bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of carbocysteine in human plasma by liquid chromatography/tandem mass spectrometry employing precolumn derivatization
Authors: Chen Xiaoyan , Zhong Dafang , Han Ying , Xie Zhiyong 
Published: January 2003

AbstractA sensitive liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed to determine carbocysteine in human plasma using 2‐pyridylacetic acid as the internal standard (IS). The method employed derivatization with 10 M hydrochloric acid/methanol, which significantly improved the ionization efficiency of carbocysteine. After methanol‐induced protein precipitation of plasma samples, carbocysteine and the IS were derivatized and subjected to LC/MS/MS analysis using atmospheric pressure chemical ionization. The method has a lower limit of quantitation of 20 ng/mL for a 0.2‐mL plasma aliquot. The intra‐ and inter‐day precision (RSD), calculated from quality control (QC) samples, was less than 7%. The accuracy, determined using QC samples, was within ± 1%. The method offered increased sensitivity, selectivity and speed of analysis over existing methods. The method was utilized to support clinical pharmacokinetic studies of carbocysteine in volunteers following oral administration. Copyright © 2002 John Wiley & Sons, Ltd.
Quantitative characterization of differential ion suppression on liquid chromatography/atmospheric pressure ionization mass spectrometric bioanalytical methods
Authors: Avery Michael J. 
Published: January 2003

AbstractIon suppression is a known phenomenon in atmospheric pressure ionization mass spectrometry. These suppression effects have been shown to adversely affect the accuracy and precision of quantitative bioanalytical methods. This paper presents a simple procedure for determining the impact of differential ion suppression on bioanalytical methods that utilize atmospheric pressure ionization mass spectrometric (APIMS) detection. This procedure was applied to the assessment of two potential internal standards, and to determine selectivity issues for another analyte which was to be measured in multiple species. Copyright © 2002 John Wiley & Sons, Ltd.
Mass calibration of a matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometer including the rise time of the delayed extraction pulse
Authors: Moskovets E. , Karger B. L. 
Published: January 2003

AbstractTo utilize fully modern MALDI‐TOF and TOF/TOF mass spectrometers with mass resolution exceeding 10 000 and 2 ppm precision of flight time measurements for high mass accuracy, the model of ion motion used in the mass calibration equation must be expanded. The standard three‐term equation providing up to 5–10 ppm (rms) mass accuracy with internal standards was modified with an additional term accounting for the finite rise time of the high‐voltage extraction pulse. This new four‐term calibration equation minimizes the effect of systematic error resulting from the fact that ion velocities are mass dependent due to the rise time of the extraction pulse. Applying this new calibration equation to a mass spectrum obtained in an axial MALDI‐TOF MS containing 70 peaks (sodiated PEG), each with a signal‐to‐noise ratio greater than 100, a mass accuracy of 1.6 ppm (rms) was obtained over the mass range 1.0–4.0 kDa compared with 3.6 ppm (rms) with the standard three‐term equation. The physical basis of the effects of the finite extraction pulse rise time on mass calibration is examined for axial MALDI‐TOF mass spectrometers, as well as for orthogonal acceleration TOF mass spectrometers. Copyright © 2002 John Wiley & Sons, Ltd.
Ion suppression in the determination of clenbuterol in urine by solid‐phase extraction atmospheric pressure chemical ionisation ion‐trap mass spectrometry
Authors: van Hout M. W. J. , Niederländer H. A. G. , de Zeeuw R. A. , de Jong G. J. 
Published: January 2003

AbstractIon suppression effects were observed during the determination of clenbuterol in urine with solid‐phase extraction/multiple‐stage ion‐trap mass spectrometry (SPE/MS3), despite the use of atmospheric pressure chemical ionisation. During SPE, a polymeric stationary phase (polydivinylbenzene) was applied. Post‐cartridge infusion of analyte to the SPE eluate after the extraction of blank urine was performed to obtain a profile of the suppression. Single and multiple‐stage MS were performed to provide insight in the suppressing compounds. The ion suppression was mainly ascribed to two m/z values, but still no identification of the compounds was achieved from the multiple‐stage MS data. No ionisable and non‐ionisable complexes and/or precipitation of clenbuterol with matrix compounds were observed. A concentration dependence of the percentage of suppression was observed. Up to 70% of the signal was suppressed upon post‐cartridge infusion of 0.22 μg/mL (at 5 μL/min) clenbuterol into the eluate, and this decreased to about 4% at infusion of 22 μg/mL clenbuterol. Molecularly imprinted polymers were used to enhance the selectivity of the extraction. Although matrix components were still present after extraction, no interference of these compounds with the analyte was observed. However, the bleeding of the imprint from the polymer (brombuterol) caused significant ion suppression. Copyright © 2002 John Wiley & Sons, Ltd.
Local institutions and natural resource management in the South Tongu District of Ghana: a case study
Authors: Koku John E. , Gustafsson Jan‐Erik 
Published: January 2003

AbstractThis paper draws on secondary and primary data derived from a field survey undertaken in Torsukpo and Agbogbla communities in the South Tongu District of Ghana to discuss possibilities of enhancing the roles of local institutions in resource management. Key issues addressed in the paper include (i) limitations which share cropping (abunu‐abusa) as a local social institutional arrangement places on tenant farmers and (ii) the role of the District Assembly with specific reference to policy provisions placed at its disposal that could be used to formulate co‐operative strategies that may help mobilize and empower the local people for effective natural resources management. To complement efforts in this direction, the paper also highlights some possible ways in which NGOs could play more effective roles in facilitating development process in the district. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment
Revisiting the logical and research considerations of competitive advantage
Authors: Arend Richard J. 
Published: January 2003

AbstractThis commentary addresses the main points made in the recent article by T. C. Powell on the logical and philosophical flaws in the main thesis of strategy research. Each one of Powell's three points is refutable. The main thesis of strategy research retains logical causation given a reasonable definition of the main explanatory variable. Strategy theory is falsifiable when the implied assumptions of the theory are exploited and the endogeneity of its explanatory variables is considered. The characterization of strategy research as pragmatic instrumentalism void of progress to the objective truth is a proposition without any logical or empirical support. Copyright © 2003 John Wiley & Sons, Ltd.
Entry mode, organizational learning, and R&D in foreign affiliates: evidence from Japanese firms
Authors: Belderbos René 
Published: January 2003

AbstractThis paper develops hypotheses concerning the role of entry mode and experience‐based organizational learning as determinants of the R&D intensity of foreign affiliates and tests these hypotheses on a sample of 420 Japanese manufacturing affiliates abroad. Entry mode has a major impact on R&D activities: the R&D intensities of acquired affiliates substantially exceed those in wholly owned greenfield affiliates, while the R&D intensities of minority owned ventures are higher if Japanese parent firms lack strong R&D capabilities at home. For greenfield operations, support is found for an incremental growth pattern of foreign R&D as a function of organizational learning and affiliate capability building. The results are consistent with the view that part of the explanation for Japanese firms' relative lack of involvement in overseas R&D must be sought in their status as ‘latecomers’ in the establishment of overseas manufacturing networks. At the same time, a number of Japanese firms have actively used foreign acquisitions and joint ventures to gain access to overseas technology and to establish overseas R&D capabilities at a faster pace. Copyright © 2002 John Wiley & Sons, Ltd.
Link between dopamine D1 and D2 receptors in rat and human striatal tissues
Authors: Seeman Philip , Tallerico Teresa 
Published: January 2003

AbstractMany psychomotor behaviors depend on an interaction between dopamine D1 and D2 receptors. This study tested the hypothesis that agonist stimulation of dopamine D1 receptors leads to the conversion of D2 receptors from a state of high affinity for dopamine into a state of low affinity for dopamine. To test this hypothesis, dopamine was competed against [3H]raclopride for binding to rat and human striatal homogenates. Although the detection of high‐affinity states of the dopamine D2 receptor in rat or postmortem human striatum is normally difficult because the proportions of such sites are very low in the presence of physiological concentrations of sodium ions, the present work found that in the presence of 100 nM SCH 23390 to block D1 receptors, a significant proportion of D2 high‐affinity sites were unmasked and readily revealed to be 10–35% of the D2 population, illustrating the presence of a strong D1–D2 link in both rat and human striata. Synapse 47:250–254, 2003. © 2003 Wiley‐Liss, Inc.
Preproenkephalin mRNA expression in rat dorsal striatum induced by selective activation of metabotropic glutamate receptor subtype‐5
Authors: Parelkar Nikhil K. , Wang John Q. 
Published: January 2003

AbstractGroup I metabotropic glutamate receptors (mGluR1 and mGluR5 subtypes) are positively coupled to phosphoinositide hydrolysis through G‐proteins and are densely expressed in medium‐sized projection neurons of striatum. Selective activation of Group I mGluRs upregulates preproenkephalin (PPE) mRNA expression in the rat dorsal striatum. This study investigated the role of one subtype of Group I receptors, mGluR5, in the regulation of PPE mRNA expression in the rat dorsal striatum using quantitative in situ hybridization. Unilateral injection of the mGluR5 selective agonist (RS)‐2‐Chloro‐5‐hydroxyphenylglycine (CHPG) into the dorsal striatum (caudoputamen) of chronically cannulated rats at doses of 50 and 200 nmol elevated basal levels of PPE mRNA in the injected dorsal striatum. The induction of PPE mRNA was evident at 1 h, remained at 3 h, and returned to normal level 6 h after CHPG injection. Pretreatment with an mGluR5 selective antagonist 2‐methyl‐6‐(phenylethynyl) pyridine hydrochloride (MPEP) at a dose of 10 mg/kg (i.p.) blocked CHPG‐stimulated PPE expression. MPEP also attenuated PPE expression induced by dopamine D2 receptor blockade with eticlopride (0.5 mg/kg, i.p.). Administration of MPEP alone had no significant effects on basal levels of PPE mRNA in the striatum. The results from the present study demonstrate that glutamatergic tone on mGluR5 possesses the ability to positively regulate PPE gene expression in striatal neurons in vivo. Moreover, activation of mGluR5 participates in the mediation of D2 antagonist‐induced PPE expression. Synapse 47:255–261, 2003. © 2003 Wiley‐Liss, Inc.
Relative levels of cytoprotection produced by analogs of choline and the role of α7‐nicotinic acetylcholine receptors
Authors: Jonnala Ramamohana R. , Graham John H. , Terry Jr. Alvin V. , Beach J. Warren , Young Jennifer A. , Buccafusco Jerry J. 
Published: January 2003

AbstractSeveral analogs of the acetylcholine precursor molecule choline have been widely studied as potential false cholinergic neurotransmitters with the therapeutic goal of using them to limit cholinergic neurotransmission. More recently, choline itself has been shown to act as a full, if low potency, agonist at the α7 subtype of the nicotinic acetylcholine receptor. This pharmacological property has been associated with the ability of nicotine and other related α7 receptor agonists to offer neuroprotection in a variety of experimental models. We confirm here that choline offers a significant degree of protection against the cytotoxicity induced by growth factor deprivation in differentiated PC‐12 cells. Choline‐induced cytoprotection (∼1 mM) was about 3 orders of magnitude less potent than that for nicotine (EC50 = 0.7 μM). Choline also exhibited only about 40% of the full cytoprotective effect of nicotine. Ethyl substitution for choline's N‐methyl groups did not result in a significant improvement over choline as a cytoprotective agent. In contrast, pyrrolidinecholine exhibited much greater potency (EC50 = 20 μM) and increased efficacy (about 55% of nicotine's effect) than choline. Like choline and nicotine, pyrrolidinecholine fully displaced [125I]α‐bungarotoxin binding (Ki = 33 μM) and chronic exposure to the analog increased cell surface binding sites. The cytoprotective effects of the analog were completely inhibited by coincubation with methyllycaconitine (MLA), a selective α7‐nicotinic receptor antagonist. These findings are consistent with the possibility that the choline structure may serve as a template for the development of novel agents with both α7‐nicotinic agonist activity and potential neuroprotective ability, as many of these compounds, including pyrrolidinecholine, are transported along with choline into the central nervous system. Synapse 47:262–269, 2003. © 2003 Wiley‐Liss, Inc.
Down‐regulation of mGluR8 in pilocarpine epileptic rats
Authors: Kral T. , Erdmann E. , Sochivko D. , Clusmann H. , Schramm J. , Dietrich D. 
Published: January 2003

AbstractActivation of presynaptic metabotropic glutamate receptors (mGluRs) leads to a powerful inhibition of glutamate release from many synaptic terminals throughout the CNS. mGluRs as autoreceptors are believed to provide a negative feedback system that prevents potentially toxic accumulation of glutamate in the extracellular space during synchronous synaptic activity such as epileptic seizures. In this study we analyzed the function of presynaptic mGluR8 on terminals of the lateral perforant pathway in the pilocarpine model of limbic epilepsy. Field excitatory postsynaptic potentials (fEPSPs) recorded in hippocampal slices of rats that developed spontaneous recurrent seizures after pilocarpine‐induced status epilepticus (SRS group) showed a significantly reduced sensitivity to Group III mGluR agonists and severe mossy fiber sprouting. The Group III mGluR agonist L(+)‐2‐amino‐4‐phosphonobutyric acid (L‐AP4, 10 μM) depressed fEPSPs in the SRS group only by 26 ± 21% compared to 50 ± 18% in untreated rats. Similarly, the mGluR8 preferring agonist (R,S)‐4‐phosphonophenylglycine (PPG, 5 μM) was significantly less effective in slices from SRS rats (43 ± 4% vs. 83 ± 5%). Concentration–response curves for L‐AP4 revealed that the EC50 values were not different between the control and SRS group (13 ± 7 μM vs. 9 ± 9 μM), while the maximal depressing effect was significantly reduced. The remaining depressing effect of L‐AP4 in the SRS group could be blocked by the Group III specific antagonists (RS)‐α‐methyl‐4‐phosphonophenylglycine (MPPG) and α‐methyl‐L‐AP4 (MAP4). Rats that did not develop SRS following pilocarpine‐induced status epilepticus were indistinguishable from control rats: fEPSPs were highly sensitive to L‐AP4 and there was no mossy fiber sprouting. The results show that pilocarpine‐induced status epilepticus can lead to a downregulation of mGluR8 and suggest that the condition of SRS is associated with a deteriorated autoregulation of glutamate release. Synapse 47:278–284, 2003. © 2003 Wiley‐Liss, Inc.
Tannery wastewater characterization and toxicity effects on Daphnia spp.
Authors: Cooman K. , Gajardo M. , Nieto J. , Bornhardt C. , Vidal G. 
Published: January 2003

AbstractTannery wastewater contains large quantities of organic and inorganic compounds, including toxic substances such as sulfides and chromium salts. The evaluation of wastewater quality in Chile nowadays is based on chemical specific measurements and toxicity tests. The goal of this research was to characterize tannery wastewater and to relate its physical/chemical parameters with its acute toxicity effect on Daphnia pulex. To distinguish the most important toxic compounds, physical/chemical techniques were applied to a grab sample of a final effluent based on the Phase I toxicity identification evaluation (TIE) procedure. In addition, the toxicity of a beamhouse effluent after an activated sludge reactor treatment was investigated on Daphnia magna (introduced species) and D. pulex (native species). Effluent from different tannery processes (soaking, beamhouse, tanning and final) demonstrated high values of chemical organic demand (COD; 2840–27 600 mg L−1), chloride (1813–16 500 mg L−1), sulfate (230–35 200 mg L−1), and total solids (8600–87 100 mg L−1). All effluents showed extremely toxic effects on D. pulex, with 24‐h mean lethal values (LC50) ranging from 0.36% to 3.61%. The Phase I TIE profile showed that toxicity was significantly reduced by air stripping, filtration, and a cationic exchange resin, with toxicity reductions ranging between 46% and 76%. The aerobically treated beamhouse effluent showed significantly less toxicity for both species (43%–74%). The chemical parameters demonstrated that the remaining toxicity of the treated beamhouse effluent was associated with its ammonia (120 mg NNH3 L−1) and chloride (11 300 mg Cl− L−1) contents. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 45–51, 2003.
Acute and sublethal effects of two insecticides on earthworms (Lumbricus terrestris L.) under laboratory conditions
Authors: Mosleh Yahia Y. , Paris‐Palacios Séverine , Couderchet Michel , Vernet Guy 
Published: January 2003

AbstractEarthworms (Lumbricus terrestris L.) were exposed to commercial formulations of endosulfan and aldicarb for 2, 7, and 15 days, and the LC10, LC25, and LC50 were determined. Worms were then exposed to LC10, LC25, and LC50 concentrations of endosulfan and LC10 and LC25 concentrations of aldicarb. The growth rate and total protein content were determined and related to endosulfan and aldicarb residues in soil and earthworms. Aldicarb was more toxic than endosulfan under the experimental conditions. The residues of endosulfan and aldicarb caused a significant reduction in the growth rate and total protein content of earthworms. The residues of endosulfan and aldicarb were monitored in soil and earthworms after 2, 7, and 15 days of exposure. The residues remaining in the soil after the experiments ranged between 37.75% and 68.54% of the applied concentration for endosulfan and between 10.13% and 67.71% of the applied concentration for aldicarb. Small amounts of both insecticides were detected in worms, and accumulation was more important for endosulfan. This study proposes the use of growth rate and total protein content as biomarkers for contamination by endosulfan and aldicarb. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 1–8, 2003.
The freshwater cyanobacterium Lyngbya aerugineo‐coerulea produces compounds toxic to mice and to mammalian and fish cells
Authors: Teneva Ivanka , Asparuhova Dafinka , Dzhambazov Balik , Mladenov Rumen , Schirmer Kristin 
Published: January 2003

AbstractDespite a growing awareness of the presence of cyanobacterial toxins, knowledge about the ability of specific species to produce toxic compounds is still rather limited. It was the overall goal of the current work to investigate if probes derived from the freshwater species Lyngbya aerugineo‐coerulea (Kutz.) Gomont, a cyanobacterium frequently found in southern Europe and not previously investigated for the presence of bioactive compounds, were capable of eliciting in vivo and in vitro toxicity. The cyanobacterial extract revealed signs of neuro‐ as well as hepatotoxicity in mice, although these signs could not be explained by the well‐known respective cyanobacterial neuro‐ and hepatotoxins saxitoxin and microcystin. Cytotoxicity was elicited by the cyanobacterial extract in all mammalian cell lines tested. As well, the rainbow trout liver cell line, RTL‐W1, was found to be susceptible to the cytotoxic effects of the extract, although the cytotoxicity was dependent on temperature. In contrast, the cyanobacterial growth medium elicited cytotoxicity independent of temperature, leading to morphological changes indicative of alterations to the cytoskeleton. Overall, the results suggest that Lyngbya aerugineo‐coerulea is an important cyanobacterium to be considered for its potential to cause health risks on environmental exposure of it to mammals and fish. Applying a combination of mammalian and piscine cell line bioassays is a unique approach that, combined with chemical analysis, could be used in the future to identify the structure and cellular mechanisms of the as‐yet‐unknown toxic Lyngbya aerugineo‐coerulea metabolites in particular and to screen cyanobacterial extracts for their toxicity in general. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 9–20, 2003.
Depuration kinetics and persistence of the cyanobacterial toxin microcystin‐LR in the freshwater bivalve Unio douglasiae
Authors: Yokoyama Atsushi , Park Ho‐Dong 
Published: January 2003

AbstractWe carried out uptake and depuration experiments in the laboratory to investigate the effects of temperature (15°C and 25°C) on the depuration kinetics and persistence of a cyanobacterial toxin, microcystin‐LR (MCYST‐LR), in a freshwater bivalve, Unio douglasiae. Bivalves were fed toxic Microcystis cells in the 15‐day uptake experiment and nontoxic diatoms in the following 15‐day depuration experiment. Each bivalve's hepatopancreas was lyophilized and extracted with a butanol:methanol:water solution for analysis of MCYST‐LR by high‐performance liquid chromatography. The toxin in the organ accumulated rapidly after the beginning of the uptake experiment and reached approximately steady‐state conditions on day 5 at concentrations of 130 ± 11 μg g−1 dry weight at 15°C and 250 ± 40 μg g−1 at 25°C. In the depuration experiments MCYST‐LR was eliminated asymptotically from the tissue. The values of the depuration rate constant (kd), calculated with a first‐order one‐compartment model, were found to be 0.142 ± 0.044 day−1 at 15°C and 0.226 ± 0.046 day−1 at 25°C. The depuration Q10 value from 15°C to 25°C equaled 1.6. This study was the first to reveal the kinetics of depuration for MCYST‐LR in a bivalve. The results show that MCYST‐LR may be eliminated slowly in autumn and winter and persist in the tissue until spring. Thus, in terms of toxicokinetics, the risk to people of being poisoned by bivalves would increase if toxic blooms occur in autumn. © 2003 Wiley Periodicals, Inc. Environ Toxicol 18: 61–67, 2003.
The preliminary development of a new self‐report measure for OCD in young people
Authors: Shafran Roz , Frampton Ian , Heyman Isobel , Reynolds Martina , Teachman Bethany , Rachman S. 
Published: January 2003

AbstractThe aim of this study was to develop a reliable self‐report instrument to assess obsessive–compulsive disorder (OCD) in young people. The children's Obsessional Compulsive Inventory (CHOCI) had good internal consistency, criterion validity and was significantly correlated with the Children's Yale‐Brown Obsessive Compulsive Scale (CY‐BOCS). This preliminary new measure could serve to provide a more efficient and accessible way of assessing OCD in young people.