bluuebunny/crossref_metadata_2025 huggingface dataset:
On Community Leadership: Stories About Collaboration in Action Research
Authors: Kelly James G. , Azelton L. Sean , Lardon Cecile , Mock Lynne O. , Tandon S. Darius , Thomas Mamie
Published: May 2004

This article provides an account of a 10‐year collaborative documentation of community leadership in an African American community on the South side of Chicago. The stories are oriented to several critical incidents in the life course of the collaboration. They are told from the perspectives of one university professor, four graduate students, and one community leader. Together they provide an account of how this research was shaped by the interactions of the research team with members of the community, how research questions emerged, methodologies were developed, ways of gathering data were tried and tested, and interpretations of data unfolded. Special attention is given to the ways in which the process and products of this research contributed to the community's own process of leadership development. The stories also discuss the various roles participants in this collaboration played both in the academic arena and in the community, and how they experienced gender, race, nationality, and social status.
Beyond the Frontstage: Trust, Access, and the Relational Context in Research with Refugee Communities
Authors: Miller Kenneth E.
Published: May 2004

This paper examines the role of trust and the concept of access as they affect the relational context in which community research, and research with refugee communities in particular, is conducted. Sociologist Irving Goffman's metaphor of frontstage and backstage behavior is used to illustrate the complexity and importance of developing of relations of trust, and thereby gaining “backstage” access, in communities that are generally closed to outsiders. It is argued that gaining authentic (“backstage”) access to refugee communities, as well as other communities that have developed a self‐protective insularity, is essential if we are to gather data that accurately reflect the actual beliefs, feelings, and experiences of community members. The paper then examines the puzzling lack of discussion regarding issues of trust, access, and the relational context in the literature on refugee mental health. Explanations for this apparent inattention are sought in the influence of the prevailing scientific paradigm that guides most research with refugees, and that shapes the values of the field's “gatekeepers,” the editors and reviewers of scholarly journals. Throughout the paper, key points are illustrated with examples drawn from the author's research with refugees from Guatemala, Bosnia, and Afghanistan.
Die Prozesse der Verhaltensänderung im Kontext des Lebensalters am Beispiel des Tabakrauchens
Authors: Ulbricht Sabina , Meyer Christian , Schumann Anja , Rumpf Hans-Jürgen , Hapke Ulfert , John Ulrich
Published: May 2004

Zusammenfassung. Das Beenden des Tabakkonsums ist in jüngeren Altersgruppen seltener als in älteren. Dies lässt vermuten, dass der Verwirklichung der Aufhörabsicht altersabhängig unterschiedliche relevante Strategien zu Grunde liegen. Das Transtheoretische Modell der Verhaltensänderung beinhaltet neben den Stadien der Änderungsbereitschaft das Konstrukt “Prozesse der Verhaltensänderung“. Anhand der zweiten Erhebungswelle einer 1996/97 begonnenen Längsschnittstudie “Transitions in Alcohol Consumption and Smoking“ wurde eine Stichprobe von N = 913, im Alter von 20-67 Jahren (Ausschöpfung: 86,1%) zu Nikotinkonsum, Nikotinabhängigkeit und den zentralen Konstrukten des TTM schriftlich befragt. Der überwiegende Teil der Probanden befand sich in den Stadien “Absichtslosigkeit“ (76.7%) und “Absichtsbildung“ (13.2%). Ältere Raucher in den Stadien “Absichtslosigkeit“ und “Absichtsbildung“ weisen einer stärkere Nutzung kognitiv-affektiver Prozesse auf als jüngere Raucher. Die Nutzung kognitiv-affektiver Prozesse geben Probanden zwischen 36-50 Jahren häufiger an als diejenigen der Gruppe 20-35 Jahre. Raucherberatung sollte berücksichtigen, dass die Anwendung der Prozesse bei älteren Rauchern bereits diskussionsfähig ist, während bei jüngeren Rauchern verstärkt auf die Nutzung der Prozesse orientiert werden sollte.
Konstruktion eines Verfahrens zur Erfassung der Motivation zu Entspannungsübungen
Authors: Ströbl Veronika , Reusch Andrea , Ellgring Heiner
Published: May 2004

Zusammenfassung. Entspannungskurse stellen eine weit verbreitete Maßnahme in der stationären Rehabilitation dar. Die Motivation der Rehabilitanden, Entspannungsübungen zu erlernen und diese langfristig auszuüben, ist allerdings nicht bekannt und es liegen keine Instrumente zu ihrer Erfassung vor. Daher wurde die Motivation zur Verhaltensänderung über die Konstrukte des Transtheoretischen Modells (Stufen der Verhaltensänderung, Selbstwirksamkeitserwartung, Entscheidungsbalance) für das Zielverhalten “Entspannungsübungen“ operationalisiert. Zusammenhänge zwischen den Konstrukten wurden in einer Querschnittstudie an einer Stichprobe von N = 138 Rehabilitanden (50.7% Männer) überprüft. Dabei zeigte sich, dass die Patienten unterschiedliche Motivationslagen aufweisen. Die Skala zur Selbstwirksamkeitserwartung erwies sich erwartungsgemäß als eindimensional mit guter interner Konsistenz. Für die Items zur Entscheidungsbalance konnten zwei Subskalen gebildet werden, die jeweils ausreichende Gütekriterien aufweisen: wahrgenommene Vorteile und wahrgenommene Nachteile. Hinweise für die Gültigkeit der Modellpostulate wurden für die Selbstwirksamkeitserwartung und die wahrgenommenen Vorteile, nicht jedoch für die wahrgenommenen Nachteile der Durchführung von Entspannungsübungen gefunden.
Storm‐induced injection of the Mississippi River plume into the open Gulf of Mexico
Authors: Yuan Jinchun , Miller Richard L. , Powell Rodney T. , Dagg Michael J.
Published: May 2004

The direct impact of the Mississippi River on the open Gulf of Mexico is typically considered to be limited due to the predominantly along‐shore current pattern. Using satellite imagery, we analyzed chl a distributions in the northern Gulf of Mexico before and after the passage of two storms: Hurricane Lili and Tropical Storm Barry. Our analyses indicate that storm‐induced eddies can rapidly inject large volumes of nutrient‐rich Mississippi River water to the open gulf, and lead to phytoplankton blooms. Although these events last only a few weeks, they transport significant amounts of fluvial substances to the ocean. These river‐ocean interactions are especially significant in tropical and subtropical regions because receiving waters are typically permanently stratified and oligotrophic.
Magnetostratigraphy of a late Miocene‐Pliocene loess‐soil sequence in the western Loess Plateau in China
Authors: Hao Qingzhen , Guo Zhengtang
Published: May 2004

Eolian deposits of Pliocene age have never been reported from the western Loess Plateau in China. Here, a 73.7 m eolian sequence is dated using magnetostratigraphic method and micromammalian fossils. The polarity zonation correlates with the geomagnetic polarity timescale (GPTS), from Chron 3Br.1r to Chron 2An.3n, indicating an age from 7.10 to 3.52 Ma BP. The sequence is characterized by clear expression of eighty‐four pairs of loess and soil layers while individual soils are basically indefinable for the eolian deposits of the same age in the eastern Loess Plateau, suggesting that the later has experienced other geological processes. This sequence extends the upper limit of the previously reported Miocene loess‐soil sequences at Qinan into the Pliocene, about 3.52 Ma BP.
Uptake of the HO2 radical by water: Molecular dynamics calculations and their implications for atmospheric modeling
Authors: Morita Akihiro , Kanaya Yugo , Francisco Joseph S.
Published: May 2004

The mass accommodation coefficient α of the HO2 radical in aqueous aerosols remains largely uncertain in atmospheric modeling. Therefore, in the present paper, a molecular dynamics computer simulation was performed to evaluate the HO2 α in liquid water. The calculations yielded an α near unity, which defines a possible upper bound of the uptake coefficient γ. Implications for a large γ in the tropospheric atmosphere are discussed using model calculations for two typical cases: remote marine air and polluted urban air. It is suggested that the concentrations of HO2 and other related species are quite sensitive to γ in the range of 0.2–1, particularly in the case of polluted urban air. In particular, the maximum diurnal HO2 concentration is reduced by 73% in marine air and by 31% in urban air, when γ = 1 is incorporated.
Surface radiation balance in Antarctica as measured with automatic weather stations
Authors: van den Broeke Michiel , Reijmer Carleen , van de Wal Roderik
Published: May 2004

We present 4 years of near‐surface radiation balance observations of four Antarctic automatic weather stations (AWS). The AWS are situated along a traverse line in Dronning Maud Land, connecting the coastal ice shelf and the inland plateau via the katabatic wind zone, covering the three major climate regimes of East Antarctica. Important differences in the radiation balance of the three regions are found. Clouds not only limit atmospheric transmissivity for shortwave radiation but also strongly enhance the albedo for the shortwave radiation that reaches the surface. As a result, the snow surface of the coastal ice shelves absorbs up to 65% less shortwave radiation in high summer than at the high plateau, where cloudy episodes and precipitation events are less frequent. In winter, over the slopes, katabatic winds maintain a continuous turbulent transport of sensible heat toward the surface, which enhances outgoing longwave radiation. As a result, the katabatic wind zone shows the largest longwave and all‐wave radiation loss in winter and over the year. Clear‐sky effective emissivity for incoming longwave radiation shows great spatial variability resulting from differences in vertical temperature and moisture profiles among the various climate zones.
Nonlocal and localized analyses of conditional mean transient flow in bounded, randomly heterogeneous porous media
Authors: Ye Ming , Neuman Shlomo P. , Guadagnini Alberto , Tartakovsky Daniel M.
Published: May 2004

We consider the numerical prediction of transient flow in bounded, randomly heterogeneous porous media driven by random sources, initial heads, and boundary conditions without resorting to Monte Carlo simulation. After applying the Laplace transform to the governing stochastic flow equations, we derive exact nonlocal (integro‐differential) equations for the mean and variance‐covariance of transformed head and flux, conditioned on measured values of log conductivity Y = ln K. Approximating these conditional moment equations recursively to second order in the standard deviation σY of Y, we solve them by finite elements for superimposed mean‐uniform and convergent flows in a two‐dimensional domain. An alternative conditional mean solution is obtained through localization of the exact moment expressions. The nonlocal and localized solutions are obtained using a highly efficient parallel algorithm and inverted numerically back into the time domain. A comparison with Monte Carlo simulations demonstrates that the moment solutions are remarkably accurate for strongly heterogeneous media with σY2 as large as 4. The nonlocal solution is only slightly more accurate than the much simpler localized solution, but the latter does not yield information about predictive uncertainty. The accuracy of each solution improves markedly with conditioning. A preliminary comparison of computational efficiency suggests that both the nonlocal and localized solutions for mean head and its variance require significantly less computer time than is required for Monte Carlo statistics to stabilize when the same direct matrix solver is used for all three (we do not presently know how using iterative solvers would have affected this conclusion). This is true whether the Laplace inversion and Monte Carlo simulations are conducted sequentially or in parallel on multiple processors and regardless of problem size. The underlying exact and recursive moment equations, as well as the proposed computational algorithm, are valid in both two and three dimensions; only the numerical implementation of our algorithm is two‐dimensional.
Model development for integrated assessment of water allocation options
Authors: Letcher R. A. , Jakeman A. J. , Croke B. F. W.
Published: May 2004

Integrated assessment is a discipline that takes a holistic, problem‐oriented approach to scientific assessment. It is increasingly being applied to consider a range of environmental issues, including water resource management problems. This paper considers lessons for integrated assessment arising from a project focused on water allocation options in the Namoi River catchment, Australia. It is seen how the problem focus of this work prescribes the requirements placed on the structure, components and conceptualisation of the integrated assessment model. A brief description of the model illustrates the ways in which these requirements are addressed. Lessons for integrated assessment arising from this work are then described. These relate to the importance of identifying the modeling problem and objectives, balancing disciplinary perspectives, selecting appropriate spatial and temporal scales, and development of trust with stakeholder groups.
Height‐integrated Joule and auroral particle heating in the night side high latitude thermosphere
Authors: Baker J. B. H. , Zhang Y. , Greenwald R. A. , Paxton L. J. , Morrison D.
Published: May 2004

Energy deposited at high latitudes by Joule and auroral particle heating perturbs the chemistry and dynamics of the neutral thermosphere. Height‐integrated heating rates can be calculated by combining Super Dual Auroral Radar Network (SuperDARN) measurements with TIMED spacecraft Global Ultraviolet Imager (GUVI) auroral images. Spatial maps of heating rates are examined during two TIMED orbits and statistical averages are presented for quiet to moderate levels of geomagnetic activity. Joule heating dominates in the evening sector auroral oval, whereas particle heating dominates after midnight. There is also a tendency for Joule heating (particle heating) to dominate in the vicinity of the region‐1 (region‐2) currents. This complementary behavior is associated with suppression of the electric field in regions of bright aurora.
Experimental and modeling study of fluid pressure‐driven fractures in Darley Dale sandstone
Authors: Vinciguerra Sergio , Meredith Philip G. , Hazzard Jim
Published: May 2004

We report measurements of acoustic emissions (AE) generated during formation and growth of pressure driven fractures in cylindrical samples of Darley Dale sandstone that were co‐axially pre‐drilled in order to allow an internal pressure to be applied. A set of 3 to 6 fractures initiate at the wall of the internal bore at a fluid pressure around three times that of the confining pressure, but only 3 propagate to the outer wall of the sample. Time and spatial distributions of acoustic emissions show two distinct bursts of activity, associated with initiation and propagation, respectively. A Particle Flow Code (PFC) model has been used to reproduce the mechanics of fracture initiation and the time and spatial distributions of AE. In both the experiments and the model, we observe a distinct phase of accelerating AE activity preceding fracture formation.
Differential metabolic networks unravel the effects of silent plant phenotypes
Authors: Weckwerth Wolfram , Loureiro Marcelo Ehlers , Wenzel Kathrin , Fiehn Oliver
Published: May 2004

Current efforts aim to functionally characterize each gene in model plants. Frequently, however, no morphological or biochemical phenotype can be ascribed for antisense or knock-out plant genotypes. This is especially the case when gene suppression or knockout is targeted to isoenzymes or gene families. Consequently, pleiotropic effects and gene redundancy are responsible for phenotype resistance. Here, techniques are presented to detect unexpected pleiotropic changes in such instances despite very subtle changes in overall metabolism. The method consists of the relative quantitation of >1,000 compounds by GC/time-of-flight MS, followed by classical statistics and multivariate clustering. Complementary to these tools, metabolic networks are constructed from pair-wise analysis of linear metabolic correlations. The topology of such networks reflects the underlying regulatory pathway structure. A differential analysis of network connectivity was applied for a silent potato plant line suppressed in expression of sucrose synthase isoform II. Metabolic alterations could be assigned to carbohydrate and amino acid metabolism even if no difference in average metabolite levels was found.
Role of metabotropic glutamate receptors in oligodendrocyte excitotoxicity and oxidative stress
Authors: Deng Wenbin , Wang Hong , Rosenberg Paul A. , Volpe Joseph J. , Jensen Frances E.
Published: May 2004

Developing oligodendrocytes (OLs) are highly vulnerable to excitotoxicity and oxidative stress, both of which are important in the pathogenesis of many brain disorders. OL excitotoxicity is mediated by ionotropic glutamate receptors (iGluRs) of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid/kainate type on these cells. Here we report that metabotropic GluRs (mGluRs) are highly expressed in OL precursors but are down-regulated in mature OLs. Activation of group 1 mGluRs attenuates OL excitotoxicity by controlling downstream oxidative stress after iGluR overactivation and also prevents nonexcitotoxic forms of oxidative stress by inhibiting reactive oxygen species accumulation and intracellular glutathione loss. The modulating effect of group 1 mGluRs on hypoxic-ischemic OL injury is not due to iGluR endocytosis that occurs in neurons in response to mGluR activation but requires activation of PKCα after G protein coupling to phospholipase C. Our results reveal a previously undescribed role for mGluRs in limiting OL injury and suggest that targeting group 1 mGluRs may be a useful therapeutic strategy for treating disorders that involve excitotoxic injury and/or oxidative stress to OLs.
Haploinsufficiency of kelch-like protein homolog 10 causes infertility in male mice
Authors: Yan Wei , Ma Lang , Burns Kathleen H. , Matzuk Martin M.
Published: May 2004

We identified a testis-specific gene encoding a protein containing a BTB/POZ domain and six kelch repeats, which we named
k
e
l
ch
h
omo
l
og
10
(KLHL10). KLHL10 displays high evolutionary conservation in mammals, as evidenced by 98.7% amino acid identity between mouse and human KLHL10. KLHL10 is exclusively expressed in the cytoplasm of elongating and elongated spermatids (steps 9-16). We generated a
Klhl10
null allele in 129S6/SvEv mouse embryonic stem cells, and obtained 47 chimeras from six independent embryonic stem cell lines. Whereas low-percentage male chimeras only produce C57BL/6J offspring, high-percentage chimeric and heterozygous males were completely infertile because of disrupted spermiogenesis characterized by asynchronous spermatid maturation, degeneration of late spermatids, sloughing of postmeiotic germ cells from the seminiferous epithelium, and marked reduction in the numbers of late spermatids. Our data demonstrate that, like protamine-1 and -2, both alleles of
Klhl10
are required for male fertility and that haploinsufficiency caused by a mutation in one allele of
Klhl10
prevents genetic transmission of both mutant and WT alleles.
TorsinA in the nuclear envelope
Authors: Naismith Teresa V. , Heuser John E. , Breakefield Xandra O. , Hanson Phyllis I.
Published: May 2004

Early-onset torsion dystonia, a CNS-based movement disorder, is usually associated with a single amino acid deletion (ΔE302/303) in the protein torsinA. TorsinA is an AAA+ ATPase in the endoplasmic reticulum, but what it does is unknown. Here, we use torsinA mutants with defects in ATP hydrolysis (E171Q, ATP-bound) and ATP binding (K108A, ATP-free) to probe torsinA's normal cellular function. Surprisingly, ATP-bound torsinA is recruited to the nuclear envelope (NE) of transfected cells, where it alters connections between inner and outer nuclear membranes. In contrast, ATP-free torsinA is diffusely distributed throughout the endoplasmic reticulum and has no effect on the NE. Among AAA+ ATPases, affinity for substrates is high in the ATP-bound and low in the ATP-free state, leading us to propose that component(s) of the NE may be substrates for torsinA. We also find that the disease-promoting ΔE302/303 mutant is in the NE, and that this relocalization, as well as the mutant's previously described ability to induce membranous inclusions, is eliminated by the K108A ATP-binding mutation. These results suggest that changes in interactions involving torsinA in the NE could be important for the pathogenesis of dystonia and point to torsinA and related proteins as a class of ATPases that may operate in the NE.
Positioning of the α-subunit isoforms confers a functional signature to γ-aminobutyric acid type A receptors
Authors: Minier Frédéric , Sigel Erwin
Published: May 2004

Fast synaptic inhibitory transmission in the CNS is mediated by γ-aminobutyric acid type A (GABAA) receptors. They belong to the ligand-gated ion channel receptor superfamily, and are constituted of five subunits surrounding a chloride channel. Their clinical interest is highlighted by the number of therapeutic drugs that act on them. It is well established that the subunit composition of a receptor subtype determines its pharmacological properties. We have investigated positional effects of two different α-subunit isoforms, α1and α6, in a single pentamer. For this purpose, we used concatenated subunit receptors in which subunit arrangement is predefined. The resulting receptors were expressed inXenopusoocytes and analyzed by using the two-electrode voltage-clamp technique. Thus, we have characterized γ2β2α1β2α1, γ2β2α6β2α6, γ2β2α1β2α6, and γ2β2α6β2α1GABAAreceptors. We investigated their response to the agonist GABA, to the partial agonist piperidine-4-sulfonic acid, to the noncompetitive inhibitor furosemide and to the positive allosteric modulator diazepam. Each receptor isoform is characterized by a specific set of properties. In this case, subunit positioning provides a functional signature to the receptor. We furthermore show that a single α6-subunit is sufficient to confer high furosemide sensitivity, and that the diazepam efficacy is determined exclusively by the α-subunit neighboring the γ2-subunit. By using this diagnostic tool, it should become possible to determine the subunit arrangement of receptors expressedin vivothat contain α1- and α6-subunits. This method may also be applied to the study of other ion channels.
Diffusion-based method for producing density-equalizing maps
Authors: Gastner Michael T. , Newman M. E. J.
Published: May 2004

Map makers have for many years searched for a way to construct cartograms, maps in which the sizes of geographic regions such as countries or provinces appear in proportion to their population or some other analogous property. Such maps are invaluable for the representation of census results, election returns, disease incidence, and many other kinds of human data. Unfortunately, to scale regions and still have them fit together, one is normally forced to distort the regions' shapes, potentially resulting in maps that are difficult to read. Many methods for making cartograms have been proposed, some of them are extremely complex, but all suffer either from this lack of readability or from other pathologies, like overlapping regions or strong dependence on the choice of coordinate axes. Here, we present a technique based on ideas borrowed from elementary physics that suffers none of these drawbacks. Our method is conceptually simple and produces useful, elegant, and easily readable maps. We illustrate the method with applications to the results of the 2000 U.S. presidential election, lung cancer cases in the State of New York, and the geographical distribution of stories appearing in the news.
The effect of interspecific oocytes on demethylation of sperm DNA
Authors: Beaujean Nathalie , Taylor Jane E. , McGarry Michelle , Gardner John O. , Wilmut Ian , Loi Pasqualino , Ptak Grazyna , Galli Cesare , Lazzari Giovanna , Bird Adrian , Young Lorraine E. , Meehan Richard R.
Published: May 2004

In contrast to mice, in sheep no genome-wide demethylation of the paternal genome occurs within the first postfertilization cell cycle. This difference could be due either to an absence of a sheep demethylase activity that is present in mouse ooplasm or to an increased protection of methylated cytosine residues in sheep sperm. Here, we use interspecies intracytoplasmic sperm injection to demonstrate that sheep sperm DNA can be demethylated in mouse oocytes. Surprisingly, mouse sperm can also be demethylated to a limited extent in sheep oocytes. Our results suggest that the murine demethylation process is facilitated either by a sperm-derived factor or by male pronuclear chromatin composition.
Arabidopsis thaliana
DNA gyrase is targeted to chloroplasts and mitochondria
Authors: Wall Melisa K. , Mitchenall Lesley A. , Maxwell Anthony
Published: May 2004

DNA gyrase is the bacterial DNA topoisomerase (topo) that supercoils DNA by using the free energy of ATP hydrolysis. The enzyme, an A
2
B
2
tetramer encoded by the
gyrA
and
gyrB
genes, catalyses topological changes in DNA during replication and transcription, and is the only topo that is able to introduce negative supercoils. Gyrase is essential in bacteria and apparently absent from eukaryotes and is, consequently, an important target for antibacterial agents (e.g., quinolones and coumarins). We have identified four putative gyrase genes in the model plant
Arabidopsis thaliana
; one
gyrA
and three
gyrB
homologues. DNA gyrase protein A (GyrA) has a dual translational initiation site targeting the mature protein to both chloroplasts and mitochondria, and there are individual targeting sequences for two of the DNA gyrase protein B (GyrB) homologues. N-terminal fusions of the organellar targeting sequences to GFPs support the hypothesis that one enzyme is targeted to the chloroplast and another to the mitochondrion, which correlates with supercoiling activity in isolated organelles. Treatment of seedlings and cultured cells with gyrase-specific drugs leads to growth inhibition. Knockout of
A. thaliana gyrA
is embryo-lethal whereas knockouts in the
gyrB
genes lead to seedling-lethal phenotypes or severely stunted growth and development. The
A. thaliana
genes have been cloned in
Escherichia coli
and found to complement gyrase temperature-sensitive strains. This report confirms the existence of DNA gyrase in eukaryotes and has important implications for drug targeting, organelle replication, and the evolution of topos in plants.
Frequent fusion and fission of plant mitochondria with unequal nucleoid distribution
Authors: Arimura Shin-ichi , Yamamoto Junko , Aida Gen Paul , Nakazono Mikio , Tsutsumi Nobuhiro
Published: May 2004

The balance between mitochondrial fusion and fission influences the reticular shape of mitochondria in yeasts. Little is known about whether mitochondria fusion occurs in plants. Plant mitochondria are usually more numerous and more grain-shaped than animal mitochondria.
blast
searches of the nuclear and mitochondrial genome sequences of
Arabidopsis thaliana
did not find any obvious homologue of mitochondrial fusion genes found in animals and yeasts. To determine whether mitochondrial fusion actually occurs in plants, we labeled mitochondria in onion epidermal cells with a mitochondria-targeted, photoconvertible fluorescent protein Kaede and then altered the fluorescence of some of the mitochondria within a cell from green to red. Frequent and transient fusion of red and green mitochondria was demonstrated by the appearance of yellow mitochondria that subsequently redivided. We also show that mitochondrial fission occasionally occurs without an equal distribution of the nucleoid (DNA–protein complex in mitochondria), resulting in the coexistence of mitochondria containing various amounts of DNA within a single cell. The heterogeneity of DNA contents in mitochondria may be overcome by the frequent and transient fusion of mitochondria.
Functional interactions of RNA-capping enzyme with factors that positively and negatively regulate promoter escape by RNA polymerase II
Authors: Mandal Subhrangsu S. , Chu Chun , Wada Tadashi , Handa Hiroshi , Shatkin Aaron J. , Reinberg Danny
Published: May 2004

Capping of the 5′ ends of nascent RNA polymerase II transcripts is the first pre-mRNA processing event in all eukaryotic cells. Capping enzyme (CE) is recruited to transcription complexes soon after initiation by the phosphorylation of Ser-5 of the carboxyl-terminal domain of the largest subunit of RNA polymerase II. Here, we analyze the role of CE in promoter clearance and its functional interactions with different factors that are involved in promoter clearance. FCP1-mediated dephosphorylation of the carboxyl-terminal domain results in a drastic decrease in cotranscriptional capping efficiency but is reversed by the presence of DRB sensitivity-inducing factor (DSIF). These results suggest involvement of DSIF in CE recruitment. Importantly, CE relieves transcriptional repression by the negative elongation factor, indicating a critical role of CE in the elongation checkpoint control mechanism during promoter clearance. This functional interaction between CE and the negative elongation factor documents a dynamic role of CE in promoter clearance beyond its catalytic activities.
Cdx2
is essential for axial elongation in mouse development
Authors: Chawengsaksophak Kallayanee , de Graaff Wim , Rossant Janet , Deschamps Jacqueline , Beck Felix
Published: May 2004

Inactivation of
Cdx2
leads to preimplantation embryonic lethality. Rescue of the implantation defect by tetraploid fusion established that
Cdx2
is necessary for trophoblastic development, vasculogenesis in the yolk sac mesoderm, allantoic growth, and chorioallantoic fusion. “Rescued”
Cdx2
mutants die at late gastrulation stages because of failure of placental development.
Cdx2
is also needed for the completion of the normal process of gastrulation and tail bud elongation. Presegmental paraxial mesoderm is severely restricted in amount and somites posterior to somite 5 are abnormal. The
Cdx2
mutation, like mutations impairing Wnt and Fgf signaling, causes posterior truncations and disturbs axial patterning of the embryonic structures, indicated by changes in the
Hox
expression domains. The gene appears to be important in the integration of the pathways controlling embryonic axial elongation, and anterior-posterior patterning.
Endogenous NO regulates superoxide production at low oxygen concentrations by modifying the redox state of cytochrome
c
oxidase
Authors: Palacios-Callender Miriam , Quintero Marisol , Hollis Veronica S. , Springett Roger J. , Moncada Salvador
Published: May 2004

We have investigated in whole cells whether, at low oxygen concentrations ([O
2
]), endogenous nitric oxide (NO) modulates the redox state of the mitochondrial electron transport chain (ETC), and whether such an action has any signaling consequences. Using a polarographic-and-spectroscopic-coupled system, we monitored redox changes in the ETC cytochromes
b
H
,
cc
1
, and
aa
3
during cellular respiration. The rate of O
2
consumption (VO
2
) remained constant until [O
2
] fell below 15 μM, whereas the onset of reduction of cytochromes
aa
3
, part of the terminal ETC enzyme cytochrome
c
oxidase, occurred at ≈50 μM O
2
. Incubation of the cells with an inhibitor of NO synthase lowered significantly (
P
< 0.05) the [O
2
] at which reduction of the cytochromes occurred. We also measured intracellular superoxide (

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) production at different [O
2
] and found there was no increase in

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generation in control cells, or those treated with the NO synthase inhibitor, when incubated at 21% O
2
. However, after 30-min exposure of control cells to 3% O
2
, an increase in

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generation was observed, accompanied by translocation to the nucleus of the transcription factor NF-κB. Both of these responses were diminished by NO synthase inhibition. Our results suggest that endogenous NO, by enhancing the reduction of ETC cytochromes, contributes to a mechanism by which cells maintain their VO
2
at low [O
2
]. This, in turn, favors the release of

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, which initiates the transcriptional activation of NF-κB as an early signaling stress response.
Plasticity and tuning by visual feedback of the stability of a neural integrator
Authors: Major Guy , Baker Robert , Aksay Emre , Mensh Brett , Seung H. Sebastian , Tank David W.
Published: May 2004

Persistent neural firing is of fundamental importance to working memory and other brain functions because it allows information to be held “online” following an input and to be integrated over time. Many models of persistent activity rely on some kind of positive feedback internal to the neural circuit concerned; however, too much feedback causes runaway firing (instability), and too little results in loss of persistence (leak). This parameter sensitivity leads to the hypothesis that the brain uses an error signal (external feedback) to tune the stability of persistent firing by adjusting the amount of internal feedback. We test this hypothesis by manipulating external visual feedback, a putative sensory error signal, in a model system for persistent firing, the goldfish oculomotor neural integrator. Over tens of minutes to hours, electronically controlled visual feedback consistent with a leaky or unstable integrator can drive the integrator progressively more unstable or leaky, respectively. Eye fixation time constants can be reduced >100-fold to <1 s. Normal visual feedback gradually retunes the integrator back to stability. Changes in the phase of the sinusoidal vestibulo-ocular response are consistent with integrator detuning, as are changes in ocular drift following eye position shifts compensating for brief passive head movements during fixations. Corresponding changes in persistent firing of integrator neurons are presented in the accompanying article. The presence, strength, and reversibility of the plasticity demonstrate that, in this system, external visual feedback plays a vital role in gradually tuning the stability of the neural integrator.
Plasticity and tuning of the time course of analog persistent firing in a neural integrator
Authors: Major Guy , Baker Robert , Aksay Emre , Seung H. Sebastian , Tank David W.
Published: May 2004

In a companion paper, we reported that the goldfish oculomotor neural integrator could be trained to instability or leak by rotating the visual surround with a velocity proportional to +/- horizontal eye position, respectively. Here we analyze changes in the firing rate behavior of neurons in area I in the caudal brainstem, a central component of the oculomotor neural integrator. Persistent firing could be detuned to instability and leak, respectively, along with fixation behavior. Prolonged training could reduce the time constant of persistent firing of some cells by more than an order of magnitude, to <1 s. Normal visual feedback gradually retuned persistent firing of integrator neurons toward stability, along with fixation behavior. In animals with unstable fixations, approximately half of the eye position-related cells had upward or unstable firing rate drift. In animals with leaky fixations, two-thirds of the eye position-related cells showed leaky firing drift. The remaining eye position-related cells, generally those with lower eye position thresholds, showed a more complex pattern of history-dependent/predictive firing rate drift in relation to eye drift. These complex drift cells often showed a drop in maximum persistent firing rate after training to leak. Despite this diversity, firing drift and the degree of instability or leak in firing rates were broadly correlated with fixation performance. The presence, strength, and reversibility of this plasticity demonstrate that, in this system, visual feedback plays a vital role in gradually tuning the time course of persistent neural firing.
Digitoxin mimics gene therapy with CFTR and suppresses hypersecretion of IL-8 from cystic fibrosis lung epithelial cells
Authors: Srivastava Meera , Eidelman Ofer , Zhang Jian , Paweletz Cloud , Caohuy Hung , Yang QingFeng , Jacobson Kenneth A. , Heldman Eliahu , Huang Wei , Jozwik Catherine , Pollard Bette S. , Pollard Harvey B.
Published: May 2004

Cystic fibrosis (CF) is a fatal, autosomal, recessive genetic disease that is characterized by profound lung inflammation. The inflammatory process is believed to be caused by massive overproduction of the proinflammatory protein IL-8, and the high levels of IL-8 in the CF lung are therefore believed to be the central mechanism behind CF lung pathophysiology. We show here that digitoxin, at sub nM concentrations, can suppress hypersecretion of IL-8 from cultured CF lung epithelial cells. Certain other cardiac glycosides are also active but with much less potency. The specific mechanism of digitoxin action is to block phosphorylation of the inhibitor of NF-κB (IκBα). IκBα phosphorylation is a required step in the activation of the NF-κB signaling pathway and the subsequent expression of IL-8. Digitoxin also has effects on global gene expression in CF cells. Of the informative genes expressed by the CF epithelial cell line IB-3, 58 are significantly (P< 0.05) affected by gene therapy with wild-type (CFTR CF transmembrane conductance regulator). Of these 58 genes, 36 (62%) are similarly affected by digitoxin and related active analogues. We interpret this result to suggest that digitoxin can also partially mimic the genomic consequences of gene therapy with CF transmembrane conductance regulator. We therefore suggest that digitoxin, with its lengthy history of human use, deserves consideration as a candidate drug for suppressing IL-8-dependent lung inflammation in CF.
Amplified fluorescence sensing of protease activity with conjugated polyelectrolytes
Authors: Pinto Mauricio R. , Schanze Kirk S.
Published: May 2004

Fluorescent conjugated polyelectrolytes with pendant ionic sulfonate and carboxylate groups are used to sense protease activity. Inclusion of the fluorescent conjugated polyelectrolyte into the assay scheme leads to amplification of the sensory response. The sensing mechanism relies on an electrostatic interaction between the conjugated polyelectrolyte and a peptide substrate that is labeled with a fluorescence quencher. Enzyme activity and hydrolysis kinetics are measured in real time by using fluorescence spectroscopy. Two approaches are presented. In the first approach, a fluorescence turn-on sensor was developed that is based on the use ofp-nitroanilide-labeled peptide substrates. In this system enzyme-catalyzed peptide hydrolysis is signaled by an increase in the fluorescence from the conjugated polyelectrolyte. The turn-on system was used to sense peptidase and thrombin activity when the concentrations of the enzyme and substrate are in the nanomolar regime. Kinetic parameters were recovered from real-time assays. In the second approach, a fluorescence turn-off sensor was developed that relies on a peptide-derivatized rhodamine substrate. In the turn-off system enzyme-catalyzed peptide hydrolysis is signaled by a decrease in the fluorescence intensity of the conjugated polyelectrolyte.
Constitutive association of the proapoptotic protein Bim with Bcl-2-related proteins on mitochondria in T cells
Authors: Zhu Yanan , Swanson Bradley J. , Wang Michael , Hildeman David A. , Schaefer Brian C. , Liu Xinqi , Suzuki Hiroyuki , Mihara Katsuyoshi , Kappler John , Marrack Philippa
Published: May 2004

Apoptosis in activated T cellsin vivorequires the proapoptotic Bcl-2 family member Bim. We show here that, despite its ability to bind LC8, a component of the microtubule dynein motor complex, most of the Bim in both healthy and apoptotic T cells is associated with mitochondria, not microtubules. In healthy resting T cells Bim is bound to the antiapoptotic proteins Bcl-2 and Bcl-xL. In activated T cells, levels of Bcl-2 fall, and Bim is associated more with Bcl-xLand less with Bcl-2. Our results indicate that, in T cells, Bim function is regulated by interaction with Bcl-2 family members on mitochondria rather than by sequestration to the microtubules.
Brain renin-angiotensin system blockade by systemically active aminopeptidase A inhibitors: A potential treatment of salt-dependent hypertension
Authors: Fournie-Zaluski Marie-Claude , Fassot Celine , Valentin Bruno , Djordjijevic Dragan , Reaux-Le Goazigo Annabelle , Corvol Pierre , Roques Bernard P. , Llorens-Cortes Catherine
Published: May 2004

The hyperactivity of the brain renin-angiotensin system (RAS) has been implicated in the development and maintenance of hypertension in several types of experimental and genetic hypertension animal models. We previously reported that in the murine brain, aminopeptidase A (APA) is involved in the conversion of angiotensin II (AngII) to AngIII and that AngIII is one of the main effector peptides of the brain RAS in the control of vasopressin release. Here we report that brain AngIII exerts a tonic stimulatory effect on blood pressure in a model of salt-dependent hypertension, the DOCA-salt rat, characterized by a depressed systemic but a hyperactive brain RAS. Similar high blood pressure accompanied by a low systemic renin state was described in some patients, especially in hypertensive African Americans who are resistant to treatment by blockers of the systemic RAS. We developed RB150, a prodrug of the specific and selective APA inhibitor, EC33. RB150 given i.v. is able to cross the blood–brain barrier, to inhibit brain APA, and to block the formation of central AngIII. A single dose of systemic RB150 (15 mg/kg, i.v.) in conscious DOCA-salt rats inhibited brain APA activity and markedly reduced blood pressure for up to 24 h. These results demonstrate the crucial role of brain APA as a candidate target for the treatment of hypertension and suggest that RB150, a potent systemically active APA inhibitor, could be the prototype of a new class of antihypertensive agents for the treatment of certain forms of hypertension.
Reversing introduced species effects: Experimental removal of introduced fish leads to rapid recovery of a declining frog
Authors: Vredenburg Vance T.
Published: May 2004

Amphibian population declines and extinctions are occurring even in the world's least impacted areas. The introduction and spread of nonnative predators is one of many proposed causes of amphibian declines. Correlational studies have shown a negative relationship between introduced fishes and declining amphibians, but little direct experimental evidence is available. This study experimentally manipulated the presence and absence of widely introduced salmonids rainbow trout (
Oncorhynchus mykiss
) and brook trout (
Salvelinus fontinalis
) to test the hypothesis that their introduction has contributed to the decline of the mountain yellow-legged frog (
Rana muscosa
). From 1996 to 2003, the introduced trout were removed from 5 lakes in a remote protected area of the Sierra Nevada, and 16 nearby lakes were used as controls, 8 with introduced trout and 8 without. To determine the vulnerable life stage, rainbow trout were placed in cages in three lakes containing amphibians. Removal of introduced trout resulted in rapid recovery of frog populations, and, in the caging experiment, tadpoles were found to be vulnerable to trout predation. Together, these experiments illustrate that introduced trout are effective predators on
R. muscosa
tadpoles and suggest (
i
) that the introduction of trout is the most likely mechanism responsible for the decline of this mountain frog and (
ii
) that these negative effects can be reversed.
Fluorescent-conjugated polymer superquenching facilitates highly sensitive detection of proteases
Authors: Kumaraswamy Sriram , Bergstedt Troy , Shi Xiaobo , Rininsland Frauke , Kushon Stuart , Xia Wensheng , Ley Kevin , Achyuthan Komandoor , McBranch Duncan , Whitten David
Published: May 2004

Sensor formats have been developed for detecting the activity of proteolytic enzymes based on fluorescent conjugated polymer superquenching. These sensors employ a reactive peptide sequence within a tether linking a quencher to a biotin. The peptide binds to sensors containing colocated biotin-binding protein and fluorescent polymer by means of biotin–biotin binding protein interactions, resulting in a strong quenching of polymer fluorescence. Enzyme-mediated cleavage of the peptide results in a reversal of the fluorescence quenching. These assays for protease activity are simple, sensitive, fast, and have the specificity required for screening chemical libraries for novel protease inhibitors in a high-throughput screening assay environment. These assays have been demonstrated for enterokinase, caspase-3/7, and β-secretase.
NO stimulation of ATP-sensitive potassium channels: Involvement of Ras/mitogen-activated protein kinase pathway and contribution to neuroprotection
Authors: Lin Yu-Fung , Raab-Graham Kimberly , Jan Yuh Nung , Jan Lily Yeh
Published: May 2004

ATP-sensitive potassium (K
ATP
) channels regulate insulin release, vascular tone, and neuronal excitability. Whether these channels are modulated by NO, a membrane-permeant messenger in various physiological and pathological processes, is not known. The possibility of NO signaling via K
ATP
channel modulation is of interest because both NO and K
ATP
have been implicated in physiological functions such as vasodilation and neuroprotection. In this report, we demonstrate a mechanism that leads to K
ATP
activation via NO/Ras/mitogen-activated protein kinase pathway. By monitoring K
ATP
single-channel activities from human embryonic kidney 293 cell-attached patches expressing sulfonylurea receptor 2B and Kir6.2, we found K
ATP
stimulation by NO donor Noc-18, a specific NO effect abolished by NO scavenger 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO) but not guanylyl cyclase inhibitor 1
H
-[1,2,4]oxadiazolo[4,3-
a
]quinoxalin-1-one (ODQ). NO stimulation of K
ATP
is indirect and requires Ras and mitogen-activated protein kinase kinase activities. Blockade of Ras activation by pharmacological means or by coexpressing either a dominant-negative or an S-nitrosylation-site mutant Ras protein significantly abrogates the effects of NO. Inhibition of mitogen-activated protein kinase kinase abolishes the NO activation of K
ATP
but suppression of phosphatidylinositol 3-kinase does not. The NO precursor
l
-Arg also stimulates K
ATP
via endogenous NO synthase and the Ras signaling pathway. In addition, in rat hippocampal neurons, the protective effect of ischemic preconditioning induced by oxygen-glucose deprivation requires K
ATP
and NO synthase activity during preconditioning. Thus, neuroprotection caused by NO released during the short episode of sublethal ischemia may be mediated partly by K
ATP
stimulation.