bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Genotype-Specific Carboxyl-Terminal Cleavage Sites of Hepatitis B Virus e Antigen Precursor and Identification of Furin as the Candidate Enzyme
Authors: Ito Kiyoaki , Kim Kyun-Hwan , Lok Anna Suk-Fong , Tong Shuping
Published: February 2009

Hepatitis B e antigen (HBeAg) is a secreted version of hepatitis B virus (HBV) core protein that promotes immune tolerance and persistent infection. It is derived from a translation product of the precore/core gene by two proteolytic cleavage events: removal of the amino-terminal signal peptide and removal of the carboxyl-terminal arginine-rich sequence. Four RXXR motifs are present at the carboxyl terminus of the HBeAg precursor, with the first two fused as151RRGRSPR157. Genotype A possesses two extra amino acids at the first motif (151RRDRGRSPR159), which weakens the first motif and separates it from the second one. Western blot analysis of patient sera revealed a single HBeAg form for genotypes B to D but two additional forms of larger sizes for genotype A. Site-directed mutagenesis and transfection experiments with human hepatoma cell lines indicated that HBeAg of genotype B is derived from cleavage at the first (151RRGR154) motif. The major HBeAg form of genotype A corresponds to cleavage at the second (156RSPR159) motif, and the other two forms are cleavage products of the first (151RRDR154) and third (166RRRR169) motifs, respectively. Only the cleavage product of the third motif of genotype A was observed in furin-deficient LoVo cells, and an inhibitor of furin-like proprotein convertases blocked cleavage of the first and second motifs in human hepatoma cells. In conclusion, our study reveals genotypic differences in HBeAg processing and implicates furin as the major enzyme involved in the cleavage of the first and second RXXR motifs.
Electron Cryo-Microscopy and Single-Particle Averaging of Rift Valley Fever Virus: Evidence for G
N
-G
C
Glycoprotein Heterodimers
Authors: Huiskonen Juha T. , Överby Anna K. , Weber Friedemann , Grünewald Kay
Published: February 2009

Rift Valley fever virus (RVFV) is a member of the genus
Phlebovirus
within the family
Bunyaviridae
. It is a mosquito-borne zoonotic agent that can cause hemorrhagic fever in humans. The enveloped RVFV virions are known to be covered by capsomers of the glycoproteins G
N
and G
C
, organized on a T=12 icosahedral lattice. However, the structural units forming the RVFV capsomers have not been determined. Conflicting biochemical results for another phlebovirus (Uukuniemi virus) have indicated the existence of either G
N
and G
C
homodimers or G
N
-G
C
heterodimers in virions. Here, we have studied the structure of RVFV using electron cryo-microscopy combined with three-dimensional reconstruction and single-particle averaging. The reconstruction at 2.2-nm resolution revealed the organization of the glycoprotein shell, the lipid bilayer, and a layer of ribonucleoprotein (RNP). Five- and six-coordinated capsomers are formed by the same basic structural unit. Molecular-mass measurements suggest a G
N
-G
C
heterodimer as the most likely candidate for this structural unit. Both leaflets of the lipid bilayer were discernible, and the glycoprotein transmembrane densities were seen to modulate the curvature of the lipid bilayer. RNP densities were situated directly underneath the transmembrane densities, suggesting an interaction between the glycoprotein cytoplasmic tails and the RNPs. The success of the single-particle averaging approach taken in this study suggests that it is applicable in the study of other phleboviruses, as well, enabling higher-resolution description of these medically important pathogens.
Engagement of the Lysine-Specific Demethylase/HDAC1/CoREST/REST Complex by Herpes Simplex Virus 1
Authors: Gu Haidong , Roizman Bernard
Published: February 2009

Among the early events in herpes simplex virus 1 replication are localization of ICP0 in ND10 bodies and accumulation of viral DNA-protein complexes in structures abutting ND10. ICP0 degrades components of ND10 and blocks silencing of viral DNA, achieving the latter by dislodging HDAC1 or -2 from the lysine-specific demethylase 1 (LSD1)/CoREST/REST repressor complex. The role of this process is apparent from the observation that a dominant-negative CoREST protein compensates for the absence of ICP0 in a cell-dependent fashion. HDAC1 or -2 and the CoREST/REST complex are independently translocated to the nucleus once viral DNA synthesis begins. The focus of this report is twofold. First, we report that in infected cells, LSD1, a key component of the repressor complex, is partially degraded or remains stably associated with CoREST and is ultimately also translocated, in part, to the cytoplasm. Second, we examined the distribution of the components of the repressor complex and ICP8 early in infection in wild-type-virus- and ICP0 mutant virus-infected cells. The repressor component and ultimately ICP8 localize in structures that abut the ND10 nuclear bodies. There is no evidence that the two compartments fuse. We propose that ICP0 must dynamically interact with both compartments in order to accomplish its functions of degrading PML and SP100 and suppressing silencing of viral DNA through its interactions with CoREST. In turn, the remodeling of the viral DNA-protein complex enables recruitment of ICP8 and initiation of formation of replication compartments.
Primary Occult Hepadnavirus Infection Induces Virus-Specific T-Cell and Aberrant Cytokine Responses in the Absence of Antiviral Antibody Reactivity in the Woodchuck Model of Hepatitis B Virus Infection
Authors: Gujar Shashi A. , Michalak Tomasz I.
Published: February 2009

Although the virological features of serologically silent hepadnaviral primary occult infection (POI) have been relatively well recognized in the woodchuck model of hepatitis B virus infection, the characteristics of accompanying immune responses remain unknown. In this study, the kinetics of woodchuck hepatitis virus (WHV)-specific and generalized (mitogen-induced) T-cell proliferative responses and cytokine expression profiles in circulating lymphoid cells and the liver, along with WHV-specific antibody responses, were investigated during experimentally induced POI and subsequent challenge with a liver-pathogenic dose (>103virions) or liver-nonpathogenic dose (50 virions) of the same virus. The data revealed that POI, which does not prompt WHV surface antigenemia, antiviral antibody response, and hepatitis or protect from challenge with a liver-pathogenic virus dose, was accompanied by the appearance of a strong WHV-specific T-cell response directed against multiple viral epitopes that intermittently persisted at low levels for up to 10-months during follow-up. Furthermore, immediately after exposure to a liver-nonpathogenic dose of WHV, lymphocytes acquired a heightened capacity to proliferate in response to mitogenic stimuli and displayed augmented expression of alpha interferon, interleukin-12 (IL-12), and IL-2, but not tumor necrosis factor alpha. Overall, the kinetics of WHV-specific and mitogen-induced T-cell proliferative and cytokine responses in POI were closely comparable to those seen in infection induced by liver-pathogenic viral doses. The data demonstrated that virus-specific T-cell proliferative reactivity is a very sensitive indicator of exposure to hepadnavirus, even to small amounts inducing serologically mute infection. They also showed that hepadnaviral POI is not only a molecularly but also an immunologically identifiable and distinctive entity.
Novel Immunocompetent Murine Tumor Model for Evaluation of Conditionally Replication-Competent (Oncolytic) Murine Adenoviral Vectors
Authors: Robinson Michael , Li Betty , Ge Ying , Ko Derek , Yendluri Satya , Harding Thomas , VanRoey Melinda , Spindler Katherine R. , Jooss Karin
Published: February 2009

Oncolytic adenoviral vectors that express immunostimulatory transgenes are currently being evaluated in clinic. Preclinical testing of these vectors has thus far been limited to immunodeficient xenograft tumor models since human adenoviruses do not replicate effectively in murine tumor cells. The effect of the immunostimulatory transgene on overall virus potency can therefore not be readily assessed in these models. Here, a model is described that allows the effective testing of mouse armed oncolytic adenovirus (MAV) vectors in immunocompetent syngeneic tumor models. These studies demonstrate that the MAV vectors have a high level of cytotoxicity in a wide range of murine tumor cells. The murine oncolytic viruses were successfully armed with murine granulocyte-macrophage colony-stimulating factor (mGM-CSF) by a novel method which resulted in vectors with a high level of tumor-specific transgene expression. The mGM-CSF-armed MAV vectors showed an improved level of antitumor potency and induced a systemic antitumor immune response that was greater than that induced by unarmed parental vectors in immunocompetent syngeneic tumor models. Thus, the oncolytic MAV-1 system described here provides a murine homolog model for the testing of murine armed oncolytic adenovirus vectors in immunocompetent animals. The model allows evaluation of the impact of virus replication and the host immune response on overall virus potency and enables the generation of translational data that will be important for guiding the clinical development of these viruses.
The Intersection of Epstein-Barr Virus with the Germinal Center
Authors: Roughan Jill E. , Thorley-Lawson David A.
Published: February 2009

The current model of Epstein-Barr virus (EBV) infection and persistence in vivo proposes that EBV uses the germinal center (the GC model) to establish a quiescent latent infection in otherwise-normal memory B cells. However, the evidence linking EBV-infected cells and the GC is only indirect and limited. Therefore, a key portion of the model, that EBV-infected cells physically reside and participate in GCs, has yet to be verified. Furthermore, recent experiments suggested that upon infection of GC cells the viral growth latency transcription program is dominant and GC functionality and phenotype are ablated, i.e., EBV infection is not consistent with GC function. In this study we show that in vivo, EBV-infected B cells in the tonsils retain expression of functional and phenotypic markers of GC cells, including bcl-6 and AID. Furthermore, these cells are physically located in the GC and express a restricted form of latency, the default latency program. Thus, the EBV default latency transcription program, unlike the growth latency program, is consistent with the retention of GC functionality in vivo. This work verifies key components of the GC model of EBV persistence and suggests that EBV and the GC can interact to produce the latently infected memory cells found in the periphery. Furthermore, it identifies latently infected GC B cells as a potential pathogenic nexus for the development of the EBV-positive, GC-associated lymphomas Hodgkin's disease and Burkitt's lymphoma.
MAVS Self-Association Mediates Antiviral Innate Immune Signaling
Authors: Tang Eric D. , Wang Cun-Yu
Published: February 2009

The innate immune system recognizes nucleic acids during viral infection and stimulates cellular antiviral responses. Intracellular detection of RNA virus infection is mediated by the RNA helicases RIG-I (
r
etinoic acid
i
nducible
g
ene
I
) and MDA-5, which recognize viral RNA and signal through the adaptor molecule MAVS (
m
itochondrial
a
nti
v
iral
s
ignaling) to stimulate the phosphorylation and activation of the transcription factors IRF3 (
i
nterferon
r
egulatory
f
actor
3
) and IRF7. Once activated, IRF3 and IRF7 turn on the expression of type I interferons, such as beta interferon. Interestingly, unlike other signaling molecules identified in this pathway, MAVS contains a C-terminal transmembrane (TM) domain that is essential for both type I interferon induction and localization of MAVS to the mitochondrial outer membrane. However, the role the MAVS TM domain plays in signaling remains unclear. Here we report the identification of a function for the TM domain in mediating MAVS self-association. The activation of RIG-I/MDA-5 leads to the TM-dependent dimerization of the MAVS N-terminal caspase recruitment domain, thereby providing an interface for direct binding to and activation of the downstream effector TRAF3 (
t
umor necrosis factor
r
eceptor-
a
ssociated
f
actor
3
). Our results reveal a role for MAVS self-association in antiviral innate immunity signaling and provide a molecular mechanism for downstream signal transduction.
In Vivo gp41 Antibodies Targeting the 2F5 Monoclonal Antibody Epitope Mediate Human Immunodeficiency Virus Type 1 Neutralization Breadth
Authors: Shen Xiaoying , Parks Robert J. , Montefiori David C. , Kirchherr Jennifer L. , Keele Brandon F. , Decker Julie M. , Blattner William A. , Gao Feng , Weinhold Kent J. , Hicks Charles B. , Greenberg Michael L. , Hahn Beatrice H. , Shaw George M. , Haynes Barton F. , Tomaras Georgia D.
Published: February 2009

The broadly neutralizing human monoclonal antibodies (MAbs) 2F5 and 4E10, both targeting the highly conserved human immunodeficiency virus type 1 (HIV-1) envelope membrane proximal external region (MPER), are among the MAbs with the broadest heterologous neutralizing activity and are of considerable interest for HIV-1 vaccine development. We have identified serum antibodies from an HIV-infected subject that both were broadly neutralizing and specifically targeted MPER epitopes that overlap the 2F5 epitope. These MPER-specific antibodies were made 15 to 20 months following transmission and concomitantly with the development of autoantibodies. Our findings suggest that multiple events (i.e., genetic predisposition and HIV-1 immune dysregulation) may be required for induction of broadly reactive gp41 MPER antibodies in natural infection.
Characterization of Pseudorabies Virus (PrV) Cleavage-Encapsidation Proteins and Functional Complementation of PrV pUL32 by the Homologous Protein of Herpes Simplex Virus Type 1
Authors: Fuchs Walter , Klupp Barbara G. , Granzow Harald , Leege Tobias , Mettenleiter Thomas C.
Published: February 2009

Cleavage and encapsidation of newly replicated herpes simplex virus type 1 (HSV-1) DNA requires several essential viral gene products that are conserved in sequence within the
Herpesviridae
. However, conservation of function has not been analyzed in greater detail. For functional characterization of the UL6, UL15, UL28, UL32, and UL33 gene products of pseudorabies virus (PrV), the respective deletion mutants were generated by mutagenesis of the virus genome cloned as a bacterial artificial chromosome (BAC) in
Escherichia coli
and propagated in transgenic rabbit kidney cells lines expressing the deleted genes. Neither of the PrV mutants was able to produce plaques or infectious progeny in noncomplementing cells. DNA analyses revealed that the viral genomes were replicated but not cleaved into monomers. By electron microscopy, only scaffold-containing immature but not DNA-containing mature capsids were detected in the nuclei of noncomplementing cells infected with either of the mutants. Remarkably, primary envelopment of empty capsids at the nuclear membrane occasionally occurred, and enveloped tegument-containing light particles were formed in the cytoplasm and released into the extracellular space. Immunofluorescence analyses with monospecific antisera of cells transfected with the respective expression plasmids indicated that pUL6, pUL15, and pUL32 were able to enter the nucleus. In contrast, pUL28 and pUL33 were predominantly found in the cytoplasm. Only pUL6 could be unequivocally identified and localized in PrV-infected cells and in purified virions, whereas the low abundance or immunogenicity of the other proteins hampered similar studies. Yeast two-hybrid analyses revealed physical interactions between the PrV pUL15, pUL28, and pUL33 proteins, indicating that, as in HSV-1, a tripartite protein complex might catalyze cleavage and encapsidation of viral DNA. Whereas the pUL6 protein is supposed to form the portal for DNA entry into the capsid, the precise role of the UL32 gene product during this process remains to be elucidated. Interestingly, the defect of UL32-negative PrV could be completely corrected in
trans
by the homologous protein of HSV-1, demonstrating similar functions. However,
trans
-complementation of UL32-negative HSV-1 by the PrV protein was not observed.
IDEMPOTENT UNINORMS ON FINITE ORDINAL SCALES
Authors: DE BAETS BERNARD , FODOR JÁNOS , RUIZ-AGUILERA DANIEL , TORRENS JOAN
Published: February 2009

In this paper we characterize all idempotent uninorms defined on a finite ordinal scale. It is proved that any such discrete idempotent uninorm is uniquely determined by a decreasing function from the set of scale elements not greater than the neutral element to the set of scale elements not smaller than the neutral element, and vice versa. Based on this one-to-one correspondence, the total number of discrete idempotent uninorms on a finite ordinal scale of n + 1 elements is equal to 2n.
THE GREATEST COMMON DIVISOR AND OTHER TRIANGULAR NORMS ON THE EXTENDED SET OF NATURAL NUMBERS
Authors: MAYOR GASPAR , MONREAL JAUME
Published: February 2009

This paper deals with triangular norms and conorms defined on the extended set N of natural numbers ordered by divisibility. From the fundamental theorem of arithmetic, N can be identified with a lattice of functions from the set of primes to the complete chain {0, 1, 2, …, +∞}, thus our knowledge about (divisible) t-norms on this chain can be applied to the study of t-norms on N. A characterization of those t-norms on N which are a direct product of t-norms on {0, 1, 2, …, +∞} is given and, after introducing the concept of T-prime (prime with respect to a t-norm T), a theorem about the existence of a T-prime decomposition is obtained. This result generalizes the fundamental theorem of arithmetic.
DYNAMIC SIMILARITY METRIC USING FUZZY PREDICATES FOR CASE-BASED PLANNING
Authors: OWAIS M. A. , AHMED M. A.
Published: February 2009

Case-based planning (CBP) is a knowledge-based planning technique which develops new plans by reusing its past experience instead of planning from scratch. The task of CBP becomes difficult when the knowledge needed for planning can not be expressed precisely. In this paper, we tackle this issue by modeling imprecise information using fuzzy predicates; and accordingly, we present a dynamic similarity metric for efficient and effective retrieval of relevant cases from a library of cases. We also present weight adaptation algorithm to allow improving the performance of the metric overtime. We use and compare the performance of Tabu search, simulated annealing, and exhaustive search algorithms in instantiating fuzzy predicates to achieve maximum similarity between a new problem and a case. Our experiments show that the proposed metric is sound. The metric along with the adaptation algorithm have been shown to be promising when compared to others. Experiments also show that simulated annealing is more efficient than Tabu search and exhaustive search in fuzzy predicates instantiation.
STABILITY OF FUZZY DYNAMIC SYSTEMS
Authors: MIZUKOSHI MARINA TUYAKO , BARROS LAÉCIO CARVALHO , BASSANEZI RODNEY CARLOS
Published: February 2009

In this work we are study the Fuzzy Initial Value Problem (FIVP) with parameters and/or initial conditions given by fuzzy sets. Starting from the flow equation of the deterministic Initial Value Problem (IVP) associates to FIVP, we obtain the FIVP flow, through the principle of Zadeh. Follow, we introduce the concept of fuzzy equilibrium stability of FIVP and some examples are given.
DEFINITION AND ADAPTATION OF WEIGHTED FUZZY LOGIC PROGRAMS
Authors: CHORTARAS ALEXANDROS , STAMOU GIORGOS , STAFYLOPATIS ANDREAS
Published: February 2009

Fuzzy logic programming has been lately used as a general framework for representing and handling imprecise knowledge. In this paper, we define the syntax and the semantics of definite weighted fuzzy logic programs, which extend definite fuzzy logic programs by allowing the inclusion of different significance weights in the individual atoms that make up the antecedent of a fuzzy logic rule. The weights add expressiveness to a fuzzy logic program and allow the determination of the level up to which an atom in the antecedent of a rule may affect the truth value of its consequent. In describing the semantics of definite weighted fuzzy logic programs we introduce the notion of the generalized weighted fuzzy conjunction operator, which can be regarded as a weighted t-norm based aggregation. We determine the properties of generalized weighted fuzzy conjunction operators and provide several examples. A methodology for constructing generalized weighted fuzzy conjunction operators using generator functions of existing t-norms is also introduced. Finally, a method for setting up a parametric weighted fuzzy logic program and automatically adapting the weights of its rules using a numerical dataset is developed.
SYNTHESIS AND ELECTRO-OPTIC PROPERTY OF INTERCALATION POLYIMIDE AND NANOHYBRID
Authors: YANG D. Y. , QIU F. X. , CAO G. R.
Published: February 2009

Intercalation nonlinear-optical (NLO) polyimide and polyimide/silica hybrid material were synthesized by the sol–gel technique. The results showed that the interpenetrating hybrid polymer networks were formed and showed excellent thermal stability. The electro-optic property suggests that this hybrid material has potential for applications in high performance optical devices.
MODELING AND ANALYSIS OF COMMONPATH PHASE SHIFTING SHEAR SYSTEM BASED ON BIREFRINGENT OPTICAL DEVICES
Authors: WANG HONGJUN , WANG ZHAO , TIAN AILING , LIU BINGCAI
Published: February 2009

In the technology of optical surface measurement, the phase-shifting shear interferometer had been widely used. In measurement, the phase-shifting was introduced in time domain, and the measurement system adopted double optical path for change phase-shifting and shear, so the measurement accuracy was limited. To decrease error, a commonpath phase-shifting shear system based on birefringent optical devices was introduced. In this system, the lateral shear and phase-shifting 0, π/2, π, 3π/2 was introduced in the commonpath optical system. Because the birefringent optical devices can introduce shear in the collinear optical system, a new Jones matrix was established. Based on the Jones matrix theory, the principle theory was analyzed in detail. In the experiment, an optical surface was measured with this system. The theoretical analysis and experiment results demonstrate the feasibility of this approach.
SOLVENT EFFECTS IN THE DETERMINATION OF THE NONLINEAR OPTICAL PROPERTIES
Authors: MENDOZA-GARCÍA A. , PAZ J. L. , GORAYEB M. , HERNÁNDEZ A. J. , CASTRO E. , MARTÍN P.
Published: February 2009

The interaction between a two-level molecular system and a high intensity electric field under the influence of a solvent was analyzed through the OSBE. To solve these equations, the average of the coherence was performed, using a generalized Lorentzian approximation for the Voigt's function as a probability distribution. Applying the convolution theorem, we were able to find an analytical expression for the coherence, from which we calculate optical properties, such as the absorption coefficient, refractive index and emitted signal intensity. In this contribution, we show numerical results for these properties, calculated for a standard model of organic colorants, Green Malaquite.
EFFECT OF SUBSTRATE TEMPERATURE ON THE MICROSTRUCTURE AND OPTICAL PROPERTIES OF ZnO NANOCRYSTALLINE THIN FILMS
Authors: XU LINHUA , LI XIANGYIN , YUAN JUN
Published: February 2009

In this work, ZnO nanocrystalline thin films were prepared by sol–gel dip-coating method on glass substrates and the effect of substrate temperature on the microstructure and optical properties of these films was investigated. The structural properties were analyzed by X-ray diffraction (XRD) and scanning probe microscope. The optical properties were studied by UV-visible spectrophotometer and fluorophotometer. The experimental results showed that if substrate temperature was relatively high, once the substrate was dipped into ZnO sol, some aggregated colloidal particles would be absorbed on it. After the ZnO gel film was annealed, the poor quality ZnO thin film was formed, which had a weak ultraviolet emission and a relatively strong defect-related visible emission.
LASER DIRECT WRITING OF LONG PERIOD FIBER GRATING BY 800 NM FEMTOSECOND LASER PULSES
Authors: RUAN SHUANGCHEN , HUANG YI , DU CHENLIN , YU YONGQIN
Published: February 2009

Femtosecond laser pulses with ultrashort time duration and ultrahigh peak power can cause the refractive index change in transparent materials and micron scale machining precision. Long period fiber gratings (LPFGs) with different periods and different grating lengths in the standard single mode fiber were fabricated, using laser direct writing method, by femtosecond laser pulses with pulse width of 200 fs at a center wavelength of 800 nm in air. The transmission spectra were studied in the range of 1510 nm to 1610 nm. Two LPFGs with period of 400 μm, and 550 μm, respectively fabricated with same irradiation power of 275 mW, were shown. The loss peak of 1552 nm, the transmission loss of 16 dB and the FWHM of 20 nm were obtained when the period of LPFG was 400 μm, while the loss peak of 1588 nm, the transmission loss of 20 dB and the FWHM of 25 nm were achieved when the period of LPFG was 550 μm. According to the theory of mode field coupling for long period grating, it was indicated that the modulation of refractive index Δn was in the level of 10-2.
RF-MBE GROWTH OF GaN ON SAPPHIRE FOR GAS SENSING APPLICATION
Authors: CHIN C. W. , HASSAN Z. , YAM F. K.
Published: February 2009

Besides SiC , a group III-V nitrides are also suitable large-band gap semiconductor materials for high-temperature gas sensor devices. In this paper, we present the study of the H2 sensitive device fabricated based on n-type GaN wafer. The GaN thin film with AlN buffer layer was grown on sapphire by RF plasma-assisted molecular beam epitaxy (RF-MBE). A few monolayers of AlN were deposited using high flux Al before the growth of the AlN buffer layer. This step is speculated to be able to form a better relaxed layer for the subsequent growth of the AlN buffer layer. Pt contacts with thickness of about 150 nm were then deposited on the GaN/AlN/Al2O3 using the sputtering system. Gas detection was carried out at room temperature. Prior to the current–voltage (I–V) measurements, the samples were annealed at temperatures ranging from 200°C to 600°C in N2 ambience. A significant change of current in the Pt/ GaN gas sensor was observed for the 600°C annealed sample when exposed to 0.5% H2 in N2 gas.
DYNAMICS OF FERROELECTRIC NANO CLUSTER IN BaTio3 OBSERVED AS A REAL TIME CORRELATION BETWEEN TWO SOFT X-RAY LASER PULSES
Authors: JI KAI , NASU KEIICHIRO , NAMIKAWA KAZUMICHI , ZHENG HANG
Published: February 2009

We carry out a theoretical investigation to clarify the dynamic property of photo-created nano-sized ferroelectric cluster observed in the paraelectric BaTiO3 as a real time correlation of speckle pattern between two soft X-ray laser pulses, at just above the paraelectric-ferroelectric phase transition temperature. Based on a model with coupled soft X-ray photon and ferroelectric phonon mode, we study the time-dependence of scattering probability by using a perturbative expansion approach. The cluster-associated phonon softening as well as central peak effects are well-reproduced in the phonon spectral function via quantum Monte Carlo simulation. Besides, it is found that the time-dependence of speckle correlation is determined by the relaxation dynamics of ferroelectric clusters. Near the transition point, cluster excitation is stable, leading to a long relaxation time, while at high temperature, cluster structure is subject to the thermal fluctuation, ending up with a short relaxation time.
DISTORTION TOLERANCE AGAINST GEOMETRY IMPERFECTIONS IN POLYMERIC MICROCAVITY DYE LASER
Authors: ZHANG RUI , POPOV SERGEI , RICCIARDI SEBASTIEN , FRIBERG ARI T. , SERGEYEV SERGEY
Published: February 2009

A polymeric solid-state microcavity dye laser of the size comparable to a lasing wavelength is modeled by means of the finite element method (FEM). Lasing modes are calculated taking into account the gain material properties, such as absorption, dispersion and fluorescence. Study of the microcavity tolerance against possible geometrical imperfections demonstrates good robustness of the chosen shape and stability of the operation under possible cavity distortions.
ORIENTATING MANIPULATION OF CYLINDRICAL PARTICLES WITH OPTICAL TWEEZERS
Authors: SUN XIUDONG , LI XUECONG , ZHANG JIANLONG
Published: February 2009

Orientating manipulations of cylindrical particles were performed by optical tweezers. Vertical and horizontal manipulations of Escherichia coli (E. coli) were carried out by changing the trapping depth and the focused laser beam shape. It was found that carbon nanotubes bundles (CNTBs) could be rotated in the linear polarized optical trap until it orientated its long axis along the linear polarization direction of the laser beam. However, E.coli could not be orientated in this way. Corresponding mechanisms were discussed based on the anisomeric electric characters of CNTBs. These orientation technologies of cylindrical objects with optical trap have potential applications in assembling nano-electric devices.
THICKNESS DEPENDENCE OF THIRD-HARMONIC GENERATION FROM SELF-ASSEMBLED REGIOREGULAR POLY(3-HEXYLTHIOPHENE) THIN FILMS ON QUARTZ GLASSES WITH DIFFERENT SURFACES
Authors: WANG XIN , RU JIASHENG , OCHIAI SHIZUYASU , YAMADA YUU , UCHIDA YOSHIYUKI , FURUHASHI HIDEO , MIZUTANI TERUYOSHI , CUI YIPING , LIU JINGNAN
Published: February 2009

Regioregular poly(3-hexylthiophene) [RR-P3HT] thin films were prepared on fused quartz glasses by spin-coating and drop-casting from the chloroform solutions. Film structures and morphologies were characterized by UV-visible absorption spectra, out-of-plane X-ray diffraction (XRD) and atomic force microscopy (AFM). Drop-cast films showed increased χ(3) of about three times higher than that of the spin-coated ones when the film thicknesses were both around 140 nm, and the magnitude of the increase was different for different thickness. The magnitudes of χ(3) for drop-cast RR-P3HT films were calculated in the range of 10-11 esu, and the phases of χ(3) lay in the range from 230 to 300° which were consistent with the contributions from two-photon absorptions (TPA). Hexamethyldisilazane (HMDS) treatment of the glass substrates could increase the χ(3) of drop-cast films further from about ten percent to several times higher. This also depended on the film thickness. These results revealed the deposition method and surface modification effects on the self-assembled RR-P3HT film structures, and the importance of higher-ordering and increased crystallinity for the enhancement of the χ(3) of the polymeric films for their applications in NLO devices.
CURRENT RECTIFICATION IN NEMATIC LIQUID CRYSTAL CELL WITH ALKANETHIOL SELF-ASSEMBLED MONOLAYER
Authors: YAO FENGFENG , PEI YANBO , SUN XIUDONG
Published: February 2009

Asymmetric current–voltage (I/V) behaviors with respect to the polarity of the voltage bias were observed in the nematic liquid crystal (NLC) cells constructed with the gold film on the silicon wafer as one substrate and an indium-tin-oxide (ITO)-coated glass slide as the other substrate. A little smaller current resulted at the positive bias corresponding to the positive voltage bias being applied to the gold film relative to the ITO-coated glass slide. When the alkanethiol self-assembled monolayer (SAM) was introduced into the above NLC cell as the aligning layer, it was able to enhance the forward current significantly, but suppress the reverse current. A current rectification ratio of ~20 was obtained at 1.5 V in the NLC cell with SAM as the aligning layer. Besides, we also characterized the effect of the optical power of 632.8 nm on the asymmetric I/V behaviors in the NLC cells without SAM and with SAM as the aligning layer.
GUIDING CHARACTERISTICS OF AN AIR WAVEGUIDE WITH LEFT-HANDED METAMATERIALS CLADDING
Authors: JIANG YONG-YUAN , SHEN ZONG-JING
Published: February 2009

The characteristics of guided modes of a planar waveguide in which an air core is sandwiched by two left-handed metamaterials are studied. The dispersion relation of the guided modes in this air waveguide is derived where the left-handed metamaterials claddings can be either isotropic or uniaxially anisotropic. We analyze the fast and slow wave characteristics of the guided modes. The problem of whether the dispersion relation of slow wave modes has a solution is explored. The relation between the electromagnetic parameters of the waveguide and the solution of the dispersion relation of the slow wave modes is discussed in detail.
BEAM COUPLING CHARACTERISTICS IN NEMATIC LIQUID CRYSTAL DOPED WITH SILVER NANOPARTICLES
Authors: JIANG YONG-YUAN , LI JING , HUANG LIN-YI
Published: February 2009

The orientational photorefractive effect was observed in the nematic liquid crystals E7 doped with silver nanoparticles. Both the self-diffraction and beam-coupling effects were studied in a two-wave-mixing experiment with an applied external DC field. The dependence of diffraction efficiency on the applied voltage, pump power, pump/signal ratio and grating constant were studied. Experimental results indicate that the optical non-linearity of NLCs can be enhanced significantly by doping silver nanoparticles. Further experiments demonstrate that the holographic grating formed in the sample can be switched on and off by the external DC field. PR two-beam coupling experiment was also performed in the Ag-doped NLCs cell. These results are of benefit to the applications of PR NLCs in holography and image processing.
SYNTHESIS, FLUORESCENCE AND ELECTROCHEMICAL PROPERTIES OF SYMMETRICAL CHROMOPHORES WITH ELECTRON ACCEPTING OXADIAZOLE
Authors: ZHU XIAOQIN , QIAN YING , HUANG WEI , LU CHANGGUI , CUI YIPING
Published: February 2009

Two symmetrical TPA chromophores containing 1,3,4-oxadiazole group were designed and synthesized through the Wittig–Horner reaction. All compounds were characterized by NMR, IR, UV and melting point. Chromophore I and II showed good thermal stability and did lose less than 5% weight on heating to about 300°C. The electrochemical property was explored by cyclic voltammetry. The HOMO and LUMO energy of compound I were estimated to be -3.65 eV and -1.09 eV. That of compound II were -3.69 eV and -1.10 eV. Both chromophores exhibited a positive solvatochromic behavior. In CH2Cl2 , the maximum peaks of single-photon-excited fluorescence (SPEF) were at 512 nm for compound I and at 495 nm for compound II with high fluorescence quantum yields 0.73 and 0.70, respectively. The two-photon-excited fluorescence (TPEF) had also been investigated. Pumped by femtosecond laser at 800 nm, strong up-conversion emissions with the central wavelength were at 532 nm for compound I and 550 nm for compound II in the solution of CH2Cl2 .
Comparative Enzymology and Structural Biology of RNA Self-Cleavage
Authors: Fedor Martha J.
Published: February 2009

Self-cleaving hammerhead, hairpin, hepatitis delta virus, and glmS ribozymes comprise a family of small catalytic RNA motifs that catalyze the same reversible phosphodiester cleavage reaction, but each motif adopts a unique structure and displays a unique array of biochemical properties. Recent structural, biochemical, and biophysical studies of these self-cleaving RNAs have begun to reveal how active site nucleotides exploit general acid-base catalysis, electrostatic stabilization, substrate destabilization, and positioning and orientation to reduce the free energy barrier to catalysis. Insights into the variety of catalytic strategies available to these model RNA enzymes are likely to have important implications for understanding more complex RNA-catalyzed reactions fundamental to RNA processing and protein synthesis.
Mechanical Signaling in Networks of Motor and Cytoskeletal Proteins
Authors: Howard Jonathon
Published: February 2009

The motions of cells and organelles are highly coordinated. They are driven by motor proteins moving along cytoskeletal filaments, and by the dynamic growth and shrinkage of the filaments themselves. The initiation of cellular motility is triggered by biochemical signaling pathways, but the coordination of motility at different locations or times is not well understood. In this review I discuss a new hypothesis that motility is coordinated through mechanical signals passing between and regulating the activity of motors and filaments. The signals are carried by forces and sensed through the acceleration of protein-protein dissociation rates. Mechanical signaling can lead to spontaneous symmetry breaking, switching, and oscillations, and it can account for a wide range of cell motions such as the flagellar beat, mitotic spindle movements, and bidirectional organelle transport. Because forces can propagate quickly, mechanical signaling is ideal for coordinating motion over large distances.
Site-Directed Spectroscopic Probes of Actomyosin Structural Dynamics
Authors: Thomas David D. , Kast David , Korman Vicci L.
Published: February 2009

Spectroscopy of myosin and actin has entered a golden age. High-resolution crystal structures of isolated actin and myosin have been used to construct detailed models for the dynamic actomyosin interactions that move muscle. Improved protein mutagenesis and expression technologies have facilitated site-directed labeling with fluorescent and spin probes. Spectroscopic instrumentation has achieved impressive advances in sensitivity and resolution. Here we highlight the contributions of site-directed spectroscopic probes to understanding the structural dynamics of myosin II and its actin complexes in solution and muscle fibers. We emphasize studies that probe directly the movements of structural elements within the myosin catalytic and light-chain domains, and changes in the dynamics of both actin and myosin due to their alternating strong and weak interactions in the ATPase cycle. A moving picture emerges in which single biochemical states produce multiple structural states, and transitions between states of order and dynamic disorder power the actomyosin engine.
Attenuation of proliferation and migration of retinal pericytes in the absence of thrombospondin-1
Authors: Scheef Elizabeth A. , Sorenson Christine M. , Sheibani Nader
Published: February 2009

Perivascular supporting cells, including vascular smooth muscle cells (VSMCs) and pericytes (PCs), provide instructive signals to adjacent endothelial cells helping to maintain vascular homeostasis. These signals are provided through direct contact and by the release of soluble factors by these cells. Thrombospondin (TSP)1 is a matricellular protein and an autocrine factor for VSMCs. TSP1 activity, along with that of PDGF, regulates VSMC proliferation and migration. However, the manner in which TSP1 and PDGF impact retinal PC function requires further investigation. In the present study, we describe, for the first time, the isolation and culture of retinal PCs from wild-type (TSP1+/+) and TSP1-deficient (TSP1−/−) immortomice. We showed that these cells express early and mature markers of PCs, including NG2, PDGF receptor-β, and smooth muscle actin as well as desmin, calbindin, and mesenchymal stem cell markers. These cells were successfully passaged and maintained in culture for several months without significant loss of expression of these markers. TSP1+/+ PCs proliferated at a faster rate compared with TSP1−/− PCs. In addition, TSP1+/+ PCs, like VSMCs, responded to PDGF-BB with enhanced migration and proliferation. In contrast, TSP1−/− PCs failed to respond to the promigratory and proliferative activity of PDGF-BB. This may be attributed, at least in part, to the limited interaction of PDGF-BB with TSP1 in null cells, which is essential for PDGF proliferative and migratory action. We observed no significant differences in the rates of apoptosis in these cells. TSP1−/− PCs were also less adherent, expressed increased levels of TSP2 and fibronectin, and had decreased amounts of N-cadherin and αvβ3-integrin on their surface. Thus, TSP1 plays a significant role in retinal PC proliferation and migration impacting retinal vascular development and homeostasis.
Fibrinogen-induced endothelin-1 production from endothelial cells
Authors: Sen Utpal , Tyagi Neetu , Patibandla Phani K. , Dean William L. , Tyagi Suresh C. , Roberts Andrew M. , Lominadze David
Published: February 2009

We previously demonstrated that fibrinogen (Fg) binding to the vascular endothelial intercellular adhesion molecule-1 (ICAM-1) leads to microvascular constriction in vivo and in vitro. Although a role of endothelin-1 (ET-1) in this Fg-induced vasoconstriction was suggested, the mechanism of action was not clear. In the current study, we tested the hypothesis that Fg-induced vasoconstriction results from ET-1 production by vascular endothelial cells (EC) and is mediated by activation of extracellular signal-regulated kinase -1/2 (ERK-1/2). Confluent, rat heart microvascular endothelial cells (RHMECs) were treated with one of the following: Fg (2 or 4 mg/ml), Fg (4 mg/ml) with ERK-1/2 kinase inhibitors (PD-98059 or U-0126), Fg (4 mg/ml) with an antibody against ICAM-1, or medium alone for 45 min. The amount of ET-1 formed and the concentration of released von Willebrand factor (vWF) in the cell culture medium were measured by ELISAs. Fg-induced exocytosis of Weibel-Palade bodies (WPBs) was assessed by immunocytochemistry. Phosphorylation of ERK-1/2 was detected by Western blot analysis. Fg caused a dose-dependent increase in ET-1 formation and release of vWF from the RHMECs. This Fg-induced increase in ET-1 production was inhibited by specific ERK-1/2 kinase inhibitors and by anti-ICAM-1 antibody. Immunocytochemical staining showed that an increase in Fg concentration enhanced exocytosis of WPBs in ECs. A specific endothelin type B receptor blocker, BQ-788, attenuated the enhanced phosphorylation of ERK-1/2 in ECs caused by increased Fg content in the culture medium. The presence of an endothelin converting enzyme inhibitor, SM-19712, slightly decreased Fg-induced phosphorylation of ERK-1/2, but inhibited production of Fg-induced ET-1 production. These results suggest that Fg-induced vasoconstriction may be mediated, in part, by activation of ERK-1/2 signaling and increased production of ET-1 that further increases EC ERK-1/2 signaling. Thus, an increased content of Fg may enhance vasoconstriction through increased production of ET-1.
Autocrine ATP release coupled to extracellular pyrophosphate accumulation in vascular smooth muscle cells
Authors: Prosdocimo Domenick A. , Douglas Dezmond C. , Romani Andrea M. , O'Neill W. Charles , Dubyak George R.
Published: February 2009

Extracellular inorganic pyrophosphate (PPi) is a potent suppressor of physiological calcification in bone and pathological calcification in blood vessels. Ectonucleotide pyrophosphatase/phosphodiesterases (eNPPs) generate PPi via the hydrolysis of ATP released into extracellular compartments by poorly understood mechanisms. Here we report that cultured vascular smooth muscle cells (VSMC) from rat aorta generate extracellular PPi via an autocrine mechanism that involves ATP release tightly coupled to eNPP activity. The nucleotide analog β,γ-methylene ATP (MeATP or AMPPCP) was used to selectively suppress ATP metabolism by eNPPs but not the CD39-type ecto-ATPases. In the absence of MeATP, VSMC generated extracellular PPi to accumulate ≥600 nM within 2 h while steadily maintaining extracellular ATP at 1 nM. Conversely, the presence of MeATP completely suppressed PPi accumulation while increasing ATP accumulation. Probenecid, which inhibits PPi efflux dependent on ANK, a putative PPi transporter or transport regulator, reduced extracellular PPi accumulation by approximately twofold. This indicates that autocrine ATP release coupled to eNPP activity comprises ≥50% of the extracellular PPi-generating capacity of VSMC. The accumulation of extracellular PPi and ATP was markedly attenuated by reduced temperature but was insensitive to brefeldin A, which suppresses constitutive exocytosis of Golgi-derived secretory vesicles. The magnitude of extracellular PPi accumulation in VSMC cultures increased with time postplating, suggesting that ATP release coupled to PPi generation is upregulated as cultured VSMC undergo contact-inhibition of proliferation or deposit extracellular matrix.
Nitric oxide-mediated protection of endothelial cells from hydrogen peroxide is mediated by intracellular zinc and glutathione
Authors: Cortese-Krott Miriam M. , Suschek Christoph V. , Wetzel Wiebke , Kröncke Klaus-Dietrich , Kolb-Bachofen Victoria
Published: February 2009

Oxidative stress may cause endothelial dysfunction and vascular disease. It has been shown that NO protects endothelial cells (EC) against H2O2-induced toxicity. In addition, it is known that NO within cells induces a zinc release from proteins containing zinc-sulfur complexes. The aim of this study was to investigate whether zinc released intracellularly by NO plays a signaling role in the NO-mediated protection against H2O2 in rat aortic EC. Our results show that the NO-mediated protection toward H2O2 depends on the activities of glutathione peroxidase and glutamate cysteine ligase (GCL), the rate-limiting enzyme of glutathione (GSH) de novo biosynthesis. Moreover, NO increases the synthesis of the antioxidant GSH by inducing the expression of the catalytic subunit of GCL (GCLC). Chelating intracellular “free” zinc abrogates the NO-mediated increase of GCLC and of cellular GSH levels. As a consequence, the NO-mediated protection against H2O2-induced toxicity is impaired. We also show that under proinflammatory conditions, both cellular NO synthesis and intracellular “free” zinc are required to maintain the cellular GSH levels. Using RNA interference and laser scanning microscopy, we found that the NO-induced expression of GCLC depends on the activation of the transcription factor Nrf2 but not on the activity of the “zinc-sensing” transcription factor MTF-1. These findings show that intracellular “free” zinc plays a signaling role in the protective activity of NO and could explain why maintenance of an adequate zinc status in the endothelium is important to protect from oxidative stress and the development of vascular disease.
Blockade of hindbrain NMDA receptors containing NR2 subunits increases sucrose intake
Authors: Guard Douglas B. , Swartz Timothy D. , Ritter Robert C. , Burns Gilbert A. , Covasa Mihai
Published: February 2009

We have previously shown that blockade of N-methyl-d-aspartate (NMDA) receptors in the caudal brain stem delays satiation and increases food intake. NMDA receptors are heterodimers made up of distinct, but different, ion channel subunits. The NR2 subunits of the NMDA receptor contain the binding site for glutamate. About half of vagal afferents express immunoreactivity for NMDA NR2B subunit and about half of the NR2B expressing afferents also express NMDA NR2C or NR2D subunits. This suggests that increased food intake may be evoked by interference with glutamate binding to NMDA channels containing the NR2B subunit. To test this, we measured deprivation-induced intake of 15% sucrose solution following fourth ventricle and intra-nucleus of the solitary tract (intra-NTS) injections of Conantokin G (Con G; NR2B blocker), d-3-(2-carboxypiperazin-4-yl)-1-propenyl-1-phosphoric acid (d-CPPene; NR2B/2A blocker), and (±)-cis-1-(phenanthren-2yl-carbonyl)piperazine-2,3-dicarboxylic acid (PPDA; NR2D/C blocker). Fourth ventricular administration of Con G (5, 20, 40, 80 ng), d-CPPene (3.0, 6.25, 12.5, 25, 50, 100 ng), and PPDA (300, 400 ng) increased sucrose intake significantly compared with control. Likewise, injections of Con G (10 ng), d-CPPene (5 ng, 10 ng), and PPDA (0.5, 1.0, 2.5, 5.0 ng) directly into the NTS significantly increased sucrose intake. These results show that hindbrain injection of competitive NMDA antagonists with selectivity or preference for the NMDA receptor NR2B or NR2C subunits increases food intake.