bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of dynamic vulcanization on co‐continuous morphology
Authors: Bhadane Prashant A. , Virgilio Nick , Favis Basil D. , Champagne Michel F. , Huneault Michel A. , Tofan Florin
Published: August 2006

This study examines the effect of dynamic vulcanization on the co‐continuous morphology in ethylene‐propylene‐diene terpolymer (EPDM)/polypropylene (PP) blends using a technique of morphology investigation involving focused ion beam (FIB) etching of the sample surface, followed by topological investigation of the sample surface using tapping mode atomic force microscopy (TMAFM). The FIB ion etching rates of EPDM and PP are distinctly different, and these differences create a significant topological contrast between the phases when subsequently analyzed by atomic force microscopy. This approach allows for the high‐resolution observation of dispersed EPDM, and phases as small as 100 nm, are clearly identified. Since it is shown that the etching rates of noncrosslinked and crosslinked EPDM are similar, it was necessary to selectively remove the noncrosslinked EPDM phase by solvent dissolution. This combination of techniques then allows for the clear distinction of polypropylene, as well as noncrosslinked and crosslinked EPDM phases in the blend. The high‐resolution micrographs together with the continuity data, surprisingly, indicate that a noncrosslinked co‐continuous EPDM phase (α‐network) transits to a finer network of crosslinked EPDM (β‐network) after dynamic crosslinking. It is suggested that this β‐network is produced as a result of the viscosity mismatch between the noncrosslinked and crosslinked EPDM melt occurring at the outer envelope of the α‐network during dynamic crosslinking. As the crosslinked material pulls away from the noncrosslinked material under dynamic melt mixing conditions, it creates a smearing effect. It is shown that the initial α‐network maintains its continuity and demonstrates a diminished pore diameter as crosslinking proceeds. Furthermore, when the noncrosslinked material is extracted almost no crosslinked phase (<1%) is found to be present in the extract. These results strongly indicate that the crosslinking proceeds initially at the outer envelope of the EPDM phase, and works its way toward the center. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Dehydration of glycerol to acetol via catalytic reactive distillation
Authors: Chiu Chuang‐Wei , Dasari Mohanprasad A. , Suppes Galen J. , Sutterlin Willam R.
Published: August 2006

Dehydration of glycerol was performed in the presence of various metallic catalysts including alumina, magnesium, ruthenium, nickel, platinum, palladium, copper, raney nickel, and copper‐chromite catalysts to obtain acetol in a single‐stage reactive distillation unit under mild conditions. The effects of operation mode, catalyst selection, glycerol‐feed flow rate, catalyst loading, and initial water content were studied to arrive at optimum conditions. High‐acetol selectivity levels (> 90%) were achieved using copper‐chromite catalyst, and operating in semi‐batch reactive distillation mode. A small amount of water content in glycerol feedstock was found to reduce the tendency for residue to form, therein extending catalyst life. The acetol from this reaction readily hydrogenates to form propylene glycol, providing an alternative route for converting glycerol to propylene glycol. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Segregation and dispersion of a binary system of particles in a fluidized bed
Authors: Galvin K. P. , Swann R. , Ramirez W. F.
Published: August 2006

The steady‐state segregation and dispersion of a binary system of particles in a liquid‐fluidized bed was investigated. One of the species had a density of 1,600 kg/m3 and the other 1,900 kg/m3, and both exhibited a narrow size range of 1.00 to 1.18 mm. A generalized model for describing the dispersion coefficient, D, was proposed. That is, D = αdUf/ϕ, where d is the particle diameter, Uf the local interstitial fluid velocity, and ϕ the local volume fraction of solids. The model had one adjustable parameter α, which was fixed at 0.7 for both particle species and for the six different superficial fluidization velocities used. The particle segregation was described with reference to the monocomponent fluidization parameters of the two species, based on the Richardson and Zaki equation. Good descriptions of the concentration profiles of the two species were produced for all superficial velocities examined. Additional experiments involving other binary systems were also conducted in order to test the generality of the model. These systems involved particles of closer settling velocities, and, hence, displayed more mixing. Very small adjustments in the terminal velocities of the species, typically 2%, were needed to achieve satisfactory agreement between the theoretical and experimental concentration profiles, with the model parameter, α, equal to 0.7. This adjustment was justified because of apparent changes in the average particle sizes of the two species due to particle‐size segregation. © 2006 American Institute of Chemical Engineers AIChE J, 2006
Teratogen update: Pseudoephedrine
Authors: Werler Martha M.
Published: August 2006

Pseudoephedrine is contained in decongestants such as the Sudafed line of products. It is an alpha‐adrenergic receptor agonist, which causes blood vessel constriction, including the therapeutic effect of reducing airflow resistance in the nasal cavity. Pseudoephedrine is one of the most commonly used medications in pregnancy, with an estimated 25% of women exposed. It has been demonstrated that alpha‐adrenergic receptor agonists slow uterine blood flow, but their effects have not been studied in relation to most reproductive outcomes in animals or humans. Two analyses of health maintenance organization pharmacy data identified 9 malformed infants among 902 first‐trimester pseudoephedrine exposures, suggesting no association with birth defects overall; however, studies of such data sets often lack sufficient power to identify risks for specific birth defects. The related compounds, epinephrine, ephedrine, and phenylephrine, have been associated with hemorrhages and cardiovascular and limb malformations in animal models. Risk of ventricular septal defects was associated with decongestant use in pregnant women in 1 recent study. The vasoconstrictive effects of these drugs raise the hypothesis that their use in early pregnancy might increase the risk of vascular disruption defects. Case‐control studies, which often do have power to identify risks related to specific birth defects, have explored this hypothesis. Decongestant use in the first trimester has been associated with small increases in risks of 3 defects thought to arise, at least in some instances, from vascular disruption–gastroschisis, small intestinal atresia, and hemifacial microsomia. These findings are somewhat consistent in terms of magnitude of effect and suggest that risks are even greater among women also exposed to the vasoconstrictive effects of cigarette smoking. There are, however, limitations to these studies, including the possibilities of inaccurate recall of exposures and confounding by indication. In addition, the majority of decongestant use is in oral form and the question of whether intranasal formulations carry risk has not been adequately addressed. Birth Defects Research (Part A) 76:445–452, 2006. © 2006 Wiley‐Liss, Inc.
Asymmetry of skeletal effects of Dominant hemimelia
Authors: Owen Mary H. , Coull Brent A. , Holmes Lewis B.
Published: August 2006

BACKGROUND: Dominant hemimelia (Dh) is a dominant mutation that arose spontaneously in mice; Dh animals exhibit reduced numbers of lumbar vertebrae and preaxial hindlimb defects. Absence of spleen occurs in both Dh/+ and Dh/Dh animals. This study was undertaken to characterize asymmetry of skeletal defects in the Dh mouse, specifically hindlimb asymmetries in association with axial defects. METHODS: A total of 29 Dh/+ and 100 +/+ fetuses (gestational day [GD] 18) were identified by phenotype and linked DNA and their skeletons were analyzed. RESULTS: The results revealed an asymmetry of hindlimb skeletal defects in Dh/+ animals. In +/+ fetuses, the left and right tibia were symmetrical with 99.0% of the animals possessing 6 lumbar vertebrae. However, Dh/+ fetuses showed asymmetry in length of left and right tibia and a reduction to 5 lumbar vertebrae in 86.2% of animals. There was a range from mild to severe asymmetry as evidenced by direct comparison of the length of the left to the right tibia of each animal. Tibial shortening was greater on the left than the right in 65.5% of Dh/+ fetuses; only 20.7% had symmetrical tibia. Oligodactyly, defined as absence of the first or second toe, was similarly more frequent on the left. CONCLUSIONS: Asymmetry is characteristic of many human limb malformations, although analysis of the molecular basis is difficult. Therefore, Dh/+ mice, which exhibit reduced numbers of lumbar vertebrae, asymmetric hindlimb defects, and complete absence of spleen, provide an important model for studying the relationship between axial patterning and asymmetric skeletal defects. Birth Defects Research (Part A) 76:474–482, 2006. © 2006 Wiley‐Liss, Inc.
Maternal birthplace and major congenital malformations among New York Hispanics
Authors: Zhu Motao , Druschel Charlotte , Lin Shao
Published: August 2006

BACKGROUND: Little is known about the association between maternal nativity and congenital malformations among Hispanics living in the United States. METHODS: We conducted a cross‐sectional study to investigate the association between maternal nativity and various congenital malformations among singleton live‐births born to Hispanic women in New York from 1993 to 2001. Birth certificates, used to identify maternal birthplace, were linked with congenital malformation registry files to obtain birth defects outcome. We examined how the risk of birth defects varied by maternal birthplace by estimating the adjusted odds ratios (aORs) using logistic regression. RESULTS: A foreign maternal birth showed statistically negative associations with overall congenital malformations (aOR, 0.70; 95% CI, 0.68–0.73), cardiovascular defects (aOR, 0.85; 95% CI, 0.77–0.93), central nervous system defects (aOR, 0.76; 95% CI, 0.63–0.91), and multiple defects (aOR, 0.80; 95% CI, 0.74–0.86). Specifically, foreign‐born Hispanic women were statistically at reduced risk to deliver live babies with cleft palate (aOR, 0.56; 95% CI, 0.40–0.80), atresia and stenosis of rectum or anus (aOR, 0.58; 95% CI, 0.35–0.97), and craniosynostosis (aOR, 0.71; 95% CI, 0.51–0.99). Hispanic mothers born in Puerto Rico had a similar risk of delivering children with birth defects compared to U.S.‐born Hispanic mothers. In contrast, Hispanic mothers born in Mexico, or Cuba and Central and South America were at reduced risk of delivering infants with overall congenital malformations (aOR, 0.64; 95% CI, 0.60–0.67) and (aOR, 0.65; 95% CI, 0.63–0.68), respectively. CONCLUSIONS: Foreign‐born Hispanic mothers had a slightly lower risk to deliver live‐born singleton infants with major congenital malformations than did U.S. born Hispanic mothers. Birth Defects Research (Part A) 76:467–473, 2006. © 2006 Wiley‐Liss, Inc.
High‐density single nucleotide polymorphism screen in a large multiplex neural tube defect family refines linkage to loci at 7p21.1–pter and 2q33.1–q35
Authors: Stamm Demetra S. , Rampersaud Evadnie , Slifer Susan H. , Mehltretter Lorraine , Siegel Deborah G. , Xie Jianzhen , Hu‐Lince Diane , Craig David W. , Stephan Dietrich A. , George Timothy M. , Gilbert John R. , Speer Marcy C. ,   the NTD Collaborative Group
Published: August 2006

BACKGROUND: Neural tube defects (NTDs) are considered complex, with both genetic and environmental factors implicated. To date, no major causative genes have been identified in humans despite several investigations. The first genomewide screen in NTDs demonstrated evidence of linkage to chromosomes 7 and 10. This screen included 44 multiplex families and consisted of 402 microsatellite markers spaced ∼10 cM apart. Further investigation of the genomic screen data identified a single large multiplex family, pedigree 8776, as primarily driving the linkage results on chromosome 7. METHODS: To investigate this family more thoroughly, a high‐density single nucleotide polymorphism (SNP) screen was performed. Two‐point and multipoint linkage analyses were performed using both parametric and nonparametric methods. RESULTS: For both the microsatellite and SNP markers, linkage analysis suggested the involvement of a locus or loci proximal to the telomeric regions of chromosomes 2q and 7p, with both regions generating a LOD* score of ˜3.0 using a nonparametric identity by descent relative sharing method. CONCLUSIONS: The regions with the strongest evidence for linkage map proximal to the telomeres on these two chromosomes. In addition to mutations and/or variants in a major gene, these loci may harbor a microdeletion and/or translocation; potentially, polygenic factors may also be involved. This single family may be promising for narrowing the search for NTD susceptibility genes. Birth Defects Research (Part A) 76:499–505, 2006. © 2006 Wiley‐Liss, Inc.
Differential teratogenic response of TNFα+/+and TNFα−/−mice to cyclophosphamide: The possible role of NF‐κB
Authors: Torchinsky Arkady , Gongadze Maka , Savion Shoshana , Fein Amos , Toder Vladimir
Published: August 2006

BACKGROUND:We observed previously that tumor necrosis factor α (TNFα)–knockout embryos are more sensitive to a cyclophosphamide (CP)–induced teratogenic insult than their TNFα‐positive counterparts, implicating molecules acting in TNFα‐activated antiapoptotic pathways in the mechanisms underlying this phenomenon. The main goal of this study was to assess whether the transcription factor nuclear factor κB (NF‐κB) may be 1 of those molecules. Such a choice is based by evidence demonstrating TNFα as a powerful activator of NF‐κB and a key role of the transcription factor in the most effective TNFα‐activated antiapoptotic cascade. Also, the expression pattern of active caspases 3, 8, and 9 was researched to assess the sensitivity of TNFα+/+and TNFα−/−embryos to CP‐induced apoptotic stimuli.METHODS:TNFα‐knockout mice were exposed to CP on day 12 of pregnancy, with or without an NF‐κB inhibitor, pyrrolidine dithiocarbamate (PDTC) and sacrificed on day 18 of pregnancy to evaluate the CP‐induced teratogenic effect. Embryos harvested 24 or 48 hr after the CP treatment were used to evaluate NF‐κB DNA‐binding and activity of caspases 3, 8, and 9.RESULTS:PDTC potentiated the CP‐induced teratogenic effect and augmented the CP‐induced suppression of NF‐κB DNA‐binding. These effects were more prominent in TNFα−/−than TNFα+/+embryos. CP‐induced caspase activation was found to be similar in TNFα−/−and TNFα+/+embryos at 24 hr after treatment. At 48 hr, TNFα−/−embryos exhibited higher levels of active caspases 8 and 9 than their TNFα‐positive counterparts.CONCLUSIONS:The results of our study allow us to hypothesize that NF‐κB may be a component of mechanisms underlying differential sensitivity of TNFα−/−and TNFα+/+mice to CP‐induced teratogenic insult. Birth Defects Research (Part A) 76:437–444, 2006. © 2006 Wiley‐Liss, Inc.
Evidence for a functional genetic polymorphism of the human retinoic acid–metabolizing enzyme CYP26A1, an enzyme that may be involved in spina bifida
Authors: Rat Emmanuel , Billaut‐Laden Ingrid , Allorge Delphine , Lo‐Guidice Jean‐Marc , Tellier Marie , Cauffiez Christelle , Jonckheere Nicolas , van Seuningen Isabelle , Lhermitte Michel , Romano Antonio , Guéant Jean‐Louis , Broly Franck
Published: August 2006

BACKGROUND: CYP26A1, together with CYP26B1 and CYP26C1, are key enzymes of all‐trans retinoic acid (RA) inactivation and their specific and restricted expression in developing embryos participate in the fine tuning RA levels. As RA is a critical regulator of gene expression during embryonic development, the imbalance between the synthesis and degradation of RA during embryogenesis could contribute to malformations and developmental defects. METHODS: A PCR–single strand conformation polymorphism (PCR‐SSCP) strategy was developed to screen for CYP26A1 sequence variations that could affect the enzyme expression and/or activity and applied to DNA samples from 80 unrelated Caucasians, comprising 40 French healthy volunteers and 40 Italian patients with spina bifida. The consequence of the 1‐bp deletion identified in the coding sequence was investigated by an in vitro functional assay using COS‐7 cells. RESULTS: A total of 7 polymorphisms were identified, comprising 1 nucleotide deletion in the coding sequence (g.3116delT) that results in a frameshift and consequently in the creation of a premature stop codon. The g.3116delT mutation is of particular interest because it was identified in a patient with spina bifida and likely encodes a truncated protein with no enzymatic activity, as demonstrated by our preliminary in vitro data. CONCLUSIONS: Despite the fact that our findings could not show any evidence that the CYP26A1 genetic polymorphism has implications in the pathogenesis of spina bifida, this work represents the first description of a functional genetic polymorphism affecting the coding sequence of the human CYP26A1 gene. Birth Defects Research (Part A) 76:491–498, 2006. © 2006 Wiley‐Liss, Inc.
Expression profiling of transforming growth factor β superfamily genes in developing orofacial tissue
Authors: Mukhopadhyay Partha , Greene Robert M. , Pisano M. Michele
Published: August 2006

BACKGROUND:

Numerous signaling molecules have been shown to participate in the dynamic process of orofacial development. Among these signal mediators, members of the transforming growth factor β (TGFβ) superfamily have been shown to play critical roles. Developing orofacial tissue expresses TGFβ and bone morphogenetic protein (BMP) mRNAs, their protein isoforms and TGFβ‐ and BMP‐specific receptors. All these molecules display unique temporospatial patterns of expression in embryonic orofacial tissue, suggesting functional roles in orofacial development. For example, the TGFβs and BMPs regulate maxillary mesenchymal cell proliferation and extracellular matrix synthesis. This is particularly noteworthy in that perturbation of either process results in orofacial clefting. Although the cellular and phenotypic effects of the TGFβ superfamily of growth factors on embryonic orofacial tissue have been extensively studied, the specific genes that function as effectors of these cytokines in orofacial development have not been well defined.

METHODS:

In the present study, oligonucleotide‐based microarray technology was utilized to provide a comprehensive analysis of the expression of the panoply of genes related to the TGFβ superfamily, as well as those encoding diverse groups of proteins functionally associated with this superfamily, during orofacial ontogenesis.

RESULTS:

Of the ˜7000 genes whose expression was detected in the developing orofacial region, 249 have been identified that encode proteins related to the TGFβ superfamily. Expression of some (27) of these genes was temporally regulated. In addition, several candidate genes, whose precise role in orofacial development is still unknown, were also identified. Examples of genes constituting this cluster include: TGFβ1‐induced antiapoptotic factor‐1 and ‐2, TGFβ‐induced factor 2, TGFβ1 induced transcript‐1 and ‐4, TGFβ‐inducible early growth response 1, follistatin‐like 1, follistatin‐like 3, transmembrane protein with EGF‐like and two follistatin‐like domains (Tmeff)‐1 and ‐2, nodal modulator 1, various isoforms of signal transducers and activators of transcription (Stat), notch, and growth and differentiation factors.

CONCLUSIONS:

Elucidation of the precise physiological roles of these proteins in orofacial ontogenesis should provide unique insights into the intricacies of the TGFβ superfamily signal transduction pathways utilized during orofacial development. Birth Defects Research (Part A) 76:528–543, 2006. © 2006 Wiley‐Liss, Inc.
Review: Hyperthermia and fever during pregnancy
Authors: Edwards Marshall J.
Published: August 2006

An episode of hyperthermia is not uncommon during pregnancy. The consequences depend on the extent of temperature elevation, its duration, and the stage of development when it occurs. Mild exposures during the preimplantation period and more severe exposures during embryonic and fetal development often result in prenatal death and abortion. Hyperthermia also causes a wide range of structural and functional defects. The central nervous system (CNS) is most at risk probably because it cannot compensate for the loss of prospective neurons by additional divisions by the surviving neuroblasts and it remains at risk at stages throughout pre‐ and postnatal life. In experimental animals the most common defects are of the neural tube, microphthalmia, cataract, and micrencephaly, with associated functional and behavioral problems. Defects of craniofacial development including clefts, the axial and appendicular skeleton, the body wall, teeth, and heart are also commonly found. Nearly all these defects have been found in human epidemiological studies following maternal fever or hyperthermia during pregnancy. Suggested future human studies include problems of CNS function after exposure to influenza and fever, including mental retardation, schizophrenia, autism, and cerebral palsy. Birth Defects Research (Part A) 76:507–516, 2006. © 2006 Wiley‐Liss, Inc.
Combined supplementation of folic acid and vitamin E diminishes diabetes‐induced embryotoxicity in rats
Authors: Gäreskog Mattias , Eriksson Ulf J. , Wentzel Parri
Published: August 2006

BACKGROUND: Oxidative stress and enhanced apoptosis may be involved in the induction of embryonic dysmorphogenesis in diabetic pregnancy. Administration of folic acid or vitamin E diminishes embryonic dysmorphogenesis. We aimed to evaluate the effect of combined treatment with folic acid and vitamin E on the disturbed development in embryos of diabetic rats. METHODS: Pregnant nondiabetic and diabetic rats were treated with daily injections of 15 mg/kg folic acid or with 5% vitamin E in the diet. A third group received combined treatment. Day 10 and day 11 embryos were evaluated for development and apoptotic profile. RESULTS: We found increased malformations, resorptions, and profound growth retardation in embryos of diabetic rats compared to control embryos. Vitamin E or folic acid alone, or the 2 compounds combined, normalized embryonic demise. Maternal diabetes caused decreased nuclear factor–κB (NF‐κB) activity and B‐cell lymphoma 2 (Bcl‐2) protein level, and increased Bcl‐2–associated x proteins (Bax) in embryos. Supplementation of vitamin E alone normalized the Bax protein level in a diabetic environment. Administration of folic acid to diabetic rats increased NF‐κB activity and Bcl‐2 protein level. Combined treatment normalized Bcl‐2 and Bax protein level in a diabetic environment. CONCLUSIONS: Combined supplementation of folic acid and vitamin E to pregnant diabetic rats diminished diabetes‐induced malformations and resorptions, concomitant with normalization of apoptotic protein levels. No treatment completely abolished the embryonic demise; therefore, other mechanisms than oxidative stress and apoptosis are likely to be involved in diabetic embryopathy. Birth Defects Research (Part A) 76:483–490, 2006. © 2006 Wiley‐Liss, Inc.
Zebrafish as a model for developmental neurotoxicity testing
Authors: Ton Christopher , Lin Yingxin , Willett Catherine
Published: August 2006

BACKGROUND:To establish zebrafish as a developmental toxicity model, we used 7 well‐characterized compounds to examine several parameters of neurotoxicity during development.METHODS:Embryos were exposed by semistatic immersion from 6 hrs postfertilization (hpf). Teratogenicity was assessed using a modified method previously developed by Phylonix. Dying cells in the brain were assessed by acridine orange staining (these cells are likely to be apoptotic). Motor neurons were assessed by antiacetylated tubulin staining and catecholaminergic neurons were visualized by antityrosine hydroxylase staining.RESULTS:Atrazine, dichlorodiphenyltrichloroethane (DDT), and 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD) were primarily teratogenic and not specifically neurotoxic. 2,4‐dichlorophenoxyacetic acid (2,4‐D), dieldrin, and nonylphenol showed specific neurotoxicity; dieldrin and nonylphenol were specifically toxic to catecholaminergic neurons. Malathion, although not teratogenic, showed some nonspecific toxicity.CONCLUSIONS:Teratogenicity measured in 96‐hpf zebrafish is predictive of mammalian teratogenicity and is useful in determining whether a compound causes specific neurotoxicity or general developmental toxicity. Induction of apoptosis or necrosis is an indicator of neurotoxicity. An effect on motor neurons in the caudal third of the embryo correlates with expected defects in motility. Overall, our results showed a strong correlation with mammalian data and suggest that zebrafish is a predictive animal model for neurotoxicity screening. Birth Defects Research (Part A) 76:553–567, 2006. Published 2006 Wiley‐Liss, Inc.
Integrity of the methylation cycle is essential for mammalian neural tube closure
Authors: Dunlevy Louisa P.E. , Burren Katie A. , Mills Kevin , Chitty Lyn S. , Copp Andrew J. , Greene Nicholas D.E.
Published: August 2006

BACKGROUND:Closure of the cranial neural tube during embryogenesis is a crucial process in development of the brain. Failure of this event results in the severe neural tube defect (NTD) exencephaly, the developmental forerunner of anencephaly.METHODS:The requirement for methylation cycle function in cranial neural tube closure was tested by treatment of cultured mouse embryos with cycloleucine or ethionine, inhibitors of methionine adenosyl transferase. Embryonic phenotypes were investigated by histological analysis, and immunostaining was performed for markers of proliferation and apoptosis. Methylation cycle intermediates s‐adenosylmethionine and s‐adenosylhomocysteine were also quantitated by tandem mass spectrometry.RESULTS:Ethionine and cycloleucine treatments significantly reduced the ratio of abundance of s‐adenosylmethionine to s‐adenosylhomocysteine and are, therefore, predicted to suppress the methylation cycle. Exposure to these inhibitors during the period of cranial neurulation caused a high incidence of exencephaly, in the absence of generalized toxicity, growth retardation, or developmental delay. Reduced neuroepithelial thickness and reduced density of cranial mesenchyme were detected in ethionine‐treated but not cycloleucine‐treated embryos that developed exencephaly. Reduced mesenchymal density is a potential cause of ethionine‐induced exencephaly, although we could not detect a causative alteration in proliferation or apoptosis prior to failure of neural tube closure.CONCLUSIONS:Adequate functioning of the methylation cycle is essential for cranial neural tube closure in the mouse, suggesting that suppression of the methylation cycle could also increase the risk of human NTDs. We hypothesize that inhibition of the methylation cycle causes NTDs due to disruption of crucial reactions involving methylation of DNA, proteins or other biomolecules. Birth Defects Research (Part A) 76:544–552, 2006. © 2006 Wiley‐Liss, Inc.
Acridin‐9‐yl exchange: A proposal for the action of some 9‐aminoacridine drugs
Authors: Šebestík Jaroslav , Šafařík Martin , Stibor Ivan , Hlaváček Jan
Published: August 2006

The finding that several derivatives of 9‐aminoacridine were deacridinylated in the presence of primary aliphatic amines during the solid phase synthesis of acridine–peptide conjugates prompted us to investigate the acridin‐9‐yl moiety transfer from a relatively low‐molecular acridine source to a high‐molecular carrier. The hydrophobic polymer was used as a model of hydrophobic core of biologically active proteins. While the α‐amino group in the peptide was found to play the role of weak acridine acceptor, the ϵ‐amino group of lysine appeared to serve as a moderate acceptor of acridine moiety. The covalent modification of the lysine residues side chain in the hydrophobic core of prion protein aggregates could thus explain the discrepancy between the ability of the acridine drug quinacrine to reduce efficiently the incidence of prion protein in cell culture and its weak prion binding affinity. © 2006 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 84: 605–614, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Bioprocess monitoring and computer control: Key roots of the current PAT initiative
Authors: Junker B.H. , Wang H.Y.
Published: August 2006

This review article has been written for the journal, Biotechnology and Bioengineering, to commemorate the 70th birthday of Daniel I.C. Wang, who served as doctoral thesis advisor to each of the co‐authors, but a decade apart. Key roots of the current PAT initiative in bioprocess monitoring and control are described, focusing on the impact of Danny Wang's research as a professor at MIT. The history of computer control and monitoring in biochemical processing has been used to identify the areas that have already benefited and those that are most likely to benefit in the future from PAT applications. Past applications have included the use of indirect estimation methods for cell density, expansion of on‐line/at‐line and on‐line/in situ measurement techniques, and development of models and expert systems for control and optimization. Future applications are likely to encompass additional novel measurement technologies, measurements for multi‐scale and disposable bioreactors, real time batch release, and more efficient data utilization to achieve process validation and continuous improvement goals. Dan Wang's substantial contributions in this arena have been one key factor in steering the PAT initiative towards realistic and attainable industrial applications. © 2006 Wiley Periodicals, Inc.
From microcarriers to hydrodynamics: Introducing engineering science into animal cell culture
Authors: Croughan Matthew S. , Hu Wei‐Shou
Published: August 2006

Professor Daniel I.C. Wang has conducted research in animal cell culture for approximately 40 years. Over that long time period and still to this day, he successfully addresses a multitude of engineering challenges, taking a unique, creative, systems‐driven but still fundamental approach. As mammalian cell culture has become the predominant method of manufacturing therapeutic proteins, the impact of his leadership, not only in research but also student recruitment and education, has played a key role in the success of the bio/pharmaceutical industry. © 2006 Wiley Periodicals, Inc.
Daniel I.C. Wang: A tribute to an inspirational leader and colleague
Authors: Hatton T. Alan
Published: August 2006

Daniel I.C. Wang has been an influential leader of the biotechnology industry over the past four decades through his inspirational research activities, the legions of students and other researchers that have studied under him, his development of many research and educational initiatives, both nationally and internationally, and the advice he has given worldwide to companies, research institutions, universities, and governments. He has played an important role in the mentoring and nurturing of junior faculty members, and has been a supportive collaborator in research and teaching. This two‐part article provides a brief overview of Danny Wang's many contributions to furthering the global development of biotechnology, with particular emphasis on his recent activities in Asia, and concludes with an account of his research collaborations with the author over the past two decades. © 2006 Wiley Periodicals, Inc.
Computer‐aided material balancing for prediction of fermentation parameters
Authors: Cooney Charles L. , Wang Henry Y. , Wang Daniel I.C.
Published: August 2006

Despite the importance of biomass as a parameter in fermentation processes, there are no commercially available sensors suitable for its measurement. An indirect approach for the assessment of biomass concentration can be based on material balances and on the direct monitoring of fermentation parameters for which there are established sensors (e.g., gaseous oxygen and carbon dioxide). As a consequence, this method requires no assumption of cellular yield coefficients or rate constants. This approach is also readily adaptable to general use since it requires only some knowledge of the compositions of the substrate, cells, and noncellular products. © 2006 Wiley Periodicals, Inc.
Computer control of the penicillin fermentation using the filtration probe in conjunction with a structured process model
Authors: Nestaas Eirik , Wang Daniel I. C.
Published: August 2006

A structured model for the penicillin fermentation is presented. This model includes three different cell types: 1) hyphae tips, 2) penicillin‐producing cells, and 3) degenerated, matabolically inactive cells. Cell degeneration has been described previously as a gradual loss of cytoplasmic material by endogenous metabolism. The rate at which such loss of cytoplasm (and activity) proceeds can be expressed as a linear function of the specific growth rate. At growth rates above some minimum value (0.0115 h−1) cell degeneration can be prevented. This model served as the control basis during open‐loop as well as closed‐loop computer control of the fermentation. Closed‐loop control was achieved through feedback information of biomass concentration using a filtration probe and was required when complex nutrients contributed significantly to the overall biomass production. © 2006 Wiley Periodicals, Inc.
A mechanistic analysis of the inoculum requirement for the cultivation of mammalian cells on microcarriers
Authors: Hu W.S. , Meier J. , Wang D.I.C.
Published: August 2006

For the cultivation of mammalian cells on microcarriers a minimum inoculum concentration is required to initiate cell attachment and subsequent cell growth. A critical cell number model has been proposed to elucidate the mechanism of the inoculum requirement. In this model it was hypothesized that after inoculation a critical number of cells per microcarrier is required for normal growth to occur; failure to acquire enough cells will impede cell growth. This critical cell number model was expressed mathematically and used to simulate cell distribution and growth on microcarriers under different cultivation conditions. By comparing the simulated growth kinetics with the experimental results, the actual critical cell number per microcarrier was identified. The critical number could be reduced by employing an improved medium for the cultivation. © 2006 Wiley Periodicals, Inc.
Hydrodynamic effects on animal cells grown in microcarrier cultures
Authors: Croughan Matthew Shane , Hamel Jean‐Francois , Wang Daniel I.C.
Published: August 2006

Hydrodynamic phenomena in microcarrier cultures are investigated with regard to the development of improved reactor designs for large‐scale operations. New concepts and theoretical models that describe new data as well as previously published data are presented. © 2006 Wiley Periodicals, Inc.
Protein refolding in reversed micelles
Authors: Hagen Anna J. , Hatton T. Alan , Wang Daniel I.C.
Published: August 2006

A novel process has been developed which uses reversed micelles to isolate denatured protein molecules from each other and allows them to refold individually. These reversed micelles are aqueous phase droplets stabilized by the surfactant AOT and suspended in iso‐octane. By adjusting conditions such that only one protein molecule is present per reversed micelle, it was possible to achieve independent folding without encountering the problem of aggregation due to interactions with neighboring molecules. The feasibility of this process was demonstrated using bovine pancreatic ribonuclease A as a model system. It was shown that denatured and reduced ribonuclease can be transferred from a buffered solution containing guanidine hydrochloride into reversed micelles to a greater extent than native enzyme under the same conditions. The denaturant concentration can then be significantly reduced in the reversed micellar phase, while retaining most of the protein, by means of extractive contacting stages with a denaturant‐free aqueous solution. Denatured and reduced ribonuclease will subsequently recover full activity inside reversed micelles within 24 h upon addition of a mixture of reduced and oxidized glutathione to reoxidize disulfide bonds. Extraction of this refolded enzyme from reversed micelles back into aqueous solution can be accomplished by contacting the reversed micelle phase with a high ionic strength (1.0 M KCI) aqueous solution containing ethyl acetate. © 2006 Wiley Periodicals, Inc.
Fed‐batch cultivation of animal cells using different medium design concepts and feeding strategies
Authors: Xie Liangzhi , Wang Daniel I.C.
Published: August 2006

In animal cell cultivation, cell density and product concentration are often low due to the accumulation of toxic end‐products such as ammonia and lactate and/or the depletion of essential nutrients. A hybridoma cell line (CRL‐1606) was cultivated in T‐flasks using a newly devised medium feeding strategy. The goals were to decrease ammonia and lactate formation by the design of an initial medium which would provide a starting environment to achieve optimal cell growth. This was followed by using a stoichiometric equation governing animal cell growth and then designing a supplemental medium for feeding strategy used to control the nutritional environment. The relationship between the stoichiometric demands for glutamine and nonessential amino acids was also studied. Through stoichiometric feeding, nutrient concentrations were controlled reasonably well. Consequently, the specific production rate of lactate was decreased by fourfold compared with conventional fed‐batch culture and by 26‐fold compared with conventional batch culture. The specific production rate of ammonia was decreased by tenfold compared with conventional fed‐batch culture and by 50‐fold compared with conventional batch culture. Most importantly, total cell density and monoclonal antibody concentration were increased by five‐ and tenfold respectively, compared with conventional batch culture. © 2006 Wiley Periodicals, Inc.
A Facile Route to the Non‐IPR Fullerene Sc3N@C68: Synthesis, Spectroscopic Characterization, and Density Functional Theory Computations (IPR=Isolated Pentagon Rule)
Authors: Yang Shangfeng , Kalbac Martin , Popov Alexey , Dunsch Lothar
Published: August 2006

Owing to the unique feature of the non‐IPR D3 (isomer 6140) C68 cage (IPR=isolated pentagon rule), Sc3N@C68 has been attracting great interest in the fullerene community. Herein we report the first high‐yield synthesis of Sc3N@C68 by the “reactive gas atmosphere” method and its facile isolation by single‐step HPLC to a high purity (≥99 %). Thus, Sc3N@C68 is isolated in sufficient quantities for its further spectroscopic characterization, while the high purity of the sample ensures the reliability of the spectroscopic data obtained. In particular, the electronic and vibrational structures of Sc3N@C68 were studied in detail experimentally and by theoretical computations. The assignment of the observed absorption bands to particular electronic transitions is given in detail on the basis of time‐dependent DFT computations. Vibrational spectroscopy of Sc3N@C68 reveals good agreement between the measured spectra and the theoretically calculated spectra. A detailed assignment of the vibrational modes, including the Sc3N cluster modes, cage modes, and vibrations of the adjacent pentagons are discussed. This study reveals that the effect of Sc3N encapsulation in the cage is much more complicated than just a formal transfer of six electrons. Consequently the electronic and vibrational spectra of the carbon cage in Sc3N@C68 cannot be adequately understood on the basis of a C686− cage alone.
Silver Coordination Complexes as Room‐Temperature Multifunctional Materials
Authors: Pucci Daniela , Barberio Giovanna , Bellusci Anna , Crispini Alessandra , Donnio Bertrand , Giorgini Loris , Ghedini Mauro , La Deda Massimo , Szerb Elisabeta Ildyko
Published: August 2006

A series of bischelate ionic silver complexes [Ag(L*)2][X] was prepared by complexation of a newly synthesized 2,2′‐bipyridine containing chiral alkoxy chains in the 4,4′ positions. The appropriate choice of the construction motifs allows the preparation of new materials in which several functionalities can be introduced. Indeed, when the anion X−is a triflate or a dodecylsulfate group, the right combination of intermolecular interactions promotes the production of liquid crystalline mesophases. Therefore, the presence of coordinating anions, which drives the supramolecular assembly, is essential to generate, at the same time, room‐temperature columnar hexagonal mesomorphism, the columnar helical supramolecular structure, and excimeric emission.
Tetrahedrane—Dossier of an Unknown
Authors: Nemirowski Adelina , Reisenauer Hans Peter , Schreiner Peter R.
Published: August 2006

To probe whether tetrahedrane should be isolable the thermodynamics and kinetics of C4H4 singlet and triplet structures were studied extensively at the CCSD(T)/cc‐pVTZ//CCSD(T)/cc‐pVDZ, CCSD(T)/cc‐pVDZ, CCSD(T)/cc‐pVDZ//B3 LYP/6–311G**, and B3 LYP/6–311G** levels of theory. The reaction of cyclopropene with atomic carbon, which was previously suggested to involve tetrahedrane as a reactive intermediate, was re‐examined experimentally with low‐temperature matrix‐isolation techniques. While experimental and theoretical results exclude the intermediacy of tetrahedrane in the above reaction, it is predicted to be an isolable molecule. Among the many C4H4 species, we pay special attention to the electronic effects on the ground state multiplicity of the respective carbenes.
Modified Pyridine‐Bis(imine) Iron and Cobalt Complexes: Synthesis, Structure, and Ethylene Polymerization Study
Authors: Pelascini Frédéric , Wesolek Marcel , Peruch Frédéric , Lutz Pierre J.
Published: August 2006

In this paper, we describe the synthesis of two new pyridine‐bis(imine)s {4‐chloro‐2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine and 2,6‐bis[1‐(2,6‐dimethylcyclohexylimino)ethyl]pyridine} and their complexation with iron and cobalt dichloride. The solid‐state structure of the iron complexes was solved and found to be very close to catalysts already described by Brookhart and Gibson. Their ability to polymerize ethylene was investigated after activation with MAO. It was thus shown that the substitution of the pyridine ring of the ligand is unfavorable: their catalytic activity is rather low. The replacement of the aromatic rings on the imine functions by dimethylcyclohexyl rings resulted in a complete loss of activity of the iron complex for oligomerization and polymerization of ethylene. With the cobalt analog, polymerization of ethylene could be achieved under the same conditions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis, Structures, and Luminescent Properties of d10 Group 12 Metal Complexes with Substituted 2,2′‐Bipyridine Ligands
Authors: Liu Xiao‐ming , Mu Xiao‐yue , Xia Hong , Ye Ling , Gao Wei , Wang Hao‐yu , Mu Ying
Published: August 2006

Four d10 group 12 metal complexes, 6‐(2‐methoxyphenyl)‐2,2′‐bipyridinezinc dichloride (2a), ‐mercury dichloride (2b), 6‐[2‐(dimethylamino)phenyl]‐2,2′‐bipyridinezinc dichloride (2c), and ‐mercury dichloride (2d), were synthesized and the structures determined by single‐crystal X‐ray crystallography. Complexes 2a and 2b are four‐coordinate and adopt a distorted tetrahedral geometry, while complexes 2c and 2d are five‐coordinate with a distorted trigonal bipyramidal geometry for the metal center. Luminescent properties of complexes 2a–2d in both solution and the solid state were studied. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Site‐Specific Recognition of Dipeptides Through Non‐Covalent Inter‐Ligand Interactions for the Hydrolysis of Dipeptide to Amino Acid Ligands Mediated by Ternary Cobalt(III) Complexes
Authors: Jitsukawa Koichiro , Mabuchi Tomohiro , Einaga Hisahiko , Masuda Hideki
Published: August 2006

Molecular recognition of dipeptide (DP) compounds is performed with a ternary cobalt(III) complex containing thetripodal tetradentate ligand bis‐N,N‐carboxymethyl‐L‐phenylalanine (H3bcmpa). The coordination structure of the complex [Co(bcmpa)(dp)]– (1–14) was spectroscopically assigned by UV/Vis, CD, and 1H NMR spectroscopic methods. Site‐specific recognition of the dipeptide on the ternary complex is achieved by various weak, non‐covalent, inter‐ligand interactions, such as hydrogen bonding, steric repulsion, and electrostatic interaction, etc. Some dipeptides having C‐terminal aromatic side‐chains also demonstrate inter‐ligand CH–π interactions between the aromatic ring and the α‐hydrogen of bcmpa. Coordination of the N‐terminal nitrogen atom of the dipeptide to cobalt at the trans(N)‐position to the tertiary nitrogen of bcmpa in the octahedral geometry provides an aminopeptidase model. Under slightly alkaline conditions, the dipeptide ligand of some of these complexes is cleaved to give the ternary complex, [Co(bcmpa)(aa)]– (aa = amino acidato). The rate for the hydrolysis of dipeptide decreases upon increasing the steric bulkiness of the C‐terminal side‐chain. In the cases of the ternary complexes [Co(bcmpa)(gly‐phe)]– (6 and 11), which have C‐terminal L‐ or D‐phenylalanine, the hydrolysis of gly‐phe to gly was completely prevented. On the other hand, the ternary cobalt(III) complexes [Co(bcmga)(gly‐phe)]– (18 and 19), where H3bcmga (bis‐N,N‐carboxymethyl‐L‐glutamic acid) is the more hydrophilic tripodal ligand, give a small amount of the corresponding cleavage product [Co(bcmga)(gly)]–. The hydrophobic sphere generated around the metal complex in 6 and 11 regulates approach of OH– ion to the amide carbonyl group. Multi‐site interactions mediated on the ternary complexes are available for the design of an artificial hydrolysis enzyme. This is the first report describing the substrate‐specific cleavage of peptides using a simple enzyme model complex. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Substituted Cyclobutenes, Their Preparation, and Their Versatility in Synthesis
Authors: Gauvry Noëlle , Lescop Cyrille , Huet François
Published: August 2006

Cyclobutene compounds are interesting intermediates that have proven to be useful in organic synthesis. This review mainly deals with preparations and reactions of some cyclobutenes disubstituted at the allylic position. Several possibilities in the area of the thermal ring opening of these compounds into dienes are explored, and some features of the selectivity of addition reactions to cyclobutenes to afford tri‐ or tetrasubstituted cyclobutanes are also examined. When suitable leaving groups are present, these cyclobutanes can yield cyclopropanes stereospecifically through ring contraction or bicyclic compounds through intramolecular cyclization. Some applications to the synthesis of nucleoside analogues and of bicyclic compounds are pointed out. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Intramolecular Nonbonding Interactions between Selenium and Sulfur – Spectroscopic Evidence and Importance in Asymmetric Synthesis
Authors: Tiecco Marcello , Testaferri Lorenzo , Santi Claudio , Tomassini Cristina , Santoro Stefano , Marini Francesca , Bagnoli Luana , Temperini Andrea , Costantino Ferdinando
Published: August 2006

Chiral sulfur‐containing electrophilic selenium reagents can be employed to effect efficient asymmetric syntheses. Spectroscopic and chemical evidence demonstrate that the observed high selectivity of the asymmetric reactions is associated with a nonbonding selenium–sulfur interaction that is present in both the crystalline form and in solution. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)