bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fast imaging of phosphocreatine in the normal human myocardium using a three‐dimensional RARE pulse sequence at 4 Tesla
Authors: Greenman Robert L. , Axel Leon , Ferrari Victor A. , Lenkinski Robert E. 
Published: August 2002

AbstractPurposeTo investigate the use of a three‐dimensional rapid acquisition with relaxation enhancement (RARE) pulse sequence for direct acquisition of phosphocreatine (PCr) images of the human myocardium.Materials and MethodsA short elliptical birdcage radiofrequency (RF) body coil was constructed to produce a uniform flip angle throughout the chest cavity. In vivo images using a spectrally‐selective RARE sequence with a spatial resolution of 1.2 cm × 1.2 cm × 2.5 cm (4 cm3) were acquired in nine minutes and 40 seconds.ResultsScans of phantoms demonstrated excellent spectral selectivity. The signal‐to‐noise ratio in the myocardium ranged from 12.6 in the anterior wall to 5.3 in the mid septum.ConclusionThis study demonstrates that PCr data can be acquired using a three‐dimensional RARE sequence with greater spatial and temporal resolution than spectroscopic techniques. J. Magn. Reson. Imaging 2002;15:467–472. © 2002 Wiley‐Liss, Inc.
Magnetic resonance image registration in multiple sclerosis: Comparison with repositioning error and observer‐based variability
Authors: Tan I Leng , van Schijndel Ronald A. , van Walderveen Marianne A.A. , Quist Marcel , Bos Reinhard , Pouwels Petra J.W. , Desmedt Pol , Adèr Herman J. , Barkhof Frederik 
Published: August 2002

AbstractPurposeTo study the use of image registration in the analysis of multiple sclerosis (MS) lesion volume and compare this with repositioning error and observer‐based variability.Materials and MethodsThe normalized mutual information (NMI) algorithm is evaluated in an accuracy study using a phantom, followed by a validation study on magnetic resonance (MR) data of MS patients. Further, using scan‐rescan MR data, the effect of registration on MS lesion volume compared with repositioning error and observer‐based variability is assessed.ResultsThe registration accuracy was near perfect in the phantom study, while the in vivo validation study demonstrated an accuracy on the order of 0.2–0.3 mm. In the scan‐rescan study, quantification accounted for 15.6% of the relative variance, repositioning for 44.4%, and registration for 40.0%.ConclusionNMI resulted in robust and accurate alignment of MR brain images of MS patients. Its use in the detection of changes in MS using large serial MR imaging (MRI) data warrants future evaluation. J. Magn. Reson. Imaging 2002;15:505–510. © 2002 Wiley‐Liss, Inc.
Mass spectrometric studies of anomeric glycopyranosyl azides
Authors: Dinya Zoltán , Benke Péter , Györgydeák Zoltán , Somsák László , Jekö József , Pintér István , Kuszman János , Praly Jean‐Pierre 
Published: August 2002

AbstractWe studied the mass spectrometric behaviour of peracetylated and underivatized anomeric hexopyranosyl azides and 5‐thioglucopyranosyl azides by means of different mass spectrometric techniques. The unstable molecular ions fragment predominantly by losing either N3 radical or N2 molecule. Loss of N2 molecule and the protonation of the derived nitrene were characteristic of the studied compounds. The presence of BF3·Et2O in the ion source is favorable for producing the protonated nitrene form. The protonated nitrene shows a new type of ring expansion rearrangement. The abundances of the [M + H − N2]+ ion makes it possible to identify the anomeric configuration of the azido group. Copyright © 2001 John Wiley & Sons, Ltd.
International Mass Spectrometry Society (IMSS)
Authors: Cooks R. G. , Gelpi E. , Nibbering N. M. M. 
Published: August 2002

AbstractThis paper gives a brief description of the recently formalized International Mass Spectrometry Society (IMSS). It is presented here in order to increase awareness of the opportunities for collaboration in mass spectrometry in an international context. It also describes the recent 15th International Mass Spectrometry Conference, held August/September 2000, in Barcelona. Each of the authors is associated with the IMSS. The 15th Conference, which covers all of mass spectrometry on a triennial basis, was chaired by Professor Emilio Gelpi of the Instituto de Investigaciones Biomedicas, Barcelona. The outgoing and founding President of the IMSS is Professor Graham Cooks, Purdue University, and the incoming President is Professor Nico Nibbering, University of Amsterdam. Similar material has been provided to the Editors of other journals that cover mass spectrometry. Copyright © 2001 John Wiley & Sons, Ltd.
Sequencing cyclic peptide inhibitors of mammalian ribonucleotide reductase by electrospray ionization mass spectrometry
Authors: Lin Shanhua , Liehr Sebastian , Cooperman Barry S. , Cotter Robert J. 
Published: August 2002

AbstractMammalian ribonucleotide reductase (mRR) is a potential target for cancer intervention. A series of lactam‐bridged cyclic peptide inhibitors (1–9) of mRR have been synthesized and tested in previous work. These inhibitors consist of cyclic and linear regions, causing their mass spectral characterization to be a challenge. We determined the fragmentation mechanism of cyclic peptides 1–9 using an ion‐trap mass spectrometer equipped with an ESI source. Low‐energy collision‐induced dissociation of sodiated cyclic peptides containing linear branches follows a general pathway. Fragmentation of the linear peptide region produced mainly a and b ions. The ring peptide region was more stable and ring opening required higher collision energy, mainly occurring at the amide bond adjacent to the lactam bridge. The sodium ion, which bound to the carbonyl oxygen of the lactam bridge, acted as a fixed charge site and directed a charge‐remote, sequence‐specific fragmentation of the ring‐opened peptide. Amino acid residues were cleaved sequentially from the C‐terminus to the N‐terminus. Our findings have established a new way to sequence cyclic peptides containing a lactam bridge based on charge‐remote fragmentation. This methodology will permit unambiguous identification of high‐affinity ligands within cyclic peptide libraries. Copyright © 2001 John Wiley & Sons, Ltd.
Characterisation of a South African human astrovirus as type 8 by antigenic and genetic analyses
Authors: Taylor Maureen B. , Walter Jolán , Berke Tamás , Cubitt W. David , Mitchell Douglas K. , Matson David O. 
Published: August 2002

AbstractHuman astroviruses (HAstV) can, on the basis of immunoassays using type‐specific rabbit antisera, be classified into eight serotypes that correlate with genotypes. Very few isolates of HAstV type 8 have been described and there is a paucity of data available with regard to the antigenic and genetic relationships between HAstV type 8 (HAstV‐8) and HAstV types 1 (HAstV‐1) to 7 (HAstV‐7). A wild‐type HAstV from a South African paediatric patient with diarrhoea was analysed antigenically, by immune electron microscopy and enzyme immunoassay, and genetically in selected regions of the ORF1a, ORF1b and ORF2 and characterised as a HAstV‐8. This HAstV‐8 strain exhibited greatest homology with HAstV‐4 in the 5′ end of the capsid gene and ORF1a and 1b, and greatest homology with HAstV‐5 in the 3′ end of the capsid region. This study confirms, by both antigenic and genetic analyses, that HAstV‐8 represents a distinct antigenic and genotype and is the first report of a HAstV‐8 from a hospitalised paediatric patient with diarrhoea in southern Africa. J. Med. Virol. 64:256–261, 2001. © 2001 Wiley‐Liss, Inc.
Replicative fitness in vivo of HIV‐1 variants with multiple drug resistance‐associated mutations
Authors: Devereux Helen L. , Emery Vincent C. , Johnson Margaret A. , Loveday Clive 
Published: August 2002

AbstractThe relative fitness of HIV‐1 viral variants containing a broad range of drug resistance‐associated mutations has been little studied in vivo. Understanding the relative fitness associated with viruses containing mutations may aid future therapeutic management. The aim of this study was to investigate the relative fitness of mutant viruses by assessing a cohort of patients who had developed resistance to many drugs and subsequently stopped all therapy. Eleven patients were assessed for drug resistance associated mutations in the protease (PR) and reverse transcriptase (RT) genes before and, at multiple time points, after stopping therapy. Relative fitness was calculated as a function of the rate of disappearance of mutant viruses when therapy was stopped. The least fit viruses were associated with the RT mutation M184I/V (11.6% less fit) and the PR mutations D30N (12.4% less fit) and M46I/L (21% less fit). Mutations at these codons were associated with significant reductions in fitness levels compared to wild‐type viruses. Mutations at codons 10, 20, 36, and 63 in the PR gene remained fairly constant when therapy was stopped and may not significantly reduce viral fitness. The rapid re‐population of wild‐type viruses may allow the recycling of antiretroviral drugs prescribed previously. J. Med. Virol. 65:218–224, 2001. © 2001 Wiley‐Liss, Inc.
Human picornavirus and coronavirus RNA in nasopharynx of children without concurrent respiratory symptoms
Authors: Nokso‐Koivisto Johanna , Kinnari Teemu J. , Lindahl Päivi , Hovi Tapani , Pitkäranta Anne 
Published: August 2002

AbstractThe prevalence of human rhino‐, entero‐, and coronaviruses was investigated by RT‐PCR in nasopharyngeal aspirates from 107 children without concurrent respiratory symptoms. The children were admitted to the hospital for elective surgery. The parents filled a questionnaire about the occurrence of respiratory symptoms four weeks before and two weeks after the surgery. The rate of viral detection was 45% in children with related past or recent respiratory infection whereas 20% of the samples taken from children without any related past or recent respiratory infections were positive for picornavirus RNA, P = 0.008. Thirty‐one (29%) of the nasopharyngeal aspirates were positive for viral RNA, 18% for rhinovirus, and 11% for enterovirus RNA. Coronavirus RNA was not found in any of the children. Fifty‐five percent of the children with virus‐positive samples had an infection‐related diagnosis. In addition, 81% of the children with virus‐positive samples had had previously respiratory symptoms or there were concurrent respiratory symptoms in other family members. Only four of the 31 virus‐positive samples were from children without infection‐related diagnosis or recent past (or immediate future) respiratory symptoms. J. Med. Virol. 66:417‐420, 2002. © 2002 Wiley‐Liss, Inc.
The ARB method
Authors: Lindenmeier Stefan , Russer Peter 
Published: August 2002

AbstractFor the general case of two interacting structures the computational effort of the adapting radiating boundaries (ARB) method is compared with the computational effort of the pure space discretizing transmission line matrix method. Since the numerical field modelling with the ARB method requires a very low computational effort, this method can be applied in a process for the automatical optimization of planar structures to prevent electromagnetic coupling phenomena. Numerical aspects of the method of ARB are shown. In two numerical examples, the ARB method is applied to the numerical modelling of the electromagnetic coupling between planar microwave structures. Copyright © 2001 John Wiley & Sons, Ltd.
Hepatocyte growth factor is a mitogen for olfactory ensheathing cells
Authors: Yan Henglin , Nie Xingtie , Kocsis Jeffery D. 
Published: August 2002

AbstractHepatocyte growth factor (HGF) is a potent mitogen for mature hepatocytes, and it has multi‐functional effects in a variety of cells in various organs. HGF stimulates DNA synthesis and promotes cell migration and morphogenesis in several cell types including the olfactory system. To characterize the potential mitogenic activity of HGF that might contribute to olfactory ensheathing cell (OEC) proliferation, we tested the ability of HGF to stimulate OEC division in vitro. OECs were obtained from adult rat olfactory bulbs and cultured in serum‐free medium, and were identified by double immunostaining for p75 and S‐100 antibodies. DNA synthesis assayed by pulsing BrdU for 24 hr showed that HGF at the concentration of 5–100 ng/ml elicited a 5–10‐fold increase of OEC proliferation. By immunocytochemical analysis, we demonstrated that c‐Met‐immunoreactivity was present in cultured OECs, and c‐Met anti‐serum significantly sequestered the activity of HGF on OECs proliferation, suggesting that HGF‐induced proliferation of OECs is mediated by the c‐Met receptor. The mitogenic activity of HGF was potentiated by addition of heregulin (HRG), but inhibited by addition of forskolin. These results demonstrate that HGF is a novel mitogen for rat OECs in vitro, and HGF/c‐Met system is involved in regulating OECs growth and development. J. Neurosci. Res. 66:698–704, 2001. © 2001 Wiley‐Liss, Inc.
Relationship between the increased cell surface α7 nicotinic receptor expression and neuroprotection induced by several nicotinic receptor agonists
Authors: Jonnala Ramamohana R. , Buccafusco Jerry J. 
Published: August 2002

AbstractNicotine and other nicotinic acetylcholine receptor agonists have been shown to exert neuroprotective actions in vivo and in vitro by an as yet unknown mechanism. Even the identification of the subtype of nicotinic receptor(s) mediating this action has not been determined. In neural cell lines, the induction of cytoprotection often requires exposure to nicotine for up to 24 hr to produce a full protective effect. One phenomenon associated with chronic exposure of neural cells to nAChR agonists is the increased expression of nAChRs (upregulation), possibly as a response to desensitization. Because nicotinic receptors desensitize rapidly in the continuous presence of agonist, we investigated whether the neuroprotective actions produced by different nicotinic receptor agonists was related to their ability to induce nicotinic receptor upregulation. Differentiated PC12 cells were preincubated for 24 hr with various nAChR ligands, and the cells were subsequently deprived of both NGF and serum to induce cytotoxicity. Under control conditions cell viability was reduced to 66.5 ± 5.4% of control by trophic factor withdrawal. For those cells pretreated with nicotine (1 nM–100 μM) cell viability increased from 74.2 ± 1.5 to 97.3 ± 4%. The neuroprotective action of nicotine was blocked by co‐treatment with either 5 μM mecamylamine or 10 nM methyllycaconitine (MLA). The high potency blockade by MLA suggested that neuroprotection was mediated through the α7 nicotinic receptor subtype. For the seven agonists examined for neuroprotective activity, only nicotine was capable of evoking a near maximal (near 100% cell viability) neuroprotective action. The next most effective group included epibatidine, 4OHGTS‐21, methycarbamylcholine, and 1,1‐dimethyl‐4‐phenyl‐piperazinium iodide. These least effective group included cytisine and tetraethylammonium. Incubation of differentiated PC12 cells with 10 μM nicotine increased the number of [125I]αbungarotoxin ([125I]αBGTbinding sites by 41% from 82.6 ± 3.67 to 117 ± 10.3 fmol/mg protein). Under similar conditions of incubation, the nicotinic receptor agonist cytisine (that was least effective in terms of neuroprotection) failed to increase the number of [125I]αBGT binding sites. Cells expressing increased levels of cell surface [125I]αBGT binding sites received added neuroprotective benefit from nicotine. Thus the induced upregulation of the α7 subtype of nicotinic receptors during chronic exposure to nicotine may be responsible for the drug's neuroprotective action. J. Neurosci. Res. 66:565–572, 2001. © 2001 Wiley‐Liss, Inc.
Altered brain phosphocreatine and ATP regulation when mitochondrial creatine kinase is absent
Authors: Kekelidze Téa , Khait Igor , Togliatti Anthony , Benzecry Jorge M. , Wieringa Be , Holtzman David 
Published: August 2002

AbstractIn cerebral gray matter, ATP concentration is closely maintained despite rapid, large increases in turnover and low substrate reserves. As seen in vivo by 31P nuclear magnetic resonance (NMR) spectroscopy, brain ATP is stable early in seizures, a state of high energy demand, and in mild hypoxia, a state of substrate deficiency. Like other tissues with high and variable ATP turnover, cerebral gray matter has high phosphocreatine (PCr) concentration and both cytosolic and mitochondrial creatine kinase (UbMi‐CK) isoenzymes. To understand the physiology of brain creatine kinases, we used 31P NMR to study PCr and ATP regulation during seizures and hypoxia in mice with targeted deletion of the UbMi‐CK gene. The baseline CK reaction rate constant (k) was higher in mutants than wild‐types. During seizures, PCr and ATP decreased in mutants but not in wild‐types. The k‐value for the CK catalyzed reaction rate increased in wild‐types but not in the mutants. Hypoxic mutants and wild‐types showed similar PCr losses and stable ATP. During recovery from hypoxia, brain PCr and ATP concentrations returned to baseline in wild‐types but were 20% higher than baseline in the mutants. We propose that UbMi‐CK couples ATP turnover to the CK catalyzed reaction rate and regulates ATP concentration when synthesis is increased. © 2001 Wiley‐Liss, Inc.
Role of specific aminotransferases in de novo glutamate synthesis and redox shuttling in the retina
Authors: LaNoue Kathyrn F. , Berkich Deborah A. , Conway Myra , Barber Alistair J. , Hu Lain‐Yen , Taylor Charles , Hutson Susan 
Published: August 2002

AbstractIn this study aminotransferase inhibitors were used to determine the relative importance of different aminotransferases in providing nitrogen for de novo glutamate synthesis in the retina. Aminooxyacetate, which inhibits all aminotransferases, blocked de novo glutamate synthesis from H14CO3− by more than 60%. Inhibition of neuronal cytosolic branched chain amino acid transamination by gabapentin or branched chain amino acid transport by the L‐system substrate analog, 2‐amino‐bicyclo‐(2,2,1)‐heptane‐2‐carboxylic acid, lowered total de novo synthesis of glutamate by 30%, suggesting that branched chain amino acids may account for half of the glutamate nitrogen contributed by transamination reactions. L‐cycloserine, an inhibitor of alanine aminotransferase, inhibited glutamate synthesis less than 15% when added in the presence of 5 mM pyruvate but 47% in the presence of 0.2 mM pyruvate. Although high levels of pyruvate blunted the inhibitory effectiveness of L‐cycloserine, the results indicate that, under physiological conditions, alanine as well as branched chain amino acids are probably the predominant sources of glutamate nitrogen in ex vivo retinas. The L‐cycloserine results were also used to evaluate activity of the malate/aspartate shuttle. In this shuttle, cytosolic aspartate (synthesized in mitochondria) generates cytosolic oxaloacetate that oxidizes cytosolic NADH via malate dehydrogenase. Because L‐cycloserine inhibits cytosolic but not mitochondrial aspartate aminotransferase, L‐cycloserine should prevent the utilization of aspartate but not its generation, thereby increasing levels of 14C‐aspartate. Instead, L‐cycloserine caused a significant decline in 14C‐aspartate. The results suggest the possibility that shuttle activity is low in retinal Müller cells. Low malate/aspartate shuttle activity may be the molecular basis for the high rate of aerobic glycolysis in retinal Müller cells. © 2001 Wiley‐Liss, Inc.
Identification and characterization of uptake systems for cystine and cysteine in cultured astrocytes and neurons: Evidence for methylmercury‐targeted disruption of astrocyte transport
Authors: Shanker Gouri , Aschner Michael 
Published: August 2002

AbstractMaintenance of appropriate intracellular glutathione (GSH) levels is crucial for cellular defense against oxidative damage. A suggested mechanism of methylmercury (MeHg) neurotoxicity implicates the involvement of oxygen radical formation and a decrease in cellular levels of GSH. Astrocytes play an important role in providing GSH precursors to neurons, and as will be discussed in this review, altered GSH homeostasis likely leads to impairment of astrocytic handling of glutamate, and neuronal energy metabolism. The review summarizes recent observations on transport systems for cysteine and cystine, precursors of GSH, in primary cultures of astrocytes and neurons, and their sensitivity to MeHg treatment. © 2001 Wiley‐Liss, Inc.
α‐cyano‐4‐hydroxycinnamate decreases both glucose and lactate metabolism in neurons and astrocytes: Implications for lactate as an energy substrate for neurons
Authors: McKenna Mary C. , Hopkins Irene B. , Carey Adrienne 
Published: August 2002

AbstractThe rates of uptake and oxidation of [U‐14C]lactate and [U‐14C]glucose were determined in primary cultures of astrocytes and neurons from rat brain, in the presence and absence of the monocarboxylic acid transport inhibitor α‐cyano‐4‐hydroxycinnamate (4‐CIN). The rates of uptake for 1 mM lactate and glucose were 7.45 ± 1.35 and 8.80 ± 1.0 nmol/30 sec/mg protein in astrocytes and 2.36 ± 0.19 and 1.93 ± 0.16 nmol/30 sec/mg protein in neuron cultures, respectively. Lactate transport into both astrocytes and neurons was significantly decreased by 0.25–1.0 mM 4‐CIN; however, glucose uptake was not affected. The rates of 14CO2 formation from 1 mM lactate and glucose were 12.49 ± 0.77 and 3.42 ± 0.67 nmol/hr/mg protein in astrocytes and 29.32 ± 2.81 and 10.04 ± 1.79 nmol/hr/mg protein in neurons, respectively. Incubation with 0.25 mM 4‐CIN decreased the oxidation of lactate and glucose to 57.1% and 54.1% of control values in astrocytes and to 13.2% and 41.6% of the control rates in neurons, respectively. Preincubation with 4‐CIN further decreased the oxidation of both glucose and lactate. Studies with glucose specifically labeled in the one and six positions demonstrated that 4‐CIN decreased mitochondrial glucose oxidation but did not impair the metabolism of glucose via the pentose phosphate pathway in the cytosol. The lack of effect of 4‐CIN on glutamate oxidation demonstrated that overall mitochondrial metabolism was not impaired. These findings suggest that the impaired neuronal function and tissue damage in the presence of 4‐CIN observed in other studies may be due in part to decreased uptake of lactate; however, the effects of 4‐CIN on mitochondrial transport would significantly decrease the oxidative metabolism of pyruvate derived from both glucose and lactate. © 2001 Wiley‐Liss, Inc.