Elimination Of Metals Research Articles

Влияние молибдата аммония на функцию почек у паратиреоидэктомированных крыс

The constant pollution of the environment increases the content of xenobiotics in the air, soil, water and contributes to their entry into the organism. Increased content of molybdenum in the environment has pathogenic effect on the human organism. It is known that the excretion of metals is mainly via the kidney, while the content of the xenobiotics in the urine may have pathogenic effects on renal function. It is of interest to study the renal functions in conditions of inflow metals in the organism.
 The aim of this work was to study the effect of experimental hypocalcaemia on uropoisis renal function at the chronic molybdenum intoxication.
 Materials and methods. Experiments were carried out on Wistar-rats. Chronic molybdenum intoxication in experimental animals was caused by intragastric injection of ammonium molybdate solution in the dose of 50mg/kg. during 1 month. Experimental hypocalcaemia was created by the parathyroidectomy.
 Results. It was noted that when a stand-alone injection of ammonium molybdate glomerular filtration rate is reduced. In the model combined with parathyroidectomy this indicator comes back to normal. Tubular water reabsorption, urinary excretion of calcium and
 protein are less pronounced than in the isolated introduction ammonium molybdate. Urine osmolarity also had a tendency to decrease. Conclusions. Experimental hypocalcaemia reduces the renal manifestations of chronic molybdenum intoxication.

The absence of a metal-on-metal bearing does not preclude the formation of a destructive pseudotumor in the hip—a case report

Sir—In reply and maybe completion of the article by Bisseling, Tan, Lu, Campbell and Susante in the August 2013 issue, I want to compliment the authors on bringing the subject of metal corrosion in head-neck tapers forward again. I would like, however, to comment as follows. The authors mention that there is little literature concerning the contribution of the head-neck taper junction to the metal levels in serum. They are right. There are nevertheless publications on this subject that they did not mention in their article. In 1991 Jacobs et al. published a study on the release and excretion of metal in patients with titanium alloy hip prostheses. The same group (1998) published a prospective, controlled longitudinal study on patients with a primary total hip arthroplasty in which they concluded that raised metal levels were rather common. Also, Kreibich et al. (1996), Pazzaglia et al. (1986), Schaffer et al. (1999), and Saikko et al. (1998) looked into the subject, while the formation of pseudotumors around cementless total hip arthroplasties was published as early as 1992 by Jacobs et al. Vundelinckx et al. (2013) reported on 19 patients with PE couplings, as mentioned by the authors. In 2003 I wrote a thesis in which, in chapter 2.5, an analysis was made of 142 titanium hip stems with CoCr heads (32 mm) and polyethylene acetabular components in a titanium shell. The patients were 5 to 9 years postoperative when analyzed, none had pseudotumors, and all were unilaterally operated on. In that study, we found 38.0% of the patients had a serum Co level higher than the reference level for metal workers of 0.27 micrograms/liter for Co (mean 8.07 (SD 5.12)) and 89.4% of the patients had a serum Cr level higher than the reference value of 0.35 micrograms/liter for Cr (mean 8.7 (SD 2,74)). Also, serum titanium levels proved to be higher than the reference value (3.3 micrograms/liter) in 88.0% of patients (mean 6.7 (SD 2,7)). Since no source other than the taper could be found and I proven that the metal levels were not associated with loosening of the prosthesis I concluded the raised metal levels were a result of abrasion or galvanic ionization at the stem-neck taper. The possibility and the occurrence of metal ion release from head-neck taper corrosion is an almost forgotten though not uncommon source of metal ions in the serum of patients after total hip arthroplasty. The majority of patients do have raised metal levels, whichever material coupling of cup and head there is. The occurrence of pseudotumors might be more related to the local immunological reaction of patients to metal ions, than to the metal itself.

Chemistry and Pharmacological Properties of Some Natural and Synthetic Antioxidants for Heavy Metal Toxicity

Heavy metals are known to cause oxidative deterioration of bio-molecules by initiating free radical mediated chain reaction resulting in lipid per-oxidation, protein oxidation and oxidation of nucleic acid like DNA and RNA. The development of effective dual functioning antioxidants, possessing both metal-chelating and free radical-scavenging properties should bring into play. Administration of natural and synthetic antioxidants like, quercetin, catechin, taurine, captopril, gallic acid, melatonin, N-acetyl cysteine, α- lipoic acid and others have been recognized in the disease prevention and clinical recovery against heavy metal intoxication. These antioxidants affect biological systems not only through direct quenching of free radicals but also via chelation of toxic metal(s). These antioxidants also, have the capacity to enhance cellular antioxidant defense mechanism by regenerating endogenous antioxidants, such as glutathione and vitamin C and E. They also influence cellular signaling and trigger redox sensitive regulatory pathways. The reactivity of antioxidants in protecting against heavy metal induced oxidative stress depends upon their structural properties, their partitioning abilities between hydrophilic and lipophilic environment and their hydrogen donation antioxidant properties. Herein, we review the structural, biochemical and pharmacological properties of selected antioxidants with particular reference to their ability to (i) chelate heavy metals from its complex (ii) ameliorate free radical (iii) terminate heavy metal induced free radical chain reaction (iv) regenerate endogenous antioxidants and, (v) excretion of metal without its redistribution.

The Role of Chelation in the Treatment of Arsenic and Mercury Poisoning

Chelation for heavy metal intoxication began more than 70years ago with the development of British anti-lewisite (BAL; dimercaprol) in wartime Britain as a potential antidote the arsenical warfare agent lewisite (dichloro[2-chlorovinyl]arsine). DMPS (unithiol) and DMSA (succimer), dithiol water-soluble analogs of BAL, were developed in the Soviet Union and China in the late 1950s. These three agents have remained the mainstay of chelation treatment of arsenic and mercury intoxication for more than half a century. Animal experiments and in some instances human data indicate that the dithiol chelators enhance arsenic and mercury excretion. Controlled animal experiments support a therapeutic role for these chelators in the prompt treatment of acute poisoning by arsenic and inorganic mercury salts. Treatment should be initiated as rapidly as possible (within minutes to a few hours), as efficacy declines or disappears as the time interval between metal exposure and onset of chelation increases. DMPS and DMSA, which have a higher therapeutic index than BAL and do not redistribute arsenic or mercury to the brain, offer advantages in clinical practice. Although chelation following chronic exposure to inorganic arsenic and inorganic mercury may accelerate metal excretion and diminish metal burden in some organs, potential therapeutic efficacy in terms of decreased morbidity and mortality is largely unestablished in cases of chronic metal intoxication.

Chelation for autism spectrum disorder (ASD).

It has been suggested that the severity of autism spectrum disorder (ASD) symptoms is positively correlated with the level of circulating or stored toxic metals, and that excretion of these heavy metals, brought about by the use of pharmaceutical chelating agents, results in improved symptoms. To assess the potential benefits and adverse effects of pharmaceutical chelating agents (referred to as chelation therapy throughout this review) for autism spectrum disorder (ASD) symptoms. We searched the following databases on 6 November 2014: CENTRAL, Ovid MEDLINE, Ovid MEDLINE In-Process, Embase,PsycINFO, Cumulative Index to Nursing and Allied Health Literature (CINAHL) and 15 other databases, including three trials registers. In addition we checked references lists and contacted experts. All randomised controlled trials of pharmaceutical chelating agents compared with placebo in individuals with ASD. Two review authors independently selected studies, assessed them for risk of bias and extracted relevant data. We did not conduct a meta-analysis, as only one study was included. We excluded nine studies because they were non-randomised trials or were withdrawn before enrolment.We included one study, which was conducted in two phases. During the first phase of the study, 77 children with ASD were randomly assigned to receive seven days of glutathione lotion or placebo lotion, followed by three days of oral dimercaptosuccinic acid (DMSA). Forty-nine children who were found to be high excreters of heavy metals during phase one continued on to phase two to receive three days of oral DMSA or placebo followed by 11 days off, with the cycle repeated up to six times. The second phase thus assessed the effectiveness of multiple doses of oral DMSA compared with placebo in children who were high excreters of heavy metals and who received a three-day course of oral DMSA. Overall, no evidence suggests that multiple rounds of oral DMSA had an effect on ASD symptoms. This review included data from only one study, which had methodological limitations. As such, no clinical trial evidence was found to suggest that pharmaceutical chelation is an effective intervention for ASD. Given prior reports of serious adverse events, such as hypocalcaemia, renal impairment and reported death, the risks of using chelation for ASD currently outweigh proven benefits. Before further trials are conducted, evidence that supports a causal link between heavy metals and autism and methods that ensure the safety of participants are needed.

Detoxical aspects of nutritional therapy using natural enterosorbents on the basis of pectins

The rate of anthropogenic pollution and reduction of the environmental quality progress quicker than adaptive possibilities of an organism. This causes pre-pathological and pathological changes. So there is a necessity of preventive measures organization to eliminate toxic load and accelerated eliminating of xenobiotics from an organism. The discoveries of the recent 15 years had been revealed the possibility to change complexons (which are used for detoxication) to dietary fibers, pectin as well. Meanwhile pectin substances are not widely used in clinical practice, and their efficiency comparing with small concentrations of cumulating poisons had not been studied yet. During the development of the detoxification nutritional therapy at patients with different pathology of the digestive system organs (with the revealed heavy metals and organochlorine pesticides) there had been organized tests of pectin efficiency (citrus and apple) for reducing the contamination with these xenobiotics. After the course of pectin treatment there had been fixed not only the reduce of toxic heavy metals, but essential microelements as well, which is connected with nonselective complexing capability of pectin substances. The probe tests also showed that course of citrus pectin treatment favored total excretion of organochlorine pesticides at 11.0% of patients, at other patients pesticide level reduced up to minimal rate (revealed by gas chromatographic method 0.0001 mg/dm³). There is a significant difference of values before and after pectin treatment. At the same time at patients who had not taken enterosorbent (compare group) the level of organochlorine pesticides after repeated tests stayed on the level close to the basic. There had been discussed mechanism of excretion of organochlorine pesticides and heavy metals with the help of pectins.

Metal-on-Metal Hip Prostheses and Systemic Health: A Cross-Sectional Association Study 8 Years after Implantation

There is public concern over the long term systemic health effects of metal released from hip replacement prostheses that use large-diameter metal-on-metal bearings. However, to date there has been no systematic study to determine which organs may be at risk, or the magnitude of any effect. We undertook a detailed cross-sectional health screen at a mean of 8 years after surgery in 35 asymptomatic patients who had previously received a metal-on-metal hip resurfacing (MoMHR) versus 35 individually age and sex matched asymptomatic patients who had received a conventional hip replacement. Total body bone mineral density was 5% higher (mean difference 0.05 g/cm2, P = 0.02) and bone turnover was 14% lower (TRAP 5b, mean difference −0.56IU/L, P = 0.006; osteocalcin, mean difference −3.08 ng/mL, P = 0.03) in the hip resurfacing versus conventional hip replacement group. Cardiac ejection fraction was 7% lower (mean absolute difference −5%, P = 0.04) and left ventricular end-diastolic diameter was 6% larger (mean difference 2.7 mm, P = 0.007) in the hip resurfacing group versus those patients who received a conventional hip replacement. The urinary fractional excretion of metal was low (cobalt 5%, chromium 1.5%) in patients with MoMHR, but creatinine clearance was normal. Diuretic prescription was associated with a 40% increase in the fractional excretion of chromium (mean difference 0.5%, P = 0.03). There was no evidence of difference in neuropsychological, renal tubular, hepatic or endocrine function between groups (P>0.05). Our findings of differences in bone and cardiac function between patient groups suggest that chronic exposure to low elevated metal concentrations in patients with well-functioning MoMHR prostheses may have systemic effects. Long-term epidemiological studies in patients with well-functioning metal on metal hip prostheses should include musculoskeletal and cardiac endpoints to quantitate the risk of clinical disease.

Mass spectrometry as a tool for studying autism spectrum disorder.

Autism spectrum disorders (ASDs) are increasing in incidence but have an incompletely understood etiology. Tools for uncovering clues to the cause of ASDs and means for diagnoses are valuable to the field. Mass Spectrometry (MS) has been a useful method for evaluating differences between individuals with ASDs versus matched controls. Different biological substances can be evaluated using MS, including urine, blood, saliva, and hair. This technique has been used to evaluate relatively unsupported hypotheses based on introduction of exogenous factors, such as opiate and heavy metal excretion theories of ASDs. MS has also been used to support disturbances in serotonin-related molecules, which have been more consistently observed in ASDs. Serotonergic system markers, markers for oxidative stress, cholesterol system disturbances, peptide hypo-phosphorylation and methylation have been measured using MS in ASDs, although further analyses with larger numbers of subjects are needed (as well as consideration of behavioral data). Refinements in MS and data analysis are ongoing, allowing for the possibility that future studies examining body fluids and specimens from ASD subjects could continue to yield novel insights. This review summarizes MS investigations that have been conducted to study ASD to date and provides insight into future promising applications for this technique, with focus on proteomic studies.

Comparison of Tissue Metal Concentrations in Zucker Lean, Zucker Obese, and Zucker Diabetic Fatty Rats and the Effects of Chromium Supplementation on Tissue Metal Concentrations

Diabetes results in several metabolic changes, including alterations in the transport, distribution, excretion, and accumulation of metals. While changes have been examined in several rat models of insulin resistance and diabetes, the metal ion concentrations in the tissues of Zucker lean, Zucker obese (an insulin resistance and early stage diabetes model), and Zucker diabetic fatty (ZDF, a type 2 diabetes model) have not previously been examined in detail. The concentration of Cu, Zn, Fe, Mg, and Ca were examined in the liver, kidney, heart and spleen, and Cr concentration in the liver and kidney of these rats were examined. Zucker obese rats have a reduction in the concentration of Cu, Zn, Fe, Mg in the liver compared to ZDF and/or lean Zucker rats, presumably as a result of the increased fat content of the liver of the obese rats. ZDF rats have increased concentrations of kidney Cu compared to the lean rats, while kidney Ca concentrations are increased in the Zucker obese rats. Spleen Fe concentrations are decreased in Zucker obese rats compared to the lean rats. No effects on metal concentrations in the heart were observed between the lean, obese, and ZDF rats, and no effects on Cr concentrations were identified. Cr(III) complexes have previously been shown to have beneficial effects on the signs of insulin resistance in Zucker obese and ZDF rats. The effects of daily gavage administration of chromium picolinate ([Cr(pic)(3)]) (1 mg Cr/kg body mass), CrCl(3) (1 mg Cr/kg body mass), and Cr3 ([Cr(3)O(propionate)(6)(H(2)O)(3)](+)) (33 μg and 1 mg Cr/kg body mass) on metal concentrations in these tissues were examined. Treatment with CrCl(3) and Cr3, but not [Cr(pic)(3)], at 1 mg Cr/kg resulted in a statistically significant accumulation of Cr in the kidney of lean and obese but not ZDF rats but resulted in lowering the elevated levels of kidney Cu in ZDF rats, suggesting a beneficial effect on this symptom of type 2 diabetes.

Byssus as a means of metal excretion route and high metal levels in fecal materials as metal retention: An experimental laboratory study using Perna viridis

The present study aimed at determining the concentrations of Cd, Pb and Zn in fecal materials, byssus and different soft tissues of Perna viridis under controlled laboratory conditions during accumulation and depuration tests and to discuss the roles played by byssus and fecal materials in the coastal waters. The present findings indicated that the byssus of P. viridis acted as an excretion routes for Cd, Pb and Zn while mussels have a retention mechanism of metals as evidenced in the high metal levels found in the fecal materials during the experimental study. This implied that mussel population played an important role in expediting the metal cycling as well as supposedly nutrient cycling in the coastal ecosystem by rapidly recycling back to the coastal environment in the underlying sediments.

Byssus as a means of metal excretion route and high metal levels in fecal materials as metal retention: An experimental laboratory study using Perna viridis

The present study aimed at determining the concentrations of Cd, Pb and Zn in fecal materials, byssus and different soft tissues of Perna viridis under controlled laboratory conditions during accumulation and depuration tests and to discuss the roles played by byssus and fecal materials in the coastal waters. The present findings indicated that the byssus of P. viridis acted as an excretion routes for Cd, Pb and Zn while mussels have a retention mechanism of metals as evidenced in the high metal levels found in the fecal materials during the experimental study. This implied that mussel population played an important role in expediting the metal cycling as well as supposedly nutrient cycling in the coastal ecosystem by rapidly recycling back to the coastal environment in the underlying sediments.

Multiple functions of the crustacean gill: osmotic/ionic regulation, acid-base balance, ammonia excretion, and bioaccumulation of toxic metals.

The crustacean gill is a multi-functional organ, and it is the site of a number of physiological processes, including ion transport, which is the basis for hemolymph osmoregulation; acid-base balance; and ammonia excretion. The gill is also the site by which many toxic metals are taken up by aquatic crustaceans, and thus it plays an important role in the toxicology of these species. This review provides a comprehensive overview of the ecology, physiology, biochemistry, and molecular biology of the mechanisms of osmotic and ionic regulation performed by the gill. The current concepts of the mechanisms of ion transport, the structural, biochemical, and molecular bases of systemic physiology, and the history of their development are discussed. The relationship between branchial ion transport and hemolymph acid-base regulation is also treated. In addition, the mechanisms of ammonia transport and excretion across the gill are discussed. And finally, the toxicology of heavy metal accumulation via the gill is reviewed in detail.

Comparison of urine toxic metals concentrations in athletes and in sedentary subjects living in the same area of Extremadura (Spain)

Cadmium (Cd), tungsten (W), tellurium (Te), beryllium (Be), and lead (Pb), are non-essential metals pervasive in the human environment. Studies on athletes during training periods compared to non-training control subjects, indicate increased loss of minerals through sweat and urine. The aim of this study was to compare the level of these trace elements, determined by inductively coupled plasma mass spectrometry (ICP-MS) in urine samples, between athletes and age-matched sedentary subjects living in the same geographical area, although anthropometric and cardiovascular measurements showed that athletes have significantly (P≤0.001) lower BMI, body fat and heart rate, whereas the muscle and bone percentage was significantly (P≤0.001) higher than in sedentary subjects. The validity of the methodology was checked by the biological certified reference material. Trace element analysis concentrations, expressed in μg/mg creatinine, of five toxic elements in urine from athletes (n=21) versus sedentary subjects, (n=26) were as follows: Cd (0.123±0.075 vs. 0.069±0.041, P≤0.05); W (0.082±0.053 vs.<limit of detection); Te (0.244±0.193 vs. 0.066±0.045, P≤0.001), Be (0.536±0.244 vs. 0.066±0.035, P≤0.001); Pb (0.938±0.664 vs. 2.162±1.444 P≤0.001). With the exception of Pb, urine toxic metal concentrations from athletes were higher than from sedentary subjects. This fact suggests that physical activity counteracts, at least in part, the cumulative effect of toxic environment by increasing the urine excretion of toxic metals in trained people.

Vermicomposting of sewage sludge by Lumbricus rubellus using spent mushroom compost as feed material: Effect on concentration of heavy metals

Vermicomposting of sewage sludge (SS) using spent mushroom compost from Pleurotus sajor-caju as feed material was conducted to determine the effect on the concentration of heavy metals, namely Cr, Cd, Pb, Cu, and Zn. Previous studies have reported the feasibility of brandling worms, Eisenia foetida, for vermicomposting SS, whereas we conducted vermicomposting by employing red worms, Lumbricus rubellus, with a combination of different percentages of SS and spent mushroom compost (SMC) for 70 days subsequent to 21 days of precomposting. The vermicompost produced in treatments with a low percentage of SS were fine in texture, dark in colour and odourless in contrast to the initial physical characteristics. Results indicate that growth in earthworm numbers and biomass gain was maximum at 25: 75 (TD) of SS: SMC compared to other treatments with 5 and 8-fold increases, respectively. The heavy metals contained in vermicompost were 0.25 ∼ 11.57-fold higher than the initial concentration due to mineralization and excretion of non-accumulated heavy metals existent in the earthworms’ gut, which were present prior to treatments. Even so, the concentration was below the limits set by EU and US biosolid compost standards and safe to be utilized as a biofertilizer and soil conditioner.

The influence of complexing pharmaceutical compositions on alkaline phosphatase

It is established that the pharmaceutical compositions xydiphon, medifon, succimer, and EDTA, which are used as complexing agents for accelerating the excretion of heavy metals from human organism, at certain concentrations inhibit enzyme alkaline phosphatase (AP). It is concluded that xydiphon and EDTA have a noticeable effect on AP activity at concentrations over 0.01 mM; medifon and succimer, at concentrations of over 0.3–0.5 mM. The enzyme’s inhibition constants and type of inhibition are determined. Xydiphon is found to manifest the highest affinity to AP (K I = 0.35 mM). It is shown by kinetic analysis that dissociative chemoinactivation of the enzyme takes place under the action of complexing agents. The corresponding kinetic parameters are calculated.

Enfermedad de Wilson

Wilson's disease is an autosomal recessive disorder of copper metabolism. It is caused by mutations in the ATP7B gene, which encodes a P-type ATPase that functions in the transport of copper inside the hepatocyte, both into the trans-Golgi compartment for incorporation into apo-caeruloplasmin, and into the bile, for excretion of the excess metal. Defective function of this protein leads to progressive copper accumulation, first in the liver but ultimately in the brain and other tissues, with mainly hepatic, neurological, psychiatric and ophthalmologic signs and symptoms. Nowadays, it still represents a diagnostic challenge due to it being an uncommon disease, with unspecific clinical manifestations, and limitations in the accuracy of the available diagnostic tests. The risk that it remains undiagnosed together with the availability of effective treatments stresses the importance of an early and correct diagnosis, with the clinic laboratory playing an essential the role.

Characterization of basolateral-to-apical transepithelial transport of cadmium in intestinal TC7 cell monolayers

Cadmium (Cd) is a toxic metal with an extremely long half-life in humans. The intestinal absorption of Cd has been extensively studied but the role the intestinal epithelium may play in metal excretion has never been considered. The basolateral (BL)-to-apical (AP) transepithelial transport of Cd was characterized in TC7 human intestinal cells. Both AP and BL uptakes varied with days in culture, and BL uptake was twofold higher compared to AP in differentiated cultures. A 50% increase in the BL uptake of 0.5 μM (109)Cd was observed at pH 8.5 in a chloride but not nitrate medium, suggesting the involvement of a pH-sensitive mechanism of transport for chloro-complexes. Fe and Zn inhibited the BL uptake of Cd whereas complexation by albumin had no effect, but the stimulatory effect of pH 8.5 was lost in the presence of albumin. The BL uptake of [(3)H]-MPP(+) and (109)Cd were both inhibited by decynium22 without reciprocal inhibition. MRP2 and MDR1 mRNA levels increased as a function of days in culture. A 25 and 20% decrease in the cellular AP efflux of Cd was observed in the presence of verapamil and probenecid, respectively. In cells treated with BSO, which lowered by 26% the total cellular thiol content, the inhibitory effect of verapamil increased, whereas that of probenecid decreased. These results reveal the existence of a decynium22-sensitive mechanism of transport for Cd at the BL membrane, and suggest the involvement of MDR1 and MRP2 in cellular Cd efflux at the AP membrane. It is conceivable that the intestinal epithelium may contribute to Cd blood excretion.

EDTA chelation therapy in the treatment of toxic metals exposure

BACKGROUND: Metal induced toxicity with wide range of physiological, biochemical and behavioral dysfunctions was reported in many studies. The chelation has been used for treatment to toxic metals’ exposure for many years. In our current clinical study, we compared different chelation protocols and two forms of EDTA (sodium calcium edetate and sodium edetate) in treatments of toxic metal exposure. METHODS: A 24 h urine samples were collected from each subject before and after treatment by Ca-EDTA or Na-EDTA. The levels of toxic and essential metals were measured by Atomic Absorption Spectrometer (AAS) with graphite furnace and by Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES). The cellular levels of ATP were determined by ATP-bioluminescence assay. Mitochondrial potential was measured by fluorometer and flow-cytometer after cells’ staining by mitochondrial dye. RESULTS: Data from over 600 patients with a variety of complaints, but not acute toxic mineral exposure, given chelation therapy with sodium EDTA or calcium EDTA, were analyzed. Ca-EDTA and Na-EDTA at intravenous infusions of 3 g per treatment were equally effective in removing lead from the body, while Ca-EDTA was more effective in aluminum removal. The removal of lead was dose dependent but non-linear. Chelation by different doses of Na-EDTA (3 g and 1 g) resulted in mean difference in lead urine less than 50%. In addition, deficiencies in essential minerals correlated with greater pre-treatment lead and aluminum levels. The intrinsic toxicity of EDTA on cells was investigated. EDTA concentrations above 600 uM reduced cellular energy metabolism. CONCLUSION: Based on our data, we proposed that low dosages of chelating agents might be preferential for patients with no–occupational exposure, as the benefit of chelation is not linear with dosage, the risk of exposure to antidotes is increasing with increased dosages, and excretion of essential metals significantly increases with increased antidote dosage.

Biomonitoring of Trace Metals (Fe, Cu, and Ni) in the Mangrove Area of Peninsular Malaysia Using Different Soft Tissues of Flat Tree Oyster Isognomon alatus

It is well documented that marine oysters are net bioaccumulators of trace metals and they can be employed as biomonitors of time-integrated measurements of bioavailable metal fractions over their lifetime. In this study, the Malaysian mangrove flat tree oyster Isognomon alatus collected from the estuaries of Lukut River (five sites), Sepang Besar River (one site), and one metal-polluted site at Kg. Pasir Puteh were dissected into muscle, mantle plus gills, byssus, and remaining soft tissues. All the four different soft tissues were analyzed for Fe, Cu, and Ni. Significant spatial differences in the accumulated metal concentrations of the oysters were found between sampling sites, and these could be attributed to anthropogenic inputs including discharges of shrimp ponds (Lukut), animal husbandry (Sepang Besar), sewage, shipping, and industrial effluents (Kg. Pasir Puteh). For Fe, the tissue distribution followed: byssus > mantle plus gill >muscle > remaining soft tissues, while for Cu and Ni, both followed byssus > remaining soft tissues > mantle plus gill > muscle. This indicated that byssus could act as an excretion route for the metals. Based on a correlation analysis between oyster tissues and sediments, selected tissues of I. alatus were shown to be good biomonitors of Ni and Cu contamination, while high regulative capacity of Fe in the oyster tissues could hardly reflect the actual Fe levels in the surroundings. However, the clustering patterns based on metal levels in the four different soft tissues were not in agreement with those based on the geochemical fractions of sediment data. This phenomenon which was due to the metal contamination might not necessarily create high bioavailabilities of metals to the biomonitor I. alatus, which might involve differences in uptake, excretion, and sequestration of metals. Similarly to the Mussel Watch approach, this study points to the very potential use of the different soft tissues of I. alatus as biomonitors for regular biomonitoring in the mangrove area of Peninsular Malaysia.

Chelation for Heavy Metals (Arsenic, Lead, and Mercury): Protective or Perilous?

Despite clinical experience that spans more than half a century, chelation for toxic heavy metals represents one of the most controversial and misapplied interventions in clinical toxicology. The prompt use of chelating agents to treat acute, life-threatening intoxication is an indication that is largely supported by experimental animal data and limited clinical research. Although chelating agents administered for chronic intoxication may accelerate the excretion of heavy metals, their therapeutic efficacy in terms of decreased morbidity and mortality is largely unestablished. Recent investigations suggest that their use in such settings might be associated with deleterious effects. Careful attention to risk-benefit issues is warranted, particularly in clinical situations in which the etiological role of heavy metals in the patient's illness is in question.