Pathology of human organic mercury poisoning: Lessons from an autopsy case

We had an opportunity to perform a general autopsy of a case with chronic organic mercury toxicosis in 2017. He had been engaged in synthesizing a variety of organic mercury compounds throughout the four years from 1966 and developed chronic organic mercury poisoning in 1969. Almost forty years on, he still remained to complain of persistent paresthesia at finger tips and tongue, and of narrowed visual field. Neurological examinations clarified a rise of two-point discrimination thresholds, a systemic increase of touch thresholds, constriction of the visual field caused by general visual depression, and sensorineural hearing loss while primary modalities of his somatic, visual, and auditory sensations were preserved. These symptoms and signs are characteristic of human organic mercury poisoning. Furthermore, he had difficulty in processing a lot of visual and auditory information at a time. His two-point discrimination thresholds and systemic elevation of touch thresholds were comparable to those of mild organic mercury poisoning cases. He had slight sensory ataxia, but not cerebellar ataxia. Brain [18F]-2-fluorodeoxyglucose positron emission tomography analysis exhibited marked hypometabolism at bilateral postcentral gyrus, striate cortex, and superior temporal gyrus, but not the cerebellum. Histopathological studies revealed considerable decrease of granular neurons and neuronal networks in bilateral primary somatosensory, visual, and auditory cortices. Those characteristic brain lesions fairly explain increase of thresholds of somatic, visual, and auditory sensations, and degradation of integrating sensory information. It is noted that damages to the peripheral nervous system and the cerebellum were not detected and that his intellectual faculties were preserved.

The life-threatening rash of poisoning

Dermatology is frequently viewed by physician and surgical colleagues as a specialty with few emergencies. Although the majority of dermatology practice is in the office setting, cutaneous emergencies do occur through referrals from primary care and as ward consults. Even though cutaneous signs of poisoning would be an uncommon emergency consultation, it is important for dermatologists to be aware of the clinical presentations so as to be able instigate appropriate time critical treatments.

Lung Function Assessment as an Early Biomonitor of Mercury-Induced Health Disorders in Artisanal and Small-Scale Gold Mining Areas in Indonesia

The evaluation of mercury impact on humans is currently nonspecific because the body characteristics (homeostasis) of each human being varies. Therefore, in the early diagnosis of mercury toxicity, one of the most important monitoring parameters is the respiratory function examination. In this study, respiratory function was examined with a portable spirometer and correlated with the mercury levels in hair from the noses and heads of subjects. Samples were taken from artisanal and small-scale gold mining (ASGM) areas (villages of East Tulabolo and Dunggilata) and control areas (villages of Bongo and Longalo) in Gorontalo Province, Indonesia. A statistical analysis with the Mann⁻Whitney test (alternative) showed significant differences in lung function between the polluted and control areas (α = 0.03). The analysis of nasal and head hair samples with particle-induced X-ray emissions (PIXE) showed that the mercury levels in the ASGM area were considerably higher than in the more homogeneous control areas. This study confirms that a pulmonary function test is a quick and precise alternative way to monitor the impact of mercury on humans, especially atmospheric mercury, because we detected a negative correlation between pulmonary function and the level of mercury in hair.

Acute mercury exposition of virgin, pregnant, and lactating rats: Histopathological kidney and liver evaluations

This work investigated the effects of mercury chloride (HgCl₂ ) acute exposure on virgin, pregnant and lactating rats by determination of renal and hepatic morphological and ultrastructural parameters and the expression of oxidative stress and stress tolerance markers, due to kidney and liver are the organs that more accumulate inorganic mercury. Adult Wistar rats virgin (90 days old), pregnant (18^th gestation day) and lactating (7^th lactation day) were injected once with HgCl₂ (5 mg/kg) or saline (controls). We observed that HgCl₂ exposure of virgin rats caused significant inflammatory infiltration and severe morphological variations, like glomeruli atrophy, dilatation of Bowman's capsule, tubular degeneration and hepatocytes alteration. Moreover, virgin rats presented mitochondrial modification, important oxidative stress and increase in stress tolerance proteins at both kidney and liver level, compared with virgin controls. In detail, virgin rats exposed to HgCl₂ presented significantly elevated level of inducible nitric oxide synthase, heat shock protein 27 and glucose regulated proteins 75 expressions at both renal tubular and hepatocytes level, respect untreated virgin rats. Interestingly, pregnant and lactating rats exposed to HgCl₂ presented weak renal and liver morphological alterations, showing weak inflammatory infiltration and no significant difference in structural mitochondrial transmembrane protein, oxidative stress markers and stress tolerance proteins expressions respect controls (virgin, pregnant and lactating rats). Although, both control and HgCl₂ -exposed pregnant and lactating rats showed renal glomeruli greater in diameter respect virgin rats. In conclusion, we believe that virgin rats are more sensitive to HgCl₂ toxicity respect pregnant and lactating rats. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1500-1512, 2017.

Ultrastructural Demonstration of Mercury Granules in the Placenta of Metallothionein-Null Pregnant Mice after Exposure to Mercury Vapor

The placenta plays an important role in the regulation of maternal to fetal transfer of toxic substances, including nonessential metals. Metallothioneins (MTs), which are known to have protective effects against heavy metal toxicity, exist in the placenta, but the exact localization of placental MTs (both MT-I and MT-III) and their physiological role in the placenta exposed to mercury are unclear. The present study was performed to examine the localization of MTs and mercury granules in the placenta of mice exposed to mercury vapor. On gestational day 16, MT-I & II-null and wild-type mice were exposed to mercury vapor at 4.9 to 5.9 mg/m3 for 2 hours. At 24 and 48 hours after exposure, the placentas were examined for mercury distribution (autometallography), MT immunoreactivity, and MT mRNA expression (in situ hybridization). No histological changes were observed in the placentas of either MT-null or wild-type mice. Mercury deposition was demonstrated along the boundary between the junctional zone and the labyrinth zone, as well as in the yolk sac, maternal decidual cells, and labyrinth trophoblasts of both MT-null and wild-type mice. MT-I & -II immunoreactivity, which was confined to wild-type mice, was demonstrated in the yolk sac and decidual cells; mercury was also shown in both structures, suggesting that mercury granules were bound to MTs. MT-III mRNA expression was observed in the yolk sac, decidual cells, and spongiotrophoblasts in both MT-null and wild-type mice. There was, however, no evidence of MT at the boundary between the junctional and labyrinth zones, where substantial mercury deposits were demonstrated. These results suggest that placental MTs and the other unknown molecules may be related to the barrier to the placental transfer of mercury.

Mercury induced haemocyte alterations in the terrestrial snail Cantareus apertus as novel biomarker

The aim of the present work was to study the response of a suite of cellular and biochemical markers in the terrestrial snail Cantareus apertus exposed to mercury in view of future use as sensitive tool suitable for mercury polluted soil monitoring and assessment. Besides standardized biomarkers (metallothionein, acetylcholinesterase, and lysosomal membrane stability) novel cellular biomarkers on haemolymph cells were analyzed, including changes in the spread cells/round cells ratio and haemocyte morphometric alterations. The animals were exposed for 14 days to Lactuca sativa soaked for 1h in HgCl2 solutions (0.5 e 1 μM). The temporal dynamics of the responses were assessed by measurements at 3, 7 and 14 days. Following exposure to HgCl2 a significant alteration in the relative frequencies of round cells and spread cells was evident, with a time and dose-dependent increase of the frequencies of round cells with respect to spread cells. These changes were accompanied by cellular morphometric alterations. Concomitantly, a high correspondence between these cellular responses and metallothionein tissutal concentration, lysosomal membrane stability and inhibition of AChE was evident. The study highlights the usefulness of the terrestrial snail C. apertus as bioindicator organism for mercury pollution biomonitoring and, in particular, the use of haemocyte alterations as a suitable biomarker of pollutant effect to be included in a multibiomarker strategy.

Mercury toxicity presenting as acrodynia and a papulovesicular eruption in a 5-year-old girl

Acrodynia is a reaction that occurs in children who have been exposed to mercury. Mercury toxicity has systemic manifestations as well as cutaneous manifestations, which can appear similar to those found in a number of other diseases. We present a case of acrodynia caused by mercury exposure in a previously healthy 5-year-old girl who developed hypertension, palmoplantar pruritus, and a papulovesicular eruption.

Health concerns of heavy metals and metalloids

There is a long history and an overwhelming amount of data on the toxicity of heavy metal compounds. Here a brief look is taken of some aspects of the toxicity of lead, cadmium, mercury and arsenic, chosen for their historical importance and environmental significance, highlighting especially the contrast between the acute and chronic toxicity of purely inorganic species and their organic derivatives. For further details of other toxic metal compounds, the reader might like to consult "Elements of murder: a history of poison" by John Emsley (2005, Oxford University Press).

Cutaneous mercury granuloma: a case report

Cutaneous mercury (Hg) granuloma is a rare disorder caused by the traumatic introduction of elemental Hg into skin or soft tissue. Typically, cutaneous elemental Hg deposits cause limited systemic effects. Prominent systemic toxicity may, however, occasionally occur. Herein we report a case of cutaneous Hg granuloma resulting in chronic painful local wounds and systemic toxicity in the form of abdominal pain, visual disturbances, and psychiatric abnormalities. The related literature also is reviewed.

[Morphologic and neurochemical effects in long-term period of mercurial intoxication (experimental data)]

The article deals with influence of longstanding inhalation of mercurial vapors on behavior of white rats, on morphologic and functional disorders in nervous system, on peculiarities of neuromediators metabolism in brain homogenate over the post-contact period.

A Child with Elemental Mercury Poisoning and Unusual Brain MRI Findings

Mercury vapor poisoning is a serious and potentially fatal problem. Neurological manifestations involving the central nervous system are seen with chronic mercury intoxication. We present the case of a 10-year-old child who demonstrated acrodynia, seizures, and visual impairment following 20 days of exposure to elemental mercury at home. The initial blood mercury concentration was 27.7 microg/L (normal <2 microg/L) and the initial 24-hour urine mercury concentration was 34.4 microg/L (normal =10 microg/L). After 9 months of treatment with D-penicillamine, the patient's clinical condition, biochemical laboratory parameters, and mercury concentrations all returned to normal. The T2-weighted MRI images of the patient's brain initially showed multiple hyperintense lesions in cerebral white matter, left globus pallidus, and putamen, which also improved.

Cellular responses in the cyprinid Leuciscus cephalus from a contaminated freshwater ecosystem

The response of wild chubs (Leuciscus cephalus) to chemical pollution was assessed in a metal contaminated river (Cecina River, Italy) through a wide battery of biomarkers which included: Comet assay detecting DNA strand breaks; diffusion assay for apoptosis induction; micronucleus test assessing chromosomal alterations; ethoxyresorufin O-deethylase (EROD) activity for the induction of cytochrome P 4501A; acetylcholinesterase (AChE) activity responsive to pesticide exposure; vitellogenin gene expression in males revealing estrogenic effects. Bioaccumulation of mercury, chromium and polycyclic aromatic hydrocarbons (PAHs) was also determined. Levels of mercury and PAHs were higher in tissues of chubs sampled from the most downstream station, reflecting an anthropogenic pollution of industrial origin. Otherwise, accumulation of Cr was quite similar in fish along the entire course of Cecina River confirming a natural origin due to local geochemical features. Biomarker responses revealed a significant increase of apoptotic cells, DNA stand breaks and micronucleus frequency in chubs from the more impacted sites. A slight EROD induction and AChE inhibition were only seen at the most downstream station demonstrating a limited impact due to PAHs and pesticides. On the other hand, the induction of vitellogenin gene in male chubs was measured in all the sites, suggesting a diffuse estrogenic effect. This study confirmed the utility of large batteries of biomarkers in biomonitoring studies and the suitability of wild chub as bioindicator organism for river basins.

Comparative evaluation of the protective effect of selenium and garlic against liver and kidney damage induced by mercury chloride in the rats

The present study was designed to compare the protective effect of selenium and garlic against liver and kidney damage induced by (ip) injection of 0.5 mg/kg mercury chloride (HgCl(2)) in rats. Thirty-six Sprague-Dawley rats were used in the present experiment and divided into six groups: one group was orally given (1 ml) saline and served as a control group; two groups of rats were given either selenium (0.1 mg/kg) or garlic (63 mg/kg) alone, once daily an oral dose for 30 successive days; other two groups of rats were given either selenium or garlic alone, once daily a dose for 15 successive days prior to HgCl(2) injection and on the next 15 successive days simultaneously with HgCl(2) injection; and the last group of rats was injected ip with HgCl(2) for 15 days and at the end of the experiment (which lasted 30 days), blood samples for the biochemical analysis were obtained from all rats after being lightly anesthetized with ether, and specimens of kidney and liver were removed and prepared for histochemical study. Computer image analysis was applied to liver and kidney tissues to evaluate the DNA density and DNA ploidy pattern in different groups. The results revealed that the rats injected with HgCl(2) showed a significant increase in levels of blood urea nitrogen (BUN), serum creatinine, alanine aminotransferase (ALT), aspartate aminotransferase (AST) by 29.3%, 62.5%, 29.46% and 30.61%, respectively, while alkaline phosphatase (ALP) showed a significant decrease by 22.6% as compared with saline control group. Rats that were given selenium in combination with the HgCl(2) injection showed a significant decrease in BUN, Serum creatinine, ALT and AST levels, while ALP was significantly increased as compared with HgCl(2) group. Also rats that were given garlic in combination with HgCl(2) injection showed a significant decrease in BUN, Serum creatinine, ALT and AST levels, although serum ALP level showed an increase as compared to HgCl(2) group. Rats that had been orally administered selenium or garlic alone did not show any significant changes in the serum level of BUN, Serum creatinine, ALT and AST but there was a significant decrease in ALP level as compared with saline control group. The cytometric results revealed that injection of HgCl(2) induced an increase in the DNA density in kidney tissues with an increase in aneuploid cells and decrease in diploid cells. However, DNA density decreased in liver tissues with mild decrease in diploid cells and little percentage of aneuploid cells. We can conclude that oral administration of either selenium or garlic produces a significant protection against liver and kidney damage induced by the HgCl(2) injection, but garlic appears to be more protective.

ALS and mercury intoxication: A relationship?

We report the case of an 81-year-old woman in whom clinical signs and features of electromyographic activity patterns were consistent with amyotrophic lateral sclerosis (ALS). Increased blood level and massive urinary excretion of mercury proved mercury intoxication. Despite a chelation treatment with Meso 2-3 dimercaptosuccininc acid (DMSA), she died after 17 months. The pathophysiology of sporadic ALS remains unclear. However, the role of environmental factors has been suggested. Among some environmental factors, exposure to heavy metals has been considered and ALS cases consecutive to occupational intoxication and accidental injection of mercury have been reported. Although no autopsy was performed, we discuss the role of mercury intoxication in the occurrence of ALS in our case, considering the results of experimental studies on the toxicity of mercury for motor neuron.

Effect of monothiol along with antioxidant against mercury-induced oxidative stress in rat

Efficacy of thiol chelators viz. N-acetyl cysteine and D-penicillamine (NAC and DPA) along with nutritional supplements viz. zinc acetate, sodium selenite and magnesium sulphate (Zn, Se and Mg) in the treatment of mercury intoxication was investigated in rats. This is of particular interest since high bonding affinity between mercuric ion and the thiol group exits. The mutual antagonism of mercury and selenium is one of the strongest examples of the interaction in the trace element field. Adult rats of Sprague-Dawley strain were administered a bolus dose of dimethyl mercury (10 mg/kg) orally. A significant rise in the aspartate aminotransferase, alanine aminotransferase, serum alkaline phosphatase, lactate dehydrogenase, gamma glutamyltranspeptidase, bilirubin and creatinine were observed. Single mercury exposure also resulted in a significant increase in lipid peroxides with a concomitant decrease in reduced glutathione level in liver, kidney and brain. A decrease in the enzymatic activities of acetyl cholinesterase in different regions of the brain was observed. These parameters were restored considerably with chelating agents along with nutritional supplementation, but NAC+Se and DPA+Mg offered significant protection in comparison with other combinations.

Elemental mercury poisoning probably causes cortical myoclonus

Mercury toxicity causes postural tremors, commonly referred to as "mercurial tremors," and cerebellar dysfunction. A 23-year woman, 2 years after injecting herself with elemental mercury developed disabling generalized myoclonus and ataxia. Electrophysiological studies confirmed the myoclonus was probably of cortical origin. Her deficits progressed over 2 years and improved after subcutaneous mercury deposits at the injection site were surgically cleared. Myoclonus of cortical origin has never been described in mercury poisoning. It is important to ask patients presenting with jerks about exposure to elemental mercury even if they have a progressive illness, as it is a potentially reversible condition as in our patient.

Baboon syndrome induced by mercury - first case report in China

A case of mercury-induced baboon syndrome was reported. A 31-year-old woman presented with itching papules and vesicles in the right axilla, which extended to the left axilla, arms, fossa poplitea, buttocks, and groin. A mercury thermometer was broken 2 days before exanthema. Patch testing to ammoniated mercury, mercury, mercuric chloride, and mercurochrome were positive. Blood and urine mercury level was marginally normal, yet showed a descending trend over time.

Toxic effects seen in a herd of beef cattle following exposure to ash residues contaminated by lead and mercury

Lead poisoning was diagnosed in three cattle along with increased mercury levels in the liver and kidney tissues of two of these animals. The clinical signs were different in each case and included salivation, anorexia, delayed menace response, delayed withdrawal reflex, head pressing, localized muscle fasciculation, reduced tongue tone, ataxia, rumen atony and seizures. Blood lead concentration was increased in all three cases to 0.76, 0.37 and 0.454ppm. Post mortem changes characteristic of lead poisoning were only recognized in one case and included cerebro-cortical oedema, cortical neuronal necrosis and endothelial proliferation, especially at the tips of the cerebral gyri. The animals were poisoned by ingestion of lead-contaminated ash residues from a bonfire. The abnormal levels of mercury in the liver and kidney tissues of two animals may also be at least partly attributable to the intake of the metal in the ash residues. The levels of mercury in the three samples from the ash residue were relatively low (1.31, 0.7 and 2.1ppm).

Modulating effects of dietary fats on methylmercury toxicity and distribution in rats

Fish consumption is the most important source of human exposure to methylmercury (MeHg). Since fish is also a rich source of n-3 polyunsaturated fatty acids, this study was conducted to examine the effects of dietary fats on MeHg-induced acute toxicity in rats. Weanling male Sprague Dawley rats were administered semi-purified casein-based isocaloric diet containing soy oil, seal oil, docosahexaenoic acid (DHA), fish oil, or lard for 28 days. Rats were then gavaged with 0, 1, or 3 mg MeHg/kg body weight (BW) per day and fed the same diet for 14 consecutive days. On 43rd day of the experiment, rats were sacrificed and blood samples were collected and analyzed for hematology. Liver and spleen were removed, fixed, and examined for pathological changes. Blood, feces, liver, and brain were analyzed for total mercury and/or MeHg contents. Serum samples were analyzed for clinical markers of hepatic injury and immunoglobulin. Total mercury contents in all tissues measured increased with dose. Mercury excretion in feces increased with dose and duration of MeHg treatment. Both diets and MeHg showed significant effects and interacted significantly on many of the toxicological endpoints measured. Many of the effects of MeHg were diet-dependent. For example, in the rats fed the lard diet, 3mg MeHg/kg BW significantly increased relative liver and spleen weight as compared with vehicle control; whereas in rats fed the fish oil, soy oil, seal oil, or DHA, this effect of MeHg was less obvious or absent, suggesting a protective effect of these diets. MeHg at 3mg/kg BW significantly decreased serum albumin level in all except DHA dietary groups, implying a protection by the DHA diet on this parameter. Only in the lard dietary group, did 3mg MeHg/kg BW significantly increase serum bilirubin level, indicating an enhancing effect of this diet on MeHg toxicity. MeHg suppressed the adaptive immune system and stimulated the innate immune system in rats in a diet-dependent fashion. The seal oil diet provided more resistance, while the fish oil diet rendered greater sensitivity to these effects of MeHg on the immune system. These results imply significant modulating effects of dietary fats on MeHg toxicity which may translate into more severe or protective clinical outcomes. Therefore, dietary fats are important factors to be considered in the risk assessment of MeHg exposure.

[Long-term survival after a suicidal intravenous injection of mercury]

The authors present extraordinary autopsy findings, i.e. metallic mercury deposits within the cardiac muscle of a 28-year-old deceased of a male sex. Eleven years previously, the man had injected metallic mercury to the vein in the elbow region with a suicidal intent. Eighteen months later, during diagnostic management of dyspnea, metallic deposits in various internal organs had been revealed and a case history of the patient was published. Subsequently, the patient failed to report for follow-up examinations, and finally, committed suicide by hanging.

Cutaneous poisoning syndromes in children: a review

PURPOSE OF REVIEW

The purpose of this article is to review cutaneous poisoning syndromes in the pediatric population and to describe the diagnostic and therapeutic challenges in the management of these conditions.

RECENT FINDINGS

In recent years, the American Academy of Pediatrics and the Center for Disease Control have been continuously monitoring the lowest blood levels of numerous elements and nutrients associated with the slightest degree of toxicity. This review will focus on the clinical presentation, recognition and management of poisoning with cutaneous manifestations such as carotenoderma, mercury, dioxin and arsenic poisoning.

SUMMARY

Despite numerous efforts of federal and local government agencies to decrease poisoning incidents among consumers, sporadic cases of cutaneous poisoning still arise. Pediatricians should be familiar with the clinical presentation of various toxic syndromes and, more importantly, be able to teach prevention during regular medical encounters.

Short-Interfering RNA-Mediated Silencing of Thioredoxin Reductase 1 Alters the Sensitivity of HeLa Cells toward Cadmium

The mammalian thioredoxin reductase (TrxR) is a selenocysteine-containing flavoprotein that regulates the thioredoxin system, one of the major systems that maintain the intracellular redox balance. We previously reported that cytosolic TrxR (TrxR1), one of three mammalian TrxR isozymes, was induced by treatment with cadmium. In the present study, to study the role of cadmium-induced TrxR1 in cellular defense, we silenced the expression of TrxR1 in HeLa cells by using small interfering RNA and examined the effect of TrxR1 silencing on the sensitivity of the cells toward cadmium. We found that the gene silencing of TrxR1 had a dual effect on cadmium-induced cell death, depending on the concentration of cadmium. The TrxR1 silencing increased the sensitivity toward a low dose (less than 10 microM) of cadmium but decreased the sensitivity toward a high dose of cadmium. These results suggested that TrxR1 might play an important role in the cellular defense system against cadmium in two ways. TrxR1 might rescue the cells from a low dose of cadmium-induced moderate injury, while it might promote the death of cells severely injured by a high dose of cadmium.

FT-IR Study of the influence of Tribulus terrestris on Mercury intoxicated mice, Mus musculus liver

FT-IR spectra of liver tissue isolated from mice, Mus musculus, have been recorded in the region of 4000 - 400 cm-1 for normal, mercury treated and recovery phase. In this study, the total protein content was found to be decreased in the liver tissues after treatment with median-lethal dose of mercuric chloride. The marked fall in the level of bio-chemical constituent in the tissue due to metal exposure indicates the rapid initiation of the breakdown of the bio-chemical constituents to meet the energy demand during toxic stress. During the recovery phase, the decreased levels of bio-chemical constituents are restored to near normal level. Methanol fractions of Tribulus terrestris fruit extract was administrated on mercury intoxicated mice for 15 days. After the administration, the mercury-intoxicated animals slowly recovered from the adverse effect of mercury poisoning with the help of plant bio-formulations. The results are discussed in detail.

Case report: subcutaneous elemental mercury injection--clinical observations and implications for tissue disposal from the histopathology laboratory

A 31-yr-old man presented to his general physician complaining of pain and swelling in the soft tissue of both hips. He initially denied knowledge of the etiology, but after elemental mercury droplets were expressed from the skin wounds by manual manipulation, he admitted that the source was self-administered sc injections. He did not provide a reason for this or give the time-frame of the injections. The areas of skin discoloration and soft tissue induration were completely excised and the wounds healed uneventfully. Blood levels of mercury declined gradually after excision. Examination of the resected skin and subcutis revealed subcutaneous abscesses containing droplets of elemental mercury, released easily when the abscesses were sectioned. Sections showed dark droplets of metallic mercury associated with necrosis and microabscess formation, with areas of foreign body giant cell reaction. Disposal of the residual tissues and mercury by incineration would release the volatile elemental mercury into the atmosphere, where it would subsequently be returned to earth in rain water, be converted to methyl mercury by microorganisms, and enter the food chain. The US Environmental Protection Agency has recommended caution in consuming foods containing methyl mercury and has provided guidelines for consuming foods believed to contain increased amounts of mercury. Mercury is readily available in the United States by over-the-counter sales to consumers, and in some cultures elemental mercury is used in ritualistic practices. Skin injection cases are infrequent, but histopathology laboratories should recognize this phenomenon and be prepared to dispose of Hg-contaminated tissues in an environmentally sound manner.

Effects of methylmercury on the microvasculature of the developing brain

The study, undertaken with the aim of further investigating the effects of methylmercury (MeHg) exposure on the developing brain, was performed in the cerebellum of chick embryos, chronically treated with a MeHgCl solution dropped onto the chorioallantoic membrane, and in control embryo cerebella. Quantitative evaluations, performed by cold vapour atomic absorption spectrophotometry, demonstrated a high mercury content in the chorioallantoic membrane, encephalon, liver and kidney of the treated embryos. The morphological observations showed severe neuronal damage consisting of degenerative changes of the granules and Purkinje neurons. The effects on astrocytes were even more severe, since they were extremely rare both in the neuropil and around the vessel wall. Compared with the controls, the cerebellar vessels of MeHg-treated embryos showed immature morphology, poor differentiation of endothelial barrier devices, and high permeability to the exogenous protein horseradish peroxidase. These findings support the hypothesis that MeHg-related neuronal sufferance may be secondary to astrocytic damage and suggest that the developmental neurotoxicity of this compound could also be related to astrocyte loss-dependent impairment of blood-brain barrier (BBB) differentiation.

A new cutaneous sign of mercury poisoning?

Chronic mercury poisoning is becoming a health concern because of extensive pollution of water and fish, and the increasing consumption of fish in the human diet. Mercury is extremely toxic to the body, especially the central nervous system, but diagnosis is difficult because of the lack of specific signs. A total of 11 patients were observed to have a nonpruritic or mildly pruritic discreet papular and papulovesicular eruption that correlated with high blood mercury levels. The mercury evidently came from increased seafood consumption. All of the patients improved when they were placed on either a seafood-free diet or chelation therapy. Physicians should suspect mercury poisoning in patients who eat a high-seafood diet who present with an asymptomatic or mildly pruritic papular or papulovesicular eruption.

Environmental exposure to mercury and its toxicopathologic implications for public health

Mercury is a toxic and hazardous metal that occurs naturally in the earth's crust. Natural phenomena such as erosion and volcanic eruptions, and anthropogenic activities like metal smelting and industrial production and use may lead to substantial contamination of the environment with mercury. Through consumption of mercury in food, the populations of many areas, particularly in the developing world, have been confronted with catastrophic outbreaks of mercury-induced diseases and mortality. Countries such as Japan, Iraq, Ghana, the Seychelles, and the Faroe Islands have faced such epidemics, which have unraveled the insidious and debilitating nature of mercury poisoning. Its creeping neurotoxicity is highly devastating, particularly in the central and peripheral nervous systems of children. Central nervous system defects and erethism as well as arrythmias, cardiomyopathies, and kidney damage have been associated with mercury exposure. Necrotizing bronchitis and pneumonitis arising from inhalation of mercury vapor can result in respiratory failure. Mercury is also considered a potent immunostimulant and -suppressant, depending on exposure dose and individual susceptibility, producing a number of pathologic sequelae including lymphoproliferation, hypergammaglobulinemia, and total systemic hyper- and hyporeactivities. In this review we discuss the sources of mercury and the potential for human exposure; its biogeochemical cycling in the environment; its systemic, immunotoxic, genotoxic/carcinogenic, and teratogenic health effects; and the dietary influences on its toxicity; as well as the important considerations in risk assessment and management of mercury poisoning.

A whitened face woman with nephrotic syndrome

Skin whitening cream from developing countries is a recognized source of chronic mercury poisoning. The authors report on a 34-year-old Indonesian domestic helper who presented with nephrotic syndrome secondary to membranous nephropathy. It was subsequently found that she used a skin whitening cream regularly that was found to contain a mercury level of almost 2,000 times above the allowable limit. Her blood and urinary mercury levels were both grossly elevated. Her symptoms improved after she stopped using the cream. However, she returned to her home country before chelating therapy could be arranged. Because mercury-containing skin products are still widely available in developing countries, the use of these products should be considered a possible cause of membranous nephropathy in immigrants from those countries.

Five years of follow-up after elemental mercury self-poisoning

A case of attempted suicide by injection of elemental mercury is described. Radiographs demonstrated the presence of widespread opacities of metallic mercury in both the lungs and the abdomen. During a 5-year follow-up, even though the patient had high concentrations of mercury in the urine and blood, only mild clinical symptoms and moderate carbon monoxide diffusing capacity reduction appeared. No biochemical evidence of damage to any organ was found.

Investigation of intracellular factors involved in methylmercury toxicity

Methylmercury is a known pollutant that causes severe central nervous system disorders. It is capable of passing through the blood-brain barrier and accumulates in cerebral cells. However, little is known regarding the mechanism of its toxicity at the molecular level. Using yeast cells, we searched for the genes involved in the expression of methylmercury toxicity, and found that genes encoding L-glutamine.D-fructose-6-phosphate amidotransferase (GFAT) and ubiquitin transferase (Ubc3) confer methylmercury resistance on the cells. It has also been shown that GFAT is the target molecule of methylmercury in yeast cells. These findings provide important clues about the mechanism underlying methylmercury toxicity in mammals.

Pathology of "toxic oils" and selected metals in the MRL/lpr mouse

The Toxic Oil Syndrome epidemic that occurred in Spain in 1981 and affected nearly 20,000 people was caused by ingestion of oil mixtures that contained analine-denatured rapeseed oil. To date, an animal model in which to identify the actual etiologic agents(s) and to investigate the pathogenesis of the disease has not been discovered. In this study, the MRL/lpr was used to assess the histopathological response of 3 "toxic oils" and 3 metals. The oils tested were a denatured rapeseed oil collected from a family who were affected by the Toxic Oil Syndrome epidemic in Spain (CO756) plus two synthesized oils (RSD and RSA). Female mice, 7 weeks of age, received an undiluted (neat) or a 1:10 diluted dose of each oil; mercury (50 ppm), cadmium (100 ppm), or lead (50 ppm). Half of each group was killed after 5 weeks of exposure and the remaining mice after 10 weeks of exposure. Body and organ weights (liver, kidney, thymus, and spleen) were recorded and selected organs were collected for histopathology. Ten weeks after treatment, body weights (BW) of the cadmium and lead groups were significantly suppressed, and the body weight of the C0756-neat group was significantly increased compared to their respective controls. Kidney/BW were decreased in the RSA-neat and RSA 1:10 groups after 10 weeks of exposure, and the kidney/BW in the mercury and cadmium groups were increased. Spontaneous development (12 weeks of age) and progression (17 weeks of age) of histopathological lesions are described for selected organs examined in the naïve mice as are changes that resulted from exposure to the "toxic oils" and metals. C0756-neat, mercury, and lead suppressed progression of the glomerulonephritis that normally occurs in the MRL/lpr mouse. Also of interest were lesions that included mononuclear cuffing of hepatic bile ducts, progression of the granulomas that formed in the renal glomeruli, vessels in the lymphoid organs that contained tightly packed lymphocytes, and the presence of plasma cells in the thymus. All 3 oils stimulated early development of the lymphoproliferative syndrome characteristic of the MRL/lpr mouse as demonstrated by an increase in the thymus/BW and spleen/BW ratios after 5 weeks of treatment. These data contribute to our knowledge of spontaneous disease progression in the thymus, spleen, lymph nodes, and kidneys in the MRL/lpr mouse and the effects of 3 different "toxic oils" and metals on the development and progression of those lesions.

Necropsy findings and environmental contaminants in common loons from New York

Diagnostic and analytical findings are presented for 105 common loons (Gavia immer) found dead or debilitated in New York (USA) from 1972-99. Aspergillosis (23% of cases) and ingestion of lead fishing weights (21%) were the most common pathologies encountered. Stranding on land, shooting, other trauma, gill nets, air sacculitis and peritonitis, and emaciation of uncertain etiology accounted for most of the remaining causes of disease or death. Analysis for total mercury in the liver of 83 loons yielded a geometric mean (gm) of 10.3 mg/kg (wet basis) and range of 0.07 to 371 mg/kg, with emaciated birds generally showing higher levels. Organochlorine contaminant levels in brain were generally low, principally consisting of PCB's (gm = 2.02 mg/kg) and DDE (0.47 mg/kg).

Recent advances in recognition of low-level methylmercury poisoning

Clinically evident neurologic damage from methylmercury exposure was well described following poisoning episodes in Japan and Iraq several decades ago. Paresthesias have been considered to be an early effect; however, additional data raise questions about whether this is the most sensitive adverse effect among adults. Fetuses are considered the most sensitive subpopulation because of the vulnerability of the developing nervous system. Over the past 5 years questions have been raised about what is an appropriate level of exposure for sensitive groups. A recent evaluation by a committee for the US National Research Council found that 0.1 microg/kg body weight per day is a scientifically justified level of methylmercury exposure for maternal-fetal pairs. The conclusions of this report and other issues are discussed in the present review. Because of anthropogenic release of mercury into the environment, methylmercury exposure from fish consumption is a pathway that is of increasing concern.

Histologic, neurologic, and immunologic effects of methylmercury in captive great egrets

Captive great egret (Ardea albus) nestlings were maintained as controls or were dosed with methylmercury chloride at low (0.5), and high doses (5 mg/kg, wet weight) in fish. Low dosed birds were given methylmercury at concentrations comparable to current exposure of wild birds in the Everglades (Florida, USA). When compared with controls, low dosed birds had lower packed cell volumes, dingy feathers, increased lymphocytic cuffing in a skin test, increased bone marrow cellularity, decreased bursal wall thickness, decreased thymic lobule size, fewer lymphoid aggregates in lung, increased perivascular edema in lung, and decreased phagocytized carbon in lung. High dosed birds became severely ataxic and had severe hematologic, neurologic, and histologic changes. The most severe lesions were in immune and nervous system tissues. By comparing responses in captive and wild birds, we found that sublethal effects of mercury were detected at lower levels in captive than in wild birds, probably due to the reduced sources of variation characteristic of the highly controlled laboratory study. Conversely, thresholds for more severe changes (death, disease) occurred at lower concentrations in wild birds than in captive birds, probably because wild birds were exposed to multiple stressors. Thus caution should be used in applying lowest observed effect levels between captive and wild studies.

Perimortem fixation of the gastric and duodenal mucosa: a diagnostic indication for oral poisoning

Two cases of fatal oral poisoning are presented. In the first case, a 40-year-old man died due to a lethal dose of mercury (blood concentration 113.8 microg/ml) and in the second, a 34-year-old man died of chloralhydrate overdose with a lethal blood concentration of trichloroethanol (52 microg/ml), the active metabolite of chloralhydrate. In both cases gross examination and histology showed an unusually well preserved gastrointestinal mucosa in addition to unspecific signs of intoxication. The two cases demonstrate that the phenomenon of perimortal fixation is a useful indication for the forensic pathologist and should direct the suspicion to oral poisoning. The detection of fixation facilitates toxicology screening by indicating that the relevant substance must have the capability to precipitate proteins.

Apparent diffusion coefficient on rat brain and nerves intoxicated with methylmercury

The effects of methylmercury chloride (MMC) on the degenerative changes in rat brain and cranial nerves were studied. Twelve Wistar rats were divided into two equal groups. The rat model of methylmercury intoxication (MMC group) was made by subcutaneously administering 10 mg mercury/g body weight daily for 7 days. Control group rats were infused with the same amount of normal saline during this period. Magnetic resonance imaging (MRI) measurements were performed before and 14 days after the first MMC administration, using a 4.7-T MR system. No significant focal changes were observed on T1- and T2-weighted MR images regarding the internal structures of the brains of the MMC-intoxicated rats, atrophy of the cerebellum, and dilatation of the arachnoid space around the brain stem of MMC-treated rats, but were demonstrated without edematous change. The apparent diffusion coefficients (ADC) of the cortex, caudate-putamen, and trigeminal nerve were not significantly different between the MMC-treated and control rats. However, the ADC parallel to the optic nerves were significantly increased in the MMC group, in contrast to the unchanged ADC perpendicular to the optic nerves. An electron microscopy study revealed a marked decrease of microtubules and moderate decrease of neurofilaments in the axons of myelinated fibers of optic nerves of the MMC-treated rats. We have thus demonstrated a disturbance in the integrity of microtubules and neurofilaments as a toxic action of MMC in the rat nervous system in vivo, particularly in the optic nerves. The use of ADC values calculated by diffusion-weighted MRI is a promising approach for the evaluation of changes in brains and nerves in methylmercury intoxication research.

Chronic inorganic mercury induced peripheral neuropathy

We report the clinical features, electrophysiological studies, and morphometric analysis of sural nerve pathology in a patient with polyneuropathy due to inorganic mercury intoxication. He developed slowly progressive generalized paralysis of all limbs after 3 months ingestion of herb drugs which contained mercuric sulfate. Electrophysiologic studies revealed axonal polyneuropathy involving both motor and sensory fibers. Sural nerve biopsy demonstrated axonal degeneration with demyelination and a predominant loss of large myelinated fibers. His muscle strength showed only mild improvement after 2 years' follow-up. We concluded that inorganic mercury exposure may induce severe axonal sensorimotor polyneuropathy in humans and that neurological deficits may persist in severe cases.

The present mercury contents of scalp hair and clinical symptoms in inhabitants of the Minamata area

A total of 191 fishermen and their family (32-82 years) living in some mercury-polluted areas along the Shiranui Sea volunteered for the present study. They made a living by fishery and had formerly eaten the methyl mercury-contaminated fish and shellfish caught there. The questionnaire on subjective symptoms, fish eating habits, and past living history was conducted on the subjects. In addition, they were clinically examined in detail by several neurologists and scalp hair was collected. With six exceptions, all the 185 subjects showed a normal total mercury level in hair (<10 ppm). The ratio of methyl mercury to total mercury was 79-94% on the average for each group examined, suggesting indirect contamination (perhaps through the food chain). Despite their low mercury level in scalp hair, however, the subjects showed various neurological symptoms, particularly, sensory disturbance (such as the glove and stocking type), at a very high rate. Thus, it seems fair to state that, in addition to officially recognized Minamata disease patients, there still exist many people with atypical, slight Minamata disease on the coast of the Shiranui Sea. The current hair mercury level is not necessarily useful as a criterion for diagnosing chronic Minamata disease because of the long lapse of time.

MR findings of Minamata disease--organic mercury poisoning

We describe MR findings in patients with Minamata disease who have been followed for a long time. All patients examined were affected after daily eating of a large quantity of methylmercury-contaminated seafood, from 1955 to 1958, and showed typical neurological findings. On MR images, the visual cortex, the cerebellar vermis and hemispheres, and the postcentral cortex are significantly atrophic in Minamata disease. The visual cortex is slightly hypointense on T1-weighted images and hyperintense on T2-weighted images, probably representing the pathologic changes of status spongiosus. MRI can demonstrate the lesions located in the calcarine area, cerebellum, and postcentral gyri, which are probably related to three of the characteristic manifestations of this disease: the constriction of the visual fields, ataxia, and sensory disturbance, respectively.

The chronic toxicity of inorganic mercury in goats: clinical signs, toxicopathological changes and residual concentrations

Chronic mercury toxicity was induced in goats by administering mercuric chloride at 100 micrograms/ml in deionized drinking water offered ad libitum for 90 days. Toxic signs of gastrointestinal disturbances and renal dysfunction developed from 43 days onwards without any mortality. The toxicity also induced nephrosis and tubular nephritis; centrilobular necrosis of liver; mild to moderate necrosis in spleen, intestine and lymph node; Zenker's degeneration of cardiac muscles; exudative pneumonia; and pial congestion, oedema and vacuolation in the brain. In addition, hyperaemia, oedema and tissue haemorrhages were evident in most of the organs. The kidneys contained the largest residues of mercury, followed by liver, spleen, intestine, lymph node, skeletal muscles, lungs, heart, brain and the omental fat. The intensity of the cytotoxic changes in the various organs was proportional to the amount of mercury accumulated.

A multidisciplinary clinical study of patients suffering from illness associated with mercury release from dental restorations: psychiatric aspects

The aim of this study was to map the psychological/psychiatric, odontological and medical aspects of patients with symptoms allegedly related to the side-effects of mercury in dental fillings. A total of 67 consecutive patients and 64 controls matched for age, sex and residential area were included in the study. The most striking result was the high prevalence of psychiatric disorders in the patients (89%) compared to the controls (6%), predominantly somatoform disorders. The personality traits differentiating the patients according to the Karolinska Scales of Personality (KSP) were somatic anxiety, muscular tension, psychasthenia and low socialization. More patients than controls showed alexithymic traits. The prevalence of diagnosed somatic diseases was higher, but not sufficiently so to explain the large difference in perceived health. The multiple symptoms and signs of distress displayed by the patients could not be explained either by the odontological data or by the medical examination. Our data indicate that the patients show sociodemographic and clinical patterns similar to those of somatizing patients. The medicalization of the suffering of these patients and the neglect of psychiatric problems prevent the use of appropriate psychotherapeutic approaches.

A review of experimental methylmercury toxicity in rats: neuropathology and evidence for apoptosis

As an animal model for examining the pathogenicity of human organic mercury intoxication, rats have been used for the reproduction of human neurologic diseases. Rats experimentally exposed to methylmercury chloride showed clinical signs of neurologic dysfunction characterized by ataxic behavior. Neuropathology of the diseased animals consisted of lesions such as: (a) degeneration of the peripheral nerve and sensory root nerve with preservation of the motor root nerve; (b) degeneration of the posterior funiculus of the spinal cord; and (c) degeneration of cerebellar granule cells with preservation of Purkinje cells. These findings suggest the human neuropathology of this toxicity. The degeneration was characterized by nerve fiber damage or neuronal cell death accompanied by astrocytic gliosis and activated macrophages or microglias. For the cerebellar granule cells, the mechanism of neuronal cell death was shown to be apoptosis. This fact was verified by histologic and ultrastructural findings as well as by in situ nick-end labeling and electrophoretic methods. Evidence of apoptosis involvement in cerebellar degeneration would provide a new viewpoint from which to analyze the selected degeneration of the nervous system in neurotoxicology.

Pathology of Minamata disease

Minamata disease, or methylmercury poisoning, was first discovered in 1956 around Minamata Bay, Kumamoto Prefecture, Japan. A similar epidemic occurred in 1965 along the Agano River, Niigata Prefecture, Japan. The neuropathology of Minamata disease has been well studied; this review focuses on human cases of Minamata disease in Kumamoto Prefecture. Nervous system lesions associated with Minamata disease have a characteristic distribution. In the cerebral cortex, the calcarine cortex was found to be involved in all cases of Minamata disease, particularly along the calcarine fissure. The destruction of nerve tissue was prominent in the anterior portions of the calcarine cortex. Occasionally, the centrifugal route from the visual and visual association areas (internal sagittal stratum) showed secondary degeneration in prolonged cases after acute onset. Postcentral, precentral, and temporal transverse cortices showed similar changes, though they were less severe. Intense lesions in the precentral cortex caused the development of secondary bilateral degeneration of the pyramidal tracts. In the cerebellum, the lesions occurred deeper in the hemisphere. The granule cell population was most affected. In the peripheral nerves, sensory nerves were more affected than motor nerves. Secondary degeneration of Goll's tracts was occasionally seen in prolonged or chronic cases.

Acute mercury poisoning by intentional ingestion of mercuric chloride

A 26-year-old woman ingested 0.9 g of mercuric chloride in a suicide attempt and developed hematemesis, melena and acute renal failure. Anuria persisted for 14 days. She was treated by plasma exchange, hemodialysis and peritoneal dialysis in combination with continued dimercaprol chelation. While hemodialysis was ineffective in removing the mercury, plasma exchange effectively eliminated mercury. After two plasma exchange therapies, mercury concentration in the blood decreased linearly on a log scale with half-lives of 23.1 days for whole blood and 19.1 days for plasma, using first-order kinetics. One month after ingestion, renal function recovered to normal as judged by serum creatine and blood urea nitrogen levels, although the beta 2-microglobulin level in urine was still elevated. At a follow-up examination four months later, renal function was found to be completely normal. This indicates that the renal damage caused by acute mercuric chloride poisoning may not be permanent.