Double Isotope Dilution Technique Research Articles

Determination of the 144Ce/238U atomic ratio in spent nuclear fuel using double spike isotope dilution mass spectrometry

Determination of the 144Ce/238U ratio in spent nuclear fuels using the double isotope dilution technique associated with thermal ionization mass spectrometry measurements.

A double-spike method for K–Ar measurement: A technique for high precision in situ dating on Mars and other planetary surfaces

A new method for K–Ar dating using a double isotope dilution technique is proposed and demonstrated. The method is designed to eliminate known difficulties facing in situ dating on planetary surfaces, especially instrument complexity and power availability. It may also have applicability in some terrestrial dating applications. Key to the method is the use of a solid tracer spike enriched in both 39Ar and 41K. When mixed with lithium borate flux in a Knudsen effusion cell, this tracer spike and a sample to be dated can be successfully fused and degassed of Ar at <1000°C. The evolved 40Ar∗/39Ar ratio can be measured to high precision using noble gas mass spectrometry. After argon measurement the sample melt is heated to a slightly higher temperature (∼1030°C) to volatilize potassium, and the evolved 39K/41K ratio measured by Knudsen effusion mass spectrometry. Combined with the known composition of the tracer spike, these two ratios define the K–Ar age using a single sample aliquot and without the need for extreme temperature or a mass determination. In principle the method can be implemented using a single mass spectrometer.Experiments indicate that quantitative extraction of argon from a basalt sample occurs at a sufficiently low temperature that potassium loss in this step is unimportant. Similarly, potassium isotope ratios measured in the Knudsen apparatus indicate good sample-spike equilibration and acceptably small isotopic fractionation. When applied to a flood basalt from the Viluy Traps, Siberia, a K–Ar age of 351±19Ma was obtained, a result within 1% of the independently known age. For practical reasons this measurement was made on two separate mass spectrometers, but a scheme for combining the measurements in a single analytical instrument is described. Because both parent and daughter are determined by isotope dilution, the precision on K–Ar ages obtained by the double isotope dilution method should routinely approach that of a pair of isotope ratio determinations, likely better than ±5%.

Determination of Cr, Cu, Ni, Sn, Sr and Zn Mass Fractions in Geochemical Reference Materials by Isotope Dilution ICP‐MS

Isotope dilution (ID) mass spectrometry is a primary method of analysis suited for the accurate and precise measurement of several trace elements in geological matrices. Here we present mass fractions and respective uncertainties for Cr, Cu, Ni, Sn, Sr and Zn in 10 silicate rock reference materials (BCR‐2, BRP‐1, BIR‐1, OU‐6, GSP‐2, GSR‐1, AGV‐1, RGM‐1, RGM‐2 and G‐3) obtained by the double ID technique and measuring the isotope ratios with an inductively coupled plasma‐mass spectrometer equipped with collision cell. Test portions of the samples were dissolved by validated procedures, and no further matrix separation was applied. Addition of spikes was designed to achieve isotope ratios close to unity to minimise error magnification factors, according to the ID theory. Radiogenic ingrowth of 87Sr from the decay of 87Rb was considered in the calculation of Sr mass fractions. The mean values of our results mostly agree with reference values, considering both uncertainties at the 95% confidence level, and also with ID data published for AGV‐1. Considering all results, the means of the combined uncertainties were &lt; 1% for Sr, approximately 2% for Sn and Cu, 4% for Cr and Ni and almost 6% for Zn.

Vascular dysfunction induced by AGE is mediated by VEGF via mechanisms involving reactive oxygen species, guanylate cyclase, and protein kinase C.

These experiments were designed to elucidate mechanisms mediating vascular dysfunction induced by advanced glycation end products (AGEs). Skin chambers were mounted on the backs of Sprague-Dawley rats and 1 week later, granulation tissue that formed in the bottom of the chamber was exposed twice daily for 7 days to glycated rat serum albumin in the presence and absence of inhibitors of reactive oxygen intermediates, nitric oxide synthase and guanylate cyclase, protein kinase C (PKC), and a neutralizing vascular endothelial growth factor (VEGF) antibody. Vascular (125)I-albumin clearance and blood flow were quantified by use of a double isotope-dilution technique and radiolabeled microspheres, respectively. Albumin permeation and blood flow were increased dose-dependently to a maximum of 2 to 3 times controls by increasing the extent of glucose modification, the concentration, or the duration of exposure to glycated albumin. These increases were significantly attenuated by probucol and superoxide dismutase; N(G)-nitro-L-arginine-methyl ester (L-NAME), a nitric oxide synthase inhibitor; LY83583, a guanylate cyclase inhibitor; and LY333531, a beta-isoform-selective protein kinase C inhibitor. A neutralizing VEGF monoclonal antibody also markedly attenuated the permeability and blood flow increases induced by glycated albumin. These observations indicate potentially important roles for oxygen free-radicals and nitric oxide in mediating permeability and blood flow changes induced by glycated proteins via mechanisms involving increased protein kinase C activity and VEGF production. Striking similarities in the mechanism by which hyperglycemia and glycated proteins induce vascular dysfunction suggest that a common pathway mediates effects of these different metabolic imbalances on vascular dysfunction.

Rapid and steady-state amino acid transport in perfused human fibroblasts and colon adenocarcinoma cells: effects of methotrexate

Initial and steady-state uptakes of serine and phenylalanine by human fibroblasts and human colon tumour cells were studied applying a double isotope dilution technique to perfused populations of cultivated cells retained on microcarrier beads. This new method permits the differentiation of the unidirectional transport parameters and can also distinguish between membrane-associated processes and independently intracellular events in isolated cells. High initial l-serine uptake values in colon adenocarcinoma cells became negative under steady-state conditions. To determine if the observed negative l-serine uptake was produced by the rapid efflux of intracellular l-[ 3H]serine, the cells were treated with methotrexate (MTX) (an inhibitor of cytosolic dihydrofolate reductase). The modified curve of l-[ 3H]serine uptake after MTX treatment suggests that, under these experimental conditions, net serine transport is non concentrative in colon tumour cells and could be modulated by the rate of intracellular serine metabolism; it also suggests that MTX does not directly affect serine transport in perfused human colon adenocarcinoma cells. Initial and steady-state uptakes of phenylalanine were high in both fibroblasts and tumour cells and were unaffected by MTX treatment.

Intrinsic Labeling of Chicken Products with a Stable Isotope of Selenium (76Se)

Chicken tissues were intrinsically labeled with a stable isotope of selenium (76Se) and were evaluated for use in a human feeding study. Laying hens were fed a low Se (0.06 ppm) basal diet for 39 days and then fed the basal diet supplemented with 0.3 ppm enriched 76Se (as selenite) for 35 days. Incorporation of 76Se into samples was determined by use of a double isotope dilution technique and a combined gas chromatography/mass spectrometry analysis. The 76Se content of the basal diet was increased by a factor of 9.7 with the addition of the enriched stable isotope. This maximal level of enrichment was approached in egg yolk (9.5-fold) and liver (9.0-fold). Enrichment was lower in egg white (7.2-fold) and breast meat (5.0-fold). Level of enrichment in a given tissue reflected both the turnover rate of the tissue and its natural selenium content. Selenium-depleted laying hens continuously fed 76Se at the 0.3 ppm level produced egg yolks and livers that were enriched sufficiently with the stable isotope for use in a human metabolic study.

Conversion of testosterone and androstenedione to estrogens in vitro by the brain of female rats.

ABSTRACT. Different areas from brains of 7- day-old female rats were incubated with testosterone- 7-3H (T) or androstenedione- 1-23H (A). Hypothalami from 120-day-old females were also incubated with T. The conversion of these precursors to estradiol (E2) and estrone (E1) was studied using double isotope dilution technique. In addition, the conversion of E2 to E1 and E1 to E2 by brain of the immature females was studied. T was converted predominantly to E2 and A to E1. The yield of E2from T was greatest in incubations of hypothalamus and amygdala, less for the combined septal and preoptic areas and least for the cortex. Conversion of T to E2 by hypothalami of adult rats was less than by that from the immatures. The yield of E1 from A was also greater in hypothalamic than in cortical incubations. There was only minimal conversion less than 3%) of E2 to E1 and of E1, to E2.(Endocrinology 94: 616, 1974)

Metabolites of testosterone in the brain of the newborn female rat after an injection of tritiated testosterone.

Hypothalamic, septal, amygdaloid and corticalareas from brains and the pituitaries of 5-day-old female rats were analyzed for their content of labeled dihydrotestosterone (DHT), androstenedione (A), 5<i>α</i>-androstan-3<i>β</i>-17<i>β</i>-diol (3<i>β</i>-Adiol), 5<i>α</i>-androstan-3<i>α</i>-17<i>β</i>-diol (3<i>α</i>Adiol), estradiol-17<i>β</i> (E₂) and estrone (Ei) 10, 15 and 30 min after an intraperitoneal injection of 20 <i>µ</i>Ci testo-sterone-7-³H (T). Two experiments were carried out. In both, tissues were pooled from 10 rats and the steroids quantified by the double isotope dilution technique. Tritiated T, A and DHT were identified in all parts of the brain studied. Together they accounted for 11.5–28.0% of the radioactivity extractable by organic solvents at 10 min and 5.5–11.3% of the radioactivity extractable at 30 min. The amount of DHT at 10 min was 1.5–3.7% of the radioactivity and fell to 0.9–2.5 % by 30 min. Specimens from the different brain areas had to be combined to provide sufficient labeled 3<i>α</i>Adiol for positive identification. The radioactivity associated with 3<i>β</i>Adiol was insufficient to establish radiochemical homogeneity. E₂ was present in identifiable amounts in the hypothalamic and combined septal and amygdaloid specimens but not in those specimens from the cortex or the pituitary. In the hypothalamus E₂ accounted for 0.31 % of the total radioactivity and for about 0.11 % of the radioactivity in the combined amygdaloid and septal specimens. The number of counts associated with the E₁ standard did not exceed the background. The ratios of the different steroids to each other varied in the different areas studied; however, there were no consistent differences in the pattern of metabolites in the different areas.

DOUBLE ISOTOPE DILUTION TECHNIQUE WlTH PARTIAL ACETYLATION OF CATECHOLAMINES (PREPARATION OF TRIACETATE)

Acta Physiologica ScandinavicaVolume 85, Issue s377 p. 5-15 DOUBLE ISOTOPE DILUTION TECHNIQUE WlTH PARTIAL ACETYLATION OF CATECHOLAMINES (PREPARATION OF TRIACETATE) First published: November 1972 https://doi.org/10.1111/j.1748-1716.1972.tb05301.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Volume85, Issues377November 1972Pages 5-15 RelatedInformation

Placental Passage and Fetal Secretion of Aldosterone

The transplacental passage and production of aldosterone by the mother and fetus were studied near term during a constant infusion of 1,2-3H-aldosterone to 9 mothers at the time of elective cesarean section. This study showed that there was a transplacental passage of aldosterone. The fetal plasma levels of 1,2-3H-aldosterone, expressed as percentage of the matternal values, ranged from 40.0 to 79.2%. The levels of non-labeled hormone, determined by a double isotope dilution technique, were consistently higher in the fetus than in the mother (mean±SD = 17.2±9.5 mμg/100 ml and 3.7±1.4 mμg/100 ml, respectively). Since the specific activities of aldosterone were lower in the fetus than in the mother (6.5 to 23.4%), and if one assumes that equilibrium between maternal and fetal compartments was reached after more than 2 h of constant infusion, it can be concluded that the fetus secretes aldosterone. The metabolic clearance: ate of aldosterone was not modified by pregnancy. The steroid blood production of the mothers was about twice the non-pregnant values. the relatively small increments might be related to the fact that our subjects were supine for at least 10 h at the time of the study.

Fluorometric assay of corticosterone after purification by bidimensional thin-layer chromatography in birds

A bidimensional thin layer chromatography (B.T.L.C.) purification process was adapted for the fluorometric assay of corticosterone in bird plasma and adrenal tissue. The degree of purification obtained is such that this simple, rapid and sensitive technique may replace the double isotope dilution technique for the accurate assay of corticosterone. The main steps are the following: — Extraction of the corticosteroids. — Purification by B.T.L.C. — Evaluation [radioactive tracer] of the recovery level, and fluorometric assay. This technique was used for a physiological approach of adrenal cortical activity in birds.

ALDOSTERONE- AND CORTISOL SECRETION RATES IN INFANTS AND CHILDREN WITH CONGENITAL ADRENAL HYPERPLASIA SUGGESTING DIFFERENT 21-HYDROXYLATION DEFECTS IN "SALT-LOSERS" AND "NON SALT-LOSERS".

ABSTRACT Aldosterone- and cortisol secretion rates were determined in nine infants and children with congenital adrenal hyperplasia (21-hydroxylation defects), three with the salt-losing type. Aldosterone secretion rates were determined before and after salt-deprivation for 4–6 days, using the double isotope dilution technique of Kliman &amp; Peterson (1960). Cortisol secretion rates were determined before and on the third day of stimulation with ACTH-gel, 2 × 60 IU per day, using the method described by Cope &amp; Black (1958). Aldosterone secretion rates were normal in the »non salt-losers« (60–125 μg/24 h) and rose after salt-deprivation (100–380 μg/24 h). Extremely low values were found in the three patients with the salt-losing type (&lt; 10 μg/24 h) and during salt-deprivation no increase was observed. Cortisol secretion rates before ACTH were in the normal range for all patients (4.2–34 mg/24 h; 12–33 mg/m2/24 h) except for one infant with the salt-losing type (&lt; 0.5 mg/24 h). ACTH raised cortisol secretion rates in all »non salt-losers« (17–104 mg/24 h), but the increase was less than could be expected under normal conditions and the relative defect in the biosynthesis of cortisol was demonstrated in this way. Cortisol secretion rates after ACTH in the »salt-losers« were distinctly lower as compared with the »non salt-losers«. »Salt-losing« and »non salt-losing« types of congenital adrenal hyperplasia as a result of 21-hydroxylation defects in the biosynthesis of cortisol and aldosterone represent two different genotypes. The results of these studies also suggest that both groups of patients represent biochemically two different types of the same disorder. This could be explained by two different genetically controlled changes in the 21-hydroxylation process, resulting in a different defect in the hydroxylation of progesterone and 17α-hydroxyprogesterone.

The in vivo stability of the tritium label in 1,2-H 3d-aldo-sterone when used for measurement of aldosterone secretion rate by the double isotope dilution technique.

The in vivo stability of the tritium label in 1,2-H 3- d-aldosterone has been demonstrated in two totally adrenalectomized patients. It is concluded that this radioactive preparation is suitable for the measurement of aldosterone secretion rate in man. It is suggested that when using the method of Kliman and Peterson, two paper chromatographies should be carried out after pH 1 hydrolysis, acetylation and oxidation.

A preliminary investigation of the levels of 3-monoiodotyrosine and 3,5-diiodotyrosine in human blood plasma using double isotope dilution technique

A preliminary investigation of the levels of 3-monoiodotyrosine and 3,5-diiodotyrosine in human blood plasma using double isotope dilution technique

The determination of thyroxine levels in human plasma by double isotope-dilution technique

A new method is described for the determination of thyroxine in the blood by double isotope-dilution technique using tritiated acetic anhydride as a radioactive reagent together with [ 131]-labelled free thyroxine or [ 14C]-labelled N-acetyl thyroxine as isotopic carriers. The method appears to estimate the readily available hormone in serum to an accuracy of 2–3%. The results of analysis of 32 samples of human serum taken from subjects having varying degrees of thyroid activity show that the thyroxine levels obtained follow the general pattern of thyroid activity very closely, in that increased thyroid function produces a high serum-thyroxine level. The ranges of values for hypofunction, euthyroid function, and hyperthyroid function were 0–3.5 μg/100 ml, 3.0–6.5 μg/100 ml, and greater than 6.5 μg/100 ml, respectively. The ratio of the thyroxine-iodine/protein-bound iodine showed a marked tendency to increase with rising thyroid function and the implications of this finding are briefly discussed.

Determination of amino acids by double isotope-dilution technique.

Determination of amino acids by double isotope-dilution technique.