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Selected AbstractsElimination Mechanisms in the Aminolysis of Sulfamate Esters of the Type NH2SO2OC6H4X , Models of Enzyme InhibitorsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2008William J. Spillane Abstract The kinetics of the reaction of 4-nitrophenyl sulfamate NH2SO2OC6H4NO2 -4 (1a) in acetonitrile (ACN) with a series of pyridines (pKa range ca. 8 units) and alicyclic amines (pKa range ca. 3.6 units) has been studied in the presence of excess amine at various temperatures. The compounds 1a,1f are important as model substrates for the medicinally important sulfamate esters 667-coumate and emate and analogues. Pseudo-first-order rate constants (kobsd.) have been obtained mainly by the release of 4-nitrophenol/4-nitrophenoxide. Slopes of plots of kobsd. vs. [amine] gave second-order rate constants (k2), and Brönsted plots were biphasic for the aminolysis (with alicyclic amines) with an initial slope ,1 = 0.53 and a subsequent slope ,2 = 0.19. The change in slope occurs near the first pKa of 1a (17.9) in ACN. Leaving-group effects were probed by using the same series of phenyl sulfamates, i.e. 1a,f and the alicyclic amines N -formylpiperazine and pyrrolidine. The reactions were considered to be dissociative in nature involving E2- and E1cB- type mechanisms with the phenyl sulfamate anion 2 being involved in pyridine and in the weaker alicyclic amines (,1 segment) and a phenyl sulfamate dianion 3 being involved with the stronger alicyclic bases (,2 segment). The calculation of Leffler indices (,) for bond-forming (base···H+) and bond-breaking (S,OAr) steps allows fuller interpretation of the mechanisms occurring, which are seen as having the N -sulfonylamines, HN=SO2 and ,N=SO2 on the reaction pathways leading to products. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] The Effects of Differences in Point of View on the Story Production of Japanese EFL StudentsFOREIGN LANGUAGE ANNALS, Issue 2 2001Taeko Kamimura Japanese college EFL students wrote two narrative stories based on the same series of pictures, one in the first-person perspective and the other in the third-person perspective. The sample writings were analyzed quantitatively and qualitatively in relation to the students' levels of English proficiency. The results showed that when the perspective was shifted from the first to the third person, the low-proficiency students' writings became poorer in quantity and quality, whereas the high-proficiency students' narratives exhibited no decrease in quantity and a slight decline in quality. On the other hand, when the perspective was switched from the third to the first person, the students' writings showed both quantitative and qualitative development, and this development was more clearly observed in the stories of those with high English proficiency. [source] Electronic and charge aspects of potential endocrine disruptors: Applications to pharmacological clusteringINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2003James W. King Abstract Quantitative structure,activity relationships in a series of 37 substituted indoles with endocrine disruptor potential were performed using the structural indices FTe (electronic) and FTc (charge), in conjunction with a clustering technique, to relate substitution patterns to reported relative binding affinities for the calf estrogen receptor. Data clusters were generated by a primary numerically descending sort of the structure indices with a concurrent secondary numerically descending sort of the binding data. Reversal of the numerical descent of the latter served to delineate cluster boundaries. Analysis within the clusters defined the effect of substituents and their molecular positions on the pharmacological data. These results confirmed in detail a similar previous study in the same series using the more general FTm index and again suggested the same structure of a molecule with greater receptor binding ability than any in the database. The methodology used in these studies permits a rational presentation and subsequent interpretation of data that initially appear to be totally random and devoid of recoverable information content. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003 [source] Building neural network models for time series: a statistical approachJOURNAL OF FORECASTING, Issue 1 2006Marcelo C. Medeiros Abstract This paper is concerned with modelling time series by single hidden layer feedforward neural network models. A coherent modelling strategy based on statistical inference is presented. Variable selection is carried out using simple existing techniques. The problem of selecting the number of hidden units is solved by sequentially applying Lagrange multiplier type tests, with the aim of avoiding the estimation of unidentified models. Misspecification tests are derived for evaluating an estimated neural network model. All the tests are entirely based on auxiliary regressions and are easily implemented. A small-sample simulation experiment is carried out to show how the proposed modelling strategy works and how the misspecification tests behave in small samples. Two applications to real time series, one univariate and the other multivariate, are considered as well. Sets of one-step-ahead forecasts are constructed and forecast accuracy is compared with that of other nonlinear models applied to the same series. Copyright © 2006 John Wiley & Sons, Ltd. [source] Immediate and Long-Term Outcome of Redo Percutaneous Mitral Valvuloplasty: Comparison with Initial Procedure in Patients with Rheumatic Mitral RestenosisJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 1 2010OSAMA RIFAIE M.D. Aims: We explored the immediate and long-term outcome of redo percutaneous mitral valvuloplasty (PMV) in a series of patients with mitral restenosis in comparison with initial PMV in the same series. Methods: We enrolled 40 consecutive patients presenting with mitral restenosis after successful initial PMV. Redo PMV was performed by the antegrade transseptal approach using either the Inoue technique or the multitrack technique. Reassessment by transthoracic echocardiography was repeated 48 hours later, and annually thereafter. Procedural success was defined as 50% or more increase of mitral valve area (MVA) with a final MVA ,1.5 cm2, without major complications. Restenosis was defined as loss of >50% of the initial gain of MVA by the preceding PMV with a final MVA <1.5 cm2. Results: Procedural success was achieved in 37 (92.5%) patients. Both the initial and redo procedures were similar concerning the final MVA and mean transmitral pressure gradient (P > 0.05 for all). The gain of MVA was higher in the initial as compared to the redo procedure (P < 0.001). The initial mitral valve score correlated negatively with the final MVA in both the initial and redo procedures, and was the only independent predictor of the time to redo procedure, by multivariate regression analysis. At long-term follow-up (61 ± 2.8 months), the mean MVA was 1.6 ± 0.3 cm2. Three patients,out of 12 available for follow-up,developed restenosis. Conclusion: Redo PMV for mitral restenosis is feasible, safe, and achieves immediate and long-term outcome comparable to initial PMV. (J Interven Cardiol 2010;23:1,6) [source] Maternal serum levels of dimeric inhibin A in pregnancies affected by trisomy 21 in the first trimesterPRENATAL DIAGNOSIS, Issue 6 2001Kevin Spencer Abstract Dimeric inhibin A was measured in maternal serum samples from 45 pregnancies affected by trisomy 21 and 493 samples from unaffected pregnancies at 10,14 weeks of gestation. Inhibin A levels in affected pregnancies were compared with levels of free ,-hCG and PAPP-A in the same series. In the trisomy 21 group, the median multiple of the median (MoM) inhibin A was not significantly elevated (1.28 vs 1.00) with only 15.5% being above the 95th centile. In contrast, the median MoM free ,-hCG was significantly increased (2.05 vs 1.00) with 36% above the 95th centile and PAPP-A was significantly reduced (0.49 vs 1.00) with 42% below the 5th centile. Inhibin A levels in the trisomy 21 group were significantly correlated with gestational age such that median levels rose from 1.04 at 11 weeks to 1.30 at 12 weeks and 1.67 at 13 weeks. These findings suggest that first trimester biochemical screening for trisomy 21, which is currently optimised using maternal serum free ,-hCG and PAPP-A and fetal nuchal translucency, will not benefit from the inclusion of inhibin A. Copyright © 2001 John Wiley & Sons, Ltd. [source] Galectins Are Differentially Expressed in Supratentorial Pilocytic Astrocytomas, Astrocytomas, Anaplastic Astrocytomas and Glioblastomas, and Significantly Modulate Tumor Astrocyte MigrationBRAIN PATHOLOGY, Issue 1 2001Isabelle Camby Galectins, a family of mammalian lectins with specificity to ,-galactosides, are involved in growth-regulatory mechanisms and cell adhesion. A relationship is assumed to exist between the levels of expression of galectins and the level of malignancy in human gliomas. A comparative study of this aspect in the same series of clinical samples is required to prove this hypothesis. Using computer-assisted microscopy, we quantitatively characterized by immunohistochemistry the levels of expression of galectins-1, -3 and-8 in 116 human astrocytic tumors of grades I to IV. Extent of transcription of galectins-1, -3, and -8 genes was investigated in 8 human glioblastoma cell lines by means of RT-PCR techniques. Three of these cell lines were grafted into the brains of nude mice in order to characterize in vivo the galectins-1, -3 and -8 expression in relation to the patterns of the tumor invasion of the brain. The role of galectin-1, -3 and -8 in tumor astrocyte migration was quantitatively determined in vitro by means of computer-assisted phase-contrast videomicroscopy. The data indicate that the levels of galectin-1 and galectin-3 expression significantly change during the progression of malignancy in human astrocytic tumors, while that of galectin-8 remains unchanged. These three galectins are involved in tumor astrocyte invasion of the brain parenchyma since their levels of expression are higher in the invasive parts of xenografted glioblastomas than in their less invasive parts. Galectin-3, galectin-1, and to a lesser extent galectin-8, markedly stimulate glioblastoma cell migration in vitro. Since bands for the transcripts of human galectins-2, -4 and -9 were apparently less frequent and intense in the 8 human glioblastoma cell lines, this system provides an excellent model to assign defined roles to individual galectins and delineate overlapping and distinct functional aspects. [source] Comparison between differentcell kinetic variables in human breast cancerCELL PROLIFERATION, Issue 2 2000F. Barzanti Cell kinetics holds a prominent role among biological factors in predicting clinical outcome and response to treatment in neoplastic patients. Different cell kinetic variables are often considered as valid alternatives to each other, but the limited size of case series analysed in several studies and the lack of simultaneous determinations of all the variables on the same tumours do not justify this conclusion. In the present study, the correlation between [3H]thymidine labelling index ([3H]dT LI), flow cytometric S phase cell fraction (FCM-S) and Ki-67 immunoreactivity (Ki-67/MIB-1) was verified and the type of correlation with the most important clinical, pathological and biological patient and tumour characteristics was investigated in a very large series of breast cancer patients. Ki-67/MIB-1, FCM-S and [3H]dT LI were determined in 609, 526 and 485 patients, respectively, and all three cell proliferation indices were evaluated in parallel on the same tumour in a series of 330 breast cancer patients. All the cell kinetic determinations were performed within the context of National Quality Control Programmes. Very poor correlation coefficients (ranging from 0.37 to 0.18) were observed between the different cell kinetic variables determined in parallel on the same series of breast cancers. Moreover, Ki-67/MIB-1 and FCM-S showed a significant relationship with histological type, grade and tumour size, whereas statistically significant correlations were not observed for [3H]dT LI. In conclusion, the results show that the different cell kinetic variables provide different biological information and cannot be considered as alternatives to each other. [source] | ||||||||||||||||