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1.
Summary Diffusion of inorganic mercury (Hg 2+) through planar lipid bilayer membranes was studied as a function of chloride concentration and pH. Membranes were made from egg lecithin plus cholesterol in tetradecane. Tracer ( 203Hg) flux and conductance measurements were used to estimate the permeabilities to ionic and nonionic forms of Hg. At pH 7.0 and [Cl –] ranging from 10–1000 mm, only the dichloride complex of mercury (HgCl 2) crosses the membrane at a significant rate. However, several other Hg complexes (HgOHCl, HgCl
3
–
and HgCl
4
2–
) contribute to diffusion through the aqueous unstirred layer adjacent to the membrane. The relation between the total mercury flux ( J
Hg), Hg concentrations, and permeabilities is: 1/ J
Hg=1/ P
ul[ Hg
t
]+1/ P
m
[HgCl 2], where [Hg
t
] is the total concentration of all forms of Hg, P
ul is the unstirred layer permeability, and P
m
is the membrane permeability to HgCl 2. By fitting this equation to the data we find that P
m
=1.3×10 –2 cm sec –1. At Cl – concentrations ranging from 1–100 mm, diffusion of Hg
t
through the unstirred layer is rate limiting. At Cl – concentrations ranging from 500–1000 mm, the membrane permeability to HgCl 2 becomes rate limiting because HgCl 2 comprises only about 1% of the total Hg. Under all conditions, chemical reactions among Hg 2+, Cl – and/or OH – near the membrane surface play an important role in the transport process. Other important metals, e.g., Zn 2+, Cd 2+, Ag + and CH 3Hg +, form neutral chloride complexes under physiological conditions. Thus, it is likely that chloride can facilitate the diffusion of a variety of metals through lipid bilayer and biological membranes. 相似文献
2.
This study evaluated the effects of HgCl 2 on renal parameters in nonlactating and lactating rats and their pups, as well as the preventive role of ZnCl 2. Rats received 27 mg kg ?1 ZnCl 2 for five consecutive days and 5 mg kg ?1 HgCl 2 for five subsequent days (s.c.). A decrease in δ‐aminolevulinic acid dehydratase ( δ‐ALA‐D) activity in the blood and an increase in urine protein content in renal weight as well as in blood and urine Hg levels were observed in lactating and nonlactating rats from Sal―Hg and Zn―Hg groups. ZnCl 2 prevented partially the δ‐ALA‐D inhibition and the proteinuria in nonlactating rats. Renal Hg levels were increased in all HgCl 2 groups, and the ZnCl 2 exposure potentiated this effect in lactating rats. Nonlactating rats exposed to HgCl 2 exhibited an increase in plasma urea and creatinine levels, δ‐ALA‐D activity inhibition and histopathological alterations (necrosis, atrophic tubules and collagen deposition) in the kidneys. ZnCl 2 exposure prevented the biochemical alterations. Hg‐exposed pups showed lower body and renal weight and an increase in the renal Hg levels. In conclusion, mercury‐induced nephrotoxicity differs considerably between lactating and nonlactating rats. Moreover, prior exposure with ZnCl 2 may provide protection to individuals who get exposed to mercury occupationally or accidentally. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
3.
Acute effects of mercuric chloride (HgCl 2) were evaluated on mice. Mice received a single dose of HgCl 2 (4.6 mg/kg, subcutaneously) for three consecutive days. Thirty minutes after the last injection with HgCl 2, mice received one single injection of 2,3-dimercapto-1-propanesulfonic acid (DMPS) or N-acetylcysteine (NAC) or diphenyl diselenide (PhSe) 2. DMPS, NAC and (PhSe) 2 were utilized as therapy against mercury exposure. At 24 h after the last HgCl 2 injection, blood, liver and kidney samples were collected. δ-Aminolevulinate dehydratase (δ-ALA-D) and Na +, K -+ ATPase activities, thiobarbituric acid-reactive substances (TBARS), non-protein thiols (NPSH) and ascorbic acid concentrations
were evaluated. Plasma aspartate (AST) and alanine (ALT) aminotransferase activities, as well as urea and creatinine levels
were determined. The group of mice exposed to Hg + (PhSe) 2 presented 100% of lethality. Exposure with HgCl 2 caused a decrease on the body weight gain and treatments did not modify this parameter. δ-ALA-D, AST and ALT activities,
TBARS, ascorbic acid levels and NPSH (hepatic and erythrocytic) levels were not changed after HgCl 2 exposure. HgCl 2 caused an increase in renal NPSH content and therapies did not modify these levels. Mice treated with (PhSe) 2, Hg + NAC and Hg + DMPS presented a reduction in plasma NPSH levels. Creatinine and urea levels were increased in mice exposed
to Hg + NAC, while Hg + DMPS group presented an increase only in urea level. Na +, K -+ ATPase activity was inhibited in mice exposed to Hg + DMPS and Hg + NAC. In conclusion, therapies with (PhSe) 2, DMPS and NAC following mercury exposure must be better studied because the formation of more toxic complexes with mercury,
which can mainly damage renal tissue. 相似文献
4.
The accumulation of inorganic mercury from sea water by plaice eggs, larvae, and adult fish has been studied using 203HgCl 2 as a tracer. The isotope was rapidly accumulated and the levels of accumulation have been related to stable element concentrations. High concentration factors were attained by many organs, but the distribution of the 203Hg was markedly different from that of the stable element. Whereas the largest fraction of the body burden of mercury is contained by muscle, only a slow rate of accumulation into this tissue was observed. In addition, the mercury in fish muscle is of the methyl form: no evidence for the methylation of the tracer was obtained. 相似文献
5.
The toxicity of heavy metals such as mercury (Hg) in humans and animals is well documented. The kidney is the primary deposition site of inorganic-Hg and target organ of its toxicity. The present study investigated the protective efficacy of flaxseed lignan-Secoisolariciresinol diglucoside (SDG) on nephrotoxicity induced by mercuric chloride (HgCl2). Rats were intraperitoneally injected with HgCl2 (2 mg/kg/day) and renal toxicity was induced. Subcutaneous administration of rats with SDG (5 mg/kg/day) as a pre-treatment caused a significant reversal of HgCl2 induced increase in blood urea, creatinine, glutathione s-transferase and catalase (CAT). On the other hand, administration of SDG with HgCl2 restored normal levels of albumin and superoxide dismutase (SOD). Histological examination of kidneys confirmed that pre-treatment of SDG before HgCl2 administration significantly reduced its pathological effects. Thus, the results of the present investigation suggest that SDG can significantly reduce renal damage, serum and tissue biochemical profiles caused by HgCl2 induced nephrotoxicity. Hence, SDG may be recommended for clinical trials in the treatment of kidney disorders caused by exposure to Hg. 相似文献
6.
Summary Studies were conducted to evaluate the uptake of mercury by wheat ( Triticum aestivum L. runar) and beans ( Phaseolus vulgaris L. marshal) growth on an oxisol with different levels of 2-methoxyethylmercury chloride (Aretan) and mercuric chloride. Dry matter and grain yields of wheat were little affected by either Aretan or mercuric chloride, although Aretan at 50 mg Hg/kg soil delayed germination by four to five days. Germination of beans grown with both compounds at the 50 mg Hg/kg soil failed completely, even after repeated sowing. Yields were somewhat, though not significantly, decreased by mercury chloride up to 5 mg Hg/kg soil.The concentration of Hg in wheat straw and grain increased significantly with increased levels of Aretan and HgCl 2 application, with more Hg taken up by the plants grown with HgCl 2 than with those grown with Aretan. Translocation of Hg to grain was greater in the plants grown with HgCl 2.The concentration of Hg in bean straw, but not grain, increased significantly with increasing levels of Aretan and HgCl 2 application, and was greater in plants grown with HgCl 2. Translocation to grain was low, with little difference between plants grown with Aretan or HgCl 2. 相似文献
7.
The accumulation of organic mercury from sea water by plaice eggs, larvae and adult fish has been studied using CH 3203HgCl as a tracer. The isotope was rapidly accumulated, the largest fraction being taken up by muscle tissue. High concentration factors were attained by many internal organs, particularly blood, spleen, and kidney. Longer biological half-times than previous estimates with 203HgCl 2 were obtained: the possible consequences of inorganic mercury accumulated from sea water being excreted at the rate for methylmercury have been calculated. 相似文献
8.
The role of rhizosphere bacteria in facilitating Se and Hg accumulation in two wetland plants, saltmarsh bulrush ( Scirpus robustus Pursh) and rabbitfoot grass ( Polypogon monspeliensis (L.) Desf.), was studied. Ampicillin-amended plants (i.e., with inhibited rhizosphere bacteria) supplied with Na 2SeO 4 or HgCl 2 had significantly lower concentrations of Se and Hg, respectively, in roots than plants without ampicillin. These results
were confirmed by inoculating axenic saltmarsh bulrush plants with bacteria isolated from the rhizosphere of plants collected
from the field; these plants accumulated significantly more Se and Hg compared to axenic controls. Therefore, rhizosphere
bacteria can increase the efficiency of Se and Hg phytoremediation by promoting the accumulation of Se and Hg in tissues of
wetland plants.
Received: 9 April 1999 / Accepted: 11 May 1999 相似文献
9.
The effects of cadmium (Cd) on gene expression were examined in four organs (gills, liver, skeletal muscles and brain) of
the zebrafish. Adult male fish were subjected to three different water contamination pressures over periods of 7 and 21 days:
control medium (C 0: no Cd added) and two contaminated media (C 1: 1.9 ± 0.6 μg Cd l −1, and C 2: 9.6 ± 2.9 μg Cd l −1). Fourteen genes involved in antioxidant defences, metal chelation, active efflux of organic compounds, mitochondrial metabolism,
DNA repair and apoptosis were selected and their expression levels investigated by quantitative real-time PCR. Cadmium concentrations
were determined in the four organs and metallothionein (MT) protein levels investigated in brain, liver and gills. Although
skeletal muscle was a poor Cd-accumulating tissue, many genes were up-regulated at day 7: mt1, cyt, bax, gadd and rad51 genes. Three additional genes, c-jun, pyc and tap, were up-regulated in muscles at day 21 whereas bax, gadd and rad51 had returned to basal levels. Surprisingly, mt1 and c-jun were the only genes displaying a differential induction after 21 days in liver, although this organ accumulated the highest
cadmium concentration. In brain, only mt1, mt2 and c-jun genes were up-regulated after 21 days. In gills, the highest response was observed after 7 days, featuring the differential
expression of oxidative stress-response hsp70 and mitochondrial sod genes, along with genes involved in mitochondrial metabolism and metal detoxification. Then, after 21 days, the expression
of almost every genes returned to basal levels while both mt1 and mt2 genes were up-regulated. 相似文献
10.
SYNOPSIS. The behavior and ultrastructure of Tetrahymena pyriformis was assessed after exposure to dosages of 8 and 16% of the lethal concentration of HgCl 2 (TLm 96 hr). The lower dosage caused no abnormal changes in cell motility, activity of the water explusion vesicles, or cell shape; the higher dosage caused deleterious changes in these parameters. The higher sublethal HgCl 2 concentration (0.50 mg/liter) elicited damage of several cell structures. This damage persisted and accumulated with time up to 24 hr. At the lower HgCl 2 dosage (0.25 mg liter) there were extensive changes after 1-hr exposure involving primarily mitochondria; however, all major changes were repaired after 24 hr of constant exposure to the HgCl 2, indicating adaptation to the toxicant. Based solely on cytotoxic evidence an attempt is made to apply the findings defining what constitutes a “safe'’concentration of HgCl 2 in the cell's environment. 相似文献
11.
The fish gill is a multifunctional organ responsible for gas exchange and ionic regulation. It is hypothesized that both morphological
and functional differentiation can be found in the gills of the aquatic air-breathing fish, Trichogaster leeri. To test this, we used the air-breathing fish, Trichogaster leeri, to investigate various morphological/functional parameters. First, we evaluated the importance of performing the aquatic
surface respiration behavior in T. leeri. A reduced survival rate was observed when fish were kept in the restrained cages in hypoxic conditions. On the gross anatomy
of gills, we found evidence of both morphological and functional modification in the first and the second gills and are responsible
for ionic regulation. There were large-bore arterioarterial shunts in the fourth gill arch. It is specialized for the transport
of oxygenated blood and is less responsive to environmental stress. In addition, the anterior and the posterior gills differed
in the Na +, K +-ATPase activity upon ionic stresses. That is, only the Na +, K +-ATPase activity of the anterior two gills was up-regulated significantly in the deionized water. Lastly, we found that the
number of mitochondria-rich cells in the first and the second gills increased following ionic stress and no difference was
found in the third and the fourth gills following such an exposure. These results supported the hypothesis that there are
morphological and functional differences between anterior and posterior gill arches within the air-breathing Trichogaster leeri. In contrast, no significant difference was found among gills in gross anatomy, filament density and Na +, K +-ATPase activity in the non-air-breather, Barbodes schwanenfeldi. 相似文献
12.
The binding of mercuric ion (Hg(II)) by small molecules in the intracellular region of intact human erythrocytes has been studied by 1H-NMR spectroscopy. HgCl 2 added to intact erythrocytes in saline-glucose suspension is found to cross the membrane and reach an equilibrium distribution among the molecules of the erythrocyte within 4 min. In the intracellular region Hg(II) reacts with GSH and hemoglobin to form the ternary mixed-ligand complex GSH-Hg(II)-hemoglobin. The analogous complex with ergothioneine is formed after all the GSH is complexed. 1H-NMR spectra show that the GSH-Hg(II)-hemoglobin complex also forms in simpler solutions containing HgCl 2, GSH and hemoglobin, whereas the complex Hg(GSH) 2 predominates in solutions of GSH and HgCl 2. The lifetime of the GSH in the GSH-Hg(II)-hemoglobin complex is shown to be less than 30 s, which provides direct evidence for the first time that Hg(II) complexes in biological systems are quite labile, even though their thermodynamic stability is large. The effectiveness of eight sulfhydryl-containing ligands, some of which have been used as antidotes for Hg(II) poisoning, for releasing GSH from its Hg(II) complex in hemolyzed erythrocytes was also studied. Dithiol ligands were found to be more effective than monothiols, with dithioerythritol the most effective of the dithiols. 相似文献
13.
Although resistance of microorganisms to Hg(II) salts has been widely investigated and resistant strains have been reported
from many eubacterial genera, there are few reports of mercuric ion resistance in extremophilic microorganisms. Moderately
thermophilic mercury resistant bacteria were selected by growth at 62 °C on Luria agar containing HgCl 2. Sequence analysis of 16S rRNA genes of two isolates showed the closest matches to be with Bacillus pallidus and Ureibacillus thermosphaericus. Minimum inhibitory concentration (MIC) values for HgCl 2 were 80 μg/ml and 30 μg/ml for these isolates, respectively, compared to 10 μg/ml for B. pallidus H12 DSM3670, a mercury-sensitive control. The best-characterised mercury-resistant Bacillus strain, B. cereus RC607, had an MIC of 60 μg/ml. The new isolates had negligible mercuric reductase activity but removed Hg from the medium
by the formation of a black precipitate, identified as HgS by X-ray powder diffraction analysis. No volatile H 2S was detected in the headspace of cultures in the absence or presence of Hg 2+, and it is suggested that a new mechanism of Hg tolerance, based on the production of non-volatile thiol species, may have
potential for decontamination of solutions containing Hg 2+ without production of toxic volatile H 2S. 相似文献
14.
Kochia sieversiana (Pall.) C. A. M., a naturally alkali-resistant halophyte, was chosen as the test organism for our research. The seedlings
of K. sieversiana were treated with varying (0–400 mM) salt stress (1:1 molar ratio of NaCl to Na 2SO 4) and alkali stress (1:1 molar ratio of NaHCO 3 to Na 2CO 3). The concentrations of various solutes in fresh shoots, including Na +, K +, Ca 2+, Mg 2+, Cl −, SO 42−, NO 3−, H 2PO 3−, betaine, proline, soluble sugar (SS), and organic acid (OA), were determined. The water content (WC) of the shoots was calculated
and the OA components were analyzed. Finally, the osmotic adjustment and ion balance traits in the shoots of K. sieversiana were explored. The results showed that the WC of K. sieversiana remained higher than 6 [g g −1 Dry weight (DW)] even under the highest salt or alkali stress. At salinity levels >240 mM, proline concentrations increased
dramatically, with rising salinity. We proposed that this was not a simple response to osmotic stress. The concentrations
of Na + and K + all increased with increasing salinity, which implies that there was no competitive inhibition for absorption of either in
K. sieversiana. Based on our results, the osmotic adjustment feature of salt stress was similar to that of alkali stress in the shoots of
K. sieversiana. The shared essential features were that the shoots maintained a state of high WC, OA, Na +, K + and other inorganic ions, accumulated largely in the vacuoles, and betaine, accumulated in cytoplasm. On the other hand,
the ionic balance mechanisms under both stresses were different. Under salt stress, K. sieversiana accumulated OA and inorganic ions to maintain the intracellular ionic equilibrium, with close to equal contributions of OA
and inorganic ions to anion. However, under alkali stress, OA was the dominant factor in maintaining ionic equilibrium. The
contribution of OA to anion was as high as 84.2%, and the contribution of inorganic anions to anion was only 15.8%. We found
that the physiological responses of K. sieversiana to salt and alkali stresses were unique, and that mechanisms existed in it that were different from other naturally alkali-resistant
gramineous plants, such as Aneurolepidium chinense, Puccinellia tenuiflora.
Responsible Editor: John McPherson Cheeseman. 相似文献
15.
The effect of Hg treatment on hemolymph and tissue ferritin in the wax moth Galleria mellonella was examined by western blotting. At 48 h after feeding HgCl 2, the level of hemolymph ferritin increased approximately 1.8‐fold over that of control insects that were not fed HgCl 2, while there was a small increase in tissue ferritin. Time series experiments showed that tissue ferritin had a typically saturated pattern, with a maximum level from 24 to 72 h, although it decreased 12 h following HgCl 2 feeding, while hemolymph ferritin first decreased but subsequently increased. Tissue ferritin in the fat body, gut and Malpighian tubules, the main tissues of ferritin expression, was upregulated over time following treatment with Hg, and in particular, tissue ferritin in the gut increased by a large amount at 12–48 h. The results suggest that in G. mellonella, the ferritin‐inducible mechanisms following treatment with HgCl 2 are different for hemolymph and tissue ferritin, as are their biochemical properties. 相似文献
16.
The effects of HgCl 2 on urinary excretion of Zn, Cu and metallothionein at different time intervals were observed in male Wistar rats. The rats were given a daily intraperitoneal injection of 203HgCl 2 (0.5 or 1.0 mg Hg kg –1) for 2 days. 203Hg, Zn, Cu and metallothionein in urine, kidney and liver were analyzed. Significant increases in urinary Zn and Cu concentrations were found in HgCl 2-dosed groups. Elevated urinary Zn and Cu concentrations were accompanied by an increased metallothionein excretion in urine at different time periods. Zn concentration in urine remained elevated during the entire observation period of 7 days. There were also increased concentrations of Cu and Zn in the renal cortex in one of the two exposed groups. The results indicate that urinary Cu and Zn are related to the manifestation of renal toxicity and/or the synthesis of metallothionein in kidney induced by mercury. 相似文献
17.
The effectiveness of 2,3-dimercaptopropanol (BAL) and meso-2,3-dimercaptosuccinic acid (DMSA) on HgCl 2-induced nephrotoxicity was studied in the rat. Seven groups of adult male rats were given a single sc toxic dose of HgCl 2 (0.68 mg/kg) followed by 0.9% saline (positive control group), BAL (15, 30, and 60 mg/kg) or DMSA (50, 100, and 200 mg/kg)
administered ip at 0, 24, 48, and 72 h thereafter. Although the renal function of HgCl 2-exposed rats was slightly improved after BAL administration, Hg concentrations in the kidney were only reduced at 60 mg/kg.
In addition, the protective effect of BAL was not dose-related. In contrast to BAL, DMSA was effective in increasing the urinary
excretion of Hg and in reducing the renal Hg content. These results show that DMSA would be more effective than BAL in preventing
or in protecting against inorganic Hg-induced nephrotoxicity. 相似文献
18.
Effects of salt and alkali stresses on growth, osmotic adjustment and ionic balance of Suaeda glauca (Bge.), an alkali-resistant succulent halophyte, were compared. The results showed that alkali stress clearly inhibited the
growth of S.
glauca. Moreover, the concentrations of Na + and K + both increased with increasing salinity under both stresses, suggesting no competitive inhibition between absorptions of
Na + and K +. The mechanism underlying osmotic adjustment during salt stress was similar to alkali stress in shoots. The shared essential
features were that organic acids, betaine and inorganic ions (dominated by Na +) mostly accumulated. On the other hand, the mechanisms governing ionic balance under both stresses were different. Under
salt stress, S.
glauca accumulated organic acids and inorganic anions to maintain the intracellular ionic equilibrium, but the anion contribution
of inorganic ions was greater than that of organic acids. However, the concentrations of inorganic anions under alkali stress
were significantly lower than those under salt stress of the same intensity, suggesting that alkali stress might inhibit uptake
of anions, such as NO 3
– and H 2PO 4
–. Under alkali stress, organic acids were the dominant factor in maintaining ionic equilibrium. The contribution of organic
acids to anions was 74.1%, while that of inorganic anions was only 25.9%. S. glauca enhanced the synthesis of organic acids, dominated by oxalic acid, to compensate for the shortage of inorganic anions. 相似文献
19.
The Pseudomonas putida strain SP1 was isolated from marine environment and was found to be resistant to 280 μM HgCl 2. SP1 was also highly resistant to other metals, including CdCl 2, CoCl 2, CrCl 3, CuCl 2, PbCl 2, and ZnSO 4, and the antibiotics ampicillin (Ap), kanamycin (Kn), chloramphenicol (Cm), and tetracycline (Tc). mer operon, possessed by most mercury-resistant bacteria, and other diverse types of resistant determinants were all located
on the bacterial chromosome. Cold vapor atomic absorption spectrometry and a volatilization test indicated that the isolated
P. putida SP1 was able to volatilize almost 100% of the total mercury it was exposed to and could potentially be used for bioremediation
in marine environments. The optimal pH for the growth of P. putida SP1 in the presence of HgCl 2 and the removal of HgCl 2 by P. putida SP1 was between 8.0 and 9.0, whereas the optimal pH for the expression of merA, the mercuric reductase enzyme in mer operon that reduces reactive Hg 2+ to volatile and relatively inert monoatomic Hg 0 vapor, was around 5.0. LD 50 of P. putida SP1 to flounder and turbot was 1.5 × 10 9 CFU. Biofilm developed by P. putida SP1 was 1- to 3-fold lower than biofilm developed by an aquatic pathogen Pseudomonas fluorescens TSS. The results of this study indicate that P. putida SP1 is a low virulence strain that can potentially be applied in the bioremediation of HgCl 2 contamination over a broad range of pH. 相似文献
20.
Summary Soft water of low buffer capacity was drawn from near the branchial surface of rainbow trout ( Salmo gairdneri) at 15°C, using opercular catheters, to determine pH changes in water passing over the gills. Latex masks allowed measurement of ventilation volume, and concentrations of carbon dioxide, oxygen, ammonia, and titratable base in expired water were compared to concentrations in inspired water. Water passing over the gills was more basic than inspired water if the inspired water was pH 4–6 (maximum increase: +0.7 pH units near pH 5). Expired water was more acidic than inspired water if the inspired water was pH 6–10 (maximum decrease: –1.7 pH units near pH 9). Ventilation volume (0.37 l·kg –1·min –1) and oxygen consumption (1.7 mmol·kg –1·h –1) were constant in the pH range 4.6–10.1, but both increased by 1.6–2.4× near pH 4. Carbon dioxide transfer near the gills was about 100 M, ammonia transfer about 15 M, and titratable base added at the gills was about 30 M. A theoretical model using CO 2, titratable base, and ammonia added at the gills, the titration characteristics of the defined soft water medium, and aquatic equilibria for CO 2 and ammonia, adequately explained the experimentally observed changes in pH near trout gills. Our observations and predictive model indicate that any gill contaminant whose toxicity varies with pH may be more or less toxic at the gills than predicted from bulk water chemistry alone.Abbreviations
pH
ex
expired pH
-
pH
in
inspired pH 相似文献
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