bluuebunny/crossref_metadata_2025_split huggingface dataset:
REPLICATION PROTEIN A 32kDa SUBUNIT (RPA p32) BINDS THE SH2 DOMAIN OF STAT3 AND REGULATES ITS TRANSCRIPTIONAL ACTIVITY
Authors: Kim Jeonghoon , Kim Dohoon , Chung Jongkyeong 
Published: September 2002

AbstractSTATs (signal transducers and activators of transcription) are transcription factors that contain SH2 domains and are activated by tyrosine phosphorylation in response to cytokines and growth factors. Replication protein A (RPA) is a heterotrimeric complex that consists of three subunits, p70, p32 and p11, and has important functions in DNA replication and metabolism. Here, we present evidence that the RPA p32 subunit binds specifically to the SH2 domain of STAT3 in a phosphotyrosine‐independent manner. We confirm their protein—protein interactions by yeast 2‐hybrid analyses and in vitro binding assays using recombinant proteins generated from bacteria and in vitro translation. We also show that STAT3 binds to RPA p32 in vivo by conducting co‐precipitation experiments. As the SH2 domain is highly involved in the tyrosine phosphorylation and the transcriptional activity of STAT3, over‐expression of RPA p32 correspondingly augmented growth factor‐stimulated tyrosine phosphorylation and transcription activities of STAT3.
C/EBPα AND C/EBPβ ARE PERSISTENTLY ASSOCIATED WITH THE RAT LIVER NUCLEAR MATRIX THROUGHOUT DEVELOPMENT AND THE ACUTE PHASE RESPONSE
Authors: Dinic Svetlana , Ivanovic‐Matic Svetlana , Bogojevic Desanka , Mihailovic Mirjana , Poznanovic Goran 
Published: September 2002

AbstractThe partitioning of C/EBPα and C/EBPβ on the nuclear matrix structure was examined during the different transcriptional activities accompanying liver development and the acute phase (AP) response. The presence of C/EBPα and C/EBPβ was established on the nuclear matrix. Their relative concentrations on the matrix always reflected the developmental stage‐ and AP‐related fluctuations observed in the nuclear extract. Thus, they progressively increased as development proceeded, whereas during the AP response, C/EBPα decreased and C/EBPβ increased. In addition, the levels of both transcription factors were always notably higher in the nuclear matrix than in the extracts. We conclude that the observed changes and overall enrichment of the nuclear matrix with regulatory proteins is a reflection of the importance of such interactions for the in vivo functioning of C/EBP proteins.
COMPARISON BETWEEN THE IN VIVO AND IN VITRO EXPRESSION OF THREE ADHESION‐SIGNALING PROTEINS IN EMBRYONIC CELLS
Authors: Ridyard Marc S. , Sanders Esmond J. 
Published: September 2002

AbstractWe have examined the relationship between the in vivo and in vitro expression of three adhesion‐signaling proteins (FAK, PYK2 and Paxillin), using cells of the early chick embryo, where pure cell populations may be isolated and cultured, and in which epithelial‐to‐mesenchymal transformation is occurring. Focal Adhesion Kinase (FAK) and Proline‐rich Tyrosine Kinase‐2 (PYK2) are related in molecular structure, and may have some overlapping functions in signal transduction associated with cell‐substratum adhesion. Paxillin, a cytoskeletal protein, is also localized to focal adhesions. We show that the immunocytochemical detection of these molecules in vivo does not reflect their in vitro localization. Focal Adhesion Kinase showed a developmentally regulated localization to the cytoplasm, but not to sites of adhesion, in epithelial cells in vivo, while Paxillin was associated with migrating mesoderm cells. Proline‐rich Tyrosine Kinase‐2 was undetectable in vivo. The level of expression of these molecules was compared under in vivo and in vitro conditions. While the expression of Focal Adhesion Kinase showed a tissue‐specific regulation of expression with the change to in vitro conditions, Proline‐rich Tyrosine Kinase‐2 showed a more uniform and less tissue‐specific up‐regulation. Levels of Paxillin expression also showed an increase with this change in conditions. We conclude that despite the structural and functional relationships between these three molecules in the developing embryo, the expression and localization of each is independently regulated. We suggest that this provides these cells with the adaptability that they require in order to respond to the changing extracellular environment in the early embryo, and to undergo epithelial‐to‐mesenchymal transformation.
INFLUENCE OF MEMBRANE FLUIDITY MODIFIERS ON LYSOSOMAL OSMOTIC SENSITIVITY
Authors: Yang Lu , Zhang Guo‐Jiang , Zhong Yi‐Gang , Zheng Yan‐Zhen 
Published: September 2002

AbstractSince lysosomes are prone to osmotic lysis, we have examined the correlation between their physical state and sensitivity to osmotic challenge, using agents which modify membrane fluidity. The latency loss of β‐hexosaminidase after an incubation in hypotonic sucrose medium was followed under different conditions of membrane fluidity, recorded by steady‐state fluorescence anisotropy of 1,6‐diphenyl‐1,3,5‐hexatriene. Increasing fluidity of the lysosomal membranes with benzyl alcohol (BA) and greater rigidity caused by cholesteryl hemisuccinate (CHS) increased and decreased the enzyme latency loss, respectively. The effects of BA and CHS treatments on osmotic sensitivity were reversible subsequently by reciprocal treatments of the lysosomes with CHS and BA, respectively. The results indicate that the physical state of the membrane does indeed affect lysosomal osmotic stability.
S100‐ANNEXIN COMPLEXES: SOME INSIGHTS FROM STRUCTURAL STUDIES
Authors: Lewit‐Bentley Anita , Réty Stéphane , Sopkova‐de Oliveira Santos Jana , Gerke Volker 
Published: September 2002

AbstractSeveral annexins have been shown to bind proteins that belong to the S100 calcium‐binding protein family. The two best‐characterized complexes are annexin II with p11 and annexin I with S100C, the former of which has been implicated in membrane fusion processes. We have solved the crystal structures of the complexes of p11 with annexin II N‐terminus and of S100C with annexin I N‐terminus. Using these structural results, as well as electron microscopy observations of liposome junctions formed in the presence of such complexes (Lambert et al., 1997 J Mol Biol 272, 42–55), we propose a computer generated model for the entire annexin II/p11 complex.
THE t‐SNARE SYNTAXIN IS SUFFICIENT FOR SPONTANEOUS FUSION OF SYNAPTIC VESICLES TO PLANAR MEMBRANES
Authors: Woodbury Dixon J. , Rognlien Kathie 
Published: September 2002

AbstractVesicular trafficking and exocytosis are directed by the complementary interaction of membrane proteins that together form the SNARE complex. This complex is composed of proteins in the vesicle membrane (v‐SNAREs) that intertwine with proteins of the target membrane (t‐SNAREs). Here we show that modified synaptic vesicles (mSV), containing v‐SNAREs, spontaneously fuse to planar membranes containing the t‐SNARE, syntaxin 1A. Fusion was Ca2+‐independent and did not occur with vesicles lacking v‐SNAREs. Therefore, syntaxin alone forms a functional fusion complex with v‐SNAREs. Our functional fusion assay uses synaptic vesicles that are modified, so each fusion event results in an observable transient current. The mSV do not fuse with protein‐free membranes. Additionally, artificial vesicles lacking v‐SNAREs do not fuse with membranes containing syntaxin. This technique can be adapted to measure fusion in other SNARE systems and should enable the identification of proteins critical to vesicle—membrane fusion. This will further our understanding of exocytosis and may improve targeting and delivery of therapeutic agents packaged in vesicles.
THY‐1 ASSOCIATED PP85–90 IS A POTENTIAL DOCKING SITE FOR SH2 DOMAIN‐CONTAINING SIGNAL TRANSDUCTION MOLECULES
Authors: Durrheim Glenda A. , Garnett David , Dennehy Kevin M. , Beyers Albert D. 
Published: September 2002

AbstractThy‐1, a glycosylphosphatidylinositol (GPI)‐anchored glycoprotein expressed at high levels on thymocytes, has been implicated in positive and negative signal transduction. We show that Thy‐1 associates with a protein of 85–90kDa, which is prominently phosphorylated in vitro as well as in vivo following the stimulation of thymocytes with pervanadate. pp85–90 is not identical to known proteins that are phosphorylated following T cell activation. The SH2 domains of fyn, csk, phosphatidylinositol 3′‐kinase, rasGAP, vav and lck bind to pp85–90 with varying affinities. The SH2 domains of ZAP70, SHP‐1 and PLCγ1 and the SH3 domains of lck, vav and HS1 did not bind to pp85–90. The molecular weight, iso‐electric point, efficient phosphorylation by fyn and lck and preferential binding to the SH2 domain of fyn compared to that of lck indicate that Thy‐1‐associated pp85–90 may be identical to a recently cloned, fyn‐associated transmembrane adaptor protein, PAG‐85.
FLOW CYTOMETRIC ANALYSIS OF THE TH1–TH2 BALANCE IN HEALTHY INDIVIDUALS AND PATIENTS INFECTED WITH THE HUMAN IMMUNODEFICIENCY VIRUS (HIV) RECEIVING A PLANT STEROL/STEROLIN MIXTURE
Authors: Breytenbach Ulrike , Clark Anel , Lamprecht Johan , Bouic Patrick 
Published: September 2002

AbstractThe Th1–Th2 balance plays a pivotal role in determining the outcome of an immune response to an infectious organism. It is proposed that during HIV infection, disease progression is characterized by a loss of Th1 activity, a shift to a more ‘allergic’ Th2‐type response and hence loss of cytotoxic cell activity against infected host cells. This study was undertaken to investigate this balance in three groups of individuals: HIV‐negative volunteers (n=10), a group of HIV‐infected patients on no therapy (n=10) as well as a group of patients managed with a mixture of plant sterols/sterolins (n=9). In parallel, their response to mitogens and the subsequent expression of the activation antigen CD69 was measured. This study was conducted by three‐colour flow cytometry in order to obviate the less sensitive cytokine secretion assays that have yielded controversial results. The results indicate that HIV‐infected patients on no therapy exhibit a pre‐dominant Th2 response (IL‐4 secretion), whereas those on the sterol/sterolin mixture exhibit a beneficial Th1 response (IFN‐γ). Surprisingly, in both patient groups, the expression of CD69 was abnormally low when compared to the uninfected volunteers, implying that chronic activation is already present in vivo. It appears that the detrimental Th2 driven response might be swung to the more beneficial Th1 response with the immune modulatory sterols/sterolin mixture. Clinical use of this mixture in HIV infection has yielded results which corroborate the above observations in that patients using the plant sterol/sterolin mixture maintain their CD4 cell numbers over an extended period of time in the absence of any anti‐retroviral therapy.
Do Angular Momentum Induced Ellipticity Correlations Contaminate Weak Lensing Measurements?
Authors: Natarajan Priyamvada , Crittenden Robert G. , Pen Ue-Li , Theuns Tom 
Published: September 2002

AbstractAlignments in the angular momentum vectors of galaxies can induce large scale correlations in their projected orientations. Such alignments arise from the tidal torques exerted on neighboring protogalaxies by the smoothly varying shear field. Weak gravitational lensing can also induce ellipticity correlations since the images of neighboring galaxies will be distorted coherently by the intervening mass distribution. Comparing these two sources of shape correlations, it is found that for current weak lensing surveys with a median redshift of zm = 1, the intrinsic signal is a contaminant on the order of 1–10% of the measured signal. However, for shallower surveys with zm ≤ 0.3, the intrinsic correlations dominate over the lensing signal. The distortions induced by lensing are curl-free, whereas those resulting from intrinsic alignments are not. This difference can be used to disentangle these two sources of ellipticity correlations. When the distortions are dominated by lensing, as occurs at high redshifts, the decomposition provides a valuable tool for understanding properties of the noise and systematic errors.
Could We Detect O2 in the Atmosphere of a Transiting Extra-solar Earth-like Planet?
Authors: Webb John K. , Wormleaton Imma 
Published: September 2002

AbstractAlthough the extra-solar planets discovered so far are of the giant, gaseous type, the increased sensitivity of future surveys will result in the discovery of lower mass planets. The detection of O2 in the atmosphere of a rocky extra-solar planet would be a potential indicator of life. In this paper we address the specific issue of whether we would be able to detect the O2 A-band absorption feature in the atmosphere of a planet similar to the Earth, if it were in orbit around a nearby star. Our method is empirical, in that we use observations of the Earth's O2 A-band, with a simple geometric modification for a transiting extra-solar planet, allowing for limb-darkening of the host star. We simulate the spectrum of the host star with the superposed O2 A-band absorption of the transiting planet, assuming a spectral resolution of ~8 kms−1(typical of current echelle spectrographs), for a range of spectral signal-to-noise ratios. The main result is that in principle we may be able to detect the O2 A-band of the transiting planet for host stars with radii R≤ 0.3Rʘ. However, using existing instrumentation and 8m telescopes, this requires target M-stars with m(V) ≈ 10 or brighter for integration times of ~10 hours or less. The number of such stars over the sky is small. Larger aperture telescopes and/or improved instrumentation efficiency would enable surveys of M-stars down to m(V) ≈ 13 and greatly improve the chances of discovering life elsewhere.
Reconnection in Pulsar Winds
Authors: Kirk J. G. , Lyubarsky Y. 
Published: September 2002

AbstractThe spin-down power of a pulsar is thought to be carried away in an MHD wind in which, at least close to the star, the energy transport is dominated by Poynting flux. The pulsar drives a low frequency wave in this wind, consisting of stripes of toroidal magnetic field of alternating polarity, propagating in a region around the equatorial plane. The current implied by this configuration falls off more slowly with radius than the number of charged particles available to carry it, so that the MHD picture must, at some point, fail. Recently, magnetic reconnection in such a structure has been shown to accelerate the wind significantly. This reduces the magnetic field in the comoving frame and, consequently, the required current, enabling the solution to extend to much larger radius. This scenario is discussed and, for the Crab Nebula, the range of validity of the MHD solution is compared with the radius at which the flow appears to terminate. For sufficiently high particle densities, it is shown that a low frequency entropy wave can propagate out to the termination point. In this case, the ‘termination shock’ itself must be responsible for dissipating the wave.This paper is dedicated to Don Melrose on his 60th birthday.
Single Dish Polarisation Calibration
Authors: Johnston Simon 
Published: September 2002

AbstractUsing the formalism of Hamaker, Bregman & Sault (1996), I derive a method for the polarisation calibration of observations made with a single radio telescope. This method is particularly appropriate for observations of pulsars, where the sign and magnitude of the circular polarisation are useful for understanding the emission processes at work. I apply the method to observations of PSR J1359–6038 made using the multibeam receiver on the Parkes radio telescope.
Annual Modulation in the Variability Properties of the IDV Source 0917+624?
Authors: Fuhrmann L. , Krichbaum T. P. , Cimò G. , Beckert T. , Kraus A. , Witzel A. , Zensus J. A. , Qian S. J. , Rickett B. J. 
Published: September 2002

AbstractThere is new evidence which identifies seasonal changes of the variability time scale in intraday variable (IDV) sources with refractive interstellar scintillation effects. Such a RISS model takes the annual change of the Earth's velocity relative to the scattering medium into account. In September 1998 we found a remarkable prolongation of the variability time scale in the IDV source 0917+624 with only small variations in flux density during a period of 5 days. This was explained as a seasonal effect, in which the velocity vector of the Earth and the interstellar medium nearly cancelled. In order to further investigate the applicability of the model for 0917+624, we performed an Effelsberg 6 cm-flux monitoring program over the course of one year. Since September 2000, the source appears to be remarkably inactive and yet (May 2001) no return to its normal, faster and stronger variability pattern is observed. Here, our observational results and a possible explanation for the current quiescence are presented.
The Size of IDV Jet Cores
Authors: Beckert T. , Krichbaum T. P. , Cimò G. , Fuhrmann L. , Kraus A. , Witzel A. , Zensus J. A. 
Published: September 2002

AbstractRadio variability on timescales from a few hours to several days in extragalactic flat spectrum radio sources is generally classified as intraday variability (IDV). The origin of this short term variability is still controversial and both extrinsic and intrinsic mechanisms must be considered and may both contribute to the observed variations. The measured linear and circular polarisation of IDV sources constrains the low energy end of the electron population. Any population of cold electrons within sources at or above the equipartition temperature of 1011 K depolarises the emission and can be ruled out. Intrinsic shock models are shown to either violate the large fraction of sources displaying IDV or they do not relax the light travel time argument for intrinsic variations. From structure function analysis, we further conclude that interstellar scintillation also leads to tight size estimates unless a very local cloud in the ISM is responsible for IDV.
A Very Rapid Extreme Scattering Event in the IDV Source 0954+658
Authors: Cimò Giuseppe , Beckert T. , Krichbaum T. P. , Fuhrmann L. , Kraus A. , Witzel A. , Zensus J. A. 
Published: September 2002

AbstractExtreme scattering events (ESEs) are dramatic variations of the flux density at gigahertz frequencies caused by ray path distortions within an isolated inhomogeneity (‘plasma lens’) in the interstellar medium. These events are characterised by a deep flux density minimum in the light curve with, in some cases, surrounding maxima. The variability time scales range from weeks to months. These phenomena show a strong frequency dependence, in which the variability amplitudes increase with wavelength. During an intraday variability (IDV) monitoring project (March 2000), a feature resembling an ESE-like event appeared in the variable light curve of 0954+658, however with a time scale of less than two days. We will discuss this effect and its implications for a better description of the interstellar medium.
New Results from an ATCA Study of Intraday Variable Radio Sources
Authors: Bignall H. E. , Jauncey D. L. , Kedziora-Chudczer L. L. , Lovell J. E. J. , Macquart J.-P. , Rayner D. P. , Tingay S. J. , Tzioumis A. K. , Clay R. W. , Dodson R. G. , McCulloch P. M. , Nicolson G. D. 
Published: September 2002

AbstractWe are undertaking an observational program using the ATCA to monitor the intraday variability (IDV) of a sample of sources at 4.8 and 8.6 GHz. The sources were selected to include the known strong southern IDV sources plus a number of sources whose IDV was recently discovered. The present monitoring program will extend over a full year in order to search for any annual cycle that may be present in the long-term IDV characteristics of these sources. In this paper we discuss the observing strategy and data analysis, and present the first results from our observations.
Brightness Temperature Constraints to Compact Synchrotron Source Radiation Obtained from IDV and VLBI Observations
Authors: Kellermann K. I. 
Published: September 2002

AbstractWe discuss the observational and theoretical constraints on the brightness temperature of compact opaque synchrotron sources. We consider the implication of observed apparent velocities on the amount of Doppler boosting and compare this with values deduced from directly measured brightness temperatures from ground and space based VLBI observations, as well as the implications of intraday variability. We also discuss the maximum rest frame brightness temperature expected under conditions of both inverse Compton cooling and equipartition conditions.
Broad-band Radio Spectra Variability of 550 AGN in 1997-2001
Authors: Kovalev Y. Y. , Kovalev Yu A. , Nizhelsky N. A. , Bogdantsov A. B. 
Published: September 2002

AbstractResults are presented of long-term monitoring at the radio telescope RATAN–600 and a model interpretation of instantaneous 1–22 GHz spectra at six frequencies for a sample of 550 compact extragalactic radio sources. The sources are selected from the Preston et al. (1985) VLBI survey and are located in the declination range from −30° to +43°. Dependence of the index of variability on frequency is analysed for different subsamples. Factors of flux density variations range from 1 to 15. A typical behaviour of spectra evolution during strong radio outbursts in various objects is recognised suggesting a common physical nature of the variability. Invoking VLBI observations in spectra–structure analysis, we find that usually more than 70% of the total emission is coming from the mas scale at frequencies higher than 5 GHz. The observed variability can be explained in the model with a relativistic jet of parsec scale in the longitudinal magnetic field or in the shock-in-jet model.
The Effect of Radiation Drag on Relativistic Bulk Flows in Active Galactic Nuclei
Authors: Luo Qinghuan 
Published: September 2002

AbstractThe effect of radiation drag on relativistic bulk flows is re-examined. Highly relativistic bulk flows in the nuclear region are subject to Compton drag, i.e. radiation deceleration as a result of inverse Compton scattering of ambient soft photon fields from emission from the accretion disk, broad line region, or dusty torus. Possible observational consequences of X-/γ-ray emission produced from Compton drag are specifically discussed.
Helium-star Mass Loss and Its Implications for Black Hole Formation and Supernova Progenitors
Authors: Pols Onno R. , Dewi Jasinta D. M. 
Published: September 2002

AbstractRecently the observationally derived stellar-wind mass-loss rates for Wolf-Rayet stars, or massive naked helium stars, have been revised downwards by a substantial amount. We present evolutionary calculations of helium stars incorporating such revised mass-loss rates, as well as mass transfer to a close compact binary companion. Our models reach final masses well in excess of 10 M⊙, consistent with the observed masses of black holes in X-ray binaries. This resolves the discrepancy found with previously assumed high mass-loss rates between the final masses of stars which spend most of their helium-burning lifetime as Wolf-Rayet stars (˜3 M⊙) and the minimum observed black hole masses (6 M⊙). Our calculations also suggest that there are two distinct classes of progenitors for Type Ic supernovae: one with very large initial masses (35 M⊙), which are still massive when they explode and leave black hole remnants, and one with moderate initial masses (˜12–20 M⊙) undergoing binary interaction, which end up with small pre-explosion masses and leave neutron star remnants.