bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplical minisuperspace. III. Integration contours in a five-simplex model
Authors: Hartle James B.
Published: July 2002

The no boundary proposal for the wave function of the universe is investigated in a minisuperspace model of pure gravity with cosmological constant. The model’s four geometries consist of five four-simplices joined together to make the surface of a five-simplex from which one four-simplex face has been removed. The model is further simplified by symmetrically choosing all the interior edges of equal length and all the edges of the four-simplex boundary of equal length. The wave function is thus a function of a single boundary squared edge length and is specified by an integral over the single interior edge length. The analytic properties of the action in the space of complex edge lengths are exhibited, its classical extrema are calculated, and the possible contours of integration defining the wave function of the universe are discussed. A descending contour of constant imaginary action is proposed along which the integral defining the wave function is convergent and which predicts classical space-time in the late universe. This contour is the analog for the model of the conformally rotated contour appropriate to Euclidean sums over asymptotically flat space-times. The wave function is evaluated numerically for this contour both directly and by semiclassical methods.
Geometry and uncertainty
Authors: Narcowich Francis J.
Published: July 2002

In the context of the Wigner–Weyl phase space formulation of quantum mechanics, a version of the uncertainty relations invariant under affine canonical transformations is derived. For a fixed Wigner distribution function possessing a finite covariance, ‘‘directions’’ of minimal uncertainty are found. The geometry of the Wigner ellipsoid and its Legendre transform, the dual Wigner ellipsoid, both of which are associated with the same covariance, is discussed. The results obtained are generalizations of the well-known fact that, for one degree of freedom, the area of the Wigner ellipse must be of order ℏ or larger. Instead of area, which is an invariant only when n=1, these results involve Poincaré invariants of certain curves and surfaces.
The uniqueness of the Bekenstein black hole
Authors: Xanthopoulos Basilis C. , Zannias Thomas
Published: July 2002

The general static, spherically symmetric, asymptotically flat solution of the Einstein equations coupled to a conformal scalar field is determined; it depends on three free parameters. One of the parameters is eliminated by the requirement that the solution admits a smooth horizon and no naked curvature singularities, leading to the black hole solution discovered by Bekenstein. Although the scalar field is unbounded on the horizon, this should not be considered as a physical pathology.
SU(1,1) Lie algebraic approach to linear dissipative processes in quantum optics
Authors: Ban Masashi
Published: July 2002

An SU(1,1) Lie algebraic formulation is presented for investigating the linear dissipative processes in quantum optical systems. The Liouville space formulation, thermo field dynamics, and the disentanglement theorem of SU(1,1) Lie algebra play essential roles in this formulation. In the Liouville space, the time-evolution equation for the state vector of a system is solved algebraically by using the decomposition formulas of SU(1,1) Lie algebra and the thermal state condition of thermo field dynamics. The presented formulation is used for investigating a dissipative nonlinear oscillator, the quantum mechanical model of phase modulation, and the photon echo in the localized electron–phonon system. This algebraic formulation gives a systematic treatment for investigating the phenomena in quantum optical systems.
Kaluza–Klein equations, Einstein’s equations, and an effective energy-momentum tensor
Authors: Wesson Paul S. , Ponce de Leon J.
Published: July 2002

Following earlier work, it is inquired how far the 5-D Kaluza–Klein equations without sources may be reduced to the Einstein equations with sources. It is shown by algebraic means that this can be done, provided the extra part of the 5-D geometry is used appropriately to define an effective 4-D energy-momentum tensor. The latter has reasonable properties, but will require further detailed study.
The pseudodifferential operator square root of the Klein–Gordon equation
Authors: Lämmerzahl Claus
Published: July 2002

A nonlocal square root of the Klein–Gordon equation is proposed. This nonlocal equation is a special relativistic equation for a scalar field of first order in the time derivative. Its space derivative part is described by a pseudodifferential operator. The usual quantum mechanical formalism can be set up. The nonrelativistic limit and the classical limit in the form of plane wave solutions and the Ehrenfest theorem are correctly included. The nonlocality of the wave equation does not disturb the light cone structure, and the relativity principle of special relativity is fulfilled. Uniqueness and existence of solutions of the Cauchy problem for this equation can be proved. The second quantized version of this theory turns out to be macrocausal.
Some high-frequency spherical gravity waves
Authors: Hogan P. A. , Futamase T.
Published: July 2002

The geometric optics approximation to a solution of Einstein’s vacuum field equations is studied using the approach of Burnett [J. Math. Phys. 30, 90 (1989)] in which the usual averaging methods are replaced by the use of weak limits. The technique is applied to calculate the gravitational field of high-frequency gravity waves produced by isolated sources. The background space–time derived is of the Robinson–Trautman form with a nonvanishing Ricci tensor and the high-frequency, small-amplitude perturbation is explicitly calculated. In general, the wave fronts are homeomorphic to two-spheres. For purely spherical waves we exhibit the plane wave limit in the geometric optics approximation and thereby recover an example given by Burnett, but with two degrees of freedom of polarization present instead of his one. The identification of a mass-loss formula of the Bondi–Sachs type in the background space–time is also discussed.
Closed orbits and their stable symmetries
Authors: Baikov V. A. , Gazizov R. K. , Ibragimov N. H. , Mahomed F. M.
Published: July 2002

What will be shown is the first-order perturbation of closed orbits for two-body problems using approximate symmetry theory. A complete group classification with respect to approximate symmetries of the first-order perturbation of the closed orbit equations corresponding to Kepler’s law and Hooke’s law is made. A discussion then follows of the connection between closed orbits and their stable symmetries.
On the complete symmetry group of the classical Kepler system
Authors: Krause J.
Published: July 2002

A rather strong concept of symmetry is introduced in classical mechanics, in the sense that some mechanical systems can be completely characterized by the symmetry laws they obey. Accordingly, a ‘‘complete symmetry group’’ realization in mechanics must be endowed with the following two features: (1) the group acts freely and transitively on the manifold of all allowed motions of the system; (2) the given equations of motion are the only ordinary differential equations that remain invariant under the specified action of the group. This program is applied successfully to the classical Kepler problem, since the complete symmetry group for this particular system is here obtained. The importance of this result for the quantum kinematic theory of the Kepler system is emphasized.
The eight tetrahedron equations
Authors: Hietarinta Jarmo , Nijhoff Frank
Published: July 2002

In this paper we derive from arguments of string scattering a set of eight tetrahedron equations, with different index orderings. It is argued that this system of equations is the proper system that represents integrable structures in three dimensions generalizing the Yang–Baxter equation. Under additional restrictions this system reduces to the usual tetrahedron equation in the vertex form. Most known solutions fall under this class, but it is by no means necessary. Comparison is made with the work on braided monoidal 2-categories also leading to eight tetrahedron equations.
Interaction between two vaporizing droplets in an intermediate Reynolds number flow
Authors: Raju M. S. , Sirignano W. A.
Published: July 2002

The dynamic properties of two vaporizing droplets moving in tandem and interacting through hydrodynamic forces are presented for the intermediate Reynolds number range of droplet motion [Re=O(100)]. The problem is relevant for dense spray applications. Depending upon certain initial parameters, the droplets can collide or separate. The behaviors of the droplets are influenced by the mass and heat transport associated with the evaporation of droplets in air. Droplet-drag coefficient, Nusselt number, droplet mass, droplet Reynolds number, and droplet spacing histories are reported for a limited number of cases following the introduction of two droplets of different radii, a′1,0 and a′2,0, at a given initial spacing, a′0, into a hot, convective fluid, which is characterized by uniform free-stream conditions. A finite-difference solution of the coupled two-phase, unsteady Navier–Stokes equations in cylindrical coordinates on a body-fitted coordinate system is adjusted continually to accommodate the changing boundary shapes resulting from the droplet movement and evaporation.

The interactions are significant for initial Reynolds number range of 50 to 200 and for initial droplet spacings of 2 to 15 droplet diameters. Drag coefficients and Nusselt numbers can differ significantly from the values for isolated droplets. Droplet collision is likely for the initially equal-sized droplets. Droplets moving in tandem collide for larger values of the ratio of the aft initial droplet diameter to the lead initial droplet diameter. A bifurcation value of this parameter is found above which increased separation of the droplets occurs. The bifurcation value increases as initial droplet spacing increases. This value depends only very weakly on the initial Reynolds number. For spacings above two diameters, the lead droplet behaves like an isolated droplet while drag coefficients for the aft droplet are significantly lower. Vaporization rate significantly affects the drag coefficients. For droplets within a few diameters of each other, the Nusselt number for the downstream droplet exhibits an entirely different character as the hot side on the droplet moves aft. Correlations of drag coefficients are reported for droplets of identical initial size. A general understanding is obtained about the modifications of droplet heating, vaporization, and drag due to the proximity of the two droplets.
Dispersion far downstream of a river junction
Authors: Smith Ronald , Daish N. C.
Published: July 2002

The merging of two rivers can have substantial and persistent effects upon the dispersion of a sudden release of pollutant from one of the tributaries. This paper quantifies the delayed time of arrival and increase in spreading attributable to the junction.
Local stability conditions in fluid dynamics
Authors: Lifschitz Alexander , Hameiri Eliezer
Published: July 2002

Three-dimensional flows of an inviscid incompressible fluid and an inviscid subsonic compressible gas are considered and it is demonstrated how the WKB method can be used for investigating their stability. The evolution of rapidly oscillating initial data is considered and it is shown that in both cases the corresponding flows are unstable if the transport equations associated with the wave which is advected by the flow have unbounded solutions. Analyzing the corresponding transport equations, a number of classical stability conditions are rederived and some new ones are obtained. In particular, it is demonstrated that steady flows of an incompressible fluid and an inviscid subsonic compressible gas are unstable if they have points of stagnation.
Onsager symmetry of transport in toroidal plasmas
Authors: Boozer Allen H.
Published: July 2002

Complete theories of transport contain thermodynamic cross terms, such as a particle flux driven by the temperature gradient. The matrix that relates the forces that drive the transport to the fluxes was shown to be symmetric by Onsager but with the choice of the forces and the fluxes rigidly constrained by thermodynamics. Those constraints for toroidal plasmas are derived and the implications are explored.
Drop deformation, breakup, and coalescence with compatibilizer
Authors: Hu Y. T. , Pine D. J. , Leal L. Gary
Published: July 2002

The effect of copolymers on the breakup and coalescence of polybutadiene (PB) drops in polydimethylsiloxane (PDMS) is studied using a four-roll mill flow cell. Copolymers are produced at the interface by a reaction between functionalized homopolymers. They reduce the interfacial tension and thus enhance breakup; they also inhibit coalescence of drops. Under the conditions of our experiments, the latter effect is much more significant than the former. For example, the addition of copolymer sufficient to reduce the interfacial tension by only 3% relative to the bare interface value is found to reduce the critical capillary number Cac for coalescence by a factor of 6. The critical capillary number for coalescence in the absence of copolymer is also measured for the first time. It is found to scale with the drop radius a as Cac∼a−0.82±0.03 and with the viscosity ratio λ as Cac∼λ−0.41±0.06.
Accurate formulas for the Landau damping rates of electrostatic waves
Authors: McKinstrie C. J. , Giacone R. E. , Startsev E. A.
Published: July 2002

Systematic perturbation methods are used to derive formulas for the Landau damping rates of electron-plasma and ion-acoustic waves. These formulas are more accurate than the standard formulas found in textbooks.
Ytterbium-doped InP light-emitting diode at 1.0 μm
Authors: Haydl W. H. , Müller H. D. , Ennen H. , Körber W. , Benz K. W.
Published: July 2002

Light-emitting pn junction diodes have been realized in ytterbium-doped InP. The p-type epitaxial layers, which contained the dopant ytterbium (Yb), were grown by liquid phase epitaxy on (100) oriented n+-type InP substrates. Ohmic contacts were alloyed, and the diodes biased in forward direction. At 77 K, emissions were observed at 1.38 eV (0.90 μm) and 1.24 eV (1.00 μm) due to near band-edge electron hole recombination and transitions between the spin-orbit levels 2F5/2→2F7/2 of  Yb3+(4f13), respectively. The dependence of the electroluminescence intensity with applied voltage is presented. The external quantum efficiency was determined to be 8×10−4 at 77 K.
Mobility of Ni versus Zr in an amorphous Ni-Zr alloy
Authors: Barbour J. C. , Nastasi M. , Mayer J. W.
Published: July 2002

A method for determining the dominant diffusing constituent in a binary amorphous alloy is demonstrated with the Ni-Zr system. Nickel is the dominant moving species in an amorphous Ni-Zr alloy near the a-Ni50Zr50 composition at 250 °C. In comparison to the Ni, the Zr has a negligible mobility under similar thermodynamic driving forces. Rutherford backscattering spectrometry is used to measure the change in the concentration of a thin film of Ni between thick amorphous layers. Based upon the change in the Ni profile, the diffusivity of Ni in an amorphous Ni-Zr alloy is between 1×10−17 and 1×10−16 cm2/s at 250 °C.
Stopband edges in the dispersion curves of Lamb waves propagating in piezoelectric periodical structures
Authors: Alippi A. , Craciun F. , Molinari E.
Published: July 2002

The fractional volume dependence of stopbands in piezoelectric periodical composite plates has been studied experimentally by exciting the band-edge resonances. The frequency and symmetry of such modes below the thickness resonance of the plate are successfully interpreted in terms of a theoretical model which provides approximate dispersion curves of the lowest Lamb waves propagating in the composite plate.
Donor gettering in GaAs by rare-earth elements
Authors: Raczyńska J. , Fronc K. , Langer J. M. , Lemańska A. , Stapor A.
Published: July 2002

Optical and electrical measurements of GaAs layers grown by liquid phase epitaxy with different amounts of Yb metal (0–1000 ppm) added to the Ga solution are reported. The presence of Yb during growth causes strong suppression of all donor-related optical transitions due to the effective removal of donors, as judged from Hall effect data. We have not found any appreciable increase of the background acceptor concentration during conductivity conversion from n-type to p-type, and thus conclude that dominant donor gettering occurs already in the Ga solution. No Yb3+ (4f 13)-related emission was detected in the as-grown GaAs layers.
Energetics by NMR: Site-specific binding in a positively cooperative system
Authors: Tochtrop Gregory P. , Richter Klaus , Tang Changguo , Toner James J. , Covey Douglas F. , Cistola David P.
Published: July 2002

Proteins with multiple binding sites exhibit a complex behavior that depends on the intrinsic affinities for each site and the energetic communication between the sites. The contributions from intrinsic affinity and cooperativity are difficult to deconvolute using conventional binding experiments that lack information about the occupancies of individual sites. Here, we report the concerted use of NMR and isothermal titration calorimetry to determine the intrinsic and cooperative binding free energies for a ligand–protein complex. The NMR measurements provided the site-specific information necessary to resolve the binding parameters. Using this approach, we observed that human ileal bile acid binding protein binds two molecules of glycocholic acid with low intrinsic affinity but an extraordinarily high degree of positive cooperativity. The highly cooperative nature of the binding provides insights into the protein's biological mechanism. With ongoing improvements in sensitivity and resolution, NMR methods are becoming more amenable to dissecting the complex binding energetics of multisite systems.
Three-dimensional modeling of and ligand docking to vitamin D receptor ligand binding domain
Authors: Yamamoto Keiko , Masuno Hiroyuki , Choi Mihwa , Nakashima Kinichi , Taga Tetsuya , Ooizumi Hiroshi , Umesono Kazuhiko , Sicinska Wanda , VanHooke Janeen , DeLuca Hector F. , Yamada Sachiko
Published: July 2002

The ligand binding domain of the human vitamin D receptor (VDR) was modeled based on the crystal structure of the retinoic acid receptor. The ligand binding pocket of our VDR model is spacious at the helix 11 site and confined at the β-turn site. The ligand 1α,25-dihydroxyvitamin D
3
was assumed to be anchored in the ligand binding pocket with its side chain heading to helix 11 (site 2) and the A-ring toward the β-turn (site 1). Three residues forming hydrogen bonds with the functionally important 1α- and 25-hydroxyl groups of 1α,25-dihydroxyvitamin D
3
were identified and confirmed by mutational analysis: the 1α-hydroxyl group is forming pincer-type hydrogen bonds with S237 and R274 and the 25-hydroxyl group is interacting with H397. Docking potential for various ligands to the VDR model was examined, and the results are in good agreement with our previous three-dimensional structure-function theory.
Spectral karyotyping suggests additional subsets of colorectal cancers characterized by pattern of chromosome rearrangement
Authors: Abdel-Rahman Wael M. , Katsura Kanade , Rens Willem , Gorman Patricia A. , Sheer Denise , Bicknell David , Bodmer Walter F. , Arends Mark J. , Wyllie Andrew H. , Edwards Paul A. W.
Published: July 2002

The abundant chromosome abnormalities in most carcinomas are
probably a reflection of genomic instability present in the tumor, so
the pattern and variability of chromosome abnormalities will reflect
the mechanism of instability combined with the effects of selection.
Chromosome rearrangement was investigated in 17 colorectal
carcinoma-derived cell lines. Comparative genomic hybridization showed
that the chromosome changes were representative of those found in
primary tumors. Spectral karyotyping (SKY) showed that translocations
were very varied and mostly unbalanced, with no translocation occurring
in more than three lines. At least three karyotype patterns could be
distinguished. Some lines had few chromosome abnormalities: they all
showed microsatellite instability, the replication error (RER)+
phenotype. Most lines had many chromosome abnormalities: at least seven
showed a surprisingly consistent pattern, characterized by multiple
unbalanced translocations and intermetaphase variation, with chromosome
numbers around triploid, 6–16 structural aberrations, and similarities
in gains and losses. Almost all of these were RER−, but one, LS411,
was RER+. The line HCA7 showed a novel pattern, suggesting a third kind
of genomic instability: multiple reciprocal translocations, with little
numerical change or variability. This line was also RER+. The
coexistence in one tumor of two kinds of genomic instability is to be
expected if the underlying defects are selected for in tumor evolution.
Trichostatin A reverses skewed expression of CD154, interleukin-10, and interferon-γ gene and protein expression in lupus T cells
Authors: Mishra Nilamadhab , Brown Doris R. , Olorenshaw Irene M. , Kammer Gary M.
Published: July 2002

In systemic lupus erythematosus (SLE), T helper cells exhibit increased and prolonged expression of cell-surface CD40 ligand (CD154), spontaneously overproduce interleukin-10 (IL-10), but underproduce interferon-gamma (IFN-γ). We tested the hypothesis that the imbalance of these gene products reflects skewed expression ofCD154,IL-10, andIFN-γ genes. Here, we demonstrate that the histone deacetylase inhibitor, trichostatin A, significantly down-regulatedCD154andIL-10and up-regulatedIFN-γ gene expression in SLE T cells. This reversal corrected the aberrant expression of these gene products, thereby enhancing IFN-γ production and inhibiting IL-10 and CD154 expression. That trichostatin A can simultaneously reverse the skewed expression of multiple genes implicated in the immunopathogenesis of SLE suggests that this pharmacologic agent may be a candidate for the treatment of this autoimmune disease.
The concerted mechanism of photo-induced biprotonic transfer in 7-azaindole dimers: A model for the secondary evolution of the classic
C
2h
dimer and comparison of four mechanisms
Authors: Catalán Javier , Pérez Pilar , del Valle Juan Carlos , de Paz J. L. G. , Kasha Michael
Published: July 2002

A mechanism is proposed for the formation in gas phase, during a short time, of the delicately symmetrical coplanar
C
2h
classic 7-azaindole (7AI) doubly hydrogen-bonded dimer. Of the five card-pack or otherwise random geometry structures most likely to be formed in the supersonic jet expansion molecular beam, none would be an obvious precursor to the
C
2h
dimer. One unstable dimer with dipole–dipole, van der Waals, and plane-to-plane hydrogen bonding is shown to be capable of unhinging about the hydrogen-bond pair as an axis, from 0° to 90° to 180°, yielding a deep minimum for the
C
2h
structure with its delicate geometry and symmetry. This relaxation mechanism is feasible in the 3-μs interval between the nozzle escape and the first laser pulse interception of the molecular beam. In the second part of the paper four published mechanisms are compared for concerted vs. two-step biprotonic phototransfer for the 7AI dimers. The dependence of the latter two models on H-atom instead of proton-transfer as an intermediate step negates the mechanism in a singlet (π,π*) electronic state by the valency repulsion, in the 3-electron orbital that would be generated. The concerted mechanism for biprotonic phototransfer is reaffirmed by the analysis of the quantum mechanical conditions set on the biprotonic transfer in the photo-excited molecular 7AI pair.
Differential activation of the human orbital, mid-ventrolateral, and mid-dorsolateral prefrontal cortex during the processing of visual stimuli
Authors: Petrides Michael , Alivisatos Bessie , Frey Stephen
Published: July 2002

There is considerable uncertainty about the precise functional contribution of the different parts of the prefrontal cortex to mnemonic processing. Changes in regional cerebral blood flow were measured with positron emission tomography in normal human subjects exposed to abstract visual designs under various conditions. It was demonstrated that the processing of stimuli that deviate from expectations involves selectively the orbitofrontal cortex, namely the part of the frontal cortex that is preferentially linked with the limbic system. By contrast, when the subject is making an explicit decision on the contents of memory (e.g., judgments of relative stimulus familiarity), the mid-ventrolateral prefrontal cortex is involved. The mid-dorsolateral prefrontal cortex is engaged when monitoring of information within working memory is required.
Transcriptional activation of NtcA-dependent promoters of
Synechococcus
sp. PCC 7942 by 2-oxoglutarate
in
vitro
Authors: Tanigawa Ryohei , Shirokane Masao , Maeda Shin-ichi , Omata Tatsuo , Tanaka Kan , Takahashi Hideo
Published: July 2002

The transcription factor NtcA is a global regulator of nitrogen homeostasis in cyanobacteria. It thus positively regulates the expression of genes related to nitrogen assimilation such as
glnA
(which encodes glutamine synthetase) and
ntcA
itself in response to nitrogen shortage or depletion. The binding of NtcA to the
glnA
and
ntcA
promoters of
Synechococcus
sp. PCC 7942
in vitro
now has been shown to be enhanced by 2-oxoglutarate.
In vitro
analysis of gene transcription also revealed that the interaction of NtcA with its promoter element was not sufficient for activation of transcription, and 2-oxoglutarate was required for transcriptional initiation by NtcA. Given that the intracellular concentration of 2-oxoglutarate is inversely related to nitrogen availability, it is proposed that this metabolite functions as a signaling molecule that transmits information on cellular nitrogen status to NtcA and thereby regulates the transcription of genes related to nitrogen assimilation in cyanobacteria.
Beneficial effects of systemic administration of recombinant human erythropoietin in rabbits subjected to subarachnoid hemorrhage
Authors: Grasso Giovanni , Buemi Michele , Alafaci Concetta , Sfacteria Alessandra , Passalacqua Marcello , Sturiale Alessio , Calapai Gioacchino , De Vico Gionata , Piedimonte Giuseppe , Salpietro Francesco M. , Tomasello Francesco
Published: July 2002

Cerebral vasospasm and ischemic damage are important causes of mortality and morbidity in patients affected by aneurysmal subarachnoid hemorrhage (SAH). Recently, i.p. administration of recombinant human erythropoietin (r-Hu-EPO) has been shown to exert a neuroprotective effect during experimental SAH. The present study was conducted to evaluate further the effect of r-Hu-EPO administration after SAH in rabbits on neurological outcome, degree of basilar artery spasm, and magnitude of neuronal ischemic damage. Experimental animals were divided into six groups: group 1 (
n
= 8), control; group 2 (
n
= 8), control plus placebo; group 3 (
n
= 8), control plus r-Hu-EPO; group 4 (
n
= 8), SAH; group 5 (
n
= 8), SAH plus placebo; group 6 (
n
= 8), SAH plus r-Hu-EPO. r-Hu-EPO, at a dose of 1,000 units/kg, and placebo were injected i.p. starting 5 min after inducing SAH and followed by clinical and pathological assessment 72 h later. Systemic administration of r-Hu-EPO produced significant increases in cerebrospinal fluid EPO concentrations (
P
< 0.001), and reduced vasoconstriction of the basilar artery (
P
< 0.05), ischemic neuronal damage (
P
< 0.001), and subsequent neurological deterioration (
P
< 0.05). These observations suggest that r-Hu-EPO may provide an effective treatment to reduce the post-SAH morbidity.
Rck2, a member of the calmodulin-protein kinase family, links protein synthesis to high osmolarity MAP kinase signaling in budding yeast
Authors: Teige Markus , Scheikl Elisabeth , Reiser Vladimir , Ruis Helmut , Ammerer Gustav
Published: July 2002

Rck2, a yeast Ser/Thr protein kinase homologous to mammalian
calmodulin kinases, requires phosphorylation for
activation. We provide evidence that in budding yeast, this step can be
executed by the osmostress-activated mitogen-activated protein kinase
Hog1. Rck2 phosphorylation was transiently increased during osmostress
or in mutants with a hyperactive high osmolarity glycerol (HOG)
pathway. This modification depended on catalytically active Hog1 kinase
and two putative mitogen-activated protein kinase phosphorylation sites
in Rck2. Immunokinase assays showed that Hog1 can directly
phosphorylate Rck2 to stimulate its enzymatic activity toward
translation elongation factor 2. We demonstrate that Hog1 and Rck2 are
necessary for attenuation of protein synthesis in response to osmotic
challenge and show that modification of elongation factor 2 induced by
osmostress depends on Rck2 and Hog1
in vivo
. Therefore,
we propose that the transient down-regulation of protein synthesis
after osmotic shock is a response not to damage but to an extracellular
signal mediated by Hog1 and Rck2.
Noninvasive imaging of protein–protein interactions in living animals
Authors: Luker Gary D. , Sharma Vijay , Pica Christina M. , Dahlheimer Julie L. , Li Wei , Ochesky Joseph , Ryan Christine E. , Piwnica-Worms Helen , Piwnica-Worms David
Published: July 2002

Protein–protein interactions control transcription, cell division, and cell proliferation as well as mediate signal transduction, oncogenic transformation, and regulation of cell death. Although a variety of methods have been used to investigate protein interactions
in vitro
and in cultured cells, none can analyze these interactions in intact, living animals. To enable noninvasive molecular imaging of protein–protein interactions
in vivo
by positron-emission tomography and fluorescence imaging, we engineered a fusion reporter gene comprising a mutant herpes simplex virus 1 thymidine kinase and green fluorescent protein for readout of a tetracycline-inducible, two-hybrid system
in vivo
. By using micro-positron-emission tomography, interactions between p53 tumor suppressor and the large T antigen of simian virus 40 were visualized in tumor xenografts of HeLa cells stably transfected with the imaging constructs. Imaging protein-binding partners
in vivo
will enable functional proteomics in whole animals and provide a tool for screening compounds targeted to specific protein–protein interactions in living animals.
Observation by fluorescence microscopy of transcription on single combed DNA
Authors: Gueroui Z. , Place C. , Freyssingeas E. , Berge B.
Published: July 2002

Molecular combing is a powerful procedure for aligning a large array of DNA molecules onto a surface. This technique usually leads to an overstretching of about 150% of the molecules' contour length. By changing the magnitude of capillary forces during the combing process, we were able to reduce the relative extension of the DNA molecules. Thus we achieved combing of T7 DNA with an extension close to its molecule contour length. We checked the ability of combed DNA to interact with DNA binding proteins. Using the T7 bacteriophage transcription system, we investigated the transcription activity of RNA polymerase on combed DNA by direct visualization of newly synthesized fluorescent RNAs. Our experiments show that no transcription activity occurs on overstretched DNA molecules, whereas we observe a transcription activity for nonoverstretched molecules. This activity is observed both in multiple initiation experiments and for one immobilized T7 RNA polymerase per promoter. These results open possibilities for the study of single enzyme actions on combed DNA by optical methods.
IL-10 is necessary for the expression of airway hyperresponsiveness but not pulmonary inflammation after allergic sensitization
Authors: Mäkelä M. J. , Kanehiro A. , Borish L. , Dakhama A. , Loader J. , Joetham A. , Xing Z. , Jordana M. , Larsen G. L. , Gelfand E. W.
Published: July 2002

Cytokines play an important role in modulating inflammatory responses and, as a result, airway tone. IL-10 is a regulatory cytokine that has been suggested for treatment of asthma because of its immunosuppressive and anti-inflammatory properties. In contrast to these suggestions, we demonstrate in a model of allergic sensitization that mice deficient in IL-10 (IL-10−/−) develop a pulmonary inflammatory response but fail to exhibit airway hyperresponsiveness in both
in vitro
and
in vivo
assessments of lung function. Reconstitution of these deficient mice with the IL-10 gene fully restores development of airway hyperresponsiveness comparable to control mice. These results identify an important role of IL-10, downstream of the inflammatory cascade, in regulating the tone of the airways after allergic sensitization and challenge.
Stimulation via CD40 can substitute for CD4 T cell function in preventing reactivation of a latent herpesvirus
Authors: Sarawar Sally R. , Lee Bong Joo , Reiter Su Khoh , Schoenberger Stephen P.
Published: July 2002

Reactivation of latent herpesviruses is a particular problem in immunocompromised individuals, such as AIDS patients, who lack effective CD4 T helper cell function. An important question is whether residual immune defenses can be mobilized to combat such opportunistic infections, in the absence of CD4 T cells. In the present study, we used a mouse model of opportunistic infection to determine whether stimulation via CD40 could substitute for CD4 T cell function in preventing reactivation of a latent herpesvirus. Treatment with an agonistic antibody to CD40 was highly effective in preventing reactivation of latent murine gammaherpesvirus (MHV-68) in the lungs of CD4 T cell-deficient mice. CD8+T cells were essential for this effect, whereas virus-specific serum antibody was undetectable and IFN-γ production was unchanged. This demonstration that immunostimulation via CD40 can replace CD4 T cell help in controlling latent virusin vivohas potential implications for the development of novel therapeutic agents to prevent viral reactivation in immunocompromised patients.
Neuronal deactivation explains decreased cerebellar blood flow in response to focal cerebral ischemia or suppressed neocortical function
Authors: Gold Lorenz , Lauritzen Martin
Published: July 2002

Functional neuroimaging in humans with acute brain damage often reveals decreases in blood flow and metabolism in areas unaffected by the lesion. This phenomenon, termed diaschisis, is presumably caused by disruption of afferent excitatory input from the lesioned area to other brain regions. By characterizing its neurophysiological basis, we used cerebellar diaschisis to study the relationship between electrical activity and blood flow during decreased neuronal activity. Here we show that focal cerebral ischemia in rats causes diaschisis in the cerebellar cortex characterized by pronounced decreases in Purkinje cell spiking activity and small decreases in cerebellar blood flow. The findings were explained by decreased excitatory input to the cerebellar cortex, i.e., deactivation, as cerebellar neuronal excitability and vascular reactivity were preserved. Functional ablation of the cerebral cortex by either spreading depression or tetrodotoxin reproduced the changes in cerebellar function with complete recovery of Purkinje cell activity and cerebellar blood flow concomitant with recovery of neocortical function. Decreases of activity involving the contralateral frontal cortex produced the largest decrease in cerebellar electrical activity and blood flow. Our data suggest that deactivation explains the decreases in blood flow and metabolism in cerebellar diaschisis observed in human neuroimaging studies. Decreases in spiking activity were 3–7 times larger than the respective decreases in flow. Therefore, under pathological conditions, neuroimaging methods based on hemodynamic signals may only show small changes, although the underlying decrease in neuronal activity is much larger.
Genetic and environmental factors modify bovine spongiform encephalopathy incubation period in mice
Authors: Manolakou Katerina , Beaton Jenny , McConnell Irene , Farquar Christine , Manson Jean , Hastie Nicholas D. , Bruce Moira , Jackson Ian J.
Published: July 2002

The incubation period (IP) and the neuropathology of transmissible spongiform encephalopathies (TSEs) have been extensively used to distinguish prion isolates (or strains) inoculated into panels of inbred mouse strains. Such studies have shown that the bovine spongiform encephalopathy (BSE) agent is indistinguishable from the agent causing variant Creutzfeldt–Jakob disease (vCJD), but differs from isolates of sporadic CJD, reinforcing the idea that the vCJD epidemic in Britain results from consumption of contaminated beef products. We present a mouse model for genetic and environmental factors that modify the incubation period of BSE cross-species transmission. We have used two mouse strains that carry the same prion protein (PrP) allele, but display a 100-day difference in their mean IP following intracerebral inoculation with primary BSE isolate. We report genetic effects on IP that map to four chromosomal regions, and in addition we find significant factors of host environment, namely the age of the host's mother, the age of the host at infection, and an X-cytoplasm interaction in the host.
Normotonic cell shrinkage because of disordered volume regulation is an early prerequisite to apoptosis
Authors: Maeno Emi , Ishizaki Yasuki , Kanaseki Toku , Hazama Akihiro , Okada Yasunobu
Published: July 2002

A major hallmark of apoptosis is normotonic shrinkage of cells. Here, we studied the relation between apoptotic cell shrinkage and apoptotic cell death. Induction of the apoptotic volume decrease (AVD) under normotonic conditions was found to be coupled to facilitation of the regulatory volume decrease (RVD), which is known to be attained by parallel operation of Cl
−
and K
+
channels, under hypotonic conditions. Both the AVD induction and the RVD facilitation were found to precede cytochrome
c
release, caspase-3 activation, DNA laddering, and ultrastructural alterations in three cell types after apoptotic insults with two distinct apoptosis inducers. Also, the AVD was not prevented by a broad-spectrum caspase inhibitor. When the AVD induction and the RVD facilitation were prevented by blocking volume-regulatory Cl
−
or K
+
channels, these cells did not show succeeding apoptotic biochemical and morphological events and were rescued from death. Thus, it is concluded that the AVD, which is caused by disordered cell volume regulation, is an early prerequisite to apoptotic events leading to cell death.
Mechanism of action of a pestivirus antiviral compound
Authors: Baginski Scott G. , Pevear Daniel C. , Seipel Marty , Sun Siu Chi Chang , Benetatos Christopher A. , Chunduru Srinivas K. , Rice Charles M. , Collett Marc S.
Published: July 2002

We report here the discovery of a small molecule inhibitor of pestivirus replication. The compound, designated VP32947, inhibits the replication of bovine viral diarrhea virus (BVDV) in cell culture at a 50% inhibitory concentration of approximately 20 nM. VP32947 inhibits both cytopathic and noncytopathic pestiviruses, including isolates of BVDV-1, BVDV-2, border disease virus, and classical swine fever virus. However, the compound shows no activity against viruses from unrelated virus groups. Time of drug addition studies indicated that VP32947 acts after virus adsorption and penetration and before virus assembly and release. Analysis of viral macromolecular synthesis showed VP32947 had no effect on viral protein synthesis or polyprotein processing but did inhibit viral RNA synthesis. To identify the molecular target of VP32947, we isolated drug-resistant (DR) variants of BVDV-1 in cell culture. Sequence analysis of the complete genomic RNA of two DR variants revealed a single common amino acid change located within the coding region of the NS5B protein, the viral RNA-dependent RNA polymerase. When this single amino acid change was introduced into an infectious clone of drug-sensitive wild-type (WT) BVDV-1, replication of the resulting virus was resistant to VP32947. The RNA-dependent RNA polymerase activity of the NS5B proteins derived from WT and DR viruses expressed and purified from recombinant baculovirus-infected insect cells confirmed the drug sensitivity of the WT enzyme and the drug resistance of the DR enzyme. This work formally validates NS5B as a target for antiviral drug discovery and development. The utility of VP32947 and similar compounds for the control of pestivirus diseases, and for hepatitis C virus drug discovery efforts, is discussed.
Identification of a chloride-formate exchanger expressed on the brush border membrane of renal proximal tubule cells
Authors: Knauf Felix , Yang Chao-Ling , Thomson R. Brent , Mentone Sue Ann , Giebisch Gerhard , Aronson Peter S.
Published: July 2002

A key function of the proximal tubule is retrieval of most of the vast quantities of NaCl and water filtered by the kidney. Physiological studies using brush border vesicles and perfused tubules have indicated that a major fraction of Cl
−
reabsorption across the apical membrane of proximal tubule cells occurs via Cl
−
-formate exchange. The molecular identity of the transporter responsible for renal brush border Cl
−
-formate exchange has yet to be elucidated. As a strategy to identify one or more anion exchangers responsible for mediating Cl
−
reabsorption in the proximal tubule, we screened the expressed sequence tag database for homologs of pendrin, a transporter previously shown to mediate Cl
−
-formate exchange. We now report the cDNA cloning of CFEX, a mouse pendrin homolog with expression in the kidney by Northern analysis. Sequence analysis indicated that CFEX very likely represents the mouse ortholog of human SLC26A6. Immunolocalization studies detected expression of CFEX, but not pendrin, on the brush border membrane of proximal tubule cells. Functional expression studies in
Xenopus
oocytes demonstrated that CFEX mediates Cl
−
-formate exchange. Taken together, these observations identify CFEX as a prime candidate to mediate Cl
−
-formate exchange in the proximal tubule and thereby to contribute importantly to renal NaCl reabsorption. Given its wide tissue distribution, CFEX also may contribute to transcellular Cl
−
transport in additional epithelia such as the pancreas and contribute to transmembrane Cl
−
transport in nonepithelial tissues such as the heart.
Transient decrease in water diffusion observed in human occipital cortex during visual stimulation
Authors: Darquié Anne , Poline Jean-Baptiste , Poupon Cyril , Saint-Jalmes Hervé , Le Bihan Denis
Published: July 2002

Using MRI, we report the observation of a transient decrease of the apparent diffusion coefficient (ADC) of water in the human brain visual cortex during activation by a black and white 8-Hz-flickering checkerboard. The ADC decrease was small (<1%), but significant and reproducible, and closely followed the time course of the activation paradigm. Based on the known sensitivity of diffusion MRI to cell size in tissues and on optical imaging studies that have revealed changes in the shape of neurons and glial cells during activation, the observed ADC findings have been tentatively ascribed to a transient swelling of cortical cells. These preliminary results suggest a new approach to produce images of brain activation with MRI from signals directly associated with neuronal activation, and not through changes in local blood flow.
Conservation of early odontogenic signaling pathways in
Aves
Authors: Chen YiPing , Zhang Yanding , Jiang Ting-Xing , Barlow Amanda J. , St. Amand Tara R. , Hu Yueping , Heaney Shaun , Francis-West Philippa , Chuong Cheng-Ming , Maas Richard
Published: July 2002

Teeth have been missing from birds (
Aves
) for at least 60 million years. However, in the chick oral cavity a rudiment forms that resembles the lamina stage of the mammalian molar tooth germ. We have addressed the molecular basis for this secondary loss of tooth formation in
Aves
by analyzing in chick embryos the status of molecular pathways known to regulate mouse tooth development. Similar to the mouse dental lamina, expression of
Fgf8, Pitx2, Barx1
, and
Pax9
defines a potential chick odontogenic region. However, the expression of three molecules involved in tooth initiation,
Bmp4
,
Msx1
, and
Msx2
, are absent from the presumptive chick dental lamina. In chick mandibles, exogenous bone morphogenetic protein (BMP) induces
Msx
expression and together with fibroblast growth factor promotes the development of
Sonic hedgehog
expressing epithelial structures. Distinct epithelial appendages also were induced when chick mandibular epithelium was recombined with a tissue source of BMPs and fibroblast growth factors, chick skin mesenchyme. These results show that, although latent, the early signaling pathways involved in odontogenesis remain inducible in
Aves
and suggest that loss of odontogenic
Bmp4
expression may be responsible for the early arrest of tooth development in living birds.
The tumor-infiltrating B cell response in medullary breast cancer is oligoclonal and directed against the autoantigen actin exposed on the surface of apoptotic cancer cells
Authors: Hansen Margit H. , Nielsen Heidi , Ditzel Henrik J.
Published: July 2002

Medullary carcinoma of the breast (MCB) is a morphologically and biologically distinct subtype of human breast cancer that, despite cytologically anaplastic features, has a more favorable prognosis than other types of breast cancer at similar stages of differentiation. It has been proposed that the improved clinical outcome is due, at least in part, to the presence of a prominent lymphoplasmacytic cell infiltrate in the tumor stroma. We studied the B lymphoplasmacytic cell infiltrates in MCB to determine the role of the antibody response produced by the local infiltrating cells. Oligoclonal predominance among tumor-infiltrating B cells in a panel of MCB patients was observed, suggesting that certain B cell clones were expanded, possibly in response to specific tumor-associated stimuli. IgG antibody phage-display libraries were generated from MCB-infiltrating lymphoplasmacytic cells of two patients, and MCB-reactive monoclonal antibodies were retrieved by selection on fresh-frozen MCB tissue sections. Analysis by mass spectrometry revealed that the antigen targeted by the dominant clones in the oligoclonal B lymphoplasmacytic response in both patients was not a cancer-specific antigen but the cytoskeletal protein β-actin. MCB exhibits an increased rate of apoptosis, and apoptotic MCB cells were shown to expose actin on the cell surface, permitting its recognition by the humoral immune system. Further, actin fragments, similar to those observed after cleavage with the apoptotic protease granzyme B, were observed in MCB tissue. Our results indicate that the major antibody response produced by tumor-infiltrating B lymphoplasmacytic cells are autoimmune in nature and a consequence of the perturbed state of increased MCB apoptosis caused by granzyme B-induced T cell cytotoxicity and/or intrinsic cellular factors of MCB cells.