[The physical basis of isotopes].
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Isotopes↗
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Clinical studies of 13C-urea breath test in Japan.
The urea breath test (UBT) using isotope carbon is a non-invasive method for diagnosing H. pylori infection. In Japan, only 13C-UBT using a stable isotope is available, since the clinical use of radioactive isotope 14C-compounds is prohibited. Since there is no worldwide standard protocol for the 13C-UBT, it is therefore important to standardize this test to obtain a cheap, easy, reproducible method. Factors affecting the outcome of 13C-UBT values include sampling times and frequency, the amount of 13C-urea, the cut-off value, the avoidance of oral urease activity, and changes in gastric emptying times and 13C-urea distribution. Mouth rinsing reduces false-positive results due to oral urease activity, particularly within 20 min after ingestion of 13C-urea. A Japanese multicenter trial has shown that the diagnostic utility of 13C-UBT is superb, with the cut-off value 2.5/1000 in 20-min samples after ingestion of 100 mg 13C-urea. The 13C-UBT is a very useful method for diagnosing H. pylori infection.
Breath Tests↗
Simultaneous determination of radioactive and stable isotopes of cobalt in environmental samples by the isotopic exchange method.
The isotopic exchange method is studied for the simultaneous determination of radioactive and stable isotopes of cobalt in environmental samples. Radioactive cobalt is isotopically exchanged with Co-CyDTA in HC1 solution of the sample. The solvent extraction method is used for the separation of Co2+ and Co-CyDTA species from each other. The amounts of radioactive and stable cobalt isotopes are calculated with activities of Co and Co-CyDTA at the exchange equilibrium. The methods for eliminating interfering ions are discussed. The results are in good concordance with those obtained by the conventional analytical methods.
Cobalt Isotopes↗
Calculation of turnover rates in stable-isotope studies.
Tserng and Kalhan have raised the question of the appropriate equation to use for the measurement of turnover rate in a stable-isotope study. In a comparison of glucose turnover measured with 2H-glucose and with 13C-glucose they used five apparently different equations and obtained conflicting answers. There is, however, no difference in principle between the use of a stable isotope as a tracer and the use of a radioactive isotope, and the rate of appearance of tracee in a steady-state system (the turnover) can therefore be shown to be proportional to the equilibrium dilution of the infused tracer. Because the sensitivity of measurement of this dilution made using a gas chromatograph-mass spectrometer is lower than that made by radioactivity measurement, the contribution to the measured turnover rate due to the infusate cannot be neglected, as it usually is in radioisotope work. A convenient calibration curve to establish this dilution is the mole ratio of the pure infusate against the area ratio for the relevant ions. Tserng and Kalhan's apparently conflicting results for glucose turnover using 13C-glucose as the tracer can all be shown to amount to approximately 11.6 mumol min-1 kg-1. This value is only slightly lower (0.05 less than P less than 0.1) than that obtained using 2H-glucose as the tracer and supports the use of 13C-glucose as an alternative.
Blood Glucose↗
Nuclear medicine--an overview.
A radioactive isotope behaves chemically and biologically like its non-radioactive counterpart. The application of this principle to medical diagnosis has evolved into a whole specialty called nuclear medicine. The development of the rectilinear scanner and gamma camera has extended the study of molecular pathways into an exciting imaging modality while developments in radiopharmaceuticals have made radionuclide imaging of many organ systems widely available. The most significant improvements have occurred in bone, hepatobiliary and cardiac imaging. Today, however, nuclear medicine is evolving into a more dynamic study of physiological processes in the body and how these processes may be affected by disease and medical treatment. Emission tomography with a new generation of both gamma and positron emitters will be integral part of nuclear medicine in the future. The challenge to develop radio-labelled antibodies for immunotherapy and immunodetection remains while many of the older techniques like radioimmunoassay, and even the simple colloid liver scan, will continue to contribute significantly to health care.
Humans↗
Preparative separation of underivatized amino acids for compound-specific stable isotope analysis and radiocarbon dating of hydrolyzed bone collagen.
Analysis of stable and radioactive isotopes from bone collagen provides useful information to archaeologists about the origin and age of bone artifacts. Isolation and analysis of single amino acids from the proteins can provide additional and more accurate information by removing contamination and separating a bulk isotope signal into its constituent parts. In this paper, we report a new method for the separation and isolation of underivatized amino acids from bone collagen, and their analysis by isotope ratio MS and accelerator MS. RP chromatography is used to separate the amino acids with nonpolar side chains, followed by an ion pair separation to isolate the remaining amino acids. The method produces single amino acids with little or no contamination from the separation process and allows for the measurement of accurate stable isotope ratios and pure samples for radiocarbon dating.
Amino Acids↗
Calculation of substrate flux using stable isotopes.
The use of stable isotope tracers to calculate substrate kinetics in humans is favored over the use of radioactive isotopes because of their greater safety and versatility. However, potential complications not met when dealing with radioactive tracers are caused by 1) the natural occurrence of the stable isotope used as a tracer and 2) the necessity to administer the tracer in an amount that cannot be treated as "massless." We therefore found it desirable to derive a theoretically valid equation for calculating the rate of appearance, Ra, of a substrate under steady-state conditions using a stable isotope tracer. This theoretically valid equation yields results that differ from those of the equations conventionally used to calculate (endogenous) Ra in steady state. Quantitative determination of the error in one of these equations revealed that for tracers commonly used in metabolic studies the error is negligible, whereas the error made in the other equation is likely to be quite high in commonly encountered situations. Finally, to allow for proper use of different definitions of isotopic enrichment that have arisen from practical considerations, we use the results derived above to determine valid equations for Ra appropriate to the two prevalent definitions.
Humans↗
Application of LS 7500 counter (Beckman) for measurement of phagocytosis of 14C labeled bacteria.
For determination of phagocytosis of Staphylococcus aureus 519 labeled with glycine-1-14C by guinea pig granulocytes, the third analytical program of LS 7500 counter was used. By measuring isotope radioactivity, the program enables evaluation of the percentage of a bound isotope in relation to the reference sample. In the present experiments the percentage of a bound isotope stands for the percentage of phagocytized bacteria calculated in relation to a reference sample, i.e. to radioactivity of bacteria added to the test. The program applied allows an automatic calculation of the percentage of phagocytized bacteria, the result being printed by a counter printer.
Animals↗
Stable isotopes for determining biokinetic parameters of tellurium in rabbits.
We have compared the use of stable and radioactive isotopes for determining the concentration of tellurium in body fluids of animals and man, specifically in the blood plasma of rabbits. Particular effort has been devoted to developing a sample-processing technique that allows the total amount of tellurium and isotope ratios to be measured by graphite furnace atomic absorption spectrometry (GFAAS) and secondary ion mass spectrometry (SIMS), respectively. The procedure employed in the SIMS analysis is discussed in detail. Investigations on the plasma clearance and the fractional intestinal absorption were carried out on four rabbits. Tracer solutions containing stable tellurium enriched in 124Te or 126Te and radioactive tellurium (121mTe or 123mTe) were administered by gavage and/or intravenously. Blood samples were drawn during the first 2 days after application. The activity of the separated plasma was measured by standard gamma ray spectrometry. After wet ashing and solvent extraction with MIBK the samples were analyzed for stable tellurium. A detection limit of 1 ng/mL of plasma could be achieved with GFAAS. For SIMS analysis the processed samples were deposited on high-purity graphite backings. Reliable isotope ratios could be determined with sample fractions containing 1 ng of tellurium or even less. The results obtained by applying stable isotopes were found to be in good agreement with the data achieved by using radioactive tracers. Studies on the intestinal absorption and the metabolic behavior of tellurium in human volunteers may thus be performed with stable isotopes.
Animals↗
Endogenous surfactant metabolism in critically ill infants measured with stable isotope labeled fatty acids.
Little is known about endogenous surfactant metabolism in infants, because radioactive isotopes used for this purpose in animals cannot be used in humans. We developed a novel and safe method to measure the endogenous surfactant kinetics in vivo in humans by using stable isotope labeled fatty acids. We infused albumin-bound [U-13C]palmitic acid (PA) and [U-13C]linoleic acid (LLA) for 24 h in eight critically ill infants (mean+/-SD: weight: 3.7+/-1.3 kg: age: 51.3+/-61.6 d) who required mechanical ventilation. The 13C enrichment of PA and LLA in surfactant phosphatidylcholine (PC), obtained from tracheal aspirates, was measured by gas chromatography combustion interface-isotope ratio mass spectrometry. We measured a significant incorporation of both 13C-PA and 13C-LLA into surfactant PC. PC-PA and PC-LLA became enriched after 8.7+/-4.9 h (range: 3.4-17.3) and 10.0+/-7.2 h (range: 3.0-22.4), respectively; the times at maximum enrichment were 49.2+/-8.9 and 45.6+/-19.3 h, respectively. The fractional synthesis rate of surfactant PC-PA ranged from 0.4 to 3.4% per h, whereas the fractional synthesis rate of PC-LLA ranged from 0.5 to 3.8% per h. The surfactant PC-PA and PC-LLA half-lives ranged from 16.8 to 177.7 and 23.8 to 144.4 h, respectively. This method provides new data on surfactant metabolism in infants requiring mechanical ventilation. We found that synthesis of surfactant from plasma PA and LLA is a slow process and that there were marked differences in PC kinetics among infants. This variability could be related to differences in lung disease and could affect the clinical course of the respiratory failure.
Carbon Isotopes↗
Stable isotopes of lithium: in vivo differential distribution between plasma and cerebrospinal fluid.
Stable and radioactive isotopes of an element have been utilized to study a variety of complex phenomena including metabolic pathways and enzyme reactions. It is generally assumed that isotopes of an element are not treated in a differential manner. Nevertheless we have demonstrated that the two stable isotopes of lithium (Li), one of mass 6 and the other with a mass of 7, are differentially taken up by red blood cells with 6-8% higher quantities of 6-lithium (6Li) being accumulated. We report here on the in vivo pharmacokinetics of Li isotopes. Nineteen adult cats were given a single dose of either 6LiCl by gastric intubation (1 meq/kg) and 2 weeks later the treatment was crossed. Plasma concentrations of the two Li isotopes were determined. In another series of studies 19 adult cats were given either 6LiCl or 7LiCl by intubation, cerebrospinal fluid (CSF) and blood samples were collected simultaneously and isotropic Li concentrations of the spinal fluid and plasma were determined. The average plasma concentration of 6Li was higher than 7-lithium (7Li) between 2 and 9 hr postadministration. The elimination curve for both isotopes had an initial fast and later slow component. For the slow component 6Li had an average half-life of 12.9 and 7Li 15.9 hr. Comparison of the CSF/plasma ratio for 6Li and for 7Li indicated that the ratios were higher for 6Li than 7Li 2-6 hr after administration. These data suggest that factors in addition to concentration gradients influence the transport of Li isotopes across the blood-brain barrier. These studies demonstrate the acute pharmacokinetics of the two Li isotopes are not the same in compartmental distribution and rate of disappearance from plasma. It is conceivable 6Li may have a greater toxic or therapeutic effect than 7Li in the treatment of manic-depressive illness.
Administration, Oral↗
Radionuclides in hot mineral spring waters in Jordan.
Hot mineral springs in Jordan are very attractive to people who seek physical healing but they are unaware of natural radioactive elements that may be contained in the hot mineral water. The activities of the natural radioactive isotopes were measured and the concentrations of the parents of their natural radioactive series were calculated. The measured radionuclides were 234Th, 226Ra, 214Pb, 214Bi, 228Ac, 228Th, 212Pb, 212Bi and 208Tl. In addition the activities of 235U and 40K were measured. The activities ranged from 0.14 to 34.8 Bq/l, while the concentrations of parent uranium and thorium isotopes ranged from 3.0 x 10(-3) to 0.59 mg/l. The results were compared with those for drinking water.
Balneology↗
Simultaneous determination of potassium and rubidium content in yeast.
Rubidium is widely used as a potassium analogue in transport studies in yeast and other organisms. As rubidium (potassium) uptake is modulated by the internal potassium concentration, it is often necessary to determine both Rb(+) and K(+) concentrations in the same cell extract. Current methods based on atomic absorption/emission spectroscopy require separate analysis for each cation. Alternatively, unsafe radioactive isotopes can be used. Here we report a convenient, non-radioactive, HPLC/conductivity-based method that allows a complete analysis of both cations with a single injection from a cell extract. The increase in Rb(+) uptake during K(+) starvation in yeast is easily demonstrated with this method.
Biological Transport, Active↗
Relationship between overexpression of NK-1R, NK-2R and intestinal mucosal damage in acute necrotizing pancreatitis.
AIM: To study the expression of neurokinin-1 receptor (NK-1R) and neurokinin-2 receptor (NK-2R) in distal ileum of acute necrotizing pancreatitis (ANP) and to evaluate the relationship between expression of these two receptors and intestinal mucosal damage. METHODS: A total of 130 adult Sprague-Dawley rats were randomly divided into two groups: the rats in ANP group (n=80) were induced by the retrograde intraductal infusion of 30 g.L(-1) sodium taurocholate. And the rats in normal control group (n=50) received laparotomy only. Sacrifices were made 6 h, 12 h, 24 h and 48 h later in ANP and normal control group after induction respectively. Intestinal mucosal permeability was studied by intrajejunal injection of 1.5 mCi radioactive isotope (99m)Tc-diethlene triamine pentacetic acid (DTPA) and the radioactivity of (99m)Tc-DTPA content in urine was measured 6 h, 12 h, 24 h and 48 h after induction. Then the pancreas and intestine were prepared for pathology. Reverse transcription polymerase chain reaction (RT-PCR) was used to determine the mRNA expression of NK-1R and NK-2R, and Western blot was used to investigate the protein level of NK-1R and NK-2R. RESULTS: In ANP rats, serious histologic damages in intestinal mucosa were observed, and the radioactivity of (99m)Tc-DTPA in urine increased significantly in the ANP group. RT-PCR revealed that NK-1R and NK-2R mRNA level was overexpressed in the distal ileum of ANP as compared with the normal control group. Western blot discovered stronger NK-1R (14-fold increase) and NK-2R (9-fold increase) immunoreactivity in the intestinal mucosa of ANP rats. Moreover, the overexpression of NK-1R was associated with mucosal pathological score (r=0.77, P<0.01) and intestinal permeability (r=0.68, P<0.01) in ANP rats. CONCLUSION: NK-1R and NK-2R contribute to disrupted neuropeptides loop balance, deteriorate intestinal damage, and are involved in pathophysiological changes in ANP.
Amylases↗
The digoxigenin (DIG) system for non-radioactive labelling and detection of nucleic acids--an overview.
The use of non-radioactive nucleic acid probes has increased dramatically over the last years. The convenience of not having to deal with radioactive isotopes combined with the stability and economy of the non-radioactive systems has led to applications in various techniques. One of the most successful labelling and detection systems is based on the hapten digoxigenin. Here, the different methods for labelling nucleic acids with digoxigenin as well as the various possibilities for detection are described. Some typical applications illustrate the utility of the DIG system.
Animals↗
Evaluation of the specificity of alkaline phosphatase-conjugated oligonucleotide probes for forensic DNA analysis.
Current methods of forensic DNA profiling by restriction fragment length polymorphism analysis rely on radioactive detection of DNA. The use of radioactive isotopes is complicated, expensive and requires elaborate safety precautions. Recently, non-radioactive detection methods involving the use of alkaline phosphatase-conjugated oligonucleotide probes have become available. These probes differ from most 32P-labeled probes in that they are synthetic oligonucleotides, whereas the 32P-labeled probes are purified plasmid inserts from cloned VNTR regions. Because of this difference, it is possible that the specificity of the non-isotopic probe will differ from that of the 32P-labeled probe. This study compares the specificity of the two types of probes by parallel analysis of a set of DNA samples, including a subset of relatively small alleles, at the loci D1S7, D2S44, D4S139, D10S28, and D17S26. We found that although the alkaline phosphatase detection method is slightly less sensitive than 32P detection, the AP-conjugated oligonucleotide probes tested have specificity comparable to, and are appropriate and suitable substitutes for, 32P-labeled plasmid inserts.
Alkaline Phosphatase↗
Can a sponge fractionate isotopes?
The study has unequivocally demonstrated that siliceous sponges Spirastrella cuspidifera and Prostylyssa foetida from the same microecological niche exhibit a high degree of species specificity, while accumulating a host of heavy metal ions (Ni, Cr, Cd, Sn, Ti, Mo, Zr). S. cuspidifera accumulated, in addition, 60Co and 63Ni, showing discrimination against other radionuclides, 137Cs and 131I, present in the ambient waters receiving controlled low level waste discharges from a B.W.R. nuclear power station. P. foetida, on the other hand, accumulated only 131I and showed discrimination against other radionuclides including 60Co, although the stable iodine concentrations in both the sponges were the same. The specific activity of 60Co (in becquerels per gram of 59Co) in S. cuspidifera and 131I (in becquerels per gram of 127I) in P. foetida were at least two orders of magnitude greater than in the ambient sea water. That of 63Ni (in becquerels per gram of 62Ni) in S. cuspidifera, on the other hand, was lower by two orders of magnitude than in either abiotic matrices from the same environment. Thus, not only did both the species show bioaccumulation of a specific element, but also preferential uptake of isotopes of the same element, though they were equally available for intake. Such differential uptake of isotopes can possibly be explained in terms of two quite different mechanisms operating, each applicable in a particular case. One is that the xenobiotic isotope enters the environment in a physicochemical form or as a complex different from that of its natural counterpart. If equilibration with the latter is slow, so that the organism acquires the xenobiotic in an unfamiliar chemical context, it may treat it as a chemically distinct entity so that its concentration factor differs from that of stable isotope, thus changing the specific activity. Alternatively, if the xenobiotic is present in the same chemical form as the stable isotope, the only way in which specific activities can be modified is by fractionation on the basis of mass of isotope. In view of the remarkable concentration factors observed for stable and radioactive isotopes of the same element and the specific activities reached, it is desirable that species of sponges, especially from the coastal and estuarine environments, be monitored to detect levels of pollution due to anthropogenic substances.
Animals↗
[Recent studies on carbohydrate, fat and protein metabolism with special reference to the works with radioactive and stabile isotopes. III. Protein metabolism].
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Carbohydrates↗