Use Of Stable Isotope Techniques Research Articles

Applicability of selected stable isotopes to study the hydrodynamics and contaminant transport within mining areas in Romania and Finland

Abstract Mining operations disturb the natural hydrological cycle at a local scale by creating new pathways for water flow and conveying large amounts of water, both for use in ore beneficiation and through the dewatering of mining workings. Sulfide minerals exposed to water and oxygen are oxidized through chemical and microbial-enhanced reactions, significantly altering the quality of water (acid mine drainage). Stable isotopes may reveal important information concerning water origin and transfer, as well as chemical processes and solute fluxes within the aqueous environment. Several case studies illustrate the use of stable isotope techniques for clarifying aspects related to water circulation in mining areas within Romania and Finland. Hydrogen and oxygen stable isotopes coupled with total dissolved solids have been used to characterize mine water and for assessing water sources, flow paths and mixing processes at some Romanian mining sites. At Talvivaara mine in Finland, water isotopes and chemical composition were used to determine the extent of waste water contamination in groundwater systems after a leakage at gypsum ponds.

Plasticity and specialisation in the isotopic niche of African clawless otters foraging in marine and freshwater habitats

Individual-level behavioural plasticity resulting from differences in environmental conditions is prevalent in many organisms and may result in phenomena such as dietary- or habitat specialisation. The isotopic niche of African clawless otters, Aonyx capensis, occupying different habitats was investigated with the use of stable isotope techniques. Stable isotope analyses revealed that African clawless otter isotopic niche varied between, as well as within, individuals and varied when compared to conspecifics occupying different habitats. Some otters varied their isotopic niche and foraging areas temporally, whilst others did not. The isotopic niche of African clawless otters in a coastal habitat overlapped substantially with previous reports on otter diet, but illustrated that otters eat more shark and molluscs than previously estimated. In freshwater habitats, not all otters had trout in their isotopic niche, although this prey item was abundantly available in the study area. Our results suggest that the African clawless otters can exhibit substantial behavioural plasticity. Such evident adaptability is likely to benefit otters and allow for extended use of non-pristine environments affected by human disturbance when sufficient quantities of prey remain available.

Carbon and nitrogen stable isotope ratios of soils and grasses as indicators of soil characteristics and biological taxa

The use of stable isotope techniques can assist in understanding interactions of plants with various abiotic and biotic processes. In the research, we focused on carbon (C) and nitrogen (N) isotopes because they are the most important resources influencing plant function and the biogeochemical cycles. The 13C/12C and 15N/14N ratios in plants and in soils and the relationships between these ratios and biological and environmental factors of widely distributed native C3 plants (couch grass, plantain and yarrow) collected from two sites in St. Petersburg, Russia were studied. The soil characteristics of the sites were rather different. This had a significant effect on the isotope ratios in plants and in soils resulting in a big difference between 13C/12C and between 15N/14N ratios in the soils, roots and leaves of the plants collected from the two sites. The variability of the C and N isotope ratios was also rather high among different plant species. Two main factors affected this variability: biological (plant species) and ecological (biogeochemical characteristics of soils). The 13C/12C and 15N/14N ratios of roots and especially leaves were typical for a particular plant species and could differ between different plant species growing simultaneously at the same site. The soil parameters (soil texture, pH, and concentrations of total C and N in the soil) were among main factors influencing the stable isotope ratios in the soil and in different parts of a plant. A strong positive relationship between 13C/12C and also between 15N/14N ratios in roots and leaves of the plants was observed. On the other hand, the correlation between ratios of 13C/12C and 15N/14N calculated only for leaves or only for roots was statistically significant and negative.

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.

Technical Note: Methionine, a precursor of methane in living plants

Abstract. When terrestrial plants were identified as producers of the greenhouse gas methane, much discussion and debate ensued not only about their contribution to the global methane budget but also with regard to the validity of the observation itself. Although the phenomenon has now become more accepted for both living and dead plants, the mechanism of methane formation in living plants remains to be elucidated and its precursor compounds to be identified. We made use of stable isotope techniques to verify the in vivo formation of methane, and, in order to identify the carbon precursor, 13C positionally labeled organic compounds were employed. Here we show that the amino acid L-methionine acts as a methane precursor in living plants. Employing 13C-labeled methionine clearly identified the sulfur-bound methyl group of methionine as a carbon precursor of methane released from lavender (Lavandula angustifolia). Furthermore, when lavender plants were stressed physically, methane release rates and the stable carbon isotope values of the emitted methane greatly increased. Our results provide additional support that plants possess a mechanism for methane production and suggest that methionine might play an important role in the formation of methane in living plants, particularly under stress conditions.

Experimental study on isotope fractionation of evaporating water of different initial isotopic composition

The studies of evaporative isotopic fractionation in controlled conditions are of particular importance for understanding the mechanism of evaporation fractionation in natural conditions. We present the measurements of the average isotopic fractionation factors during the evaporation of water having different initial isotopic compositions at constant temperature. The results show that the isotopic composition of residual water become more enriched over the time and the initial isotopic composition of evaporating water has considerable effect on the average isotopic fractionation factors. The average isotopic fractionation factors in evaporation of Water A and Water B under the present experimental conditions were found to be 0.9817 ± 0.0044 and 0.9887 ± 0.0031 for oxygen and 0.9178 ± 0.0182 and 0.9437 ± 0.0169 for hydrogen, respectively. The findings of this work should lead to a better understanding and use of stable isotope techniques in isotope hydrology by using a simple technique of evaporation pan.

The use of stable isotope techniques in egg authentication schemes: A review

The popularity of eggs is increasing worldwide, increased production is expected over the next few years, and it appears that protein production from eggs is more sustainable than other protein rich food production, such as beef. Recall of eggs has also occurred due to health scares. Hence, systems/tools are needed to ensure and guarantee egg traceability/authenticity. This review focuses on the current state of knowledge with regards to the use of stable isotope techniques for egg authentication schemes. A brief overview of egg production, usage, environmental benefits, traceability, and of alternative analytical methods for egg identification will also be provided.

Recent progress in stable isotope methods for assessing vitamin metabolism

Recent developments in mass spectrometric methodology, in particular the widespread adoption of liquid chromatography/mass spectrometry, have presented investigators with new opportunities to investigate micronutrient absorption and metabolism. This review focuses on recent reports of the use of stable isotope techniques to facilitate research into vitamin uptake and utilization in humans. Stable isotopes are used principally in two ways, as analytical standards in isotope dilution assays and as tracers in studies of physiology. There have been a number of advances in both fields recently for almost all of the vitamins. In particular, the effects of food preparation and meal composition on vitamin bioavailability are being probed more widely than before. A considerable amount of method development has been reported. We now have the opportunity to consolidate our understanding of vitamin metabolism to better inform the dietary recommendations for optimal health.

Pathway Proteomics and Chemical Proteomics Team Up in Drug Discovery

Over the last 5 years, impressive technical advances in mass spectrometry-based analysis of proteins have enabled the parallel analysis of subproteomes and entire proteomes, thus triggering the departure from the traditional single gene-single protein – single target paradigm. Today, immunoaffinity chromatography as well as generic purification methods employing engineered composite affinity tags make streamlined identification of protein complexes as molecular machines possible. In addition, use of stable isotope techniques in protein mass spectrometry allows for the characterization of protein complex composition and posttranslational modifications in an increasingly quantitative fashion. Together, these methodologies allow the elucidation of medically relevant biological pathways, and the study of the interaction of their protein components with therapeutic agents, on a much larger scale. The present review discusses some of the current experimental strategies, with a focus on applications in neurobiology.

Use of stable-isotope techniques to validate infant feeding practices reported by Bangladeshi women receiving breastfeeding counseling

Background:The World Health Organization recommends exclusive breastfeeding until age 6 mo. Studies relying on mothers’ self-reported behaviors have shown that lactation counseling increases both the rate and duration of exclusive breastfeeding.Objective:We aimed to validate reported infant feeding practices in rural Bangladesh; intakes of breast milk and nonbreast-milk water were measured by the dose-given-to-the mother deuterium dilution technique.Design:Subjects were drawn from the large-scale Maternal and Infant Nutrition Interventions, Matlab, study of combined interventions to improve maternal and infant health, in which women were randomly assigned to receive either exclusive breastfeeding counseling or standard health care messages. Data on infant feeding practices were collected by questionnaire at monthly visits. Intakes of breast milk and nonbreast-milk water were measured in a subsample of 98 mother-infant pairs (mean infant age: 14.3 wk) and compared with questionnaire data reporting feeding practices.Results:Seventy-five of the 98 subjects reported exclusive breastfeeding. Mean (±SD) breast milk intake was 884 ± 163 mL/d in that group and 791 ± 180 mL/d in the group reported as nonexclusively breastfed (P= 0.0267). Intakes of nonbreast-milk water were 40 ± 80.6 and 166 ± 214 mL/d (P< 0.0001), respectively. Objective cross-validation using deuterium dilution data showed good accuracy in reporting of feeding practices, although apparent misreporting was widely present in both groups.Conclusions:The dose-given-to-the-mother deuterium dilution technique can be applied to validate reported feeding behaviors. Whereas this technique shows that the reports of feeding practices were accurate at the group level, it is not adequate to distinguish between feeding practices in individual infants.

Stable isotopes in arid and semi-arid forest systems

The use of stable isotope techniques in forest ecology research has grown steadily over the last two decades. This trend will continue, as stable isotopes can serve as valuable integrators of how plants have interacted, today and in the past, with their physical environment or with other organisms. This is particularly relevant in dry areas due to the strong limitation of resources. After a brief introduction about the theoretical background of stable isotopes in plant physiology, this review highlights recent advances in forest ecology that have embraced this methodology, at different spatial and temporal scales, and with special emphasis on arid and semi-arid systems.

Trophic interactions of Antarctic seals as determined by stable isotope signatures

The diets and trophic interactions among Weddell, crabeater, Ross, and leopard seals in the eastern Ross Sea, Antarctica, were investigated by the use of stable isotope techniques during the 1999–2000 summer seasons. The δ13C and δ15N values in seal serum clearly distinguished the three Antarctic pack-ice seal species at different trophic positions (Weddell>Ross>crabeater). These patterns appeared to reflect a close linkage to their known foraging ecology and diving behaviors, and agreed well with their presumed dietary diversity. The more enriched δ13C and δ15N values in male Weddell seals than those in females suggested differences in foraging preferences between them. Significant differences in δ15N were also found among different age groups of Weddell seals. A strong correlation between the C:N ratios and serum cholesterol was probably due to extremely high cholesterol levels in phocids. Comparisons of isotope data with harbor seals revealed distinct differences between Antarctic phocids and the northern seal species.

Homocysteine metabolism in renal disease.

Hyperhomocysteinemia, a new cardiovascular risk factor, occurs in 85-100% of patients with end-stage renal disease. The exact mechanism by which renal function is linked to plasma homocysteine has not been definitively established. There is reasonably good clinical evidence that hyperhomocysteinemia in itself does not cause renal insufficiency. Two, not mutually exclusive, hypotheses are that in renal failure: i) homocysteine disposal is impaired in the kidneys themselves and ii) extra-renal homocysteine metabolism is defective, possibly due to uremic toxins. Several methods have been applied to investigate kidney and whole-body sulfur amino acid metabolism in healthy subjects and in patients with different degrees of renal failure. Arteriovenous extraction studies have not found a significant homocysteine disposal in the human kidney. Methods to study whole-body homocysteine metabolism have included measurement of plasma metabolites, calculation of plasma homocysteine elimination after oral loading and the use of stable isotope techniques with methionine tracers. The results implicate a decreased homocysteine clearance instead of an increased production as the cause of hyperhomocysteinemia in renal failure, but the exact site of the impaired clearance remains controversial.

Stable Isotopes in Plant Ecology

▪ Abstract The use of stable isotope techniques in plant ecological research has grown steadily during the past two decades. This trend will continue as investigators realize that stable isotopes can serve as valuable nonradioactive tracers and nondestructive integrators of how plants today and in the past have interacted with and responded to their abiotic and biotic environments. At the center of nearly all plant ecological research which has made use of stable isotope methods are the notions of interactions and the resources that mediate or influence them. Our review, therefore, highlights recent advances in plant ecology that have embraced these notions, particularly at different spatial and temporal scales. Specifically, we review how isotope measurements associated with the critical plant resources carbon, water, and nitrogen have helped deepen our understanding of plant-resource acquisition, plant interactions with other organisms, and the role of plants in ecosystem studies. Where possible we also introduce how stable isotope information has provided insights into plant ecological research being done in a paleontological context. Progress in our understanding of plants in natural environments has shown that the future of plant ecological research will continue to see some of its greatest advances when stable isotope methods are applied.

Stable isotope techniques in the study of biological processes and functioning of ecosystems. Unkovich M, Pate J, McNeill A, Gibbs DJ, eds. 2001.

Stable isotope techniques in the study of biological processes and functioning of ecosystems. Unkovich M, Pate J, McNeill A, Gibbs DJ, eds. 2001.

Variation in δ15N and δ13C trophic fractionation: Implications for aquatic food web studies

Use of stable isotope techniques to quantify food web relationships requires a priori estimates of the enrichment or depletion in δ15N and δ13C values between prey and predator (known as trophic fractionation; hereafter Δδ15N and Δδ13C). We conducted a broad‐scale analysis of Δδ15N and Δδ13C from aquatic systems, including three new field estimates. Carnivores had significantly higher Δδ15N values than herbivores. Furthermore, carnivores, invertebrates, and lab‐derived estimates were significantly more variable than their counterparts ( f‐test, p &lt; 0.00001). Δδ13C was higher for carnivores than for herbivores (p = 0.001), while variances did not differ significantly. Excluding herbivores, the average Δδ15N and Δδ13C were 3.4‰ and 0.8‰, respectively. But even with unbiased fractionation estimates, there is variation in isotopic fractionation that contributes to error in quantitative isotope model outputs. We simulated the error variance in δ15N‐based estimates of trophic position and two‐source δ13C diet mixing models, explicitly considering the observed variation in Δδ15N and Δδ13C, along with the other potential error sources. The resultant error in trophic position and mixing model outputs was generally minor, provided that primary consumers were used as baseline indicators for estimating trophic position and that end member d13C values in dietary mixing models were sufficiently distinct.

Stable isotope evidence for the food web consequences of species invasions in lakes

Species invasions pose a serious threat to biodiversity and native ecosystems1,2; however, predicting and quantifying the impacts of invasive species has proven problematic3,4,5,6. Here we use stable isotope ratios to document the food-web consequences of the invasion of two non-native predators, smallmouth bass and rock bass, into Canadian lakes. Invaded lakes had lower littoral prey-fish diversity and abundance than uninvaded reference lakes. Consistent with this difference, lake trout from invaded lakes had more negative δ13C values (-29.2‰ versus -27.4‰) and reduced trophic positions (3.3 versus 3.9) than those from reference lakes, indicating differences in food-web structure. Furthermore, a comparison of the pre- and post-invasion food webs of two recently invaded lakes showed that invasion was followed by substantial declines in littoral prey-fish abundance and the trophic position of lake trout, reflecting a shift in the diet of lake trout towards zooplankton and reduced dependence on littoral fish. This study demonstrates the use of stable isotope techniques to detect changes in food-web structure following perturbations; in this instance, bass-induced food-web shifts may have severe consequences for native species and ecosystems.

Assessing the performance of woody plants in uptake and utilisation of carbon, water and nutrients: Implications for designing agricultural mimic systems

This article introduces a series of innovative experimental approaches for monitoring current and past performances of woody plant species in utilisation of key resources within ecosystems. We demonstrate how such information might be useful for monitoring the progress of any novel agricultural system which attempts to mimic such natural systems. The experimental data presented principally involve the use of stable isotope techniques coupled to collection and analysis of substances transported in the sap of xylem and phloem. Study species examined are sugar maple (Acer saccharum), tagasaste (Chamaecytisus proliferus), blue gum (Eucalyptus globulus), and acorn banksia (Banksia prionotes). Topics covered include investigations of (a) seasonal changes in water source utilisation using hydrogen stable isotope analyses, (b) water loss from tree roots to the surrounding soil (termed hydraulic lift) using hydrogen stable isotope analyses, (c) relationships between carbon isotope discrimination of plant dry matter and whole-plant water-use efficiency, (d) phloem sap analysis as a means for assessing aspects of a plant's water and nutrient status, (e) carbon isotope ratios of foliage and annual growth rings as they relate to seasonal changes in carbon isotope ratios of phloem translocate, and (f) the composition of simultaneously collected samples of xylem and phloem sap as a means of monitoring current plant performance in uptake and mobilisation of key mineral resources. The chapter concludes with discussion of prospective uses of the above- mentioned techniques in study of managed ecosystems in which woody species play pivotal roles in maintenance of functional stability.

The use of stable isotope techniques for nutritional and metabolic research in paediatrics.

Stable isotope methods are increasingly used in paediatrics for clinical diagnosis and research due to marked improvements in analytical technologies and better availability of suitable tracers. The safety of stable isotopes is of major importance for use in children. Large amounts of deuterium well above the doses applied under clinical conditions may induce adverse effects. In contrast, heavier stable isotopes such as 13C, 15N or 18O do not induce adverse effects even at the highest enrichments obtained, and they are safe. Breath tests with measurements of 13CO2 enrichment after oral application of a tracer can reliably evaluate helicobacter pylori infection and gastric emptying kinetics. Combined with an estimation of total CO2 production, 13CO2 breath tests allow estimation of the absorption and oxidation of 13C-labelled substrates, such as medium- and long-chain triglycerides, and demonstrates the beneficial effect of carnitine supplements on fat oxidation in primary carnitine deficiency. The study of metabolic processes may require the sampling of blood for isotopic analyses of metabolites of the applied tracer. Gas chromatography-isotope ratio mass spectrometry can detect tracer in individual components from small plasma samples. The high precision enabled us to utilize the small differences in natural 13C-enrichment between dietary fats to study fatty acid turnover in term infants, in whom the dietary fat source was switched to corn oil with a slightly higher 13C-content. With this approach we demonstrated active conversion of linoleic into arachidonic acid. We also applied biotechnologically produced, U-13C labelled linoleic and alpha-linolenic acids to infants and detected the conversion of these essential fatty acids to their longer chain polyunsaturated derivatives, with an apparent change of conversion activity with age. Moreover, it has become possible to measure tissue protein synthesis from small biopsy samples obtained in situ without surgery, such as forceps biopsies of rectal tumors. These few examples of recent developments demonstrate the great clinical and scientific potential of stable isotope methods in future paediatric applications.

13C urea breath test

Helicobacter pylori is one of the most common causes of chronic bacterial infection in humans, and is associated with many diseases of the upper gastrointestinal tract. The prevalence of infection...