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1

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An Evaluation of Bivalves as Biomonitors of Heavy Metals Pollution in Marine Waters (1999)

Boening, Dean W.

Springer

Environmental monitoring and assessment 55 (1999), S. 459-470

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ISSN: 1573-2959

Keywords: bioaccumulation ; biomonotoring ; bioavailability ; bivalves ; bioindicator

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract Heavy metals (namely Cr, Cu, Zn, As, Hg, Pb, Ni, and Ag) that are present at concentrations common in ambient marine waters can cause adverse effects in shellfish. Such effects can significantly impact the trophic structure of a biological community. Heavy metals uptake is dependent on both geochemical and biological factors. In bivalves, the extent of accumulation is a function of several biotic and abiotic variables. Based on several criteria, (including: an ability to accumulate metals without suffering mortality, habitation within, and continuous exposure to, the contaminated matrix, hardiness, and ease of sampling) bivalve molluscs have proven to be useful biomonitors for a host of inorganic contaminants. It is essential that the biomonitoring plan is not only site specific, but that it considers the use of indigenous species whenever possible. This paper will provide a general review of studies that have employed bivalved shellfish as sentinel bioindicators in marine environments impacted by heavy metals, and give suggestions for conducting biomonitoring assays.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005995217901

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2

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Uptake of Copper by Neon Tetras (Paracheirodon innesi) in the Presence and Absence of Particulate and Humic Matter (1999)

Tao, Shu ; Liang, Tao ; Liu, Changfa ; [et al.]

Springer

Ecotoxicology 8 (1999), S. 269-275

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ISSN: 1573-3017

Keywords: fish ; speciation ; copper ; bioavailability ; bioaccumulation

Source: Springer Online Journal Archives 1860-2000

Topics: Energy, Environment Protection, Nuclear Power Engineering

Notes: Abstract Neon tetras Paracheirodon innesi were exposed to various species of copper during exposures to evaluate the bioavailability of free copper (0 to 2 mg/l), copper apparently complexed to humic substances (0 to 160 mg/l), and copper adsorbed on kaolin clays (0 to 182 mg/l). The results of the experiments demonstrated that free copper is the most bioavailable form. Both humic substances and kaolin clay particulates reduced copper bioavailability to the fish. However, fish accumulated a fraction of copper complexed to humic substances and part of copper adsorbed on kaolin clays.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008977131711

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3

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Absolute Bioavailability and Absorption Profile of Cyanamide in Man (1999)

Colom, Helena ; Pruñonosa, Joan ; Peraire, Concepción ; [et al.]

Springer

Journal of pharmacokinetics and pharmacodynamics 27 (1999), S. 421-436

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ISSN: 1573-8744

Keywords: cyanamide ; absorption ; bioavailability ; man ; first-pass effect ; pre-systemic metabolism ; absorbed amount

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract A pharmacokinetic study of cyanamide, an inhibitor of aldehyde dehydrogenase (EC1.2.1.3) used as an adjuvant in the aversive therapy of chronic alcoholism, has been carried out in healthy male volunteers following intravenous and oral administration. Cyanamide plasma levels were determined by a sensitive HPLC assay, specific for cyanamide. After intravenous administration cyanamide displayed a disposition profile according to a two-compartmental open model. Elimination half-life and total plasma clearance values ranged from 42.2 to 61.3 min and from 0.0123 to 0.0190 L · kg −1 · min−1, respectively. After oral administration of 0.3, 1.0, and 1.5 mg/kg $$x -$$ ± SEM values of Cmax, tmax (median) and AUC were 0.18 ± 0.03, 0.91 ± 0.11, and 1.65 ± 0.27 μg · ml −1 ; 13.5, 13.5, and 12 min; and 8.59 ± 1.32, 45.39 ± 1.62, and 77.86 ± 17.49 μg · ml −1 · min, respectively. Absorption was not complete and the oral bioavailability, 45.55 ± 9.22, 70.12 ± 4.73, and 80.78 ± 8.19% for the 0.3, 1.0, and 1.5 mg/kg doses, respectively, increased with the dose administered. The models that consider a first-order absorption process alone (whether with a fixed or variable bioavailability value as a function of dose) or with loss of drug due to presystemic metabolism (with zero-order or Michaelis–Menten kinetics) were simultaneously fitted to plasma level data obtained following 1 mg/kg iv and 0.3, 1.0, and 1.5 mg/kg oral administrations. The model that best fit the data was that with a first-order absorption process plus a loss by presystemic metabolism with Michaelis–Menten kinetics, suggesting the presence of a saturable first-pass effect.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1020969106163

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4

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Grapefruit Juice Activates P-Glycoprotein-Mediated Drug Transport (1999)

Soldner, Andrea ; Christians, Uwe ; Susanto, Miki ; [et al.]

Springer

Pharmaceutical research 16 (1999), S. 478-485

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ISSN: 1573-904X

Keywords: grapefruit juice ; bioavailability ; active transport ; intestine ; cytochrome P450 3A metabolism

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract Purpose. Grapefruit juice (GJ) is known to increase the oral bioavailability of many CYP3A-substrates by inhibiting intestinal phase-I metabolism. However, the magnitude of AUC increase is often insignificant and highly variable. Since we earlier suggested that CYP3A and P-glycoprotein (P-gp) form a concerted barrier to drug absorption, we investigated the role of P-gp in GJ-drug interactions. Methods. The transcellular bidirectional flux of drugs that are (i) CYP3A-and/or P-gp substrates (Vinblastine, Cyclosporine, Digoxin, Fexofenadine, Losartan) or that are (ii) primary CYP3A-substrates (Felodipine, Nifedipine) was evaluated across MDCK-MDR1 cell monolayers with or without GJ, verifying monolayer integrity at all times. Results. While both apical-to-basal (A-B) and basal-to-apical (B-A) fluxes of all CYP3A/P-gp substrates tested were increased in the presence of GJ, the resulting net efflux (B-A/A-B) was in all cases significantly greater with GJ than control (Vin, 28.0 vs. 5.1; CsA, 9.9 vs. 2.8; Dig, 22. 9 vs. 14.7, Fex, 22.3 vs. 11.1, Los, 39.6 vs. 26). In contrast, no such GJ flux effect was observed with Pel and Nif, substrates of CYP3A only (2 vs. 1.7 and 1.2 vs. 1.3). Conclusions. GJ significantly activates P-gp-mediated efflux of drugs that are substrates of P-gp, potentially partially counteracting the CYP3A-inhibitory effects of GJ.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1011902625609

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5

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Biopharmaceutical Approaches for Developing and Assessing Oral Peptide Delivery Strategies and Systems: In Vitro Permeability and In Vivo Oral Absorption of Salmon Calcitonin (1999)

Sinko, Patrick J. ; Lee, Yong-Hee ; Makhey, Vijaya ; [et al.]

Springer

Pharmaceutical research 16 (1999), S. 527-533

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ISSN: 1573-904X

Keywords: permeability ; bioavailability ; rats ; dogs ; humans ; oral delivery ; peptides ; and salmon calcitonin

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology

Notes: Abstract Purpose. To evaluate a biopharmaceutical approach for selecting formulation additives and establishing the performance specifications of an oral peptide delivery system using sCT as a model peptide. Methods. The effect of formulation additives on sCT effective permeability and transepithelial electrical resistance (TEER) was evaluated in side-by-side diffusion chambers using rat intestinal segments. Baseline regional oral absorption of sCT was evaluated in an Intestinal and Vascular Access Port (IVAP) dog model by administration directly into the duodenum, ileum, and colon by means of surgically implanted, chronic catheters. The effect of varying the input rate and volume of the administered solution on the extent of sCT absorption was also evaluated. Citric acid (CA) was utilized in all studies to cause a transient reduction in local pH. In vitro samples and plasma samples were analyzed by radioimmunoassay (RIA). Two oral delivery systems were prepared based on the results of the in vitro and IVAP studies, and evaluated in normal dogs. Results. Maximal permeability enhancement of sCT was observed using taurodeoxycholate (TDC) or lauroyl carnitine (LC) in vitro. Ileal absorption of sCT was higher than in other regions of the intestine. Low volume and bolus input of solution formulations was selected as the optimal condition for the IVAP studies since larger volumes or slower input rates resulted in significantly lower sCT bioavailability (BA). Much lower BA of sCT was observed when CA was not used in the formulation. The absolute oral bioavailability (mean ± SD) in dogs for the control (sCT + CA) and two proprietary sCT delivery systems was 0.30% ± 0.05%, 1.10 ± 0.18%, and 1.31 ± 0.56%, respectively. Conclusions. These studies demonstrate the utility of in vitro evaluation and controlled in vivo studies for developing oral peptide delivery strategies. Formulation additives were selected, the optimal intestinal region for delivery identified, and the optimal release kinetics of additives and actives from the delivery system were characterized. These methods were successfully used for devising delivery strategies and fabricating and evaluating oral sCT delivery systems in animals. Based on these studies, sCT delivery systems have been fabricated and tested in humans with favorable results.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1018819012405

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6

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Root-induced modifications of the exchange of phosphate ion between soil solution and soil solid phase (1999)

Morel, C. ; Hinsinger, P.

Springer

Plant and soil 211 (1999), S. 103-110

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ISSN: 1573-5036

Keywords: bioavailability ; isotopic evaluation ; phosphate ion exchange ; phosphorus ; rhizosphere ; soil solution

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The uptake of phosphorus (P) by roots results in a depletion of phosphate ions (PO4) in the rhizosphere. The corresponding decrease in PO4 concentration in the soil solution (CP) gives rise to a replenishment of P from the solid phase which is time- and CP-dependent. This PO4 exchange which reflects the buffer power of the soil for PO4 also varies with the composition and the physico-chemical conditions of the soil. As root activity can modify these physico-chemical conditions in the rhizosphere, the question arises whether these modifications affect the ability of PO4 bound to the soil solid phase to exchange with PO4 in soil solution. The aim of the present work was to measure and compare the parameters which describe the amount of PO4 bound to soil solid phase that is capable to replenish solution P for both rhizosphere and bulk soils. The soil sample was a P-enriched, calcareous topsoil collected from a long-term fertiliser trial. Rhizosphere soil samples were obtained by growing dense mats of roots at the surface of 3 mm thick soil layer for one week. Three plant species were compared: oilseed rape (Brassica napus L., cv Goeland) pea (Pisum sativum L., cv. Solara) and maize ( Zea mays L., cv. Volga). The time- and CP-dependence of the PO4 exchange from soil to solution were described using an isotopic dilution method. The measured CP values were 0.165 mg P L−1 for bulk soil and 0.111, 0.101 and 0.081 mg P L−1 for rhizosphere soils of maize, pea and rape, respectively. The kinetics of the PO4 exchange between liquid and solid phases of soil were significantly different between rhizosphere and bulk soils. However, when changes in CP were accounted for, the parameters describing the PO4 exchange with time and CP between soil solution and soil solid phase were found to be very close for bulk and rhizosphere soils. For this calcareous and P-enriched soil, plant species differed in their ability to deplete PO4 in solution. The resulting changes in the ability of the soil solid phase to replenish solution PO4 were almost fully explained by the depletion of soil solution P.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004485432261

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7

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Two-liquid-phase bioreactors for enhanced degradation of hydrophobic/toxic compounds (1999)

Déziel, Eric ; Comeau, Yves ; Villemur, Richard

Springer

Biodegradation 10 (1999), S. 219-233

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ISSN: 1572-9729

Keywords: bioavailability ; biodegradation ; bioreactor ; biotreatment ; NAPL ; toxicity

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Two-liquid-phase culture systems involve the addition of a water-immiscible, biocompatible and non-biodegradable solvent to enhance a biocatalytic process. Two-liquid-phase bioreactors have been used since the mid-seventies for the microbial and enzymatic bioconversion of hydrophobic/toxic substrates into products of commercial interest. The increasing popularity of bioremediation technologies suggests a new area of application for this type of bioreactor. The toxicity and the limited bioavailability of many pollutants are important obstacles that must first be overcome in order to improve biodegradation processes. Two-liquid-phase bioreactors have the potential to resolve both limitations of biotreatment technologies by the enhancement of the mass-transfer rate of compounds with low bioavailability, and by the controlled delivery of apolar toxic compounds. This technology can also be useful in accelerating the enrichment of microorganisms degrading problematic pollutants. In this paper, we discuss the application of two-liquid-phase bioreactors to enhance the biodegradation of toxic/poorly bioavailable contaminants. Important microbial mechanisms involved in this type of system are described. Uptake of the substrates can be achieved by microorganisms freely dispersed in the aqueous phase and/or bound at the interface between the aqueous and the immiscible phases. Production of surface-active compounds and adhesion abilities are microbial features involved in the process. General guidelines for the design of two-liquid-phase bioreactors for biodegradation purposes are presented. Solvent selection should be established on specific criteria, which depend on the characteristics of target compound(s) and the microorganism(s) implicated in the biodegradation process. The central importance of maximizing the interfacial surface area is highlighted. The potential of this approach as an alternative to current biotreatment technologies is also discussed.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008311430525

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8

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Plant availability of selenite and selenate as influenced by the competing ions phosphate and sulfate (1999)

Hopper, Jennifer L. ; Parker, David R.

Springer

Plant and soil 210 (1999), S. 199-207

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ISSN: 1573-5036

Keywords: antagonism ; bioavailability ; phytotoxicity ; selenium ; speciation

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The relative plant availability of selenate versus selenite depends on the concentrations of competing ions, specifically sulfate and phosphate, respectively. In solution culture, the concentration of phosphate is typically 100- to 1000-fold greater than in soil solution, an artifact that could lead to underestimation of the phytoavailability of selenite. A nutrient solution study was conducted to compare the availability of selenite and selenate to perennial ryegrass (Lolium perenne L. cv. Evening Shade) and strawberry clover (Trifolium fragiferrum L. cv. O'Conner) at basal concentrations of SO4 (0.5 mM) and PO4 (2 μM) similar to those found in soil solution. Concentrations up to 5 mM SO4 and 200 μM PO4 allowed quantitative comparison of the efficacy of the competing ions. In both species, selenite was more phytotoxic than selenate, especially for shoot growth. Selenate was less toxic, and tended to preferentially inhibit root growth. Translocation percentages were much higher with selenate (≥84%) than with selenite (≤47%). A 10-fold increase in sulfate decreased uptake from selenate by 〉90% in both species. In ryegrass, 10-fold increases in phosphate caused 30% to 50% decreases in Se accumulation from selenite, but in clover such decreases only occurred in the roots. Sulfate-selenate antagonisms were thus stronger than phosphate-selenite antagonisms. Nonetheless, conventional nutrient solutions with millimolar phosphate will significantly underestimate Se availability from selenite, and moderate levels of sulfate salinity can inhibit selenate uptake sufficiently to reverse the apparent relative availability of the two forms of Se.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1004639906245

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9

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Vertical gradients for particulate Cu fractions in estuarine water over tidal flats (1999)

Gerringa, L.J.A. ; Hummel, H. ; Moerdijk-Poortvliet, T.C.W.

Springer

Hydrobiologia 405 (1999), S. 149-161

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ISSN: 1573-5117

Keywords: copper ; speciation ; estuary ; bioavailability ; particulate organic carbon ; bivalve

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The speciation of particulate copper was determined at several depths (0, 5 and 15 cm above the sediment surface) in the water column above intertidal flat systems in the polluted estuary Westerschelde (WS) and the relatively un-polluted Oosterschelde sea-arm (OS), in order to assess differences in water quality between the main body of water routinely determined in monitoring programmes and that at the sediment–water interface which is factually interacting with the benthic organisms. The bioavailable fraction was estimated by two sequential extraction's: a pH=5 acetic acid (Ac) and a pH=8 Na-dodecylsulphate (Dod) extraction. Irrespective the different character of the systems, when the differences in salinity were taken into account, dissolved fractions (DOC, pH) differed hardly between seasons and stations. Although occasionally a quantitative differentiation between sampling depths could occur, with higher particulate concentrations (Cu, Ac-Cu, Dod-Cu, C, sediment, POC, chlorophyll a) near the sediment-water interface, the qualitative properties (Cu/POC, Ac-Cu/POC, Dod-Cu/POC, Chl-a/POC, C/N) of the water remained constant all over the tidal cycle and between depths. The measurements carried out during monitoring programmes in main water streams thus result in a strong under-estimation of the quantities of particulate substances (seston, POC, chlorophyll a, Cu) available to the benthos at intertidal flats, whereas the qualitative (relative) properties are correctly estimated. With regard to the interaction with benthic organisms, it is concluded that the unexpected levels of Cu in the clam Macoma balthica (equal or higher in the OS than in the polluted Westerschelde) are partly caused by differences in sediment Cu concentrations (Hummel et al., 1997). Additionally the low concentration of suitable, chlorophyll a related, food in OS force the clam to filtrate at higher rates, whereby a higher volume of water and thus ultimately an equal or higher amount of Cu, will be taken in.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1003863207950

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10

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Arsenic tissue concentration of immature mice one hour after oral exposure to gold mine tailings (1999)

Golub, Mari S. ; Keen, Carl L. ; Commisso, Joel F. ; [et al.]

Springer

Environmental geochemistry and health 21 (1999), S. 199-209

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ISSN: 1573-2983

Keywords: arsenic mine tailings ; bioavailability ; ICP/MS ; mice ; development

Source: Springer Online Journal Archives 1860-2000

Topics: Geosciences , Medicine

Notes: Abstract A potentially high bioavailability of arsenic in gold mine tailings from a site in northern California has been suggested by solubility studies. To help address this issue, an in vivo dosing study was conducted using 12‐day‐old Swiss Webster mouse pups (n=8/group). A sample of size‐fractionated mine tailings from the site (〈20 μm particle size, 691 μg g−1 arsenic) was prepared as an aqueous suspension and administered by gavage in a volume that provided 4 mg As/kg body weight. The control group received the same volume of a commercial soil (1 μg g−1 As) of similar particle size (〈60 μm). No mortality or toxic signs were noted in either group. Tissue samples were collected 1 h after gavage, freeze‐dried, microwave‐digested and analysed for arsenic by ICP/MS (detection limit 2 ng As g−1 dry weight). Arsenic concentrations (ng As g−1 dry weight) in tissues from the pups who received mine tailings were significantly higher than in control tissues. The mean elevation in arsenic concentration was highest in the liver (3364% of control, p〈0.0001), followed by blood (818 of control, p〈0.0001), skin (207% of control, p=0.07), and brain (143% of control, p〈0.0001). The carcass arsenic concentration (excluding the GI tract, liver, brain and skin) was 138 of control (p=0.02). The data indicate uptake of arsenic from weathered mine tailings by the immature mouse pups after oral exposure.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1006604928479

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