Cadmium tolerance and accumulation by two species of <Emphasis Type="Italic">Iris</Emphasis>

Seedlings of Iris lactea var. chinensis (Fisch.) Koidz. and I. tectorum Maxim. were subjected to 0–160 mg l⁻¹ Cd in hydroponic system and harvested after 42 days to determine effects on root and shoot dry mass. A subset of 16-day-old seedlings was exposed to 1000 mg l⁻¹ Cd to characterize sub-cellular localization of Cd in root cells. The Cd contents in the shoots of I. lactea var. chinensis reached 529 μg g⁻¹ dry weight (dw) at 80 mg l⁻¹ Cd treatment and in the shoots of I. tectorum reached 232 μg g⁻¹ dw at 40 mg l⁻¹ Cd treatment, without showing signs of visible toxicity. The Cd contents in the shoots of both two test species exceeded 100 μg g⁻¹, the critical value of Cd hyperaccumulator. The indices of tolerance (ITs) of I. lactea var. chinensis were higher than those of I. tectorum under 10–160 mg l⁻¹Cd stress. Sub-cellular localization of Cd in root cells was evaluated using transmission electron microscopy (TEM) and Cd deposits were found in the cell walls, in the cytoplasm and on the inner surface of xylem vessels in the root tip of I. lactea var. chinensis and I. tectorum. A few cells in the root tip of I. tectorum were necrotic. The results showed that the tolerance and accumulation of Cd by I. lactea var. chinensis were higher than those of I. tectorum, suggesting that I. lactea var. chinensis has potential application in phytoremediation.     

Uptake and accumulation and oxidative stress in garlic (Allium sativum L.) under lead phytotoxicity

The effects of different concentrations of Pb on growth of Allium sativum L, Pb uptake and accumulation, antioxidant enzyme activity and malondialdehyde content were investigated. The results indicated that shoot growth at high concentration of Pb (10⁻³ M) and roots growth at 10⁻³ M and 10⁻⁴ M Pb were significantly inhibited. Lead ions were accumulated mainly in the roots and only small amounts were translocated to bulbs and shoots. SOD activities in shoot and roots exposed to 10⁻³ M Pb were observed to be high. Plants exposed to 10⁻³ M Pb showed a significant increase in POD activity in roots versus the control and other Pb treatments. In roots, CAT activity and MDA concentration at 10⁻³ M Pb is high significantly. The mechanisms of Pb toxicity and tolerance in garlic are briefly discussed.     

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.     

Change in life cycle parameters and feeding rate of <Emphasis Type="Italic">Ceriodaphnia silvestrii</Emphasis> Daday (Crustacea,Cladocera) exposure to dietary copper

Changes in life cycle parameters (survival, growth, reproduction) and feeding rate of the tropical cladoceran Ceriodaphnia silvestrii as affected by Cu contaminated algae Pseudokirchneriella subcapitata were investigated. The dietary copper exposure ranged from 3 × 10⁻¹⁵ to 68 × 10⁻¹⁵ g Cu algal cell⁻¹. Low waterborne copper exposure (around 10⁻¹⁰ mol l⁻¹ free Cu²⁺ ions) was kept in the experiments. The results show an increasing toxic effect on C. silvestrii with copper increase in algal cells; at the highest copper exposure, all life cycle parameters were significantly affected. A concentration of 38 × 10⁻¹⁵ g Cu algal cell⁻¹ reduced egg hatching percentile and the number of neonates produced per female, but did not cause any statistically significant effect on animals survival nor to the number of eggs produced per female. The following sequence of events was observed from the lowest to the highest copper contamination: reproduction, feeding rate, body length and, at last, survival was affected. We conclude that algal cells are an important route of copper exposure and toxicity to cladocerans.     

Perylene Toxicity in the Estuarine Environment of Ria de Aveiro (Portugal)

Perylene, a 5-ring polycyclic aromatic hydrocarbon is common in estuarine sediments and its toxicity in the benthic and planktonic compartments is not yet clarified. The objectives of this work were: (1) to follow the toxicity of high concentrations of perylene (110 mg l⁻¹) on benthic bacteria and macrofauna (amphipod Corophium multisetosum); (2) to determine the effects of a low load of perylene (2 μg l⁻¹) on the metabolism of suspended bacteriobenthos after 9-day exposure, mimicking the effects of tidal erosion; (3) to contrast the effects of this low perylene load on the particle-free bacterioplankton and on the suspended and particle-adhered bacteriobenthos. No impact was detected in bacterial abundance exposed to 110 mg perylene l⁻¹ for 9 days. This concentration of perylene evoked no acute effects in C. multisetosum but, chronic toxicity assays revealed statistically significant negative effects on survival, growth and number of pregnant females. The bacterioplankton and the suspended bacteriobenthos, exposed to 2 μg perylene l⁻¹ during 2 weeks, responded with altered profiles of activity when compared to the control suspension. These values ranged, respectively, for bacterial biomass production from 134 to 210 and from 24 to 184 μg C l⁻¹ h⁻¹, for aminopeptidase from 1824 to 11,127 and from 1464 to 15,488 nmol l⁻¹ h⁻¹, and for β-glucosidase from 87 to 400 and from 57 to 1278 nmol l⁻¹ h⁻¹. The rate of oxygen consumption in the perylene-exposed suspension (0.04–2.85 mmol O₂ kg⁻¹ dw sed h⁻¹) exhibited a clearly distinct profile in relation to the control (0.57–1.60 mmol O₂ kg⁻¹ dw sed h⁻¹). The overall reactivity of the bacteriobenthos to perylene was interpreted as the result of toxic pressure followed by evolution of a diverse bacterial community.     

Evaluation of genotoxicity and effects on reproduction of nonylphenol in <Emphasis Type="Italic">Oreochromis niloticus</Emphasis> (Pisces: cichlidae)

Nonylphenol ethoxylate (NPE) is widely used as a component of detergents, paints, pesticides, and many other products. In the aquatic environment NPE breakdown to 4-nonylphenol (NP), which is more stable and persistent. NP is estrogenic in fish, avian, and mammals and is described as an environmental pollutant with endocrine disruptor characteristics. The genotoxicity of NP was evaluated through micronuclei assay and single cell gel electrophoresis (Comet assay) in peripheral erythrocytes of Oreochromis niloticus exposed in vivo. The study on reproductive development was also carried out in male and female gonads of O. niloticus. Lethal concentration (LC 50%) of 0.032 ml l⁻¹ was previously determined. We ran assays with O. niloticus exposed to concentrations of 1.0, 10.0, and 16.0 μl l⁻¹ of NP diluted in water. Our results showed that NP was not genotoxic. However, 3-day exposure to NP in concentrations of 1.0, 10.0, and 16.0 μl l⁻¹ of water increased the frequency of reproductive stages in males and females. The histology of the reproductive tract of the treated fish was significantly altered in females treated with 16.0 μl l⁻¹ of water when compared to controls. Analogous estrogenic effects were observed, such as accelerated maturation of oocytes and spermatogenesis. These results showed that the O. niloticus reproductive system is sensitive to NP estrogenicity.     

Organic acids on the growth, anatomical structure, biochemical parameters and heavy metal accumulation of Iris lactea var. chinensis seedling growing in Pb mine tailings

The effect of citric acid (CA) and ethylene diamine tetraacetic acid (EDTA) on the growth, anatomical structure, physiological responses and lead (Pb) accumulation of Iris lactea var. chinensis seedling growing in Pb mine tailings for 30 days were studied. Results showed that the dry weights (DW) of roots decreased significantly under both levels of CA. The DWs of leaves and roots treated with 2 mmol/kg EDTA decreased significantly and were 23 and 54 %, respectively, lower than those of the control. The tolerant indexes of I. lactea var. chinensis under all treatments of organic acids were lower than control. The root tip anatomical structure was little affected under the treatments of 2 mmol/kg CA and 2 mmol/kg EDTA compared with control. However, the formation of photosynthesizing cells was inhibited by the treatment of 2 mmol/kg EDTA. The concentrations of chlorophyll a, chlorophyll b and total carotenoids in the leaves treated with 2 mmol/kg EDTA significantly decreased. Higher CA level and lower EDTA level could trigger the synthesis of ascorbic acid and higher level of EDTA could trigger the synthesis of glutathione. CA and EDTA could promote Pb accumulation of I. lactea var. chinensis and Pb concentration in the leaves and roots at 2 mmol/kg EDTA treatment increased significantly and reached to 160.44 and 936.08 μg/g DW, respectively, and 1.8 and 1.6 times higher than those of the control. The results indicated that I. lactea var. chinensis could be used to remediate Pb tailing and the role of EDTA in promoting Pb accumulation was better than CA did.     

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.     

Nickel and phosphorous sorption efficiencies, tissue accumulation kinetics and morphological effects on Eichhornia crassipes

The aim of the research was to assess the uptake efficiencies of Ni and P, their distribution in tissues along time and their toxic effects on the internal and external morphologies of Eichhornia crassipes. Aquaria with plants exposed to 1 mg Ni l⁻¹ or 5 mg P l⁻¹ and control were arranged in triplicate. Water and plants (aerial parts and roots) were sampled along 30 days. Ni uptake and tissue bioaccumulation kinetics was significantly faster than that of P. Mean root length, number of leaves, biomass and chlorophyll concentration were negatively affected by Ni, while these parameters were significantly increased by P in comparison with the control. Stele and metaxylem vessel cross-sectional areas (CSA) in the P treatment were significantly lower in comparison with that obtained in the Ni treatment and in control. Metaxylem vessels CSA in plants exposed to Ni were significantly higher while the number of vessels was significantly lower than those obtained in the control. Despite the toxic effects, E. crassipes efficiently accumulated Ni, probably due to the morphological plasticity of its root system.     

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.     

The extrapulmonary effects of increasing doses of formoterol in patients with asthma

Objective: To assess the cardiovascular and metabolic responses to increasing doses of formoterol administered from a dry powder inhaler. Methods: Twenty patients with mild to moderate asthma were given 12, 24, 48 and 96 μg of formoterol or a matched placebo on separate days. The doses were administered using a randomised, cross-over, double-blind design. The effects on heart rate, blood pressure, electromechanical systole (QS₂I), the electrocardiographic QTc interval, plasma potassium (K); blood glucose and FEV₁ were assessed prior to, and for 9 h following each dose. Results: There was no difference between the maximum effects of formoterol 12 μg and placebo; the 24 μg dose significantly decreased plasma K (−0.2 mmol · l⁻¹) and increased blood glucose (1.8 mmol · l⁻¹) compared to placebo. The two highest doses affected most of the variables with the 96 μg dose being significantly different from placebo for all indices, heart rate (9 beats · min⁻¹), systol BP (4 mmHg), diastolic BP (−3 mmHg), QS₂I (−11 ms), QTc (17 ms), plasma K (−0.5 mmol · l⁻¹) and blood glucose (2.6 mmol · l⁻¹). All doses of formoterol increased FEV₁. Conclusion: Although there were dose-dependent effects on the extrapulmonary measurements, only the effects at the highest dose may be of clinical significance. Received: 17 June 1997 / Accepted in revised form: 12 November 1997     

The effect of the apolipoprotein E phenotype on cholesteryl ester transfer protein activity, plasma lipids and apolipoprotein A I levels in hypercholesterolaemic patients on colestipol and lovastatin treatment

Background: Apolipoprotein E (apo E) allele E 4 is associated with high atherogenic lipid levels and coronary heart disease. Cholesteryl ester transfer protein (CETP) transfers cholesteryl esters from (high density lipoprotein) HDL to other lipoproteins. CETP gene expression is enhanced in hypercholesterolaemia and correlates with plasma apo E concentration. Objective: The effect of the apo E phenotype on plasma CETP activity and the hypolipidaemic efficacy of colestipol and lovastatin was studied in patients with type II a or II b hypercholesterolaemia. Results: The baseline mean plasma total, low density lipoprotein (LDL) and HDL cholesterol, triglyceride, apolipoprotein A I (apo A I) concentrations and CETP activity were 8.89 mmol · l⁻¹, 6.78 mmol · l⁻¹, 1.39 mmol · l⁻¹, 1.59 mmol · l⁻¹, 1.49 g · l⁻¹ and 114 nmol · h⁻¹ · ml⁻¹, respectively. The colestipol-induced changes were −26%, −36%, +5%, +12%, −1% and −17%, and the lovastatin-induced changes −34%, −44%, +6%, −18%, +1% and −19%. The lipid and apo A I concentrations or the CETP activity did not differ statistically significantly according to the apo E phenotype, although the HDL cholesterol and apo A I levels were lowered in patients with apo E 4/4 but elevated in patients with the other phenotypes. The CETP activity correlated with the LDL cholesterol concentration (r = 0.52, P = 0.01) and the change in the LDL cholesterol during colestipol (r = 0.51, P = 0.02) and lovastatin (r = 0.65, P = 0.001) treatment, but only in patients without the apo E 4 allele. Conclusion: Colestipol and lovastatin reduced CETP activity to the same amount, regardless of the apo E phenotype. The apo E phenotype seems to modify the interaction between CETP activity and LDL cholesterol in hypercholesterolaemia and during pharmacological lowering of cholesterol. Received: 13 May 1998 / Accepted in revised form: 3 October 1998     

Potential anthelmintics: polyphenols from the tea plant <Emphasis Type="Italic">Camellia sinensis</Emphasis> L. are lethally toxic to <Emphasis Type="Italic">Caenorhabditis elegans</Emphasis>

A novel gallate of tannin, (−)-epigallocatechin-(2β→O→7′,4β→8′)-epicatechin-3′-O-gallate (8), together with (−)-epicatechin-3-O-gallate (4), (−)-epigallocatechin (5), (−)-epigallocatechin-3-O-gallate (6), and (+)-gallocatechin-(4α→8′)-epigallocatechin (7), were isolated from the tea plant Camellia sinensis (L.) O. Kuntze var. sinensis (cv., Yabukita). The structure of 8, including stereochemistry, was elucidated by spectroscopic methods and hydrolysis. The compounds, along with commercially available pyrogallol (1), (+)-catechin (2), and (−)-epicatechin (3), were examined for toxicity towards egg-bearing adults of Caenorhabditis elegans. The anthelmintic mebendazole (9) was used as a positive control. Neither 2 nor 3 were toxic but the other compounds were toxic in the descending order 8, 7 ≈ 6, 9, 4, 5, 1. The LC₅₀ (96 h) values of 8 and 9 were evaluated as 49 and 334 μmol L⁻¹, respectively. These data show that many green tea polyphenols may be potential anthelmintics.     

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.     

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.     

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.     

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.     

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.     

Interethnic differences of <Emphasis Type="Italic">PEPT2</Emphasis> (<Emphasis Type="Italic">SLC15A2</Emphasis>) polymorphism distribution and associations with cephalexin pharmacokinetics in healthy Asian subjects

Objectives  The aims of this study were to characterize the population frequency of PEPT2 (SLC15A2) polymorphic variants in three Asian ethnic populations, namely Chinese, Malay and Asian Indian, and to investigate the associations of ethnicity (Chinese vs. Asian Indian), PEPT2 haplotype and cephalexin pharmacokinetics in healthy Asian subjects. Methods   PEPT2 polymorphisms were screened from a cohort of 96 Chinese, 96 Malay and 96 Asian Indian subjects. Cephalexin (1000 mg, orally) pharmacokinetics was characterized in an additional 15 Chinese and 15 Asian Indian healthy subjects. These 30 subjects were subsequently genotyped for their PEPT2 polymorphisms. Results  In total, ten common single nucleotide polymorphisms (SNPs) were detected in the three populations, forming two PEPT2 haplotypes. There were significant ethnic differences in PEPT2 haplotype distribution: the frequencies of the *1 and *2 alleles were 0.307 and 0.693 in the Chinese population, 0.495 and 0.505 in the Malay population and 0.729 and 0.271 in Asian Indian population, respectively. The C _max of cephalexin was significantly lower in the Chinese (29.80 ± 4.09 μg ml⁻¹) population than in the Asian Indian one (33.29 ± 4.97 μg ml⁻¹; P = 0.045). This difference could be explained by the higher average body weight of the Chinese population. There was no other significant difference in cephalexin pharmacokinetics between either ethnic or PEPT2 genotype groups. Conclusion   PEPT2 polymorphism distributions differ significantly between Chinese, Malay and Asian Indian populations. However, cephalexin pharmacokinetics is not meaningfully different between Chinese and Asian Indians. The association between the PEPT2 haplotype and cephalexin pharmacokinetics could not be confirmed, and future studies under better controlled conditions are needed.