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61.
The N-acylethanolamine phospholipids (NAPE) are precursors for N-acylethanolamines (NAE), including anandamide (20∶4-NAE), which is a ligand for the cannabinoid receptors. Previously, NAPE
were believed to be found only in injured tissue, e.g., after neurodegenerative insults. Neuronal injury may occur in response
to seizure activity. Therefore, we investigated the effect of pentylenetetrazol (PTZ)-induced seizures in PTZ-kindled mice
on the level of NAPE in the brain. Male NMRI mice were kindled with PTZ injections 3 times/wk, thereby developing clonic seizures
in response to PTZ. Mice were killed within 30 min after the clonic seizure on the test day (12th injection) and the brains
were collected. Eight species of NAPE were analyzed as the glycerophospho-N-acylethanolamines by high-performance liquid chromatography-coupled electrospray ionization mass spectrometry. No effect
of the PTZ kindling on the NAPE levels in murine brains was observed. Total NAPE in control mice cortex (n=4) was 16.4±3.0 μmol/g wet weight of which 20∶4-NAPE accounted for 3.6 mol%, and the major species was 16∶0-NAPE, accounting
for 52.1 mol%. Determination of the activity of NAPE-hydrolyzing phospholipase D and of N-acyltransferase in brain membrane preparations from adult and 3-d-old mice revealed an enzyme pattern in the adult mice that
was favorable for NAE accumulation as opposed to NAPE accumulation. Thus, there was no difference in NAPE levels; at present,
however, this does not exclude that NAE may accumulate during seizure. 相似文献
62.
Detection of tyrosine phosphorylated peptides by precursor ion scanning quadrupole TOF mass spectrometry in positive ion mode 总被引:9,自引:0,他引:9
Phosphorylation is a common form of protein modification. To understand its biological role, the site of phosphorylation has to be determined. Generally, only limited amounts of phosphorylated proteins are present in a cell, thus demanding highly sensitive procedures for phosphorylation site determination. Here, a novel method is introduced which enables the localization of tyrosine phosphorylation in gel-separated proteins in the femtomol range. The method utilizes the immonium ion of phosphotyrosine at m/z 216.043 for positive ion mode precursor ion scanning combined with the recently introduced Q2-pulsing function on quadrupole TOF mass spectrometers. The high resolving power of the quadrupole TOF instrument enables the selective detection of phosphotyrosine immonium ions without interference from other peptide fragments of the same nominal mass. Performing precursor ion scans in the positive ion mode facilitates sequencing, because there is a no need for polarity switching or changing pH of the spraying solvent. Similar limits of detection were obtained in this approach when compared to triple-quadrupole mass spectrometers but with significantly better selectivity, owing to the high accuracy of the fragment ion selection. Synthetic phosphopeptides could be detected at 1 fmol/microL, and 100 fmol of a tyrosine phosphorylated protein in gel was sufficient for the detection of the phosphorylated peptide in the unseparated digestion mixture and for unambiguous phosphorylation site determination. The new method can be applied to unknown protein samples, because the identification and localization of the modification is performed on the same sample. 相似文献
63.
Bom N van der Steen AF Nosir YF Kasprzak JD 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2000,214(2):141-149
The heart can be studied using ultrasound techniques. The shape of the heart, its chambers, wall thicknesses, wall tissue characteristics as well as motion of walls and valve leaflets are all diagnostic information. In addition, the blood velocity and its timing within the cardiac cycle is an important diagnostic tool. In the present paper focus will be limited to the analysis of the left ventricular function as observed with two-dimensional and three-dimensional echocardiography and the characteristics of backscattered ultrasound information from the left ventricular chamber wall. Function of the heart is often studied by observation of local wall motion or comparison of chamber volume in maximum and minimum shapes during the cardiac cycle (ejection fraction). Integrated backscatter from the wall is described in examples of cardiac transplantation and hypertrophy. Study of cyclic variation of frequency-dependent attenuation and integrated backscatter indicates that these are independent parameters. 相似文献
64.
This paper presents a decision support system, named the CLG-DSS model, which makes it possible for decision makers to assess various uncertainties in project appraisal in a systematic and explicit way. This model, a decision support system (DSS) developed within the Danish Centre for Logistics and Freight Transport (CLG) is based on cost-benefit analysis (CBA) embedded in a wider multi-criteria analysis (MCA) by the use of some principles for composite modelling assessment (COSIMA). The CLG-DSS model is set up to make use of scenario analysis (SA) and Monte Carlo simulation (MCS). A particular concern in the model is the handling of varying information across the assessment criteria and the application of SA to inform the MCS parameter setting. After the presentation of the modelling principles some ex-post case calculations for the Øresund Fixed Link are illuminating different aspects of appraisal uncertainty and thereby, at the same time, demonstrate the features of the CLG-DSS model as a useful decision support tool. It is finally concluded that appraisal of large infrastructure projects can be effectively supported by dealing with uncertainty issues in accordance with the principles described. 相似文献
65.
Giuseppina Puzzilli Bogdan Govoreanu Fernanda Irrera Maarten Rosmeulen Jan Van Houdt 《Microelectronics Reliability》2007,47(4-5):508
In this work, charge trapping in SiO2/Al2O3 dielectric stacks is characterized by means of pulsed capacitance–voltage measurements. The proposed technique strongly reduces the measurement time and, as a consequence, the impact of charge trapping on the measurement results. Flat band voltage shift and fast current transient during short stress pulses are systematically monitored and the centroid and the amount of the trapped charge are extracted using a first-order model. 相似文献
66.
Zhijun Yang Zhengrong Yang Trygve Eftestøl Petter A. Steen Weiping Lu Robert G. Harrison 《Applied Artificial Intelligence》2013,27(6):588-597
This article presents a methodology based on the mixture model to classify the real biomedical time series. The mixture model is shown to be an efficient probabilistic density estimation scheme aimed at approximating the posterior probability distribution of a certain class of data. The approximation is conducted by employing a weighted mixture of a finite number of Gaussian kernels whose parameters and mixing coefficients are estimated iteratively through a maximum likelihood method. A database of the real electrocardiogram (ECG) time series of out-of-hospital cardiac arrest patients suffering ventricular fibrillation (VF) with known defibrillation outcomes was adopted to evaluate the performance of this model and confirm its efficiency compared with other classification methods. 相似文献
67.
Nicholas R. Goodwin Steen Magnussen Nicholas C. Coops Michael A. Wulder 《International journal of remote sensing》2013,34(12):3263-3271
In this technical note we present a new technique using mixed linear models for characterizing a mountain pine beetle (Dendroctonus ponderosae Hopkins) infestation from multiyear satellite imagery. The main benefit of our approach is an ability to determine the statistical significance of each annual spectral change. Knowledge of the annual spectral change characteristics can then be used to statistically determine if a disturbance event has occurred, the timing of a given disturbance event, as well as to provide information for clustering fitted multitemporal reflectance curves (i.e. spectral trajectories) with a common shape. The spatial clustering of spectral trajectories provides insights into the nature of the disturbance and recovery imposed by infestation over a 14-year period. 相似文献
68.
The advantages and open questions of the combination of modulation excitation spectroscopy and phase sensitive detection (PSD) with X-ray absorption spectroscopy (XAS) for the analysis of heterogeneous catalysts at work are reviewed. The characteristic spectral signatures of two different edges (Pd K and Pt L3) are described in relation to the red-ox chemistry of Pd/Al2O3 and Pt/Al2O3 with respect to NO reduction by CO and CO oxidation, respectively. Both examples demonstrate that PSD makes XAS sensitive to potentially active species for the catalytic reaction. 相似文献
69.
70.
The paper describes the findings from a study of students’ use and experience of technologies. A series of in-depth case studies were carried out across four subject disciplines, with data collected via survey, audio logs and interviews. The findings suggest that students are immersed in a rich, technology-enhanced learning environment and that they select and appropriate technologies to their own personal learning needs. The findings have profound implications for the way in which educational institutions design and support learning activities. 相似文献