf > new leaf > stem, and fine root > new leaf > old leaf > coarse root > stem, respectively. Furthermore, the Δ13C values under CK and MS conditions were all in the order of root < leaf δ13C and Δ13C values of new leaves had the highest correlation coefficients with respect to WUE, which indicated that the stable carbon isotope technique is suitable for the determination of the WUE of B. ischaemum. (4) The WUE was affected by different environmental factors under different water regimes. Leaf temperature, atmospheric water vapor pressure, and air temperature were the most important factors affecting WUE under CK, MS, and SS conditions, respectively. This research provides a theoretical basis for the feasibility of using the stable carbon isotope method to determine the WUE of B. ischaemum, and for elucidating the mechanism underlying the response of B. ischaemum to water stress. 参考文献 相似文献 引证文献

Elucidating the origin of milk products on the Chinese market using hydrogen and oxygen stable isotope technique

Elucidating the origin of milk products on the Chinese market using hydrogen and oxygen stable isotope technique

Stable Isotope Techniques for the Assessment of Host and Microbiota Response During Gastrointestinal Dysfunction.

The International Atomic Energy Agency convened a technical meeting on environmental enteric dysfunction (EED) in Vienna (October 28-30, 2015; https://nucleus.iaea.org/HHW/Nutrition/EED_Technical_Meeting/index.html) to bring together international experts in the fields of EED, nutrition, and stable isotope technologies. Advances in stable isotope-labeling techniques open up new possibilities to improve our understanding of gastrointestinal dysfunction and the role of the microbiota in host health. In the context of EED, little is known about the role gut dysfunction may play in macro- and micronutrient bioavailability and requirements and what the consequences may be for nutritional status and linear growth. Stable isotope labeling techniques have been used to assess intestinal mucosal injury and barrier function, carbohydrate digestion and fermentation, protein-derived amino acid bioavailability and requirements, micronutrient bioavailability and to track microbe-microbe and microbe-host interactions at the single cell level. The noninvasive nature of stable isotope technologies potentially allow for low-hazard, field-deployable tests of gut dysfunction that are applicable across all age groups. The purpose of this review is to assess the state-of-the-art use of stable isotope technologies and to provide a perspective on where these technologies can be exploited to further our understanding of gut dysfunction in EED.