bluuebunny/crossref_metadata_2025 huggingface dataset:
The Power of the Denominator: A Proposal for More Comprehensive Modeling of Risk Factors in Ice Hockey Injuries
Authors: Stuart MJ , Smith AM , Larson DR
Published: May 2004

In the sport of ice hockey, the incidence of injury has been investigated at multiple levels of participation based on collective player exposure, which assumes equal playing time among participants. However, playing time varies enormously between individual players on a given team because of variability in the number and length of shifts. Individual player monitoring, although laborintensive, more accurately identifies risk factors for sustaining injuries. Specific player exposure data are necessary for detailed analysis of factors such as style of play, illegal activities, equipment, player size, and officiating. In addition, prospective, uniform and accurate collection of exposure data may permit meaningful comparison of injury rates between levels of participation in ice hockey and also among different sports. Refinement of data collection tools that determine individual player injury exposure will increase the power of the denominator and facilitate prevention of ice hockey injuries.
Modeling Variability in Service Loading Spectra
Authors: Socie DF , Pompetzki MA
Published: May 2004

This paper describes a methodology for statistically extrapolating a single measured service loading history to the expected long-term service usage spectra. The measured time history first is processed into a rainflow counted histogram. Nonparametric kernel smoothing techniques are employed to convert the rainflow histogram of cycles into a probability density histogram. Once the probability density histogram is obtained, Monte Carlo methods are used to produce a rainflow histogram of any desired number of cycles. A new loading history then is reconstructed from the expected rainflow histogram, which can be combined with a probabilistic fatigue analysis to obtain an estimate of the durability of a structure. Obtaining an estimate of the loading spectra for a ground vehicle is difficult because there are many users, each with different service usage. The extrapolating methodology is extended to combine data from several users to obtain loading spectra that represent more severe users in the population.
Effect of Individual Component Life Distribution on Engine Life Prediction
Authors: Zaretsky EV , Hendricks RC , Soditus SM
Published: May 2004

The effect of individual engine component life distributions on engine life prediction was determined. A Weibull-based life and reliability analysis of the NASA Energy Efficient Engine was conducted. The engine's life at a 95 and 99.9 % probability of survival was determined based on the engine manufacturer's original life calculations and assumed values of each of the component's cumulative life distributions as represented by a Weibull slope. The lives of the high-pressure turbine (HPT) disks and blades also were evaluated individually and as a system in a similar manner. Knowing the statistical cumulative distribution of each engine component with reasonable engineering certainty is a condition precedent to predicting the life and reliability of an entire engine. The life of a system at a given reliability will be less than the lowest-lived component in the system at the same reliability (probability of survival). Where Weibull slopes of all the engine components are equal, the Weibull slope had a minimal effect on engine L0.1 life prediction. However, at a probability of survival of 95 % (L5 life), life decreased with increasing Weibull slope.
Wear and Structural Fatigue Simulation of Crosslinked Ultra-High Molecular Weight Polyethylene for Hip and Knee Bearing Applications
Authors: Wang A , Manley M , Serekian P
Published: May 2004

There have been increasing concerns about the structural fatigue resistance of crosslinked UHMWPE devices due to deterioration of certain mechanical properties. However, due to the lack of clear correlation between specific mechanical properties and clinical performance, these concerns remain theoretical. In order to evaluate the potential benefits and risks of various crosslinked polyethylene materials for hip and knee bearing applications, two clinically relevant worst-case scenarios were simulated on functional devices. In the first worst-case scenario, cemented all-poly patellar components were tested under simulated stair-climbing conditions with rotational misalignment. In the second worst-case scenario, metal-backed thin acetabular liners were tested in a hip joint simulator under rim-loading conditions. Various types of crosslinked UHMWPE were prepared according to published process descriptions of commercial materials. While significant levels of volumetric wear reduction were confirmed by both the patellar and hip simulator tests, mixed results were obtained on the structural integrity of the devices. The latter was more significantly affected by the post-irradiation thermal treatment history than by the total dose of irradiation. Re-melting following irradiation led to catastrophic fractures of both rim-loaded liners and rotational-malaligned patellar pegs. The key mechanical property that was positively identified to correlate with the structural fatigue performance of crosslinked polyethylene materials was the ultimate tensile strength, whereas tensile elongation within 250% and 400% range had no effect on structural integrity. However, the results presented in this study should not be misconstrued with respect to the potential clinical performance of irradiation crosslinked and re-melted polyethylene liners with proper designs. In fact, the true outcome of all the crosslinked materials can only be revealed by long-term clinical follow-up.
Parametric Study on Cement Grout and Aggregate Media for Preplaced Aggregate Grouting
Authors: Zhang J , Swaddiwudhipong S , Lee SL
Published: May 2004

Experimental programs were designed carefully and appropriate testing materials were selected for the parametric study on the flow of cement grout through aggregate media during the preplaced aggregate grouting process in concrete construction. Experimental investigations include the testing and evaluation of the viscosity of cement grout, the intrinsic permeability coefficient, and the porosity of the aggregate media. The time dependency and shear history dependency of the rheological properties of the cement grout are incorporated in the viscosity tests so as to be able to simulate more accurately the grouting process. The average shear rate of the flow is estimated from the flow velocity by determining the average nominal radius of the imaginary flow channel from the permeability testing. The resulting parameters include the yield stress and plastic viscosity of the cement grout and their time dependency, intrinsic permeability and porosity of the aggregate media, and the average nominal radius of the imaginary flow channel.
Toughness Characterization of Fiber-Reinforced Concrete: Which Standard to Use?
Authors: Banthia N , Mindess S
Published: May 2004

The major advantage of fiber-reinforced concrete (FRC) over its plain counterpart is in its improved energy absorption capability, or ‘toughness.’ There are currently several standard test methods available to characterize the toughness of fiber-reinforced concrete, but little is known of the relationship between the toughness results they produce for a given fiber-reinforced concrete. An attempt is made here to compare the results produced by three of these techniques: ASTM C 1018, ASTM C 1399, and JSCE SF-4 for the same concrete and to assess the subjectivity encountered in toughness characterization. It was found that there is no firm and reliable correlation between these three procedures; they would rank different FRCs differently. Only a weak correlation exists between the toughness parameters generated by the C 1399 and the SF-4 standards, and the correlation is highly dependent on the fiber type. The ASTM C 1018 procedure is the least reliable of all and produces Toughness Indices and RM,N values that are very difficult to interpret.
Geotechnical Properties of Compressible Materials Used for Induced Trench Construction
Authors: McAffee RP , Valsangkar AJ
Published: May 2004

Results of a testing program to measure the compressibility and shear strength parameters of compressible fill materials commonly used for induced trench construction are presented. The geotechnical properties of sawdust, wood chips, and hay have been determined. A large-scale consolidometer and direct shear testing apparatus were used to perform the tests. To resolve strain compatibility issues, the mobilized friction angle corresponding to an appropriate shear displacement value is reported. The experimental results are compared to geotechnical properties of several other compressible materials reported in the literature that also have been used in induced trench applications. The results presented in this paper can be used to perform numerical modeling of induced trenches where these compressible materials are commonly used.
A Dissociation of Motion and Spatial-Pattern Vision in the Avian Telencephalon: Implications for the Evolution of “Visual Streams”
Authors: Nguyen Angela P. , Spetch Marcia L. , Crowder Nathan A. , Winship Ian R. , Hurd Peter L. , Wylie Douglas R. W.
Published: May 2004

The ectostriatum is a large visual structure in the avian telencephalon. Part of the tectofugal pathway, the ectostriatum receives a large ascending thalamic input from the nucleus rotundus, the homolog of the mammalian pulvinar complex. We investigated the effects of bilateral lesions of the ectostriatum in pigeons on visual motion and spatial-pattern perception tasks. To test motion perception, we measured performance on a task requiring detection of coherently moving random dots embedded in dynamic noise. To test spatial-pattern perception, we measured performance on the detection of a square wave grating embedded in static noise. A double dissociation was revealed. Pigeons with lesions to the caudal ectostriatum showed a performance deficit on the motion task but not the grating task. In contrast, pigeons with lesions to the rostral ectostriatum showed a performance deficit on the grating task but not the motion task. Thus, in the avian telencephalon, there is a separation of visual motion and spatial-pattern perception as there is in the mammalian telencephalon. However, this separation of function is in the targets of the tectofugal pathway in pigeons rather than in the thalamofugal pathway as described in mammals. The implications of these findings with respect to the evolution of the visual system are discussed. Specifically, we suggest that the principle of parallel visual streams originated in the tectofugal pathway rather than the thalamofugal pathway.
Encoding-Specific Effects of Social Cognition on the Neural Correlates of Subsequent Memory
Authors: Mitchell Jason P. , Macrae C. Neil , Banaji Mahzarin R.
Published: May 2004

To examine whether social cognition recruits distinct mental operations, we measured brain activity during social (“form an impression of this person”) and relatively nonsocial (“remember the order in which person information is presented”) orienting tasks. Extending previous research on the neural basis of social cognition, the impression formation task differentially engaged an extensive region of the dorsomedial prefrontal cortex (PFC). In contrast, the nonsocial sequencing task differentially engaged the superior frontal and parietal gyri, precentral gyrus, and the caudate. In addition, we compared encoding activations for subsequently remembered (i.e., hits) to subsequently forgotten (i.e., misses) items. The brain regions in which the blood oxygenation level-dependent signal distinguished subsequent hits from subsequent misses depended on which orienting task was performed at encoding: subsequent memory was correlated with encoding activity only in the medial PFC for impression formation trials but in the right hippocampus for sequencing trials. These data inform two interrelated cognitive issues. First, results underscore the neuroanatomical distinctiveness of social cognition and suggest that previous psychological theories may have neglected important functional differences in how the human brain instantiates social and nonsocial cognitive processes. Second, by demonstrating that activity in different brain regions correlates with subsequent memory as a function of the orienting task performed at encoding, these data provide evidence of the neural basis for encoding specificity, the principle that memory is critically determined by the cognitive process engaged by the initial study episode.
Long-Term Alterations in Neuroimmune Responses after Neonatal Exposure to Lipopolysaccharide
Authors: Boissé Lysa , Mouihate Abdeslam , Ellis Shaun , Pittman Quentin J.
Published: May 2004

Fever is an integral part of the host's defense to infection that is orchestrated by the brain. A reduced febrile response is associated with reduced survival. Consequently, we have asked if early life immune exposure will alter febrile and neurochemical responses to immune stress in adulthood. Fourteen-day-old neonatal male rats were givenEscherichia colilipopolysaccharide (LPS) that caused either fever or hypothermia depending on ambient temperature. Control rats were given pyrogen-free saline. Regardless of the presence of neonatal fever, adult animals that had been neonatally exposed to LPS displayed attenuated fevers in response to intraperitoneal LPS but unaltered responses to intraperitoneal interleukin 1β or intracerebroventricular prostaglandin E2. The characteristic reduction in activity that accompanies fever was unaltered, however, as a function of neonatal LPS exposure. Treatment of neonates with an antigenically dissimilar LPS (Salmonella enteritidis) was equally effective in reducing adult responses toE. coliLPS, indicating an alteration in the innate immune response. In adults treated as neonates with LPS, basal levels of hypothalamic cyclooxygenase 2 (COX-2), determined by semiquantitative Western blot analysis, were significantly elevated compared with controls. In addition, whereas adult controls responded to LPS with the expected induction of COX-2, adults pretreated neonatally with LPS responded to LPS with a reduction in COX-2. Thus, neonatal LPS can alter CNS-mediated inflammatory responses in adult rats.
Hippocampal Place Cells Are Not Controlled by Visual Input during the Small Irregular Activity State in the Rat
Authors: Jarosiewicz Beata , Skaggs William E.
Published: May 2004

In the actively foraging rat, hippocampal pyramidal cells have strong spatial correlates. Each “place cell” fires rapidly only when the rat enters a particular delimited portion of its environment, called the “place field” of that cell. Hippocampal pyramidal cells also exhibit spatial selectivity during a physiological state that occurs during sleep, termed “small irregular activity” (SIA), because of the appearance of the hippocampal EEG. It is not known whether rats determine their current location in space during SIA using current visual information or whether they recall the location in which they fell asleep. To address this question, we recorded spikes from ensembles of CA1 pyramidal cells and hippocampal EEG while rats slept along the edge of a large circular recording arena with minimal local features in a room with prominent distal visual cues. To move the rats to a new location in the room while they were sleeping, we slowly rotated the recording arena on which they slept to a new orientation in the room. Hippocampal place cell activity in subsequent SIA episodes reflected the location in the room in which the rats fell asleep, rather than the location to which they were moved, although the alignment of the rats' spatial map was governed by the room cues in the subsequent active foraging session. Thus, the hippocampal population activity during SIA does not result from the processing of current visual information but instead probably reflects a memory for the location in which the rat fell asleep.
Inhibition of Neurotransmitter Release by a Nonphysiological Target Requires Protein Synthesis and Involves cAMP-Dependent and Mitogen-Activated Protein Kinases
Authors: Ghirardi Mirella , Benfenati Fabio , Giovedì Silvia , Fiumara Ferdinando , Milanese Chiara , Montarolo Pier Giorgio
Published: May 2004

During the development of neuronal circuits, axonal growth cones can contact many inappropriate targets before they reach an appropriate postsynaptic partner. Although it is well known that the contact with synaptic partners upregulates the secretory machinery of the presynaptic neuron, little is known about the signaling mechanisms involved in preventing the formation of connections with inappropriate target cells. Here, we show that the contact with a nonphysiological postsynaptic target inhibits neurotransmitter release from axonal terminals of theHelixserotonergic neuron C1 by means of an active mechanism requiring ongoing protein synthesis and leading to the inhibition of cAMP-dependent protein kinase (PKA) and mitogen-activated protein kinase (MAPK)-extracellular signal-related kinase (Erk) pathways. The reversal of the inhibitory effect of the nonphysiological target by blockade of protein synthesis was prevented by cAMP-PKA or MAPK-Erk inhibitors, whereas disinhibition of neurotransmitter release promoted by cAMP-PKA activation was not affected by MAPK-Erk inhibitors. The data indicate that the inhibitory effect of the nonphysiological target on neurotransmitter release is an active process that requires protein synthesis and involves the downregulation of the MAPK-Erk and cAMP-PKA pathways, the same protein kinases that are activated after contact with a physiological target neuron. These mechanisms could play a relevant role in the prevention of synapse formation between inappropriate partners by modulating the neurotransmitter release capability of growing nerve terminals according to the nature of the targets contacted during their development.
An Overview of the Pharmacokinetic Disposition of Darbepoetin alfa
Authors: Zamboni William C. , Stewart Clinton F.
Published: May 2004

Darbepoetin alfa is a new erythropoiesis‐stimulating protein that has five carbohydrate chains compared with three in recombinant human erythropoietin (r‐HuEPO, epoetin alfa). Owing to its increased carbohydrate content, the terminal half‐life of darbepoetin alfa is 2–3‐fold greater than that of r‐HuEPO in patients with chronic kidney disease or cancer. This pharmacokinetic property may allow for less frequent administration of darbepoetin alfa compared with r‐HuEPO. Although several regimens are still being tested, a predictable increase was observed in serum concentrations of darbepoetin alfa and no clinically relevant accumulation was seen with once‐weekly administration for up to 48 weeks. Preliminary data in patients with cancer suggest that concurrent chemotherapy may influence the pharmacokinetics of darbepoetin alfa. Therefore, the timing of dosing relative to chemotherapy may be important. Darbepoetin alfa, through its potential for less frequent dosing, offers a more convenient treatment option than r‐HuEPO for patients with anemia secondary to cancer or kidney disease.
Overview of Cancer‐Related Anemia: Focus on the Potential Role of Darbepoetin alfa
Authors: Valley Amy W.
Published: May 2004

Cancer‐associated anemia is common and has many causes, including the effects of the underlying disease and cancer treatment. The effect of anemia on patients with cancer was not appreciated fully until relatively recently. Several well‐designed studies have demonstrated the relationship between anemia and fatigue, and the effect of fatigue on quality of life. These data have resulted in a greater awareness of anemia in cancer and have increased the use of recombinant human erythropoietin (r‐HuEPO, epoetin alfa) therapy for the treatment of anemia. Recombinant HuEPO produces a hemoglobin response in 50–60% of patients with cancer; however, to obtain this response rate, frequent dosing is required. Darbepoetin alfa, a recently developed erythropoietic protein, has a longer half‐life than that of r‐HuEPO, enabling less frequent dosing, and has a greater in vivo activity. In studies of patients with cancer who develop anemia, darbepoetin alfa has proved to be well tolerated and effective, and its advantages make it a potential improved treatment option for anemia in these patients.
Inverted duplication of 15q with terminal deletion in a multiple malformed newborn with intrauterine growth failure and lethal phenotype
Authors: Rita Genesio , Daniele De Brasi , Anna Conti , Annamaria Borghese , Pasqua Di Micco , Pasquale Di Costanzo , Dario Paladini , Paola Ungaro , Lucio Nitsch
Published: May 2004

We describe the cytogenetic and molecular characterization of an inverted duplication of chromosome 15q with evidence of a terminal deletion of the same rearranged chromosome. The proband was a multiple congenital malformed female with a prenatal diagnosis of trisomy 15q and an extremely severe clinical course. The phenotype of the patient was characterized by marked intrauterine growth retardation, congenital heart defect, “horseshoe” kidney, hand contractures, and clubfeet. The exitus came at 20 days because of progressive cardio‐respiratory impairment. Overall, the clinical phenotype appeared more severe than usual trisomy 15q syndrome. Postnatal cytogenetic and molecular studies unraveled a “de novo” inverted duplication of 15q (q21.3→q26.3), associated with the deletion of the 15q telomere and part of the band 15q26.3. A single copy region spanning approximately 600 kb between the duplicated segments was present. Correlation between the clinical findings of the patient and the phenotype of trisomy 15q reported in literature is also provided. © 2004 Wiley‐Liss, Inc.
Functional disomy of Xp including duplication of DAX1 gene with sex reversal due to t(X;Y)(p21.2;p11.3)
Authors: Sanlaville Damien , Vialard François , Thépot François , Vue‐Droy Luce , Ardalan Azarnouche , Nizard Patrice , Corré Alain , Devauchelle Bernard , Martin‐Denavit Tanguy , Nouchy Marc , Malan Valérie , Taillemite Jean‐Louis , Portnoï Marie‐France
Published: May 2004

Translocations involving the short arms of the X and Y in human chromosomes are uncommon. One of the best‐known consequences of such exchanges is sex reversal in 46,XX males and some 46,XY females, due to exchange in the paternal germline of terminal portions of Xp and Yp, including the SRY gene. Translocations of Xp segments to the Y chromosome result in functional disomy of the X chromosome with an abnormal phenotype and sex reversal if the DSS locus, mapped in Xp21, is present. We describe a 7‐month‐old girl with severe psychomotor retardation, minor anomalies, malformations, and female external genitalia. Cytogenetic analysis showed a 46,X,mar karyotype. The marker was identified as a der(Y)t(Xp;Yp) by fluorescence in situ hybridisation analysis. Further studies with specific locus probes of X and Y chromosomes made it possible to clarify the break points and demonstrated the presence of two copies of the DAX1 gene, one on the normal X chromosome and one on the der(Y). The karyotype of the child was: 46,X,der(Y)t(X;Y)(p21.2;p11.3). The syndrome resulted from functional disomy Xp21.2‐pter, with sex reversal related to the presence of two active copies of the DAX1 gene located in Xp21. Few cases of Xp disomy with sex reversal have been reported, primarily related to Xp duplications with 46,XY karyotype, and less often to Xp;Yq translocations. To our knowledge, our patient with sex reversal and a t(Xp;Yp) is the second reported case. © 2004 Wiley‐Liss, Inc.
Research and developments of a multi‐modal MIR engine for commercial applications in East Asia1
Authors: Jang Jyh‐Shing Roger , Lee Hong‐Ru , Chen Jiang‐Chuen , Lin Cheng‐Yuan
Published: May 2004

This article describes the research and development of an efficient Music Information Retrieval (MIR) engine that is embedded in a karaoke software package targeted for Asian people's need of music retrieval. The MIR engine has a multi‐modal interface that allows queries by singing, humming, tapping, speaking, and writing. In particular, we discuss the design philosophy, technical barriers, and performance evaluation of such an engine, as well as its current and potential commercial applications. Feedbacks and feature requests from users, which greatly influence our future work, are also addressed.
Music information retrieval research and its context at the University of Waikato
Authors: Bainbridge David
Published: May 2004

This article describes the digital music library work at the University of Waikato, New Zealand. At the heart of the project is a music information retrieval workbench for evaluating algorithms and performing experiments used in conjunction with four datasets of symbolic notation ranging from contemporary to classical pieces. The outcome of this experimentation is woven together with strands from our larger digital library project to form the Web‐based music digital library MELDEX (short for melody index). An overview of the workbench software architecture is given along with a description of how this fits the larger digital library design, followed by several examples of MELDEX in use.
Vorgespannter Stahlbeton
Authors: Buschmeyer Wilhelm , Fastabend Michael
Published: May 2004

Im Beitrag wird ein Überblick über das neue Regelwerk für die Bemessung und Konstruktion vorgespannter Betonbauwerke mit internen Spanngliedern ohne Verbund gegeben. Für die Auslegung derartiger Tragwerke wird ein Entwurfskonzept zur Sicherstellung hoher Dauerhaftigkeitsanforderungen während der vorgesehenen Nutzungsdauer mit Schwerpunkt auf dem Gebiet des Flachdecken‐, Brücken‐ und Behälterbaus diskutiert. Empfehlungen zur Wahl eines hierfür geeigneten Vorspanngrades werden im Zusammenhang mit Ausführungsbeispielen vorgestellt.
Verankerung externer Spannglieder an Querträgerscheiben
Authors: Hegger Josef , Neuser Jens U.
Published: May 2004

Die sorgfältige Bemessung und Konstruktion von Verankerungs‐ und Umlenkstellen ist Voraussetzung für sichere und dauerhafte Brückenbauwerke mit externer Vorspannung. Das Tragverhalten der Verankerungskonstruktionen läßt sich mit herkömmlichen Stabwerkmodellen beschreiben. Es wird ein Bemessungsmodell mit einfachen Gleichungen bzw. Diagrammen für Querträgerscheiben hergeleitet und beispielhaft angewendet.
Zur Ermittlung des Böenreaktionsfaktors bei turbulenzerregten Bauwerksschwingungen unter Windlast
Authors: Rosemeier Gustav‐Erich
Published: May 2004

Bei schwingungsanfälligen Bauwerken ist die Ermittlung des Böenreaktionsfaktors von entscheidender Bedeutung. Bei großen Schwingungsamplituden kann durch die aktivierte aerodynamische Dämpfung eine erhebliche Vergrößerung der Gesamtdämpfung einer Struktur eintreten. Hierfür wird eine einfache Schätzformel bereitgestellt. Weiterhin wird nachgewiesen, daß der Böenreaktionsfaktor oft maximal den Wert eines einmaligen Impulses annimmt, bei dem die Windgeschwindigkeit in kurzer Zeit von sehr kleinen Werten auf den Maximalwert springt. Der Normentwurf E‐DIN 1055‐4: 2001‐03 überschätzt den quasistatischen Anteil der Windlast bei der Berechnung des Böenreaktionsfaktors. Deshalb wird hier ein Verbesserungsvorschlag erläutert, der mit den eigenen Parameterstudien besser übereinstimmt.
Conformational studies on enkephalins using the MOLS technique
Authors: Vengadesan K. , Gautham N.
Published: May 2004

Conformational studies of two linear enkephalin molecules, Met‐enkephalin and Leu‐enkephalin, have been carried using the mutually orthogonal Latin squares (MOLS) technique with the ECEPP/3 force field. This technique was developed recently in our laboratory to perform an unbiased search of the conformational space of peptides and to locate low energy conformations. The present study identified all the folds predicted by other studies, and in addition picked up other energetically favorable structures. The results suggest that the peptide backbone exists as a mixture of folded and unfolded forms (approximately 50% each). The study also provides information on the distribution of the low energy conformations that we have classified on the basis of structural motifs, backbone hydrogen‐bonding patterns, and root mean square deviations in atomic positions. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Ultrabright fluorescein‐labeled antibodies near silver metallic surfaces
Authors: Lakowicz Joseph R. , Malicka Joanna , Huang Jun , Gryczynski Zygmunt , Gryczynski Ignacy
Published: May 2004

Fluorescein‐labeled antibodies are widely used in clinical assays and fluorescence microscopy. The fluorescent signal per labeled antibody is limited by fluorescein self‐quenching, which occurs when the antibody is heavily labeled with multiple fluoresceins. We examined immunoglobulin G (IgG) when labeled with 0.7 to about 30 fluoresceins per antibody molecule. The extent of self‐quenching was decreased, and the signal increased, when the labeled antibody was in close proximity to metallic silver particles. Time‐resolved measurements showed that the intensity increase was due in part to a silver‐induced increase in the radiative decay rate. These results suggest the use of labeled antibodies conjugated to silver particles as ultrabright probes for imaging or analytical applications. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Photophysical and Phototoxic Properties of the Antibacterial Fluoroquinolones Levofloxacin and Moxifloxacin
Authors: Viola Giampietro , Facciolo Laura , Canton Marcella , Vedaldi Daniela , Dall'Acqua Francesco , Aloisi Gian Gaetano , Amelia Matteo , Barbafina Arianna , Elisei Fausto , Latterini Loredana
Published: May 2004

Two antibacterial fluoroquinolones, levofloxacin and moxifloxacin, were investigated to evaluate their photophysical properties and to explore the mechanism of their phototoxicity. Photophysical experiments were carried out in aqueous solution by stationary and time‐resolved fluorimetry, and by laser flash photolysis, to obtain information on the various decay pathways of the excited states of the drugs and on transient species formed upon irradiation. The results obtained show that levofloxacin is able to photosensitize red blood cell lysis in an oxygen‐independent way and induce a high decrease in cell viability after UVA irradiation, although to a lesser degree than the racemic mixture ofloxacin. Moxifloxacin, which is an 8‐MeO‐substituted fluoroquinolone, is less phototoxic than the other compounds. Cellular phototoxicity was inhibited by the addition of superoxide dismutase, catalase, and free radical and hydroxyl radical scavengers (BHA, GSH, mannitol, and DMTU), indicating the involvement of superoxide anion and/or a radical mechanism in their cytotoxicity. A good correlation was observed between lipid peroxidation, protein photodamage, and cellular phototoxicity, indicating that test compounds exert their toxic effects mainly in the cellular membrane. Experiments carried out on pBR322 DNA show that these derivatives do not significantly photocleave DNA directly, but single‐strand breaks were evidenced after treatment of photosensitized DNA by two base‐excision‐repair enzymes, and Endo III.
Chemical Biology of the Sugar Code
Authors: Gabius Hans‐Joachim , Siebert Hans‐Christian , André Sabine , Jiménez‐Barbero Jesús , Rüdiger Harold
Published: May 2004

A high‐density coding system is essential to allow cells to communicate efficiently and swiftly through complex surface interactions. All the structural requirements for forming a wide array of signals with a system of minimal size are met by oligomers of carbohydrates. These molecules surpass amino acids and nucleotides by far in information‐storing capacity and serve as ligands in biorecognition processes for the transfer of information. The results of work aiming to reveal the intricate ways in which oligosaccharide determinants of cellular glycoconjugates interact with tissue lectins and thereby trigger multifarious cellular responses (e.g. in adhesion or growth regulation) are teaching amazing lessons about the range of finely tuned activities involved. The ability of enzymes to generate an enormous diversity of biochemical signals is matched by receptor proteins (lectins), which are equally elaborate. The multiformity of lectins ensures accurate signal decoding and transmission. The exquisite refinement of both sides of the protein–carbohydrate recognition system turns the structural complexity of glycans—a demanding but essentially mastered problem for analytical chemistry—into a biochemical virtue. The emerging medical importance of protein–carbohydrate recognition, for example in combating infection and the spread of tumors or in targeting drugs, also explains why this interaction system is no longer below industrial radarscopes. Our review sketches the concept of the sugar code, with a solid description of the historical background. We also place emphasis on a distinctive feature of the code, that is, the potential of a carbohydrate ligand to adopt various defined shapes, each with its own particular ligand properties (differential conformer selection). Proper consideration of the structure and shape of the ligand enables us to envision the chemical design of potent binding partners for a target (in lectin‐mediated drug delivery) or ways to block lectins of medical importance (in infection, tumor spread, or inflammation).
Classifying Enzymes from Selectivity Fingerprints
Authors: Grognux Johann , Reymond Jean‐Louis
Published: May 2004

Fingerprints of lipases and esterases have been recorded by using an array of chiral fluorogenic aliphatic esters of increasing chain length (C4–C16). Classification of the enzyme series was carried out with selectivity data by clustering and principal component analysis (PCA). Enzymes were classified on the basis of selectivity for chain length (C4–C6 vs. C10–C16) and of middle‐chain‐length (C8–C10) reactivity. A minimum set of nine substrates was defined by cluster analysis of relative reactivities of each substrate for the different enzymes. This selectivity‐based analysis is general. It does not require a common reference substrate to react with all enzymes or vice versa, and is independent of knowing the exact concentration of active protein in the enzyme samples.
A Powerful Antiradiation Compound Revealed by a New High‐Throughput Screening Method
Authors: Meunier Stéphane , Desage‐El Murr Marine , Nowaczyk Stéphanie , Le Gall Thierry , Pin Serge , Renault Jean‐Philippe , Boquet Didier , Créminon Christophe , Saint‐Aman Eric , Valleix Alain , Taran Frédéric , Mioskowski Charles
Published: May 2004

We present a new high‐throughput screening method for the selection of powerful water‐soluble antiradiation compounds. This method, which uses conventional immunoassay techniques, allowed the capacity of a given compound to protect thymidine from irradiation to be evaluated. By applying this assay to an antioxidant library, we showed for the first time that norbadione A, a well‐known mushroom pigment, has pronounced atypical antiradiation properties.
Functional Evaluation of Carbohydrate‐Centred Glycoclusters by Enzyme‐Linked Lectin Assay: Ligands for Concanavalin A
Authors: Köhn Maja , Benito Juan M. , Ortiz Mellet Carmen , Lindhorst Thisbe K. , García Fernández José M.
Published: May 2004

The affinities of the mannose‐specific lectin concanavalin A (Con A) towards D‐glucose‐centred mannosyl clusters differing in the anomeric configuration of the monosaccharide core, nature of the bridging functional groups and valency, have been measured by a competitive enzyme‐linked lectin assay. Pentavalent thioether‐linked ligands (5 and 7) were prepared by radical addition of 2,3,4,6‐tetra‐O‐acetyl‐1‐thio‐α‐D‐mannopyranose to the corresponding penta‐O‐allyl‐α‐ or ‐β‐D‐glucopyranose, followed by deacetylation. The distinct reactivity of the anomeric position in the D‐glucose scaffold was exploited in the preparation of a tetravalent cluster (10) that keeps a reactive aglyconic group for further manipulation, including incorporation of a reporter group or attachment to a solid support. Hydroboration of the double bonds in the penta‐O‐allyl‐α‐D‐glucopyranose derivative and replacement of the hydroxy groups with amine moieties gave a suitable precursor for the preparation of pentavalent and 15‐valent mannosides through the thiourea‐bridging reaction (17 and 20, respectively). The diastereomeric 1‐thiomannose‐coated clusters 5 and 7 were demonstrated to be potent ligands for Con A, with IC50 values for the inhibition of the Con A–yeast mannan association indicative of 6.4‐ and 5.5‐fold increases in binding affinity (valency‐corrected values), respectively, relative to the value for methyl α‐D‐mannopyranoside. The tetravalent cluster 10 exhibited a valency‐corrected relative lectin‐binding potency virtually identical to that of the homologous pentavalent mannoside 7. In sharp contrast, replacement of the 1‐thiomannose wedges of 5 with α‐D‐mannopyranosylthioureido units (17) virtually abolished any multivalent or statistic effects, with a dramatic decrease of binding affinity. The 15‐valent ligand 20, possessing classical O‐glycosidic linkages, exhibited a twofold increase in lectin affinity relative to the penta‐O‐(thioglycoside) 5; it is less efficient based on the number of mannose units. The results illustrate the potential of carbohydrates as polyfunctional platforms for glycocluster construction and underline the importance of careful design of the overall architecture in optimising glycocluster recognition by specific lectins.
Comparative Analysis of Putative Agonist‐Binding Modes in the Human A1 Adenosine Receptor
Authors: Gutiérrez‐de‐Terán Hugo , Pastor Manuel , Centeno Nuria B. , Åqvist Johan , Sanz Ferran
Published: May 2004

A recent study reported a model of the human A1 adenosine receptor and its agonist binding site, proposing two putative binding modes in the same binding site for the natural agonist, adenosine. The present work investigates the flexibility of this binding site by exhaustive exploration with the natural agonist and with three other adenosine derivatives: N6‐cyclopentyladenosine (CPA), 2‐chloro‐N6‐cyclopentyladenosine (CCPA), and 5′‐N‐ethylcarboxamidoadenosine (NECA). Our aim was to find a common binding mode for agonists that would explain the role in the binding process of the different substitutions allowed at the 2, N6, and 5′ positions of adenosine. This problem was addressed through docking simulations, molecular dynamics studies, and estimations of the ligand‐binding free energy with both the AUTODOCK scoring function and the linear interaction energy (LIE) approach. The results point to a single receptor‐binding position that explains the effects of the different chemical modifications on the adenosine derivatives considered here.
Two‐Dimensional Multiarray Formation of Hepatocyte Spheroids on a Microfabricated PEG‐Brush Surface
Authors: Otsuka Hidenori , Hirano Akihiro , Nagasaki Yukio , Okano Teruo , Horiike Yasuhiro , Kataoka Kazunori
Published: May 2004

A two‐dimensional microarray of ten thousand (100×100) hepatocyte heterospheroids, underlaid with endothelial cells, was successfully constructed with 100 μm spacing in an active area of 20×20 mm on microfabricated glass substrates that were coated with poly(ethylene glycol) brushes. Cocultivation of hepatocytes with endothelial cells was essential to stabilize hepatocyte viability and liver‐specific functions, allowing us to obtain hepatocyte spheroids with a diameter of 100 μm, functioning as a miniaturized liver to secret albumin for at least one month. The most important feature of this study is that these substrates are defined to provide an unprecedented control of substrate properties for modulating cell behavior, employing both surface engineering and synthetic polymer chemistry. The spheroid array constructed here is highly useful as a platform of tissue and cell‐based biosensors and detects a wide variety of clinically, pharmacologically, and toxicologically active compounds through a cellular physiological response.
Light‐Activated Transcription and Repression by Using Photocaged SERMs
Authors: Shi Youheng , Koh John T.
Published: May 2004

Recently developed methods to regulate the spatial and temporal patterning of genes in a light‐directed manner hold promise as powerful tools for exploring the function of genes that act through their unique spatiotemporal patterning. To further explore the application of photocaged ligands of nuclear receptors to control gene expression patterning, the actions of photocaged analogues of selective estrogen‐receptor modulators (SERMs) have been evaluated. Photocaged derivatives of hydroxytamoxifen (NB‐Htam) and guanidine tamoxifen (NB‐Gtam) have been synthesized that selectively antagonize ERα‐ and ERβ‐mediated transcription at classic estrogen response elements (EREs) in response to light. When present only intracellularly, Htam and Gtam provide a similar transient repression response. When SERMs are allowed to diffuse out of the cell, transcription is recovered at a similar rate for Htam and Gtam (6.4 and 5.6 h−1), but is notably faster than is observed with the covalently binding SERM tamoxifen aziridine (Taz) (3.8 h−1). This suggests that the duration of agonist action is controlled by ligand off‐rates/diffusion and not by receptor turnover. Gtam activates ERβ‐mediated transcription at AP1 sites in a similar way to what has previously been reported for Htam. NB‐Gtam and NB‐Tam provide a light‐activated transcription response at AP1‐driven reporters, thus illustrating the unique ability of photocaged SERMs to simultaneously mediate light‐activated transcription and repression.
A Novel Bis‐aziridinylnaphthoquinone with Anti‐Solid Tumor Activity in which Induced Apoptosis is Associated with Altered Expression Of Bcl‐2 Protein
Authors: Huang Sheng‐Tung , Tsai Hsin‐Da , Kuo Hsien‐Shou , Yang Yu‐Ping , Peng Yi‐Chen , Lin Yuh‐Ling
Published: May 2004

Aziridine‐containing compounds have been of interest as anticancer agents since the late 1970s. The design, synthesis, and study of aziridinylnaphthoquinone analogues to obtain compounds with enhanced activity/toxicity profiles are an ongoing research effort in our group. A series of bis‐aziridinylnaphthoquinone derivatives has been prepared, and the cytotoxic activities of these synthetic bis‐aziridinylnaphthoquinone derivatives has been investigated. The synthetic derivatives displayed significant cytotoxicity against human carcinoma cell lines and weak cytotoxic activities against skin fibroblasts (SF). The bis‐aziridinylnaphthoquinone 1 c was the most effective of the tested analogues at reducing the viability of Hep2 cells, with an LD50 value of 5.23 μM, and also exhibited weak cytotoxic activity against SF cells, with an LD50 value of 54.12 μM. The DNA alkylation and DNA interstrand cross‐linking abilities of 1 c were also investigated. Bis‐aziridinylnaphthoquinone 1 c was an effective agent for alkylation of DNA after chemical reduction in vitro, and its bifunctional alkylating moieties were able to cross‐link DNA. We also report here our efforts to determine direct antitumor effects of 1 c on Hep2 cells. Growth arrest in Hep2 cells was preceded by early induction of G2‐M cell cycle arrest at 0.75 μM of 1 c after culture for 24 h, and was then followed by apoptosis after 60 h. This was associated with decreased expression of antiapoptotic bcl2 protein (by 78 %) upon culture with 3.0 μM of 1 c after 60 h. Our results suggest that 1 c is a novel antitumor aziridinylnaphthoquinone with therapeutic potential against solid tumors.
Cover Picture: Two‐Dimensional Multiarray Formation of Hepatocyte Spheroids on a Microfabricated PEG‐Brush Surface (ChemBioChem 6/2004)
Authors: Otsuka Hidenori , Hirano Akihiro , Nagasaki Yukio , Okano Teruo , Horiike Yasuhiro , Kataoka Kazunori
Published: May 2004

The cover picture shows a simple and effective way to construct a 2D microarray of 10 000 hepatocyte heterospheroids, underlaid with endothelial cells, through a combination of surface PEG treatment and subsequent microfabrication of plasma etching. The micropatterned PEG‐treated region works to repel proteins and consequently inhibits cell adhesion, while the glass circular domains (Ø=100 μm), separated by PEG‐treated regions (l=100 μm), provide cell adhesive regions. This spheroid array is very useful as a platform for tissue and cell‐based biosensors, which can be used as an alternative to animal experiments in a variety of situations. For more details, see the article by Kataoka et al. on p. 850 ff.
Reactions of Substituted (1,3‐Butadiene‐1,4‐diyl)magnesium, 1,4‐Bis(bromomagnesio)butadienes and 1,4‐Dilithiobutadienes with Ketones, Aldehydes and PhNO To Yield Cyclopentadiene Derivatives and N‐Ph Pyrroles by Cyclodialkenylation
Authors: Fang Hongyun , Li Guotao , Mao Guoliang , Xi Zhenfeng
Published: May 2004

1,4‐Dilithiobutadiene derivatives 1, 1,4‐bis(bromomagnesio)butadiene derivatives 2 and metallacyclic (1,3‐butadiene‐1,4‐diyl)magnesium reagents 3 were prepared and their reactions with ketones, aldehydes, and PhNO were investigated. Multiply substituted cyclopentadienes and N‐Ph pyrroles were formed by unprecedented reaction conditions. The carbonyl group of aldehydes and ketones was deoxygenated during the reaction and behaved formally as a one‐carbon unit; the NO moiety of PhNO was cleaved to afford N‐Ph pyrrole derivatives. Furthermore, different reactivities among these three types of reagents 1, 2 and 3 were revealed. The 1,4‐dilithium reagents 1 readily reacted with both aldehydes and ketones; the 1,4‐dimagnesium reagents 2 reacted with aldehydes, but not ketones; the metallacyclopentadiene reagents of magnesium 3 showed higher reactivity and did react with ketones.
Role of the aging vasculature and Erb B‐2 signaling in epidermal growth factor‐dependent intravasion of breast carcinoma cells
Authors: Price Daniel J. , Avraham Shalom , Jiang Shuxian , Fu Yigong , Avraham Hava Karsenty
Published: May 2004

BACKGROUND

The risks for developing breast carcinoma and dying from the disease increase with age. Mortality from breast carcinoma usually is due to metastatic disease. Metastatic cells are able to invade into the vascular tissue in a growth factor‐dependent manner. Because breast carcinoma mortality increases with age, examination of breast carcinoma interactions with young and aged endothelial cells is essential.

METHODS

We studied a series of breast epithelial cells (HMT‐3522 cells) that exhibited either noninvasive characteristics (S‐1 cells) or epidermal growth factor (EGF)‐dependent invasive characteristics (T4‐2 cells).

RESULTS

Increased invasion of HMT‐3522 cells was observed across an aged rat brain microvascular endothelial cell (BMEC) monolayer that was isolated from aged rats (24 months) compared with young rats (age 1 month). This increased invasion was inhibited by the specific EGF receptor inhibitor, AG1478, and by the Erb B‐2‐specific inhibitor, AG825. To analyze further the contribution of Erb B‐2 to the EGF‐dependent invasion of HMT‐3522 cells, T4‐2 cells were treated with the Erb B‐2‐specific therapeutic antibody trastuzumab and with the specific inhibitor AG825 and were then assayed for invasion. Both inhibitors led to a significant decrease in EGF‐dependent invasion. Erb B‐2 expression was found to be elevated in T4‐2 cells (≈ 5‐fold higher) compared with S‐1 cells. However, treatment of T4‐2 cells with the specific Erb B‐2 inhibitor, AG825, failed to inhibit EGF‐mediated signaling to phosphatidylinositol 3‐kinase or extracellular‐regulated kinases 1 and 2.

CONCLUSIONS

The current study findings indicate that aging of endothelium may contribute to the invasive phenotype of breast carcinoma cells and that “cross‐talk” between Erb B‐2 and EGF receptor is required for the intravasion of these cells into the surrounding vasculature. Cancer 2004. © 2004 American Cancer Society.