bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of epibatidine on spontaneous and evoked neurotransmitter release in the mouse and guinea pig isolated vas deferens
Authors: Williams D J , Brain K L , Cunnane T C
Published: February 2007

Background and purpose:

Nicotinic agonists increase sympathetic field‐stimulus‐evoked contraction of the rodent vas deferens, presumably by increasing evoked neurotransmitter release. This presumption was tested in two species.

Experimental approach:

The effect of the nicotinic acetylcholine receptor (nAChR) agonist epibatidine on neurotransmitter release in mouse and guinea pig isolated vas deferens was investigated using contraction studies and conventional intracellular recording techniques.

Key results:

In 12 of 14 mouse vasa deferentia, slow bath application of epibatidine (100 nM) had no significant effect on excitatory junction potential (EJP) amplitude and spontaneous EJP (SEJP) frequency. However, rapid application of epibatidine to the mouse vas deferens caused an increase in SEJP frequency (by 530%), with no effect on EJP amplitude. Despite the absence of an effect on EJPs, electrically‐evoked contractions of the mouse vas deferens were significantly increased in the presence of epibatidine (by 50%). A transient contraction was reliably induced by a higher epibatidine concentration (1 μM). This contraction was significantly reduced in the presence of prazosin, tetrodotoxin, or α,β‐methyleneATP. Epibatidine did not induce a contraction in the presence of a combination of prazosin, α,β‐methyleneATP and cyclopentolate. In guinea pig vasa deferentia, bath‐applied epibatidine potentiated EJP amplitude in a biphasic pattern, lasting for at least 30 minutes.

Conclusion and implications:

The nAChR‐mediated augmentation of neurogenic contraction is indeed prejunctional, but in the mouse arises from an increase in spontaneous neurotransmitter release that primes smooth muscle for subsequent contraction, while in the guinea pig there is a direct augmentation of evoked neurotransmitter (ATP) release.

British Journal of Pharmacology(2007)150,906–912. doi:10.1038/sj.bjp.0707183
Effect of conduction band nonparabolicity on the dark current in a quantum well infrared detector
Authors: Panda Sudhira , Panda B. K. , Fung S.
Published: February 2007

Taking into account electron scattering with confined plasmon-phonon coupled modes in a many-body formalism, the dark currents in a quantum well structure based on the Al0.27Ga0.73As∕GaAs heterojunctions have been calculated The nonparabolicity of the conduction band, finite temperature, and applied bias has been included in the calculation of the scattering rates. Good agreement with the experiments has been obtained by the inclusion of the nonparabolicity of the conduction band in the theory.
High-resolution core-level photoemission study on GaAs(111)B surfaces
Authors: Nakamura Kenya , Mano Takaaki , Oshima Masaharu , Yeom H. W. , Ono Kanta
Published: February 2007

GaAs ( 111 ) B surfaces grown by molecular-beam epitaxy have been investigated in situ using synchrotron radiation photoemission spectroscopy. For the GaAs(111)B-2×2 phase, the Ga 3d core-level spectra consists of one dominating component while the As 3d spectra are decomposed into four components. This analysis is fully consistent with an As-trimer model where As-trimers in T4 or H3 position exist on top of As atoms in the uppermost double layer. On the other hand, the core-level spectra for the 19×19 surface disagree with the hexagonal ring structural model.
Work of adhesion in laser-induced delamination along polymer-metal interfaces
Authors: Fedorov A. , van Tijum R. , Vellinga W. P. , De Hosson J. Th. M.
Published: February 2007

Laser-induced delamination is a recent technique aimed at characterizing adhesive strength of thin polymer coatings on metal substrates. A laser pulse is used to create a blister that initiates further delamination of the film under pressure. To process the experimental data a simple elastic model was developed. The model predicts values for the blister height and pressure in fair agreement with the experimental findings. The critical stress state required for delamination and the work of adhesion are derived. To account for possible plastic deformation computer simulations using finite elements with a mixed mode cohesive zone were carried out. The polymer coating is described with a constitutive law that includes an elastic response, yielding and hardening with increasing strain. The stress fields calculated with finite element model are in agreement with those predicted by the elastic model and it suggests that the contribution of plastic deformation to the work of adhesion is rather limited. Comparative analysis of these two approaches is presented. The theoretical predictions are compared to experimental results obtained for the 40μm thick polyethylene terephthalate film on steel substrate.
Soliton stability in some knot soliton models
Authors: Adam C. , Sánchez-Guillén J. , Wereszczyński A.
Published: February 2007

We study the issue of stability of static solitonlike solutions in some nonlinear field theories which allow for knotted field configurations. Concretely, we investigate the Aratyn-Ferreira-Zimerman model [Phys. Lett. B 456, 162 (1999); Phys. Rev. Lett. 83, 1723 (1999)], based on a Lagrangian quartic in first derivatives with infinitely many conserved currents, for which infinitely many soliton solutions are known analytically. For this model we find that sectors with different (integer) topological charges (Hopf index) are not separated by an infinite energy barrier. Further, if variations which change the topological charge are allowed, then the static solutions are not even critical points of the energy functional. We also explain why soliton solutions can exist at all, in spite of these facts. In addition, we briefly discuss the Nicole model [J. Phys. G 4, 1363 (1978)], which is based on a sigma-model-type Lagrangian. For the Nicole model we find that different topological sectors are separated by an infinite energy barrier.
Neumark operators and sharp reconstructions: The finite dimensional case
Authors: Beneduci Roberto
Published: February 2007

A commutative positive operator valued (POV) measure F with real spectrum is characterized by the existence of a projection valued measure E (the sharp reconstruction of F) with real spectrum such that F can be interpreted as a randomization of E. This paper focuses on the relationships between this characterization of commutative POV measures and Neumark’s extension theorem. In particular, we show that in the finite dimensional case there exists a relation between the Neumark operator corresponding to the extension of F and the sharp reconstruction of F. The relevance of this result to the theory of nonideal quantum measurement and to the definition of unsharpness is analyzed.
High precision electrostatic potential calculations for cylindrically symmetric lenses
Authors: Edwards David
Published: February 2007

A method is developed for a potential calculation within cylindrically symmetric electrostatic lenses using mesh relaxation techniques, and it is capable of considerably higher accuracies than currently available. The method involves (i) creating very high order algorithms (orders of 6, 8, and 10) for determining the potentials at points in the net using surrounding point values, (ii) eliminating the effect of the large errors caused by singular points, and (iii) reducing gradients in the high gradient regions of the geometry, thereby allowing the algorithms used in these regions to achieve greater precisions—(ii) and (iii) achieved by the use of telescopic multiregions. In addition, an algorithm for points one unit from a metal surface is developed, allowing general mesh point algorithms to be used in these situations, thereby taking advantage of the enhanced precision of the latter. A maximum error function dependent on a sixth order gradient of the potential is defined. With this the single point algorithmic errors are able to be viewed over the entire net. Finally, it is demonstrated that by utilizing the above concepts and procedures, the potential of a point in a reasonably high gradient region of a test geometry can realize a precision of less than 10−10.
Deviations from Vegard’s rule in Al1−xInxN (0001) alloy thin films grown by magnetron sputter epitaxy
Authors: Seppänen T. , Hultman L. , Birch J. , Beckers M. , Kreissig U.
Published: February 2007

Al 1 − x In x N (0001) thin films of the pseudobinary AlN–InN system were grown epitaxially onto (111)-oriented MgO wafers with seed layers of Ti1−yZryN by dual direct current magnetron sputtering under ultrahigh vacuum conditions. The relaxed film c-axis lattice parameters determined by x-ray diffraction were studied as a function of composition in the range of 0.07<x<0.82 measured by Rutherford backscattering spectrometry. We find a relative deviation by as much as 37% from the linear dependency described by Vegard’s rule for the lattice parameter versus film composition. The highest relative deviations were found at low InN mole fractions, while the largest absolute deviation was found at x=0.63. This shows that Vegard’s rule is not directly applicable to determine the compositions in the wurtzite Al1−xInxN system.
Critical film thickness dependence on As flux in In0.27Ga0.73As∕GaAs(001) films
Authors: Riposan A. , Mirecki Millunchick J. , Pearson Chris
Published: February 2007

The transition between planar and nonplanar growth is examined for compressively strained In0.27Ga0.73As∕GaAs(001) films using reflection high energy electron diffraction, atomic force microscopy, and scanning tunneling microscopy (STM). For a narrow range of temperature and composition, the critical thickness (tSK) is strongly dependent on As flux. For high values of As flux, tSK increases by more than a factor of 2. The morphology of three-dimensional islands formed during the initial stages of nonplanar growth is also characterized by high resolution STM.
Magnetoimpedance of single and multilayered FeCuNbSiB films in frequencies up to 1.8GHz
Authors: Corrêa M. A. , Viegas A. D. C. , da Silva R. B. , de Andrade A. M. H. , Sommer R. L.
Published: February 2007

In this work, very high magnetoimpedance measured at frequencies up to 1.8GHz in nanostructured Fe73.5Cu1Nb3Si13.5B9∕Cu films is reported. Magnetoimpedance ratios of 280% and 50% were observed in multilayered and sandwiched samples, respectively. For the last one, the magnetoimpedance ratio exhibited a nearly constant value in the frequency range of 10–200MHz. The results are discussed in terms of the anisotropies present in all samples and by considering the connection of magnetoimpedance effects with ferromagnetic resonance phenomena.
Dopant dependence on passivation and reactivation of carrier after hydrogenation
Authors: Fukata N. , Sato S. , Morihiro H. , Murakami K. , Ishioka K. , Kitajima M. , Hishita S.
Published: February 2007

The formation of hydrogen (H)-related complexes and H effects on boron (B) and phosphorus (P) dopants was investigated in B- or P-doped silicon (Si) crystal treated with high concentration of H. The reactivation process of dopant carriers by annealing after hydrogenation was significantly different between the p-type and n-type specimens. The difference is likely to be attributable to the formation of H-related defects based on the stable sites of the H atoms, i.e., complicated H multiple trapping centers are formed by bond breaking due to H atoms in only p-type B-doped Si.
A tetrode based fast pulsed microwave source for electron cyclotron resonance breakdown experiments
Authors: Yadav Vipin K. , Sathyanarayana K. , Purohit D. , Bora D.
Published: February 2007

To study electron cylotron resonance (ECR) breakdown and afterglow plasma in an experimental linear plasma system, a pulsed microwave source with rapid rise and fall of microwave power is desired. A pulsed microwave source with fast rise and fall capability for ECR breakdown experiments has been designed and tested for performance in the system. A tetrode, controlled by a modulator card, is used as a fast switch to initiate microwave power from a conventional magnetron operating at 2.45 GHz. The typical rise time of microwave power is ∼3 μs and a fall time of ∼10 μs. Using this scheme in a realistic pulsed microwave source at 800 W power, ECR breakdown of neutral gas is achieved and the plasma delay and fall time are observed from the plasma density measurements using a Langmuir probe. The design details of the fast rise pulsed microwave source are presented in this article with initial experimental results.
Aqueous microdrop manipulation and mixing using ferrofluid dynamics
Authors: Song Woo-Bin , Ding Zhenwen , Son Chulwoo , Ziaie Babak
Published: February 2007

In this letter, the authors present a simple method to manipulate free microdroplets using ferrofluid dynamics. For droplet transport, a set of periodic lines of ferrofluid on top of a silicon wafer is created by a single strip magnet and dynamically changed by the rotation of a magnetic stirrer underneath it. It is demonstrated that the speed of droplet movement depends on the rotation speed of the magnetic stirrer as well as the size of the droplet. For better droplet mixing efficiency, a discontinuous pattern at the mixing spots is created by adding a smaller strip magnet to the above setup.
Room temperature fast synthesis of zinc oxide nanowires by inductive heating
Authors: Luo Lei , Sosnowchik Brian D. , Lin Liwei
Published: February 2007

ZnO nanowires have been rapidly synthesized using inductive heating in a room temperature environment. Nanowires with random and aligned orientations were grown on silicon and 4H-SiC (0001) substrates in less than 5min, respectively, using ZnO/graphite as the solid source powder. Scanning electron microscopy showed nanowire diameters of 20–120nm and lengths up to 5μm, and transmission electron microscopy verified the single-crystalline lattice of the nanowires. Electrical properties were studied by connecting a single ZnO nanowire in the field-effect transistor configuration. This demonstration further illustrates the feasibility of a simple and fast nanoscale synthesis using inductive heating for nanomaterial synthesis.
Magnetic characterization of CoFeB∕MgO and CoFe∕MgO interfaces
Authors: Negusse Ezana , Lussier A. , Dvorak J. , Idzerda Y. U. , Shinde S. R. , Nagamine Y. , Furukawa S. , Tsunekawa K. , Djayaprawira D. D.
Published: February 2007

The use of CoFeB ferromagnetic electrodes in place of CoFe has been shown to significantly increase the tunneling magnetoresistance (TMR) of MgO based magnetic tunnel junctions (MTJs). By using soft x-ray scattering techniques, we show that the behavior of the magnetic moments located at the CoFe–MgO interface are drastically different from the rest of the CoFe film, whereas the magnetic response of the CoFeB–MgO interfacial moments is coherent with the film’s bulk. Our results support the view that the high TMR values observed in MgO based MTJs with CoFeB electrodes are due to the uniform magnetic response of the entire CoFeB electrode including the MgO interfacial moments.
Electrical activity of intragrain defects in polycrystalline silicon layers obtained by aluminum-induced crystallization and epitaxy
Authors: Van Gestel D. , Romero M. J. , Gordon I. , Carnel L. , D’Haen J. , Beaucarne G. , Al-Jassim M. , Poortmans J.
Published: February 2007

Defect etching revealed a very large density (∼109cm−2) of intragrain defects in polycrystalline silicon (pc-Si) layers obtained through aluminum-induced crystallization of amorphous Si and epitaxy. Electron-beam-induced current measurements showed a strong recombination activity at these defects. Cathodoluminescence measurements showed the presence of two deep-level radiative transitions (0.85 and 0.93eV) with a relative intensity varying from grain to grain. These results indicate that the unexpected quasi-independence on the grain size of the open-circuit voltage of these pc-Si solar cells is due to the presence of numerous electrically active intragrain defects.
Third order nonlinear susceptibility of InN at near band-gap wavelengths
Authors: Naranjo F. B. , González-Herráez M. , Fernández H. , Solis J. , Monroy E.
Published: February 2007

The authors report room-temperature measurements of the third order nonlinear susceptibility modulus ∣χ(3)∣ of thick (∼600nm) InN layers. Transmission measurements provide a room-temperature value for the optical band gap of the samples slightly above 1500nm. Third order nonlinear optical susceptibility has been measured using degenerate four wave mixing experiments at wavelengths near and above band gap. ∣χ(3)∣ values of (4.2–10)×10−10esu were measured at this wavelength range. The associated relaxation time of the generated population grating at 1500nm was measured. The obtained value of 4.8ps is consistent with a nonradiative recombination mechanism.
Organic small molecule field-effect transistors with Cytop™ gate dielectric: Eliminating gate bias stress effects
Authors: Kalb W. L. , Mathis T. , Haas S. , Stassen A. F. , Batlogg B.
Published: February 2007

Organic field-effect transistors with unprecedented resistance against gate bias stress are described. The single crystal and thin-film transistors employ the organic gate dielectric Cytop™. This fluoropolymer is highly water repellent and shows a remarkable electrical breakdown strength. The single crystal transistors are consistently of very high electrical quality: near zero onset, very steep subthreshold swing [average: 1.3nFV∕(decadecm2)] and negligible current hysteresis. Furthermore, extended gate bias stress only leads to marginal changes in the transfer characteristics. It appears that there is no conceptual limitation for the stability of organic semiconductors in contrast to hydrogenated amorphous silicon.
A morphometric study of Breutelia pendula and B. elongata (Bryophyta, Bartramiaceae)
Authors: Jolley Helen , Klazenga Niels
Published: February 2007

A morphometric study of the mosses Breutelia pendula (Sm.) Mitt. and B. elongata (Hook.f. & Wilson) Mitt. was conducted in order to investigate the species delimitation between these two species, and to ascertain the status of B. elongata in Australia, in particular Victoria. As a result, B. elongata is no longer considered to occur in continental Australia. Useful characters to distinguish between the newly circumscribed species include the size of the marginal teeth, whether or not the alar cells are inflated, the leaf width and the set of the leaves. Bartramia crassa Hook.f. & Wilson, which was previously considered a synonym of B. elongata, is synonymised with B. pendula.
Predictors of completion of a hepatitis B vaccination schedule in attendees at a primary health care centre
Authors: Macdonald Virginia , Dore Gregory J. , Amin Janaki , van Beek Ingrid
Published: February 2007

Background: In Australia, rates of hepatitis B (HBV) transmission continue to be higher in certain populations, including commercial sex workers and injecting drug users (IDU). This study aims to identify rates and predictors of completion of a HBV vaccination schedule in ‘high-risk’ attendees of a primary health care centre in Sydney. Methods: All clients who attended Kirketon Road Centre, a primary health care centre located in Kings Cross, Sydney, with no evidence of HBV immunity were included in the cohort. The study design was observational with historical controls. The main outcome measure was completion of a three-dose HBV vaccine schedule in the study period. Results: Among 2085 clients who received a first vaccination, 1013 (49%) received a second and 435 (21%) received a third vaccination. Univariate analysis found that significant predictors of completion of the vaccine schedule were intention to administer an accelerated schedule (OR 1.49, P = 0.004), not being an IDU (OR 1.29, P = 0.02) and shorter time between first visit and first vaccine dose (OR 1.24, P for trend <0.0001); however, on multivariate analysis, not being an IDU was no longer a predictor of vaccine completion. Conclusion: Implementation of an accelerated vaccination schedule improved completion rates but they were still low, despite the provision of free vaccination in a service specifically targeting the needs of sex workers, IDU and other marginalised populations. Increasing HBV vaccine uptake and completion rates in Australian adults is an important public health issue not only for the prevention of HBV but also for the future application of other potential vaccines, including those against HIV and hepatitis C.
Sexual risk assessment in general practice: evidence from a New South Wales survey
Authors: Khan Asaduzzaman , Plummer David , Hussain Rafat , Minichiello Victor
Published: February 2007

Background: Physicians’ inadequate involvement in sexual risk assessment has the potential to miss many asymptomatic cases. The present study was conducted to explore sexual risk assessment by physicians in clinical practice and to identify barriers in eliciting sexual histories from patients. Methods: A stratified random sample of 15% of general practitioners (GP) from New South Wales was surveyed to assess their management of sexually transmissible infections (STI). In total, 409 GP participated in the survey with a response rate of 45.4%. Results: Although nearly 70% of GP regularly elicited a sexual history from commercial sex workers whose presenting complaint was not an STI, this history taking was much lower (<10%) among GP for patients who were young or heterosexual. About 23% never took a sexual history from Indigenous patients and 19% never elicited this history from lesbian patients. Lack of time was the most commonly cited barrier in sexual history taking (55%), followed by a concern that patients might feel uncomfortable if a sexual history was taken (49%). Other constraints were presence of another person (39%) and physician’s embarrassment (15%). About 19% of GP indicated that further training in sexual history taking could improve their practice. Conclusions: The present study identifies inconsistent involvement by GP in taking sexual histories, which can result in missed opportunities for early detection of many STI. Options for overcoming barriers to taking sexual histories by GP are discussed.
Contact tracing for sexually transmitted infections in New South Wales, Australia
Authors: McCarthy Melissa , Haddow Lewis J. , Furner Virginia , Mindel Adrian
Published: February 2007

Background: Contact tracing is an important strategy in the control of sexually transmitted infections (STI) because it encourages individuals who may be unaware they have been exposed to an infection to be tested and treated. The aim of this study was to review STI contact tracing procedures in NSW by sexual health clinics (SHC), public health units (PHU) and general practitioners (GP). Methods: A questionnaire study carried out in 2004–2005 of SHC, PHU and a random sample of GP in NSW. SHC and PHU participated in structured interviews and GP completed questionnaires at educational workshops or through a mail-out. Interviews and questionnaires addressed current contact tracing practice and methods of improving the service. Results: All 35 SHC, 6/18 (33%) PHU and 172/212 (81%) of the GP who responded to the survey undertook contact tracing for STI. Chlamydia was the STI most commonly traced by SHC (34/35, 97%) and GP (165/172, 96%). HIV was the STI most commonly traced by PHU (5/6, 83%). Only 23/172 (13%) GP were familiar with the ‘Australasian contact tracing manual’. The commonest barriers to tracing for SHC and GP included patient reluctance (SHC 60%, GP 71%), and the lack of contact details for partners (SHC 46%, GP 60%). GP identified the availability of information for patients (82%) and more training (55%) as necessary resources for optimal contact tracing. Conclusions: SHC and GP frequently undertook contact tracing for some STI; PHU do so less frequently. Barriers to contact tracing are similar for all health-care providers. For GP, there is a need for increased training and the development of written policies and agreed pathways for referral.
Risk factors for incident HIV infection in men having sex with men: a case-control study
Authors: Read Tim R. H. , Hocking Jane , Sinnott Vikki , Hellard Margaret
Published: February 2007

Background: HIV notifications affecting men having sex with men (MSM) in Victoria, Australia have been increasing. This study aimed to determine current risk factors for HIV infection in this population. Methods: Case-control study. Cases were MSM infected within the previous year (incident cases) as indicated by a previous negative test or seroconversion illness. Controls were MSM with a negative HIV test at the same clinic. From May 2001 to May 2003, cases and controls were interviewed about sexual behaviour, drug and alcohol use and mental health and sexually transmissible infections (STI) in the year before their HIV diagnosis. Results: Twenty-six cases and 52 controls were recruited. Risk factors in the year before diagnosis of incident HIV infection included: receptive unprotected anal intercourse (UAI) with ejaculation with casual partners (odds ratio [OR] and 95% confidence interval 57.2 [6.7, 489.4]); insertive UAI with ejaculation with >1 casual partners (OR 19.2 [2.2, 168.9]); having >14 casual partners at sex venues (OR 3.2 [1.1, 9.1]); and consuming >60 g alcohol at one sitting at least weekly (OR 3.6 [1.1, 11.4]). Cases were also more likely to have anal sex with >100 partners in their life and cases had more casual partners than controls in the year before the test. Cases were more likely to have consumed alcohol or amphetamines during a high-risk sexual episode in the year before the test. Conclusions: UAI remains the most important behavioural risk for HIV in Australian MSM. Risk is increased by larger numbers of partners, partners met at sex venues and sex under the influence of alcohol.
Human adenoviruses types associated with non-gonococcal urethritis
Authors: Tabrizi Sepehr N. , Ling Alison E. , Bradshaw Catriona S. , Fairley Christopher K. , Garland Suzanne M.
Published: February 2007

Background: Role of adenoviruses in non-gonococcal urethritis (NGU) has been reported in only a few studies. The aim of the study was to detect and type adenoviruses in men presenting with NGU. Methods: 636 heterosexual and homosexual men presenting with NGU from Melbourne, Australia were recently evaluated for various aetiological organisms including adenovirus. We utilised methods including polymerase chain reaction for detection followed by sequence analysis to type positive samples. Results: Overall, 12 samples from patients with NGU had adenovirus detected. Five types were identified: type 4 (subgenus E), type 35 (subgenus B), and types 9, 37 and 49 (subgenus D). The presence of mixed adenovirus strains was not detected in any sample. Conclusion: Overall, subgenus B, D and E were predominant in this patient population.
Addressing sexually transmissible infection in HIV-positive patients. A clinical audit
Authors: Esler Danielle , Ooi Catriona
Published: February 2007

Australian guidelines for sexual history taking and sexually transmissible infection (STI) screening of HIV-positive patients do not exist. An audit was conducted to assess current practices of sexual history taking and STI testing of HIV-positive patients attending Hunter New England Sexual Health Unit.
Focal adhesion kinase modulates tension signaling to control actin and focal adhesion dynamics
Authors: Schober Markus , Raghavan Srikala , Nikolova Maria , Polak Lisa , Pasolli H. Amalia , Beggs Hilary E. , Reichardt Louis F. , Fuchs Elaine
Published: February 2007

In response to αβ1 integrin signaling, transducers such as focal adhesion kinase (FAK) become activated, relaying to specific machineries and triggering distinct cellular responses. By conditionally ablating Fak in skin epidermis and culturing Fak-null keratinocytes, we show that FAK is dispensable for epidermal adhesion and basement membrane assembly, both of which require αβ1 integrins. FAK is also dispensible for proliferation/survival in enriched medium. In contrast, FAK functions downstream of αβ1 integrin in regulating cytoskeletal dynamics and orchestrating polarized keratinocyte migration out of epidermal explants. Fak-null keratinocytes display an aberrant actin cytoskeleton, which is tightly associated with robust, peripheral focal adhesions and microtubules. We find that without FAK, Src, p190RhoGAP, and PKL–PIX–PAK, localization and/or activation at focal adhesions are impaired, leading to elevated Rho activity, phosphorylation of myosin light chain kinase, and enhanced tensile stress fibers. We show that, together, these FAK-dependent activities are critical to control the turnover of focal adhesions, which is perturbed in the absence of FAK.
Rer1p competes with APH-1 for binding to nicastrin and regulates γ-secretase complex assembly in the early secretory pathway
Authors: Spasic Dragana , Raemaekers Tim , Dillen Katleen , Declerck Ilse , Baert Veerle , Serneels Lutgarde , Füllekrug Joachim , Annaert Wim
Published: February 2007

The γ-secretase complex, consisting of presenilin, nicastrin, presenilin enhancer-2 (PEN-2), and anterior pharynx defective-1 (APH-1) cleaves type I integral membrane proteins like amyloid precursor protein and Notch in a process of regulated intramembrane proteolysis. The regulatory mechanisms governing the multistep assembly of this “proteasome of the membrane” are unknown. We characterize a new interaction partner of nicastrin, the retrieval receptor Rer1p. Rer1p binds preferentially immature nicastrin via polar residues within its transmembrane domain that are also critical for interaction with APH-1. Absence of APH-1 substantially increased binding of nicastrin to Rer1p, demonstrating the competitive nature of these interactions. Moreover, Rer1p expression levels control the formation of γ-secretase subcomplexes and, concomitantly, total cellular γ-secretase activity. We identify Rer1p as a novel limiting factor that negatively regulates γ-secretase complex assembly by competing with APH-1 during active recycling between the endoplasmic reticulum (ER) and Golgi. We conclude that total cellular γ-secretase activity is restrained by a secondary ER control system that provides a potential therapeutic value.
Phosphomimetic Mutation of Ser-187 of SNAP-25 Increases both Syntaxin Binding and Highly Ca2+-sensitive Exocytosis
Authors: Yang Yan , Craig Tim J. , Chen Xiaohui , Ciufo Leonora F. , Takahashi Masami , Morgan Alan , Gillis Kevin D.
Published: February 2007

The phosphorylation targets that mediate the enhancement of exocytosis by PKC are unknown. PKC phosporylates the SNARE protein SNAP-25 at Ser-187. We expressed mutants of SNAP-25 using the Semliki Forest Virus system in bovine adrenal chromaffin cells and then directly measured the Ca2+ dependence of exocytosis using photorelease of caged Ca2+ together with patch-clamp capacitance measurements. A flash of UV light used to elevate [Ca2+]i to several μM and release the highly Ca2+-sensitive pool (HCSP) of vesicles was followed by a train of depolarizing pulses to elicit exocytosis from the less Ca2+-sensitive readily releasable pool (RRP) of vesicles. Carbon fiber amperometry confirmed that the amount and kinetics of catecholamine release from individual granules were similar for the two phases of exocytosis. Mimicking PKC phosphorylation with expression of the S187E SNAP-25 mutant resulted in an approximately threefold increase in the HCSP, whereas the response to depolarization increased only 1.5-fold. The phosphomimetic S187D mutation resulted in an ∼1.5-fold increase in the HCSP but a 30% smaller response to depolarization. In vitro binding assays with recombinant SNARE proteins were performed to examine shifts in protein–protein binding that may promote the highly Ca2+-sensitive state. The S187E mutant exhibited increased binding to syntaxin but decreased Ca2+-independent binding to synaptotagmin I. Mimicking phosphorylation of the putative PKA phosphorylation site of SNAP-25 with the T138E mutation decreased binding to both syntaxin and synaptotagmin I in vitro. Expressing the T138E/ S187E double mutant in chromaffin cells demonstrated that enhancing the size of the HCSP correlates with an increase in SNAP-25 binding to syntaxin in vitro, but not with Ca2+-independent binding of SNAP-25 to synaptotagmin I. Our results support the hypothesis that exocytosis triggered by lower Ca2+ concentrations (from the HCSP) occurs by different molecular mechanisms than exocytosis triggered by higher Ca2+ levels.
Thermosensitive TRPV Channel Subunits Coassemble into Heteromeric Channels with Intermediate Conductance and Gating Properties
Authors: Cheng Wei , Yang Fan , Takanishi Christina L. , Zheng Jie
Published: February 2007

Heat-sensitive transient receptor potential (TRP) channels (TRPV1–4) form the major cellular sensors for detecting temperature increases. Homomeric channels formed by thermosensitive TRPV subunits exhibit distinct temperature thresholds. While these subunits do share significant sequence similarity, whether they can coassemble into heteromeric channels has been controversial. In the present study we investigated the coassembly of TRPV subunits using both spectroscopy-based fluorescence resonance energy transfer (FRET) and single-channel recordings. Fluorescent protein–tagged TRPV subunits were coexpressed in HEK 293 cells; FRET between different subunits was measured as an indication of the formation of heteromeric channels. We observed strong FRET when fluorescence signals were collected selectively from the plasma membrane using a “spectra FRET” approach but much weaker or no FRET from intracellular fluorescence. In addition, no FRET was detected when TRPV subunits were coexpressed with members of the TRPM subfamily or CLC-0 chloride channel subunits. These results indicate that a substantial fraction of TRP channels in the plasma membrane of cotransfected cells were heteromeric. Single-channel recordings confirmed the existence of multiple heteromeric channel forms. Interestingly, heteromeric TRPV channels exhibit intermediate conductance levels and gating kinetic properties. As these subunits coexpress both in sensory neurons and in other tissues, including heart and brain, coassembly between TRPV subunits may contribute to greater functional diversity.
Prions spread via the autonomic nervous system from the gut to the central nervous system in cattle incubating bovine spongiform encephalopathy
Authors: Hoffmann Christine , Ziegler Ute , Buschmann Anne , Weber Artur , Kupfer Leila , Oelschlegel Anja , Hammerschmidt Baerbel , Groschup Martin H.
Published: February 2007

To elucidate the still-unknown pathogenesis of bovine spongiform encephalopathy (BSE), an oral BSE challenge and sequential kill study was carried out on 56 calves. Relevant tissues belonging to the peripheral and central nervous system, as well as to the lymphoreticular tract, from necropsied animals were analysed by highly sensitive immunohistochemistry and immunoblotting techniques to reveal the presence of BSE-associated pathological prion protein (PrPSc) depositions. Our results demonstrate two routes involving the autonomic nervous system through which BSE prions spread by anterograde pathways from the gastrointestinal tract (GIT) to the central nervous system (CNS): (i) via the coeliac and mesenteric ganglion complex, splanchnic nerves and the lumbal/caudal thoracic spinal cord (representing the sympathetic GIT innervation); and (ii) via the Nervus
vagus (parasympathetic GIT innervation). The dorsal root ganglia seem to be subsequently affected, so it is likely that BSE prion invasion of the non-autonomic peripheral nervous system (e.g. sciatic nerve) is a secondary retrograde event following prion replication in the CNS. Moreover, BSE-associated PrPSc was already detected in the brainstem of an animal 24 months post-infection, which is 8 months earlier than reported previously. These findings are important for the understanding of BSE pathogenesis and for the development of new diagnostic strategies for this infectious disease.
Identification of novel canine rabies virus clades in the Middle East and North Africa
Authors: David Dan , Hughes Gareth J. , Yakobson Boris A. , Davidson Irit , Un Hikmat , Aylan Orhan , Kuzmin Ivan V. , Rupprecht Charles E.
Published: February 2007

Four novel phylogenetic clades of canine rabies virus (RABV) variants have been identified in the Middle East and North Africa. The three novel Middle Eastern clades comprise RABV isolates from the borders between Israel and neighbouring countries. The North African clade (Africa 4) comprises four RABV isolates from Egypt and one from Israel. We characterized various RABV lineages antigenically by using a panel of monoclonal antibodies to the nucleoprotein (N) and phylogenetically by analysis of entire N gene sequences. The estimated mean substitution rate for the N gene alignment (2.7×10−4substitutions per site per year) is comparable with previous estimates for RABV. The application of a molecular clock indicates the emergence of current canine RABV diversity to have occurred at about the same time (approx. 1870) in the Middle East and Europe, following divergence from established lineages in Africa and Asia.
Development and characterization of an infectious cDNA clone of the virulent Bucyrus strain of Equine arteritis virus
Authors: Balasuriya Udeni B. R. , Snijder Eric J. , Heidner Hans W. , Zhang Jianqiang , Zevenhoven-Dobbe Jessika C. , Boone Josh D. , McCollum William H. , Timoney Peter J. , MacLachlan N. James
Published: February 2007

Strains ofEquine arteritis virus(EAV) differ in the severity of the disease that they induce in horses. Infectious cDNA clones are potentially useful for identification of genetic determinants of EAV virulence; to date, two clones have been derived from a cell culture-adapted variant of the original (Bucyrus) isolate of EAV, and it has previously been shown that recombinant virus derived from one of these (rEAV030) is attenuated in horses. A complete cDNA copy of the genome of the virulent Bucyrus strain of EAV has now been assembled into a plasmid vector. In contrast to rEAV030, recombinant progeny virus derived from this clone caused severe disease in horses, characterized by pyrexia, oedema, leukopenia, high-titre viraemia and substantial nasal shedding of virus. The availability of infectious cDNA clones that produce recombinant viruses of different virulence to horses will facilitate characterization of the virulence determinants of EAV through reverse genetics.
Correlation between the induction of Th1 cytokines by an attenuated equine infectious anemia virus vaccine and protection against disease progression
Authors: Zhang Xiaoyan , Wang Ying , Liang Hua , Wei Li , Xiang Wenhua , Shen Rongxian , Shao Yiming
Published: February 2007

The equine infectious anemia virus (EIAV) donkey-leukocyte attenuated vaccine (DLV) has been used to protect against equine infectious anaemia (EIA) disease for several decades in China. The attenuated mechanism and immunological protective mechanisms remain to be elucidated. To identify responses that correlate with the protection against disease, we immunized horses with DLV, followed by challenge with an EIAV wild-type strain LN. All vaccinated horses were asymptomatic and had a low level of virus replication (<10 copies ml−1). The expression level of cytokines including gamma interferon, interleukin 2 and 12 in DLV immunized horses was 5–100-fold higher than that in non-vaccinated controls (n=4, P<0.01). After challenge with virulent LN, horses vaccinated with DLV showed lower viral loads (<103 copies ml−1) with no temperature increase, except for one transient febrile episode in one animal. In contrast, horses in the non-vaccinated control group experienced much higher viral loads (>107 copies ml−1) and intermittent febrile episodes. Cytokine production in the DLV-vaccinated horses increased and attained a plateau level at approximately 50 days post-vaccination, and exceeded 107 copies per 107 peripheral blood mononuclear cells (PBMCs) 1–3 months post-challenge. However, non-vaccinated control horses died after several fever episodes (⩾39 °C), which coincided with higher viral load (106–107 copies ml−1) and lower cytokine production (<104 copies per 107 PBMCs). The results indicate that high levels of EIAV-specific cytokines induced by the attenuated EIAV vaccine may contribute to the protective immune response against EIA disease.
Seroprevalence of human papillomaviruses and Chlamydia trachomatis and cervical cancer risk: nested case–control study
Authors: Naucler Pontus , Chen Hui-Chi , Persson Kenneth , You San-Lin , Hsieh Chang-Yao , Sun Chien-An , Dillner Joakim , Chen Chien-Jen
Published: February 2007

A nested case–control study of invasive and in situ cervical cancer was performed within a community-based cohort of 13 595 Taiwanese women assembled in 1991, with a follow-up period of 9 years. Baseline serum or plasma samples were analysed for antibodies against human papillomavirus (HPV) types 6, 16 and 18 and Chlamydia trachomatis. In total, 114 cases (42 incident cases identified during follow-up and 72 prevalent cases identified at baseline) and 519 matched controls were included in the study. HPV-16 seropositivity was strongly associated with cervical cancer (OR=6.33; 95 % CI 3.45–11.62). Overall, C. trachomatis was not associated with cervical cancer, but was associated with cervical cancer in analyses restricted to incident cases of cancer (OR=2.94; 95 % CI 1.17–7.42) or to cases in which serum samples were analysed (OR=3.13; 95 % CI 1.16–8.47). An antagonistic interaction between HPV-6 and -16 was found in a multiplicative model. These results suggest that different HPV types might interfere in cervical carcinogenesis and that C. trachomatis is associated with cervical cancer in prospective studies, and support the notion that HPV-16 seropositivity is strongly associated with cervical cancer.
Thermostable variants are not generally represented in foot-and-mouth disease virus quasispecies
Authors: Mateo Roberto , Luna Eva , Mateu Mauricio G.
Published: February 2007

A severe limitation to fully realize the dramatic potential for adaptation of RNA virus quasispecies may occur if mutations in vast regions of the sequence space of virus genomes lead to significant decreases in biological fitness. In this study the detection and selection by heat of thermostable variants from different foot-and-mouth disease virus (FMDV) populations were attempted, in order to explore whether FMDV may generally accept a substantial increase in thermostability without compromising its infectivity. The results obtained with both uncloned and cloned populations of different serotypes, recovered from cytolytic or persistent infections and subjected to either very few passages or extensive passaging in cells, indicate that the presence of thermostable virus variants, even in small proportions, is not a general feature of FMDV quasispecies. This suggests that no substantial increase in the thermostability of FMDV may readily occur without a negative effect on viral function.
Evaluation of the vaccine potential of an equine herpesvirus type 1 vector expressing bovine viral diarrhea virus structural proteins
Authors: Rosas Cristina T. , König Patricia , Beer Martin , Dubovi Edward J. , Tischer B. Karsten , Osterrieder Nikolaus
Published: February 2007

Bovine viral diarrhea virus(BVDV) is an economically important pathogen of cattle that is maintained in the population by persistently infected animals. Virus infection may result in reproductive failure, respiratory disease and diarrhoea in naïve, susceptible bovines. Here, the construction and characterization of a novel vectored vaccine, which is based on the incorporation of genes encoding BVDV structural proteins (C, Erns, E1, E2) into a bacterial artificial chromosome of the equine herpesvirus type 1 (EHV-1) vaccine strain RacH, are reported. The reconstituted vectored virus, rH_BVDV, expressed BVDV structural proteins efficiently and was indistinguishable from parental vector virus with respect to growth properties in cultured cells. Intramuscular immunization of seronegative cattle with rH_BVDV resulted in induction of BVDV-specific serum neutralizing and ELISA antibodies. Upon experimental challenge infection of immunized calves with the heterologous BVDV strain Ib SE5508, a strong anamnestic boost of the neutralizing-antibody response was observed in all vaccinated animals. Immunized animals presented with reduced viraemia levels and decreased nasal virus shedding, and maintained higher leukocyte counts than mock-vaccinated controls.
Identification of transcripts and protein products of the UL31, UL37, UL46, UL47, UL48, UL49 and US4 gene homologues of avian infectious laryngotracheitis virus
Authors: Helferich Dorothee , Veits Jutta , Mettenleiter Thomas C. , Fuchs Walter
Published: February 2007

In the present study, the transcription and protein expression of seven genes of infectious laryngotracheitis virus (ILTV) were investigated: UL31 and UL37 possess homologues in all known avian and mammalian herpesviruses, whereas UL46–UL49 and US4 are only conserved in most alphaherpesviruses. A peculiarity of the ILTV genome is the translocation of UL47 from the unique long region to a position upstream of US4 within the unique short region. Northern blot analyses revealed that all of the analysed genes were transcribed most abundantly during the late (γ) phase of replication, but the only true late (γ2) gene was UL47. Using monospecific rabbit antisera, the protein products of all of the genes could be detected and localized in ILTV-infected cells. Considerable amounts of the UL31, UL47 and UL48 gene products were found in the cell nuclei, whereas the other proteins were restricted largely to the cytoplasm. Like the respective tegument proteins of other herpesviruses, the UL37 and UL46–UL49 gene products of ILTV were incorporated into virus particles, whereas the UL31 protein and the glycoprotein encoded by US4 (gG) were not detectable in purified virions. It was also demonstrated that the UL48 protein of ILTV is able to activate an alphaherpesvirus immediate-early gene promoter, which is also a typical feature of other UL48 homologues. Taken together, these results indicate that the functions of all of the investigated ILTV proteins are related to those of their homologues in other alphaherpesviruses.
Mapuera virus, a rubulavirus that inhibits interferon signalling in a wide variety of mammalian cells without degrading STATs
Authors: Hagmaier K. , Stock N. , Precious B. , Childs K. , Wang L.-F. , Goodbourn S. , Randall R. E.
Published: February 2007

Mapuera virus(MPRV) is a paramyxovirus that was originally isolated from bats, but its host range remains unknown. It was classified as a member of the genusRubulaviruson the basis of structural and genetic features. Like other rubulaviruses it encodes a V protein (MPRV/V) that functions as an interferon (IFN) antagonist. Here we show that MPRV/V differs from the IFN antagonists of other rubulaviruses in that it does not induce the proteasomal degradation of STAT proteins, key factors in the IFN signalling cascade. Rather, MPRV/V prevents the nuclear translocation of STATs in response to IFN stimulation and inhibits the formation of the transcription factor complex ISGF3. We also show that MPRV/V blocks IFN signalling in cells from diverse mammalian species and discuss the IFN response as a barrier to cross-species infections.