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"Cadmium"
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Cadmium Complexes—A Novel Family in the Coordination Chemistry of 1,2-bisacenaphthenes
This work presents the synthesis routes for the first representatives of cadmium complexes based on 1,2-bis(arylimino)acenaphthene (Ar-bian). The reaction of CdCl[sub.2] with bis-(2,4,6-trimethylphenylimino)acenaphthene (tmp-bian) in a 1-to-1 molar ratio led to a dimeric complex [Cd[sub.2](tmp-bian)[sub.2]Cl[sub.2](µ-Cl)[sub.2]] (1). Further treatment of complex 1 with silver triflate as a chloride-eliminating agent, followed by the addition of one equivalent of tmp-bian, resulted in the formation of a mixture consisting of [Cd[sub.2](tmp-bian)[sub.2](H[sub.2]O)[sub.4](µ-Cl)[sub.2]](OTf)[sub.2] (2) and [Cd(tmp-bian)[sub.2](OTf)[sub.2]] (3). To obtain complex 3 in its individual form, a reaction of Cd(OTf)[sub.2] with two equivalents of tmp-bian was carried out. The characterization of the complexes was conducted through a range of analytical methods, including X-ray diffraction analysis, elemental analysis, as well as IR and [sup.1]H NMR-spectroscopies. Redox properties of 1 and 3 were investigated by means of cyclic voltammetry. Cyclic voltammograms revealed irreversible reduction processes centered on the tmp-bian ligand, which were confirmed by quantum chemical calculations.
Journal Article
Metallothionein and Cadmium Toxicology—Historical Review and Commentary
More than one and a half centuries ago, adverse human health effects were reported after use of a cadmium-containing silver polishing agent. Long-term cadmium exposure gives rise to kidney or bone disease, reproductive toxicity and cancer in animals and humans. At present, high human exposures to cadmium occur in small-scale mining, underlining the need for preventive measures. This is particularly urgent in view of the growing demand for minerals and metals in global climate change mitigation. This review deals with a specific part of cadmium toxicology that is important for understanding when toxic effects appear and, thus, is crucial for risk assessment. The discovery of the low-molecular-weight protein metallothionein (MT) in 1957 was an important milestone because, when this protein binds cadmium, it modifies cellular cadmium toxicity. The present authors contributed evidence in the 1970s concerning cadmium binding to MT and synthesis of the protein in tissues. We showed that binding of cadmium to metallothionein in tissues prevented some toxic effects, but that metallothionein can increase the transport of cadmium to the kidneys. Special studies showed the importance of the Cd/Zn ratio in MT for expression of toxicity in the kidneys. We also developed models of cadmium toxicokinetics based on our MT-related findings. This model combined with estimates of tissue levels giving rise to toxicity, made it possible to calculate expected risks in relation to exposure. Other scientists developed these models further and international organizations have successfully used these amended models in recent publications. Our contributions in recent decades included studies in humans of MT-related biomarkers showing the importance of MT gene expression in lymphocytes and MT autoantibodies for risks of Cd-related adverse effects in cadmium-exposed population groups. In a study of the impact of zinc status on the risk of kidney dysfunction in a cadmium-exposed group, the risks were low when zinc status was good and high when zinc status was poor. The present review summarizes this evidence in a risk assessment context and calls for its application in order to improve preventive measures against adverse effects of cadmium exposures in humans and animals.
Journal Article
Hexakis Dibromide Tetrahydrate
Cadmium(II) complexes with thiolate ligands have received considerable attention because of their intriguing structural features and relevance to metalloproteins. In this study, a new cadmium(II)–rhodium(III) trinuclear complex, [CdRh(apt)[sub.3][sub.2]]Br[sub.2]·4H[sub.2]O (1, apt = 3-aminopropanethiolate), was synthesized by the reaction of fac-[Rh(apt)[sub.3]] with cadmium bromide. Compound 1 was characterized using elemental analysis, X-ray fluorescence and IR spectroscopies, and powder X-ray diffraction study. Single-crystal X-ray analysis revealed that the cadmium(II) center in 1 was surrounded by six thiolato S atoms from two fac-[Rh(apt)[sub.3]] units.
Journal Article
The liver in itai-itai disease (chronic cadmium poisoning): pathological features and metallothionein expression
Cadmium (Cd) is a highly hepatotoxic heavy metal, which is widely dispersed in the environment. Acute Cd hepatotoxicity has been well studied in experimental animals; however, effects of prolonged exposure to Cd doses on the liver remain unclear. In the present study, to evaluate chronic Cd hepatotoxicity, we examined specimens from cases of itai-itai disease, the most severe form of chronic Cd poisoning. We compared 89 cases of itai-itai disease with 27 control cases to assess Cd concentration in organs. We also examined 80 cases of itai-itai disease and 70 control cases for histopathological evaluation. In addition, we performed immunohistochemistry for metallothionein, which binds and detoxifies Cd. Hepatic Cd concentration was higher than Cd concentration in all other organs measured in the itai-itai disease group, whereas it was second highest following renal concentration in the control group. In the liver in the itai-itai disease group, fibrosis was observed at a significantly higher rate than that in the control group. Metallothionein expression was significantly higher in the itai-itai disease group than that in the control group. Prolonged exposure to low doses of Cd leads to high hepatic accumulation, which can then cause fibrosis; however, it also causes high expression of metallothionein, which is thought to reduce Cd hepatotoxicity.
Journal Article
The Uptake, Transfer, and Detoxification of Cadmium in Plants and Its Exogenous Effects
Cadmium (Cd) exerts a toxic influence on numerous crucial growth and development processes in plants, notably affecting seed germination rate, transpiration rate, chlorophyll content, and biomass. While considerable advances in Cd uptake and detoxification of plants have been made, the mechanisms by which plants adapt to and tolerate Cd toxicity remain elusive. This review focuses on the relationship between Cd and plants and the prospects for phytoremediation of Cd pollution. We highlight the following issues: (1) the present state of Cd pollution and its associated hazards, encompassing the sources and distribution of Cd and the risks posed to human health; (2) the mechanisms underlying the uptake and transport of Cd, including the physiological processes associated with the uptake, translocation, and detoxification of Cd, as well as the pertinent gene families implicated in these processes; (3) the detrimental effects of Cd on plants and the mechanisms of detoxification, such as the activation of resistance genes, root chelation, vacuolar compartmentalization, the activation of antioxidant systems and the generation of non-enzymatic antioxidants; (4) the practical application of phytoremediation and the impact of incorporating exogenous substances on the Cd tolerance of plants.
Journal Article
Health Risk Assessment of Dietary Cadmium Intake: Do Current Guidelines Indicate How Much is Safe?
Cadmium (Cd), a food-chain contaminant, is a significant health hazard. The kidney is one of the primary sites of injury after chronic Cd exposure. Kidney-based risk assessment establishes the urinary Cd threshold at 5.24 μg/g creatinine, and tolerable dietary intake of Cd at 62 μg/day per 70-kg person. However, cohort studies show that dietary Cd intake below a threshold limit and that tolerable levels may increase the risk of death from cancer, cardiovascular disease, and Alzheimer's disease.
We evaluated if the current tolerable dietary Cd intake guideline and urinary Cd threshold limit provide sufficient health protection.
Staple foods constitute 40-60% of total dietary Cd intake by average consumers. Diets high in shellfish, crustaceans, mollusks, spinach, and offal add to dietary Cd sources. Modeling studies predict the current tolerable dietary intake corresponding to urinary Cd of 0.70-1.85 μg/g creatinine in men and 0.95-3.07 μg/g creatinine in women. Urinary Cd levels of < 1 μg/g creatinine were associated with progressive kidney dysfunction and peripheral vascular disease. A urinary Cd of 0.37 μg/g creatinine was associated with breast cancer, whereas dietary Cd of 16-31.5 μg/day was associated with 25-94% increase in risk of estrogen receptor-positive breast cancer.
Modeling shows that dietary intake levels for Cd exceed the levels associated with kidney damage and many other adverse outcomes. Thus, the threshold level of urinary Cd should be re-evaluated. A more restrictive dietary intake guideline would afford enhanced health protection from this pervasive toxic metal. Citation: Satarug S, Vesey DA, Gobe GC. 2017. Health risk assessment of dietary cadmium intake: do current guidelines indicate how much is safe? Environ Health Perspect 125:284-288; http://dx.doi.org/10.1289/EHP108.
Journal Article
Reproductive effects of cadmium on sperm function and early embryonic development in vitro
Cadmium is a major environmental toxicant that is released into the atmosphere, water and soil in the form of cadmium oxide, cadmium chloride, or cadmium sulfide via industrial activities, such as the manufacturing of batteries and pigments, metal smelting and refining and municipal waste incineration. In the present study, we investigated the effects of cadmium exposure on sperm quality parameters, fertilization capacity and early embryonic development. Our study showed that in vitro incubation of human or mouse sperms with cadmium for a long time (up to 24 hours) could significantly decreased sperm motility in a concentration- and time-dependent manner. Exposure to cadmium in the environment for a short term (30 min) did not affect sperm motility but significantly reduced in vitro fertilization rate. We also evaluated the effects of cadmium at concentrations of 0.625 μg/ml, and 1.25 μg/ml on early embryonic development in vitro and observed that the blastocyst formation rate dramatically decreased with increasing cadmium concentration. This finding emphasizes the hazardous effects of cadmium on sperm quality as well as on natural embryo development and raises greater concerns regarding cadmium pollution.
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