Search results for "carbon isotopes"
showing 10 items of 111 documents
Consistent isotopic differences between Schistocephalus spp. parasites and their stickleback hosts
2015
Published version available at http://dx.doi.org/10.3354/dao02893 Parasite−host systems show markedly variable patterns in isotopic fractionation: parasites can be either depleted or enriched in 15N and 13C as compared to their hosts. However, it remains unknown whether isotopic fractionation patterns are similar in comparable parasite−host systems from markedly different ecosystems. Results of this study show that large-sized Schistocephalus spp. endoparasites are consistently depleted in 15N (by on average −2.13 to −2.20‰) as compared to their nine-spined stickleback Pungitius pungitius and three-spined stickleback Gasterosteus aculeatus hosts. The differences between parasites and host f…
Past aquatic environments in the Levant inferred from stable isotope compositions of carbonate and phosphate in fish teeth
2019
Here we explore the carbon and oxygen isotope compositions of the co-existing carbonate and phosphate fractions of fish tooth enameloid as a tool to reconstruct past aquatic fish environments and harvesting grounds. The enameloid oxygen isotope compositions of the phosphate fraction (δ18OPO4) vary by as much as ~4‰ for migratory marine fish such as gilthead seabream (Sparus aurata), predominantly reflecting the different saline habitats it occupies during its life cycle. The offset in enameloid Δ18OCO3-PO4 values of modern marine Sparidae and freshwater Cyprinidae from the Southeast Mediterranean region vary between 8.1 and 11.0‰, similar to values reported for modern sharks. The mean δ13C …
Real-Time Nuclear Magnetic Resonance Detection of Fumarase Activity Using Parahydrogen-Hyperpolarized [1- 13 C]Fumarate
2019
Hyperpolarized fumarate can be used as a probe of real-time metabolism in vivo, using carbon-13 magnetic resonance imaging. Dissolution dynamic nuclear polarization is commonly used to produce hyperpolarized fumarate, but a cheaper and faster alternative is to produce hyperpolarized fumarate via PHIP (parahydrogen-induced polarization). In this work, we trans-hydrogenate [1-13C]acetylene dicarboxylate with para-enriched hydrogen using a commercially available Ru catalyst in water to produce hyperpolarized [1-13C]fumarate. We show that fumarate is produced in 89% yield, with succinate as a side product in 11% yield. The proton polarization is converted into 13C magnetization using a constant…
Continental weathering and climatic changes inferred from clay mineralogy and paired carbon isotopes across the early to middle Toarcian in the Paris…
2014
Abstract Lower Toarcian strata (Lower Jurassic) have been extensively studied with a view to understanding the oceanographic, climatic and biological processes that drove the Earth's system into an Oceanic Anoxic Event (OAE). For this time period, the evolution of the European marine seaways is now relatively well constrained owing to multiple geochemical studies, but investigations regarding climatic trends in the continental realm remain sparse. In the present study, we test the clay mineralogy as a continental climate-sensitive proxy in the well-documented Sancerre core (southern Paris Basin). We compare variations in the kaolinite content with p CO 2 fluctuations (derived from paired ca…
Suppression of intestinal microbiota-dependent production of pro-atherogenic trimethylamine N-oxide by shifting L-carnitine microbial degradation.
2014
Abstract Aims Trimethylamine-N-oxide (TMAO) is produced in host liver from trimethylamine (TMA). TMAO and TMA share common dietary quaternary amine precursors, carnitine and choline, which are metabolized by the intestinal microbiota. TMAO recently has been linked to the pathogenesis of atherosclerosis and severity of cardiovascular diseases. We examined the effects of anti-atherosclerotic compound meldonium, an aza-analogue of carnitine bioprecursor gamma-butyrobetaine (GBB), on the availability of TMA and TMAO. Main methods Wistar rats received L-carnitine, GBB or choline alone or in combination with meldonium. Plasma, urine and rat small intestine perfusate samples were assayed for L-car…
Regional variations in the chemical and helium–carbon isotope composition of geothermal fluids across Tunisia
2011
Abstract Tunisia has numerous thermo-mineral springs. Previous studies have shown that their chemical composition and occurrence are strongly influenced by the regional geology. However little work has been done so far to study the isotopic composition of volatiles associated with these geothermal manifestations. Here, we report on the results of an extensive survey of both natural hot springs and production wells across Tunisia, aimed at investigating the spatial distribution of thermal fluids' geochemical characteristics and He–C isotopic composition. The chemistry of the analyzed samples highlights the heterogeneity of the water mineralization processes in Tunisia, as a consequence of th…
A Neandertal dietary conundrum: Insights provided by tooth enamel Zn isotopes from Gabasa, Spain
2022
The characterization of Neandertals’ diets has mostly relied on nitrogen isotope analyses of bone and tooth collagen. However, few nitrogen isotope data have been recovered from bones or teeth from Iberia due to poor collagen preservation at Paleolithic sites in the region. Zinc isotopes have been shown to be a reliable method for reconstructing trophic levels in the absence of organic matter preservation. Here, we present the results of zinc (Zn), strontium (Sr), carbon (C), and oxygen (O) isotope and trace element ratio analysis measured in dental enamel on a Pleistocene food web in Gabasa, Spain, to characterize the diet and ecology of a Middle Paleolithic Neandertal individual. Based on…
Trophic Transfer of Trace Elements in an Isotopically Constructed Food Chain From a Semi-enclosed Marine Coastal Area (Stagnone di Marsala, Sicily, M…
2012
Trace element accumulation is particularly important in coastal and transitional environments, which act as contaminant buffers between the continental and marine systems. We compared trace element transfer to the biota in two locations with different open-sea exposures in a semi-enclosed marine coastal area (Stagnone di Marsala, Sicily, Italy) using isotopically reconstructed food chains. Samples of sediment, macroalgae, seagrasses, invertebrates, fish, and bird feathers were sampled in July 2006 and analysed for stable carbon and nitrogen isotopes (δ(13)C, δ(15)N) and trace elements (arsenic [As], cadmium [Cd], total mercury [THg], and lead [Pb]). Trophic magnification factors were calcul…
Transport and partitioning of 13C-photoassimilate between peach fruiting shoots
2008
We used a non-intrusive method (13CO2 feeding) and a manipulative approach to see whether fruiting shoots in peach trees are autonomous or may import carbon from neighboring shoots under forced conditions, and whether the degree of autonomy is influenced by the source-sink relationship on the shoot. In three experiments, leaf to fruit ratio (L:F) of selected fruiting shoots was moderately (2005 and 2006) or strongly (extreme enforcing 2006) altered to either encourage or discourage movement of carbon from 13C-labeled sending shoots (SFS) to receiving fruiting shoots (RFS), both located on the same main scaffold of V-shaped peach trees. At stage I and III of fruit growth, fruit and shoot tip…
EFFECTS OF SENSITIZED AND UNSENSITIZED LONGWAVE U.V.-IRRADIATION ON THE SOLUTION PROPERTIES OF DNA
1971
— Two types of photoreactions occur in DNA irradiated in aqueous systems with longwave u.v.-light (Λ > 295 nm), namely, (a) thymine dimerization, and (b) single- and double-strand breakage of the sugar phosphate backbone; these two reactions are unrelated. The presence of acetophenone as a photosensitizer caused an increase in dimerization by a factor of 16, and an increase in single-strand breaks by a factor of 4. The number of thymine dimers per single-strand break is about 100 in the sensitized and 25 in the unsensitized reaction. The alteration of the radius of gyration of DNA molecules is that expected by the degradation observed. At the same time the change in hyperchromicity is very …