Determination of long distance transport of Cs+, Co2+ and Zn2+ ions in vascular plants by autoradiography and gamma-spectrometry

Heavy metals and radionuclides can enter the food chain via cereals and vegetables grown in contaminated soils. In the case of microelements such as zinc, studies have not focused only to assessing its environmental risk, but also to enhancing its uptake by plants as an important growth-limiting factor. In our study, digitalized autoradiograms of whole plants of celery (Apium graveolens L.), tobacco (Nicotiana tabacum L.) and sunflower (Helianthus annuus L.) grown in hydroponic nutrient media spiked with 137CsCl, 60CoCl2 and 65ZnCl2 were used for quantitative determination of uptake, long-distance transport and distribution of Cs+, Co2+ and Zn2+ ions in plant tissues. Results from autoradiography and gammaspectrometry of plants showed, that cesium was translocated to aboveground part of the plants with the shoot-to-root ratio 1.0 : 0.6. On the contrary, cobalt and zinc were more immobilized in roots, with the shoot-to-root ratio up to 1.0 : 3.8. The highest concentration of cesium, cobalt and zinc, expressed in specific radioactivity per unit of leaf surface (Bq/cm2) was found in top, rapidly growing leaves, the lowest concentration in the oldest leaves in low position. Detection limits 3, 2 and 14 Bq/cm2 by using X-ray film for 137Cs, 60Co and 65Zn, respectively were obtained. These data correspond to detection limits 10.5 pg Cs+/cm2, 7.2 pg Co2+/cm2 and 785 pg Zn2+/cm2 at specific radioactivity of commercially available 137CsCl, 60CoCl2 and 65ZnCl2. Resolutions 1-2 mm was sufficient for visualization of metal uptake and distribution in roots, stalks, leaves and leaf venation. Obtained data are part of quantitative study of uptake and translocation of both low level-radioactive contamination in plants and microelements applied as fertilizers.

Interactions of Nereistoxin and Its Analogs with Vertebrate Nicotinic Acetylcholine Receptors and Molluscan ACh Binding Proteins

Nereistoxin (NTX) is a marine toxin isolated from an annelid worm that lives along the coasts of Japan. Its insecticidal properties were discovered decades ago and this stimulated the development of a variety of insecticides such as Cartap that are readily transformed into NTX. One unusual feature of NTX is that it is a small cyclic molecule that contains a disulfide bond. In spite of its size, it acts as an antagonist at insect and mammalian nicotinic acetylcholine receptors (nAChRs). The functional importance of the disulfide bond was assessed by determining the effects of inserting a methylene group between the two sulfur atoms, creating dimethylaminodithiane (DMA-DT). We also assessed the effect of methylating the NTX and DMA-DT dimethylamino groups on binding to three vertebrate nAChRs. Radioligand receptor binding experiments were carried out using washed membranes from rat brain and fish (Torpedo) electric organ; [3H]-cytisine displacement was used to assess binding to the predominantly high affinity alpha4beta2 nAChRs and [125I]-alpha-bungarotoxin displacement was used to measure binding of NTX and analogs to the alpha7 and skeletal muscle type nAChRs. While the two quaternary nitrogen analogs, relative to their respective tertiary amines, displayed lower α4β2 nAChR binding affinities, both displayed much higher affinities for the Torpedo muscle nAChR and rat alpha7 brain receptors than their respective tertiary amine forms. The binding affinities of DMA-DT for the three nAChRs were lower than those of NTX and MeNTX. An AChBP mutant lacking the C loop disulfide bond that would potentially react with the NTX disulfide bond displayed an NTX affinity very similar to the parent AChBP. Inhibition of [3H]-epibatidine binding to the AChBPs was not affected by exposure to NTX or MeNTX for up to 24 hr prior to addition of the radioligand. Thus, the disulfide bond of NTX is not required to react with the vicinal disulfide in the AChBP C loop for inhibition of [3H]-epibatidine binding. However, a reversible disulfide interchange reaction of NTX with nAChRs might still occur, especially under reducing conditions. Labeled MeNTX, because it can be readily prepared with high specific radioactivity and possesses relatively high affinity for the nAChR-rich Torpedo nAChR, would be a useful probe to detect and identify any nereistoxin adducts.

Synthesis of typical sulfonamide antibiotics with [14C]- and [13C]-labelling on phenyl ring for environmental studies

Background As a kind of widely used antibiotics, sulfonamide antibiotics (SAs) has become ubiquitous environmental contaminants that caused public concerns. The behavior of SAs in complex environmental system need to be elucidated, which is hampered by unavailability or high cost of isotope-labelled SAs. Results Using commercially available uniformly [l4C]- and [l3C]-labelled aniline as starting material, we synthesized [phenyl-ring-14C]- and [phenyl-ring-l3C]-labelled sulfamethoxazole (SMX), sulfamonomethoxine (SMM), and sulfadiazine (SDZ) using four-step (via condensation of labelled N-acetylsulfanilyl chloride and aminoheterocycles) or five-step (via condensation of labelled N-acetylsulfonamide and chloroheterocycles) reactions in good yields (5.0−22.5% and 28.1−54.1% for [14C]- and [13C]-labelled SAs, respectively) and high purities (> 98.0%). Conclusion The synthesis of [l4C]-labelled SAs could be completed on milligram-level, being feasible for preparation of labelled SAs with high specific radioactivity. This study provides efficient and maneuverable methods to obtain a variety of [14C]- or [13C]-labelled SAs for studies on their environmental behavior, such as fate, transformation, and bioaccumulation.

Deposition velocities of some natural radionuclides from the atmosphere at Ninh Thuan and Dong Nai of Vietnam

The deposition velocities of Be-7, K-40, Th-232, U-238 and Pb-210 radionuclides from the atmosphere at Ninh Thuan and Dong Nai monitoring stations of Vietnam were investigated. The deposition velocity was calculated based on it’s specific radioactivity in aerosols and deposition density in fallout samples. The data of the deposition velocities of radionuclides from the atmosphere are needed as input data for the models to simulate atmospheric radioactive dispersion and assess the public dose around nuclear facilities. The radioactivity of Be-7, K-40, Th-232, U-238 and Pb-210 nuclides in aerosols and fallout samples were analyzed by using a low level background gamma spectrometer equipped with HPGe detector of high resolution. The results show that the deposition velocities of Be-7, K-40, Th-232, U-238 and Pb-210 nuclides from the air are in ranges of 0.04÷1.71; 1.84÷27.46; 1.46÷23.63; 0.80÷26.13 and 0.06÷1.53 (cm/s), with average values of 0.55; 13.81; 8.22; 8.12 and 0.58 (cm/s), respectively. The deposition velocities of the radionuclides in the survey areas are comparable with those found in tropical and subtropical regions and these results could be served as the database of the World radioactive transport parameters.

Natural radioactivity of coal in the context of radioecological safety and rational use

Introduction. Environmental contamination with natural radioactive elements is an urgent ecological problem of the coal industry. Radiation hazard associated with natural radionuclides in coals and enclosing rock is a poorly studied problem requiring special attention. Radionuclides and their combustion products in coals, i. e. ash and slag waste and gas aerosol emissions, released into the biosphere, become the sources of pollution. Radiation monitoring is required in the course of geological prospecting, deposits development and rational use. The research aims to systematize research and analytical material on specific radioactivity of coal and their combustion products, and update the problem of radioecological safety monitoring. Methodology includes studying data on specific radioactivity of coal at various deposits, studying natural radioactivity of coal, enclosing rock and ash and slag waste, describing ash and slag waste and radon as a source of radioactive contamination, assessing potential radon hazard of mine workings, and analyzing ash composition characteristics for toxicologic estimation of ash dumps and their effect on the environment. Results. Generalized data on radionuclide concentration in coal burned at the CHP facilities, slag and fly ash are presented. Radionuclide specific concentration is much higher in ash and slag waste of coal heat power industry than in initial coal. It is caused by the radionuclide concentration in the products of coal combustion. Potential hazard of radon released from rock is revealed, and ash composition is characterised for toxicologic estimation of ash dumps. Conclusions. Uncontrolled coal combustion exacerbates the problem of radioecological safety due to radioactive aerosol emission and the formation of ash and slag waste with increased concentration of natural radionuclides. System monitoring of radioactivity level in the course of geological prospecting, mining, processing and combustion will allow reducing radionuclides entering the fuel cycle and environment.

Synthesis of 13С- and 14С-labeled linoleic acids for use in diagnostic breath tests for hepatobiliary system disorders

At present, there is a need for a simple, noninvasive, highly specific and sensitive diagnostic test for hepatobiliary system disorders. Compounds labeled with carbon isotopes are widely used in various diagnostic breath tests; they are safe and can reliably detect a metabolic disorder or enzyme deficiency. The aim of this study was to synthesize 13С- and 14С-labeled linoleic acids suitable for use in hepatobiliary breath tests in terms of purity. In the synthesis of 13С-labeled linoleic acid, the chemical yield for 1-bromo-8,11-heptadecadien was 86.4% and the chemical yield for barium carbonate-13С, 96.0%. In the synthesis of 14С-labeled linoleic acid, the chemical yield for 1-bromo-8,11-heptadecadien was 87.39%; for barium carbonate-14С it was 97.1%. The specific radioactivity of 14С-labeled linoleic acids was 45.36 ± 0.02 mCi/g. The radiochemical yield of the reaction was 96.0%. The proposed method is suitable for batch production.

Sensitivity and Resolution Study of a Small-Field γ-Camera System on a Tomographic Level

The sensitivity and the spatial resolution of a small-field γ-Camera system based on a Position Sensitive Photomultiplier Tube (PSPMT) on a tomographic level are examined in this study. A cylindrical Gel-Phantom (d = 40 mm, h = 50 mm) with cylindro-conoidal tubes and capillaries (from 64 to 640 mm3 in volume) containing water solution of 99mTc is used as a test phantom in the present work. A total of 24 projections covering the full angle region (0°-360°) are obtained with the γ-Camera system under examination. The planar information is further analyzed to reconstruct the tomographic images taking into account all off-line corrections needed to remove barreloid deformations appearing at the edges of the Field-of- View. The reconstruction procedure is performed with iterative algorithms and for comparison reasons two different techniques (MLEM and accelerated ART) are used. The variety of the 99mTc-volumes in the phantom with the given specific radioactivity and the phantom axial asymmetry, due to the diÆerent radial distances of the tubes in the gel environment, allow a realistic characterization of the system’s performance on a tomographic level. Obtained experimental results for the system sensitivity and spatial resolution are presented and discussed in this work.

Immune system stimulation increases the plasma cysteine flux and whole-body glutathione synthesis rate in starter pigs1

Glutathione (GSH) is the major intracellular thiol that plays a role in numerous detoxification, bio-reduction, and conjugation reactions. The availability of Cys is thought to be the rate-limiting factor for the synthesis of GSH. The effects of immune system stimulation (ISS) on GSH levels and the GSH synthesis rate in various tissues, as well as the plasma flux of Cys, were measured in starter pigs fed a sulfur AA (SAA; Met + Cys) limiting diet. Ten feed-restricted gilts with initial body weight (BW) of 7.0 ± 0.12 kg were injected i.m. twice at 48-h intervals with either sterile saline (n = 4; ISS−) or increasing amounts of Escherichia coli lipopolysaccharide (n = 6; ISS+). The day after the second injection, pigs received a primed constant infusion of 35S-Cys (9,300 kBq/pig/h) for 5 h via a jugular catheter. Blood and tissue free Cys and reduced GSH were isolated and quantified as the monobromobimane derivatives by HPLC. The rate of GSH synthesis was determined by measurement of the specific radioactivity of GSH and tissue free Cys at the end of the infusion period. Plasma Cys and total SAA levels were reduced (16% and 21%, respectively), but plasma Cys flux was increased (26%) by ISS (P < 0.05). Immune system stimulation increased GSH levels in the plasma (48%; P < 0.05), but had no effect on GSH levels in the liver, small and large intestines, heart, muscle, spleen, kidney, lung, and erythrocytes. The fractional synthesis rate (FSR) of GSH was higher (P < 0.05) in the liver (34%), small intestine (78%), large intestine (72%), heart (129%), muscle (37%), and erythrocytes (47%) of ISS+ pigs compared to ISS− pigs. The FSR of GSH tended (P = 0.08) to be higher in the lungs (45%) of ISS+ pigs than in ISS− pigs. The absolute rate of GSH synthesis was increased by ISS (mmol/kg wet tissue/d ± SE, ISS− vs. ISS+; P < 0.05) in the liver (5.22 ± 0.22 vs. 7.20 ± 0.59), small intestine (2.54 ± 0.25 vs. 4.52 ± 0.56), large intestine (0.61 ± 0.06 vs. 1.06 ± 0.16), heart (0.21 ± 0.03 vs. 0.48 ± 0.08), lungs (1.50 ± 0.10 vs. 2.90 ± 0.21), and muscle (0.21 ± 0.03 vs. 0.34 ± 0.04), but it remained unchanged in erythrocytes, the kidney, and the spleen (P > 0.80). The current findings suggest that GSH synthesis is increased during ISS, contributing to enhanced maintenance sulfur amino acid requirements in starter pigs during ISS.