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Thomas A Ternes - One of the best experts on this subject based on the ideXlab platform.
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capturing the oxic transformation of Iopromide a useful tool for an improved characterization of predominant redox conditions and the removal of trace organic compounds in biofiltration systems
Water Research, 2019Co-Authors: J Muller, Thomas A Ternes, Manoj Schulz, Kevin S Jewell, Nina Hermes, Jorg E Drewes, U HubnerAbstract:Abstract The biological degradation of many trace organic compounds has been reported to be strongly redox dependent. The traditional characterization of redox conditions using the succession of inorganic electron acceptors such as dissolved oxygen and nitrate falls short in accurately describing the critical transition state between oxic and suboxic conditions. Novel monitoring strategies using intrinsic redox tracers might be suitable to close that gap. This study investigated the potential use of the successive biological transformation of the iodinated contrast medium Iopromide as an intrinsic tracer of prevailing redox conditions in biofiltration systems. Iopromide degradation in biofiltration systems was monitored by quantifying twelve known biological transformation products formed under oxic conditions. A novel dimensionless parameter (TIOP) was introduced as a measure for the successive transformation of Iopromide. A strong correlation between the consumption of dissolved oxygen and Iopromide transformation emphasized the importance of general microbial activity on Iopromide degradation. However, results disproved a direct correlation between oxic (>1 mg/L O2) and suboxic (
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anaerobic transformation of the iodinated x ray contrast medium Iopromide its aerobic transformation products and transfer to further iodinated x ray contrast media
Environmental Science & Technology, 2018Co-Authors: Maria Redeker, Arne Wick, Bjorn Meermann, Thomas A TernesAbstract:The iodinated X-ray contrast medium (ICM) Iopromide and its aerobic transformation products (TPs) are frequently detected in the effluents of wastewater treatment plants and in different compartments of the aquatic environment. In this study, the anaerobic transformation of Iopromide and its aerobic TPs was investigated in water–sediment systems. Iopromide, its final aerobic TP didespropanediol Iopromide (DDPI), and its primary aniline desmethoxyacetyl Iopromide (DAMI) were used as model substances. Five biologically formed anaerobic TPs of Iopromide and DAMI and six of DDPI, and the respective transformation pathways, were identified. The TPs were formed by successive deiodination and hydrolysis of amide moieties. Quantification of the iodinated TPs was achieved by further development of a complementary liquid chromatography (LC)–quadrupole time-of-flight mass spectrometry (Q-ToF-MS) and LC–inductively coupled plasma – mass spectrometry (ICP-MS) strategy without needing authentic standards, despite sever...
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Anaerobic Transformation of the Iodinated X‑ray Contrast Medium Iopromide, Its Aerobic Transformation Products, and Transfer to Further Iodinated X‑ray Contrast Media
2018Co-Authors: Maria Redeker, Arne Wick, Bjorn Meermann, Thomas A TernesAbstract:The iodinated X-ray contrast medium (ICM) Iopromide and its aerobic transformation products (TPs) are frequently detected in the effluents of wastewater treatment plants and in different compartments of the aquatic environment. In this study, the anaerobic transformation of Iopromide and its aerobic TPs was investigated in water–sediment systems. Iopromide, its final aerobic TP didespropanediol Iopromide (DDPI), and its primary aniline desmethoxyacetyl Iopromide (DAMI) were used as model substances. Five biologically formed anaerobic TPs of Iopromide and DAMI and six of DDPI, and the respective transformation pathways, were identified. The TPs were formed by successive deiodination and hydrolysis of amide moieties. Quantification of the iodinated TPs was achieved by further development of a complementary liquid chromatography (LC)–quadrupole time-of-flight mass spectrometry (Q-ToF-MS) and LC–inductively coupled plasma – mass spectrometry (ICP-MS) strategy without needing authentic standards, despite several TPs coeluting with others. A database with predicted anaerobic TPs of ICMs was derived by applying the transformation rules found for the anaerobic transformation pathways of Iopromide and diatrizoate to further ICMs (iomeprol and iopamidol) and their aerobic TPs already reported in the literature. The environmental relevance of the identified transformation pathways was confirmed by identifying an experimental TP and two predicted TPs using suspect screening of water taken from anaerobic bank filtration zones
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electrochemical treatment of Iopromide under conditions of reverse osmosis concentrates elucidation of the degradation pathway
Water Research, 2014Co-Authors: Lutke C Eversloh, Manoj Schulz, N Henning, Thomas A TernesAbstract:Abstract Application of reverse osmosis for the reuse of treated wastewater on the one hand offers a way to provide high quality effluent waters. On the other hand reverse osmosis concentrates exhibiting highly concentrated contaminants are produced simultaneously. Electrochemical treatment of those concentrates is regarded as one possible answer to the problem of their disposal into surface waters. Nevertheless, due to the diversity of direct and indirect degradation processes during electrolysis, special care has to be taken about the formation of toxic transformation products (TPs). In this study the electrochemical transformation of the X-ray contrast medium Iopromide was investigated as a representative of biologically persistent compounds. For this purpose, anodic oxidation at boron doped diamond as well as cathodic reduction using a platinum electrode were considered. Kinetic analyses revealed a transformation of 100 μM Iopromide with first order kinetic constants between 0.6 and 1.6 × 10 −4 s −1 at the beginning and a subsequent increase of the reaction order due to the influence of secondary oxidants formed during electrolysis. Mineralization up to 96% was achieved after about 7.5 h. At shorter treatment times several oxidatively and reductively formed transformation products were detected, whereas deiodinated Iopromide represented the major fraction. Nevertheless, the latter exhibited negligible toxicological relevance according to tests on vibrio fisheri. Additional experiments utilizing a divided cell setup enabled the elucidation of the transformation pathway, whereas emerging TPs could be identified by means of high resolution mass spectrometry and MS n -fragmentations. During electrolysis the iodine released from Iopromide was found to 90% as iodide and to 10% as iodate even in the open cell experiments, limiting the potential formation of toxic iodo-disinfection by-products. Chlorinated TPs were not found.
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occurrence of iodinated x ray contrast media and their biotransformation products in the urban water cycle
Environmental Science & Technology, 2011Co-Authors: Jennifer Lynne Kormos, Manoj Schulz, Thomas A TernesAbstract:A LC tandem MS method was developed for the simultaneous determination of four iodinated X-ray contrast media (ICM) and 46 ICM biotransformation products (TPs) in raw and treated wastewater, surface water, groundwater, and drinking water. Recoveries ranged from 70% to 130%, and limits of quantification (LOQ) varied between 1 ng/L and 3 ng/L for surface water, groundwater and drinking water, and between 10 ng/L and 30 ng/L for wastewater. In a conventional wastewater treatment plant, iohexol, iomeprol, and Iopromide were transformed to >80%, while iopamidol was transformed to 35%. In total, 26 TPs were detected above their LOQ in WWTP effluents. A significant change in the pattern of ICM TPs was observed after bank filtration and groundwater infiltration under aerobic conditions. Predominately, these TPs are formed at the end of the microbial transformation pathways in batch experiments with soil and sediment. These polar ICM TPs, such as iohexol TP599, iomeprol TP643, Iopromide TP701A, and Iopromide TP643...
Bruno Scheller - One of the best experts on this subject based on the ideXlab platform.
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dose response to paclitaxel coated balloon catheters in the porcine coronary overstretch and stent implantation model
Investigative Radiology, 2011Co-Authors: Bettina Kelsch, Ulrich Speck, Bruno Scheller, Melanie Biedermann, Yvonne P Clever, Silvio Schaffner, Dirk Mahnkopf, Bodo CremersAbstract:Objective:There is little published information regarding the efficacy of paclitaxel-coated balloon catheters except for the Iopromide-containing formulation, and less is known about the kind of toxicity at overdose. The aim of our study was to assess 2 different paclitaxel matrix formulations on an
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addition of paclitaxel to contrast media prevents restenosis after coronary stent implantation
Journal of the American College of Cardiology, 2003Co-Authors: Bruno Scheller, Ulrich Speck, Alexander Schmitt, Michael Bohm, Georg NickenigAbstract:Abstract Objectives The present study was designed to test the efficacy of paclitaxel added to the contrast agent Iopromide in the prevention of restenosis. Background Contrast media adhere to the coronary vessel wall for some seconds after injection. Such a layer of contrast agent could serve as a matrix for antiproliferative drugs. Methods Thirty-four stents were implanted into the left anterior descending and circumflex coronary arteries of 17 pigs, using a 1.2:1.0 overstretch ratio. The unsupplemented contrast agent Iopromide-370 was used as a control; the treatment groups were treated with 80 ml intracoronary Iopromide plus either 100 or 200 μmol/l paclitaxel, or 80 ml intravenous Iopromide plus 200 μmol/l paclitaxel. Quantitative angiography and histomorphometry were used to assess comparable baseline parameters between the treatment groups. Results A short time incubation (3 min) almost completely inhibited vascular smooth muscle cell proliferation, sustained for up to 12 days. Whereas intravenous paclitaxel had no effect, intracoronary application of paclitaxel reduced the diameter stenosis from 55 ± 13% to 29 ± 18% and 13 ± 12%. Late lumen loss dropped from 1.94 ± 0.35 mm under the control condition to 1.19 ± 0.55 mm with 100 μmol/l paclitaxel and to 0.82 ± 0.54 mm with 200 μmol/l paclitaxel. Histomorphometry revealed a corresponding dose-dependent reduction of the neointimal area and restenosis by intracoronary Iopromide paclitaxel. Assessment of left ventricular function and myocardial histology revealed no adverse effects of intracoronary paclitaxel application. Conclusions This study provides evidence that intracoronary application of a taxane dissolved in a contrast medium profoundly inhibits in-stent restenosis. This novel, widely feasible approach may be suited for the prevention of restenosis in a broad spectrum of interventional treatment regimens.
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contrast media as carriers for local drug delivery successful inhibition of neointimal proliferation in the porcine coronary stent model
European Heart Journal, 2003Co-Authors: Bruno Scheller, Ulrich Speck, Alexander Schmitt, Michael Bohm, Bernd F M Romeike, Milos Sovak, Hans Peter StollAbstract:Background Lipophilic taxanes can be dissolved in contrast media at significantly higher concentration than in saline. As contrast media have occasionally been observed to delineate the contour of coronary arteries for some seconds they may serve as a matrix for an antiproliferative drug aimed at preventing restenosis. The aim of this study was to test a novel taxane-contrast agent formulation for this new approach in the setting of coronary stenting. Methods and results In cell culture experiments (bovine vascular smooth muscle cells), 60-min incubation with contrast agent-taxane formulations (Iopromide–paclitaxel, Iopromide–protaxel) induced a significant, concentration-dependent inhibition of vascular smooth muscle cell (VSMC) proliferation over 12 days. Shorter incubation times of 10 and 3min showed the same efficacy. For in vivo investigation, 16 stents were implanted into the coronary arteries of eight pigs using a 1.3 to 1 overstretch ratio. A control group received Iopromide 370 alone while the treatment group was injected with a Iopromide-protaxel formulation at a dose of 74μmol/l, which is far below protaxel levels inducing systemic toxicity. Quantitative angiography and histomorphometry of the stented arteries asserted statistic equality of the baseline parameters between the control and treatment groups. After 28 days, the treatment group showed a marked reduction of the parameters characterizing in-stent restenosis, especially a 34% reduction of the neointimal area. Conclusions First evidence is provided that using a contrast agent as solvent for a taxane constitutes a new drug delivery mechanism able to inhibit in-stent restenosis in the porcine restenosis model.
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acute cardiac tolerance of current contrast media and the new taxane protaxel using Iopromide as carrier during porcine coronary angiography and stenting
Investigative Radiology, 2002Co-Authors: Bruno Scheller, Ulrich Speck, Alexander Schmitt, Michael Bohm, Milos Sovak, Wolfram Clauss, Hans Peter StollAbstract:Scheller B, Speck U, Schmitt A, et al. Acute cardiac tolerance of current contrast media and the new taxane protaxel using Iopromide as carrier during porcine coronary angiography and stenting. Invest Radiol 2002;37:29–34.rationale and objectives.The systemic tolerance thresholds of modern low-osmol
Diana S. Aga - One of the best experts on this subject based on the ideXlab platform.
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Biodegradability of Iopromide products after UV/H2O2 advanced oxidation
Chemosphere, 2015Co-Authors: Olya S. Keen, Nancy G. Love, Diana S. Aga, Karl G. LindenAbstract:Iopromide is an X-ray and MRI contrast agent that is virtually non-biodegradable and persistent through typical wastewater treatment processes. This study determined whether molecular transformation of Iopromide in a UV/H2O2 advanced oxidation process (AOP) can result in biodegradable products. The experiments used Iopromide labeled with carbon-14 on the aromatic ring to trace degradation of Iopromide through UV/H2O2 advanced oxidation and subsequent biodegradation. The biotransformation assay tracked the formation of radiolabeled (14)CO2 which indicated full mineralization of the molecule. The results indicated that AOP formed biodegradable Iopromide products. There was no (14)C released from the pre-AOP samples, but up to 20% of all radiolabeled carbon transformed into (14)CO2 over the course of 42 days of biodegradation after Iopromide was exposed to advanced oxidation (compared to 10% transformation in inactivated post-AOP controls). In addition, the quantum yield of photolysis of Iopromide was determined using low pressure (LP) and medium pressure (MP) mercury lamps as 0.069 ± 0.005 and 0.080 ± 0.007 respectively. The difference in the quantum yields for the two UV sources was not statistically significant at the 95% confidence interval (p = 0.08), which indicates the equivalency of using LP or MP UV sources for Iopromide treatment. The reaction rate between Iopromide and hydroxyl radicals was measured to be (2.5 ± 0.2) × 10(9) M(-1) s(-1). These results indicate that direct photolysis is a dominant degradation pathway in UV/H2O2 AOP treatment of Iopromide. Other iodinated contrast media may also become biodegradable after exposure to UV or UV/H2O2.
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application of metabolite profiling tools and time of flight mass spectrometry in the identification of transformation products of Iopromide and iopamidol during advanced oxidation
Environmental Science & Technology, 2015Co-Authors: Randolph R Singh, Nancy G. Love, Karl G. Linden, Yaal Lester, Ekin G Atillagokcumen, Diana S. AgaAbstract:The efficiency of wastewater treatment systems in removing pharmaceuticals is often assessed on the basis of the decrease in the concentration of the parent compound. However, what is perceived as “removal” during treatment may not necessarily mean mineralization of the pharmaceutical compound but simply conversion into different transformation products (TPs). Using liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (LC-QToF-MS), we demonstrated conversion of Iopromide in wastewater to at least 14 TPs after an advanced oxidation process (AOP) using UV (fluence = 1500 mJ/cm2) and H2O2 (10 mg/L). Due to the complexity of the wastewater matrix, the initial experiments were performed using a high concentration (10 mg/L) of Iopromide in order to facilitate the identification of TPs. Despite the high concentration of Iopromide used, cursory inspection of UV and mass spectra only revealed four TPs in the chromatograms of the post-AOP samples. However, the use of METLIN database and st...
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Application of Metabolite Profiling Tools and Time-of-Flight Mass Spectrometry in the Identification of Transformation Products of Iopromide and Iopamidol during Advanced Oxidation
2015Co-Authors: Randolph R. Singh, Nancy G. Love, Karl G. Linden, Yaal Lester, Ekin G. Atilla-gokcumen, Diana S. AgaAbstract:The efficiency of wastewater treatment systems in removing pharmaceuticals is often assessed on the basis of the decrease in the concentration of the parent compound. However, what is perceived as “removal” during treatment may not necessarily mean mineralization of the pharmaceutical compound but simply conversion into different transformation products (TPs). Using liquid chromatography coupled to a quadrupole time-of-flight mass spectrometer (LC-QToF-MS), we demonstrated conversion of Iopromide in wastewater to at least 14 TPs after an advanced oxidation process (AOP) using UV (fluence = 1500 mJ/cm2) and H2O2 (10 mg/L). Due to the complexity of the wastewater matrix, the initial experiments were performed using a high concentration (10 mg/L) of Iopromide in order to facilitate the identification of TPs. Despite the high concentration of Iopromide used, cursory inspection of UV and mass spectra only revealed four TPs in the chromatograms of the post-AOP samples. However, the use of METLIN database and statistics-based profiling tools commonly used in metabolomics proved effective in discriminating between background signals and TPs derived from Iopromide. High-resolution mass data allowed one to predict molecular formulas of putative TPs with errors below 5 ppm relative to the observed m/z. Tandem mass spectrometry (MS/MS) data and isotope pattern comparisons provided necessary information that allowed one to elucidate the structure of Iopromide TPs. The presence of the proposed Iopromide TPs was determined in unspiked wastewater from a municipal wastewater treatment plant, but no Iopromide and TPs were detected. Using analogous structural modifications and oxidation that results from the AOP treatment of Iopromide, the potential TPs of iopamidol (a structurally similar compound to Iopromide) were predicted. The same mass fragmentation pattern observed in Iopromide TPs was applied to the predicted iopamidol TPs. LC-QToF-MS revealed the presence of two iopamidol TPs in unspiked AOP-treated wastewater
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enhanced biodegradation of Iopromide and trimethoprim in nitrifying activated sludge
Environmental Science & Technology, 2006Co-Authors: Angela L Batt, Sungpyo Kim, Diana S. AgaAbstract:Iopromide (an X-ray contrast agent) and trimethoprim (an antibacterial drug) are frequently detected pharmaceuticals in effluents of wastewater treatment plants (WWTPs) and in surface waters due to their persistence and high usage. Laboratory-scale experiments showed that a significantly higher removal rate in nitrifying activated sludge as compared to conventional activated sludge was observed for both Iopromide and trimethoprim. When the activity of the nitrifying bacteria was inhibited, the percent removal of Iopromide decreased from 97 to 86% while trimethoprim removal decreased from 70 to 25%. The metabolite of Iopromide identified when nitrification was not inhibited was a dehydroxylated Iopromide at the two side chains. However, when the nitrifying bacteria were inhibited the metabolite identified was a carboxylate, formed during the oxidation of the primary alcohol on the side chain of Iopromide. These results suggest that the nitrifying bacteria are important in the observed biodegradation of iop...
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structural characterization of metabolites of the x ray contrast agent Iopromide in activated sludge using ion trap mass spectrometry
Analytical Chemistry, 2006Co-Authors: Sandra Perez, Peter Eichhorn, Diana S. AgaAbstract:Identification of degradation products of environmental contaminants is a challenging task because not only are they present in very low concentrations but they are also mixed with complex matrixes that interfere with detection. This work illustrates a simple approach using ion trap mass spectrometry combined with H/D-exchange experiments to elucidate the structures of Iopromide metabolites formed during biodegradation in activated sludge. Iopromide is an X-ray contrast agent that has been detected frequently in effluents of wastewater treatment plants and in surface waters due to its persistence and high usage. Three metabolites produced by oxidation of the primary alcohols (forming carboxylates) on the side chains of Iopromide were identified in a batch reactor with mixed liquor from a conventional activated sludge. Derivatization of the carboxylic acid to form a methyl ester and interpretation of the MS2 data of this derivative aided in the confirmation of the identities of these metabolites. Furthermo...
Gregor Jost - One of the best experts on this subject based on the ideXlab platform.
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the effect of iodinated contrast agent properties on renal kinetics and oxygenation
Investigative Radiology, 2012Co-Authors: Diana Constanze Lenhard, Hubertus Pietsch, Philipp Lengsfeld, Annalena Frisk, Gregor JostAbstract:OBJECTIVE: We analyzed renal kinetics and renal oxygenation in rats after administration of several classes and formulations of contrast agents (CAs) with a focus on the influence of osmolality and substance-specific properties. MATERIALS AND METHODS: We investigated the renal kinetics of a nonionic, dimeric CA (iodixanol) formulated in 3 different osmolalities (hypo-osmolar, iso-osmolar, low-osmolar) and compared it to nonionic, low-osmolar (Iopromide), and ionic, low-osmolar CAs (ioxaglate) using computed tomography for a period of 24 hours. The CAs were administered intravenously at a dosage of 4 g iodine/kg body weight. The average exposure was calculated, and urine viscosities were compared before the injection and during the time intervals of 0 to 60 minutes and 60 to 120 minutes after the injection. Renal oxygenation levels of the renal cortex and medulla were estimated using blood-oxygen-level-dependent magnetic resonance imaging. We used histologic methods to systematically analyze the gravity of vacuole formation based on the physicochemical and substance-specific properties of each CA. RESULTS: Iso-osmolar and hypo-osmolar iodixanol and, to a lesser extent, iodixanol/mannitol accumulated rapidly in the kidneys during the first 5 minutes of the injection and remained higher 2, 4, 6, and 24 hours after the injection compared with Iopromide and ioxaglate, which showed fast iodine excretion. Similarly, lower renal blood oxygen levels were estimated for all iodixanol formulations as compared with ioxaglate and Iopromide. The incidence of vacuole formation was high for all iodixanol formulations and for ioxaglate (6 of 6 rats) and low for Iopromide (1 of 6 rats). Moderate severity of vacuoles was determined for the iodixanol solutions; minimal severity, for ioxaglate and Iopromide. CONCLUSIONS: We identified a superior profile for the low-osmolar CAs compared with the iso-osmolar CAs regarding rapid excretion, short-term renal exposure, and renal oxygenation.
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the osmolality of nonionic iodinated contrast agents as an important factor for renal safety
Investigative Radiology, 2012Co-Authors: Diana C Lenhard, Hubertus Pietsch, Martin A Sieber, Rainer Ernst, Philipp Lengsfeld, Peter Ellinghaus, Gregor JostAbstract:Objective Nonionic iodinated contrast agents (CAs) can be divided into monomeric, low-osmolar, and dimeric, iso-osmolar classes. In clinical practice, renal tolerance of CAs is a concern, especially in patients with impaired renal function. With regard to renal safety, we wanted to evaluate the role of osmolality and viscosity in renal tolerance. Material and methods We generated a formulation (iodixanol/mannitol) consisting of the dimeric iodixanol with an osmolality of the monomeric Iopromide. Male Han-Wistar rats were intravenously injected with low-osmolar Iopromide 300, iso-osmolar iodixanol 320, and iodixanol/mannitol. Saline and diatrizoate were used as controls. A total number of 227 rats were used in the following experiments. We compared the impact of osmolality on renal iodine retention using computed tomography 2 and 24 hours postinjection (p.i.). The animals were killed 2, 24, and 72 hours after injection, and the kidneys were excised for further investigations. Changes in renal cell proliferation were analyzed by 5-bromo-2'-deoxyuridine incorporation 48 hours p.i. as a degree of tissue regeneration after induced injury. To specify potential renal injury, we quantified the expression of acute kidney injury (AKI) markers (kidney injury marker-1 [KIM-1], neutrophil gelatinase-associated lipocalin [NGAL], and plasminogen activator inhibitor-1 [PAI-1]) by quantitative real-time polymerase chain reaction. Furthermore, the kidneys were analyzed histologically, including immunofluorescence analysis. Results After intravenous application of the CAs into Han-Wistar rats, renal iodine concentration was increased (3-fold) for iodixanol 2 hours p.i. and iodine retention was detected to be prolonged 24 hours p.i. compared with Iopromide injection (iodixanol, 520 ± 50 Hounsfield Units [HU] vs Iopromide, 42 ± 5 HU). The higher iodine concentration 2 hours p.i. upon iodixanol injection was reduced almost to the level of Iopromide when injecting iodixanol/mannitol (Iopromide: 289 ± 68 HU vs iodixanol/mannitol: 343 ± 68 HU). In addition, iodixanol application induced increased renal cell proliferation (2.7-fold vs saline), indicating renal injury, which was significantly lower in Iopromide-treated animals (1.6-fold vs saline). More detailed analysis of markers for AKI revealed that iodixanol significantly induced the expression of PAI-1 (7.7-fold at 2 hours) as well as KIM-1 (2.1-fold) and NGAL (3.2-fold) at 2 and 24 hours when compared with saline treatment. In contrast, the expression of markers for AKI was low after Iopromide (1.4-fold NGAL, 1.7-fold PAI-1, KIM-1 not significant) and iodixanol/mannitol (1.6-fold NGAL, 2.6-fold PAI-1, KIM-1 not significant) injection. Conclusion The present results clearly show that prolonged iodine retention and the enhanced expression of kidney injury markers are caused mainly by the explicitly higher urine viscosity induced by iodixanol. We conclude that the osmolality of low-osmolar CAs such as Iopromide induces a positive diuretic effect that is responsible for rapid iodine clearance and prevents increased expression of acute injury markers in the kidney.
H F Leung - One of the best experts on this subject based on the ideXlab platform.
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synergy of sulfate and hydroxyl radicals in uv s2o82 h2o2 oxidation of iodinated x ray contrast medium Iopromide
Chemical Engineering Journal, 2011Co-Authors: Wei Chu, Yr R Wang, H F LeungAbstract:Abstract The degradation of iodinated X-ray contrast medium, Iopromide, by UV irradiation with the assistance of combined oxidants of S2O82− and H2O2 has been investigated. The effects of various parameters, including different wavelengths of UV irradiation, UV intensities, initial solution pH levels, dosages of oxidants, dosing sequence, and the presence of non-target organic matters, have been evaluated. The Iopromide decay follows pseudo-first-order kinetics. The UV at 254 nm exhibits higher decay rate of Iopromide than the others (300 and 350 nm) due to stronger photon energy of 254 nm and the relatively higher absorptivity of S2O82−, H2O2 and Iopromide nearby this wavelength. Optimum pH level was determined to be around 4.34. The mechanism is complicated because of the involvement of the scavenging, recombination, self-decomposition and/or stability of the involved oxidant (S2O82− and H2O2) and radicals (SO4 − and HO ) as discussed in the paper. Iopromide decay rate is linearly proportional to the [S2O82−], however a nonlinear-optimal rate was observed by varying [H2O2] due to the formation of weaker radicals via overdosing of H2O2. Additionally, the sequential addition of S2O82− to UV/H2O2 or H2O2 to UV/S2O82− was found no better than the UV/S2O82−/H2O2. This is because the quenching of already formed SO4 − by newly added H2O2 (or vice versa the quenching of HO by S2O82−). The simultaneous addition of S2O82− and H2O2, however, will slightly delay the generation rates of SO4 − and OH due to the competition of photons between S2O82− and H2O2, which can reduce both the radical-scavenging reactions and the peak radical concentration in the solution, thus maximizing the utilization of precious radicals. The presence of non-target organics, especially the humic acid, in the UV/S2O82−/H2O2 process will quench the radicals, a pre-treatment is recommended to lessen this problem in real application.
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Synergy of sulfate and hydroxyl radicals in UV/S2O82- /H2O2 oxidation of iodinated X-ray contrast medium Iopromide
Elsevier, 2011Co-Authors: Chu W, Yr Wang, H F LeungAbstract:The degradation of iodinated X-ray contrast medium, Iopromide, by UV irradiation with the assistance of combined oxidants of S 2O 8 2- and H 2O 2 has been investigated. The effects of various parameters, including different wavelengths of UV irradiation, UV intensities, initial solution pH levels, dosages of oxidants, dosing sequence, and the presence of non-target organic matters, have been evaluated. The Iopromide decay follows pseudo-first-order kinetics. The UV at 254 nm exhibits higher decay rate of Iopromide than the others (300 and 350 nm) due to stronger photon energy of 254 nm and the relatively higher absorptivity of S 2O 8 2-, H 2O 2 and Iopromide nearby this wavelength. Optimum pH level was determined to be around 4.34. The mechanism is complicated because of the involvement of the scavenging, recombination, self-decomposition and/or stability of the involved oxidant (S 2O 8 2- and H 2O 2) and radicals (SO 4 •- and HO•) as discussed in the paper. Iopromide decay rate is linearly proportional to the [S 2O 8 2-], however a nonlinear-optimal rate was observed by varying [H2O2] due to the formation of weaker radicals via overdosing of H 2O 2. Additionally, the sequential addition of S 2O 8 2- to UV/H 2O 2 or H 2O 2 to UV/S 2O 8 2- was found no better than the UV/S 2O 8 2-/H 2O 2. This is because the quenching of already formed SO 4 •- by newly added H 2O 2 (or vice versa the quenching of HO• by S 2O 8 2-). The simultaneous addition of S 2O 8 2- and H 2O 2, however, will slightly delay the generation rates of SO 4 •- and OH• due to the competition of photons between S 2O 8 2- and H 2O 2, which can reduce both the radical-scavenging reactions and the peak radical concentration in the solution, thus maximizing the utilization of precious radicals. The presence of non-target organics, especially the humic acid, in the UV/S 2O 8 2-/H 2O 2 process will quench the radicals, a pre-treatment is recommended to lessen this problem in real application.Department of Civil and Environmental Engineerin
