bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biomechanical and ultrastructural comparison of cryopreservation and a novel cellular extraction of porcine aortic valve leaflets
Authors: Courtman David W. , Pereira Christopher A. , Omar Sue , Langdon Shari E. , Lee J. Michael , Wilson Gregory J. 
Published: May 2005

AbstractHeart valve substitutes of biological origin often fail by degenerative mechanisms. Many authors have hypothesized that mechanical fatigue and structural degradation are instrumental to in vivo failure. Since the properties of the structural matrix at implantation may predetermine failure, we have examined the ultrastructure, fracture, mechanics, and uniaxial high‐strain‐rate viscoelastic properties of: (1) fresh, (2) cryopreserved, and (3) cellular extracted porcine aortic valve leaflets. The cellular extraction process is being developed in order to reduce immunological attack and calcification. Cryopreservation causes cellular disruption and necrotic changes throughout the tissue, whereas extraction removes all cells and lipid membranes. Both processes leave an intact collagen and elastin structural matrix and preserve the high‐strain‐rate viscoelastic characteristics of the fresh leaflets. Extraction does cause a 20% reduction in the fracture tension and increases tissue extensibility, with the percent strain at fracture rising to 45.3 ± 4 (mean ± SEM) from 31.5 ± 3 for fresh leaflets. However, extraction does preserve matrix structure and mechanics over the physiological loading range. Glutaraldehyde fixation produces increased extensibility, increased elastic behavior, and, when applied to extracted leaflets, it causes a marked drop in fracture tension, to 50% of that for fresh leaflets. The combination of extraction and fixation may lead to early degenerative failure. The cellular extraction technique alone may be a useful alternative to glutaraldehyde fixation in preparing bioprosthetic heart valves. © 1995 John Wiley & Sons, Inc.
Polyvinylidene fluoride (PVDF) as a biomaterial: From polymeric raw material to monofilament vascular suture
Authors: Laroche Gaétan , Marois Yves , Guidoin Robert , King Martin W. , Martin Louisette , How Thien , Douville Yvan 
Published: May 2005

AbstractThis study identified the effects of various manufacturing processes on the crystalline microstructure, mechanical properties, and biocompatibility of a polyvinylidene fluoride (PVDF) suture. To achieve this, changes in the crystalline microstructure and the tensile behavior of PVDF monofilaments were monitored in vitro after different thermal processing, coloration, and sterilization treatments. In addition, the in vivo biocompatibility of the manufactured and sterilized PVDF suture was assessed by using it to anastomose a preclotted polyester vascular prosthesis as a thoracoabdominal bypass in a series of dogs. The tissue response was followed by histologic and scanning electron microscopy over implantation periods ranging from 4 h to 6 months. Differential scanning calorimetry and infrared spectroscopy (FTIR‐ATR) showed that thermal processing and the addition of a coloring agent had a direct effect on modifying the crystalline microstructure and hence changing the mechanical properties. For example, thermal processing converted some of the α phase into the β and γ polymorphs, whereas coloration led only to a major increase in the β‐to‐α ratio. The tensile properties were found to be optimized when the relative proportion of the β and γ phases combined compared to the α form gave rise to an FTIR A509/A532 absorption ratio between 4.0 and 4.5. Sterilization was found to cause some modifications to the crystalline microstructure near the surface of the monofilaments, but it did not change their mechanical properties. Pathologic examination of the anastomotic regions after different periods of implantation revealed a minimal cellular response, with no mineralization, intimal hyperplasia, or excessive fibrous tissue reaction. This good biocompatibility, together with other desirable characteristics such as ease of manipulation and satisfactory mechanical strength, makes PVDF an attractive alternative monofilament suture material for cardiovascular surgery. © 1995 John Wiley & Sons, Inc.
Estimation of ideal mechanical strength and critical porosity of calcium phosphate cement
Authors: Ishikawa K. , Asaoka K. 
Published: May 2005

AbstractThe ideal mechanical strength and critical porosity of calcium phosphate cement (CPC) were estimated to help determine ways to improve its properties. CPC at various porosities was made by packing CPC paste, at various powder‐to‐liquid (P/L) ratios (2.0–6.0), into a mold under various pressures (0–173 MPa). The mechanical strength of CPC, in terms of diametral tensile strength (DTS), increased with decreases in porosity. Intercrystalline fracture was observed in specimens made without the application of pressure, while fracture within the crystals increased with the packing pressure. These observations support the application of the relationship between DTS and porosity in fractographic equations. The ideal wet DTS and critical porosity of CPC were estimated to be 102 MPa and 63%, respectively. The minimum porosity of the currently used CPC was approximately 26–28%, even when it was packed under 173 MPa, and the maximum DTS value was thus approximately 13–14 MPa. Because reducing the porosity of currently used CPC would be difficult, we conclude that in CPC‐related research, we should focus on ways in which to accelerate bone‐replacing behavior, in addition to improving the mechanical strength of CPC. © 1995 John Wiley & Sons, Inc.
Oxidative and hydrolytic stability of a novel acrylic terpolymer for biomedical applications
Authors: Veleva Anka N. , Khan Saad A. , Cooper Stuart L. 
Published: May 2005

AbstractOxidative and hydrolytic biostability assessment was carried out on a novel acrylic material made of hexamethyl methacrylate (HMA), methyl methacrylate (MMA), and methacrylic acid (MAA). To simulate the in vivo microenvironment, solutions of H2O2/CoCl2 and buffered solutions of cholesterol esterase (CE) and phospholipase A2 (PLA) were used. As controls, film specimens were incubated in deionized water. Samples were incubated in these solutions at 37°C for 10 weeks before physical and mechanical properties were evaluated by size exclusion chromatography (SEC), 1H‐ nuclear magnetic resonance (1H‐NMR), acid‐base titration, and Instron tensile testing. The results from this study indicate excellent biostability of HMA‐MMA‐MAA terpolymers and thus their potential for use in biomedical devices for long‐term implantation. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
ATP‐dependent protein kinases in bacteria
Authors: Cozzone Alain J. 
Published: May 2005

AbstractProtein phosphorylation has been shown to occur in over fifty different bacterial species and, therefore, seems to be a universal device among prokaryotes. Most of the protein kinases responsible for this modification of proteins share the common property of using adenosine triphosphate as phosphoryl donnor. However, they differ from one another in a number of structural and functional aspects. Namely, they exhibit a varying acceptor amino acid specificity and can be classified, on this basis, in three main groups: protein‐histidine kinases, protein‐serine/threonine kinases and protein‐tyrosine kinases. © 1993 Wiley‐Liss, Inc.
The role of phosphorylation of HPr, a phosphocarrier protein of the phosphotransferase system, in the regulation of carbon metabolism in gram‐positive bacteria
Authors: Reizer Jonathan , Romano Antonio H. , Deutscher Josef 
Published: May 2005

AbstractHPr of the Gram‐positive bacterial phosphotransferase system (PTS) can be phosphorylated by an ATP‐dependent protein kinase on a serine residue or by PEP‐dependent Enzyme I on a histidyl residue. Both phosphorylation events appear to influence the metabolism of non‐PTS carbon sources. Catabolite repression of the gluconate (gnt) operon of B. subtilis appears to be regulated by the former phosphorylation event, while glycerol kinase appears to be regulated by the latter phosphorylation reaction. The extent of our understanding of these processes will be described. © 1993 Wiley‐Liss, Inc.
Response regulation in bacterial chemotaxis
Authors: Lukat Gudrun S. , Stock Jeffry B. 
Published: May 2005

AbstractThe signal transduction system that mediates bacterial chemotaxis allows cells to moduate their swimming behavior in response to fluctuations in chemical stimuli. Receptors at the cell surface receive information from the surroundings. Signals are then passed from the receptors to cytoplasmic chemotaxis components: CheA, CheW, CheZ, CheR, and CheB. These proteins function to regulate the level of phosphorylation of a response regulator designated CheY that interacts with the flagellar motor switch complex to control swimming behavior. The structure of CheY has been determined. Magnesium ion is essential for activity. The active site contains highly conserved Asp residues that are required for divalent metal ion binding and CheY phosphorylation. Another residue‐at the active site, Lys109, is important in the phosphorylation‐induced conformational change that facilitates communication with the switch complex and another chemotaxis component, CheZ. CheZ facilitates the dephosphorylation of phospho‐CheY. Defects in CheY and CheZ can be suppressed by mutations in the flagellar switch complex. CheZ is thought to modulate the switch bias by varying the level of phospho‐CheY. © 1993 Wiley‐Liss, Inc.
Development and implementation of a multisite evaluation for the Women, Co‐Occurring Disorders and Violence Study
Authors: Giard Julienne , Hennigan Karen , Huntington Nicholas , Vogel Wendy , Rinehart Debbie , Mazelis Ruta , Nadlicki Terri , Veysey Bonita M. 
Published: May 2005

AbstractIn this article we describe the development and implementation of the Substance Abuse and Mental Health Services Administration's (SAMHSA's) multisite Women, Co‐Occurring Disorders and Violence Study (WCDVS), highlighting some of the challenges encountered, decisions made, and lessons learned. Four themes are discussed. First, the unique contributions of the consumer/survivor/recovering (C/S/R) women to the research process are described through instances where their knowledge and advocacy were clearly influential. Second, the solutions chosen to address research design challenges are recounted, as are the ways in which these choices played out. Third, the procedures for standardizing recruitment, data collection, and data management across sites are described. Finally, the strategies employed by the nine sites to retain contact with this challenging population are reviewed and successful techniques are highlighted. © 2005 Wiley Periodicals, Inc. J Comm Psychol 33: 411–427, 2005.
Racial/ethnic differences in social vulnerability among women with co‐occurring mental health and substance abuse disorders: Implications for treatment services
Authors: Amaro Hortensia , Larson Mary Jo , Gampel Joanne , Richardson Erin , Savage Andrea , Wagler Debra 
Published: May 2005

AbstractLittle attention has been given to racial/ethnic differences in studies of co‐occurring disorders among women. In this article, we present findings from analyses conducted on the influence of racial/ethnic differences on the demographic and clinical profiles of 2,534 women in the Substance Abuse and Mental Health Services Administration‐sponsored Women, Co‐Occurring Disorders and Violence Study. Black and Hispanic women demonstrated more disadvantaged economic and social life conditions than White women. After controlling for socioeconomic differences, Hispanic women experienced more criminal justice involvement than others did, and both Black and Hispanic women were more likely to be exposed to community violence although they did not demonstrate more severe clinical symptoms than White women. In the design and delivery of services racial/ethnic differences should be considered, and research questions regarding underlying explanatory factors raised. © 2005 Wiley Periodicals, Inc. J Comm Psychol 33: 495–511, 2005.
Recent advances in rational gene transfer vector design based on poly(ethylene imine) and its derivatives
Authors: Neu Michael , Fischer Dagmar , Kissel Thomas 
Published: May 2005

AbstractThe continually increasing wealth of knowledge about the role of genes involved in acquired or hereditary diseases renders the delivery of regulatory genes or nucleic acids into affected cells a potentially promising strategy. Apart from viral vectors, non‐viral gene delivery systems have recently received increasing interest, due to safety concerns associated with insertional mutagenesis of retro‐viral vectors. Especially cationic polymers may be particularly attractive for the delivery of nucleic acids, since they allow a vast synthetic modification of their structure enabling the investigation of structure‐function relationships. Successful clinical application of synthetic polycations for gene delivery will depend primarily on three factors, namely (1) an enhancement of the transfection efficiency, (2) a reduction in toxicity and (3) an ability of the vectors to overcome numerous biological barriers after systemic or local administration. Among the polycations presently used for gene delivery, poly(ethylene imine), PEI, takes a prominent position, due to its potential for endosomal escape. PEI as well as derivatives of PEI currently under investigation for DNA and RNA delivery will be discussed.This review focuses on structure‐function relationships and the physicochemical aspects of polyplexes which influence basic characteristics, such as complex formation, stability or in vitro cytotoxicity, to provide a basis for their application under in vivo conditions. Rational design of optimized polycations is an objective for further research and may provide the basis for a successful cationic polymer‐based gene delivery system in the future. Copyright © 2005 John Wiley & Sons, Ltd.
Preparative gas chromatography with glass capillary columns
Authors: Roeraade J. , Enzell C. R. 
Published: May 2005

AbstractThe present paper describes an automated system for preparative gas chromatography with glass capillary columns, controlled by a microprocessor. The effluent from the capillary column is divided by a pneumatically controlled splitter and any desired split ratio between traps and detector can be obtained. Moreover, a second pneumatic control allows instantaneous change‐over to a different split ratio, thus minimizing loss of material during collection.The effluent containing the compounds of interest is passed through a multiple manifold and collected in coiled glass capillary traps. To ensure maximum trapping efficiency even for very small amounts of material, the inner walls of the capillary traps are wetted with a suitable solvent, which gives a quantitative recovery of micro‐ and nanogram amounts of material.After repetitive sampling, sufficient amounts of material can be obtained for NMR spectroscopy and possibilities exist to enrich trace components with the aid of a double column system. Two examples of such applications are given, employing mixtures of both synthetic and natural origin.
Selective determination of substituted PAH in aerosols using liquid CO2‐extraction, HPLC prefractionation on chemically activated silica, and HRGC combined with negative ion mass spectrometry
Authors: Stray H. , Manø S. , Mikalsen A. , Oehme M. 
Published: May 2005

AbstractA method is described which allows the determination of different substituted polycyclic aromatic hydrocarbons (PAH) such as NO2‐PAH, carbazoles, keto‐PAH, and aza‐arenes in aerosol samples. Liquid CO2‐extraction is used to minimize the loss of reactive compounds. High performance liquid chromatography on chemically activated silica is employed to prefractionate the samples into subfractions with a minimum of overlap between different PAH compound classes. Both electron capture detection and negative ion chemical ionization combined with capillary gas chromatography are used for identification and quantification. The latter method also allows distinction between isomers with different toxic properties when N2O/CH4 reaction gas mixtures are used. Selectivity for tetrachlorodibenzo‐p‐dioxins as against pesticides and polychlorinated biphenyls can be improved by this technique. The applicability of the method is critically discussed and different examples are given.
Practical aspects of mixed mobile phases in capillary supercritical fluid chromatography
Authors: Fields S. M. , Markides K. E. , Lee M. L. 
Published: May 2005

AbstractStudies of mixed mobile phases in supercritical fluid chromatography must include consideration of a number of factors. Phase equilibria and critical parameters of a mixed fluid are very important in both the solvent delivery system and in the chromatographic column. The effects of pressure and temperature on retention with mixed mobile phases were studied and compared to estimated density values. System equilibration times with regard to pressure, temperature, and composition were studied. A mixed mobile phase was applied to the analysis of a high‐molecular‐weight metalloporphyrin.
Classification of polymer batch variations by dynamic headspace/capillary gas chromatography/multivariate data analysis
Authors: Hagman A. , Karlsson K. , Jacobsson S. 
Published: May 2005

AbstractGas chromatographic profiles have been generated from different batches of a polypropylene/polyethylene copolymer. The profiles generated from polymer pellets have been obtained by dynamic headspace/capillary gas chromatography analysis. Initially 10 to 40 peaks were chosen at random from the quantitative reports and transferred to a data table. After appropriate scaling the table has been analyzed by a multivariate statistic program, SIMCA (Soft Independent Modeling of Class Analogy) a pattern recognition technique. The method has been used to differentiate batches according to sensory qualities of the final packaging product and changes in polymer peilet production.
Quantitative determination of airbone C1‐ and C2‐halocarbons by GC/ECD
Authors: Frank H. , Frank W. 
Published: May 2005

AbstractThe atmospheric levels of C1‐ and C2‐halocarbons are determined by trapping on an adsorbent, thermodesorption, cryofocussing, gas chromatographic separation on a thick‐film capillary, and electron‐capture detection. The various aspects relevant to reliability and accuracy are discussed, such as type of adsorbent, range of detector response, and levels of contaminants present in blanks. These in turn have implications for optimum sample size and amount of adsorbent. The adopted method is suitable for routine analysis of airborne halocarbons at variable locations. The air concentrations of C1‐ and C2‐halocarbons on the ground of mountain forests are similar to those in cities, a fact which supports the hypothesis that chlorocarbons are involved in the initiation of a phytotoxicological phenomenon commonly referred to as “forest decline”.
CGC analysis of the essential oils of citrus fruits on 100 μm i.d. columns
Authors: Lancas F. , David F. , Sandra P. 
Published: May 2005

AbstractNarrow bore columns (100 μm) have successfully been applied in the analysis of commercial lemon oils. On these columns, high resolution is obtained in a short analysis time. Different Brazillian lemon oils are characterized qualitatively and quantitatively.
Enantiomer separation of 2‐halocarboxylic acid esters by chiral complexation gas chromatography
Authors: Schurig V. , Ossig A. , Link R. 
Published: May 2005

AbstractThe enantiomer separation of 2‐halocarboxylic acid esters on two chiral nickel(II) bis‐((perfluoroacyl)terpeneketonates) by complexation gas chromatography is described. The quantitative entiomer separation of branched 2‐halocarboxylic acid esters is achieved with nickel (II) bis (3‐(heptafluorobutanoyl)(1R, 2S)‐pinan‐4‐onate) 1 while unbranched 2‐halocarboxylic acid esters are preferably separated on nickel(II) bis(3‐(heptafluorobutanoyl)‐(1S)‐10‐methylenecamphorate) 2. The metal chelates 1 and 2 are accessible in both enantiomeric forms allowing the determination of the enantiomeric excess (ee) effective and reliable.
Determination of Broxaterol in Plasma by Coupled HPLC‐GC
Authors: Gianesello V. , Bolzani L. , Brenn E. , Gazzaniga A. 
Published: May 2005

AbstractFor the analysis of broxaterol 1‐(3‐bromoisoxazol‐5‐yl)‐2‐(tert‐butylamino)ethanol in human plasma and urine an on‐line HPLC‐GC apparatus was used applying the “concurrent solvent evaporation” technique described in previous studies. Broxaterol is quantitatively determined by capillary GC with ECD detection, after extraction from plasma and derivatization. The detection limit of 0.03 ng/ml permits pharmacokinetic studies in man after oral and intravenous administration of the drug.
Determination of the calcium entry blocker verapamil in plasma by capillary gas chromatography with on‐column injection
Authors: Rosseel M. T. , Belpaire F. M. 
Published: May 2005

AbstractA specific, sensitive, and accurate assay for quantitation of verapamil has been developed. The method involves a single extraction step with n‐heptane, followed by evaporation at room temperature under nitrogen. 0.1 μl of the extract was injected into a capillary column coated with crosslinked 5% phenylmethylsilicone. The column separated verapamil, norverapamil, and its internal standard within 15 minutes using temperature programming from 90 to 290°C. The lower limit of detection was 1 ng/ml for verapamil. The calibration curve was linear in the concentration range (5–300 ng/ml). Plasma concentration data from dogs receiving intravenous verapamil infusion are presented.
High performance microcolumn exclusion chromatography of proteins and peptides
Authors: Gankina E. S. , Kever J. J. , Kostiuk I. O. , Saminsky A. E. , Belenkii B. G. 
Published: May 2005

AbstractA new method for the determination of the molecular weight of proteins and peptides has been developed. It is based on microcolumn exclusion chromatography in trifluoroacetic acid on silica gel sorbents of different porosities with a linear molecular‐weight calibration dependence in the range of 5 × 102 ‐ 7 × 104 Da. It was shown that in this eluent proteins and peptides adopt the random‐coil conformation and do not undergo hydrolysis for 2–3 days at room temperature.
GC column effluent splitter for problematic solvents introduced in large volumes: Determination of di‐(2‐ethylhexyl) phthalate in triglyceride matrices as an application
Authors: Pacciarelli B. , Müller E. , Schneider R. , Grob K. , Steiner W. , Fröhlich D. 
Published: May 2005

AbstractIntroduction of solutions of up to several milliliters by on‐column injection of large volumes or by coupled HPLC‐GC may cause problems with GC detectors (FID, AFID, MS). For instance, dichloromethane forms large amounts of hydrochloric acid and carbon black in FIDs.A column effluent splitter was developed for keeping the major portion of the solvent vapors away from the detector; approximately 99% of the vapor is vented while the remaining 1% of vapor is used for detecting the widths of the solvent peaks. During analysis, the split ratio is reversed by a strong increase of the resistance to the gas flow through the split exit line.The system was used for the determination of di‐(2‐ethylhexyl)‐phthalate (DEHP) in triglyceride matrices of various foods. Direct determination by HPLC is not sufficiently sensitive, whereas direct analysis by GC is hindered by the triglycerides. Solutions of fats or oils were pre‐separated on a silica column using dichloro‐methanelcyclohexane 1:l with addition of 0.05 % acetonitrile as eluent. The HPLC fraction containing the DEHP was transferred to GC through a loop‐type interface using concurrent solvent evaporation. Detection limits were around 0.1 ppm.