Effects of cadmium hyperaccumulation on the concentrations of four trace elements in <Emphasis Type="Italic">Lonicera japonica</Emphasis> Thunb.

Hyperaccumulators are important in the phytoremediation of cadmium (Cd)-contaminated soil. In this study, Cd accumulation and the interactions between Cd and four other trace elements (Fe, Mn, Cu, and Zn) in Lonicera japonica Thunb. were investigated. As a result of exposure to soil containing 50 mg kg⁻¹ Cd, stem and shoot Cd concentrations reached 344.49 ± 0.71 and 286.12 ± 9.38 μg g⁻¹ DW respectively, without showing symptoms of visible damage to the plants. This suggests that L. japonica has a strong tolerance to Cd. It is proposed that trace metal elements are involved in the Cd-detoxification mechanisms shown by hyperaccumulators. There is a synergistic interaction in accumulation and translocation between Cd and Fe and a significantly negative correlation between Cd and Cu or Zn concentrations in L. japonica plant tissues. The imbalanced trace element concentrations influences detoxification processes to Cd, therefore, L. japonica could be considered as a new Cd-hyperaccumulator model to investigate the metal tolerance strategies of plants.     

Effects of selected heavy metals (Pb, Cu, Ni, and Cd) in the aquatic medium on the restoration potential and accumulation in the stem cuttings of the terrestrial plant, Talinum triangulare Linn

The heavy metal (Cu, Pb, Ni, and Cd) accumulation capacity of the stem cuttings of the terrestrial, ornamental plant, Talinum triangulare was assessed in hydroponic medium. The stem cuttings of T. triangulare, grew well in distilled water regenerating roots and aerial parts. On exposure to various concentrations of Cu, Pb, Ni, and Cd, a concentration dependent decrease was observed in the number of leaves produced and roots regenerated and an increase in the number of days required for the initiation of roots. The number of leaves produced showed an increasing trend in almost all treatment concentrations of Cu, Pb, Ni, and Cd with an increase in the duration of experiment, whereas, with an increase in the treatment concentration of metals a significant (P < 0.05) decrease was observed in the number of leaves produced. The number of days required for root initiation in metal solutions, however, increased with increasing concentration of Cu, Pb, Ni, and Cd. The root development was completely arrested from 10 mg l⁻¹ of Ni and 4 mg l⁻¹ of Cd. Compared to the control, a significant decrease was recorded in the number of roots produced in all treatment concentrations of Cu, Pb, Ni, and Cd. Pink colouration of metal solution consequent to leaching of plant pigment from T. triangulare was observed which was not persistent and disappeared after a few days. Decaying of stem was observed when exposed to Ni and Cd but not to Cu and Pb. Although, copper accumulation by T. triangulare at treatment concentration of 15 and 20 mg l⁻¹ exceeded 1,000 mg kg⁻¹ dry matter, necessary pot culture experiment is required before “T. triangulare” can be definitely classified as a Cu hyperaccumulator.     

Growth and antioxidant response in <Emphasis Type="Italic">Hydrocharis dubis</Emphasis> (Bl.) Backer exposed to linear alkylbenzene sulfonate

A two-week exposure experiment was designed to investigate the toxicity of linear alkylbenzene sulfonate (LAS) on the aquatic plant Hydrocharis dubis (Bl.) Backer, focusing on growth, photosynthetic pigments and the activities of antioxidant enzymes. No significant differences were observed in the growth parameters of H. dubis when H. dubis was exposed to lower LAS doses (≤10 mg l⁻¹). However, lower LAS doses remarkably promote the dry weight accumulation of H. dubis. Higher doses of LAS (>10 mg l⁻¹) resulted in significant decreases in all growth parameters of H. dubis. No significant effect on pigment contents was observed at up to 50 mg l⁻¹ LAS, beyond which pigment contents declined gradually. Malondialdehyde (MDA) content did not show obvious differences when H. dubis plants were exposed to ≤50 mg l⁻¹ LAS. Peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT) activities showed a concentration-dependent increase up to LAS concentrations of 0.1–10 mg l⁻¹, followed by a clear decrease. The results of this study suggest that LAS significantly inhibited the growth and physiology of H. dubis when the dose of LAS exceeded 10 mg l⁻¹ . Therefore, LAS at current environmental concentrations dose not appear to cause evident phytotoxic effects on H. dubis.     

Effects of metal pyrithione antifoulants on freshwater macrophyte <Emphasis Type="Italic">Lemna gibba</Emphasis> G3 determined by image analysis

Copper pyrithione (CuPT₂) and zinc pyrithione (ZnPT₂) are two popular antifouling agents that prevent biofouling. Research into the environmental effects of metal pyrithiones has mainly focused on aquatic animal species such as fish and crustaceans, and little attention has been paid to primary producers. There have been few reports on residues in environmental matrices because of the high photolabile characteristics of the agents. Residue analyses and ecological effects of the metabolites and metal pyrithiones are not yet fully understood. This study was undertaken to assess the effects of CuPT₂, ZnPT₂, and six metabolites (PT₂: 2,2′-dithio-bispyridine N-oxide, PS₂: 2,2′-dithio-bispyridine, PSA: pyridine-2-sulfonic acid, HPT: 2-mercaptopyridine N-oxide, HPS: 2-mercaptopyridine, and PO: pyridine N-oxide) on a freshwater macrophyte. A 7-day static bioassay using axenic duckweed Lemna gibba G3 was performed under laboratory conditions. Toxic effects of test compounds were assessed by biomass reduction and morphological changes were determined in image analysis. Concentrations of ZnPT₂ and CuPT₂ and those of PT₂ and HPT in the medium were determined by derivatizing 2,2′-dithio-bispyridine mono-N-oxide with pyridine disulfide/ethylene diamine tetra-acetic acid reagent that was equimolar with pyrithione. The toxic intensity of the compounds was calculated from the measured concentrations after 7-day exposure. ZnPT₂, CuPT₂, PT₂, and HPT inhibited the growth of L. gibba with EC₅₀ ranging from 77 to 140 μg/l as calculated from the total frond number as the conventional index, whereas the other four metabolites had less effect even at 10 mg/l. The presence of the former four toxic derivatives resulted in abnormally shaped and unhealthily colored fronds, whose size was about 20% of the control fronds. EC₅₀, calculated from the healthy frond area determined in image analysis, ranged from 10 to 53 μg/l. Thus, image analysis as part of a duckweed bioassay can detect the toxic effects of pyrithione derivatives with 3–10 times higher sensitivity than the traditional index.     

Bioaccumulation and degradation of pesticide fluroxypyr are associated with toxic tolerance in green alga <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

The herbicide fluroxypyr is widely used for controlling weeds and insects but intensive use of fluroxypyr has resulted in its widespread contamination in soils and aquatic ecosystems. To evaluate the eco-toxicity of fluroxypyr to green algae, bioaccumulation and degradation of fluroxypyr in Chlamydomonas reinhardtii, a model unicellular alga, along with its biological adaptation to fluroxypyr toxicity were investigated. The microalgae were treated with fluroxypyr at 0.05–1.00 mg l⁻¹ for 2 days or 0.50 mg l⁻¹ for 1–5 days. The growth of C. reinhardtii was stimulated at low levels of fluroxypyr (0.05–0.5 mg l⁻¹) but inhibited at high concentrations (0.75–1.00 mg l⁻¹). Fluroxypyr was significantly accumulated by C. reinhardtii. Interestingly, the accumulated fluroxypyr could be rapidly degraded in the cells. On day 5 more than 57% of cellular fluroxypyr was degraded. Our results indicated that accumulation and degradation of fluroxypyr occurred simultaneously. Treatment with 0.05–1.00 mg l⁻¹ fluroxypyr for 30 min induced significant production of reactive oxygen species and as a consequence resulted in accumulation of peroxides and DNA degradation. Additionally, activities of several major antioxidant enzymes were activated in C. reinhardtii exposed to high levels of fluroxypyr. Overall, the present studies represent the initial comprehensive analyses of the green alga C. reinhardtii in adaptation to the fluroxypyr-contaminated aquatic ecosystems.     

Physiological response of Cu and Cu mine tailing remediation of <Emphasis Type="Italic">Paulownia fortunei</Emphasis> (Seem) Hemsl

The physiological responses and Cu accumulation of Paulownia fortunei (Seem) Hemsl. were studied under 15.7–157 μmol L⁻¹ Cu treatments in liquid culture for 14 days; the impacts of Cu concentration in the seedlings were evaluated under Cu mine tailing culture with acetic acid and EDTA treatment for 60 days. Results showed that the concentrations of Chl-a, Chl-b and Carotenoids significantly increased (p < 0.05) at 15.7–78.7 μmol L⁻¹Cu treatment and significantly decreased at 157 μmol L⁻¹ treatment after 14 days of Cu exposure. The activities of superoxide dismutase (SOD) and catalase (CAT) significantly increased as Cu levels were enhanced and the activities of both SOD and CAT under 157 μmol L⁻¹ Cu stress were 2.9 and 1.9 times higher than that of control, respectively. The concentrations of proline and soluble sugars in the leaves of P. fortunei significantly increased as the Cu concentrations were elevated. Cu concentrations in roots, stems and leaves of P. fortunei increased significantly as Cu levels increased and reached 1911, 101 and 93 μg g⁻¹ dry weights (DW) at 157 μmol L⁻¹ Cu treatment, respectively. The seedlings of P. fortunei cultivated in Cu tailing experienced unsuccessful growth and loss of leaves in all treatments due to poor nutrition of the Cu tailing. The dry weight of P. fortunei increased under all the treatments of acetic acid after 60 days exposure. However, dry weight significantly decreased under both levels of EDTA. The Cu concentrations increased significantly in roots and decreased in leaves when each was treated with both concentrations of acetic acid. The Cu concentrations in the roots, stems and leaves increased significantly, and the concentrations of Cu in the stems and leaves under the treatment of 2 μmol L⁻¹ EDTA reached 189.5 and 763.1 μg g⁻¹ DW, respectively. The result indicated that SOD, CAT, proline and soluble sugars played an important role in coping with the oxidative stress of copper. Acetic acid could promote growth and EDTA at the experimental levels, which could also enhance Cu absorption and translocation into the stems and leaves of P. fortune. Furthermore, acetic acid and EDTA could be rationally utilized in Cu-contaminated soil.     

Acute and chronic effects of sodium and potassium on the tropical freshwater cladoceran <Emphasis Type="Italic">Pseudosida ramosa</Emphasis>

In this study, the toxicities of sodium and potassium to the tropical freshwater cladoceran Pseudosida ramosa were assessed. Acute toxicity tests on this species showed that the 48-h LC₅₀ of Na⁺ was 556 mg l⁻¹, while that of K⁺ was 17.7 mg l⁻¹. Long-term exposure of female P. ramosa to sodium reduced the total number of survivors from 10 to 6 at a concentration of 249 mg l⁻¹, 21-day fecundity from 20.4 to 14.3 eggs female⁻¹ at concentrations ranging from 72 to 249 mg l⁻¹, 21-day fertility from 20.1 to 6.5 neonates female⁻¹ at concentrations ranging from 25 to 249 mg l⁻¹. Furthermore, fecundity of each brood from the second to the fifth was significantly lower at 249 mg l⁻¹ and fertility of each brood from the first to the fifth at concentrations ranging from 25 to 249 mg l⁻¹. A significant decrease in fertility was associated with an increase in the number of aborted eggs. Long-term exposure to potassium decreased the 21-day fecundity of P. ramosa from 14.2 to 10.8 eggs female⁻¹ at a concentration of 11 mg l⁻¹ and fertility (fourth brood only) at 6.2 and 11 mg l⁻¹. Tropical reservoirs located near areas where the soil is overloaded with fertilizers and ferti-irrigation with vinasse already show concentrations of Na⁺ and K⁺ very close to those producing sub-lethal long-term effects on P. ramosa. A possible consequence is that organisms of the aquatic biota cannot adapt and freshwater taxa may become locally extinct, transferring dominance to salt-tolerant taxa.     

Development of a microalgal PAM test method for Cu(II) in waters: comparison of using spectrofluorometry

Test methods are needed to monitor Cu concentrations in reservoirs and water supplies. Dictyosphaerium chlorelloides (Chlorophyta) cells were immobilized in a silicate sol–gel and the toxic effects of Cu(II) were examined using different techniques: fluorescence measurements (using a spectrofluorometer with an optic fiber coupled to a flow cell or a 96-well-plate reader) or by Pulse Amplitude Modulation (PAM) parameters using a portable instrument and the pulse saturation method. Fm′ and qN were the most sensitive indicator parameters when performing Cu analysis in water. D. chlorelloides PAM biosensor presented a detection limit of 0.6 mg l⁻¹ for Cu(II), within the limits to establish if Cu concentrations exceeded regulatory levels. Moreover, a 1.9 mg Cu l⁻¹ (30 μM) resistant strain of the D. chlorelloides microalgae was produced in order to obtain more selectivity on the metal determination.     

The combined effect of copper and low pH on antioxidant defenses and biochemical parameters in neotropical fish pacu, <Emphasis Type="Italic">Piaractus mesopotamicus</Emphasis> (Holmberg, 1887)

Copper sulfate is widely used in aquaculture. Exposure to this compound can be harmful to fish, resulting in oxidative metabolism alterations and gill tissue damage. Pacu, Piaractus mesopotamicus, (wt = 43.4 ± 3.35 g) were distributed in experimental tanks (n = 10; 180 l) and exposed for 48 h to control (without copper addition), 0.4Cu (0.4 mg l⁻¹), 0CupH (without copper addition, pH = 5.0) and 0.4CupH (0.4 mg l⁻¹, pH = 5.0). In liver and red muscle, the superoxide dismutase (SOD) was responsive to the increases in the aquatic copper. The plasmatic intermediary metabolites and hematological variables in the fish of group 0.4Cu were similar to those of the control group. Conversely, the exposure to 0.4CupH caused an increase in the plasmatic lactate, number of red blood cells (RBC) and hemoglobin (Hb). Plasmatic copper concentration [Cu_p] increased in group 0.4Cu and 0.4CupH, which is higher in group 0.4CupH, suggests an effect of water pH on the absorbed copper. Exposure to 0.4Cu and 0.4CupH resulted in a reduction in the Na⁺/K⁺-ATPase activity and an increase in metallothionein (MT) in the gills. Exposure to 0CupH caused a decrease in glucose and pyruvate concentrations and an increase in RBC, Hb, and the branchial Na⁺/K⁺-ATPase activity. These responses suggest that the fish triggered mechanisms to revert the blood acidosis, save energy and increase the oxygen uptake. MT was an effective biomarker, responding to copper in different pHs and dissolved oxygen. Combined-factors caused more significant disturbance in the biomarkers than single-factors.     

The mysid <Emphasis Type="Italic">Siriella armata</Emphasis> as a model organism in marine ecotoxicology: comparative acute toxicity sensitivity with <Emphasis Type="Italic">Daphnia magna</Emphasis>

Siriella armata (Crustacea, Mysidacea) is a component of the coastal zooplankton that lives in swarms in the shallow waters of the European neritic zone, from the North Sea to the Mediterranean. Juveniles of this species were examined as standard test organisms for use in marine acute toxicity tests. The effects of reference toxicants, three trace metals (Copper, Cadmium and Zinc), and one surfactant, sodium dodecyl sulfate (SDS) were studied on S. armata neonates (<24 h) reared in the laboratory. Acute toxicity tests were carried out with filtered sea water on individual chambers (microplate wells for metals or glass vials for SDS) incubated in an isothermal room at 20°C, with 16 h light: 8 h dark photoperiod for 96 h. Each neonate was fed daily with 10–15 nauplii of Artemia salina. Acute (96 h) LC₅₀ values, in increasing order, were 46.9 μg/L for Cu, 99.3 μg/L for Cd, 466.7 μg/L for Zn and 8.5 mg/L for SDS. The LC₁₀, NOEC and LOEC values were also calculated. Results were compared with Daphnia magna, a freshwater cladoceran widely used as a standard ecotoxicological test organism. Acute (48 h) LC₅₀ values were 56.2 μg/L for Cu, 571.5 μg/L for Cd, 1.3 mg/L for Zn and 27.3 mg/L for SDS. For all the reference toxicants studied, the marine mysid Siriella armata showed higher sensitivity than the freshwater model organism Daphnia magna, validating the use of Siriella mysids as model organisms in marine acute toxicity tests.     

Metal sensitivity of the embryonic development of the ramshorn snail <Emphasis Type="Italic">Marisa cornuarietis</Emphasis> (Prosobranchia)

We investigated the effects of metal ions on the embryonic development of the ramshorn snail, Marisa cornuarietis, by exposing embryos to varying concentrations of copper (0, 50, 100, and 250 μg Cu²⁺/L), lead (0, 5, 10, and 15 mg Pb²⁺/L), lithium (0, 1, 2.5, and 3 mg Li⁺/L), or palladium (0, 50, 100, and 500 μg Pd²⁺/L). Effects of these metals were examined by recording mortality, the rate of tentacles and eyes formation, heart rate, hatching success, and weight after hatching. Compared to the control, we found a significant delay in the formation of tentacles and eyes after treatment with 100 μg Cu²⁺/L, 15 mg Pb²⁺/L, 2.5 mg Li⁺/L or 500 μg Pd²⁺/L. The heart rate decreased significantly at 500 μg Pd²⁺/L. At 10 mg Pb²⁺/L, 2.5 mg Li⁺/L, or 500 μg Pd²⁺/L, hatching was delayed significantly; 50 μg Cu²⁺/L induced a significantly earlier hatching, and reduced body weight. The LC₅₀ values were calculated to be about 50 μg Cu²⁺/L, 500 μg Pd²⁺/L, 2500 μg Li⁺/L, and 10000 μg Pb²⁺/L. These results show that the embryonic development of M. cornuarietis is about as sensitive to copper and lithium, compared to the most sensitive fishes used in embryo toxicity testing. Even though the MariETT is a laboratory-based assay focusing on toxicological endpoints of a selected model species, future application is envisaged to include testing of “natural” samples such as stream water or sediment interstitial water.     

Phytoassessment of acid mine drainage: Lemna gibba bioassay and diatom community structure

An integrated multilevel phytoassessment of an acid mine drainage (AMD, pH range 3.3–6.8) in southern Portugal was performed. A 7-day phytotoxicity bioassay with the duckweed Lemna gibba (chlorosis, necrosis, growth) was carried out, both in the laboratory and in situ, combined with an analysis of the resident epilithic diatom community. The toxicity test was performed with water from the AMD gradient, an unpolluted river control and acidified control water, in order to discriminate potential pH-effects from combined pH- and metal-effects. Diatom communities discriminated well among the sites (alkalophilic species versus halobiontic, acidobiontic and acidophilic species), showing inter-site differences to be larger than intra-site seasonal variations. In L. gibba exposed to AMD, necrosis and growth inhibition were higher in situ compared to the laboratory experiments. L. gibba was more sensitive to AMD than to acidified water. Already after 4 days, growth rate inhibition in L. gibba proved to be a reliable indicator of AMD-stress. Ecotoxicological thresholds obtained with L. gibba corresponded with those obtained previously with animals of intermediate tolerance to AMD. The results were summarised in a multimetric index.     

The physiological response and sub-cellular localization of lead and cadmium in Iris pseudacorus L.

The seedling development and physiological responses of Iris pseudacorus L. to Pb and Cd and their combination were studied for 28 days liquid culture and sub-cellular localization of Pb and Cd in the root tip cells treated with 2,070 mg L⁻¹ Pb and 1,000 mg L⁻¹Cd for 16 days sand culture was evaluated. Results showed that the dry weights (DWs) of shoots and roots of I. pseudacorus were significantly decreased at 500 mg L⁻¹Pb and 25 mg L⁻¹Cd + 500 mg L⁻¹Pb treatments and the root DWs under all treatments were significantly decreased in comparison with that of control. The concentrations of Chla in the leaves were decreased at all treatments, while, the concentrations of Chlb and total carotenoids were not significantly decreased under 25 mg L⁻¹Cd and 25 mg L⁻¹Cd + 500 mg L⁻¹Pb treatments. The MDA and proline concentrations and POD activities in the shoots and roots were increased under treatments of 500 mg L⁻¹Pb and 25 mg L⁻¹Cd + 500 mg L⁻¹Pb, but POD activities in the shoots and roots and MDA concentrations in the shoots were significantly decreased at 25 mg L⁻¹ Cd treatment. The results of sub-cellular localization of Pb and Cd showed that numerous Pb deposits were found on the inner surface of died cell walls in the cortex treated with 2,070 mg L⁻¹ Pb and Cd deposits were found in the cell wall treated with 1,000 mg L⁻¹ Cd. Pb and Cd deposits were not found in the cytoplasm. The results indicated that POD and proline showed strong beneficial properties against Pb and Cd stress and there were some mechanisms keeping most cells with normal activities in the plant from Pb toxicity by sacrificing a few cells that accumulated a large amount Pb. Sub-cellular localizations of Pb and Cd in the root tip cells of I. pseudacorus were little difference with the localizations in other species of Iris in the previous studies.     

Homeostatic regulation of elemental stoichiometry by Lemna gibba L. G3 when nutrient interact with toxic metals

We investigated responses of Lemna gibba L. to exposure to UO₂ ²⁺ and AsO₄ ³⁻ under variable PO₄ ³⁻ concentration. Total plant phosphorus (P_tot) in L. gibba and accumulation of dissolved organic carbon (DOC) in the media were quantified and tested for correlation with plant yield and initial concentrations of PO₄ ³⁻, UO₂ ²⁺ and AsO₄ ³⁻. The accumulation of DOC in medium was high under low PO₄ ³⁻ supply and increased loading of either UO₂ ²⁺ or AsO₄ ³⁻. The P_tot was low in high initial concentration of UO₂ ²⁺ and AsO₄ ³⁻ as well under acute low PO₄ ³⁻ supply. The DOC accumulation correlated negatively to the P_tot. This reveals interaction between PO₄ ³⁻ and UO₂ ²⁺ or AsO₄ ³⁻ in the medium interferes with the uptake process of PO₄ ³⁻. Hence, the DOC accumulation is exudation of low molecular weight organic substance by L. gibba in response to the reduced P_tot: biomass ratio (carbon in the yield) due to delimited acquisition of phosphorus from the medium. It is a homeostatic regulation of the stoichiometry, which is disturbed during the interaction between PO₄ ³⁻ and UO₂ ²⁺ or AsO₄ ³⁻. Further investigations are necessary to relate these interactions to traditional resource stoichiometry elements of C, N, and P.     

Body condition and mercury concentration in apparently healthy goosander (<Emphasis Type="Italic">Mergus merganser</Emphasis>) wintering in the Odra estuary,Poland

Goosanders (Mergus merganser, ad, adult n = 42: M, males 33 and F, females 9; im, immature n = 17: M 8, F 9) were collected in 2005 at wintering site in the River Odra estuary (Poland). The body size (BM, body mass; BL, body length; KL, keel length), weights of organs (LM, liver; KM, kidneys; EM, encephalon), and two condition-related indices (BM/BL and BM/KL) were determined. Based on BM/BL and BM/KL indices, the birds were divided into 3 condition groups: A (very good), B (good), and C (moderate). Total mercury (Hg) concentrations (mg kg⁻¹ dry weight) were determined in liver, kidney, brain, breast muscle, and bone of 17 birds (ad, n = 8: 8 M, 1 F; im, n = 9: 6 M, 3 F). The highest Hg concentrations (in n = 17) were recorded in liver and kidney (14.7 and 9.9 mg kg⁻¹, respectively); the concentrations found in muscle and brain were lower (2.3 and 1.3 mg kg⁻¹, respectively), the lowest concentrations being typical of bone (0.08 mg kg⁻¹). Mercury concentrations in the same organs of immature and adult goosanders, as well as males and females, did not differ significantly. On the other hand, distinct differences in Hg concentrations in the organs studied (except for the liver) were observed between individuals assigned to Group A (n = 11) and C (n = 6). Mercury levels were higher in the birds characterised by very good condition, which was most probably related to those birds being more efficient hunters, consuming higher amounts of Hg-containing fish. Significant and negative correlations between the muscle Hg concentration and the two condition-related indices (r > –0.70) were recorded in Group A only: the higher the concentration, the lower the BM/LM and BM/KL values.     

The effects of nickel on the reproductive ability of three different marine copepods

Lethal and sublethal toxicity of Nickel (Ni) to three marine copepods Tigriopus japonicus, Apocyclops borneoensis and Acartia pacifica was investigated. The 48-h LC50 values were 17.70, 13.05 and 2.36 mg l⁻¹ Ni, respectively. A. pacifica was found to be the most sensitive to Ni in acute exposure tests. In order to assess sublethal effects of Ni on copepod reproduction, the test organisms were exposed to four nominal Ni concentrations 0, 10, 100, 1000 μg l⁻¹ Ni. The results indicated that offspring production of T. japonicus and A. borneoensis was significantly reduced after exposure to 10 μg l⁻¹ Ni. Whereas egg production and egg hatching success of A. pacifica were significantly reduced at 100 and 10 μg l⁻¹ Ni, respectively. Exposure of copepods to the highest Ni concentration caused a severely reduced nauplii production from T. japonicus, A. borneoensis and A. pacifica by 87.8, 56.9 and 65.8%, respectively, and a significantly reduced egg production of A. pacifica by 74.4%. These results show that Ni excess in the coastal environment can have detrimental effects on reproduction of copepods.     

Enzymatic alterations and RNA/DNA ratio in intestine of rainbow trout, <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>, induced by chronic exposure to carbamazepine

We investigated the effect of long-term exposure to carbamazepine (CBZ) on the enzymatic alterations and RNA/DNA ratio in intestine tissue of rainbow trout. Fish were exposed to sublethal concentrations of CBZ (1.0 μg/l, 0.2 or 2.0 mg/l) for 42 days. Digestive enzymes (proteolytic enzymes and amylase) and energy metabolic enzyme (Na⁺-K⁺-ATPase) and antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT], glutathione peroxidase [GPx], and glutathione reductase [GR]) in fish intestine were measured. In addition, intestinal RNA/DNA ratio was determined after 42 days exposure. Carbamazepine exposure at 2.0 mg/l led to significantly inhibited (P < 0.05) activity of Na⁺-K⁺-ATPase. Activities of the antioxidant enzymes SOD, CAT, and GPx in CBZ-treated groups gradually increased at lower concentration of CBZ (1.0 μg/l and 0.2 mg/l), then significantly inhibited (P < 0.05) at 2.0 mg/l. After 42 days, the RNA/DNA ratio in fish intestine was significantly lower (P < 0.05) in groups exposed to CBZ at 2.0 mg/l than in other groups. However, there was no statistical significance (P > 0.05) in the activities of digestive enzymes (proteolytic enzyme and amylase) and GR in all groups. In short, prolonged exposure to CBZ resulted in different responses of various enzymes and significantly lower RNA/DNA ratio in fish intestine. Furthermore, molecular and genetic mechanisms of these physiological responses in fish are not clear, which need to be further studied.     

Essential metal (Cu,Zn) exposures alter the activity of ATPases in gill,kidney and muscle of tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

An acute (96 h—0.1, 0.5, 1.0, 1.5 μg/ml) and chronic (up to 30 days—0.05 μg/ml) protocols of Cu and Zn were applied to freshwater fish Oreochromis niloticus to investigate these essential metal effects on the activities of gill, kidney and muscle Na⁺/K⁺-ATPase, Mg²⁺-ATPase and Ca²⁺-ATPase. In vitro effects of both metals (20 min—0.1, 0.5, 1.0, 1.5 μg/ml) were also measured to be able to compare both exposure routes. Data showed that ATPase activities, in general, decreased following all the exposure conditions, though there were some increases especially in Mg²⁺-ATPase activity. Among the enzymes, Na⁺/K⁺-ATPase and Ca²⁺-ATPase appeared to be more sensitive than Mg²⁺-ATPase to the metals. The data also indicated that effects of Cu on ATPase activity in the tissues of O. niloticus were stronger than the effects of Zn, possibly due to higher toxic effects of Cu. In vivo and in vitro exposures of metals showed similar trends with a few exceptions, especially in the gill. Variability of ATPase activity is determined by tissue type, metal species, concentration and duration. This work showed that even essential metals can alter significantly activities of ATPases in fish and thus suggests using them as a sensitive biomarker in metal contaminated waters.     

Can Lemna minor mitigate the effects of cadmium and nickel exposure in a Neotropical fish?

We aimed to evaluate if Lemna minor can mitigate the observed effects of cadmium (Cd) and nickel (Ni) exposure in Prochilodus lineatus. Fish were exposed for 96 h to 20 µg L^-1 of Cd, 1.5 mg L^-1 of Ni, or to a mixture of these two metals. In all tests, one group was exposed to the metals with duckweed on the water surface, and other group was exposed only to the metals, without plants. After each exposure, samples of P. lineatus tissues were collected to evaluate multiple biomarkers. Duckweed prevented bioaccumulation in some fish tissues and attenuated changes in acetylcholinesterase activity, increases in erythrocytic nuclear abnormality frequency, and hyperglycemia. However, the changes in plasma ion concentrations, reduction in activity of ion transport enzymes, and histological damage were not mitigated. Therefore, we concluded that L. minor partially attenuates the effects caused by Cd and Ni exposure.     

l‐Cysteine enhances nutrient absorption via a cystathionine‐β‐synthase‐derived H2S pathway in rodent jejunum

Hydrogen sulphide (H₂S) is generated endogenously from l ‐cysteine (l ‐Cys) by the enzymes cystathionine‐β‐synthase (CBS) and cystathionine‐γ‐lyase (CSE). In addition, l ‐Cys is commonly used as a precursor in the food and pharmaceutical industries. The aim of the present study is to determine whether l ‐Cys regulates intestinal nutrient transport. To that end, the presence of CBS and CSE in the jejunum epithelium was assessed by immunohistochemistry, Western blotting and the methylene blue assay. In addition, in vivo l ‐Cys (100 mg/kg, administered immediately after the glucose load) significantly increased blood glucose levels 30 min after the oral administration of glucose to mice. This effect of l ‐Cys was completely blocked by amino‐oxyacetic acid (AOA; 50 mg/kg; administered at the same time as l ‐Cys) an inhibitor of CBS. Measurements of the short‐circuit current (I_sc) in the rat jejunum epithelium revealed that l ‐Cys (1 mmol/L; 6 min before the administration of l ‐alanine) enhances Na⁺‐coupled l ‐alanine or glucose transport, and that this effect is inhibited by AOA (1 mmol/L;10 min before the administration of l ‐Cys), but not d ,l ‐propargylglycine (PAG;1 mmol/L; 10 min before the administration of l ‐Cys), a CSE inhibitor. Notably, l ‐Cys‐evoked enhancement of nutrient transport was alleviated by glibenclamide (Gli;0.1 mmol/L; 10 min before the administration of l ‐Cys), a K⁺ channel blocker. Together, the data indicate that l ‐Cys enhances jejunal nutrient transport, suggesting a new approach to future treatment of nutrition‐related maladies, including a range of serious health consequences linked to undernutrition.