Role Of Hg Research Articles

Factors influencing mercury levels in Leach's storm-petrels at northwest Atlantic colonies

Mercury (Hg) is a globally distributed heavy metal, with negative effects on wildlife. Its most toxic form, methylmercury (MeHg), predominates in aquatic systems. Levels of MeHg in marine predators can vary widely among individuals and populations. Leach's storm-petrels (Hydrobates leucorhous) have elevated levels of Hg but the role of Hg in storm-petrel population declines is unknown. In this study, we used egg and blood samples to study variation in Hg exposure among several northwest Atlantic colonies during breeding seasons, thereby evaluating relative toxicity risk within and among colonies. Total mercury (THg) concentrations were higher with increasing colony latitude, and were more pronounced in blood than in eggs. THg concentrations in blood were mostly associated with low toxicity risk in birds from the southern colonies and moderate risks in birds from the northern colonies; however, those values did not affect hatching or fledging success. THg concentrations in both eggs and blood were positively correlated with δ34S, emphasizing the role of sulfate-reducing bacteria in methylation of THg acquired through marine food webs, which is consistent with enriched δ34S profiles. By associating tracking data from foraging trips with THg from blood, we determined that blood THg levels were higher when storm-petrel's intensive search locations were over deeper waters. We conclude that spatial variation in THg concentrations in Leach's storm-petrels is attributable to differences in ocean depth at foraging locations, both at individual and colony levels. Differences in diet among colonies observed previously are the most likely cause for observed blood THg differences. As one of the few pelagic seabird species breeding in Atlantic Canada, with limited overlap in core foraging areas among colonies, Leach's storm-petrels can be used as biomonitors for less sampled offshore pelagic regions. The global trend in Hg emissions combined with legacy levels warrant continued monitoring for toxicity effects in seabirds.

Dynamic handgrip exercise for the evaluation of mitral valve regurgitation: an echocardiographic study to identify exertion induced severe mitral regurgitation

Handgrip exercise (HG) has been occasionally used as a stress test in echocardiography. The effect of HG on mitral regurgitation (MR) is not well known. This study aims to evaluate this effect and the possible role of HG in the echocardiographic evaluation of MR. 722 patients with MR were included (18% primary, 82% secondary disease). We calculated effective regurgitant orifice area (EROA) and regurgitant volume (RVOL) at rest and during dynamic HG. Increase in MR was defined as any increase in EROA or RVOL. We analyzed the data to identify possible associations between clinical or echocardiographic parameters and the effect of HG on MR. MR increased during dynamic HG in 390 of 722 patients (54%) (∆EROA = 25%, ∆RVOL = 27%). Increase of regurgitation occurred in 66 of 132 patients with primary MR (50%) and in 324 of 580 patients with secondary MR (55%). This increase was associated with larger baseline EROA and RVOL, but it was independent from other clinical or echocardiographic parameters. In secondary MR, dynamic HG led to a reclassification of regurgitation severity from non-severe at rest to severe MR during HG in 104 of 375 patients (28%). There was a significant association between this upgrade in MR classification and higher New York Heart Association (NYHA) class (OR 1.486, 95%-CI 1.138–1.940, p = 0.004). Dynamic HG exercise increases MR in about half of patients independent of the etiology. Dynamic HG may be used to identify symptomatic patients with non-severe secondary MR at rest but severe MR during exercise.

Ageing and preservation of HgS-enriched ancient human remains deposited in confinement

Mankind has been exposed to mercury (Hg) for thousands of years, but little information on the role of Hg on the preservation of ancient human remains has been addressed. In particular, the Maya people were expose to cinnabar (HgS), a naturally occurring mineral. Because in the Maya culture the red colour was symbolic of blood and blood sacrifice and associated to death and rebirth, For these reason, they often decorated burial chambers and covered sarcophagi, and corpses of important members of their society with HgS. However, scarce information has become available on the effects of HgS on the preservation of Maya human remains. This paper reports on the preservation of HgS-human remains, kept in sarcophagi away from sunlight and environmental humidity. Two HgS-enriched human remains collected from the Temples of the Scriptures (TS) and Temple XIII (TXIII) in the archaeological site of Palenque, Chiapas, Mexico were studied by radiocarbon dating, high resolution scanning and transmission electron microscopy, and energy dispersive X-ray spectroscopy. Conventional radiocarbon ages for S-TS and S-TXIII were 1360 ± 30 CE and 3100 ± 30 BCE, respectively, evidencing difference in age between the archaeological remains proximal to 1740 yrs. The more ancient specimen, S-TXIII, was linked to the excellent preservation of collagen preservation of collagen fibrils. The more recent remains (S-TS) displayed more abundant and richly diverse biological components, including highly porous tubules with irregular low and high accumulation of Hg in the walls, and ovoid protuberances. Micrographs showed excellently preserved biotubules denoting calcite permineralization, however, the presence of Hg provoked mineral dissolution explained in terms of biological activity. Mercury was found abundantly in ancient bone, which was explained because the dissolution of HgS after interacting with bioorganic material, and the formation of Hg-organic complexes. S-TS showed trace amounts of Hg and S, which were attributed to metabolic activity of microorganisms causing Hg volatilization and S decomposition. Furthermore, although microelemental analysis for both specimens showed the association of Hg with S, and HgS to be the source of these elements, the distribution of Hg clearly showed that the two royal characters held different lifestyle. On the one hand, Hg distribution in bone for the specimens showed that S-TXIII contained Hg in the regions covered by HgS; on the other hand, S-TS contained Hg throughout the bone structure. These results were interpreted to mean that both specimens S-TXII were covered by S-TS after dead and in addition, S-TS belonged in life to a character who was also exposed to Hg via inhalation or consumption of contaminated food, or liquids.

Anti-Inflammatory Potential of Hecogenin in Experimental Animals: Possible Involvement of Inflammatory Cytokines and Myeloperoxidase.

Hecogenin is a steroidal sapogenin plays important role in treatment of variety of inflammatory diseases. We have investigated the anti-inflammatory effects of Hecogenin (50 µg/animal) (HG), Fluticasone (50 µg/animal) (FC) and Hecogenin+Fluticasone (HG+FC) combination (25 µg/animal, each) on various inflammatory models. The anti-inflammatory effect of HG, FC and HG+FC combination was studied on % inhibition of dry weight of granuloma tissue, Δ ear weight, myeloperoxidase assay, serum pro-inflammatory cytokines, colon weight to length ratio, macroscopic lesions, adhesion score, diarrhoea score and histopathological analysis of ear and colon tissue on Cotton pellets induced granuloma in rats, Croton oil induced ear edema in mice and TNBS induced granuloma in rats. Topical administration of HG and its combination with FC showed significant decrease (p<0.001) in the % inhibition of dry weight of granuloma tissue, Δ ear weight, myeloperoxidase level, serum pro-inflammatory cytokines levels, colon weigh to length ratio as compared with Cotton pellets treated with acetone groups and Croton oil treated animals. Further histopathological analysis of ear tissue showed significant decrease in dermal thickness and epidermal hyperplasia and colon tissue showed reduction of edema, infiltration of inflammatory cells and normalization of crypt structure compared to DC animals. Thus, the findings of present study suggest the possible role of HG in the treatment of inflammation by reducing the dose of FC in combination with HG.

Role of Hg...Hg Interactions in Structure Stability of [HgX]- (X = Cl, Br, I) Based Inorganic-Organic Hybrid Compounds

Role of Hg...Hg Interactions in Structure Stability of [HgX]- (X = Cl, Br, I) Based Inorganic-Organic Hybrid Compounds

Effect of adding different contents of mercury to magnesium on discharge and corrosion performances of magnesium anode sheet

Discharge and corrosion performances of magnesium alloy anode sheets with content of Hg 1∼3 wt % were investigated. The results show that adding the element of Hg can promote discharge performance of magnesium alloy sheet in two ways: (i) adding an appropriate amount of Hg could inhibit the microgalvanic corrosion and prevent the formation of thick corrosion product film on the matrix surfaces, (ii) the second phase of Mg3Hg could activate magnesium matrix, improve peak voltage and effective discharge time. However, when the content of Hg exceeded tolerance limit, the corrosion rate of magnesium sheets would be accelerated greatly. The activation mechanism and the role of Hg in the process of corrosion product falling off were also investigated. The magnesium alloy anode sheets with Hg content between 1.65 and 2.16 wt % have the best discharge performance.

The plausibility of a role for mercury in the etiology of autism: a cellular perspective

Autism is defined by a behavioral set of stereotypic and repetitious behavioral patterns in combination with social and communication deficits. There is emerging evidence supporting the hypothesis that autism may result from a combination of genetic susceptibility and exposure to environmental toxins at critical moments in development. Mercury (Hg) is recognized as a ubiquitous environmental neurotoxin and there is mounting evidence linking it to neurodevelopmental disorders, including autism. Of course, the evidence is not derived from experimental trials with humans but rather from methods focusing on biomarkers of Hg damage, measurements of Hg exposure, epidemiological data, and animal studies. For ethical reasons, controlled Hg exposure in humans will never be conducted. Therefore, to properly evaluate the Hg-autism etiological hypothesis, it is essential to first establish the biological plausibility of the hypothesis. This review examines the plausibility of Hg as the primary etiological agent driving the cellular mechanisms by which Hg-induced neurotoxicity may result in the physiological attributes of autism. Key areas of focus include: (1) route and cellular mechanisms of Hg exposure in autism; (2) current research and examples of possible genetic variables that are linked to both Hg sensitivity and autism; (3) the role Hg may play as an environmental toxin fueling the oxidative stress found in autism; (4) role of mitochondrial dysfunction; and (5) possible role of Hg in abnormal neuroexcitory and excitotoxity that may play a role in the immune dysregulation found in autism. Future research directions that would assist in addressing the gaps in our knowledge are proposed.

Response of Cu0.5(Tl0.5−yHgy)Ba2Ca3Zn2Cu2O12−δ (y=0, 0.15, 0.25 and 0.35) superconductors in electric and magnetic fields

The superconducting properties of the Cu0.5(Tl0.5−yHgy)Ba2Ca3Zn2Cu2O12−δ compound have been studied by resistivity and ac magnetic susceptibility measurements. Mercury substitution has been found to improve the superconductivity of the Cu0.5Tl0.5Ba2Ca3Zn2Cu2O12−δ (CuTl-1234) compound, which is evidenced by the improvement of physical properties such as zero resistivity critical temperature, critical current density and flux pinning. The main objective of the present study was to examine the possible role of Hg in enhancing the superconducting properties of CuTl-1234. Post-annealing of the samples was also carried out at 550 °C in an oxygen atmosphere. The oxygen post-annealing enhanced the intergranular coupling and the superconducting properties of Cu1−xTlx-1234 samples. But ac susceptibility measurements under different magnetic fields show that CuTlHg-1234 has superior flux pinning characteristics as compared to Cu1−xTlx-1234, which make them useful for applications in external magnetic fields.

Aquaporin Isoforms Involved in Physiological Volume Regulation of Murine Spermatozoa1

Murine epididymal spermatozoa were dispersed in a medium of native osmolality and then transferred to a hypo-osmotic medium to mimic the physiological osmotic challenge, as encountered upon ejaculation into the female tract. The addition of quinine to block sperm K(+)-channels for volume regulation resulted in a size increase of viable cells. Preincubation in 0.1 mM HgCl(2), a standard aquaporin inhibitor, prevented such cell swelling. Addition of the K(+)-ionophore valinomycin to quinine-swollen sperm reversed the swelling, but not after pretreatment of the swollen sperm by HgCl(2). Aqp7, Aqp8, and Aqp9 mRNAs were identified in spermatozoa by RT-PCR, and the entire open reading frames were sequenced and compared with the GenBank database. Western blotting demonstrated specific protein signals for sperm AQP7 and AQP8 expression but probably not AQP9. The role of Hg(2+)-insensitive AQP7, if any, in sperm volume regulation was studied in transgenic mice. Spermatozoa from Aqp7(-/-) mice were the same size as wild-type sperm in basal conditions. Quinine-swollen volume, swelling reversal by valinomycin, and inhibition by Hg(2+) were also similar, indicating efficient water transport in the absence of AQP7. However, both water influx and efflux occurred faster in Aqp7(-/-) sperm than wild-type. This faster water movement in the knockout mouse spermatozoa was explainable by an upregulation of Aqp8 expression as revealed by quantitative PCR. Therefore, the Hg(2+)-sensitive AQP8, which was localized in elongated spermatids and spermatozoa, is a likely candidate for a water channel responsible for physiological sperm volume regulation crucial to in vivo fertilization.

Role of Hg in electronic properties in perovskite oxides HgMO3(M=Pb, Sn)

Role of Hg in electronic properties in perovskite oxides HgMO3(M=Pb, Sn)

A chemical assessment of the suitability of allyl- iso-propyltelluride as a Te precursor for metal organic vapour phase epitaxy

The chemical studies, which led to the testing of allyl- iso-propyltelluride (allylTePr i) as a Te precursor in metal organic vapour phase epitaxy are presented. The pyrolysis in hydrogen of allylTePr i gave products including 1,5-hexadiene, propane and propene. Co-pyrolysis of dimethylcadmium (Me 2Cd) and allylTePr i gave the hydrocarbons expected from the pyrolysis of the individual precursors plus additional hydrocarbons including 2-methylpropane and 1-butene. Plots of percentage decomposition versus temperature, which proved extremely useful in determining the likely growth temperatures for both CdTe and HgTe, showed that allylTePr i is less stable than both Pr 2 iTe (di- iso-propyltelluride) and Me 2Cd. The possible role of Hg in the growth of CdTe is also discussed. The chemistry of allylTePr i is well suited for use as an efficient precursor for epitaxial growth of tellurium containing semiconductors since there is very little formation of other organotellurium compounds on pyrolysis.

The role of Hg 63P0 atoms in mercury photosensitization. IV. Origin of the 4850 Å and 3350 Å bands

The continuous emission bands at 4850 Å and 3350 Å, attributed to the decay of electronically excited mercury molecules, have been studied in a flow system in which Hg 63P1 atoms were generated in the presence of nitrogen. The mechanism presented to account for the formation and decay of these eximers incorporates the assumption that these bands are derived by spontaneous emission from the A30u− and A31u states of the mercury molecule respectively. It is proposed that the A31u state is the precursor of the A30u− state.