Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Accumulation

  • abnormal accumulation
  • acid accumulation
  • asset accumulation
  • biomass accumulation
  • brain iron accumulation
  • ca2+ accumulation
  • cadmium accumulation
  • camp accumulation
  • capital accumulation
  • carbohydrate accumulation
  • carbon accumulation
  • catenin accumulation
  • cd accumulation
  • cell accumulation
  • cellular accumulation
  • cgmp accumulation
  • chlorophyll accumulation
  • collagen accumulation
  • concomitant accumulation
  • copper accumulation
  • cyclic gmp accumulation
  • cytoplasmic accumulation
  • damage accumulation
  • decreased accumulation
  • drug accumulation
  • dry matter accumulation
  • electron accumulation
  • enhanced accumulation
  • eosinophil accumulation
  • excessive accumulation
  • extensive accumulation
  • fat accumulation
  • fe accumulation
  • fluid accumulation
  • gas accumulation
  • glycogen accumulation
  • gradual accumulation
  • greater accumulation
  • h2o2 accumulation
  • heavy metal accumulation
  • hepatic iron accumulation
  • high accumulation
  • highest accumulation
  • histamine accumulation
  • human capital accumulation
  • hydrocarbon accumulation
  • increased accumulation
  • increased intracellular accumulation
  • intracellular accumulation
  • ion accumulation
  • iron accumulation
  • knowledge accumulation
  • large accumulation
  • leukocyte accumulation
  • lipid accumulation
  • lipofuscin accumulation
  • litter accumulation
  • local accumulation
  • macrophage accumulation
  • marked accumulation
  • massive accumulation
  • matrix accumulation
  • matter accumulation
  • maximum accumulation
  • mercury accumulation
  • metal accumulation
  • mrna accumulation
  • mucus accumulation
  • n accumulation
  • na+ accumulation
  • neutrophil accumulation
  • nitrite accumulation
  • nuclear accumulation
  • nutrient accumulation
  • oil accumulation
  • organic matter accumulation
  • p accumulation
  • peat accumulation
  • petroleum accumulation
  • phosphate accumulation
  • plaque accumulation
  • preferential accumulation
  • progressive accumulation
  • proline accumulation
  • protein accumulation
  • rainfall accumulation
  • rapid accumulation
  • ro accumulation
  • se accumulation
  • sediment accumulation
  • selective accumulation
  • significant accumulation
  • snow accumulation
  • species accumulation
  • specific accumulation
  • starch accumulation
  • sugar accumulation
  • surface accumulation
  • tissue accumulation
  • transcript accumulation
  • triglyceride accumulation
  • virus accumulation
  • wealth accumulation
  • wood accumulation
  • zinc accumulation
  • zn accumulation

  • Terms modified by Accumulation

  • accumulation curve
  • accumulation decreased
  • accumulation efficiency
  • accumulation layer
  • accumulation level
  • accumulation pattern
  • accumulation period
  • accumulation potential
  • accumulation process
  • accumulation rate
  • accumulation step
  • accumulation time

  • Selected Abstracts


    EVOLUTION, Issue 1 2003
    Abstract., A simple, deterministic analysis predicts that accumulation of Dobzhansky-Muller incompatibilities by a spatially structured population strongly depends on the number of negative interactions of an allele. If an allele can be incompatible with alleles at only one locus, incompatibilities accumulate linearly with time. In contrast, if an allele can participate in multiple pairwise incompatibilities with alleles at different loci, the expected number of incompatibilities eventually increases quadratically. [source]


    The elicitation of cystatin accumulation in tomato leaves was studied with mature and seedling cv. Bonnie Best. Repetitive mechanical injury (MI) or methyl jasmonate (MJ) treatment of seedlings elicited plentiful cystatin accumulation in the leaves when plants were held at 30C under continuous lighting. Cystatin accumulation in leaves of MI seedlings decreased by 50% when incubated at a reduced light period of 12 h light/day. Cystatin accumulation in MJ treated plants was not influenced by reducing the light period from 24 h to 12 h/day. Cystatin accumulation after MJ treatment was optimal at 35C and negligible at 40C. At ambient field conditions (I8,33C), MJ treated seedlings still accumulated a significant amount of cystatin; however, very little cystatin accumulated in leaves of MI seedlings under these conditions of lower temperature and light exposure. The leaves of mature plants accumulated less cystatin after MJ or MI treatment than did those of seedlings. [source]


    L. BULUT
    ABSTRACT Quality reduction in honey during storage is indicated by hydroxymethylfurfural (HMF) accumulation and darkening of color. The effects of moisture content and temperature on HMF accumulation and color change in honey during storage were investigated. HMF accumulation and color change followed first- and zero-order reaction kinetics, respectively. The moisture content affected the rate of the two degradation reactions depending on the storage temperature. Reduction in moisture content caused an increase in rate constant for HMF accumulation at 20 and 30C, but there was no significant effect of moisture content at 40C. Rate constants for change in lightness and total color change values increased with increasing moisture content at 20 and 30C. The highest rate constant for change in color values was obtained at a moisture content of 18% at 40C. PRACTICAL APPLICATIONS Hydroxymethylfurfural accumulation and color change are two major quality degradations in honey during storage. This study shows that the rates of these two degradations are dependent on moisture content of honey. In addition, effect of moisture content on the rates of reactions was dependent on temperature of storage. Therefore, producers need to consider the effects of both moisture content and storage temperature in reducing quality loss in honey during storage. [source]


    JOURNAL OF PHYCOLOGY, Issue 3 2006
    Rochelle G. Labiosa
    Phytoplankton in nature must acclimate to a wide range of light conditions resulting from diel light cycles, ocean circulation and mixing, cloud cover, and the variable bio-optical characteristics of the water column. In this study, we used whole-genome cDNA microarrays to investigate the effects of a gradually fluctuating daily light cycle on gene expression in the cyanobacterium Synechocystis sp. strain PCC6803. From these data, we developed a conceptual framework depicting the diel regulation of metabolic pathways in the cell. The framework is focused on potential photoacclimation responses, including the regulation of the photosystems, cell division, and DNA replication. The mRNA abundance of genes involved in many metabolic pathways, and particularly those encoding proteins that function in photosynthesis and DNA replication, changed markedly over the course of the day. The levels of mRNA encoding polypeptides important for the formation of the light-harvesting apparatus, photosystems I and II, and cell division were found in high concentrations during the day. The transcript levels of many genes encoding enzymes involved in anabolic processes also increased considerably during the day. In contrast, transposon transcripts and mRNAs encoding proteins involved in DNA replication, cell wall synthesis, and respiratory activity were not found in high concentrations during the day. Although gradually varying light exposure induced significant changes in transcript accumulation within Synechocystis, the direction of these changes differed between our study and previous studies in which there was an abrupt transition between irradiances. [source]


    JOURNAL OF PHYCOLOGY, Issue 3 2003
    Francesco Pomati
    The metabolic effect of three different concentrations of lidocaine hydrochloride (0.01, 0.1, and 1 ,M) on growth and saxitoxin (STX) production of the freshwater cyanobacterium Cylindrospermopsis raciborskii (Wolosznska) T3 was analyzed. Lidocaine hydrochloride increased both the growth rate and the final growth yield in the toxic cyanobacterium, with a maximum of 25% and 18% for a 1-,M dose, respectively. Moreover, C. raciborskii T3 samples harvested at the end of the growth phase and analyzed for STX content by HPLC showed an increase in STX intracellular concentration of 14.3% and 49.3% after exposure to 0.01 and 0.1 ,M lidocaine hydrochloride, respectively, whereas 1 ,M lidocaine hydrochloride resulted in a 114% incremental change in STX content. The time course of the 1-,M lidocaine hydrochloride effect showed the highest rate of increase in mean STX intracellular concentration (298%) within the first 2 h after induction. The increase in STX content induced by lidocaine hydrochloride in C. raciborskii T3 was dependent on the concentration of Na+ ions in the culture medium and alkaline pH. The results suggest a possible action of lidocaine hydrochloride on membrane ion fluxes and the hypothesis of a potential linkage between cyanobacterial homeostasis and STX regulation. [source]


    JOURNAL OF PHYCOLOGY, Issue 2 2002
    Mirash Zhekisheva
    The chlorophyte Haematococcus pluvialis accumulates large quantities of astaxanthin under stress conditions. Under either nitrogen starvation or high light, the production of each picogram of astaxanthin was accompanied by that of 5 or 3,4 pg of fatty acids, respectively. In both cases, the newly formed fatty acids, consisting mostly of oleic (up to 34% of fatty acids in comparison with 13% in the control), palmitic, and linoleic acids, were deposited mostly in triacylglycerols. Furthermore, the enhanced accumulation of oleic acid was linearily correlated with that of astaxanthin. Astaxanthin, which is mostly monoesterified, is deposited in globules made of triacylglycerols. We suggest that the production of oleic acid-rich triacylglycerols on the one hand and the esterification of astaxanthin on the other hand enable the oil globules to maintain the high content of astaxanthin esters. [source]


    METROECONOMICA, Issue 4 2004
    Gilberto Tadeu Lima
    ABSTRACT This paper develops a post-Keynesian dynamic model of accumulation, growth and distribution in which endogenous technological innovation plays a significant role. Firms' rate of labour-saving technological innovation is made to depend non-linearly on the distributive (wage and profit) shares, with the latter determining both the incentives to innovate and the availability of funding to carry it out. As it turns out, the direction and the intensity of the effect of a change in distribution on the rates of accumulation and growth depend on the prevailing distribution, with a similar dependence applying,alongside the relative bargaining power of capitalists and workers,to the dynamic stability properties of the system. Hence, the model does not rely on full capacity utilization being reached for a change in the accumulation and growth regime to take place. [source]


    Our results show that there is no single explanation for the growth performance of the countries in our sample. The results, particularly with reference to the role of embodied technology are comforting in terms of policy implications for countries such as Singapore, where, given the capital output ratios, there are lower returns to future capital accumulation. The possibility of capital being embodied through technological change makes future prospects much brighter for such a country. [source]


    In this paper, we construct a three-sector endogenous growth model in which long-run growth is propelled by human capital accumulation. We show that although the addition of a home sector to the standard two-sector endogenous growth model preserves the well-behaved balanced growth equilibrium properties, it generates new transitional dynamics around the balanced growth path. It is shown that, when there is a positive shock to physical capital, our model is more likely to exhibit paradoxical growth than are standard multisector endogenous growth models that exclude home production. Our analysis adds new results to those from the related literature on leisure. [source]


    Article first published online: 15 JAN 2010, OSCAR AFONSO
    We present a dynamic, non-scale general equilibrium model with two human-capital types where Schumpeterian R&D and human-capital accumulation are the engines of growth and wage inequality. In particular, wage inequality is encouraged by relative changes in supply and demand of both human-capital types. Relative supply restricts employed human-capital levels. Relative demand is instantly affected by a new general-purpose technology and, as in the skill-biased technological change literature, by technological-knowledge bias. By considering substitutability between technologies and complementarity between inputs, the bias is driven by the price channel (not by the market-size channel) and is affected by human-capital accumulation. [source]


    ARCHAEOMETRY, Issue 4 2010
    T. De TORRES
    The age of Neanderthal remains and associated sediments from El Sidrón cave has been obtained through different dating methods (14CAMS, U/TH, OSL, ESR and AAR) and samples (charcoal debris, bone, tooth dentine, stalagmitic flowstone, carbonate-rich sediments, sedimentary quartz grains, tooth enamel and land snail shells). Detrital Th contamination rendered Th/U dating analyses of flowstone unreliable. Recent 14C contamination produced spurious age-values from charcoal samples as well as from inadequately pretreated tooth samples. Most consistent 14C dates are grouped into two series: one between 35 and 40 ka and the other between 48 and 49 ka. Most ESR and AAR samples yielded concordant ages, ranging between 39 and 45 ka; OSL dating results permitted adequate bracketing of the sedimentary layer that contained the human remains. Our results emphasize the value of multi-dating approaches for the establishment of reliable chronologies of human remains. [source]


    A. Racey
    Eocene nummulite accumulations, also referred to as nummullte "banks", form Important hydrocarbon reservoirs in Tunisia and Libya and may constitute exploration targets in other parts of North Africa, the Mediterranean and the Middle East. Porosities commonly average 10,20% and permeabilities 10,50md. Foraminifera of the genus Nummulites may comprise up to 98% of the bioclasts in these carbonate reservoirs, although only one or two species may be present. The absence of associated fauna is generally taken to indicate an oligotrophic depositional environment. In this paper, the palaeoecology of the genus Nummulites is discussed together with depositional models for two nummulitic carbonate reservoirs , the Middle Eocene Seeb Limestone of Oman and the Early Eocene El Garia/Jdeir Formation of Tunisia and Libya. The El Garia and Seeb Limestone Formations were deposited in ramp settings, and comprise a series of amalgamated sheets or low-relief banks. In the Hasdrubal field offshore Tunisia, where the El Garia Formation constitutes the reservoir rock, most of the nummulites have been redeposited from shallow into deeper waters whilst in the Bourri field (offshore Libya) they occur as an in situ "bank". Nummulite accumulations often show evidence that both physical reworking (scouring, winnowing and imbrication) and biological processes (reproduction strategies and bioturbation) have influenced their formation. A general model is outlined for discriminating between physically and ecologically produced biofabrics, and the implications for reservoir quality are discussed. [source]

    Greater growth hormone and insulin response in women than in men during repeated bouts of sprint exercise

    ACTA PHYSIOLOGICA, Issue 2 2009
    M. Esbjörnsson
    Abstract Aim:, In a previous study, sprint training has been shown to increase muscle cross-sectional area in women but not in men [Eur J Appl Physiol Occup Physiol 74 (1996) 375]. We hypothesized that sprint exercise induces a different hormonal response in women than in men. Such a difference may contribute to explaining the observed gender difference in training response. Method:, Metabolic and hormonal response to three 30-s sprints with 20-min rest between the sprints was studied in 18 physically active men and women. Results:, Accumulation of blood lactate [interaction term gender (g) × time (t): P = 0.022], and plasma ammonia (g × t: P < 0.001) after sprint exercise was greater in men. Serum insulin increased after sprint exercise more so in women than in men (g × t: P = 0.020), while plasma glucose increased in men, but not in women (g × t: P < 0.001). Serum growth hormone (GH) increased in both women and men reaching similar peak levels, but with different time courses. In women the peak serum GH level was observed after sprint 1, whereas in men the peak was observed after sprint 3 (g × t; P < 0.001). Serum testosterone tended to decrease in men and increase in women (g × t: P = 0.065). Serum cortisol increased approx. 10,15% after sprint exercise, independent of gender (time: P = 0.005). Conclusion:, Women elicited a greater response of serum GH and insulin to sprint exercise. This may contribute to explaining the earlier observed muscle hypertrophy in women in response to sprint training. [source]

    The Effects of a Baby Boom on Stock Prices and Capital Accumulation in the Presence of Social Security

    ECONOMETRICA, Issue 2 2003
    Andrew B. Abel
    Is the stock market boom a result of the baby boom? This paper develops an overlapping generations model in which a baby boom is modeled as a high realization of a random birth rate, and the price of capital is determined endogenously by a convex cost of adjustment. A baby boom increases national saving and investment and thus causes an increase in the price of capital. The price of capital is mean,reverting so the initial increase in the price of capital is followed by a decrease. Social Security can potentially affect national saving and investment, though in the long run, it does not affect the price of capital. [source]

    Financialization and the Role of Real Estate in Hong Kong's Regime of Accumulation

    ECONOMIC GEOGRAPHY, Issue 2 2003
    Alan Smart
    Abstract: The greater dominance of finance in the global economic system is widely considered to have increased instability and created difficulties in constructing modes of regulation that could stabilize post-Fordist regimes of accumulation. Heightened competition and the discipline of global finance restrict the use of Fordist strategies that expand social wages to balance production and consumption. Robert Boyer suggested a model for a possible stable finance-led growth regime. His hypothesis is that once there are sufficient stocks of property in a nation, expenditures that are based on capital gains, dividends, interest, and pensions can compensate for diminished wage-based demand. We contend that the neglect of real estate is a serious limitation, since housing wealth is more significant than other forms of equity for most citizens, and thus that it fails to capture the impact of the perceptions and choices of ordinary citizens. We then argue that features of a finance-led regime of accumulation and a property-based mode of regulation appeared in Hong Kong relatively early. A case study of Hong Kong is used to extend Boyer's discussion, as well as to diagnose Hong Kong's experience for its lessons on the impact of such developments. [source]

    Poverty Traps and Human Capital Accumulation

    ECONOMICA, Issue 270 2001
    Carlotta Berti Ceroni
    In this paper I show that persistent inequality in the distribution of human capital and a negative relation between initial inequality and steady-state aggregate output may follow from the fact that the poor require relatively higher returns to increase expenditure on education. Moreover, I show that poverty traps emerging in models where individual transitions do not depend on aggregate dynamics, though not robust to the introduction of idiosyncratic uncertainty, may still be relevant observationally, if idiosyncratic shocks occur with low probability. In this context, I also analyse the implications of introducing a public education system. [source]

    Accumulation and filtering of nanoparticles in microchannels using electrohydrodynamically induced vortical flows

    ELECTROPHORESIS, Issue 14 2008
    Maika Felten
    Abstract We present an approach for the accumulation and filtering of nano- and microparticles in microfluidic devices that is based on the generation of electric traveling waves in the radio-frequency range. Upon application of the electric field via a microelectrode array, complex particle trajectories and particle accumulation are observed in well-defined regions in a microchannel. Through the quantitative mapping of the 3-D flow pattern using two-focus fluorescence cross-correlation spectroscopy, two vortices could be identified as one of the sources of the force field that induces the formation of particle clouds. Dielectrophoretic forces that directly act on the particles are the second source of the force field. A thorough 2-D finite element analysis identifies the electric traveling wave mechanism as the cause for the unexpected flow behavior observed. Based on these findings, strategies are discussed, first, for avoiding the vortices to optimize electrohydrodynamic micropumps and, secondly, for utilizing the vortices in the development of microdevices for efficient particle accumulation, separation, and filtering. Such devices may find numerous biomedical applications when highly diluted nano- and microsuspensions have to be processed. [source]

    Dermal benzene and trichloroethylene induce aneuploidy in immature hematopoietic subpopulations in vivo

    Cynthia R. Giver
    Abstract Accumulation of genetic damage in long-lived cell populations with proliferative capacity is implicated in tumorigenesis. Hematopoietic stem cells (hsc) maintain lifetime hematopoiesis, and recent studies demonstrate that hsc in leukemic patients are cytogenetically aberrant. We postulated that exposure to agents associated with increased leukemia risk would induce genomic changes in cells in the hsc compartment. Aneusomy involving chromosomes 2 and 11 in sorted hsc (Lin,c-kit+Sca-1+) and maturing lymphoid and myeloid cells from mice that received topical doses of benzene (bz) or trichloroethylene (TCE) was quantified using fluorescence in situ hybridization. Six days after bz or TCE exposure, aneuploid cells in the hsc compartment increase four- to eightfold in a dose- and schedule-independent manner. Aneuploid lymphoid and myeloid cells from bz- and TCE-treated mice approximate controls, except after repeated benzene exposures. Aneuploid cells are more frequent in the hsc compartment than in mature hematopoietic subpopulations. Hematotoxicity was also quantified in bz- and TCE-exposed hematopoietic subpopulations using two colony-forming assays: CFU-GM (colony-forming units/granulocyte-macrophage progenitors) and CAFC (cobblestone area,forming cells). Data indicate that bz is transiently cytotoxic (,1 week) to hsc subpopulations, and induces more persistent toxicity (>2 weeks) in maturing, committed progenitor subpopulations. TCE is not hematotoxic at the doses applied. In conclusion, we provide direct evidence for induction of aneuploidy in cells in the hsc compartment by topical exposure to bz and TCE. Disruption of genomic integrity and/or toxicity in hsc subpopulations may be one step in leukemic progression. Environ. Mol. Mutagen. 37:185,194, 2001. © 2001 Wiley-Liss, Inc. [source]

    Accumulation of toxic metals (Pb and Cd) in the sea urchin Diadema aff. antillarum Philippi, 1845, in an oceanic island (Tenerife, Canary Islands)

    Ofelia Dolores Hernández
    Abstract This document shows the results obtained from a study on the concentration of toxic heavy metals in the internal tissue and exoskeleton of sea urchins, collected from their natural habitat. The levels of lead and cadmium were measured by Graphite Furnace Atomic Absorption Spectrometry. The mean concentrations of lead and cadmium in the internal tissue were 304.04 and 260.54 ,g/kg respectively, whereas in the shell they were 185.02 and 142.48 ,g/kg. We also performed a statistical analysis of the differences in the distribution of metals between their exoskeleton and their internal content, a correlation study of the metal content in internal tissue and shell and sampling areas, and a correlation study between the metal content and sample size. Since the sea urchin Diadema antillarum presents a wide range of variation in metal content, this study suggests that this species is an excellent bioindicator of heavy metal contamination. © 2009 Wiley Periodicals, Inc. Environ Toxicol, 2010. [source]

    Phosphate regulates uranium(VI) toxicity to Lemna gibba L. G3

    Martin Mkandawire
    Abstract The influence of phosphate on the toxicity of uranium to Lemna gibba G3 was tested in semicontinuous culture with synthetic mine water developed as an analogue of surface water of two abandoned uranium mining and ore processing sites in Saxony, Germany. Six concentrations of uranium were investigated under five different supply regimes of PO43, at constant pH (7.0 ± 0.5) and alkalinity (7.0 ± 1.6 mg L,1 total CO32,). The results showed significant inhibition of specific growth rates in cultures exposed to the highest uranium concentrations (3500 and 7000 ,g U L,1) at lowest PO43, supply of 0.01 mg L,1. An increase of phosphate concentration from 0.01 to 8.0 mg L,1 resulted in an increase of EC50 from 0.9 ± 0.2 to 7.4 ± 1.9 mg L,1 (significant with Student's t test, P > 0.05). The accumulation of uranium in L. gibba increased exponentially with the increase in uranium concentration in cultures with 0.01 and 0.14 mg PO43, L,1. Accumulation also increased significantly when PO43, supply was increased from 0.14 to 1.36 mg PO43, L,1 for all uranium concentrations. However, as the supply of PO43, gradually increased from 1.36 to 8.0 mg PO43, L,1, uranium bioaccumulation increased slightly but insignificantly before leveling off. Uranium speciation modeling with PhreeqC geochemical code predicted increases in the proportions of uranyl phosphate species when PO43, concentrations increase in the media. Most of these uranyl phosphate species have a high probability of precipitation [saturation indices (SI) > 0.93]. Therefore, the alleviation of uranium toxicity to L. gibba with phosphates is due to interactions among components of the media, mainly uranyl and phosphate which results in precipitation. Consequently, bioavailable fractions of uranium to L. gibba are reduced. This might explain lack of consistent EC50 values for uranium to most aquatic organisms. © 2007 Wiley Periodicals, Inc. Environ Toxicol 22: 9,16, 2007. [source]

    Accumulation and DNA damage in fathead minnows (Pimephales promelas) exposed to 2 brominated flame-retardant mixtures, Firemaster® 550 and Firemaster® BZ-54

    Jonathan S. Bearr
    Abstract Firemaster® 550 and Firemaster® BZ-54 are two brominated formulations that are in use as replacements for polybrominated diphenyl ether (PBDE) flame retardants. Two major components of these mixtures are 2,3,4,5-tetrabromo-ethylhexylbenzoate (TBB) and 2,3,4,5-tetrabromo-bis(2-ethylhexyl) phthalate (TBPH). Both have been measured in environmental matrices; however, scant toxicological information exists. The present study aimed to determine if these brominated flame-retardant formulations are bioavailable and adversely affect DNA integrity in fish. Fathead minnows (Pimephales promelas) were orally exposed to either FM 550, FM BZ54, or the nonbrominated form of TBPH, di-(2-ethylhexyl) phthalate (DEHP) for 56 d and depurated (e.g., fed clean food) for 22 d. At several time points, liver and blood cells were collected and assessed for DNA damage. Homogenized fish tissues were extracted and analyzed on day 0 and day 56 to determine the residue of TBB and TBPH and the appearance of any metabolites using gas chromatography-electron-capture negative ion mass spectrometry (GC/ECNI-MS). Significant increases (p,<,0.05) in DNA strand breaks from liver cells (but not blood cells) were observed during the exposure period compared with controls, although during depuration these levels returned to control. Both parent compounds, TBB and TBPH, were detected in tissues at approximately 1% of daily dosage along with brominated metabolites. The present study provides evidence for accumulation, metabolism, and genotoxicity of these new formulation flame retardants in fish and highlights the potential adverse effects of TBB- and TBPH-formulated fire retardants to aquatic species. Environ. Toxicol. Chem. 2010;29:722,729. © 2009 SETAC [source]

    Mercury-induced reproductive impairment in fish,,

    Kate L. Crump
    Abstract Mercury is a potent neurotoxin, and increasing levels have led to concern for human and wildlife health in many regions of the world. During the past three decades, studies in fish have examined the effects of sublethal mercury exposure on a range of endpoints within the reproductive axis. Mercury studies have varied from highly concentrated aqueous exposures to ecologically relevant dietary exposures using levels comparable to those currently found in the environment. This review summarizes data from both laboratory and field studies supporting the hypothesis that mercury in the aquatic environment impacts the reproductive health of fish. The evidence presented suggests that the inhibitory effects of mercury on reproduction occur at multiple sites within the reproductive axis, including the hypothalamus, pituitary, and gonads. Accumulation of mercury in the fish brain has resulted in reduced neurosecretory material, hypothalamic neuron degeneration, and alterations in parameters of monoaminergic neurotransmission. At the level of the pituitary, mercury exposure has reduced and/or inactivated gonadotropin-secreting cells. Finally, studies have examined the effects of mercury on the reproductive organs and demonstrated a range of effects, including reductions in gonad size, circulating reproductive steroids, gamete production, and spawning success. Despite some variation between studies, there appears to be sufficient evidence from laboratory studies to link exposure to mercury with reproductive impairment in many fish species. Currently, the mechanisms underlying these effects are unknown; however, several physiological and cellular mechanisms are proposed within this review. [source]

    Accumulation of polycyclic aromatic hydrocarbons in rural soils based on mass balances at the catchment scale

    Tilman Gocht
    Abstract Polycyclic aromatic hydrocarbons (PAHs) are hydrophobic organic pollutants that are ubiquitously distributed in the environment at relatively high concentrations. In our study we investigated the long-term fate of atmospheric PAHs in soils of rural areas, resulting from diffuse pollution based on mass balances at the catchment scale. By determining PAHs in several environmental compartments, estimates of soil storages and water fluxes were made and compared with atmospheric deposition. The results indicate that more than 90% of the incoming PAHs remain in the catchments and accumulate in the topsoils. Furthermore, revolatilization of PAHs from soils and degradation in the soils is very limited, resulting in ongoing accumulation in topsoils, in particular for low-volatile PAHs. Combustion-derived carbonaceous particles were detected in atmospheric deposition as well as in the soil samples. Since these particles are very strong adsorbents, they are suspected to play a key role in the environmental fate of the diffuse distributed PAHs. [source]

    Accumulation of tributyltin in Hyalella azteca as an indicator of chronic toxicity: Survival, growth, and reproduction

    Adrienne J. Bartlett
    Abstract The chronic toxicity of tributyltin (TBT) was examined by exposing two successive generations of the freshwater amphipod, Hyalella azteca, to sediments spiked with TBT. Survival was the most sensitive measure of effect, with lethal concentration resulting in 50% mortality (LC50) values on a water and body concentration basis ranging from 76 to 145 ng Sn/L and 2,790 to 4,300 ng Sn/g, respectively. Individual growth of amphipods was not negatively affected by TBT, and although reproduction might be more sensitive than survival, the data were too variable to use on a routine basis. There were no detectable TBT-induced differences in the response between first- and second-generation animals. The relationship between toxicity and bioaccumulation of TBT in H. azteca was determined and can be used as a tool to predict the toxicity of TBT in environmental samples. Body concentrations exceeding 2,000 ng Sn/g in H. azteca exposed to field-collected samples would indicate that chronic toxicity due to TBT is likely occurring in amphipod populations at those sites. [source]

    Accumulation and distribution of polychlorinated dibenzo- p -dioxin, dibenzofuran, and polychlorinated biphenyl congeners in atlantic salmon (Salmo salar)

    Pirjo Isosaari
    Abstract Adult Atlantic salmon (Salmo salar) were fed on four diets containing polychlorinated dibenzo- p -dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) for 30 weeks. Lipid-normalized concentrations showed that all congeners were equally partitioned between whole-fish and fillet samples. Skinned fillet accumulated approximately 30% of the total PCDD/F and PCB content in fish. Accumulation efficiencies in whole fish were 43% for 2,3,7,8-chlorinated dibenzo- p -dioxins and dibenzofurans, 83% for dioxin-like PCBs, and 78% for other PCB congeners. Among PCDD/Fs, tetra- and pentachlorinated congeners were preferentially accumulated in salmon, whereas hepta- and octachlorinated dibenzo- p -dioxins were excreted in the feces. Substitution patterns that were associated with a preferential accumulation of PCBs in salmon included non- ortho substitution and tetrachlorination. Accumulation efficiencies and lipid-normalized biomagnification factors (BMFs) were not influenced by the PCDD/F and PCB concentrations of the diets. Biomagnification (BMF > 1) of tetra- and pentachlorinated dibenzo- p -dioxins and dibenzofurans and of all the PCBs was observed. Differences in the behavior of PCDD/F and PCB congeners resulted in a selective enrichment of the most toxic congeners in salmon. [source]

    Accumulation of 137Cs by larvae of the midge Chironomus riparius from sediment: Effect of potassium

    Lieven Bervoets
    Abstract We studied the effect of potassium on the uptake of radiocesium from sediment by larvae of the midge Chironomus riparius. Sediment ingestion rate was determined for one week. After 24 h the gut content remained constant, indicating that equilibrium was reached between sediment ingestion and sediment elimination. These data were used to account for radiocesium present in the gut in subsequent uptake experiments. Reference sediment was equilibrated with solutions containing different concentrations of potassium: 1, 10, 100, and 1,000 ,M. Adsorption of 137Cs to the sediment was investigated. Three different radiocesium levels (0.3, 0.6, and 1.2 KBq/ml) were applied at the four different potassium levels. In all cases more than 94% of all radiocesium was adsorbed to the sediment within 48 h. The sediment, equilibrated with the four different potassium levels, was spiked with a constant amount of 296 Bq/ml 137Cs. Accumulation by midge larvae was followed for one week, and subsequently elimination was followed for another week. No significant differences in radiocesium levels in midge larvae among the treatments were found after one week of exposure. However, using a one-compartment accumulation model, a small but significant effect of potassium in water and sediment on the uptake and elimination rate constants (ka and ke) was found. These results indicate that although differences were rather small, radiocesium accumulation decreased with increasing potassium level in the sediment. [source]

    Application of sewage sludge to arable land,soil concentrations of polybrominated diphenyl ethers and polychorinated dibenzo- p -dioxins, dibenzofurans, and biphenyls, and their accumulation in earthworms

    Nadja Matscheko
    Abstract Soils from five agricultural sites, three research sites, and two privately owned farms were analyzed for polychlorinated dibenzo- p -dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polychlorinated biphenyls (PCBs), and polybronimated diphenylethers (PBDEs). In soils that had not been treated with sludge (reference soils), the international toxic equivalents (I-TEQs) were 0.6 to 1.5 pg/g dry matter (DM) for the PCDD/Fs, which are low compared to generally reported background soil levels in Europe. The concentrations of sum of six penta- and hexa-PCBs were 450 to 1,400 pg/g DM. The PBDEs 47 and 99 dominated among the tri- to hepta-PBDEs analyzed (8,80 pg/g DM). The impact of adding 1 to 3 tonnes of sludge (DM) per hectare per year on the concentrations was studied at the three research sites by calculating ratios of the compounds in sludge-treated soil to reference soil (S/R ratio). The concentrations of I-TEQs did not increase in the sludge-treated soil, whereas the S/R ratios for PBDEs were greater than one. Also, although the PCB contents were higher in the sludge-treated soils, the background sources were more important for the concentrations of PCBs than of PBDEs. The largest increase in the S/R ratios was found at a private farm where large amounts of sludge had been used in the past. Accumulation of the compounds in earthworms from the sites also was investigated. The biota-soil accumulation factors (BSAFs) of the tested compounds declined in the following order: ortho -PCBs , PBDEs > non-ortho -PCBs > 2,3,7,8-substituted PCDD/Fs. The average BSAF for ortho -PCBs was five (organic matter/lipids), and the lowest BSAFs (0.1,0.8) found were for octachlorodibenzo- p -dioxin. To our knowledge, accumulation of PBDEs in earthworms has not been published previously. [source]

    Accumulation of DDT and mercury in prothonotary warblers (Protonotaria citrea) foraging in a heterogeneously contaminated environment

    Kevin D. Reynolds
    Abstract Foraging areas of adult prothonotary warblers (Protonotaria citrea) were determined using standard radiotelemetry techniques to determine if soil concentrations of p,p,dichlorodiphenyltrichloroethane (p,p,DDT) and mercury in foraging areas could be used to predict contaminant levels in diets and tissues of nestling warblers. Adult warblers were fitted with transmitters and monitored for approximately 2 d while foraging and feeding 6- to 8-d-old nestlings. Foraging ecology data were integrated with contaminant levels of soil, diets, and tissues into a comprehensive analysis of geographic variation in contaminant exposure and uptake using linear regression. Concentrations of 1,1-dichloro-2,2-bis(p -chlorophenyl)ethylene (DDE) and mercury in nestling tissues varied considerably across the study site. Mean concentration of DDE was greater in eggs than all other tissues, with individual samples ranging from 0.24 to 8.12 ,g/kg. In general, concentrations of DDT in soil were effective in describing the variation of contaminants in adipose samples. Concentrations of mercury in soils accounted for 78% of the variation in kidney samples. This was the best relationship of any of the paired variables. All other relationships showed relatively poor predictive ability. [source]

    Toxicokinetics of waterborne bisphenol a in landlocked salmon (Salmo salar m. Sebago) eggs at various temperatures

    Jani O. Honkanen
    Abstract Eye-pigmented eggs of landlocked salmon were exposed to waterbone [14C]-labeled bisphenol A at four temperatures (2, 6, 8, and 12°C). Both in accumulation and depuration experiments, the eggs were exposed to a bisphenol A concentration of 1 ,g/L for 196 h. In the depuration experiment, the exposed eggs were placed into clean water for 96 h. At each sampling time, the eggs were dissected into three parts (eggshell, embryo, and yolk sac), and all of these parts were weighed and analyzed separately in a liquid scintillation counter. The results show that waterborne bisphenol A accumulates in developing salmon eggs. Accumulation of bisphenol A showed a clear trend both in whole eggs and in dissected parts: the higher the temperature, the higher the uptake rate constant and the concentration of bisphenol A. Steady state was reached only in the embryos at the lowest temperature; in other cases, accumulation was linear. Depuration was significant only in the embryos at 2 and 6°C. As the accumulation and the depuration results show, the elimination of bisphenol A was evidently more significant at lower temperatures. [source]

    Chronic effects of silver exposure on ion levels, survival, and silver distribution within developing rainbow trout (Oncorhynchus mykiss) embryos

    Christine M. Guadagnolo
    Abstract Rainbow trout embryos were chronically exposed to silver (as AgNO3) in moderately hard water (120 mg CaCO3/L, 0.70 mM Cl,, 1.3 mg/L dissolved organic matter, 12.3 ± 0.1 °C) at nominal concentrations of 0.1, 1, and 10 ,g/L (measured = 0.117 ± 0.008, 1.22 ± 0.16, and 13.51 ± 1.58 ,g/L, respectively) to investigate the effects on mortality, ionoregulation, and silver uptake and distribution of the embryo. Mortalities in the low concentrations (0.1 and 1.2 ,g/L) were not significantly different from controls throughout embryonic development (days 1,32 postfertilization). Mortalities of embryos in the 13.5-,g/L treatment reached 56% by day 32 postfertilization (33% when accounting for control mortality), by which time more than 50% of surviving embryos had hatched. Accumulation of silver in whole embryos of 1.2- and 13.5-,g/L treatments reached the highest concentrations of 0.13 and 0.24 ,g/g total silver, respectively, by day 32, but whole embryo silver burden was not correlated with mortality. Silver concentrations in different compartments of the whole embryo (chorion, dissected embryo, and yolk) were greatest just before hatch and were higher in the chorion for all experimental treatments. Up to 85% of total whole embryo silver content was bound to the chorion, which acts as a protective barrier during silver exposure. Whole embryo Na+ concentration in the 13.5-,g/L treatment was significantly reduced relative to controls from days 23 to 32 postfertilization, and levels in the embryo were reduced by 40% at day 32 postfertilization, indicating that silver toxicity in the whole embryo is associated with an ion regulatory disturbance that is similar to the acute effect of AgNO3 in juvenile and adult trout. [source]