Study on antithrombotic and antiplatelet activities of low molecular weight fucoidan from Laminaria japonica

The antithrombotic and antiplatelet effects of two fucoidan fractions with low molecular weight and different sulfate content from Laminaria japonica were compared in order to examine the influence of chemical character on their antithrombotic activity and the possible mechanism. Both LMW fucoidan fractions exhibited favorable antithrombotic activity in an Fecl3-induced arterial thrombosis. The antithrombotic activity of LMW fucoidan was related with decrease of TXB2 and whole blood viscosity and hematocrit. LMW fucoidan showed a correlation between anticoagulant, antiaggregant and antithrombotic effects in vivo. For LMW fucoidan, antithrombotic activity required high dose of 5-10 nmol kg-1, concomitantly with increase in anticoagulant activity and inhibition of platelet aggregation. Administration of LMW fucoidan significantly promoted the 6-keto-PGF1α content and decreased the TXB2 content, indicating its inhibition of tissue factor pathway and regulation of metabolism of arachidonic acid. By comparison, highly sulfated fucoidan LF2 with Mw 3900 seemed to be a more suitable choice for antithrombotic drug for its antithrombotic activity accompanied with specific inhibitory activity on platelet aggregation, low anticoagulant activity and low hemorrhagic risk in vivo.     

Influence of albumen on aggregation and O<Subscript>2</Subscript> evolution of protoplasm from <Emphasis Type="Italic">Bryopsis hypnoides</Emphasis> Lamourou

The extruded protoplasm from the coenocytic green alga, Bryopsis hypnoides Lamouroux, was able to reform a cell wall and develop further into a mature alga in seawater. In this paper, the influence of albumen on the ability of aggregation and on the photosynthesis of protoplasm was examined. Results show that the protoplasm of B. hypnoides could aggregate in either albumen or chicken egg, which is similar to that in seawater. However unlike in seawater, the aggregation from B. hypnoides in albumen and chicken egg failed to develop into a mature individual. Interestingly, the protoplasm of B. hypnoides could maintain its photosynthetic O2 evolution in albumen and chicken egg, while the time in chicken egg was longer than that in albumen.     

Response of Yesso scallop Patinopecten yessoensis to acute temperature challenge: physiological and biochemical parameters

Water temperature is generally considered to be a major factor affecting the physiological and biochemical activities of marine bivalves. Here, the physiological and biochemical responses of Yesso scallop, Patinopecten yessoensis, to acute water temperature changes in summer were studied. Scallops were transferred directly to a lower temperature (T_dec treatment) (from 23°C to 15°C) or to a higher temperature (T_dec treatment) (from 15°C to 23°C) for 72 h, respectively. Results showed that the oxygen consumption and ammonia-N excretion rates of P. yessoensis decreased significantly in the T_dec treatment but increased dramatically at 6 h in the T_dec treatment (P <0.05). In the T dec treatment, hepatopancreas antioxidant enzyme activities, superoxide dismutase (SOD) and catalase (CAT) activities, increased substantially within 72 h (P <0.05). However, a significant decrease in CAT activity was found at 12 h in the T_dec treatment (P <0.01). A significant enhancement of acid phosphatase (ACP) activity and malondialdehyde (MDA) content was detected when scallops were acutely exposed to a temperature of 15°C. The levels of Cu/Zn-SOD gene expression in their gills up-regulated significantly in response to acute temperature changes (P <0.01). These data suggest that acute temperature change affects physiological and biochemical functions, and improve our knowledge of P. yessoensis under conditions of thermal stress.

     

Steroids from green alga <Emphasis Type="Italic">Chaetomorpha basiretorsa</Emphasis> Setchell

Six steroids have been isolated from ethanolic extract of green alga Chaetomorpha basiretorsa Setchell by a combination of repeated normal phase silica gel and Sephadex LH-20 gel column chromatography as well as recrystallization. Using spectroscopic methods including MS and NMR, their structures were determined as β-1awsaritol （1）, saringosterol （2）, 24-hydroperoxy-24-vinyl- cholesterol （3）, β-stigmasterol （4）, stigmast-4-en-3α, 6β-diol （5）, 29-hydroxystigmasta-5, 24 （28）-dien-3β-ol （6）. All these compounds were obtained from this genus for the first time and they were inactive （IC50〉10μg/ml） against KB, Bel-7402, PC-3M, Ketr 3 and MCF-7 cell lines.     

Chemical constituents of marine algal-derived endophytic fungus Exophiala oligosperma EN-21

Seven compounds (1–7) were identified from the cultivation of the endophytic fungus Exophiala oligosperma (EN-21) that was isolated from the inner tissue of the marine red alga Laurencia similis. Their structures were identified with spectroscopic and chemical methods as 2-phenoxynaphthalene (1), (2S, 3R, 4E, 8E)-1-O-β-D-glucopyranosyl-3-hydroxy-2-[(R)-2′-hydroxyoctadecanoyl] amino-9-methyl-4, 8-octadeca-diene (2), (22E,24R)-ergosta-7,22-dien-3β,5α,6β-triol (3), (22E, 24R)-3β, 5α, 9α-trihydroxy- ergosta-7, ...     

Oxygen consumption and ammonia-N excretion of Meretrix meretrix in different temperature and salinity

Effects of temperatures and salinities on oxygen consumption and ammonia-N excretion rate of clamMeretrix meretrix were studied in laboratory from Oct. 2003 to Jan. 2004. Two schemes were designed in incremented temperature at 10, 15, 20, 25°C at 31.5 salinity and in incremented salinity at 16.0, 21.0, 26.0, 31.5, 36.0, and 41.0 at 20°C, all for 8–10 days. From 10 to 25°C, both respiration and excretion rate were increased. One-way ANOVA analysis demonstrated significant difference (P<0.01) in physiological parameters in this temperature range except between 15 and 20°C. The highestQ ₁₀ thermal coefficient value (12.27) was acquired between 10 and 15°C, and about 1 between 15 and 20°C, indicatingM. meretrix could well acclimate to temperature changes in this range. Salinity also had significant effects on respiration and excretion rate (P<0.05). The highest values of respiration and excretion rate ofM. meretrix were recorded at 16.0 salinity (20°C). These two physiological parameters decreased as salinity increased until reached the minimumQ ₁₀ value at 31.5 (20°C), then again, these parameters increased with increasing salinity from 31.5 to 41.0.M. meretrix can catabolize body protein to cope with osmotic pressure stress when environmental salinity is away from its optimal range. No significant difference was observed between 26.0 and 36.0 in salinity (P>0.05), suggesting that a best metabolic salinity range for this species is between 26.0 and 36.0. This work is supported by National High-Tech R & D Program of China. (863 Program) (2002AA603014).     

Lipid oxidation and fatty acid composition in salt-dried yellow croaker (<Emphasis Type="Italic">Pseudosciaena polyactis</Emphasis>) during processing

Lipid oxidation in salt-dried yellow croaker (Pseudosciaena polyactis) was evaluated during processing with commonly used analytical indices, such as the peroxide value (POV), the thiobarbituric acid reactive substances (TBARS) value, and oxidative-relative lipoxygenase (LOX) activity. Additionally, fatty acids were analyzed using gas chromatography-mass spectrometry. Both POV and TBARS increased significantly (P < 0.05) at the rinsing stage. POV reached its peak value of 3.63 meq O₂ per kg sample at the drying stage, whereas TBARS constantly increased from 0.05 to 0.20 mg MDA per kg sample. Processing of salt-dried yellow croaker had an extremely significant (P < 0.01) effect on LOX activity. Twenty-six fatty acids were identified. Combined eicosapentaenoic acid (EPA; C20:5n3) and docosahexaenoic acid (DHA; C22:6n3) content varied between (19.20 ± 0.37) mg g^?1 and (23.45 ± 1.05) mg g^?1. The polyunsaturated fatty acid/saturated fatty acid (PUFA/SFA) ratio in yellow croaker was 0.73–1.10, and the n-6/n-3 PUFA ratio was approximately 0.13–0.20. The contents of most fatty acids varied significantly (P < 0.05) during the different processing stages, and these differences were caused by lipid oxidation. C18:0, C16:1n7, C19:0, and C22:6n3 showed clear changes in principle component one of a principle components analysis. These fatty acids are potential markers for evaluating lipid oxidation in fish muscle because there was a significant correlation between these markers and TBARS and LOX activity (P < 0.05) with Pearson’s coefficients > 0.931.     

Dietary guaiacol improves the growth of juvenile abalone, <Emphasis Type="Italic">Haliotis discus hannai</Emphasis> Ino

We conducted a preliminarily study on the effects of dietary guaiacol on growth performance of abalone, Haliotis discus hannai Ino. Seven semi-purified diets were formulated with graded levels of guaiacol (0, 5, 10, 50, 100, 500, and 1 000 mg kg⁻¹). Abalone (initial weight: 0.29 ± 0.01 g; initial shell length: 8.55 ± 0.27 mm) were fed with these diets in a re-circulated water system for 152 days. Guaiacol significantly improved the specific growth rate (SGR) (P<0.05); excessive dietary guaiacol (1 000 mg kg⁻¹) led to significantly high mortality (P<0.05), and lipid content in the soft body increased significantly after dietary guaiacol (P<0.05). Activities of catalase and phenoloxidase (PO) in the viscera were significantly stimulated by dietary guaiacol (P<0.05). Broken-line analysis based on SGR indicated that the minimum dietary guaiacol for the optimal growth of juvenile abalone is 15.43 mg kg⁻¹.     

Effect of dopamine injection on the hemocyte count and prophenoloxidase system of the white shrimp Litopenaeus vannamei

Effects of dopamine injection on the hemocyte count, phenoloxidase activity, serine proteinase activity, proteinase in-hibitor activity and α2-macroglobulin-like activity in L. vannamei were studied. Results showed that dopamine injection resulted in a significant effect on the parameters measured (P < 0.05), while no significant difference was observed in the control group (0.85% NaCl). In the experimental groups,the hemocyte count reached the minimum in 3 h;granular and semi-granular cells became stable after 12 h and hyaline cells and the total hemocyte count became stable after 18 h. Phenoloxidase activity reached the minimum in 6 h, and then became stable after 9 h. Serine protease activity and proteinase inhibitor activity reached the minimum in 3 h, and α2-macro-globulin-like activity reached the maximum in 3 h,and all the three parameters became stable after 12 h. The results suggest that the activating mechanisms of the proPO system triggered by dopamine are different from those triggered by invasive agents or sponta-neously activated under a normal physical condition.     

Subunit composition and chromophore content of R-phycoerythrin fromPorphyra haitanensis

R-phycoerythrin fromPorphyra haitanensis exists in two aggregation states with different molecular weights. A more highly aggregated form, RPE I, was chromatographed on Bio-Rex 70 column with urea solution (pH 3.0) as eluent, and the molecular weights of the 3 subunits (α, β, γ) obtained were determined on SDS-PAGE at 18000, 19200 and 30000, respectively. α subunit carried two phycoerythrobilin (PEB); β subunit, three PEB and one phycourobilin (PUB); γ subunit, one PEB and three PUB chromophores. The molar ratio of α, β, and γ subunits of RPE I was 6: 6: 1, and their subunit composition was confired to be (αβ)₆γ on account of the molecular weight of RPE I, 232000. A lower aggregated form, RPE II, contained α and β subunits similar to those of RPE I, but its subunit composition was the (αβ) monomer of RPE. Contribution No. 2108 from the Institute of Oceanology, Chinese Academy of Sciences     

Effects of ration, temperature and body weight on metabolism in young black porgy

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｍｅｔａｂｏｌｉｓｍｉｎｆｉｓｈｉｎｃｌｕｄｅｓｓｔａｎｄａｒｄｍｅｔａｂｏｌｉｓｍ(ＲＳ)ｒｏｕｔｉｎｅｍｅｔａｂｏｌｉｓｍ(ＲＲ),ｓｐｅｃｉｆｉｃｄｙｎａｍｉｃａｃｔｉｏｎ(ＳＤＡ)ａｎｄａｃｔｉｖｅｍｅｔａｂｏｌｉｓｍ(ＲＡ),ｒｅｌａｔｅｄａｓ:　　ＲＴ=ＲＳ ＲＲ ＳＤＡ ＲＡｗｈｅｒｅＲＳｉｓｔｈｅｍｅｔａｂｏｌｉｓｍｏｆｔｈｅｆｉｓｈａｔｒｅｓｔ;ＲＲｔｈｅｍｅｔａｂｏｌｉｓｍｏｆｔｈｅｒｏｕｔｉｎｅｌｙａｃｔｉｖｅｆｉｓｈ;ＳＤＡｔｈｅｍｅｔａｂｏｌｉｓｍｏｆｔｈ…     

Immunotoxicity effect of benzo[α]pyrene on scallop Chlamys farreri

The toxic effects of benzo[α]pyrene (B[α]P) at different concentrations (0.1, 0.5, 1, 2.5 and 7.5 μgL⁻¹) on scallop (Chlamy farreri) immune system were studied. The results showed that B[α]P had significant toxic effects on the haemocyte counts, neutral red uptake, phagocytosis, bacteriolytic and antibacterial activity (P<0.05), while the seawater control and acetone control had no significant differences. The haemocyte counts, neutral red uptake, phagocytosis and bacteriolytic activity in all B[α]P treatment groups as well as antibacterial activity in groups of 0.5, 1, 2.5 and 7.5 μgL⁻¹ B[α]P decreased significantly (P<0.05). Some of these indices tended to be stable on the sixth day and others on the ninth day, and the indices showed clear time- and concentration-response to B[α]P. Bacteriolytic activity in 0.1μgL⁻¹ B[α]P treatment group and antibacterial activity in 0.1 μgL⁻¹ and 0.5 μgL- B[α]P treatment groups increased at the beginning of exposure and reached their peaks on day 1 and day 6, respectively. Following that, both activities decreased gradually and became stable after day 9. When all the indices reached stability, they were significantly lower than those in control group (P<0.05), except for antibacterial activity in 0.1 μgL⁻¹ B[α]P treatment group (P>0.05). Thus, B[α] has evident toxic effects on scallop immune system, which supports the view that a relationship exists between pollution and immunomodulation in aquatic organisms.     

Abundance and spatial dynamics of bacterioplankton in the Seven Rila Lakes, Bulgaria

In the high mountain oligotrophic Seven Rila Lakes (2 095–2 535 m a.s.l.) bacterial abundance was recorded in July and September 2006. In July, bacterial abundance (average (3.32±2.5)×10⁵ cell/ml) in the lakes correlated negatively with elevation, while in September (average (26.39±7.1)×10⁵ cell/ml) this pattern was altered and the greatest abundance of bacteria occurred at the highest ((39.05±1.5)×10⁵ cell/ml) and the lowest ((30.63±6.0)×10⁵ cell/ml) elevated lakes. Regression analyses suggested that the principal factor controlling bacterial abundance, in both July and September, was inorganic nitrogen (NO₃-N and NH₄-N; R ²=0.70, P<0.05). Other major regulating factors were temperature (R ²=0.66, P<0.03) in July and filter-feeding zooplankton (R ²=0.95, P<0.01) in September. All factors, except NO₃-N, had a positive effect on bacterial abundance.     

Tissue Expression and Stock Variation of Isozymes of Stone Flounder （Kareius bicoloratus）

Tissue expression and stock variation of isozymes of stone flounder (Kareius bicoloratus) were analyzed with horizontal starch gel electrophoresis. For the fourteen enzymes assayed, 31 loci were recorded. The results indicated that all the isozymes ex- amined were obviously tissue-specific. The expressions of SOD*, GDH*, G3PDH-2* and ADH-2* were detected only in liver, SDH-1*, MDH-1* and ADH-1* only in muscle, and LDH-B* and LDH-C* only in eyes. In comparison, MDH-2*, GPI-3* and SDH-2* were detected in all tissues examined. Other loci examined were detected in a variety of tissues. Muscle and liver were se- lected to detect the isozyme variation of the two geographic stocks of Qingdao and Weihai, Shandong Province, China. The percent- ages of polymorphic loci (P0.99) were 29.17% and 25.00%, the observed heterozygosities (H0) were 0.028 ± 0.014 and 0.040 ± 0.019, and the expected heterozygosities (He) were 0.039 ± 0.017 and 0.052 ± 0.022 in Qingdao and Weihai stock, respectively. The coeffi- cient of gene differentiation (Fst) and genetic distance (D) between the two stocks was 0.012 and 0.0011, respectively, indicating that the genetic differentiation is low between them. Compared with other species of Pleuronectiformes, both the percentage of polymor- phic loci and the mean heterozygosity of K. bicoloratus were at a middle level.     

The antitumor effect of bromophenol derivatives <Emphasis Type="Italic">in vitro</Emphasis> and <Emphasis Type="Italic">Leathesia nana</Emphasis> extract <Emphasis Type="Italic">in vivo</Emphasis>

To investigate the antitumor effect of bromophenol derivatives in vitro and Leathesia nana extract in vivo, six bromophenol derivatives 6-(2,3-dibromo-4,5-dihydroxybenzyl)-2,3-dibromo-4,5-dihydroxy benzyl methyl ether (1), (+)-3-(2,3-dibromo-4,5-dihydroxyphenyl)-4-bromo-5,6-dihydroxy-1,3-dihydroisobenzofuran (2), 3-bromo-4-(2,3-dibromo-4,5-dihydroxybenzyl)-5-methoxymethyl-pyrocatechol (3), 2,2′,3,3′-tetrabromo-4,4′,5,5′-tetrahydroxy-diphenylmethane (4), bis(2,3-dibromo-4,5-dihydroxybenzyl) ether (5), 2,2′,3-tribromo-3′,4,4′,5-tetrahydroxy-6′-ethyloxymethyldiphenylmethane (6) were isolated from brown alga Leathesia nana, and their cytotoxicity were tested by MTT assays in human cancer cell lines A549, BGC-823, MCF-7, B16-BL6, HT-1080, A2780, Bel7402 and HCT-8. Their inhibitory activity against protein tyrosine kinase (PTK) with over-expression of c-kit was analyzed also by ELISA. The antitumor activity of ethanolic extraction of Leathesia nana (EELN) was evaluated on S₁₈₀-bearing mice. All compounds showed very potent cytotoxicity against all of the eight cancer cell lines with IC₅₀ below 10 μg/mL. In PTK inhibition study, all bromophenol derivatives showed moderate inhibitory activity and compounds 2, 5 and 6 showed significant bioactivity with the inhibition ratio of 77.5%, 80.1% and 71.4%, respectively. Pharmacological studies reveal that EELN could inhibit the growth of Sarcoma 180 tumor and increase the indices of thymus and spleen to improve the immune system remarkably in vivo. Results indicated that the bromophenol derivatives and EELN can be used as potent antitumor agents for PTK over-expression of c-kit and considered in a new therapeutic strategy for treatment of cancer. Supported by the National High Technology Research and Development Program of China (863 Program, No. 2007AA09Z410) and Knowledge Innovation Program of Chinese Academy of Sciences (No. KZCX2-YW-209)     

Non-specific immune response of bullfrog <Emphasis Type="Italic">Rana catesbeiana</Emphasis> to intraperitoneal injection of bacterium <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

Non-specific immune response of bullfrog Rana catesbeiana to pathogenic Aeromonas hydrophila was studied to 60 individuals in two groups. Each bullfrog in bacterium-injected group was injected intraperitoneally （i.p.） with 0.2 ml bacterial suspension at a density of 5.2 × 10^6 CFU/ml, while each one in control group injected i.p. with 0.2 ml sterile saline solution （0.85%, w/v）. Three bullfrogs in both groups were sampled at 0, 1, 3, 7, 11, 15 and 20 days post-injection （dpi） for the evaluation of non-specific immune parameters. It was observed that intraperitoneal injection of A. hydrophila significantly increased the number of leucocytes and that of NBT-positive cells in peripheral blood. Significant increases in serum bactericidal activity and serum acid phosphatase activity were also observed in the bacterium-injected frogs when compared with those in the control group. However, a significant reduction was detected in vitro in phagocytosis activity of peripheral blood phagocytes. No significant difference in changes in the number of peripheral erythrocytes, serum superoxide dismutase （SOD） activity, and lysozyme activity was detected between the two groups. It is suggested that bullfrogs may produce a series of non-specific immune reactions in response to the A. hydrophila infection.     

Antioxidation activities of low-molecular-weight gelatin hydrolysate isolated from the sea cucumber <Emphasis Type="Italic">Stichopus japonicus</Emphasis>

Gelatin extracted from the body wall of the sea cucumber (Stichopus japonicus) was hydrolyzed with flavourzyme. Low-molecular-weight gelatin hydrolysate (LMW-GH) of 700–1700 Da was produced using an ultrafiltration membrane bioreactor system. Chemiluminescence analysis revealed that LMW-GH scavenges high free radicals in a concentration-dependent manner; IC₅₀ value for superoxide and hydroxyl radicals was 442 and 285 μg mL⁻¹, respectively. LMW-GH exhibited excellent inhibitory characteristics against melanin synthesis and tyrosinase activity in B16 cells. Furthermore, LMW-GH notably increased intracellular glutathione (GSH), which in turn suppressed melanogenesis. LMW-GH performs antioxidation activity, holding the potential of being used as a valuable ingredient in function foods, cosmetics and pharmaceuticals or nutriceuticals.     

Isolation and characterization of collagen from squid (Ommastrephes bartrami) skin

Collagen of squid (Ommastrephes bartrami) skin was examined in the present study. Histology showed that collagen fiber in the skin was partially cross-linked with muscle fiber. Acid-solubilized collagen (ASC) and pepsin-solubilized collagen (PSC) were extracted from the skin and characterized. The results of amino acid composition and electrophoretic patterns revealed that ASC and PSC were both type I collagen, containing α1 and α2 chains. FTIR (fourier transform infrared spectroscopy) investigations confirmed the existence of helical arrangements in PSC of squid skin. The denaturation temperature (T_d) and shrinkage temperature (T_s) of PSC were 29.4°C and 52.8°C, respectively.     

Variations of ion-transport enzyme activities during early development of the shrimps <Emphasis Type="Italic">Fenneropenaeus chinensis</Emphasis> and <Emphasis Type="Italic">Marsupenaeus japonicus</Emphasis>

The ion-transport enzyme activities were studied in the nauplii 1–2, zoea 1–3, mysis 1–3, and postlarva 1–7 of the shrimps Marsupenaeus japonicus and Fenneropenaeus chinensis. The results showed that total ATPase, Na⁺-K⁺-ATPase, and V-ATPase (V-type H⁺-ATPase) activities increased during the early development for both the species, from zero in nauplii to stable levels after zoea stage. The enzyme activities of the latter species were significantly higher than those of the former species after zoea stage (F>F _0.05). The contributions of Na⁺-K⁺-ATPase, V-ATPase and HCO₃ ⁻-ATPase to the total ATPase activity of the two species varied in different developmental stages and accounted for 40%–70%, 22%–46% and 2%–13% in M. japonicus from zoea to postlarva stage, whilst the shares of them were 42%–69%, 28%–44% and 2.5%–22%, respectively in F.chinensis. These findings suggest the possible culture of the two species with varying water quality, especially the salinity and pH.     

Bioaccumulation of Pb<Superscript>2+</Superscript> and its effects on growth,morphology and pigment contents of <Emphasis Type="Italic">Spirulina</Emphasis> (<Emphasis Type="Italic">Arthrospira</Emphasis>) <Emphasis Type="Italic">platensis</Emphasis>

A laboratory experiment was conducted to assess the bioaccumulation of Pb²⁺ and its effects on growth, morphology and pigment contents of Spirulina (Arthrospira) platensis. The specimen cultured in Zarrouk liquid medium was treated with various initial metal concentrations (0, 5, 10, 30, 50 and 100 μg mL⁻¹). The growth of S. platensis was adversely affected by Pb²⁺ at high concentrations (30, 50 and 100 μg mL⁻¹). However, at low concentrations (5 μg mL⁻¹), Pb²⁺ could stimulate its growth slightly. The pigment contents (chlorophyll α and β carotene) were decreased in a dose-dependent manner. The highest reductions (67% and 53% respectively in chlorophyll α and β carotene) were observed in 100 μg mL⁻¹ treatment group. The LC₅₀ (96 h) of Pb²⁺ was measured as 75.34 μg mL⁻¹. Apart from a few cases of filament breakages at elevated concentrations (50 and 100 μg mL⁻¹), morphological abnormalities are not specific. Metal bioaccumulation increased with Pb²⁺ concentrations, but decreased with exposure time. The maximum accumulated amount was 188 mg g⁻¹ dry weight. The bioconcentration factor (BCF) reached to a peak at day 2, followed by a gradual reduction for all the exposure concentrations. S. platensis is able to tolerate considerably high Pb²⁺ concentrations. Consequently it can be used as a potential species to remove heavy metal from contaminated waters.