Evaluation of general stress, detoxification pathways, and genotoxicity in rainbow trout exposed to rare earth elements dysprosium and lutetium.

Rare earth elements (REEs) have been recently identified as emergent contaminants because of their numerous and increasing applications in technology. The impact of REEs on downstream ecosystems, notably aquatic organisms, is of particular concern, but has to date been largely overlooked. The purpose of this study was thus to evaluate the toxicity of lanthanide metals, lutetium (Lu) and dysprosium (Dy) in rainbow trout after 96 h of exposure. The lethal concentration (LC50) was determined and the expression of 14 genes involved in different pathways such as oxidative stress, xenobiotic detoxification, mitochondrial respiration, DNA repair, protein folding and turnover, inflammation, calcium binding and ammonia metabolism were quantified in surviving fish. In parallel, lipid peroxidation (LPO), DNA damage (DSB), metallothionein level (MT) and cyclooxygenase activity (COX) were examined. The acute 96 h-LC50 data revealed that Lu was more toxic than Dy (1.9 and 11.0 mg/L, respectively) and was able to affect all investigated pathways by changing the expression of the studied genes, to the exception of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST). It also induced a decrease in DNA repair at concentrations 29 times below the LC50. This suggests that Lu could trigger a general stress to disrupt the cell homeostasis leading to genotoxicity without promoting oxidative stress. However, Dy induced modulation in the expression of genes involved in the protection against oxidative stress, detoxification, mitochondrial respiration, immunomodulation, protein turnover and an increase in the DNA strand breaks at concentrations 170 times lower than LC50. Changes in mRNA level transcripts could represent an early signal to prevent against toxicity of Dy, which exhibited inflammatory and genotoxic effects. This study thus provides useful knowledge enhancing our understanding of survival strategies developed by rainbow trout to cope with the presence of lanthanides in the environment.

New insights on the impacts of e-waste towards marine bivalves: The case of the rare earth element Dysprosium.

With the technological advances and economic development, the multiplicity and wide variety of applications of electrical and electronic equipment have increased, as well as the amount of end-of-life products (waste of electrical and electronic equipment, WEEE). Accompanying their increasing application, there is an increasing risk to aquatic ecosystems and inhabiting organisms. Among the most common elements present in WEEE are rare earth elements (REE) such as Dysprosium (Dy). The present study evaluated the metabolic and oxidative stress responses of mussels Mytilus galloprovincialis exposed to an increasing range of Dy concentrations, after a 28 days experimental period. The results obtained highlighted that Dy was responsible for mussel's metabolic increase associated with glycogen expenditure, activation of antioxidant and biotransformation defences and cellular damage, with a clear loss of redox balance. Such effects may greatly impact mussel's physiological functions, including reproduction capacity and growth, with implications for population conservation. Overall the present study pointed out the need for more research on the toxic impacts resulting from these emerging pollutants, especially towards marine and estuarine invertebrate species.

Structural, Mechanical, Imaging and in Vitro Evaluation of the Combined Effect of Gd3+ and Dy3+ in the ZrO2-SiO2 Binary System.

Mechanical strength and biocompatibility are considered the main prerequisites for materials in total hip replacement or joint prosthesis. Noninvasive surgical procedures are necessary to monitor the performance of a medical device in vivo after implantation. To this aim, simultaneous Gd3+ and Dy3+ additions to the ZrO2-SiO2 binary system were investigated. The results demonstrate the effective role of Gd3+ and Dy3+ to maintain the structural and mechanical stability of cubic zirconia ( c-ZrO2) up to 1400 °C, through their occupancy of ZrO2 lattice sites. A gradual tetragonal to cubic zirconia ( t-ZrO2 → c-ZrO2) phase transition is also observed that is dependent on the Gd3+ and Dy3+ content in the ZrO2-SiO2. The crystallization of either ZrSiO4 or SiO2 at elevated temperatures is delayed by the enhanced thermal energy consumed by the excess inclusion of Gd3+ and Dy3+ at c-ZrO2 lattice. The addition of Gd3+ and Dy3+ leads to an increase in the density, elastic modulus, hardness, and toughness above that of unmodified ZrO2-SiO2. The multimodal imaging contrast enhancement of the Gd3+ and Dy3+ combinations were revealed through magnetic resonance imaging and computed tomography contrast imaging tests. Biocompatibility of the Gd3+ and Dy3+ dual-doped ZrO2-SiO2 systems was verified through in vitro biological studies.

Acute dysprosium toxicity to Daphnia pulex and Hyalella azteca and development of the biotic ligand approach.

The toxicological understanding of rare earth elements (REEs) in the aquatic environment is very limited but of increasing concern. The objective of this research is to compare the toxicological effect of the REE dysprosium to the freshwater invertebrates Daphnia pulex and Hyalella azteca and in the more sensitive organism, understand the toxicity modifying influence of Ca, Na, Mg, pH and dissolved organic matter (DOM). Standard methods (Environment Canada) were followed for testing and culture in media of intermediate hardness (60mg CaCO3 mg/L) at pH 7.8 with Ca at 0.5, Na 0.5, Mg 0.125 (mM) and 23°C. Acute toxicity tests were done with <24h old neonates for 48h in the case of D. pulex and with 2-9 days old offspring for 96h tests with Hyalella. The potential protective effect of cationic competition was tested with Ca (0.5-2.0mM), Na (0.5-2.0mM) and Mg (0.125-0.5mM). The effect of pH (6.5-8.0) and Suwannee River DOM complexation (at dissolved organic carbon (DOC) concentrations of 9 and 13mg C/L) were evaluated. Dissolved Dy concentrations were lower than total (unfiltered) indicating precipitation, particularly at higher concentrations. Acute toxicity of Dy to H. azteca and D. pulex revealed Hyalella to be 1.4 times more sensitive than Daphnia. Additions of Ca and Na but not Mg provided significant protection against Dy toxicity to Hyalella. Similarly, low pH was associated with reduction in toxicity. Exposures which were pH buffered with and without MOPS were significantly different and indicated that MOPS enhanced Dy toxicity. DOM also mitigated Dy toxicity. Biotic ligand based parameters (LogK values) were calculated based on free ion relationships as determined by geochemical equilibrium modeling software (WHAM ver. 7.02). The logK value for Dy(3+) toxicity to Hyalella was 7.75 while the protective influence of Ca and Na were 3.95 and 4.10, respectively. This study contributes data towards the development of site specific water quality guidelines and criteria for Dy and possibly REEs in general and offers insight into the complex bio-geochemical nature of this element.

Effects of chronic γ-irradiation on the aquatic microbial microcosm: equi-dosimetric comparison with effects of heavy metals.

Effects of chronic γ-irradiation were investigated in the aquatic microcosm consisting of flagellate algae Euglena gracilis as producers, ciliate protozoa Tetrahymena thermophila as consumers and bacteria Escherichia coli as decomposers. At 1.1 Gy day(-1), no effects were observed. At 5.1 Gy day(-1), cell densities of E. coli showed a tendency to be lower than those of controls. At 9.7 and 24.7 Gy day(-1), population decrease was observed in E. coli. E. gracilis and T. thermophila died out after temporal population decrease and subsequent population increase in T. thermophila. It is likely that this temporal population increase was an indirect effect due to interspecies interactions. Effect dose rates of γ-rays were compared with effect concentrations of some metals using the radiochemoecological conceptual model and the effect index for microcosm. Comparison of these community-level effects data with environmental exposure data suggests that ionising radiation, gadolinium and dysprosium have low risks to affect aquatic microbial communities while manganese, nickel and copper have considerable risks. Effects of chronic irradiation were smaller than those of acute irradiation, and an acute to chronic ratio was calculated to be 28 by dividing an acute dose by chronic daily dose rate at which the effect index was 10%. This ratio would be useful for community-level extrapolation from acute to chronic radiation effects.

Synthesis, characterization and cytotoxic/cytostatic activity of La(III) and Dy(III) complexes.

New La(III) and Dy(III) complexes of deprotonated 4-hydroxy-3[1-(4-nitrophenyl)-3-oxobutyl]-2H-1-benzopyran-2-one (Acenocoumarol) were synthesized and characterized using FT-IR, FT-Raman, (1)H NMR spectra, and elemental analyses. The ligand and its lanthanide(III) complexes were tested for their cytotoxic/cytostatic activity against two tumor cell lines and peritoneal mouse macrophages. The La(III) and Dy(III) complexes exhibit good activity against melanoma B16 and fibrosarcoma L929 and they are stronger inhibitors of tumor cell proliferation compared to the ligand without influencing normal cell viability and NO release by mouse peritoneal macrophages.

Toxicity of dysprosium shift reagents in the isolated perfused rat kidney.

Sodium and water spectra were acquired from the isolated perfused rat kidney by using a double-tuned probe designed to have high X nucleus sensitivity and low 1H sensitivity. Both DyTTHA and DyPPP were used to distinguish intra and extracellular 23Na resonances before and after the onset of hypoxia. Only DyPPP was useful in separating the two compartments, with a maximal chemical shift difference produced at a concentration of 4.5 mM. Both shift reagents were nephrotoxic at concentrations under 5 mM and produced an immediate decrease in renal-concentrating capacity and increases in fractional sodium and potassium excretion and increased renal vascular resistance. These disturbances of renal physiological parameters were accompanied by progressive broadening of the renal H2O resonance. 1H NMR may be a subtle means of monitoring nephrotoxicity.

Studies of nutritional safety of some heavy metals in mice.

Heavy metals have been proposed as nutrient markers to allow the accurate determination of the time of passage, nutrient intake, or apparent utilization of multiple nutrients. In order to evaluate possible toxic effects of scandium, chromium, lanthanum, samarium, europium, dysprosium, terbium, thulium, and ytterbium oxides, and barium sulfate upon growth, general development, reproduction, and lactation, mice were fed different levels of these compounds for three generations. The amount of elements fed were 0,110, 100, and 1000 times the use amount. The use amounts were (in ppm2.) : Sc, 0.12; Cr, 0.02; La.0.40;; Sm. 0.80; Eu, 0.036:TB, 1.20; Dy, 1.20; Tm. 0.08; Tb, 0.12; and Ba, 0.008. The use amount was one-fifth of the concentration required for activation analysis. Mortality and morbidity were negligible. No consistent growth rate changes were observed; however, different groups showed different growth rates during different generations. The number of mice born showed no significant differences amoung treatment groups. Survival, growth rate, hematology, morphological development, maturation, reproduction, and lactational performance were comparable in mice fed the different levels of 10 heavy metal oxides to those mice fed the basal diet.