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H Exposure (h + exposure)
Selected AbstractsThe effects of copper on the microbial community of a coral reef spongeENVIRONMENTAL MICROBIOLOGY, Issue 1 2001Nicole S. Webster Marine sponges often harbour communities of symbiotic microorganisms that fulfil necessary functions for the well-being of their hosts. Microbial communities associated with the sponge Rhopaloeides odorabile were used as bioindicators for sublethal cupric ion (Cu2+) stress. A combined strategy incorporating molecular, cultivation and electron microscopy techniques was adopted to monitor changes in microbial diversity. The total density of sponge-associated bacteria and counts of the predominant cultivated symbiont (,-proteobacterium strain NW001) were significantly reduced in response to Cu2+ concentrations of 1.7 µg l,1 and above after 14 days of exposure. The number of operational taxonomic units (OTUs) detected by restriction fragment length polymorphism (RFLP) decreased by 64% in sponges exposed to 223 µg l,1 Cu2+ for 48 h and by 46% in sponges exposed to 19.4 µg l,1 Cu2+ for 14 days. Electron microscopy was used to identify 17 predominant bacterial morphotypes, composing 47% of the total observed cells in control sponges. A reduction in the proportion of these morphotypes to 25% of observed cells was evident in sponges exposed to a Cu2+ concentration of 19.4 µg l,1. Although the abundance of most morphotypes decreased under Cu2+ stress, three morphotypes were not reduced in numbers and a single morphotype actually increased in abundance. Bacterial numbers, as detected using fluorescence in situ hybridization (FISH), decreased significantly after 48 h exposure to 19.4 µg l,1 Cu2+. Archaea, which are normally prolific in R. odorabile, were not detected after exposure to a Cu2+ concentration of 19.4 µg l,1 for 14 days, indicating that many of the microorganisms associated with R. odorabile are sensitive to free copper. Sponges exposed to a Cu2+ concentration of 223 µg l,1 became highly necrosed after 48 h and accumulated 142 ± 18 mg kg,1 copper, whereas sponges exposed to 19.4 µg l,1 Cu2+ accumulated 306 ± 15 mg kg,1 copper after 14 days without apoptosis or mortality. Not only do sponges have potential for monitoring elevated concentrations of heavy metals but also examining changes in their microbial symbionts is a novel and sensitive bioindicator for the assessment of pollution on important microbial communities. [source] Assessment of sediment quality of Yangtze River estuary using zebrafish (Danio rerio) embryosENVIRONMENTAL TOXICOLOGY, Issue 3 2010Lingling Wu Abstract Yangtze River estuary is one of the largest estuaries worldwide. In this study, the sediment quality of Yangtze River estuary was evaluated using zebrafish (Danio rerio) embryos. Freshly fertilized zebrafish eggs (2 h after fertilization) were exposed to the whole sediment and its organic phase of extract, respectively. The parameters, including survival rate, abnormality, hatching rate, and heart rate of the zebrafish embryos, were recorded during the 96-h exposure. The results demonstrated that the concentrations of heavy metals (Zn, Cu, Cd, Ni, Cr, and As) and low-molecular weight PAHs (Fluorene) in the sediment of Yangtze River estuary exceeded their corresponding effects range low values. The maximum concentrations of Zn and Fluorene in the sediment samples were 239.6 ,g/g and 45.9 ng/g, respectively. In both whole sediment test and organic extract test, the survival rate and heart rate of zebrafish embryos were reduced, as well as abnormalities and delayed hatching were induced. For example, the highest mortality of the embryos was 39% in the whole sediment exposure. Overall, the occurrence of toxic compounds in the sediment of Yangtze River estuary may have potentially teratogenic effect on biota. The sediment from the upstream of Yangtze River estuary have more observed toxic effects on zebrafish embryos than that form the downstream. Therefore, more attention should be paid to control these pollutants, especially heavy metals in the Yangtze River estuary. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010. [source] Difference in the sensitivity to chemical compounds between female and male neonates of Daphnia magnaENVIRONMENTAL TOXICOLOGY, Issue 5 2008Erika Ikuno Abstract Daphnia magna usually produce female offspring by parthenogenesis, and thus only female neonates are used to evaluate the environmental toxicity to chemicals. Additionally, it is known that male daphnids are induced by exposure to a juvenile hormone, methyl farnesoate, during late ovarian development. In this study, we investigated the concentration of methyl farnesoate in a 24-h exposure producing 100% males, and the difference in sensitivity to chemical compounds, potassium dichromate, pentachlorophenol, and paraquat, between females and males, referring to OECD Test Guideline 202. The results show that the minimum concentration for 100%-male induction of methyl farnesoate in adult females was 50 ,g/L. In addition, acute toxicity tests (immobility test) with the other chemicals showed that male neonates have higher tolerance to potassium dichromate and pentachlorophenol than females for at least 24 h after birth, while no sex difference was observed in the sensitivity to paraquat. The differences in the median effective concentrations in these compounds between female and male neonates suggest two different overall modes of action. Using female daphnids for environmentally toxicity testing seems reasonable, since the females are more sensitive to chemicals than males. Furthermore, the method of male induction established in this study could be used for screening of endocrine disruptors. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Effects of a saxitoxin-producer strain of Cylindrospermopsis raciborskii (cyanobacteria) on the swimming movements of cladoceransENVIRONMENTAL TOXICOLOGY, Issue 2 2008Aloysio da S. Ferrão Filho Abstract This study evaluated the effects of a saxitoxin-producer strain (T3) of the cyanobacteria species Cylindrospermopsis raciborskii on the swimming movements of three cladoceran species (Daphnia gessneri, D. pulex, and Moina micrura). Acute toxicity bioassays were designed to access the effects of T3 strain, of a nonsaxitoxin producer strain (NPLP-1) of the same species and of a raw water sample from Funil reservoir (Rio de Janeiro, Brazil), that contained this and other cyanobacteria. In the acute bioassays, animals were exposed to C. raciborskii filaments or Funil water for 24,48 h and then transferred to food suspensions without cyanobacterial filaments for a further 48 h. During the exposure time to T3 strain filaments there was a decrease in the number of swimming individuals, with animals showing progressive immobilization. The same effect was observed with Funil water sample. Animals stayed alive on the bottom of the test tube and recovered swimming movements when transferred to food suspensions without toxic cells. This effect was not observed with the strain NPLP-1. The cladoceran D. pulex showed to be extremely sensitive to T3 strain and to Funil water containing C. raciborskii filaments, showing complete paralysis after 24-h exposure to T3 cell densities of 103 and 104 cells mL,1, and after 24-h exposure to only 10% of raw water. However, D. gessneri was not sensitive to both T3 and to Funil water, whereas M. micrura was intermediate in sensitivity. This is the first report on the effects of cyanobacterial saxitoxins on movements of freshwater cladocerans, showing also difference in sensitivity among closely related Daphnia species. © 2008 Wiley Periodicals, Inc. Environ Toxicol, 2008. [source] Cadmium tolerance in the Nile tilapia (Oreochromis niloticus) following acute exposure: Assessment of some ionoregulatory parametersENVIRONMENTAL TOXICOLOGY, Issue 1 2006Sofia Garcia-Santos Abstract The Nile tilapia (Oreochromis niloticus) can tolerate very high levels of waterborne cadmium. It has one of the highest 96 h LC50 recorded for a freshwater teleost fish (14.8 mg/L Cd; hardness 50 mg/L CaCO3). Cadmium is known to perturb ion balance in teleost fishes. However, in an acute time course experiment, plasma Na+ concentrations were unaffected, and plasma Ca2+ values only decreased after 96 h exposure in a dose-independent manner. Branchial Na+/K+ -ATPase activity and ,-subunit protein level expression in crude gill homogenates were not affected by Cd exposure during this period. Branchial chloride cell numbers, identified as Na+/K+ -ATPase immunoreactive cells using immunohistochemistry, decreased 24 h after exposure but recovered thereafter. Histopathological changes did not follow a consistent pattern of variation with exposure time, and the alterations noted in gill epithelium were basically nonspecific to cadmium. Because of its tolerance, it can be concluded that the tilapia O. niloticus would not be a suitable test organism to evaluate sublethal toxicity of cadmium and the realistic impact of this pollutant in the environment. However, it certainly could contribute significantly to our understanding of the toxic mechanism of cadmium exposure in aquatic organisms. This is the first work to investigate the effect of waterborne pollutants on Na+/K+ -ATPase ,-subunit protein expression in fish gills. © 2006 Wiley Periodicals, Inc. Environ Toxicol 21: 33,46, 2006. [source] Influence of stability on the acute toxicity of CdSe/ZnS nanocrystals to Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 6 2010Heather E. Pace Abstract The acute toxicity of polymer-coated CdSe/ZnS quantum dots (QDs) to Daphnia magna was investigated using 48-h exposure studies. The principal objective was to relate the toxicity of QDs to specific physical and chemical aspects of the QD. As such, two different CdSe core diameters, 2,nm QDs (green-emitting) and 5,nm QDs (red-emitting), and two different surface coatings, polyethylene oxide (PEO) and 11-mercaptoundecanoic acid (MUA) were studied. The QDs were characterized before and after the 48-h exposure using fluorescence, ultrafiltrations (3 kDa), and inductively coupled plasma-atomic emission spectrometry (ICP-AES) metal analysis. In addition, flow field flow fractionation-inductively coupled plasma-mass spectrometry (Fl FFF-ICP-MS) was used as a more extensive characterization technique to determine particle size and composition as well as identify other potential constituents in the QD solutions. The more stable QDs (PEO) were found to be less acutely toxic than the QDs with accelerated dissolution (MUA), suggesting QD stability has significant impact on the nanoparticles' short-term toxicity. The emergence of dissolved Cd2+ in solution indicates that the toxicity of the MUA QDs is likely due to Cd poisoning, and a mass-based dose response occurred as a consequence of this mode of action. Alternatively, the PEO QDs caused acute toxicity without observed particle dissolution (i.e., no detectable metals were solubilized), suggesting an alternative mode of toxic action for these nanoparticles. Results of the present study suggest that using particle number, instead of mass, as a dose metric for the PEO QDs, produces markedly different conclusions, in that smaller core size does not equate to greater toxicity. Environ. Toxicol. Chem. 2010;29:1338,1344. © 2010 SETAC [source] The effects of continuous and pulsed exposures of suspended clay on the survival, growth, and reproduction of Daphnia magnaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2010Sarah E. Robinson Abstract Suspended sediments are a natural component of aquatic ecosystems, but anthropogenic activity such as land development can result in significant increases, especially after rain events. Continuous exposures of suspended clay and silt have been shown to affect growth and reproduction of Cladocera, leading to a decrease in population growth rate. The mechanism of clay toxicity in these filter-feeding organisms is clogging of the gut tract, resulting in decreased food uptake and assimilation. When placed in clean water, daphnids can purge clay from their gut and recover. In many surface waters, aquatic organisms experience episodic exposures of high concentrations of suspended solids driven by rain events. However, little is known about the consequences of pulsed exposures on individuals and populations. The objective of the present study was to characterize the effects of continuous and pulsed exposures of natural and defined clays on survival, growth, and reproduction of Daphnia magna. Two defined clays, montmorillonite and kaolinite, as well as clay isolated from the Piedmont region of South Carolina, USA, were used. Continuous exposures of clays elicited a dose dependent decrease in survival. Toxicity varied depending on clay source with montmorillonite,>,natural clay,>,kaolinite. Pulsed exposures caused a decrease in survival in a 24 h exposure of 734 mg/L kaolinite. Exposure to 73.9 mg/L also caused an increase in the time to gravidity, although there was not a corresponding decrease in neonate production over 21 d. No significant effects resulted from 12 h exposures even at 730 mg/L, almost 10 times the 24-h reproductive effects concentration. This suggests that exposure duration impacted toxicity more than exposure concentration in these pulsed exposures. Environ. Toxicol. Chem. 2010;29:168,175. © 2009 SETAC [source] Response of the freshwater alga Chlorella vulgaris to trichloroisocyanuric acid and ciprofloxacin,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2008Xiangping Nie Abstract The effects of trichloroisocyanuric acid (TCCA) and ciprofloxacin (CPFX) on the freshwater alga Chlorella vulgaris were assessed by toxicity bioassays and by the values of biomarkers in phase I and phase II. The biomarkers included growth rate, concentration of chlorophyll a, activities of 7-ethoxyresorufin- O -dealkylases (EROD), glutathione S -transferase (GST), catalase (CAT), and total glutathione (GSH). Ciprofloxacin was a weaker growth inhibitor than TCCA but, at a concentration of greater than 12.5 mg/L, decreased the growth of C. vulgaris. Concentration of chlorophyll a showed a similar trend. The 96-h median effective concentration (EC50; i.e., 50% reduction in growth relative to the control) of CPFX was 20.6 mg/L. Trichloroisocyanuric acid was a strong growth inhibitor and, at concentrations of greater than 0.80 mg/L, caused 100% inhibition on 24-h exposure. The 96-h EC50 of TCCA was 0.313 mg/L. Ciprofloxacin and TCCA affected the phase I and phase II enzyme activities differently. On exposure to CPFX, both EROD and GSH decreased at low CPFX concentrations (<5.0 mg/L) and increased at high CPFX concentrations (>12.5 mg/L), and CAT and GST exhibited induction at low concentrations and inhibition at high concentrations. In TCCA exposure, GST activity was significantly stimulated, and GSH concentration was increased. Catalase activity increased only at TCCA concentrations of greater than 0.12 mg/L, and no change in EROD activity was observed. [source] Influence of water quality and age on nickel toxicity to fathead minnows (Pimephales promelas)ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2004Tham Chung Hoang Abstract This research characterized the effects of water quality and organism age on the toxicity of nickel (Ni)to fathead minnows (Pimephales promelas) to facilitate the accurate development of site-specific water-quality criteria. Nickel sulfate hexa-hydrate (NiSO4·6H2O) was used as the Ni source for performing acute toxicity tests (median lethal concentration after 96-h exposure [96-h LC50]) with <1-d-old and 28-d-old P. promelas under varying regimes of hardness, pH, alkalinity, and natural organic matter (NOM). The toxicity of Ni was inversely related to water hardness between hardness values of 20 and 150 mg/L (as CaCO3). Below 30 mg/L alkalinity, Ni toxicity was related to alkalinity. The effect of pH was confounded by hardness and the presence of NOM. In the absence of NOM, the toxicity of Ni increased as pH increased at high hardness and alkalinity. In general, 28-d-old fish were less sensitive than <1-d-old fish to Ni. This lower sensitivity ranged from 12-fold at low hardness and alkalinity (20 and 4 mg/L, respectively) to 5-fold at high hardness and alkalinity (100 and 400 mg/L, respectively). The presence of NOM (10 mg/L as dissolved organic carbon [DOC]) reduced Ni toxicity by up to 50%, but this effect appeared to be saturated above DOC at 5 mg/L. Incubating Ni with the NOM solution from 1 to 17 days had no effect on Ni toxicity. When using multivariate analysis, the 96-h LC50 for Ni was a function offish age, alkalinity, hardness, and NOM (96-h LC50 = ,0.642 + 0.270(fish age) + 0.005(alkalinity) + 0.018(hardness) + 0.138(DOC)). When using this model, we found a strong relationship between measured and predicted 96-h LC50 values (r2 = 0.94) throughout the treatment water qualities. The biotic ligand model (BLM) did not accurately predict Ni toxicity at high or low levels of alkalinity. Results of our research suggest that the BLM could be improved by considering NiCO3 to be bioavailable. [source] Ecdysteroid synthesis and imaginal disc development in the midge Chironomus riparius as biomarkers for endocrine effects of tributyltinENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2002Torsten Hahn Abstract Acute effects of the endocrine disruptor bis (tri- n -butyltin) oxide (TBTO) on molting-hormone biosynthesis and imaginaldisc development were investigated in larvae of the midge Chironomus riparius (Meigen). Ecdysteroid synthesis was measured by 24-h incubation of molting-hormone-synthesizing tissues (prothoracic glands) in vitro with or without the addition of TBTO. The amount of ecdysteroids produced was analyzed by radioimmunoassay. Developmental effects in vivo were investigated by determining the developmental phase of the genital imaginal discs before and after a 48-h exposure to TBTO in water. Sex-specific effects were found with both endpoints. Ecdysteroid synthesis was significantly reduced (analysis of variance [ANOVA], p , 0.005) in female larvae at all concentrations (TBTO-Sn at 50, 500, and 5,000 ng/L), whereas a significant elevation of the biosynthesis rate occurred in male larvae in the 500-ng/L treatment (ANOVA, p , 0.05). In vivo experiments with development of the genital imaginal disc within a 48-h exposure period revealed a significantly slower development in female larvae and a significantly faster development in male larvae (contingency tables, p , 0.001) at all concentrations tested (TBTO-Sn at 10, 50, 200, and 1,000 ng/L). These results partly coincided with the in vitro effects on molting-hormone synthesis. The 48-h median lethal concentration (LC50) was 25 ,g/L (20,30 ,g/L 95% confidence intervals). The combination of in vitro and in vivo methods has proven to be a useful approach for the detection of endocrine effects of TBTO in C. riparius at levels 2,000-fold below the LC50 value. High sensitivity and short test duration suggest that chironomids may have potential as freshwater sentinel organisms for endocrine-disrupting chemicals. [source] Effect of mercury and Gpi-2 genotype on standard metabolic rate of eastern mosquitofish (Gambusia holbrooki),ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2001Christopher Paul Tatara Abstract Previous studies demonstrated differential mortality among mosquitofish of different Gpi-2 genotypes during acute mercury and arsenate exposures. Mercury-exposed mosquitofish also had Gpi-2 genotype-specific differences in glycolytic and Krebs cycle metabolite pools. The mortality and metabolite data suggested that mosquitofish bearing specific Gpi-2 genotypes might differ in metabolic efficiency, with less efficient Gpi-2 genotypes having higher standard metabolic rates (SMRs) and shorter times to death during acute mercury exposure. Effect of Gpi-2 genotype on SMR was assessed with a factorial arrangement of six Gpi-2 genotypes and two exposure sequences (Control , Control; Control , 100 ,g/L Hg). The SMRs were estimated by measuring oxygen consumption using an indirect, closed-circuit, computer-controlled respirometer. A 48-h exposure to 100 ,g/L of mercury resulted in a 16.7% elevation of SMR above control levels (p = 0.001). The Gpi-2 genotype and the number of heterozygous loci per individual had no significant effect on SMR in mercury-exposed mosquitofish. The experimental results do not support the hypothesis that Gpi-2 genotype-specific differences in glycolytic and Krebs cycle metabolite pools and mortality in mosquitofish exposed to mercury are associated with differences in SMR. [source] Response of Daphnia magna to pulsed exposures of chlorpyrifos,ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 2 2000Rami B. Naddy Abstract Because aquatic organisms can be exposed to contaminants in an episodic manner, it is necessary to determine whether standard toxicity tests adequately simulate the toxicity of short-lived compounds, such as the organophosphate insecticide chlorpyrifos (CPF). We conducted experiments to evaluate the effect of binary combinations of concentration, duration, and interval of CPF exposures to Daphnia magna. Organisms were monitored for changes in survival and/or reproduction after pulsed exposure to CPF at 0.12, 0.25, 0.5, or 1.0 ,g/L. The exposure duration resulting in a 50% response in survival was 6.5 h at 1.0 ,g/L, 12.2 h at 0.5 ,g/L, and 48 h at 0.25 ,g/L. Daphnids exposed to two 12-h pulses of CPF at 0.5 ,g/L responded similarly (,85% mortality) regardless of the pulse interval (0, 3, 7, 14 d). However, daphnids were able to survive a 12-h exposure of CPF at 0.5 ,g/L if the exposure regime was separated into two 6-h pulses with a minimum interval of 3 d. Further experiments suggested that the interval studies may have been potentially confounded, because organisms exposed on day 3, 7, or 14 seemed more sensitive than those exposed as neonates. Additionally, no latent effects were measured for daphnids that survived the initial exposure. [source] Pollen beetle in the UK; the start of a resistance problem?EPPO BULLETIN, Issue 1 2008D. M. Richardson In 2003, the first report of poor control of pollen beetle Meligethes aeneus at a site in South East England in the UK was investigated but resistance to pyrethroid insecticides was not confirmed in subsequent laboratory testing. Bioassays of 26 UK samples of M. aeneus collected in 2004 with the pyrethroid lambda-cyhalothrin showed little or no divergence from the response expected of a fully susceptible strain. In 2006 samples of pollen beetle from the UK were sent to Germany, and again these were shown to be fully susceptible. In 2007 using test kits supplied by Udo Heimbach, BBA, 19 samples of pollen beetle were tested, again from across the UK. Results indicated that a small number of individuals were fully resistant, surviving the highest dose of lambda-cyhalothrin tested (0.375 microg/L) after 5-h exposure at 4 sites, and after 24-h exposure at 2 of these sites. [source] STED Microscopy to Monitor Agglomeration of Silica Particles Inside A549 Cells,ADVANCED ENGINEERING MATERIALS, Issue 5 2010Sabrina Schübbe The widespread use of engineered nanomaterials increases the exposure of the materials to humans. Therefore, it is necessary to know how these materials interact with cells. One approach is to trace particles by fluorescent labeling. The aim of the present work was to study the behavior of silica particles in A549 cells. For the first time, we applied stimulated emission depletion (STED) microscopy for this approach. Therefore, SiO2 particles conjugated with Atto647N were prepared by L -arginine-catalyzed hydrolysis of tetraethoxysilane. The Atto647N labeled SiO2 particles exhibit a mean size of 128,±,7,nm and a zeta-potential of ,11,mV in cell culture medium. STED microscopy enables subdiffraction resolution imaging of single Atto647N labeled SiO2 particles not only in pure solution but also in a cellular environment. To visualize Atto647N labeled SiO2 particles inside A549 cells, the membrane was labeled and image stacks, that give three-dimensional information, were taken after 5, 24, and 48 h exposure of particles to cells. During this incubation period, an increase in particle uptake was observed and STED micrographs allowed us to evaluate the agglomeration of Atto647N labeled SiO2 particles inside A549 cells. Our results show that STED microscopy is a powerful technique to study particles in a cellular environment. [source] Effects of Endotoxin Exposure on Cationic Amino Acid Transporter Function in Ovine Peripheral Blood Mononuclear CellsEXPERIMENTAL PHYSIOLOGY, Issue 2 2003Megan F. Clark Rodent models of sepsis differ from clinical human disease in that humans make substantially less whole-body nitric oxide and have different cellular responses to endotoxin. Sheep, when exposed to endotoxin, behave in a manner more similar to humans. Many studies of rodent peripheral blood mononuclear cells (PBMCs) exposed to endotoxin demonstrate increased cationic amino acid transporter function (particularly through the y+ transporter) to supply arginine substrate to upregulated nitric oxide synthase. Whether this is true in sheep is not known. We have studied cationic amino acid transport in sheep PBMCs stimulated with endotoxin, using labelled lysine. PBMCs stimulated both in vitro and in vivo show an initial reduction in total and y+ lysine transport (after 1-2 h exposure to endotoxin): a previously undescribed effect of endotoxin. In in vitro activated cells, the reduction in y+ transport was prevented by the lipoxygenase inhibitor, nordihydroguaretic acid (NDGA), and the phospholipase inhibitor 4-bromophenacyl bromide (4-BPAB), but not cyclohexamide or a number of other inhibitors of intracellular second-messenger pathways. In contrast after 14 h incubation, the expected increase in total and y+ lysine transport was seen. The increase in y+ transport could be prevented by cyclohexamide, dexamethasone, ibuprofen, the protein kinase C inhibitor sphingosine, NDGA and 4-BPAB. These results suggest that in response to endotoxin exposure there is an initial decrease in y+ activity mediated by a lipoxygenase product, followed by a substantial increase in y+ activity mediated by the products of either cyclo-oxygenase or lipoxygenase. Cyclo-oxygenase and/or lipoxygenase inhibition might be useful in reducing arginine transport, and hence nitric oxide production, in these cells. [source] Selenium affects biosilica formation in the demosponge Suberites domunculaFEBS JOURNAL, Issue 15 2005Effect on gene expression, spicule formation Selenium is a trace element found in freshwater and the marine environment. We show that it plays a major role in spicule formation in the demosponge Suberites domuncula. If added to primmorphs, an in vitro sponge cell culture system, it stimulates the formation of siliceous spicules. Using differential display of transcripts, we demonstrate that, after a 72-h exposure of primmorphs to selenium, two genes are up-regulated; one codes for selenoprotein M and the other for a novel spicule-associated protein. The deduced protein sequence of selenoprotein M (14 kDa) shows characteristic features of metazoan selenoproteins. The spicule-associated protein (26 kDa) comprises six characteristic repeats of 20 amino acids, composed of 10 distinct hydrophobic regions (, 9 amino acids in length). Recombinant proteins were prepared, and antibodies were raised against these two proteins. Both were found to stain the central axial filament, which comprises the silicatein, as well as the surface of the spicules. In the presence of selenium, only the genes for selenoprotein M and spicule-associated protein are up-regulated, whereas the expression of the silicatein gene remains unchanged. Finally we show that, in the presence of selenium, larger silica aggregates are formed. We conclude that selenium has a stimulatory effect on the formation of siliceous spicules in sponges, and it may be involved in the enzymatic synthesis of biosilica components. [source] The newly isolated lytic bacteriophages st104a and st104b are highly virulent against Salmonella entericaJOURNAL OF APPLIED MICROBIOLOGY, Issue 1 2006G. O'Flynn Abstract Aims:, To screen Irish faecal samples from a variety of sources with a view to isolating novel anti- Salmonella phages and to subsequently evaluate their lytic capability. Methods and Results:, Two novel anti- Salmonella phages st104a and st104b were isolated from a screening programme based on their lytic capability. The phages produced significantly larger plaques (2 mm) on the chosen indicator Salmonella enterica strain, DPC6046, when compared with the well-known control phage, Felix 01 (0·5 mm). Both phages st104a and st104b were found to have a broad host range within the Salm. enterica species. During in vitro trials, both phages (st104a and st104b) reduced Salm. enterica numbers more than 99% within 1 h. In vivo studies, involving the addition of the phage to porcine gastric juice (pH 2·5) demonstrated that phage st104a and phage Felix 01 were capable of surviving (10 and 30% survival respectively) the acidic conditions, unlike st104b, which was undetectable after 2 h exposure. Conclusions:, Two novel lytic anti- Salmonella phages were isolated and characterized. Significance and Impact of the Study:, With the exception of phage Felix 01, there has been relatively little phage therapy work performed using lytic Salmonella phage. In this study, the lytic phages st104a and st104b were isolated as a result of a faecal screening programme. Subsequently, phage st104a was found to have potential for biocontrol of Salm. enterica numbers if administered orally to pigs given their survival in porcine gastric juice, whereas, phage st104b may have potential in reducing cell numbers if applied by alternative approaches. [source] Effect of single and binary combinations of plant-derived molluscicides on different enzyme activities in the nervous tissue of Achatina fulicaJOURNAL OF APPLIED TOXICOLOGY, Issue 1 2003I. G. Rao Abstract Effect of single and binary treatments of plant-derived molluscicides on different enzymes,acetylcholinesterase (AChE), lactic dehydrogenase (LDH) and acid/alkaline phosphatase (ACP/ALP),in the nervous tissue of the harmful terrestrial snail Achatina fulica were studied. Sublethal in vivo 24-h exposure to 40% and 80% LC50 of Azadirachta indica oil, Cedrus deodara oil, Allium sativum bulb powder, Nerium indicum bark powder and binary combinations of A. sativum (AS) + C. deodara (CD) and CD + A. indica (AI) oils significantly altered the activity of these enzymes in the nervous tissue of Achatina fulica. The binary treatment of AS + CD was more effective against AChE, LDH, and ALP than the single ones. However, binary treatment of AI + CD was more effective against ALP. Copyright © 2003 John Wiley & Sons, Ltd. [source] Chronic toxicity/oncogenicity study of styrene in cd-1 mice by inhalation exposure for 104 weeksJOURNAL OF APPLIED TOXICOLOGY, Issue 3 2001George Cruzan Abstract Groups of 70 male and 70 female Charles River CD-1 mice were exposed whole body to styrene vapor at 0, 20, 40, 80 or 160 ppm 6 h per day 5 days per week for 98 weeks (females) or 104 weeks (males). The mice were observed daily; body weights, food and water consumption were measured periodically, a battery of hematological and clinical pathology examinations were conducted at weeks 13, 26, 52, 78 and 98 (females)/104 (males). Ten mice of each gender per group were pre-selected for necropsy after 52 and 78 weeks of exposure and the survivors of the remaining 50 of each gender per group were necropsied after 98 or 104 weeks. An extensive set of organs from the control and high-exposure mice were examined histopathologically, whereas target organs, gross lesions and all masses were examined in all other groups. Styrene had no effect on survival in males. Two high-dose females died (acute liver toxicity) during the first 2 weeks; the remaining exposed females had a slightly higher survival than control mice. Levels of styrene and styrene oxide (SO) in the blood at the end of a 6 h exposure during week 74 were proportional to exposure concentration, except that at 20 ppm the SO level was below the limit of detection. There were no changes of toxicological significance in hematology, clinical chemistry, urinalysis or organ weights. Mice exposed to 80 or 160 ppm gained slightly less weight than the controls. Styrene-related non-neoplastic histopathological changes were found only in the nasal passages and lungs. In the nasal passages of males and females at all exposure concentrations, the changes included respiratory metaplasia of the olfactory epithelium with changes in the underlying Bowman's gland; the severity increased with styrene concentration and duration of exposure. Loss of olfactory nerve fibers was seen in mice exposed to 40, 80 or 160 ppm. In the lungs, there was decreased eosinophilia of Clara cells in the terminal bronchioles and bronchiolar epithelial hyperplasia extending into alveolar ducts. Increased tumor incidence occurred only in the lung. The incidence of bronchioloalveolar adenomas was significantly increased in males exposed to 40, 80 or 160 ppm and in females exposed to 20, 40 and 160 ppm. The increase was seen only after 24 months. In females exposed to 160 ppm, the incidence of bronchiolo-alveolar carcinomas after 24 months was significantly greater than in the controls. No difference in lung tumors between control and styrene-exposed mice was seen in the intensity or degree of immunostaining, the location of tumors relative to bronchioles or histological type (papillary, solid or mixed). It appears that styrene induces an increase in the number of lung tumors seen spontaneously in CD-1 mice. Copyright © 2001 John Wiley & Sons, Ltd. [source] Overexpression of GSTA2 protects against cell cycle arrest and apoptosis induced by the DNA inter-strand crosslinking nitrogen mustard, mechlorethamineJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 2 2005Jingping Xie Abstract The effectiveness of bifunctional alkylating nitrogen mustard compounds in chemotherapy is related to their ability to form DNA inter-strand crosslinks. Patients exposed to DNA inter-strand crosslinking (ICL) agents subsequently experience an elevated incidence of myelodysplastic syndromes (MDS) and MDS related acute myeloid leukemia. Fanconi's anemia (FA) patients are deficient in the repair of crosslink DNA damage and they experience a high incidence of MDS. These observations indicate that hematopoietic cells are specific target for the transforming effects of DNA crosslinking damage. Changes in transcript levels were characterized in human hematopoietic cells occurring in response to the nitrogen mustard, mechlorethamine (HN2), but not in response to monofunctional analogs. Only modest changes in a few gene transcripts were detected in HL60 cells exposed to levels of HN2 tittered to maximal dose that caused growth suppression with minimal cell death and allowed eventual resumption of normal cell growth. Under conditions of transient growth suppression, a subset of glutathione-S-transferase (GST) isoenzyme genes was consistently upregulated three to fourfold by HN2, but not by monofunctional analogs. Subsequent efforts to confirm the changes detected by microarray analyses revealed an unexpected dependence on treatment conditions. The GST alpha class A2 subfamily member transcripts were upregulated 24 h after a 1 h exposure to HN2 that caused an extensive, but transient block in late S/G2 cell cycle phase, but were minimally altered with continuous exposure. The 1-h exposure to HN2 caused a transient late S/G2 cell cycle arrest in both the HL-60 cell line and the Colo 320HSR human colon cancer cell line. Overexpression of GSTA2 by transient transfection protected Colo 320HSR cells against both cycle arrest and apoptosis following exposure to HN2. Overexpression of GSTA2 in Colo 320HSR cells induced after exposure to HN2 did not alter cycle arrest or apoptosis. The results indicate that human GSTA2 facilitates the protection of cells from HN2 damage and not repair. Our results are consistent with the possibility that GSTA2 polymorphisms, variable isoenzyme expression, and variable induced expression may be factors in the pathogenesis of MDS. © 2005 Wiley-Liss, Inc. [source] Mechanisms involved in hydroxycamptothecin-induced apoptosis of gastric cancer cellsJOURNAL OF DIGESTIVE DISEASES, Issue 1 2002Shui Ping TU OBJECTIVE: Hydroxycamptothecin (HCPT) is a unique antitumor drug that acts directly on topoisomerase I and inhibits its activity. However, the mechanism of HCPT-induced apoptosis is unclear. In the present study, the mechanism of HCPT-induced apoptosis in gastric cancer cells was investigated by detecting the expression of p53, c - myc, bcl-2, bcl-xl and bcl-xs genes in gastric cancer cells. METHODS: Apoptosis of gastric cancer cells (SGC-7901, MKN-45) was determined by terminal deoxyribonucleotidyl transferase-mediated dUTP, digoxigenin nick-end labeling (TUNEL) and flow cytometry. The mRNA and protein levels of the p53, c-myc, bcl-2, bcl-xl and bcl-xs genes were tested by reverse transcription,polymerase chain reaction analysis and immunocytochemical stain, respectively. RESULTS: Hydroxycamptothecin may induce apoptosis in different differentiated gastric cancer cells. The effect of HCPT-induced apoptosis on gastric cancer cells was dependent on the dose of HCPT used and the time of exposure to HCPT. Both SGC-7901 and MKN-45 cells manifested some morphological features of apoptosis after 12 h exposure to HCPT, including cell shrinkage, nuclear condensation, DNA fragmentation and formation of apoptotic bodies. Some typical subdiploid peaks before the G0/G1 phase were observed. The apoptotic rates induced by 10 ,g/mL HCPT in SGC-7901 and MKN-45 cells were 21.88 and 12.34%, respectively. The mRNA and protein levels of p53 and bcl-2 were downregulated after treatment with HCPT in SGC-7901 cells. However, the c-myc, bcl-xl and bcl-xs protein levels were unchanged in SGC-7901 cells. In MKN-45 cells, the mRNA and protein levels of p53 increased after treatment with HCPT, whereas the protein levels of bcl-2, c-myc, bcl-xl and bcl-xs remained unchanged. CONCLUSIONS: Our results indicate that HCPT-induced apoptosis in gastric cancer cells may be regulated through modulation of the expression of p53 and bcl-2 genes. [source] Effects on acid-base balance, methaemoglobinemia and nitrogen excretion of European eel after exposure to elevated ambient nitriteJOURNAL OF FISH BIOLOGY, Issue 3 2002C.-Y. Huang Haemoglobin, methaemoglobin, blood nitrite concentration and acid-base balance were measured in European eel Anguilla anguilla following exposure to 0 (control), 0·142, 0·356, 0·751 and l·549 mM nitrite in fresh water for 24 h. Blood GOT (glutamate oxaloacetate transaminase) and GPT (glutamate pyruvate transaminase) activities and whole animal ammonia-N and urea-N excretions were also measured. Blood nitrite, methaemoglobin, PO2 (oxygen partial pressure), GOT, and whole animal ammonia-N excretion and urea-N excretion increased directly with increasing ambient nitrite concentrations, whereas blood pH, PCO2, and HCO,3 were inversely related to ambient nitrite concentration. An accumulation of nitrite in the blood of A. anguilla following 24 h exposure to elevated ambient nitrite as low as 0·751 mM increased its blood methaemoglobin, PO2, GOT and nitrogen excretion, but decreased its PCO2 (carbon dioxide partial pressure), HCO,3 and functional haemoglobin. [source] The effect of parental acclimation to spawning salinity on the survival of larval Cynoscion nebulosusJOURNAL OF FISH BIOLOGY, Issue 3 2002C. J. Kucera The yolk and oil depletion of eggs and larvae of spotted seatrout Cynoscion nebulosus, produced by fish collected from two bays with historically different salinity regimes (Matagorda Bay (MB; 18-24%) and Upper Laguna Madre (ULM; 40,50%), Texas, U.S.A. and spawned in salinities of 20, 30 and 40%, differed in their response to both salinity and history. Time to 90% yolk depletion was significantly longer for low salinity bay fish (MB) kept at 20%, but not for high salinity bay fish (ULM) at 20%. The neutral buoyancy salinity of 1 and 2 day old MB 20% larvae was significantly lower than that of MB larvae spawned in 30 or 40%. Overall, eggs and larvae spawned by MB fish were able to hatch out and survive to 3 days post-hatch in lower salinities than those from ULM. Furthermore, the tolerance of eggs and larvae to very low salinities increased with decreasing spawning salinity. The ability of 1,9 day old ULM, but not MB, larvae to survive 18 h exposure to salinities above or below that of spawning exhibited an age-dependent pattern with day 3 being the most sensitive. This study shows that the response of spotted seatrout eggs and larvae to changes in salinity is dependent upon the spawning salinity of the adults and the prevailing salinity regime within the bay. [source] Susceptibility of channel catfish, Ictalurus punctatus (Rafinesque), to Edwardsiella ictaluri challenge following copper sulphate exposureJOURNAL OF FISH DISEASES, Issue 10 2007B R Griffin Abstract Channel catfish, Ictalurus punctatus (Rafinesque), with or without a preliminary 24 h exposure to 2 mg copper sulphate L,1, were challenged with 7.5 × 106 colony forming units L,1 of Edwardsiella ictaluri to determine the effect of copper sulphate on disease resistance. Catfish previously exposed to copper sulphate were significantly more resistant to the bacterial challenge than those not exposed. Catfish not exposed to copper sulphate suffered 35.5% mortality while catfish exposed to copper sulphate experienced 14.1% mortality. Copper concentrations were the same in tank waters of both exposed and control fish at the time of challenge, eliminating the possibility that copper in the water may have been toxic to bacteria. Copper concentrations in freeze dried and ground tissues of unexposed, exposed, and purged channel catfish were highest in fish before copper sulphate exposures suggesting that elevated tissue levels of copper were not responsible for the increased resistance to bacterial challenge. Competition for sites of bacterial attachment to gill or epithelial cells may account for the reduction in mortality; although this is not supported by the low copper content of fish tissue after copper exposure. [source] Effect of endotoxin pretreatment on hepatic stellate cell response to ethanol and acetaldehydeJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 11 2001Silvia C Quiroz Abstract Background and Aim: The role of endotoxin in alcohol-induced liver damage is well recognized. How pre-exposure to endotoxin might affect alcohol injury is not known. We herein studied the effect of endotoxin pretreatment on hepatic stellate cell (HSC) response to ethanol and acetaldehyde. Methods: Rat HSC (CFSC-2G) were exposed to media supplemented with 1 ,g/mL lipopolysaccharide (LPS). This was followed by a 24 h exposure to media containing LPS plus 50 mmol/L ethanol or 175 ,mol/L acetaldehyde. Lipid peroxidation, collagen, and tumor necrosis factor (TNF)-,, interleukin (IL)-1,, IL-6 and transforming growth factor (TGF)-,1 secretion were determined at the end of both periods of exposure. Results: Lipopolysaccharide pretreatment did not modify lipid peroxidation induced by ethanol or acetaldehyde alone. Glutathione (GSH) content decreased to 4.2 ± 0.5 and 16.3 ± 0.8 nmol protein after exposure to ethanol or acetaldehyde alone, and decreased further with LPS pretreatment (2.4 ± 0.2 and 2.7 ± 0.3 nmol/mg protein, respectively). Oxidized GSH (GSSG) content increased in ethanol and acetaldehyde LPS-pretreated cells only. Collagen secretion increased to 988 ± 82 and 1169 ± 91 ,g/106 cells after exposure to acetaldehyde or LPS alone. Lipopolysaccharide pretreatment enhanced collagen secretion significantly in both ethanol- and acetaldehyde-treated cells (969 ± 56 and 1360 ± 72 ,g/106 cells, respectively). Interleukin-6 production increased to 288 ± 48, 1195 ± 86 and 247 ± 35 pg/mL per 106 cells after ethanol, acetaldehyde and LPS exposure, and increased further with LPS pretreatment in ethanol-exposed cells (680 ± 23 pg/mL 106 cells). Conclusion: Lipopolysaccharide pretreatment of HSC adds to the damage produced by ethanol and acetaldehyde by diminishing GSH content and increasing GSSG content, collagen and IL-6 secretion. [source] Mechanism of the protective effect of hypothermia on ammonia toxicity in astrocytesJOURNAL OF NEUROCHEMISTRY, Issue 2002C. Zwingmann Ammonia is a key factor in the pathogenesis of hepatic encephalopathy (HE). Acute ammonia treatment causes energy failure of astrocytes, which are able to compensate partly by increased anaerobic metabolism as a means of making up for the energetic shortfall. As hypothermia offers protection from severe encephalopathy and lactate accumulation in liver failure, we investigated the mechanism by which hypothermia protects against ammonia toxicity by multinuclear NMR spectroscopy. 12 h exposure to 5 mm NH4CL decreased the phosphocreatine (PCr)/creatine (Cr) and ATP/ADP ratios to 65 and 76% of control, increased synthesis and release of glutamine to 200,250% and led to a significant stimulation of glycolytic activity reflected by increased uptake and consumption of glucose and accumulation of de novo synthesized intra- and extracellular lactate to 161 and 230% of control. The protective effect of mild hypothermia was evident from inhibiton of lactate accumulation and restoration of ammonia-induced depletion of PCr/Cr. Moderate hypothermia led to an increase of PCr/Cr ratio and inhibited lactate synthesis to 14% of normothermic control, but did not prevent the ATP decrease. While hypothermia inhibited glycolytic flux, intracellular glutamine remained elevated. The results suggest that hypothermia-induced protection against ammonia toxicity results from reduction of cellular energy demand leading to inhibition of anaerobic glucose metabolism and a compensatory stimulation of mitochondrial energy production. Acknowledgements:, Funded by CIHR Canada. [source] Antibacterial activity of silver inorganic agent YDA fillerJOURNAL OF ORAL REHABILITATION, Issue 4 2004S. Ohashi summary, YDA filler is an antibacterial agent that is currently in commercial dental use. In this study, we attempted to determine whether it exerts an antibacterial effect on human saliva bacteria, and to determine whether it can be used in dental materials. CFUs in 1 mL stimulated human saliva were examined using blood agar and mitis salivarius agar after immersion, with or without YDA filler. The antibacterial effect was compared with that of Ketac-Silver. Dental materials containing 5% wt YDA filler were prepared for in vitro testing on S. mutans and A. viscosus. Furthermore, we examined the in vitro cytotoxicity of experimental MMA resin containing YDA filler on HeLa cells. Human saliva bacteria and mutans streptococci showed reduced viability following exposure to YDA filler after 12 h. The concentration of silver ions released by YDA filler was below 1 ppm after 12 h. Two tested strains showed reduced viability following exposure to dental materials containing YDA filler. In another experiment, MMA resin containing YDA filler did not show cytotoxicity on HeLa cells after 24- and 48-h exposure. Thus, YDA filler may help in the development of antibacterial dental materials, such as composite resin, glass,ionomer or temporary cement. [source] A comparison of the in vitro cytotoxicity of two root canal sealersJOURNAL OF ORAL REHABILITATION, Issue 4 2003M. Dartar Öztan summary, The purpose of this study was to compare the cytotoxicity of an epoxy resin-based sealer (AH Plus) and a silicone-based sealer (Roeko Seal Automix, RSA). Cytotoxicity was assessed using the MTT assay for mitochondrial enzyme activity and haemocytometer viable cell counting after 24, 48 and 72-h exposure to L929 cells. AH Plus and RSA showed no statistically significant difference in the degree of toxicity. Both sealers had a low toxic influence on the cells during the experimental period. This study indicates that epoxy resin-based sealer AH Plus and the silicone-based sealer RSA have similar levels of cytotoxicity to mouse fibroblasts. [source] A novel synthetic peptide vector system for optimal gene delivery to bone marrow stromal cellsJOURNAL OF PEPTIDE SCIENCE, Issue 3 2007Pan Haitao Abstract A 23-amino acid, bifunctional, integrin-targeted synthetic peptide was evaluated for ex vivo gene delivery to rabbit bone marrow stromal cells (BMSCs). The peptide (K)16GRGDSPC consists of an amino terminal domain of 16 lysines for electrostatic binding of DNA, and a 7-amino acid integrin-binding domain at the carboxyl terminal. PcDNA3-EGFP plasmids were transfected into BMSCs by (K)16GRGDSPC and the positive cells gave out a bright green fluorescence. High levels of gene delivery of pcDNA3-TGF-,1 plasmids were obtained with 2 to 4 µg/ml DNA concentration, with (K)16GRGDSPC at an optimal peptide: DNA w/w ratio of 3:1, with a required exposure time of more than 4 h but shorter than 24 h for BMSC exposure to the peptide/DNA complexes with completely absent serum in the initial stage; with 100 µM chloroquine and at least 8 h exposure for BMSC exposure to chloroquine; with a fusogenic peptide at an optimal (K)16GRGDSPC/DNA/fusogenic peptide w/w ratio of 3:1:5; and with Lipofectamine 2000 at an optimal (K)16GRGDSPC/DNA/Lipofectamine 2000 w/w ratio of 3:1:2 at a constant DNA concentration of 2 µg/ml. Chloroquine, the fusogenic peptide and Lipofectamine 2000 all significantly promoted gene delivery, but chloroquine was more effective than the fusogenic peptide and had obvious synergistic effects with Lipofectamine 2000. Under optimal conditions, TGF-,1 gene was transfected into BMSCs without observable toxicity, and the stable expression was examined by RT-PCR and Western blot analysis. The stable transgenic cells showed obvious bands. This novel synthetic peptide, providing a new way for the use of polylysine and RGD motif in DNA vector system, is potentially well suited to ex vivo gene delivery to BMSCs for experimental and clinical applications in the field of bone tissue engineering. Copyright © 2006 European Peptide Society and John Wiley & Sons, Ltd. [source] EFFECT OF COPPER ON ALGAL COMMUNITIES FROM OLIGOTROPHIC CALCAREOUS STREAMS1JOURNAL OF PHYCOLOGY, Issue 2 2002Helena Guasch Two sets of experiments were done to quantify the effects of chronic copper exposure on natural peri- phyton in a nonpolluted calcareous river. The results of short-term (up to 6 h exposure) experiments corroborated the significance of pH on copper toxicity. Copper toxicity increased when pH was reduced from 8.6 to 7.7, and this was related to the effect of pH on copper speciation (free copper concentration increased from 0.2% to 2.3% of total copper). Longer term experiments demonstrated that periphyton communities exposed to copper under pH variation (8.2,8.6) were already affected at 10 ,g·L,1 (20,80 ng·L,1 Cu2+) after 12 days of exposure. Copper exposure caused stronger effects on structural (algal biomass and community structure) than on functional (photosynthetic efficiency) parameters of peri- phyton. Changes in community composition included the enhancement of some taxa (Gomphonema gracile), the inhibition of others (Fragilaria capucina and Phormidium sp.), and the appearance of filament malformations (Mougeotia sp.). The results of our study demonstrated that several weeks of exposure to copper (10,20 ,g·L,1) were sufficient to cause chronic changes in the periphyton of oligotrophic calcareous rivers. This degree of copper pollution can be commonly found in the Mediterranean region as a result of agricultural practices and farming activities. [source] | ||||||||||||||||||||||