Response to copper and cadmium stress in wild-type and copper tolerant strains of the lichen alga <Emphasis Type="Italic">Trebouxia erici</Emphasis>: metal accumulation,toxicity and non-protein thiols

Cysteine, glutathione (GSH) and phytochelatins were determined in the cells of both wild and copper tolerant strains of the lichen alga Trebouxia erici following short-term (24 h) exposure to copper and cadmium and long-term (4 weeks) exposure to copper. Both metals caused concentration dependent synthesis of phytochelatins (PC₂–PC₅), but cadmium was a more potent activator of phytochelatin synthesis, even inducing synthesis of PC₅. The copper-tolerant strain did not reveal a higher degree of phytochelatin synthesis than the wild strain, and at 5 μM Cu production of phytochelatins was in fact significantly lower. Lower levels of phytochelatin correlated with significantly decreased intracellular copper content in the copper-tolerant strain. Both strains maintained high GSH levels even at a high copper concentration of 5 μM, and only the highest copper concentration (10 μM) was toxic for both strains, causing a decrease of GSH and PC content in algal cells. Cadmium had less effect on GSH in the cells of both tested strains. In the long term experiments, only relatively small amounts of PC₂ were detected in both strains, but the copper-tolerant strain retained significantly higher levels of reduced glutathione, probably due to the lesser degree of oxidative stress caused by Cu. The significant increase of cysteine synthesis in the copper-tolerant strain found in the present study may be related to copper tolerance in T. erici, while decreased intracellular Cu uptake, detoxification by PCs and increased free proline levels for protection of chloroplast membranes may also be implicated.     

Copper-induced changes in the growth, oxidative metabolism, and saponin production in suspension culture roots of Panax ginseng in bioreactors

Roots of Panax ginseng exposed to various concentrations of Cu (0.0, 5, 10.0, 25.0, and 50.0 μM) accumulated high amounts of Cu in a concentration-dependent and duration-dependent manner. Roots treated with 50 μM Cu resulted in 52% and 89% growth inhibition after 20 and 40 days, respectively. Saponin synthesis was stimulated at a Cu concentration between 5 and 25 μM but decreased at 50 μM Cu. Malondialdehyde content (MDA), lipoxygenase activity (LOX), superoxide ion (O₂ ^•−) accumulation, and H₂O₂ content at 5 and 10 μM Cu-treated roots were not increased but strongly increased at 50 μM Cu resulting in the oxidation of ascorbate (ASC) and glutathione (GSH) to dehydroascorbate (DHA) and glutathione disulfide (GSSG), respectively indicating a clear oxidative stress. Seven well-resolved bands of superoxide dismutase (SOD) were detected in the gel and an increase in SOD activity seemed to be mainly due to the induction of Fe-SOD 3. Five to 10 μM Cu slightly induced activity of ascorbate peroxidase (APX) and dehydroascorbate reductase (DHAR), guaiacol peroxidase (G-POD) but inhibited monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR) enzyme activities. No changes in catalase (CAT) activity and in activity gel were found up to 25 μM Cu, but both G-POD and CAT activities were inhibited at 50 μM Cu. Glutathione metabolism enzymes such as γ-glutamylcysteine synthetase (γ-GCS), glutathione-S-transferase (GST), and glutathione peroxidase activities (GPx) were activated at 5 and 10 μM Cu but were strongly inhibited at 50 μM Cu due to the Cu accumulation in root tissues. The strong depletion of GSH at 50 μM Cu was associated to the strong induction of γ-glutamyltranspeptidase (γ-GGT) activity. These results indicate that plant could grow under Cu stress (5–25 μM) by modulating the antioxidant defense mechanism for combating Cu induced oxidative stress.     

Cadmium accumulation and interactions with zinc, copper, and manganese, analysed by ICP-MS in a long-term Caco-2 TC7 cell model

The influence of long-term exposure to cadmium (Cd) on essential minerals was investigated using a Caco-2 TC7 cells and a multi-analytical tool: microwave digestion and inductively coupled plasma mass spectrometry. Intracellular levels, effects on cadmium accumulation, distribution, and reference concentration ranges of the following elements were determined: Na, Mg, Ca, Cr, Fe, Mn, Co, Ni, Cu, Zn, Mo, and Cd. Results showed that Caco-2 TC7 cells incubated long-term with cadmium concentrations ranging from 0 to 10 μmol Cd/l for 5 weeks exhibited a significant increase in cadmium accumulation. Furthermore, this accumulation was more marked in cells exposed long-term to cadmium compared with controls, and that this exposure resulted in a significant accumulation of copper and zinc but not of the other elements measured. Interactions of Cd with three elements: zinc, copper, and manganese were particularly studied. Exposed to 30 μmol/l of the element, manganese showed the highest inhibition and copper the lowest on cadmium intracellular accumulation but Zn, Cu, and Mn behave differently in terms of their mutual competition with Cd. Indeed, increasing cadmium in the culture medium resulted in a gradual and significant increase in the accumulation of zinc. There was a significant decrease in manganese from 5 μmol Cd/l exposure, and no variation was observed with copper.     

Effect of feeding supplemental copper on performance,fatty acid profile and on cholesterol contents and oxidative stability of meat of rabbits

One hundred and four rabbits, five weeks old at the beginning of the experiment, were divided into four groups according to a feed additive treatment. Rabbits of the 1st, 2nd, 3rd and 4th group were fed a basal granulated feed (control), basal feed supplemented with CuSO₄ · 5H₂O at 50mg Cu · kg^‐1, basal feed supplemented with 150mg Cu · kg^‐1, and the latter feed supplemented with 100mg · kg^‐1 vitamin E, respectively. The duration of the experiment was 42 days. Addition of Cu at 150mg · kg.^‐1 increased weight gain non‐significantly by 9.1%. This effect was the most pronounced in the first two weeks of fattening. The lowest mortality was observed in rabbits fed the highest amount of additives (7.7% vs. 19.2% in the control). Rabbits were slaughtered at the age of 11 weeks. Neither treatment influenced proportions of saturated, monounsaturated and polyunsaturated fatty acids in lipids extracted from the loin and hindleg muscles. In rabbits fed the highest amount of copper and vitamin E, the cholesterol concentration was significantly decreased by 13.6% and 17.9% in the loin and hindleg meat, respectively. Effects of Cu added at 50mg · kg^‐1 were marginal. Copper had no effect on the oxidative stability of meat, measured as thiobarbituric acid‐reactive substances in meat stored at 4°C for 0, 3 and 8 days. Vitamin E added in excess of nutritional requirement improved the oxidative stability of meat. In copper‐fed rabbits, Cu accumulated in the liver, but not in muscles. Feeding of the basal feed for 7 days to rabbits previously fed copper sulphate decreased the hepatic Cu concentration by 14.0 to 24.4%     

The effects of copper, iron and zinc on digestive enzyme activity in the hybrid tilapia Oreochromis niloticus (L.) ×Oreochromis aureus (Steindachner)

The present experiment was conducted to study effects of Cu, Fe and Zn on activities of digestive enzymes of the hybrid tilapia Oreochromis niloticus×Oreochromis aureus. The acidic protease activities increased 65·5 and 55·1% by addition of homogenates of digesta‐containing stomach with copper (75 mg l⁻¹) and zinc (50 mg l⁻¹) respectively. Addition of Cu and Zn increased the activities of protease in the hepatopancreas homogenates by 132·7 and 38·1% respectively, and reduced the activity of protease in the digesta‐containing intestine homogenates by 11·0 and 13·8% respectively. Addition of Fe (50 mg l⁻¹) increased the acidic protease activity by 96·7% but did not alter the activities of protease in the intestine and hepatopancreas. Addition of Cu markedly inhibited activities of amylase in intestine and hepatopancreas homogenates, while Zn addition showed no effects. Addition of Fe reduced activities of amylase in the intestine homogenates by 47·9% but had no effect on amylase activities in the hepatopancreas. When Cu (75 mg kg⁻¹), Fe (50 mg kg⁻¹) and Zn (50 mg kg⁻¹) were supplemented to basal diet for 3 weeks, the activities of amylase in hepatopancreas homogenates increased 125·3, 215·6 and 70·0%, respectively, the activities of amylase in intestine increased 79·8, 74·6 and 48·5%, respectively, and the activities of lipase in intestine increased 90·5, 149·8 and 84·0%, respectively. Supplementation of Cu, Fe or Zn into diet had no effects on activity of protease in all digestive organs. Therefore, the results suggest that effects of Cu, Fe and Zn on activity of digestive enzymes in vitro were different from those seen in vivo, and that the positive effects of Cu, Fe and Zn supplemented to fish diet would be valuable information for formulating fish feed.     

Relationship between copper- and zinc-induced oxidative stress and proline accumulation in<Emphasis Type="Italic"> Scenedesmus</Emphasis> sp.

A 4-h exposure of Scenedesmus sp. to Cu or Zn enhanced intracellular levels of both test metals and proline. The level of intracellular proline increased markedly up to 10 µM Cu, but higher concentrations were inhibitory. However, intracellular proline consistently increased with increasing concentration of Zn in the medium. Cu and Zn induced oxidative stress in the test alga by increasing lipid peroxidation and membrane permeability, and by reducing SH content. Pretreatment of the test alga with 1 mM proline for 30 min completely alleviated Cu-induced lipid peroxidation, minimized K⁺ efflux and also reduced depletion of the SH pool. But proline pretreatment could only slightly reduce Zn-induced oxidative stress. Interestingly, proline pretreatment increased the level of Cu (25–54%) and Zn (19–49%) inside the cells. It did not affect the activities of superoxide dismutase, ascorbate peroxidase or catalase, but improved glutathione reductase activity under Cu and Zn stress. A comparison of the effects of proline pretreatment on lipid peroxidation by Cu, Zn, methyl viologen and ultraviolet-B radiation suggests that proline protects cells from metal-induced oxidative stress by scavenging reactive oxygen species rather than by chelating metal ions. Pretreatment of cells with a known antioxidant (ascorbate) and a hydroxyl radical scavenger (sodium benzoate) considerably reduced metal-induced lipid peroxidation and proline accumulation. However, sodium benzoate had a very mild effect on Zn-induced lipid peroxidation and proline accumulation. The present study demonstrates that proline possibly acts by detoxifying reactive oxygen species, mainly hydroxyl radicals, rather than by improving the antioxidant defense system under metal stress.Abbreviations APOX Ascorbate peroxidase - CAT Catalase - GR Glutathione reductase - MDA Malondialdehyde - MV Methyl viologen - ROS Reactive oxygen species - SH Sulphydryl - SOD Superoxide dismutase - UV-B Ultraviolet-B radiation     

Changes of Blue Mussels Mytilus edulis L. Lipid Composition Under Cadmium and Copper Toxic Effect

The lipid and fatty acid composition of the blue mussels Mytilus edulis L. gills and digestive glands was evaluated after 24 and 72 h of cadmium (Cd) and copper (Cu) exposure. Mussels were exposed to different cadmium (10, 100, and 500 μg/L) and copper (5, 50, and 250 μg/L) concentrations. Similar stress response of predominant membrane phospholipids level as well as polyenoic and non-methylene interrupted (NMI) fatty acids content was observed in mussel gills under both cadmium and copper effects. Increased NMI fatty acids level after 24 h, the metal ions treatment suggests that these acids contribute to the protective response to the membrane oxidative stress caused by accumulation of the metals. The content of cholesterol, some minor membrane phospholipids, and storage lipids (triacylglycerols, TAG) in the mussels’ organs alter significantly under the cadmium and copper effect. A two-step response at the digestive glands TAG level depends on the duration of the cadmium and copper treatments (24 and 72 h) on the mussels. The results demonstrate that Cd and Cu impact has adverse effects on gills and digestive glands lipid and fatty acids composition. The type of observed effects varies with the nature and concentration of the metal ions and depends on the role of the metals in the mussels’ life activity.     

Growth and antioxidant system of the cyanobacterium Synechococcus elongatus in response to microcystin-RR

Microcystins, one type of the cyanobacterial toxins, show a broad range of hazardous effects on other organisms. Most of the researches on the toxic effects of microcystins have involved in animals and higher plants. Little work, however, has been done on evaluating the mechanisms of microcystin toxicity on algae. In this study, the toxicological effects of microcystin-RR (MC-RR) on the cyanobacterium Synechococcus elongatus were investigated. For this purpose, six physio-biochemical parameters (cell optical density, reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), glutathione peroxidase (GSH-Px) and glutathione S-transferase (GST)) were tested in algal cells when exposed to 100 g^–1 microcystin-RR. The results showed that the growth of Synechococcus elongatus (expressed as optical density) was significantly inhibited compared with the control. At the same time, the treated algae exhibited a pronounced increase in production of ROS and MDA after 6 days exposure to microcystin-RR. Significant changes in GSH levels and GSH-Px, GSH activities were also detected in algal cells, with higher values being observed in the toxin treated algae after 6 days exposure. GST activities in the treated algae exhibited a decline after exposure and rapid augmentation on day 3, thereafter, they kept at a high level when compared to the control group. GSH contents and GSH-Px activities were also significantly raised in the toxin-treated algae cells from day 3, but they showed a sharp decrease on day 4, which was the onward of cell proliferation. These results suggested that oxidative stress manifested by elevated ROS levels and MDA contents might be responsible for the toxicity of microcystin to Synechococcus elongatus and the algal cells could improve their antioxidant ability through the enhancement of enzymatic and non-enzymatic preventive substances.     

Influence of long-term exposure to copper on the lichen photobiont <Emphasis Type="Italic">Trebouxia erici</Emphasis> and the free-living algae <Emphasis Type="Italic">Scenedesmus quadricauda</Emphasis>

In the present work, the long-term effect (14 days) of copper on the levels of intracellular and total copper accumulation, growth, assimilation pigment composition, chlorophyll a fluorescence, soluble protein content and oxidative status (production of hydrogen peroxide and superoxide) in two algal species (Scenedesmus quadricauda and Trebouxia erici) was assessed. Scenedesmus quadricauda is a free-living alga while Trebouxia erici is the photobiont of a lichen. The presence of copper negatively affected growth, assimilation pigments, chlorophyll a fluorescence, soluble protein content and oxidative status in both the algae. However, Scenedesmus was much more sensitive compared to Trebouxia.     

Tolerance and bioaccumulation of copper in Phragmites australis and Zea mays

The effects of copper on the growth, tolerance indices, mineral composition (N, P, K, Fe, Zn and Mn) and metal uptake of reed (Phragmites australis [Cav. Trin. ex Steudel]) and maize (Zea mays L.) were investigated in hydroponic experiments at copper concentrations ranging from 0.5 to 157 M Cu. A reduction in root length was shown to be a good indicator of copper toxicity, concentrations of 15.7 and 78.7 M Cu inhibiting root growth in maize and reed, respectively. The reed was significantly more tolerant of copper than maize and at 7.85 M Cu (external concentration), reed can be described as a Cu tolerant plant, and maize as a Cu non-tolerant species. As a result of Cu toxicity, the concentrations of macronutrients N, P and K decreased in both shoot and root of maize, while the concentrations were hardly affected in reed tissues. Fe concentration increased in shoots and roots of maize and in roots of reed with increasing Cu treatments, leading to highly significant (p<0.01) linear relationships between tissue Fe and Cu concentrations. The bioconcentration factor (BCF) of Cu was higher in roots than in shoots of both plant species, ranging from 612 to 1592 in reed for the Cu treatments tested. In the roots of maize, BCF of Cu increased from 349 to 1931 when increasing Cu in nutrient solution from 7.85 M to 78.5 M. Therefore, reed could be useful in wastewater treatments for the removal of Cu. However, the use of reed in phytoextraction of Cu from contaminated soils is limited by the low accumulation rate in shoots and although reed can be more efficient than maize for Cu phytoextraction, harvesting the full biomass, including roots, may be required.     

Susceptibility to oxidative stress and modulated expression of antioxidant genes in the copper-exposed polychaete Perinereis nuntia

To identify and evaluate potentially useful biomarkers for oxidative stress as early warning indices in the polychaete, Perinereis nuntia, we exposed P. nuntia to copper (Cu) and measured several biomarker enzymes (glutathione S-transferase; GST, glutathione peroxidase; GPx, Metallothionein-like protein; MTLPs, and catalase; CAT) and genes (Pn-GSTs, Pn-CAT, and Pn-MT) with a cellular oxidative index, reactive oxygen species (ROS) level. Accumulated Cu concentrations in P. nuntia increased in a time-dependent manner. Intracellular ROS reached high levels 6h after exposure in P. nuntia with an increase of GST activity and glutathione (GSH) content. Particularly, GSH in polychaetes showed a positive correlation with Cu contents accumulated in P. nuntia. Messenger RNA expressions of GST sigma and GST omega showed relatively high expressions at 50 μg/L of Cu exposure, even though the moderate increase of rest of GST isoforms was also observed. Also regarding long-term exposure, we reared P. nuntia in sediments for 15 days, and found that there was an obvious increase of Pn-GSTs, Pn-CAT, and Pn-MT genes with elevated concentrations of Cu and Cd in polychaete body, compared to initial levels, suggesting that P. nuntia in sediment was affected by metals as well as by other organic pollutants to induce oxidative stress genes and enzymes. These findings suggest that oxidative stress is a potential modulator of defense system of P. nuntia. Several potential biomarker genes are available as early warning signals for environmental biomonitoring.     

ADSORPTION AND UPTAKE OF COPPER BY THE GREEN ALGA SCENEDESMUS SUBSPICATUS (CHLOROPHYTA)1

Copper (II) accumulation has been investigated in the green alga Scenedesmus subspicatus G. Brinkmann considering both adsorption and uptake kinetics. Experiments were conducted in a Cu- and PH-buffered medium at different free Cu²⁺ concentrations that were neither growth limiting nor toxic. We distinguished between adsorption on the cell surface and intracellular uptake by extracting copper from the cells with EDTA. Data from short-term experiments were compared with data obtained from experiments under steady state conditions. The accumulation of Cu can be described by two processes, an initial fast adsorption occurring within a minute followed by a slower intracellular uptake. Metal uptake followed Michaelis-Menten kinetics and is mediated by two systems, one with low and the other with high affinity. The maximum uptake rates (1.30 × 10^?-¹⁰ mol·[g dry wt algae]^?1· min^?1, 3.67 × 10^?-⁹ mol·[g dry wt algae]^?1·min^?1), and the half-saturation constants (6.84 × 10^?-¹⁴ M, 2.82 × 10^?-¹² M) for the two uptake systems were determined using the Lineweaver-Burk plot. The calculated maximum concentration of binding sites on the surface of the algae is initially higher (9.0 × 10^?-⁶ mol Cu.[g dry wt algae]^?1) than under steady state conditions (2.9 × 10^?-⁶ mol Cu·[g dry wt algae]^?1). This suggests that the initial binding to the algal surface comprises the binding to specific transport ligands as well as to inert adsorption sites. The conditional stability constant of the Cu binding to surface ligands was calculated as log K_Cu= 11.0 at pH 7.9. This freshwater alga has a high ability to accumulate Cu, reflecting its adaptation to the bioavailable concentration of copper.     

Effects of exogenous nitric oxide on photosynthesis,antioxidative ability,and mineral element contents of perennial ryegrass under copper stress

A hydroponics experiment was conducted to test the effects of sodium nitroprusside (SNP, a donor of NO) supplied with different concentrations on copper (Cu) toxicity in ryegrass seedlings (Lolium perenne L.). Excess Cu (200 µM) reduced chlorophyll content, resulting a decrease in photosynthesis. Cu stress induced the production of hydrogen peroxide (H₂O₂) and superoxide anion (O₂^{? ?}), leading to malondialdehyde (MDA) accumulation. Furthermore, activities of antioxidant enzymes in Cu-treated seedlings such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were decreased. In addition, Cu stress inhibited the uptake of K, Mg, Fe, and Zn and increased Ca content in roots. Moreover, in leaves of Cu-stressed seedlings, K, Fe, and Zn contents were decreased and the contents of Ca and Mg were not affected significantly. In Cu-treated seedlings, Cu concentration in roots was higher than in leaves. Addition of 50, 100, 200 µM SNP in Cu-mediated solutions increased chlorophyll content and photosynthesis, improved antioxidant enzyme activities, reduced Cu-induced oxidative damages, kept intracellular ion equilibrium under Cu stress, increased Cu concentration in roots and inhibited Cu accumulation in leaves. In particular, addition of 100 µM SNP had the best effect on promoting growth of ryegrass seedlings under Cu stress. However, the application of 400 µM SNP had no obvious alleviating effect on Cu toxicity in ryegrass seedlings.     

Symbiotic Chlorella sp. of the ciliate Paramecium bursaria do not prevent acidification and lysosomal fusion of host digestive vacuoles during infection

Summary. Each symbiotic Chlorella sp. of the ciliate Paramecium bursaria is enclosed in a perialgal vacuole derived from the host digestive vacuole, and thereby the alga is protected from digestion by lysosomal fusion. Algae-free cells can be reinfected with algae isolated from algae-bearing cells by ingestion into digestive vacuoles. To examine the timing of acidification and lysosomal fusion of the digestive vacuoles and of algal escape from the digestive vacuole, algae-free cells were mixed with isolated algae or yeast cells stained with pH indicator dyes at 25 ± 1 °C for 1.5 min, washed, chased, and fixed at various time points. Acidification of the vacuoles and digestion of Chlorella sp. began at 0.5 and 2 min after mixing, respectively. All single green Chlorella sp. that had been present in the host cytoplasm before 0.5 h after mixing were digested by 0.5 h. At 1 h after mixing, however, single green algae reappeared in the host cytoplasm, arising from those digestive vacuoles containing both nondigested and partially digested algae, and the percentage of such cells increased to about 40% at 3 h. At 48 h, the single green algae began to multiply by cell division, indicating that these algae had succeeded in establishing endosymbiosis. In contrast to previously published studies, our data show that an alga can successfully escape from the host’s digestive vacuole after acidosomal and lysosomal fusion with the vacuole has occurred, in order to produce endosymbiosis. Correspondence and reprints: Biological Institute, Faculty of Science, Yamaguchi University, Yoshida 1677-1, Yamaguchi 753-8512, Japan.     

Use of allylthiourea to produce soluble methane monooxygenase in the presence of copper

Methanotrophs expressing soluble methane monooxygenase (sMMO) may find use in a variety of industrial applications. However, sMMO expression is strongly inhibited by copper, and the growth rate may be limited by the aqueous solubility of methane. In this study, addition of allylthiourea decreased intracellular copper in Methylosinus trichosporium OB3b, allowing sMMO production at Cu/biomass ratios normally not permitting sMMO synthesis. The presence of about 1.5 μmoles intracellular Cu g⁻¹ dry biomass resulted in sMMO activity of about 250 μmoles 1-napthol formed per hour gram dry biomass whether this intracellular Cu concentration was achieved by Cu limitation or by allylthiourea addition. No loss of sMMO activity occurred when the growth substrate was switched from methane to methanol when allylthiourea had been added to growth medium containing copper. Addition of copper to medium that was almost copper-free increased the yield of dry biomass from methanol from 0.20 to 0.36 g g⁻¹, demonstrating that some copper was necessary for good growth. This study demonstrated a method by which sMMO can be produced by M. trichosporium OB3b while growing on methanol in copper-containing medium.     

Schistosoma mansoni: N-acetylcysteine downregulates oxidative stress and enhances the antischistosomal activity of artemether in mice

Artemether (Art), a derivative of the antimalarial artemisinin, also exhibit antischistosomal properties. N-acetylcysteine (NAC) has a diversity of applications, largely because of the chemical properties of the thiol moiety present in its structure. The ability of this moiety to sweep reactive oxygen species is well-established with NAC. This study investigates the ability of NAC to enhance the therapeutic potential of Art against adult Schistosoma mansoni infection and evaluates the protective role of this antioxidant on S. mansoni-induced oxidative stress. Mice were divided into five groups; normal (i), infected control (ii), infected treated with NAC, 300 mg/kg 5 days a week/4weeks (iii), infected treated with Art (300 mg/kg) 7 weeks post infection (iv) and infected treated with both NAC and Art (v). Results showed that Art produced a significant reduction in total number of worms when used alone. Also, it decreased hepatic ova count significantly accompanied with an increase in the percentage of dead ova. Treatment with NAC alone increased the percentage of dead ova; meanwhile, it enhanced the decrease in total number of worms and hepatic ova count when used with Art. Infection with S. mansoni significantly increased tissue GSH, GR, SOD and serum ALT and GGT, while decreased the activities of GST, GPx and the levels of proteins and albumin compared to normal control. Treatment with NAC alone approximately recovered the contents of GSH, activities of GPx and levels of serum albumin, ALT and GGT relative to normal control. A tendency for normalization in activities of the antioxidant enzymes mentioned above and serum levels of liver function tests was observed in the groups treated with Art alone or Art + NAC. Conclusion: NAC downregulates oxidative stress induced by S. mansoni infection and enhances the therapeutic potential of artemether against adult schistosomes.     

Physiological and ultrastructural changes in <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> as affected by changed GSH level and Cu excess

We investigated the responses of wild-type Arabidopsis thaliana plants to the excess of Cu under conditions of the changed intracellular level of reduced glutathione (GSH) after application of buthionine sulfoximine (BSO) or exogenous GSH to the nutrient solution. BSO (500 μM) decreased and exogenous GSH (500 μM) increased GSH level, while increasing Cu concentration (from 5 to 50 μM) resulted in a decreased GSH content in the roots, but in its increased content in the shoots. BSO did not affect plant growth in contrast to exogenous GSH and Cu, which significantly reduced plant fresh weight. Both Cu and BSO or GSH induced changes in the root structure and leaf chloroplasts ultrastructure. Cu did not induce phytochelatin accumulation. Application of BSO or exogenous GSH did not significantly affect either the GSH level in the Cu-treated plants (except for 50/50 and 50/500 μM/μM Cu/GSH treatments increasing intracellular GSH content in the roots) or Cu toxicity to plants. These results suggest that GSH is not directly involved in Cu detoxification and tolerance in A. thaliana, yet it influences the proper anatomical structure of plants.     

Accumulation, subcellular localization and ecophysiological responses to copper stress in two Daucus carota L. populations

Copper accumulation, subcellular localization and ecophysiological responses to excess copper were investigated using pot culture experiments with two Daucus carota L. populations, from a copper mine and an uncontaminated field site, respectively. Significant differences of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) concentrations and antioxidant enzyme [superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX)] activities of leaves under Cu treatment were observed between the two populations. At high Cu concentrations (400 and 800 mg kg⁻¹), a significant increase in contents of MDA and H₂O₂ but a significant decrease in activities of SOD, CAT and APX were observed in uncontaminated population. Contrarily, the population from copper mine maintained a lower level of MDA and H₂O₂ but higher activities of SOD, CAT and APX. Copper accumulation in roots and shoots increased significantly with the increase of copper concentrations in soils in the two populations. No significant difference of the total Cu in roots and shoots was found between the two populations at same copper treatment. There were also no striking differences of cell wall-bound Cu and protoplasts Cu of leaves between the two populations. The difference was that Cu concentration in vacuoles of leaves was 1.5-fold higher in contaminated site (CS) population than in uncontaminated site population. Hence, more efficient vacuolar sequestration for Cu and maintaining high activities of SOD, CAT and APX in the CS population played an important role in maintaining high Cu tolerance.