Exposure to domoic acid affects larval development of king scallop Pecten maximus (Linnaeus, 1758)

Domoic acid (DA) is a highly toxic phycotoxin produced by bloom forming marine diatoms Pseudo-nitzschia spp. Bivalves can accumulate this toxin to a high level through their feeding activities, and thus illness or death in can occur in consumers of bivalves. In this study, king scallop, Pecten maximus, larvae were exposed to dissolved domoic acid (DA) for 25d, and the toxin accumulation and effects of harbouring this toxin were investigated. Scallop larvae incorporated DA continuously during the larval culture period and accumulated a maximum DA level of 5.21pgind(-1) when exposed to a solution of 50ngml(-1) dissolved DA. As a result of the DA treatment, larval growth, measured in terms of shell length and the appearance of the eye-spot, and larval survival were significantly compromised. This is the first study on DA incorporation dynamics in P. maximus larvae, signifying the potential of using shellfish larvae for the study on mechanisms of phycotoxin accumulation. The negative effect of DA exposure suggests that this toxin could possibly influence natural recruitment in P. maximus, and it may be necessary to protect hatchery-cultured scallop larvae from DA during toxic Pseudo-nitzschia blooms.     

Depuration and anatomical distribution of the amnesic shellfish poisoning (ASP) toxin domoic acid in the king scallop Pecten maximus

The depuration kinetics of the domoic acid of four body fractions (digestive gland, adductor muscle, gonad+kidney and gills+mantle) of the scallop Pecten maximus was studied over 295 days. The scallops, which had acquired the toxins during a Pseudo-nitzschia australis episode that took place the week before the beginning of the experiment, were maintained in tanks with running seawater. All the body fractions, except the adductor muscle, decreased their domoic acid burden throughout the experiment. The amount of toxin in the muscle dropped sharply at the start of the experiment but increased again at the end, to levels that were higher than the initial ones. Several dynamic models of depuration kinetics, which included the depuration of each fraction (excluding the adductor muscle) and the transfers between them, were constructed, implemented and fitted to the data to obtain their parameters. The estimated depuration rates were very low, both considering and not considering the transfer of toxin between organs or the effect of weight loss. There were strong differences in the domoic acid burden of the body fractions studied but not between their depuration rates. No net transfer from the digestive gland, the tissue with highest domoic acid concentration, to the other fractions was found, as the inclusion of these processes in the models produced only a marginally better fit to the data. The depuration of domoic acid was slightly, but significantly, affected by biomass. Weight loss induced domoic acid loss, suggesting that part of the depuration may be produced by the direct loss of bivalve cells. The concentration or dilution effect, due to decreases or increases in biomass, documented for other species and toxins, has little importance in Pecten maximus.     

Distribution and linkage of domoic acid (amnesic shellfish poisoning toxins) in subcellular fractions of the digestive gland of the scallop Pecten maximus

The king scallop Pecten maximus accumulates domoic acid, the main amnesic shellfish poisoning toxin, in the digestive gland for a long time. To try to find if the cause of this characteristic is the binding of the toxin to some cellular component, the subcellular distribution of domoic acid in the cells of the digestive gland was studied, by means of serial centrifugation, ultrafiltration and size exclusion chromatography (SEC). Domoic acid was found to be present mostly in soluble form in the cytosol, as more than 90% was found in the supernatant after a centrifugation of 1 h at 45,000 × g, and passed a 10 kDa ultrafilter. The retention time of the peak with an absorption maximum of 242 nm – the one characteristic of domoic acid – observed in the SEC chromatograms of the scallop samples was found identical to be one of a reference solution of the toxin, indicating therefore, that domoic acid is free in the cytosol of the digestive gland of Pecten maximus. This finding turns the focus from binding to the lack of membrane transporters in this species of the scallop as the cause of the long retention time of domoic acid in this species.     

The role of cysteine conjugation in the detoxification of microcystin-LR in liver of bighead carp (Aristichthys nobilis): a field and laboratory study

The role of glutathione (GSH) and cysteine (Cys) conjugates in the detoxification of microcystin-LR (MC-LR) in bighead carp (Aristichthys nobilis) was examined under laboratory and field conditions. Wild individuals of bighead carp were collected from 5 eutrophic lakes along the Yangtze River, while in laboratory experiment, bighead carp were injected intraperitoneally with 500 μg purified MC-LR/kg body weight (bw). Contents of MC-LR and its glutathione (MC-LR-GSH) and cysteine conjugates (MC-LR-Cys) in the liver of bighead carp were determined by liquid chromatography electrospray ionization mass spectrum (LC–ESI–MS). In laboratory experiment, low concentrations of MC-LR-GSH (mean: 0.042 μg/g dry weight (DW)) were always detectable, and the mean ratio of MC-LR-Cys to MC-LR-GSH was 6.55. While, in field study, relatively high MC-LR-Cys concentration (mean: 0.22 μg/g DW) was detected, whereas MC-LR-GSH was occasionally detectable, and the average ratio of MC-LR-Cys to MC-LR-GSH was as high as 71.49. A positive correlation was found between MC-LR-Cys concentration in the liver of bighead carp and MC-LR content in seston from the five lakes (r = 0.85). These results suggest that MC-LR-Cys might be much more important than MC-LR-GSH in the detoxification of MC-LR in fish liver, and that cysteine conjugation of MC-LR might be a physiological mechanism for the phytoplanktivorous bighead carp to counteract toxic cyanobacteria.     

Patterns of Hg Bioaccumulation and Transfer in Aquatic Food Webs Across Multi-lake Studies in the Northeast US

The northeastern USA receives some of the highest levels of atmospheric mercury deposition of any region in North America. Moreover, fish from many lakes in this region carry Hg burdens that present health risks to both human and wildlife consumers. The overarching goal of this study was to identify the attributes of lakes in this region that are most likely associated with high Hg burdens in fish. To accomplish this, we compared data collected in four separate multi-lake studies. Correlations among Hg in fish (4 studies) or in zooplankton and fish (2 studies) and numerous chemical, physical, land use, and ecological variables were compared across more than 150 lakes. The analysis produced three general findings. First, the most important predictors of Hg burdens in fish were similar among datasets. As found in past studies, key chemical covariates (e.g., pH, acid neutralizing capacity, and SO₄) were negatively correlated with Hg bioaccumulation in the biota. However, negative correlations with several parameters that have not been previously identified (e.g., human land use variables and zooplankton density) were also found to be equally important predictors. Second, certain predictors were unique to individual datasets and differences in lake population characteristics, sampling protocols, and fish species in each study likely explained some of the contrasting results that we found in the analyses. Third, lakes with high rates of Hg bioaccumulation and trophic transfer have low pH and low productivity with relatively undisturbed watersheds suggesting that atmospheric deposition of Hg is the dominant or sole source of input. This study highlights several fundamental complexities when comparing datasets over different environmental conditions but also underscores the utility of such comparisons for revealing key drivers of Hg trophic transfer among different types of lakes.     

Evaluation of the toxicity of chemical compounds using digestive acini of the bivalve mollusc Pecten maximus L. maintained alive in vitro

The digestive gland of bivalve molluscs is a model of choice for experiments in ecotoxicology because of its implication in detoxification processes moreover of its classical functions in digestive phenomena. All physiological deteriorations of this organ, related or not to pollution, can lead to animal death. The recent development of a method allowing digestive acini of Pecten maximus to be maintained alive in vitro for 96 h opens up new research prospects in ecotoxicology. The action of contaminants considered to be cytotoxic or genotoxic in the literature were tested on this model. The results show the high cytotoxicity of ethylmethane sulphonate 80 and 5 mM after 2 h of contact with acini. Other compounds such as 4-nitroquinoline-N-oxide 0.1 mM, cadmium chloride 10(-5) M and atrazine 10(-4) M, which were weakly toxic after 2 h, became highly toxic after 48 h of contact. Compounds such as 4-nitroquinoline-N-oxide 1 mM, which were not cytotoxic after 2 h, proved to be the most genotoxic of all those tested. Others, such as MMS 1 mM, cadmium chloride 10(-4) and 10(-5) M, and atrazine 10(-5) M, showed an unconfirmed tendency to be genotoxic. The results obtained with this 'acinus' model seem more readily transposable to the whole organism than those obtained with 'isolated cell' models, in that acini can be considered as digestive glands 'in miniature'.     

Interactions between Filter-Feeding Bivalves and Toxic Diatoms: Influence on the Feeding Behavior of Crassostrea gigas and Pecten maximus and on Toxin Production by Pseudo-nitzschia

Among Pseudo-nitzschia species, some produce the neurotoxin domoic acid (DA), a source of serious health problems for marine organisms. Filter-feeding organisms—e.g., bivalves feeding on toxigenic Pseudo-nitzschia spp.—are the main vector of DA in humans. However, little is known about the interactions between bivalves and Pseudo-nitzschia. In this study, we examined the interactions between two juvenile bivalve species—oyster (Crassostrea gigas) and scallop (Pecten maximus)—and two toxic Pseudo-nitzschia species—P. australis and P. fraudulenta. We characterized the influence of (1) diet composition and the Pseudo-nitzschia DA content on the feeding rates of oysters and scallops, and (2) the presence of bivalves on Pseudo-nitzschia toxin production. Both bivalve species fed on P. australis and P. fraudulenta. However, they preferentially filtered the non-toxic Isochrysis galbana compared to Pseudo-nitzschia. The presence of the most toxic P. australis species resulted in a decreased clearance rate in C. gigas. The two bivalve species accumulated DA in their tissues (up to 0.35 × 10⁻³ and 5.1 × 10⁻³ µg g⁻¹ for C. gigas and P. maximus, respectively). Most importantly, the presence of bivalves induced an increase in the cellular DA contents of both Pseudo-nitzschia species (up to 58-fold in P. fraudulenta in the presence of C. gigas). This is the first evidence of DA production by Pseudo-nitzschia species stimulated in the presence of filter-feeding bivalves. The results of this study highlight complex interactions that can influence toxin production by Pseudo-nitzschia and accumulation in bivalves. These results will help to better understand the biotic factors that drive DA production by Pseudo-nitzschia and bivalve contamination during Pseudo-nitzschia blooms.     

Congenital syphilis in Mocambique: the diagnostic complementary role of laboratory and radiological investigations

Congenital syphilis has been and continues to be a principal public health problem in developing countries. Despite the wide experience acquired, physicians still have problems in diagnostic evaluation. We report 88 cases of congenital syphilis at Central Hospital of Maputo (Mocambique), emphasizing the role of serological and roentgenographic examinations, the 2 commonest diagnostic tools. X-ray examination was particularly important to confirm the diagnosis of congenital syphilis in 76.2 percent of sero-positive children and to sustain the diagnosis in another subgroup of seronegative children (4.5 percent). Periostitis was a constant finding in all positive x-ray examinations and was associated with osteochondritis in 47.7 percent and with osteomyelitis in 18.2 percent of cases. Serologic test for syphilis was positive in 95.4 percent of the study population and was essential to make the diagnosis in 19.3 percent of cases with negative x-rays examination. So, laboratory and, in a complementary way, roentgenographic findings allow to confirm the diagnosis of congenital syphilis in 100 percent of cases. Serological test in the mother is a useful examination as well, with a high percentage of positivity (78.4 percent); however in accordance to the present study it fails to add any new case of congenital syphilis already detected by serological and roentgenographic examination in the child.     

Evidence of species-specific detoxification processes for trace elements in shorebirds

This study investigated sub-lethal effects and detoxification processes activated in free-ranging Red Knots (RKs) (Calidris canutus) from the Pertuis Charentais on the Atlantic coast of France, and compared the results with previous data obtained on another shorebird species, the Black-tailed Godwit (Limosa limosa). The concentrations of 13 trace elements (Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, Zn) were assessed in the liver, kidneys, muscle and feathers. Stable isotope analyses of carbon and nitrogen were carried out to determine whether differences in diet explained variations in elemental uptake. The mRNA expression of relevant genes (cytochrome c oxidase 1, acetyl-CoA carboxylase, Cu/Zn and Mn superoxide dismutase, catalase, metallothionein, malic enzyme), antioxidant enzyme activities (catalase, glutathione peroxidase (GPx), superoxide dismutase), and metallothionein (MT) levels were investigated to shed light on trace element detoxification and toxic effects. Although Red Knots were characterized by elevated As and Se concentrations which were potentially toxic, most elements were usually below toxicity threshold levels. The results strongly suggested a dietary specialization of Red Knots, with individuals feeding on higher trophic status prey experiencing higher As, Hg and Se burdens. Red Knots and Godwits also showed discrepancies in elemental accumulation and detoxification processes. Higher As and Se concentrations in Red Knots enhanced catalase gene expression and enzyme activity, while Godwits had higher Ag, Cu, Fe and Zn levels and showed higher MT production and GPx activity. The results strongly suggest that detoxification pathways are essentially trace element- and species-specific.     

Induction of glutathione-S-transferases in primary cultured digestive gland acini from the mollusk bivalve Pecten maximus (L.): application of a new cellular model in biomonitoring studies

In the last three decades, marine invertebrates have been used to monitor environmental health conditions and potential pollution, e.g. in the Mussel Watch Program. The whole animal or specific organs are used to determine contamination levels and disturbances. In the present study, a new in vitro cell culture model was validated for pollution monitoring. A commercial species, the scallop Pecten maximus, was tested for the presence and induction of phase II glutathione-S-transferase (GST) enzymes. These activities were monitored for a year, and the results were found to be consistent with those in the literature. Tributyltin, ethylmethane sulfonate and the water-soluble fraction of crude oil were assayed in, in vitro induction studies. A rapid increase of GST activities was observed within 24 h with all compounds tested, and a time- as well as a dose-response was established. This in vitro cell culture model seems suitable for routine use to predict the effects of pollutants on whole organisms within an ecosystem and in fisheries.     

Malaria vaccines: from the laboratory to the field

The demonstration of the i) acquired protective immunity in adults living in endemic areas, ii) cure of malaria patients with passive transfer of specific immunoglobulins, and iii) protection conferred by vaccination with sporozoites attenuated by radiation, justifies the search for a malaria vaccine. Given the improbability that a vaccine directed against a single antigen will be completely protective, the preferred option is to combine several antigens of different stages of the parasite in a multi-component multi-stage vaccine which is likely to protect both the travellers and the populations living in endemic areas. Potential manufacturing technologies include recombinant proteins, synthetic peptides and DNA vaccines, the relevant genes encoding malaria antigens being inserted into a plasmid or a live vector such as vaccinia or poxvirus. A number of human trials using different antigens and technologies have been carried out in the last ten years. Three vaccines have undergone safety and efficacy testing in the field. SPf66, comprising a linear polymerised synthetic peptide with several distinct epitopes, has been extensively evaluated in different epidemiological settings. The efficacy overall was 23%, but was only 2% in African infants, the most susceptible group. The circumsporozoite recombinant protein fused with the antigen S of the hepatitis B virus and formulated in a potent adjuvant (RTS,S) led to a high, but short-term, level of protection against infection and disease in Gambian adults. The first pure asexual blood-stage vaccine comprising three antigens of the merozoite stage (MSP1&2 and RESA, Combination B) had an efficacy of 62% in reducing parasite density in Papua New Guinean children. A malaria vaccine that can reduce the burden of disease in the most affected populations is thus an achievable goal, and each trial provides additional knowledge about mechanisms of protection as well as about new vaccine technology.     

An update on the detoxification processes for silica particles and asbestos fibers: successess and limitations

Inhalation of asbestos fibers and crystalline silica produces a number of diseases including fibrosis and cancer. Investigations into the mechanisms involved in mineral particle-induced toxicity indicated the importance of their surfaces in the pathological consequences. Masking of the surface sites has therefore featured prominently in a number of detoxification processes that have been investigated. The majority of the detoxification processes were, however, conducted to elucidate the involvement of a particular surface site in the toxicity of a specific mineral. Others were investigated with the aim of large industrial applications to be applied during mining, handling, processing, transporting, and disposing of minerals. It can be concluded that, to date, there is no single detoxification process that could be applied universally to all different types of mineral particles. Those that have shown some success could not completely abolish all adverse effects. Further elucidation of mechanisms of particle-induced toxicity may open new possibilities for detoxification processes.     

Use of quinones in brain-tumor therapy: preliminary results of preclinical laboratory investigations

Failure of current chemotherapeutic agents to effectively treat human brain tumors has prompted the search for alternative regimens based on the inherent metabolic pathways of target cells. One way to accomplish this goal would be to design drugs in an inactive form, which upon entry into the cell would be transformed to a toxic metabolite by a naturally occurring pathway. One such pathway may be the reductive activation of naphthoquinones with one or two side chains capable of alkylation, such as 2,3-dibromomethyl-1,4-naphthoquinone (DBNQ). This reductive activation can be catalyzed by the flavoprotein DT-diaphorase [NAD(P)H:quinone oxidoreductase]. We have found that both rat 9L and some human brain-tumor cell lines contain very high levels of this enzyme and that halogenated dimethyl naphthoquinones, such as DBNQ, are highly toxic to these cells in vitro. Moreover, we have found that the cytotoxic effects of DBNQ on human tumor and murine bone marrow stem cells can be prevented or lessened by pretreatment of the cells with dicoumarol, a potent inhibitor of DT-diaphorase. Since dicoumarol does not cross the blood-brain barrier, the potential exists for human brain tumors to be destroyed with halogenated dimethylquinones and for peripheral host toxicity to be prevented by coadministration of dicoumarol.     

Clinical and laboratory evaluation of aspoxicillin in the pediatric field

The authors have carried out the clinical and laboratory evaluation of aspoxicillin (ASPC, TA-058). The results were as follows: Antibacterial activities The susceptibility to ASPC was estimated by plate dilution method on 26 strains each of S. aureus, E. coli, Salmonella and P. aeruginosa and 19 strains of S. marcescens isolated from clinical specimens. Minimum inhibitory concentration (MIC) of ASPC against E. coli and Salmonella was about twice active to compare with ampicillin (ABPC), but MIC of ASPC against S. aureus was two-fold less active than that of ABPC. Antimicrobial activities of ASPC against S. marcescens were similar to that of ABPC, while against P. aeruginosa its activities were two-fold higher than that of carbenicillin. Serum levels and urinary excretions When ASPC was administered at 20 mg/kg by one shot intravenous injection, serum concentration was 75 micrograms/ml after 15 minutes and half-life (T 1/2 beta) was 1.65 hours. Urinary excretion within 6 hours after ASPC injection reached to 245.6 mg (26.1%). The reason of this law urinary excretion rate was due to the underlying disease (hydronephrosis). In case of 20 mg/kg administration of ASPC by intravenous drip infusion, peak serum level reached to 88 micrograms/ml at the end of injection, and half-life (T 1/2 beta) was 0.77 hour. Since ASPC degradation by beta-lactamase was proceeded, urinary excretion of this case was not measured by microbiological method. Penicillonic acid and its epimer were detected by HPLC method. It was found that beta-lactamase producing strain was S. marcescens which was isolated by urine culture.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preliminary and clinical investigations of cefmetazole in the obstetric and gynecological field

1. The serum concentration of cefmetazole (CMZ) was 56.8 +/- 13.3 micrograms/ml at 1 hour after one-shot intravenous injection of 2 g. Half-life was 1.1 hours, indicating that the drug is adsorbed rapidly. In addition, CMZ was detected at high concentrations in the endometrium, myometrium, ovary, uterine tube and cervix uteri. The concentration was especially high in the uterine tube and ovary. It was also demonstrated in the fetus and fetal membrane, though at low concentration. 2. Clinically one-shot intravenous injection of 1 to 2 g of CMZ were given 2 times daily to 15 patients with intrauterine infection, adnexitis, intrapelvic infection or postoperative wound infection. The drug was evaluated to be effective in 15 or 80% of them. No special side effects were found.     

Importance of bacterial biodegradation and detoxification processes of microcystins for environmental health

Microcystins (MC) the most frequently reported cyanobacterial harmful algal bloom toxins primarily found in some species of freshwater genera pose a serious threat to human and animal health. To reduce health risks associated with MC exposure it is important to remove these toxins found in drinking and recreational waterbodies. Since the physical and chemical water treatment methods are inefficient in completely degrading MC, alternative approaches to effectively detoxify MC have become the focus of global research. The aim of this review was to provide the current approach to cost-effective biological treatment methods which utilize bacteria to degrade MC without generation of harmful by-products. In addition, the catabolic pathways involved in MC-degradation involving proteins encoded mlr gene cluster, intermediate products and efficiencies of bacteria strain/bacteria community are presented and compared.     

Retinoid X receptor alpha regulates glutathione homeostasis and xenobiotic detoxification processes in mouse liver

Retinoid X receptor alpha (RXRalpha) plays a pivotal role in regulating liver metabolism. RXRalpha-mediated gene expression involved in amino acid metabolism was examined using the NIA Mouse 15K cDNA microarray containing 15,000 different expressed sequence tags. Seven amino acid metabolic genes, three of which encode enzymes involved in phase II detoxification process, were identified as RXRalpha target genes in mouse liver. Glutamate-cysteine ligase catalytic subunit (GCLC), glutathione S-transferasemu, and glutathione peroxidase 1 were down-regulated in the liver of hepatocyte RXRalpha-deficient mice. The down-regulation of GCLC in RXRalpha-deficient mice led to 40% and 45% reductions in the rate of glutathione (GSH) synthesis and level of hepatic GSH, respectively. Primary hepatocytes from RXRalpha-deficient mice were more sensitive to t-butylhydroperoxide-induced oxidative stress. However, GSH diminished RXRalpha-deficient mice were resistant to acetaminophen (APAP)-induced hepatotoxicity. Analysis of phase I detoxification genes revealed that CYP1A2 and CYP3A11 were up-regulated in wild-type mice but down-regulated in RXRalpha-deficient mice after APAP administration. Taken together, the data indicate that RXRalpha centrally regulates both phase I and phase II drug metabolism and detoxification. Regulation of hepatic GSH levels by RXRalpha is essential to protect hepatocytes from oxidative stress, whereas up-regulation of phase I drug metabolism genes by RXRalpha may render the liver more sensitive to APAP-induced toxicity.     

Nordihydroguaiaretic acid: hepatotoxicity and detoxification in the mouse

Larrea tridentata (Moc & Sess) Cov. (Zygophyllaceae) is an ethnobotanically important plant found in the American Southwest and northern Mexico. Although numerous beneficial effects have been attributed to this plant, several case reports have demonstrated high doses of Larrea-containing herbals induce hepatotoxicity and nephrotoxicity in humans. Nordihydriguaiaretic acid (NDGA) is a lignan found in high amounts (up to 10% by dry weight) in the leaves and twigs of L. tridentata. Previously, NDGA has been shown to induce cystic nephropathy in the rat, however, no reports have been made concerning this compound's hepatotoxic potential. Here, we report that intraperitoneal adminstration of NDGA is lethal in the mouse (LD₅₀=75 mg/kg). Administration is associated with a time and dose-dependent increase in serum alanine aminotransferase levels, which suggest liver damage. Indeed, freshly isolated mouse hepatocytes are more sensitive to NDGA than human melanoma cells. Furthermore, we have identified glucuronidation as a potential detoxification mechanism for NDGA. Both mono and diglucuronide conjugates of NDGA are formed after intravenous dosing. The monoglucuronide is also formed after incubation of NDGA with human hepatic microsomes; suggesting that glucuronide conjugation is important in the metabolism of NDGA by humans. In summary, this report indicates that NDGA may contribute to the hepatotoxicity of L. tridentata and provides preliminary information on NDGA metabolism.