Sensitivity of spore germination and germ tube elongation of Saccharina japonica to metal exposure

The sensitivity of early life stages of the brown seaweed Saccharina japonica to six metals (Cd, Cu, Hg, Ni, Pb, Zn) and two waste-water samples were investigated and a new toxicity bioassay developed. The two endpoints used were spore germination and germ tube elongation with an exposure time of 24 h. Optimal test conditions determined for photon irradiance, pH, salinity and temperature were darkness, pH 8, 35‰ and 15°C, respectively. The toxicity ranking of five metals was: Hg (EC₅₀ of 41 and 42 μg l⁻¹) > Cu (120 and 81 μg l⁻¹) > Ni (2,009 and 1,360 μg l⁻¹) > Zn (3,024 and 3,897 μg l⁻¹) > Pb (4,760 and 4,429 μg l⁻¹) > Cd (15,052 and 7,541 μg l⁻¹) for germination and germ tube elongation, respectively. The sensitivities to Cd, Cu and Ni were greater in germ tube elongation than in germination process. When tested against two different waste-water samples (processed animal and printed circuit board waste-water) values of EC₅₀ were between 21.29 and 32.02% for germination and between 5.33 and 8.98% for germ tube elongation. Despite differences in their chemical composition, the toxic effects of waste-water samples, as indicated by EC₅₀ values, did not differ significantly for the same endpoints. The CV range for both germination and germ tube elongation was between 4.61 and 37.69%, indicating high levels of precision of the tests. The results compare favourably with those from more established test procedures employing micro- and macroalgae. The advantages and potential limitations of the bioassay for the assessment of anthropogenic impacts on coastal ecosystems and commercial cultivation areas in near-shore environments are discussed.     

Acute toxicity of nonylphenols and bisphenol A to the embryonic development of the abalone <Emphasis Type="Italic">Haliotis diversicolor supertexta</Emphasis>

Acute toxic effects and mechanisms of two typical endocrine disrupting chemicals, nonylphenols (NPs) and bisphenol A (BPA), to the embryonic development of the abalone Haliotis diversicolor supertexta, were investigated by the two-stage embryo toxicity test. The 12-h median effective concentrations (EC₅₀) of NPs and BPA to the trochophore development were 1016.22 and 30.72 μg L⁻¹, respectively, and the respective 96-h EC₅₀ values based on the completion of metamorphosis (another experimental endpoint) were reduced to 11.65 and 1.02 μg L⁻¹. Longer exposure time and magnified exposure concentrations in the benthic diatom, that serves as both food source and settlement substrate during the metamorphosis, via bioaccumulation, led to the higher sensitivity of metamorphosis to target EDCs compared with the trochophore development. The hazard concentrations for 5% of the species (HC₅) could be employed as the safety thresholds for the embryonic development of the abalone. The 12-h HC₅ values of NPs and BPA were 318.68 and 13.93 μg L⁻¹, respectively, and the respective 96-h HC₅ values were 0.99 and 0.18 μg L⁻¹, which were at environmentally relevant levels. Results of proteomic responses revealed that NPs and BPA altered various functional proteins in the abalone larvae with slight differences between each chemical and affected various physiological functions, such as energy and substance metabolism, cell signalling, formation of cytoskeleton and cilium, immune and stress responses at the same time, leading to the failure of metamorphosis.     

Effects of an anionic surfactant (FFD-6) on the energy and information flow between a primary producer (<Emphasis Type="Italic">Scenedesmus obliquus</Emphasis>) and a consumer (<Emphasis Type="Italic">Daphnia magna</Emphasis>)

The effects of a commercially available anionic surfactant solution (FFD-6) on growth and morphology of a common green alga (Scenedesmus obliquus) and on survival and clearance rates of the water flea Daphnia magna were studied. The surfactant-solution elicited a morphological response (formation of colonies) in Scenedesmus at concentrations of 10–100 μl l⁻¹ that were far below the No Observed Effect Concentration (NOEC) value of 1,000 μl l⁻¹ for growth inhibition. The NOEC-value of FFD-6 for colony-induction was 3 μl l⁻¹. Daphnia survival was strongly affected by FFD-6, yielding LC_50–24h and LC_50–48h of 148 and 26 μl l⁻¹, respectively. In addition, clearance rates of Daphnia feeding on unicellular Scenedesmus were inhibited by FFD-6, yielding a 50% inhibition (EC_50–1.5h) at 5.2 μl l⁻¹ with a NOEC of 0.5 μl l⁻¹. When Daphnia were offered FFD-6-induced food in which eight-celled colonies (43 × 29 μm) were most abundant, clearance rates (~0.14 ml ind.⁻¹ h⁻¹) were only 25% the rates of animals that were offered non-induced unicellular (15 × 5 μm) Scenedesmus (~0.56 ml ind.⁻¹ h⁻¹). As FFD-6 concentrations in the treated food used in the experiments were far below the NOEC for clearance rate inhibition, it is concluded that the feeding rate depression was caused by the altered morphology of the Scenedesmus moving them out of the feeding window of the daphnids. The surfactant evoked a response in Scenedesmus that is similar to the natural chemically induced defensive reaction against grazers and could disrupt the natural information conveyance between these plankton organisms.     

Inter-population comparisons of copper resistance and accumulation in the red seaweed, Gracilariopsis longissima

Copper (Cu) resistance and accumulation of five populations of the red seaweed Gracilariopsis longissima collected from sites in south west England (Fal Estuary, Helford Estuary and Chesil Fleet) that differ in their degree of Cu contamination was assessed under controlled laboratory conditions, on two separate occasions (April and October). The effects of a range of Cu concentrations (0–250 μg l⁻¹) on relative growth rates was the same for all populations with reductions observable at concentrations as low as 12 μg l⁻¹ and cessation of growth at 250 μg l⁻¹. There was no significant difference in the calculated EC₅₀ values for the April and October samples, with means of 31.1 and 25.8 μg l⁻¹, respectively. Over the range of concentrations used in this study, copper content increased linearly and the pattern of accumulation was the same for all populations at both time periods. From the linear regressions of the pooled data a concentration factor of 2.25 × 10³ was calculated. These results imply that G. longissima has an innate tolerance to Cu and that populations have not evolved copper-tolerant ecotypes. In laboratory studies, accumulated Cu was released when transferred to ‘clean’ seawater with approximately 80% being lost after 8 days, with no significant difference between populations in their response. The results from a 30 days in situ transplantation experiment using two populations from the Fal Estuary provided further evidence for dynamic changes in Cu content in response to changes in Cu bioavailability. The findings in this study are discussed in the context of implications for seaweed biomonitoring.     

Tolerance and accumulation of lead by species of <Emphasis Type="Italic">Iris</Emphasis> L.

Seedling development, accumulation and distribution of lead (Pb) in Iris lactea var. chinensis (Fisch.) Koidz. and I. tectorum Maxim. were studied using plants grown in sand culture and exposed to 0–10 mmol l⁻¹ concentrations of Pb supplied as Pb(NO₃)₂ for 28 days. A significant reduction in dry weight (dw) of shoots and roots of I. lactea var. chinensis was observed at 6 and 10 mmol l⁻¹, respectively, and a significant reduction in dw of shoots and roots of I. tectorum was observed at 6 mmol l⁻¹. Concentration of Pb in the shoots and roots of I. lacteal var. chinensis exposed to 4 mmol l⁻¹ Pb reached 1,109 μg g⁻¹ and 2,408 μg g⁻¹ dw, respectively. The index of tolerance (IT) of I. lactea var. chinensis among 0–8 mmol l⁻¹ Pb treatments were not significantly different, while those of I. tectorum at 6 mmol l⁻¹ Pb were significantly decreased. The results indicated that I. lactea var. chinensis was more tolerant to Pb than I. tectorum. Sub-cellular localization of Pb in root cells was evaluated using transmission electron microscopy (TEM) and Pb deposits were found along the plasma membrane of some root tip cells of I. lactea var. chinensis treated at 10 mmol l⁻¹ Pb. Deposits of Pd were also observed along the surface, in the root tip cell wall and in the cytoplasm of a few malformed cells of I. tectorum exposed at 10 mmol l⁻¹ Pb treatment. One possible mechanism to explain these observations may be that most cells can maintain normal activities in the plant by sacrificing a small number of cells that accumulate a large amount Pb and show toxicity. Future studies should be designed to test this hypothesis.     

Chronic exposure to pentavalent arsenic of larval leopard frogs (Rana pipiens): bioaccumulation and reduced swimming performance

Arsenic (As) is mainly released to the environment from anthropogenic sources, with inorganic pentavalent As (As [V]) predominant in surface water. In this study, Rana pipiens were exposed to As (V) in water at environmentally relevant concentrations (control, 10, 20, 150, 500, and 1,000 μg l⁻¹) in a static-renewal system from post-hatch stage through metamorphosis for 113 days. There was no significant effect of As exposure on tadpole survival, growth, and percent metamorphosis. Maximum swimming speed was significantly slower in the As-treated groups compared with the control. During the period of tail resorption (Gosner stage 42–46), no significant differences in age at metamorphosis, survival, length of tail resorption period, snout-vent length of metamorphs, and sex ratio were found among treatments. Whole body As concentrations ranged from <0.6 to 5.31 mg kg⁻¹ dry mass, and were significantly higher in the 150, 500, and 1,000 μg l⁻¹ treatments than the control. Based on our data, larval tissue concentrations of As close to that reported in previous field studies were not associated with any significant effects except decreased tadpole swimming speed.     

Valve movement response of the mussel Mytilus galloprovincialis to metals (Cu, Hg, Cd and Zn) and phosphate industry effluents from Moroccan Atlantic coast

Valve activity was measured in the Mediterranean mussel Mytilus galloprovincialis in response to sublethal concentrations of four metals (Hg, Cu, Zn and Cd) and two phosphate industry effluents from the Atlantic coast of Morocco. Valve movements were monitored using a proximity inductive sensor which could display all activity figures from full closure to wide opening of the shell valves. In a 1 h exposure experiments, all metals induced a decrease in the time of normal opening and the appearance of sequences of stress behaviour, including enhanced valve adductions and complete closure at high concentrations. Mercury (tested from 5 to 75 μg Hg l⁻¹) was the most toxic to the valve activity, with a threshold effective concentration at 10 μg Hg l⁻¹ and full valve closure occurring at 50 μg Hg l⁻¹. Copper (15–150 μg Cu l⁻¹) showed a toxic effect starting at threshold concentration of 20 μg Cu l⁻¹ and induced full valve closure at 150 μg Cu l⁻¹. Zinc (100–500 μg Zn l⁻¹) was effective in reducing the time of normal opening (threshold concentration at 100 μg Zn l⁻¹) but no complete closure was recorded in any of the tested concentrations. For cadmium (1000–5000 μg Cd l⁻¹), the valve activity was insensitive for exposures under 2000 μg Cd l⁻¹. Results for the testing of several samplings of the phosphate industry effluents (Safi and Jorf Lasfar) showed that their toxicity varied over the time. The effluent of the Jorf Lasfar plant (2–9.4%) was, however, more toxic than that of Safi (1–25%). In the light of these results, the sensitivity of the valve activity of Mytilus galloprovincialis to pollutants and its usefulness for in situ monitoring of coastal pollution in Morocco are discussed.     

Biomarker assessment of toxicity with miniaturised bioassays: diclofenac as a case study

The development of suitable biomarker-based microbioassays with model species with ecological relevance would help increase the cost-efficiency of routine environmental monitoring and chemical toxicity testing. The anti-inflammatory drug diclofenac has been widely reported in the environment but ecotoxicological data are scarce. The aim of this work is to assess the acute and chronic sublethal toxicity of diclofenac in relevant taxa of aquatic and riparian ecosystems (the fish Danio rerio and the fern Polystichum setiferum). Reliable biomarkers of cell viability (mitochondrial activity), plant physiology (chlorophyll), growth (DNA content) or oxidative damage (lipid peroxidation) were assessed as sensitive endpoints of toxicity. DNA quantification shows that diclofenac induces acute lethal phytotoxicity at 24 and 48 h (LOECs 30 and 0.3 μg l⁻¹, respectively). Hormetic effects in mitochondrial activity in spores of Polystichum setiferum mask lethality, and adverse effects are only observed at 48 h (LOEC 0.3 μg l⁻¹). In chronic exposure (1 week) LOEC for DNA is 0.03 μg l⁻¹. Mitochondrial activity shows a strong hormetic stimulation of the surviving spore population (LOEC 0.3 μg l⁻¹). Little changes are observed in chlorophyll autofluorescence (LOEC 0.3 μg l⁻¹). A very short exposure (90 min) of zebrafish embryos induces a reduction of lipid peroxidation at 0.03 μg l⁻¹. Environmental concentrations of diclofenac can be deleterious for the development of significant populations of sensitive individuals in aquatic and riparian ecosystems.     

Assessing abalone growth inhibition risk to cadmium and silver by linking toxicokinetics/toxicodynamics and subcellular partitioning

The purpose of this study was to link toxicokinetics/toxicodynamics and subcellular partitioning for assessing the susceptibility and the growth inhibition risks of abalone Haliotis diversicolor supertexta exposed to waterborne and foodborne cadmium (Cd) and silver (Ag). We reanalyzed published data on growth inhibition and subcellular partitioning associated with the present mechanistic model to explore the correlations among elimination (k _e), detoxification (k _d), and recovery (k _r) rate constants and to assess the growth inhibition risk. We found a positive correlation among k _e, k _d, and k _r in abalone exposed to Ag. We also employed a life-stage based probabilistic assessment model to estimate the growth inhibition risk of abalone to environmentally relevant Cd (5–995 μg l⁻¹) and Ag (0.05–9.95 μg l⁻¹) concentrations in Taiwan. The results showed that abalone had a minimum 20% probability of the growth inhibition risk exposed to Cd, whereas Ag exposure was not likely to pose the risk. The maximum biomasses were estimated to be 0.0039 and 0.0038, 61.61 and 43.87, and 98.88 and 62.97 g for larvae, juveniles, and adults of abalone exposed to the same levels of Cd and Ag, respectively. Our study provides a useful tool to detect potential growth biomass of abalone populations subjected to Cd and Ag stresses and mechanistic implications for a long-term ecotoxicological risk assessment in realistic situations.     

Suitability of <Emphasis Type="Italic">Daphnia similis</Emphasis> as an alternative organism in ecotoxicological tests: implications for metal toxicity

The acute toxicity of metals to Daphnia similis was determined and compared to other daphnid species to evaluate the suitability of this organism in ecotoxicology bioassays. To verify the performance D. similis in toxicity tests, we also investigated the effect of Pseudokirchneriella subcapitata at 1 × 10⁵ and 1 × 10⁶ cells ml⁻¹ on Cd and Cr acute toxicity to the cladoceran. Daphnid neonates were exposed to a range of chromium and cadmium concentrations in the absence and presence of the algal cells. Metal speciation calculations using MINEQL⁺ showed that total dissolved metal concentrations in zooplankton culture corresponded to 96.2% free Cd and 100% free Cr concentrations. Initial total dissolved metal concentrations were used for 48 h-LC₅₀ determination. LC₅₀ for D. similis was 5.15 × 10⁻⁷ mol l⁻¹ dissolved Cd without algal cells, whereas with 1 × 10⁵ cells ml⁻¹, it was significantly higher (7.15 × 10⁻⁷ mol l⁻¹ dissolved Cd). For Cr, the 48 h-LC₅₀ value of 9.17 × 10⁻⁷ mol l⁻¹ obtained for the cladoceran in tests with 1 × 10⁶ cells ml⁻¹ of P. subcapitata was also significantly higher than that obtained in tests without algal cells (5.28 × 10⁻⁷ mol l⁻¹ dissolved Cr). The presence of algal cells reduced the toxicity of metals to D. similis, as observed in other studies that investigated the effects of food on metal toxicity to standard cladocerans. Comparing our results to those of literature, we observed that D. similis is as sensitive to metals as other standardized Daphnia species and may serve as a potential test species in ecotoxicological evaluations.     

Multidrug resistance modulation in vivo: The effect of cyclosporin A alone or with dexverapamil on idarubicin pharmacokinetics in acute leukemia

Objective: To determine the effect of the coadministration of the multidrug resistance (MDR) modulators cyclosporin A (CyA) alone or plus dexverapamil (D-Ver) on idarubicin (IDA) pharmacokinetics in patients with acute leukemia. Methods: Pharmacokinetic studies were performed in 27 patients with a diagnosis of acute myelogenous leukemia (AML), who were being treated with a combination chemotherapy regimen including idarubicin and cytarabine for the induction of a first remission (n = 14), or of a second remission (n = 7), or for remission consolidation (n = 6). Of these 27 patients, nine were coadministered CyA and seven were coadministered CyA plus D-Ver as MDR modulators. Blood was sampled at appropriate intervals after each of the three IDA daily administrations. IDA and idarubicinol (IDAOL) were assayed by HPLC. Pharmacokinetic evaluations were performed by means of a two-compartment open model with zero-order absorption and first-order elimination using the WinNonlin pharmacokinetic software package. Results: CyA markedly increased the area under the concentration time-curve (AUC) of both IDA [558.26 (197.25) μg · h · l⁻¹ vs 315.44 (158.28) μg · h · l⁻¹; P < 0.01] and IDAOL [2896.60 (736.38) μg · h · l⁻¹ vs 1028.49 (603.95) μg · h · l⁻¹; P < 0.001] when coadministered as a single modulator, due to a lower total body clearance (CL) [83.51 (52.44) l · h⁻¹ · m⁻² vs 139.65 (69.45) l · h⁻¹ · m⁻²; NS]. When patients received two MDR modulators simultaneously (D-Ver plus CyA), IDA exposure was essentially the same as in those of the no inhibitor group [331.29 (95.49) μg · h · l⁻¹ vs 315.44 (158.28) μg · h · l⁻¹; NS], whereas the IDAOL total body exposure was greater than in the no inhibitor group [2030.32 (401.11) μg · h · l⁻¹ vs 1028.49 (603.95) μg · h · l⁻¹; P < 0.01], even if less than in patients receiving CyA as a single MDR modulator (IDA + CyA group) [AUC 2030.32 (401.11) μg · h · l⁻¹ vs 2896.60 (736.38) μg · h · l⁻¹; P < 0.05], suggesting an antagonistic effect against those of CyA on IDA and IDAOL elimination and/or an unpredictable redistribution. The main pharmacokinetic parameters of IDA, such as CL and volume of distribution at steady state (Vd_ss), were remarkably affected by the coadministration of CyA or CyA plus D-Ver, but no statistically significant difference was noted because of IDA pharmacokinetic interpatient variation. Conclusion: The results show that CyA alone at a dose of 10 mg · kg⁻¹ daily significantly increased systemic body exposure to both IDA and IDAOL in acute leukemia, and suggest that these pharmacokinetic effects were at least partially decreased when D-Ver was coadministered with CyA. Our findings raise important questions concerning the need for a dosage adjustment of IDA when MDR modulators are coadministered. Received: 2 June 1998 / Accepted in revised form: 3 December 1998     

Turbidity mitigates lead toxicity to cladocerans (Cladocera)

To test the hypothesis that sediment would have a synergistic effect on the toxicity of lead to cladocerans, we performed life table demography experiments with two pelagic (Diaphanosoma birgei and Moina micrura) and one littoral (Alona rectangula) cladoceran species. Life table demography experiments were conducted at three levels of turbidity (0, 17 and 170 NTU) and six concentrations of lead (as PbCl₂) from 0 to 0.71 mg l⁻¹. Median lethal concentrations (LC₅₀) for A. rectangula, D. birgei and M. micrura were 7.06 ± 0.39, 3.16 ± 0.25 and 3.24 ± 0.69 mg l⁻¹ of Pb. Life table study showed that in general, the presence of sediments in test jars allowed an overall increase of 20–75% in both survivorship and reproduction of the cladoceran species exposed to different concentrations of Pb. At 0.04 mg l⁻¹ of Pb, the population growth rates were 0.127 for A. rectangula, 0.037 for D. birgei and 0.471 d⁻¹ for M. micrura in the absence of sediments but were elevated in their presence (0.309, 0.141 and 0.722 d⁻¹, respectively). The data have been discussed in relation to their importance in shallow, turbid Mexican waterbodies.     

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.     

Interactions of silver nanoparticles with the marine macroalga, Ulva lactuca

The marine macroalga, Ulva lactuca, has been exposed for 48 h to different concentrations of Ag added as either silver nanoparticles (AgNP) or aqueous metal (AgNO₃) and the resulting toxicity, estimated from reductions in quenching of chlorophyll-a fluorescence, and accumulation of Ag measured. Aqueous Ag was toxic at available concentrations as low as about 2.5 μg l⁻¹ and exhibited considerable accumulation that could be defined by the Langmuir equation. AgNP were not phytotoxic to the macroalga at available Ag concentrations up to at least 15 μg l⁻¹ and metal measured in U. lactuca was attributed to a physical association of nanoparticles at the algal surface. At higher AgNP concentrations, a dose–response relationship was observed that was similar to that for aqueous Ag recorded at much lower concentrations. These findings suggest that AgNP are only indirectly toxic to marine algae through the dissolution of Ag⁺ ions into bulk sea water, albeit at concentrations orders of magnitude greater than those predicted in the environment.     

In vitro and in vivo effects of cadmium on cholinesterases in Nile tilapia fingerlings: implications for biomonitoring aquatic pollution

Effects of cadmium on in vitro and in vivo cholinesterase (ChE) activities of brain and muscle tissues of Oreochromis niloticus fingerlings were evaluated, considering its potential use in biomonitoring tropical water pollution. Results show that in vitro ChE activities were depressed significantly by millimolar concentration ranges of Cd²⁺. The IC₅₀ values of Cd²⁺ on in vitro ChE activity in brain and muscle tissues were 1.56 and 4.31 mM, respectively. Exposure of fish to environmentally relevant concentrations of Cd²⁺ (5–30 μg l^−l) for 28 days evoked only a transient inhibition (21–34%) of in vivo ChE activities. Prior exposure and co-exposure of fish to 15 μg l⁻¹ of Cd²⁺ enhanced the extent of inhibition of ChE levels induced by the organophosphorous insecticide chlorpyrifos. As high concentrations of cadmium have the potential to depress ChE activities, monitoring of metal levels in water bodies with suspected high levels of metal inputs is necessary to accurately interpret the fish ChE inhibition data in relation to insecticide contaminations.     

Dissolved organic carbon reduces uranium toxicity to the unicellular eukaryote <Emphasis Type="Italic">Euglena gracilis</Emphasis>

The influence of dissolved organic carbon (DOC), in the form of Suwannee River fulvic acid (SRFA), on uranium (U) toxicity to the unicellular eukaryote, Euglena gracilis (Z strain), was investigated at pH 6. In a background medium without SRFA, exposure of E. gracilis to 57 μg L⁻¹ U resulted in a 50% reduction in growth (IC₅₀). The addition of 20 mg L⁻¹ DOC (as SRFA), reduced U toxicity 4 to 5-fold (IC₅₀ increased to 254 μg L⁻¹ U). This reduction in toxicity was also evident at more sensitive effect levels with a 10% reduction in growth (IC₁₀) occurring at 5 μg L⁻¹ U in the background medium and at 17 μg L⁻¹ U in the SRFA medium, respectively. This amelioration of toxicity with the addition of SRFA was linked to a decrease in the bioavailability of U, with geochemical speciation modelling predicting 84% of U would be complexed by SRFA. The decrease in bioavailability of U in the presence of SRFA was also evident from the 11–14 fold reduction in the cellular concentration of U compared to that of E. gracilis in the background medium. Stepwise multiple linear regression analyses indicated that UO₂ ²⁺ alone explained 51% of the variation in measured U toxicity to E. gracilis. Preliminary U exposures to E. gracilis in the presence of a reactive oxygen species probe, suggest exposure to ≥60 μg L⁻¹ U may induce oxidative stress, but this endpoint was not considered to be a sensitive biological indicator.     

Comparison of the pharmacokinetics of tirilazad mesylate in healthy volunteers and stable subjects with mild liver cirrhosis

Objective: The pharmacokinetics of tirilazad mesylate and an active reduced metabolite, U89678, were studied in 7 volunteers with mild cirrhosis of the liver and seven age, sex, weight and smoking status matched healthy normal volunteers. Subjects received a single intravenous infusion of 2.0 mg ⋅kg⁻¹ tirilazad mesylate over 10 min. Results: Mean tirilazad AUC_0–∞ was 8.83 μmol h⋅l⁻¹ and 18.6 μmol h⋅l⁻¹ in healthy volunteers and cirrhotic subjects, respectively. Mean tirilazad clearance in cirrhotics (12.7 l⋅h⁻¹) was approximately 2.1 fold lower than in healthy volunteers (27.8 l⋅h⁻¹). The differences were statistically significant. Mean U-89678 AUC_0–∞ in cirrhotic subjects (3.88 μmol h⋅l⁻¹) was 2.5 fold higher than in healthy controls (1.53 μmol h⋅l⁻¹), but the difference was marginally significant. Conclusion: These results indicate that clearance of both tirilazad mesylate and U89678 is decreased in subjects with hepatic impairment. This observation may be attributed either to decreases in liver blood flow and/or intrinsic clearance. The results of this study thus suggest that increased monitoring and or a reduction in tirilazad dosing may be necessary in patients with hepatic impairment. Received: 10 August 1995/Accepted in revised form: 10 July 1995     

Toxicological effects of cypermethrin to marine phytoplankton in a co-culture system under laboratory conditions

The growth of three marine phytoplankton species Skeletonema costatum, Scrippsiella trochoidea and Chattonella marina and the response of the antioxidant defense system have been investigated on exposure to commercial cypermethrin for 96 h and 32 days in a co-culture system. Growth of the three species was generally comparable over 96 h with an inoculation of 1:3:6.5 (C. marina:S. trochoidea:S. costatum), with stimulation at 5 μg l⁻¹ and inhibition under higher concentrations (50, 100 μg l⁻¹). However, when inoculating at ratios of 1:1:1 during a 32 day test, S. costatum became the most sensitive species and was significantly inhibited in all test groups under the dual stresses of cypermethrin and interspecies competition. The growth of C. marina was significantly inhibited at the concentrations higher than 5 μg l⁻¹, while the growth of S. trochoidea was significantly promoted at low concentrations. Superoxide dismutase (SOD) activities significantly increased during 6–12 h exposure periods in test treatments at low concentrations, and enhanced in the control as well due to interspecies competition. The lipid peroxidation product malondialdehyde was enhanced at high concentrations, but did not increase in control and low concentration cultures with high SOD activities, indicating that algal cells activated the antioxidant enzymes promptly to protect the cells from lipid membrane damage. Results from this study suggested that cypermethrin pollution in maricultural sea waters might lead to a shift in phytoplankton community structure from diatom to harmful dinoflagellate species, and thus potentially stimulatory for harmful algal blooms.     

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.