bluuebunny/crossref_metadata_2025_split huggingface dataset:
Loss of adenomatous polyposis coli in Bergmann glia disrupts their unique architecture and leads to cell nonautonomous neurodegeneration of cerebellar Purkinje neurons
Authors: Wang Xiaohong , Imura Tetsuya , Sofroniew Michael V. , Fushiki Shinji 
Published: March 2011

AbstractThe tumor suppressor adenomatous polyposis coli (APC) is a multifunctional protein that inhibits the Wnt/beta‐catenin signaling pathway and regulates the microtubule and actin cytoskeletons. Using conditional knockout (CKO) mice in which the APC gene is inactivated in glial fibrillary acidic protein (GFAP)‐expressing cells, we show a selective and critical role for APC in maintaining the morphology and function of cerebellar Bergmann glia, which are specialized astroglia that extend polarized radial processes from the Purkinje cell layer to the pial surface. APC‐CKO mice developed Bergmann glia normally until the accumulation of beta‐catenin started around postnatal day 10 (P10). Their radial fibers then became shortened with a marked reduction of branching collaterals and their cell bodies translocated into the molecular layer followed by loss of their pial contact and transformation into stellate‐shaped cells by P21. Purkinje neurons were normal in appearance and number at P21, but there was significant loss of Purkinje neurons and cerebellar atrophy by middle age. Outside the cerebellum, neither beta‐catenin accumulation nor morphological changes were identified in GFAP‐expressing astroglia, indicating region‐specific effects of APC deletion and an essential role for APC in maintaining the unique morphology of Bergmann glia as compared with other astroglia. These results demonstrate that loss of APC selectively disrupts the Bergmann glial scaffold in late postnatal development and leads to cerebellar degeneration with loss of Purkinje neurons in adults, providing another potential mechanism for region‐specific non‐cell autonomous neurodegeneration. © 2011 Wiley‐Liss, Inc.
Transoral laser surgery versus radiotherapy: Systematic review and meta‐analysis for treatment options of T1a glottic cancer
Authors: Abdurehim Yasin , Hua Zhang , Yasin Yalkun , Xukurhan Ayihen , Imam Ilham , Yuqin Fan 
Published: March 2011

AbstractBackgroundThe objective of this study was to conduct a systematic review and meta‐analysis to compare the oncologic and functional outcomes between transoral laser surgery (TLS) and radiotherapy (RT).MethodsAn electronic library search of the relevant English‐ and Chinese‐language literature was conducted. Potentially eligible articles were reviewed. Qualified articles were selected and evaluated.ResultsNo significant differences were identified between TLS and RT with respect to local control, overall survival, disease‐specific survival, and posttreatment voice quality. However, larynx preservation was significantly higher in patients initially treated with TLS than those initially treated with RT.ConclusionsThe approach for optimal treatment of T1a glottic cancer remains unanswered. This results from the relatively inconclusive evidence obtained from the current literature. Properly designed, prospective, randomized, or well‐controlled studies will be required. Similar methodologies for treatment and reporting need to be established to make a valid and meaningful comparison between studies. © 2011 Wiley Periodicals, Inc. Head Neck, 2012
Consideration of dosimetry in evaluation of ToxCast™ data
Authors: Aylward Lesa L. , Hays Sean M. 
Published: March 2011

ABSTRACTThe US Environmental Protection Agency (US EPA) Toxcast™ program has the stated goal of predicting hazard, characterizing toxicity pathways and prioritizing the toxicity testing of environmental chemicals through the use of in vitro high‐throughput screening (HTS) assays. This analysis integrates data from biomonitoring and from in vivo toxicity and pharmacokinetic studies to examine the physiological relevance of the tested and responding in vitro concentrations for five case study chemicals: triclosan, 2,4‐dichlorophenoxyacetic acid, perfluorooctanoic acid, monobutyl phthalate and mono‐2(ethylhexyl)phthalate. This analysis also examines the ToxCast™ phase 1 data set for approximately 50 chemicals belonging to four ‘common mechanism groups’ which have been the subject of cumulative risk assessments by the US EPA for both the pattern of key responses and the relative potencies of included chemicals compared with the in vivo relative potencies. Responding concentrations in vitro were generally in the range of serum or plasma concentrations associated with no‐observed to lowest‐observed effect levels for the case study chemicals, while available biomonitoring data demonstrating actual exposures were generally lower. ToxCast™ assay endpoints related to acetylcholinesterase (AChE) inhibition had low sensitivity for detecting organophosphate pesticides but good sensitivity for detecting N‐methyl carbamates. However, in vitro relative potencies did not correlate with in vivo potency. Both qualitative and quantitative predictive power is probably affected by the lack of comprehensive metabolic activity in most current in vitro systems explored in the ToxCast™ program, and this remains a fundamental challenge for high‐throughput toxicity screening efforts. Copyright © 2011 John Wiley & Sons, Ltd.
Reduction in fluoride‐induced genotoxicity in mouse bone marrow cells after substituting high fluoride‐containing water with safe drinking water
Authors: Podder Santosh , Chattopadhyay Ansuman , Bhattacharya Shelley 
Published: March 2011

ABSTRACTTreatment of mice with 15 mg l−1 sodium fluoride (NaF) for 30 days increased the number of cell death, chromosomal aberrations (CAs) and ‘cells with chromatid breaks’ (aberrant cells) compared with control. The present study was intended to determine whether the fluoride (F)‐induced genotoxicity could be reduced by substituting high F‐containing water after 30 days with safe drinking water, containing 0.1 mg F ions l−1. A significant fall in percentage of CAs and aberrant cells after withdrawal of F‐treatment following 30 days of safe water treatment in mice was observed which was highest after 90 days, although their levels still remained significantly high compared with the control group. This observation suggests that F‐induced genotoxicity could be reduced by substituting high F‐containing water with safe drinking water. Further study is warranted with different doses and extended treatment of safe water to determine whether the induced damages could be completely reduced or not. Copyright © 2011 John Wiley & Sons, Ltd.
Toxicokinetics of captan and folpet biomarkers in orally exposed volunteers
Authors: Berthet Aurélie , Bouchard Michèle , Danuser Brigitta 
Published: March 2011

ABSTRACTThe time courses of key biomarkers of exposure to captan and folpet was assessed in accessible biological matrices of orally exposed volunteers. Ten volunteers ingested 1 mg kg−1 body weight of captan or folpet. Blood samples were withdrawn at fixed time periods over the 72 h following ingestion and complete urine voids were collected over 96 h post‐dosing. The tetrahydrophthalimide (THPI) metabolite of captan along with the phthalimide (PI) and phthalic acid metabolites of folpet were then quantified in these samples. Plasma levels of THPI and PI increased progressively after ingestion, reaching peak values ~10 and 6 h post‐dosing, respectively; subsequent elimination phase appeared monophasic with a mean elimination half‐life (t½) of 15.7 and 31.5 h, respectively. In urine, elimination rate time courses of PI and phthalic acid evolved in parallel, with respective t½ of 27.3 and 27.6 h; relatively faster elimination was found for THPI, with mean t½ of 11.7 h. However, phthalic acid was present in urine in 1000‐fold higher amounts than PI. In the 96 h period post‐treatment, on average 25% of folpet dose was excreted in urine as phthalic acid as compared with only 0.02% as PI. The corresponding value for THPI was 3.5%. Overall, THPI and PI appear as interesting biomarkers of recent exposure, with relatively short half‐lives; their sensitivity to assess exposure in field studies should be further verified. Although not a metabolite specific to folpet, the concomitant use of phthalic acid as a major biomarker of exposure to folpet should also be considered. Copyright © 2011 John Wiley & Sons, Ltd.
Toxicokinetics of captan and folpet biomarkers in dermally exposed volunteers
Authors: Berthet Aurélie , Bouchard Michèle , Vernez David 
Published: March 2011

ABSTRACTTo better assess biomonitoring data in workers exposed to captan and folpet, the kinetics of ring metabolites [tetrahydrophthalimide (THPI), phthalimide (PI) and phthalic acid] were determined in urine and plasma of dermally exposed volunteers. A 10 mg kg−1 dose of each fungicide was applied on 80 cm2 of the forearm and left without occlusion or washing for 24 h. Blood samples were withdrawn at fixed time periods over the 72 h following application and complete urine voids were collected over 96 h post‐dosing, for metabolite analysis. In the hours following treatment, a progressive increase in plasma levels of THPI and PI was observed, with peak levels being reached at 24 h for THPI and 10 h for PI. The ensuing elimination phase appeared monophasic with a mean elimination half‐life (t½) of 24.7 and 29.7 h for THPI and PI, respectively. In urine, time courses PI and phthalic acid excretion rate rapidly evolved in parallel, and a mean elimination t½ of 28.8 and 29.6 h, respectively, was calculated from these curves. THPI was eliminated slightly faster, with a mean t½ of 18.7 h. Over the 96 h period post‐application, metabolites were almost completely excreted, and on average 0.02% of captan dose was recovered in urine as THPI while 1.8% of the folpet dose was excreted as phthalic acid and 0.002% as PI, suggesting a low dermal absorption fraction for both fungicides. This study showed the potential use of THPI, PI and phthalic acid as key biomarkers of exposure to captan and folpet. Copyright © 2011 John Wiley & Sons, Ltd.
Selective separation of n‐butanol from aqueous solutions by pervaporation using silicone rubber‐coated silicalite membranes
Authors: Ikegami Toru , Negishi Hideyuki , Sakaki Keiji 
Published: March 2011

AbstractBACKGROUND: To use butanol as a liquid fuel and feedstock, it is necessary to establish processes for refining low‐concentration butanol solutions. Pervaporation (PV) employing hydrophobic silicalite membranes for selective recovery of butanol is a promising approach. In this study, the adsorption behavior of components present in clostridia fermentation broths on membrane material (silicalite powder) was investigated. The potential of PV using silicone rubber‐coated silicalite membranes for the selective separation of butanol from model acetone–butanol–ethanol (ABE) solutions was investigated.RESULTS: The equilibrium adsorbed amounts of ABE per gram of silicalite from aqueous solutions of binary mixtures at 30 °C increased as follows: ethanol (95 mg) < acetone (100 mg) < n‐butanol (120 mg). The amount of butanol adsorbed is decreased by the adsorption of acetone and butyric acid. In the separation of ternary butanol/water/acetone mixtures, the enrichment factor for acetone decreased, compared with that in binary acetone/water mixtures. In the separation of a model acetone–butanol–ethanol (ABE) fermentation broth containing butyric acid by PV using a silicone rubber‐coated silicalite membrane, the permeate butanol concentration was comparable with that obtained in the separation of a model ABE broth without butyric acid. The total flux decreased with decreasing feed solution pH.CONCLUSION: A silicone rubber‐coated silicalite membrane exhibited highly selective PV performance in the separation of a model ABE solution. It is very important to demonstrate the effectiveness of PV in the separation of actual clostridia fermentation broths, and to identify the factors affecting PV performance. Copyright © 2011 Society of Chemical Industry
Rainfall variability in Congo‐Brazzaville: 1932–2007
Authors: Samba Gaston , Nganga Dominique 
Published: March 2011

AbstractThe interannual variability of rainfall amounts and rainy days is analysed from synoptic stations located in different climatic zones of Congo‐Brazzaville over the common period 1932–2007. The annual and seasonal rainfall evolution is appreciated using standardized indices. Trends examined were based on the non‐parametric Mann‐Kendall test (the major synoptic stations point out alternative periods of anomalies—positive and negative). A majority of negative anomalies is recorded during the 1930s and 1940s. The decade 1950 shows mainly positive anomalies with the exception of 1958 which records a general precipitation deficit all across Congo. The decade 1960 is characterized by precipitation excess over the whole Congo. The decades 1980 and 1990 experience the largest rainfall deficit (about 10–20% below the long‐term mean). The evolution of the precipitation at Brazzaville is particularly stable, although there are large positive anomalies during the 1990s. The transition between positive and negative anomalies decades is not uniform across Congo. The progressive non‐parametric Mann‐Kendall trend test shows that there is stability in the annual rainfall and rainy days over the southern area in the period 1932–2007. By contrast, the annual rainfall for the northern stations shows a significant decline since about the 1980s. In the south the decline is observable only in the evolution of the March–May seasonal rainfall. In most of the stations there is a precipitation increase during the September‐November rainy season. Copyright © 2011 Royal Meteorological Society
Dynamical problems in the theory of polymer solutions
Authors: Fixman Marshall 
Published: March 2011

AbstractQualitative discrepancies are found between what is predicted by available theory and what is actually observed, for several concentration regimes of the dynamical properties of polymer solutions. The difficulties are most severe, from the standpoint of experiment or simulation as well as theory, for the entanglement concentration regime. However, the classical problems of chain polymers in dilute solution are not fully understood. For example, the constants of proportionality that relate hydrodynamic radii to the radius of gyration, in the nondraining limit and in theta solvents, may not be universal constants. That is, the proportionality constants may vary with polymer and solvent species. Discrepancies between theory and experiment are discussed for the two different systems, dilute chains and semidilute rods. Speculation is offered on the resolution of these difficulties.
Environment induced changes in DNA structure
Authors: Baase Walter A. , Schellman John A. 
Published: March 2011

AbstractInvestigations over the past decade have disclosed that the structure of DNA in solution is far from uniform and static. The present view of DNA structure is that it is: 1) dynamically variable, displaying relatively large flexibility in both bending and torsional modes, 2) it is not perfectly helical because of sequence dependent departures from a regular helix and 3) it is capable of adopting entirely different conformations, including a switch in the sense of the helix as is the case for the B to Z transition, as well as new folding patterns as is the case for cation induced DNA collapse.One of the principal problems in the field today is the detection and evaluation of structural changes in solution. Many experimental techniques are in use and a number of these will be reviewed. The discussion includes models of flexible DNA, the structural aspects revealed by several experimental techniques, and results for a number of systems in which solution environment brings about changes in structure.
Synthetic membrane active polyelectrolytes in design of artificial immunogens and vaccines
Authors: Kabanov Victor A. 
Published: March 2011

AbstractChemical binding or strong complexing of individual antigens (proteins, polysaccharides) or antigenic determinants with non‐natural membrane active polyelectrolytes results in formation of effective immunogens with high protective properties. These artificial antigenic conjugates develop strong immunogenicity also in the absence of T‐cells. The strength of the immune response is not controlled by Ir‐genes. An antigenic moiety of a conjugate is responsible for its “focusing” on B‐lymphocytes of the proper clone. Linear polyion moiety being adsorbed on the cell membrane surface aggregates membrane proteins and induces nonspecific transmembrane ionic permeability. K+‐flux from the cell and Ca+2‐flux into the cell disturb cell homeostasis and thus, pull trigger mechanism of K+, Na+‐ATPase and Ca+2‐ATPase activity. Then the cell synthesizing apparatus starts to operate. The covalent conjugates of Salmonella typhimurium and influenza A‐virus individual antigens with synthetic polyelectrolytes seem to represent a new generation of vaccinating macromolecules.
Liquid crystal polymers 23. Steric and polar effects of large substituents in thermotropic aromatic polyesters with decamethylene spacers
Authors: Furukawa Akira , Lenz Robert W. 
Published: March 2011

AbstractA series of thermotropic aromatic polyesters based on a triad ester mesogenic unit containing an arylsulfonyl substituted hydroquinone group and a decamethylene spacer group was prepared. The large arylsulfonyl substituent was substituted in the para‐position with either electron donating or accepting groups to study the effect of steric and polar interactions on the thermal transitions of these polymers and on the thermodynamic parameters of their isotropization transitions. All polymers formed nematic melts, and a regular decrease in T1, ΔH1 and ΔS1 was observed with increasing molecular radius of the substituted hydroquinone group. However, a polarity or polarizability effect was superimposed on these relationships. Model compounds containing the same aromatic ester triad were prepared and their thermotropic properties were compared to those of the polymers. Essentially identical effects were observed for both.
Polyurethane elastomers from tdi and castor oil
Authors: Cuadrado T. R. , Williams R. J. J. 
Published: March 2011

AbstractPolyurethane elastomers were prepared by reacting castor oil with toluene diisocyanate (TDI) in pure (80:20) and crude (TDI R) grades. Different elastomers were prepared by using several stoichiometric imbalances, always in defect of NCO groups. Their characterization involved the determination of the glass transition temperature (TMA), the sol fraction (extraction with toluene) and the concentration of elastically active network chains (swelling in benzene). Experimental results were compared with theoretical predictions resulting from a statistical model of the network formation.
Applicability of the configurational analysis to some problems of interest in polymer science
Authors: Riande Evaristo 
Published: March 2011

AbstractComparison between theoretical and experimental values of configuration dependent properties of polymers is used to estimate the values of the conformational energies associated with the rotational states of molecular chains. It is shown that the critical interpretation of the configurational properties of the polymers obtained by cationic polymerization of heterocycles, may be an useful tool to elucidate the ring‐opening mechanisms. The influence of the molecular flexibility in both the glass transition temperature and melting temperature of polymers is discussed in terms of the configurational entropy.
Control of particle size distribution in latices through periodic operation of continuous emulsion polymerization reactors
Authors: Gugliotta L. M. , Meira G. R. 
Published: March 2011

AbstractA method is proposed which allows to obtain latices with prespecified number particle size distributions (NPSD), with the only restriction that the said distributions must be monotonically descendent. To this effect, the forced periodic operation of the total feed flow into a continuous stirred‐tank reactor (CSTR) is considered. The method is limited to emulsion polymerizations occurring within intervals 1 and 2 of Harkins' mechanism (1), and verifying kinetics of case II (2,3,4). Furthermore, because the procedure has been developed through a steady state (SS) model, the method is strictly valid in the limit of very low frequencies of oscillation. The technique is illustrated by means of a numerical example.
Addition reactions of carbocations with alkenes: Studies on the mechanism of carbocationic polymerization
Authors: Mayr Herbert , Pock Rudolf , Schneider Reinhard 
Published: March 2011

AbstractIn certain cases, Lewis acid catalyzed addition reactions of alkyl halides with alkenes terminate at the 1:1 product stage. This telomerization reaction has been employed to study the efficiency of initiating systems of carbocationic polymerization and the relative reactivities of alkenes towards carbenium ions. A direct determination of addition rate constants is possible in some cases.
Vinyl ethers with a functional group: Living cationic polymerization and synthesis of monodisperse polymers
Authors: Higashimura Toshinobu , Aoshima Sadahito , Sawamoto Mitsuo 
Published: March 2011

AbstractThe living cationic polymerization of vinyl ethers (VEs) having a (polar) functional pendant has been achieved by the hydrogen iodide/iodine (HI/I2) initiating system to give polymers with a very narrow molecular weight distribution (MWD) (Mw/Mn ≤ 1.2). The functional pendants include benzyl, saturated or unsaturated ester, (poly) oxyethylene, and substituted phenoxyl groups. Although these polar groups often disturb cationic vinyl polymerization by inducing chain transfer and termination, the HI/I2 initiator cleanly polymerized the “functionalized” VEs without side reactions, mostly in nonpolar media at low temperatures below −15 °C. The HI/I2‐initiated living polymerization also provided facile methods to synthesize new functional polymers, including water‐soluble polymers, macromolecular amphiphiles, and macromers, all having a narrow MWD. The simplest example is the living polymerization of VEs carrying an oxyethylene chain [‐(CH2CH2O)n‐R] as pendant, which directly yields water‐soluble polymers. The debenzylation of poly(benzyl VE) prepared with HI/I2 led to poly(vinyl alcohol). Polymers of the saturated ester‐containing monomers (2‐acetoxyethyl and 2‐benzoyloxyethyl VEs) were readily hydrolyzed into poly (2‐hydroxyethyl VE), soluble in water and swellable in methanol. This lead was extended to the synthesis of a new amphiphile, poly(cetyl VE‐b‐2‐hydroxyethyl VE), from a block copolymer of cetyl and 2‐acetoxyethyl VEs prepared by their sequential living polymerization initiated with HI/I2. An adduct between HI and 2‐vinyloxyethyl methacrylate [CH3‐CH(I)‐OCH2CH2OCOC(CH3) =CH2] was found to initiate living polymerizations of VEs in the presence of iodine; the products were methacrylate‐type macromers carrying a poly(VE) side chain with a narrow chain‐length distribution.
Some new examples of cationic polymerization
Authors: Schulz Rolf C. , Eifel Heinz‐Werner , Perner Thomas , Mühlbach Klaus 
Published: March 2011

AbstractSynthesis and properties of cis‐and trans‐methoxyvinyl chloride (MVC) are described. magnified imageBoth of these monomers can be polymerized with cationic initiators. From the 13C‐NMR spectra it was concluded, that poly‐(trans‐MVC) is mainly threo‐diisotactic. Copolymerization of cis‐MVC with for instance trans‐MVC or styrene or 1,3‐dioxolane is also described.The ring‐opening polymerization of 2‐phenyl‐2‐oxazoline under different conditions was investigated. magnified imageThe molecular weights, determined by light‐scattering and GPC are in the range between 10 000 and 350 000. A[η] ‐M‐ equation was derived. By hydrolysis with hydrochlorid acid high molecular weight poly(iminoethylene) was obtained.The ring‐opening polymerization of 1‐azabicyclooctane [4.2.0] (conidine) with different catalysts as well as the properties of the polymers were studied in detail. magnified imageBy means of a “mixed‐mechanism technique” well defined styrene‐conidine diblock copolymers are available.