bluuebunny/crossref_metadata_2025_split huggingface dataset:
The development and validation of a high performance liquid chromatography (HPLC)/tandem mass spectrometry assay for fenticonazole in human plasma and comparison with an HPLC‐UV method
Authors: Speed William , Long Jeffrey M. , Simmonds Roger J. , Enos Trevor A. 
Published: May 2005

AbstractA method is described for the determination of fenticonazole in human female plasma. The method utilizes high performance liquid chromatography coupled to atmospheric pressure positive‐ion chemical ionization triple quadrupole mass spectrometry. Multiple reaction monitoring is employed for selectivity and sensitivity which enables quantification over the range 0.5–20 ng mL−1 with acceptable precision and accuracy. A comparison is made with an existing HPLC‐UV assay and the utility of the technology of combined liquid chromatography and tandem mass spectrometry for subnanogram per mL assays is discussed.
Matrix‐assisted laser desorption/ionization combined with quadrupole ion‐trap mass spectrometry for the direct analysis of colour couplers adsorbed on solid substrates
Authors: Bristow Anthony W. T. , Creaser Colin S. 
Published: May 2005

AbstractA method has been developed for the study of samples adsorbed on solid substrates using matrix‐assisted laser desorption/ionization combined with quadrupole ion‐trap mass spectrometry. The introduction of ions generated externally to the ion trap facilitates the direct analysis of molecules contained on substrates without the need for a lengthy extraction procedure. The method is demonstrated for the analysis of colour coupler compounds separated by thin‐layer chromatography and present on a photographic substrate.
Ebrotidine and its metabolites studied by mass spectrometry with electrospray ionization. Comparison of tandem and in‐source fragmentation
Authors: Rozman E. , Albet C. , Galcerán M. T. 
Published: May 2005

AbstractElectrospray ionization was used for the analysis of ebrotidine and its potential metabolites. Since standard electrospray gave only the quasi‐molecular ions for most of the compounds, two collision‐induced dissociation (CID) experiments were carried out in order to obtain structural information: tandem mass spectrometry (MS/MS) and in‐source fragmentation by increasing the cone voltage (CVF, cone voltage fragmentation). CVF produced more fragmentation than MS/MS, and the intensities of the fragments formed were also greater. Unlike MS/MS spectra, CVF spectra gave ions which showed retention of the bromine isotope pattern, adducts with acetate and dehydration. The general fragmentation pathways observed for ebrotidine and its derivatives were basically the same for the CVF and MS/MS experiments. Most of the fragments were formed by the breaking of bonds to heteroatomics. In order to analyse biological samples containing ebrotidine and its biotransformation products, an HPLC/MS separation procedure with simultaneous UV detection was developed, allowing the identification of ebrotidine and its metabolites in human urine.
The effect of addition of carbon powder to samples in liquid secondary ion mass spectrometry: Improved ionization of apolar compounds
Authors: Rozenski Jef , Herdewijn Piet 
Published: May 2005

AbstractAddition of carbon or graphite powder, to either the matrix or the sample if no matrix is used, facilitates the formation of sample ions. For most of the compounds investigated, [M + H]+ ions are observed. For long‐chain alcohols, [M − 1]+ ions are formed. This new analysis method allows mass spectra of compounds, that hitherto were difficult or impossible to ionize, using liquid secondary mass spectrometry to be obtained and enhances the signal intensity of poorly ionizable compounds. Using this technique in the negative ion mode, a spectrum of Fomblin® can be obtained which is suitable for calibration purpose over a mass range of 1400 u. The observed effect is possibly due to enhancement of the field strength at the sample surface in the presence of carbon powder. No evidence of contamination of the ion source was visible after four weeks of intensive use of this technique.
A comparison of femtosecond and nanosecond multiphoton ionization and dissociation for some nitro‐molecules
Authors: Ledingham Kenneth W. D. , Deas Robert M. , Marshall Archibald , McCanny Thomas , Singhal Ravi P. , Kilic Hamdi S. , Kosmidis Costantine , Langley Andrew J. , Shaikh Waseem 
Published: May 2005

AbstractResonance‐enhanced multiphoton ionization spectrometry (REMPI), using time‐of‐flight mass spectrometers and tuned lasers, has proved an important ultra‐sensitive analytical technique. Nevertheless, conventional nanosecond REMPI suffers from a number of shortcomings: most importantly, REMPI often fails through rapidly (pre)dissociating states. In the case of thermally labile molecules, which include the nitro‐molecules, either no or very small parent or high/mass fragment ion peaks exist, making the interpretation of the mass spectra ambiguous at best and often impossible. Femtosecond laser mass spectrometry (FLMS) can often ‘defeat’ these dissociative states, resulting in large parent or high‐mass fragment ion peaks which make the interpretation less ambiguous. In the present paper, nanosecond and femtosecond multiphoton ionization and fragmentation are compared using time‐of‐flight mass spectrometry for NO2 gas and a number of different nitro‐molecules: nitromethane, nitrobenzene, m‐nitrotoluene, dinitrotoluene and trinitrotoluene.
Molecular weight determination of megadalton DNA electrospray ions using charge detection time‐of‐flight mass spectrometry
Authors: Fuerstenau Stephen D. , Benner W. Henry 
Published: May 2005

AbstractWe present results obtained with a novel mass spectrometer capable of determining the mass of multiply charged electrospray ions generated from samples of macromolecules in the megadalton (MDa) size range. The instrument utilizes a sensitive amplifier which can detect the charge on a single ion as it passes through a tube detector. A velocity measurement of an ion with known electrostatic energy provides the ion's mass‐to‐charge ratio. Simultaneous detection of the ion charge permits a mass assignment to be made for each ion. Electrospray ions of DNA and polymer molecules with masses greater than 1 × 106 Da and charge numbers (z) in excess of 425 e− are readily detected in this mass spectrometer. The weights of small particles were also measured. The on‐axis single‐ion detection configuration provides a duty cycle of nearly 100% and extends the practical application of electrospray mass spectrometry to the analysis of very large molecules with relatively inexpensive instrumentation.
Plasma desorption time‐of‐flight mass spectrometric elucidation of the mechanisms of adhesion enhancement between plasma‐treated PEEK–carbon composite and an epoxyamine adhesive
Authors: Nsouli B. , Allali H. , Debre O. , Oladipo A. A. , Thomas J. P. , Rumeau P. , Chabert B. , Soulier J. P. 
Published: May 2005

AbstractPlasma desorption time‐of‐flight mass spectrometry (PD‐TOFMS) using accelerated argon ions (9 MeV) has been successfully used for characterizing the surface modifications induced at the surface of poly(ether etherketone) (PEEK) by cold plasma treatments. While the intact polymer structure leads to the emission of negative ions from fragmentation of the repeat unit, the degradation of such a structure under plasma exposure gives rise to production of oxidized fragments. It is demonstrated that this production is highest for a plasma using a mixture of O2 and N2 (20:80), and that as a function of treatment duration, the rate of oxidation of the modified surface layer correlates with adhesive strength, at least in a first step. PD‐TOFMS is used for analysis of the failure patterns of epoxyamine adhesive/PEEK/carbon composite in order to localize the fracture position. It is concluded that the increase of the cohesion of the interphase layer as a function of the plasma treatment duration leads to a shift from the interphase/PEEK interface to the bulk of the matrial.
Characterization of a recombinant antihaemophilia‐a factor (factor VIII‐δII) by matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Bihoreau N. , Veillon J. F. , Ramon C. , Scohyers J. M. , Schmitter J. M. 
Published: May 2005

AbstractFactor VIII‐ΔII is a genetically engineered deletion variant of factor VIII, expressed by recombinant Chinese hamster ovary cells. This 1436‐residues‐long protein has a molecular mass, calculated from its sequence, of 164 954 Da and exhibits seven potential glycosylation sites. The glycoprotein, secreted as a single polypeptide chain, can be cleaved after Arg740 to generate a heavy‐light chain complex of 90‐80 kDa as revealed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) analysis. Due to its high mass range and excellent senstitivity, matrix‐assisted laser desorption/ionization‐mass spectrometry (MALDI‐MS) has been chosen to play a key role in the precise determination of the molecular masses of recombinant factor VIII and the localization of the post‐translational modifications within the protein. Native factor VIII‐ΔII displays a molecular mass of 178 kDa. The masses measured by MALDI for the heavy and light chains are respectively 89 900 Da and 87 100 Da. These mass values, found reproducible from batch to batch, are used to characterize factor VIII‐ΔII during the course of preclinical studies. The difference from the theoretical molecular masses and the observation of broad molecular peaks suggest that recombinant FVIII‐ΔII has been effectively glycosylated by the host cell on both heavy and light chains. Similarly to plasma‐derived factor VIII, the recombinant protein is proteolyzed by thrombin to generate the A1/A2/A3‐C1‐C2 trimer that is the active form of factor VIII in the coagulation pathway. MALDI‐MS analysis of activated factor VIII‐ΔII suggested the presence of N‐linked oligosaccharides in the proteolyzed light chain (A3‐C1‐C2 of 77 750 Da) and in the A1 domain (46 400 Da) of the heavy chain. By contrast, the similarity between the experimental and theoretical masses of the A2 domain indicated that its single potential glycosylation site has not been utilized.
Neurophysiological investigation of effects of the D‐1 agonist SKF 38393 on tonic activity of substantia nigra dopamine neurons
Authors: Carlson Joanne H. , Bergstrom Debra A. , Weick Barton G. , Walters Judith R. 
Published: May 2005

AbstractThe effects of the D‐1 agonist SKF 38393 on tonic activity of rat substantia nigra pars compacta dopamine neurons were studied using extracellular, single‐unit recording techniques. Unlike nonselective D‐1/D‐2 dopamine agonists or the D‐2 agonist quinpirole, SKF 38393 did not inhibit dopamine neuronal activity when applied iontophoretically or when administered intravenously in doses up to 20 mg/kg to chloral hydrateanesthetized rats. Moreover, pretreatment with SKF 38393 did not alter the inhibitory response of these neurons to apomorphine or the D‐2 agonist quinpirole. However, in locally anesthetized, gallamine‐treated, artificially respired rats, dopamine cell activity was significantly altered by i.v. administration of SKF 38393; firing rate increases and decreases were observed. Administration of the inactive enantiomer of SKF 38393, S‐SKF 38393, did not induce similar changes in parallel experiments. These results support the idea that unlike D‐2 autoreceptor stimulation, D‐1 receptor stimulation does not exert a direct local effect on dopamine neurons in the substantia nigra pars compacta and suggest that D‐1 receptor stimulation at sites postsynaptic to the dopamine cells may indirectly affect the activity of some dopamine neurons through long‐loop feedback mechanisms.
Human brain receptor autoradiography using whole hemisphere sections: A general method that minimizes tissue artefacts
Authors: Quirion Rémi , Robitaille Yves , Martial Johanne , Chabot Jean‐Guy , Lemoine Pierrette , Pilapil Carmencita , Dalpé Michel 
Published: May 2005

AbstractA general method for the preparation of high‐quality, mostly ice‐crystal‐artefact‐free whole human brain hemisphere sections is described. Upon receipt, hemispheres are divided; one is then fixed in buffered 10% formalin for neuropathological analysis while the other is cut in 8–10‐mm‐thick coronal slices that are then rapidly frozen in 2‐methylbutane at −40°C (10–15 sec) before being placed in the brain bank at −80°C. Such rapid freezing markedly decreases the formation of ice‐crystal artefacts. Whole‐hemisphere 20‐μm thick sections are then cut and mounted onto lantern‐type gelatin‐coated slides. These sections are subsequently used for both qualitative and quantitative in vitro receptor autoradiography. Examples of data obtained are given by using various radioligands labelling “classical” neutrotransmitter, neuropeptide, enzyme, and ion channel receptor binding sites. This method should be useful for the obtention of various receptor maps in human brain. Such information could be most useful for in vivo receptor visualization studies using positron emission tomography (PET) scanning. It could also indicate if a given receptor population is specifically and selectively altered in certain brain diseases, eventually leading to the development of new therapeutic approaches.
Effects of dopamine depletion on the spontaneous activity of type I striatal neurons: Relation to local dopamine concentration and motor behavior
Authors: Orr William B. , Stricker Edward M. , Zigmond Michael J. , Berger Theodore W. 
Published: May 2005

AbstractThe relation between the electrophysiological activity of Type I striatal neurons, local dopamine (DA) concentration, and motor behavior in rats was investigated using intraventricular administration of the neurotoxin 6‐hydroxydopamine (6‐HDA) and extracellular single‐unit recording. Results are compared with findings of past experiments in which the activity of Type II striatal neurons was examined after comparable 6‐HDA‐induced lesions. Several differences between the present observations and the earlier results were found. First, although large depletions (greater than 50%) of DA local to the site of the recording were required before the spontaneous firing rate of either cell type was increased, the levels necessary for this effect were found to be less for Type I cells than for Type II neurons. Second, although DA depletions of greater than 50% always were associated with increased Type I cell activity, depletions of greater than 95% resulted in spontaneous firing rates that were lower than those observed after depletions of approximately 90%. Thus, the relation between extent of dopaminergic depletion and Type I cell firing rate was biphasic, whereas that relation previously was found to be monophasic for Type II neurons. Finally, whereas increased Type I cell activity in the lateral striatum was associated with the aphagia, adipsia, and akinesia induced by large DA‐depleting brain lesions, increased Type II cell activity in the medial striatum was found to be associated with these impairments. Because accumulating evidence suggests that the functioning of the lateral striatum is more critical for these behaviors, however, it is proposed that the substrate of the behavioral dysfunctions resulting from DA depletion is the Type I cell population in lateral striatum.
Excitation of locus coeruleus neurons by an adenoine 3′,5′‐cyclic monophosphate‐activated inward current: Extracellular and intracellular studies in rat brain slices
Authors: Wang Y.‐Y. , Aghajanian G. K. 
Published: May 2005

AbstractThe firing rate of locus coeruleus (LC) neurons in rat brain slices was increased reversibly by agents that either elevate intracellular levels of adenosine 3′,5′‐cyclic monophosphate (cAMP) or mimic its actions (e.g., forskolin, an activator of adenylate cyclase, 8‐Br‐cAMP, a membrane permeable analog of cAMP, and Ro20‐1724, a preferential inhibitor of cAMP‐phosphodiesterase). Intracellular recordings showed that 8‐Br‐cAMP and forskolin induce a depolarization of LC neurons, accompanied by a decrease in input resistance. The 8‐Br‐cAMP‐ and forskolin‐elicited depolarization persisted in the presence of cobalt, a calcium channel blocker. Steady‐state current‐voltage curves revealed that in the voltage range of –50 to –120 mV, 8‐Br‐cAMP and forskolin induced an inward current, which did not reverse at the potassium equilibrium potential and could not be blocked by tetrodotoxin. Partial replacement of sodium with Tris or choline markedly reduced the depolarization elicited by 8‐Br‐cAMP.We conclude that 8‐Br‐cAMP and forskolin act through a common mechanism to increase the firing rate of locus coeruleus neurons by inducing a cAMP‐activated inward current, carried out at least in part by sodium ions.
Excitation of K X‐rays for a wide range of elements (25 ⩽ Z ⩽ 82) by direct interaction of beta particles from phosphorus‐32
Authors: LaBrecque J. J. , Rosales P. A. 
Published: May 2005

AbstractThe relative sensitivities of low–medium and high‐Z elements from manganese to lead were investigated via their Kα x‐rays employing 75 μCi of 32P. This was accomplished by preparing various synthetic mixtures of elements in the range 25 ⩽ Z⩽ 82, then simply introducing 32P solution to form source‐samples. The advantages of excitation with 32P, a pure β‐emitter with a βmax. energy at 1709 keV, include the following: excitation of all the Kα x‐rays from manganese to lead; the relative sensitivities of the K x‐rays are all within one order of magnitude; the source itself does not produce any spectral lines; and the background can be greatly reduced by filtering. Excitation with 32P is compared with that of a conventional 109Cd source and some possible applications are discussed.
The value of B‐type natriuretic peptide and big endothelin‐1 for detection of severe pulmonary hypertension in heart transplant candidates
Authors: Kubánek Miloš , Málek Ivan , Kautzner Josef , Hegarová Markéta , Wiendl Martin , Lupinek Petr , Karasová Ludmila , Lánská Věra 
Published: May 2005

AbstractBackground:Severe pulmonary hypertension (PH) and increased pulmonary vascular resistance (PVR) are important risk factors that predict early postoperative mortality after orthotopic heart transplantation. The aim of our study was to determine the value of B‐type natriuretic peptide (BNP) and big endothelin‐1 (big ET1) for prediction of severe PH in heart transplant candidates.Methods:The study population included 43 potential heart transplant candidates (38 males, mean age 52±7 years). All underwent repeated right‐heart catheterizations (2–5 studies) at an interval of 3–4 months, giving a total of 124 examinations, associated with blood sampling for BNP and big ET1 analysis. Severe PH was defined as the mean pulmonary artery pressure (MPAP)>40 mmHg.ResultsSignificantly high PVR (PVR>3.0 Wood units and TPG>15 mmHg) was noted on 12 occasions in 10 patients; always in the presence of severe PH. Low BNP levels (<67 pg/ml) ruled out the presence of severe PH with a 100% sensitivity, however, with a low specificity (34%). An increase in plasma BNP>30 pg/ml (>40% of initial value) in subjects with a previous MPAP–40 mmHg detected development of severe PH with a 100% sensitivity and an 80–88% specificity. As a total of 58% of patients presented repeatedly with MPAP≤40mmHg, serial BNP testing could reduce the need for hemodynamic studies in this subgroup down to 12–20%.Conclusions:Serial BNP testing in hemodynamically stable heart transplant candidates with MPAP–40 mmHg allows reliable detection of development of severe PH, and may significantly reduce the need for repeated right‐heart catheterizations in these patients.
Functional mitral regurgitation predicts 1‐year mortality in elderly patients with systolic chronic heart failure
Authors: Cioffi Giovanni , Tarantini Luigi , De Feo Stefania , Pulignano Giovanni , Del Sindaco Donatella , Stefenelli Carlo , Di Lenarda Andrea , Opasich Cristina 
Published: May 2005

AbstractBackground and aim:Mitral regurgitation (MR) has been demonstrated to be a powerful predictor of adverse outcome in middle‐aged patients with chronic heart failure (CHF). In this study, we sought to define the prognostic impact of functional mitral regurgitation in a population of elderly patients with systolic CHF.Methods:One hundred seventy‐five outpatients aged >70 years with validated CHF and left ventricular ejection fraction <40% underwent clinical and echocardiographic evaluations at baseline. Mitral regurgitation was diagnosed by Color Doppler and quantified in 5 categorical values using a 0–4+ grading system. Outcome measures included 1‐year mortality and hospitalization for worsening CHF.Results:The distribution of patients according to the 5 different degrees of MR detected at baseline was: absent=11%, 1+=31%, 2+=38%, 3+=16%, 4+=4%. The relationship between MR and mortality was direct and approximately linear (r=0.39, p=0.00001). The prevalence of death in the 5 subgroups was 0%, 7%, 15%, 45%, 57%, respectively. Multivariate logistic regression analysis showed that MR was the strongest predictor of death (OR 4.47, 95% CI 1.50–13.0), independently of the presence of diabetes mellitus, older age and larger left ventricular end‐diastolic volume. No association was found between MR and hospitalization for worsening CHF (r=0.08, p=0.41).Conclusions:This study establishes the direct and independent relationship between MR severity and one‐year mortality among elders with systolic CHF. Conversely, MR does not provide useful information regarding the risk of subsequent hospitalization for worsening CHF.
Validation of the PAC‐SYM questionnaire for opioid‐induced constipation in patients with chronic low back pain
Authors: Slappendel Robert , Simpson Karen , Dubois Dominique , Keininger Dorothy L. 
Published: May 2005

AbstractBackground The Patient Assessment of Constipation Symptoms (PAC‐SYM) questionnaire is a 12‐item self‐report instrument divided into abdominal, rectal and stool domains.Aims This study aimed to (1) evaluate the psychometric properties of PAC‐SYM in assessing the symptoms and severity of opioid‐induced constipation; (2) test for differences in opioid‐induced constipation between Durogesic® fentanyl transdermal reservoir (TDF) and oral sustained‐release morphine (SRM) in patients with chronic low back pain (CLBP).Methods In a 13‐month, open‐label, parallel‐group study, 680 patients were randomised to receive either TDF (n = 338) or SRM (n = 342) for CLBP. Assessments were recorded at Visit 1 (baseline), Visit 5 (Day 29) and Visit 17 (Month 13). Concurrent validity, clinical validity and responsiveness of PAC‐SYM were determined based on patients' confirmation of constipation (CC) scores. Differences in PAC‐SYM scores between treatment groups were also evaluated.Results The study included 677 patients, of whom 638 were opioid‐naïve. Mean PAC‐SYM scores for constipated patients were substantially higher than for non‐constipated patients, demonstrating good clinical validity for PAC‐SYM. The PAC‐SYM could detect changes in bowel function over the treatment period, indicating responsiveness. Homogeneity of each symptom domain exceeded Cronbach's α coefficient of 0.70, suggesting good internal consistency and reliability. Changes in mean PAC‐SYM scores from baseline to Visit 5 and Visit 17 were significantly lower for the TDF group than for the SRM group, indicating that the TDF group experienced less severe constipation.Conclusion PAC‐SYM is a reliable, valid and responsive measure of the presence and severity of opioid‐induced constipation symptoms.