bluuebunny/crossref_metadata_2025_split huggingface dataset:
RADIAL SPINDLE AND THE PHENOTYPE OF THE MAIZE MEIOTIC MUTANT, DV
Authors: Shamina Natalia , Dorogova Natalia , Trunova Svetlana 
Published: September 2002

AbstractThe morphological phenotype of the maize meiotic mutant dv (divergent spindle) has been further analysed by visualization of the division spindle and examination of its fine structure in mother cells of pollen. Previous research showed that dv blocks convergence of spindle fibres at the poles. New observations reveal abnormalities caused by this mutation, with dv showing disturbances in nuclear envelope breakdown during vesiculation, preventing the spindle fibres from adopting a bipolar orientation (with convergence on the poles). The anomalies result in radial spindles which are similar to monoastral spindles in animal cells.
CHANGES IN POLYAMINE METABOLISM DURING GLUCOCORTICOID‐INDUCED PROGRAMMED CELL DEATH IN MOUSE THYMUS
Authors: Hegardt Cecilia , Andersson Gunnar , Oredsson Stina M. 
Published: September 2002

AbstractWhen mice are injected with dexamethasone, cortical thymocytes are deleted through programmed cell death (PCD). We have used this in vivo model system to investigate the kinetics of PCD and cell proliferation in relation to polyamine metabolism for 16h after injection of dexamethasone. As a marker for PCD, we used the appearance of a sub‐G1peak in the DNA histogram. When a sub‐G1peak appeared at 4h after dexamethasone treatment, the activity of the polyamine catabolic enzyme spermidine/spermine N1‐acetyltransferase (SSAT) was significantly increased and the activity of the polyamine biosynthetic enzyme S‐adenosylmethionine decarboxylase (AdoMetDC) was significantly decreased compared to the activities found in the thymi of control mice. Despite the significant changes in the activities of SSAT and AdoMetDC, the only change in the polyamine pool during the experimental period was that of putrescine. Presumably the complexity of this in vivo system masks changes in the spermidine and spermine pools that were expected in relation to the increased SSAT activity and decreased AdoMetDC activity.
EFFECTS OF THE MYOSIN INHIBITOR 2,3‐BUTANEDIONE MONOXIME (BDM) ON CELL SHAPE, LOCOMOTION AND FLUID PINOCYTOSIS IN HUMAN POLYMORPHONUCLEAR LEUCOCYTES
Authors: Urwyler N. , Eggli P. , Keller H. U. 
Published: September 2002

AbstractWe investigated the role of myosin in polymorphonuclear leucocyte (PMN) shape changes, locomotion, and fluid pinocytosis using the myosin inhibitor 2,3 butanedione monoxime (BDM). Treatment of resting spherical PMNs with BDM produced spheroid cells showing small continuous shape changes (IC50=15.5m m BDM) and occasionally small blebs. Cell polarity, as induced by the chemotactic peptide fNLPNTL or by colchicine, and locomotion were completely suppressed (IC50=8.4 to 10m m). Suppression of fNLPNTL‐ or colchicine‐induced cell polarity produced spheroid cells, suppression of PMA‐induced shape changes and fluid pinocytosis produced non‐motile spherical cells (IC50=25 to 30m m BDM). BDM suppressed formation of lamellipodia but not formation of blebs. Suppression of microvilli by BDM as observed in resting spherical cells was partially antagonized by PMA. The results suggest that myosin is involved in stabilizing the shape of resting spherical cells, including microvilli, and that myosin is required for cell polarity, locomotion, fluid pinocytosis and for formation of lamellipodia, but not for formation of blebs.
KCl STIMULATION AND ULTRASTRUCTURAL RESPONSES OF TANNIC ACID‐STAINED CHOLINERGIC SYNAPTIC TERMINALS
Authors: Fox Geoffrey Q. , Kriebel Mahlon E. 
Published: September 2002

AbstractThe quantal‐vesicular hypothesis equates miniature end‐plate potentials (MEPPs) with fusions of synaptic vesicles. MEPP production thus predicts vesicle losses, increases in vesicle fusions and increases in terminal plasma membrane. MEPP production and these ultrastructural parameters have been evaluated in the cholinergic presynaptic terminals of skate electric organ following tannic acid saline incubation, known to promote capture and selective staining of dense‐core granule fusions, and KCl stimulation, known to elevate MEPP production dramatically in these cholinergic terminals. After pretreatment in tannic acid—elasmobranch saline, KCl stimulation produced MEPPs at 40/s/μm2of terminal surface for several minutes with gradual reduction to spontaneous levels by 25–30min. No loss of vesicles, no vesicle fusions, no expansions of plasma membrane and no tannic acid enhanced staining of vesicles or vacuoles accompanied the generation of 800MEPPs/μm3of terminals having densities of 567 vesicles/μm3. No ultrastructural footprints were found to support the notion that unnaturally high rates of vesicular exocytosis had occurred.
FUSION OF SENDAI VIRUS WITH VESICLES OF OLIGOMERIZABLE LIPIDS: A MICROCALORIMETRIC ANALYSIS OF MEMBRANE FUSION
Authors: Ravoo Bart Jan , Weringa Wilke D. , Engberts Jan B. F. N. 
Published: September 2002

AbstractSendai virus fuses efficiently with small and large unilamellar vesicles of the lipid 1,2 ‐di‐n ‐hexadecyloxypropyl‐ 4 ‐(beta‐nitrostyryl) phosphate (DHPBNS) at pH 7.4 and 37°C, as shown by lipid mixing assays and electron microscopy. However, fusion is strongly inhibited by oligomerization of the head groups of DHPBNS in the bilayer vesicles. The enthalpy associated with fusion of Sendai virus with DHPBNS vesicles was measured by isothermal titration microcalorimetry, comparing titrations of Sendai virus into (i) solutions of DHPBNS vesicles (which fuse with the virus) and (ii) oligomerized DHPBNS vesicles (which do not fuse with the virus), respectively. The observed heat effect of fusion of Sendai virus with DHPBNS vesicles is strongly dependent on the buffer medium, reflecting a partial charge neutralization of the Sendai F and HN proteins upon insertion into the negatively‐charged vesicle membrane. No buffer effect was observed for the titration of Sendai virus into oligomerized DHPBNS vesicles, indicating that inhibition of fusion is a result of inhibition of insertion of the fusion protein into the target membrane. Fusion of Sendai virus with DHPBNS vesicles is endothermic and entropy‐driven. The positive enthalpy term is dominated by heat effects resulting from merging of the protein‐rich viral envelope with the lipid vesicle bilayers rather than by the fusion of the viral with the vesicle bilayers per se.
EARLY DEVELOPMENT OF THE GUT: NEW LIGHT ON AN OLD HYPOTHESIS
Authors: Rawdon Benjamin B. 
Published: September 2002

AbstractThis review deals with the early development of the gut. It draws largely on information provided from the study of avian embryos. Evidence that concerns the early determination of the regional fate of the endoderm and mesoderm of the gut is reviewed. Gut endoderm can undergo a limited degree of differentiation from a remarkably early age when cultured in the absence of mesoderm and there is evidence that points to the establishment of a pre‐pattern in the early mesoderm before the genes responsible for patterning in gut are active. Initially, at least at cranial levels, those parts of the mesoderm and endoderm that are in contact are not those parts that will ultimately be in apposition; the consequence of this for any signalling between these layers is considered. In the light of the above information, the probable role of mesenchyme in gut development is re‐examined.
REGULATION OF GENE EXPRESSION BY GC‐RICH DNA CIS ‐ELEMENTS
Authors: Hapgood Janet P. , Riedemann Johann , Scherer Sonja D. 
Published: September 2002

AbstractGC‐rich DNA cis elements are important transcriptional regulatory elements present in the promoter, enhancer and locus control regions of many eukaryotic genes from several species. This review attempts to examine the structure, function and biological significance of GC‐rich cis ‐regulatory elements and their cognate binding proteins, with a view to understanding their role in regulation of gene expression.
ASSESSMENT OF THE ANTITUMOUR ACTIVITY OF TARGETED IMMUNOSPECIFIC ALBUMIN MICROSPHERES LOADED WITH CISPLATIN AND 5‐FLUOROURACIL: TOXICITY AGAINST A RODENT OVARIAN CARCINOMA IN VITRO
Authors: Truter Ernest J. , Santos Aldina S. , Els Willem J. 
Published: September 2002

AbstractThe 3‐(4,5 dimethylthiazol‐2‐yl)‐2,5 diphenyltetrazolium bromide (MTT) assay is used successfully to estimate the number of viable cells in drug screening trials. We used the MTT assay to assess the viability of a rodent ovarian carcinoma cell line (DMBA‐OC‐1R) after exposure to combinations of cisplatin and 5‐fluorouracil as free drug and in encapsulated (conjugated and unconjugated) forms. After 48h of exposure to free drugs, a significant trend towards cell cytotoxicity could be observed and this was well established by 120h. Cells treated with drug‐containing immuno‐microspheres showed a similar initial decrease in cell viability after 96h, and this was maintained for 128h. These results suggest that immuno‐microspheres loaded with chemotherapeutic drugs have the potential to be successfully used in the treatment of ovarian cancer.
EFFECT OF HYALURONAN ON MMP EXPRESSION AND ACTIVATION
Authors: Isnard N. , Legeais J‐M. , Renard G. , Robert L. 
Published: September 2002

Matrix metalloproteases (MMPs) play a crucial role in tissue remodelling in a variety of physiological and pathological processes. Hyaluronan is also involved in the same processes. Several cytokines and growth factors are involved in the regulation of the biosynthesis of hyaluronan and also of MMPs. The activity of MMPs has been shown to be regulated at the level of transcription and activation of the zymogen form.In order to explore the possible relationship between matrix components and especially hyaluronan, we studied the effect of hyaluronan on MMP expression (biosynthesis and activation) in the culture of human skin fibroblasts and corneal keratocytes (explant cultures and cell cultures). These cells were shown to exhibit distinct phenotypes as far as matrix biosynthesis is concerned. Using a synthetic substrate N‐Suc(ala)3pNA, we measured elastase‐type endopeptidase activity produced by fibroblasts and keratocytes and characterized the MMPs by zymography.Hyaluronan added to fibroblast cultures stimulated the membrane‐bound elastase‐type endopeptidase activity in a dose dependent fashion. Similar results were obtained with keratocyte cultures. In the presence of 1mg/ml hyaluronan there was an increase in MMP expression and also an activation of latent MMPs both by fibroblasts and keratocytes.
Australian Cosmic Ray Modulation Research
Authors: Duldig M. L. 
Published: September 2002

AbstractAustralian research into variations of the cosmic ray flux arriving at the Earth has played a pivotal role for more than 50 years. The work has been largely led by the groups from the University of Tasmania and the Australian Antarctic Division, and has involved the operation of neutron monitors and muon telescopes from many sites. In this paper, the achievements of the Australian researchers are reviewed and future experiments are described. Particular highlights include: the determination of cosmic ray modulation parameters; the development of techniques for modelling ground-level enhancements; the confirmation of the Tail-In and Loss-Cone sidereal anisotropies; the Spaceship Earth collaboration; and the Solar Cycle latitude survey.
The Structure of the Gravitational Lens System B1152+199
Authors: Edwards P. G. , Lovell J. E. J. , Hirabayashi H. , Jauncey D. L. , Toft S. 
Published: September 2002

AbstractWe have commenced a program to monitor the gravitational lens B1152+199 with the Australia Telescope Compact Array (ATCA) to search for variability of the lensed components with the goal of measuring the lensing time delay. As part of this program we made a 9 hour full-synthesis observation in June 2000 to derive a ‘template’ for model-fitting the shorter, multi-epoch, monitoring observations. We report here on the results of this full-synthesis observation and on three additional epochs of monitoring for time variation.
Gravitational Lensing and Modified Newtonian Dynamics
Authors: Mortlock Daniel J. , Turner Edwin L. 
Published: September 2002

AbstractGravitational lensing is most often used as a tool to investigate the distribution of (dark) matter in the universe, but, if the mass distribution is known a priori, it becomes, at least in principle, a powerful probe of gravity itself. Lensing observations are a more powerful tool than dynamical measurements because they allow measurements of the gravitational field far away from visible matter. For example, modified Newtonian dynamics (MOND) has no relativistic extension, and so makes no firm lensing predictions, but galaxy–galaxy lensing data can be used to empirically constrain the deflection law of a MONDian point-mass. The implied MONDian lensing formalism is consistent with general relativity, in so far as the deflection experienced by a photon is twice that experienced by a massive particle moving at the speed of light. With the deflection law in place and no invisible matter, MOND can be tested wherever lensing is observed.
The Hubble Constant from (CLASS) Gravitational Lenses
Authors: Koopmans L. V. E. , Collaboration The CLASS 
Published: September 2002

AbstractOne of the main objectives of the Cosmic Lens All-Sky Survey (CLASS) collaboration has been to find gravitational lens (GL) systems at radio wavelengths that are suitable for the determination of time delays between image pairs. The survey is now near completion and at least 18 GL systems have been found. Here, I will discuss our efforts to measure time delays from several of these systems with the ultimate aim of constraining the Hubble Constant (H0). Thus far three CLASS GL systems (B0218+357, B1600+434 and B1608+656) have yielded measurements of time delays, from which values of H0 ≈ 60–70 km s−1 Mpc−1 have been estimated. Although most GL systems give similar values of H0, statistical and systematic uncertainties are still considerable. To reduce these uncertainties, I will mention two monitoring programs that we are undertaking to (re)measure time delays in 14 CLASS GL systems and address several important issues for the near future.
From Amateur Astronomer to Observatory Director: The Curious Case of R. T. A. Innes
Authors: Orchiston Wayne 
Published: September 2002

AbstractRobert Innes was one of a select band of amateur astronomers who made the transition to professional ranks towards the end of the nineteenth century. Initially he had a passion for mathematical astronomy, but after settling in Sydney he developed a taste for observational astronomy, specialising in the search for new double stars. He quickly became known for his success in this field and for his publications on solar system perturbations, and with John Tebbutt's patronage managed to secure a clerical position at the Royal Observatory, Cape of Good Hope. Once there he continued to observe in his spare time and to publish, and, with strong support from Sir David Gill, was appointed founding Director of the Transvaal Observatory. By the time he died in 1933, Innes had received an honorary D.Sc. from Leiden University, and had established an international reputation as a positional astronomer.This paper provides an interesting case study of a well-known ‘amateur-turned-professional’, and an example of the ways in which patronage played a key role in nineteenth and early twentieth century Australian and South African astronomy.
Lower Hybrid Drive in Solar Magnetic Reconnection Regions: Implications for Electron Acceleration and Solar Heating
Authors: Cairns Iver H. 
Published: September 2002

AbstractLower hybrid (LH) drive involves the resonant acceleration of electrons parallel to the magnetic field by lower hybrid waves, often driven by ions with ring or ring-beam distributions. Charge-exchange between hydrogen atoms and protons with relative motions perpendicular to the magnetic field leads to ring distributions of pickup ions, with concomitant perpedicular ion ‘heating’. This paper considers the combination of LH drive and charge-exchange in the outflow regions of magnetic reconnection sites in the solar chromosphere and lower corona, showing that the combined mechanism naturally predicts major perpendicular ion heating and parallel electron acceleration, and exploring the mechanism’s relevance to specific solar reconnection phenomena, heating of the solar atmosphere, and production of energetic electrons that generate solar radio emission. Although primarily qualitative, analysis shows that the mechanism has numerous attractive aspects, including perpendicular ion heating that increases linearly with ion mass, parallel electron acceleration, predicted ion and electron temperatures that span those of the chromosphere and lower corona, and parallel electron speeds spanning those for type III bursts. Applications to chromospheric explosive events and low-lying active regions, and to heating the chromosphere, appear particularly suitable. Sweeping of plasma frozen-in to chromospheric and coronal magnetic field lines across the neutral atmosphere due to motions of sub-photospheric fields represents an obvious and important generalisation of the mechanism away from reconnection sites. The requirements that the neutrals not be strongly collisionally coupled to the plasma and that sufficient neutrals are available for charge-exchange restricts the LH drive mechanism to above the photosphere but below where the corona is essentially fully ionised. LH drive may thus be important in heating the chromosphere and low corona while other heating mechanisms dominate at higher altitudes. Although attractive thus far, quantitative analyses of LH drive in these contexts are necessary before definitive conclusions are reached.
Generation of Coronal Currents by the Solar Convection Zone
Authors: Galloway D. J. , Uchida Y. , Weiss N. O. 
Published: September 2002

AbstractSolar flares are thought to be caused by reconnection of magnetic fields and their associated electric currents in the solar corona. The currents have to be there to provide available energy over and above the current-free minimum energy state, but what generates them has been little discussed. This paper investigates the idea that twisting motions in the turbulent convection zone below may provide a natural source for the currents and explain some of their properties. The twists generate upward-propagating Alfvén waves with a Poynting flux of the right order of magnitude to power a flare. Depending on the depth it takes place, the twisting event that initiates a particular flare may occur hours, days or even months before the flare itself.
Filaments in the Galactic Centre—with Special Reference to the ‘Snake’
Authors: Bicknell Geoffrey V. , Li Jianke 
Published: September 2002

AbstractThe non-thermal filaments in the Galactic centre constitute one of the great mysteries of this region of the Galaxy. We summarise the observational data on these filaments and critically review the various theories which currently outnumber the observed filaments. We summarise our theory for the longest of these filaments, the Snake, and discuss the relevance of this model for the other filaments in the Galactic centre region. The physics involved in our model for the Snake involves much of the physics that has dominated the career of Professor Don Melrose. In particular, the diffusion of relativistic electrons in the Snake is determined from the theory of resonant scattering by Alfvén waves.
Probing the pc- and kpc-scale Environment of the Powerful Radio Galaxy Hercules A
Authors: Gizani Nectaria A. B. , Garrett M. A. , Leahy J. P. 
Published: September 2002

AbstractWe present the kpc-scale behaviour of the powerful extragalactic radio source Hercules A and the behaviour of the intracluster gas in which the radio source is situated. We have found that Hercules A exhibits a strong Laing-Garrington effect. The X-ray observations have revealed an extended X-ray emission elongated along the radio galaxy axis. The estimated temperature of the cluster is kT=2.45 keV and the central electron density is n○≃7.8×10−3 cm−3 which reveals a hot, dense environment in which Hercules A is situated. From the combined study of the radio and X-ray data we have estimated a central value of 3 ≲ B○(μG)≲9.We also present the most recent results from the analysis of the radio data on the pc-scale structure of the radio galaxy, observed at 18 cm by the EVN–MERLIN array. A faint but compact radio source, coincident with the optical centre of Hercules A, was detected by the EVN at 18 mas resolution. The total flux density of the EVN core is 14.6 mJy. Its angular size is 18×7 mas with a position angle of ≃139°. There is also evidence for extended emission in the NW–SE direction, most probably from the eastern pc-scale jet. If this is true then there is a misalignment between the direction of the pc-eastern and the aligned kpc-scale jets of ≃35°.
Multi-wavelength Behaviour of III Zw2
Authors: Salvi Nikita , Page Mat J. , Stevens Jason A. , Mason Keith O. , Wu Kinwah 
Published: September 2002

AbstractIII Zw2 was observed with XMM-Newton in July 2000. Its X-ray spectrum can be described by a power law of photon index Γ≈1.7 with a Gaussian line at 6.7 KeV. There is no significant evidence of intrinsic absorption within the source or of a soft X-ray excess. Multi-wavelength light curves over a period of 25 years show related variations from the radio to X-rays. We interpret the radio to optical emission as synchrotron radiation, self-absorbed in the radio/millimetre region, and the X-rays as mainly due to Compton up-scattering of low energy photons by the population of high energy electrons that give rise to the synchrotron radiation.
Radiation Fields in Blazars — a Possible Extension of the Small Scale Symbiosis (Disk/Jet) into a Large Scale (Dust/Dust) Symbiosis
Authors: Donea Alina-C. , Protheroe Raymond J. 
Published: September 2002

AbstractIn blazar models both protons and electrons may be efficiently accelerated in jets and produce γ-rays. Here we discuss the interactions of these γ-rays with different radiation fields. The external radiation fields within a few parsecs from the black hole involved in such interactions could be the direct radiation from the accretion disk coupled with the jet, the infrared radiation from a dusty torus, and the emission line radiation from the broad line region surrounding the accretion disk. The optical thickness for absorption of γ-ray photons in the external radiation fields is analysed for blazars and quasars.Based on the unification theory of active galactic nuclei we briefly review the evidence for the existence of small scale dust tori in blazars/FR I. We propose that the existing jet–accretion disk symbiosis extrapolates to a large scale symbiosis between other important dusty constituents of the blazar/FR I family.
Models of Variability in Blazar Jets
Authors: Mastichiadis Apostolos , Kirk John G. 
Published: September 2002

AbstractDuring the last decade multiwavelength observations of blazars have revealed many interesting patterns in their emission across the EM spectrum. In the present article we will review the time-dependent one-zone models and the models which advocate an acceleration and a radiation zone, and we will make some comparisons between them, especially in light of recent observations of the so-called TeV blazars.
Optical to Far-IR Observations of 3C 446
Authors: Leech K.J. , Saxton R. , Barr P. , Santos-Lleo M. , Jiminez-Bailon E. , Diaz R. , Ghosh K. , Soundararajaperumal S. 
Published: September 2002

AbstractThe OVV blazar 3C 446 was monitored over seven months in 1997 with ground based telescopes and instruments on ESA's Infrared Space Observatory (ISO). The aim was to try to detect variations in the IR and see if these were correlated with optical variations. The object varied in the optical and near-IR during this period, but did not vary in the far-IR. Despite being a factor of ten weaker than in 1983, the optical-IR SED exhibited the same slope. The new far-IR observations from ISO allow us to determine the location of the turnover in the spectrum, caused by synchrotron self-absorption. It occurs just longwards of 100 μm.