bluuebunny/crossref_metadata_2025_split huggingface dataset:
First‐trimester screening for Down syndrome in France combining fetal nuchal translucency measurement and biochemical markers
Authors: Muller Françoise , Benattar Clarisse , Audibert François , Roussel Nathalie , Dreux Sophie , Cuckle Howard 
Published: October 2003

AbstractBackgroundIn France, there is a strictly regulated National Screening Programme for Down syndrome, based on second‐trimester maternal serum markers. A prospective study of nuchal translucency together with retrospective evaluation of maternal serum markers was carried out to inform decisions on whether to move the programme to the first trimester.MethodsBetween January 1998 and June 2001, all women who presented for their prenatal care at 12 participating maternity units were, regardless of age, invited to provide a blood sample and to attend for an NT scan at 11 to 13 weeks. The results were used to derive Gaussian distribution parameters. Detection and false‐positive rates were computed in two ways: statistical modelling and directly. The cut‐off risk was 1 in 250 at term.ResultsA total of 5694 women with singleton pregnancies were screened including 26 with Down syndrome and 24 with other aneuploidies. The model‐predicted detection and false‐positive rates for combined ultrasound and serum screening were 81 and 4.5% compared to 64 and 6.0% for ultrasound alone. The directly observed rates were 73 and 4.7%, compared to 62 and 5.0% respectively.ConclusionIn France, first‐trimester screening with nuchal translucency and maternal serum markers is likely to achieve a high screening efficiency. This has important implications for the national screening policy. Copyright © 2003 John Wiley & Sons, Ltd.
Do women prefer to have screening tests for Down syndrome that have the lowest screen‐positive rate or the highest detection rate?
Authors: Mulvey Sheila , Zachariah Rebecca , McIlwaine Kate , Wallace Euan M. 
Published: October 2003

AbstractObjectiveTo assess whether women have a preference for Down syndrome screening test performance.MethodsA structured questionnaire exploring women's preferences for screening test performance was administered to women attending their first prenatal visit who wished to have Down syndrome screening performed.ResultsOne hundred and twenty women were interviewed. The majority of women (n = 80) chose a screening test with a low screen‐positive rate rather than the highest detection rate. The reasons given for this preference were a desire to minimise the risk of miscarriage of a normal baby and a belief that a detection rate of 80 to 90% was acceptable. However, older women (>37 years) chose a test with the highest detection rate possible, regardless of the higher screen‐positive rate, preferring to miscarry a normal baby as a result of a diagnostic test rather than miss the detection of a baby with Down syndrome. Preferences were not influenced by previous screening experience.ConclusionsWomen express different preferences for screening test performance. Maternal age rather than previous screening experiences appears to be the major influence in these choices. Copyright © 2003 John Wiley & Sons, Ltd.
Fetal cells and DNA in maternal blood
Authors: Jackson Laird 
Published: October 2003

AbstractAlthough fetal cells have been known to escape to the maternal circulation for a number of years, research attempts to use them for prenatal diagnosis have not had any consistent success. This review attempts to trace the history of such attempts and to document their progress and reasons for success or failure. The opinions of recent conferences including that of the US National Institute of Child Health and Human Development, a sponsor of major US research in the field, are reported and discussed. It is concluded that although basic work has demonstrated the biologic availability of both fetal cells and their free DNA representatives in the maternal circulation at gestational ages relevant to prenatal diagnosis, much work remains to develop practical technology for their consistent recovery and assay. Copyright © 2003 John Wiley & Sons, Ltd.
Fetal chromosomal analysis of pregnancies following intracytoplasmic sperm injection with amniotic tissue culture
Authors: Samli Hale , Solak Mustafa , Imirzalioǧlu Necat , Beyatlı Yavuz , Şimşek Solmaz , Kahraman Semra 
Published: October 2003

AbstractObjectivesThe objective of this study was to determine the incidence of chromosomal anomalies in a complete cohort of ICSI pregnancies.MethodsFrom January 1996 to December 2000, 1500 consecutive patients who had become pregnant after Intracytoplasmic Sperm Injection (ICSI) were given prenatal genetic counseling and 98 of them (6.5%) who accepted amniocentesis were studied. Amniocentesis was performed between 14 and 20th weeks of their pregnancy. Amniotic tissue cultures were processed according to Hoehn et al. A minimum of 20 metaphases were examined on each preparation. Both parents were also evaluated with peripheral blood karyotyping.ResultsAmniocentesis and karyotyping was performed to evaluate the 142 fetuses from 98 ICSI pregnancies. Karyotypes from peripheral leucocytes of the parents were also evaluated. Chromosomal anomalies were detected from 6 out of the 142 (4.2%) fetuses. The anomalies were as follows, ‘46,XX/69,XXX/92,XXXX’, ‘46,XY/69,XXY/92,XXYY’, ‘47,XY + 21’, ‘46,XY/47,XY + 7’, ‘47,XXY’, and ‘45,X0’. All except one pregnancy were terminated with the consent of the couples. Fetal tissue cultures were also studied after the termination of the pregnancy in order to confirm prenatal diagnosis. We did not detect abnormal karyotype from the parents of these fetuses.ConclusionsThe ratio of chromosomal abnormalities seems to be slightly increased in ICSI pregnancies. Paternal factors due to morphologically abnormal spermatozoa, maternal factors due to increased mother age and more frequently, de novo occurring sex chromosomal abnormalities may be responsible for this outcome. Copyright © 2003 John Wiley & Sons, Ltd.
Trisomy 13 and trisomy 18 in a defined population: epidemiological, genetic and prenatal observations
Authors: Parker M. J. , Budd J. L. S. , Draper E. S. , Young I. D. 
Published: October 2003

AbstractObjectivesTo establish precise incidence figures for trisomy 13 and trisomy 18 in the former Trent region, to identify current prenatal diagnostic practice, and to assess the potential impact of the introduction of recently devised prenatal diagnostic practices.MethodsAn audit of all cases of trisomy 13 and trisomy 18 ascertained through the records of the Trent Congenital Anomalies Register and the Trent Regional Cytogenetic Laboratories.ResultsForty‐four cases of trisomy 13 and 88 cases of trisomy 18 were ascertained. Advanced maternal age effects were observed. Of all cases, 64% were first detected through chromosomal analysis initiated because of abnormalities noted on fetal anomaly scanning in the second trimester, whereas only 3% of cases were detected through the serum‐screening programme currently offered for Down syndrome. In 11% of cases, the diagnosis was first suspected after birth. Twelve percent of couples chose to continue pregnancy following chromosomal confirmation of a suspected diagnosis.ConclusionThe introduction of a highly sensitive prenatal diagnostic screening programme would have a major impact on the timing and proportions of all trisomy 13 and 18 cases diagnosed in pregnancy as gauged by current practice. It is important that health professionals involved in prenatal counselling be aware that, as with Down syndrome and anencephaly, around 12% of prospective parents of a child with trisomy 13 or 18 choose to continue rather than terminate the pregnancy. Copyright © 2003 John Wiley & Sons, Ltd.
Maternal weight correction of maternal serum PAPP‐A and free β‐hCG MoM when screening for trisomy 21 in the first trimester of pregnancy
Authors: Spencer Kevin , Bindra Renu , Nicolaides Kypros H. 
Published: October 2003

AbstractObjectiveTo assess the suitability of either the log‐linear or reciprocal‐linear regression procedure for maternal weight correction of biochemical marker MoMs in the first trimester.MethodsData from two prospective first‐trimester OSCAR screening programmes including 32 010 women with first‐trimester maternal serum‐free β‐hCG and PAPP‐A measured by the Kryptor analyser was analysed by regression analysis to provide parameters for the log‐linear and reciprocal‐linear MoM correction procedures. Assessment was made by goodness of fit to the data. The impact on detection rate and false‐positive rate of the different correction procedures was assessed using statistical modelling with biochemical markers alone.ResultsBoth log‐linear and reciprocal‐linear correction were shown to fit the data well. For free β‐hCG, the log‐linear procedure was marginally superior to the reciprocal‐linear procedure (r2 = 0.986 v 0.980), whilst for PAPP‐A the reciprocal‐linear procedure was marginally better (r2 = 0.991 v 0.985). Log‐linear correction reduced the variance for both markers more than did the reciprocal‐linear procedure. For free β‐hCG, the sd was reduced from 0.2675 to 0.2605 and for PAPP‐A, it was reduced from 0.2545 to 0.2336. Correcting for maternal weight was shown to reduce the population false‐positive rate from 7.0 to 6.5%, whilst maintaining the same detection rate at a risk cut‐off of 1 in a 100. At individual levels, a two‐fold variation in risk was demonstrated depending upon the individual's weight.ConclusionsTo provide accurate individual patient‐specific risks for trisomy 21, maternal weight must be taken into account and should be a mandatory data item for screening programmes. Maternal weight correction in the first trimester using free β‐hCG and PAPP‐A can be best achieved using the log‐linear procedure. Copyright © 2003 John Wiley & Sons, Ltd.
Mild pyelectasis: evaluating the relationship between gestational age and renal pelvic anterior–posterior diameter
Authors: Odibo Anthony O. , Marchiano Dominic , Quinones Joanne N. , Riesch Deborah , Egan Jim F. X. , Macones George A. 
Published: October 2003

AbstractObjectiveTo determine the relationship between gestational age and renal pelvic anterior–posterior diameter and the feasibility of developing gestational age–specific thresholds for the diagnosis of mild pyelectasis.MethodsCross‐sectional study of 420 singleton fetuses between 16 and 39 weeks' gestation. The mean renal AP diameter as a function of gestational age was determined using fractional polynomial regression models and centile plots were generated. Assessment of goodness of fit for each regression model was performed.ResultsThere was a positive correlation between gestational age and renal pelvic AP diameter (Pearson's Correlation Coefficient 0.65). Using the derived mean and standard deviations of renal AP diameter, gestational‐age specific 95% reference levels were generated. The sensitivity, specificity, positive, and negative predictive values of using the gestational age‐specific cutoffs for predicting persistent postnatal renal anomaly were 80%; 99%; 29%; and 99% respectively.ConclusionThere is a positive correlation between gestational age and renal pelvic AP diameters. Reliable gestational age‐specific renal AP thresholds for diagnosis of pyelectasis are provided. Copyright © 2003 John Wiley & Sons, Ltd.
NMR, solvation and theoretical investigations of conformational isomerism in 2‐X‐cyclohexanones (X=NMe2, OMe, SMe and SeMe)
Authors: Freitas Matheus P. , Tormena Cláudio F. , Garcia Janaína C. , Rittner Roberto , Abraham Raymond J. , Basso Ernani A. , Santos Francisco P. , Cedran Jaime C. 
Published: October 2003

AbstractThe conformational equilibria of 2‐N,N‐dimethylamino‐ (1), 2‐methoxy‐ (2), 2‐methylthio‐ (3) and 2‐methylselenocyclohexanone (4) were determined in various solvents by measurement of the 3JH‐2,H‐3 couplings. The observed couplings were analyzed using theoretical and solvation calculations to give both the conformer energies in the solvents studied plus the vapor‐phase energies and the coupling constants for the distinct conformers. These gave the conformer energies and couplings of 2–4. The intrinsic couplings for the 2‐N,N‐dimethylamino compound were determined by the molecular mechanics PCMODEL program. The axial conformation in 1 is the most polar and also more stable in DMSO solution (Eeq−Eax=0.05 kcal mol−1) and the pure liquid, while the equatorial conformer predominates in the remaining solvents studied (except in CCl4, where self‐association is observed). In the methoxy ketone (2) the equatorial conformation is more stable in the vapor (Eeq−Eax=−0.30 kcal mol−1) and in all solvents. The opposite behavior is shown by 3 and 4, where the axial conformation is the more stable one in the vapor phase (Eeq−Eax=1.60 and 2.95 kcal mol−1 for 3 and 4, respectively) and is still the prevailing conformer in solution. The axial predominance for 3 and 4 is attributed to hyperconjugation between the electron lone pair of the hetero‐substituent and the π*CO orbital. This interaction is stronger for 3 and 4 than in the case of 1 and 2, where the ‘gauche effect’ in the equatorial conformation should be more effective in stabilizing this conformation. Copyright © 2003 John Wiley & Sons, Ltd.
Mechanism and structure–reactivity correlation in the homogeneous, unimolecular elimination kinetics of 2‐substituted ethyl methylcarbonates in the gas phase
Authors: Chuchani Gabriel , Marquez Edgar , Herize Armando , Domínguez Rosa María , Tosta María , Brusco Doris 
Published: October 2003

AbstractThe gas‐phase elimination kinetics of 2‐substituted ethyl methylcarbonates were determined in a static reaction system over the temperature range of 323–435°C and pressure range 28.5–242 Torr. The reactions are homogeneous, unimolecular and follow a first‐order rate law. The kinetic and thermodynamic parameters are reported. The 2‐substituents of the ethyl methylcarbonate (CH3OCOOCH2CH2Z, Z=substituent) give an approximate linear correlation when using the Taft–Topsom method, log(kZ/kH)=−(0.57±0.19)σα+(1.34±0.49)σR− (r=0.9256; SD=0.16) at 400°C. This result implies the elimination process to be sensitive to steric factors, while the electronic effect is unimportant. However, the resonance factor has the greatest influence for a favorable abstraction of the β‐hydrogen of the Cβ—H bond by the oxygen carbonyl. Because ρα is significant, a good correlation of the alkyl substituents of carbonates with Hancock's steric parameters was obtained: log(kR/kH) versus ESC for CH3OCOOCH2CH2R at 400°C, R=alkyl, δ=−0.17 (r=0.9993, SD=0.01). An approximate straight line was obtained on plotting these data with the reported Hancock's correlation of 2‐alkyl ethylacetates. This result leads to evidence for the β‐hydrogen abstraction by the oxygen carbonyl and not by the alkoxy oxygen at the opposite side of the carbonate. The carbonate decompostion is best described in terms of a concerted six‐membered cyclic transition state type of mechanism. Copyright © 2003 John Wiley & Sons, Ltd.
Exothermic thermal reaction of dopamine with 3,5‐dinitrobenzoic acid
Authors: Ito Yoshikatsu , Arimoto Satoru 
Published: October 2003

AbstractPyrolysis of the crystalline 1 : 1 molecular complex DAċdnba, which was prepared from cocrystallization of dopamine (DA) and 3,5‐dinitrobenzoic acid (dnba), was studied. This cocrystal decomposed violently at the melting‐point, leading to the formation of a black solid along with a tiny amount of 3‐amino‐5‐nitrobenzoic acid (1). The pyrolysis reaction was followed by differential scanning calorimetry (DSC) and one large exothermic peak was observed at the decomposition temperature. In view of the DSC patterns for cocrystal DAċdnba and other compounds, it seems that both a catechol moiety and an amino group of DA in addition to a strong electron acceptor such as dnba are required for the appearance of the exothermic peak. On the basis of (a) elemental analysis of the black solid and (b) other pyrolysis experiments for cocrystals PAċdnba (PA: β‐phenylethylamine), BAċdnba (BA: benzylamine), DMDAċdnba (DMDA: O,O′‐dimethyldopamine) and DHBAċdnba (DHBA: 3,4‐dihydroxybenzylamine), it is assumed that the black solid was formed mainly through elimination of more than one molecule of water from one molecule of DAċdnba. Copyright © 2003 John Wiley & Sons, Ltd.
Nonexponential decay of reactive intermediates: new challenges for spectroscopic observation, kinetic modeling and mechanistic interpretation
Authors: Carpenter Barry K. 
Published: October 2003

AbstractA thermally generated reactive intermediate is generally presumed to consist of a population with a distribution of lifetimes characterized by a single, well‐defined parameter, τ. The decay of an instantaneously generated population, whose conversion to products occurred by parallel unimolecular steps, would be expected to be defined by a simple, single‐exponential expression: A(t)=A0 exp(−t/τ), where A(t) is the population at time t, and A0 is the population at t=0. In this model, the lifetime is also related to the first‐order rate constants, ki, for the unimolecular product‐forming steps; specifically τ = (Σiki)−1. The ratio of the products is equal to the ratio of the rate constants for their formation. Given an accurate potential energy surface (PES) for the reaction, one would expect to be able to compute the values of the ki under the specified reaction conditions, and hence both the lifetime of the intermediate and the ratio of products. This simple picture, which has formed the basis for most mechanistic investigation of reactive intermediates, and most kinetic modeling of reactions in which they are involved, has been challenged in recent years by molecular dynamics (MD) simulations, which have predicted that a variety of thermally generated intermediates should exhibit bimodal or even multimodal lifetime distributions. In several cases the shortest lifetime populations have been found to lead to products in a ratio quite different from that for the longer‐lived populations, and also quite unlike that expected from RRKM or transition state theory calculations based on the same PES used for the MD simulations. This commentary reviews the origins of this behavior and discusses the challenges of designing experiments to test the predictions. Copyright © 2003 John Wiley & Sons, Ltd.
Kinetics and mechanisms of the gas‐phase elimination of N‐phenylglycine and its ethyl ester
Authors: Domínguez Rosa M. , Tosta Maria , Chuchani Gabriel 
Published: October 2003

AbstractThe elimination kinetics of the title compounds were determined over the temperature range 290.4–420.3°C and pressure range 14.5–44.0 Torr. The reactions, carried out in seasoned vessels and in the presence of the free radical inhibitor toluene, are homogeneous, unimolecular and follow a first‐order rate law. The rate coefficient is expressed by the following Arrhenius equation: for N‐phenylglycine ethyl ester, log [I1 (s−1)]=(12.13±0.38)− (193.6±4.9) kJ mol−1 (2.303 RT)−1; and for N‐phenylglycine, log [k1 (s−1)]=(12.95±0.52)−(177.4±5.8) kJ mol−1 (2.303 RT)−1. Both substrates yield mainly N‐methylaniline and a small amount of aniline. N‐Phenylglycine as a neutral amino acid decomposes 130 times faster than its ethyl ester at 380°C. The mechanisms of these elimination reactions are presented and discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Anharmonic contributions to the nuclear relaxation first hyperpolarizability for push–pull molecules
Authors: Squitieri Emilio 
Published: October 2003

AbstractThe nuclear relaxation first hyperpolarizability of a push–pull molecule was studied using the simple valence‐bond charge‐transfer model and analytical evaluation of electrical properties method. A relationship between the nuclear relaxation and electronic contributions to the first hyperpolarizability was derived, which incorporates the harmonic and anharmonic terms associated with the ground‐state potential energy. We show that the anharmonic contribution is as important as that of the harmonic contribution and it follows the trend of the electronic contribution. Copyright © 2003 John Wiley & Sons, Ltd.
Preparation and chiral recognition ability of cellulose 3,5‐dimethylphenylcarbamate immobilized on silica gel through radical polymerization
Authors: Kubota Takateru , Yamamoto Chiyo , Okamoto Yoshio 
Published: October 2003

AbstractPolysaccharide‐immobilized chiral stationary phases (CSPs) were prepared by the polymerization of cellulose 3,5‐dimethylphenylcarbamate, having a polymerizable vinyl group, such as 4‐vinylphenylcarbamate or 2‐methacryloyloxyethylcarbamate, at the 6‐position, with a vinyl monomer, such as styrene, isoprene, t‐butyl acrylate, or t‐butyl methacrylate, on silica gel under various conditions. Their chiral recognition abilities were then evaluated with high‐performance liquid chromatography. The immobilized cellulose 3,5‐dimethylphenylcarbamate remained on the silica gel even if washed with tetrahydrofuran, which could dissolve the cellulose derivative. The chiral recognition abilities of the immobilized CSPs were similar to those of the coated CSPs when the vinyl monomer content was low. The chiral recognition abilities of the obtained immobilized CSPs slightly depended on the vinyl monomers. The immobilization of the cellulose derivatives was more efficiently attained on the silica gel modified with a vinyl compound. The cellulose derivatives, randomly having a vinyl group at the 2‐, 3‐, or 6‐position of the glucose unit, were prepared by a one‐pot reaction. The immobilization efficiency of these derivatives was slightly lower than that of the derivative with the vinyl group at the 6‐position. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3703–3712, 2003
Liquid‐crystalline stereoregular polyketone prepared from a mesogenic vinylarene and carbon monoxide
Authors: Kawashima Yasutoyo , Nozaki Kyoko , Hiyama Tamejiro , Yoshio Masafumi , Kanie Kiyoshi , Kato Takashi 
Published: October 2003

AbstractIsotactic and syndiotactic polyketones were synthesized by the alternating copolymerizations of a mesogenic vinylarene, 4‐cyano‐4′‐[8‐(4‐vinylphenyl)octyl‐1‐oxy]biphenyl, with carbon monoxide, and this revealed the influence of backbone tacticity on their thermal properties. The isotactic polyketone was an amorphous polymer that did not show any mesophase, whereas the syndiotactic polyketone exhibited liquid crystallinity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3556–3563, 2003
Further progress in atom transfer radical polymerizations conducted in a waterborne system
Authors: Li Mei , Matyjaszewski Krzysztof 
Published: October 2003

AbstractAn improved atom transfer radical polymerization (ATRP) process was developed for use in a waterborne miniemulsion system. To conduct a successful ATRP in a heterogeneous waterborne system, it is of great importance to ensure control over the polymerization process while preserving colloidal stability. Efforts devoted to optimization of reaction conditions and improvement in the overall productivity of the process allowed the development of a novel, practical initiation system for ATRP suitable for use in a miniemulsion procedure that can provide copolymers of well‐defined composition (e.g., block copolymers) and topologies (e.g., multiarm polymer). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3606–3614, 2003