bluuebunny/crossref_metadata_2025 huggingface dataset:
Ethnic Differences in Predictors of Support for Municipal Affirmative Action Contracting*
Authors: Klineberg Stephen L. , Kravitz David A.
Published: May 2003

Objective. This study explores attitudes toward municipal affirmative action contracting among Anglos, African Americans, and Hispanics, testing predictors of support separately for each group and measuring changes over time.

Methods. In five successive annual Houston‐area surveys, U.S.‐born Anglos, African Americans, Hispanics, and Hispanic immigrants evaluated a strong version of the city's affirmative action contracting program.

Results. Ethnic contrasts in support were partly mediated by differences on the predictors. The predictors of affirmative action attitudes varied greatly by ethnic group. Changes in support across the five years appeared to be associated with the 1997 campaign surrounding the effort to end the city's affirmative action program, and with subsequent policy modifications.

Conclusions. The ethnic divisions and the recent increases among all groups in support for the city's program underscore the value of crafting carefully targeted and flexible policies that are perceived to be responding only to documented disadvantage.
Does Ethnicity Matter? Descriptive Representation in Legislatures and Political Alienation Among Latinos*
Authors: Pantoja Adrian D. , Segura Gary M.
Published: May 2003

Objective. This article uses a political empowerment approach to explore the effect that descriptive representation in legislatures has on levels of political alienation among Latinos.

Methods. Using data from the 1997 Tomás Rivera Policy Institute post‐election survey carried out in California and Texas, supplemented with data on the ethnicity of legislators serving each respondent, we test this political empowerment thesis.

Results. The presence of Latino representatives in the state assembly, state senate, and/or U.S. House is associated with lower levels of political alienation among Latino constituents. The effect is modest, and we find that other factors—demographic, political, and ethnic‐specific—also exert powerful influences on levels of political alienation among Latinos.

Conclusions. Although finding modest evidence for the political empowerment thesis, descriptive representation alone is not a panacea for creating politically engaged personas among Latinos.
HOW CELLS AVOID ERRORS IN METABOLIC AND SIGNALING NETWORKS
Authors: MITTENTHAL JAY , CLARKE BERTRAND , SCHEELINE ALEXANDER
Published: May 2003

We examine features of intracellular networks that make errors less probable and beneficial responses more probable. In a false negative (F-) error, a network does not respond to input. A network is reliable if it operates with a low probability of a F-error. Features that promote reliability include fewer reactions in sequence, more alternative pathways, no side reactions and negative feedback. In a false positive (F+) error, a network produces output without input. Here, a network is specific if it has a low probability of a F+error. Conjunctions of signals within or between pathways can improve specificity through sigmoid steady-state response curves, kinetic proofreading and checkpoints. Both reliability and specificity are important in networks that regulate the fate of a cell and in networks with hubs or modules, and this includes scale-free networks. Some networks discriminate among several inputs by responding to each input through a different combination of pathways.
ON MAGNETOCONDUCTIVITY OF METALLIC MANGANITE PHASES AND HETEROSTRUCTURES
Authors: DZERO M. , GOR'KOV L. P. , KRESIN V. Z.
Published: May 2003

We use the double exchange (DE) model via degenerate orbitals and tight-binding approximation to study the magnetoconductivity of a canted A-phase of pseudo-cubic manganites. It is argued that the model is applicable in a broad concentration range for manganites A 1 - x B x MnO 3 with the tolerance factor t close to one. As for the substitutional disorder, scattering on random Jahn–Teller distortions of MnO 6 octahedra is chosen. We emphasize an intimate correlation between the carrier concentration and resistivity value of metallic manganites. Magnetoresistance as a function of magnetization is calculated for a canted A-phase for both in-plane and out-of-plane current directions. A contact between two manganite phases is considered and structure of the transition region near the contact is discussed. Numerical calculations show charge re-distribution near the contact and a large screening length of the order of five inter-atomic distances. We employed our results to interpret data obtained in recent experiments on La 0.4 Sr 0.6 MnO 3/ La 0.55 Sr 0.45 MnO 3 superlattices. We also briefly discuss the relative importance of the cooperative Jahn–Teller distortions, double exchange mechanism and super-exchange interactions for the formation of the A-phase at increasing Sr concentrations x > 0.45 in La 1 - x Sr x MnO 3 which suggest that the Jahn–Teller contraction of octahedra, c/a < 1, plays a prevailing role.
RENORMALIZATION-GROUP APPROACH TO THE STOCHASTIC NAVIER–STOKES EQUATION: TWO-LOOP APPROXIMATION
Authors: ADZHEMYAN L. Ts. , ANTONOV N. V. , KOMPANIETS M. V. , VASIL'EV A. N.
Published: May 2003

The field theoretic renormalization group is applied to the stochastic Navier–Stokes equation that describes fully developed fluid turbulence in d > 2 dimensions. For the first time, the complete two-loop calculation of the renormalization constant, the β function, the fixed point and the ultraviolet correction exponent is performed. The Kolmogorov constant and the inertial-range skewness factor are expressed in terms of universal (in the sense of the theory of critical behavior) quantities, which allows one to construct for them a regular perturbative calculational scheme. The practical calculations are performed up to the second order of the ε-expansion (two-loop approximation). The results obtained are in a good agreement with the experiment. The large d behavior of these quantities is briefly discussed. The possibility of the extrapolation of the ε-expansion beyond the threshold where the sweeping effects become important is demonstrated by the example of a Galilean-invariant quantity, the equal-time pair correlation function of the velocity field.
OPTIMAL LISTING POLICY FOR IPOs IN THE GERMAN FINANCIAL MARKET
Authors: ECKERT MANFRED
Published: May 2003

Using an existing theoretical model, we investigate a firm's decision to go public empirically. In other words, should their shares be listed on either the 1st Market Segment, or on the Neuer Markt Segment (modelled on NASDAQ) of the Frankfurt Stock Exchange, provided the fact, that the listing requirements for both market segments are fulfilled is the major question of this paper.

A binary choice model (the so-called dichotomous Probit-model) is used, i.e., a regression on a dummy dependent variable will be conducted, using also a mixture of qualitative and quantitative explanatory variables describing the particular market best, to test for German circumstances and conclusions are drawn.
PARAMETER DEFINABILITY IN THE RECURSIVELY ENUMERABLE DEGREES
Authors: NIES ANDRÉ
Published: May 2003

The biinterpretability conjecture for the r.e. degrees asks whether, for each sufficiently large k, the [Formula: see text] relations on the r.e. degrees are uniformly definable from parameters. We solve a weaker version: for each k ≥ 7, the [Formula: see text] relations bounded from below by a nonzero degree are uniformly definable. As applications, we show that Low1is parameter definable, and we provide methods that lead to a new example of a ∅-definable ideal. Moreover, we prove that automorphisms restricted to intervals [d, 1], d ≠ 0, are [Formula: see text]. We also show that, for each c ≠ 0, (ℕ, +, ×) can be interpreted in [0, c] without parameters.
The Process of Conscientization: Xicanas/Xicanos Experiences in Claiming Authentic Voice
Authors: Berta-Ávila Margarita
Published: May 2003

This article is a theoretical piece that reflects on the process many Xicanas/Xicanos undergo to break their silence and claim authentic voice. Based on the work of Paulo Freire, the theory of conscientization, which embodies the tenets of reflection, dialogue, and transformation, is used as an alternative framework to conceptualize this experience. When Xicanas/Xicanos name, reflect, and dialogue about their realities, this process becomes one way to counteract oppressive practices and create transformation.
Insights Into Biliteracy Development: Toward a Bidirectional Theory of Bilingual Pedagogy
Authors: Dworin Joel E.
Published: May 2003

Insights into English-Spanish biliteracy development among elementary school students are discussed. The term biliteracy describes children’s literate competencies in two languages, to whatever degree, developed either simultaneously or successively. The main focus is on several recent theoretical perspectives on biliteracy and their relevance for the development of a bilingual pedagogy. Three main aspects of literacy and bilingualism that question some widely held views of language learning and biliteracy development are addressed.
Pax5 determines B- versus T-cell fate and does not block early myeloid-lineage development
Authors: Cotta Claudiu V. , Zhang Zheng , Kim Hyung-Gyoon , Klug Christopher A.
Published: May 2003

Progenitor B cells deficient in Pax5 are developmentally multipotent, suggesting that Pax5 is necessary to maintain commitment to the B-cell lineage. Commitment may be mediated, in part, by Pax5 repression of myeloid-specific genes. To determine whether Pax5 expression in multipotential cells is sufficient to restrict development to the B-cell lineage in vivo, we enforced expression of Pax5 in hematopoietic stem cells using a retroviral vector. Peripheral blood analysis of all animals reconstituted with Pax5-expressing cells indicated that more than 90% of Pax5-expressing cells were B220+ mature B cells that were not malignant. Further analysis showed that Pax5 completely blocked T-lineage development in the thymus but did not inhibit myelopoiesis or natural killer (NK) cell development in bone marrow. These results implicate Pax5 as a critical regulator of B- versus T-cell developmental fate and suggest that Pax5 may promote commitment to the B-cell lineage by mechanisms that are independent of myeloid gene repression.
Analytical evaluation of thermally induced residual stresses in ground components
Authors: Walsh D G , Torrance A A , Tiberg J
Published: May 2003

Although thermally induced tensile residual stresses have been known to occur in ground components, it has not been possible to predict the critical temperature at which these stresses begin to manifest themselves in the workpiece. In this paper, a model of the formation of thermally induced tensile residual stresses is proposed and a simple method of calculating the critical temperature above which tensile residual stresses occur is developed. The analysis makes use of dimensional methods to characterize the critical temperature. In addition, a formula characterizing the yield strength as a function of temperature was developed. The model was then validated using finite element techniques and some experimental data. The analysis reveals that it is possible to determine the critical temperature above which tensile residual stresses will be manifested based on readily available material properties. A case study illustrates the application of the technique.
Finite element analysis of cyclic indentation of an elastic-perfectly plastic half-space by a rigid sphere
Authors: Yan S L , Li L Y
Published: May 2003

This paper presents a numerical study on the cyclic indentation of an elastic-perfectly plastic half-space by a rigid sphere. The study is performed using non-linear finite element methods. Results of contact pressure distribution, relationships between contact force, displacement and contact radius during loading, unloading and reloading are presented. The results show that the deformation during unloading from a contact beyond the elastic limit is perfectly elastic. However, the pressure distribution returns to the Hertzian elliptical distribution only when the maximum pressure at the contact centre is below 1.6αy. The reloading curve is found to be exactly the same as the unloading curve and the pressure distributions in reloading and unloading are the same for the same contact force. The influence of the plastic permanent deformation and residual stresses on the contact behaviour during reloading is discussed.
Kinematic and dynamic equations of a planar parallel manipulator
Authors: Wang L-P , Wang J-S , Li Y-W , Lu Y
Published: May 2003

This paper presents an inverse dynamic formulation using the Newton-Euler approach for a planar parallel manipulator, which is used in a new five-axis hybrid machine tool. The inverse kinematics of the manipulator is given and the velocity and the acceleration formulae are derived. The driving forces acting on the legs are determined according to the dynamic formulation. The formulation has been implemented in a program and has been used for some typical trajectories planned for a numerical simulation experiment. The simulation results reveal the nature of the variation of the driving forces in the hybrid machine tool and justify the dynamic control model. The dynamic modelling approach presented in this paper can also be applied to other parallel manipulators with less than six degrees of freedom.
On the occurrence of the T-loop RNA folding motif in large RNA molecules
Authors: KRASILNIKOV ANDREY S. , MONDRAGÓN ALFONSO
Published: May 2003

The T-loop RNA folding motif may be considered as a five-nucleotide motif composed of a U-turn flanked by a noncanonical base pair. It was recently proposed that the flanking noncanonical base pair is always a UA trans Watson-Crick/Hoogsteen base pair stacked on a Watson-Crick base pair on one side. Here we show that structural analysis of several large RNA molecules, including the recently solved crystal structure of the specificity domain of Bacillus subtilis RNase P, combined with sequence analysis, indicates a broader sequence consensus for the motif. Additionally, we show that the flanking base pair does not necessarily stack on a Watson-Crick base pair and the 3′ terminus of the five-nucleotide motif is often followed by a sharp turn in the phosphate backbone rather than just a bulged base or bases.
Substrate specificity and reaction kinetics of an X-motif ribozyme
Authors: LAZAREV DENIS , PUSKARZ IZABELA , BREAKER RONALD R.
Published: May 2003

The X-motif is an in vitro-selected ribozyme that catalyzes RNA cleavage by an internal phosphoester transfer reaction. This ribozyme class is distinguished by the fact that it emerged as the dominant clone among at least 12 different classes of ribozymes when in vitro selection was conducted to favor the isolation of high-speed catalysts. We have examined the structural and kinetic properties of the X-motif in order to provide a framework for its application as an RNA-cleaving agent and to explore how this ribozyme catalyzes phosphoester transfer with a predicted rate constant that is similar to those exhibited by the four natural self-cleaving ribozymes. The secondary structure of the X-motif includes four stem elements that form a central unpaired junction. In a bimolecular format, two of these base-paired arms define the substrate specificity of the ribozyme and can be changed to target different RNAs for cleavage. The requirements for nucleotide identity at the cleavage site are GD, where D = G, A, or U and cleavage occurs between the two nucleotides. The ribozyme has an absolute requirement for a divalent cation cofactor and exhibits kinetic behavior that is consistent with the obligate binding of at least two metal ions.
The effect of nonsense codons on splicing: A genomic analysis: FIGURE 1.
Authors: ZHANG XIANG , LEE JAMES , CHASIN LAWRENCE A.
Published: May 2003

The phenomenon of nonsense-associated altered splicing raises the possibility that the recognition of in-frame nonsense codons is used generally for exon identification during pre-mRNA splicing. However, nonsense codon frequencies in pseudo exons and in regions flanking 5′ splice sites are no greater than that expected by chance, arguing against the widespread use of this strategy as a means of rejecting potential splice sites.
The interaction of the cap-binding complex (CBC) with eIF4G is dispensable for translation in yeast
Authors: BARON-BENHAMOU JULIE , FORTES PURI , INADA TOSHIFUMI , PREISS THOMAS , HENTZE MATTHIAS W.
Published: May 2003

In eukaryotes, the m7GpppN cap structure is added to all nascent RNA polymerase II transcripts, and serves important functions at multiple steps of RNA metabolism. The predominantly nuclear cap-binding complex (CBC) binds to the cap during RNA synthesis. The predominantly cytoplasmic eukaryotic initiation factor 4F (eIF4F) is thought to replace CBC after export of mature mRNA to the cytoplasm, and mediates the bulk of cellular translation. Yeast as well as mammalian CBC interacts in vitro with eIF4G, a subunit of eIF4F. In this work, we investigate a potential role of this interaction during translation in yeast. We identify a mutation (DR548/9AA) in Tif4631p, one of two isoforms of yeast eIF4G, that abolishes its binding to CBC. Cells expressing this mutant protein as the sole source of eIF4G grow at wild-type rates, and bulk cellular translation, as assessed by metabolic labeling and polysome profile analysis, is unchanged. Importantly, we find that the DR548/9AA mutation neither diminishes nor delays the translation of newly induced reporter mRNA. Finally, microarray analysis reveals marked transcriptome alterations in CBC subunit deletion strains, whereas eIF4G point mutants have essentially a wild-type transcriptome composition. Collectively, these data suggest that in yeast, the phenotypic consequences of CBC deletions are separable from its interaction with eIF4G, and that the CBC–eIF4G interaction is dispensable for a potential “pioneering round” of translation in yeast.
Causal uncertainty, claimed and behavioural self‐handicapping
Authors: Thompson Ted , Hepburn Jonathan
Published: May 2003

Background: Causal uncertainty beliefs involve doubts about the causes of events, and arise as a consequence of non‐contingent evaluative feedback: feedback that leaves the individual uncertain about the causes of his or her achievement outcomes. Individuals high in causal uncertainty are frequently unable to confidently attribute their achievement outcomes, experience anxiety in achievement situations and as a consequence are likely to engage in self‐handicapping behaviour.

Aims: Accordingly, we sought to establish links between trait causal uncertainty, claimed and behavioural self‐handicapping.

Sample: Participants were N=72 undergraduate students divided equally between high and low causally uncertain groups.

Method: We used a 2 (causal uncertainty status: high, low) × 3 (performance feedback condition: success, non‐contingent success, non‐contingent failure) between‐subjects factorial design to examine the effects of causal uncertainty on achievement behaviour. Following performance feedback, participants completed 20 single‐solution anagrams and 12 remote associate tasks serving as performance measures, and 16 unicursal tasks to assess practice effort. Participants also completed measures of claimed handicaps, state anxiety and attributions.

Results: Relative to low causally uncertain participants, high causally uncertain participants claimed more handicaps prior to performance on the anagrams and remote associates, reported higher anxiety, attributed their failure to internal, stable factors, and reduced practice effort on the unicursal tasks, evident in fewer unicursal tasks solved.

Conclusions: These findings confirm links between trait causal uncertainty and claimed and behavioural self‐handicapping, highlighting the need for educators to facilitate means by which students can achieve surety in the manner in which they attribute the causes of their achievement outcomes.
Advances in Microporous and Mesoporous Solids—Highlights of Recent Progress
Authors: Stein A.
Published: May 2003

This report highlights developments in the fields of microporous and mesoporous materials that were published mostly during the year 2002. Selected examples are provided to illustrate new zeolite structures, porous coordination materials, mesoporous solids with new compositions, controlled morphologies, and increased hydrothermal and thermal stabilities, as well as porous solids with tunable pore openings or other structural features that can be dynamically modified. A number of applications are discussed, including stabilization of reactive guests, separations, electronic materials, and sensors.
Low Molecular Weight Gelators with Hexagonal Order in Their Liquid‐Crystal Phases and Gel States: 5‐Cyano‐2‐(3,4,5‐trialkoxybenzoylamino)tropones
Authors: Hashimoto M. , Ujiie S. , Mori A.
Published: May 2003

5‐Cyano‐2‐(3,4,5‐trialkoxybenzoylamino)tropones form hexagonal structures in both liquid‐crystalline and gel states. The Figure shows an environmental scanning electron microscopy image of octanol gels. Hydrogen bonding between the tropone carbonyl group and the NH group of troponoid amides plays an important role in flattening the molecules, allowing tighter packing structures and more stable columnar mesophases and gel states.
Organic Light‐Emitting Devices Fabricated from Semiconducting Nanospheres
Authors: Piok T. , Gamerith S. , Gadermaier C. , Plank H. , Wenzl F.P. , Patil S. , Montenegro R. , Kietzke T. , Neher D. , Scherf U. , Landfester K. , List E.J.W.
Published: May 2003

The fabrication of organic light‐emitting devices(OLEDs) from semiconducting polymer nanospheres (SPNs) deposited from aqueous dispersions is described. It is found that the active device layer consists of a homogeneous single layer of light‐emitting SPNs. The OLEDs exhibit an electroluminescence onset at the SPN energy gap, which can be attributed to field‐enhanced charge‐carrier injection at the nanostructured Al cathode.
High‐Density, Ordered Ultraviolet Light‐Emitting ZnO Nanowire Arrays
Authors: Liu C.H. , Zapien J.A. , Yao Y. , Meng X.M. , Lee C.S. , Fan S.S. , Lifshitz Y. , Lee S.T.
Published: May 2003

Polycrystalline ZnO nanowires have been grown in anodic aluminum oxide templates using a dry vapor‐deposition method. The nanowires have a high aspect ratio and a uniform density of 1010–1011 cm–2 over a large area (∼ 20 mm2). Room‐temperature photoluminescence measurements show lasing modes between 381 and 389 nm above a threshold power density of 100 kW/cm2 (see Figure).
Benchtop Fabrication of Submicrometer Metal Line and Island Arrays Using Passivative Microcontact Printing and Electroless Plating
Authors: Moran C.E. , Radloff C. , Halas N.J.
Published: May 2003

An entirely benchtop method of fabricating long‐range, planar arrays of discrete metal structures on glass or SiO2/Si surfaces without the use of e‐beam or photolithography, resist masks, or chemical etching is reported. This approach combines microcontact printing and directed electroless plating for the controlled deposition of islands or lines of gold or silver. The Figure shows gold lines ca. 50 nm in height deposited on a pre‐patterned glass surface.
On the Replication of Block Copolymer Templates by Poly(dimethylsiloxane) Elastomers
Authors: Kim D.H. , Lin Z. , Kim H.‐C. , Jeong U. , Russell T.P.
Published: May 2003

Both positive and negative replicas of copolymer arrays are produced using crosslinked poly(dimethylsiloxane). Negative replicas of the nanoscopic features are manufactued by entrapping air within the microdomains. Positive replicas are produced with ∼ 1:1 aspect ratios by the PDMS filling the nanoscopic, cylincrical cavities. The Figure shows an AFM image of a negative replica (size: 2 μm × 2 μm, inset: Fourier transform of image).
Mining longitudinal web queries: Trends and patterns
Authors: Wang Peiling , Berry Michael W. , Yang Yiheng
Published: May 2003

This project analyzed 541,920 user queries submitted to and executed in an academic Website during a four‐year period (May 1997 to May 2001) using a relational database. The purpose of the study is three‐fold: (1) to understand Web users' query behavior; (2) to identify problems encountered by these Web users; (3) to develop appropriate techniques for optimization of query analysis and mining. The linguistic analyses focus on query structures, lexicon, and word associations using statistical measures such as Zipf distribution and mutual information. A data model with finest granularity is used for data storage and iterative analyses. Patterns and trends of querying behavior are identified and compared with previous studies.
Graph structure in three national academic Webs: Power laws with anomalies
Authors: Thelwall Mike , Wilkinson David
Published: May 2003

The graph structures of three national university publicly indexable Webs from Australia, New Zealand, and the UK were analyzed. Strong scale‐free regularities for page indegrees, outdegrees, and connected component sizes were in evidence, resulting in power laws similar to those previously identified for individual university Web sites and for the AltaVista‐indexed Web. Anomalies were also discovered in most distributions and were tracked down to root causes. As a result, resource driven Web sites and automatically generated pages were identified as representing a significant break from the assumptions of previous power law models. It follows that attempts to track average Web linking behavior would benefit from using techniques to minimize or eliminate the impact of such anomalies.
Information science abstracts: Tracking the literature of information science. Part 2: A new taxonomy for information science
Authors: Hawkins Donald T. , Larson Signe E. , Caton Bari Q.
Published: May 2003

Subject classifications and thesauri have become more important than ever in the Web environment. Efforts made to organize information into subject classifications, or taxonomies, offer users the opportunity to substantially improve the effectiveness of their search and retrieval activities. This article continues earlier research on the development of a new definition of the field of information science and the creation of a “map” of the field showing subjects central to it and their relationships to those on the periphery. A case study describes the creation of a new classification structure (taxonomy) for the Information Science Abstracts (ISA) database, aiming to reflect and accommodate the rapid and continued technological and market changes affecting the information industry today and into the future. Based on a sample of some 3,000 ISA abstracts, two validation experiments were conducted by a three‐member team comprising a database editor, a reference librarian, and an abstractor‐indexer, who represent three of the major communities within the information science field. In the first experiment, the sample of abstracts was classified according to the proposed new taxonomy; after analysis of the data and revision of the taxonomy, it was revalidated and fine tuned in a second experiment. Indexer consistency measures obtained in this study were significantly higher than those found in previous studies. The taxonomy resulting from this research employs the concepts, definition, and map of information science previously developed. It presents them in an organized hierarchical view of the field and thus makes a significant contribution to information science.
Expression of the Kv1.1 ion channel subunit in the auditory brainstem of the big brown bat, Eptesicus fuscus
Authors: Rosenberger Melissa H. , Fremouw Thane , Casseday John H. , Covey Ellen
Published: May 2003

Voltage‐gated potassium channels play an important role in shaping membrane properties that underlie neurons' discharge patterns and the ways in which they transform their input. In the auditory system, low threshold potassium currents such as those created by Kv1.1 subunits contribute to precise phaselocking and to transient onset responses that provide time markers for temporal features of sounds. The purpose of the present study was to compare information about the distribution of neurons expressing the KV 1.1 in the brainstem auditory nuclei with the distribution of neurons with known functional properties in the auditory system of the big brown bat, Eptesicus fuscus. We used immunocytochemistry and light microscopy to look at the distribution of Kv1.1 subunits in the brainstem auditory nuclei. There was prominent expression in cell types known to contain high levels of Kv1.1 in other species and known to respond to auditory signals with high temporal precision. These included octopus cells and spherical bushy cells of the cochlear nucleus and principal neurons of the medial nucleus of the trapezoid body. In addition, we found high levels of Kv1.1 in neurons of the columnar subdivision of the ventral nucleus of the lateral lemniscus and in ventral periolivary cell groups. Neurons with high levels of Kv1.1 were differentially distributed in the intermediate nucleus of the lateral lemniscus and in the inferior colliculus, suggesting that these structures contain functionally distinct cell populations, some of which may be involved in high‐precision temporal processing. J. Comp. Neurol. 462:101–120, 2003. © 2003 Wiley‐Liss, Inc.
Dual mechanisms governing muscle cell death in tadpole tail during amphibian metamorphosis
Authors: Nakajima Keisuke , Yaoita Yoshio
Published: May 2003

The tadpole tail, which is twice as long as the body, is induced to resorb completely by thyroid hormone within several days during the anuran metamorphosis. To investigate the underlying mechanism, we undertook two approaches. First, we examined the effect of dominant‐negative thyroid hormone receptor (DNTR) on muscle cell death in vitro. The overexpression of DNTR suppressed the death of a tail‐derived myoblastic cell line induced by thyroid hormone. Second, tadpole tails were injected with a reporter gene and the DNTR expression construct, and the reporter gene expression in muscle cells was followed during the spontaneous metamorphosis. DNTR overexpression inhibited a decrease of the reporter gene expression that began at stage 57 in the control tadpoles but only delayed massive muscle cell death at stage 63 when tails shrink very rapidly. Some remained even a few weeks after the metamorphosis, although most DNTR‐overexpressing cells died by the end of the metamorphosis. These results led us to propose that thyroid hormone induces the suicide of muscle cells (the cell‐autonomous death) in the tail between stage 57 and 62 and that both the murder and suicide mechanisms execute muscle cell death in stage 62–64 to remove muscle promptly and completely. Developmental Dynamics 227:246–255, 2003. © 2003 Wiley‐Liss, Inc.
Platelet‐derived growth factor signaling as a cue of the epithelial–mesenchymal interaction required for anuran skin metamorphosis
Authors: Utoh Rie , Shigenaga Sachi , Watanabe Yusuke , Yoshizato Katsutoshi
Published: May 2003

The anuran remodels the larval skin into the adult counterpart during metamorphosis. The construction of the precursor of adult epidermis (preadult epidermis) in Xenopus laevis larvae was coordinated with the development of the secondary connective tissue (s‐ct) underneath the basement membrane, suggesting that the epithelial–mesenchymal interaction plays a critical role in the metamorphic conversion of the larval skin. mRNAs of platelet‐derived growth factor A (PDGF‐A) and PDGF receptor (PDGFR) ‐α were markedly up‐regulated in the skin during spontaneous and thyroid hormone (TH) ‐induced metamorphosis. In situ hybridization experiments identified preadult epidermal basal cells and fibroblasts in developing subepidermal connective tissues at the late prometamorphic stage as PDGF‐A and PDGFR‐α mRNA‐expressing cells, respectively. We developed an in vitro model of larval skin that was remodeled to the adult skin under the influence of TH. The presence of either of AG1296, a specific inhibitor of PDGFR tyrosine kinase autophosphorylation, or an excess of recombinant proteins of the soluble extracellular domain of PDGFR‐α inhibited the following TH‐induced processes, the proliferation of adult basal cells, the terminal differentiation of adult basal cells, and the activation of subepidermal fibroblasts. However, the inhibitors did not inhibit the TH‐induced proliferation of preadult basal cells. We concluded that PDGF/PDGFR signaling is one of the prime cues in the epithelial‐mesenchymal interaction required for the metamorphic skin remodeling. Developmental Dynamics 227:157–169, 2003. © 2003 Wiley‐Liss, Inc.
Phenotype of the zebrafish masterblind (mbl) mutant is dependent on genetic background
Authors: Sanders L.H. , Whitlock K.E.
Published: May 2003

The zebrafish masterblind (mbl) mutant is characterized by the lack of olfactory placodes and optic vesicles, reduced telencephalon, an expanded epiphysis (Heisenberg et al. [1996] Development 123:191–203), and enlarged jaw. To understand the cellular events giving rise to the olfactory placode defect of this mutant, we examined the expression pattern of the distal‐less‐3 (dlx3) gene in mbl. In the mutant, dlx3, which is normally expressed in the developing nose and ear, showed reduced expression in the olfactory placode field, but normal expression in the developing ear. To determine whether the loss of dlx3 expression was due to cell loss, we assayed cell death by using TUNEL labeling. Although cell death in the mutant was not concentrated in the region of dlx3 expression, there was increased cell death in the forebrain, epiphysis, and jaw region, as compared with that in wild‐type controls. This cell death phenotype was cyclical in nature, showing an increase and decrease in cell death on a roughly 24‐hr cycle. Further analysis showed that this cyclical phenotype was specific to the genetic background. The severity of the mbl phenotype, including cell death, expanded epiphysis, and enlarged jaw, decreased when the mutation was moved from the original “TL” background to the “AB” background. Thus, the severity of developmental defects in the mbl mutant is strongly dependent on genetic background. We examined the contribution of cell death to the morphologic defects of mbl by blocking cell death by using zVADfmk, a known caspase inhibitor. We found that this treatment partially rescued the expanded jaw defect and that this rescue was dependent on the genetic background. Therefore, the mbl mutant phenotypes result, in part, from genetic background effects that alter the pattern of programmed cell death early in development. Developmental Dynamics 227:291–300, 2003. © 2003 Wiley‐Liss, Inc.
EGF‐stimulated signaling by means of PI3K, PLCγ1, and PKC isozymes regulates branching morphogenesis of the fetal mouse submandibular gland
Authors: Koyama Noriko , Kashimata Masanori , Sakashita Hideaki , Sakagami Hiroshi , Gresik Edward W.
Published: May 2003

Branching morphogenesis of fetal mouse submandibular glands (SMGs) partly depends on the epidermal growth factor (EGF) receptor that triggers at least three intracellular signaling pathways involving (1) the mitogen‐activated protein kinases ERK‐1/2, (2) phospholipase Cγ1 (PLCγ1), and (3) phosphatidylinositol‐3‐kinase (PI3K). PLCγ1 directly activates protein kinase C (PKC) isozymes; PI3K stimulates protein kinase B (PKB, also known as Akt), which ultimately activates PKCs and other proteins. We reported that the pattern of phosphorylation of ERK‐1/2 in response to EGF in SMGs varies with fetal age and that blockade of EGF‐stimulated ERK‐1/2 signaling partially inhibits branching (Kashimata et al. [2000] Dev. Biol. 220:183–196). Here, we report on components of the PLCγ1, PI3K, and PKC families of signaling molecules in fetal SMGs from the 13th day of gestation to postnatal ages. Western blotting revealed that (1) PLCγ1 is present from E13 to E18 but drops off precipitously to negligible levels on the day of birth and thereafter, and (2) PI3K, PKB(Akt), and several PKC isozymes are expressed from E13 onward through adult life. Both PLCγ1 and PI3K are phosphorylated in response to EGF. Inhibition of PI3K by LY294002 inhibited EGF‐stimulated branching, but inhibition of PLCγ1 by U73122 had no effect. Western blotting showed that the concentrations of 8 PKC isozymes vary with age in the fetal and postnatal SMG. However, general inhibition of PKCs by Calphostin C or specific inhibition of PKCα or of PKCϵ by Gö6976 or Ro‐32‐0432, respectively, increased EGF‐stimulated branching. Calphostin C also increased EGF‐stimulated phosphorylation of ERK‐1/2. These findings indicate that signaling from the EGF receptor in the fetal mouse SMG varies with development and triggers stimulatory effects by means of ERK‐1/2 and PI3K but inhibitory effects by means of PKC isozymes. Developmental Dynamics 227:216–226, 2003. © 2003 Wiley‐Liss, Inc.
Synthesis of 11C‐Labelled Amides by Palladium‐Mediated Carboxamination Using [11C]Carbon Monoxide, in situ Activated Amines and 1,2,2,6,6‐Pentamethylpiperidine
Authors: Karimi Farhad , Langström Bengt
Published: May 2003

Twenty‐seven 11C‐labelled amides were synthesised using [11C]carbon monoxide in low concentrations, palladium(0), organohalides and amines in a small micro‐autoclave (200 μL). The focus of the study was to improve the radiochemical yields in this palladium‐mediated amide synthesis when employing less‐reactive amines, such as methylamine, [(2R)‐1‐ethylpyrrolidin‐2‐yl]methylamine (40) and 2‐(pyridin‐2‐yl)ethanamine (41). The radiochemical yields were improved when utilizing 1,2,2,6,6‐pentamethylpiperidine (pempidine) in combination with the amine substrates. The 11C‐labelled amides were obtained mostly in high radiochemical yields (in the range 16−94%) and the specific radioactivity varied between 650 and 1250 GBq/μmol. 1‐(1,3‐Benzodioxol‐5‐yl[13C]carbonyl)piperidine (6a) was synthesised to verify the labelling position (δ = 169.8 ppm) using 13C NMR spectroscopy. The radiochemical purity of the target compounds was determined by analytical HPLC and exceeded 95%. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
(Aryl)(phosphanyl)Carbene: Ground‐ and Excited‐State Reactions
Authors: Despagnet‐Ayoub Emmanuelle , Gornitzka Heinz , Bourissou Didier , Bertrand Guy
Published: May 2003

Cyclopropanation, carbene coupling, and photolytically induced 1,2‐migration reactions are reported for the stable singlet [bis(diisopropylamino)phosphanyl][o,o′‐bis(trifluoromethyl)phenyl]carbene (1). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
An Efficient Total Synthesis of Pedunculagin by Using a Twofold Intramolecular Double Esterification Strategy
Authors: Khanbabaee Karamali , Großer Mathias
Published: May 2003

The total synthesis of naturally occurring pedunculagin (1) was achieved by the twofold intramolecular double esterification of enantiomerically pure (S)‐hexabenzyloxydiphenic acid (4) with the D‐glucose‐derived sugar 2 as the key step. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Stereoselective Preparation of 10α‐ and 10β‐Aryl Derivatives of Dihydroartemisinin
Authors: Haynes Richard K. , Chan Ho‐Wai , Cheung Man‐Ki , Chung Shuk Ting , Lam Wai‐Lun , Tsang Hing‐Wo , Voerste Arnd , Williams Ian D.
Published: May 2003

Lewis acid‐catalysed arylation of the 10β‐benzoate and, less effectively, the 10α‐benzoate of dihydroartemisinin [DHA] with activated aromatic compounds, including naphthalenes, stereoselectively, provides 10α‐aryl derivatives including disubstituted naphthalene derivatives. 2‐Methoxynaphthalene provides the 1‐, rather than the 3‐substituted derivative. In contrast, 10β‐aryl derivatives are obtained stereoselectively from the 10β‐bromide, generated in situ from trimethylsilyl bromide and the TMS ether of 10α‐DHA, and the corresponding aryl Grignard reagents. The 10α‐aryl compounds are shown by NMR spectroscopy and X‐ray crystallographic analysis to possess a chair pyranose ring with equatorial aryl group, whereas the 10β‐aryl derivatives have a twist‐boat pyranose ring with equatorial aryl group. The stereochemistry of the Lewis acid‐catalysed arylations, which is common to that observed for the Lewis acid‐catalysed arylation of pyranosyl glycosides with axial anomeric leaving groups in general, may be rationalized in terms of axial attack from the α or si face of the half‐chair oxonium ion intermediate. On the other hand, the Grignard reagents activate the axial bromide to elimination through complexation, and thereby the aryl nucleophile attacks the incipient oxonium ion from the β or re face. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
A Binuclear Phthalocyanine Containing Two Different Metals
Authors: Calvete Mario , Hanack Michael
Published: May 2003

The unsymmetrical binuclear phthalocyanine 4a and the symmetrical binuclear phthalocyanine 4b with two different metals (Ni and Cu), as well as the correspondent binuclear phthalocyanines with two Ni atoms (4c and 4d) were synthesized from the benzoannulated dicyano‐substituted Ni phthalocyanine 2. Atomic absorption spectroscopy verified unambiguously the presence of Ni and Cu in the binuclear phthalocyanines. The proposed synthetic route demonstrates great versatility towards substitution at the peripheral positions of the ring and the variation of the chelating central metal. Complexes 4a−4d are soluble in common organic solvents of medium polarity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Gliogenic and neurogenic progenitors of the subventricular zone: Who are they, where did they come from, and where are they going?
Authors: Marshall Christine A.G. , Suzuki Satoshi O. , Goldman James E.
Published: May 2003

The subventricular zone (SVZ) of the perinatal forebrain gives rise to both neurons and glia. The mechanisms governing the phenotypic specification of progenitors within this heterogeneous germinal zone are unclear. However, the characterization of subpopulations of SVZ cells has given us a better understanding of the basic architecture of the SVZ and presents us with the opportunity to ask more detailed questions regarding phenotype specification and cell fate. Recent work demonstrating the embryonic origins of SVZ cells is summarized, and a model describing the formation of the perinatal SVZ, noting contributions of cells from pallial as well as subpallial germinal zones, is presented. We further address differences among classes of SVZ cells based on molecular profile, phenotype, and migration behavior and present a model summarizing the organization of perinatal SVZ cells along coronal, sagittal, and horizontal axes. A detailed description of the SVZ in the adult, outlining classes of cells based on morphology, molecular profile, and proliferative behavior, was recently reported by Doetsch et al. (Proc Natl Acad Sci USA 93:14895–14900, 1997). Potential relationships among cells within the perinatal and adult SVZ will be discussed. GLIA 43:52–61, 2003. © 2003 Wiley‐Liss, Inc.
GFAP: Functional implications gleaned from studies of genetically engineered mice
Authors: Messing Albee , Brenner Michael
Published: May 2003

GFAP is the major intermediate filament of mature astrocytes, and its relatively specific expression in these cells suggests an important function. To study the role of the GFAP gene, mice have been created carrying null alleles (no protein), modified alleles (altered protein), or added wild type alleles (elevated protein). Surprisingly, absence of GFAP has relatively subtle effects on development. On the other hand, over‐expression can be lethal, and led to the discovery that GFAP coding mutations are responsible for most cases of Alexander disease, a devastating neurodegenerative disorder. Here we review what the various GFAP mouse models reveal about GFAP and astrocyte function. GLIA 43:87–90, 2003. © 2003 Wiley‐Liss, Inc.
Precursors of neurons, neuroglia, and ependymal cells in the CNS: What are they? Where are they from? How do they get where they are going?
Authors: Morest D. Kent , Silver Jerry
Published: May 2003

Neurons, neuroglia (astrocytes and oligodendrocytes), and ependymal cells are three distinct categories of neural cells in the central nervous system. In the mature brain and spinal cord, the classical histological criteria define these cells by their microscopic structure very well. During development, the precursors for all of these cells reside within the epithelium of the neural plate and its successor, the neural tube. These precursor cells are the undifferentiated, primitive neuroepithelium of the classical literature. As the cerebral vesicles enlarge and their walls thicken, the primitive neuroepithelial cells elongate, maintaining a radial orientation until they migrate. Although many, but not all, of these cells span the extent of the ventricular wall, they are the precursors of neurons, neuroglia, and ependymal cells. Thus, it is useful to retain their classical designation as primitive neuroepithelial cells and to treat them as neural precursor cells. Neural precursor cells are neither neuroglia nor neurons. It is not appropriate to call them radial glial cells anymore than it is to call them radial neuronal cells. The term “radial glia” has long been used to describe the mature, elongated astrocytes, represented by Bergmann cells in the cerebellum and Müller cells in the retina. Inevitably, during development, transitional forms between neural precursor cells and the neurons, neuroglia, and ependymal cells will occur. Such transitional cells are known as neuroblasts, glioblasts, or ependymoblasts, even though they may be postmitotic. Alternative terms are “immature neurons,” “immature neuroglia,” and “immature ependymal cells.” The migration of many neural precursor cells is accomplished by translocation rather than free cellular locomotion. There is both direct and indirect evidence to document the translocation of the nuclear/perikaryal/somal complex through the leading process of primitive neuroepithelial cells. This is conspicuous in the neocortex, where the discrete radial arrangement of pyramidal cells may result from translocation of neuroblasts, while their leading processes still contact the pial surface. Migration by translocation occurs throughout the CNS. GLIA 43:6–18, 2003. © 2003 Wiley‐Liss, Inc.
Thromboresistance of alkali‐ and heat‐treated titanium metal formed with apatite
Authors: Muramatsu Kazuaki , Uchida Masaki , Kim Hyun‐Min , Fujisawa Akira , Kokubo Tadashi
Published: May 2003

Fibrin deposition and platelet adhesion onto alkali‐ and heat‐treated titanium metal (AH‐Ti), alkali‐ and water‐treated titanium metal (Wa‐Ti), and alkali‐ and heat‐treated titanium metal formed with apatite (Ap‐Ti) in simulated body fluid (SBF) were evaluated by exposure to anticoagulated blood or washed platelet suspension (WPS) under static conditions and subsequent observation with scanning electron microscopy (SEM). The results were compared with those for commercially pure titanium metal (cp‐Ti). Thrombus formation on AH‐Ti and Wa‐Ti, which were exposed to heparinized whole blood for 1 h, was significantly less than that on cp‐Ti, on which pronounced depositions of fibrin‐erythrocytes and lymphocytes were observed. No thrombus was observed on Ap‐Ti, possibly because of a high adsorption of heparin. Morphological change of platelets attached to surfaces via adsorbed plasma proteins was found to a significant extent on AH‐Ti and Wa‐Ti exposed to WPS. However, there was almost no difference between cp‐Ti and Ap‐Ti in round morphology of adherent platelets. These findings suggested that Ap‐Ti exhibits stronger antithrombogenic characteristics than cp‐Ti and other materials examined in heparinized blood. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 65A: 409–416, 2003