Effects Of Mercury Ions Research Articles

Effect of mercury ions on cysteine metabolism in Xenopus laevis tissues

The effect of mercury ions on the level of cysteine, glutathione, sulfane sulfur, and on the activity of rhodanese, 3-mercaptopyruvate sulfurtransferase (MPST) and γ-cystathionase in brain, heart muscle, liver, kidneys, testes and skeletal muscle of adult Xenopus laevis was investigated. Frogs of both sexes were exposed for 7 or 14days to 1.353mgL−1 (ppm) of mercury chloride (HgCl2) dissolved in water. The activity of the investigated enzymes participating in cysteine metabolism depends on cysteine in their active sites. Mercury ions can bind to –SH groups and, therefore, lower the activity of enzymes and change the level of sulfane sulfur, a product of l-cysteine desulfuration. The effect of mercury was found to depend on the time of exposure and the kind of tissue. In the liver, the main site of glutathione biosynthesis, the ratio of GSH to GSSG was essentially unchanged. The total glutathione level was decreased after 7days of exposure to mercury, similarly as the activity of rhodanese. Sulfane sulfur levels were significantly increased after a shorter duration, while they decreased after a longer time of exposure. The kidney, brain and testes were able to enhance the level of GSH, probably thanks to high γ-glutamyltranspeptidase activity. These tissues showed an increased value of GSH/GSSG ratio during the shorter exposure to mercury. The activity of sulfurtransferases was decreased, especially after the longer exposure to mercury. In the heart and skeletal muscle, the level of GSH, sulfane sulfur, and the activity of the investigated sulfurtransferases was diminished after 14days of exposure to Hg. It can be concluded that the main mechanism of toxic Hg activity is generation of reactive oxygen species in cells due to depleted GSH level, and a decreased sulfurtransferases activity either by blocking or oxidation of their –SH groups, what in consequence results in a diminished sulfane sulfur levels in tissues, especially the heart and testes.

Co-intensification of cyanide leaching gold by mercury ions and oxidant

The effects of mercury ions on gold cyanidation were studied. The results show that under low cyanide concentration, gold cyanide process is controlled by CN − transfer, while at higher cyanide concentration, there forms passivation on gold surface. Therefore, chemical oxidation of gold in cyanide solution of higher concentration is controlled by surface reaction. Small quantity of additions of mercury ions bring about great increases in anodic gold dissolution rate, decreases the passivation and reduces the equilibrium activated energy. In addition, they also markedly change the effect pattern of cyanide concentration. Mercury ions show positive effects on cathodic reduction of oxygen and raise the rate of electrochemical step of the cathodic reduction of oxygen. Addition of a certain amount of hydrogen peroxide is confirmed to be an effective way for intensification of cathodic process on gold electrode. Active potential range and current peak on anodic dissolution are enlarged when being co-intensified with Hg 2+ and hydrogen peroxide. Co-intensifying effect may be obtained and gold leaching rate is considerably increased on cyanide leaching of gold from gold concentrates.

The peculiarities of the effect of mercury ions on the kinetics of gold electrodeposition from cyanide solutions

The peculiarity of the catalytic effect of complex mercury ions (in the concentration of 10−5 to 10−4 M) on the gold electrodeposition from cyanide solutions are studied. It is shown that, all other conditions being the same, the catalytic activity of mercury ions is much lower than that of earlier studied thallium and lead ions. Another peculiarity of catalytic effect of mercury ions is the necessity of prolonged (for tens minutes) contact of gold with the mercury-containing solution. Possible explanation for the obtained regularities is proposed.

Effect of radioactive and non-radioactive mercury on wheat germination and the anti-toxic role of glutathione

Studies to test the noxious effect of mercury ions on wheat germination and seedling growth showed that germination rate, shoot length, and fresh weights varied as a function of their concentration in the treatment solutions. At the same concentration, the radioactive mercury proved to be more harmful to the living seeds and seedlings. The detoxification action of glutathione for both radioactive and non-radioactive mercury was also followed. After a seven-day period of germination in the presence of the investigated compounds, the wheat plantlets were cut from the seeds, and their height, weight, and residual radioactivity were measured. The shoot length decreased from 8.1 (blank) to 4.6 cm (non-radioactive mercury) or even to 2.5 cm (203Hg), while glutathione had both an anti-toxic and an anti-radiotoxic effect (6.4 and 6.0 cm, respectively). The root weight of the lot decreased from 1.7 to 0.7 g and 0.4 g, respectively, while glutathione showed a healing action (1.5 and 1.7 g). The radioactive ions accumulated especially in roots (35.5 %), and less in shoots (11.2 %). Results were statistically validated.

Influence of Mercury Ions on Electrical Properties of Rat Proximal and Distal Renal Tubules

The present study was designed to elucidate the acute effects of mercury ions on electrogenic transport systems in rat proximal and distal convoluted tubules. Male Munich Wistar rats were anesthetized with Inactin and prepared for micropuncture in the usual way. Under control conditions, the transepithelial potential difference (PDte) approaches -3.2 +/- 0.6 mV in early proximal tubules, +2.1 +/- 0.3 mV in late proximal tubules, and -17.8 +/- 1.8 mV in distal convoluted tubules. PDte of neither early nor late proximal tubules was significantly affected by the acute application of mercury ions. In the distal tubules, mercury ions (10 mumol/l) lead to a gradual depolarization of the epithelium from -17.8 +/- 1.8 to -9.3 +/- 2.7 mV within 8 min. A linear correlation between PDte under control conditions and depolarization caused by amiloride is seen. The slope of this correlation is significantly reduced during the application of mercury ions. In conclusion, mercury ions decrease the distal PDte an effect possibly contributing to altered renal electrolyte excretion following the acute administration of mercury ions. The depolarization is, at least in part, due to an inhibition of amiloride-sensitive sodium channels at the luminal cell membrane of principal cells.

The Effect of Deleterious Concentrations of Mercury on the Photosynthesis and Growth of Chlorella pyrenoidosa

AbstractThe effect of mercury ions on the photosynthesis and growth of Chlorella pyrenoidosa in a balanced medium has been studied and compared with the effect of copper. In many ways Hg treated algae behave like algae treated with Cu in concentrations of the same molarity, but important deviations occur. Hg acts at a lower and in a more narrow range of concentrations than does Cu due to a more specific binding. The depressing effect of Hg is not counteracted by other cations such as potassium and sodium, and iron has only a slight effect. Cell division is stopped after Hg addition and there is no accumulation of assimilation products. On the contrary the cells become pale yellow. Preliminary studies indicate a light‐independent leakage in the cytoplasmatic membrane leading to an outflow of potassium ions. This is the primary action of both Hg and Cu poisoning, but the leakage does not seem to be correlated with the decrease of photosynthesis. After a lapse of time — dependent on the mercury/cell concentration ratio — a detoxication takes place probably due to the binding of Hg to “insensitive sites” in the cells. Probable mechanisms for the action of Hg on photosynthesis and growth are discussed.