Different Concentrations Of Mercury Research Articles

Determination of mercury and nickel by amperometric biosensor prepared with thermostable lactate dehydrogenase

Response of biosensor prepared with the thermostable bacterial LDH enzyme was analyzed in the presence of mercury and nickel. For electrode preparation, the enzyme was purified and immobilized on a gold sheet coated by PGA-pyrrole polymeric material. The working electrode was tested at increasing concentration of lactate in the presence of two different concentrations of mercury and nickel. Current response of biosensor decreased from 0.32 μA to 0.09 μA and 4.13 μA to 2.63 μA when 25×10 −7 mmol/L mercury and 17×10 −5 mmol/L nickel were included in the working solution, respectively. Sensitivity of the electrode decreased from 0.010 2 μA/(mmol·L −1) to 0.0043 μA/(mmol·L −1) in the presence of 25×10 −7 mmol/L mercury. On the other hand, the presence of nickel did not result in a decrease in electrode sensitivity. The results pointed out that the prepared biosensor is useful to detect mercury in a sample containing both mercury and nickel together.

Effect of mercury on the total and electrophoretic profile of proteins and on the activity of some enzymes in gills of three species of freshwater clam : Unio tigridis, Pseudontopsis euphraticus and Anodonta sp.

A three species of clam Unio tigridis, Pseudontopsis euphraticus and Anodonta sp. were collected from Al-Habaniya lake, Al-Anbar/Iraq .The animals were exposed to three concentrations of mercury: 0.1, 0.2 and 0.4 mg / l. First group of animals were exposed for three weeks, second group for two weeks and the third group for one week. At the end of the exposure period, the animals were dissected ,then the gills removed for the further study on proteins and enzymes. The results were : 1- Total protein concentration in the gills decreased at different concentrations. We observed prominent effect of mercury on the electrophoretic bands of proteins with the decrease in the intensity of protein bands or induction of new bands. 2- The activity of the three enzymes : Alkaline phosphatase , GPT and GOT were not stable, increased or decreased in different species at different concentrations of mercury, for example, the activity of alkaline phosphatase increased in second species at the second concentration , the activity of GPT decreased in first species at the first concentration and the activity of GOT decreased in the three species at third concentration of mercury.

Response of antioxidant enzymes in rice (Oryza sauva L. cv. Dongjin) under mercury stress

We studied the effects of different concentrations of mercury (0.0 to 100 µM) on growth and photosynthetic efficiency in rice plants treated for 21 d. In addition, we investigated how this metal affected the malondialdehyde (MDA) content as well as the activity of five antioxidant enzymes — superoxide dismutase (SOD), ascorbate peroxidase (APX), glutathione reductase (GR), guaiacol peroxidase (POD), and catalase (CAT). Photosynthetic efficiency (Fµ/Fm) and seedling growth decreased as the concentration of Hg was increased in the growth media. Plants also responded to Hg-induced oxidative stress by changing the levels of their antioxidative enzymes. Enhanced lipid peroxidation was observed in both leaves and roots that had been exposed to oxidative stress, with leaves showing higher enzymatic activity. Both SOD and APX activities increased in treatments with up to 50 µM Hg, then decreased at higher concentrations. In the leaves, both CAT and POD activities increased gradually, with CAT levels decreasing at higher concentrations. In the roots, however, CAT activity remained unchanged while that of POD increased a bit more than did the control for concentrations of up to 10 µM Hg. At higher Hg levels, both CAT and POD activities decreased. GR activity increased in leaves exposed to no more than 0.25 µM Hg, then decreased gradually. In contrast, its activity was greatly inhibited in the roots. Based on these results, we suggest that when rice plants are exposed to different concentrations of mercury, their antioxidative enzymes become involved in defense mechanisms against the free radicals that are induced by this stress.

Toxicological response of a cyanobacterium,Phormidium fragile, to mercury

The effects of different concentrations of mercury on the cyanobacterium Phormidium fragile were studied. The results revealed that the dry biomass yield, protein content, chlorophyll a and carotenoids decreased with increased concentration of mercury from 0.01 to 1.5 mg L-. Also, malate dehydrogenase (MDH), glutamate dehydrogenase (GIDH) and nitrate reductase activity was suppressed by increased metal concentration whereas glutamic-oxalacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT) were hardly affected. Mercury uptake increased at the higher levels of the metal. On the other hand, all the amino acid components gradually increased with rise of the metal level except isoleucine, histidine and methionine which were suppressed by the smaller doses and completely disappeared by the larger doses of the metal.

Comparative and interactive effects of mercury, cadmium and lead on tissue GSH levels in Oreochromis aureus (Steindachner): implications for monitoring heavy metal pollution

The effects of 45 days exposure to mercury, cadmium and lead on tissue GSH levels were studied in Oreochromis aureus (Steindachner). Liver, brain, gill filaments, intestine and caudal muscle were assayed after exposure to these heavy metals singly, or in combination. Significant increases in intestinal GSH concentrations consistently occurred after exposure to mixtures of heavy metals. Exposure to cadmium or lead did not change hepatic GSH levels, while exposure to two different concentrations of mercury caused significant increases in hepatic GSH.

Optimization of procedures for mercury-203 instrumental neutron activation analysis in human urine

Mercury, a known neurotoxin, has been implicated in the etiology and pathogenesis of such disease states as Alzheimer's and Parkinson's diseases. There is concern that the exposure to mercury vapor released from dental amalgam restorations is a potential health hazard. Measurement of mercury concentrations in blood or urine may be useful in diagnosis of mercury poisoning and in assessing the extent of exposure. This study describes the optimization of pre-neutron activation analysis procedures such as sampling, selection of irradiation and counting vials and acid digestion in order to minimize mercury loss via volatilization and/or permeation through containers. Therefore, the determination of mercury can be complicated by these potential losses. In the optimized procedure 20 mL of urine was spiked with three different concentrations of mercury, digested with concentrated nitric acid, and placed in polypropylene vials for irradiation and counting. Analysis was performed by subtracting the Se-75 photopeak contribution to the 279 keV Hg-203 photopeak and applying the method of standard additions. Urinary mercury concentrations in normal human subjects were determined to be of the order of 10 ng/mL.

Interaction of heavy metal toxicants with brain constitutive nitric oxide synthase.

This study was designed to evaluate the in vitro effects of transition heavy metal cations on activity of constitutive isoform of nitric oxide synthase (cNOS) in rat brain. NOS activity was determined in the cytosolic fractions of rat cerebral hemispheres by conversion of 3H-L-arginine to 3H-L-citrulline. Different concentrations of mercury (Hg2+), nickel (Ni2+), manganese (Mn2+), zinc (Zn2+), cadmium (Cd2+), lead (Pd2+) and calcium (Ca2+) were tested on NOS activity. While all the cations caused inhibition, there were differences in the apparent inhibition constants (Ki) among the cations. With the exception of calcium ion no other cation required preincubation with the enzyme preparation. These results indicate that while calcium ion modulate cNOS activity at regulatory site(s), inhibitory influence of toxic heavy metal cations may be exerted on the catalytic site(s) either by direct binding to it or by interfering with the electron transfer during catalysis.

Susceptibility of different yeast species to environmental toxic metals

The purpose of the study reported here was to investigate the relative resistance of yeast species to various metallic and metalloid ions, with a view to gaining more knowledge on this subject, as resistant species may become dominant in habitats contaminated with the relevant metals. Saccharomyces cerevisiae, Candida albicans and Candida tropicalis were grown in media containing different concentrations of mercury (as HgCl 2), cadmium (as CdCl 2), lead (as Pb(CH 3COO) 2), arsenic (as Na 2HAsO 4) and selenium (as Na 2SeO 3) for various intervals. Invariably, the two Candida species turned out to be more resistant to all the metals studied than S. cerevisiae. The metal showing the highest toxicity for these species was mercury, with cadmium being the second, lead, the third and arsenic and selenium being the least toxic elements. Strains showing resistance to mercury were isolated, even in the case of S. cerevisiae.

Effect of mercury and cadmium on the growth of Anacystis nidulans

Anacystis nidulans is a member of the cyanobacteria, one of the largest and most diverse groups in the prokaryotic kingdom. Cyanobacteria are excellent organisms to serve as models for the investigation of a wide variety of biological problems such as acting as environmental pollution indicators. There have been several studies on the effects of heavy metals on A. nidulans. Some of these elements, such as copper, are known to be essential nutrients for cyanobacteria. Others, like cadmium, are not known to be necessary for normal growth and metabolism. Large amounts of either essential or non-essential elements can be toxic. Toxic metals, such as mercury and cadmium are a major water pollution problem. Metals come from natural weathering processes of the earth's crust, industrial discharge, pest or disease control agents applied to plants, urban run-off, mining, soil erosion, sewage effluents, air pollution fallout and other sources. This study investigates the growth of Anacystis under different concentrations of mercury and cadmium. 13 refs., 2 figs.

Use of algal fluorescence for determination of phytotoxicity of heavy metals and pesticides as environmental pollutants

The phytotoxicity of heavy metals and pesticides was studied by using the fluorescence induction from the alga Dunaliella tertiolecta. The complementary area calculated from the variable fluorescence induction was used as a direct parameter to estimate phytotoxicity. The value of this parameter was affected when algae were treated with different concentrations of mercury, copper, atrazine, DCMU, Dutox, and Soilgard. The toxic effect of these pollutants was estimated by monitoring the decrease in the complementary area, which reflects photosystem II photochemistry. Further, the authors have demonstrated the advantage of using the complementary area as a parameter of phytotoxicity over using variable fluorescence yield. The complementary area of algal fluorescence can be used as a simple and sensitive parameter in the estimation of the phytotoxicity of polluted water.

The effect of mercury on some aquatic plants

Three aquatic plants, Hydrilla verticillata Presl, Pistia stratiotes L. and Salvinia molesta D.S. Mitchell, were treated with different concentrations of mercury ranging from 1 to 1000 μg litre −1 at three different exposure durations, i.e. 1,3 and 5 h. All were found to be severely affected by mercury. Foliar injury, chlorophyll content and phytomass showed perceptible effects with increasing exposure to the metal. In the case of floating plants a positive relationship was obtained between Leaf Injury Index (LII) and doses of the metal. The possible use of aquatic plants in general, and floating plants in particular, as simple bioassay material in biomonitoring and toxicity studies is discussed with special reference to LII as a simple biomonitoring parameter.

Respiratory tract retention of inhaled air pollutants: Report 1 : Mercury absorption by inhaling through the nose and expiring through the mouth at various concentrations

To study atmospheric mercury absorption in human respiratory passage-ways, mercury in expired air was measured in three different states of breathing: steady breathing, deep breathing and breath held after inspiration. In this study, air containing mercury was inhaled through the nose and expired through the mouth. The concentration of mercury in the exhaled air was determined by the technique of gold-amalgam trapping, heat vaporization, and flameless atomic absorption measurement. The subjects were 13 male adults, aged 25–62 years, and 38 cases were observed. Four different concentrations of mercury, 1–3, 4–6, 10–11, and 20–30 μg/m 3 were used, and absorption for each was determined. When the concentration was 1–3 μg/m 3, the absorption was 74–92%, the average being 82.5%. At concentrations of 4–6, 10–11, and 20–30 μg/m 3, the absorption was 76.6–100%, 75.5–99.2%, and 79.9–95.9% respectively, and the average was 88.8%, 85.2%, and 87.7% respectively. A slightly higher rate of mercury absorption was observed in deep breathing than in steady breathing, and when expiration was suppressed for some time after inspiration, the rate increased remarkably to 97.4–99.7%. Prolonged retention of inhaled air containing mercury in the respiratory tract is believed to have caused the increased absorption.

Tissue Residues of Mercury in Broilers Fed Fish Meals Containing Different Concentrations of Mercury

Two herring meals containing 0.17 and 0.22 p.p.m. of mercury respectively were fed to broilers at dietary levels of 5, 10 and 17.1%. The amounts of mercury present in the diet from this source thus varied from 0.0085 to 0.0376 p.p.m. Growth rate and mortality to eight weeks of age were unaffected by the level or source of herring meal in the diet. The amount of mercury ingested by the birds fed any of the diets resulted in negligible effects on the concentration of mercury present in breast or leg muscle. There was, however, significant accumulation of mercury in liver, kidney, claw and feather tissue, which reflected the dietary concentration of mercury. The amount present in the feathers was high as 0.845 p.p.m. This amount may be sufficiently high to warrant concern when feathers are processed into meal.

On the site and mechanism of mercury vapor resorption in the lung. A study in the guinea pig using mercuric nitrate Hg 203.

The percentage of whole-body mercury found in the lungs of guinea pigs exposed to mercury vapor for ten minutes was in the same range as after one hour’s exposure (25% to 33%). The highest concentrations of mercury were found in peripheral lung structures. The same distribution was found at different concentrations of mercury in the air. Only one tenth of the values were found in corresponding structures of animals injected with mercuric nitrate. Most of the mercury deposited in alveolar tissues is therefore probably deposited there directly from the air. The results are considered to indicate the following: that mercury vapor penetrates to the alveoli; that most of it is quickly transferred to the blood; and that a small fraction is deposited in the pulmonary tissues, from where it is slowly eliminated to the rest of the body.

Effect of Calcium on Cardiac Reactions to Mercury.

The response of the isolated frog heart to mercury in normal Ringer was first studied by Salant and Kleitman,1 but as far as we are aware no investigation has been previously reported on the effect of mercury in solutions containing different amounts of calcium. Experiments were therefore carried out with this object in view, Straub's method being used.After trying different concentrations of mercury, we found that a solution of 1:100,000 in normal Ringer, containing 0.012% calcium chloride, best served the purpose as a basis of comparison. The immediate effect of this amount of mercury was not constant, no changes being observed in most cases, and moderate depression only occurred in some experiments, thus corroborating the observations of Salant and Kleitman, which were made with Simpson's method, modified by his pupil, Livingston. We noticed, however, that in some experiments a gradual decline, especially in the strength of the contractions, occurred, and at the end of one to 3 hours, the amplitude sho...