Albumin and fibrinogen kinetics in sepsis: a prospective observational study

Background The measurement of circulating substrate concentrations does not provide information about substrate kinetics. It, therefore, remains unclear if a decrease in plasma concentration of albumin, as seen during critical illness, is a consequence of suppressed production in the liver or increased peripheral clearance. In this study, using stable isotope tracer infusions, we measured albumin and fibrinogen kinetics in septic patients and in a control group of non-septic subjects. Methods With the approval from the institutional Research Ethics Board and after obtaining written informed consent from patients or their substitute decision maker, mechanically ventilated patients with sepsis and patients scheduled for elective coronary artery bypass grafting were enrolled. Patients in the non-sepsis group were studied on the day before surgery. The stable isotope L-[ring-2H5]phenylalanine was used to measure absolute synthesis rates (ASR) of albumin and fibrinogen. A priming dose of L-[ring-2H5]phenylalanine (4 µmol/kg) was given followed by a six-hour infusion at a rate of 0.15 µmol/kg/min. At baseline and hourly thereafter, blood was drawn to measure isotope enrichments by gas chromatography/mass spectrometry. Very low density lipoprotein apolipoprotein-B 100 isotopic enrichment was used to represent the isotopic enrichment of the phenylalanine precursor pool from which the liver synthesizes proteins. Plasma albumin and fibrinogen concentrations were also measured. Results Mean plasma albumin in septic patients was decreased when compared to non-septic patients, while synthesis rates were comparable. Mean plasma fibrinogen and ASR in septic patients was increased when compared to non-septic patients. In non-septic patients, no statistically significant correlation between plasma albumin and ASR was observed but plasma fibrinogen significantly correlated with ASR. In septic patients, plasma albumin and fibrinogen significantly correlated with ASR. Conclusions While septic patients showed lower plasma albumin levels than non-septic patients, albumin synthesis was similar in the two groups suggesting that hypoalbuminemia during sepsis was not caused by suppressed hepatic production but a result of enhanced clearance from the circulation. Hyperfibrinogenemia in septic patients was a consequence of increased fibrinogen production. Trial registration: ClinicalTrials.gov: NCT02865408 (registered on August 12, 2016) and ClinicalTrials.gov: NCT02549443 (registered on September 15, 2015).

Light contamination in stable isotope-labelled internal peptide standards is frequent and a potential source of false discovery and quantitation error in proteomics

In mass spectrometry-based proteomics, heavy internal standards are used to validate target peptide detections and to calibrate peptide quantification. Here we report light contamination present in heavy labelled synthetic peptides of high isotopic enrichment. Application of such peptides as assay-internal standards potentially compromises the detection and quantification especially of low abundant cellular peptides. Therefore, it is important to adopt guidelines to prevent false-positive identifications of endogenous light peptides as well as errors in their quantification from biological samples.

Structural Characterization of Iron Oxide Grown On 18% Ni-Co-Mo-Ti Ferrous Base Alloy Aged Under Superheated Steam Atmosphere

18% Ni-Co-Mo-Ti Ferrous base alloys are special materials, widely used in the industry of ​​isotopic enrichment after specific annealing and aging thermal treatment. The desirable high mechanical properties can then be attained by adequate aging heat treatment, answering the structural materials specifications required by defense applications in aerospace and nuclear engineering. For instance, the isotopic enrichment, in rocket engine envelope application, when associated with high temperature and chemical residues like acidic solutions, can induce corrosion and hydrogen embrittlement in martensite structures. To limit these corrosion and hydrogen embrittlement phenomena, an adherent and protective layer of iron oxides can be grown on the material surface by using adequate atmosphere during the aging treatment. Due to its application in strategic areas, the characterization of these oxide layers in maraging steels is of importance as well as the understanding of their growth kinetics. For this purpose, several techniques, such as Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Glow Discharge Optical Emission Spectroscopy (GDOES), Microabrasive wear testing, Hardness, Grazing Incidence X-ray Diffraction (GIXRD) and X-ray Photoelectron Spectroscopy (XPS), have been performed for chemical and structural characterization of the oxide films formed after vapor exposed thermal aging at 510°C . The oxide layer consists mostly in two sub-layers composed by magnetite (Fe3O4) and an external layer of hematite (Fe2O3). A thick interface between the oxide layer and the bulk is enriched in Ti and Mo, whereas the analyses of deep bulk material show an enriched area with Ni and Co.

Synthesis of Stable Isotope Labeled D5-Cyhalothrin, D5-Fenpropathrin and D5-Fenvalerate from Deuterium Phenol

: A convenient synthetic route of deuterium-labeled D5-cyhalothrin, D5-fenpropathrin, and D5-fenvalerate is described with 98.7%, 98.5%, and 98.3% isotopic enrichment and high chemical purities using D6-phenol as labeled starting material. These structures and isotope-abundance were confirmed by 1H NMR and mass spectrometry. The prepared D5-cyhalothrin, D5-fenpropathrin, and D5-fenvalerate can be used as an internal standard reagent for the determination of residual pyrethroids of food and environment.

Syntheses and characterization of N,N-dialkyl- carbamic acids suitable for the isotopic enrichment of 13CO2

We describe the direct syntheses of N,N–diethylcarbamic acid (DECA) and of N,N-dibutylcarbamic acid (DBCA), from CO2 and the corresponding secondary amines. After isolation in crystalline form (no previous reports were found on separated and pure DECA and DBCA), the obtained dialkylcarbamic acids were characterized by spectral methods (FT- IR and NMR). Formation and decomposition reactions of these carbamic acids may play potential role in the 13CO2 – 12CO2 isotopic enrichment and by this, in decreasing the greenhouse effect of the flue gases via absorbing CO2 in secondary amines applying mild, green technologies.

Statistical evaluation of the correlation pattern between rising global temperature and stable water isotopes in precipitation.

<p>Statistical evaluation of the correlation pattern between rising global temperature and stable water isotopes in precipitation.</p><p>Lukas Ditzel, Jonas Schramm, Matthias Gassmann</p><p>Department of Hydrology and Substance Balance, University of Kassel, Kurt-Wolters-Strasse 3, 34125 Kassel, Germany</p><p> </p><p>Stable water isotopes in precipitation on the northern hemisphere are usually following a predictable pattern throughout the year, with high amounts in summer and low amounts of deuterium and <sup>18</sup>O in the winter season. Backed by a richness of available date from the International Atomic Energy Agency (IAEA), one can mostly expect an annual sinusoidal form of isotope data, when looking at data for a certain region in the northern hemisphere.</p><p>Since the driving factor for isotopic enrichment or depletion is isotopic fractionation, the seasonal behavior is strongly correlated to air-temperature. The correlation between temperature and fractionation is strong enough to explain most of the greater deviations from the sinusoidal form like in arid regions. It occurs that globally rising temperatures, initiated by climate change, should have an impact on the sinusoidal form of the stable water isotope time series. We assumed, that rising temperatures will lead to higher contents of deuterium and <sup>18</sup>O in the precipitation of the northern hemisphere. Due to the availability of data and the long time series, which are needed for robust answers, we focused our work on European and North-American data. First analyses showed a positive correlation between rising air-temperatures and isotopic content, but not all regions. Other effects like the elevation- and continental-effect were dampening the effect of rising global temperatures, especially in coastal regions or islands such as Ireland. More continental regions, however, are showing a rise for isotopic enrichment in precipitation. We analyzed this trend by the calculation of the trend-components of these time-series via Loess and validated them by using the Mann-Kendall-Test. Furthermore, we separated sets of data into monthly clusters and looked for rising temperature trends in every month over the size of the available time series. This second analysis was performed for the time series from weather stations in Berlin, Vienna and Krakow covering almost 40 years of monthly isotope data.</p>

Gut bacteria are essential for normal cuticle development in herbivorous turtle ants

Across the evolutionary history of insects, the shift from nitrogen-rich carnivore/omnivore diets to nitrogen-poor herbivorous diets was made possible through symbiosis with microbes. The herbivorous turtle ants Cephalotes possess a conserved gut microbiome which enriches the nutrient composition by recycling nitrogen-rich metabolic waste to increase the production of amino acids. This enrichment is assumed to benefit the host, but we do not know to what extent. To gain insights into nitrogen assimilation in the ant cuticle we use gut bacterial manipulation, 15N isotopic enrichment, isotope-ratio mass spectrometry, and 15N nuclear magnetic resonance spectroscopy to demonstrate that gut bacteria contribute to the formation of proteins, catecholamine cross-linkers, and chitin in the cuticle. This study identifies the cuticular components which are nitrogen-enriched by gut bacteria, highlighting the role of symbionts in insect evolution, and provides a framework for understanding the nitrogen flow from nutrients through bacteria into the insect cuticle.