bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lack of Effect of P‐glycoprotein Inhibition on Renal Clearance of Dicloxacillin in Patients with Cystic Fibrosis
Authors: Beringer Paul M. , Kriengkauykiat Jane , Zhang Xiyun , Hidayat Levita , Liu Shanshan , Louie Stan , Synold Tim , Burckart Gilbert J. , Rao Purush A. , Shapiro Bertrand , Gill Mark 
Published: June 2008

Study Objective. To determine whether upregulation of P‐glycoprotein is responsible for the enhanced renal clearance of dicloxacillin in patients with cystic fibrosis.Design. Single‐center, prospective, open‐label, randomized, three‐part crossover pharmacokinetic study.Setting. General clinical research center.Subjects. Eleven patients with cystic fibrosis and 11 age‐matched healthy volunteers.Intervention. All subjects received a single oral dose of dicloxacillin 500 mg alone, dicloxacillin 500 mg plus probenecid (an organic anion transport inhibitor) 1 g, and dicloxacillin 500 mg plus cyclosporine (a P‐glycoprotein inhibitor) 5 mg/kg; each treatment was separated by a washout period of 48 hours. A bolus dose of iothalamate meglumine 456 mg was administered on each study day as a marker of glomerular filtration.Measurements and Main Results. Blood and urine samples were taken serially up to 6 hours after each dose. Pharmacokinetics of dicloxacillin and iothalamate were determined by using compartmental and noncompartmental methods. Quantitative polymerase chain reaction was performed on peripheral blood mononuclear cells to measure expression of multidrug resistance 1 (MDR1) messenger RNA (mRNA). Genotyping for ABCB1 was performed to determine the presence of single nucleotide polymorphisms (exons 21 and 26). In both healthy subjects and patients with cystic fibrosis, compared with dicloxacillin alone, coadministration with probenecid produced a significantly lower renal clearance of dicloxacillin, whereas coadministration with cyclosporine resulted in no significant change; renal clearance was not significantly different between the two study groups. No correlation was found between MDR1 mRNA expression and renal clearance of dicloxacillin. The renal excretion of dicloxacillin was significantly greater in subjects with the ABCB1 exon 26 TT polymorphism when compared with subjects with the CT genotype.Conclusion. We found no significant difference in the pharmacokinetics of dicloxacillin between patients with cystic fibrosis and healthy volunteers. Renal clearance of dicloxacillin was significantly reduced in the presence of probenecid but not with cyclosporine, suggesting that the rate‐limiting step in tubular secretion of dicloxacillin is uptake mediated by the organic anion transporter, and not P‐glycoprotein inhibition.
Diversity of Antimicrobial Use and Resistance in 42 Hospitals in the United States
Authors: Pakyz Amy , Powell J. Patrick , Harpe Spencer E. , Johnson Chris , Edmond Michael , Polk Ron E. 
Published: June 2008

Study Objective. To measure diversity (or heterogeneity) of antibiotic use in a sample of hospitals in the United States and to assess an association with bacterial resistance.Design. Observational cross‐sectional study.Setting. Forty‐two general medical‐surgical hospitals, mostly in the Eastern United States.Data Source. Administrative claims data and hospital antibiograms during 2003.Measurements and Main Results. Antibiotic use was measured by defined daily dose (DDD), and diversity was assessed by using Simpson's Index and the Shannon‐Weiner Index. Aggregated antibiograms (from 17 hospitals) were used to assess resistance. There were a total of 3,655,579 patient‐days during 2003, with a mean ± SD of 87,037 ± 62,679 patient‐days/hospital. Mean ± SD antibiotic use was 704 ± 244 DDD/1000 patient‐days/hospital, and fluoroquinolones represented the largest single class. Mean ± SD diversity by Simpson's Index was 0.861 ± 0.022/hospital, and a strong correlation was noted between the two diversity measures. Multivariate analysis found no significant relationship between diversity and the proportion of resistant pathogens.Conclusion. Diversity of aggregate antibiotic use can be measured, but additional investigations are needed to determine if it is a useful strategy to contain resistance.
Safety and Efficacy of Simvastatin for the Treatment of Dyslipidemia in Human Immunodeficiency Virus‐Infected Patients Receiving Efavirenz‐Based Highly Active Antiretroviral Therapy
Authors: Rahman Anita P. , Eaton Susan A. , Nguyen Sean T. , Bain Amy M. , Payne Kenna D. , Bedimo Roger , Busti Anthony J. 
Published: June 2008

Study Objectives.To evaluate the safety and efficacy of simvastatin for treatment of dyslipidemia in patients with the human immunodeficiency virus (HIV) who were receiving efavirenz‐based highly active antiretroviral therapy (HAART), and to evaluate the effect of simvastatin when added to efavirenz on CD4+count, HIV viral load, and frequency of attainment of patient‐specific National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III lipid goals.Design.Retrospective medical record review.Setting.Veterans Affairs health care system in Dallas, Texas.Patients.Thirteen HIV‐infected men who received a stable efavirenz‐based HAART regimen concurrently with simvastatin 20 mg/day, and 19 HIV‐negative men who received simvastatin 20 mg/day (controls).Measurements and Main Results.Demographic, clinical, and laboratory data were collected before and after starting simvastatin. Reductions in lipid profile values in the HIV‐infected group versus HIV‐negative group were as follows: total cholesterol −20% versus −28% (p=0.15), low‐density lipoprotein cholesterol (LDL) −36% versus −41% (p=0.06), non‐high‐density lipoprotein cholesterol (non‐HDL) −22% versus −33% (p=0.212), and total cholesterol:HDL ratio −33% versus −30% (p=0.26). These effects were seen without any documented adverse drug reactions or changes in viral and immunologic control. However, 28% fewer HIV‐infected patients were able to achieve NCEP ATP III LDL goals compared with HIV‐negative subjects.Conclusion.These preliminary comparative data suggest that simvastatin can be safely and effectively used to treat dyslipidemia in HIV‐infected patients receiving efavirenz‐based HAART without compromising viral or immunologic control. However, our results are suggestive of slight lessening of the LDL‐lowering effects, which might be explained by the known reduction in simvastatin levels with efavirenz. Furthermore, fewer HIV‐infected patients were able to meet their NCEP ATP III goals compared with HIV‐negative controls, highlighting the difficulty in treating this population to current standards of care.
Collateral Geochemical Impacts of Agricultural Nitrogen Enrichment from 1963 to 1985: A Southern Wisconsin Ground Water Depth Profile
Authors: Browne Bryant A. , Kraft George J. , Bowling Juliane M. , DeVita William M. , Mechenich David J. 
Published: June 2008

AbstractIn this study, we used chlorofluorocarbon (CFC) age‐dating to investigate the geochemistry of N enrichment within a bedrock aquifer depth profile beneath a south central Wisconsin agricultural landscape. Measurement of N2O and excess N2allowed us to reconstruct the total NO3−and total nitrogen (TN) leached to ground water and was essential for tracing the separate influences of soil nitrification and ground water denitrification in the collateral geochemical chronology. We identify four geochemical impacts due to a steady ground water N enrichment trajectory (39 ± 2.2 μmol L−1yr−1,r2= 0.96) over two decades (1963–1985) of rapidly escalating N use. First, as a by‐product of soil nitrification, N2O entered ground water at a stable (r2= 0.99) mole ratio of 0.24 ± 0.007 mole% (N2O–N/NO3–N). The gathering of excess N2O in ground water is a potential concern relative to greenhouse gas emissions and stratospheric ozone depletion after it discharges to surface water. Second, excess N2measurements revealed that NO3−was a prominent, mobile, labile electron acceptor comparable in importance to O2.Denitrification transformed 36 ± 15 mole% (mol mol−1× 100) of the total N within the profile to N2gas, delaying exceedance of the NO3−drinking water standard by approximately 6 yr. Third, soil acids produced from nitrification substantially increased the concentrations of major, dolomitic ions (Ca, Mg, HCO3−) in ground water relative to pre‐enrichment conditions. By 1985, concentrations approximately doubled; by 2006, CFC age‐date projections suggest concentrations may have tripled. Finally, the nitrification induced mobilization of Ca may have caused a co‐release of P from Ca‐rich soil surfaces. Dissolved P increased from an approximate background value of 0.02 mg L−1in 1963 to 0.07 mg L−1in 1985. The CFC age‐date projections suggest the concentration could have reached 0.11 mg L−1in ground water recharge by 2006. These results highlight an intersection of the N and P cycles potentially important for managing the quality of ground water discharged to surface water.
Humic Acid Formation in Artificial Soils Amended with Compost at Different Stages of Organic Matter Evolution
Authors: Adani Fabrizio , Spagnol M. 
Published: June 2008

AbstractA composting process was conducted under optimal conditions for 150 d, obtaining three biomasses at different levels of maturity: raw material (RM), fresh compost obtained after 11 d of composting (FC), and evolved compost (EC) obtained after 150 d of composting. During the composting process, HAs were extracted and fully characterized by mass balance, DRIFT, and 1H and 13C‐nuclear magnetic resonance spectroscopy. Each compost sample was incubated for 180 d in an artificial soil, after which HA extraction was repeated and characterized. To compare composts containing different amounts of labile organic matter (OM), an equal amount of unhydrolyzable OM was added to the soils. Our results indicated that compost HAs consist of a biologically and chemically stable fraction (i.e., the unhydrolyzable HA [U‐HA]) and a labile fraction, whose relative contents depended on the composting duration. Humic acid from more EC contained a higher amount of recalcitrant fraction (aromatic carbon) and a lesser amount of labile fraction (aliphatic carbon) than HA from RM and FC. These results suggest that the humification process during composting preserves the more recalcitrant fraction of the compost‐alkali soluble/acid insoluble fraction (HA‐fraction). Incubation of composts in soil showed that due to the higher labile fraction content, HAs from raw material were more degraded than those from EC. The abundance of labile carbon of soil amended with less‐evolved compost (RM and FC) allowed the more recalcitrant fractions of U‐HA to be more preserved than in EC. These results suggest that less‐evolved compost could contribute more than well evolved compost to the stable soil OM.
The Effect of River Pulsing on Sedimentation and Nutrients in Created Riparian Wetlands
Authors: Nahlik Amanda M. , Mitsch William J. 
Published: June 2008

AbstractSedimentation under pulsed and steady‐flow conditions was investigated in two created flow‐through riparian wetlands in central Ohio over 2 yr. Hydrologic pulses of river water lasting for 6 to 8 d were imposed on each wetland from January through June during 2004. Mean inflow rates during pulses averaged 52 and 7 cm d−1 between pulses. In 2005, the wetlands received a steady‐flow regime of 11 cm d−1 with no major hydrologic fluctuations. Thirty‐two sediment traps were deployed and sampled once per month in April, May, June, and July for two consecutive years in each wetland. January through March were not sampled in either year due to frozen water surfaces in the wetlands. Gross sedimentation (sedimentation without normalizing for differences between years) was significantly greater in the pulsing study period (90 kg m−2) than in the steady‐flow study period (64 kg m−2). When normalized for different hydrologic and total suspended solid inputs between years, sedimentation for April through July was not significantly different between pulsing and steady‐flow study periods. Sedimentation for the 3 mo that received hydrologic pulses (April, May, and June) was significantly lower during pulsing months than in the corresponding steady‐flow months. Large fractions of inorganic matter in collected sediments indicated that allochthonous inputs were the main contributor to sedimentation in these wetlands. Organic matter fractions of collected sediments were consistently greater in the steady‐flow study period (1.8 g kg−1) than in the pulsed study period (1.5 g kg−1), consistent with greater primary productivity in the water column during steady‐flow conditions.
Effects of Agronomic Practices on Phytoremediation of an Aged PAH‐Contaminated Soil
Authors: Olson Paul E. , Castro Ana , Joern Mark , DuTeau Nancy M. , Pilon‐Smits Elizabeth , Reardon Kenneth F. 
Published: June 2008

AbstractPhytoremediation offers an ecologically and economically attractive remediation technique for soils contaminated with polycyclic aromatic hydrocarbons (PAHs). In addition to the choice of plant species, agronomic practices may affect the efficiency of PAH phytoremediation. Inorganic nutrient amendments may stimulate plant and microbial growth, and clipping aboveground biomass might stimulate root turnover, which has been associated with increases in soil microbial populations. To assess the influence of fertilization and clipping on PAH dissipation in a nutrient‐poor, aged PAH‐contaminated soil, a 14‐mo phytoremediation study was conducted using perennial ryegrass (Lolium perenne) as a model species. Six soil treatments were performed in replicate: unplanted; unplanted and fertilized; planted; planted and fertilized; planted and clipped; and planted, clipped, and fertilized. Plant growth, soil PAH concentrations, and the concentrations of total and PAH‐degrading microorganisms were measured after 7 and 14 mo. Overall, planting (with nearly 80% reduction in total PAHs) and planting + clipping (76% reduction in total PAHs) were the most effective treatments for increased PAH dissipation after 14 mo. Fertilization greatly stimulated plant and total microbial growth, but negatively affected PAH dissipation (29% reduction in total PAHs). Furthermore, unplanted and fertilized soils revealed a similar negative impact (25% reduction) on PAH dissipation after 14 mo. Clipping did not directly affect PAH dissipation, but when combined with fertilization (61% reduction in total PAHs), appeared to mitigate the negative impact of fertilization on PAH dissipation. Therefore, fertilization and clipping may be included in phytoremediation design strategies, as their combined effect stimulates plant growth while not affecting PAH dissipation.
Sorption of the Veterinary Antimicrobials Sulfadimethoxine and Ormetoprim in Soil
Authors: Sanders S. M. , Srivastava P. , Feng Y. , Dane J. H. , Basile J. , Barnett M. O. 
Published: June 2008

AbstractCurrently, limited research on the fate of antimicrobials in the environment exists, once they are discharged in human and animal wastes. Sorption of two antimicrobials, sulfadimethoxine (SDM) and ormetoprim (OMP), was investigated in two soils and sand using a series of batch experiments. Because OMP and SDM are often administered in combination, their sorption was also investigated in combination as co‐solutes. The rate of SDM and OMP sorption was rapid over the first few hours of the experiments, which then slowed considerably after 16 to 68 h. OMP sorption was enhanced at high concentrations when in combination with SDM, with linear sorption coefficients ranging from 1.3 to 58.3 L·kg−1 in the single solute experiments and 4.96 to 89.7 L·kg−1 in the co‐solute experiments. Sorption of OMP as a single solute seems to provide a better fit with the Freundlich equation, which became more linear (n approached 1) when SDM was present. Overall, SDM sorbed less than OMP in the two soils and sand. SDM linear sorption coefficients ranged from 0.4 to 25.8 L·kg−1 as a single solute and 2.5 to 22.1 L·kg−1 as a co‐solute. Sorption of SDM becomes more nonlinear (n < 1) when SDM is present in combination with OMP. Overall, sorption of both antimicrobials increased in the selected soils and sand as the organic matter, clay content, and cation exchange capacity increased. These experiments indicate relatively low sorption of SDM and OMP in natural soils, making them a potential threat to surface and ground water.
Nitrogen, Tillage, and Crop Rotation Effects on Nitrous Oxide Emissions from Irrigated Cropping Systems
Authors: Halvorson Ardell D. , Del Grosso Stephen J. , Reule Curtis A. 
Published: June 2008

AbstractWe evaluated the effects of irrigated crop management practices on nitrous oxide (N2O) emissions from soil. Emissions were monitored from several irrigated cropping systems receiving N fertilizer rates ranging from 0 to 246 kg N ha−1 during the 2005 and 2006 growing seasons. Cropping systems included conventional‐till (CT) continuous corn (Zea mays L.), no‐till (NT) continuous corn, NT corn–dry bean (Phaseolus vulgaris L.) (NT‐CDb), and NT corn–barley (Hordeum distichon L.) (NT‐CB). In 2005, half the N was subsurface band applied as urea‐ammonium nitrate (UAN) at planting to all corn plots, with the rest of the N applied surface broadcast as a polymer‐coated urea (PCU) in mid‐June. The entire N rate was applied as UAN at barley and dry bean planting in the NT‐CB and NT‐CDb plots in 2005. All plots were in corn in 2006, with PCU being applied at half the N rate at corn emergence and a second N application as dry urea in mid‐June followed by irrigation, both banded on the soil surface in the corn row. Nitrous oxide fluxes were measured during the growing season using static, vented chambers (1–3 times wk−1) and a gas chromatograph analyzer. Linear increases in N2O emissions were observed with increasing N‐fertilizer rate, but emission amounts varied with growing season. Growing season N2O emissions were greater from the NT‐CDb system during the corn phase of the rotation than from the other cropping systems. Crop rotation and N rate had more effect than tillage system on N2O emissions. Nitrous oxide emissions from N application ranged from 0.30 to 0.75% of N applied. Spikes in N2O emissions after N fertilizer application were greater with UAN and urea than with PCU fertilizer. The PCU showed potential for reducing N2O emissions from irrigated cropping systems.
The Determination of Carbon Dioxide Concentration Using Atmospheric Pressure Ionization Mass Spectrometry/Isotopic Dilution and Errors in Concentration Measurements Caused by Dryers
Authors: DeLacy Brendan G. , Bandy Alan R. 
Published: June 2008

AbstractAn atmospheric pressure ionization mass spectrometry/isotopically labeled standard (APIMS/ILS) method has been developed for the determination of carbon dioxide (CO2) concentration. Descriptions of the instrumental components, the ionization chemistry, and the statistics associated with the analytical method are provided. This method represents an alternative to the nondispersive infrared (NDIR) technique, which is currently used in the atmospheric community to determine atmospheric CO2 concentrations. The APIMS/ILS and NDIR methods exhibit a decreased sensitivity for CO2 in the presence of water vapor. Therefore, dryers such as a nafion dryer are used to remove water before detection. The APIMS/ILS method measures mixing ratios and demonstrates linearity and range in the presence or absence of a dryer. The NDIR technique, on the other hand, measures molar concentrations. The second half of this paper describes errors in molar concentration measurements that are caused by drying. An equation describing the errors was derived from the ideal gas law, the conservation of mass, and Dalton's Law. The purpose of this derivation was to quantify errors in the NDIR technique that are caused by drying. Laboratory experiments were conducted to verify the errors created solely by the dryer in CO2 concentration measurements post‐dryer. The laboratory experiments verified the theoretically predicted errors in the derived equations. There are numerous references in the literature that describe the use of a dryer in conjunction with the NDIR technique. However, these references do not address the errors that are caused by drying.
Evidence for Struvite in Poultry Litter: Effect of Storage and Drying
Authors: Hunger Stefan , Sims J. Thomas , Sparks Donald L. 
Published: June 2008

AbstractThe use of spectroscopic techniques (especially phosphorus‐31 nuclear magnetic resonance [31P‐NMR] and X‐ray absorption near edge structure spectroscopy) has recently advanced the analysis of the speciation of P in poultry litter (PL) and greatly enhanced our understanding of changes in P pools in PL that receive alum (aluminum sulfate) to reduce water‐soluble P and control ammonia emissions from poultry houses. Questions remain concerning changes of P species during long‐term storage, drying, or after application of PL to cropland or for other uses, such as turfgrass. In this study, we investigated a set of six PL samples (of which three were alum‐amended and three were unamended) that had been characterized previously. The P speciation was analyzed using solid‐state 31P‐NMR spectroscopy, and the mineralogy was analyzed by powder X‐ray diffraction (XRD) after storing the samples moist and dried for up to 5 yr under controlled conditions. The magnesium ammonium phosphate mineral struvite was identified in all but one PL samples. Struvite concentrations were generally lower in dried samples (≤14%) than in samples stored moist (23 and 26%). The moist samples also had higher concentrations of phosphate bound to aluminum hydroxides. Solid‐state NMR spectroscopy was in general more sensitive than XRD in detecting and quantifying P species. Although phosphate associated with calcium and aluminum made up a large proportion of P species, they were not detected by XRD.
Simulated Effects of Sulfur Deposition on Nutrient Cycling in Class I Wilderness Areas
Authors: Elliott Katherine J. , Vose James M. , Knoepp Jennifer D. , Johnson Dale W. , Swank Wayne T. , Jackson William 
Published: June 2008

AbstractWe predicted the effects of sulfate (SO4) deposition on wilderness areas designated as Class I air quality areas in western North Carolina using a nutrient cycling model (NuCM). We used three S deposition simulations: current, 50% decrease, and 100% increase. We measured vegetation, forest floor, and root biomass and collected soil, soil solution, and stream water samples for chemical analyses. We used the closest climate stations and atmospheric deposition stations to parameterize NuCM. The areas were: Joyce Kilmer (JK), Shining Rock (SR), and Linville Gorge (LG). They differ in soil acidity and nutrients, and soil solution and stream chemistry. Shining Rock and LG have lower soil solution base cation and higher acidic ion concentrations than JK. For SR and LG, the soil solution Ca/Al molar ratios are currently 0.3 in the rooting zone (A horizon), indicating Al toxicity. At SR, the simulated Ca/Al ratio increased to slightly above 1.5 after the 30‐yr simulation regardless of S deposition reduction. At LG, Ca/Al ratios ranged from 1.6 to 2.4 toward the end of the simulation period, the 100% increase scenario had the lower value. Low Ca/Al ratios suggest that forests at SR and LG are significantly stressed under current conditions. Our results also suggest that SO4 retention is low, perhaps contributing to their high degree of acidification. Their soils are acidic, low in weatherable minerals, and even with large reductions in SO4 and associated acid deposition, it may take decades before these systems recover from depletion of exchangeable Ca, Mg, and K.