bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of alcohols, as dimethylglycine esters, by electrospray ionization tandem mass spectrometry
Authors: Johnson David W. 
Published: September 2002

AbstractDimethylglycine (DMG) esters are new derivatives for the rapid, sensitive and selective analysis of primary and secondary alcohols, in complex mixtures, by electrospray ionization tandem mass spectrometry (ESI‐MS/MS). Their development was inspired by the use of the complementary dimethylaminoethyl esters for the trace, rapid analysis of fatty acids. DMG esters are simply prepared by heating a dichloromethane solution of the imidazolide of dimethylglycine, containing triethylamine, and an alcohol. DMG esters of long‐chain fatty alcohols, isoprenoidal alcohols and hydroxy‐acids are analysed by electrospray ionization tandem mass spectrometry with a precursor ion of m/z 104 scan. Diols, glyceryl esters, glyceryl ethers and some sterols are analysed by a neutral loss of 103 Da scan. Trimethylglycine (TMG) ester iodides, prepared by alkylation of DMG esters with methyl iodide, are more sensitive derivatives for molecules containing secondary alcohol groups, such as cholesterol and gibberellic acid. They are analysed by a precursor ion of m/z 118 scan. DMG or TMG derivatives were shown to be at least comparable and sometimes an order of magnitude more sensitive than N‐methylpyridyl ether derivatives for ESI‐MS/MS analysis of the different classes of alcohols. Applications of these derivatives for the diagnosis of inherited disorders and the analysis of natural products are presented. Copyright © 2001 John Wiley & Sons, Ltd.
Characterization of the vulcanization products of squalene by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry: model studies on the vulcanization of natural rubber
Authors: Gros M. , Borrós S. , Amabilino D.B. , Veciana J. , Folch I. 
Published: September 2002

AbstractA method for the characterization of the vulcanization reaction products of squalene using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) was developed. Squalene was chosen as a model molecule for natural rubber. Different matrix–solvent pairs were evaluated with the spectrometer functioning in the linear mode, working with positive/negative high voltages and different laser powers. The study led to the following important conclusions. The identification of squalene requires a cationizing agent whereas the identification of the two families of curing systems used, a sulfenamide and a thiuram, requires only the use of a matrix (dithranol and dihydroxybenzoic acid, respectively). For the first time, the intermediate compounds such as squalene derivatives with pendant sulfur‐containing groups and interacting with zinc as well as cross‐linked squalene were identified. Only a matrix is required and the solvent acetonitrile leads to better spectra than THF (which oligomerizes during sample preparation). Adequate sample treatment is critical to the success of the method. Suitable conditions were found for the characterization of the vulcanization reaction. MALDI‐TOFMS appears to be an important tool for the analysis and deconvolution of the mechanisms of the vulcanization of natural rubber. Copyright © 2001 John Wiley & Sons, Ltd.
Quantitative detection of N7‐(2‐hydroxyethyl)guanine adducts in DNA using high‐performance liquid chromatography/electrospray ionization tandem mass spectrometry
Authors: Liao Pao‐Chi , Li Ching‐Ming , Hung Chien‐Wen , Chen Shu‐Hui 
Published: September 2002

AbstractHigh‐performance liquid chromatography (HPLC) was combined with electrospray ionization tandem mass spectrometry (ESI‐MS/MS) to develop a sensitive and selective method for the quantitative measurement of N7‐(2‐hydroxyethyl)guanine (N7‐HEG) adducts in DNA obtained from ethylene oxide‐exposed biological samples. Selected reaction monitoring (SRM) was used as the detection mode while the fragmentation product ion at m/z 152 generated from the precursor protonated N7‐HEG (m/z 196) was monitored. The detection limits for N7‐HEG were estimated by twofold serial dilution and determined to be 4 fmol in neat standard solution and 16 fmol when a matrix effect is considered. When the mass spectrometer was operated in the selected ion monitoring mode using only the first quadrupole (without MS/MS function), the detection limits increased to 128 fmol and 1 pmol (when matrix effect is considered), respectively. A good linear correlation (R2 = 0.999) was observed for signal intensities obtained by injecting 16 fmol–33 pmol of N7‐HEG into the HPLC/ESI‐MS/MS system. Hep G2 cells were incubated for 8 h with medium containing various concentrations of ethylene oxide (ranging from 0.05 to 5.0 mM). A dose–response relationship was established, indicating that the adduct formation increases with the exposure level. The method shows potential, although the detection limit needs to be lowered for practical applications, for use in monitoring N7‐HEG formation in other biological systems. Copyright © 2001 John Wiley & Sons, Ltd.
Density functional computations of proton affinity and gas‐phase basicity of proline
Authors: Marino T. , Russo N. , Tocci E. , Toscano M. 
Published: September 2002

AbstractAn Erratum has been published for this article in Journal of Mass Spectrometry 37(2) 2002, 232.The proton affinity and gas‐phase basicity of proline were evaluated by using density functional theory coupling the B3‐LYP hybrid functional with the extended 6–311++G** basis set. Cis and trans conformations of the carboxyl moiety for both exo and endo ring structures were considered for the neutral proline. The results show that the most stable structure of proline has the endo ring conformation with the carboxyl group in the cis position. The structure at the global minimum is stabilized by an intramolecular hydrogen bond. The nitrogen of the ring in the exo form is the preferred protonation site. The calculated proton affinity (924.3 kJ mol−1) and gas‐phase basicity (894.4 kJ mol−1) are in very good agreement with the experimental counterparts. Copyright © 2001 John Wiley & Sons, Ltd.
Spontaneous N → O acyl shift in the [M + H]+ ions of [MeBmt1]‐cyclosporins in an ion trap
Authors: Jegorov Alexandr , Havlíček Vladimír 
Published: September 2002

AbstractIn an ion trap the protonated molecules of the cyclic undecapeptides cyclosporins having 3‐hydroxy‐4‐methyl‐2‐methylamino‐6‐octenoic acid (MeBmt) in their backbone undergo an N → O peptidyl shift into the corresponding [M + H]+ ions of isocyclosporins. This rearrangement does not take place in cyclosporins [Bmt1]Cs and [3′‐deoxy‐MeBmt1]Cs. In cyclosporin [Thr2]Cs having two threonines in the molecule, only one of them participates in the N,O‐acyl transfer. It can be concluded that the presence of the basic N‐methylamino group of MeBmt, which can serve as the primary site of protonation, is necessary for isocyclosporin formation. A dominating ion series originating from the primary cleavage between MeBmt (first position in the cyclosporin ring) and amino acid residue at the neighbouring eleventh position is then observed in collision‐induced dissociation spectra of protonated molecules of cyclosporins. This ‘isocyclosporin’ ion series can effectively be used for easy and complete cyclosporin sequencing using a tandem mass spectrometric (MS3) experiment in an ion trap. The paper further introduces an improved Gross mass spectral nomenclature for cyclic peptide sequencing and several techniques for the generation of protonated molecules of cyclosporins. Their preparation represents the fundamental requirement for smooth sequencing of cyclosporins by tandem mass spectral techniques. Copyright © 2001 John Wiley & Sons, Ltd.
Liquid chromatography/mass spectrometry in anabolic steroid analysis—optimization and comparison of three ionization techniques: electrospray ionization, atmospheric pressure chemical ionization and atmospheric pressure photoionization
Authors: Leinonen Antti , Kuuranne Tiia , Kostiainen Risto 
Published: September 2002

AbstractThe applicability of liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the detection of the free anabolic steroid fraction in human urine was examined. Electrospray ionization (ESI), atmospheric pressure chemical ionization and atmospheric pressure photoionization methods were optimized regarding eluent composition, ion source parameters and fragmentation. The methods were compared with respect to specificity and detection limit. Although all methods proved suitable, LC/ESI‐MS/MS with a methanol–water gradient including 5 mM ammonium acetate and 0.01% acetic acid was found best for the purpose. Multiple reaction monitoring allowed the determination of steroids in urine at low nanogram per milliliter levels. LC/MS/MS exhibited high sensitivity and specificity for the detection of free steroids and may be a suitable technique for screening for the abuse of anabolic steroids in sports. Copyright © 2002 John Wiley & Sons, Ltd.
Prevalence, isolation, and partial sequence analysis of hepatitis E virus from domestic animals in China
Authors: Wang You‐Chun , Zhang Hua‐yuan , Xia Ning‐shao , Peng Geng , Lan Hai‐Yun , Zhuang Hui , Zhu Yong‐Hong , Li Shao‐Wei , Tian Ke‐Gong , Gu Wen‐Jie , Lin Jing‐Xiang , Wu Xing , Li He‐Min , Harrison Tim J. 
Published: September 2002

AbstractEvidence that hepatitis E is zoonotic is accumulating. Serum samples were collected from pigs, cattle, and goats from various regions of China to determine whether they had been infected with hepatitis E virus (HEV). An in‐house enzyme immunoassay (EIA) and reverse transcriptase‐polymerase chain reaction (RT‐PCR) with primers from open reading frame (ORF) 2 were used to detect anti‐HEV antibodies and HEV RNA. The mean positivity rates of anti‐HEV antibody for pigs and cattle were 78.8% and 6.3% but none of the goat sera were positive. Pigs may be more susceptible to infection with HEV than cattle or goats. Five of 263 pig sera were positive for HEV RNA and four of these five were also positive for anti‐HEV. The PCR products (nt 6007–6354) were cloned and sequenced and compared to other HEV sequences in the nucleotide databases. The five sequences shared 83–93% identity to each other at the nucleotide level and 74–79%, 73–74%, 73–78%, and 83–99% identity to HEV genotypes 1, 2, 3, and 4, respectively. They were closely related to human isolates of HEV genotype 4. Phylogenetic analyses also place these swine sequences in HEV genotype 4, resembling most closely viruses isolated from Chinese patients with acute hepatitis. These data support the hypothesis that sporadic hepatitis E in China is zoonotic. J. Med. Virol. 67:516–521, 2002. © 2002 Wiley‐Liss, Inc.
HHV‐6 infects human aortic and heart microvascular endothelial cells, increasing their ability to secrete proinflammatory chemokines
Authors: Caruso Arnaldo , Rotola Antonella , Comar Manola , Favilli Flavia , Galvan Monica , Tosetti Maria , Campello Cesare , Caselli Elisabetta , Alessandri Giulio , Grassi Manuela , Garrafa Emirena , Cassai Enzo , Di Luca Dario 
Published: September 2002

AbstractEndothelial cells are important targets for herpesvirus infection. To evaluate the biological effects of human herpesvirus‐6 (HHV‐6) infection, adult heart microvascular and aortic endothelial cells were examined for in vitro susceptibility to HHV‐6 and for the alterations induced by viral infection on the production of monocyte chemoattractant protein‐1 (MCP‐1) and interleukin‐8 (IL‐8). Analysis by reverse transcription‐polymerase chain reaction and by in situ polymerase chain reaction showed that HHV‐6 replicates in endothelium in the absence of cytopathic effects, and that viral sequences were present in 20% umbilical vein and in 10% aortic and 1% microvascular endothelium. HHV‐6 infection upregulated the production of MCP‐1 and IL‐8, with differences observed between aortic and microvascular endothelium. These findings demonstrate that endothelial cells represent a potential reservoir for HHV‐6 infection, and the altered pattern of chemokine production can lead to attraction of immunocompetent cells and to the development of inflammatory processes. J. Med. Virol. 67:528–533, 2002. © 2002 Wiley‐Liss, Inc.
Neuroinvasion during delayed primary HHV‐7 infection in an immunocompetent adult with encephalitis and flaccid paralysis
Authors: Ward K.N. , Kalima P. , MacLeod K.M. , Riordan T. 
Published: September 2002

AbstractAntibody avidity tests have been used to detect primary human herpesvirus‐7 (HHV‐7) infection in an immunocompetent 19‐year‐old man with encephalitis and flaccid paralysis for which all other suspected causes had been excluded. The finding of the viral DNA in the cerebrospinal fluid (CSF) but not in serum samples suggests that primary HHV‐7 infection with invasion of the central nervous system and consequential disease had occurred. As almost all adults are infected with HHV‐7 in early childhood, the present case of delayed primary infection with serious symptoms must be exceptionally rare and no cases of such late acquisition of the virus have been documented in the literature. This report of HHV‐7 DNA in the CSF of an immunocompetent adult is also unique. J. Med. Virol. 67:538–541, 2002. © 2002 Wiley‐Liss, Inc.
Impaired fibrinolysis in the pathogenesis of dengue hemorrhagic fever
Authors: van Gorp Eric C.M. , Setiati Tatty E. , Mairuhu Albert T.A. , Suharti Catharina , Cate Hugo ten , Dolmans Wil M.V. , van der Meer Jos W.M. , Hack C. Erik , Brandjes Dees P.M. 
Published: September 2002

AbstractThe mechanisms contributing to bleeding complications in dengue hemorrhagic fever were studied by investigating the pattern of activation of the coagulation and fibrinolytic systems in 50 children with severe dengue hemorrhagic fever. Thirteen patients (26%) died, and activation of coagulation was most pronounced in the deceased group. Fibrinolysis was also activated, but this activation was relatively weak compared with that of coagulation as a result of persistently high plasminogen activator inhibitor levels. Plasminogen activator inhibitor also prevented a switch from the procoagulant to the profibrinolytic state in lethal dengue hemorrhagic fever, which was further enhanced by an acquired protein C deficiency. The present study is the first to demonstrate such a mechanism in a viral infection. This imbalance between coagulation and fibrinolysis may be used as a prognostic marker, but it may also be a target for future therapeutic intervention. J. Med. Virol. 67:549–554, 2002. © 2002 Wiley‐Liss, Inc.
Foodborne outbreak caused by a Norwalk‐like virus in India
Authors: Girish R. , Broor S. , Dar L. , Ghosh D. 
Published: September 2002

AbstractAn outbreak of acute gastroenteritis occurred in the nurses' hostel of a civil hospital in Delhi, after a farewell party involving 130 nurses and some of the housekeeping staff. All affected persons had eaten salad sandwiches at the party. Stool samples were collected from six of these patients on the second day of infection. All six samples, when tested for the presence of common bacteria, parasites, and rotavirus, were found to be negative. The clinical features of this outbreak matched the criteria set for outbreaks caused by Norwalk‐like viruses (NLVs). Reverse transcription‐polymerase chain reaction (RT‐PCR) was carried out on these six samples, using primers from the RNA‐dependent RNA polymerase (RdRp) gene of NLVs. Immunoelectron microscopy was carried out on two of the samples, using convalescent phase serum. All six samples were positive for genogroup (GG) II NLVs by RT‐nested PCR. Aggregates of 32‐nm viral particles were visualized by immunoelectron microscopy in one of the two samples. Sequencing of the RdRp gene was done on amplicons from three samples; phylogenetic analysis placed the isolates NDV/1999 in a Toronto virus cluster of GG II NLVs. This is the first report of a food‐borne outbreak attributable to NLVs from India. J. Med. Virol. 67:603–607, 2002. © 2002 Wiley‐Liss, Inc.
Circulation of the novel G9 and G8 rotavirus strains in Nigeria in 1998/1999
Authors: Steele A.D. , Nimzing L. , Peenze I. , de Beer M.C. , Geyer A. , Angyo I. , Gomwalk N.E. 
Published: September 2002

AbstractAn epidemiological survey investigating the prevalence of rotavirus infection in infants and young children with acute diarrhoea was undertaken in Jos State, Nigeria, between January 1998 and April 1999. In total, 672 faecal specimens were collected from children aged between 1 and 60 months with acute infantile gastroenteritis. The 10–20% stool suspensions were examined by an ELISA for the presence of group A rotavirus antigen (Rotavirus IDEIA, Dako, UK). Only 116 specimens (17.3%) were positive for the group A rotavirus antigen detected by this ELISA. The rotavirus‐positive specimens were analysed with monoclonal antibodies specific for rotavirus VP6 subgroup I and II, and for VP7 serotypes G1–G4, G8, and G9. Of the rotavirus strains that could be subgrouped, VP6 subgroup I and II strains circulated at similar levels. Amongst the strains that could be serotyped, VP7 G9 strains predominated occurring in 17 cases, with G3 (n = 10) and G1 (n = 9) strains occurring in lower numbers. Four G8 strains were detected and only one G2 and no G4 strains were identified. This report extends the description of the global distribution of G9 rotavirus strains. J. Med. Virol. 67:608–612, 2002. © 2002 Wiley‐Liss, Inc.
Time domain global modelling of EM propagation in semiconductor using irregular grids
Authors: Tsai Hsiao‐Ping , Coccioli Roberto , Itoh Tatsuo 
Published: September 2002

AbstractA two‐dimensional finite volume time domain (FVTD) method using a triangular grid is applied to the analysis of electromagnetic wave propagation in a semiconductor. Maxwell's equations form the basis of all electromagnetic phenomena in semiconductors and the drift‐diffusion model is employed to simulate charge transport phenomena in the semiconductor. The FVTD technique is employed to solve Maxwell's equations on an irregular grid and the finite box method is implemented on the same grid to solve the drift‐diffusion model for carrier concentration. The locations of unknowns have been chosen to allow linking coupled Maxwell's equations and transport equations in a seamless way. To achieve suitable accuracy and computational efficiency, using irregular grid topology allows a finer mesh in doped region and at junction, and a coarser mesh in substrate and insulting regions. The proposed scheme has been implemented and verified by characterizing electromagnetic wave propagation at microwave frequency in a semiconductor slab with arbitrary doping profile. Copyright © 2002 John Wiley & Sons, Ltd.
Direct isolation of committed neuronal progenitor cells from transgenic mice coexpressing spectrally distinct fluorescent proteins regulated by stage‐specific neural promoters
Authors: Sawamoto Kazunobu , Yamamoto Atsuyo , Kawaguchi Ayano , Yamaguchi Masahiro , Mori Kensaku , Goldman Steven A. , Okano Hideyuki 
Published: September 2002

AbstractMany tissues arise from pluripotent stem cells through cell‐type specification and maturation. In the bone marrow, primitive stem cells generate all the different types of blood cells via the sequential differentiation of increasingly committed progenitor cells. Cell‐surface markers that clearly distinguish stem cells, restricted progenitors, and differentiated progeny have enabled researchers to isolate these cells and to study the regulatory mechanisms of hematopoiesis. Neuronal differentiation appears to involve similar mechanisms. However, neural progenitor cells that are restricted to a neuronal fate have not been characterized in vivo, because specific cell‐surface markers are not available. We have developed an alternative strategy to identify and isolate neuronal progenitor cells based on dual‐color fluorescent proteins. To identify and isolate directly progenitor cells from brain tissue without the need for either transfection or intervening cell culture, we established lines of transgenic mice bearing fluorescent transgenes regulated by neural promoters. One set of transgenic lines expressed enhanced yellow fluorescent protein (EYFP) in neuronal progenitor cells and neurons under the control of the Tα1 α‐tubulin promoter. Another line expressed enhanced green fluorescent protein (EGFP) in immature neural cells under the control of the enhancer/promoter elements of the nestin gene. By crossing these lines we obtained mice expressing both transgenes. To isolate neuronal progenitor cells directly from the developing brain, we used flow cytometry, selecting cells that expressed EGFP and EYFP simultaneously. We expect this strategy to provide valuable material with which to study the mechanisms of neurogenesis and to develop cell‐based therapies for neurological disorders. J. Neurosci. Res. 65:220–227, 2001. © 2001 Wiley‐Liss, Inc.
Models of brain injury and alterations in synaptic plasticity
Authors: Albensi Benedict C. 
Published: September 2002

AbstractAnimal models are crucial for understanding human pathophysiological processes and for understanding how connections are injured, lost, or even regenerated and/or repaired. When animal models are used in conjunction with theoretical computational models, an ideal combination is achieved that potentially yields insight and encourages the formation of new theories concerning connectionism, cognitive functioning, and synaptic mechanisms. Mechanisms regulating glutamate receptor activation and intracellular calcium levels are important for normal synaptic transmission. These mechanisms (and others) are also critical during and after brain injury when the potential exists for these mechanisms to function pathologically. Interestingly enough, the regulation of glutamate receptor activation and intracellular calcium levels is also involved in normal processes of neuronal and synaptic plasticity. In addition, studies have shown that neurotrophins and cytokines, which are released after brain injury, can be neuroprotective and may also be important in synaptic plasticity. Furthermore, synaptic plasticity is a phenomenon thought by many to be necessary for memory encoding. If this is the case, then research described in this review has significant scientific merit concerning plasticity and memory and clinical benefit for understanding pathophysiologic processes associated with brain injury and memory impairment. This paper reviews the application of experimental animal models of brain injury for simulating conditions of stroke, trauma, and epilepsy (and/or seizure generation) and the associated cellular mechanisms of brain injury. The paper also briefly addresses the advantage of using computational models in combination with experimental models for hypothesis building and for aiding in the interpretation of empirical data. Finally, it reviews studies concerning brain injury and synaptic plasticity. J. Neurosci. Res. 65:279–283, 2001. © 2001 Wiley‐Liss, Inc.