bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation and characterization of ball‐milled Nafion® powders for membrane applications
Authors: Haynes Shawn D. , Mitchell Brian S. 
Published: June 2004

AbstractA method for producing Nafion® powder from commercially available pellets, and using this powder to produce membranes, is described. A description of particle size distribution, chemical composition, and thermal properties of Nafion® powders prepared by high‐energy ball milling of pellets is given. Nafion® powders prepared in this manner exhibit thermal behavior similar to that of the precursor pellets; however, traces of iron from the milling materials are shown to be present through transmission electron microscopy analysis of the particles. The membranes prepared by hot pressing of the Nafion® powders also show thermal behavior similar to that of the precursor pellet materials. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2275–2281, 2004
Influence of interchain forces and supermolecular structure on the drawing behavior of nylon 66 fibers in the presence of supercritical carbon dioxide
Authors: Hu Xianbo , Lesser Alan J. 
Published: June 2004

AbstractThe drawing behavior and mechanical properties of as‐spun and highly oriented nylon 66 fibers drawn in supercritical carbon dioxide (SCCO2) were investigated. Conditions including different temperatures, CO2 pressures, and plasticizers with different polarity were systematically studied. Results indicate that CO2 is an efficient plasticizer for as‐spun nylon 66 fibers as shown by decreases in the draw stress. In contrast, CO2 shows only a slight influence on the drawability of highly oriented nylon 66 fiber. The effect of other plasticizers such as water, methanol, and ethanol on the drawability of nylon 66 fibers is very similar to that of CO2. Tenacity and modulus of one‐stage drawn fibers were less than 0.8 and 5.0 GPa, respectively. Fibers with the highest tenacity and modulus, 0.96/5.04 and 1.06/5.04 GPa, were obtained by two‐stage drawing in SCCO2 from as‐spun and drawn nylon 66 fibers, respectively. The main reason for the extremely low draw ratios (<6.0) of nylon 66 fibers was the presence of hydrogen bonds in the crystalline phase. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2282–2288, 2004
Polystyrene and polyester polyurethane elastomer blends compatibilized by SMA
Authors: Cassu Silvana Navarro , Felisberti Maria Isabel 
Published: June 2004

AbstractBlends of polystyrene (PS) with polyester polyurethane elastomer (PU‐es) were compatibilized by addition of poly(styrene‐co‐maleic anhydride) (SMA) containing 7 wt % of maleic anhydride. Binary nonreactive (PS/PU‐es) blends, binary reactive (SMA/PU‐es) blends, and ternary reactive blends (PS/SMA/PU‐es) were prepared with 10 and 20 wt % of PU‐es. The maleic anhydride content in the ternary reactive blends was varied through addition of different SMA amounts from 0.5 to 5 wt %. Polyurethane in the blends was crosslinked by using dicumyl peroxide or sulfur to improve its mechanical properties. The experimental processing conditions, such as temperature and rotor speed in an internal mixer, were analyzed before blend preparation by processing the individual polymers, PS and SMA, and the PS/PU‐es nonreactive blend (90/10), to prevent the degradation of the polymer during melt mixing and to assure macroscopic homogeneity. The torque behavior during the mixture indicated a grafting copolymerization, which was responsible for the significant drop of the PU‐es domain size in the glassy matrix, as observed by scanning electronic microscopy (SEM). The miscibility of the glassy matrix, which was shown to be dependent on the composition and the phase behavior of ternary blends, became very complex as the SMA concentration increased, as concluded from dynamical–mechanical analysis. Blends containing 20 wt % of PU‐es presented an increase up to a factor of 2 in the deflection at break in relation to PS. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2297–2304, 2004
Metabolic effects and the methylenetetrahydrofolate reductase (MTHFR) polymorphism associated with neural tube defects in southern Brazil
Authors: Félix Têmis Maria , Leistner Sandra , Giugliani Roberto 
Published: June 2004

AbstractBACKGROUNDThe importance of metabolic factors in neural tube defects (NTDs) has been the focus of many investigations. Several authors have suggested that abnormalities in homocysteine metabolism, such as hyperhomocysteinemia, folate deficiency, and low vitamin B12, may be responsible for these malformations and that both nutritional factors and genetic abnormalities are associated with them.METHODSWe conducted a case‐control study to investigate the influence of biochemical and genetic factors in NTDs in infants in southern Brazil. Levels of folate, vitamin B12, total homocysteine (t‐Hcy) and the 677C>T and 1298A>C polymorphisms of the MTHFR gene were analyzed in 41 NTD child–mother pairs and 44 normal child–mother control pairs.RESULTSSubjects in the case group had a higher mean blood folate level than those in the control group. The level of vitamin B12 was lower in mothers in the NTD group than in control mothers (p = 0.004). The level of t‐Hcy was not different in the two groups, but t‐Hcy and vitamin B12 were correlated (p = 0.002). There was no difference in the genotype distribution for 677C>T and 1298A>C polymorphisms of MTHFR in the case and control pairs. The level of t‐Hcy was correlated with 677TT.CONCLUSIONSDespite the small sample in this study, we suggest that low vitamin B12 and, consequently, hyperhomocysteinemia are important risk factors for NTDs in our population. Birth Defects Research (Part A), 2004. © 2004 Wiley‐Liss, Inc.
Maternal vitamin B‐6 and folate status and risk of oral cleft birth defects in the Philippines
Authors: Munger Ronald G. , Sauberlich Howerde E. , Corcoran Christopher , Nepomuceno Buena , Daack‐Hirsch Sandra , Solon Florentino S. 
Published: June 2004

AbstractBACKGROUNDVitamin deficiencies induce oral clefts in animal experiments, but the role of specific nutrients in human oral clefts is uncertain.METHODSAssociations between maternal vitamin B‐6 and folate status and risk of nonsyndromic cleft lip, with or without cleft palate (CL/P), were examined in case–control studies at two sites in the Philippines—Negros Occidental and Davao. Cases were mothers of affected children and control mothers were those who had no children with oral clefts.RESULTSThe risk of having a CL/P‐affected child increased with increasing tertile of vitamin B‐6 deficiency in both Negros Occidental and Davao (odds ratios [ORs] and 95% confidence intervals [CIs] for sites combined = 1.0 [reference], OR, 2.94; 95% CI, 1.51–5.73; OR, 4.98; 95% CI, 2.56–9.67). Poor B‐6 status had a stronger association with CL/P among mothers with lower versus higher plasma folate levels. Increasing tertiles of plasma folate were marginally associated with an increased risk of clefts in both sites combined (1.0 [reference]; OR, 1.58; 95% CI, 0.93–2.68; OR, 1.59; 95% CI, 0.94–2.70). Increasing tertiles of erythrocyte folate were associated with a decreased risk of CL/P in Negros Occidental (1.0 [reference]; OR, 0.34; 95% CI, 0.13–0.90; OR, 0.46; 95% CI, 0.20–1.09) and an increased risk in Davao (1.0 [reference]; OR, 1.23; 95% CI, 0.54–2.81; OR, 4.85; 95% CI, 2.24–10.50). The inconsistent associations between folate status and CL/P risk appeared to be a result of statistical interaction between folate, vitamin B‐6, and case–control status that produced different results in study areas of higher versus lower prevalence of vitamin B‐6 deficiency.CONCLUSIONSPoor maternal vitamin B‐6 status was consistently associated with an increased risk of CL/P at two sites in the Philippines. Folate‐CL/P associations were inconsistent and may be related to the vitamin B‐6 status or other characteristics of the populations under study. Birth Defects Research (Part A), 2004. © 2004 Wiley‐Liss, Inc.
Thymidylate synthase repeat polymorphisms and risk of neural tube defects in a population from the northern United Kingdom
Authors: Wilding Craig S. , Relton Caroline L. , Sutton Matthew J. , Jonas Pat A. , Lynch Sally‐Ann , Tawn E. Janet , Burn John 
Published: June 2004

AbstractBACKGROUNDA 28‐bp repeat polymorphism in the 5′UTR of the thymidylate synthase (TYMS) gene represents a candidate risk factor for neural tube defects (NTDs) due to involvement in folate‐dependent homocysteine metabolism. Non‐Hispanic, white, U.S. citizens carrying at least one 2× 28‐bp repeat allele have recently been shown to be at a four‐fold increased risk of spina bifida (SB). We investigated the association between this polymorphism and risk of NTD in families affected by NTDs and controls from the northern United Kingdom (UK).METHODSPCR was performed on genomic DNA extracted from blood or mouth swabs of family members affected by NTDs (mothers, fathers, and cases), and unaffected controls (mothers and infants) to determine the number of 28‐bp repeat units within the promoter region of TYMS. Case–control and TDT analyses of the influence of TYMS genotype on risk of NTD, or NTD pregnancy, were conducted.RESULTSOdds ratio (OR) analysis indicated that individuals carrying the 2× 28‐bp repeat allele either in homozygous or heterozygous form, are not at increased risk of NTDs, or of having an NTD affected pregnancy. Control population allele frequencies are seen to be markedly different between the U.S. controls and those in this study.CONCLUSIONSTYMS polymorphism appears to be not universally associated with NTD risk across Caucasian samples. The elevated risk of spina bifida in U.S. samples appears to be driven by an unusually low risk allele (2× 28 bp) frequency in control samples. Family based (TDT) testing of U.S. samples is therefore advocated. Birth Defects Research (Part A), 2004. © 2004 Wiley‐Liss, Inc.
Is lack of morning sickness teratogenic? A prospective controlled study
Authors: Boskovic Rada , Rudic Natasha , Danieliewska‐Nikiel Barbara , Navioz Yvette , Koren Gideon 
Published: June 2004

AbstractBACKGROUNDCase‐control studies have suggested that the nausea and vomiting of pregnancy (NVP) may have a protective effect against specific malformations. These suggestions have been interpreted as if the lack of NVP may put mothers at an increased teratogenic risk.METHODSA prospective, cohort‐controlled study was done comparing pregnancy outcome in women not experiencing NVP with those experiencing NVP at two levels of clinical severity. Women who called the Motherisk program about first‐trimester exposure to drugs and who had not experienced NVP were included as the study group. The NVP Healthline enrolled two control groups of women with NVP treated with a doxylamine‐pyridoxine combination for morning sickness. These women were exposed during the first trimester of gestation to either higher than the standard dose (5–12 tablets/day) or a standard dose (1–4 tablets/day) of doxylamine‐pyridoxine. The women in all three groups were followed up four to six months after the expected date of birth to ascertain pregnancy outcomes and child health.RESULTSThere were no major malformations among offspring of 130 women not experiencing NVP. There were two major malformations among 246 women experiencing NVP. The two control groups of women with NVP had similar distributions of gestational ages, birth rates, as well as rates of miscarriages and stillbirths, as in the no‐NVP group.CONCLUSIONSThis study did not show an association between lack of NVP and an increase in the overall rates of major malformations. Birth Defects Research (Part A), 2004. © 2004 Wiley‐Liss, Inc.
Epidemiologic characteristics of anotia and microtia in California, 1989–1997
Authors: Shaw Gary M. , Carmichael Suzan L. , Kaidarova Zhanna , Harris John A. 
Published: June 2004

AbstractBACKGROUNDThere is a paucity of epidemiologic information about the external ear malformations anotia and microtia.METHODSUsing data from a large population‐based registry, we explored prevalences and maternal/infant characteristics associated with anotia and microtia. Data were derived from the California Birth Defects Monitoring Program, a population‐based active surveillance system for collecting information on infants and fetuses with congenital malformations using multiple source ascertainment. Approximately 2.5 million births (live‐born and stillborn) occurred during the ascertainment period, 1989–1997. Information on maternal and infant/fetal characteristics was obtained from California birth certificate and fetal death files.RESULTSThe prevalence of anotia/microtia was 2.50 per 10,000 live births and stillbirths. Isolated cases, i.e., those live births and stillbirths with no other accompanying anomaly diagnoses, revealed a prevalence of 0.63 per 10,000, whereas among nonisolated cases, the prevalence was 1.53 per 10,000 live births and stillbirths. Prevalences of isolated anotia/microtia were substantially higher among U.S.‐born Hispanics, foreign‐born Hispanics, and Asians compared to non‐Hispanic whites, with relative risks ranging from three‐ to seven‐fold. Similar prevalences for maternal race/ethnicity (except for Asians) were observed for live births and stillbirths with nonisolated cases of anotia/microtia, but the magnitude of risks were lower than those observed for isolated cases. Prevalence of nonisolated anotia/microtia was substantially lower among women whose education was 12 years or more.CONCLUSIONSThese data reveal descriptive epidemiologic features of anotia/microtia most notably substantial risks associated with race/ethnic groups and lower maternal education. Additional study for factors associated with these characteristics could reveal clues for the etiology of these ear anomalies. Birth Defects Research (Part A), 2004. © 2004 Wiley‐Liss, Inc.
Developmental consequences of abnormal folate transport during murine heart morphogenesis
Authors: Tang Louisa S. , Wlodarczyk Bogdan J. , Santillano Daniel R. , Miranda Rajesh C. , Finnell Richard H. 
Published: June 2004

AbstractBACKGROUNDFolic acid is essential for the synthesis of nucleotides and methyl transfer reactions. Folic acid–binding protein one (Folbp1) is the primary mediator of folic acid transport into murine cells. Folbp1 knockout mouse embryos die in utero with multiple malformations, including severe congenital heart defects (CHDs). Although maternal folate supplementation is believed to prevent human conotruncal heart defects, its precise role during cardiac morphogenesis remains unclear. In this study, we examined the role of folic acid on the phenotypic expression of heart defects in Folbp1 mice, mindful of the importance of neural crest cells to the formation of the conotruncus.METHODSTo determine if the Folbp1 gene participates in the commitment and differentiation of the cardiomyocytes, relative levels of dead and proliferating precursor cells in the heart were examined by flow cytometry, Western blot, and immunohistostaining.RESULTSOur studies revealed that impaired folic acid transport results in extensive apoptosis‐mediated cell death, which concentrated in the interventricular septum and truncus arteriosus, thus being anatomically restricted to the two regions of congenital heart defects. Together with a reduced proliferative capacity of the cardiomyocytes, the limited size of the available precursor cell pool may contribute to the observed cardiac defects. Notably, there is a substantial reduction in Pax‐3 expression in the region of the presumptive migrating cardiac neural crest, suggesting that this cell population may be the most severely affected by the massive cell death.CONCLUSIONSOur findings demonstrate for the first time a prominent role of the Folbp1 gene in mediating susceptibility to heart defects. Birth Defects Research (Part A), 2004. © 2004 Wiley‐Liss, Inc.
Developmental evaluation of children born to mothers occupationally exposed to waste anesthetic gases
Authors: Ratzon Navah Z. , Ornoy Asher , Pardo Asher , Rachel Margolin , Hatch Maureen 
Published: June 2004

AbstractBACKGROUNDThe etiology of developmental delay in children is frequently unknown. Increasing evidence supports the possibility that environmental and occupational factors might be part of the basis for such delays. This study focuses on the development of children born to mothers who were exposed during their pregnancy to waste anesthetic gases.METHODSThe study population included 40 children aged 5–13 years born to female anesthesiologists and nurses working in operating rooms (OpRs) exposed to waste anesthetic gases, and 40 unexposed children born to female nurses and physicians who worked in hospitals during their pregnancy but did not work in OpRs. The unexposed group was matched for children's age and gender and maternal occupation (nurses vs. doctors). By means of standardized developmental tests, the present study population was evaluated for their medical and neurodevelopmental state. Questionnaires were given for the detection of attention and activity levels as perceived by the parents. Additional questionnaires dealt with information concerning developmental milestones, maternal and fetal morbidity, and gynecological history.RESULTSNo differences were noted between the groups as newborns or in developmental milestones at the age of 5–13 years; however, the mean score of gross motor ability was significantly lower in the exposed versus the unexposed group. Additionally, the mean score of the DSM‐III‐R Parent‐Teacher Questionnaire (PTQ) (i.e., measure of inattention/hyperactivity) was higher in the exposed group. The level of exposure, as measured by the number of weekly hours in the OpRs, was significantly and negatively correlated with fine motor ability and the score of IQ performance.CONCLUSIONSOur study supports the hypothesis that occupational exposure to anesthetic gases might be a risk factor for minor neurological deficits of children born to mothers who work in OpRs and therefore indicates the need for more studies in this area and perhaps more caution among OpR pregnant women and employers. Birth Defects Research (Part A), 2004. © 2004 Wiley‐Liss, Inc.
Rubella virus and birth defects: Molecular insights into the viral teratogenesis at the cellular level
Authors: Atreya C.D. , Mohan K.V.K. , Kulkarni S. 
Published: June 2004

AbstractBACKGROUNDIn utero rubella virus (RV) infection of a fetus can result in birth defects that are often collectively referred to as congenital rubella syndrome (CRS). In extreme cases, fetal death can occur. In spite of the availability of a safe and effective vaccine against rubella, recent worldwide estimates are that more than 100,000 infants are born with CRS annually.RECENT PROGRESSRecently, several significant findings in the field of cell biology, as well as in the RV replication and virus‐cell interactions, have originated from the authors' laboratory, and other researchers have provided insights into RV teratogenesis. It has been shown that 1) an RV protein induces cell‐cycle arrest by generating a subpopulation of tetraploid nuclei (i.e., 4N DNA) cells, perhaps representative of the tetraploid state following S phase in the cell cycle, due to its interaction with citron‐K kinase (CK); 2) RV infection induces apoptosis in cell culture, and 3) CK functional perturbations lead to tetraploidy, followed by apoptosis, in specific cell types.CONCLUSIONSBased on several similarities between known RV‐associated fetal and cellular manifestations and CK deficiency–associated phenotypes, it is reasonable to postulate that P90‐CK interaction in RV‐infected cells interferes with CK function and induces cell‐cycle arrest following S phase in a subpopulation, perhaps representative of tetraploid stage, which could lead to subsequent apoptosis in RV infection. Taking all these observations to the fetal organogenesis level, it is plausible that P90‐CK interaction could perhaps be one of the initial steps in RV infection–induced apoptosis‐associated fetal birth defects in utero. Birth Defects Research (Part A), 2004. © 2004 Wiley‐Liss, Inc.
A study of the conformations of valinomycin in solution phase
Authors: Wang Feng , Zhao Chunxia , Polavarapu Prasad L. 
Published: June 2004

AbstractVibrational absorption and vibrational circular dichroism (VCD) spectra of valinomycin are measured, in different solvents, in the ester and amide carbonyl stretching regions. The influence of cations, namely Li+, Na+, K+, and Cs+, in methanol‐d4 solvent is also investigated. Ab initio quantum mechanical calculations using density functional theory and 6–31G* basis set are used to predict the absorption and VCD spectra. A bracelet‐type structure for valinomycin that reproduces the experimental absorption and VCD spectra in inert solvents is identified. For the structure of valinomycin in polar solvents, a propeller‐type structure was optimized, but further investigations are required to confirm this structure. A symmetric octahedral environment for the ester carbonyl groups in the valinomycin–K+ complex is supported by the experimental VCD spectra. The results obtained in the present study demonstrate that even for large macrocyclic peptides, such as valinomycin, VCD can be used as an independent structural tool for the study of conformations in solution. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Detection of single nucleotide variations by a hybridization proximity assay based on molecular beacons and luminescence resonance energy transfer
Authors: Root Douglas D. , Vaccaro Carlos , Zhang Zhiling , Castro Miguel 
Published: June 2004

AbstractA powerful combination of molecular beacon and luminescence resonance energy transfer technology reveals alterations in nucleic acid structure by as little as a single nucleotide in a novel hybridization proximity assay. The assay measures the length of a single‐stranded target when a terbium chelate‐labeled molecular beacon hybridizes to one side of the nucleic acid segment to be measured and an acceptor probe carrying a convention fluorophore hybridizes to the opposite end of the target. Using a test sequence shortened incrementally by deleting single nucleotides, this assay reports a nearly linear relationship between sequence length and the distance separating acceptor and donor probes. Consequently, this assay can be used to detect alternative splicing, allele types, rearrangements, insertion, and deletion events by measuring separation distances within a predefined region. Furthermore, the use of terbium chelates in molecular beacons can produce exceptionally high signal‐to‐background ratios compared to the use of conventional fluorophores. Principles of optimal probe design are investigated experimentally and by computational simulations of plausible molecular beacon folding. Some molecular beacon designs form dimers that reduce their maximal response to target sequences. A simple assay to detect such dimers is reported as a tool to help improve the design of molecular beacons. Optimally designed molecular beacons with terbium chelates and hybridization proximity assays are expected to expand their applications in the analysis and screening of genetic diseases. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004