bluuebunny/crossref_metadata_2025 huggingface dataset:
Facile Preparation of Strontium Tungstate and Tungsten Trioxide Hollow Spheres
Authors: Zhao Xiufeng , Cheung Teresa L. Y. , Zhang Xitian , Ng Dickon H. L. , Yu Jiaguo
Published: June 2006

A simple and low‐cost technique was developed to produce unique SrWO4 and WO3 hollow spheres. The SrWO4 hollow spheres were prepared via a precipitation reaction between SrCl2 and Na2WO4 in the presence of polymethacrylic acid, and the synthesis of WO3 spheres used the as‐prepared SrWO4 hollow spheres as both precursors and templates. After soaking in HNO3 and calcinations, the SrWO4 were completely transformed into WO3 while the hollow structures were perfectly retained. The “polymer‐cation template” model was proposed to describe the formation of the SrWO4 hollow spheres. This technique is feasible in fabricating other inorganic hollow‐structured materials.
Microstructures and Adhesion of the Oxide Scale Formed on Titanium Aluminum Carbide Substrates
Authors: Lin Zhijun , Zhuo Mujin , Zhou Yanchun , Li Meishuan , Wang Jingyang
Published: June 2006

Microstructures of oxidized Ti3AlC2 and Ti2AlC were investigated using transmission electron microscopy. The presence of Ti‐rich precipitates in the Al2O3 oxide scale and the enrichment of Ti in the Al2O3 grain boundaries were identified. High diffusivity of Al in the carbides contributes to the selective oxidation of Al. Moreover, the adhesive strength between the oxide scales and the substrates exceeds 85 MPa. Strong adhesive strength contributes to the thermal‐cyclic stability of the oxide scales.
Fabrication of Stable Al2O3 Slurries and Dense Green Bodies Using Wet Jet Milling
Authors: Omura Naoki , Hotta Yuji , Sato Kimiyasu , Kinemuchi Yoshiaki , Kume Shoichi , Watari Koji
Published: June 2006

A wet jet milling process was used as a novel method to prepare Al2O3 slurries. The wet jet‐milled slurries showed very low viscosity compared with the ball‐milled slurries. Moreover, the viscosity of the wet jet‐milled slurries was constant for long times, whereas that of the ball‐milled slurries increased rapidly with time. Al2O3 particles after wet jet milling retained initial surface conditions, although Al2O3 particles after ball milling yielded more OH groups on the surface. Casting rate was sensitive to the solid content and preparation method of slurry. The relative density of the green bodies prepared from the wet jet‐milled slurries was about 65% or more and was independent of the slurry solid content. On the other hand, the relative density of the green bodies prepared from the ball‐milled slurries increased with increasing solid content and was higher than 60% at the solid content of 50% by volume. Linear shrinkage of the sintered bodies prepared from the wet jet‐milled slurries was very low and independent of the solid content of the slurry whereas that of the sintered bodies prepared from the ball‐milled slurries increased with decreasing solid content.
Reactive Hot Pressing of ZrB2–SiC–ZrC Ultra High‐Temperature Ceramics at 1800°C
Authors: Wu Wen‐Wen , Zhang Guo‐Jun , Kan Yan‐Mei , Wang Pei‐Ling
Published: June 2006

A ZrB2–SiC–ZrC composite was prepared from a mixture of zirconium, silicon, and B4C via reactive hot pressing at a relatively low temperature (1800°C) for 60 min under 20 MPa in an argon atmosphere. The relative density was 96.8%, the micro‐hardness (Hv10) was 16.7 GPa, and the fracture toughness was 5.1 MPa·m1/2. The presence of ZrC was helpful for the densification process and improved the mechanical properties of the composite. A model of the microstructure development of the composite was proposed to explain the phase distribution.
Sintering Behavior of In Situ Cobalt Oxide‐Doped Cerium–Gadolinium Oxide Prepared by Flame Spray Pyrolysis
Authors: Jud Eva , Gauckler Ludwig , Halim Samuel , Stark Wendelin
Published: June 2006

Ce0.9Gd0.1O1.95 (CGO10) and in situ cobalt oxide‐doped CGO10 were prepared by pilot‐scale flame spray synthesis, yielding powders with an average particle size of 40 nm. Cobalt oxide was shown to be a very effective sintering aid for CGO10 and lowered the maximum sintering temperature from 1450° to about 1200°C. Sintering studies revealed that in situ cobalt oxide‐doped CGO10 exhibited a temperature of maximum shrinkage rate of 880°C for a dopant concentration of 1 mol% CoO1−x, whereas for conventionally cobalt oxide‐doped CGO10, this temperature was 914°C. This decrease is believed to be a result of a more homogeneous dopant distribution of the in situ cobalt oxide‐doped CGO nanopowders as compared with the powders in which the doping was introduced as nitrates.
Isothermal Oxidation of Ta2AlC in Air
Authors: Gupta S. , Filimonov D. , Barsoum M. W.
Published: June 2006

The oxidation behavior, in air, of bulk polycrystalline Ta2AlC samples was studied in the 600°–900°C temperature range. A protective, essentially X‐ray amorphous, oxide layer—which does not appear to be resistant to thermal cycling—forms at 600°C. This layer is comprised of Ta, Al, and O. At 700°C and above, it is compositionally quite uniform, but porous and highly cracked. No phase separation was observed at the micrometer scale. The oxide layers consisted of the crystalline phases, Ta2O5 and TaAlO4, and an X‐ray amorphous phase. In the 700°–900°C temperature range, the oxidation kinetics were found to be linear.
Use of HEMA in Gelcasting of Ceramics: A Case Study on Fused Silica
Authors: Zhang Yu , Cheng Yi‐Bing
Published: June 2006

Gelcasting is a useful method for producing high‐strength ceramic green parts. However, industry has been reluctant to use the gelcasting technique because the most commonly used gel, acrylamide (AM), is a neurotoxin. Here we report an attempt at the gelcasting of fused silica material using a low‐toxicity gel, 2‐hydroxyethyl methacrylate (HEMA). The HEMA‐based aqueous system was found to perform as well as AM‐based systems in terms of the properties of gelcasting suspensions, cast green parts, and densified components. The new gelcasting system should be readily applicable to other ceramic materials.
Pb(Zn1/3Ta2/3)O3–PbTiO3 Derived from Mechanical Activation
Authors: Soon Kokwah , Xue Junmin , Wang John
Published: June 2006

Nanocrystalline Pb(Zn1/3Ta2/3)O3 (PZTa) of perovskite structure, which cannot be synthesized by either the conventional solid‐state reaction of mixed oxides or wet chemistry routes, has been successfully synthesized via a mechanical activation route. The effects of PbTiO3 (PT) doping in PZTa on the phase formation, thermal stability of the nanocrystalline perovskite phase, and dielectric properties of the resulting PZTa–PT are studied. PZTa doped with a low PT content exhibited a diffuse phase transition, while those with high PT contents demonstrated an expected sharp phase transition at the Curie temperature.
Characterization and Mechanical Performance of the Mg‐Stabilized β‐Ca3(PO4)2 Prepared from Mg‐Substituted Ca‐Deficient Apatite
Authors: Kannan Sanjeevi , Lemos Alexandra F. , Rocha Jorge H. G. , Ferreira Jose M. F.
Published: June 2006

The preparation of Mg‐stabilized β‐tricalcium phosphate (β‐TCP) was carried out by an aqueous precipitation method and the characterization of the powders was performed by powder X‐ray diffraction, FT‐IR spectra, Raman spectroscopy, and elemental analysis. The transformation of calcium‐deficient apatite into β‐TCP has occurred in the range of 700°–800°C. The calculated values for lattice parameters confirm the stabilization role played by Mg. The thermal stability of the Mg‐stabilized β‐TCP powders was evident until 1400°C, thus broadening the sintering temperature range without transformation into the undesirable α‐TCP. Accordingly, the mechanical properties of the Mg‐stabilized β‐TCP were improved in comparison with those of pure β‐TCP.
Numerical Simulation of Effect of Methyltrichlorosilane Flux on Isothermal Chemical Vapor Infiltration Process of C/SiC Composites
Authors: Wei Xi , Cheng Laifei , Zhang Litong , Xu Yongdong , Zeng Qingfeng
Published: June 2006

A two‐dimensional axisymmetrical mathematical model for the isothermal chemical vapor infiltration process of C/SiC composites was developed. Transport phenomena of momentum, energy, and mass in conjunction with infiltration‐induced changes of preform structure were taken into account. The integrated model was implemented by the finite‐element method to simulate numerically the isothermal chemical vapor infiltration (ICVI) process of C/SiC composites at different methyltrichlorosilane (MTS) fluxes. The influence of MTS flux on concentration distribution and time‐dependent densification behaviors of C/SiC composites was studied in detail. Calculation results imply that MTS flux has an obvious influence on infiltration in micro‐pores and little influence on infiltration in macro‐pores. Increasing flux will lead to an evident acceleration for infiltration in micro‐pores. Moderate flux is preferable by a combination of both a relatively high infiltration rate and a relatively low fabrication cost. This model is helpful to understand the fundamentals of the ICVI process for the fabrication of C/SiC composites.
Preparation and Properties of Hydrothermally Stable γ‐Alumina‐Based Composite Mesoporous Membranes
Authors: Zahir Md. Hasan , Sato Koji , Mori Hiroshi , Iwamoto Yuji , Nomura Mikihiro , Nakao Shin‐ichi
Published: June 2006

We report here on our thermal and hydrothermal investigations comparing mesoporous γ‐Al2O3 membrane with single and double dopant membranes prepared by the sol–gel method. Improvements in the hydrothermal stability of mesoporous γ‐Al2O3 by transition (Ga3+) or rare‐earth (La3+) cations are discussed, along with the effectiveness of double dopant (Ga3+–La3+). The amounts of Ga2O3 oxide used varied between 0.0 and 30 mol% and those of La2O3 between 6 and 15 mol%. The thermal and hydrothermal (up to 75% steam) stability of nine types of membranes fabricated on an asymmetric porous α‐Al2O3 support by means of a dip‐coating process was characterized by H2 gas permeation at 500°C. By conducting tests with wide variations in dopant concentrations, material characterizations, and gas permeance performance, we have been able to optimize the key parameters for hydrothermally stable systems.
Influence of Dipolar Fields on the Photochemical Reactivity of Thin Titania Films on BaTiO3 Substrates
Authors: Burbure Nina V. , Salvador Paul A. , Rohrer Gregory S.
Published: June 2006

The photochemical properties of TiO2 films supported on BaTiO3 were investigated to test the hypothesis that dipolar fields from a ferroelectric substrate would affect the reactivity of the supported film. Photochemical reaction products were formed on the TiO2 surface in patterns that correspond to the underlying domain structure of BaTiO3. As the film thickness increases from 10 to 100 nm, the titania more effectively screens the ferroelectric field, and the pattern of reaction products is obscured. It is concluded that dipolar fields from the ferroelectric substrate influence charge carrier transport in the film and spatially localize the reaction products.
Effect of drug‐induced cytotoxicity on glucose uptake in Hodgkin's lymphoma cells
Authors: Banning Ursula , Barthel Henryk , Mauz‐Körholz Christine , Kluge Regine , Körholz Dieter , Sabri Osama
Published: June 2006

Abstract:  Background: In Hodgkin's lymphoma, F‐18‐fluoro‐deoxy‐d‐glucose positron emission tomography (FDG‐PET) is used for staging and response evaluation after chemotherapy. However, drug‐mediated downregulation of glucose uptake in viable Hodgkin's lymphoma cells might limit the use of FDG‐PET. Methods: We analyzed the effect of etoposide on cell viability and uptake of F‐18‐fluoro‐deoxy‐d‐glucose or the glucose analog 2‐[N‐(7‐nitrobenz‐2‐oxa‐1,3‐diazol‐4‐yl)amino]‐2‐deoxyglucose (2‐NBDG) in vitro. Results: Etoposide induced a dose‐dependent cytotoxicity in HDLM‐2 cells which was significantly correlated with reduced FDG uptake. However, it also significantly increased the portion of viable cells which did not take up 2‐NBDG. Interestingly, etoposide‐induced cytotoxicity was mainly mediated via caspase‐dependent mechanisms, whereas the cell death induced by deprivation of glucose was mediated via caspase‐independent mechanisms. Conclusion: Etoposide‐mediated reduction of glucose uptake by Hodgkin's lymphoma cells is mainly caused by cell death. In a small fraction of viable cells, etoposide might downregulate glucose transporters and/or hexokinase activity and by that inhibit glucose uptake. This, however, might not lead to false‐negative results of response evaluation in Hodgkin's lymphoma patients after chemotherapy, because inhibition of glucose uptake itself seems to be a strong inducer of cell death. Altogether, this study provides important in vitro evidence to clarify the mechanisms by which FDG‐PET monitors the effect of anti‐cancer treatment in Hodgkin's lymphoma patients.
Polymorphisms in Exons 1B and 1C of the Type I Interleukin‐1 Receptor Gene in Patients with Endometriosis
Authors: D'Amora Paulo , Sato Hélio , Girão Manoel JBC , Silva Ismael DCG , Schor Eduardo
Published: June 2006

Problem  To study possible correlation between the prevalence of polymorphisms in the type I interleukin‐1 receptor gene and pelvic endometriosis.

Method of study  Genotypes of 223 women were analyzed: 109 women with surgically and histologically confirmed endometriosis and 114 healthy women. Distributions of two single‐base polymorphisms of the human interleukin‐1 receptor type I (IL‐1RI) gene were evaluated: PstI, due to a C→T transition in exon 1B and BsrBI a C→A transition at position 52 in exon 1C. Polymorphisms were detected by polymerase chain reaction (PCR) followed by restriction fragment length polymorphism analysis (RFLP) resolved on 3% agarose gels stained with ethidium bromide.

Results  Genotypes for PstI polymorphisms did not differ significantly among control and endometriosis (P = 0.058). However, in relation to BsrBI polymorphism, protective risk was observed for the development of endometriosis [OR 0.39–IC 95% (0.2–0.9)].

Conclusions  BsrBI heterozygote genotype (C/A) showed protective effect against endometriosis development.
Determining the physical properties of flax fibre for industrial applications: the influence of agronomic practice
Authors: Norton A.J. , Bennett S.J. , Hughes M. , Dimmock J.P.R.E. , Wright D. , Newman G. , Harris I.M. , Edwards‐Jones G.
Published: June 2006

Field trials of fibre flax were sown in 2002 and 2003 comprising 29 and 26 flax varieties, respectively. In 2002, two nitrogen treatments of 40 and 80 kg ha−1 were imposed. The trials were sprayed with a desiccating herbicide prior to retting at 35 and 15 days after midpoint of flowering in 2002 and 2003, respectively, and were harvested once retting had completed. Fibre was extracted from the flax stems using a laboratory‐scale scutcher and hackling pins, and long and total fibre yields were determined. The breaking load of flax technical fibres was assessed using a novel technique employing ‘zero twist’ yarns. Fineness was assessed using the Wool Industries Research Association airflow method. The tenacity of a single technical fibre was then derived from the average breaking load of the yarn and knowledge of its fineness. Both flax variety and season were found to contribute to variations in fibre fineness and strength, with the dry season in 2003 leading to less variation across the varieties and much finer fibres. Few of the varieties were found to be stable across seasons, and environmental variation accounted for 96% of the variation in fibre fineness between years, and 69% of the variation in tensile strength and breaking load. Fibre yield was found to be related to fibre fineness, with the coarser fibres corresponding to higher yields. The new yarn test presented herein has been shown to be a valid and useful method for determining the tensile properties of technical flax. The varieties and the sample sizes required to adequately measure variation in fibre properties are discussed.
Ruminant‐mediated Seed Dispersal of an Economically Valuable Tree in Indian Dry Forests1
Authors: Prasad Soumya , Krishnaswamy Jagdish , Chellam Ravi , Goyal Surendra Prakash
Published: June 2006

Ruminant‐mediated seed dispersal, an understudied process in tropical forests, was examined via Phyllanthus emblica–Axis axis interaction. A captive Axis deer regurgitated intact P. emblica seeds after retaining them in the rumen for 7–27 h. At Rajaji National Park, a considerable fraction (22%) of deer‐regurgitated P. emblica seeds germinated, although lower than unconsumed seeds (72%). The size and strength of seeds like P. emblica might ensure that ruminants regurgitate them intact instead of defecating them.
A strong – correlation in radio pulsars with implications for torque variations
Authors: Urama J. O. , Link B. , Weisberg J. M.
Published: June 2006

We present an analysis of the spin-down parameters for 131 radio pulsars for which has been well determined. These pulsars have characteristic ages ranging from 103 to 108 yr and spin periods in the range 0.4-30 s; nearly equal numbers of pulsars have as have . We find a strong correlation of with , independent of the sign of. We suggest that this trend can be accounted for by small, stochastic deviations in the spin-down torque that are directly proportional (in magnitude) to the spin-down torque.
The escape fraction of ionizing photons from galaxies at z = 0–6
Authors: Inoue Akio K. , Iwata Ikuru , Deharveng Jean-Michel
Published: June 2006

The escape fraction of ionizing photons from galaxies is a crucial quantity controlling the cosmic ionizing background radiation and the reionization. Various estimates of this parameter can be obtained in the redshift range z= 0–6, either from direct observations or from the observed ionizing background intensities. We compare them homogeneously in terms of the observed flux density ratio of ionizing (∼900 Å rest-frame) to non-ionizing ultraviolet (∼1500 Å rest-frame) corrected for the intergalactic absorption. The escape fraction is found to increase by an order of magnitude, from a value less than 0.01 at z ≲ 1 to about 0.1 at z ≳ 4.
Muscle microvascular oxygenation in chronic heart failure: role of nitric oxide availability
Authors: Ferreira L. F. , Hageman K. S. , Hahn S. A. , Williams J. , Padilla D. J. , Poole D. C. , Musch T. I.
Published: June 2006

Aim:  To test the hypothesis that diminished vascular nitric oxide availability might explain the inability of individuals with chronic heart failure (CHF) to maintain the microvascular PO2’s (PO2mv ∝ O2 delivery‐to‐uptake ratio) seen in healthy animals.

Methods:  We superfused sodium nitroprusside (SNP; 300 μm), Krebs–Henseleit (control, CON) and l‐nitro arginine methyl ester (l‐NAME; 1.5 mm) onto the spinotrapezius muscle and measured PO2mv by phosphorescence quenching in female Sprague–Dawley rats (n = 26) at rest and during twitch contractions (1 Hz). Seven rats served as controls (Sham) while CHF was induced by myocardial infarction. CHF rats were grouped as moderate (MOD; n = 15) and severe CHF (SEV; n = 4) according to morphological data and baseline PO2mv.

Results:  In contrast to Sham and MOD,l‐NAME did not affect the PO2mv response (dynamics and steady‐state) of SEV when compared with CON. SNP restored the PO2mv profile of SEV to that seen in Sham animals during CON. Specifically, the effect of l‐NAME expressed as Δ(l‐NAME – CON) were: Baseline PO2mv [in mmHg, ΔSham = −7.0 ± 1.6 (P < 0.05); ΔSEV =−1.2 ± 2.1], end‐contractions PO2mv [in mmHg, ΔSham = −5.0 ± 1.0 (P < 0.05); ΔSEV = −2.5 ± 0.5] and time constant of PO2mv decrease [in s, ΔSham = −6.5 ± 3.0 (P < 0.05); ΔSEV = −3.2 ± 1.8].

Conclusion:  These data provide the first direct evidence that the pathological profiles of PO2mv associated with severe CHF can be explained, in part, by a diminished vascular NO availability.
Efficacy and connectivity of intracolumnar pairs of layer 2/3 pyramidal cells in the barrel cortex of juvenile rats
Authors: Feldmeyer Dirk , Lübke Joachim , Sakmann Bert
Published: June 2006

Synaptically coupled layer 2/3 (L2/3) pyramidal neurones located above the same layer 4 barrel (‘barrel‐related’) were investigated using dual whole‐cell voltage recordings in acute slices of rat somatosensory cortex. Recordings were followed by reconstructions of biocytin‐filled neurones. The onset latency of unitary EPSPs was 1.1 ± 0.4 ms, the 20–80% rise time was 0.7 ± 0.2 ms, the average amplitude was 1.0 ± 0.7 mV and the decay time constant was 15.7 ± 4.5 ms. The coefficient of variation (c.v.) of unitary EPSP amplitudes decreased with increasing EPSP peak and was 0.33 ± 0.18. Bursts of APs in the presynaptic pyramidal cell resulted in EPSPs that, over a wide range of frequencies (5–100 Hz), displayed amplitude depression. Anatomically the barrel‐related pyramidal cells in the lower half of layer 2/3 have a long apical dendrite with a small terminal tuft, while pyramidal cells in the upper half of layer 2/3 have shorter and often more ‘irregularly’ shaped apical dendrites that branch profusely in layer 1. The number of putative excitatory synaptic contacts established by the axonal collaterals of a L2/3 pyramidal cell with a postsynaptic pyramidal cell in the same column varied between 2 and 4, with an average of 2.8 ± 0.7 (n= 8 pairs). Synaptic contacts were established predominantly on the basal dendrites at a mean geometric distance of 91 ± 47 μm from the pyramidal cell soma. L2/3‐to‐L2/3 connections formed a blob‐like innervation domain containing 2.8 mm of the presynaptic axon collaterals with a bouton density of 0.3 boutons per μm axon. Within the supragranular layers of its home column a single L2/3 pyramidal cell established about 900 boutons suggesting that 270 pyramidal cells in layer 2/3 are innervated by an individual pyramidal cell. In turn, a single pyramidal cell received synaptic inputs from 270 other L2/3 pyramidal cells. The innervation domain of L2/3‐to‐L2/3 connections superimposes almost exactly with that of L4‐to‐L2/3 connections. This suggests that synchronous feed‐forward excitation of L2/3 pyramidal cells arriving from layer 4 could be potentially amplified in layer 2/3 by feedback excitation within a column and then relayed to the neighbouring columns.
Evidence for both adenosine A1and A2Areceptors activating single vagal sensory C‐fibres in guinea pig lungs
Authors: Chuaychoo Benjamas , Lee Min‐Goo , Kollarik Marian , Pullmann Rudolf , Undem Bradley J.
Published: June 2006

We addressed the hypothesis that single vagal afferent C‐fibres can be stimulated via either the adenosine A1or A2Areceptor subtypes. The effect of adenosine on the nerve terminals of vagal sensory nerve subtypes was evaluated in anex vivoperfused guinea pig lung preparation using extracellular recording techniques. Adenosine (10 μm) consistently evoked action potential discharge in lung C‐fibre terminals arising from the nodose ganglia, but failed to evoke action potential discharge in most jugular ganglion C‐fibres. Adenosine also failed to activate stretch‐sensitive nodose A‐fibres in the lungs. The selective A1antagonist DPCPX (0.1 μm) or the selective A2Aantagonist SCH 58261 (0.1 μm) partially inhibited the nodose C‐fibre activation by adenosine, and the combination of both antagonists almost completely inhibited the response. The adenosine‐induced action potential discharge in nodose C‐fibres was mimicked by either the selective A1agonist CCPA (1 μm) or the selective A2Aagonist CGS 21680 (1 μm). Single cell PCR techniques revealed that adenosine A1and A2Areceptor mRNA was expressed in individual nodose neurons retrogradely labelled from the lungs. The gramicidin‐perforated patch clamp technique on neurons retrogradely labelled from the lungs was employed to study the functional consequence of adenosine receptor agonists directly on neuronal membrane properties. Both the selective A1agonist CCPA (1 μm) and the selective A2Aagonist CGS 21680 (1 μm) depolarized the airway‐specific, capsaicin‐sensitive, nodose neurons to action potential threshold. The data support the hypothesis that adenosine selectively depolarizes vagal nodose C‐fibre terminals in the lungs to action potential threshold, by stimulation of both adenosine A1and A2Areceptor subtypes located in the neuronal membrane.
Neurally mediated vasoconstriction is capable of decreasing skin blood flow during orthostasis in the heat‐stressed human
Authors: Shibasaki Manabu , Davis Scott L. , Cui Jian , Low David A. , Keller David M. , Durand Sylvain , Crandall Craig G.
Published: June 2006

Given the large increase in cutaneous vascular conductance (CVC) during whole‐body heat stress, this vascular bed is important in the regulation of blood pressure during orthostatic stress. In this thermal state, changes in CVC are reported to be due to withdrawal of active vasodilator activity. The purpose of this study was to identify, contrary to the current line of thinking, whether cutaneous vasoconstrictor neural activity is enhanced and capable of contributing to reductions in CVC during an orthostatic challenge of heat‐stressed individuals. Healthy normotensive subjects were pretreated, subcutaneously, with botulinum toxin A (BTX‐A) to inhibit the release of neurotransmitters from cutaneous active vasodilator nerves. On the experimental day, microdialysis probes were placed in the BTX‐A‐treated site and in an adjacent untreated site. In protocol 1, internal temperature was elevated ∼0.7°C, followed by the application of lower body negative pressure (LBNP; −30 mmHg). LBNP reduced CVC at the BTX‐A‐treated sites (Δ4.2 ± 2.9%max), as well as at the control site (Δ9.8 ± 4.1%max). In protocol 2, after confirming the absence of cutaneous vasodilatation at the BTX‐A‐treated site during whole‐body heating, CVC at this site was elevated to a similar level relative to the control site (55.4 ± 13.4 versus 60.7 ± 10.4%max, respectively) via intradermal administration of isoproterenol prior to LBNP. Similarly, when flow was matched between sites, LBNP reduced CVC at both the BTX‐A‐treated (Δ15.3 ± 4.6%max) and the control sites (Δ8.8 ± 5.6%max). These data suggest that the cutaneous vasoconstrictor system is engaged and is capable of decreasing CVC during an orthostatic challenge in heat‐stressed individuals.
Membrane potential‐regulated Ca2+ signalling in development and maturation of mammalian cerebellar granule cells
Authors: Nakanishi Shigetada , Okazawa Makoto
Published: June 2006

In many developing neuronal cell types, the resting membrane potential is relatively depolarized, then gradually hyperpolarizes during the early postnatal period. The regulatory roles of membrane potential changes in neuronal development and maturation have been extensively studied in developing cerebellar granule cells, using primary culture under depolarizing and non‐depolarizing conditions in combination with in vivo analysis. Depolarization enhances calcium entry via voltage‐sensitive Ca2+ channels (VSCCs) and activates Ca2+–calmodulin‐dependent protein kinase (CaMK) and calcineurin phophatase (CaN). The activation of CaN induces many genes encoding extracellular and intracellular signalling molecules implicated in granule cell development. The inactivation of CaN in turn up‐regulates many other genes characteristic of mature granule cells, including NR2C NMDA receptor and GABAAα1 and α6 receptors. The induction of NR2C also requires CaMK‐up‐regulated brain‐derived neurotrophic factor (BDNF), indicating a convergence of signalling mechanism of the CaMK and CaN cascades. The inactivation of CaN maintains the phosphorylated and sumoylated form of a transcriptional myocyte enhances factor 2A (MEF2A) regulator. This form of MEF2A acts as a transcriptional repressor and is essential for the dendritic morphogenesis of differentiated granule cells. Collectively, the membrane potential change and the resulting Ca2+ signalling play a pivotal role in development and maturation of neuronal cells.
Arterial oxygenation influences central motor output and exercise performance via effects on peripheral locomotor muscle fatigue in humans
Authors: Amann Markus , Eldridge Marlowe W. , Lovering Andrew T. , Stickland Michael K. , Pegelow David F. , Dempsey Jerome A.
Published: June 2006

Changing arterial oxygen content (C) has a highly sensitive influence on the rate of peripheral locomotor muscle fatigue development. We examined the effects of C on exercise performance and its interaction with peripheral quadriceps fatigue. Eight trained males performed four 5 km cycling time trials (power output voluntarily adjustable) at four levels of C (17.6–24.4 ml O2 dl−1), induced by variations in inspired O2 fraction (0.15–1.0). Peripheral quadriceps fatigue was assessed via changes in force output pre‐ versus post‐exercise in response to supra‐maximal magnetic femoral nerve stimulation (ΔQtw; 1–100 Hz). Central neural drive during the time trials was estimated via quadriceps electromyogram. Increased C from hypoxia to hyperoxia resulted in parallel increases in central neural output (43%) and power output (30%) during cycling and improved time trial performance (12%); however, the magnitude of ΔQtw (−33 to −35%) induced by the exercise was not different among the four time trials (P > 0.2). These effects of C on time trial performance and ΔQtw were reproducible (coefficient of variation = 1–6%) over repeated trials at each F on separate days. In the same subjects, changing C also affected performance time to exhaustion at a fixed work rate, but similarly there was no effect of ΔC on peripheral fatigue. Based on these results, we hypothesize that the effect of C on locomotor muscle power output and exercise performance time is determined to a significant extent by the regulation of central motor output to the working muscle in order that peripheral muscle fatigue does not exceed a critical threshold.
Cardiac and vascular KATP channels in rats are activated by endogenous epoxyeicosatrienoic acids through different mechanisms
Authors: Lu Tong , Ye Dan , Wang Xiaoli , Seubert John M. , Graves Joan P. , Bradbury J. Alyce , Zeldin Darryl C. , Lee Hon‐Chi
Published: June 2006

We have reported that epoxyeicosatrienoic acids (EETs), the cytochrome P450 (CYP) epoxygenase metabolites of arachidonic acid (AA), are potent sarcolemmal ATP‐sensitive K+ (KATP) channel activators. However, activation of cardiac and vascular KATP channels by endogenously produced EETs under physiological intracellular conditions has not been demonstrated and direct comparison of the mechanisms whereby EETs activate the KATP channels in cardiac myocytes versus vascular smooth muscle cells has not been made. In this study, we examined the effects of AA on KATP channels in freshly isolated cardiac myocytes from rats, wild‐type (WT) and transgenic mice overexpressing CYP2J2 cDNA, and mesenteric arterial smooth muscle cells from rats. We also compared the activation of cardiac and vascular KATP channels by extracellularly and intracellularly applied 11,12‐EET. We found that 1 μm AA enhanced KATP channel activities in both cardiac and vascular smooth muscle cells, and the AA effects were inhibited by preincubation with CYP epoxygenase inhibitors. Baseline cardiac KATP current densities in CYP2J2 transgenic mice were 190% higher than those of WT mice, and both were reduced to similar levels by CYP epoxygenase inhibition. Western blot analysis showed that expression of Kir6.2 and SUR2A was similar between WT and CYP2J2 transgenic hearts. 11,12‐EET (5 μm) applied intracellularly enhanced the KATP currents by 850% in cardiac myocytes, but had no effect in vascular smooth muscle cells. In contrast, 11,12‐EET (5 μm) applied extracellularly increased KATP currents by 520% in mesenteric arterial smooth muscle cells, but by only 209% in cardiac myocytes. Preincubation with 100 μmm‐iodobenzylguanidine or 5 μm myristoylated PKI amide did not alter the activation of cardiac KATP channels by 5 μm 11,12‐EET, but significantly inhibited activation of vascular KATP channels. Moreover, EET only enhanced the inward component of cardiac KATP currents, but activated both the inward and outward components of vascular KATP currents. Our results indicate that endogenously derived CYP metabolites of AA potently activate cardiac and vascular KATP channels. EETs regulate cardiac electrophysiology and vascular tone by KATP channel activation, albeit through different mechanisms: the cardiac KATP channels are directly activated by EETs, whereas activation of the vascular KATP channels by EETs is protein kinase A dependent.
Plio-Pleistocene Ice Volume, Antarctic Climate, and the Global δ
18
O Record
Authors: Raymo M. E. , Lisiecki L. E. , Nisancioglu Kerim H.
Published: June 2006

We propose that from ∼3 to 1 million years ago, ice volume changes occurred in both the Northern and Southern Hemispheres, each controlled by local summer insolation. Because Earth's orbital precession is out of phase between hemispheres, 23,000-year changes in ice volume in each hemisphere cancel out in globally integrated proxies such as ocean δ
18
O or sea level, leaving the in-phase obliquity (41,000 years) component of insolation to dominate those records. Only a modest ice mass change in Antarctica is required to effectively cancel out a much larger northern ice volume signal. At the mid-Pleistocene transition, we propose that marine-based ice sheet margins replaced terrestrial ice margins around the perimeter of East Antarctica, resulting in a shift to in-phase behavior of northern and southern ice sheets as well as the strengthening of 23,000-year cyclicity in the marine δ
18
O record.
Early Pleistocene Glacial Cycles and the Integrated Summer Insolation Forcing
Authors: Huybers Peter
Published: June 2006

Long-term variations in Northern Hemisphere summer insolation are generally thought to control glaciation. But the intensity of summer insolation is primarily controlled by 20,000-year cycles in the precession of the equinoxes, whereas early Pleistocene glacial cycles occur at 40,000-year intervals, matching the period of changes in Earth's obliquity. The resolution of this 40,000-year problem is that glaciers are sensitive to insolation integrated over the duration of the summer. The integrated summer insolation is primarily controlled by obliquity and not precession because, by Kepler's second law, the duration of the summer is inversely proportional to Earth's distance from the Sun.
Arginylation of ß-Actin Regulates Actin Cytoskeleton and Cell Motility
Authors: Karakozova Marina , Kozak Marina , Wong Catherine C. L. , Bailey Aaron O. , Yates John R. , Mogilner Alexander , Zebroski Henry , Kashina Anna
Published: June 2006

Posttranslational arginylation is critical for mouse embryogenesis, cardiovascular development, and angiogenesis, but its molecular effects and the identity of proteins arginylated in vivo are unknown. We found that β-actin was arginylated in vivo to regulate actin filament properties, β-actin localization, and lamella formation in motile cells. Arginylation of β-actin apparently represents a critical step in the actin N-terminal processing needed for actin functioning in vivo. Thus, posttranslational arginylation of a single protein target can regulate its intracellular function, inducing global changes on the cellular level, and may contribute to cardiovascular development and angiogenesis.
Microwave-Assisted Synthesis of Fluoroquinolones and Their Nucleosides as Inhibitors of HIV Integrase
Authors: Adams Martina M. , Bats Jan W. , Nikolaus Nadja V. , Witvrouw Myriam , Debyser Zeger , Engels Joachim W.
Published: June 2006

Six fluoroquinolone ribonucleosides were synthesized by using microwave irradiation starting from fluoroanilines. In most cases the microwave application proved superior in time and yield, especially the one step decarboxylation of the carboxyquinolone esters3a-3cand the Vorbrüggen glycosylation. The former led to the new type of fluoroquinolone ribosides8a-8c. Compound8cin the crystal structure showed C3'-endo and anti conformation. The nucleosides were examined, but found inactive against the replication of HIV-1(IIIB) in cell culture, while they were toxic for the cells at a 50% cytotoxic concentration ranging from 31 to >125 μg/ml. But measurements of the inhibitory effects against HIV-1 integrase enzymatic activity showed an interesting activity for compound8c.
New and Efficient Synthesis of Racemic Cyclopent-3-en-1-yl Nucleoside Analogues and Their Derivatives
Authors: Reichardt Bastian , Ludek Olaf R. , Meier Chris
Published: June 2006

A new, efficient synthesis of racemic cyclopent-3-en-1-yl nucleoside analogues has been developed starting from cyclopentadiene. The key step is the regioselective hydroboration of an intermediately formed mixture of two alkylated cyclopentadienes to give one cyclopentenol. The remaining double bond was further functionalized by hydroboration, epoxidation, cis-hydroxylation and cyclopropanation.
1-(2-Deoxy-2-fluoro-β-D-arabinofuranosyl)-5-[36Cl]chlorouracil; Radiosynthesis and Preliminary Biodistribution Studies in an Experimental Murine Tumor Model
Authors: Wiebe Leonard I. , Knaus Edward E. , Iwashina Takashi , Misra Hemant , Lee Yip W.
Published: June 2006

The nucleoside to nucleic acids pathways are attractive targets for molecular imaging of cell proliferation, for radionuclide-based radiotherapy, for following molecular processes and for drug design, development and delivery. This paper describes the preparation of several radiolabelled nucleosides for comparitive study as markers of tumour cell proliferation. 1-(2-Deoxy-2-fluoro-β-D-arabinofuranosyl)-5-[36Cl]chlorouracil (F[36Cl]ClAU)1 was synthesized by reaction of 1-(2-deoxy-2-fluoro-arabinofuranosyl)uracil (FAU) with Na36Cl in the presence of 2 M HNO3 (32% radiochemical yield; 13.5 MBq/mmol). 1-(2-Deoxy-2-fluoroarabinofuranosyl)-5-fluoro/bromo/iodouracils radiolabelled with carbon-14 ([2-14C]FFAU; 1.5 GBq/mmol), bromine-82 (F[82Br]BrAU; 167 MBq/mmol) and iodine-125 (F[125I]IAU; 10.4 GBq/mmol) were synthesized according to literature methods. These radiolabelled halopyrimidine nucleosides were administered by i.v. injection into BDF1 mice bearing transplanted Lewis Lung tumors. Uptake of test compounds by target (tumor) tissue was low, and not dissimilar to the reported uptake of their high-specific-activity 5-halopyrimidine nucleoside counterparts. Selected biodistribution data are presented. In general, clearance from blood was rapid, with less that one percent of the injected dose remaining in the blood within 1 h of injection. Tumor uptake was approximately 2% of the injected dose per g of tumor for F[36Cl]ClAU and F[125I]IAU, with [2-14C]FFAU showing less that 2% per g and F[82Br]BrAU with over 3% per g at this time after injection. Data are compared to those for the respective high-specific-activity counterparts.
Synthesis and Biological Evaluation of Some 4'-C-(Hydroxymethyl)-α- and -β-D-Arabinofuranosyl Pyrimidine and Adenine Nucleosides
Authors: Griffon Jean-François , Shaddix Sue C. , Parker William B. , Al-Madhoun Ashraf S. , Eriksson Staffan , Montgomery John A. , Secrist III John A.
Published: June 2006

A series of 4'-C-(hydroxymethyl) analogs of pyrimidine and purine nucleosides have been prepared utilizing standard methodologies, and the α and β anomers were separated. These analogs are part of our continuing efforts to identify new anticancer drugs as well as to explore the substrate specificities of these analogs with the initial activating enzymes in the metabolic pathway leading to nucleoside triphosphates. Although not cytotoxic to CCRF-CEM cells (an acute lymphoblastic leukemia of T-cell origin), many of these compounds were utilized as substrates for the various human nucleoside kinases, including deoxycytidine kinase, thymidine kinase 1, and thymidine kinase 2. Because the 4'-C-(hydroxymethyl) analog of arabinofuranosyl cytosine was identified as a good substrate with deoxycytidine kinase, its metabolism in CEM cells was evaluated. These results indicated that nucleosides with this modification could be activated in human cells without cytotoxicity, which suggested that they should be examined for antiviral activity.
Purine and Pyrimidine Nucleoside Analogs of 3'-C-Methyladenosine as Antitumor Agents
Authors: Cappellacci Loredana , Franchetti Palmarisa , Petrelli Riccardo , Riccioni Sara , Vita Patrizia , Jayaram Hiremagalur N. , Grifantini Mario
Published: June 2006

3'-C-Methyladenosine (3'-Me-Ado) is a mechanism-based ribonucleotide reductase inhibitor endowed with antitumor activity against both human leukemia and carcinoma cell lines. In this paper, we report the synthesis and antitumor evaluation of a series of purine and pyrimidine 3'-C-methylribonucleoside analogs of 3'-Me-Ado. A stereoselective synthesis of the arabino analog of 3'-Me-Ado is also described. Among the tested compounds, only 3'-C-methyluridine showed moderate antitumor activity against human myelogenous leukemia K562 cell line.
Anthropometric and physiological characteristics of junior elite volleyball players
Authors: Duncan M J , Woodfield L , al-Nakeeb Y
Published: June 2006

Objectives:To investigate the anthropometric and physiological characteristics of junior elite volleyball players.

Method:Twenty five national level volleyball players (mean (SD) age 17.5 (0.5) years) were assessed on a number of physiological and anthropometric variables. Somatotype was assessed using the Heath-Carter method, body composition (% body fat, % muscle mass) was assessed using surface anthropometry, leg strength was assessed using a leg and back dynamometer, low back and hamstring flexibility was assessed using the sit and reach test, and the vertical jump was used as a measure of lower body power. Maximal oxygen uptake was predicted using the 20 m multistage fitness test.

Results:Setters were more ectomorphic (p<0.05) and less mesomorphic (p<0.01) than centres. Mean (SD) of somatotype (endomorphy, mesomorphy, ectomorphy) for setters and centres was 2.6 (0.9), 1.9 (1.1), 5.3 (1.2) and 2.2 (0.8), 3.9 (1.1), 3.6 (0.7) respectively. Hitters had significantly greater low back and hamstring flexibility than opposites. Mean (SD) for sit and reach was 19.3 (8.3) cm for opposites and 37 (10.7) cm for hitters. There were no other significant differences in physiological and anthropometric variables across playing positions (all p>0.05).

Conclusion:Setters tend to be endomorphic ectomorphs, hitters and opposites tend to be balanced ectomorphs, whereas centres tend to be ectomorphic mesomorphs. These results indicate the need for sports scientists and conditioning professionals to take the body type of volleyball players into account when designing individualised position specific training programmes.
Is fatigue all in your head? A critical review of the central governor model
Authors: Weir J P , Beck T W , Cramer J T , Housh T J
Published: June 2006

The central governor model has recently been proposed as a general model to explain the phenomenon of fatigue. It proposes that the subconscious brain regulates power output (pacing strategy) by modulating motor unit recruitment to preserve whole body homoeostasis and prevent catastrophic physiological failure such as rigor. In this model, the word fatigue is redefined from a term that describes an exercise decline in the ability to produce force and power to one of sensation or emotion. The underpinnings of the central governor model are the refutation of what is described variously as peripheral fatigue, limitations models, and the cardiovascular/anaerobic/catastrophe model. This argument centres on the inability of lactic acid models of fatigue to adequately explain fatigue. In this review, it is argued that a variety of peripheral factors other than lactic acid are known to compromise muscle force and power and that these effects may protect against “catastrophe”. Further, it is shown that a variety of studies indicate that fatigue induced decreases in performance cannot be adequately explained by the central governor model. Instead, it is suggested that the concept of task dependency, in which the mechanisms of fatigue vary depending on the specific exercise stressor, is a more comprehensive and defensible model of fatigue. This model includes aspects of both central and peripheral contributions to fatigue, and the relative importance of each probably varies with the type of exercise.
Human growth hormone doping in sport
Authors: Saugy M , Robinson N , Saudan C , Baume N , Avois L , Mangin P
Published: June 2006

Background and objectives:Recombinant human growth hormone (rhGH) has been on the list of forbidden substances since availability of its recombinant form improved in the early 1990s. Although its effectiveness in enhancing physical performance is still unproved, the compound is likely used for its potential anabolic effect on the muscle growth, and also in combination with other products (androgens, erythropoietin, etc.). The degree of similarity between the endogenous and the recombinant forms, the pulsatile secretion and marked interindividual variability makes detection of doping difficult. Two approaches proposed to overcome this problem are: the indirect method, which measures a combination of several factors in the biological cascade affected by administration of GH; and the direct method, which measures the difference between the circulating and the recombinant (represented by the unique 22 kD molecule) forms of GH. This article gives an overview of what is presently known about hGH in relation to sport. The available methods of detection are also evaluated.

Methods:Review of the literature on GH in relation to exercise, and its adverse effects and methods of detection when used for doping.

Results and conclusion:The main effects of exercise on hGH production and the use and effects of rhGH in athletes are discussed. Difficulties encountered by laboratories to prove misuse of this substance by both indirect and direct analyses are emphasised. The direct method currently seems to have the best reliability, even though the time window of detection is too short. hGH doping is a major challenge in the fight against doping. The effect of exercise on hGH and its short half-life are still presenting difficulties during doping analysis. To date the most promising method appears to be the direct approach utilising immunoassays.
Glucocorticosteroids in football: use and misuse: Figure 1
Authors: Dvorak J , Feddermann N , Grimm K
Published: June 2006

Background and objectives:Glucocorticosteroids are widely used in medicine and have shown unchallenged therapeutic potential in several chronic inflammatory and other diseases. They are also widely used in sports medicine for the treatment of conditions such as asthma and acute injuries. In fact, as banned substances, most requests for therapeutic use exemption concern glucocorticosteroids. Nevertheless, their beneficial effect in certain conditions in sports, where inflammation is only a secondary reaction, remains to be validated. This paper aimed to provide a comprehensive review of the literature covering the therapeutic use of glucocorticosteroids since 1977 in conditions ranging from chronic rheumatic illness to peritendinous or intra-articular injection in acute injuries.

Methods:Search of the medical literature published between 1977 and 2006 using PubMed. Articles relevant to the question “When and if at all is the use of glucocorticosteroids justified in football?” were selected and analysed.

Results and conclusions:The findings clearly point out that, despite the common use of glucocorticosteroids in acute injuries in sports, there is actually limited evidence of the true benefits of such a practice. Physicians must take the possible adverse effects into consideration. In an athlete with clinically verified asthma, inhalational glucocorticosteroids remain first line therapy. Finally, for the purposes of education and prevention of misuse, it should be stressed that a measurable performance enhancing effect of glucocorticoids could not be proved on the basis of the results of the scientific studies to date.