Radioisotope Tracer Technique Research Articles

Response of carbon fixation, allocation, and growth to source-sink manipulation by defoliation in vegetative citrus trees.

Source-sink balance in plants determines carbon distribution, and altering it can impact carbon fixation, transport, and allocation. We aimed to investigate the effect of altered source-sink ratios on carbon fixation, transport, and distribution in 'Valencia' sweet orange (Citrus x sinensis) by various defoliation treatments (0%, 33%, 66%, and 83% leaf removal). Gas exchange parameters were measured on 0 and 10 days after defoliation using A/Ci response curves, and leaf export was measured two days after defoliation using radioisotope tracer techniques. Greater defoliation increased the maximum rate of carboxylation (Vcmax), electron transport rate (J1200), and triose-phosphate utilization rate (TPU). Leaf export was unaffected by defoliation but increased in leaves closer to the shoot apex. Basipetal translocation velocity in the trunk remained unaltered, indicating that more photosynthates remained in the shoot rather than being transported directly to the root sink. Defoliated plants initiated more new flush shoots but accumulated less shoot biomass per plant after 8 weeks. Carbon allocation to fine roots was smaller in defoliated plants, suggesting defoliation led to retention of carbohydrates in aboveground organs such as the trunk and other shoots from previous growing cycles. In conclusion, the low source-sink ratio increased carbon fixation without impacting individual leaf export in citrus. The results suggest that intermediate sinks such as the aboveground perennial organs play a role in mediating the translocation velocity. Further research is necessary to better understand the dynamics of source-sink regulation in citrus trees.

Influence of salinity gradients on the diffusion of water and ionic species in dual porosity clay samples

Most of the available data on diffusion in natural clayey rocks consider tracer diffusion in the absence of a salinity gradient despite the fact that such gradients are frequently found in natural and engineered subsurface environments. To assess the role of such gradients on the diffusion properties of clayey materials, through-diffusion experiments were carried out in the presence and absence of a salinity gradient using salt-diffusion and radioisotope tracer techniques. The experiments were carried out with vermiculite samples that contained equal proportions of interparticle and interlayer porosities so as to assess also the role played by the two types of porosities on the diffusion of water and ions. Data were interpreted using both a classical Fickian diffusion model and with a reactive transport code, CrunchClay that can handle multi-porosity diffusion processes in the presence of charged surfaces. By combining experimental and simulated data, we demonstrated that (i) the flux of water diffusing through vermiculite interlayer porosity was minor compared to that diffusing through the interparticle porosity, and (ii) a model considering at least three types of porous volumes (interlayer, interparticle diffuse layer, and bulk interparticle) was necessary to reproduce consistently the variations of neutral and charged species diffusion as a function of salinity gradient conditions.

Analysis of phosphorus forms on different soil types using heterogeneous isotope exchange reaction

Pot experiments and soil incubation were carried out to follow the processes of added phosphorus (P) fertilizer using radioisotope tracer technique, heterogeneous isotope exchange. Four types of soils were investigated (Dystric Arenosol (Humic), Calcic Vertisol (Gleyic), Rendzic Phaeozem (Hyperhumic), Calcic Gleysol(Arenic, Humic)). The changes of phosphate fractions (water-soluble (Pw), isotopically exchangeable (PIE), ammonium lactate soluble phosphorus (PAL), and tightly sorbed phosphorus (Ptightly)) in soil were determined as a function of P supply, incubation time and the plant culture. The soil samples were incubated at different times (1, 3, 13 weeks) and phosphate quantities. 0, 40, 80, 160, 320 mg P/kg soil doses of P fertilizer were added to the soils. After incubation, perennial ryegrass (Lolium perenne L.) was sown. A significant correlation was found between the sum of Pw and PIE and Puptake of plant proving that these values can be good indicators of plant available phosphorus. During plant culture, the Pw and PIE values always decrease showing that plant directly utilizes these phosphate forms. The transformation of added phosphate to tightly sorbed phosphate is the highest for soils with great humus content.

Characterisation of soil phosphorus forms in the soil-plant system using radioisotopic tracer method

Soil incubation and pot experiments were conducted to follow the sorption processes of added phosphorus (P) fertiliser using the radioisotope tracer technique. Increasing doses of P fertiliser (40, 80, 160, 320 mg P/kg soil) were added to Chernozem and Arenosol and incubated for 1, 3, and 13 weeks. After incubation, perennial ryegrass (Lolium perenne L.) was sown in one group of pots, and the experiment had been continuing for another 9 weeks. The yield, grass P uptake, isotopically exchangeable (P<sub>IE</sub>), water-soluble (P<sub>W</sub>), and ammonium lactate soluble phosphorus (P<sub>AL</sub>) fractions of soils were measured. On Chernozem, plant P uptake, P<sub>IE</sub>, P<sub>W</sub> and P<sub>AL</sub> were significantly less in the case of the longest incubation period compared to shorter incubations. This suggests a transformation of P into tightly sorbed form. On Arenosol, there were only small changes in the parameters as the incubation period increased, suggesting less intense P transformation to tightly sorbed form. The P<sub>W</sub>/P<sub>IE</sub> ratio enhanced with increasing P-doses, and the ratios were higher on Arenosol. On Arenosol, the higher P doses caused a greater increase of P<sub>W</sub> than on Chernozem. The P<sub>IE</sub> + P<sub>W</sub> showed a good correlation with plant P uptake proving this value can be a good indicator of plant-available phosphorus.

Iron physiological requirements in Chinese adults assessed by the stable isotope labeling technique

BackgroundIron is a kind of essential trace mineral in the human body, while the studies on its physiological requirement are very limited recently, especially in China. And most studies were performed with the radioisotope tracer technique, which was harmful to health. This study aimed to first get the value of iron physiological requirements in Chinese adults assessed by the stable isotope labeling technique.MethodsForty-four eligible young Chinese healthy adults were randomly recruited from the Bethune Military Medical College (Shijiazhuang, Hebei, China) between January 2010 and March 2011, and 19 subjects were included in the final data analysis. After adaptive diets and observation, subjects received 58Fe intravenously. The baseline venous blood sample and general information were collected on day 0. Venous blood samples were also collected on day 14, 30, 60, 100, 120, 150, 240, 330, 425, 515, 605, 767, 1155, respectively. The blood samples were acid digested by a Microwave Digestion System and then analyzed by the MC-ICP-MS and Atomic Absorption Spectroscopy to get the abundance of Fe isotopes and the total iron concentration respectively. The circulation rate (the proportion of blood iron to whole body iron) could be calculated by the intake amount, background content and the peak isotope content. When the abundance changed stably, the iron physiological requirement could be calculated by the iron loss in a period of time.ResultsThe abundance of 58Fe reached its peak on day 14, and changed stably from day 425. The average circulation rate was 84%, with no significance difference between the 2 genders. The mean iron requirement in females was 1101.68 μg/d, and the mean requirement adjusted by body weight was 20.69 μg/kg.d. For males, the mean iron requirement was 959.9 μg/d, and the requirement adjusted by body weight was 14.04 μg/kg.d.ConclusionOur study has obtained the data about the iron physiological requirements of Chinese adults using stable isotope labeling technique, which could provide the basis for adjusting iron DRIs of Chinese people in the future.Trial registrationThe trial was registered at the Chinese Clinical Trial Registry (No: ChiCTR-TRC-09000581).

Aquatic live animal radiotracing studies for ecotoxicological applications: Addressing fundamental methodological deficiencies

The use of live animal gamma radioisotope tracer techniques in the field of ecotoxicology allows laboratory studies to accurately monitor contaminant biokinetics in real time for an individual organism. However, methods used in published studies for aquatic organisms are rarely described in sufficient detail to allow for study replication or an assessment of the errors associated with live animal radioanalysis to be identified. We evaluate the influence of some important methodological deficiencies through an overview of the literature on live aquatic animal radiotracer techniques and through the results obtained from our radiotracer studies on four aquatic invertebrate species. The main factors discussed are animal rinsing, radioanalysis and geometry corrections. We provide examples of three main techniques in live aquatic animal radiotracer studies to improve data quality control and demonstrate why each technique is crucial in interpreting the data from such studies. The animal rinsing technique is also relevant to non-radioisotope tracer studies, especially those involving nanoparticles. We present clear guidance on how to perform each technique and explain the importance of proper reporting of the validation of each technique for individual studies. In this paper we describe methods that are often used in lab-based radioecology studies but are rarely described in great detail. We hope that this paper will act as the basis for standard operating procedures for future radioecology studies to improve study replication and data quality control.

Non-destructive radiotracer technique in characterisation of nuclear grade anion exchange resins Tulsion A-30 and Dowex 550A LC

The present study deals with the application of non-destructive radio isotopic tracer technique to evaluate the performance of nuclear grade resins Tulsion A-30 and Dowex 550A LC. The evaluation was made by testing the performance of the two resins during iodide and bromide ion-isotopic exchange reactions. It was observed that at a constant temperature of 30°C, as the concentration of labelled iodide ion solution increases from 0.001 mol/L to 0.004 mol/L, the percentage of iodide ions exchanged increases from 66.90% to 74.10% for Dowex 550A LC resins and from 60.70% to 67.80% for Tulsion A-30 resins. Similar trend was observed for the two resins during bromide ion-isotopic exchange reaction. The overall results indicate superior performance of Dowex 550A LC resins over Tulsion A-30 resins under identical operational conditions of temperature and ionic concentration of external solution.

Methane oxidation activity and diversity of aerobic methanotrophs in pH-neutral and semi-neutral thermal springs of the Kunashir Island, Russian Far East

Aerobic methane oxidation has been mostly studied in environments with moderate to low temperatures. However, the process also occurs in terrestrial thermal springs, where little research on the subject has been done to date. The potential activity of methane oxidation and diversity of aerobic methanotrophic bacteria were studied in sediments of thermal springs with various chemical and physical properties, sampled across the Kunashir Island, the Kuriles archipelago. Activity was measured by means of the radioisotope tracer technique utilizing (14)C-labeled methane. Biodiversity assessments were based on the particulate methane monooxygenase (pmoA) gene, which is found in all known thermophilic and thermotolerant methanotrophs. We demonstrated the possibility of methane oxidation in springs with temperature exceeding 74°C, and the most intensive methane uptake was shown in springs with temperatures about 46°C. PmoA was detected in 19 out of 30 springs investigated and the number of pmoA gene copies varied between 10(4) and 10(6) copies per ml of sediment. Phylogenetic analysis of PmoA sequences revealed the presence of methanotrophs from both the Alpha- and Gammaproteobacteria. Our results suggest that methanotrophs inhabiting thermal springs with temperature exceeding 50°C may represent novel thermophilic and thermotolerant species of the genera Methylocystis and Methylothermus, as well as previously undescribed Gammaproteobacteria.

In vitro studies on intestinal peptide transport in horses1

Published data on the physiology of nutrient transport across the equine intestine are limited, and the existence and relevance of peptide transporters are still unknown in the horse. In the present study, the equine intestinal peptide transport was investigated by Ussing chamber experiments using the radioisotope tracer technique and by uptake studies into brush border membrane vesicles (BBMV). Jejunal mucosae of 16 healthy adult horses were used. Tissue samples were mounted in Ussing chambers, and electrophysiological parameters as well as unidirectional flux rates of the radiolabelled dipeptide glycylglutamine (Gly-Gln) were determined. The short-circuit current (Isc) response to the luminal addition of Gly-Gln was significantly greater compared to the Isc response to glycylsarcosine (Gly-Sar) addition (P<0.01). Positive net flux rates were determined indicating absorption of the dipeptide. The addition of Gly-Sar reduced the flux rates significantly (P<0.01), suggesting that both peptides compete for the same transport system. The flux rates were not affected by changes in luminal pH value. Uptake studies into BBMV demonstrated an uphill transport in both the absence and the presence of an inwardly directed H+-gradient with the H+-mediated uphill transport being significantly greater than the transport under equilibrium conditions (P<0.001). A Na+-gradient did not cause an uphill transport. The Gly-Gln uptakes displayed Michaelis-Menten kinetics with the Km value for the H+-dependent Gly-Gln uptake being significantly different from the Km value for the Gly-Gln uptake under equilibrium conditions (P<0.05). In conclusion, the study demonstrated for the first time that dipeptides are transcellularly transported across the equine small intestine. The results indicate the presence of at least 2 transport systems for peptide absorption in the horse: 1 secondary active H+-mediated cotransport and 1 that is capable of an uphill transport energized by a mechanism other than a H+ or a Na+-gradient.

Radioisotopic Tracer Technique for Characterization of Nuclear and Non-Nuclear Grade Ion Exchange Resins Tulsion A-23 and Indion-810

In the present paper 82Br radioactive tracer isotopes was used for characterization of nuclear and non-nuclear grade ion exchange resins Tulsion A-23 and Indion-810 respectively. The bromide ion-isotopic exchange reactions were performed by equilibrating 1.000 g of conditioned resins in bromide form with labeled bromide ion solution of different concentrations ranging from 0.001 M to 0.004 M, in the temperature range of 30.0 °C to 45.0 °C. The resins were characterized by comparing the values of specific reaction rate (min-1), amount of bromide ion exchanged (mmol) and percentage of bromide ions exchanged under identical experimental conditions. It was observed that the above values decrease with rise in temperature and increases with increase in concentration of labeled bromide ion solution. From the experimental values of specific reaction rate, amount and percentage of bromide ions exchanged, it was observed that Tulsion A-23 resins are superior to Indion-810 resins under identical experimental conditions.

Radioisotopic Tracer Technique for Characterization of Nuclear and Non-Nuclear Grade Ion Exchange Resins Tulsion A-23 and Indion-810

In the present paper 82Br radioactive tracer isotopes was used for characterization of nuclear and non-nuclear grade ion exchange resins Tulsion A-23 and Indion-810 respectively. The bromide ion-isotopic exchange reactions were performed by equilibrating 1.000 g of conditioned resins in bromide form with labeled bromide ion solution of different concentrations ranging from 0.001 M to 0.004 M, in the temperature range of 30.0 °C to 45.0 °C. The resins were characterized by comparing the values of specific reaction rate (min-1), amount of bromide ion exchanged (mmol) and percentage of bromide ions exchanged under identical experimental conditions. It was observed that the above values decrease with rise in temperature and increases with increase in concentration of labeled bromide ion solution. From the experimental values of specific reaction rate, amount and percentage of bromide ions exchanged, it was observed that Tulsion A-23 resins are superior to Indion-810 resins under identical experimental conditions.

In vitro studies on intestinal calcium and phosphate transport in horses

Transepithelial transport mechanisms play a key role in regulating the absorption and secretion of calcium (Ca 2 + ) and inorganic phosphate (P i) in the gastrointestinal tract. Although intestinal disorders with imbalances in macromineral homeostasis are frequently observed in horses, available data on intestinal Ca 2 + and P i transport are limited. The aim of the present study was to characterize the intestinal Ca 2 + and P i transport functionally by using the in vitro radioisotope tracer technique with Ussing chambers and to identify components involved in Ca 2 + transport at both mRNA and protein level. Among the different intestinal segments, the duodenum showed significant and highest active Ca 2 + absorption. The findings from RT-PCR and Western blot analysis suggest that the epithelial Ca 2 + channel TRPV6, the cytosolic calcium binding protein calbindin-D 9K and the plasma membrane calcium ATPase PMCA may be involved in active transcellular Ca 2 + transport. Regarding the P i transport, the results indicate significant active P i secretion in the jejunum, but the contributing mechanisms remain unclear. A significant inhibiting effect of ouabain as an antagonist of the basolateral Na +/K +-ATPase on the serosal-to-mucosal P i transport suggests a pivotal role of Na + in jejunal P i transport in the horse.

A Prospective Randomized Trial Using Blood Volume Analysis in Addition to Pulmonary Artery Catheter, Compared With Pulmonary Artery Catheter Alone, to Guide Shock Resuscitation in Critically Ill Surgical Patients

Measurement of blood volume (BV) may guide fluid and red blood cell management in critically ill patients when capillary leak from shock and fluid resuscitation makes assessment of intravascular volume difficult. This is a prospective randomized trial of critically ill surgical patients with septic shock, severe sepsis, severe respiratory failure, and/or cardiovascular collapse. The control group received fluid management based on pulmonary artery catheter parameters and red blood cell transfusions based on hematocrit values. The BV group received fluid and red blood cell transfusions based on BV analyses in addition to pulmonary artery catheter parameters. Blood volume was measured using the radioisotope tracer technique with iodine 131-labeled albumin. This allowed direct measurement of plasma volume and calculation of the red blood cell volume. The control group was blinded to the BV results. There were statistically significantly more times when the control group (compared with the BV group) demonstrated hypervolemia (48% vs. 37%) and red blood cell deficiency (33% vs. 16%). There was a delay in red blood cell transfusions administered to the control group by 1.5 +/- 2 days at which time the abnormality became clinically evident. Blood volume analyses provided additional information to the clinicians resulting in a change in treatment in 44% of the time to patients randomized to the BV group. The mortality rates were significantly different between the two groups (8% for the BV group and 24% in the control group; P = 0.03). Blood volume measurements allowed the physicians to promptly treat physiologic disturbances in both red blood cell volume and plasma volume, resulting in improved survival.

Numerical Simulations for Pollutant Transport using Radioisotope Data in River System

A tracer experiment using radioisotope was carried out to investigate the characteristics of a pollutant transport and to estimate the dispersion coefficients in a river system. A well-known radioisotope tracer technique was applied to measure the dispersion coefficients. The radioisotope Br in the form of aqueous ammonium bromide was used to estimate the flow patterns and dispersion phenomena in river. The radioisotope was instantaneously injected into a flow as a point source by an underwater glass-vial crusher. The dispersion coefficients are determined by moment method based on the measured radioisotope data. Two-dimensional numerical models were used to simulate the flow fields and the concentration distributions of the radioisotope injected into the river. The calculated results were compared with the measured ones. Trajectory model have been developed to estimate the unknown source position and the calculated results showed reasonable values within error range.

Analysis on the characteristics of a pollutant dispersion in river environment

A tracer experiment using a radioisotope was carried out to investigate the characteristics of pollutant transport and to estimate the dispersion coefficients in a river system. A well-known radioisotope tracer technique was applied to measure the dispersion coefficients in Daejong river which is located in the southeast area in Korea. The dispersion coefficients were determined by moment, routing and analytical methods based on the measured radioisotope data. Two-dimensional numerical models were used to simulate the flow fields and the concentration distributions of the radioisotope injected into the river. The calculated results were compared with the measurements. As a comparative study, the computed concentration distributions agreed well in the case of the usage of the dispersion coefficients determined by the moment method.

Physiological and molecular characterization of methotrexate transport by Malpighian tubules of adult Drosophila melanogaster

A radioisotope tracer technique and quantitative PCR were used to study the mechanisms and regulation of transepithelial transport of the type II organic anion methotrexate (MTX) by the Malpighian tubules of Drosophila melanogaster. Transport of MTX was saturable and Na +-independent; the kinetic parameters J max and K t were 437 fmol min −1 and 23.5 μM, respectively. The transport of MTX was competitively inhibited by phenol red and probenecid; non-competitively inhibited by salicylate, verapamil and MK-571; and uncompetitively inhibited by Texas Red. Dietary exposure to 0.1 mM MTX led to dramatic increases in gene expression for several members of the ABC family of transporters in both the Malpighian tubules and the gut. Our results suggest that multiple transporters are upregulated in response to dietary exposure to MTX. Increased levels of the protein products which may result from expression of these genes may enhance elimination of toxic compounds such as MTX or its metabolites.

Microbial Chlorination of Organic Matter in Forest Soil: Investigation Using 36Cl-Chloride and Its Methodology

Chloride, which comes into the forest ecosystem largely from the sea as aerosol (and has been in the past assumed to be inert), causes chlorination of soil organic matter. Studies of the chlorination showed that the content of organically bound chlorine in temperate forest soils is higher than that of chloride, and various chlorinated compounds are produced. Our study of chlorination of organic matter in the fermentation horizon of forest soil using radioisotope 36Cl and tracer techniques shows that microbial chlorination clearly prevails over abiotic, chlorination of soil organic matter being enzymatically mediated and proportional to chloride content and time. Long-term (>100 days) chlorination leads to more stable chlorinated substances contained in the organic layer of forest soil (overtime; chlorine is bound progressively more firmly in humic acids) and volatile organochlorines are formed. Penetration of chloride into microorganisms can be documented by the freezing/thawing technique. Chloride absorption in microorganisms in soil and in litter residues in the fermentation horizon complicates the analysis of 36Cl-chlorinated soil. The results show that the analytical procedure used should be tested for every soil type under study.

Short time mixing response in a big flotation cell

A new approach to characterizing the mixing evolution and mass transport patterns in big flotation cells was developed. The procedure consists of using a non-invasive radioisotope tracer technique which allows for the continuous measurement of the local concentration of liquid and solid phases at different points in the cell. This approach was developed to characterize the mixing performance of a 130 m 3 self-aerated flotation cell at El Teniente copper concentrator, Codelco, Chile. Short-term mixing was experimentally characterized by using appropriate radioisotope tracers for liquid and solids. 82Br in solution was used as liquid tracer and 24Na was used to trace the solid, considering three particle size classes: + 150, − 150 + 45 and − 45 μm, for non-floatable gangue mineral. From the experimental data, a dynamic mixing model was developed to represent the internal short time mixing, as well as the overall mixing conditions in the pulp and froth zones in a big flotation cell. Results showed a mixing time of around 100 s, for liquid and solids, while the pulp mean residence time was 350 s. It was found that the feed pulp circulates 1.4 times through the impeller zone before reaching a well mixed condition in the cell. Also the feed pulp, on average, circulates approximately 5.0 times through the impeller zone, before leaving the cell into the tailings flowrate. From grade and solid percent axial profiles measurement, it was also shown that the pulp zone was reasonably well mixed with minor segregation of coarse minerals, and a very distinctive pulp–froth interface was clearly observed showing the significant Cu and Mo upgrading in the froth zone.

Positron Imaging Studies of Rotating Drums

The potential of the radioisotope tracer technique of positron emission tomography (PET) and the related techniques of positron emission projection imaging (PEPI) and positron emission particle tracking (PEPT) is illustrated with reference to laboratory scale studies of particulate motion in rotating drums, operating either in batch or continuous flow modes. Sand grains, glass beads and TiO2 granules down to 0.5mm diameter were labelled. Using PEPT the transition between rolling and slumping modes has been identified and the velocity profile within the active layer has been determined for a range of drum diameters. PEPI has been used to measure and explain residence time distributions, while all three techniques have been used to study segregation based on particle size, both radially and axially within the drum. Data on particle motion within a novel baffled drum is also presented.

Transepithelial transport of salicylate by the Malpighian tubules of insects from different orders

The organic anion salicylate is a plant secondary metabolite that protects plants against phytophagous insects. In this study, a combination of salicylate-selective microelectrodes and a radioisotope tracer technique was used to study the transepithelial transport of salicylate by the Malpighian tubules of 10 species of insects from five orders. Our results show that salicylate is transported into the lumen of the Malpighian tubules in all the species evaluated, except Rhodnius prolixus. The transepithelial transport of salicylate by the Malpighian tubules of Drosophila simulans, Drosophila erecta, Drosophila sechellia, and Acheta domesticus was saturable, Na +-dependent and inhibited by α-cyano-4-hydroxycinnamic acid. This transport system resembles that previously found in tubules of Drosophila melanogaster. In contrast, transepithelial transport of salicylate by Malpighian tubules of Tenebrio molitor, Plagiodera versicolora, Aedes aegypti, and Trichoplusia ni was unaffected by Na +-free bathing saline. The presence of both salicylate and salicylate metabolites in the secreted fluid samples from the Malpighian tubules of A. domesticus, R. prolixus, T. molitor, and T. ni indicates that insect Malpighian tubules may both transport and metabolize salicylate. The highest capacities to rid the hemolymph of salicylate were found in T. molitor, P. versicolora and Drosphila spp. Our results suggest that transport of salicylate by the Malpighian tubules might contribute to elimination of this organic anion from the hemolymph, particularly in some species that encounter high levels of organic anion in the diet.