bluuebunny/crossref_metadata_2025_split huggingface dataset:
Olig genes are expressed in a heterogeneous population of precursor cells in the developing spinal cord
Authors: Liu Ying , Rao Mahendra S. 
Published: December 2003

AbstractRecent results from multiple laboratories have identified Olig genes as important in regulating glial differentiation. Here we show that Olig2 expression at early stages of development (prior to E16.5) identifies a domain in the developing spinal cord, which contains a heterogeneous population of progenitors that includes stem cells and glial progenitors. We show that Nkx2.2 and Olig2, which are present initially in nonoverlapping domains, are coexpressed at later stages, likely due to a second wave of Olig expression. We find that Olig1, like Olig2, is present in cells that coexpress astrocytic and radial glial markers and that Olig1/2 double knockouts lead to a loss of oligodendrocytes with preservation of NG2 expression. These results coupled with previously published data indicate that Olig1/2 and Nkx2.2, while clearly important in regulating early progenitor cell differentiation, do not unambiguously demonstrate the existence of an oligodendrocyte‐neuron precursor or negate the existing retroviral lineage and clonal analysis data that suggest the existence of other types of precursors such as oligodendrocyte‐astrocyte precursors or neuronal precursors. Published 2003 Wiley‐Liss, Inc.
The 4C5 antigen is associated with Schwann cell migration during development and regeneration of the rat peripheral nervous system
Authors: Yfanti Eleni , Sidera Katerina , Margaritis Lukas H. , Patsavoudi Evangelia 
Published: December 2003

AbstractThe monoclonal antibody 4C5 recognizes a cell surface antigen of the developing central nervous system (CNS) and peripheral nervous system (PNS). In vitro antibody perturbation experiments have shown that the 4C5 antigen is involved in horizontal and vertical migration processes of granule cells during development of the rodent cerebellum. Moreover, results concerning the cellular localization and temporal expression of the 4C5 antigen during development and after injury of the rat sciatic nerve suggested that it may participate in Schwann cell migrations that occur during the above processes. To test this possibility, we examined the effects of our function‐blocking antibody on Schwann cell migration in three in vitro bioassays: in tissue cultures from developing sciatic nerve, in dorsal root ganglion cultures on cryostat sections of normal or denervated adult sciatic nerve, and in pure Schwann cell cultures. The results showed that the presence of monoclonal antibody 4C5 in all the above culture systems strongly inhibited Schwann cell migration, indicating that the 4C5 antigen participates in migration processes that take place during development and regeneration of the peripheral nervous system. Moreover, staining of migrating Schwann cells in the presence of monoclonal antibody 4C5 with rhodamine‐phalloidin showed that 4C5 antigen activity is associated with actin cytoskeletal organization of these cells, and more specifically with lamellipodia formation. © 2003 Wiley‐Liss, Inc.
Transamination by Polymeric Enzyme Mimics
Authors: Zhou Wenjun , Liu Lei , Breslow Ronald 
Published: December 2003

AbstractPyridoxamine was linked to a series of polyethylenimines (PEIs) with Mn=600, 1800, 10,000, and 60,000, both simply permethylated and with additional attached dodecyl chains. They were examined in the transamination of pyruvic acid and of phenylpyruvic acid, and showed MichaelisMenten behavior. The values of k2 and of KM determined showed only small variations with polymer size. Thus, the previously reported strong advantage of pyridoxamines attached to the Mn=60,000 PEI, relative to simple pyridoxamine alone, is seen to almost the same extent with the smaller PEIs.
A Facile Enzymatic Synthesis of Isotopically Labeled 2‐Methyl‐D‐erythritol 2,4‐Cyclodiphosphate by Spinach Chloroplast Stroma
Authors: Gao Wenyun , Raschke Maja , Alpermann Henriette , Zenk Meinhart H. 
Published: December 2003

AbstractFor the investigation of the ultimate and penultimate steps of the deoxyxylulose phosphate pathway in plants and microorganisms, and to solve intracellular transport problems, we have developed a facile enzymatic preparation of 2‐methyl‐D‐erythritol 2,4‐cyclodiphosphate in highly radioactive form. Use has been made of spinach chloroplast stroma, as well as the stroma of Capsicum annuum and Narcissus pseudonarcissus chromoplasts, which were shown to transform differently labeled 1‐deoxy‐D‐xylulose 5‐phosphate quantitatively into that cyclic diphosphate in the presence of cofactors. This method can also be exploited to synthesize milligram quantities of 13C‐labeled cyclic diphosphate. It is shown that recombinant Escherichia coli deoxyxylulose phosphate synthase is catalytically active and can be used to synthesize the labeled starting material for further enzymatic work, as well as for feeding of intact plants. The pH and temperature stability of the deoxyxylulose 5‐phosphate and the cyclic diphosphate have been determined. Uniformly 13C‐ or 14C‐labeled pyruvate, and uniformly 13C‐ or 14C‐labeled D‐glyceraldehyde 3‐phosphate were synthesized in almost quantitative yields from uniformly 13C‐ or 14C‐labeled D‐glucose en route to deoxyxylulose 5‐phosphate.
Mechanistic Investigation of Phenylalanine Ammonia Lyase by Using N‐Methylated Phenylalanines
Authors: Viergutz Sandra , Poppe László , Tomin Anna , Rétey János 
Published: December 2003

AbstractN‐Methyl‐L‐phenylalanine (5), N‐methyl‐4‐nitro‐L‐phenylalanine (6), and N,N‐dimethyl‐4‐nitro‐L‐phenylalanine (7⋅H+) were investigated as substrates or inhibitors of phenylalanine ammonia lyase from Petroselinum crispum. Whereas the former was a reluctant substrate (Km =6.6 mM, kcat =0.22 s−1), no reverse reaction could be detected by using methylamine and (E)‐cinnamate (2). The Km value for ammonia in the reverse reaction by using (E)‐cinnamate (2) was determined to be 4.4 and 2.6M at pH 8.8 and 10, respectively. The N‐methylated 4‐nitro‐L‐phenylalanines 6 and 7 showed only strong inhibitory effects (Ki =130 nM and 8 nM, resp.). These and former results are discussed in terms of the mechanism of action of phenyalalanine and histidine ammonia lyases.
Facile Orthoester Formation in a Model Compound of the Taxol Oxetane: Are Biologically Active Epoxy Esters, Orthoesters, and Oxetanyl Esters Latent Electrophiles?
Authors: Giner José‐Luis , Faraldos Juan A. 
Published: December 2003

AbstractA steroidal oxetanyl ester was synthesized in eight steps as a biomimetic model of taxol oxetane. The model compound was surprisingly reactive under acidic conditions, rearranging in the absence of H2O to a [2.2.1]‐bicyclic orthoester. Both the oxetanyl ester and the orthoester readily hydrolyze to produce the same triol monoacetate. On the basis of the oxetanyl ester/orthoester rearrangement, a novel biochemical function is suggested for the epoxy esters and oxetanyl esters found in taxoids whereby dioxonium ions, generated from these functional groups, react with cellular proteins to form mixed orthoesters or ethers. A similar process could be involved in the mechanism of action of natural orthoesters such as resiniferatoxin.
Enantioselective Synthesis of a Polyfunctionalized Tetracycle Related to Pentacyclic Triterpenes by Using an Anionic Cycloaddition Reaction
Authors: Rouillard Alain , Bonin Marc‐André , Deslongchamps Pierre 
Published: December 2003

AbstractHerein we report a convergent enantioselective synthesis of a polyfunctionalized ABCD tetracycle by using an anionic cycloaddition reaction between a chiral bicyclic CD Nazarov intermediate (see 6), derived from the (−)‐Weiland–Mischer ketone, and an achiral cyclohexenone (see 5) adequately functionalized to furnish the ring A of pentacyclic triterpenes (Scheme 5). The chiral bicyclic CD Nazarov intermediate forms ring B upon cycloaddition with the achiral cyclohexenone to yield an ABCD tetracycle with a cis‐anti‐trans‐anti‐trans configuration (see 4). Further transformations on this adduct allowed reduction of the angular aldehyde function at C(10) to a Me group (→17) and introduction of an unsaturation at C(5)C(6) by using the ketone function at C(7) (→ 3; Scheme 6).
Designing New α,β‐Unsaturated Thioesters for the Catalytic, Enantioselective FriedelCrafts Alkylation of Indoles
Authors: Bandini Marco , Melloni Alfonso , Tommasi Simona , Umani‐Ronchi Achille 
Published: December 2003

AbstractA new class of α,β‐unsaturated S‐(1,3‐benzoxazol‐2‐yl) thioesters of type 2 have been synthesized and effectively employed as electrophiles in the stereoselective alkylation of indoles. The combination of electronic as well as steric properties of such Michael acceptors allowed us to carry out FriedelCrafts alkylations of various substituted indoles in the presence of a catalytic amount (20 mol‐%) of chiral cationic [PdII(Tol‐binap)] complexes. With the optimized catalytic system (PdCl2(MeCN)2/Tol‐binap/AgSbF6), the desired β‐indolyl‐substituted thioderivatives 4 were obtained in good yield, with an enantiomeric excess (ee) of up to 86%. The remarkable versatility of the enantiomerically enriched thioesters 4 was demonstrated by quantitatively transforming them into optically active β‐indolyl esters and amides under mild conditions. With this stereoselective, catalytic FriedelCrafts reaction, we open up the way towards new α,β‐unsaturated compounds that could be suitable candidates for the preparation of a number of optically active β‐substituted carboxylic compounds.
Microphysiometric Measurement of PAF Receptor Responses to Ginkgolides
Authors: Krane Sonja , Kim So Ra , Abrell Leif M. , Nakanishi Koji 
Published: December 2003

AbstractMicrophysiometry was used to evaluate the effects of terpene trilactone and flavonoid constituents of Ginkgo biloba on human platelet‐activating‐factor receptor (PAFR). Inhibition of the platelet‐activating factor response by terpene trilactones was confirmed using this functional assay. Ginkgolide B (GB) and 10‐O‐benzyl‐GB showed the strongest inhibition (81 and 93%, resp.) of the PAFR response, while the flavonoids rutin, quercetin, and kaempferol showed negligible response inhibition. G. biloba extract mixtures were also tested, and results indicate possible synergistic effects among various components.
Inhibition of Diamino Pelargonic Acid Aminotransferase, an Enzyme of the Biotin Biosynthetic Pathway, by Amiclenomycin: A Mechanistic Study
Authors: Mann Stéphane , Florentin Dominique , Lesage Denis , Drujon Thierry , Ploux Olivier , Marquet Andrée 
Published: December 2003

AbstractThe mechanism of action of amiclenomycin (1a), a naturally occuring inhibitor of diaminopelargonic acid aminotransferase, has been established. The enzyme catalyzes the formation of an aromatic adduct between the inhibitor and pyridoxal‐5′‐phosphate. The structure of the adduct, determined by mass spectrometry, is in agreement with the reported X‐ray crystal structure. Kinetic parameters, characteristic of kcat inhibitors, have been observed, with a KI value of 2 μM and a kinact value of 0.4 min−1. The irreversibility of the inactivation observed, in spite of the absence of covalent bond between the inhibitor and the protein, reveals the high affinity of the adduct for the active site. Two other cis‐1‐amino‐4‐substituted‐cyclohexa‐2,5‐dienes, 3a and 4a, were also found to efficiently inhibit the enzyme. The trans‐isomers were either much less potent (1b) or inactive (3b and 4b). The aminocyclohexadiene moiety, which is, apparently, responsible for the inhibition, could constitute an original pharmacophore for the design of new herbicides.
Amphiphilic Homochiral Oligopeptides Generated via Phase Separation of Nonracemic α‐Amino Acid Derivatives and Lattice‐Controlled Polycondensation in a Phospholipid Environment
Authors: Rubinstein Irina , Bolbach Gérard , Weygand Markus J. , Kjaer Kristian , Weissbuch Isabelle , Lahav Meir 
Published: December 2003

AbstractRacemic S‐ethyl thioesters of Nε‐stearoyllysine (= S‐ethyl (R,S)‐2‐amino‐6‐(stearoylamino)hexanethioate) and S‐ethyl thioesters of γ‐stearyl glutamic acid (=stearyl (R,S)‐4‐amino‐5‐(ethylsulfanyl)‐5‐oxopentanoate) self‐assemble as separated two‐dimensional crystalline monolayers within an achiral phospholipid environment of racemic 1,2‐dipalmitoylglycerol (DPG) and 1,2‐dipalmitoylglycero‐3‐phosphoethanolamine (DPPE), as demonstrated by grazing‐incidence X‐ray‐diffraction (GIXD) measurements performed on the surface of H2O. Lattice‐controlled polycondensation within these crystallites with deuterium‐enantiolabeled monomers was initiated by injecting aqueous solutions of Ag+ or I2/KI beneath the monolayers, which yielded mixtures of diastereoisomeric oligopeptides containing up to six to eight repeating units, as analyzed by MALDI‐TOF mass spectrometry. Analysis of the diastereoisomeric distribution showed an enhanced relative abundance of the oligopeptides with homochiral sequences containing three or more repeating units. Within the DPPE monolayers, the nucleophilic amino group of the phospholipid operates as an initiator of polymerization at the periphery of the monomer two‐dimensional crystallites. Enhanced relative abundance of enantiomerically enriched homochiral oligopeptides was obtained by the polycondensation of nonracemic monomers. This enhancement indicated a phase separation into racemic and enantiomorphous monomer crystallites within the phospholipid environment, although this separation could not be observed directly by GIXD. A possible role that might have been played by crystalline assemblies for the abiotic generation and amplification of oligopeptides with homochiral sequences is discussed.
The Regulation of the Calcium Signal by Membrane Pumps
Authors: Krebs Joachim , Helms Volkhard , Griesinger Christian , Carafoli Ernesto 
Published: December 2003

AbstractCalcium may have a static, structure‐stabilizing role in biological organs like the bones and the teeth, or may fulfill a dynamic function in cells as a regulator of signal‐transduction pathways. This is made possible by the properties of the Ca2+ ion (e.g., high dehydration rate, great flexibility in coordinating ligands, largely irregular geometry of the coordination sphere). Since Ca2+ is a universal carrier of signals, the control of its homeostasis is of central importance for the organism. It involves exchanges between the skeleton (which is the major calcium reservoir) and the extracellular and intracellular fluids. It also involves the intestine and the kidney, the organs of Ca absorption and release, respectively. The highly integrated homeostasis process consists of a number of hormonally controlled feedback loops, and an elaborate system of membrane channels, exchangers, and pumps that control the Ca2+ flux into and out of cells.
Informal learning and the transfer of learning: How managers develop proficiency
Authors: Enos Michael D. , Kehrhahn Marijke Thamm , Bell Alexandra 
Published: December 2003

AbstractThis study examined how the extent to which managers engaged in informal learning, perceptions of support in
the transfer environment, and level of managerial proficiency related to transfer of learning in twenty core
managerial skills. The results suggested that informal learning is predominantly a social process and that
managers with high levels of proficiency who experience low levels of coworker, supervisor, and organizational
support learn managerial skills mostly from informal learning and transfer learning more frequently. New
perspectives are offered on the interrelationship between informal learning and transfer of learning, the role of
metacognition and self‐regulation in informal learning, and the influence of informal learning in the
development of managerial proficiency.
An examination of learning transfer system characteristics across organizational settings
Authors: Holton Elwood F. , Chen Hsin‐Chih , Naquin Sharon S. 
Published: December 2003

AbstractNo previous research in the United States has compared and contrasted learning transfer systems across
organizations and training types, primarily because no standard instruments were used in previous research.
This study, based on a subset of responses in the Learning Transfer System Inventory response database, is the
first to conduct such a comparison. Using a subset of 1,099 respondents, transfer systems are compared across
three organization types, eight organizations, and nine types of training. MANOVA and univariate ANOVA were
used to compare transfer systems. The results suggest that transfer systems differ across organizational types,
organizations, and training types. Implications for HRD practice and future research directions are
discussed.
Genesis of the European initiative in insolvency law
Authors: Omar Paul J. 
Published: December 2003

AbstractThis article deals with the history behind the initiative that led to the adoption of the European Insolvency Regulation 2000. It covers the background to the proposals, the content of the various drafts that have merged over the past four decades and criticism of the proposals by commentators. Copyright © 2003 John Wiley & Sons, Ltd.
Migrant remittances and family ties: a case study in China
Authors: Cai Qian 
Published: December 2003

AbstractThe migration of China's population, especially rural‐to‐urban migration, has attracted considerable attention from both researchers and policy‐makers. However, few studies have considered the issue of remittances sent home by migrants. This subject is of importance for three reasons: first, remittances have become a striking feature of Chinese internal migration; second, remittances are a unique form of transfers which tell something about intra‐familial relationships; and, third, the study of remittances is relatively absent in the the China migration literature to date. Guided by the theories of family adaptive strategy, altruism, and self‐interest, this study explores how temporary vs. permanent migration status influences migrants' propensity to remitting and the amount remitted. It also considers how family ties, both emotional and economical, affect migrants' remitting behaviour. The data are drawn from the Hubei Survey of Fertility, Migration and Social Change and we show that family ties are the most important and distinct factors in affecting migrants' remittances. Temporary migration status, being male and wage also have positive and statistically significant effects. Education, surprisingly, has little influence on either the decision to remit or the amount to remit. In conclusion, we consider the policy implications of these findings. Copyright © 2003 John Wiley & Sons, Ltd.
Editiorial introduction: labour migration and the family in Asia
Authors: Boyle Paul , Graham Elspeth , Yeoh Brenda 
Published: December 2003

AbstractThis paper introduces a special issue on ‘Labour migration and the family in Asia’. It provides a brief review of economic approaches to labour migration, including some studies that have recognised the importance of the family in migration decision‐making. Most of this work continues to be based on a broad human capital framework and we highlight some of the limitations of such a theoretical model, including their failure to deal adequately with gender roles or the deeper structures that influence migration, such as globalisation, colonialism and national and local government policies. We also consider the importance of remittances in family‐related labour migration and their value in developing economies. In summary this paper, and the other papers selected for the special issue, contribute to the debate about the limitations of the human capital model, and help us to understand labour migration and the family in the Asian context. Copyright © 2003 John Wiley & Sons, Ltd.
Assessment of wear in extensively irradiated UHMWPE cups in simulator studies
Authors: Oonishi Hironobu , Clarke Ian C , Yamamoto Kengo , Masaoka Toshinori , Fujisawa Akira , Masuda Shingo 
Published: December 2003

AbstractHigher levels of UHMWPE crosslinking currently are being advocated for improved wear resistance of acetabular cups. Pioneering Japanese studies, begun in 1971, have achieved good clinical results with UHMWPE irradiated to 1000 kGy for use with a cemented‐cup design. The objective of our study was to use contemporary simulator techniques to determine the in vitro wear performance of such high‐dose irradiated cups. Extruded UHMWPE cups were processed with 500, 1000, and 1500 kGy of gamma‐radiation doses under vacuum, annealed, and machined to shape. The cups were mated with 26‐mm alumina heads and run in a multidirectional simulator with bovine serum. Over a 6‐million cycle (Mc) study, the weight loss of the nonirradiated control cups averaged 52.8 mg/Mc + 1.4% (wear = 57.2 mm3/Mc). In contrast, the irradiated wear cups had a consistent weight gain. Thus cups with irradiation of 500–1500 kGy had no detectable wear in this study. The original machining marks still were partially evident in the wear zones, along with some macrofissures in the 1000‐ and 1500‐kGy cups. Areas adjacent to the fissures showed delaminating plaques of 100–300 μm in size. It also was noted that the wear cups systematically gained more weight than their corresponding soak controls. Each 200‐kGy radiation gain increased the fluid sorption ratio by 10%. The increased fluid sorption and evidence of some surface deterioration may indicate that such high‐dose irradiated cups are more susceptible to mechanical damage. This indicates that we should take care to ensure that our desire to reduce the wear debris to a zero amount does not result in a modified UHMWPE that lacks the necessary mechanical properties for contemporary metal‐backed cup designs. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 52–60, 2004
Numerical osteobonding evaluation of electrically polarized hydroxyapatite ceramics
Authors: Nakamura Satoshi , Kobayashi Takayuki , Yamashita Kimihiro 
Published: December 2003

AbstractEnhanced osteobonding abilities of electrical polarized hydroxyapatite (HA) ceramics were statistically evaluated by a bone morphometric technique. HA ceramics with an average charge of 3.9 μCcm−2 were implanted in tibial and femoral diaphyses of New Zealand white rabbits. Estimation of the affinity index, defined as the ratio of the direct bonding length to the HA ceramic length, significantly showed more active osteobonding ability with a negatively charged surface than with a positively charged surface and a nonpolarized HA 1 week after administration. The enhanced osteobonding ability attributed to the stimulated osteoids in the vicinity of the positively charged surface ranked above the nonpolarized surface. Although amounts of the newly formed bone on the HA surfaces increased with implantation period in all of the observation areas, the negatively charged surface was almost covered with bone and had the best index value of 94.0% at 4 weeks. The superior osteobonding activity of the negatively charged surfaces was statistically proven. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 90–94, 2004