bluuebunny/crossref_metadata_2025 huggingface dataset:
Features of wavy vortices in a curved channel from experimental and numerical studies
Authors: Ligrani P. M. , Finlay W. H. , Fields W. A. , Fuqua S. J. , Subramanian C. S.
Published: July 2002

Evidence of time-dependent, wavy vortex motions associated with undulating and twisting Dean vortices is obtained experimentally in a curved channel with 40 to 1 aspect ratio, and mild curvature (radius ratio=0.979). These results are compared with direct numerical simulations of the time-dependent, three-dimensional Navier–Stokes equations using periodic boundary conditions in the spanwise and streamwise directions. When viewed in cross section, experimental visualizations of undulating and twisting vortex flows show rocking motion and changes in the direction of the flow between vortices that are like those observed in the simulations. Experimental spectra show that undulating vortices are replaced by the higher-frequency, shorter streamwise wavelength twisting vortices at higher Reynolds numbers. When undulating vortices are present, experimental power spectra and visualizations give frequencies that are somewhat lower than the most unstable frequencies predicted by linear stability analysis. When twisting vortices are present, experimental power spectra give fundamental and harmonic frequencies in good agreement with simulated values and with values from linear stability analysis. Twisting is present in experimental spectra over the largest Reynolds number range in spectra measured near the concave wall within inflow regions and near the concave wall near individual vortices. Fundamental amplitudes in these spectra are strongly dependent upon Reynolds number as well as on the location within the vortex pair structure. Twisting is connected to local increases of the longitudinal Reynolds stress. Like twisting, these increases occur first near the concave surface near inflow regions as the Reynolds number increases. Distributions of time-averaged streamwise velocity, streamwise vorticity, radial vorticity, and spanwise vorticity in cross-sectional planes during twisting show good quantitative and qualitative agreement with simulation results. During undulation, time-averaged radial vorticity, spanwise vorticity, and streamwise velocity distributions also compare well. In general, experimental wavy vortices are somewhat less regular than the temporally and spatially periodic wavy vortices observed in the simulations, or in Taylor–Couette flow.
Linearized gyrofluid model of the alpha-destabilized toroidal Alfvén eigenmode with continuum damping effects
Authors: Spong D. A. , Carreras B. A. , Hedrick C. L.
Published: July 2002

The toroidicity-induced shear Alfvén eigenmode (TAE) can be destabilized by energetic particle populations through inverse Landau damping. It may also be significantly damped by coupling with adjacent shear Alfvén continua. A gyrofluid model with Landau closure that includes both of these effects is developed and applied to this instability. The model consists of the usual reduced magnetohydrodynamic (MHD) equations for the evolution of the poloidal flux and toroidal component of vorticity, coupled with equations for the density and parallel velocity moments of the energetic species. The latter two equations include Landau damping/growth effects through use of a consistent closure relation, which is equivalent to a two-pole approximation to the plasma dispersion function. These equations are solved numerically using a three-dimensional initial value code (tae/fl) in toroidal geometry. The unstable TAE growth rate and continuum damping rates are compared with recent analytical estimates, and reasonable agreement is obtained.
Nonlinear evolution of a strongly sheared cross-field plasma flow
Authors: Romero H. , Ganguli G.
Published: July 2002

A study is presented of the nonlinear evolution of a magnetized plasma in which a localized electron cross-field flow is present. The peak velocity of the flow is denoted by V0; LE represents the flow’s shear scale length; and the regime ρe<LE<ρi is considered, where ρi and ρe denote the ion and electron Larmor radii, respectively. It is shown that if the shear frequency ωs=V0/LE is larger than the lower-hybrid frequency, ωLH, then the system dynamics is dominated by the onset of the electron–ion-hybrid (EIH) mode which leads to the formation of coherent (vortexlike) structures in the electrostatic potential of the ensuing lower-hybrid waves. The wavelength of these structures is on the order of LE, and correlates well with that predicted by the linear theory of the EIH mode. Since the characteristic wavelength is longer than ρe, the corresponding phase velocity is low enough that there results significant direct resonant ion acceleration perpendicular to the confining magnetic field. When ωs≳3ωLH, the system exhibits significant anomalous viscosity (typically an order of magnitude larger than that due to Coulomb collisions), which increases as the shear frequency is increased. As ωs is reduced below ωLH, shear effects are no longer dominant and a smooth transition takes place in which the system dynamics is governed by the short wavelength (on the order of ρe) lower-hybrid drift instability.
Global Alfvén modes: Theory and experiment*
Authors: Turnbull A. D. , Strait E. J. , Heidbrink W. W. , Chu M. S. , Duong H. H. , Greene J. M. , Lao L. L. , Taylor T. S. , Thompson S. J.
Published: July 2002

It is shown that the theoretical predictions and experimental observations of toroidicity-induced Alfvén eigenmodes (TAE’s) are now in good agreement, with particularly detailed agreement in the mode frequencies. Calculations of the driving and damping rates predict the importance of continuum damping for low toroidal mode numbers and this is confirmed experimentally. However, theoretical calculations in finite-β, shaped discharges predict the existence of other global Alfvén modes, in particular the ellipticity-induced Alfvén eigenmode (EAE) and a new mode, the beta-induced Alfvén eigenmode (BAE). The BAE mode is calculated to be in or below the same frequency range as the TAE mode and may contribute to the experimental observations at high β. Experimental evidence and complementary analyses are presented confirming the presence of the EAE mode at higher frequencies.
Discrete tones generated by the impingement of a high-speed jet on a circular cylinder
Authors: Umeda Y. , Maeda H. , Ishii R.
Published: July 2002

Discrete tones generated from the interaction of high-speed jets with solid boundaries are investigated experimentally. Measurement of far-field pressure waves and Schlieren flow visualization were conducted. Emphasis is placed upon the generation mechanism of a discrete tone that is generated when a circular cylinder is placed in a jet at a high Reynolds number. This discrete tone was observed to be generated for jet exit Mach numbers greater than 0.6 and distances from the nozzle lip to the cylinder less than about eight times the nozzle diameter. By the Schlieren flow visualization, it is confirmed that this discrete tone is radiated from the jet by a strong feedback resonance. When an eddy (a ring vortex) interacts with the cylinder, an acoustic pulse is emitted with a strong directional peak in the upstream direction. The acoustic pulse propagates outside the jet and, upon reaching the nozzle lip, forces the generation of a new eddy. As the new eddy approaches the cylinder it regains the strength of the original eddy by extracting energy from the potential core of the jet and so maintains the cycle.
The effect of a uniform magnetic field on the onset of steady Marangoni convection in a layer of conducting fluid with a prescribed heat flux at its lower boundary
Authors: Wilson S. K.
Published: July 2002

In this paper a combination of analytical and numerical techniques are used to analyze the effect of a uniform vertical magnetic field on the onset of steady Marangoni convection in a horizontal layer of quiescent, electrically conducting fluid with a uniform vertical temperature gradient subject to a prescribed heat flux at its rigid lower boundary. Critical Marangoni numbers for the onset of instability are calculated which are significantly different from those calculated previously in the case of an isothermal lower boundary. Analytical results for the behavior of the critical Marangoni number in the asymptotic limit of large magnetic field strength are also obtained. It is concluded that the magnetic field always has a stabilizing effect on the onset of steady Marangoni convection, but that when the free surface is deformable situations with a sufficiently large Marangoni number will always have unstable modes no matter how strong the applied magnetic field is.
Experiments on stability and oscillatory behavior of planar buoyant plumes
Authors: Cetegen B. M. , Dong Y. , Soteriou M. C.
Published: July 2002

Experiments on the onset of buoyant instabilities leading to periodic formation of vortical structures in planar buoyant plumes of helium and helium/air mixtures injected into quiescent air are reported for a range of nozzle widths (w=20–70 mm), plume fluid densities (pure helium to that approaching air), and velocities at the nozzle exit. First, the plume parameters corresponding to the onset of the oscillatory instability were experimentally determined by varying the nozzle exit velocity for different nozzle widths and plume fluid densities in two different nozzle configurations. These configurations corresponded to a freestanding rectangular nozzle and a rectangular nozzle surrounded by a flat plate in the plane of the nozzle exit. The observed plume behavior in the near field was characterized as nonoscillatory, transitional, or pulsatile. The onset of pulsations in the near field of these buoyant plumes (within a height of two nozzle widths) was best correlated in terms of the plume source Reynolds number and the plume fluid to ambient density ratio. It was also found that the boundary conditions surrounding the nozzle exit had an influence on the onset of plume instability in the near field. Specifically, at a given plume to the ambient density ratio, the plumes with flat plate surround were found to transition to the oscillatory state at a lower value of the threshold velocity and therefore are less stable than the plumes originating from freestanding nozzles. Subsequently, the plume oscillation frequencies were measured as a function of plume width, plume source velocity, and the density ratio for a range of these parameters. The plume oscillation frequency was found to correlate well in terms of the nondimensional parameters, Strouhal number, S=(fw)/Vp, and Richardson number, Ri=[(ρ∞−ρp)gw]/ρ∞Vp2, yielding a correlation S=0.55Ri0.45 determined for 1<Ri<102. This correlation is somewhat different from that of the axisymmetric buoyant plumes, which can be attributed to the differences in mixing rates and the strength of the local buoyancy flux in planar and axisymmetric plumes. The vortical structures formed in the unstable plumes also exhibit several distinct vortex pair modes. The centers of the formed vortex pairs, in general, do not remain colinear and distort with respect to each other when compared with the axisymmetric plume vortex rings, which are toroidal. The convection speeds of the vortex pair centers were also measured and reported in this study.
Effects of non-Maxwellian (super-Gaussian) electron velocity distribution on the spectrum of Thomson scattering
Authors: Zheng Jian , Yu C. X. , Zheng Z. J.
Published: July 2002

The dynamic form factor for Thomson scattering with a non-Maxwellian (super-Gaussian) electron velocity distribution is analytically and numerically studied for the first time. Both the ion and electron features of the spectra for α>1 are found to be affected strongly. For the ion feature, the use of the usual theoretical spectra with the assumption of a Maxwellian distribution for fitting the measured Thomson scattering spectra may have resulted in some errors in calculating the plasma parameters in high-Z plasmas irradiated with high intensity light. However, it is impossible to use the ion feature of the measured spectra alone to deduce the form of the electron distribution. For the electron feature, the spectral shape (in particular the peak amplitude) changes sensitively with the distribution index. It would be possible to detect the super-Gaussian distribution by simultaneously measuring the ion and electron features of the spectra.
Testing the ρ* scaling of thermal transport models: Predicted and measured temperatures in the Tokamak Fusion Test Reactor dimensionless scaling experiments
Authors: Mikkelsen D. R. , Scott S. D. , Dorland W.
Published: July 2002

Theoretical predictions of ion and electron thermal diffusivities are tested by comparing calculated and measured temperatures in low (L) mode plasmas from the Tokamak Fusion Test Reactor [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)] nondimensional scaling experiments. The DIII-D [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)] L-mode ρ* scalings, the transport models of Rebut-Lallia-Watkins (RLW), Boucher’s modification of RLW, and the Institute for Fusion Studies-Princeton Plasma Physics Laboratory (IFS-PPPL) model for transport due to ion temperature gradient modes are tested. The predictions use the measured densities in order to include the effects of density profile shape variations on the transport models. The uncertainties in the measured and predicted temperatures are discussed. The predictions based on the DIII-D scalings are within the measurement uncertainties. All the theoretical models predict a more favorable ρ* dependence for the ion temperatures than is seen. Preliminary estimates indicate that sheared flow stabilization is important for some discharges, and that inclusion of its effects may bring the predictions of the IFS-PPPL model into agreement with the experiments.
Magnetic island deformation due to sheared flow and viscosity
Authors: Ren C. , Chu M. S. , Callen J. D.
Published: July 2002

A partial differential equation for a two-dimensional magnetohydrodynamic (MHD) equilibrium with flow and viscosity is derived. The equation is used to describe the deformation of the magnetic island caused by the viscous drag of a sheared flow. The deformation is characterized by the phase gradient of the magnetic perturbation across a magnetic island. This phase gradient has been observed experimentally in electron cyclotron emission data from the DIII-D tokamak [J. L. Luxon and L. G. Davis, Fusion Technol. 8, 441 (1985)].
Waveguiding effects in laser-induced aqueous etching of semiconductors
Authors: Podlesnik Dragan V. , Gilgen Heinz H. , Osgood Richard M.
Published: July 2002

The rapid, ultraviolet-induced aqueous etching produces vertical, high-aspect features in GaAs samples of different crystal orientations. Much of the speed and anisotropy of the etching is attributed to the formation of efficient hollow, optical waveguides. These guides have been characterized by measuring the optical loss and the field distribution within the guide. The optical loss is typically small and does not restrict the etching of deep features.
New 10 μm infrared detector using intersubband absorption in resonant tunneling GaAlAs superlattices
Authors: Levine B. F. , Choi K. K. , Bethea C. G. , Walker J. , Malik R. J.
Published: July 2002

We demonstrate a novel 10.8 μm superlattice infrared detector based on doped quantum wells of GaAs/AlGaAs. Intersubband resonance radiation excites an electron from the ground state into the first excited state, where it rapidly tunnels out producing a photocurrent. We achieve a narrow bandwidth (10%) photosensitivity with a responsivity of 0.52 A/W and an estimated speed of 30 ps.
Optical detection in thin granular films of Y-Ba-Cu-O at temperatures between 4.2 and 100 K
Authors: Leung M. , Broussard P. R. , Claassen J. H. , Osofsky M. , Wolf S. A. , Strom U.
Published: July 2002

It is demonstrated here that granular films of Y-Ba-Cu-O may serve as optical detectors, operating at wavelengths from the visible to the far infrared, at temperatures well above that of liquid helium. Preliminary measurements using a blackbody source show that an upper bound of the minimum detectable power is 1 μW. The response time as determined by a pulsed far-infrared source is of the order 20 ns. Methods to improve the sensitivity will be discussed.
Electrostatic collection of debris resulting from 193 nm laser etching of polyimide
Authors: von Gutfeld R. J. , Srinivasan R.
Published: July 2002

Ablated debris produced by 193 nm laser irradiation of polyimide can be preferentially collected on charged wire or plate electrodes placed on the polymer surface. Scanning micrographs indicate several types of debris structure depending on laser fluence and applied potential. The fragment morphology and possible charging mechanisms are discussed. The collected debris is believed to consist of pure carbon.
The evolution and development of cranial form in
Homo
sapiens
Authors: Lieberman Daniel E. , McBratney Brandeis M. , Krovitz Gail
Published: July 2002

Despite much data, there is no unanimity over how to define
Homo sapiens
in the fossil record. Here, we examine cranial variation among Pleistocene and recent human fossils by using a model of cranial growth to identify unique derived features (autapomorphies) that reliably distinguish fossils attributed to “anatomically modern”
H. sapiens
(AMHS) from those attributed to various taxa of “archaic”
Homo
spp
.
(AH) and to test hypotheses about the changes in cranial development that underlie the origin of modern human cranial form. In terms of pattern, AMHS crania are uniquely characterized by two general structural autapomorphies: facial retraction and neurocranial globularity. Morphometric analysis of the ontogeny of these autapomorphies indicates that the developmental changes that led to modern human cranial form derive from a combination of shifts in cranial base angle, cranial fossae length and width, and facial length. These morphological changes, some of which may have occurred because of relative size increases in the temporal and possibly the frontal lobes, occur early in ontogeny, and their effects on facial retraction and neurocranial globularity discriminate AMHS from AH crania. The existence of these autapomorphies supports the hypothesis that AMHS is a distinct species from taxa of “archaic”
Homo
(e.g.,
Homo neanderthalensis
).
Soybean
ENOD40
encodes two peptides that bind to sucrose synthase
Authors: Röhrig Horst , Schmidt Jürgen , Miklashevichs Edvins , Schell Jeff , John Michael
Published: July 2002

ENOD40
is expressed at an early stage in root nodule organogenesis in legumes. Identification of
ENOD40
homologs in nonleguminous plants suggests that this gene may have a more general biological function.
In vitro
translation of soybean
ENOD40
mRNA in wheat germ extracts revealed that the conserved nucleotide sequence at the 5′ end (region I) encodes two peptides of 12 and 24 aa residues (peptides A and B). These peptides are synthesized
de novo
from very short, overlapping ORFs. Appropriate ORFs are present in all legume
ENOD40
s studied thus far. In this case small peptides are directly translated from polycistronic eukaryotic mRNA. The 24-aa peptide B was detected in nodules by Western blotting. Both peptides specifically bind to the same 93-kDa protein, which was affinity purified from soybean nodules. Using peptide mass fingerprinting, we identified this binding protein as nodulin 100, which is a subunit of sucrose synthase. Based on our data we suggest that ENOD40 peptides are involved in the control of sucrose use in nitrogen-fixing nodules.
Transgenic mice neuronally expressing baculoviral p35 are resistant to diverse types of induced apoptosis, including seizure-associated neurodegeneration
Authors: Viswanath Veena , Wu Zhijin , Fonck Carlos , Wei Qize , Boonplueang Rapee , Andersen Julie K.
Published: July 2002

Apoptosis is a cell-suicide process that appears to play a central role not only during normal neuronal development but also in several neuropathological disease states. An important component of this process is a proteolytic cascade involving a family of cysteine proteases called caspases. Caspase inhibitors have been demonstrated to be effective in inhibiting neuronal cell death in various apoptotic paradigms. We have created transgenic mice that neuronally express the baculoviral caspase inhibitor p35. Neuronal expression of the p35 protein was found to confer functional caspase inhibitory activity and prevent apoptosis in isolated cerebellar granular cultures induced to undergo apoptosis either via staurosporine treatment or through withdrawal of extracellular potassium. Neuronal expression of p35 was also found to attenuate neurodegeneration associated with the excitotoxic glutamate analogue kainic acid (KA)
in vitro
and
in vivo
. Organotypic hippocampal cultures isolated from p35 transgenics demonstrated lowered caspase activity and decreased apoptosis compared with wild type when exposed to KA.
In vivo
injection of KA also produced decreased caspase activity and cell death in p35 transgenics vs. wild type. These results suggest that the presence of p35 in neurons
in vivo
is protective against various types of apoptosis, including seizure-related neurodegeneration, and that caspases may be attractive potential targets for preventing neuronal injury associated with diseases such as epilepsy. These mice also provide a valuable tool for exploring the role of caspases in other neuropathological conditions in which apoptosis has been implicated.
Biomimetic self-assembly of a functional asymmetrical electronic device
Authors: Boncheva Mila , Gracias David H. , Jacobs Heiko O. , Whitesides George M.
Published: July 2002

This paper introduces a biomimetic strategy for the fabrication of asymmetrical, three-dimensional electronic devices modeled on the folding of a chain of polypeptide structural motifs into a globular protein. Millimeter-size polyhedra—patterned with logic devices, wires, and solder dots—were connected in a linear string by using flexible wire. On self-assembly, the string folded spontaneously into two domains: one functioned as a ring oscillator, and the other one as a shift register. This example demonstrates that biomimetic principles of design and self-organization can be applied to generate multifunctional electronic systems of complex, three-dimensional architecture.
The pollen determinant of self-incompatibility in
Brassica campestris
Authors: Takayama Seiji , Shiba Hiroshi , Iwano Megumi , Shimosato Hiroko , Che Fang-Sik , Kai Naoko , Watanabe Masao , Suzuki Go , Hinata Kokichi , Isogai Akira
Published: July 2002

Many flowering plants possess self-incompatibility (SI) systems that prevent inbreeding. In
Brassica
, SI is controlled by a single polymorphic locus, the
S
locus. Two highly polymorphic
S
locus genes,
SLG
(
S
locus glycoprotein) and
SRK
(
S
receptor kinase), have been identified, both of which are expressed predominantly in the stigmatic papillar cell. We have shown recently that SRK is the determinant of the
S
haplotype specificity of the stigma. SRK is thought to serve as a receptor for a pollen ligand, which presumably is encoded by another polymorphic gene at the
S
locus. We previously have identified an
S
locus gene,
SP11
(
S
locus protein 11), of the
S
9
haplotype of
Brassica campestris
and proposed that it potentially encodes the pollen ligand. SP11 is a novel member of the PCP (pollen coat protein) family of proteins, some members of which have been shown to interact with SLG. In this work, we identified the
SP11
gene from three additional
S
haplotypes and further characterized the gene. We found that (
i
)
SP11
showed an
S
haplotype-specific sequence polymorphism; (
ii
)
SP11
was located in the immediate flanking region of the
SRK
gene of the four
S
haplotypes examined; (
iii
)
SP11
was expressed in the tapetum of the anther, a site consistent with sporophytic control of
Brassica
SI; and (
iv
) recombinant SP11 of the
S
9
haplotype applied to papillar cells of
S
9
stigmas, but not of
S
8
stigmas, elicited SI response, resulting in inhibition of hydration of cross-pollen. All these results taken together strongly suggest that SP11 is the pollen
S
determinant in SI.
Genetic control of development of the mushroom bodies, the associative learning centers in the
Drosophila
brain, by the
eyeless, twin of eyeless
, and
dachshund
genes
Authors: Kurusu Mitsuhiko , Nagao Tomoko , Walldorf Uwe , Flister Susanne , Gehring Walter J. , Furukubo-Tokunaga Katsuo
Published: July 2002

Mushroom bodies (MBs) are the centers for olfactory associative learning and elementary cognitive functions in the
Drosophila
brain. By high-resolution neuroanatomy, we show that
eyeless
(
ey
),
twin of eyeless
, and
dachshund (dac
), which are implicated in eye development, also are expressed in the developing MBs. Mutations of
ey
completely disrupted the MB neuropils, and a null mutation of
dac
resulted in marked disruption and aberrant axonal projections. Genetic analyses demonstrated that, whereas
ey
and
dac
synergistically control the structural development of the MBs, the two genes are regulated independently in the course of MB development. These data argue for a distinct combinatorial code of regulatory genes for MBs as compared with eye development and suggest conserved roles of
Pax6
homologs in the genetic programs of the olfactory learning centers of complex brains.
Arabidopsis
cytochrome P450s that catalyze the first step of tryptophan-dependent indole-3-acetic acid biosynthesis
Authors: Hull Anna K. , Vij Rekha , Celenza John L.
Published: July 2002

Plants synthesize numerous secondary metabolites that are used as developmental signals or as defense against pathogens. Tryptophan (Trp)-derived secondary metabolites include camalexin, indole glucosinolates, and indole-3-acetic acid (IAA); however, the steps in their synthesis from Trp or its precursors remain unclear. We have identified two
Arabidopsis
cytochrome P450s (CYP79B2 and CYP79B3) that can convert Trp to indole-3-acetaldoxime (IAOx), a precursor to IAA and indole glucosinolates.
Targeted disruption of the
Kcnq1
gene produces a mouse model of Jervell and Lange– Nielsen Syndrome
Authors: Casimiro Mathew C. , Knollmann Björn C. , Ebert Steven N. , Vary Jay C. , Greene Anne E. , Franz Michael R. , Grinberg Alexander , Huang Sing Ping , Pfeifer Karl
Published: July 2002

KCNQ1
encodes KCNQ1, which belongs to a family
of voltage-dependent K
+
ion channel proteins. KCNQ1
associates with a regulatory subunit, KCNE1, to produce the cardiac
repolarizing current,
I
Ks
. Loss-of-function
mutations in the human
KCNQ1
gene have been linked to
Jervell and Lange–Nielsen Syndrome (JLNS), a disorder characterized by
profound bilateral deafness and a cardiac phenotype. To generate a
mouse model for JLNS, we created a line of transgenic mice that have a
targeted disruption in the
Kcnq1
gene. Behavioral
analysis revealed that the
Kcnq1
−/−
mice
are deaf and exhibit a shaker/waltzer phenotype. Histological
analysis of the inner ear structures of
Kcnq1
−/−
mice revealed gross morphological
anomalies because of the drastic reduction in the volume of endolymph.
ECGs recorded from
Kcnq1
−/−
mice
demonstrated abnormal T- and P-wave morphologies and prolongation of
the QT and JT intervals when measured
in vivo
, but not
in isolated hearts. These changes are indicative of cardiac
repolarization defects that appear to be induced by extracardiac
signals. Together, these data suggest that
Kcnq1
−/−
mice are a potentially valuable
animal model of JLNS.
Pim serine/threonine kinases regulate the stability of Socs-1 protein
Authors: Chen X. Peter , Losman Julie A. , Cowan Simone , Donahue Elizabeth , Fay Scott , Vuong Bao Q. , Nawijn Martijn C. , Capece Danielle , Cohan Victoria L. , Rothman Paul
Published: July 2002

Studies ofSOCS-1-deficient mice have implicated Socs-1 in the suppression of JAK-STAT (Janus tyrosine kinase-signal transducers and activators of transcription) signaling and T cell development. It has been suggested that the levels of Socs-1 protein may be regulated through the proteasome pathway. Here we show that Socs-1 interacts with members of the Pim family of serine/threonine kinases in thymocytes. Coexpression of the Pim kinases with Socs-1 results in phosphorylation and stabilization of the Socs-1 protein. The protein levels of Socs-1 are significantly reduced in thePim-1−/−,Pim-2−/−mice as compared with wild-type mice. Similar toSocs-1−/−mice, thymocytes fromPim-1−/−,Pim-2−/−mice showed prolonged Stat6 phosphorylation upon IL-4 stimulation. These data suggest that the Pim kinases may regulate cytokine-induced JAK-STAT signaling through modulation of Socs-1 protein levels.
Somatosensory feedback modulates the respiratory motor program of crystallized birdsong
Authors: Suthers Roderick A. , Goller Franz , Wild J. Martin
Published: July 2002

Birdsong, like human speech, involves rapid, repetitive, or episodic motor patterns requiring precise coordination between respiratory, vocal organ, and vocal tract muscles. The song units or syllables of most adult songbirds exhibit a high degree of acoustic stereotypy that persists for days or months after the elimination of auditory feedback by deafening. Adult song is assumed to depend on central motor programs operating independently from immediate sensory feedback. Nothing is known, however, about the possible role of mechanoreceptive or other somatosensory feedback in the motor control of birdsong. Even in the case of human speech, the question of “how and when sensory information is used in normal speaking conditions… remains unanswered” and controversial [Smith, A. (1992)Crit. Rev. Oral Biol. Med.3, 233–267]. We report here evidence for somatosensory modulation of ongoing song motor patterns. These patterns include the respiratory muscles that, in both birdsong and speech, provide the power for vocalization. Perturbing respiratory pressure by a brief, irregularly timed injection of air into the cranial thoracic air sac during song elicited a compensatory reduction in the electrical activity of the abdominal expiratory muscles, both in hearing and deafened adult northern cardinals (Cardinalis cardinalis). This muscle response was absent or reduced during quiet respiration, suggesting it is specifically linked to phonation. Our findings indicate that somatosensory feedback to expiratory muscles elicits compensatory adjustments that help stabilize, in real time, the subsyringeal pressure against fluctuations caused by changes in posture or physical activity.
Progressive photoreceptor degeneration, outer segment dysplasia, and rhodopsin mislocalization in mice with targeted disruption of the retinitis pigmentosa-1 (
Rp1
) gene
Authors: Gao Jiangang , Cheon Kyeongmi , Nusinowitz Steven , Liu Qin , Bei Di , Atkins Karen , Azimi Asif , Daiger Stephen P. , Farber Debora B. , Heckenlively John R. , Pierce Eric A. , Sullivan Lori S. , Zuo Jian
Published: July 2002

Retinitis pigmentosa (RP), a common group of human retinopathic diseases, is characterized by late-onset night blindness, loss of peripheral vision, and diminished or absent electroretinogram (ERG) responses. Mutations in the photoreceptor-specific gene
RP1
account for 5–10% of cases of autosomal dominant RP. We generated a mouse model of the RP1 form of RP by targeted disruption of the mouse ortholog (
Rp1
) of human
RP1
. In
Rp1
−/−
mice, the number of rod photoreceptors decreased progressively over a period of 1 year, whereas that of cone photoreceptors did not change for at least 10 months. Light and electron microscopic analysis revealed that outer segments of
Rp1
−/−
rods and cones were morphologically abnormal and became progressively shorter in length. Before photoreceptor cell death, rhodopsin was mislocalized in inner segments and cell bodies of
Rp1
−/−
rods. Rod ERG amplitudes of
Rp1
−/−
mice were significantly smaller than those of
Rp1
+/+
mice over a period of 12 months, whereas those of
Rp1
+/−
mice were intermediate. The decreases in cone ERG amplitudes were slower and less severe than those in rods. These findings demonstrate that Rp1 is required for normal morphogenesis of photoreceptor outer segments and also may play a role in rhodopsin transport to the outer segments. The phenotype of
Rp1
mutant mice resembles the human RP1 disease. Thus, these mice provide a useful model for studies of RP1 function, disease pathology, and therapeutic interventions.
Mapping of contact sites in complex formation between light-activated rhodopsin and transducin by covalent crosslinking: Use of a chemically preactivated reagent
Authors: Itoh Yoshiki , Cai Kewen , Khorana H. Gobind
Published: July 2002

Contact sites in interaction between light-activated rhodopsin and
transducin (T) have been investigated by using a chemically
preactivated crosslinking reagent,
N-
succinimidyl
3-(2-pyridyldithio)propionate. The 3
propionyl-
N
-succinimidyl group in the reagent was
attached by a disulfide exchange reaction to rhodopsin mutants
containing single reactive cysteine groups in the cytoplasmic loops.
Complex formation between the derivatized rhodopsin mutants and T was
carried out by illumination at λ > 495 nm. Subsequent increase in
pH (from 6 to 7.5 or higher) of the complex resulted in crosslinking of
rhodopsin to the T
α
subunit. Crosslinking to
T
α
was demonstrated for the rhodopsin mutants K141C,
S240C, and K248C, and the crosslinked sites in T
α
were
identified for the rhodopsin mutant S240C. The peptides carrying the
crosslinking moiety were isolated from the trypsin-digested peptide
mixture, and their identification was carried out by matrix-assisted
laser desorption ionization–time of flight mass spectrometry. The main
site of crosslinking is within the peptide sequence, Leu-19–Arg-28 at
the N-terminal region of T
α
.
The total
results show that both the N and the C termini of T
α
are
in close vicinity to the third cytoplasmic loop of rhodopsin in the
complex between rhodopsin and T.
A molecular analysis of dietary diversity for three archaic Native Americans
Authors: Poinar Hendrik N. , Kuch Melanie , Sobolik Kristin D. , Barnes Ian , Stankiewicz Artur B. , Kuder Tomasz , Spaulding W. Geofferey , Bryant Vaughn M. , Cooper Alan , Pääbo Svante
Published: July 2002

DNA was extracted from three fecal samples, more than 2,000 years
old, from Hinds Cave, Texas. Amplification of human mtDNA sequences
showed their affiliation with contemporary Native Americans, while
sequences from pronghorn antelope, bighorn sheep, and cottontail rabbit
allowed these animals to be identified as part of the diet of these
individuals. Furthermore, amplification of chloroplast DNA sequences
identified eight different plants as dietary elements. These archaic
humans consumed 2–4 different animal species and 4–8 different plant
species during a short time period. The success rate for retrieval of
DNA from paleofeces is in strong contrast to that from skeletal remains
where the success rate is generally low. Thus, human paleofecal remains
represent a source of ancient DNA that significantly complements and
may in some cases be superior to that from skeletal tissue.
Restoration of fragile histidine triad (
FHIT
) expression induces apoptosis and suppresses tumorigenicity in lung and cervical cancer cell lines
Authors: Roz Luca , Gramegna Marcella , Ishii Hideshi , Croce Carlo M. , Sozzi Gabriella
Published: July 2002

Loss of expression of the Fhit protein is often associated with the development of many human epithelial cancers, including lung and cervical carcinomas. Restoration of Fhit expression in cell lines derived from these tumors has however yielded conflicting results, prompting the need for careful evaluation of the oncosuppressive potential of
FHIT
. In the present study, we have investigated the effect of Fhit reintroduction in seven lung cancer and three cervical cancer cell lines. To achieve efficient gene transfer and high levels of transgene expression, we have used an adenoviral vector to transduce the
FHIT
gene. The induction of apoptosis was evaluated by using the terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling assay and propidium iodide staining. Activation of caspases was detected by using Western blot analysis, and tumorigenic potential of transduced cells in the nude mouse was also assessed. Restoration of Fhit expression induced apoptosis in all Fhit-negative cell lines, with Calu-1, H460, and A549 being the most susceptible among the lung cancer cell lines and SiHa cells among cervical carcinomas. Activation of caspase-8 was always associated with Fhit-mediated apoptosis, and
in vivo
tumorigenicity was either abolished by
FHIT
gene transfer (in H460 and SK-Mes cells) or strongly suppressed (in A549 and SiHa cells). Our data demonstrate oncosuppressive properties and strong proapoptotic activity of the Fhit protein in lung and cervical cancer cell lines and strengthens the hypothesis of its possible use as a therapeutic tool.
Bfa1 can regulate Tem1 function independently of Bub2 in the mitotic exit network of
Saccharomyces cerevisiae
Authors: Ro Hyeon-Su , Song Sukgil , Lee Kyung S.
Published: July 2002

In budding yeast, exit from mitosis is achieved by inactivation of Cdc28/Clb2 activity. Although it is not clear at present how mitotic exit is triggered, a growing body of evidence suggests that the Tem1 GTPase plays a critical role in mediating this pathway and that Bfa1 and Bub2 constitute a two-component GTPase-activating protein to negatively regulate Tem1. Here, we have demonstrated that introduction of
bfa1
Δ suppresses the growth defects associated with the
cdc5–1
mutation significantly better than that of
bub2
Δ, suggesting that Bfa1 may have a previously uncharacterized role in this pathway. Overexpression of
BFA1
efficiently arrested the cell cycle at postanaphase even in the absence of
BUB2
, whereas overexpression of
BUB2
weakly induced mitotic arrest only in the presence of
BFA1
. Coimmunoprecipitation and
in vitro
binding studies indicate that Bfa1 binds strongly to Tem1 independently of Bub2. Provision of GDP+AlF

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, which mimics the GTPase transition state, enhanced the Bub2-Tem1 interaction both
in vitro
and
in vivo
. Interestingly, introduction of
bfa1
Δ, but not
bub2
Δ, greatly increased the interaction between Tem1 and Cdc15, a step that is thought to be critical for activating the mitotic exit network. Our data suggest that, in addition to its role as a putative, two-component GTPase-activating protein with Bub2, Bfa1 also can play a role in the regulation of mitotic exit by directly inhibiting the interaction between Tem1 and Cdc15 even in the absence of Bub2.
Fluorescence polarization of green fluorescence protein
Authors: Inoué Shinya , Shimomura Osamu , Goda Makoto , Shribak Mykhailo , Tran P. T.
Published: July 2002

We report here the striking anisotropy of fluorescence exhibited by crystals of native green fluorescence protein (GFP). The crystals were generated by water dialysis of highly purified GFP obtained from the jellyfish
Aequorea
. We find that the fluorescence becomes six times brighter when the excitation, or emission, beam is polarized parallel (compared with perpendicular) to the crystal long axis. Thus, the major dipoles of the fluorophores must be oriented very nearly parallel to the crystal long axis. Observed in a polarizing microscope between
parallel
polars instead of either a polarizer or analyzer alone, the fluorescence polarization ratio rises to an unexpectedly high value of about 30:1, nearly the product of the fluorescence excitation and emission ratios, suggesting a sensitive method for measuring fluorophore orientations, even of a single fluorophore molecule. We have derived equations that accurately describe the relative fluorescence intensities of crystals oriented in various directions, with the polarizer and analyzer arranged in different configurations. The equations yield relative absorption and fluorescence coefficients for the four transition dipoles involved. Finally, we propose a model in which the elongated crystal is made of GFP molecules that are tilted 60° to align the fluorophores parallel to the crystal long axis. The unit layer in the model may well correspond to the arrangement of functional GFP molecules, to which resonant energy is efficiently transmitted from Ca
2+
-activated aequorin, in the jellyfish photophores.
Role for FGFR2IIIb-mediated signals in controlling pancreatic endocrine progenitor cell proliferation
Authors: Elghazi Lynda , Cras-Méneur Corentin , Czernichow Paul , Scharfmann Raphael
Published: July 2002

Pancreatic development is a classic example of epithelium–mesenchyme interaction. During embryonic life, signals from the mesenchyme control the proliferation of precursor cells within the pancreatic epithelium and their differentiation into endocrine or acinar cells. It has been shown that signals from the mesenchyme activate epithelial cell proliferation but repress development of the pancreatic epithelium into endocrine cells. Here, experiments with specific inhibitors established that mesenchymal effects on epithelial cell development depended on the mitogen-activated protein kinase pathway. Then we demonstrated that these effects of the mesenchyme were mimicked by fibroblast growth factor 7 (FGF7), a specific ligand of FGFR2IIIb, which is a tyrosine kinase receptor of the FGF-receptor family. When pancreatic epithelium expressing FGFR2IIIb was grown with FGF7, epithelial cell growth occurred in a concentration-dependent manner, whereas endocrine tissue development was repressed. The epithelial cells that proliferated in response to FGF7 were endocrine pancreatic precursor cells, as shown by their differentiation en masse into endocrine cells on FGF7 removal. Thus, efficient propagation of pancreatic progenitor cells can be achieved
in vitro
by exposure to FGF7, which does not affect their ability to differentiate en masse into endocrine cells on FGF7 removal.
Naive T cells proliferate strongly in neonatal mice in response to self-peptide/self-MHC complexes
Authors: Le Campion Armelle , Bourgeois Christine , Lambolez Florence , Martin Bruno , Léaument Sandrine , Dautigny Nicole , Tanchot Corinne , Pénit Claude , Lucas Bruno
Published: July 2002

Adult naive T cells, which are at rest in normal conditions, proliferate strongly when transferred to lymphopenic hosts. In neonates, the first mature thymocytes to migrate to the periphery reach a compartment devoid of preexisting T cells. We have extensively analyzed the proliferation rate and phenotype of peripheral T cells from normal C57BL/6 and T cell antigen receptor transgenic mice as a function of age. We show that, like adult naive T cells transferred to lymphopenic mice, neonatal naive T cells proliferate strongly. By using bone-marrow transfer and thymic-graft models, we demonstrate that the proliferation of the first thymic emigrants reaching the periphery requires T cell antigen receptor-self-peptide/self-MHC interactions and is regulated by the size of the peripheral T cell pool.
A Los1p-independent pathway for nuclear export of intronless tRNAs in
Saccharomyces
cerevisiae
Authors: Feng Wenqin , Hopper Anita K.
Published: July 2002

Los1p, the
Saccharomyces cerevisiae
exportin-t homologue, binds tRNA and functions in pre-tRNA splicing and export of mature tRNA from the nucleus to the cytosol. Because
LOS1
is unessential in yeast, other pathways for tRNA nuclear export must exist. We report that Cca1p, which adds nucleotides C, C, and A to the 3′ end of tRNAs, is a multicopy suppressor of the defect in tRNA nuclear export caused by
los1
null mutations. Mes1p, methionyl-tRNA synthetase, also suppresses the defect in nuclear export of tRNA
Met
in
los1
cells. Thus, Cca1p and Mes1p seem to function in a Los1p-independent tRNA nuclear export pathway. Heterokaryon analysis indicates that Cca1p is a nucleus/cytosol-shuttling protein, providing the potential for Cca1p to function as an exporter or an adapter in this tRNA nuclear export pathway. In yeast, most mutations that affect tRNA nuclear export also cause defects in pre-tRNA splicing leading to tight coupling of the splicing and export processes. In contrast, we show that overexpressed Cca1p corrects the nuclear export, but not the pre-tRNA-splicing defects of
los1
∷
Kan

r

cells, thereby uncoupling pre-tRNA splicing and tRNA nuclear export.
Cardiac βARK1 inhibition prolongs survival and augments β blocker therapy in a mouse model of severe heart failure
Authors: Harding Victoria B. , Jones Larry R. , Lefkowitz Robert J. , Koch Walter J. , Rockman Howard A.
Published: July 2002

Chronic human heart failure is characterized by abnormalities in
β-adrenergic receptor (βAR) signaling, including increased levels
of βAR kinase 1 (βARK1), which seems critical to the pathogenesis
of the disease. To determine whether inhibition of βARK1 is
sufficient to rescue a model of severe heart failure, we mated
transgenic mice overexpressing a peptide inhibitor of βARK1
(βARKct) with transgenic mice overexpressing the sarcoplasmic
reticulum Ca
2+
-binding protein, calsequestrin (CSQ). CSQ
mice have a severe cardiomyopathy and markedly shortened survival
(9 ± 1 weeks). In contrast, CSQ/βARKct mice exhibited
a significant increase in mean survival age (15 ± 1 weeks;
P
< 0.0001) and showed less cardiac dilation, and
cardiac function was significantly improved (CSQ vs.
CSQ/βARKct, left ventricular end diastolic dimension
5.60 ± 0.17 mm vs. 4.19 ± 0.09 mm,
P
<
0.005; % fractional shortening, 15 ± 2 vs. 36 ± 2,
P
< 0.005). The enhancement of the survival rate
in CSQ/βARKct mice was substantially potentiated by chronic
treatment with the βAR antagonist metoprolol (CSQ/βARKct
nontreated vs. CSQ/βARKct metoprolol treated, 15 ± 1
weeks vs. 25 ± 2 weeks,
P
< 0.0001). Thus,
overexpression of the βARKct resulted in a marked prolongation in
survival and improved cardiac function in a mouse model of severe
cardiomyopathy that can be potentiated with β-blocker therapy. These
data demonstrate a significant synergy between an established
heart-failure treatment and the strategy of βARK1 inhibition.
A locus for female discrimination behavior causing sexual isolation in
Drosophila
Authors: Doi Motomichi , Matsuda Muneo , Tomaru Masatoshi , Matsubayashi Hiroshi , Oguma Yuzuru
Published: July 2002

The genetic basis of sexual isolation that contributes to
speciation is one of the unsolved questions in evolutionary biology.
Drosophila ananassae
and
Drosophila
pallidosa
are closely related, and postmating isolation has not
developed between them. However, females of both species discriminate
their mating partners, and this discrimination contributes to strong
sexual isolation between them. By using surgical treatments, we
demonstrate that male courtship songs play a dominant role in female
mate discrimination. The absence of the song of
D.
pallidosa
dramatically increased interspecies mating with
D. ananassae
females but reduced intraspecies mating
with
D. pallidosa
females. Furthermore, genetic analysis
and chromosomal introgression by repeated backcrosses to
D.
pallidosa
males identified possible loci that control female
discrimination in each species. These loci were mapped on distinct
positions near the
Delta
locus on the middle of the left
arm of the second chromosome. Because the mate discrimination we
studied is well developed and is the only known mechanism that prevents
gene flow between them, these loci may have played crucial roles in the
evolution of reproductive isolation, and therefore, in the speciation
process between these two species.