bluuebunny/crossref_metadata_2025 huggingface dataset:
ARMS: an algebraic recursive multilevel solver for general sparse linear systems
Authors: Saad Y. , Suchomel B.
Published: September 2002

This paper presents a general preconditioning method based on a multilevel partial elimination approach. The basic step in constructing the preconditioner is to separate the initial points into two parts. The first part consists of ‘block’ independent sets, or ‘aggregates’. Unknowns of two different aggregates have no coupling between them, but those in the same aggregate may be coupled. The nodes not in the first part constitute what might be called the ‘coarse’ set. It is natural to call the nodes in the first part ‘fine’ nodes. The idea of the methods is to form the Schur complement related to the coarse set. This leads to a natural block LU factorization which can be used as a preconditioner for the system. This system is then solved recursively using as preconditioner the factorization that could be obtained from the next level. Iterations between levels are allowed. One interesting aspect of the method is that it provides a common framework for many other techniques. Numerical experiments are reported which indicate that the method can be fairly robust. Copyright © 2002 John Wiley & Sons, Ltd.
A method for representing boundaries in discrete element modelling—part II: Kinematics
Authors: Kremmer M. , Favier J. F.
Published: September 2002

The application of the DEM to engineering problems involving the dynamic behaviour of discontinuous media has necessitated the introduction of moving boundary surfaces. In this paper a method is presented for modelling three‐dimensional moving boundary surfaces within the discrete element framework. The surfaces of boundary objects are discretized into triangular planar surfaces using the finite wall method. Wall elements are grouped and each group is associated with a single discrete boundary object which may move independently. Movement comprises any combination of translation and rotation of wall element groups, subject to a given acceleration and velocity during a calculation cycle. The scheme is explicit due to rigidity of the wall elements which are stationary fixed in position and orientation over a time step. Any in‐plane velocity is handled as a contact point velocity within a calculation cycle. The kinematic conditions at each calculation cycle may be pre‐defined or returned from a separate calculation of rigid body motion of the boundary object. The method provides a means for coupling sphere‐based particle dynamics with rigid body dynamics and structural analysis of boundary components. Copyright © 2001 John Wiley & Sons, Ltd.
Three‐dimensional cohesive modeling of dynamic mixed‐mode fracture
Authors: Ruiz Gonzalo , Pandolfi Anna , Ortiz Michael
Published: September 2002

A cohesive formulation of fracture is taken as a basis for the simulation of processes of combined tension‐shear damage and mixed‐mode fracture in specimens subjected to dynamic loading. Our three‐dimensional finite‐element calculations account explicitly for crack nucleation, microcracking, the development of macroscopic cracks and inertia. In particular, a tension‐shear damage coupling arises as a direct consequence of slanted microcrack formation in the process zone. We validate the model against the three‐point‐bend concrete beam experiments of Guo et al. (International Journal of Solids and Structures 1995; 32(17/18):2951–2607), John (PhD Thesis, Northwestern University, 1988), and John and Shah (Journal of Structural Engineering 1990; 116(3):585–602) in which a pre‐crack is shifted from the central cross‐section, leading to asymmetric loading conditions and the development of a mixed‐mode process zone. The model accurately captures the experimentally observed fracture patterns and displacement fields, as well as crack paths and crack‐tip velocities, as a function of pre‐crack geometry and loading conditions. In particular, it correctly accounts for the competition between crack‐growth and nucleation mechanisms. Copyright © 2001 John Wiley & Sons, Ltd.
Selective serotonin reuptake inhibitors alter NPY immunostaining in the rat hypothalamus
Authors: Acebes I. , Saracíbar G. , Echevarría E. , Casado A. , Valiente F.J. , Pascual J. , Casis L.
Published: September 2002

Chronic fluoxetine administration in rats generates a significant decrease in NPY immunostaining in the paraventricular and supraoptic nuclei, with respect to controls. However, a significant increase was found in arcuate nucleus. A lack of changes was observed in periventricular and suprachiasmatic nuclei, lateral hypothalamic area and medial preoptic area. Similar results were observed after chronic administration of sertraline. NPY expression is altered in appetite regulatory regions after in vivo chronic treatment with selective serotonin reuptake inhibitors, suggesting that arcuate‐paraventricular NPY projection impairment is involved in the anorectic effects of these drugs.
Cortical activation patterns in functional magnetic resonance images following monaural pure tone stimulation
Authors: Suzuki M. , Kouzaki H. , Ito R. , Shiino A. , Nishida Y. , Kitano H.
Published: September 2002

To investigate cross‐projection of pure tone stimulation, optimal stimulation level and cross‐talk effect, we examined the auditory processing of monaural pure‐tone stimuli using functional magnetic resonance imaging (fMRI). We examined fMRI responses to monaural pure tones (1 kHz, 95 or 115 dB SPL) in 11 subjects with normal hearing and 4 patients with with profound unilateral deafness. Group analysis showed bilateral cortical activation in primary auditory and auditory association regions at 115 dB SPL. The activation was strong and mostly contralateral. At 95 dB SPl, only 2 of 11 subjects showed weak cortical activation. No activated area in the auditory cortex was observed in subjects with profound unilateral deafness in response to monaural stimulation of the deaf ear. The results supported the cross‐projection of pure tone stimulation. Pure tone with 115 dB SPL was needed to obtain intense and stable activation without cross‐talk using conventional boxcar model.
On the relationship between finite volume and finite element methods applied to the Stokes equations
Authors: Ye Xiu
Published: September 2002

We investigate the relationship between finite volume and finite element approximations for the lower‐order elements, both conforming and nonconforming for the Stokes equations. These elements include conforming, linear velocity‐constant pressure on triangles, conforming bilinear velocity‐constant pressure on rectangles and their macro‐element versions, and nonconforming linear velocity‐constant pressure on triangles and nonconforming rotated bilinear velocity‐constant pressure on rectangles. By applying the relationship between the two methods, we obtain the convergence finite volume solutions for the Stokes equations. © 2001 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 17: 440–453, 2001.
Measuring the hospital practice environment: A Canadian context
Authors: Estabrooks Carole A. , Tourangeau Ann E. , Humphrey Charles K. , Hesketh Kathryn L. , Giovannetti Phyllis , Thomson Donna , Wong Jennifer , Acorn Sonia , Clarke Heather , Shamian Judith
Published: September 2002

The primary purpose of this study is to document the psychometric properties of the revised Nursing Work Index (NWI‐R) in the context of a large Canadian sample of registered nurses. A self‐administered survey containing the NWI‐R was completed by 17,965 registered nurses working in 415 hospitals in three Canadian provinces. Using exploratory principal components analysis, with a forced one‐factor solution, the practice environment index was obtained. In addition, key assumptions were tested from previous work about the rationale for the aggregation of NWI‐R responses. In the Canadian context the one‐factor solution provides a parsimonious index of the practice environment of registered nurses working in acute care hospitals. Further work is needed to determine the predictive capability of this index and its relevance to cross‐national organizational contexts. © 2002 Wiley Periodicals, Inc. Res Nurs Health 25:256–268, 2002
Understanding the kinetics and network formation of dimethacrylate dental resins
Authors: Lovell Lale G. , Berchtold Kathryn A. , Elliott Jeannine E. , Lu Hui , Bowman Christopher N.
Published: September 2002

Dimethacrylate monomers are commonly used as the organic phase of dental restorative materials but many questions remain about the underlying kinetics and network formation in these highly crosslinked photopolymer systems. Several novel experimental and modeling techniques that have been developed for other multifunctional (meth)acrylates were utilized to gain further insight into these resin systems. Specifically, this work investigates the copolymerization behavior of­bis‐GMA (2,2‐bis[p‐(2‐hydroxy‐3‐methacryloxyprop‐1‐oxy)‐phenyl]propane) and TEGDMA (triethylene glycol dimethacrylate), two monomers typically used for dental resin formulations. Near‐infrared spectroscopy, electron paramagnetic resonance spectroscopy, as well as dynamic mechanical and dielectric analysis were used to characterize the kinetics, radical populations, and structural properties of this copolymer system. In addition, a kinetic model is described that provides valuable information about the network evolution during the formation of this crosslinked polymer. The results of these numerous studies illustrate that all of the aforementioned techniques can be readily applied to dental resin systems and consequently can be used to obtain a wealth of information about these systems. The application of these techniques provides insight into the complex polymerization kinetics and corresponding network formation, and as a result, a more complete understanding of the anomolous behaviors exhibited by these systems, such as diffusion controlled kinetics and conversion dependent network formation, is attained. Copyright © 2001 John Wiley & Sons, Ltd.
Hyperbranched polyesters and their application in dental composites: monomers for low shrinking composites
Authors: Klee J. E. , Schneider C. , Hölter D. , Burgath A. , Frey H. , Mülhaupt R.
Published: September 2002

Using trimethylolpropane (TMP) and 2,2‐bishydroxymethylpropionic acid (Bis‐MPA), aliphatic hyperbranched polyesters (HBP) were synthesized, with a degree of branching of DB = 0.47 and a degree of polymerization of Pn = 16.5. Aromatic HBPs with repetitive units of 2,2‐bis(4‐hydroxyphenyl)pivalonic acid (Bis‐PVA) lead to a higher DB = 0.48 and Pn = 30.5 compared to the aliphatic HBP. Reactive functionalization of the hyperbranched polymers was achieved via esterification of mixtures of methacrylic acid and carboxylic acids. In this manner, i‐butyric acid and methacryloyl terminated HBPs were obtained. They have a low viscosity ranging from 200 to 364 Pa*s and exhibit relatively low volume shrinkage (1.9 to 3.6%) during photoinitiated cure. Dental composites with volume shrinkage of 0.5 to 1.5% have been prepared using these methacryloyl terminated HBPs in combination with a Ba/alumosilicate glass filler. Copyright © 2001 John Wiley & Sons, Ltd.
Evaluation of neat resins based on methacrylates modified with methacryl‐POSS, as potential organic–Inorganic hybrids for formulating dental restoratives
Authors: Gao Feng , Tong Yuhua , Schricker Scott R. , Culbertson Bill M.
Published: September 2002

Three series of neat resins, based on methacrylates or dimethacrylates modified with 1‐[3‐(methacryl)propyl]‐3,5,7,9,11,13,15‐heptacyclopentylpentacyclo[9.5.113,­9.15,15.17,13]octasiloxane (Methacryl‐POSS or POSS‐MA), were evaluated. Incorporation of POSS‐MA into the polymeric matrix was accomplished in three ways: (a) resins series I was formulated with one‐pot copolymerization of a bis‐GMA/diluent monomer with POSS‐MA; (b) the copolymer of 2‐hydroxylethyl methacrylate (HEMA) and POSS‐MA, with a weight ratio of 1 : 1, was first made, then the copolymer hydroxyl groups were converted into methacrylate groups to get a macromer; finally the macromer was copolymerized with bis‐GMA/diluents to formulate the second series of neat resins; (c) copolymer of POSS‐MA and t‐butyl methacrylate (t‐BMA) or 2‐ethylhexyl methacrylate (EHMA) were first made, then they were combined with a mixture of bis‐GMA and the corresponding diluent to make the third kind of neat resins. The amount of POSS incorporated into the neat resin matrix was controlled at 5, 10 and 15 wt%. Incorporating only 5 wt% substantially reduced the shrinkage of the prepared neat resins. The percentage of methacrylate‐functionalized POSS monomer in the bis‐GMA/diluent base, was compared to neat resins prepared without the POSS. The mechanical properties of neat resin having POSS were improved for approaches (b) and (c), but remained at the same level as the neat resins without POSS for approach (a). The results show that miscibility between the POSS component and the matrix, especially the diluent, plays a very important role in the improvement of the properties of the formulated thermosets. Copyright © 2001 John Wiley & Sons, Ltd.
Mechanical properties of interface‐free polyacrylate‐silica hybrid sol–gel materials for potential dental applications
Authors: Wei Yen , Jin Danliang , Xu Jigeng , Baran George , Qiu Kun‐Yuan
Published: September 2002

The mechanical properties of polyacrylate‐silica hybrid sol‐gel materials have been investigated in comparison with conventional resin composites. The hybrid materials with a wide range of silica content were synthesized via the sol–gel reactions of the silica precursor tetraethyl orthosilicate (TEOS) with acrylate copolymers of methyl methacrylate (MMA) with 3‐(trimethoxysilyl)propyl methacrylate (MSMA). In these materials, the polymer chains are uniformly distributed in and covalently bonded to the inorganic silica host matrix at the molecular level without macroscopic organic–inorganic phase separation. The hybrid materials are transparent and non‐porous. In the standard compression test, the hybrid materials exhibited strain hardening behavior which was absent in the conventional PMMA‐silica composites. Their mechanical properties can be fine‐tuned by varying the polyacrylate‐silica composition in the synthesis and are superior over conventional composites at similar silica contents. These hybrid materials are promising for potential dental applications. Copyright © 2001 John Wiley & Sons, Ltd.
Aqueous catalysis by novel macromolecule metal complexes with molecular recognition abilities
Authors: Karakhanov Edward A. , Kardasheva Yulia S. , Maximov Anton L. , Runova Elena A. , Buchneva Tatyana A. , Gaevskiy Mihail A. , Zhuchkova Anna Ya. , Filippova Tatyana Yu.
Published: September 2002

A number of water‐soluble macromolecular metal complexes on the basis of polyethers, β‐cyclodextrins, calix[4] and calix[6]arenes functionalized by oligoethylene oxide blocks, catechol, ethylendiamine, acetylacetone, 2,2′‐dipiridyl, phosphines and nitrile containing groups have been developed. Complexes showed high catalytic activity in aqueous hydroformylation, biphasic Wacker‐type oxidation of various higher olefines, alkane oxidation, hydroxylation of benzene and phenol. These catalysts can be multiply reused. The application of host compounds results the extremely selectivities. Copyright © 2001 John Wiley & Sons, Ltd.
Chromogenic polymer gels for reversible transparency and color control with temperature at a constant volume
Authors: Seeboth A. , Kriwanek J. , Lötzsch D. , Patzak A.
Published: September 2002

The preparation and characterization of novel chromogenic materials has developed extremely rapid in the last years. Among them, thermotropic and thermochromic polymer gel networks have met with growing interest, because of their advanced properties. These novel polymer gels exhibit pronounced changes in transparency and/or color intensity in a practically relevant temperature range. For many future technical applications it is an essential condition, that the volume of the used gel materials is independent of temperature. A current overview of this field is given. Copyright © 2002 John Wiley & Sons, Ltd.
Vis‐sensitive photopolymer containing vinyl ether compound and pyrromethene dye
Authors: Noppakundilograt Supaporn , Suzuki Shota , Urano Toshiyuki , Miyagawa Nobukazu , Takahara Shigeru , Yamaoka Tsuguo
Published: September 2002

A visible light(vis)‐sensitive photoresist based on the concept of chemical amplification was developed utilizing poly(p‐hydroxystyrene) (PHS), 2,2‐bis[4‐(2‐(vinyloxy)‐ethoxy)phenyl]propane (BPA‐DEVE) as a crosslinking agent, N‐trifluoromethylsulfonyloxy‐1,8‐naphthalimide (NIT) as a photoacid generator (PAG) and pyrromethene dyes such as 1,3,5,7,9‐pentamethylbipyrromethene difluoroborate (PRH) and 2,8‐diethyl‐1,3,5,7,9‐pentamethylbipyrromethene difluoroborate (PRE) and 3,3′‐carbonylbis(7,7′‐diethylaminocoumarin) (KCD). On irradiation with an argon ion laser, the photopolymer comprising PRH and PRE exhibited a high sensitivity of 65 and 46 mJ cm−2, respectively. It is suggested that the sensitization mechanism of the pyrromethene dye/PAG system involves singlet electron transfer. The sensitivity of the photoresist increased with the decreasing molecular weight of PHS because of the high dissolution rate. Copyright © 2002 John Wiley & Sons, Ltd.
Development of an analytical method for the determination of betaines in higher plants by capillary electrophoresis at low pH
Authors: Zhang Jinghua , Nishimura Naoki , Okubo Akira , Yamazaki Sunao
Published: September 2002

In recent years the role of betaines in higher plants has been extensively investigated in relation to environmental stress response. This paper reports the establishment of a simple, rapid and reliable method for the determination of betaines using capillary electrophoresis (CE) at low pH. Betaines were first converted to their phenacyl esters and the crude reaction mixture was then applied directly to CE without any pre‐treatment. Employing an electrolyte running solution at pH 3 gave a well‐resolved electropherogram for the esters of glycine betaine (1), trigonelline, proline betaine, γ‐butyro betaine, and carnitine. The content of 1 and its variation in plant samples collected from high‐salinity areas in north China and west Australia are presented. Copyright © 2002 John Wiley & Sons, Ltd.
Direct analysis of abscisic acid in crude plant extracts by liquid chromatography—electrospray/tandem mass spectrometry
Authors: Gómez‐Cadenas Aurelio , Pozo Oscar J. , García‐Augustín Pilar , Sancho Juan V.
Published: September 2002

A new method, based on liquid chromatography–electrospray/tandem mass spectrometry, for the determination of abscisic acid (ABA), an essential plant hormone that regulates key metabolic pathways and responses to environmental cues, has been developed. Substantial changes in extraction procedures are also proposed. Data indicate that the organic solvents classically used as extraction buffers can be substituted by an aqueous solution, resulting in the same amounts of extracted ABA. The new method, which uses minute amounts of plant tissue, has an estimated limit of detection below 50 pmol ABA/g, and the sensitivity of the technique allows the analysis of ABA in crude plant extracts. Overall, this new rapid, sensitive and accurate procedure to determine ABA will allow analysis of multiple samples in a short time and represents a clear advantage in comparison with the conventional procedures involving many preparative steps and large amounts of plant tissue. Copyright © 2002 John Wiley & Sons, Ltd.
Quantitative determination of oleane derivatives in Terminalia arjuna by high performance thin layer chromatography
Authors: Singh D. V. , Verma R. K. , Gupta M. M. , Kumar Sushil
Published: September 2002

A simple, precise and rapid high performance thin layer chromatographic method has been developed for the simultaneous quantitative determination of five oleane derivatives, namely, arjunic acid, arjunolic acid, arjungenin, arjunetin and arjunglucoside I from stem bark extract of Terminalia arjuna. The isolation and separation of these compounds was carried out on 60F254 layers eluted with chloroform:methanol (90:10), and the analytes were visualised through colour development with vanillin in concentrated sulphuric acid:ethanol. Scanning and quantification of the spots at 640 nm showed good recoveries in the range 96.40–101.7%. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of andrographolide, deoxyandrographolide and neoandrographolide in the Chinese herb Andrographis paniculata by micellar electrokinetic capillary chromatography
Authors: Zhao Jingxiang , Yang Gengliang , Liu Haixing , Wang Dexian , Song Xiurong , Chen Yi
Published: September 2002

In this paper a micellar electrokinetic capillary chromatographic (MEKC) method has been developed for determining the active components (andrographolide, deoxyandrographolide and neoandrographolide) in water:ethanol extracts of the Chinese crude herb Andrographis paniculata and its preparations (Chuanxinlian and Xiaoyan Lidan tablets). The optimum separation conditions were 15 mM sodium dodecyl sulphate in 30 mM borate buffer (pH 9.5) with UV detection wavelength at 214 nm and a constant voltage of 16 kV. An HPLC method was employed in order to validate the MEKC method with respect to separation efficiency, sensitivity, linearity and repeatability. The two methods are shown to be complementary because of their different selectivity and thus are very suitable for cross‐validation studies. The MEKC method is demonstrated to be more appropriate for the analysis of the active compounds in A. paniculata in that it is easier and less expensive to use and does not suffer from contamination of the chromatographic column. Copyright © 2002 John Wiley & Sons, Ltd.
High‐Performance Capillary Electrophoresis Analysis of mate infusions prepared from stems and leaves of Ilex paraguariensis using Automated Micellar Electrokinetic Capillary Chromatography
Authors: Pomilio Alicia B. , Trajtemberg Silvia , Vitale Arturo A.
Published: September 2002

An automated micellar electrokinetic capillary chromatographic method has been developed in order to determine xanthines, e.g. caffeine, theobromine and theophylline, and chlorogenic acid in samples of yerba mate (Ilex paraguariensis). The target constituents were detected by photodiode array, and quantified by an external standard method. In addition, each constituent was collected separately and identified by EIMS. The method has been used to analyse 30 samples of mate infusions prepared at 30 and 75°C with milled leaves and stems of 14 commercial brands which had been subjected to different elaboration processes. Suspended powdered material of each infusion was also analysed after three sieving steps. There was a remarkable difference in the relative xanthine composition of the finely suspended material, the amount of which varied according to the yerba mate brand, the elaboration process and the temperature of the infusion. The importance of these results with respect to gastrointestinal disorders which have been observed by habitual consumers of mate are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
A comparison of different lysis buffers to assess allele dropout from single cells for preimplantation genetic diagnosis
Authors: Thornhill Alan R. , McGrath John A. , Eady Robin A. J. , Braude Peter R. , Handyside Alan H.
Published: September 2002

Single cell polymerase chain reaction (PCR) for preimplantation genetic diagnosis (PGD) requires high efficiency and accuracy. Allele dropout (ADO), the random amplification failure of one of the two parental alleles, remains the most significant problem in PCR‐based PGD testing since it can result in serious misdiagnosis for compound heterozygous or autosomal dominant conditions. A number of different strategies (including the use of lysis buffers to break down the cell and make the DNA accessible) have been employed to combat ADO with varying degrees of success, yet there is still no consensus among PGD centres over which lysis buffer should be used (ESHRE PGD Consortium, 1999). To address this issue, PCR amplification of three genes (CFTR, LAMA3 and PKP1) at different chromosomal loci was investigated. Single lymphocytes from individuals heterozygous for mutations within each of the three genes were collected and lysed in either alkaline lysis buffer (ALB) or proteinase K/SDS lysis buffer (PK). PCR amplification efficiencies were comparable between alkaline lysis and proteinase K lysis for PCR products spanning each of the three mutated loci (ΔF508 in CFTR 90% vs 88%; R650X in LAMA3 82% vs 78%; and Y71X in PKP1 91% vs 87%). While there was no appreciable difference between ADO rates between the two lysis buffers for the LAMA3 PCR product (25% vs 26%), there were significant differences in ADO rates between ALB and PK for the CFTR PCR product (0% vs 23%) and the PKP1 PCR product (8% vs 56%). Based on these results, we are currently using ALB in preference to PK/SDS buffer for the lysis of cells in clinical PGD. Copyright © 2001 John Wiley & Sons, Ltd.
Congenital nephrotic syndrome presenting with increased nuchal translucency in the first trimester
Authors: Souka A. P. , Skentou H. , Geerts L. , Bower S. , Nicolaides K. H.
Published: September 2002

Congenital nephrotic syndrome of the Finnish type (CNF) and diffuse mesangial sclerosis (DMS) are rare causes of renal failure in infants. We report two cases, one of each condition, presenting with increased nuchal translucency at the 11–14‐week scan, and review the literature. Copyright © 2002 John Wiley & Sons, Ltd.
Maternal serum activin A and inhibin A in trisomy 18 pregnancies at 10–14 weeks
Authors: Spencer Kevin , Liao Adolfo W. , Ong Charas Y. T. , Flack Nicola J. , Nicolaides Kypros H.
Published: September 2002

In 45 cases of trisomy 18 and 493 control pregnancies at 10–14 weeks of gestation, maternal serum inhibin A, total activin A, free β‐hCG and PAPP‐A were measured. In the trisomy 18 pregnancies the median values were 0.74 MoM for inhibin A, 1.23 MoM for activin A, 0.38 MoM for free β‐hCG and 0.16 MoM for PAPP‐A. The degree of deviation from normal in the levels of inhibin and activin is small in comparison with free β‐hCG and PAPP‐A and they are therefore unlikely to be of value in improving the sensitivity of 90% for a 1% false‐positive rate achieved by screening with fetal nuchal translucency and maternal serum free β‐hCG and PAPP‐A. Copyright © 2001 John Wiley & Sons, Ltd.
Prenatal diagnosis of 45,X and 45,X mosaicism: the need for thorough cytogenetic and clinical evaluations
Authors: Huang Bing , Thangavelu Maya , Bhatt Sucheta , J. Sandlin Constance , Wang Shengbiao
Published: September 2002

Objectives

Mosaicism involving a 45,X cell line is relatively common in prenatal diagnosis. In prenatally diagnosed cases, the prognosis of non‐mosaic 45,X and 45,X/46,XY mosaicism are different. Therefore, accurate identification of a cell line containing Y chromosome is critical for genetic counseling and postnatal management.

Methods

We investigated the ultrasound findings and outcomes of pregnancies with a 45,X cell line identified during mid‐trimester cytogenetic analysis.

Results

A total of 105 cases were found to have a 45,X cell line by standard cytogenetic analysis. Seventy‐four cases were found to have non‐mosaic 45,X at initial diagnosis. Of these 74 cases, 68 had abnormal ultrasound findings that were characteristic of Turner syndrome. Of the six cases with normal ultrasound findings, ultrasound examination was normal with male genitalia identified in three cases. Thorough cytogenetic and fluorescent in situ hybridization (FISH) analysis identified Y chromosome material in all three cases, one with a dicentric Y;14 chromosome and the other two cases with a marker chromosome containing Sex‒determining Region (SRY) material in a small portion of the cells. In contrast, in 31 cases with a mosaic 45,X karyotype, ultrasound abnormality was identified only in one case.

Conclusions

The present data suggest the need for follow‐up ultrasound examination and thorough cytogenetic and molecular analysis for Y chromosome material in 45,X cases with normal ultrasound findings. Copyright © 2002 John Wiley & Sons, Ltd.
Thermocoagulation of fetal sacrococcygeal teratoma
Authors: Hang Lam Yung , Hoi Yin Tang Mary , Wai Hung Shek Tony
Published: September 2002

Fetal sacrococcygeal teratoma can lead to a high output cardiac failure resulting in hydrops fetalis. One of the prenatal therapeutic options is to occlude the feeding vessels by radiofrequency ablation. We present a case of fetal sacrococcygeal teratoma diagnosed at 13 weeks of gestation. The tumour increased in size more than 100‐fold over 5 weeks causing polyhydramnios and cardiac and placental enlargement. Thermocoagulation was performed at 18 weeks' gestation by passing an insulated electric wire through an 18‐gauge needle placed close to the feeding vessels of the tumour at its neck. Blood supply to the tumour was successfully reduced. However, fetal death was diagnosed 2 days after the procedure. We speculate that it may be safer to limit the extent of coagulation in one attempt but to repeat the procedure at a later stage when necessary. Copyright © 2002 John Wiley & Sons, Ltd.
The development of the fetal thymus: an in utero sonographic evaluation
Authors: Zalel Yaron , Gamzu Ronni , Mashiach Shlomo , Achiron Reuven
Published: September 2002

Objectives

To establish a nomogram for fetal thymus size during gestation.

Methods

The study is a prospective, cross‐sectional evaluation of 403 male and female fetuses between 14 and 38 weeks of normal singleton pregnancies. Measurements of fetal thymus size were performed by high‐resolution transvaginal ultrasonography between 14 and 17 weeks' gestation, and by transabdominal ultrasonography after 18 weeks' gestation.

Results

Adequate thymus size measurements were obtained in all 403 fetuses. Thymus size as a function of gestational age was expressed by the regression equation: (square root) thymus size (mm)=–39.39+4.41×gestational age (weeks). The correlation coefficient, r=0.965, was found to be highly statistically significant (p<0.0001). The normal mean and the 90% prediction limits were defined.

Conclusion

The present data offer the normal range of fetal thymus size from early stages of gestation that may allow intrauterine assessment of its development. It may be helpful in the prenatal diagnosis of thymic pathologies. Copyright © 2002 John Wiley & Sons, Ltd.
A second case of intrauterine growth retardation and primary hypospadias associated with a trisomy 22 placenta but with biparental inheritance of chromosome 22 in the fetus
Authors: Bryan Jennifer , Peters Michelle , Pritchard Gary , Healey Sue , Payton Diane
Published: September 2002

We report a case of severe intrauterine growth retardation (IUGR) and hypospadias in association with trisomy 22 diagnosed following chorionic villus sampling (CVS). Subsequent analysis of amniotic fluid cultures showed a normal male karyotype, 46,XY. As a previous case had been reported with similar abnormalities, in association with maternal uniparental disomy (UPD) 22, molecular studies were also performed. Microsatellite marker studies showed biparental inheritance. Follow‐up studies after delivery showed a normal cell line in lymphocytes with the trisomy appearing to be confined to the placenta. The present case concurs with other earlier reports that maternal UPD for chromosome 22 has no impact on the phenotype. The features seen in the fetus are most likely the result of placental dysfunction due to trisomy, tissue‐specific mosaicism and/or the effects of local growth restriction. Copyright © 2002 John Wiley & Sons, Ltd.
Testing normality of fetal DNA concentration in maternal plasma at 10–12 completed weeks' gestation: a preliminary approach to a new marker for genetic screening
Authors: Farina Antonio , Caramelli Elisabetta , Concu Manuela , Sekizawa Akihiko , Ruggeri Roberto , Bovicelli Luciano , Rizzo Nicola , Carinci Paolo
Published: September 2002

Objectives

To test the distribution of fetal DNA in maternal plasma expressed as gen/eq in a population of normal pregnancies.

Methods

Peripheral blood samples were obtained from 63 women (85% ⩾35 years of age at delivery) bearing a euploid male fetus. Each patient underwent chorionic villus sampling (CVS) for karyotype analysis and/or β‐ thalassemia screening. Ultrasound scanning was used to determine gestational age. At 10–12 weeks' gestation, a peripheral blood sample was collected followed by CVS. To detect the Y chromosome‐specific sequences (SRY) quantitative polymerase chain reaction (PCR) analysis was used. Normal distribution of the data was tested by means of the Kolmogorov‐Smirnov (KS) test. A Symmetry test (reliability p>0.05) was used to evaluate the reliability of the median.

Results

Only after natural logarithmic transformation did the data display a normal distribution. The median value of fetal DNA was 23.3 gen/eq (range 2.08–195), interquartile range 18.57–45.4. A Pearson test showed a significant correlation between gestational age and fetal DNA concentration (r=0.25, p=0.045).

Conclusion

The present finding is a preliminary step towards a possible integration of fetal DNA with other variables (biochemical and/or ultrasound). It may serve to improve the discrimination of the screening for genetic diseases in the first trimester. Because of the relatively high dispersion, adjustments for possible covariates would appear to be necessary in further studies. Copyright © 2002 John Wiley & Sons, Ltd.
Prenatal diagnosis of congenital heart disease in the Naples area during the years 1994–1999 — the experience of a joint fetal–pediatric cardiology unit
Authors: Paladini Dario , Russo MariaGiovanna , Teodoro Adele , Pacileo Giuseppe , Capozzi Giovanni , Martinelli Pasquale , Nappi Carmine , Calabrò Raffaele
Published: September 2002

Objectives

To analyse the spectrum and frequencies of observed malformations; to evaluate associated extracardiac and chromosomal anomalies and outcomes in each diagnostic category; to demonstrate the need for a multidisciplinary approach to the diagnosis of CHD in the fetus.

Methods

From January 1994 to December 1999, 450 cases of CHD were detected among 4052 pregnancies at risk of fetal CHD seen at our combined unit. Confirmation of the diagnosis was not available in 50 cases, leaving 400 cases for analysis. From our computerized database, the following variables were retrieved and analysed: indication, gestational age at diagnosis, associated extracardiac anomalies, karyotype, natural history, pregnancy and feto‐neonatal outcome.

Results

CHDs most commonly detected were VSD (75 cases), AVSD (40 cases) and HLH (37 cases). The aneuploidy rate was 29.3% in the 355 cases submitted for karyotyping (25.9% in the whole series), with a prevalence of trisomy 21 and 18 (48 and 30 cases, respectively). The aneuploidy rate was highest for AVSD (80%), coarctation (49%), tetralogy of Fallot and VSD (45%). Associated extracardiac anomalies were present in 29.5% of the cases (118/400). As for pregnancy outcome, there were 150 (37.5%) terminations of pregnancy, 16 (4%) intrauterine fetal deaths and 85 (21.3%) neonatal deaths. The remaining 149 neonates are alive (37.3% survival rate). The termination rate for pregnancies in which CHD was detected at a gestational age <25 weeks was 65.2%. Evolutive changes determined progressive prognostic deterioration in 21 cases (5%), consisting of semilunar valve obstructions and development of ventricular hypoplasia.

Conclusions

The high association rate with extracardiac and chromosomal anomalies (29.3% and 25.9%) and the possible progressive prognostic deterioration require a multidisciplinary team for correct management and follow‐up. Survival of fetuses with certain CHD is severely reduced, in comparison with postnatal figures, for the common association with aneuploidies. Copyright © 2002 John Wiley & Sons, Ltd.
Shortened fetal long bones: a possible in utero manifestation of placental function
Authors: Zalel Yaron , Lehavi Ofer , Schiff Eyal , Shalmon Bruria , Cohen Shlomi , Schulman Adrian , Achiron Reuven
Published: September 2002

Shortened fetal long bones (SFLB) are usually indicative of a skeletal dysplasia. Our aim in this observational retrospective study was to describe a new association between SFLB, small for gestational age (SGA) fetuses and placental abnormalities, and to suggest an aetiologic explanation. During the last decade we have evaluated nine cases in which SFLB (more than 2SD below the mean) was associated with SGA, abnormal maternal serum placental hormones and abnormal placental sonography. Six cases had significantly increased second trimester maternal serum βhCG and four developed toxaemia of pregnancy or had chronic hypertension. On histology, mature placentas with vascular abnormalities, including chorangiosis, large infarcts and slightly increased syncytial knots were noted. The combination of SFLB, SGA fetuses and placental abnormalities (sonographic, as well as histological) suggested a possible common pathway in the aetiology of this association. Copyright © 2002 John Wiley & Sons, Ltd.
Prenatal diagnosis of Niemann–Pick diseases types A, B and C
Authors: Vanier Marie T.
Published: September 2002

Prenatal diagnosis of Niemann–Pick disease types A and B is routinely accomplished by sphingomyelinase assay. For Niemann–Pick type C disease, demonstration of an abnormal intracellular cholesterol trafficking is a complex procedure, and mutational analysis (NPC1 or NPC2/HE1 gene), whenever feasible, represents a major advance. Copyright © 2002 John Wiley & Sons, Ltd.
Early prenatal diagnosis of major cardiac anomalies in a high‐risk population
Authors: Comas Gabriel C. , Galindo A. , Martínez J. M. , Carrera J. M. , Gutiérrez‐Larraya F. , de la Fuente P. , Puerto B. , Borrell A.
Published: September 2002

Objective

To examine the accuracy of early fetal echocardiography performed in a high‐risk population combining transvaginal and transabdominal routes.

Methods

A series of 330 high‐risk pregnancies were screened by transvaginal and transabdominal scan at 12–17 weeks' gestation in a prospective multicentre trial in Spain between September 1999 and May 2001. A total of 334 fetal heart examinations were performed, including four twin pregnancies. Maternal age ranged from 17 to 46 years (mean 33 years with 36% of women over 34 years). The median gestational age at scan was 14.2 weeks (range 12–17 weeks). For each fetus, visualization of the four‐chamber view, the origin of the great arteries, aortic and ductal arches and systemic venous return was attempted in a segmental approach. B‐mode and colour/pulsed Doppler flow imaging were used in all cases. The duration of complete heart examination was less than 30 minutes. The examinations were performed by three experienced operators. Reliability was assessed by conventional transabdominal echocardiography at 20–22 weeks, by postnatal follow‐up in the first three months of life, and/or by autopsy in cases of termination of pregnancy.

Results

The rate of successful visualization of the fetal heart was 94.6% (316/334). In 48 out of 334 (14.4%) fetuses the final diagnosis was abnormal. In 38 out of 48 (79.2%) cases with heart defects the diagnosis was suspected at early echocardiography. In the group with congenital heart defects, 27 cases had an abnormal karyotype (56.3%) and 31 cases showed extracardiac anomalies (64.6%). There were 10 false‐negative cases at early scan. There were no false‐positive diagnoses.

Conclusions

This experience stresses the usefulness of early fetal echocardiography when performed by expert operators on fetuses specifically at risk for cardiac disease. The high rate of successful visualization of the fetal heart provides a reliable diagnosis of major cardiac defects at this early stage of pregnancy. Copyright © 2002 John Wiley & Sons, Ltd.
Outcomes of pregnancies diagnosed with Klinefelter syndrome: the possible influence of health professionals†
Authors: M. Marteau Theresa , Nippert Irma , Hall Sue , Limbert Caroline , Reid Margaret , Bobrow Martin , Cameron Alan , Cornel Martina , van Diem Mariet , Eiben Bernd , García‐Miñaur Sixto , Goujard Janine , Kirwan Donna , McIntosh Karen , Soothill Peter , Verschuuren‐Bemelmans Corien , de Vigan Catherine , Walkinshaw Stephen , Abramsky Lenore , Louwen Frank , Miny Peter , Horst Jürgen
Published: September 2002

Objective

To describe the association between the outcomes of pregnancies diagnosed with Klinefelter syndrome (KS) and the speciality of the health professional providing pre‐ and post‐diagnostic counselling.

Method

Data were extracted from the case notes of the 111 cases of KS diagnosed prenatally between 1986 and 1997 in eight geographical regions in five European countries. The data extracted included: outcome of pregnancy, maternal age, social class, parity, gestational age at diagnosis, year of diagnosis and specialities of the health professionals conducting pre‐ and post‐diagnosis consultations.

Results

The overall termination rate was 44% (49/111: 95% confidence interval: 35 to 54). Using multivariable logistic regression analysis, the only significant predictor of continuation of the pregnancy was the specialities of the health professionals conducting post‐diagnosis counselling: the affected pregnancy was more likely to continue when post‐diagnosis counselling involved only a genetics specialist (relative risk: 2.42 (1.14 to 5.92)).

Conclusion

There is an association between whether or not a woman terminates a pregnancy affected by an unfamiliar fetal anomaly and the professional background of the health professional providing post‐diagnostic counselling. The causal nature of this association remains to be determined. Copyright © 2002 John Wiley & Sons, Ltd.
Prenatal diagnosis of sex chromosome aneuploidy: possible reasons for high rates of pregnancy termination
Authors: Sagi Michal , Meiner Vardiella , Reshef Nurith , Dagan Judith , Zlotogora Joel
Published: September 2002

Sex chromosome aneuploidy (SCA), when detected in amniocentesis, is usually an unexpected result of a test carried out for another purpose. For most SCAs, the prognosis is milder and less predictable than trisomy 21, and therefore parents are faced with a difficult decision regarding the option of pregnancy termination. While studies from Europe and the USA report a declining trend in termination rates for SCA, our local experience is different. During the period 1989–1998, we diagnosed 60 SCA (including mosaics) in 20 106 amniocenteses (0.29%) and 48 (80%) of these pregnancies were terminated, a significantly higher proportion than has been reported in Europe and the USA. The present study shows that the difference between our experience and others' may be related to differences in cultural norms and values. Thirty women were interviewed, of whom 23 terminated and seven continued the pregnancy. Interview analyses showed that the main reason behind the decision to terminate the pregnancy was associated with the parents' fear of non‐specific abnormality of the child, and concerns about abnormal sexual development. Although genetic counseling practised in our center aims to be non‐directive, 56% of the women reported that the counseling was either directive towards termination, or that they at least felt that the counselor's attitude was pro‐termination. Most women (93%) reported themselves as having come to terms with their decision. Copyright © 2001 John Wiley & Sons, Ltd.
Prenatal diagnosis of mosaicism for triploidy and trisomy 13
Authors: Phelan Mary C. , Curtis Rogers R. , Michaelis Ron C. , Lynn Moore C. , Blackburn Will
Published: September 2002

Mosaicism for trisomy 13 and triploidy was detected by amniocentesis performed at 18 weeks' gestation because of fetal anomalies. Pregnancy continued and a live‐born male was delivered vaginally at 37 weeks. The infant had features common to both trisomy 13 and triploidy: intrauterine growth retardation (IUGR), small abnormal ears, cleft palate, and a small jaw. In addition, he had complete cutaneous syndactyly of fingers 3 and 4 and partial syndactyly of the toes, as seen in triploidy. Mixoploidy for trisomy 13 and triploidy was confirmed postnatally in blood, skin, and placenta. Examination of chromosome heteromorphisms and DNA markers suggested the presence of two maternal contributions in the triploid cell line. In addition, the extra chromosome 13 in the trisomic cell line was derived from the mother. Copyright © 2001 John Wiley & Sons, Ltd.
Embryonic and fetal globins are expressed in adult erythroid progenitor cells and in erythroid cell cultures
Authors: Lau Elizabeth T. , Kwok Yvonne K. , Chui David H. K. , Wong Hong Soo , Luo Hong Yuan , Tang Mary H. Y.
Published: September 2002

The understanding of human hemoglobin ontogeny during development is of biological and clinical importance. Molecular and immunocytological techniques were used to study the expression of embryonic zeta (ζ), epsilon (ε), and fetal gamma (γ) globin genes in newborn cord blood, peripheral blood from men, pregnant and non‐pregnant women, and in vitro mononuclear cell cultures. We have shown that embryonic and fetal globin mRNA and peptides are expressed in cultured erythroid cells and in circulating blood cells from newborns, adult non‐pregnant women and from men. The findings suggest that during erythroid cell differentiation in newborns and adults, there is a transient recapitulation of sequential globin chain expression as found during embryonic and fetal development. Furthermore, these findings underscore the need for caution in using embryonic and fetal globin chains as markers to identify erythroid cells of fetal origin in maternal circulation for prenatal diagnosis. Copyright © 2001 John Wiley & Sons, Ltd.
Pulmonary stenosis and reactive right ventricular hypertrophy in the recipient fetus as a consequence of twin‐to‐twin transfusion
Authors: Marton Tamás , Hajdú Júlia , Papp Csaba , Patkós Péter , Hruby Ervin , Papp Zoltán
Published: September 2002

The present study describes an association between adverse outcome in the twin‐to‐twin transfusion syndrome (TTTS) and pulmonary stenosis or reactive right ventricular hypertrophy. Six discordant monozygotic twin pregnancies with TTTS are described. Ventricular hypertrophy and atrioventricular valvular regurgitation occurred in all the recipient twins with pulmonary valvular stenosis in three cases and infundibular stenosis in one case. The recipient twin in one pair and both twins in another pregnancy died as a consequence of immaturity but the remaining twins all survived. Surgical intervention was required in one baby for valvular pulmonary stenosis. Our observations suggest that elevated blood pressure in the transfusion recipient may play an important role in pathogenesis. We hypothesise that both pulmonary stenosis and right chamber hypertrophy are secondary to hemodynamic changes. Although we have found valvular pulmonary stenosis in three recipients and infundibular stenosis in only one, this (obstruction to outflow) could be due to right chamber hypertrophy. Copyright © 2001 John Wiley & Sons, Ltd.
Prenatal evaluation of fetal renal function based on serum beta2‐microglobulin assessment
Authors: Ciardelli Valentina , Rizzo Nicola , Farina Antonio , Vitarelli Marisa , Boni Paola , Bovicelli Luciano
Published: September 2002

The relationship between fetal renal function (FRF) and fetal serum beta2‐microglobulin (B2MG) was investigated by comparing its value in 112 unaffected fetuses with that of 23 fetuses presenting with urinary tract malformations (UTM). Fetal serum level of B2MG was totally unrelated to gestational age; its value increased in cases of severe impairment of FRF but was similar to controls in all mild uropathies (p<0.05). Evaluating serum B2MG could be beneficial in fetuses with severe renal damage, but is of no use in unilateral UTM since only the global FRF is tested and not the function of each single kidney. Copyright © 2001 John Wiley & Sons, Ltd.