Temporal and spatial variability in the heavy-metal content of Dreissena polymorpha (Pallas) (Mollusca: Bivalvia) from the Kleines Haff (northeastern Germany)

The present investigation was performed on zebra mussels, Dreissena polymorpha (Pallas), which were sampled from the Kleines Haff. As a part of the Oder estuary, the Kleines Haff acts as a sink for the load of the river Oder. Mussel shells and mussel tissue were analyzed for their content of selected heavy metals, based on the composition of the suspended matter. Mussels were sampled in May, July, August and September 1996 at different locations and divided into three groups regarding their body size. The data show that concentrations of lead, cadmium and mercury vary during the year. Mussel shells and mussel tissue showed seasonal and local differences in heavy-metal concentration. Between the size classes, however, there was no significant difference, with one exception: the lead content in tissues was significantly higher in large mussels (>2.5 cm shell length) than in small ones (<1.9 cm). The concentrations of lead and cadmium clearly decreased in mussel shells from May to September, while they increased in mussel tissues. The lead concentration in the tissue corresponded to that of mercury. The highest values measured for mercury were 218 μg/kg dry weight (DW), for cadmium 1030 μg/kg DW and for lead 6182 μg/kg DW. The average concentration of heavy metals in mussel tissue was 9 to nearly 170 times lower than in the surrounding sediment and seston. It can be assumed that a balance exists between the concentration of heavy metals in the mussels' food and the mussels themselves.     

Zinc,cadmium, mercury and selenium in polar bears (Ursus maritimus) from Central East Greenland

Muscle, liver, and kidney tissues from 38 polar bears (Ursus maritimus) caught in the Scoresby Sound area, Central East Greenland, were analysed for zinc, cadmium, mercury and selenium. In general, cadmium concentrations were low in muscle, liver and kidney tissue, with geometric means (g.m.) of 0.022 (range: <0.015–0.085), 0.841 (range: 0.092–3.29) and 13.1 (range: 1.04–115) g Cd/g wet weight (ww) respectively. This finding can be explained by low cadmium levels in the blubber of ringed seals. The concentration of mercury in muscle tissue was low (g.m. 0.071; range: 0.039–0.193 g Hg/g ww), whereas concentrations in liver and kidney tissue were relatively high (liver: g.m. 7.87; range: 1.35–24.8 g Hg/g ww, and kidney: g.m. 15.2; range: 1.59–66.6 g Hg/g ww). Mercury and cadmium were positively correlated with age in liver and kidney. Zinc was positively correlated with age in kidney, and selenium was correlated with age in liver. Contrary to other marine mammals, polar bears had higher mercury levels in the kidneys than in the liver. In all three tissues polar bears had significantly lower cadmium levels than ringed seals from the same area. Mercury levels were likewise significantly lower in the muscle tissue of polar bears than in ringed seals, whereas levels in the liver and kidney were significantly higher. The previous geographic trend for cadmium and mercury found in Canadian polar bears could be extended to cover East Greenland as well. Hence cadmium levels were higher in Greenland than in Canada, while the opposite was the case for mercury. Greenland polar bears had higher mercury and cadmium contents in livers and kidneys than polar bears from Svalbard. The mercury levels in muscle and liver tissue from polar bears from East Greenland were twice as high as found in bears from western Alaska, but half the levels found in northern Alaska. Cadmium and zinc were partially correlated in kidney tissue, and this was found for mercury and selenium as well. Cadmium and zinc showed molar ratios close to unity with the highest concentrations occurring in kidney tissue, while the levels of zinc exceeded cadmium in muscle and liver tissue by up to several decades. Mercury and selenium showed molar ratios close to unity in liver and kidneys.     

Enteromorpha as a monitor of heavy metals in estuaries

An account is given of the use of Enteromorpha to monitor zinc, cadmium, mercury and lead pollution in six estuaries and the British North Sea coast. The ranges for each element were: Zn, 19–437 µg g^–1; µg g^–1 Cd, 0.07–4.8 µg g^–1; Hg, 0.02–0.23 µg g^–1. It is suggested that tissue analysis of Enteromorpha is one of the most useful biological techniques available in estuaries for pin-pointing aqueous (as opposed to sediment) metal contamination, and also for providing data suitable for world-wide comparisons. Provisional values are given for concentrations corresponding to moderate and high pollution.Deceased     

Chronic effects of cadmium on two species of mysid shrimp:Mysidopsis bahia andMysidopsis bigelowi

Two species of mysid shrimp, the sub-tropicalMysidopsis bahia and the northern temperateMysidopsis bigelowi, were exposed simultaneously to cadmium (as CdCl₂) in a continuous-flow bioassay system to determine the effect on survival and reproductive success. Temperature and salinity were maintained at 21 ± 1°C and 30,respectively. The 96-h LC50 was 110 µg ^–1 for both species. The 23-day life cycle LC50 forM. bahia was 19.5 µg ^–1 and forM. bigelowi the 27-day LC-50 was 14.8 µg ^–1. At 10 µg ^–1 a series of morphological aberrations were observed in both species at the onset of sexual maturity. Carapace malformations apparently prevented molting after the release of the initial brood and resulted in death of brooding females. As a result, although the initial reproductive rate at this concentration was successful, successive broods could not be produced. For both species in this study the no observed effect concentration was 5.1 µg ^–1; the effect concentration was 10.0 µg ^–1. Mechanisms were postulated in this study to explain the effect of cadmium on the molting process and on calcification and enzymatic reactions of osmosis.Contribution No. 257 of the U.S. Environmental Protection Agency.Contribution No. 257 of the U.S. Environmental Protection Agency.     

Uptake and distribution of cadmium in maize inbred lines

Genotypic variation in uptake and distribution of cadmium (Cd) was studied in 19 inbred lines of maize (Zea mays L.). The inbred lines were grown for 27 days on an in situ Cd-contaminated sandy soil or for 20 days on nutrient solution culture with 10 µg Cd L^-1. The Cd concentrations in the shoots showed large genotypic variation, ranging from 0.9 to 9.9 µg g^-1 dry wt. for the Cd-contaminated soil and from 2.5 to 56.9 µg g^-1 dry wt. for the nutrient solution culture. The inbred lines showed a similar ranking for the Cd concentrations in the shoots for both growth media (r²=0.89). Two main groups of inbreds were distinguished: a group with low shoot, but high root Cd concentrations (shoot: 7.4±5.3 µg g^-1 dry wt.; root: 206.0±71.2 µg g^-1 dry wt.; shoot Cd excluder) and a group with similar shoot and root Cd concentrations (shoot: 54.2±3.4 µg g^-1 dry wt.; root: 75.6±11.2 µg g^-1 dry wt.; non-shoot Cd excluder). The classification of the maize inbred lines and the near equal whole-plant Cd uptake between the two groups demonstrates that internal distribution rather than uptake is causing the genotypic differences in shoot Cd concentration of maize inbred lines. Zinc (Zn), a micronutrient chemically related to Cd, showed an almost similar distribution pattern for all maize inbred lines. The discrepancy in the internal distribution between Cd and Zn emphasizes the specificity of the Cd distribution in maize inbred lines.     

Effect of anticancer drugs on the release of tumour necrosis factor in vitro

Summary The anticancer drugs Adriamycin, bleomycin, vincristine, 4-hydroperoxycyclophosphamide, FK156 and FK565 and the immunosuppressive drug cyclosporin-A were tested for their effect on lipopolysaccharide-induced tumour necrosis factor- (TNF) release from rat peritoneal exudate cells in vitro. FK565 resulted in a marked enhancement of TNF release when added to cultures at doses of 1 µg/ml and 10 µg/ml. However, FK156, Adriamycin, bleomycin, 4-hydroperoxycyclophosphamide, vincristine and cyclosporin A did not affect the release of TNF under the same conditions. Puromycin inhibited the release of TNF in the same system at non-cytotoxic doses of 1 µg/ml and 10 µg/ml.     

Effect of growth on reproduction in the freshwater amphipod, Hyalella azteca (Saussure)

A gradient in H. azteca growth was created by reducing food ration. Tests were initiated with neonates (48 h old) and the effects of an altered food ration on survival and growth were examined after 10 and 49 days. Growth rates decreased significantly with reduced food ration (10 day growth rates ranged from 1.2 µg d^–1 in the highest feeding regime to 0.5 µg d^–1 in lowest feeding regime). Survival after 10 days was not affected by ration, ranging from 86 to 96%. A growth rate of 1.2 µg d^–1 at day 10 resulted in mean dry weight (1.0 mg), survival (62%) and reproduction (9.3 neonates/female) at day 49 similar to reported values for this species. Growth rates 0.9 µg d^–1 at day 10 corresponded to significantly reduced reproduction at day 49 (i.e., < 1 neonate per female). Time to the onset of amplexus increased with decreasing ration suggesting reduced ration may have delayed reproduction.     

A nontoxicPseudomonas exotoxin a induces active immunity and passive protective antibody againstPseudomonas exotoxin a intoxication

Pseudomonas exotoxin A (PE) is one of the most potent cytotoxic agents produced byPseudomonas aeruginosa. In this study, we examined the possibility of using PE with a deletion of 38 carboxyl-terminal amino acid residues, designated PE(576–613), for active immunization against PE-mediated disease. We first examined the toxic effects of PE and PE(576–613) on 5- and 9-week-old ICR mice. The results show that the subcutaneous administration of PE(576–613) at a dose of 250 µg was still nontoxic to 5- and 9-week-old ICR mice, while native PE was lethal at a dose of 0.5 and 1 µg, respectively. PE(576–613) was then used to immunize ICR mice. The minimum dose of PE(576–613) that could effectively induce anti-PE antibodies in 5- and 9-week-old ICR mice was found to be 250 ng. However, immunization with 250 ng PE(576–613) failed to protect the immunized mice from a lethal dose of PE. The effective immunization dose of PE(576–613) that could protect mice against a 2 µg PE challenge was found to be 15 µg. In addition, sera obtained from PE(576–613)-immunized ICR mice were able to neutralize PE intoxication and effectively protect mice from PE. Thus, PE(576–613) may be used as an alternative route to new PE vaccine development.     

Tumor necrosis factor α modifies resistance to interferon α in vivo: First clinical data

Summary Patients with Philadelphia-positive chronic-phase chronic myelogenous leukemia (CML) resistant to interferon (IFN) were treated in a phase I/II study with recombinant human tumor necrosis factor to overcome IFN resistance. Doses of 40, 80, 120 or 160 µg/m² TNF were given as 2-h infusions on 5 consecutive days every 3 weeks. IFN (4 × 10⁶ IU/m² s.c., daily) treatment was continued. Six patients were treated, completing 1–24 (median, 12) treatment cycles. Five of the six patients achieved partial hematological remission, while the remaining patient had to stop treatment because of WHO grade 4 thrombocytopenia following the first TNF cycle. No complete hematologic remission or cytogenetic improvement was seen. Side-effects were similar to those described for both substances alone. Maximum tolerable TNF doses usually varied between 80 µg/m² and 160 µg/m². To examine possible pathways of TNF activity in these patients, interferon receptor status and (2–5)-oligoadenylate synthetase levels were examined in peripheral blood mononuclear cells. Both parameters remained unchanged during TNF treatment. These preliminary data point to significant clinical efficacy of additionally applyed TNF in IFN-resistant CML patients.     

Fate and effects of cadmium in an experimental marine ecosystem

Two recirculated marine seawater systems (capacities: 150 and 300 l) were used for the study on cadmium accumulation of biological filter sludge, by the musselMytilus edulis and the plaicePleuronectes platessa for a period of up to 300 days. In the contaminated system Cd concentrations varied from 2.5 to 7.0 g/l with a mean of 4.6±1.15 g/l (control: 1.04±0.46 g/l). Accumulation of Cd by the filter sludge from the control system as well as from the contaminated system was significant. Mean concentrations of control-and contaminated sludge over the experimental period were 2.01±0.86 ng Cd/mg dry wt and 9.98±3.55 ng Cd/mg dry wt respectively. Accumulation of Cd byM. edulis both in the control and in the contaminated system was considerable. After 163 days of exposure the whole body burden of mussels rose from 0.3 ng Cd/mg dry wt to around 10 ng Cd/mg dry wt in the controls and to 70 ng Cd/mg dry wt in the contaminated systems. Accumulation of Cd byP. platessa was analysed in backbone, fins, gills, liver, muscle (fillet), otolith and skin (dorsal and ventral) over a period of 280 days. Elevated Cd contents of livers from control specimens were noticed after 200 days and reached 1.75 ng Cd/mg dry wt in liver. There was considerable accumulation in the liver (maximum values: 3.0 ng Cd/mg dry wt) and gills (6.0 ng Cd/mg dry wt) of specimens from the contaminated system, Cd contents of plaice exposed for identical periods of time were very variable. Growth of plaice living in the contaminated system was at times significantly slower than that of the control group. Of the three biological objects tested-filter sludge,M. edulis, P. platessa—the mussel seemed to be the most sensitive indicator of elevated Cd-concentrations, while the reaction of the plaice was slow and less distinct.     

In situ nutrient assays of periphyton growth in a lowland Costa Rican stream

Nutrient limitation of primary production was experimentally assessed using an in situ bioassay technique in the Quebrada Salto, a third-order tropical stream draining the northern foothills of the Cordillera Central in Costa Rica. Bioassays employed artificial substrata enriched with nutrients that slowly diffuse through an agar-sand matrix (Pringle & Bowers, 1984). Multiple comparisons of regression coefficients, describing chlorophyll-a accrual through time for different nutrient treatments, revealed positive micronutrient effect(s). Micronutrient treatment combinations (Fe, B, Mn, Zn, Co, Mo, EDTA), supplemented with and without nitrate and phosphate, exhibited significantly greater chlorophyll-a accrual over all other treatments (P < 0.05), supporting over three times that of the control after 14-d of substratum colonization. Neither of the major nutrients (N or P) produced a significant stimulation, although the N treatment displayed 50% more chlorophyll-a than the control after 14-d. Similarly, Si, EDTA, and Si + N + P treatments did not exhibit chlorophyll-a response curves that were significantly different from the control. During the experiment, mean NH₄-N and (NO₂ + NO₃)-N concentrations in the Salto were 2.0 µM (28.6 µg · l^–1) and 7.2 µM (100.2 µg · l ^–1), respectively. High concentrations of PO₄-P ( = 2.0 µM; 60.9 µg · l^–1) and TP ( = 3.0 µM; 94.0 µg · l^–1) were also found, and consequently low molar N:P ratios = 4.7). Despite the potential for N limitation in the system, both N and P appear to be at growth saturating levels. This may be due to micronutrient limitation and/or light limitation of periphyton growth in densely shaded upstream portions of the stream.     

Dynamics of byssal thread production in <Emphasis Type="Italic">Crenomytilus grayanus</Emphasis> and <Emphasis Type="Italic">Modiolus modiolus</Emphasis> (Bivalvia) upon reattachment to substrate

It was established that the process of repeated attachment to a substrate in bivalve mollusks Crenomytilus grayanus (Grays mussel) and Modiolus modiolus (the northern horse mussel) involved several successive stages which took in vitro about one month at a water temperature of 19 ± 2°C. Comparison with Grays mussel revealed that the northern horse mussel had a higher rate of byssal thread production and a greater thread number by the end of the complete formation of the byssus complex. The observed differences are explained by the adaptation of mollusks to habitation in different biotopes.Original Russian Text Copyright © 2004 by Biologiya Morya, Selin, Vekhova.     

Evaluation of radio- and chemotoxic effects of125I-UdR on tumour growth and host survival

Summary The toxicity of 5-iodo-2-deoxyuridine (I-UdR) was assayed in male C57 BL/6J mice bearing the syngeneic mammary adenocarcinoma EO 771 by injecting different doses of cold I-UdR or 125-iodine labelled I-UdR. Host survival, tumour growth, DNA-precursor incorporation, whole-body retention and tumour activity loss rates were chosen as biological end points.There was no measurable effect on host survival up to doses of 5 µg I-UdR or 50 µCi¹²⁵I-UdR per mouse during a mean life-span of 25 days. Adjusted to a constant amount of 0.55 µg I-UdR/mouse, radiotoxicity of¹²⁵I-UdR on tumour growth (up to 17 days after implantation), tracer incorporation, whole-body and tumour retention (up to 12 days after¹²⁵I-UdR injection) could be excluded up to a dosage of 50 µCi¹²⁵I-UdR/mouse.It is concluded that in situ evaluation of tumour activity loss rates in carcinoma EO 771 is not disturbed by toxic effects of I-UdR or¹²⁵I-UdR within the dose limits mentioned.     

Modulation of adrenal cell functions by cadmium salts. 5. Cadmium acetate and sulfate effects on basal and ACTH-stimulated steroidogenesis

In vitro and in vivo cadmium toxicity studies focus almost exclusively on CdCl₂ effects. Only a few studies have used adrenocortical cells and tissue to determine cadmium salt effects during stress of adrenocorticotropin stimulation. Because several biologically relevant water-soluble cadmium salts exist, this study extended work with CdCl₂ to evaluate the acute adrenocortical cell steroid secretory responses to non-lethal cadmium acetate (CdAc₂) and CdSO^{4 4} concentrations. Control or ACTH-stimulated cultured Y-1 mouse adrenal tumor cells (ATCC) which secrete 20-dihydroprogesterone (20-DHP) were incubated for 0.5 h in serum-free medium (FMEM) with or without 0.5, 1.0, 5.0, 10.0, 50.0, 100.0, 500.0 and 1000.0 µg CdAc₂ or CdSO⁴/ml FMEM (1.9, 3.8, 19.0, 38.0, 190.0, 380.0 and 1900.0 µmol/L, respectively). For each salt, cell viability was measured at the end of the incubation using live cell trypan blue exclusion. In addition, cumulative CdAc₂ effects during 4 h incubations and effect reversibility were determined for control and stimulated cells. After each experimental incubation, the 20-DHP secreted into the medium was determined by radioimmunoassay. Over 80% of all control or ACTH-stimulated cells were viable after incubation in the presence or absence of various CdAc₂ or CdSO⁴ concentrations. Cadmium acetate and sulfate inhibited basal and ACTH-stimulated steroid secretion in a dose-dependent manner. For basal steroid secretion the CdAc₂ concentration that first significantly inhibited was 0.5 µg/ml medium (1.9 µmol/L); stimulated secretion was significantly inhibited beginning at 5.0 µg/ml (19.0 µmol/L) and the concentration reducing stimulated 20-DHP secretion by 50% (IC₅₀) was 5.6 µg/ml (21.3 µmol/L). Similarly, the first CdSO⁴ concentration to significantly inhibit basal and ACTH-stimulated steroid secretion was 10.0 µg/ml medium (39.0 µmol/L); the IC₅₀ was 7.8 µg/ml (29.8 µmol/L). Except that basally secreting Cd^{2+ 2+}-treated cells almost doubled 20-DHP secretion after Cd²⁺ removal and subsequent incubation with ACTH, all basal and ACTH-stimulated steroid secretion was irreversibly inhibited by every CdAc₂ concentration. All CdAc₂ concentrations initiated and maintained cumulative inhibitory effects on basal and ACTH-stimulated steroid secretion over a 4 h period. Reversibility and cumulative CdSO⁴ treatment studies were not conducted. Based on the results from the present studies, both CdAc₂ and CdSO⁴ appeared to incrementally inhibit control and ACTH-stimulated steroidogenesis without affecting cell viability and to be more potent inhibitors of adrenocortical cell steroid secretion than CdCl₂. Finally, CdAc₂ effects on control and stimulated cells were cumulative and irreversible.     

Evaluation of differential cytotoxic effects of the oil spill dispersant Corexit 9500

Aims

The British Petroleum (BP) oil spill has raised several ecological and health concerns. As the first response, BP used a chemical dispersant, Corexit-9500, to disperse the crude oil in the Gulf of Mexico to limit shoreline contamination problems. Nevertheless, portions of this oil/Corexit mixture reached the shoreline and still remain in various Gulf shore environments. The use of Corexit itself has become a significant concern since its impacts on human health and environment is unclear.

Main methods

In this study, in vitro cytotoxic effects of Corexit were evaluated using different mammalian cells.

Key findings

Under serum free conditions, the LC50 value for Corexit in BL16/BL6 cell was 16 ppm, in 1321N1 cell was 33 ppm, in H19-7 cell was 70 ppm, in HEK293 was 93 ppm, and in HK-2 cell was 95 ppm. With regard to the mechanisms of cytotoxicity, we hypothesize that Corexit can possibly induce cytotoxicity in mammalian cells by altering the intracellular oxidative balance and inhibiting mitochondrial functions. Corexit induced increased reactive oxygen species and lipid peroxide levels; also, it depleted glutathione content and altered catalase activity in H19-7 cells. In addition, there was mitochondrial complex-I inhibition and increase in the pro-apoptotic factors including caspase-3 and BAX expression.

Significance

The experimental results show changes in intracellular oxidative radicals leading to mitochondrial dysfunctions and apoptosis in Corexit treatments, possibly contributing to cell death. Our findings raise concerns about using large volumes of Corexit, a potential environmental toxin, in sensitive ocean environments.     

Coastal upwelling, primary production and mussel growth in the Rías Baixas of Galicia

The Rías Baixas are four flooded tectonic valleys located on the northwest Iberian Peninsula that support a mussel production of about 250 × 10⁶ kg y^–1 from 3337 mussel rafts. Mussel production in this region is the highest in Europe and one of the most intensive in the world, giving employment to 9000 people directly and 20000 indirectly. The causes of this high mussel production are discussed through the analysis of published and some unpublished information. The interaction between coastal upwelling and the circulation patterns in the Rías, which channel the 3-dimensional variability of the open ocean into a 2-dimensional system, promotes a massive response in the productivity of phytoplankton populations inside the Rías, even during weak upwelling events along the coast. Coastal upwelling in the area typically occurs between March–April and September–October. The mean value of gross primary production during the whole upwelling season is 1.4 g C m^–2 d^–1, although high sporadic values of 4 g C m^–2 d^–1 may occur during upwelling relaxation events, when phytoplankton export to the coastal shelf is restricted. Mussel growth occurs mainly during the upwelling season. It is estimated that mussel harvest extracts 10% of the primary production. The phytoplankton response to upwelling provides food of high quality (f 0.5) that determines high absorption efficiency (0.6), whereas the characteristics of the Rías maintains the seston concentration at levels (0.5 – 1.3 mg TPM l^–1 and <5 mg Chl a m^–3) below the threshold of pseudo-faeces production. The physiological behaviour of mussels indicates that the high yield of mussel culture in the Rías of Galicia is a consequence of the particular characteristics of the seston.     

Wirkungen von Rohöl-Emulgatorgemischen auf marine Fischbrut und deren Nährtiere

Zusammenfassung 1. Es wurde die Einwirkung eines Rohöl-Emulgatorgemisches (Irak-Öl/Moltoclar) auf die Larven vonClupea harengus L. undAgonus cataphractus L. sowie auf Wildplankton untersucht.2. Bei Emulgatorkonzentrationen von 2,5 bis 5,0 mg/l war die Letalitätsgrenze erreicht.3. Subletale Schädigungen ließen sich bis zu einer Konzentration von 0,5 mg/l deutlich nachweisen.4. Irak-Rohöl hatte keine schädigenden Wirkungen auf Heringslarven.

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Effects of crude oil-emulsifier mixtures on marine fish fry and their food animals

The effects of crude oil-emulsifier mixtures on the larvae ofClupea harengus L. andAgonus cataphractus L. are described. The herring larvae tested had total lengths of 20 to 26 mm; the larvae ofAgonus cataphractus were investigated shortly after their first food intake. Samples of wild plankton from daily catches (used as food during rearing experiments) were also tested. The different dilutions were obtained from the following initial mixture: 20 ml emulsifier Moltoclar, 80 ml Irak crude oil, 900 ml stale sea water (32 S ). Dilutions with the following content of the emulsifier were used: 50 mg/l, 25 mg/l, 5 mg/l, 2.5 mg/l, 0.5 mg/l, 50µg/l, 5µg/l, 0.5µg/l. Lethal concentrations ranged from 2.5 to 5.0 mg/l. Sublethal damages were clearly ascertained down to a concentration of 0.5 mg/l. Irak crude oil alone did not cause damage to herring larvae during the observation period of 4 days.

     

Pumping behaviour and filtration rate of the freshwater mussel Potomida littoralis as a tool for rapid detection of water contamination

In order to evaluate the ability of the freshwater bivalve Potomida littoralis for use as a biodetector of aquatic pollution, the short-term effects of some pollutants (metals, antifouling product and effluents) on pumping activity of this mussel were studied qualitatively (pumping behaviour) and quantitatively (filtration rate). The method of the flow sensing at the exhalent siphon showed that the normal activity of P. littoralis was characterized by a continuous pattern of pumping with occasional and brief interruptions. When exposed to toxic stress, the exhalent flow immediately shifted to an intermittent pattern with periods of pumping alternating with periods of pause that could last several minutes. The threshold concentrations of heavy metals/antifouling agent inducing this type of activity within 2 h were: 25 g l^–1 for copper, 90 g l^–1 for cadmium, 5 g l^–1 for mercury, 3000 g l^–1 for zinc and 700 g l^–1 for the antifouling agent Mexel. Both the effluent samples of the urban wastewater of Marrakech city tested were found to be toxic.The filtration rate of control animals ranged from 0.91 to 1.72 l h^–1 g^–1 animal, while after 3 h exposure to Cu, Cd, Hg and the effluent E1 and E2, filtration rates were decreased by concentrations above the threshold levels set as toxic for the pumping activity.The sensitivity of P. littoralis to pollution and its usefulness as biodetector for rapid toxicity screening is discussed and a procedure for the detection of pollution in Moroccan freshwater is proposed.     

The impact of an industrially contaminated lake on heavy metal levels in its effluent stream

Levels of cadmium and zinc in various components of Williamson Ditch (an industrially contaminated stream flowing into Palestine Lake), Trimble Creek (a stream draining Palestine Lake) and the Tippecance River (a river receiving Trimble Creek) were determined. Water, sediment, plant, fish and clam samples were analyzed for cadmium and zinc content by atomic absorption spectrophotometry. Unweighted mean metal concentrations in Trimble Creek were the following: water, 51 µg Zn/1 and 4.2 µg Cd/1; sediment, 592 µg Zn/g and 48.8,µg Cd/g; plants, 375 µm Zn/g and 7.91 µg Cd/g; fish, 145 µg Zn/g and 6.02 µg Cd/g. These concentrations were generally lower than those found in Williamson Ditch and higher than those found in the Tippecanoe River or background levels previously reported for other aquatic ecosystems.     

TBARS,carnitine, and reduced glutathione levels in human bladder carcinoma

In this study, we investigated tissue levels of reduced glutathione (GSH) and carnitine as well as thiobarbituric acid reactive substances (TBARS, as a marker of lipid peroxidation) levels in bladder carcinoma and control group of patients. The average GSH, carnitine and TBARS levels for tumor group were respectively 7.11 ± 3.3 g/mg protein, 1.81 ± 0.39 nmol/mg protein, and 4.29 ± 3.2 mol/mg protein, versus 14.45 ± 4.11 g/mg protein, 2.14 ± 0.66 nmol/mg protein, and 2.3 ± 0.6 mol/mg protein for normal bladder tissues. Thus, tissue reduced glutathione levels (GSH) were significantly lower in patients as compared with the control group (p < 0.001) whereas average TBARS levels in the tumor group were found to be higher than those in control group. The average tissue carnitine levels in the patient group were found to be lower compared with the control group but the difference was not statistically significant (p > 0.05).