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Methods in molecular exercise physiology
Published in Adam P. Sharples, James P. Morton, Henning Wackerhage, Molecular Exercise Physiology, 2022
Adam P. Sharples, Daniel C. Turner, Stephen Roth, Robert A. Seaborne, Brendan Egan, Mark Viggars, Jonathan C. Jarvis, Daniel J. Owens, Jatin G. Burniston, Piotr P. Gorski, Claire E. Stewart
Mass spectrometry is used to identify proteins by comparing the accurately measured masses of their peptides and peptide fragments against protein and gene databases. Each protein has a unique linear sequence of amino acids that is created during ribosomal translation based on instructions from mRNA. Likewise, each amino acid has a characteristic elemental composition (e.g. carbon, hydrogen and nitrogen) and therefore a predictable mass. The preparation of samples for mass spectrometry also involves the digestion of proteins into peptides using proteases that have a specific cleavage specificity, which imparts fixed information onto the samples. For example, peptides generated by trypsin digestion have either a lysine (K) or arginine (R) residue at their C terminus. When measured at a sufficient level of accuracy, the peptide mass along with the masses of the fragments from that peptide are sufficient to unambiguously identify the peptide and therefore the parent protein (Figure 2.11). The intensity of peptide and fragment ion peaks can also be used to infer the relative abundance of proteins amongst different samples, and if deuterium oxide (D2O or ‘heavy water’) was provided during the experiment (64), the peptide mass spectra can be used to calculate the synthesis rate of each protein.
The Poisoned Chalice
Published in Alan Perkins, Life and Death Rays, 2021
In February 1990 routine health monitoring of staff working at the Point Lepreau Nuclear Generating Station in New Brunswick on the east coast of Canada showed elevated levels of radioactivity in urine samples. A disgruntled 33-year-old assistant plant operator Daniel George Maston, who worked at the power plant, took a sample of heavy water from the boron reactor moderator system and poured it into the chilled 5 gallon water dispenser in the staff dining area. Heavy water which is also known as deuterium oxide is not radioactive itself, but it is used to cool the reactor and becomes radioactive as it circulates through the reactor core. Eight employees drank the contaminated water. One individual who was working in a high-temperature area was carrying out stress work, requiring alternating periods of work, rest and rehydration. He consumed significantly more water than the other employees. The incident was discovered when the urine samples from the staff showed elevated urinary levels of tritium, a radioactive form of hydrogen (hydrogen-3). Maston was arrested and during a short court hearing witnesses described him as a ‘quiet guy’. A number of workers at the plant thought that this was intended as a bad practical joke rather than a malicious act. The long-term health consequences on the affected staff were considered to be negligible.
Gastrointestinal Tract
Published in Charles Paul Lambert, Physiology and Nutrition for Amateur Wrestling, 2020
Water and electrolytes pretty much pass through the stomach to the small intestine without being absorbed, and once in the small intestine, the absorption of these vital nutrients begins in the duodenum and the jejunum. Interestingly, Jeukendrup et al. (2009) found that the addition of glucose to water at a concentration of 3% was more effective than water alone with regard to the appearance of the solution in the circulation after ingestion. This was the case as the appearance of deuterium oxide added to a solution after ingestion is indicative of both gastric emptying and intestinal absorption. The addition of glucose at a concentration of 6% and 9% resulted in slower appearance in the circulation than that of the 3% concentration of glucose. The authors eluded to data which suggest that the glucose is essential for glucose and sodium cotransport and the osmosis of water after the cotransport of glucose and sodium. Thus, the addition to of glucose to plain water at a low concentration is an important consideration for maximizing fluid delivery to the circulation.
Older Adult Cancer Patients Under Palliative Care With a Prognosis of 30 Days or More: Clinical and Nutritional Changes
Published in Journal of the American College of Nutrition, 2021
Josiane C. Vettori, Luanda G. da Silva, Karina Pfrimer, Alceu A. Jordão Junior, Júlio C. Moriguti, Eduardo Ferriolli, Nereida K. C. Lima
Body composition was evaluated by the deuterium oxide method, which has as its principle the dilution of this isotope in the body’s water compartment, that is, labeled water is diluted in total body water, providing the determination of its volume by dilution equations, since the amount of deuterium ingested is known. Thus, deuterium oxide dilution is highly accurate and accurate and is considered the gold standard for determining total body water (17). From the determination of this content, one can estimate the amount of fat free mass and fat mass (18, 19). To this end, the volunteers were asked to fast for a period of 8 hours (overnight). In the morning, each volunteer received 1 ml/kg of deuterium oxide (99.9% deuterium oxide, Cambridge Isotope, USA) diluted to 7%, followed by 50 ml of natural water for complete deuterium ingestion and washing of mouth. Saliva samples were taken before ingestion of the dose and 3 hours after ingestion. Samples were stored at 10 °C until analysis. Deuterium enrichment of saliva samples was determined by isotropic ratio mass spectrometry (Europa Scientific Hydra System, Cheshire, UK) after equilibration with 100% hydrogen by the aluminum platinum catalyst method. Body composition was determined according to the protocol of Schoeller et al. (20).
Glucosinolate-Enriched Fractions from Maca (Lepidium meyenii) Exert Myrosinase-Dependent Cytotoxic Effects against HepG2/C3A and HT29 Tumor Cell Lines
Published in Nutrition and Cancer, 2022
Raquely M. Lenzi, Luciano H. Campestrini, Simone C. Semprebon, Jonas A.R. Paschoal, Monique A.G. Silva, Selma F. Zawadzki-Baggio, Mário S. Mantovani, Carmen L.O. Petkowicz, Juliana B.B. Maurer
For NMR experiments, the samples (1‒5 mg) were dissolved in deuterium oxide (D2O). 13C-NMR and heteronuclear single quantum coherence (HSQC) were obtained using Bruker equipment (model DRX 400, Avance series; Bruker, Karlsruhe, Germany) at 30 °C with TMSP-d4 as the internal standard (δ = 0).
The application of proteomics in muscle exercise physiology
Published in Expert Review of Proteomics, 2020
Stuart J Hesketh, Ben N Stansfield, Connor A Stead, Jatin G Burniston
Proteomic studies have been conducted in free-living animals by supplementing their diet with stable isotope-labeled amino acids such as deuterated valine [44] or leucine [47]. However, the palatability of synthetic diets can be low and may require lengthy periods of transition from the animals’ standard chow before experimental interventions can take place. Deuterium oxide (2H2O; ‘heavy water’), on the other hand, is a stable isotope that can be used for biosynthetic labeling experiments in vivo that is not associated with changes to the feeding or drinking habits of animals [48]. Deuterium oxide also obviates the requirement for intravenous infusion in humans and so lessens the burden on participants and enables studies to be conducted under free-living conditions over short (hours – days) or longer (weeks – months – years) time periods. Labeling of the precursor pool occurs intracellularly meaning experiments that use 2H2O are also less influenced by the metabolism or transport rates of amino acids amongst different tissues [49]. Deuterium becomes incorporated in to almost all amino acids in vivo and, therefore, gives a proportionally greater signal than methods that rely on labeling of a single amino acid. Metabolic labeling of proteins with deuterium results in a shift in the mass isotopomer pattern of peptides analyzed by mass spectrometry [50], which can be used to calculate the fraction of newly synthesized protein on a protein-by-protein basis. The first analyses of deuterium-labeled samples that used peptide mass spectrometry [51,52] investigated albumin synthesis in blood samples from laboratory rodents. In Hesketh et al. [53], we built from these studies and incorporated 2D gel electrophoresis separation of muscle to investigate 8 proteins in the heart, diaphragm and fast- and slow-twitch muscles of rat using peptide mass spectrometry. The FSR of individual proteins ranked differently between different muscles [53], which warns against the extrapolation of findings across muscles that have different functions. Indeed, follow-up analysis of protein-specific FSR in fast- versus slow-twitch rat muscles [54] found the long-established paradigm that protein turnover is greater in slow- compared to fast-twitch muscle does not hold true when data are reported at the individual protein level.