bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of the
Saccharomyces cerevisiae ERG27
gene encoding the 3-keto reductase involved in C-4 sterol demethylation
Authors: Gachotte D. , Sen S. E. , Eckstein J. , Barbuch R. , Krieger M. , Ray B. D. , Bard M.
Published: July 2002

The last unidentified gene encoding an enzyme involved in ergosterol biosynthesis in
Saccharomyces cerevisiae
has been cloned. This gene, designated
ERG27
, encodes the 3-keto sterol reductase, which, in concert with the C-4 sterol methyloxidase (
ERG25
) and the C-3 sterol dehydrogenase (
ERG26
), catalyzes the sequential removal of the two methyl groups at the sterol C-4 position. We developed a strategy to isolate a mutant deficient in converting 3-keto to 3-hydroxy-sterols. An ergosterol auxotroph unable to synthesize sterol or grow without sterol supplementation was mutagenized. Colonies were then selected that were nystatin-resistant in the presence of 3-ketoergostadiene and cholesterol. A new ergosterol auxotroph unable to grow on 3-ketosterols without the addition of cholesterol was isolated. The gene (YLR100w) was identified by complementation. Segregants containing the YLR100w disruption failed to grow on various types of 3-keto sterol substrates. Surprisingly, when
erg27
was grown on cholesterol- or ergosterol-supplemented media, the endogenous compounds that accumulated were noncyclic sterol intermediates (squalene, squalene epoxide, and squalene dioxide), and there was little or no accumulation of lanosterol or 3-ketosterols. Feeding experiments in which
erg27
strains were supplemented with lanosterol (an upstream intermediate of the C-4 demethylation process) and cholesterol (an end-product sterol) demonstrated accumulation of four types of 3-keto sterols identified by GC/MS and chromatographic properties: 4-methyl-zymosterone, zymosterone, 4-methyl-fecosterone, and ergosta-7,24 (28)-dien-3-one. In addition, a fifth intermediate was isolated and identified by
1
H NMR as a 4-methyl-24,25-epoxy-cholesta-7-en-3-one. Implications of these results are discussed.
Diversity and phylogeny of gephyrin: Tissue-specific splice variants, gene structure, and sequence similarities to molybdenum cofactor-synthesizing and cytoskeleton-associated proteins
Authors: Ramming Markus , Kins Stefan , Werner Nikos , Hermann Achim , Betz Heinrich , Kirsch Joachim
Published: July 2002

Gephyrin is essential for both the postsynaptic localization of inhibitory neurotransmitter receptors in the central nervous system and the biosynthesis of the molybdenum cofactor (Moco) in different peripheral organs. Several alternatively spliced gephyrin transcripts have been identified in rat brain that differ in their 5′ coding regions. Here, we describe gephyrin splice variants that are differentially expressed in non-neuronal tissues and different regions of the adult mouse brain. Analysis of the murine gephyrin gene indicates a highly mosaic organization, with eight of its 29 exons corresponding to the alternatively spliced regions identified by cDNA sequencing. The N- and C-terminal domains of gephyrin encoded by exons 3–7 and 16–29, respectively, display sequence similarities to bacterial, invertebrate, and plant proteins involved in Moco biosynthesis, whereas the central exons 8, 13, and 14 encode motifs that may mediate oligomerization and tubulin binding. Our data are consistent with gephyrin having evolved from a Moco biosynthetic protein by insertion of protein interaction sequences.
Deciphering the folding kinetics of transmembrane helical proteins
Authors: Orlandini Enzo , Seno Flavio , Banavar Jayanth R. , Laio Alessandro , Maritan Amos
Published: July 2002

Nearly a quarter of genomic sequences and almost half of all
receptors that are likely to be targets for drug design are integral
membrane proteins. Understanding the detailed mechanisms of the folding
of membrane proteins is a largely unsolved, key problem in structural
biology. Here, we introduce a general model and use computer
simulations to study the equilibrium properties and the folding
kinetics of a
C
α
-based two-helix bundle
fragment (comprised of 66 aa) of bacteriorhodopsin.
Various intermediates are identified and their free energy are
calculated together with the free energy barrier between them. In 40%
of folding trajectories, the folding rate is considerably increased by
the presence of nonobligatory intermediates acting as traps. In all
cases, a substantial portion of the helices is rapidly formed. This
initial stage is followed by a long period of consolidation of the
helices accompanied by their correct packing within the membrane. Our
results provide the framework for understanding the variety of folding
pathways of helical transmembrane proteins.
Control of cocaine-seeking behavior by drug-associated stimuli in rats: Effects on recovery of extinguished operant-responding and extracellular dopamine levels in amygdala and nucleus accumbens
Authors: Weiss Friedbert , Maldonado-Vlaar Carmen S. , Parsons Loren H. , Kerr Tony M. , Smith Diana L. , Ben-Shahar Osnat
Published: July 2002

The conditioning of the pharmacological actions of cocaine with environmental stimuli is thought to be a critical factor in the long-term addictive potential of this drug. Cocaine-related stimuli may increase the likelihood of relapse by evoking drug craving, and brain-imaging studies have identified the amygdala and nucleus accumbens (NAcc) as putative neuroanatomical substrates for these effects of cocaine cues. To study the significance of environmental stimuli in the recovery of extinguished cocaine-seeking behavior, male Wistar rats were trained to associate discriminative stimuli (SΔs) with response-contingent availability of intravenous cocaine vs. saline. The rats then were subjected to repeated extinction sessions during which cocaine, saline, and the respective SΔs were withheld until the animals reached an extinction criterion of ≤4 responses over three consecutive sessions. Subsequent re-exposure to the cocaine SΔ, but not the nonreward SΔ, produced strong recovery of responding at the previously active lever in the absence of any further drug availability. The efficacy and behavioral selectivity of the cocaine SΔ remained unaltered throughout an 8-day test period. Exposure to the cocaine SΔ significantly increased dopamine efflux in the NAcc and amygdala as measured by intracranial microdialysis in a separate group of rats. Dopamine levels remained unaltered in the presence of the nonreward SΔ. The results demonstrate that cocaine-predictive stimuli elicit robust and persistent cocaine-seeking behavior, and that this effect may involve activation of dopamine transmission in the NAcc and amygdala.
Suppression of HIV replication in the resting CD4+T cell reservoir by autologous CD8+T cells: Implications for the development of therapeutic strategies
Authors: Chun Tae-Wook , Justement J. Shawn , Moir Susan , Hallahan Claire W. , Ehler Linda A. , Liu Shuying , McLaughlin Mary , Dybul Mark , Mican JoAnn M. , Fauci Anthony S.
Published: July 2002

CD8+T cell-mediated antiviral activity against HIV has been described consistently in infected individuals; however, the role of this activity in controlling replication of HIV in the latently infected, resting CD4+T cell reservoir is unclear. By using anex vivosystem, we show that replication of HIV in this viral reservoir is effectively suppressed in coculture by autologous CD8+T cells in long-term nonprogressors (LTNPs) and in patients whose viremia was controlled by highly active antiretroviral therapy (HAART), but not in therapy-naive patients who had substantial levels of plasma viremia. This antiviral activity was largely independent of cytotoxic CD8+T lymphocytes (CTL). When the role of soluble CD8+T cell-derived factors was examined, we found that CC-chemokines played a major role in inhibition of viral replication in the latent viral reservoir in some LTNPs and patients receiving HAART, but not in chronically infected patients who were not receiving antiretroviral therapy. Potent antiviral activity, independent of CC-chemokines, was found mainly in patients in whom HAART was initiated shortly after the acute phase of HIV infection. These results indicate that CD8+T cells provide potent suppressive activity against HIV replication in the latent viral reservoir via direct cellular contact in patients who are naturally LTNPs or in those who are treated with HAART. Furthermore, the profound antiviral activity exerted by non-CC-chemokine soluble factors in infected patients who began HAART early in HIV infection suggests that preservation of this HIV-suppressive mechanism by early initiation of therapy may play an important role in the containment of viral replication in infected patients following interruption of therapy.
Nutrition et intelligence
Authors: Mongeau Estelle , Larivée Serge
Published: July 2002

Dans cet article, divisé en cinq parties de longueur inégale, les auteurs recensent les écrits sur les relations entre l'intelligence et la nutrition. Dans les deux premières parties, ils présentent brièvement les données sur l'ampleur de la malnutrition dans le monde et l'apport des études des fonctions cognitives chez l'animal pour la compréhension de l'effet de la malnutrition chez l'humain. La troisième partie, plus substantielle, est consacrée aux effets d'une dénutrition générale, d'une carence en fer, en zinc et en iode ainsi qu'aux effets des vitamines sur l'intelligence. Au cours des deux dernières parties, les auteurs mettent en évidence l'importance d'une part de l'allaitement maternel sur les performances intellectuelles et académiques et, d'autre part, du petit déjeuner sur les capacités d'apprentissage.
Vieillissement et Démence de Type Alzheimer: influence du type de connecteur sur la compréhension et la mémorisation de phrases
Authors: Calmettes Stéphanie , Brouillet Denis
Published: July 2002

Le but de cette étude est d'examiner l'effet de différents types de connecteur (causal, adversatif, additif) sur la compréhension et la mémorisation de phrases chez des sujets jeunes, âgés et présentant une Démence de Type Alzheimer (DTA). Les trois groupes de sujets (N = 48) lisaient des paires d'énoncés reliés ou non par un connecteur en Auto‐Présentation Segmentée. Ils ont effectué ensuite différentes épreuves: reconnaissance de verbe, questions de compréhension, questions inférentielles et une épreuve de complétion. Les résultats montrent que si la présence d'un connecteur, quel qu'il soit, a peu d'effet sur les performances des sujets jeunes et âgés sains, elle a par contre un impact important sur celles des sujets DTA: le connecteur semble être chez les sujets DTA un indice pour le travail d'intégration interpropositionnelle. En outre, le traitement du connecteur adversatif semble leur poser plus de problèmes que le traitement d'un connecteur causal et additif.
L'étude de la colère au sein des relations conjugales
Authors: Laughrea Kathleen , Bélanger Claude , McDuff John Wright et Pierre
Published: July 2002

Un certain nombre d'études ont porté sur les enjeux impliqués dans la définition et le traitement de la violence conjugale. Peu de recherches se sont cependant attardées à mesurer la colère dans les échanges dyadiques. L'objectif de cette étude consiste à évaluer les liens potentiels entre la colère et le niveau d'adaptation de couple. L'échantillon se compose de 220 couples provenant des populations normale et clinique. Les résultats indiquent que la colère des partenaires est étroitement liée. De plus, l'intensité des sentiments de colère, les traits de personnalité colérique et la répression de cette émotion chez un partenaire explique une partie importante de sa détresse conjugale, et à un niveau moindre, de celle de l'autre. Les implications théoriques et cliniques de ces résultats sont discutées.
Attentional Selectivity in Short‐term Memory: Similarity of Process, Not Similarity of Content, Determines Disruption
Authors: Macken William , Tremblay Sébastien , Alford David , Jones Dylan
Published: July 2002

Background sound substantially disrupts serial recall, even under conditions where participants are explicitly told to ignore it. Study of such a phenomenon may serve to illuminate the manner in which information from various sources interacts in memory, as well as the extent to which unattended information is processed. A review of the literature is presented that points to a number of conclusions. First, that interference occurs in memory, not on the basis of similarity of content between relevant and irrelevant material, but rather on the basis of similarity of process. Specifically, in a serial recall task, the key memory process is that of order retention, and therefore, order information in the sequence of auditory events interferes with the process of ordering within the rehearsal set. Second, that organisation and interference within memory are intimately connected with perceptual processes.
Moving with the Goalposts: Carrying out curriculum research in a period of constant change
Authors: Paechter Carrie
Published: July 2002

ABSTRACT This article reviews the author's experiences as an educational researcher working in a period of constant structural, curriculum and policy change. The author argues that, although the changing national context significantly altered the focus and conduct of the research, it is still possible to remain true to at least some of one's original aims, providing that both the researcher and the research planned are flexible and that reflexivity is built into the methodologies used. Flexibility regarding researcher role and the foci of both data collection and analysis are particularly important in this context. The analysis is illustrated with examples from two funded projects: one concerned with the planning and assessment of interdisciplinary course work projects and the other with power and gender relations in the negotiation of the design and technology curriculum.
Environmental factors as a conceptual framework for examining cognitive performance in Chinese adults
Authors: Schaie K. W. , Nguyen H. T. , Willis S. L. , Dutta Ranjana , Yue G. A.
Published: July 2002

Cognitive abilities were examined across the lifespan for a Chinese sample, taking into consideration gender, education, and environmental factors. Participants were tested on the ” ve subtests of the Primary Mental Abilities (PMA), a psychometric instrument measuring cognitive abilities. Environmental factors were assessed with a measure known as the Life Complexity Inventory (LCI), which provides information on the many aspects of the participants’ micro-environment. A MANOVA was used to examine patterns of cohort and gender differences in intellectual performance, and significant main effects for cohort were found. Polynomial trend analyses confirmed that age was linearly related to most mental abilities. Of the seven environmental factors, only the Intellectual Environment factor was significantly associated with all ability scores with positive correlations ranging from r = .20 to .32. Positive correlations indicate that a particular environmental factor is associated with higher ability or greater ‘ exibility.
The Persistent Impact of Language on Global Operations
Authors: Welch Denice E. , Welch Lawrence S. , Marschan-Piekkari Rebecca
Published: July 2002

In studies of firms' internationalisation, language has tended to be bundled into 'cultural and psychic distance boxes'. In this article, an attempt is made to unbundle the impact of language through (a) an examination of the way in which language influences the pattern of foreign market expansion; and (b) an analysis of how a firm may try to cope with language diversity by adopting a common corporate language. We conclude that attempts to impose a common corporate language may hinder or alter information flows, knowledge transfer, and communication.
Hereditary Degenerative Retinopathies: Optimism for Somatic Gene Therapy
Authors: Shastry Barkur S.
Published: July 2002

Retinitis pigmentosa comprises a large and exceptionally heterogeneous group of hereditary disorders of the retina. As a result of an extensive investigation around the world, primary genetic lesions have been described in many genes. Some of these genes encode enzymes that are involved in the signal transduction pathway. On the basis of in vitro functional assays and standard transgenic and knock‐out experiments, it has been proposed that normal cell functions are disrupted because of an abnormal protein‐folding and metabolic errors or structural defects in the membrane. This ultimately leads to a gene‐mediated cell death known as apoptosis. Various gene transfer approaches using mouse models further suggest that the degeneration can be rescued to some extent. Although many questions remain to be answered, investigations during the last 10 years have enormously increased our understanding of this exceptionally heterogeneous disorder and give hope for an effective gene therapy and a possible cure.
Xlrbpa, a Double-stranded RNA-binding Protein Associated with Ribosomes and Heterogeneous Nuclear RNPs
Authors: Eckmann Christian R. , Jantsch Michael F.
Published: July 2002

We have cloned and characterized Xlrbpa, a double-stranded RNA-binding protein from Xenopus laevis. Xlrbpa is a protein of 33 kD and contains three tandemly arranged, double-stranded RNA-binding domains (dsRBDs) that bind exclusively to double-stranded RNA in vitro, but fail to bind either single-stranded RNA or DNA. Sequence data and the overall organization of the protein suggest that Xlrbpa is the Xenopus homologue of human TAR-RNA binding protein (TRBP), a protein isolated by its ability to bind to human immunodeficiency virus (HIV) TAR-RNA. In transfection assays, TRBP has also been shown to inhibit the interferon-induced protein kinase PKR possibly by direct physical interaction. To determine the function of Xlrbpa and its human homologue we studied the expression and intracellular distribution of the two proteins. Xlrbpa is ubiquitously expressed with marked quantitative differences amongst all tissues. Xlrbpa and human TRBP can be detected in the cytoplasm and nucleus by immunofluorescence staining and Western blotting.

Sedimentation gradient analyses and immunoprecipitation experiments suggest an association of cytoplasmic Xlrbpa with ribosomes. In contrast, a control construct containing two dsRBDs fails to associate with ribosomes in microinjected Xenopus oocytes. Nuclear staining of Xenopus lampbrush chromosome preparations showed the association of the protein with nucleoli, again indicating an association of the protein with ribosomal RNAs. Additionally, Xlrbpa could be located on lampbrush chromosomes and in snurposomes. Immunoprecipitations of nuclear extracts demonstrated the presence of the protein in heterogeneous nuclear (hn) RNP particles, but not in small nuclear RNPs, explaining the chromosomal localization of the protein. It thus appears that Xlrbpa is a general double-stranded RNA-binding protein which is associated with the majority of cellular RNAs, ribosomal RNAs, and hnRNAs either alone or as part of an hnRNP complex.
Two Functional States of the CD11b A-Domain: Correlations with Key Features of Two Mn2+-complexed Crystal Structures
Authors: Li Rui , Rieu Philippe , Griffith Diana L. , Scott David , Amin Arnaout M.
Published: July 2002

In the presence of bound Mn2+, the three- dimensional structure of the ligand-binding A-domain from the integrin CR3 (CD11b/CD18) is shown to exist in the “open” conformation previously described only for a crystalline Mg2+ complex. The open conformation is distinguished from the “closed” form by the solvent exposure of F302, a direct T209–Mn2+ bond, and the presence of a glutamate side chain in the MIDAS site. Approximately 10% of wild-type CD11b A-domain is present in an “active” state (binds to activation-dependent ligands, e.g., iC3b and the mAb 7E3). In the isolated domain and in the holoreceptor, the percentage of the active form can be quantitatively increased or abolished in F302W and T209A mutants, respectively. The iC3b-binding site is located on the MIDAS face and includes conformationally sensitive residues that undergo significant shifts in the open versus closed structures. We suggest that stabilization of the open structure is independent of the nature of the metal ligand and that the open conformation may represent the physiologically active form.
Desmoplakin Is Required Early in Development for Assembly of Desmosomes and Cytoskeletal Linkage
Authors: Gallicano G. Ian , Kouklis Panos , Bauer Christoph , Yin Mei , Vasioukhin Valeri , Degenstein Linda , Fuchs Elaine
Published: July 2002

Desmosomes first assemble in the E3.5 mouse trophectoderm, concomitant with establishment of epithelial polarity and appearance of a blastocoel cavity. Throughout development, they increase in size and number and are especially abundant in epidermis and heart muscle. Desmosomes mediate cell–cell adhesion through desmosomal cadherins, which differ from classical cadherins in their attachments to intermediate filaments (IFs), rather than actin filaments. Of the proteins implicated in making this IF connection, only desmoplakin (DP) is both exclusive to and ubiquitous among desmosomes. To explore its function and importance to tissue integrity, we ablated the desmoplakin gene. Homozygous −/− mutant embryos proceeded through implantation, but did not survive beyond E6.5. Mutant embryos proceeded through implantation, but did not survive beyond E6.5. Surprisingly, analysis of these embryos revealed a critical role for desmoplakin not only in anchoring IFs to desmosomes, but also in desmosome assembly and/or stabilization. This finding not only unveiled a new function for desmoplakin, but also provided the first opportunity to explore desmosome function during embryogenesis. While a blastocoel cavity formed and epithelial cell polarity was at least partially established in the DP (−/−) embryos, the paucity of desmosomal cell–cell junctions severely affected the modeling of tissue architecture and shaping of the early embryo.
Two Compartments for Insulin-Stimulated Exocytosis in 3t3-L1 Adipocytes Defined by Endogenous Acrp30 and Glut4
Authors: Bogan Jonathan S. , Lodish Harvey F.
Published: July 2002

Insulin stimulates adipose cells both to secrete proteins and to translocate the GLUT4 glucose transporter from an intracellular compartment to the plasma membrane. We demonstrate that whereas insulin stimulation of 3T3-L1 adipocytes has no effect on secretion of the α3 chain of type VI collagen, secretion of the protein hormone adipocyte complement related protein of 30 kD (ACRP30) is markedly enhanced. Like GLUT4, regulated exocytosis of ACRP30 appears to require phosphatidylinositol-3-kinase activity, since insulin-stimulated ACRP30 secretion is blocked by pharmacologic inhibitors of this enzyme. Thus, 3T3-L1 adipocytes possess a regulated secretory compartment containing ACRP30. Whether GLUT4 recycles to such a compartment has been controversial. We present deconvolution immunofluorescence microscopy data demonstrating that the subcellular distributions of ACRP30 and GLUT4 are distinct and nonoverlapping; in contrast, those of GLUT4 and the transferrin receptor overlap. Together with supporting evidence that GLUT4 does not recycle to a secretory compartment via the trans-Golgi network, we conclude that there are at least two compartments that undergo insulin-stimulated exocytosis in 3T3-L1 adipocytes: one for ACRP30 secretion and one for GLUT4 translocation.
Evidence for a Replication Function of Ffa-1, theXenopusOrthologue of Werner Syndrome Protein
Authors: Chen Chin-Yi , Graham Jeanine , Yan Hong
Published: July 2002

DNA replication in higher eukaryotic cells occurs at a large number of discrete sites called replication foci. We have previously purified a protein, focus-forming activity 1 (FFA-1), which is involved in the assembly of putative prereplication foci in Xenopus egg extracts. FFA-1 is the orthologue of the Werner syndrome gene product (WRN), a member of the RecQ helicase family. In this paper we show that FFA-1 colocalizes with sites of DNA synthesis and the single-stranded DNA binding protein, replication protein A (RPA), in nuclei reconstituted in the egg extract. In addition, we show that two glutathione S-transferase FFA-1 fusion proteins can inhibit DNA replication in a dominant negative manner. The dominant negative effect correlates with the incorporation of the fusion proteins into replication foci to form “hybrid foci,” which are unable to engage in DNA replication. At the biochemical level, RPA can interact with FFA-1 and specifically stimulates its DNA helicase activity. However, in the presence of the dominant negative mutant proteins, the stimulation is prevented. These results provide the first direct biochemical evidence of an important role for FFA-1 in DNA replication.
Hitchhiking fads en route to peroxisomes
Authors: Subramani Suresh
Published: July 2002

A unique aspect of protein translocation across the peroxisomal membrane is that folded and oligomeric proteins get across this membrane (Purdue and Lazarow, 2001). The generality of this rule, its specific features, and its mechanism are not fully understood. A paper in this issue addresses, in a very thorough fashion, the assembly, cofactor binding, and import of an oligomeric protein, acyl-CoA oxidase (Aox), into the peroxisome matrix (Titorenko et al., 2002, this issue).
L1 Antibodies Block Lymph Node Fibroblastic Reticular Matrix Remodeling In Vivo
Authors: Di Sciullo Gino , Donahue Tim , Schachner Melitta , Bogen Steven A.
Published: July 2002

L1 is an immunoglobulin superfamily adhesion molecule highly expressed on neurons and involved in cell motility, neurite outgrowth, axon fasciculation, myelination, and synaptic plasticity. L1 is also expressed by nonneural cells, but its function outside of the nervous system has not been studied extensively. We find that administration of an L1 monoclonal antibody in vivo disrupts the normal remodeling of lymph node reticular matrix during an immune response. Ultrastructural examination reveals that reticular fibroblasts in mice treated with L1 monoclonal antibodies fail to spread and envelop collagen fibers with their cellular processes. The induced defect in the remodeling of the fibroblastic reticular system results in the loss of normal nodal architecture, collapsed cortical sinusoids, and macrophage accumulation in malformed sinuses. Surprisingly, such profound architectural abnormalities have no detectable effects on the primary immune response to protein antigens.
Stimulus-dependent Synergism of the Antiapoptotic Tumor Necrosis Factor Receptor–associated Factor 2 (TRAF2) and Nuclear Factor κB Pathways
Authors: Lee Soo Young , Kaufman David R. , Mora Ana L. , Santana Angela , Boothby Mark , Choi Yongwon
Published: July 2002

Tumor necrosis factor (TNF) signaling leads to pleiotropic responses in a wide range of cell types, in part by activating antiapoptotic and proapoptotic signaling pathways. Thus, although TNF can cause apoptosis and may prove useful in the treatment of malignancies, most cells are resistant to TNF-induced cell death unless de novo protein synthesis is inhibited. Previous studies suggested that TNF activation of the nuclear factor (NF)-κB transcription factor family antagonizes the proapoptotic signals initiated by TNF-α. TNF receptor–associated factor (TRAF)2 has also been shown to mediate crucial antiapoptotic signals during TNF stimulation, yet is not essential in activation of NF-κB under physiologic conditions, thus raising questions about the relationship between these antiapoptotic pathways. We report here that inhibition of TRAF2 and NF-κB function in primary cells, by coexpression of a constitutive repressor of multiple NF-κB/Rel proteins (IκBα.DN) and a dominant negative form of TRAF2 (TRAF2.DN), synergistically enhanced TNF-induced apoptosis. The effects were stimulus dependent, such that neither inhibitory molecule affected Fas- and daunorubicin-induced apoptosis to the same degree as TNF-induced death. These findings indicate that the NF-κB and TRAF2 pathways activate independent antiapoptotic mechanisms which act in concert to suppress the proapoptotic signals induced by TNF-α.
A Novel Element Upstream of the Vγ2 Gene in the Murine T Cell Receptor γ Locus Cooperates with the 3′ Enhancer to Act as a Locus Control Region
Authors: Baker Jeanne E. , Kang Joonsoo , Xiong Na , Chen Tempe , Cado Dragana , Raulet David H.
Published: July 2002

Transgenic expression constructs were employed to identify a cis-acting transcription element in the T cell receptor (TCR)-γ locus, called HsA, between the Vγ5 and Vγ2 genes. In constructs lacking the previously defined enhancer (3′ECγ1), HsA supports transcription in mature but not immature T cells in a largely position-independent fashion. 3′ECγ1, without HsA, supports transcription in immature and mature T cells but is subject to severe position effects. Together, the two elements support expression in immature and mature T cells in a copy number–dependent, position-independent fashion. Furthermore, HsA was necessary for consistent rearrangement of transgenic recombination substrates. These data suggest that HsA provides chromatin-opening activity and, together with 3′ECγ1, constitutes a T cell–specific locus control region for the TCR-γ locus.
Tetracycline-controllable Selection of CD4+ T Cells: Half-Life and Survival Signals in the Absence of Major Histocompatibility Complex Class II Molecules
Authors: Witherden Deborah , van Oers Nicolai , Waltzinger Caroline , Weiss Arthur , Benoist Christophe , Mathis Diane
Published: July 2002

A system that allows the study, in a gentle fashion, of the role of MHC molecules in naive T cell survival is described. Major histocompatibility complex class II–deficient mice were engineered to express Eα chains only in thymic epithelial cells in a tetracycline (tet)-controllable manner. This resulted in tet-responsive display of cell surface E complexes, positive selection of CD4+8– thymocytes, and generation of a CD4+ T cell compartment in a class II–barren periphery. Using this system, we have addressed two unresolved issues: the half-life of naive CD4+ T cells in the absence of class II molecules (3–4 wk) and the early signaling events associated with class II molecule engagement by naive CD4+ T cells (partial CD3 ζ chain phosphorylation and ZAP-70 association).
𝑈(𝔤)-finite locally analytic representations
Authors: Schneider P. , Teitelbaum J. , Prasad Dipendra
Published: July 2002

In this paper we continue our algebraic approach to the study of locally analytic representations of a

p
p

-adic Lie group

G
G

in vector spaces over a non-Archimedean complete field

K
K

. We characterize the smooth representations of Langlands theory which are contained in the new category. More generally, we completely determine the structure of the representations on which the universal enveloping algebra

U
(

g

)

U(\mathfrak g)

of the Lie algebra

g

\mathfrak g

of

G
G

acts through a finite dimensional quotient. They are direct sums of tensor products of smooth and rational

G
G

-representations. Finally we analyze the reducible members of the principal series of the group

G
=
S

L
2

(

Q

p

)

G=SL_2(\mathbb Q_p)

in terms of such tensor products.
RNA movies: visualizing RNA secondary structure spaces.
Authors: Evers D , Giegerich R
Published: July 2002

MOTIVATION: RNA Movies is a system for the visualization of RNA secondary structure spaces. Its input is a script consisting of primary and secondary structure information. From this script, the system fully automatically generates animated graphical structure representations. In this way, it creates the impression of an RNA molecule exploring its own two-dimensional structure space. RESULTS: RNA Movies has been used to generate animations of a switching structure in the spliced leader RNA of Leptomonas collosoma and sequential foldings of potato spindle tuber viroid transcripts. AVAILABILITY: Demonstrations of the animations mentioned in this paper can be viewed on our Bioinformatics web server under the following address: http://BiBiServ.TechFak.Uni-Bielefeld. DE/rnamovies/. The RNA Movies software is available upon request from the authors.
Quinupristin/dalfopristin: therapeutic potential for vancomycin-resistant enterococcal infections
Authors: Moellering Robert C.
Published: July 2002

Vancomycin-resistant Enterococcus faecium (VREF) is an opportunistic pathogen, which causes infections among severely ill, hospitalized patients, in whom it is likely to increase the risk of progressive local or systemic disease and to worsen the prognosis. Because these organisms are often highly resistant to penicillin, ampicillin and many other antimicrobials including the glycopeptides, there are few proven therapeutic alternatives for the treatment of infection caused by VREF. Quinupristin/dalfopristin is highly active against VREF in vitro. A prolonged post-antibiotic effect, good polymorphonuclear leucocyte/macrophage penetration and slow release, and active metabolites allow this agent to be used with an 8 or 12 h dosing interval. The combined results from a Phase III non-comparative study and an emergency-use study of quinupristin/dalfopristin for the treatment of VREF infection produced a clinical response rate (cure or improvement) in 142 (73.6%) of 193 clinically evaluable patients. The baseline pathogen was eradicated or presumed eradicated from 110 of 156 (70.5%) bacteriologically evaluable patients. Fifty-two per cent of the severely ill patients in these two studies died, but no death was attributed to quinupristin/dalfopristin therapy. The most common adverse event was arthralgia (9.1%). Quinupristin/dalfopristin has demonstrated efficacy for the treatment of serious VREF infections, including those that have failed conventional therapy.
The Werner syndrome protein contributes to induction of p53 by DNA damage
Authors: Blander Gil , Zalle Noa , Martinez Leal Juan Fernando , Bar‐Or Ruth Lev , Yu Chang‐En , Oren Moshe
Published: July 2002

Mutations in the p53 tumor‐suppressor gene promote increased genomic instability and cancer. Mutations in the WRN gene, encoding a DNA helicase, underlie the segmental progeroid Werner syndrome (WS). WS is also associated with increased genomic instability and elevated cancer risk. The p53 and WRN proteins can engage in direct protein‐protein interactions. We report that excess WRN elicits increased cellular p53 levels and potentiates p53‐mediated apoptosis. Importantly, cells derived from WS patients exhibit an attenuated and delayed induction of p53 by UV or by the topoisomerase I inhibitor camptothecin. These results suggest that WRN may participate in the activation of p53 in response to certain types of DNA damage. Furthermore, the failure to induce p53 effectively may contribute to enhanced genomic instability and elevated cancer risk in WS patients.
Prolonged hypoxia during cell development protects mature manganese superoxide dismutase‐deficient astrocytes from damage by oxidative stress
Authors: COPIN JEAN‐CHRISTOPHE , GASCHE YVAN , LI YIBING , CHAN PAK H.
Published: July 2002

Mouse astrocytes deficient in the mitochondrial form of superoxide dismutase do not grow in culture under 20% atmospheric O2 levels. By flow cytometry, immunocytochemistry, and enzymatic analysis we have shown that the oxygen block of cell division is due to a decrease in the number of cells entering the S phase of the cell cycle and is concomitant with higher DNA oxidation and impairment of mitochondrial functions. Seeding the cells under 5% O2 until the cultures become confluent can circumvent this problem. An initial hypoxic environment increases the resistance of manganese superoxide dismutase‐deficient astrocytes to superoxide radicals artificially produced by paraquat treatment, preserves respiratory activity, and allows normoxic division during a subsequent passage. DNA oxidation is then not higher than in wild‐type control cells. However, the adaptation of the cells is not due to compensation by other enzymes of the antioxidant defense system and is specific to cells totally lacking manganese superoxide dismutase. Alteration of the phenotype by prior hypoxia exposure in the SOD2‐deficient mutant provide a unique model to study adaptative mechanisms of cellular resistance to oxygen toxicity.—Copin, J.‐C., Gasche, Y., Li, Y., Chan, P. H. Prolonged hypoxia during cell development protects mature manganese superoxide dismutase‐deficient astrocytes from damage by oxidative stress. FASEB J. 15, 525‐534 (2000)
Integrin‐associated protein (CD47/IAP) contributes to T cell arrest on inflammatory vascular endothelium under flow
Authors: TICCHIONI MICHEL , RAIMONDI VINCENT , LAMY LAURENCE , WIJDENES JOHN , LINDBERG FREDERIK P. , BROWN ERIC J. , BERNARD ALAIN
Published: July 2002

Integrin‐associated protein (CD47/IAP) is a pentaspan molecule that regulates integrin functions. We prepared a CD47‐deficient Jurkat T cell line to assess its role in the arrest of T cells on inflammatory endothelium. Under flow conditions, constitutive arrest of CD47‐deficient cells is strongly decreased as compared to the original cell line, whereas reexpression of CD47 reestablishes their ability to stop. Moreover, cells transfected with a chimera made with the extracellular portion of CD47 and the transmembrane domain of CD7 or several truncated forms of CD47 show that the first transmembrane domain and a short cytoplasmic loop are sufficient for this process. CD47 effect is indirect and depends mainly on the α4β1/VCAM‐1 pathway, as shown by blocking antibodies. We detected on endothelium the two CD47 counter receptors known to date: thrombospondin and SIRP1α. Blocking experiments show that both are involved. Overall, CD47 participates in the constitutive arrest of T lymphocytes on inflamed vascular endothelium by up‐regulating a 4β1 integrins.—Ticchioni, M., Raimondi, V., Lamy, L., Wijdenes, J., Lindberg, F. P., Brown, E. J., Bernard, A. Integrin‐associated protein (CD47/IAP) contributes to T cell arrest on inflammatory vascular endothelium under flow. FASEB J. 15, 341‐350 (2001)
Mutations in the Drosophila dTAK1 gene reveal a conserved function for MAPKKKs in the control of rel/NF-κB-dependent innate immune responses
Authors: Vidal Sheila , Khush Ranjiv S. , Leulier François , Tzou Phoebe , Nakamura Makoto , Lemaitre Bruno
Published: July 2002

In mammals, TAK1, a MAPKKK kinase, is implicated in multiple signaling processes, including the regulation of NF-κB activity via the IL1-R/TLR pathways. TAK1 function has largely been studied in cultured cells, and its in vivo function is not fully understood. We have isolated null mutations in the Drosophila dTAK1 gene that encodes dTAK1, a homolog of TAK1. dTAK1 mutant flies are viable and fertile, but they do not produce antibacterial peptides and are highly susceptible to Gram-negative bacterial infection. This phenotype is similar to the phenotypes generated by mutations in components of the Drosophila Imd pathway. Our genetic studies also indicate that dTAK1 functions downstream of the Imd protein and upstream of the IKK complex in the Imd pathway that controls the Rel/NF-κB like transactivator Relish. In addition, our epistatic analysis places the caspase, Dredd, downstream of the IKK complex, which supports the idea that Relish is processed and activated by a caspase activity. Our genetic demonstration of dTAK1's role in the regulation ofDrosophila antimicrobial peptide gene expression suggests an evolutionary conserved role for TAK1 in the activation of Rel/NF-κB-mediated host defense reactions.
Spin–orbit interaction and the Thomas precession: A comment on the lab frame point of view
Authors: Muñoz Gerardo
Published: July 2002

The spin–orbit interaction and Thomas precession calculation is almost always done in the electron’s rest frame. We show here that the alternative use of the lab frame is interesting in its own right, both because naive expectations fail and because it requires the presence of a “hidden momentum” contribution.
An introduction to breakdown phenomena in disordered systems
Authors: da Silveira Rava
Published: July 2002

The rupture of a medium under stress typifies breakdown phenomena. More generally, the latter encompass the dynamics of systems of many interacting elements governed by the interplay of a driving force with a pinning disorder, resulting in a macroscopic transition. A simple mean-field formalism incorporating these features is presented and applied to systems representative of fracture phenomena, social dilemmas, and magnets out of equilibrium. The similarities and differences in the corresponding mathematical structures are emphasized. The solutions are best obtained from a graphical method, from which very general conclusions may be drawn. In particular, the various classes of disorder distribution are treated without reference to a particular analytical or numerical form, and are found to lead to qualitatively different transitions. Finally, the notion of effective (or phenomenological) theory is introduced and illustrated for nonequilibrium disordered magnets.
A comparison of threshold estimation methods in children 6–11 years of age
Authors: Buss Emily , Hall Joseph W. , Grose John H. , Dev Madhu B.
Published: July 2002

Estimating detection threshold for auditory stimuli in children can be problematic because of lapses in attention and the time limits usually imposed by scheduling restrictions or fatigue. Data reported here were collected to compare the stability of threshold estimation procedures in testing children ages 6 to 11 in a three-alternative, forced-choice paradigm. Stimuli consisted of a 1-kHz tonal signal and a Gaussian noise masker, bandpass filtered between 500–2000 Hz and presented at 25-dB spectrum level. The signal was either presented for 400 ms in the presence of a continuous masker (simultaneous masking) or for 10 ms just prior to a 400-ms masker (backward masking). For each masking paradigm the 79% correct threshold was assessed via each of three procedures: 3-down, 1-up adaptive staircase (Levitt), maximum likelihood estimation (MLE), and method of constant stimuli. Percent correct was measured at the end of the study for a signal 10 dB above the previously determined threshold in order to estimate the most appropriate psychometric function asymptote for fitting data collected via the method of constant stimuli. Both the MLE and Levitt procedures produced equally stable threshold estimates for both conditions and age groups. This was the case despite considerable variability in backward-masking thresholds.
Noise in miniature microphones
Authors: Thompson Stephen C. , LoPresti Janice L. , Ring Eugene M. , Nepomuceno Henry G. , Beard John J. , Ballad William J. , Carlson Elmer V.
Published: July 2002

The internal noise spectrum in miniature electret microphones of the type used in the manufacture of hearing aids is measured. An analogous circuit model of the microphone is empirically fit to the measured data and used to determine the important sources of noise within the microphone. The dominant noise source is found to depend on the frequency. Below 40 Hz and above 9 kHz, the dominant source is electrical noise from the amplifier circuit needed to buffer the electrical signal from the microphone diaphragm. Between approximately 40 Hz and 1 kHz, the dominant source is thermal noise originating in the acoustic flow resistance of the small hole pierced in the diaphragm to equalize barometric pressure. Between approximately 1 kHz and 9 kHz, the noise originates in the acoustic flow resistances of sound entering the microphone and propagating to the diaphragm. To further reduce the microphone internal noise in the audio band requires attacking these sources. A prototype microphone having reduced acoustical noise is measured and discussed.
Response of an embedded fiber optic ultrasound sensor
Authors: Dorighi John , Krishnaswamy Sridhar , Achenbach Jan D.
Published: July 2002

In this work the response of an embedded fiber optic Fabry–Perot ultrasound sensor has been investigated. Calculations were performed that model the fiber as a cylindrical elastic inclusion subjected to obliquely incident harmonic plane waves. The phase shift of the light traveling in the fiber was calculated along the principal strain axes as a function of ultrasonic frequency and incident angle. Experiments were performed to validate the calculations. Induced phase shifts were measured for the cases of normally incident ultrasound impinging upon a fiber sensor submerged in water as well as embedded in epoxy. The case of obliquely incident ultrasound at angles up to 4 deg was also investigated for a fiber embedded in epoxy. The experimental measurements were performed over a bandwidth from 2 to 8 MHz.
Temporal and spectral estimations of harmonics-to-noise ratio in human voice signals
Authors: Qi Yingyong , Hillman Robert E.
Published: July 2002

The quantity, harmonic-to-noise ratio (HNR), has been used to estimate the level of noise in human voice signals. HNR estimation can be accomplished in two ways: (1) on a time-domain basis, in which HNR is computed directly from the acoustic waveform; and (2) on a frequency-domain basis, in which HNR is computed from a transformed representation of the waveform. An algorithm for computing HNR in the frequency domain was modified and tested in the work described here. The modifications were designed to reduce the influence of spectral leakage in the computation of harmonic energy, and to remove the necessity of spectral baseline shifting prescribed in one existing algorithm [G. de Krom, J. Speech Hear. Res. 36, 254–266 (1993)]. Frequency-domain estimations of HNR based on this existing algorithm and our modified algorithm were compared to time-domain estimations on synthetic signals and human pathological voice samples. Results indicated a highly significant, linear correlation between frequency- and time-domain estimations of HNR for our modified approach.
Lamb wave assessment of fiber volume fraction in composites
Authors: Seale Michael D. , Smith Barry T. , Prosser W. H. , Zalameda Joseph N.
Published: July 2002

Among the various techniques available, ultrasonic Lamb waves offer a convenient method of examining composite materials. Since the Lamb wave velocity depends on the elastic properties of a material, an effective tool exists to evaluate composites by measuring the velocity of these waves. Lamb waves can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material. This paper discusses a study in which Lamb waves were used to examine fiber volume fraction variations of approximately 0.40–0.70 in composites. The Lamb wave measurements were compared to fiber volume fractions obtained from acid digestion tests. Additionally, a model to predict the fiber volume fraction from Lamb wave velocity values was evaluated.
Modeling of subcritical penetration into sediments due to interface roughness
Authors: Thorsos Eric I. , Jackson Darrell R. , Williams Kevin L.
Published: July 2002

Recent experimental results reveal acoustic penetration into sandy sediments at grazing angles below the critical angle. A mechanism for this subcritical penetration is described based on scattering at a rough water–sediment interface. Using perturbation theory, a numerically tractable three-dimensional model is used for simulating experiments. The rough interface scattering has been treated using formally averaged methods as well as with single rough surface realizations. Data-model comparisons show that scattering by interface roughness is a viable hypothesis for the observed subcritical penetration.