bluuebunny/crossref_metadata_2025 huggingface dataset:
THE ACTIN CYTOSKELETON: Integrating Form and Function at the Synapse
Authors: Dillon Christian , Goda Yukiko
Published: March 2005

Synapses are highly specialized intercellular junctions that mediate the transmission of information between axons and target cells. A fundamental property of synapses is their ability to modify the efficacy of synaptic communication through various forms of synaptic plasticity. Recent developments in imaging techniques have revealed that synapses exhibit a high degree of morphological plasticity under basal conditions and also in response to neuronal activity that induces alterations in synaptic strength. The underlying molecular basis for this morphological plasticity has attracted much attention, yet its functional significance to the mechanisms of synaptic transmission and synaptic plasticity remains elusive. These morphological changes ultimately require the dynamic actin cytoskeleton, which is the major structural component of synapses. Delineating the physiological roles of the actin cytoskeleton in supporting synaptic transmission and synaptic plasticity, therefore, paves the way for gaining molecular insights into when and how synaptic machineries couple synapse form and function.
Restoration of normal vascular relaxation mechanisms in cerebral arteries by chromosomal substitution in consomic SS.13BNrats
Authors: Drenjancevic-Peric Ines , Phillips Shane A. , Falck John R. , Lombard Julian H.
Published: March 2005

This study sought to identify the mechanisms of vascular relaxation that are rescued in middle cerebral arteries (MCA) of SS.13BNconsomic rats by substituting chromosome 13 containing the renin gene from Brown Norway (BN) rats into the Dahl salt-sensitive (SS) genetic background. Isolated MCA from SS rats exhibited an indomethacin-sensitive constriction in response to acetylcholine (ACh) and hypoxia. ACh-induced dilation was NO dependent and hypoxic dilations were cyclooxygenase (COX) dependent in BN and SS.13BNrats. In SS rats, hypoxic dilation was restored by indomethacin and abolished by inhibiting cytochrome P-450 epoxygenases, suggesting a role for epoxyeicosatrienoic acids. MCA from SS and SS.13BNrats constricted and MCA from BN rats dilated in response to the stable prostacyclin analog iloprost. MCA from SS.13BNand BN rats (but not SS rats) dilated in response to the prostaglandin E2receptor agonist butaprost. Hypoxia increased prostacyclin release in cerebral arteries from all the strains, whereas thromboxane A2production was reduced in BN rat vessels only. These data suggest that SS rats may be less sensitive to vasodilator prostaglandins and that normalization of renin-angiotensin system regulation causes a switch from production of COX-derived vasoconstrictor metabolites (in SS rats) toward NO-dependent relaxation in response to ACh- and prostaglandin-dependent dilation in response to hypoxia in SS.13BNrats.
Evaluation and Transferability of the Noah Land Surface Model in Semiarid Environments
Authors: Hogue Terri S. , Bastidas Luis , Gupta Hoshin , Sorooshian Soroosh , Mitchell Ken , Emmerich William
Published: March 2005

This paper investigates the performance of the National Centers for Environmental Prediction (NCEP) Noah land surface model at two semiarid sites in southern Arizona. The goal is to evaluate the transferability of calibrated parameters (i.e., direct application of a parameter set to a “similar” site) between the sites and to analyze model performance under the various climatic conditions that can occur in this region. A multicriteria, systematic evaluation scheme is developed to meet these goals. Results indicate that the Noah model is able to simulate sensible heat, ground heat, and ground temperature observations with a high degree of accuracy, using the optimized parameter sets. However, there is a large influx of moist air into Arizona during the monsoon period, and significant latent heat flux errors are observed in model simulations during these periods. The use of proxy site parameters (transferred parameter set), as well as traditional default parameters, results in diminished model performance when compared to a set of parameters calibrated specifically to the flux sites. Also, using a parameter set obtained from a longer-time-frame calibration (i.e., a 4-yr period) results in decreased model performance during nonstationary, short-term climatic events, such as a monsoon or El Niño. Although these results are specific to the sites in Arizona, it is hypothesized that these results may hold true for other case studies. In general, there is still the opportunity for improvement in the representation of physical processes in land surface models for semiarid regions. The hope is that rigorous model evaluation, such as that put forth in this analysis, and studies such as the Project for the Intercomparison of Land-Surface Processes (PILPS) San Pedro–Sevilleta, will lead to advances in model development, as well as parameter estimation and transferability, for use in long-term climate and regional environmental studies.
Desmoplastic small round cell tumour : Cytological and immunocytochemical features
Authors: Granja Nara M , Begnami Maria D , Bortolan Jeni , Filho Adhemar L , Schmitt Fernando C
Published: March 2005

Background:

Desmoplastic small round cell tumor (DSRCT) is a rare and highly aggressive neoplasm. The cytological diagnosis of these tumors can be difficult because they show morphological features quite similar to other small round blue cells tumors. We described four cases of DSRCT with cytological sampling: one obtained by fine needle aspiration biopsy (FNAB) and three from serous effusions. The corresponding immunocytochemical panel was also reviewed.

Methods:

Papanicolaou stained samples from FNAB and effusions were morphologically described. Immunoreaction with WT1 antibody was performed in all cytological samples. An immunohistochemical panel including the following antibodies was performed in the corresponding biopsies: 34BE12, AE1/AE3, Chromogranin A, CK20, CK7, CK8, Desmin, EMA, NSE, Vimentin and WT1.

Results:

The smears showed high cellularity with minor size alteration. Nuclei were round to oval, some of them with inconspicuous nucleoli. Tumor cells are clustered, showing rosette-like feature. Tumor cells in effusions and FNA were positive to WT1 in 3 of 4 cytology specimens (2 out 3 effusions and one FNA). Immunohistochemical reactions for vimentin, NSE, AE1/AE3 and WT1 were positive in all cases in tissue sections.

Conclusion:

The use of an adjunct immunocytochemical panel coupled with the cytomorphological characteristics allows the diagnosis of DSRCT in cytological specimens.
Effect of humic acids on toxicity of DDT and chlorpyrifos to freshwater and estuarine invertebrates
Authors: Mézin Laurent C. , Hale Robert C.
Published: March 2005

The effects of dissolved humic acids(HA)on the acute toxicities of the organophosphate pesticide chlorpyrifos and the organochlorine pesticide 4,4′-dichlorodiphenyltrichloroethane (DDT) were assessed by using freshwater crustaceans (Cerio-daphnia dubia) and saltwater crustaceans (Americamysis bahia). The effects of filtered Aldrich HAs (10–100 mg/L) on organism mortality were determined. Humic acids had no effect on mortality of A. bahia for either pesticide at a salinity of 20%, but greatly reduced the mortality of C. dubia for both pesticides in freshwater (0%). In the latter case, the effect was proportional to the HA concentration. The difference in toxicity mitigation as a function of salinity is believed to be due to conformational changes in the HA molecules, which impact pesticide—HA binding, rather than to organismal effects.
Biomarker responses and chemical analyses in fish indicate leakage of polycyclic aromatic hydrocarbons and other compounds from car tire rubber
Authors: Stephensen Eiríkur , Adolfsson-Erici Margaretha , Celander Malin , Hulander Mats , Parkkonen Jari , Hegelund Tove , Sturve Joachim , Hasselberg Linda , Bengtsson Madeleine , Förlin Lars
Published: March 2005

Rubber tire material contains toxic compounds including oils rich in polycyclic aromatic hydrocarbons (PAH), so-called highly aromatic (HA) oils, as well as other reactive additives used as antioxidants, antiozonants, and vulcanization accelerators. The toxicity of rubber tire leachates to aquatic organisms has been demonstrated before. However, previous studies have focused on lethal rather than sublethal effects. We kept rainbow trout (Oncorhynchus mykiss) in tanks with two types of tires: a tire containing HA oils in the tread or a tire free of HA oils in the tread. After 1 d of exposure, an induction of cytochrome P4501A1 (CYP1A1) was evident in both exposed groups, measured as elevated ethoxyresorufin-O-deethylase (EROD) activity and increased CYP1A1 mRNA levels. After two weeks of exposure, EROD activity and CYP1A1 mRNA were still high in fish exposed to leachate from HA oil-containing tire, whereas the effect was somewhat lower in fish exposed to leachate from HA oil-free tread tire. Compounds in the tire leachates also affected antioxidant parameters. Total glutathione concentration in liver as well as hepatic glutathione reductase, glutathione S-transferase, and glucose-6-phosphate dehydrogenase activities were markedly elevated after two weeks of exposure in both groups. The responses were greater in the group exposed to leachate from HA oil-free tread tire. Vitellogenin measurements did not indicate leakage of estrogenic compounds from the tires. Chemical analyses of bile from exposed fish revealed the presence of hydroxylated PAH as well as aromatic nitrogen compounds indicating uptake of these compounds by the fish.
Occurrence of neutral and acidic drugs in the effluents of Canadian sewage treatment plants
Authors: Metcalfe Chris D. , Koenig Brenda G. , Bennie Don T. , Servos Mark , Ternes Thomas A. , Hirsch Roman
Published: March 2005

Samples of influent (untreated) and effluent (treated) from 18 sewage treatment plants (STPs) in 14 municipalities in Canada were analyzed for residues of selected prescription and nonprescription drugs. Several neutral and acidic drugs were detected in effluents, including analgesic/anti-inflammatory agents, lipid regulators, and an antiepileptic drug, carbamazepine. Residues were extracted from effluents by solid-phase extraction, followed by either methylation and analysis of acidic drugs by gas chromatography/mass spectrometry or direct analysis of neutral drugs by liquid chromatography/tandem mass spectrometry. Analgesic/anti-inflammatory drugs such as ibuprofen and naproxen, as well as the metabolite of acetylsalicyclic acid, salicylic acid, were often detected in final effluents at μg/L concentrations. The acidic lipid regulator, clofibric acid, and the analgesic/anti-inflammatory drug diclofenac were not detected in any final effluent samples, which is not consistent with data from Europe. The precursor to clofibric acid, clofibrate, is not widely prescribed as a lipid regulator in Canada. However, the lipid regulators bezafibrate and gemfibrozil were detected in some samples of influent and effluent. The chemotherapy drugs ifosfamide and cyclophosphamide and the anti-inflammatory phenazone were not detected in influent or effluent samples, but the vasodilator drug pentoxyfylline was detected at ng/L concentrations in some final effluents. The widespread occurrence of carbamazepine at concentrations as high as 2.3 μg/L may be explained by use of this drug for other therapeutic purposes besides treatment of epilepsy and its resistance to elimination in STPs. The rates of elimination of ibuprofen and naproxen appeared to be elevated in STPs with hydraulic retention times for sewage greater than 12 h.
Issues of replicability in Monte Carlo modeling: A case study with a pesticide leaching model
Authors: Dubus Igor G. , Janssen Peter H. M.
Published: March 2005

Sensitivity and uncertainty analyses based on Monte Carlo sampling were undertaken for various numbers of runs of the pesticide leaching model (PELMO). Analyses were repeated 10 times with different seed numbers. The ranking of PELMO input parameters according to their influence on predictions for leaching was stable for the most influential parameters. For less influential parameters, the sensitivity ranking was severely influenced by the seed number used. For uncertainty analyses, probabilities of exceeding a particular concentration were significantly influenced by the seed number used in the random sampling of values for the two parameters considered, even for those cases in which 5,000 model runs were undertaken (coefficient of variation of 10 replicated analyses, 5%). A decrease in the variability of exceedance probabilities could be achieved by further increasing the number of model runs. However, this may prove to be impractical when complex deterministic models with a relatively long running time are used. Attention should be paid to replicability aspects by modelers when devising their approach to assessing the uncertainty associated with the modeling and by decision makers when examining the results of probabilistic approaches.
The effects of low hardness and pH on copper toxicity to Daphnia magna
Authors: Long Kristen E. , Van Genderen Eric J. , Klaine Stephen J.
Published: March 2005

The majority of metal toxicity data available for freshwater organisms have been generated in laboratory water at pH > 6.5 and hardness > 50 mg/L as CaCO3. Extrapolation of these results to soft surface waters (i.e., hardness ≤ 40 mg/L as CaCO3), similar to predominant conditions in the southeastern United States, may prove challenging. For example, South Carolina has surface waters that average 20 mg/L as CaCO3, and exist at extremes of 1 and 600 mg/L as CaCO3. This research characterized the acute toxicity of Cu to Daphnia magna in waters with low hardness and low pH. The 48-h total Cu median lethal concentrations were related to water hardness over a hardness range of 8 to 51 mg/L as CaCO3. Although toxicological differences existed between water hardness of 7 and 20 mg/L as CaCO3 (p = 0.0001), differences in pH (range 5.5–8.5) did not influence acute Cu toxicity. Results of these laboratory studies will provide the data needed to more accurately predict organism response to Cu in waters with low pH and low hardness.
The effect of counterion and percolation on the toxicity of lead for the springtail Folsomia candida in soil
Authors: Bongers Marina , Rusch Ben , van Gestel Cornelis A. M.
Published: March 2005

In standard soil toxicity tests, heavy metals are amended as water-soluble salts. The role of the counterion in metal salt toxicity is scarcely looked into. In this study, we assessed the contribution of nitrate and chloride to the toxicity of lead to Folsomia candida in a natural standard soil. Both lead salts were tested according the standard test protocol as well as after percolation of the soil with deionized water. Lead nitrate was more toxic than lead chloride for survival as well as reproduction. Percolation proved to be an effective method to remove counterions from the soil. Survival of F. candida increased for both metal salts when percolation was included. Percolation reduced the reproduction toxicity of lead, the effect of which was largest for the nitrate salt. In percolated treatments, the nitrate and chloride lead salts did not differ in toxicity. It is concluded that counterions contribute to metal toxicity and that nitrate is more toxic to F. candida than chloride.
Effect of prairie grass on the dissipation, movement, and bioavailability of selected herbicides in prepared soil columns
Authors: Belden Jason B. , Phillips Todd A. , Coats Joel R.
Published: March 2005

Phytoremediation of pesticide-contaminated sites using a prairie grass mixture (big bluestem, yellow indiangrass, and switch grass) has been suggested as a low-cost in situ remediation strategy. In this study, the proposed phytoremediation technique was applied to artificially prepared soil columns that were fortified with high concentrations of four herbicides (atrazine, alachlor, metolachlor, and pendimethalin). The fate and toxicity of the herbicides were compared with results from soil columns lacking vegetation. After either 150 or 240 d of phytoremediation, soils were watered with 7.5 cm of water, and leachate was collected. Columns were then divided into three sections (top, middle, bottom). For each section of the column, chemical analysis (ethyl acetate and water extractions), earthworm accumulation tests, and lettuce seedling growth tests were performed. The leachate was chemically analyzed and tested for chronic toxicity to algae. Atrazine and alachlor degraded rapidly in the column, and the total amount recoverable was less than 2% of applied. After 250 d, vegetation reduced the total recoverable amounts of metolachlor and pendimethalin by 78 and 39%, respectively. Metolachlor was the only compound found in leachate, and the amounts recovered were reduced 5- to 20-fold by vegetation. Vegetation decreased the bioavailability of pendimethalin as measured by 8-d, earthworm bioaccumulation factors (BAFs) and lettuce seedling growth assays. Decreases in mobility and bioavailability indicate that this technique may stabilize pesticide residues in addition to increasing dissipation rates.
Relative sensitivity distribution of aquatic invertebrates to organic and metal compounds
Authors: von der Ohe Peter Carsten , Liess Matthias
Published: March 2005

In the field, a multitude of species can be exposed to numerous toxicants; thus, the sensitivity of individual species to particular toxicants must be known to predict effects and to analyze changes in species composition. For most species, no information about their toxicant sensitivity is available. To address this limitation, we have grouped the available information to assign sensitivities to aquatic invertebrate taxa relative to Daphnia magna. With respect to organic compounds, most taxa of the orders Anisoptera, Basommatophora, Coleoptera, Decapoda, Diptera, Ephemeroptera, Eulamellibranchiata, Heteroptera, Hirudinea, Isopoda, Oligochaeta, Prosobranchia, Trichoptera, Tricladida, and Zygoptera are less sensitive than D. magna. Some taxa of the Amphipoda, Plecoptera, and Cladocera (other than D. magna) are significantly more sensitive. For organic compounds, approximately 22% of the investigated taxa were more sensitive than D. magna. Most taxa of the orders Amphipoda, Basommatophora, Diptera, Ephemeroptera, Eulamellibranchiata, Heteroptera, Isopoda, Oligochaeta, and Tricladida are significantly less sensitive than D. magna to metal compounds. The taxa belonging to the Crustacea, with the exception of the order Isopoda, are much more sensitive. For metal compounds, approximately 30% of the investigated taxa were more sensitive than D. magna. Hence, D. magna is among the most sensitive taxa regarding both groups of toxicants. The sensitivities for several taxa are listed, and use of the relative sensitivity distribution to link toxicant effects in mesocosm studies and field investigations is discussed.
Estrogenic compounds affect development of harpacticoid copepod Tigriopus japonicus
Authors: Marcial Helen S. , Hagiwara Atsushi , Snell Terry W.
Published: March 2005

The aim of this investigation was to evaluate the impact of estrogenic compounds onthe harpacticoid copepod Tigriopus japonicus after continuous exposure to environmentally relevant concentrations. Natural estrogen (17β-estradiol), three known estrogenic compounds in vertebrates (bisphenol A, 4-nonylphenol, p-t-octylphenol), and an invertebrate molting hormone (20-hydroxyecdysone) were tested for their effects on development and reproductive characters in two successive generations of T. japonicus. Less than 24-h-old nauplii (parentals) were exposed to four sublethal concentrations of these compounds for 21 d at 25°C. The first brood of nauplii (F1) produced was monitored further under the same culture conditions and exposures to test compounds. Results showed that all estrogenic compounds affected development (both in number of days to reach copepodid stage and sexual maturity) in the parental generation. Similar effects were apparent in the F1; however, fecundity, sex ratio, and survival were not significantly affected, even at concentrations as high as 10 μg/L (nominal concentration). The invertebrate molting hormone 20-hyroxyecdysone had no detectable effect on any of the endpoints tested but gave the lowest 48-h 50% lethal concentration (LC50) value. The results suggest that endocrine disruption could occur in copepods following exposure to environmentally relevant concentrations of estrogenic compounds, especially if they are exposed starting from embryonic development.
Derivation of a chronic site-specific water quality standard for selenium in the Great Salt Lake, Utah, USA
Authors: Brix Kevin V. , Deforest David K. , Cardwell Rick D. , Adams William J.
Published: March 2005

The purpose of this study was to develop a site-specific water quality standard for selenium in the Great Salt Lake, Utah, USA. The study examined the bioavailability and toxicity of selenium, as selenate, to biota resident to the Great Salt Lake and the potential for dietary selenium exposure to aquatic dependent birds that might consume resident biota. Because of its high salinity, the lake has limited biological diversity with bacteria, algae, diatoms, brine shrimp, and brine flies being the only organisms present in the main (hypersaline) portions of the lake. To evaluate their sensitivity to selenium, a series of acute and chronic toxicity studies were conducted on brine shrimp (Artemia franiciscana), brine fly (Ephydra cinerea), and a hypersaline alga (Dunaliella viridis). The resulting acute and chronic toxicity data indicated that resident species are more selenium tolerant than many freshwater species. Because sulfate is known to reduce selenate bioavailability, this selenium tolerance is thought to result in part from the lake's high ambient sulfate concentrations (>5,800 mg/L). The acute and chronic test results were compared to selenium concentrations expected to occur in a mining effluent discharge located at the south end of the lake. Based on these comparisons, no appreciable risks to resident aquatic biota were projected. Field and laboratory data collected on selenium bioaccumulation in brine shrimp demonstrated a linear relationship between water and tissue selenium concentrations. Applying a dietary selenium threshold of 5 mg/kg dry weight for aquatic birds to this relationship resulted in an estimate of 27 μg/L Se in water as a safe concentration for this exposure pathway and an appropriate chronic site-specific water quality standard. Consequently, protection of aquatic birds represents the driving factor in determining a site-specific water quality standard for selenium.
Behavioral response of young rainbow trout (Oncorhynchus mykiss) to forest fire-retardant chemicals in the laboratory
Authors: Wells Jason B. , Little Edward E. , Calfee Robin D.
Published: March 2005

Fire-retardant chemicals often are applied in relatively pristine and environmentally sensitive areas that are potentially inhabited by endangered or threatened aquatic species. Avoidance of contaminants is an adaptive behavior that may reduce exposure to harmful conditions. We evaluated the avoidance responses of rainbow trout (Oncorhynchus mykiss) to concentrations of fire-retardant chemicals and alternate constituent formulations ranging from 0.65 to 26 mg/L. Countercurrent avoidance chambers were used in a flow-through design with receiving water at each end and a drain at the center to create a distinct boundary between treatment water and reference water. Rainbow trout consistently avoided water treated with retardants at all concentrations tested. The magnitude of the avoidance response did not appear to follow a concentration-response relationship, but rather was an all-or-none response.
Glycosidation of chlorophenols by Lemna minor
Authors: Day James A. , Saunders F. Michael
Published: March 2005

Metabolic fate of xenobiotics in plant tissues has an important role in the ultimate fate of these compounds in natural and engineered systems. Chlorophenols are an important class of xenobiotics used in a variety of biocides and have been shown to be resistant to microbial degradation. Three chlorophenyl glycosides were extracted from tissues of Lemna minor exposed to 2,4-dichlorophenol (DCP). The products were identified as 2,4-dichlorophenyl-β-D-glucopyranoside (DCPG), 2,4-dichlorophenyl-β-D-(6-O-malonyl)-glucopyranoside (DCPMG) and 2,4-dichlorophenyl-β-D-glucopyranosyl-(6→1)-β-D-apiofuranoside (DCPAG). Identification was based on reverse phase retention (C18), electrospray mass spectra collected in negative and positive mode (ESI-NEG and ESI-POS, respectively), and nuclear magnetic resonance (NMR) spectra comparisons to reference materials synthesized in the laboratory. Liquid chromatography-mass spectrometry (LC-MS) analysis of plants exposed to 2,4,5-trichlorophenol (TCP) formed analogous compounds: 2,4,5-trichlorophenyl-β-D-glucopyranoside (TCPG), 2,4,5-trichlorophenyl-β-D-(6-O-malonyl)-glucopyranoside (TCPMG) and 2,4,5-trichlorophenyl-β-D-glucopyranosyl-(6→1)-β-D-apiofuranoside (TCPAG). Enzyme catalyzed hydrolysis with β-glucosidase was ineffective in releasing the β-glucosides with chemical modifications at C6. Presence of these glucoconjugates confirmed that L. minor was capable of xenobiotic uptake and transformation. Identification of these products suggested that chlorophenols were incorporated into vacuoles and cell walls of L. minor.
Use of vegetative furrows to mitigate copper loads and soil loss in runoff from polyethylene (plastic) mulch vegetable production systems
Authors: Rice Pamela J. , Harman-Fetcho Jennifer A. , Teasdale John R. , Sadeghi Ali M. , McConnell Laura L. , Coffman C. Benjamin , Herbert Rachel R. , Heighton Lynne P. , Hapeman Cathleen J.
Published: March 2005

The transport of runoff with high copper concentrations and sediment loads into adjacent surface waters can have adverse effects on nontarget organisms as a result of increased turbidity and degraded water quality. Runoff from vegetable production utilizing polyethylene mulch can contain up to 35% of applied copper, a widely used fungicide/bactericide that has adverse effects on aquatic organisms. Copper is primarily transported in runoff with suspended particulates; therefore, implementation of management practices that minimize soil erosion will reduce copper loads. Replacing bare-soil furrows with furrows planted in rye (Secale cereale) significantly improved the sustainability of vegetable production with polyethylene mulch and reduced the potential environmental impact of this management practice. Vegetative furrows decreased runoff volume by >40% and soil erosion by >80%. Copper loads with runoff were reduced by 72% in 2001, primarily as a result of reduced soil erosion since more than 88% of the total copper loads were transported in runoff with suspended soil particulates. Tomato yields in both years were similar between the polyethylene mulch plots containing either bare-soil or vegetative furrows. Replacing bare-soil furrows with vegetative furrows greatly reduces the effects of sediments and agrochemicals on sensitive ecosystems while maintaining crop yields.
Phase distribution of synthetic pyrethroids in runoff and stream water
Authors: Liu Weiping , Gan Jay J. , Lee Sangjin , Kabashima John N.
Published: March 2005

Synthetic pyrethroids (SPs) are a group of hydrophobic compounds with significant aquatic toxicity. Their strong affinity to suspended solids and humic materials suggests that SPs in natural surface water are distributed in solid-adsorbed, dissolved organic matter (DOM)-adsorbed, and freely dissolved phases. The freely dissolved phase is of particular importance because of its mobility and bioavailability. In the present study, we used solid-phase microextraction to detect the freely dissolved phase, and we evaluated the phase distribution of bifenthrin and permethrin in stream and runoff waters. In stream water, most SPs were associated with the suspended solids and, to a lesser extent, with DOM. The freely dissolved phase contributed only 0.4% to 1.0%. In runoff effluents, the freely dissolved concentration was 10% to 27% of the overall concentration. The predominant partitioning into the adsorbed phases implies that the toxicity of SPs in surface water is reduced because of decreased bioavailability. This also suggests that monitoring protocols that do not selectively define the freely dissolved phase can lead to significant overestimation of toxicity or water-quality impacts by SPs.
Anaerobic transformation of compounds of technical toxaphene. 2. Fate of compounds lacking geminal chlorine atoms
Authors: Ruppe Steffen , Neumann Anke , Braekevelt Eric , Tomy Gregg T. , Stern Gary A. , Maruya Keith A. , Vetter Walter
Published: March 2005

The major toxaphene metabolites in sediment and soils (2-exo,3-endo,6-exo,8,9,10-hexachlorobornane [B6-923] and2-endo,3-exo,5-endo,6-exo,8,9,10-heptachlorobornane [B7-1001]) were incubated with the isolated gram-negative bacterium Dehalospirillum multivorans. Within 14 d, biotransformation of B7-1001 was nearly quantitative, resulting in two penta- and six hex-achlorobornanes, as well as one unsaturated hexachloro compound of technical toxaphene. The major transformation product (˜50% of all metabolites) was identified as 2-exo,3-endo,5-exo,8,9,10-hexachlorobornane (B6-903). Abiotic dehydrochlorination of B7-1001 with methanolic KOH resulted in the formation and subsequent identification of the lone unsaturated compound as 2,5-endo,6-exo,8,9,10-hexachloroborn-2-ene. Thus, dehydrochlorination was found to be a minor process of the anaerobic transformation of toxaphene. Biotransformation of 70% of amended B6-923 within 14 d demonstrated that reductive dechlorination was not exclusively associated with geminal Cl atoms, as previously suggested. Three pentachlorobornanes were identified as transformation products, one of which was identical with a transformation product of B7-1001. This commonality unequivocally proves this metabolite to be 2-exo,3-endo,8,9,10-pentachlorobornane. Fifteen previously unknown metabolites of B6-923, B7-1001, and other toxaphene compounds identified in this study were detected in sediment from Lake Ontario (Canada), underscoring the importance of microbial toxaphene transformation in natural, aquatic environments.
Toxicokinetics of sediment-associated polybrominated diphenylethers (flame retardants) in benthic invertebrates (Lumbriculus variegatus, oligochaeta)
Authors: Leppänen Matti T. , Kukkonen Jussi V. K.
Published: March 2005

Polybrominated diphenylethers (PBDEs) are ubiquitous environmental contaminants showing rapid temporal increase in some sample types. The compounds are known to biomagnify in aquatic food webs and are assumed to archive into sediments and soils. Currently, no direct evidence indicates whether sediment-associated PBDEs are available for biota. The aim of the present study was to explore the uptake and elimination of two common congeners (47 and 99) in sediment-inhabiting invertebrates to shed light on possible bioavailability of sediment-associated PBDEs. Two clean lake sediments were spiked with environmentally relevant concentrations of 14C-labeled tetra- and pentabromo diphenylether, and oligochaetes (Lumbriculus variegatus) were exposed for three or four weeks to allow kinetic accumulation calculations. Subsequent depuration tests were performed after three weeks of exposure to obtain depuration rates. Both congeners were clearly bioavailable, and only slight differences in steady-state tissue concentrations were found between the four sediment-ingesting oligochaete treatments (biota sediment accumulation factors [BSAFs], 3.0–3.7). The tetrabromo diphenylether-exposed oligochaetes that did not ingest sediment had clearly lower influx rates (0.1 vs 1–3 nmol h-1) than sediment-ingesting worms. Also, the estimated BSAF (1.8) was statistically different from that of the sediment-ingesting oligochaetes. These findings support the significance of feeding behavior in bioaccumulation of very hydrophobic organic contaminants. Depuration of both congeners was biphasic, indicating two kinetically different compartments in L. variegatus. Compartment A made up 73 to 92% of total radioactivity in tissues and had relatively fast depuration rates (half-lives, 10.5–47.5 h); the smaller compartment B had very slow depuration rates. No significant biotransformation of PBDEs was evident. The present study clearly demonstrates that the sediment-associated PBDEs, like other hydrophobic organic contaminants of environmental concern, are not totally sequestered from sediment-inhabiting oligochaetes and are subject to trophic transfer.
Mercury concentrations in fish from forest harvesting and fire-impacted Canadian Boreal lakes compared using stable isotopes of nitrogen
Authors: Garcia Edenise , Carignan Richard
Published: March 2005

otal mercury (Hg)concentration was determined in several piscivorous and nonpiscivorous species of fish from 38 drainage lakes with clear-cut, burnt, or undisturbed catchments located in the Canadian Boreal Shield. Mercury concentrations increased with increasing fish trophic position as estimated using stable isotopes of nitrogen (N; r2 = 0.52, 0.49, and 0.30 for cut, reference, and burnt lakes, respectively; p < 0.01). Mercury biomagnification per %‰ δ15N varied from 22 to 29% in the three groups of lakes. Mercury availability to organisms at the base of the food chain in lakes with cut catchments was higher than that in reference lakes. In cut lakes, Hg concentrations in fish were significantly related to ratio of the clear-cut area to lake area (or lake volume; r = +0.82 and +0.74, respectively, p < 0.01). Both impact ratios were, in turn, significantly correlated with dissolved organic carbon. These findings suggest that differential loading of organic matter–bound Hg to lakes can affect Hg cycling. In addition, Hg concentrations exceeded the advisory limit for human consumption (0.5 μg/g wet wt) from the World Health Organization in all top predatory species (northern pike, walleye, and burbot) found in cut and in two partially burnt lakes. Thus, high Hg concentrations in fish from forest-harvested and partially burnt lakes may reflect increased exposure to Hg relative to that in lakes not having these watershed disturbances.
Comparison of different microbial bioassays to assess metal-contaminated soils
Authors: Tandy Susan , Barbosa Vera , Tye Andy , Preston Sara , Paton Graeme , Zhang Hao , McGrath Steve
Published: March 2005

These experiments compared the sensitivity of four different types of bioassay over time after five metals were added to a wide range of soils at the maximum concentrations in the European Union Sewage Sludge Directive. Three were chronic assays (most probable number of Rhizobium leguminosarum, soil microbial C and Biolog substrate utilization). The fourth bioassay, an acute biosensor, employed a lux-marked luminescent bacterium (Escherichia coli) in the soil pore water. Five metals were added to 23 different soils as a mixture at Zn = 300, Cd = 3, Pb = 300, Cu = 135, and Ni = 75 mg/kg as nitrate salts and compared with unamended controls. Zinc and Cu were the metals most likely to be toxic at the concentrations used here. In the case of Rhizobium, the number of cells in soil was not affected after 11d; however, by 818 d the numbers had decreased by four orders of magnitude with increasing concentrations of Zn and Cu in soil solution. Microbial biomass also was not affected after 11d, but significantly decreased with increased Zn (p < 0.001) and Cu (p < 0.01) in soil solution after 818 d. Toxicity to the soil microbial biomass increased with time, whereas the toxicity to the biosensor remained the same. Biolog substrate utilization profiles were not responsive to the concentrations used here.
Field exposure of frog embryos and tadpoles along a pollution gradient in the Fox River and Green Bay ecosystem in Wisconsin, USA
Authors: Karasov William H. , Jung Robin E. , Vanden Langenberg Susan , Bergeson Tara L. E.
Published: March 2005

We raised embryos and tadpoles of green frogs (Rana clamitans melanota) and leopard frogs (R. pipiens) in situ along a contamination gradient in the Fox River/Green Bay ecosystem (WI, USA). Differences in exposure were reflected by significant positive regressions between concentrations in sediment and in frogs of polychlorinated biphenyl (PCB) congeners and some heavy metals (Cd, Cr, and Pb), which could have predictive value for estimating exposure of amphibians to contaminants in this ecosystem and, perhaps, in others. On average, non-ortho-substituted coplanar PCBs made up a very small percentage (average, 0.2%) of the PCB congeners in all samples analyzed, with larger fractions accounted for by mono- and di-ortho congeners (average, 19%) and routine congeners (average, 81%). Hatchability of frog embryo batches and anuran species richness at the sites were negatively correlated with level of contamination, but tadpole growth and survival were not. Sediment and tissue levels of PCBs and metals generally were correlated with each other, confounding the association of effects on frogs with any particular contaminant. It is also plausible that high levels of un-ionized ammonia (NH3) reduced hatching success of green frog, but not leopard frog, embryos in the field enclosures. Other environmental factors that were present but unmeasured in the field, such as ultraviolet-B radiation as well as water flow and level fluctuations, might have caused differences in hatching success at the field sites.
Effects of perchlorate exposure on resting metabolism, peak metabolism, and thyroid function in the prairie vole (Microtus ochrogaster)
Authors: Isanhart John P. , McNabb F. M. Anne , Smith Philip N.
Published: March 2005

Perchlorate, the oxidizer component in most solid rocket propellant formulations, is known to inhibit the uptake of iodide into the thyroid gland, thereby reducing production of the thyroid hormones, triiodothyronine and thyroxine (T4). Thyroid hormones regulate metabolism in endothermic organisms and are responsible for maintenance of homeothermic body temperatures. Little is known about the effects of perchlorate on metabolic capacity. The objectives of the present study were to determine if subchronic (51 d; 0, 1, and 10 mg/kg/d) and chronic (180 d; 0.75 mg/kg/d) perchlorate exposure in adult male prairie voles (Microtus ochrogaster) would alter resting metabolic rates as a result of decreased circulating thyroid hormone concentrations and to determine if perchlorate exposure disrupts thermogenesis in mammals exposed to cold stress. Voles exposed to perchlorate for 51 or 180 d experienced no significant alterations in resting metabolic rates at any point during the exposure period. Additionally, the treatment had no effect on peak metabolic rates or plasma thyroid hormone concentrations. However, thyroid gland T4 concentrations were significantly lower in perchlorate-exposed voles than in controls, indicating that thyroid gland T4 content may be a more sensitive endpoint than other thyroid variables for assessing perchlorate exposure. Overall, the present study did not provide evidence for energetic alterations associated with perchlorate exposure at concentrations that are higher than those typically found in groundwater or surface water in the environment.
Web search strategies and human individual differences: A combined analysis
Authors: Ford Nigel , Miller David , Moss Nicola
Published: March 2005

This is the second of two articles published in this issue of JASIST sreporting the results of a study investigating relationships between Web search strategies and a range of human individual differences. In this article we provide a combined analysis of the factor analyses previously presented separately in relation to each of three groups of human individual difference (study approaches, cognitive and demographic features, and perceptions of and approaches to Internet‐based information seeking). It also introduces two series of regression analyses conducted on data spanning all three individual difference groups. The results are discussed in terms of the extent to which they satisfy the original aim of this exploratory research, namely to identify any relationships between search strategy and individual difference variables for which there is a prima facie case for more focused systematic study. It is argued that a number of such relationships do exist. The results of the project are summarized and suggestions are made for further research.
SP100B is a repressor of gene expression
Authors: Wilcox Kent W. , Sheriff Scott , Isaac Anne , Taylor Jerry L.
Published: March 2005

Mammalian cell nuclei exhibit discrete sites where specific proteins characteristically localize. PML nuclear bodies (PML NBs) (nuclear domain 10s (ND10s)) are the primary localization site for the promyelocytic leukemia (PML) protein and the SP100 autoantigen. The observations that some PML and SP100 isoforms can function as transcriptional regulators, that both the size and number of PML bodies increase in response to interferon treatment, and that many mammalian viruses encode proteins that mediate disruption of PML bodies suggest that these sites suppress viral infection, perhaps by repressing viral gene expression. We hypothesized that a component of PML NBs functions as a repressor of gene expression. To test this hypothesis, we characterized the effect of PML or SP100 isoforms on expression of transfected reporter genes. PML‐I, PML‐VI, and SP100A did not repress reporter gene expression. In contrast, SP100B repressed reporter gene expression, especially under conditions in which the reporter gene expression was elevated by a viral transactivator or addition of trichostatin A to the culture medium. The SP100B DNA binding domain was required for repression. SP100B had no detectable effect on the amount, methylation pattern, or topological form of plasmid DNA in the nuclei of transfected cells. The demonstrated repressive activity of SP100B supports the hypothesis that SP100B is a component of an innate immune response that represses expression of ectopic DNA. © 2005 Wiley‐Liss, Inc.
Imprinting centers, chromatin structure, and disease
Authors: Soejima Hidenobu , Wagstaff Joseph
Published: March 2005

Two regions that best exemplify the role of genetic imprinting in human disease are the Prader–Willi syndrome/Angelman syndrome (PWS/AS) region in 15q11‐q13 and the Beckwith–Wiedemann syndrome (BWS) region in 11p15.5. In both regions, cis‐acting sequences known as imprinting centers (ICs) regulate parent‐specific gene expression bidirectionally over long distances. ICs for both regions are subject to parent‐specific epigenetic marking by covalent modification of DNA and histones. In this review, we summarize our current understanding of IC function and IC modification in these two regions. © 2005 Wiley‐Liss, Inc.
Improved artery delineation in dual‐stack coronary magnetic resonance angiography using parallel imaging at 3 T
Authors: Huber Michael E. , Kozerke Sebastian , Boesiger Peter
Published: March 2005

Purpose

To improve vessel sharpness and T2 preparation (T2Prep) in dual‐stack three‐dimensional coronary magnetic resonance angiography (MRA) by shortening the time delays between the magnetization preparation pulses and the imaging stacks using sensitivity encoding (SENSE) at 3 T.

Materials and Methods

By combining dual‐stack three‐dimensional coronary MRA with the parallel imaging technique SENSE at 3 T, the acquisition duration of each three‐dimensional imaging stack was shortened by a factor of 2. The proposed technique was implemented and tested in experiments with a moving phantom and in measurements on six healthy volunteers.

Results

The time delay between the navigator, T2Prep, and second imaging stack was reduced by 37%, relative to conventional dual‐stack angiography without parallel imaging. This enabled the achievement of comparable high‐vessel sharpness values for the left and the right coronary arteries relative to values known from conventional single‐stack three‐dimensional coronary MRA at 3 T.

Conclusion

Parallel imaging allows for improved vessel visualization in dual‐stack coronary MRA, given shorter temporal delays between navigator, T2Prep, and the actual image acquisitions, and thus considerably facilitates simultaneous acquisition of high‐resolution angiograms of the left and right coronary systems. J. Magn. Reson. Imaging 2005;21:443–448. © 2005 Wiley‐Liss, Inc.
Peripheral axon caliber and conduction velocity are decreased after burn injury in mice
Authors: Higashimori Haruki , Whetzel Thomas P. , Mahmood Tamara , Carlsen Richard C.
Published: March 2005

Peripheral neuropathies are reported to arise as a result of the systemic inflammatory response produced by a full‐thickness cutaneous burn injury. This study was designed to characterize the magnitude and time course of functional and morphological changes in peripheral axons that arise after a full‐thickness dermal burn injury in an animal model. A 20% body surface area (20% BSA) full‐thickness dermal burn was applied to the back of C57BL6 female mice. Longitudinal H‐ and M‐wave recordings were used to determine the conduction velocities (CV) of large myelinated motor and sensory axons in the tibial nerve of sham control and burn‐injured mice. Motor CVs were significantly reduced from 6 h to 28 days after the burn, and sensory CVs were significantly reduced from 7 to 14 days after the burn. Morphological evaluation also showed that the mean caliber of large axons in tibial nerves and L5 ventral and dorsal roots in burned mice was significantly decreased. The results demonstrate that both functional and morphological deficits may be produced in peripheral nerve axons at sites well removed from a full‐thickness dermal burn injury. The neural deficits may contribute to changes in neuromuscular transmission and the development of limb and respiratory muscle weakness that also accompany burn injury. Muscle Nerve, 2005
Analysis of correlated domain motions in IgG light chain reveals possible mechanisms of immunological signal transduction
Authors: Król Marcin , Roterman Irena , Piekarska Barbara , Konieczny Leszek , Rybarska Janina , Stopa Barbara , Spólnik Paweł
Published: March 2005

It was shown experimentally that binding of a micelle composed of Congo red molecules to immunological complexes leads to the enhanced stability of the latter, and simultaneously prevents binding of a complement molecule (C1q). The dye binds in a cavity created by the removal of N‐terminal polypeptide chain, as observed experimentally in a model system—immunoglobulin G (IgG) light chain dimer. Molecular Dynamics (MD) simulations of three forms of IgG light chain dimer, with and without the dye, were performed to investigate the role of N‐terminal fragment and self‐assembled ligand in coupling between V and C domains. Root‐mean‐square distance (RMSD) time profiles show that removal of N‐terminal fragment leads to destabilization of V domain. A micelle composed of four self‐assembled dye molecules stabilizes and fixes the domain. Analysis of root‐mean‐square fluctuation (RMSF) values and dynamic cross‐correlation matrices (DCCM) reveals that removal of N‐terminal fragment results in complete decoupling between V and C domains. Binding of self‐assembled Congo red molecules improves the coupling, albeit slightly. The disruption of a small β‐sheet composed of N‐ and C‐terminal fragments of the domain (NC sheet) is the most likely reason for the decoupling. Self‐assembled ligand, bound in the place originally occupied by N‐terminal fragment, is not able to take over the function of the β‐sheet. Lack of correlation of motions between residues in V and C domains denotes that light chain–Congo red complexes have hampered ability to transmit conformational changes between domains. This is a likely explanation of the lack of complement binding by immunological complexes, which bind Congo red, and supports the idea that the NC sheet is the key structural fragment taking part in immunological signal transduction. Proteins 2005. © 2005 Wiley‐Liss, Inc.