A simple prediction of total body water to aid quality control in isotope dilution studies in subjects 3-87 years of age

The principal method of measuring total body water (TBW) is by isotope dilution. Also, the doubly labelled water method, which is the method of choice for measuring total energy expenditure (TEE) in free-living individuals, includes calculation of TBW as the dilution space of the tracer. TBW was measured in 261 subjects (135 males and 126 females), aged 3-87, including healthy children, children with HIV and adults with non-insulin dependent diabetes mellitus (type 2 diabetes), mild hypertension, pancreatic cancer and lung cancer, either in studies of body composition or TEE. A linear relationship was found between TBW and height in all subjects. When TBW is plotted against height cubed (Ht3, m3) the regression line can be forced through the origin. Considering only adults with 18.5>body mass index <29.9 and all children (n=220), this yielded TBW (l)=7.40 x Ht3, R2=0.95. This simple linear relationship between measured TBW and Ht3 compared favourably with other prediction methods, assuming TBW is a constant proportion (55%) of body weight and TBW predicted from height and weight (mean difference between measured and predicted TBW 0.55 l compared with -1.95 and -1.20 l, respectively). Absolute errors were greater at higher TBW, but use of a log10 transformation reduced this effect. This simple relationship of TBW with Ht3 is too crude to be used as a body composition predictor in individual subjects as it ignores, for instance, body shape. However, it can be used as a quality control tool. Here, use of a log10 transformation and residual plot can serve to identify outliers, which can be checked for gross errors in data input and if necessary samples are re-analysed.     

Assessment of the amount of body water in the Red Knot (Calidris canutus): an evaluation of the principle of isotope dilution with 2H, (17)O, and (18)O as measured with laser spectrometry and isotope ratio mass spectrometry

We have used the isotope dilution technique to study changes in the body composition of a migratory shorebird species (Red Knot, Calidris canutus) through an assessment of the amount of body water in it. Birds were quantitatively injected with a dose of water with elevated concentrations of 2H, (17)O, and (18)O. Thereafter, blood samples were taken and distilled. The resulting water samples were analysed using an isotope ratio mass spectrometry (for 2H and (18)O only) and a stable isotope ratio infrared laser spectrometry (2H, (17)O, and (18)O) to yield estimates of the amount of body water in the birds, which in turn could be correlated to the amount of body fat. Here, we validate laser spectrometry against mass spectrometry and show that all three isotopes may be used for body water determinations. This opens the way to the extension of the doubly labelled water method, used for the determination of energy expenditure, to a triply labelled water method, incorporating an evaporative water loss correction on a subject-by-subject basis or, alternatively, the reduction of the analytical errors by statistically combining the (17)O and (18)O measurements.     

The role of technology in the past and future development of the doubly labelled water method

The doubly labelled water method is an isotope-based technique that is used to measure the energy demands of free-living animals and humans. It is based on the observation that, in the body, the oxygen in carbon dioxide is in complete isotope exchange equilibrium with the oxygen in body water. Hence, a label of isotopic oxygen in body water is eliminated by both respiratory CO(2) and water turnover, whereas a similarly introduced label of deuterium is eliminated only by water flux. The difference in isotope fluxes therefore permits estimation of CO(2) production, which is correlated to energy demands. The doubly labelled water method has been advanced predominantly by technological advances in mass spectrometry. Although it was first described in the 1950s, it was only used on small animals and in low numbers because the costs of the isotopes were a primary constraint. However, advances in mass spectrometry precision and accuracy in the 1980s made it possible to reduce the quantities of isotope used, and hence apply the method on humans, although still in small numbers. The advent of continuous flow inlets in the 1990s made possible the processing of samples in much larger numbers and the sample sizes of studies have expanded. Ironically, however, the technique is now under treat because of technological advances in another area (positron emission tomography), which has generated an enormous demand for (18)O and pushed up the price of isotopes. A continuation of this trend might drive prices to levels where sustained application of the method in human studies is questionable. Replacing determination of isotope enrichments currently performed by isotope ratio mass spectrometry with determinations made by stable isotope infrared laser spectrometry may be a technological advance that will get us out of this problem.     

NMR, EPR, and mass spectroscopy estimates of the antiradical activity of water with modified isotope composition

The dynamics of the change in the deuterium content in plasma of laboratory animal blood is studied by nuclear magnetic resonance spectroscope using water with modified isotope composition. The change in deuterium content in lyophilized animal tissues is determined by mass spectrometry. The content of paramagnetic centers in a dose and in pathology is determined on an electron paramagnetic resonance spectrometer.     

Body Water,Lean Body and Fat Mass of Healthy Children as Measured by Deuterium Oxide Dilution

Abstract

Body composition of 165 healthy children was measured using the well-established method of deuterium oxide (²H₂O) dilution. After distribution of an oral load of 2.0 ml ²H₂O/kg body weight body water was estimated from the ²H₂O concentration in urine. Lean body mass was then calculated from body water using previously published age dependent ratios of the water content of the lean body mass. Fat mass was calculated as the difference of body weight and lean body mass. A good correlation was found between body water and body weight. Linear regression revealed TBW = 0.589 BW + 0.728 (r = 0.99). Body water, lean body mass and fat mass were found to change with age. The fat content of the body increases during the first six months of life. It then decreases until four to five years then rising again until 15 years of age.     

Changes in isotopic composition of metals enriched in hydrogen

We have studied changes in the isotopic composition of niobium and palladium as well as of titanium film structures over ceramics enriched in deuterium. We have also investigated changes in the isotopic composition of copper under thermally activated copper diffusion into nickel. An intense isotope exchange between the atoms of the matrices and impurities enriched in deuterium and changes in the isotopic composition of copper during diffusion into nickel were observed. The relationships seen in the experiments lead us to suggest that the changes in the isotope ratio may be caused (along with plausible nuclear transformations) by a strong isotopic effect involved in cold diffusion induced by hydrogen migration. Institute of Strength Physics and Materials Science of the SB RAS. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 61–65, April, 1999.     

Deuterium transport and isotope effects in type 316L stainless steel at high temperatures for nuclear fusion and nuclear hydrogen technology applications

We present the first complete data set for the permeability, diffusivity, and solubility of both deuterium and hydrogen in 316L stainless steel (316L SS) obtained over a wide temperature range of 350–850 °C that accommodates both nuclear fusion and nuclear hydrogen technology applications. The deuterium results were also compared with the hydrogen results to estimate the isotope effect. The isotope effect ratio for diffusivity was different from the classical prediction. Furthermore, some of our results were compared with the results previously reported for 316 SS. Results and discussion are presented with an emphasis on the deuterium permeation and isotope effects.     

Synthesis of deuterium-labelled fluorobenzoic acids to be used as internal standards in isotope dilution mass spectrometry

A method for the deuterium labelling of fluorobenzoic acids (FBAs) via acidic H/D exchange of the aromatic hydrogen atoms in concentrated D₂SO₄ is described. The synthesis is shown to be easy, fast, low-priced and without the use of catalysts or further purification. The use of at least double-deuterated FBAs as internal standards in organic isotope dilution mass spectrometry allows the determination of FBAs in complex matrices with highest possible accuracy in combination with a simplified analytical evaluation.     

[15N]Methacetin-und [15N]Ammoniumtest zur Leberfunktionsprüfung im Kindesalter

The stable isotope content of samples of precipitation and of the river water throughout the Piracicaba basin in Brazil was measured over a two-year period. The isotope values of precipitation follow a consistent pattern of relatively depleted values of both deuterium and oxygen 18 during the rainy summers and enriched ones during the dry winters, with all values aligned slightly above the Global Meteoric Water Line. The isotopic composition of the river water throughout the basin shows a remarkable spatial coherence and much smaller scatter of data than those of the precipitation. The isotope composition of river water is close to that of the precipitation in the rainy season, however, with a consistent lower d-excess value by 1‰–2‰. This is attributed to evaporative water loss in the basin, in part an expression of the recycling of water due to the anthropogenic activity in the region. The more divergent values are recorded during high-water stages in the rivers. In many cases, the floods during the beginning of the rainy season are characterized by an enrichment of the heavy isotopes and lower d-excess values when compared to the precipitation, with the opposite situation later in the rainy season. This is interpreted as resulting from the watershed/riverflow interaction pattern, and it thus suggests that the isotope composition can monitor the hydrologic situation in the basin and its changes.     

The Piracicaba River basin: isotope hydrology of a tropical river basin under anthropogenic stress

The stable isotope content of samples of precipitation and of the river water throughout the Piracicaba basin in Brazil was measured over a two-year period. The isotope values of precipitation follow a consistent pattern of relatively depleted values of both deuterium and oxygen 18 during the rainy summers and enriched ones during the dry winters, with all values aligned slightly above the Global Meteoric Water Line. The isotopic composition of the river water throughout the basin shows a remarkable spatial coherence and much smaller scatter of data than those of the precipitation. The isotope composition of river water is close to that of the precipitation in the rainy season, however, with a consistent lower d-excess value by 1/1000-2/1000. This is attributed to evaporative water loss in the basin, in part an expression of the recycling of water due to the anthropogenic activity in the region. The more divergent values are recorded during high-water stages in the rivers. In many cases, the floods during the beginning of the rainy season are characterized by an enrichment of the heavy isotopes and lower d-excess values when compared to the precipitation, with the opposite situation later in the rainy season. This is interpreted as resulting from the watershed/riverflow interaction pattern, and it thus suggests that the isotope composition can monitor the hydrologic situation in the basin and its changes.     

Application of the Nuclear Reaction Analysis Online Technique to Study the Diffusion of Deuterium in Metals

Nuclear reaction analysis online technique has been applied to study the diffusion of deuterium in metals. Investigations ensuring the application of the new method have been performed. These investigations include the development of a device for diffusion annealing of samples in the chamber of an accelerator and an algorithm for taking into account the effect of radiation defects on the diffusion coefficients. Test measurements of the diffusion coefficients of deuterium in nickel in the temperature range from 130 to–60°С have been performed. For negative temperatures, experimental data on the diffusion of a hydrogen isotope in a metal have been obtained for the first time by a direct method and it has been shown that the online nuclear reaction analysis provides reliable data.     

Administering labelled water to exclusively breast-fed infants in studies involving stable isotope dilution techniques

Stable isotope techniques using deuterium or (18)O are reference methods for assessing total body water (TBW) for body composition. In combination, they provide total energy expenditure and human milk intake in exclusively breast-fed (EBF) infants. These techniques require an oral administration of an accurately quantified dose of labelled water to infants, who often have no prior experience of consuming water. In the present study, (18)O labelled water was administered to 47 EBF infants at two time points. Route of administration, duration of dosing and spills were quantified and recorded. Eighty-seven out of 94 (92.6%) dose administrations were successful. In two-thirds of dose administrations, >90% of the prepared dose was consumed. Spills ranged from 0.2% to 57%. Approaches to correct for spills can introduce bias in the calculation of TBW. Minimising and recording all dose spills is an important issue for the accuracy and precision of stable isotope techniques, when applied to EBF infants.     

Comment on ‘activated chemisorption of methane and tunneling: A second look’ by T.C. Lo and G. Ehrlich

We have previously reanalyzed the data of Lo and Ehrlich on the activated chemisorption of CH₄ and CD₄ on W(211) in terms of a tunneling model. In the Letter cited above, Lo and Ehrlich criticize the tunneling model due to an insensitivity of the model with respect to the mass of the heavier isotope. In this Comment we show why the mass insensitivity is a natural consequence of the smaller tunneling probability for the deuterium isotope, and not a breakdown in the model.     

Fractionation of Oxygen and Hydrogen Isotopes at the Hydrate Gas forming in the Sea Sediments

The paper gives data on isotope composition of interstitial and near-bottom waters sampled in a region of gas-hydrate formation in the Sea of Okhotsk. The studies shows that heavy isotope of oxygen and hydrogen is used in gas-hydrate formation, with the result that isotope composition of its constitution water constitutes δ¹⁸O = +1.99‰, δD = +23‰ relatively to SMOW. Formation of autogenic carbonates leads to isotope exchange with interstitial water wich, in turn, changes its primary isotope composition in the direction of increasing of O-18 content. The near-bottom waters are isotope-light relatively to the SMOW standard and to the mean isotope composition of interstitial water in the studied region of gas-hydrate spreading.     

Isotopic composition of atmospheric moisture from pan water evaporation measurements

A continuous and reliable time series data of the stable isotopic composition of atmospheric moisture is an important requirement for the wider applicability of isotope mass balance methods in atmospheric and water balance studies. This requires routine sampling of atmospheric moisture by an appropriate technique and analysis of moisture for its isotopic composition. We have, therefore, used a much simpler method based on an isotope mass balance approach to derive the isotopic composition of atmospheric moisture using a class-A drying evaporation pan. We have carried out the study by collecting water samples from a class-A drying evaporation pan and also by collecting atmospheric moisture using the cryogenic trap method at the National Institute of Hydrology, Roorkee, India, during a pre-monsoon period. We compared the isotopic composition of atmospheric moisture obtained by using the class-A drying evaporation pan method with the cryogenic trap method. The results obtained from the evaporation pan water compare well with the cryogenic based method. Thus, the study establishes a cost-effective means of maintaining time series data of the isotopic composition of atmospheric moisture at meteorological observatories. The conclusions drawn in the present study are based on experiments conducted at Roorkee, India, and may be examined at other regions for its general applicability.     

Low-temperature plasticity of pure parahydrogen

Stress-strain curves of single crystals of pure (99.9999 mol%) parahydrogen (p-H₂) were measured in the temperature range 1.8–4.2 K under conditions of stepped uniaxial stretching. The parahydrogen under study has a significantly decreased deuterium (stable isotope) content ([D]/[H] ～ 0.005–0.006 at %) as compared to the natural isotope composition. The deuterium content was decreased using for the first time a method in which parahydrogen was crystallized and then melted and the vapor thus obtained was distilled. It was revealed that the yield stress of the single crystals decreases anomalously as the temperature is decreased. The anomalous behavior indicates a coherent band motion of defects (most likely, dislocation kinks) resulting in low-temperature plasticity of the pure p-H₂ studied.     

Condensed Phase Isotope Effects

It is well known that the condensed phase physical properties of molecular isotopic isomers are not the same. These differences in the vapor pressure, molar volume, surface tension, etc., are purely quantal phenomena. The effects are most exterme for isotopic substitution at hydrogen isotopes. Of the various physical properties which have been investigated the isotope effect on vapour pressure (VPIE) shows the largest ralative effects. In face, for hydrogen-deuterium substitution they range all the way from about inverse 2% per deuterium atom for nonpolar hydrocarbons (by inverse we mean that the molecule substituted with the heavier isotope has the higher vapor pressure) to as much as 20% normal (P_H > P_D ) per deuterium atom for molecules which are strongle associated in the condensed phase. Such effects are about one order of magnitude larger than isotope effects which are observed in most systems on molar volumes, surface tension, etc. (Thus, for example, benxene at 20°C shows a rather small VPIE of 0.4% per atom D 3 but the molar volume effect is only 0.05% per D and the surface tension effect 0.03% [4].) This it would appear is the reason a majority of recent studies have been directed toward the VPIE. The emphasis in this paper reflects that trend and the balance of the discussion will deal almost exclusively with the vapor pressure isotope effect.     

Large deuterium isotope effects and their use: a historical review

Isotope effects are differences in the properties of the isotopes of an element resulting in different reaction rates of a corresponding compound, in equilibrium constants and in the spectra. Shortly after the discovery of stable isotopes of hydrogen, oxygen, and carbon, Jacob Bigeleisen formulated a theory of isotope effects and calculated possible maximum values. Large isotope effects of (2)H (deuterium) against (1)H (protium) were seen to possibly influence interpretations of reaction mechanisms if corresponding labelling is used. Much work was invested to ensure the safety of deuterium use in men in spite of the large isotope effect. On the other hand, large deuterium isotope effects gave rise to several practical applications. Examples are the enhancement of the stability of some technical products against oxidative and against hydrolytic degradation (oils, pharmaceuticals) as well as alterations of the detoxification metabolism of pharmaceuticals in vivo.     

Interactions between hydrogen isotopes and carbon monoxide on rhenium

The rate of absorption by a clean rhenium filament of carbon monoxide and deuterium from a mixture of the two gases was little different in the early stages from that of the two gases individually. However, continued exposure of the deuterium-covered filament to carbon monoxide led to ready replacement, the sticking probability of carbon monoxide being about 80% of its value on a clean filament. A similar experiment with a hydrogen deuteride-covered filament led to a gas phase hydrogen isotope composition consistent with dissociative adsorption of hydrogen deuteride.     

Stable isotope composition of the meteoric precipitation in Croatia

The precipitation is the input into the water system. Its stable isotope composition has to be known for the proper use and management of water resources. Croatia is not well represented in the Global Network of Isotopes in Precipitation (GNIP) database, and the geomorphology of the country causes specific local conditions. Therefore, at the Stable Isotope Laboratory (SILab), Rijeka, we monitor the stable isotope composition (δ¹⁸O, δ²H) of precipitation. Since δ¹⁸O and δ²H are well correlated, we concentrate the discussion on the δ¹⁸O distribution. Together with GNIP, our database contains 40 stations in Croatia and in the neighbouring countries. Their different latitudes, longitudes and altitudes give information of great detail, including the influence of the topographic structure on the precipitation in the south-eastern part of Europe, as well as the complex interplay of the different climate conditions in the area. Within a few hundred kilometres, the stable isotope values display a significant change from the maritime character in the south (mean δ¹⁸O around?6 to?8%‰) to the continental behaviour in the north (mean δ¹⁸O around?8 to?11%‰). Depending on the location, the mean δ¹⁸O values vary with altitude at a rate of approximately?0.2%‰/100 m and?0.4%‰/100 m, respectively. Also the deuterium excess has been found to depend on location and altitude. The data are being used to construct a δ¹⁸O map for the entire area.