bluuebunny/crossref_metadata_2025_split huggingface dataset:
Caspase activity in newt spermatogonial apoptosis induced by prolactin and cycloheximide
Authors: Yazawa Takashi , Fujimoto Kenta , Yamamoto Takashi , Abé Shin‐Ichi 
Published: September 2002

AbstractWe previously showed in vivo and in vitro, that among the spermatogenic stages of the newt, prolactin (PRL) induces apoptosis specifically in the penultimate stage of secondary spermatogonia. In the current report, we demonstrate in vitro that cycloheximide (CHX), an inhibitor of protein synthesis, induces morphological apoptotic changes similar to those caused by PRL, such as chromatin condensation and apoptotic body formation. Next, we found that Z‐VAD‐fmk, an inhibitor of various caspases, suppressed the apoptosis induced by PRL and CHX, but ICE inhibitor Ac‐YVAD‐CHO or caspase‐3 inhibitor Ac‐DEVD‐CHO did not. As high caspase activity was present in extracts of testes treated with CHX, we suggest that an unidentified caspase induces the morphological changes of apoptosis in newt spermatogonia. Mol. Reprod. Dev. 59:209–214, 2001. © 2001 Wiley‐Liss, Inc.
19F‐MRI of perflubron for measurement of oxygen partial pressure in porcine lungs during partial liquid ventilation
Authors: Laukemper‐Ostendorf Simone , Scholz Alexander , Bürger Katja , Heussel Claus P. , Schmittner Marc , Weiler Norbert , Markstaller Klaus , Eberle Balthasar , Kauczor Hans‐Ulrich , Quintel Michael , Thelen Manfred , Schreiber Wolfgang G. 
Published: September 2002

AbstractA method for in vivo measurement of oxygen partial pressure (pO2) in porcine lungs during partial liquid ventilation (PLV) with perflubron (PFOB) was developed. A pulse sequence for high‐resolution MRI of the distribution of PFOB in the lung after intratracheal administration was developed as well. Moreover, quantitative measurements of longitudinal relaxation time T1 of 19F resonances for assessment of regional pO2 are described. Due to the need to acquire data during a single expiratory breathhold, only low SNRs were achieved in vivo. Therefore, simulations were performed to investigate the influence of background noise on T1 values calculated from data with low SNR. Based on these simulations, a postprocessing strategy was developed to correct for systematic errors by background noise prior to quantitative analysis. Results of a pilot study in pigs under conditions of PLV are presented. Magn Reson Med 47:82–89, 2002. © 2002 Wiley‐Liss, Inc.
Dynamic changes of ADC, perfusion, and NMR relaxation parameters in transient focal ischemia of rat brain
Authors: van Dorsten F.A. , Olàh L. , Schwindt W. , Grüne M. , Uhlenküken U. , Pillekamp F. , Hossmann K.‐A. , Hoehn M. 
Published: September 2002

AbstractThe potential of multiparametric MRI parameters for differentiating between reversibly and irreversibly damaged brain tissue was investigated in an experimental model of focal brain ischemia in the rat. The middle cerebral artery (MCA) was occluded by intraluminal suture insertion for 60 or 90 min, followed by 4.5 h of reperfusion. The apparent diffusion coefficient (ADC) of brain water, T1 and T2 relaxation times, and CBFi, an MR‐derived index of cerebral perfusion, were repeatedly measured and correlated with the outcome from the ischemic impact. A novel user‐independent approach for segmentation of ADC maps into classes of increasing injury was introduced to define regions of interest (ROIs) in which these parameters were evaluated. MCA occlusion led to a graded decline of ADC, which corresponded with both the severity of flow reduction and an increase in T1 and T2 relaxation times. Removal of the suture led to a triphasic restitution of blood flow consisting of a fast initial rise, a secondary decline, and final normalization. Postischemic reperfusion led to a rise of ADC irrespective of the duration of ischemia. However, the quality of recovery declined with increasing severity of the ischemic impact. Throughout the observation time, T1 and T2 showed a continuous increase, the intensity of which correlated with the severity of ADC decline during ischemia. Particularly with longer ischemia time, elevated T2 in combination with reduced ADC yielded a lower probability of recovery during recirculation, while intraischemic perfusion information contributed less to the prediction of outcome. In conclusion, the combination of MR parameters at the end of ischemia correlated with the probability of tissue recovery but did not permit reliable differentiation between reversibly and irreversibly damaged tissue. Magn Reson Med 47:97–104, 2002. © 2002 Wiley‐Liss, Inc.
RF safety of wires in interventional MRI: Using a safety index
Authors: Yeung Christopher J. , Susil Robert C. , Atalar Ergin 
Published: September 2002

AbstractWith the rapid growth of interventional MRI, radiofrequency (RF) heating at the tips of guidewires, catheters, and other wire‐shaped devices has become an important safety issue. Previous studies have identified some of the variables that affect the relative magnitude of this heating but none could predict the absolute amount of heating to formulate safety margins. This study presents the first theoretical model of wire tip heating that can accurately predict its absolute value, assuming a straight wire, a homogeneous RF coil, and a wire that does not extend out of the tissue. The local specific absorption rate (SAR) amplification from induced currents on insulated and bare wires was calculated using the method of moments. This SAR gain was combined with a semianalytic solution to the bioheat transfer equation to generate a safety index. The safety index (°C/(W/kg)) is a measure of the in vivo temperature change that can occur with the wire in place, normalized to the SAR of the pulse sequence. This index can be used to set limits on the spatial peak SAR of pulse sequences that are used with the interventional wire. For the case of a straight resonant wire in a tissue with very low perfusion, only about 100 mW/kg/°C spatial peak SAR may be used at 1.5 T. But for ≤10‐cm wires with an insulation thickness ≥30% of the wire radius that are placed in well‐perfused tissues, normal operating conditions of 4 W/kg spatial peak SAR are possible at 1.5 T. Further model development to include the influence of inhomogeneous RF, curved wires, and wires that extend out of the sample are required to generate safety indices that are applicable to common clinical situations. We propose a simple way to ensure safety when using an interventional wire: set a limit on the SAR of allowable pulse sequences that is a factor of a safety index below the tolerable temperature increase. Magn Reson Med 47:187–193, 2002. © 2002 Wiley‐Liss, Inc.
Single‐shot T measurement to establish optimum echo time for fMRI: Studies of the visual, motor, and auditory cortices at 3.0 T
Authors: Clare Stuart , Francis Susan , Morris Peter G. , Bowtell Richard 
Published: September 2002

AbstractThe signal change in fMRI is dependent on the echo time and the rate of decay of transverse magnetization. The latter factor may vary across regions of the brain as a result of variations in field homogeneity. Previous measurements of the signal change with echo time have generally employed relatively slow multi‐echo techniques, which may be sensitive to movement and habituation effects. Here a fast T measurement technique, involving the generation of six low‐resolution echo planar images from a single FID, is described, and its use in the evaluation of the optimum echo time for visual, motor, and auditory fMRI experiments at 3.0 T is outlined. Magn Reson Med 45:930–933, 2001. © 2001 Wiley‐Liss, Inc.
Nicotinic synapses formed between chick ciliary ganglion neurons in culture resemble those present on the neurons in vivo
Authors: Chen Min , Pugh Phyllis C. , Margiotta Joseph F. 
Published: September 2002

AbstractWe studied nicotinic synapses between chick ciliary ganglion neurons in culture to learn more about factors influencing their formation and receptor subtype dependence. After 4–8 days in culture, nearly all neurons displayed spontaneous excitatory postsynaptic currents (sEPSCs), which occurred at about 1 Hz. Neurons treated with tetrodotoxin displayed miniature EPSCs (mEPSCs), but these occurred at low frequency (0.1 Hz), indicating that most sEPSCs are actually impulse driven. The sEPSCs could be classified by decay kinetics as fast, slow, or biexponential and, reminiscent of the situation in vivo, were mediated by two major nicotinic acetylcholine receptor (AChR) subtypes. Fast sEPSCs were blocked by α‐bungarotoxin (αBgt), indicating dependence on αBgt‐AChRs, most of which are α7 subunit homopentamers. Slow sEPSCs were unaffected by αBgt, and were blocked instead by the α3/β2‐selective α‐conotoxin‐MII (αCTx‐MII), indicating dependence on α3*‐AChRs, which lack α7 and contain α3 subunits. Biexponential sEPSCs were mediated by both αBgt‐ and α3*‐AChRs because they had fast and slow components qualitatively similar to those comprising simple events, and these were reduced by αBgt and blocked by αCTx‐MII, respectively. Fluorescence labeling experiments revealed both αBgt‐ and α3*‐AChR clusters on neuron somata and neurites. Colabeling with antisynaptic vesicle protein antibody suggested that some α3*‐AChR clusters, and a few αBgt‐AChR clusters are associated with synaptic sites, as is the case in vivo. These findings demonstrate the utility of ciliary ganglion neuron cultures for studying the regulation of nicotinic synapses, and suggest that mixed AChR subtype synapses characteristic of the neurons in vivo can form in the absence of normal inputs or targets. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 265–279, 2001
Sorption and transport of linear alkane hydrocarbons in biaxially oriented polyethylene terephthalate
Authors: Dhoot S. N. , Freeman B. D. , Stewart M. E. , Hill A. J. 
Published: September 2002

AbstractEquilibrium sorption and uptake kinetics of n‐butane and n‐pentane in uniform, biaxially oriented, semicrystalline polyethylene terephthalate films were examined at 35 °C and for pressures ranging from 0 to approximately 76 cmHg. Sorption isotherms were well described by the dual‐mode sorption model. Sorption kinetics were described either by Fickian diffusion or a two‐stage model incorporating Fickian diffusion at short times and protracted polymer structural relaxation at long times. Diffusion coefficients increased with increasing penetrant concentration. n‐Butane solubility was lower than that of n‐pentane, consistent with the more condensable nature of n‐pentane. However, n‐butane diffusion coefficients were higher than those of n‐pentane. Infinite‐dilution, estimated amorphous phase diffusion and solubility coefficients were well correlated with penetrant critical volume and critical temperature, respectively. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1160–1172, 2001
Structural and mechanical behavior of nylon‐6 films. II. Uniaxial and biaxial drawing
Authors: Penel‐Pierron L. , Séguéla R. , Lefebvre J.‐M. , Miri V. , Depecker C. , Jutigny M. , Pabiot J. 
Published: September 2002

AbstractThe plastic behavior of polyamide‐6 (or nylon‐6) films under uniaxial and biaxial tensile drawing is studied in relation to structural features. Quenched films in the mesomorphic β form are more ductile than films in the predominant stable α form. Films in the major γ crystalline form are intermediate between films in the β and α forms. Under uniaxial drawing, a great part of the β phase undergoes strain‐induced phase change into the α form, involving strain hardening of the material. The β→α phase change is more pronounced above 120 °C because of additional thermal reorganization. The γ form that is thermally stable up to 200 °C also undergoes a strain‐induced phase change above 120 °C, but the reorganization is much less important than for the β phase. Biaxial drawing can only be achieved below 120 °C with quenched films. This is likely due to the high mechanical anisotropy of the H‐bonded sheetlike structure of both the α and γ phases that is suspected to develop catastrophic splitting under a normal stress component, notably above 120 °C because of the collapse of the paraffin‐like van der Waals interactions between the sheets. The disordered distribution of the H bonds in the mesomorphic β structure of the quenched films is more appropriate for biaxial drawing. The strain‐induced β→α phase reorganization, which might have been a serious prejudice, proved to be much reduced during biaxial drawing below 120 °C. The mechanism of the strain‐induced phase change is discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 1224–1236, 2001
Toxicological screening of urine for drugs by liquid chromatography/time‐of‐flight mass spectrometry with automated target library search based on elemental formulas
Authors: Gergov Merja , Boucher Brian , Ojanperä Ilkka , Vuori Erkki 
Published: September 2002

AbstractThe present study describes a novel approach for utilizing liquid chromatography/time‐of‐flight mass spectrometry (LC/TOFMS) in qualitative screening analysis. An LC/TOFMS method was developed for screening toxicologically relevant substances in urine samples. After solid phase extraction and LC separation, the method included full spectrum acquisition followed by automatic internal calibration, searching against a target library, and reporting positive identifications. The target library, containing 433 toxicologically relevant substances in the mass range of 105–734 Da, was created simply by entering the elemental formulas of substances into the instrument software for the calculation of their respective monoisotopic masses. In addition to parent drugs, the library contained selected urinary drug metabolites, based on their structures available in the literature. Identification was based on the exact masses of the compounds. The LC/TOFMS method provided 5–10 ppm mass accuracy for a majority of identified compounds in authentic urine samples. Compared with established thin‐layer and gas chromatographic methods, the LC/TOFMS method produced similar findings in urine with the additional advantage of metabolite identification without actual reference substances. Copyright © 2001 John Wiley & Sons, Ltd.
Analysis of bacterial lipodepsipeptides by matrix‐assisted laser desorption/ionisation time‐of‐flight and high‐performance liquid chromatography with electrospray mass spectrometry
Authors: Monti Simona Maria , Gallo Monica , Ferracane Rosalia , Borrelli Rosa Cinzia , Ritieni Alberto , Greco Maria Luigia , Graniti Antonio , Fogliano Vincenzo 
Published: September 2002

AbstractStrains of certain plant pathogenic bacteria, in particular several pathovars ofPseudomonas syringae, are known to produce cyclic lipodepsipeptides (LDPs) endowed with peculiar structural features and noticeable biological activities. In this study, a mass spectrometry procedure is proposed for screening LDP‐producing bacterial strains and for identifying and assessing individual LDPs. After matrix‐assisted laser desorption/ionisation time‐of‐flight (MALDI‐TOF) screening of thirteenP. syringaestrains for LDP production, the extracts from culture filtrates of eight positive strains were subjected to electrospray mass spectrometry for the identification of LDPs. Five strains were found to produce two forms of syringomycins (SR‐E and SR‐G) and two forms of syringopeptin 25 (SP25Aand SP25B); two strains produced SR‐E, SR‐G and a new form of SP22; one strain produced syringotoxin (ST) and syringostatin A (SS‐A) in addition to SP25Aand SP25B. The yield in culture of two major LPDs: SR‐G (3.2–13.8 mg L−1) and SP25A(41.6–231.5 mg L−1) was assessed by and high‐performance liquid chromatography with electrospray mass spectrometry (HPLC/ESI‐MS) in both scan and single ion monitoring (SIM) modes. Results of this investigation showed that the mass spectrometry protocol developed here is a precise and reliable method for screening bacterial strains for LDP production and for assessing the amount of each metabolite under various culture conditions. This could be of practical value in view of potential applications, e.g. biocontrol of post‐harvest fungal diseases. Copyright © 2001 John Wiley & Sons, Ltd.
Studies on the association of 2‐thiazolidinecarboxylic acid and antimony potassium tartrate: chiral recognition and prediction of absolute configuration by electrospray ionization mass spectrometry
Authors: Arakawa Ryuichi , Kobayashi Mako , Fukuo Tsuyoshi , Shiraiwa Tadashi 
Published: September 2002

AbstractOptically active 2‐thiazolidinecarboxylic acid (2‐THC), a substrate for D‐amino acid oxidase in animal kidney, is known to undergo racemization quickly in solution. The association of (+)‐ and (−)‐2‐THC with antimony potassium tartrate K2[Sb2(L or D‐tart)2] was studied by electrospray ionization mass spectrometry (ESI‐MS). We observed that relative intensities of associated ions in acetonitrile/water solution were changing as the racemization progressed. For [Sb2(L‐tart)2]2−, the intensities of the associated ions increased as (+)‐2‐THC underwent racemization to a (−)‐isomer; on the other hand, the intensity of the associated ion decreased as (−)‐2‐THC underwent racemization to a (+)‐isomer. In the case of [Sb2(D‐tart)2]2−, an opposite effect on the intensities of the associated ions was observed. The change in the intensities of associated ions can be used for chiral recognition of (+)‐2‐THC and (−)‐2THC. Stereochemical models of the association of the optical isomers with [Sb2(L‐ or D‐tart)2]2− were constructed from the consideration of both hydrogen bonding of NH‐O functions and HSAB (hard and soft acids and bases) interaction of S and Sb atoms. Comparison of the stereochemical models with the ESI‐MS results enabled us to predict the absolute configurations of the 2‐THC isomers. Copyright © 2001 John Wiley & Sons, Ltd.
Interdiffusion coefficients and conductivity in gold/nickel bilayer thin films on silicon(111) wafers
Authors: Abdul‐Lettif A. M. , Rammo N. N. , Makadsi M. N. 
Published: September 2002

AbstractInterdiffusion in the gold/nickel bilayer thin films deposited on silicon(111) wafers in the temperature range 200–500 °C has been studied using x‐ray photoelectron spectroscopy (XPS), sheet resistance measurements (SRM) and x‐ray diffraction. Two independent methods have been used to determine the diffusion coefficients: the accumulation concentration of nickel on the gold surface using XPS; and the variation of sheet resistance as a function of annealing time and temperature.The diffusion coefficients deduced from XPS and SRM are (4.0 × 10−11 cm2 s−1) exp(−0.79 eV/kT) and (4.8 × 10−11 cm2 s−1) exp(−0.83 eV/kT), respectively. It is shown that diffusion of nickel through the gold layer causes a considerable loss in conductivity of the bilayer thin films. Copyright © 2001 John Wiley & Sons, Ltd.
SIMS quantification of Si1−xGex alloys using polyatomic secondary ions
Authors: Dong Gui , Liangzhen Cha , Rong Liu , Wee A. T. S. 
Published: September 2002

AbstractThe matrix effect in Si1−xGex alloys (x ≤ 0.5) grown by ultrahigh vacuum chemical vapour deposition was investigated with an O2+ primary beam in a Cameca IMS 6f instrument. The results showed that the matrix effect in Si1−xGex alloys was significant when the Ge fraction was >0.25, and it turned out to be more pronounced at low impact energies. Nevertheless, the composition of Si1−xGex alloys could be quantified based on the linear variation of appropriate secondary ion intensity ratios against the Ge concentration. The use of polyatomic secondary ions to measure the composition of SiGe alloys is reported in this paper. By this method, both the dopant and matrix elements in a Si/Si1−xGex/Si heterojunction bipolar transistor sample have been quantified by SIMS. The germanium fractions thus determined agree well with values obtained by double‐crystal x‐ray diffraction. Copyright © 2001 John Wiley & Sons, Ltd.
FTIR mechanistic studies on the selective catalytic reduction of NOx by methane and ethane over supported cobalt catalysts
Authors: Hadjiivanov K. , Tsyntsarski B. , Ivanova E. , Klissurski D. , Marinova Ts. 
Published: September 2002

AbstractThe NOx species formed after NO adsorption and NO+O2 co‐adsorption on Co‐ZSM‐5, CoY, Co/SiO2 (high cobalt dispersion) and Co/SiO2 (low cobalt dispersion) were studied by means of IR spectroscopy. It was found that NO adsorption on all samples leads to the formation of Co2+(NO)2 species, which are stable on Co‐ZSM‐5 and CoY but are destroyed during evacuation on Co/SiO2. The stable species produced upon NO+O2 co‐adsorption are different kinds of surface NOx− anionic species. The principal compounds formed on Co‐ZSM‐5 and Co/SiO2 with a high cobalt dispersion are surface monodentate nitrates, characterized by an IR band at ∼1535 cm−1. These nitrates are thermally stable but easily interact with hydrocarbons which confirms that they are key species in selective catalytic reduction (SCR). No monodentane nitrates are formed on CoY and Co/SiO2 with a low cobalt dispersion, which accounts for the low SCR activity reported for such samples. Copyright © 2001 John Wiley & Sons, Ltd.
Two‐dimensional crystallization of nitrobenzene on a monolayer of stearic acid characterized by scanning tunnelling microscopy
Authors: Lei S. B. , Wang C. , Yin S. X. , Xu Q. M. , Bai C. L. 
Published: September 2002

AbstractUsing a monolayer of stearic acid molecules as a buffer layer, nitrobenzene has been immobilized on highly oriented pyrolytic graphite (HOPG) and imaged by scanning tunnelling microscopy (STM) with submolecular resolution. The results indicate that the image contrast is determined by the lowest unoccupied molecular orbital (LUMO) whether a positive or negative bias is applied. This strategy can be used as a general method to characterize small organic molecules by STM under ambient conditions. Copyright © 2001 John Wiley & Sons, Ltd.
Electron inelastic mean free paths (IMFPs) in binary Au–Cu alloys determined by elastic peak electron spectroscopy
Authors: Krawczyk M. , Zommer L. , Jablonski A. , Robert C. , Pavluch J. , Bideux L. , Gruzza B. 
Published: September 2002

AbstractNumerous data on the inelastic mean free path (IMFP) of electrons have been published, mainly for elemental solids and some inorganic and organic compounds. However, there is limited information available for IMFP values of binary alloy systems. Although IMFP values for different energies can be calculated for alloys from predictive formulae, IMFPs can be measured experimentally by elastic peak electron spectroscopy (EPES). In the present work, the IMFPs for three Au–Cu alloys — Au (25 at.%)–Cu (75 at.%), Au (50 at.%)–Cu (50 at.%), Au (75 at.%)–Cu (25 at.%) — were determined for the first time. The EPES experiments have been performed in three laboratories using spectrometers with different geometries and energy resolutions. The experiments were performed with the use of an Au standard (relative measurements) and without a standard material (absolute measurements). Two Monte Carlo algorithms were used to calculate the IMFPs. The IMFP energy dependence for the alloy samples has been obtained in the primary electron energy range 200–2000 eV. The measured IMFPs were compared with IMFPs calculated from two predictive formulae, i.e. the TPP‐2M equation of Tanuma et al. and the G‐1 equation of Gries. The scatter between the measured IMFPs and those calculated from the predictive formulae has been analysed statistically. The root‐mean‐square deviation from IMFP values calculated from the TPP‐2M equation was 1.81–5.97 Å, depending on the alloy surface composition and the particular EPES measurement, and it was smallest for the Au25Cu75 alloy. The mean percentage deviation from the TPP‐2M IMFPs was ∼27%. Copyright © 2001 John Wiley & Sons, Ltd.