Degradation of organic mercury in high salt environments by a marine aerobic bacterium Alteromonas macleodii KD01.

Mercury (Hg), particularly organic mercury, poses a global concern due to its pronounced toxicity and bioaccumulation. Bioremediation of organic mercury in high-salt wastewater faces challenges due to the growth limitations imposed by elevated Cl- and Na+ concentrations on microorganisms. In this study, an isolated marine bacterium Alteromonas macleodii KD01 was demonstrated to degrade methylmercury (MeHg) efficiently in seawater and then was applied to degrade organic mercury (MeHg, ethylmercury, and thimerosal) in simulated high-salt wastewater. Results showed that A. macleodii KD01 can rapidly degrade organic mercury (within 20 min) even at high concentrations (>10 ng/mL), volatilizing a portion of Hg from the wastewater. Further analysis revealed an increased transcription of organomercury lyase (merB) with rising organic mercury concentrations during the exposure process, suggesting the involvement of mer operon (merA and merB). These findings highlight A. macleodii KD01 as a promising candidate for addressing organic mercury pollution in high-salt wastewater.

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.

Differential Cell Metabolic Pathways in Gills and Liver of Fish (White Seabream Diplodus sargus) Coping with Dietary Methylmercury Exposure.

Mercury (Hg) is a dangerous and persistent trace element. Its organic and highly toxic form, methylmercury (MeHg), easily crosses biological membranes and accumulates in biota. Nevertheless, understanding the mechanisms of dietary MeHg toxicity in fish remains a challenge. A time-course experiment was conducted with juvenile white seabreams, Diplodus sargus (Linnaeus, 1758), exposed to realistic levels of MeHg in feed (8.7 µg g-1, dry weight), comprising exposure (E; 7 and 14 days) and post-exposure (PE; 28 days) periods. Total Hg levels increased with time in gills and liver during E and decreased significantly in PE (though levels of control fish were reached only for gills), with liver exhibiting higher levels (2.7 times) than gills. Nuclear magnetic resonance (NMR)-based metabolomics revealed multiple and often differential metabolic changes between fish organs. Gills exhibited protein catabolism, disturbances in cholinergic neurotransmission, and changes in osmoregulation and lipid and energy metabolism. However, dietary MeHg exposure provoked altered protein metabolism in the liver with decreased amino acids, likely for activation of defensive strategies. PE allowed for the partial recovery of both organs, even if with occurrence of oxidative stress and changes of energy metabolism. Overall, these findings support organ-specific responses according to their sensitivity to Hg exposure, pointing out that indications obtained in biomonitoring studies may depend also on the selected organ.

Deciphering the Global Proteomic Profile Involved in Methylmercury-Induced Cerebellar Neurodegeneration and Motor Dysfunction in Adult Rats.

Mercury is a ubiquitous pollutant in the environment with potential neurotoxic effects. Several populations are susceptible to mercurial exposure, especially methylmercury (MeHg) at low doses for long periods through food consumption. Given this, the present work aimed to assess the effects of long-term MeHg exposure on the cerebellum of rats from a translational perspective using a representative dose, assessing molecular, biochemical, morphological, and behavioral parameters. The model was produced by administering 40 µg/kg of MeHg for 60 days to adult male Wistar rats by oral gavage. As a result of this exposure, the animals presented motor deficits in open field and rotarod tests which were associated with an increase in total mercury content in cerebellar parenchyma, a reduction in antioxidant competence against peroxyl radicals, and increased nitrite and lipid peroxidation levels. The proteomic approach showed 317 modulated proteins. Such findings were associated with reductions in mature neuron and Purkinje cell densities and glial fibrillary acidic protein immunostained areas and increased microglial density. In addition, decreases in myelin basic protein and synaptophysin immunostaining were also observed. The results thus provided new evidence of the mechanisms underlying complex MeHg-induced neurodegeneration, especially the proteins underlying the biochemical and morphological features associated with motor dysfunction.

Consequences of thimerosal on human erythrocyte hemoglobin: Assessing functional and structural protein changes induced by an organic mercury compound.

BACKGROUND: Thimerosal (TM) is an organic mercury compound used as a preservative in many pharmacological inputs. Mercury toxicity is related to structural and functional changes in macromolecules such as hemoglobin (Hb) in erythrocytes (Ery). METHOD: Human Hb and Ery were used to evaluate O2 uptake based on the TM concentration, incubation time, and temperature. The influence of TM on the sulfhydryl content, production of reactive oxygen species (ROS), and membrane fragility was also evaluated. Raman spectra and atomic force microscopy (AFM) profiles for Ery in the presence and absence of TM were calculated, and docking studies were performed. RESULTS: At 37 °C, with 2.50 µM TM (higher concentration) and after 5 min of incubation in Hb and Ery, we observed a reduction in O2 uptake of up to 50 %, while HgCl2, which was used as a positive control, showed a reduction of at least 62 %. Total thiol assays in the presence of NEM (thiol blocker) quantified the preservation of almost 60 % of free SH in Ery. Based on the Raman spectrum profile from Ery-TM, structural differences in the porphyrinic ring and the membrane lipid content were confirmed. Finally, studies using AFM showed changes in the morphology and biomechanical properties of Ery. Theoretical studies confirmed these experimental results and showed that the cysteine (Cys) residues present in Hb are involved in the binding of TM. CONCLUSION: Our results show that TM binds to human Hb via free Cys residues, causing conformation changes and leading to harmful effects associated with O2 transport.

Organic mercury solid phase chemoselective capture for proteomic identification of S-nitrosated proteins and peptides.

Cysteine S-nitrosation mediates NO signaling and protein function under pathophysiological conditions. Herein, we provide a detailed protocol regarding the organic mercury chemoselective enrichment of S-nitrosated proteins and peptides. We discuss key aspects of the enrichment strategy and provide technical tips for the best performance of the experimental protocol.

DNA-templated fluorescent silver nanoclusters on-off switch for specific and sensitive determination of organic mercury in seafood.

Organic mercury including methyl-mercury and ethyl-mercury (CH3Hg+ and C2H5Hg+) has high toxicity and bio-accumulation, and thus is easy to generate bio-amplification in food chain. Hence, the specific detection of organic mercury has great significance for objectively assessing the health risk of mercury in seafood. We herein designed an aptamer (AS-T7), which consists of a silver nanoclusters (AgNCs) scaffold sequence (AS) and a T-rich sequence (AT7), for simultaneously synthetizing DNA-templated AgNCs and recognizing organic mercury, and further developed a label-free fluorescent method for the sensitive and specific determination of organic mercury (CH3Hg+ and C2H5Hg+ total concentration) by using DNA-templated AgNCs as signal. Without organic mercury, Ag+ in the mixture of aptamer and Ag+ was bond on AS of aptamer to form AS-templated AgNCs after reduction, and thus emitted strong fluorescence. Whereas, in the presence of organic mercury, CH3Hg+/C2H5Hg+ was bond on AT7 of aptamer to generate photoinduced electron transfer (PET) between CH3Hg+/C2H5Hg+ and AS-templated AgNCs, and thus results in fluorescence quenching of AS-templated AgNCs. The fluorescent method could be used to rapidly detect organic mercury with a detection limit of 5.0 nM (i.e. 1.01 ng Hg/g), which meets the U.S. EPA standard of 0.3 mg/kg (wet). The method was successfully used to detect organic mercury in water and fish muscle with a recovery of 96%-104% and an inter-days RSD (n = 5) < 7%. The success of the study promised a reliable method for rapid and specific detection of organic mercury in environmental and biological samples.

A nanozyme-based enhanced system for total removal of organic mercury and SERS sensing.

Total removal of organic mercury in industrial wastewater is a crucially important task facing environmental pollution in the current world. Herein, we demonstrate the fabrication of Au-NiFe layered double hydroxide (LDH)/rGO nanocomposite as not only an efficient nanozyme with oxidase-like activity but also an efficient surface-enhanced Raman spectroscopy (SERS) substrate to determine organic mercury, with the minimum detection concentration as low as 1 × 10-8 M. According to the binding energy of X-Ray photoelectron spectrometer (XPS) and the free radicals of electron paramagnetic resonance (EPR) spectra, the mechanism of catalytic enhanced degradation is the production of Au-amalgam on Au surface, accelerating the electron transfer and the generation of O2•- radicals from oxygen molecules and •CH3 radicals from the methyl group in MeHg to participate the oxidase-like reaction. Furthermore, the Au-NiFe LDH/rGO nanocomposite is able to degrade and remove 99.9% of organic mercury in two hours without the secondary pollution by Hg2+. In addition, the material can be used for the multiple degradation-regeneration cycles in actual applications, which is significant in terms of the environmental and economic point of view. This work may open a new horizon for both highly sensitive detection and thorough degradation of organic mercury in environmental science and technology.

Evaluation of Dietary Organic and Inorganic Mercury Threshold Levels on Induced Mercury Toxicity in a Marine Fish Model.

Mercury as one of the most toxic elements can be present in organic or inorganic form in marine fishes, which may cause a potential threat to public health. In this study, we investigated to determine the dietary organic (O-Hg) and inorganic (I-Hg) mercury threshold levels on induced mercury toxicity in juvenile olive flounder, Paralichthys olivaceus as a marine fish model. Twenty-eight fish averaging 3.1 ± 0.05 g (mean ± SD) were arbitrarily assigned to each of 27 tanks. Each tank was arbitrarily restricted to triplicates of nine experimental diets for eight weeks. The experimental diets were manufactured to contain 0 (Control), 10 (I-Hg10, O-Hg10), 20 (I-Hg20, O-Hg20), 40 (I-Hg40, O-Hg40) and 160 (I-Hg160, O-Hg160) mg/kg diet in organic form as methylmercury (MeHg) or in inorganic form as mercuric chloride (HgCl2). At the termination of the experimental trial, weight gains (WGs) of fish fed the control and 10 (I-Hg10, O-Hg10) diets were remarkably higher than those of fish fed the 20 (I-Hg20, O-Hg20), 40 (I-Hg40, O-Hg40) and 160 (I-Hg160, O-Hg160) (p < 0.05). Specific growth rate and feed efficiency of fish fed control and 10 (I-Hg10, O-Hg10) diets were significantly higher than those of fish fed 40 (I-Hg40, O-Hg40) and 160 (I-Hg160, O-Hg160) diets. In comparison to the dietary inorganic mercury, dietary MeHg bioaccumulation rates were significantly higher in the tissue levels according to the dietary inclusion levels. MeHg accumulated mostly in kidney, followed by liver and gill tissues. HgCl2 accumulated in tissues, in decreasing order, liver > kidney > gills. A broken-line regression model for percentage of WG indicated that the threshold toxicity level for an Hg-incorporated diet of juvenile olive flounder could be 13.5 mg Hg/kg in the form of HgCl2 and 8.7 mg Hg/kg in the form of MeHg.

Neuropathology associated with exposure to different concentrations and species of mercury: A review of autopsy cases and the literature.

BACKGROUND: Human exposure to mercury (Hg) is widespread and both organic and inorganic Hg are routinely found in the human brain. Millions of people are exposed to methyl Hg (MeHg) due to the consumption of fish and to inorganic Hg from dental amalgams, small scale gold mining operations, use of Hg containing products, or their occupations. Neuropathology information associated with exposures to different species of Hg is primarily based on case reports of single individuals or collections of case studies involving a single species of Hg at toxic exposure levels such as occurred in Japan and Iraq. METHODS/RESULTS: This study brings together information on the neuropathological findings and deposition of Hg in the central nervous system of people exposed to different species of Hg at varying concentrations. The low dose exposures were lifetime exposures while the high dose exposures were generally acute or short term by different exposure routes with survival lasting various lengths of time. Total and inorganic Hg deposits were identified in formalin-fixed, paraffin embedded tissues from both low and high exposure Hg cases. Low concentration exposures were studied in adult brains from Rochester, New York (n = 4) and the Republic of Seychelles (n = 17). Rochester specimens had mean total Hg concentrations of 16-18 ppb in the calcarine, rolandic, and cerebellar cortices. Inorganic Hg averaged between 5-6 ppb or 30-37% for the cerebral and cerebellar cortices of the Rochester subjects. Total Hg was approximately 10-fold higher in specimens from Seychelles, where consumption of ocean fish is high and consequently results in exposure to MeHg. The predominant Hg species was MeHg in both the Rochester and Seychelles brain specimens. Histologically, cerebral and cerebellar cortices from Rochester and Seychelles specimens were indistinguishable. High concentration exposures were studied in brains from four adults who were autopsied at variable time periods after exposure to organic Hg (methyl or dimethyl) or inorganic Hg (inhaled vapor or intravenous injection of metallic Hg). In contrast to the Seychellois adults, these individuals had acute or subacute exposures to lethal or significantly higher concentrations. The pattern of Hg deposition differed between subjects with high organic Hg exposure and high inorganic Hg exposure. In the organic Hg cases, glia (astrocytes and microglia) and endothelial cells accumulated more Hg than neurons and there were minimal Hg deposits in cerebellar granule and Purkinje cells, anterior horn motor neurons, and neocortical pyramidal neurons. In the inorganic Hg cases, Hg was seen predominantly in neurons, vascular walls, brainstem, and cerebellar and cerebral deep gray nuclei. The presence of inorganic Hg in neural and neural supporting cells in the four high exposure Hg cases was not closely correlated with cellular pathology; particularly in the inorganic Hg cases. CONCLUSIONS: Different Hg species are associated with differing neuropathological patterns. No neuropathological abnormalities were present in the brains of either Rochester or Seychelles residents despite substantial differences in dietary MeHg exposure. Increasing concentrations of inorganic Hg were present in the brain of relatively low exposure subjects with increasing age.

Metal organic framework assisted in situ complexation for miniaturized solid phase extraction of organic mercury in fish and Dendrobium officinale.

Zirconium-based metal-organic frameworks, namely Zr-based MOF, was employed as adsorbent material in the miniaturized solid phase extraction of organic mercury compounds in food prior to capillary electrophoresis-diode array detector analysis. The synthesized adsorbent was characterized by different spectroscopic techniques. Parameters influencing the extraction and complexation of methylmercury chloride, ethylmercury chloride and phenylmercury chloride such as type of eluent solvent, type and amount of adsorbent were investigated. In addition, linear ranges contained 2.00-300.00 ng mL-1 for MeHg+, 5.00-500.00 ng mL-1 for EtHg+ and PhHg+, and the established method presented good linearity (R2 ≥ 0.998). Under the optimized experimental conditions, the ranges of detection limit and quantitation limit were 0.022-0.067 ng mL-1 and 0.073-0.220 ng mL-1, respectively. The relative standard deviations of intra- and inter-day analysis were less than 3.2 and 3.1%, respectively. Trueness of the present method was successfully accomplished by means of the recovery assays (81.4-98.5%) in the blank samples with two concentration levels. The repeatability %RSD of the method was lower than 2.7%. Overall, the developed approach proved to have the latent capability to be utilized in routine analysis of organic mercury compounds in fish and Dendrobium officinale.

Examining the evidence that ethylmercury crosses the blood-brain barrier.

Scientific research can provide us with factual, repeatable, measurable, and determinable results. As such, scientific research can provide information that can be used in the decision-making process in the care of patients and in public policy. Although it has been suggested that ethylmercury (C2H5Hg+)-containing compounds do not cross the blood-brain barrier (BBB), this review examines the literature that addresses the question as to whether ethylmercury-containing compounds cross the BBB. The review will begin with cellular studies that provide evidence for the passive and active transport of mercury species across the BBB. Then, animal and clinical studies will be presented that specifically examine whether mercury accumulates in the brain after exposure to ethylmercury-containing compounds or Thimerosal (an ethylmercury-containing compound used as a preservative in vaccines and other drugs that metabolizes or degrades to ethylmercury-containing compounds and thiosalicylate). The results indicate that ethylmercury-containing compounds are actively transported across membranes by the L (leucine-preferring)-amino acid transport (LAT) system, the same as methylmercury-containing compounds. Further, 22 studies from 1971 to 2019 show that exposure to ethylmercury-containing compounds (intravenously, intraperitoneally, topically, subcutaneously, intramuscularly, or intranasally administered) results in accumulation of mercury in the brain. In total, these studies indicate that ethylmercury-containing compounds and Thimerosal readily cross the BBB, convert, for the most part, to highly toxic inorganic mercury-containing compounds, which significantly and persistently bind to tissues in the brain, even in the absence of concurrent detectable blood mercury levels.

Mercury levels in Southern Ocean squid: Variability over the last decade.

The concentrations of total and proportions of organic mercury were measured in tissues of 355 individuals of 8 species of Southern Ocean squid (Alluroteuthis antarcticus, Bathyteuthis abyssicola, Filippovia knipovitchi, Galiteuthis glacialis, Gonatus antarcticus, Kondakovia longimana, Psychroteuthis glacialis and Slosarczykovia circumantarctica). Squid were caught around South Georgia (Scotia Sea) during 5 cruises, between the austral summers of 2006/07 to 2016/17 to evaluate temporal changes in bioaccumulation and tissue partitioning. Total mercury concentrations varied between 4 ng g-1 and 804 ng g-1 among all tissues. Net accumulation of mercury in muscle with size was observed in A. antarcticus, B. abyssicola and P. glacialis, but no relationship was found for S. circumantarctica and lower concentrations were observed in larger individuals of G. glacialis. Muscle tissues had the highest mercury concentrations in the majority of species, except for F. knipovitchi for which the digestive gland contained highest concentrations. In terms of the percentage of organic mercury in the tissues, muscle always contained the highest values (67%-97%), followed by the digestive gland (22%-38%). Lowest organic mercury percentages were found consistently in the gills (9%-19%), suggesting only low levels of incorporation through the dissolved pathway and/or a limited redistribution of dietary organic mercury towards this tissue. Overall, results are indicative of a decreasing trend of mercury concentrations in the majority of analysed species over the last decade. As cephalopods are an important Southern Ocean trophic link between primary consumers and top predators, these changes suggest decreasing mercury levels in lower trophic levels and an alleviation of the mercury burden on higher predators that consume squid.

Baseline concentrations of mercury species within sediments from Qatar's coastal marine zone.

Baseline concentration of total mercury (THg), organic extractable mercury and methylmercury (CH3Hg) concentrations in sediments from the northeastern, eastern and southeastern parts of the Arabian Gulf were assessed. Surface sediments were collected from eleven stations from the coastal waters of Qatar. All analyses were performed on homogenised samples. Total mercury analysis was performed by Cold Vapour Atomic Absorption Spectrometry (CVAAS), and methylmercury was analysed by Cold Vapour Atomic Fluorescence spectrometry (CVAFS) after aqueous phase ethylation of the extracted samples. Total mercury (THg) in sediments varied from 8.0 µg/kg to 34.3 µg/kg. Methylmercury was detected in all stations and ranged from 1.46 µg/kg to 3.10 µg/kg accounting for 5.4% to 18.4% of total mercury. Total organic carbon (TOC) ranged from 0.16 to 0.72%, while Organic extractable mercury ranged from 1.55 µg/kg to 13.3 µg/kg. Analysis, the grain size within these sediments, was carried out previously paving the way for studying the influence of these parameters on the sedimentary mercury concentration. Speciation was also assessed, as were relations between the measured mercury fractions.

Potential of Organic Mercury-resistant Bacteria Isolated from Mercury Contaminated Sites for Organic Mercury Remediation.

BACKGROUND AND OBJECTIVE: Efforts at organic mercury detoxification can be carried out using resistant bacteria that can live in an environment contaminated with the compound. This study aimed at isolating and identifying resistant bacteria from mercury-contaminated environments and analysing their ability to detoxify organic mercury. MATERIALS AND METHODS: Soil samples were obtained from 3 gold processing locations that make use of mercury in Tanoyan Village, Bolaang Mongondow district, North Sulawesi province. The identification was carried out on the mercury-resistant bacteria through morphological and molecular tests. Bacteria which were highly resistant to mercury were examined for their ability to detoxify phenyl mercury (organic mercury). RESULTS: The study showed that 8 mercury-resistant bacterial colonies could be isolated from the three soil samples. The bacteria were able to grow in LB broth containing 10 mg L-1 of phenyl mercury. Four isolates (AA, BB, CC and DD) were even able to grow in 40 mg L-1 of phenyl mercury. According to the identification tests, those bacteria were Pseudomonas sp. (AA, DD), Pseudomonas aeruginosa (BB) and Proteus mirabilis (CC). Testing of organic mercury against isolates of bacteria which are highly resistant to it in order to determine their detoxification capacity revealed that all four isolates could reduce levels of the compound in media, based on the results, starting from the highest was Pseudomonas sp. 74.99%, then Pseudomonas aeruginosa 60.23% and Proteus mirabilis 47.59% after 24 h of incubation. CONCLUSION: The study suggested that there are four bacteria that have potentials to remediate organic mercury contamination sites.

Direct speciation analysis of organic mercury in fish and kelp by on-line complexation and stacking using capillary electrophoresis.

To determine organic mercury (Hg) species that could not be detected by ultraviolet (UV), a highly automated on-line complexation method was established, which combined with normal stacking by capillary electrophoresis-diode array detector. The approach was based on the fact that the compounds and complex reagent interacted to form hydrophilic chelates under the effect of the separation voltage, which was effectively separated and detected by UV. Key parameters, such as the type and concentration of complex reagent, separation voltage and so on were systematically investigated. Under the optimized conditions, the precision and repeatability were in the range of 0.16-3.31% and 0.17-1.21%, respectively. Furthermore, PhHg, EtHg and MeHg were effectively separated and determined in fresh fish (Silver carp) muscle and kelp (Kombu) with the recoveries of 84.63-111.39% and 75.68-114.76%, respectively. The proposed method had the advantages of easy-operating, cost-efficient, stable and reliable compared to off-line complexation method.

Comparison of Visual Functions of Two Amazonian Populations: Possible Consequences of Different Mercury Exposure.

The present study investigated the visual perimetry and color vision of two Amazonian populations differently exposed to mercury. Ten riverines environmentally exposed to mercury by fish eating and 34 gold-miners occupationally exposed to mercury vapor. The visual perimetry was estimated using the Förster perimeter and the color vision was evaluated using a computerized version of Farnsworth-Munsell test. Riverine and gold-miners' hair mercury concentrations were quantified. Mercury hair concentration of the riverines was significantly higher than that from gold-miners. Riverines had lower perimetric area than the gold-miners. The errors in the hue ordering test of both Amazonian populations were larger than the controls (non-exposed subjects), but there was no difference between themselves. Riverines had significant multiple association between the visual function and hair mercury concentration, while the gold-miners has no significant association with the exposure. We concluded that the different ways of mercury exposure led to similar visual outcomes, with greater impairment in riverines (organic mercury exposed subjects).

Low doses of methylmercury exposure during adulthood in rats display oxidative stress, neurodegeneration in the motor cortex and lead to impairment of motor skills.

Despite the vast distribution among tissues, the central nervous system (CNS) represents the main target of methylmercury (MeHg) toxicity. However, few studies have evaluated the effects of MeHg exposure on the CNS at equivalent doses to human environmental exposure. In our study, we evaluated the motor cortex, an important area of motor control, in adult rats chronically exposed to MeHg in a concentration equivalent to those found in fish-eating populations exposed to mercury (Hg). The parameters evaluated were total Hg accumulation, oxidative stress, tissue damage, and behavioral assessment in functional actions that involved this cortical region. Our results show in exposed animals a significantly greater level of Hg in the motor cortex; increase of nitrite levels and lipid peroxidation, associated with decreased antioxidant capacity against peroxyl radicals; reduction of neuronal and astrocyte density; and poor coordination and motor learning impairment. Our data showed that chronic exposure at low doses to MeHg is capable of promoting damages to the motor cortex of adult animals, with changes in oxidative biochemistry misbalance, neurodegeneration, and motor function impairment.

Saint Ioannis Lampadistis, the first possible case of blindness due to organic mercury poisoning in history.

Saint Ioannis Lampadistis is a Cypriot saint of the Greek Orthodox Church, widely venerated in his island of origin. He lived during the 11th century and was blinded by ingesting contaminated fish in the mountainous area of Galata, withdrew from civil life when he was 18, and died at the age of 22. The reason for his blindness remains unknown, though it is widely attributed to an unknown poison related to the copper mines of the region. As fish is the end reservoir of organic mercury, it is quite possible that his blindness was the result of heavy metal toxicity. Organic mercury is associated with CNS atrophy and hypoplasia, and blindness is a frequent presenting symptom. While not much is known about the saint's clinical symptoms (as his ecclestiastical biography focuses on his example and miracles), organic mercury poisoning could explain his sudden loss of vision, thus possibly making him the first-recorded case of organic mercury poisoning in history.

Transfer of mercury and phenol derivatives across the placenta of Baltic grey seals (Halichoerus grypus grypus).

The placenta is an intermediary organ between the female and the developing foetus. Some chemical substances, including the most harmful ones, exhibit the ability to accumulate in or penetrate through the placenta. The aim of the study was to determine the role of the placenta of the Baltic grey seal (Halichoerus grypus grypus) in the transfer of endocrine disrupting compounds (EDCs) - (bisphenol A, 4-tert- octylphenol, 4- nonylphenol), as well as total and organic mercury. 30 placentas were collected from grey seals pupping under human care at the Hel Marine Station in the years 2007-2016. The assays were conducted using the technique of high-preformance liquid chromatography (phenol derivatives) and atomic absorption spectrometry (mercury and selenium). A measurable level of EDCs was indicated in the placentas of grey seals. It was established that the inorganic Hg form was accumulated in the placenta, and that its concentrations were an order of magnitude higher than the concentrations of the organic form, which penetrated to the foetus. Similar observations were made for phenol derivatives - bisphenol A, 4-tert- octylphenol and 4-nonylphenol. For this compound group the placenta was a barrier, but the properties of phenol derivatives suggest the possibility of their penetration through this organ.