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PubMed2002

Variations of lead isotopes and airborne particulate concentrations from the Kozani basin, West Macedonia, Greece.

The spread and variation in 206Pb/207Pb ratios make Pb isotopes a powerful tool when it comes to detecting trends in airborne particulates originating mainly from power plants. This study was conducted to determine the source of pollution in Kozani area, an affected industrial area. Lead isotopic ratios of air filters under certain meteorological conditions were compared to Pb isotope analyses sampled from lignite mines, but also to Pb isotope analyses of cultivations in soil originating from the reclamation of old abandoned lignite-mines. The particles taken into consideration have an aerodynamic diameter less than 10 microm (PM10). The measurements were carried out in a central part of the town of Kozani, West Macedonia, for one year observation period. The lead isotope values of air filters and of wheat in the Kozani area are between the values of lignite Pb and of Greek gasoline.

Air Pollutants↗
PubMed2003

[Mineral absorption from dual stable isotopic technique].

Isotope technique is the most accurate method to assess the bioavailability of trace elements. Due to the hazard of radioisotopes, it can't be used to such populations as infants and pregnant women. With the development of stable isotope technique, more and more researches were conducted with stable isotopes. The newly developed dual stable isotope technique was preferred because of its accuracy. While the papers published using such technique till now usually contained the estimation of the blood volume and hemoglobin incorporation. Because of such estimation, errors would be introduced into the results. To obtain the accurate result from the data available, this paper described a rigorous method to calculate the trace element bioavailability. The dual stable isotopic technique was discussed in detail in this paper. From the assumption of the method to their performance, the author described the procedure of calculation of the mineral absorption from the MS data and why. This method was described by using iron as an example, and can be used in similar studies.

Absorption↗
PubMedDate not supplied

[Connection of the carbon isotopic composition of human hair with its functional state].

Temporal variations of carbon isotope composition of hair taken from faces of three men with different health state were studied. Drastic enrichment (up to 20%) of hair carbon in heavy isotope, as compared to the basic line reflecting background isotope variations was discovered in one of the men under test. This enrichment correlated with his worsened state of health. Then carbon isotope composition of hair returned to the background level. Probable explanation of this correlation was suggested in terms of earlier described mechanism of carbon isotope fractionation in a living cell.

Carbon Isotopes↗
PubMedDate not supplied

[Distribution of the heavy isotope of carbon (13C) in biological systems].

Causes conditioning fractionation of carbon isotopes in biological systems are considered. Concepts of E. M. Galimov are discussed. According to these concepts distribution of carbon isotopes between biomolecules and their fragments is quaziequilibrium, i. e. it differs from the equilibrium one by a constant multiplier, which is the same for all the biomolecules of an organism but different for various organisms. These concepts have no theoretical grounds and do not agree with the experimental evidence available. An analysis of experimental data, as well as theoretical considerations, indicate that the observed differences in isotope composition of metabolytes and their fragments in the living organisms are conditioned by the kinetic isotope effects of carbon at the stages of their enzymic transformations and by the portion of substances participating in the reaction. It means that these differences do not depend directly on the constants characterizing the equilibrium distribution of carbon isotopes between corresponding compounds and between different groups inside their molecules.

Animals↗
PubMed1986

In vivo gallbladder absorption: a new dual-isotope technique.

Available methods for measuring in vivo gallbladder absorption preclude the use of animals in which hepatic bile enters the gallbladder via accessory or aberrant channels. However, accessory bile ducts are present in many of the animal models currently used in gallstone research. The aim of this study, therefore, was to evaluate a new dual-isotope technique that corrects for accessory bile flow and to compare data on electrolyte and water absorption with those derived from the standard, single-isotope technique. Prairie dogs underwent gallbladder exclusion by cystic duct ligation and common bile duct cannulation. Carbon 14-polyethylene glycol-labeled lactated Ringer's solution was instilled into the gallbladder while tritiated cholic acid was administered intravenously to label the bile acid pool. There is no correlation between water or electrolyte absorption and time, nor between water and electrolyte absorption, when these parameters are calculated by the standard, single-isotope technique. In contrast, use of the dual-isotope technique quantifies accessory bile duct flow and yields a linear increase in water and electrolyte absorption, both of which are time dependent. These data suggest that the dual-isotope technique provides a means to accurately measure in vivo gallbladder absorption in animals with or without accessory bile ducts.

Absorption↗
PubMedDate not supplied

[Theoretical analysis of the relation between the cell state and pathways of carbon isotope fractionation in metabolic processes].

On a dynamic model of fractionation of carbon isotopes in the living cell there are considered relationships between the distribution of carbon isotopes in the structures approximating basic biochemical fractions, their isotopic composition and parameters characterizing the dynamics of carbon metabolism, i.e. efficient carbon isotope separation factor in pyruvate enzymic decarboxylation, degree of its transformation at primary and secondary decarboxylation and ratios between the currents of carbon substrates. A wide range of variations of cell isotope parameters resulting from the change of its functional states was revealed. Possible applications of the relationships observed for studying biological systems are shown.

Carbon Isotopes↗
PubMed1982

Further validation of the plasma isotope ratio method for measurement of cholesterol absorption in man.

Recently we evaluated an isotope ratio method (IRM) for measurement of cholesterol absorption in 14 patients (15 experiments) hospitalized in the metabolic ward by comparing it to simultaneous measurements with a fecal radioactivity method (FRM) and found good to excellent agreement between two procedures (Samuel, P., J. R. Crouse, and E. H. Ahrens, Jr. 1978 J. Lipid Res. 19: 82-93). This comparison has now been extended to additional studies carried out in eight hospitalized patients (19 experiments). Of the 34 comparisons between the IRM and the FRM in our hands, 29 were technically acceptable (chromic oxide fecal recovery >/=80%): percent cholesterol absorption was 43.1 +/- 12% by the FRM and 46.0 +/- 11% by the IRM, exhibiting an accuracy within 3.5% at the 95% and 4.7% at the 99% confidence levels. In addition, various procedural modifications of the IRM were studied in out-patients. The measurement of isotope ratios in a single blood sample (analyzed in sextuplicate) on the third day (or later) following the tests gave identical results to those obtained from six to eight daily blood samplings. Blood samples drawn at any time during the day gave cholesterol absorption values similar to those obtained from samples drawn following an overnight fast. Absorption tests carried out before and 1 hr after breakfast, lunch, or dinner, or giving the oral isotope in three divided daily doses all yielded identical results with tests carried out in the am in the fasting state. Cholesterol absorption was markedly reduced when the oral radiolabeled cholesterol was administered in orange juice vs. liquid formula, milk or a solution of glucose and amino acids, consistent with the well-known fact that gallbladder contraction is a critical requirement of cholesterol absorption. A meal high in cholesterol consumed on the day of the test did not influence the results of the absorption measurements. Furthermore, addition of three eggs per day (~750mg cholesterol) for 3 weeks to a low-cholesterol poly-unsaturated fat diet caused no significant change in percent cholesterol absorption in any of eight patients. We conclude that the isotope ratio method accurately and precisely measures cholesterol absorption in man, and that it is suitable not only for in- but also for out-patient studies.-Samuel, P., D. J. McNamara, E. H. Ahrens, Jr., J. R. Crouse, and T. Parker. Further validation of the plasma isotope ratio method for measurement of cholesterol absorption in man.

Absorption↗
PubMed1995

Contribution of tissue lead to blood lead in adult female subjects based on stable lead isotope methods.

Public health and medical recommendations on prevention of lead toxicity rely on use of blood lead concentrations to assess lead exposure and predict onset of adverse health effects. Blood lead levels have generally been thought to reflect recent environmental lead exposures. However, tissue lead stores are accumulated over a long time period (i.e., years). These tissue stores, primarily from bone, can be remobilized as part of both normal physiologic and pathologic processes. Although chemical analyses do not differentiate lead isotopes, mass spectrometric determinations can differentiate the quantities of stable lead isotopes present in particular samples (e.g., lead 207, lead 206, lead 204, and lead 208). Selected geographic locations may have distinct isotopic profiles. For example, on mainland Australia the 206Pb/204Pb ratios reported in both environmental lead sources and blood samples are typically less than 17.0. By contrast, stable lead isotope profiles in blood samples of adult women immigrating from Eastern Europe and the former Soviet Union usually have 206Pb/204Pb ratios greater than 17.5 and as high as 18.5 on entry into Australia. Longitudinal monitoring of blood samples to determine stable lead isotope profiles by mass spectrometry and chemical analyses of blood samples for total lead content were conducted over a 300-day period. These data show that between 45% and 70% of lead in blood comes from long-term tissue lead stores. Recognition that the predominant source of lead in blood was tissue stores rather than the contemporaneous environment should greatly modify recommendations on use of blood lead to monitor occupational or environmental interventions. In addition, internal biokinetics of lead, documented through presence of tissue lead in blood, underlie the long-term health risks of lead exposure. Transfer of lead to the fetus from maternal tissue stores represents a special area of concern.

Adult↗
PubMed1996

13C NMR spectroscopy and gas chromatograph--combustion--isotope ratio mass spectrometry: complementary applications in monitoring the metabolism of 13C-labelled polyunsaturated fatty acids.

This review aims to describe some recent and novel applications of stable isotope tracer technology to study the metabolism of 13C-polyunsaturated fatty acids. Stable isotope methodology has existed for several decades, and in that sense, it is not novel per se. However, in the past 10 years, developments in the fields of isotope ratio mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy, and biological approaches to labelling tracer compounds with stable isotopes have provided new opportunities in fatty acid research. Sample preparation for isotope ratio mass spectrometry has been converted from a manual combustion method to an on-line or continuous flow method, making it much more versatile and easier to use. Similarly, 13C-NMR spectroscopy has recently developed as a remarkably useful method for monitoring metabolic steps and pathways both in vivo and at the molecular level. Coincident with these improvements in instrumentation, the commercial availability of numerous uniformly 13C-labelled compounds has made these studies more affordable. The application of some of these developments to questions in the field of polyunsaturated fatty acid metabolism is described.

Animals↗
PubMed1996

[Optimal isotope composition of biogenic chemical elements on board of manned spacecrafts].

Isotope composition of biogenic chemical elements (BCE) is discussed. A hypothesis is offered that biochemical and biomedical processes must be influenced as by the isotope composition of hydrogen and oxygen, so by the composition of stable isotopes of all the BCE constituting plants, animals, and humans. Biochemical, toxicological and other biomedical analyses should be performed to determine the best BCE isotope composition. These must be followed by development of methods, technologies, and life support systems to form and maintain the best isotope composition inside spacecraft habitable modules.

Humans↗
PubMed1997

A review of the use of radio-isotopes in medicine and medical research in Australia (1947-73).

Recent reports in the Australian media have claimed that after the Second World War 'hundreds of (Australians) were injected with radioactive materials in medical experiments that continued in Australian hospitals until the 1960s'. These claims prompted a review of archival records of the Australian Radiation Laboratory (ARL) that are held by the Australian Archives pertaining to the medical uses of radio-isotopes during the period 1947-73. The material examined indicates that the procurement, distribution, and therapeutic and diagnostic uses of radio-isotopes were stringently controlled by the Radio-isotopes Standing committee (RSC) until 1973, when the responsibility of regulation of medical uses of radio-isotopes passed to the Therapeutic Goods Administration. On the basis of available information it appears that the claims made by the media that many Australians were subjected to unconscionable medical experiments are unjustified. A full report has been released by the Commonwealth Minister for Human Services and Health. The following is an abridged version of that report, detailing some of the more contentious uses of radio-isotopes for medical purposes in Australia during the period 1947-73.

Advisory Committees↗
PubMed1998

[Study of gastric emptying by dual isotopes. Corrections due to contamination].

The evaluation of gastric emptying by the double isotope technique involves some methodologic conditioning. Among them contamination correction or interference in the energy windows of the activity of the two isotopes used in the marking of the solids and fluids of the test food are important. The results of an experiment in which a phantom was used to evaluate the contamination between indio 111 (DTPA-Ca111In) and technecium 99m (colloid99mTc). Three test studies were posteriorly performed in healthy volunteers and 27 studies in a control group (13 males, mean age of 33 years, mean body mass index 39.02 kg/m). In these studies the contamination was corrected with the acquisition, following an initial swallow of juice marked with 111In, of activity in the windows of both isotopes. The contamination of 111In (isotope of greatest radiation energy) in the window of 99mTc was 24% in the phantom and 20%, 23% and 26% in the three initial study tests. The mean contamination in the control group was of 22% with limits of 19% to 29% and a standard deviation of 3%. Despite the comparable results, the usefulness of the individualized contamination calculation in the studies of gastric emptying with dual isotope to minimize the methodologic errors of this technique is discussed.

Adult↗
PubMed1998

Oxygen isotope exchange between refractory inclusion in Allende and solar nebula gas.

A calcium-aluminum-rich inclusion (CAI) from the Allende meteorite was analyzed and found to contain melilite crystals with extreme oxygen-isotope composition (approximately 5 percent oxygen-16 enrichment relative to terrestrial oxygen-16). Some of the melilite is also anomalously enriched in oxygen-16 compared with oxygen isotopes measured in other CAIs. The oxygen isotopic variation measured among the minerals (melilite, spinel, and fassaite) indicates that crystallization of the CAI started from oxygen-16-rich materials that were probably liquid droplets in the solar nebula, and oxygen isotope exchange with the surrounding oxygen-16-poor nebular gas progressed through the crystallization of the CAI. Additional oxygen isotope exchange also occurred during subsequent reheating events in the solar nebula.

Crystallization↗
PubMed1988

Study of isotope effects on protein binding by gas chromatography/mass spectrometry of theophylline-phenobarbitone and 2H, 13C, 15N isotopomers.

We describe a comparative study of human serum albumin (HSA) binding by equilibrium dialysis (pH 7.4, 37 degrees C, 3 h) for two groups of isotopic analogues: theophylline and 1-C(2H3)theophylline; unlabelled, 5(ethyl(2H5],-5(phenyl(2H5] and 1,3-15N;2-13C-phenobarbitone. Bound and free drug fractions are quantified by combined gas chromatography/mass spectrometry. In three instances, protein binding parameters are greatly affected by isotopic substitution, namely for: theophylline and 1-C(2H3)theophylline with isotope effects on total binding site concentration (N), affinity constant (Ka) and extent of HSA binding (%) respectively, equal to: NL/NH = 0.51; KaL/KaH = 1.78; %L/%H = 0.96 (L (light) and H (heavy) represent the unlabelled and labelled analogue respectively); phenobarbitone/-5-(phenyl(2H5]phenobarbitone, NL/NH = 1.72; KaL/KaH = 0.56; %L/%H = 1.26; phenobarbitone/1,3-15N;2-13C phenobarbitone, NL/NH = 2.95; KaL/KaH = 0.44; %L/%H = 1.32, together with a change from one (saturable) to two (saturable + non-saturable) families of albumin binding sites in the latter case. Contrasting with these data, no HSA binding isotope effect was observed on phenobarbitone C5 ethyl deuteration.

Carbon Isotopes↗
PubMed2002

Tracing the diet of the monitor lizard Varanus mabitang by stable isotope analyses (delta(15)N, delta(13)C).

In this study, we used analyses of stable isotopes of nitrogen (delta(15)N) and carbon (delta(13)C) to determine the trophic ecology of the monitor lizard Varanus mabitang. Stable isotopes from claws, gut contents, and soft tissues were measured from the type specimen. Samples from Varanus olivaceus, Varanus prasinus, Varanus salvator, the herbivorous agamid lizard Hydrosaurus pustulatus, and some plant matter were included for comparison. Our data show a rapid decrease in delta(13)C (about 10 per thousand) from food plants towards gut contents and soft tissues of herbivorous species. For the varanids, we found a significant linear correlation of decreasing delta(13)C and increasing delta(15)N from herbivorous towards carnivorous species. In terms of trophic isotope ecology, the type specimen of V. mabitang is a strict herbivore. Thus it differs significantly in its isotopic composition from the morphologically next closest related species V. olivaceus. The most highly carnivorous species is V. salvator, while delta(15)N values for V. prasinus and V. olivaceus are intermediate. Claws provide very valuable samples for such measurements, because they can be sampled from living animals without harm. Additionally, their range of variability is relatively small in comparison with measurements from soft tissues.

Animal Feed↗
PubMed2005

Kinetic isotope effects of nucleoside hydrolase from Escherichia coli.

rihC is one of a group of three ribonucleoside hydrolases found in Escherichia coli (E. coli). The enzyme catalyzes the hydrolysis of selected nucleosides to ribose and the corresponding base. A family of Vmax/Km kinetic isotope effects using uridine labeled with stable isotopes, such as 2H, 13C, and 15N, were determined by liquid chromatography/mass spectrometry (LC/MS). The kinetic isotope effects were 1.012+/-0.006, 1.027+/-0.005, 1.134+/-0.007, 1.122+/-0.008, and 1.002+/-0.004 for [1'-13C], [1-15N], [1'-2H], [2'-2H], and [5'-2H2] uridine, respectively. A transition state based upon a bond-energy bond-order vibrational analysis (BEBOVIB) of the observed kinetic isotope effects is proposed. The main features of this transition state are activation of the heterocyclic base by protonation of/or hydrogen bonding to O2, an extensively broken C-N glycosidic bond, formation of an oxocarbenium ion in the ribose ring, C3'-exo ribose ring conformation, and almost no bond formation to the attacking nucleophile. The proposed transition state for the prokaryotic E. coli nucleoside hydrolase is compared to that of a similar enzyme isolated from Crithidia fasciculata (C. fasciculata).

Amino Acid Sequence↗
PubMedDate not supplied

Stable isotope laser spectrometer for exploration of Mars.

On Earth, measurements of the ratios of stable carbon isotopes have provided much information about geological and biological processes. For example, fractionation of carbon occurs in biotic processes and the retention of a distinctive 2-4% contrast in 13C/12C between organic carbon and carbonates in rocks as old as 3.8 billion years constitutes some of the firmest evidence for the antiquity of life on the Earth. We have developed a prototype tunable diode Laser spectrometer which demonstrates the feasibility of making accurate in situ isotopic ratio measurements on Mars. This miniaturized instrument, with an optical path length of 10 cm, should be capable of making accurate 13C/12C and 15N/14N measurements. Gas samples for measurement are to be produced by pyrolysis using soil samples as small as 50 mg. Measurements of 13C/12C, 18O/16O and 15N/14N have been made to a precision of better than 0.1% and various other isotopes are feasible. This laser technique, which relies on the extremely narrow emission linewidth of tunable diode lasers (<0.001 cm(-1)) has favorable features in comparison to mass spectrometry, the standard method of accurate isotopic ratio measurement. The miniature instrument could be ready to deploy on the 2003 or other Mars lander missions.

Carbon Dioxide↗
PubMed1998

A new general method for the biosynthesis of stable isotope-enriched peptides using a decahistidine-tagged ubiquitin fusion system: an application to the production of mastoparan-X uniformly enriched with 15N and 15N/13C.

A new strategy is described for the production of peptides enriched with stable isotopes. Peptides of interest are expressed in Escherichia coli (E. coli) cells as recombinant fusion proteins with Saccharomyces cerevisiae ubiquitin. This method yields as much as 30-100 mg/l of isotope-enriched fusion proteins in minimal media. A decahistidine tag attached to the N-terminus of ubiquitin enables a one-step purification of the fusion protein via Ni(2+)-chelating affinity chromatography. The ubiquitin moiety is then easily and specifically cleaved off by a protease, yeast ubiquitin hydrolase. Since this enzyme is also expressed at a high level in E. coli cells and can be purified in one step, the presented strategy has an advantage in view of costs over others that use commercially available proteases. In addition, since ubiquitin fusion proteins easily refold, the fusion protein can be expressed either in a soluble form or as inclusion bodies. This flexibility enables us to prepare peptides that are unstable in a soluble state in E. coli cells. As an example, the expression and the uniform stable isotope enrichment with 15N and/or 13C are described for mastoparan-X, a tetradecapeptide known to activate GTP-binding regulatory proteins. An amide group at the C-terminus of this peptide can also be formed by our method. The presented system is considered powerful for the stable isotope enrichment of short peptides with proton resonances that are too severely overlapped to be analyzed solely by proton NMR.

Amino Acid Sequence↗