bluuebunny/crossref_metadata_2025 huggingface dataset:
Opsonization of polyethylene wear particles regulates macrophage and osteoblast responses in vitro
Authors: Elfick A.P.D. , Green S.M. , McCaskie A.W. , Birch M.A.
Published: September 2004

The cellular reaction to wear debris may result in the failure of an artificial joint's fixation to the skeleton. The influence of debris opsinization on cell activity has received little attention. This study seeks to establish whether different proteinaceous culture environments may invoke variant cellular responses to debris challenge. Consideration of the zeta potential of a low density polyethylene particle group and an ex vitro ultrahigh molecular weight polyethylene particle group revealed that the nature of the protein adsorbants is related to the concentration of the proteins in solution. Furthermore, the composition of the adsorbed layer was shown to vary with the spectra of proteins in solution. In standard cell culture conditions zeta potential approached zero, indicating the high probability of particle agglomeration. Cell challenge studies with U937 macrophages showed that BSA and FCS protein adsorption mediated increased cell adhesion, while bovine IgG showed little change over control values. No changes in behavior of osteoblastic cells were observed in similar experiments. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 244–251, 2004
Somatic gene targeting with RNA/DNA chimeric oligonucleotides: an analysis with a sensitive reporter mouse system
Authors: Ino Asami , Yamamoto Seiji , Kaneda Yasufumi , Kobayashi Ichizo
Published: September 2004

Background

Targeted gene correction provides a potentially powerful method for gene therapy. RNA/DNA chimeric oligonucleotides were reported to be able to correct a point mutation with a high efficiency in cultured rodent cells, in the body of mice and rats, and in plants. The efficiency of correction in the liver of rats was claimed to be as high as 20% after tail‐vein injection. However, several laboratories have failed to reproduce the high efficiency.

Methods

In order to sensitively detect and measure sequence changes by the chimeric oligonucleotides, we used Muta™Mouse, a transgenic mouse system for mutation detection in vivo. It carries, on its chromosome, multiple copies of the lambda phage genome with the lacZ+ gene. Two chimeric oligonucleotides were designed to make a point mutation at the active site of the LacZ gene product. They were injected into the liver with HVJ liposomes, which were demonstrated to allow reliable gene delivery. One week later, DNA was extracted from the liver, and lambda::lacZ particles were recovered by in vitro packaging. The lacZ‐negative phage was detected by selection with phenyl‐beta‐D‐galactoside.

Results

The mutant frequency of the injected mice was at the same level as the control mouse (∼1/10000). Our further restriction analysis and sequencing did not detect the designed mutations.

Conclusions

Gene correction frequency in mouse liver by these oligonucleotides was shown to be less than 1/20000 in our assay with the Muta™Mouse system. Copyright © 2004 John Wiley & Sons, Ltd.
Production of lentiviral vectors by transient expression of minimal packaging genes from recombinant adenoviruses
Authors: Kuate Seraphin , Stefanou Daniela , Hoffmann Dennis , Wildner Oliver , Überla Klaus
Published: September 2004

Background

The potential of lentiviral vectors for clinical gene therapy has not yet been evaluated. One of the reasons is the cytotoxicity of lentiviral packaging genes which makes the generation of stable producer cell lines difficult. Therefore, a novel packaging system for lentiviral vectors based on transient expression of packaging genes by recombinant adenoviruses was developed.

Methods

Adenoviral vectors expressing VSV‐G, codon‐optimized HIV‐1 gag‐pol, and codon‐optimized SIV gag‐pol under the control of a tetracycline‐regulatable promoter (adenoviral lenti‐pack vectors) were constructed and the production levels of this vector system were evaluated.

Results

The generated adenoviral lenti‐pack vectors could be grown to high titers when transgene expression was suppressed and no evidence for instabilities was obtained. Cells stably transfected with a SIV‐based vector construct were converted into lentiviral vector producer cells by infection with the adenoviral lenti‐pack vectors. Lentiviral vector titers obtained were as high as vector titers obtained by transient cotransfection experiments. A protocol was developed that allowed preparation of lentiviral vector stocks with undetectable levels of contaminating adenoviral lenti‐pack vectors.

Conclusions

The adenoviral lenti‐pack vectors described should provide a convenient alternative approach to inducible packaging cell lines for large‐scale lentiviral vector production. Transient expression of cytotoxic lentiviral packaging genes by the adenoviral lenti‐pack vectors circumvents loss of titers during prolonged culture of packaging cell lines. The design of the adenoviral lenti‐pack vectors should reduce the risk of transfer of packaging genes to target cells and at the same time provide flexibility with respect to the lentiviral vector constructs that can be packaged. Copyright © 2004 John Wiley & Sons, Ltd.
Widespread gene transduction to the central nervous system by adenovirus in utero: implication for prenatal gene therapy to brain involvement of lysosomal storage disease
Authors: Shen Jin‐Song , Meng Xing‐Li , Maeda Hiroshi , Ohashi Toya , Eto Yoshikatsu
Published: September 2004

Background

In some lysosomal storage diseases, considerable alterations of the central nervous system (CNS) occur prior to birth and neurodegeneration progresses rapidly soon after birth causing early death in patients. No effective treatment is available after birth. Treatment may need to be initiated before birth to prevent the onset or progression of neurological changes and thereby irreversible brain damage. The aim of this study is to investigate the feasibility and effectiveness of brain‐directed prenatal gene therapy for lysosomal storage diseases.

Methods

Recombinant adenovirus encoding the lacZ gene was injected into the lateral ventricles of mouse embryos and the pattern of gene transduction to the CNS was investigated. In the therapeutic experiment, adenovirus expressing β‐glucuronidase was injected into the cerebral ventricles of the embryos of mucopolysaccharidosis VII mice and the therapeutic effects on the brain were evaluated.

Results

Injection of adenoviral vectors to the cerebral ventricles of mouse embryos led to widespread gene transduction throughout the brain and the spinal cord and transgene expression persisted over 10 months in those surviving the procedure. The prenatal transduction of the therapeutic gene to the brain of the mucopolysaccharidosis VII mouse efficiently prevented lysosomal storage in most brain cells before birth until 4 months after birth.

Conclusions

Brain‐directed in utero gene therapy through an intra‐ventricular route would be an effective strategy to treat some lysosomal storage diseases with early and severe CNS alterations. Copyright © 2004 John Wiley & Sons, Ltd.
Development of a validated HPLC method for the determination of B‐complex vitamins in pharmaceuticals and biological fluids after solid phase extraction
Authors: Chatzimichalakis Pavlos F. , Samanidou Victoria F. , Verpoorte Robert , Papadoyannis Ioannis N.
Published: September 2004

An HPLC method was developed for the simultaneous determination of seven water‐soluble vitamins, viz. thiamine, riboflavin, nicotinic acid, nicotinamide, pyridoxine, cyanocobalamin, and folic acid, in multivitamin pharmaceutical formulations and biological fluids (blood serum and urine). Separation was achieved at ambient temperature on a Phenomenex Luna C18 (150×4.6 mm) analytical column. Gradient elution was performed starting at a 99 : 1 A:B v/v composition, where A: 0.05 M CH3COONH4/CH3OH (99/1) and B: H2O/CH3OH (50/50), at a flow rate of 0.8 mL/min. After a 4‐min isocratic elution the composition was changed to 100% of B in 18 min and elution continued isocratically for 8 min. Detection was performed with a photodiode array detector at 280 nm. Each vitamin was quantitatively determined at its maximum wavelength. Spectral comparison was used for peak identification in real samples. Detection limits were in the range of 1.6–3.4 ng, per 20‐μL injection, while linearity held up to 25 ng/μL. Accuracy, intra‐day repeatability (n = 6), and inter‐day precision (n = 7) were found to be satisfactory. Theobromine (2 ng/μL) was used as internal standard. Sample preparation of biological fluids was performed by SPE on Supelclean LC‐18 cartridges with methanol‐water 85/15 v/v as eluent. Extraction recoveries from biological matrices ranged from 84.6% to 103.0%.
Elektrochemisches Rauschen bei der Korrosion
Authors: Göllner J.
Published: September 2004

Ausgehend von den Ursachen, den Quellen des elektrochemischen Rauschens, wird an mehreren Beispielen die gute Korrelation zwischen verschiedenen Systemparametern und den Rauscherscheinungen gezeigt. Bei Beachtung einiger Randbedingungen bieten sich sehr gute Möglichkeiten, das Rauschen für eine Art Frühwarnsystem bei der Anlagenüberwachung zu nutzen. Es wird aber auch gezeigt, dass das elektrochemische Rauschen, wie die Korrosion überhaupt, eine äußerst komplexe Erscheinung ist und dass das Nichtbeachten bestimmter Einflüsse und Parameter zu dramatischen Fehleinschätzungen führen kann.
Rauschuntersuchungen zur Spaltkorrosion
Authors: Schneider M. , Springer A. , Galle K.
Published: September 2004

Al‐Mg‐Si‐Legierungen gewinnen im Flugzeugbau zunehmend an Bedeutung als Alternative zu Al‐Cu‐Mg‐Legierungen. Beständig gegen allgemeine Korrosion unter atmosphärischen Bedingungen ist es die Lokalkorrosion, die zum Bauteilversagen führen kann. Besonders gefährlich ist der Korrosionsangriff in konstruktiv bedingten Spalten. Loch‐ oder Spaltkorrosionsprozesse unterteilen sich in ein Initialstadium ohne sichtbare Schädigung und eine Phase raschen Korrosionsfortschrittes. Der Übergang eines passiven Korrosionssystems in ein solches Initialstadium ist jedoch von sehr kleinen Fluktuationen des Stromes und des Potentials gekennzeichnet. Die Messung dieser Fluktuationen ist Gegenstand der Elektrochemischen Rauschanalyse (ENA) und gibt so bereits im Vorschädigungsstadium Aufschluss über die Aktivität eines Korrosionssystems.

Mit Hilfe der ENA wird der Einfluss von Spaltbedingung, Potential und Zeit auf das Initialstadium der Spaltkorrosion einer Legierung vom Typ AA 6013 nachgewiesen.
Elektrochemische Rauschmessungen unter praxisnahen Bedingungen der chemischen Industrie
Authors: Finke M. , Diekmann H. , Schlecker H.
Published: September 2004

Das Corrosion Monitoring nach dem Messprinzip des elektrochemischen Rauschens erlaubt aufgrund seiner hohen Nachweisempfindlichkeit eine genaue online Aussage über das betreffende Korrosionssystem in real‐time. Da sich in der Vergangenheit Probleme bei der Datenspeicherung und ‐verarbeitung zeigten, konnten bisherige Systeme basierend auf diesem Messprinzip ihre Verwendbarkeit noch nicht nachweisen. Durch den Einsatz modernster Technologie und die Auswahl geeigneter Analyse‐Tools ist das Verfahren jetzt soweit entwickelt, dass der Anwender eine schnelle Übersicht über den Datenumfang erhält. Durch deren Auswertung lassen sich so Kriterien ermitteln, die für die Bewertung des Korrosionssystems unerlässlich sind. Aufgrund dieser Voraussetzungen ist ein Einsatz in chemischen Produktionsanlagen erst möglich, um die generelle Eignung dieses Verfahrens nachzuweisen. Interessant ist hier die Störempfindlichkeit und Reproduzierbarkeit der Messungen. Für die Bewertung müssen die Betriebsparameter ergänzt mit herkömmlichen Befunden mit denen des elektrochemischen Rauschens verglichen werden. Anhand von Beispielen aus den Bereichen der kontinuierlichen und diskontinuierlichen Produktionsverfahren wurde das Messprinzip der elektrochemischen Rauschdiagnose auf seine Praxistauglichkeit untersucht. Dabei wurde eine gute Reproduzierbarkeit der Messergebnisse festgestellt, die sich zeitlich sehr gut mit den Betriebsparametern im Einklang bringen lassen. Auch eine gute Übereinstimmung zu den visuellen Korrosionsbefunden bzw. langjährigen Erfahrungen ist gegeben. Somit bietet sich das Verfahren besonders als Ergänzung zum Erfassen zeitlich veränderter Zustände oder aber bei diskontinuierlichen Abläufen an, um Aussagen hinsichtlich der Korrosivität zu den einzelnen Prozessschritten zu treffen.
The effect of electrolyte stirring and laminar flow on measured electrochemical noise
Authors: Legat A.
Published: September 2004

In the present paper the influence of various types of electrolyte movement on the characteristics of measured electrochemical noise (EN) has been investigated. For this reason the measurements were performed during different phases: in a still solution, during stirring, as well as in laminar flow. In order to relate the measured EN to the development of corrosion processes, digitized images of the electrodes were recorded continuously during these measurements. After the tests were finished, the corroded electrode surfaces were examined also by the scanning electron microscope (SEM). It was established that the characteristics of EN, in general, change significantly with the movement of the solution. On the other hand, no clear difference was observed between the EN signals measured during stirring and those obtained during laminar flow. This observation, combined with the results obtained in a passive environment and in a very aggressive still solution, confirmed that the main source for the change of EN characteristics during electrolyte movement is the transformation of corrosion processes. The direct effect of the electrolyte movement on the measured EN (modulation of signals due to spatio‐temporal flow disturbances) was found to be insignificant compared to the influence of the corrosion processes themselves.
Elektrochemische Rauschmessungen an partiell beschichteten Oberflächen verschiedener Werkstoffe
Authors: Oelßner W. , Berthold F.
Published: September 2004

Defekte oder funktionsbedingte Unterbrechungen in der Polymerbeschichtung von metallischen Werkstoffen sind bevorzugte Ausgangspunkte verstärkten Korrosionsangriffs. Die von diesen Stellen ausgehende Unterwanderung von Beschichtungen ist von großer praktischer Relevanz und daher auch nach wie vor Gegenstand eingehender wissenschaftlicher Untersuchungen. Neben bereits seit längerer Zeit angewandten Untersuchungsmethoden bietet die elektrochemische Rauschmessung eine weitere Möglichkeit, die Delamination und Korrosionsphänomene in der Umgebung von Defekten in Beschichtungen in Abhängigkeit von den Substrat‐ und Beschichtungsmaterialien, dem Korrosionsmedium, den Umgebungsbedingungen sowie weiteren Einflussgrößen in situ zu untersuchen und sehr frühzeitig nachzuweisen. In der vorliegenden Arbeit werden Ergebnisse von derartigen Rauschmessungen an zwei sehr unterschiedlichen Korrosionssystemen vorgestellt.
Using thionates for noise eperiments – a reasonable combination?
Authors: Ritter S. , Dorsch T. , Kilian R.
Published: September 2004

The detection of intergranular corrosion (IGC) initiation of austenitic stainless steel (AISI 347) coupon specimens was investigated using electrochemical noise (EN) measurements. The tests were performed in acidic sodium tetrathionate (Na2S4O6) solution. The IGC initiation in tetrathionate solution could not be clearly detected by the electrochemical potential noise signal due to interferences of the noise signal with chemical processes which occurred in the test solution. This was confirmed by tests with inert platinum specimens. It was concluded that EN results obtained by tests in thionate or comparable sulfur containing solutions should be regarded with great care and verified, e.g., by tests with inert specimens.
Einfluss der Schleifbehandlung auf das Korrosionsverhalten von Chrom‐Nickel‐Stählen
Authors: Burkert A. , Schilling K. , Heyn A.
Published: September 2004

Die Erzeugung geschliffener Oberflächen bei hochlegierten Chrom‐Nickel‐Stählen aus dekorativen Gründen z. B. beim Einsatz im Bereich Innenarchitektur kann sich u. U. problematisch hinsichtlich der Korrosionsbeständigkeit auswirken. Bei den Untersuchungen zum Einfluss der Verfahrensparameter beim industriellen Schleifen zur Erzeugung eines bestimmten optischen Erscheinungsbildes stellte sich heraus, dass die Rauheit allein kein Maß für die zu erwartende Korrosionsbeständigkeit darstellt. Die Variation verschiedener Schleifparameter, aber auch die Art des Schleifmittels können einen erheblichen Einfluss auf die Korrosionsbeständigkeit ausüben. Neben den Ergebnissen verschiedener Auslagerungsversuche werden elektrochemische Untersuchungen an den geschliffenen Oberflächen vorgestellt. Dabei konnte mittels elektrochemischer Rauschmessungen die unterschiedliche Korrosionsneigung der Oberflächen nachgewiesen werden.
Rauschmessungen zur Früherkennung der Korrosionsneigung mechanisch gefügter Bleche
Authors: Heyn A. , Göllner J. , Burkert A.
Published: September 2004

Auf dem Gebiet des mechanischen Fügens ist eine rege Entwicklung zu verzeichnen. Der Einsatz neuer Materialien, neuer Nietformen, neuer Schutzschichten, veränderter Fertigungstechnologien, die Notwendigkeit zur Mischbauweise, veränderte mediale Belastungen, geforderte Langzeitgarantien usw. lassen vielfältige alte und neue Fragen hinsichtlich der Korrosionsbeständigkeit auftreten. Herkömmliche Korrosionsprüfverfahren geben oft nur unzureichende Antworten auf diese Fragen. Mit dem Einsatz des elektrochemischen Rauschens ist es möglich, in kurzer Zeit aussagekräftige Ergebnisse über Material‐ und Bauteileigenschaften zu erhalten, da eine Metalloberfläche ständig Signale über ihren Zustand aussendet, auch wenn man nicht misst. Neben der Möglichkeit, die Korrosionsneigung zu bestimmen, lassen sich über die Rauschmessungen auch bestimmte Verarbeitungsfehler und Oberflächendefekte nachweisen. Die Anwendung dieser Methode bietet somit Möglichkeiten zur Prozessoptimierung und Qualitätssicherung mechanisch gefügter Bauteile, oder auch zur Einschätzung bestehender Fügeverbindungen.
Instrumentierung von Sprühnebelprüfverfahren
Authors: Göllner J. , Heyn A. , Burkert A.
Published: September 2004

In der industriellen Praxis ist die Sprühnebelprüfung eine häufig eingesetzte Prüfmethode zum Nachweis der Produktqualität von Halbzeugen und Zulieferteilen hinsichtlich ihrer Korrosionsbeständigkeit. Aus diesem Grund gehören die Klima‐ und Sprühnebelprüfungen zu den am weitesten verbreiteten Korrosionsprüfverfahren. Jedoch kann man über den zeitlichen Verlauf der Korrosion, ob linear, exponentiell, logarithmisch o.ä. keine Aussage treffen. Weiterhin sind die Prüfbedingungen bei den Sprühnebelprüfungen verschärft, um eine Verkürzung der Messzeit zu erreichen. Damit verändert man unter Umständen die Korrosionsmechanismen. Die Sprühnebelprüfung kann jedoch auch ohne Verwendung von zu scharfen, praxisfremden Prüfmedien deutlich an Erkennbarkeit gewinnen, indem man elektrochemische in‐situ Messungen (Rauschmessungen) anwendet. Im Gegensatz zu herkömmlichen elektrochemischen Messungen, bei denen die untersuchten Proben von einem bulk‐Elektrolyten umgeben sind, basieren die Messungen unter Sprühnebelbedingungen auf der Bildung eines Elektrolytfilms an den Probenoberflächen, sowie an den Innenwänden der Prüfkammer und der Anbauten (z. B. Probenhalter). Die Messeffekte weichen nicht grundlegend von konventionellen Messungen ab, die nutzbaren Signale sind jedoch von den Eigenschaften des Elektrolytfilms (Ausbreitung auf der Oberfläche, Leitfähigkeit, Dicke) abhängig. Die erfolgreiche Anwendung von Rauschmessungen unter Sprühnebelbedingungen wird für einige Beispiele der Korrosionsprüfung gezeigt.
Amorphous‐Crystalline PSnPEOn Heteroarm Star Copolymers: Crystallinity and Crystallization Kinetics
Authors: Koutsopoulou Eleni , Tsitsilianis Constantinos
Published: September 2004

Summary: The crystallization behavior and kinetics of poly(ethylene oxide) in polystyrene/poly(ethylene oxide) heteroarm star copolymers were studied by differential scanning calorimetry and optical microscopy. A comparison between star and linear amorphous‐crystalline block copolymers showed that the macromolecular architecture is an important factor affecting crystallinity. The following points were observed: the equilibrium melting point is higher in the star copolymers, the crystallinity reduces as the number of arms increases, leading to smaller and ill‐defined spherulites, and crystallization proceeds faster in linear copolymers at low supercooling.

Half crystallization times, t1/2, calculated from the Avrami analysis of the latent heats, obtained during the isothermal crystallization experiments as a function of supercooling, ΔT, for all copolymers.

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Half crystallization times, t1/2, calculated from the Avrami analysis of the latent heats, obtained during the isothermal crystallization experiments as a function of supercooling, ΔT, for all copolymers.
New Epoxy Resins Cured with Tetraaminophenyladamantane (TAPA)
Authors: Wei Qian , Lazzeri Andrea , Di Cuia Flavia , Scalari Marco , Galoppini Elena
Published: September 2004

Summary: New epoxy materials are needed with low dielectric constants (Dk or εr), low loss (Df or tan δ) in the giga‐hertz frequency range and high glass transition temperatures (Tgs) for next generation fiber reinforced printed circuit boards. In this work, the incorporation of adamantane into an epoxy network has been investigated. In particular, this has been achieved by means of a new adamantane‐based, tetra‐functional crosslinking agent (1,3,5,7‐tetrakis(4‐aminophenyl)adamantane or TAPA) which was specifically synthesized and subsequently characterized for this study. The properties of EPON Resin 828 cured with the newly synthesized TAPA have been compared with the commonly used commercial curing agent 4,4′‐diaminodiphenylsulfone (DDS). It was found that the epoxy polymer cured with TAPA exhibited superior thermal properties as well as a good dielectric performance at high frequencies.

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Characterization of Metallocene Epdm Terpolymers with High Diene and Propylene Content Crosslinked by Dicumyl Peroxide and β‐Radiation
Authors: Nicolás Javier , Ressia Jorge Aníbal , Vallés Enrique Marcelo , Merino Juan Carlos , Pastor José María
Published: September 2004

Summary: Two metallocene EPDMs with the same weight fraction of ethylene but differing in diene content were crosslinked, either by dicumyl peroxide (DCP) or β‐radiation. The effect of different diene and propylene content on the molecular structure and the mechanical properties once the materials were crosslinked was studied. The final gel content was very high due to the large level of unsaturations. The crosslinking process was monitored by FTIR spectroscopy by following the decay of unsaturations and the variation of the carbonyl groups that are related to the oxidation grade. It was found that β‐radiation crosslinked samples exhibited a lower oxidation grade than those crosslinked by DCP. An oscillant disc rheometer was employed to follow the evolution of the rheological properties, the scorch time, and the time corresponding to full cure during the crosslinking reaction with DCP. In addition, in order to characterize the state of cure we have studied the rheological properties in shear employing a dynamic parallel plate geometry. These results were correlated with those obtained from the molecular characterization of the soluble fraction by size exclusion chromatography. The experiments indicate that, at low irradiation doses, there is a high rate of chain scission reactions that cause an important decrease in storage modulus. Whereas, at high irradiation doses the rate of chain scission reactions diminishes, thus the storage modulus increases but it still remains at lower levels than those corresponding to the original terpolymers. The tensile properties, hardness (Shore A) and compression set tests also suggest the presence of chain scission reactions.

Storage modulus (G′) versus frequency for a β‐irradiated sample.

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Storage modulus (G′) versus frequency for a β‐irradiated sample.
Study of Laser‐Induced Photopolymerizations by Optical Pyrometry
Authors: Lin Patrick , Falk Benjamin , Jang Myoungsouk , Crivello James V.
Published: September 2004

Summary: Studies of the 355 nm laser induced free radical and cationic photopolymerization reactions of mono‐ and multifunctional monomers were conducted. These investigations were carried out with the aid of a specially constructed optical pyrometry instrument that provides rapid, reproducible temperature versus time profiles for these fast photopolymerization reactions. Using this technique, the effects of various reaction parameters and monomer structures on the rate and extent of the photopolymerization reactions were examined.

Optical pyrometry instrument for the monitoring of laser‐induced photopolymerizations.

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Optical pyrometry instrument for the monitoring of laser‐induced photopolymerizations.
Mixed Alkyl‐ and Alkoxy‐Substituted Poly[(phenylene ethynylene)‐alt‐(phenylene vinylene)] Hybrid Polymers: Synthesis and Photophysical Properties
Authors: Egbe Daniel Ayuk Mbi , Sell Stephan , Ulbricht Christoph , Birckner Eckhard , Grummt Ulrich‐Walter
Published: September 2004

Summary: We report the synthesis, characterisation and photophysical properties of mixed alkyl‐ and alkoxy‐substituted poly[(phenylene ethynylene)‐alt‐(phenylene vinylene)] hybrid polymers with the general constitutional unit: (PhCCPhCCPhCHCHPhCHCH)n (7). The polymers were obtained through the Horner‐Wadsworth‐Emmons olefination reaction of alkyl‐substituted luminophoric dialdehydes, 5a–b, and alkoxy‐substituted bisphosphonates. Contrary to their alkoxy‐substituted congeners, 10a–b, which exhibit solution fluorescence quantum yields close to unity, dialdehydes (5a–b) fluoresce poorly at room temperature, but show phosphorescence at 77 K. High molecular weight polymers were obtained showing poor solubility compared to solely alkoxy‐substituted polymers (11) of the same backbone constitutional units. The presence of alkyl side groups in 7 leads to a 15 nm blue shift of their absorption spectra relative to 11. Both types of polymers show however identical emission spectra with only a slight blue shift (3–4 nm) of the emission peak of 7 relative to 11. This clearly proves that the chromophore system responsible for the emission in both types of compounds is located around the lower‐energy, alkoxy‐substituted phenylene‐vinylene portion of the polymers as confirmed by fluorescence kinetics investigations.

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A rapid method for the discrimination of genes encoding classical Shiga toxin (Stx) 1 and its variants, Stx1c and Stx1d, in Escherichia coli
Authors: Kuczius Thorsten , Bielaszewska Martina , Friedrich Alexander W. , Zhang Wenlan
Published: September 2004

Subtyping of Shiga toxin (Stx)‐encoding genes by conventional polymerase chain reaction (PCR) is time‐consuming. We developed a single step real‐time fluorescence PCR with melting curve analysis to distinguish rapidly stx1 from its variants, stx1c and stx1d. Melting temperatures (Tm) of 206 Stx‐producing Escherichia coli (STEC) identified to harbor stx1 or stx1c were analyzed using a specific hybridization probe over the variable region. 170 of 171 stx1‐harboring STEC displayed Tm of 69°C to 70°C, whereas 34 of 35 strains containing stx1c had Tm of 65°C–66°C. This constant and reproducible difference of 4°C demonstrated that melting curve analysis is a reliable technique to differentiate stx1 from stx1c. Two isolates displayed atypical Tm. Sequence analysis showed that one of them was 100% identical to stx1d within a 511 bp DNA stretch. Our data demonstrate that real‐time PCR is a rapid and reliable tool to differentiate stx1 from stx1c and stx1d and to detect new stx1 variants. Because stx1‐harboring STEC cause diarrhoea and hemolytic‐uremic syndrome, whereas those containing stx1c are often shed asymptomatically, a rapid differentiation between stx1 and its variants using the procedure developed here has both clinical implications and a direct significance for the risk assessment analysis of STEC isolated from foods.
Dynamics in disordered block copolymers and miscible blends composed of poly(vinyl ethylene) and polyisoprene
Authors: Hirose Yuji , Urakawa Osamu , Adachi Keiichiro
Published: September 2004

We investigated the segmental and terminal relaxation dynamics of a well‐characterized disordered diblock copolymer, poly(isoprene‐b‐vinyl ethylene) (PI‐PVE), and miscible blends of polyisoprene (PI)/poly(vinyl ethylene) (PVE), using dielectric and viscoelastic spectroscopies. Generally, the concentration fluctuation (CF) amplitude of a disordered diblock copolymer is smaller than that of the miscible blend, especially in a length scale longer than the size of the whole block chain. To test whether the difference in the CF amplitudes causes the difference in the segmental relaxation spectra, we compared the shape of the dielectric loss curves between PI‐PVE and PI/PVE with the same composition (PI/PVE ratio = 17:83). However, no appreciable difference was observed, indicating that the CF amplitudes in PI‐PVE and PI/PVE are not so different in the length scale of the segmental motions. We also examined the effect of distinct friction coefficients of the PI and PVE chains on the terminal relaxation dynamics by comparisons of the viscoelastic and dielectric normal mode relaxations in PI‐PVE. The former probes the whole chain motion and the latter probes motions of the PI block. Shift factors (aT) for the viscoelastic and dielectric relaxations were compared. The dielectric normal mode aT was found to have weaker temperature dependence than the viscoelastic aT, which indicates that the friction for the PI block chain is lower than the average friction for the PI‐PVE chain. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4084–4094, 2004
Hole spin surfaces in A3B5 semiconductors
Authors: Dargys A.
Published: September 2004

Properties of spin surfaces of heavy‐mass, light‐mass and split‐off bands of GaAs, InAs, GaP, InP, GaSb, and InSb are presented under various approximations. A simple two‐band, analytically solvable model is used as a starting point and the reference. It is shown that the strongest deviation from the simple spherical and parabolic two‐band model comes from the valence band nonparabolicity and nonshpericity. The spin‐splitting in all three valence bands was found to have negligible influence on shape of the spin surfaces at thermal hole energies. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sonographic measurement of cervical length in preterm prelabor amniorrhexis
Authors: Tsoi E. , Fuchs I. , Henrich W. , Dudenhausen J. W. , Nicolaides K. H.
Published: September 2004

Objective

To determine whether sonographic measurement of cervical length in pregnancies complicated by preterm prelabor amniorrhexis helps distinguish between those women who deliver within 7 days and those who do not.

Methods

In 101 women with singleton pregnancies presenting with preterm prelabor amniorrhexis at 24–36 (median, 32) weeks of gestation cervical length was measured by transvaginal ultrasound. Exclusion criteria were active labor defined by the presence of cervical dilatation of ≥ 3 cm and iatrogenic delivery for fetal or maternal indication when not in active labor. The clinical management was determined by the attending obstetrician. The primary outcome of the study was delivery within 7 days of presentation.

Results

Delivery within 7 days of presentation occurred in 58/101 (57%) pregnancies. Logistic regression analysis demonstrated that significant independent contribution in the prediction of delivery within 7 days was provided by cervical length (odds ratio (OR) = 0.91, 95% CI 0.86–0.96, P = 0.001), gestation at presentation (OR = 1.35, 95% CI 1.14–1.59, P = 0.001) and presence of contractions at presentation (OR = 3.07, 95% CI 1.05–8.92, P = 0.039) with no significant independent contribution from ethnic origin, maternal age, body mass index, parity, previous history of preterm delivery, cigarette smoking, vaginal bleeding or the administration of tocolytics, antibiotics or steroids.

Conclusion

In women with preterm prelabor amniorrhexis prediction of delivery within 7 days is provided by cervical length, gestation and presence of contractions at presentation. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.
Low power microwave interaction with phospholipase C and D signal transduction pathways in myogenic cells
Authors: Donato Andrea , Ceci Paola , Cannavò Andrea , Tomei Francesco , Naro Fabio
Published: September 2004

Ionic channel proteins are possible sites of microwave interaction at the cell membrane level. Patch‐clamp data, using single channel and total current recording, indicated that low level microwave fields may modify some functional parameters of the nicotinic acetylcholine receptor in primary chick myotubes, suggesting a possible effect of microwaves on myogenic cells. Here, we investigated the biological relevance of such results, in relation to the possible involvement of intracellular signaling processes. We exposed L6–C5 myogenic cells to low power electromagnetic fields and observed the consequences on hormonal activation of phospholipases C and D. We found that increased inositol phospholipid turnover, induced by acetylcholine and arginine vasopressin activation of phospholipase C, was not modified in microwave irradiated myoblasts or myotubes. Moreover, vasopressin‐dependent phospholipase D activation, assessed by measuring the [3H]‐free choline release, was not modified by microwave irradiation. Our conclusions suggest that low level microwave fields do not modify signal transduction pathways activated by acetylcholine and vasopressin in L6–C5 myogenic cells.
Response of clupeid fish to ultrasound: a review
Authors: Popper Arthur N. , Plachta Dennis T.T. , Mann David A. , Higgs Dennis
Published: September 2004

A number of species of clupeid fish, including blueback herring, American shad, and gulf menhaden, can detect and respond to ultrasonic sounds up to at least 180 kHz, whereas other clupeids, including bay anchovies and Spanish sardines, do not appear to detect sounds above about 4 kHz. Although the location for ultrasound detection has not been proven conclusively, there is a growing body of physiological, developmental, and anatomical evidence suggesting that one end organ of the inner ear, the utricle, is likely to be the detector. The utricle is a region of the inner ear that is very similar in all vertebrates studied to date, except for clupeid fish, where it is highly specialized. Behavioural studies of the responses of American shad to ultrasound demonstrate that they show a graded series of responses depending on the sound level and, to a lesser degree, on the frequency of the stimulus. Low-intensity stimuli elicit a non-directional movement of the fish, whereas somewhat higher sound levels elicit a directional movement away from the sound source. Still higher level sounds produce a “wild” chaotic movement of the fish. These responses do not occur until shad have developed the adult utricle that has a three-part sensory epithelium. We speculate that the response of the American shad (and, presumably, other clupeids that can detect ultrasound) to ultrasound evolved to help these species detect and avoid a major predator – echolocating cetaceans. As dolphins echolocate, the fish are able to hear the sound at over 100 m. If the dolphins detect the fish and come closer, the nature of the behavioural response of the fish changes in order to exploit different avoidance strategies and lower the chance of being eaten by the predators.
Diel vertical behaviour, predator–prey relationships, and occupation of space by jack mackerel (Trachurus murphyi) off Chile
Authors: Bertrand Arnaud , Barbieri Maria Angela , Córdova Jose , Hernández Carola , Gómez Fabián , Leiva Francisco
Published: September 2004

In the southeastern Pacific, jack mackerel (Trachurus murphyi, Carangidae) is a heavily exploited pelagic species, and its presence in Chilean waters in autumn and winter is assumed to be mainly due to an inshore feeding migration. Predator–prey relationships are known to depend on the spatial and temporal scale of observation, but they can also be strongly affected by factors such as diel vertical migration. In studying the case of jack mackerel in detail, we used data from three acoustic surveys carried out in central Chile in 1997, 1998, and 1999. In terms of spatial occupation, jack mackerel behaviour is “atypical” behaviour, i.e. more aggregated during the night than during the day. The patterns we observed can be related to their nocturnal active foraging behaviour. Diel feeding behaviour is therefore a key factor in the aggregating behaviour of jack mackerel and its vulnerability to the purse-seine fishery that targets these nocturnal aggregations. This particular fish diel feeding behaviour also affected predator–prey relationships in relation to the spatial scale. Positive correlations at a “small” spatial scale (<7–25 km) were observed during the night when jack mackerel foraged, but not during the day. Finally, we show that prey biomass was lower where jack mackerel were abundant, which could indicate a jack mackerel top–down control on prey communities.
Influence of seismic shooting on the lesser sandeel (Ammodytes marinus)
Authors: Hassel Arne , Knutsen Tor , Dalen John , Skaar Kristian , Løkkeborg Svein , Misund Ole Arve , Østensen Øivind , Fonn Merete , Haugland Eli Kyrkjebø
Published: September 2004

A field experiment on the effect of seismic shooting on the lesser sandeel (Ammodytes marinus) was conducted on the fishing grounds in the southeastern part of the North Sea in May 2002. Sandeel buried in the sand at night were trapped in steel frame cages (2.0 × 1.8 × 2.0 m) deployed in positions with high abundance of fish located by a van Veen grab. In an experimental area, three sandeel cages were exposed to full-scale seismic shooting for about 2.5 d. Cameras in the cage and on a remotely operated vehicle (ROV) were used to monitor the activity of the enclosed fish. A control area about 35 km southeast of the seismic shooting area was established with two sandeel cages. The distribution and abundance of the lesser sandeel during daytime in the experimental region were regularly monitored by acoustic surveying, but the present methodology could not demonstrate that seismic shooting caused any change in sandeel abundance. Repeated grab surveys were conducted using a van Veen grab for a predetermined set of localities almost every night during the experimental period, both prior to and after seismic shooting. The results indicate that the seismic shooting had a moderate effect on the behaviour of the lesser sandeel. We did not observe any immediate lethal effect, neither from the cage experiments nor from the grab samples. The total mortality in the cages of about 35% on average, both in the experimental group and the control group, was probably a result of injuries during deployment, due to handling and confinement. Analyses of landing data from the Norwegian sandeel trawlers show a temporary drop in the sandeel landings for a short period after the seismic experiment.
Cutaneous stimulation from patella tape causes a differential increase in vasti muscle activity in people with patellofemoral pain
Authors: MacGregor Kerren , Gerlach Sharon , Mellor Rebecca , Hodges Paul W.
Published: September 2004

Patella taping reduces pain in individuals with patellofemoral pain (PFP), although the mechanism remains unclear. One possibility is that patella taping modifies vasti muscle activity via stimulation of cutaneous afferents. The aim of this study was to investigate the effect of stretching the skin over the patella on vasti muscle activity in people with PFP. Electromyographic activity (EMG) of individual motor units in vastus medialis obliquus (VMO) was recorded via a needle electrode and from surface electrodes placed over VMO and vastus lateralis (VL). A tape was applied to the skin directly over the patella and stretch was applied via the tape in three directions, while subjects maintained a gentle isometric knee extension effort at constant force. Recordings were made from five separate motor units in each direction. Stretch applied to the skin over the patella increased VMO surface EMG and was greatest with lateral stretch. There was no change in VL surface EMG activity. While there was no net increase in motor unit firing rate, it was increased in the majority of motor units during lateral stretch. Application of stretch to the skin over VMO via the tape can increase VMO activity, suggesting that cutaneous stimulation may be one mechanism by which patella taping produces a clinical effect. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Daughter‐specific repression of Saccharomyces cerevisiae HO: Ash1 is the commander
Authors: Cosma Maria Pia
Published: September 2004

The GATA‐1‐like factor Ash1 is a repressor of the HO gene, which encodes an endonuclease that is responsible for mating‐type switching in the yeast Saccharomyces cerevisiae. A multi‐step programme, which involves a macromolecular protein complex, the secondary structure of ASH1 mRNA and the cell cytoskeleton, enables Ash1 to asymmetrically localize to the daughter cell nucleus in late anaphase and to repress HO transcription. The resulting Ash1 activity prevents the daughter cell from switching mating type. How does Ash1 inhibit transcription of HO exclusively in the daughter cell? In this review, a speculative model is proposed and discussed. Through its action as a daughter‐specific repressor, Ash1 can be considered to be an ancestral regulator of cell fate in eukaryotes.
Creation and discovery of ligand–receptor pairs for transcriptional control with small molecules
Authors: Schwimmer Lauren J. , Rohatgi Priyanka , Azizi Bahareh , Seley Katherine L. , Doyle Donald F.
Published: September 2004

The nuclear receptor retinoid X receptor (RXR) is a ligand-activated transcription factor. To create receptors for a new ligand, a structure-based approach was used to generate a library of ≈380,000 mutant
RXR
genes. To discover functional variants within the library, we used chemical complementation, a method of protein engineering that uses the power of genetic selection. Wild-type RXR has an EC
50
of 500 nM for 9-
cis
retinoic acid (9cRA) and an EC
50
of >10 μM for the synthetic retinoid-like compound LG335 in yeast. The library produced ligand–receptor pairs with LG335 that have a variety of EC
50
values (40 nM to >2 μM) and activation levels (10–80% of wild-type RXR with 9cRA) in yeast. The variant I268V;A272V;I310L;F313M has an EC
50
for LG335 of 40 nM and an EC
50
for 9cRA of >10 μM in yeast. This variant has essentially the reverse ligand specificity of wild-type RXR and is transcriptionally active at a 10-fold-lower ligand concentration in yeast. This EC
50
is 25-fold lower than the best receptor we have engineered through site-directed mutagenesis, Q275C;I310M;F313I. Furthermore, the variants' EC
50
values and activation levels in yeast and mammalian cells correlate. This protein engineering method should be extendable to produce other functional ligand–receptor pairs, which can be selected and characterized from libraries within weeks. Coupling large library construction with chemical complementation could be used to engineer proteins that bind virtually any small molecule for conditional gene expression, applications in metabolic engineering, and biosensors and to engineer enzymes through genetic selection.
Automated prediction of protein function and detection of functional sites from structure
Authors: Pazos Florencio , Sternberg Michael J. E.
Published: September 2004

Current structural genomics projects are yielding structures for proteins whose functions are unknown. Accordingly, there is a pressing requirement for computational methods for function prediction. Here we presentphunctioner, an automatic method for structure-based function prediction using automatically extracted functional sites (residues associated to functions). The method relates proteins with the same function through structural alignments and extracts 3D profiles of conserved residues. Functional features to train the method are extracted from the Gene Ontology (GO) database. The method extracts these features from the entire GO hierarchy and hence is applicable across the whole range of function specificity. 3D profiles associated with 121 GO annotations were extracted. We tested the power of the method both for the prediction of function and for the extraction of functional sites. The success of function prediction by our method was compared with the standard homology-based method. In the zone of low sequence similarity (≈15%), our method assigns the correct GO annotation in 90% of the protein structures considered, ≈20% higher than inheritance of function from the closest homologue.
De novo
design of conformationally flexible transmembrane peptides driving membrane fusion
Authors: Hofmann Mathias W. , Weise Katrin , Ollesch Julian , Agrawal Prashant , Stalz Holger , Stelzer Walter , Hulsbergen Frans , de Groot Huub , Gerwert Klaus , Reed Jennifer , Langosch Dieter
Published: September 2004

Fusion of biological membranes is mediated by distinct integral membrane proteins, e.g., soluble
N
-ethylmaleimide-sensitive factor attachment protein receptors and viral fusion proteins. Previous work has indicated that the transmembrane segments (TMSs) of such integral membrane proteins play an important role in fusion. Furthermore, peptide mimics of the transmembrane part can drive the fusion of liposomes, and evidence had been obtained that fusogenicity depends on their conformational flexibility. To test this hypothesis, we present a series of unnatural TMSs that were designed
de novo
based on the structural properties of hydrophobic residues. We find that the fusogenicity of these peptides depends on the ratio of α-helix-promoting Leu and β-sheet-promoting Val residues and is enhanced by helix-destabilizing Pro and Gly residues within their hydrophobic cores. The ability of these peptides to refold from an α-helical state to a β-sheet conformation and backwards was determined under different conditions. Membrane fusogenic peptides with mixed Leu/Val sequences tend to switch more readily between different conformations than a nonfusogenic peptide with an oligo-Leu core. We propose that structural flexibility of these TMSs is a prerequisite of fusogenicity.
The Interaction of Tactile Information and Movement Amplitude in a Multijoint Bimanual Circle-Tracing Task: Phase Transitions and Loss of Stability
Authors: Buchanan John J. , Ryu Young U.
Published: September 2004

Adaptive behaviour in bimanual coordination was examined with the use of a bimanual circle-tracing task. Circle diameter and tactile information were manipulated to form four tracing conditions: tracing a pair of 3-cm diameter circles with the tips of the index fingers (3F) or hand-held styli (3S) and tracing a pair of 10-cm diameter circles with the tips of the index fingers (10F) or hand-held styli (10S). Movement frequency was increased in all conditions. In the 3F, 3S, and 10S tracing conditions, an abrupt transition from asymmetric to symmetric coordination was the main adaptive response, while in the 10F tracing condition, phase wandering was the main adaptive response. Enhancement of fluctuations in relative phase, a signature of loss of stability, occurred before the transition from asymmetric to symmetric coordination. Movement frequency and movement amplitude interact as control parameters in this task. The results are discussed with reference to tactile surface contact and joint motion as sources of sensory information that can be used to stabilize bimanual coordination patterns. The presence or absence of tactile information is directly linked to the specific form of adaptive behaviour (phase transition or phase wandering) that emerges as a function of required movement amplitude and required pacing frequency.