bluuebunny/crossref_metadata_2025 huggingface dataset:
HIV envelope induces a cascade of cell signals in non-proliferating target cells that favor virus replication
Authors: Cicala Claudia , Arthos James , Selig Sara M. , Dennis Glynn , Hosack Douglas A. , Van Ryk Donald , Spangler Marion L. , Steenbeke Tavis D. , Khazanie Prateeti , Gupta Neil , Yang Jun , Daucher Marybeth , Lempicki Richard A. , Fauci Anthony S.
Published: July 2002

Certain HIV-encoded proteins modify host-cell gene expression in a manner that facilitates viral replication. These activities may contribute to low-level viral replication in nonproliferating cells. Through the use of oligonucleotide microarrays and high-throughput Western blotting we demonstrate that one of these proteins, gp120, induces the expression of cytokines, chemokines, kinases, and transcription factors associated with antigen-specific T cell activation in the absence of cellular proliferation. Examination of transcriptional changes induced by gp120 in freshly isolated peripheral blood mononuclear cells and monocyte-derived-macrophages reveals a broad and complex transcriptional program conducive to productive infection with HIV. Observations include the induction of nuclear factor of activated T cells, components of the RNA polymerase II complex including TFII D, proteins localized to the plasma membrane, including several syntaxins, and members of the Rho protein family, including Cdc 42. These observations provide evidence that envelope-mediated signaling contributes to the productive infection of HIV in suboptimally activated T cells.
The rate-limiting step in the folding of a large ribozyme without kinetic traps
Authors: Fang X.-W. , Thiyagarajan P. , Sosnick T. R. , Pan T.
Published: July 2002

A fundamental question in RNA folding is the nature of the rate-limiting step. Folding of large RNAs often is trapped by the need to undo misfolded structures, which precludes the study of the other, potentially more interesting aspects in the rate-limiting step, such as conformational search, metal ion binding, and the role of productive intermediates. The catalytic domain of the
Bacillus subtilis
RNase P RNA folds without a kinetic trap, thereby providing an ideal system to elucidate these steps. We analyzed the folding kinetics by using fluorescence and absorbance spectroscopies, catalytic activity, and synchrotron small-angle x-ray scattering. Folding begins with the rapid formation of early intermediates wherein the majority of conformational search occurs, followed by the slower formation of subsequent intermediates. Before the rate-limiting step, more than 98% of the total structure has formed. The rate-limiting step is a small-scale structural rearrangement involving prebound metal ions.
A deletion-generator compound element allows deletion saturation analysis for genomewide phenotypic annotation
Authors: Huet François , Lu Jeffrey T. , Myrick Kyl V. , Baugh L. Ryan , Crosby Madeline A. , Gelbart William M.
Published: July 2002

With the available eukaryotic genome sequences, there are predictions of thousands of previously uncharacterized genes without known function or available mutational variant. Thus, there is an urgent need for efficient genetic tools for genomewide phenotypic analysis. Here we describe such a tool: a deletion-generator technology that exploits properties of a double transposable element to produce molecularly defined deletions at high density and with high efficiency. This double element, called
P
{
wHy
}, is composed of a “deleter” element
hobo
, bracketed by two genetic markers and inserted into a “carrier”
P
element. We have used this
P
{
wHy
} element in
Drosophila melanogaster
to generate sets of nested deletions of sufficient coverage to discriminate among every transcription unit within 60 kb of the starting insertion site. Because these two types of mobile elements, carrier and deleter, can be found in other species, our strategy should be applicable to phenotypic analysis in a variety of model organisms.
Transepithelial transport of HIV-1 by M cells is receptor-mediated
Authors: Fotopoulos Grigorios , Harari Alexandre , Michetti Pierre , Trono Didier , Pantaleo Giuseppe , Kraehenbuhl Jean-Pierre
Published: July 2002

Human colon carcinoma Caco-2 cell monolayers undergo conversion into cells that share morphological and functional features of M cells when allowed to interact with B lymphocytes. A lymphotropic (X4) HIV-1 strain crosses M cell monolayers and infects underlying CD4
+
target cells. Transport requires both lactosyl cerebroside and CXCR4 receptors, which are expressed on the apical surface of Caco-2 and M cells. Antibodies specific for each receptor block transport. In contrast, a monotropic (R5) HIV-1 strain is unable to cross M cell monolayers and infect underlying monocytes, despite efficient transport of latex beads. Caco-2 and M cells do not express CCR5, but transfection of these cells with CCR5 cDNA restores transport of R5 virus, which demonstrates that HIV-1 transport across M cells is receptor-mediated. The follicle-associated epithelium covering human gut lymphoid follicles expresses CCR5, but not CXCR4, and lactosyl cerebroside, suggesting that HIV-1 infection may occur through M cells and enterocytes at these sites.
Herbivory, plant resistance, and climate in the tree ring record: Interactions distort climatic reconstructions
Authors: Trotter R. Talbot , Cobb Neil S. , Whitham Thomas G.
Published: July 2002

To understand climate change, dendrochronologists have used tree ring analyses to reconstruct past climates, as well as ecological processes such as herbivore population dynamics. Such reconstructions, however, have been hindered by a lack of experiments that separate the influences of confounding impacts on tree rings, such as herbivores and the interactions of multiple factors. Our long-term experiments with scale insects on resistant and susceptible pines demonstrate three major points that are important to the application of this commonly used tool. (
i
) Herbivory reduced tree ring growth by 25–35%. (
ii
) The impact on ring growth distorted climate reconstruction, resulting in the overestimation of past moisture levels by more than 2-fold. Our data suggest that, if distortion because of herbivory has been a problem in previous reconstructions, estimates of the magnitude of recent climate changes are likely to be conservative. (
iii
) Our studies support a detectible plant resistance × herbivore × climate interaction in the tree ring record. Because resistance and susceptibility to herbivory are known to be genetically based in many systems, the potential exists to incorporate plant genetics into the field of dendrochronology, where it may be used to screen distortions from the tree ring record.
The molecular basis of the coloration mechanism in lobster shell: β-Crustacyanin at 3.2-Å resolution
Authors: Cianci Michele , Rizkallah Pierre J. , Olczak Andrzej , Raftery James , Chayen Naomi E. , Zagalsky Peter F. , Helliwell John R.
Published: July 2002

The binding of the carotenoid astaxanthin (AXT) in the protein multimacromolecular complex crustacyanin (CR) is responsible for the blue coloration of lobster shell. The structural basis of the bathochromic shift mechanism has long been elusive. A change in color occurs from the orange red of the unbound dilute AXT (λ
max
472 nm in hexane), the well-known color of cooked lobster, to slate blue in the protein-bound live lobster state (λ
max
632 nm in CR). Intriguingly, extracted CR becomes red on dehydration and on rehydration goes back to blue. Recently, the innovative use of softer x-rays and xenon derivatization yielded the three-dimensional structure of the A
1
apoprotein subunit of CR, confirming it as a member of the lipocalin superfamily. That work provided the molecular replacement search model for a crystal form of the β-CR holo complex, that is an A
1
with A
3
subunit assembly including two bound AXT molecules. We have thereby determined the structure of the A
3
molecule
de novo
. Lobster has clearly evolved an intricate structural mechanism for the coloration of its shell using AXT and a bathochromic shift. Blue/purple AXT proteins are ubiquitous among invertebrate marine animals, particularly the Crustacea. The three-dimensional structure of β-CR has identified the protein contacts and structural alterations needed for the AXT color regulation mechanism.
Synergism between trematode infection and pesticide exposure: A link to amphibian limb deformities in nature?
Authors: Kiesecker Joseph M.
Published: July 2002

The apparently rapid increase in the prevalence of amphibian limb deformities has led to substantial interest from ecologists and public health professionals. Hypotheses proposed to explain the deformities fall into two broad categories: chemical contaminants and trematode infection. Although there are convincing experimental demonstrations that certain factors can lead to some deformities, the causes for recent increases in amphibian malformation remain controversial. Moreover, no experimental studies on amphibian deformities have been conducted in the field, and no studies have attempted to examine the synergistic effects of trematode infection and exposure to chemical contaminants. Here, I present the results of field and laboratory experiments that link increased trematode infection, and increased limb deformities, to pesticide exposure. Field experiments conclusively demonstrated that exposure to trematode infection was required for the development of limb deformities in wood frogs,Rana sylvatica. However, deformities were more common at sites adjacent to agricultural runoff. Laboratory experiments corroborated the association between pesticide exposure and increased infection with pesticide-mediated immunocompetency as the apparent mechanism. Given the conservative contaminant exposure levels used [Environmental Protection Agency (EPA) drinking water standards] and the widespread use of many pesticides, these negative impacts may help to explain pathogen-mediated amphibian declines in many regions.
Correlation of somatic hypermutation specificity and A-T base pair substitution errors by DNA polymerase η during copying of a mouse immunoglobulin κ light chain transgene
Authors: Pavlov Youri I. , Rogozin Igor B. , Galkin Alexey P. , Aksenova Anna Y. , Hanaoka Fumio , Rada Christina , Kunkel Thomas A.
Published: July 2002

To test the hypothesis that inaccurate DNA synthesis by mammalian DNA polymerase η (pol η) contributes to somatic hypermutation (SHM) of Ig genes, we measured the error specificity of mouse pol η during synthesis of each strand of a mouse Ig κ light chain transgene. We then compared the results to the base substitution specificity of SHM of this same gene in the mouse. Thein vitroandin vivobase substitution spectra shared a number of common features. A highly significant correlation was observed for overall substitutions at A-T pairs but not for substitutions at G-C pairs. Sixteen mutational hotspots at A-T pairs observedin vivowere also found in spectra generated by mouse pol ηin vitro. The correlation was strongest for errors made by pol η during synthesis of the non-transcribed strand, but it was also observed for synthesis of the transcribed strand. These facts, and the distribution of substitutions generatedin vivo, support the hypothesis that pol η contributes to SHM of Ig genes at A-T pairs via short patches of low fidelity DNA synthesis of both strands, but with a preference for the non-transcribed strand.
Eye contact detection in humans from birth
Authors: Farroni Teresa , Csibra Gergely , Simion Francesca , Johnson Mark H.
Published: July 2002

Making eye contact is the most powerful mode of establishing a communicative link between humans. During their first year of life, infants learn rapidly that the looking behaviors of others conveys significant information. Two experiments were carried out to demonstrate special sensitivity to direct eye contact from birth. The first experiment tested the ability of 2- to 5-day-old newborns to discriminate between direct and averted gaze. In the second experiment, we measured 4-month-old infants' brain electric activity to assess neural processing of faces when accompanied by direct (as opposed to averted) eye gaze. The results show that, from birth, human infants prefer to look at faces that engage them in mutual gaze and that, from an early age, healthy babies show enhanced neural processing of direct gaze. The exceptionally early sensitivity to mutual gaze demonstrated in these studies is arguably the major foundation for the later development of social skills.
Energetic communication between mitochondria and nucleus directed by catalyzed phosphotransfer
Authors: Dzeja Petras P. , Bortolon Ryan , Perez-Terzic Carmen , Holmuhamedov Ekshon L. , Terzic Andre
Published: July 2002

Exchange of information between the nucleus and cytosol depends on the metabolic state of the cell, yet the energy-supply pathways to the nuclear compartment are unknown. Here, the energetics of nucleocytoplasmic communication was determined by imaging import of a constitutive nuclear protein histone H1. Translocation of H1 through nuclear pores in cardiac cells relied on ATP supplied by mitochondrial oxidative phosphorylation, but not by glycolysis. Although mitochondria clustered around the nucleus, reducing the distance for energy transfer, simple nucleotide diffusion was insufficient to meet the energetic demands of nuclear transport. Rather, the integrated phosphotransfer network was required for delivery of high-energy phosphoryls from mitochondria to the nucleus. In neonatal cardiomyocytes with low creatine kinase activity, inhibition of adenylate kinase-catalyzed phosphotransfer abolished nuclear import. With deficient adenylate kinase, nucleoside diphosphate kinase, which secures phosphoryl exchange between ATP and GTP, was unable to sustain nuclear import. Up-regulation of creatine kinase phosphotransfer, to mimic metabolic conditions of adult cardiac cells, rescued H1 import, suggesting a developmental plasticity of the cellular energetic system. Thus, mitochondrial oxidative phosphorylation coupled with phosphotransfer relays provides an efficient energetic unit in support of nuclear transport.
Ligand-independent growth hormone receptor dimerization occurs in the endoplasmic reticulum and is required for ubiquitin system-dependent endocytosis
Authors: Gent Jürgen , van Kerkhof Peter , Roza Marcel , Bu Guojun , Strous Ger J.
Published: July 2002

The regulatory effect of growth hormone (GH) on its target cells is mediated via the GH receptor (GHR). GH binding to the GHR results in the formation of a GH-(GHR)
2
complex and the initiation of signal transduction cascades via the activation of the tyrosine kinase JAK2. Subsequent endocytosis and transport to the lysosome of the ligand-receptor complex is regulated via the ubiquitin system and requires the presence of an intact ubiquitin-dependent endocytosis (UbE) motif in the cytosolic tail of the GHR. Recently, the model of ligand-induced receptor dimerization has been challenged. In this study, ligand-independent GHR dimerization is demonstrated in the endoplasmic reticulum and at the cell surface by coimmunoprecipitation of an epitope-tagged truncated GHR with wild-type GHR. In addition, evidence is provided that the extracellular domain of the GHR is not required to maintain this interaction. Internalization of a chimeric receptor, which fails to dimerize, is independent of an intact UbE-motif. Therefore, we postulate that dimerization of GHR molecules is required for ubiquitin system-dependent endocytosis.
Polyvalent cation receptor proteins (CaRs) are salinity sensors in fish
Authors: Nearing J. , Betka M. , Quinn S. , Hentschel H. , Elger M. , Baum M. , Bai M. , Chattopadyhay N. , Brown E. M. , Hebert S. C. , Harris H. W.
Published: July 2002

To determine whether calcium polyvalent cation-sensing receptors (CaRs) are salinity sensors in fish, we used a homology-based cloning strategy to isolate a 4.1-kb cDNA encoding a 1,027-aa dogfish shark (
Squalus acanthias
) kidney CaR. Expression studies in human embryonic kidney cells reveal that shark kidney senses combinations of Ca
2+
, Mg
2+
, and Na
+
ions at concentrations present in seawater and kidney tubules. Shark kidney is expressed in multiple shark osmoregulatory organs, including specific tubules of the kidney, rectal gland, stomach, intestine, olfactory lamellae, gill, and brain. Reverse transcriptase–PCR amplification using specific primers in two teleost fish, winter flounder (
Pleuronectes americanus
) and Atlantic salmon (
Salmo salar
), reveals a similar pattern of CaR tissue expression. Exposure of the lumen of winter flounder urinary bladder to the CaR agonists, Gd
3+
and neomycin, reversibly inhibit volume transport, which is important for euryhaline teleost survival in seawater. Within 24–72 hr after transfer of freshwater-adapted Atlantic salmon to seawater, there are increases in their plasma Ca
2+
, Mg
2+
, and Na
+
that likely serve as a signal for internal CaRs, i.e., brain, to sense alterations in salinity in the surrounding water. We conclude that CaRs act as salinity sensors in both teleost and elasmobranch fish. Their tissue expression patterns in fish provide insights into CaR functions in terrestrial animals including humans.
Genome sequence of a serotype M3 strain of group AStreptococcus: Phage-encoded toxins, the high-virulence phenotype, and clone emergence
Authors: Beres Stephen B. , Sylva Gail L. , Barbian Kent D. , Lei Benfang , Hoff Jessica S. , Mammarella Nicole D. , Liu Meng-Yao , Smoot James C. , Porcella Stephen F. , Parkins Larye D. , Campbell David S. , Smith Todd M. , McCormick John K. , Leung Donald Y. M. , Schlievert Patrick M. , Musser James M.
Published: July 2002

Genome sequences are available for many bacterial strains, but there has been little progress in using these data to understand the molecular basis of pathogen emergence and differences in strain virulence. Serotype M3 strains of group AStreptococcus(GAS) are a common cause of severe invasive infections with unusually high rates of morbidity and mortality. To gain insight into the molecular basis of this high-virulence phenotype, we sequenced the genome of strain MGAS315, an organism isolated from a patient with streptococcal toxic shock syndrome. The genome is composed of 1,900,521 bp, and it shares ≈1.7 Mb of related genetic material with genomes of serotype M1 and M18 strains. Phage-like elements account for the great majority of variation in gene content relative to the sequenced M1 and M18 strains. Recombination produces chimeric phages and strains with previously uncharacterized arrays of virulence factor genes. Strain MGAS315 has phage genes that encode proteins likely to contribute to pathogenesis, such as streptococcal pyrogenic exotoxin A (SpeA) and SpeK, streptococcal superantigen (SSA), and a previously uncharacterized phospholipase A2(designated Sla). Infected humans had anti-SpeK, -SSA, and -Sla antibodies, indicating that these GAS proteins are madein vivo. SpeK and SSA were pyrogenic and toxic for rabbits. Serotype M3 strains with the phage-encodedspeKandslagenes increased dramatically in frequency late in the 20th century, commensurate with the rise in invasive disease caused by M3 organisms. Taken together, the results show that phage-mediated recombination has played a critical role in the emergence of a new, unusually virulent clone of serotype M3 GAS.
A Tat subunit vaccine confers protective immunity against the immune-modulating activity of the human immunodeficiency virus type-1 Tat protein in mice
Authors: Agwale S. M. , Shata M. T. , Reitz M. S. , Kalyanaraman V. S. , Gallo R. C. , Popovic M. , Hone D. M.
Published: July 2002

The rational design of new therapies against HIV-1 necessitates an improved understanding of the mechanisms underlying the production of ineffective immune responses to HIV-1 in most infected individuals. This report shows that the CD8+T cell responses to gp120 were greatly diminished in mice vaccinated with a bicistronic gp120-Tat DNA vaccine, compared with those induced by a DNA vaccine encoding gp120 alone. The CD8+T cell responses induced by the latter included strong gp120-specific IFN-γ secretion and protective antiviral immunity against challenge by a vaccinia-envpseudotype. The degree to which Tat influenced CD8+T cell responses depended on the bioactivity of Tat. Thus, a bicistronic DNA vaccine that expresses gp120 and a truncated Tat defective for LTR activation elicited strong IFN-γ -secreting CD8+T cell responses to gp120 but conferred only marginal protection against the vaccinia-envchallenge. The effect of Tat was completely blocked, however, by immunization with inactivated Tat protein before vaccination with the bicistronic gp120-Tat DNA vaccine.
Early kinetic intermediate in the folding of acyl-CoA binding protein detected by fluorescence labeling and ultrarapid mixing
Authors: Teilum Kaare , Maki Kosuke , Kragelund Birthe B. , Poulsen Flemming M. , Roder Heinrich
Published: July 2002

Early conformational events during folding of acyl-CoA binding protein (ACBP), an 86-residue α-helical protein, were explored by using a continuous-flow mixing apparatus with a dead time of 70 μs to measure changes in intrinsic tryptophan fluorescence and tryptophan-dansyl fluorescence energy transfer. Although the folding of ACBP was initially described as a concerted two-state process, the tryptophan fluorescence measurements revealed a previously unresolved phase with a time constant τ = 80 μs, indicating formation of an intermediate with only slightly enhanced florescence of Trp-55 and Trp-58 relative to the unfolded state. To amplify this phase, a dansyl fluorophore was introduced at the C terminus by labeling an I86C mutant of ACBP with 5-IAEDANS [5-((((2-iodoacetyl)amino)ethyl)amino)naphthalene-1-sulfonic acid]. Continuous-flow refolding of guanidine HCl-denatured ACBP showed a major increase in tryptophan-dansyl fluorescence energy transfer, indicating formation of a partially collapsed ensemble of states on the 100-μs time scale. A subsequent decrease in dansyl fluorescence is attributed to intramolecular quenching of donor fluorescence on formation of the native state. The kinetic data are fully accounted for by three-state mechanisms with either on- or off-pathway intermediates. The intermediate accumulates to a maximum population of 40%, and its stability depends only weakly on denaturant concentration, which is consistent with a marginally stable ensemble of partially collapsed states with ∼1/3 of the solvent-accessible surface buried. The findings indicate that ultrafast mixing methods combined with sensitive conformational probes can reveal transient accumulation of intermediate states in proteins with apparent two-state folding mechanisms.
Human influenza viruses activate an interferon-independent transcription of cellular antiviral genes: Outcome with influenza A virus is unique
Authors: Kim Mee-Jung , Latham Anita Ghate , Krug Robert M.
Published: July 2002

We examine the IFN-α/β-independent activation of cellular transcription that constitutes an early antiviral response of cells against influenza A and B viruses, which cause widespread epidemics in humans. We show that influenza B virus induces the synthesis in human cells of several mature mRNAs encoded by genes containing an IFN-α/β-stimulated response element (ISRE). Consequently, the IFN regulatory factor-3 transcription factor, which is required for the transcription of ISRE-controlled genes, is activated after influenza B virus infection. The production of these cellular mRNAs, some of which encode antiviral proteins, is independent of not only IFN-α/β, but also viral protein synthesis. These mature cellular antiviral mRNAs are not produced after infection with influenza A virus, but IFN regulatory factor-3 is activated and the transcription of the ISRE-controlled p56 gene is induced. Consequently, like other newly synthesized cellular premRNAs in influenza A virus-infected cells, the posttranscriptional processing of premRNAs encoded by ISRE-controlled genes is inhibited. Previous work has established that such posttranscriptional inhibition is mediated by the viral NS1A protein. This unique, global countermeasure against the early, IFN-α/β-independent antiviral response of cells may be an important factor in the pathogenicity of influenza A virus infection.
Molecular recognition of oxygen by protein mimics: Dynamics on the femtosecond to microsecond time scale
Authors: Zou Shouzhong , Baskin J. Spencer , Zewail Ahmed H.
Published: July 2002

Molecular recognition by biological macromolecules involves many elementary steps, usually convoluted by diffusion processes. Here we report studies of the dynamics, from the femtosecond to the microsecond time scale, of the different elementary processes involved in the bimolecular recognition of a protein mimic, cobalt picket-fence porphyrin, with varying oxygen concentration at controlled temperatures. Electron transfer, bond breakage, and thermal “on” (recombination) and “off” (dissociation) reactions are the different processes involved. The reaction on-rate is 30 to 60 times smaller than that calculated from standard Smoluchowski theory. Introducing a two-step recognition model, with reversibility being part of both steps, removes the discrepancy and provides consistency for the reported thermodynamics, kinetics, and dynamics. The transient intermediates are configurations defined by the contact between oxygen (diatomic) and the picket-fence porphyrin (macromolecule). This intermediate is critical in the description of the potential energy landscape but, as shown here, both enthalpic and entropic contributions to the free energy are important. In the recognition process, the net entropy decrease is −33 cal mol
−1
K
−1
; Δ
H
is −13.4 kcal mol
−1
.
Protocols, practices, and the reproduction of technique in molecular biology*
Authors: Lynch Michael
Published: July 2002

Protocols are one of the main organizational resources in molecular biology. They are written instructions that specify ingredients, equipment, and sequences of steps for making technical preparations. Some protocols are published in widely used manuals, while others are hand‐written variants used by particular laboratories and individual technicians. It is widely understood, both in molecular biology and in social studies of science, that protocols do not describe exactly what practitioners do in the laboratory workplace. In social studies of science, the difference between protocols and the actual practices of doing them often is used to set up ironic contrasts between ‘messy’ laboratory practices and the appearance of technical order. Alternatively, in ethnomethodological studies of work, the difference is examined as a constitutive feature, both of the livedwork of doing technical projects, and of the administrative work of regulating and evaluating such projects. The present article takes its point of departure from ethnomethodology, and begins with a discussion of local problems with performing molecular biology protocols on specific occasions. The discussion then moves to particular cases in criminal law in which defense attorneys crossexamine forensic technicians and lab administrators. In these interrogations, the distinction between protocols and actual practices animates the dialogue and becomes consequential for judgments in the case at hand. The article concludes with a discussion of administrative science: the work of treating protocols and paper trails as proxies for actual ‘scientific’ practices.
Improvisational choreography in teleservice work*
Authors: Whalen Jack , Whalen Marilyn , Henderson Kathryn
Published: July 2002

This naturalistic study of the ordinary work practice of sales representatives employed by the call centre of a large office‐equipment company focuses on the actions of those sales reps during their calls with customers. We show how this work performance is organized through an improvisational choreography of action involving not only the turn‐by‐turn interchange with customers on the telephone but also the concurrent utilization of a variety of tools and artefacts. While ‘improvise’ and ‘choreograph’ may appear to be conceptually incongruent, our analysis demonstrates that even though these teleservice workers recurrently fabricate their actions out of materials and means that are conveniently on hand, the convenience is often carefully arranged to afford such extemporaneous composition. Finally, we conclude from this analysis that the traditional topics of ‘work routines’ and ‘routinization’ need to be respecified in order to take into account how any ‘routine’ is a contingently produced result (and in this centre, a craft‐like performance).
Cognitive euroscience: Scalar variability in price estimation and the cognitive consequences of switching to the euro
Authors: Dehaene Stanislas , Marques J. Frederico
Published: July 2002

The present paper examines the ability to evaluate prices in a familiar currency (French francs, Portugese escudos, or Irish punt) and in an unfamiliar currency (euro). Participants evaluated prices for different items either by selecting the most appropriate price from a set of alternatives (in a timed or not-timed version) or by directly producing a price estimate for each item. The results followed Weber's law: The standard deviation of estimated prices was proportional to their mean. The Weber fraction was stable for the familiar currency in different countries, but was significantly higher for the unfamiliar currency. We suggest that price estimation relies on a learned mapping between items and their prices as represented by distributions of activation on an internal number line. The observed Weber fraction reflects the degree of expertise with a given currency as well as a minimal variability intrinsic to the number line itself.
The Death of Neoclassical Economics
Authors: Colander David
Published: July 2002

The term “neoclassical economics” was born in 1900; in this paper I am proposing economist-assisted terminasia; by the powers vested in me as president of the History of Economics Society, I hereby declare the term neoclassical economics dead. Let me be clear about what I am sentencing to death—it is not the content of neoclassical economics. As I will discuss below, it is difficult to determine what that content is, and even if I wanted to kill the content, I have no role in determining content. The role of historians of thought is to record, not determine, content. What I am declaring dead is the term.
Back to labour markets - who got ahead in post-communist societies after 1989?
Authors: Diewald Martin , Solga Heike , Goedicke Anne
Published: July 2002

This article explores the restructuring of the employment system in post-communist societies, taking East Germany after 1989 as an example. Due to the German Democratic Republic's ‘accession’ to the Federal Republic of Germany in 1990, the transitional process here was a particular one. More than other post-communist transformations, the East German case is seen as a prototype of a ‘simple’ adaptation process. In this study we explore whether such a simple adaptation process actually occurred, with the allocation mechanisms used in West Germany being transferred to East Germany. We investigate how different kinds of human resources accumulated and exhibited before 1989 helped to promote individual career mobility after 1989. One of the central and surprising results of the analyses is that individual assets (such as mobility competencies acquired under the state-socialist regime) were of only secondary importance for success and failure in the unified labour market.
An HRD/DER-independent ER quality control mechanism involves Rsp5p-dependent ubiquitination and ER-Golgi transport
Authors: Haynes Cole M. , Caldwell Sabrina , Cooper Antony A.
Published: July 2002

We have identified a new pathway of ER-associated degradation in Saccharomyces cerevisiae that functions separately from the HRD/DER pathway comprised of Hrd1p, Hrd3p, Der1p, and Ubc7p. This pathway, termed Hrd1p independent-proteolysis (HIP), is capable of recognizing and degrading both lumenal (CPY* and PrA*), and integral membrane proteins (Sec61–2p) that misfold in the ER. CPY* overexpression likely saturates the HRD/DER pathway and activates the HIP pathway, so the slowed degradation kinetics of CPY* in a hrd1Δ strain is restored to a wild-type rate when CPY* is overexpressed. Substrates of HIP require vesicular trafficking between the ER and Golgi apparatus before degradation by the ubiquitin-proteasome system. Ubiquitination of HIP substrates does not involve the HRD/DER pathway ubiquitin ligase Hrd1p, but instead uses another ubiquitin ligase, Rsp5p. HIP is regulated by the unfolded protein response as Ire1p is necessary for the degradation of CPY* when overexpressed, but not when CPY* is expressed at normal levels. Both the HIP and HRD/DER pathways contribute to the degradation of CPY*, and only by eliminating both is CPY* degradation completely blocked.
Rapid exchange of mammalian topoisomerase IIα at kinetochores and chromosome arms in mitosis
Authors: Tavormina Penny A. , Côme Marie-George , Hudson Joanna R. , Mo Yin-Yuan , Beck William T. , Gorbsky Gary J.
Published: July 2002

Astable cell line (GT2-LPk) derived from LLC-Pk was created in which endogenous DNA topoisomerase IIα (topoIIα) protein was downregulated and replaced by the expression of topoIIα fused with enhanced green fluorescent protein (EGFP–topoIIα). The EGFP–topoIIα faithfully mimicked the distribution of the endogenous protein in both interphase and mitosis. In early stages of mitosis, EGFP–topoIIα accumulated at kinetochores and in axial lines extending along the chromosome arms. During anaphase, EGFP–topoIIα diminished at kinetochores and increased in the cytoplasm with a portion accumulating into large circular foci that were mobile and appeared to fuse with the reforming nuclei. These cytoplasmic foci appearing at anaphase were coincident with precursor organelles of the reforming nucleolus called nucleolus-derived foci (NDF). Photobleaching of EGFP–topoIIα associated with kinetochores and chromosome arms showed that the majority of the protein rapidly exchanges (t1/2 of 16 s). Catalytic activity of topoIIα was essential for rapid dynamics, as ICRF-187, an inhibitor of topoIIα, blocked recovery after photobleaching. Although some topoIIα may be stably associated with chromosomes, these studies indicate that the majority undergoes rapid dynamic exchange. Rapid mobility of topoIIα in chromosomes may be essential to resolve strain imparted during chromosome condensation and segregation.
Scotin, a novel p53-inducible proapoptotic protein located in the ER and the nuclear membrane
Authors: Bourdon J.-C. , Renzing J. , Robertson P.L. , Fernandes K.N. , Lane D.P.
Published: July 2002

p53 is a transcription factor that induces growth arrest or apoptosis in response to cellular stress. To identify new p53-inducible proapoptotic genes, we compared, by differential display, the expression of genes in spleen or thymus of normal and p53 nullizygote mice after γ-irradiation of whole animals. We report the identification and characterization of human and mouse Scotin homologues, a novel gene directly transactivated by p53. The Scotin protein is localized to the ER and the nuclear membrane. Scotin can induce apoptosis in a caspase-dependent manner. Inhibition of endogenous Scotin expression increases resistance to p53-dependent apoptosis induced by DNA damage, suggesting that Scotin plays a role in p53-dependent apoptosis. The discovery of Scotin brings to light a role of the ER in p53-dependent apoptosis.
Retention of a cell adhesion complex at the paranodal junction requires the cytoplasmic region of Caspr
Authors: Gollan Leora , Sabanay Helena , Poliak Sebastian , Berglund Erik O. , Ranscht Barbara , Peles Elior
Published: July 2002

An axonal complex of cell adhesion molecules consisting of Caspr and contactin has been found to be essential for the generation of the paranodal axo-glial junctions flanking the nodes of Ranvier. Here we report that although the extracellular region of Caspr was sufficient for directing it to the paranodes in transgenic mice, retention of the Caspr–contactin complex at the junction depended on the presence of an intact cytoplasmic domain of Caspr. Using immunoelectron microscopy, we found that a Caspr mutant lacking its intracellular domain was often found within the axon instead of the junctional axolemma. We further show that a short sequence in the cytoplasmic domain of Caspr mediated its binding to the cytoskeleton-associated protein 4.1B. Clustering of contactin on the cell surface induced coclustering of Caspr and immobilized protein 4.1B at the plasma membrane. Furthermore, deletion of the protein 4.1B binding site accelerated the internalization of a Caspr–contactin chimera from the cell surface. These results suggest that Caspr serves as a “transmembrane scaffold” that stabilizes the Caspr/contactin adhesion complex at the paranodal junction by connecting it to cytoskeletal components within the axon.
Cortical recruitment of nonmuscle myosin II in early syncytial Drosophila embryos
Authors: Royou Anne , Sullivan William , Karess Roger
Published: July 2002

The nuclei of early syncytial Drosophila embryos migrate dramatically toward the poles. The cellular mechanisms driving this process, called axial expansion, are unclear, but myosin II activity is required. By following regulatory myosin light chain (RLC)–green fluorescent protein dynamics in living embryos, we observed cycles of myosin recruitment to the cortex synchronized with mitotic cycles. Cortical myosin is first seen in a patch at the anterocentral part of the embryo at cycle 4. With each succeeding cycle, the patch expands poleward, dispersing at the beginning of each mitosis and reassembling at the end of telophase. Each cycle of actin and myosin recruitment is accompanied by a cortical contraction. The cortical myosin cycle does not require microtubules but correlates inversely with Cdc2/cyclinB (mitosis-promoting factor) activity. A mutant RLC lacking inhibitory phosphorylation sites was fully functional with no effect on the cortical myosin cycle, indicating that Cdc2 must be modulating myosin activity by some other mechanism. An inhibitor of Rho kinase blocks the cortical myosin recruitment cycles and provokes a concomitant failure of axial expansion. These studies suggest a model in which cycles of myosin-mediated contraction and relaxation, tightly linked to Cdc2 and Rho kinase activity, are directly responsible for the axial expansion of the syncytial nuclei.
Mossy fiber Zn2+ spillover modulates heterosynapticN-methyl-d-aspartate receptor activity in hippocampal CA3 circuits
Authors: Ueno Sayaka , Tsukamoto Masako , Hirano Tomoya , Kikuchi Kazuya , Yamada Maki K. , Nishiyama Nobuyoshi , Nagano Tetsuo , Matsuki Norio , Ikegaya Yuji
Published: July 2002

Although Zn2+ is contained in large amounts in the synaptic terminals of hippocampal mossy fibers (MFs), its physiological role in synaptic transmission is poorly understood. By using the newly developed high-sensitivity Zn2+ indicator ZnAF-2, the spatiotemporal dynamics of Zn2+ was monitored in rat hippocampal slices. When high-frequency stimulation was delivered to the MFs, the concentration of extracellular Zn2+ was immediately elevated in the stratum lucidum, followed by a mild increase in the stratum radiatum adjacent to the stratum lucidum, but not in the distal area of stratum radiatum. The Zn2+ increase was insensitive to a non–N-methyl-d-aspartate (NMDA) receptor antagonist but was efficiently attenuated by tetrodotoxin or Ca2+-free medium, suggesting that Zn2+ is released by MF synaptic terminals in an activity-dependent manner, and thereafter diffuses extracellularly into the neighboring stratum radiatum. Electrophysiological analyses revealed that NMDA receptor–mediated synaptic responses in CA3 proximal stratum radiatum were inhibited in the immediate aftermath of MF activation and that this inhibition was no longer observed in the presence of a Zn2+-chelating agent. Thus, Zn2+ serves as a spatiotemporal mediator in imprinting the history of MF activity in contiguous hippocampal networks. We predict herein a novel form of metaplasticity, i.e., an experience-dependent non-Hebbian modulation of synaptic plasticity.
A developmental conundrum
Authors: DasGupta Ramanuj , Rhee Horace , Fuchs Elaine
Published: July 2002

Wnt signaling orchestrates morphogenetic processes in which changes in gene expression are associated with dramatic changes in cell organization within developing tissue/organss. Upon signaling, excess β-catenin not utilized at cell–cell junctions becomes stabilized, where it can provide the transcriptional activating domain for Lef/Tcf DNA binding proteins. In skin epithelium, forced stabilization of β-catenin in epidermis promotes hair follicle morphogenesis, whereas conditional removal of β-catenin in hair progenitor cells specifies an epidermal fate. We now report that a single protein, a stabilized version of β-catenin lacking the COOH-terminal transactivation domain, acts in epidermis to promote hair fates and in hair cells to promote epidermal fate. This reveals fundamental differences in ways that epidermal and hair cells naturally respond to β-catenin signaling. In exploring the phenotype, we uncovered mechanistic insights into the complexities of Lef1/Tcf/β-catenin signaling. Importantly, how a cell will respond to the transgene product, where it will be localized, and whether it can lead to activation of endogenous β-catenin/Tcf/Lef complexes is specifically tailored to skin stem cells, their particular lineage and their relative stage of differentiation. Finally, by varying the level of β-catenin signaling during a cell fate program, the skin cell appears to be pliable, switching fates multiple times.
Degeneracy of Antigen Recognition as the Molecular Basis for the High Frequency of Naive A2/Melan-A Peptide Multimer+ CD8+ T Cells in Humans
Authors: Dutoit Valérie , Rubio-Godoy Verena , Pittet Mikäel J. , Zippelius Alfred , Dietrich Pierre-Yves , Legal Frédérique Anne , Guillaume Philippe , Romero Pedro , Cerottini Jean-Charles , Houghten Richard A. , Pinilla Clemencia , Valmori Danila
Published: July 2002

In contrast with the low frequency of most single epitope reactive T cells in the preimmune repertoire, up to 1 of 1,000 naive CD8+ T cells from A2+ individuals specifically bind fluorescent A2/peptide multimers incorporating the A27L analogue of the immunodominant 26–35 peptide from the melanocyte differentiation and melanoma associated antigen Melan-A. This represents the only naive antigen-specific T cell repertoire accessible to direct analysis in humans up to date. To get insight into the molecular basis for the selection and maintenance of such an abundant repertoire, we analyzed the functional diversity of T cells composing this repertoire ex vivo at the clonal level. Surprisingly, we found a significant proportion of multimer+ clonotypes that failed to recognize both Melan-A analogue and parental peptides in a functional assay but efficiently recognized peptides from proteins of self- or pathogen origin selected for their potential functional cross-reactivity with Melan-A. Consistent with these data, multimers incorporating some of the most frequently recognized peptides specifically stained a proportion of naive CD8+ T cells similar to that observed with Melan-A multimers. Altogether these results indicate that the high frequency of Melan-A multimer+ T cells can be explained by the existence of largely cross-reactive subsets of naive CD8+ T cells displaying multiple specificities.
CD4+CD25+ Regulatory T Cells Can Mediate Suppressor Function in the Absence of Transforming Growth Factor β1 Production and Responsiveness
Authors: Piccirillo Ciriaco A. , Letterio John J. , Thornton Angela M. , McHugh Rebecca S. , Mamura Mizuko , Mizuhara Hidekazu , Shevach Ethan M.
Published: July 2002

CD4+CD25+ regulatory T cells inhibit organ-specific autoimmune diseases induced by CD4+CD25−T cells and are potent suppressors of T cell activation in vitro. Their mechanism of suppression remains unknown, but most in vitro studies suggest that it is cell contact–dependent and cytokine independent. The role of TGF-β1 in CD4+CD25+ suppressor function remains unclear. While most studies have failed to reverse suppression with anti–transforming growth factor (TGF)-β1 in vitro, one recent study has reported that CD4+CD25+ T cells express cell surface TGF-β1 and that suppression can be completely abrogated by high concentrations of anti–TGF-β suggesting that cell-associated TGF-β1 was the primary effector of CD4+CD25+-mediated suppression. Here, we have reevaluated the role of TGF-β1 in CD4+CD25+-mediated suppression. Neutralization of TGF-β1 with either monoclonal antibody (mAb) or soluble TGF-βRII-Fc did not reverse in vitro suppression mediated by resting or activated CD4+CD25+ T cells. Responder T cells from Smad3−/− or dominant-negative TGF-β type RII transgenic (DNRIITg) mice, that are both unresponsive to TGF-β1–induced growth arrest, were as susceptible to CD4+CD25+-mediated suppression as T cells from wild-type mice. Furthermore, CD4+CD25+ T cells from neonatal TGF-β1−/− mice were as suppressive as CD4+CD25+ from TGF-β1+/+ mice. Collectively, these results demonstrate that CD4+CD25+ suppressor function can occur independently of TGF-β1.
Tail End of the S6 Segment
Authors: Ding Shinghua , Horn Richard
Published: July 2002

The permeation pathway in voltage-gated potassium channels has narrow constrictions at both the extracellular and intracellular ends. These constrictions might limit the flux of cations from one side of the membrane to the other. The extracellular constriction is the selectivity filter, whereas the intracellular bundle crossing is proposed to act as the activation gate that opens in response to a depolarization. This four-helix bundle crossing is composed of S6 transmembrane segments, one contributed by each subunit. Here, we explore the cytoplasmic extension of the S6 transmembrane segment of Shaker potassium channels, just downstream from the bundle crossing. We substituted cysteine for each residue from N482 to T489 and determined the amplitudes of single channel currents and maximum open probability (Po,max) at depolarized voltages using nonstationary noise analysis. One mutant, F484C, significantly reduces Po,max, whereas Y483C, F484C, and most notably Y485C, reduce single channel conductance (γ). Mutations of residue Y485 have no effect on the Rb+/K+ selectivity, suggesting a local effect on γ rather than an allosteric effect on the selectivity filter. Y485 mutations also reduce pore block by tetrabutylammonium, apparently by increasing the energy barrier for blocker movement through the open activation gate. Replacing Rb+ ions for K+ ions reduces the amplitude of single channel currents and makes γ insensitive to mutations of Y485. These results suggest that Rb+ ions increase an extracellular energy barrier, presumably at the selectivity filter, thus making it rate limiting for flux of permeant ions. These results indicate that S6T residues have an influence on the conformation of the open activation gate, reflected in both the stability of the open state and the energy barriers it presents to ions.