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.     

Linking behavioural alterations with biomarkers responses in the European seabass Dicentrarchus labrax L. exposed to the organophosphate pesticide fenitrothion

The acute effects of the organophosphate insecticide fenitrothion on Dicentrarchus labrax juveniles were investigated through a bioassay using biomarkers and swimming behaviour as effect criteria. After 96 h of exposure to sub-lethal concentrations of fenitrothion, the swimming velocity and several biomarkers were individually determined, namely: brain acetylcholinesterase (AChE) activity; muscle cholinesterases (ChE), lactate dehydrogenase and isocitrate dehydrogenase activities; liver ethoxyresorufin-O-deethylase (EROD), glutathione S-transferases, glutathione peroxidase, glutathione reductase, catalase and superoxide dismutase (SOD) activities and lipid peroxidation levels (LPO). A significant decrease of the swimming velocity (LOEC = 2 mg l⁻¹), an inhibition of both AChE (LOEC = 0.06 mg l⁻¹) and ChE activities (LOEC = 0.03 mg l⁻¹), and a positive and significant correlation between the swimming velocity and AChE were found in exposed fish, suggesting an influence of the inhibition of these enzymes in the swimming velocity decrease. An increase of EROD activity (LOEC = 1 mg l⁻¹), indicating the involvement of this enzyme in fenitrothion biotransformation, and a negative and significant correlation between EROD activity and swimming velocity were also found, suggesting that the two findings may somehow be related. Furthermore, results show a significant induction of SOD (LOEC = 0.13 mg l⁻¹) without LPO increase, suggesting that the enzyme is preventing oxidative stress damage. No significant alterations were found in any of the other parameters tested. Thus, exposure of seabass to fenitrothion in the wild at concentrations similar to those tested here may have adverse consequences at population level as neurotransmission and swimming ability are essential for fish performance and survival.     

Biological responses of maize (Zea mays) plants exposed to chlorobenzenes. Case study of monochloro-, 1,4-dichloro- and 1,2,4-trichloro-benzenes

A 7-day-exposure time experiment was designed to investigate the phytotoxicity of chlorobenzenes (CBs) on Zea mays seedlings, focusing on the growth and generation of oxidative stress. Significant growth inhibition (based on biomass gain) was observed for exposure to monochlorobenzene (MCB), dichlorobenzene (DCB) and trichlorobenzene (TCB) concentrations higher than 10 mg l⁻¹. It would seem that CBs inhibit cell division, since the mitotic index decreased for roots exposed to DCB at 80 mg l⁻¹ dose (8%) and to all the TCB concentrations tested (20% inhibition). CBs exposure resulting in an increase in the oxidative stress response in maize seedlings [reactive oxygen species like H₂O₂, antioxidant enzymes (POD, GR), lipid peroxidation] correlated to the compound’s degree of chlorination, where damage increasing with the number of chlorine atoms (MCB < DCB < TCB). This biological response was also dependent on the dose-exposure. Z. mays exposed to CBs at concentrations <10 mg l⁻¹ did not induce sufficient oxidative damage to cause root cell death. Therefore, CBs at current environmental concentrations are unlikely to produce evident phytotoxic effects on Z. mays seedlings.     

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.     

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.     

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.     

Hypoxia-induced oxidative DNA damage links with higher level biological effects including specific growth rate in common carp, Cyprinus carpio L

Both hypoxia and hyperoxia, albeit in different magnitude, are known stressors in the aquatic environment. Adopting an integrated approach, mirror carp (Cyprinus carpio L.), were exposed chronically (i.e. 30 days) to hypoxic (1.8 ± 1.1 mg O₂ l⁻¹) and hyperoxic (12.3 ± 0.5 mg O₂ l⁻¹) conditions and resultant biological responses or biomarkers were compared between these two treatments as well as with fish held under normoxic conditions (7.1 ± 1.04 mg O₂ l⁻¹). The biomarkers determined included the activities of glutathione peroxidase (GPx), measurement of oxidative DNA damage (using modified Comet assay employing bacterial enzymes: Fpg and Endo-III), haematological parameters, histopathological and ultrastructural examination of liver and gills. Specific growth rate (SGR) of the fish, as an important ecotoxicological parameter was also determined over the exposure period. The study suggested that while the levels of hepatic GPx were unaffected, there was a significant difference in activity in the blood plasma under different exposure conditions; the hyperoxic group showed increased GPx activity by approximately 37% compared to normoxic group and the hypoxic group showed a decrease by approximately 38% than the normoxic group. Interestingly, oxidative DNA damage was significantly higher in both hypoxic and hyperoxic by approximately 25% compared to normoxic conditions, Fpg showing enhanced level of damage compared to the Endo-III treatment (P < 0.001). The haematological parameters showed enhanced values under hypoxic conditions. Transmission electron microscopic (TEM) studies revealed damage to liver and gill tissues for both the treatments. Interestingly, SGR of fish was significantly lowered in hypoxic by approx. 30% compared to normoxic condition and this was found to be correlated with DNA damage (R = −0.82; P = 0.02). Taken together, these results indicate that prolonged exposure to both hypoxic and hyperoxic conditions induce oxidative stress responses at both DNA and tissue levels, and hypoxia can result in compensatory changes in haematological and growth parameters which could influence Darwinian fitness of the biota with wider ecological implications.     

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.     

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.     

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.     

Valve movement response of the freshwater clam Corbicula fluminea following exposure to waterborne arsenic

We developed an inductance-based valvometry technique as a detection system to measure the valve daily activity in freshwater clam Corbicula fluminea in response to waterborne arsenic. Our findings reveal that C. fluminea experiences a valve opening in the absence of arsenic predominantly in the morning hours (03:00–08:00) with a mean daily opening/closing period of 21.32 (95% CI: 20.58–22.05) h. Amplification of daily activity occurred in the presence of arsenic. Behavioral toxicity assays revealed arsenic detection thresholds of 0.60 (95% CI: 0.53–0.66) mg l⁻¹ and 0.35 (95% CI: 0.30–0.40) mg l⁻¹ for response times of 60 and 300 min, respectively. The proposed valve daily activity model was linked with response time-specific Hill dose-response functions to predict valve opening/closing behavior in response to arsenic. The predictive capabilities were verified satisfactory with the measurements. Our results implicate a biomonitoring system by valve daily activity in C. fluminea to identify safe water uses in areas with elevated arsenic.     

Comparative pharmacokinetics of dirithromycin and erythromycin in normal volunteers with special regard to accumulation in polymorphonuclear leukocytes and in saliva

Objective: In a randomized cross-over study, we assessed pharmacokinetics and intracellular concentrations in polymorphonuclear leukocytes (PMN) and saliva of erythromycin and erythromycylamine, the active metabolite of dirithromycin. Methods: Ten healthy volunteers received 1 g erythromycin b.i.d. or 500 mg dirithromycin qd for 5 days (wash out period, 35 days). Concentrations of erythromycin and erythromycylamine were measured in serum, urine, saliva, and granulocytes by bioassay and high-performance liquid chromatography (HPLC) on days 1, 3, and 5 of each study period, respectively. Results: While maximal serum concentrations (C_max) and the area under the data (AUD_tot) of erythromycin were significantly higher (C_max 1.44 mg · l⁻¹, AUD_tot 5.66 mg · h · l⁻¹) than those of erythromycylamine (C_max 0.29 mg · l⁻¹, AUD_tot 1.96 mg · h · l⁻¹), erythromycylamine had a significantly higher mean residence time (21 h) than erythromycin (5.5 h). Erythromycylamine accumulated significantly more in PMN than erythromycin;␣the accumulation factor of erythromycylamine was 100 with a maximal intracellular concentration of 13.4 mg · l⁻¹, whereas the maximal accumulation factor of erythromycin was 4 with a maximal intracellular concentration of 6.1 mg · l⁻¹. There were no significant differences in maximal saliva concentrations (erythromycin 0.35 mg · l⁻¹, erythromycylamine 0.31 mg · l⁻¹). Received: 16 September 1996 / Accepted in revised form: 12 February 1997     

Toxicity of lead, cadmium and mercury on embryogenesis, survival, growth and metamorphosis of Meretrix meretrix larvae

In order to assess the toxicity of heavy metals on the early development of Meretrix meretrix, the effects of mercury (Hg), cadmium (Cd) and lead (Pb) on embryogenesis, survival, growth and metamorphosis of larvae were investigated. The EC₅₀ for embryogenesis was 5.4 μg l⁻¹ for Hg, 1014 μg l⁻¹ for Cd and 297 μg l⁻¹ for Pb, respectively. The 96 h LC₅₀ for D-shaped larvae was 14.0 μg l⁻¹ for Hg, 68 μg l⁻¹ for Cd and 353 μg l⁻¹ for Pb, respectively. Growth was significantly retarded at 18.5 μg l⁻¹ (0.1 μM) for Hg, 104 μg l⁻¹ (1 μM) for Cd and 197 μg l⁻¹ (1 μM) for Pb, respectively. The EC₅₀ for metamorphosis, similar to 48 h LC₅₀, was higher than 96 h LC₅₀. Our results indicate that the early development of M. meretrix is highly sensitive to heavy metals and can be used as a test organism for ecotoxicology bioassays in temperate and subtropical regions.     

Oxidative stress and DNA damage in the earthworm <Emphasis Type="Italic">Eisenia fetida</Emphasis> induced by toluene,ethylbenzene and xylene

Superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT), and the comet assay (SCGE) were used as biomarkers to evaluate the oxidative stress and genotoxicity of toluene, ethylbenzene and xylene in earthworms (Eisenia fetida). The results indicated that the exposure of the three pollutants caused a stress response of the three enzymes, an approximate bell-shaped change (a tendency of inducement firstly and then inhibition with increasing concentrations of the pollutants) was mostly found. The three enzymes tested differed in their sensitivity to different pollutants. While the activity of POD was not significantly changed within the concentration range, the concentration thresholds for significant (P < 0.05) responses to toluene based on SOD and CAT were 5 mg kg⁻¹, respectively. Similarly, the concentration thresholds for significant (P < 0.05) responses to ethylbenzene based on CAT and POD were 10 and 5 mg kg⁻¹, respectively, while the activity of SOD was not significantly changed within the concentration range. Significant responses to xylene based on CAT and POD were 5 mg kg⁻¹, respectively, while the activity of SOD was significantly (P < 0.05) induced at 10 mg kg⁻¹. The SCGE assay results showed that these three pollutants could significantly (P < 0.01) induce DNA damage in earthworms and the clear dose-dependent relationships were displayed, indicating potential genotoxic effects of toluene, ethylbenzene, and xylene on E. fetida. The inducement of DNA damage may be attributed to the oxidative attack of toluene, ethylbenzene, and xylene. Toluene seemed to be more genotoxic as it could induce the higher extent of DNA damage than ethylbenzene and xylene. The results suggest that the SCGE assay of earthworms is simple and efficient for diagnosing the genotoxicity of pollutants in terrestrial environment.     

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.     

Distribution and metabolism of N G-nitro-l-arginine methyl ester in patients with septic shock

Objective: The pharmacokinetics of N ^G-nitro-l-arginine methyl ester (l-NAME), an inhibitor of nitric oxide (NO) synthesis, was investigated in patients with septic shock. Methods: Blood was sampled at intervals before, during and after 12-h infusion of l-NAME 1 mg · kg⁻¹ · h⁻¹ in nine septic shock patients for determination of plasma concentrations by high-performance liquid chromatography (HPLC). In three patients the renal clearance of the drug was determined. Results: Incubation of l-NAME with plasma and blood in vitro revealed hydrolysis to N ^G-nitro-l-arginine (l-NOARG), the active inhibitor of NO synthesis. l-NOARG did not undergo further degradation. Continuous intravenous infusion of 1 mg · kg⁻¹ · h⁻¹ of l-NAME for 12 h in patients with septic shock increased blood pressure and resulted in increasing plasma concentrations of l-NOARG (C_max 6.2 μg · ml⁻¹ at 12 h) whereas l-NAME concentrations reached a plateau within 1.5 h (C_max 1.0 μg · ml⁻¹). After the infusion was stopped l-NAME disappeared from the plasma rapidly (half-life 19.2 min) whereas l-NOARG concentration declined slowly (half-life 22.9 h). The calculated volume of distribution for l-NAME was 0.45 l · kg⁻¹ body weight and 1.96 l · kg⁻¹ for l-NOARG. The renal clearance for l-NOARG was 3.5% of total body clearance for l-NOARG, whereas l-NAME could not be detected in urine. Conclusion: We conclude that vasoconstriction with l-NAME in septic patients may result from hydrolysis to l-NOARG, the active inhibitor of NO synthesis. The long plasma half-life and large volume of distribution for l-NOARG suggests extensive distribution to extravascular tissues. Since renal excretion is minimal, elimination of the metabolite l-NOARG follows other pathways. Received: 13 March 1998 / Accepted in revised form: 30 June 1998     

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.     

Antimicrobial activity of isolate HL-12 against Clavibacter michiganensis subsp. michiganensis in the presence of cadmium

An actinomycete, strain HL-12, that was isolated from a farmland on the Huajiachi campus of Zhejiang University was capable of inhibiting the growth of Clavibacter michiganensis subsp. michiganensis (Cmm) and was identified as a member of Streptomyces. Its antimicrobial activity against Cmm was measured using the agar plate sensitivity method in pure culture and evaluated by the inhibition ratio of Cmm in soil. The inhibitory activity of strain HL-12 against Cmm following exposure to low concentrations of Cd was greater than the inhibitory activity following exposure to high concentrations of Cd both in liquid culture and in soil. A stronger inhibition was also seen following a 24 h preculture in the presence of Cd in liquid culture. The growth of Cmm in soil was stimulated at low concentrations of Cd (<5.0 mg Cd kg⁻¹ dry soil) but inhibited when cultured in high concentrations of Cd (5.0 and 10.0 mg Cd kg⁻¹ dry soil). A higher inhibition ratio of strain HL-12 against Cmm, which was over 40% after soil incubation for 2 weeks, was observed following exposure to low concentrations of Cd (<5.0 mg Cd kg⁻¹ dry soil).     

Effect of stiripentol on carbamazepine plasma concentration and metabolism in epileptic children

Objective: To study the relationship between the plasma concentration of stiripentol (STP), a new antiepileptic drug, and its inhibitory effect on the formation of carbamazepine epoxide (CBZE) in epileptic children treated with carbamazepine (CBZ) either alone or in combination with another antiepileptic drug. Methods: Minimum plasma concentration of antiepileptic drugs was measured before initiation of STP therapy (day 0) and on days 28 (STP 60 mg⋅kg⁻¹⋅day⁻¹) and 84 (STP 90 mg⋅kg⁻¹⋅day⁻¹) by HPLC. Results: The CBZE/CBZ plasma concentration ratio decreased exponentially with increasing minimum plasma STP concentration (r = 0.80). The asymptote of the curve allowed the calculation of the minimum plasma STP concentration required to obtain the maximum inhibitory effect, i.e. 6.7 mg⋅l⁻¹. Conclusion: The inhibitory effect of STP on CBZ metabolism expressed as the CBZE/CBZ plasma concentration ratio is dependent on STP plasma concentration, with a maximum effect at an average of 7 mg⋅l⁻¹. The present data suggest that in order to evaluate the anticonvulsant efficacy of STP as add-on therapy, the minimum plasma STP concentration should be maintained above 7 mg⋅l⁻¹ and the dosage of CBZ should simultaneously be decreased in steps by more than 50% to minimize the change in CBZ plasma concentration. Received: 27 September 1995 / Accepted in revised form: 5 January 1996     

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.