bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparison of some variational formulas for the free energy as applied to hard-sphere crystals
Authors: Barnes C. Daniel , Kofke David A.
Published: November 2002

We examine several variational methods for determining bounds on the free energy of model crystalline phases, as applied to hard spheres in one and three dimensions. Cell- and harmonic-based reference systems are considered. Methods that provide the tightest bounds on the free energy are similar in form to free-energy perturbation, and are prone to inaccuracy from inadequate sampling. Gibbs–Bogoliubov formulas are reliable but weaker. For hard potentials they can give only a lower bound, indicating that their ability to provide upper bounds for other potentials is limited. Nevertheless, bounds given by Gibbs–Bogoliubov when applied with the optimal harmonic system prescribed by Morris and Ho [Phys. Rev. Lett. 74, 940 (1995)] yields impressive results; for hard spheres at higher density it is, within confidence limits, equal to the exact hard-sphere free energy.
Electrostatic attraction between ionic reverse micelles with dielectric discontinuity
Authors: Chen Peilong
Published: November 2002

We have calculated the thermally-averaged electrostatic attractive potential between two spherical ionic reverse micelles in a medium of a different dielectric constant. Specifically the attractions between the charge density fluctuations in one micelle and interface polarizations on the other are computed. For water-in-oil microemulsions, we find that these contributions completely overwhelm those from correlated fluctuations in charge densities between two micelles.
Tunable photonic band schemes of opals and inverse opals infiltrated with liquid crystals
Authors: Takeda Hiroyuki , Yoshino Katsumi
Published: November 2002

When an optically birefringent nematic liquid crystal is infiltrated into the void regions of opals and inverse opals, degeneracies seen in photonic band schemes are found theoretically to disappear, resulting in the appearance of several new weak peaks in the reflection spectra. Tunabilities of the reflection peaks upon applied electric fields are discussed as a function of refractive indices and anisotropies of liquid crystals. Much larger tunabilities are demonstrated in inverse opals infiltrated with liquid crystals.
Growth dynamics of Si1−yCy and Si1−x−yGexCy on Si(001) surface from disilane, germane, and methylsilane
Authors: Price R. W. , Tok E. S. , Woods N. J. , Zhang J.
Published: November 2002

This letter reports on a study of the growth dynamics of Si or SiGe containing a small fraction of carbon using disilane, germane, and methylsilane precursors. Dynamic changes in growth rates are observed using the intensity oscillations of reflection high-energy electron diffraction and from x-ray diffraction rocking curve measurements on final layer structures. The growth rate of carbon containing alloys is found to be reduced compared to layers grown without the methylsilane precursor. Temperature programmed desorption is used to study the effect of carbon on H2 desorption and disilane adsorption. The results indicate that the main cause of the decrease in growth rate is the reduction of sticking coefficient of disilane on the carbon containing Si(001) surfaces.
Generation of bright low-divergence high-order harmonics in a long gas jet
Authors: Lee D. G. , Kim H. T. , Hong K. H. , Nam C. H. , Choi I. W. , Bartnik A. , Fiedorowicz H.
Published: November 2002

Guided propagation of intense 28 fs laser pulses through a long gas jet made it feasible to produce a bright 27th harmonic from argon with a divergence of 0.5 mrad. This harmonic saturated an x-ray charge-coupled device of an extreme ultraviolet spectrometer in a single laser shot of 5 mJ. The low-divergence harmonic generation resulted from a well-guided pumping laser pulse, achieved by balancing diffraction and plasma defocusing with nonlinear self-focusing, and a large harmonic-generation cross section.
An electrically injected InAs/GaAs quantum-dot photonic crystal microcavity light-emitting diode
Authors: Sabarinathan J. , Bhattacharya P. , Yu P-C. , Krishna S. , Cheng J. , Steel D. G.
Published: November 2002

An electrically injected InAs/GaAs self-organized quantum-dot photonic crystal microcavity light-emitting diode operating at 1.04 μm is demonstrated. Light–current characteristics are obtained for devices with two- and five-defect period cavities with maximum light output of 0.17 μW measured in the surface-normal direction. Near-field images were also obtained for an injection current of 8.35 mA, showing light confinement within a few periods of the photonic crystal defect microcavity.
Strain splitting of the Γ5 and Γ6 free excitons in GaN
Authors: Reynolds D. C. , Hoelscher J. , Litton Cole , Collins T. C.
Published: November 2002

High quality GaN crystals have been grown by the hydride vapor phase epitaxy process. The thick layers grown by this process have the potential to provide lattice-matched and thermally-matched substrates for further epitaxial growth. The current sample was grown on a sapphire substrate, resulting in both lattice and thermal mismatch, which produces strain in the as-grown-layer. These in-grown strains result in energy shifts as well as splittings of the free excitons due to combined strain and spin exchange.
Efficient short-wavelength light emission from asymmetric double quantum wells by using electron and hole collection into the same narrow quantum well
Authors: Hirose Y. , Hosoda M. , Domoto C. , Nishimura T. , Aida T.
Published: November 2002

We propose an effective method for carrier injection into the high-energy Γ ground state in a narrow quantum well (QW) in asymmetric double QW systems using Γ–X–Γ electron transfer and simultaneous hole tunneling. Although the high-energy state is type-II band-aligned for the electrons, our method enables an efficient injection of both electrons and holes into the same narrow QW, and it thus demonstrates relatively strong light emission from the higher energy state.
High temperature efficient deuterium permeation and oxidation (Al,Ti)N barriers deposited on stainless steel
Authors: Bazzanella N. , Checchetto R. , Miotello A. , Patton B. , Kale A. N. , Kothari D. C.
Published: November 2002

We have shown that reduction of deuterium permeation through AISI 316L stainless steel can be obtained by the deposition of an (Al,Ti)N coating: a 1.7-μm-thick coating was able to reduce the deuterium permeation flux by a factor 100–1000 in the 473–873 K temperature range. This result is related to the very low diffusivity of the deuterium migrating species in the nitride: in the examined temperature range the evaluated values of the deuterium diffusion coefficient are on the order of 10−12–10−11 cm2/s with an activation energy as low as 0.37±0.03 eV: this activation energy may be related to the defect microstructure of the sample. The (Al,Ti)N layer, which is produced on an industrial scale as an anticorrosive and wear resistant coating, has shown good properties as an oxidation barrier during thermal treatment in air at temperatures up to 873 K.
H mode power threshold database for ITER
Authors: F. Ryter  , H Mode Database Working Group: J.A. Snipes  , R.S. Granetz  , M. Greenwald  , O.J.W.F. Kardaun  , A. Kus  , F. Ryter  , U. Stroth  , J. Kollermeyer  , S.J. Fielding  , M. Valovic  , J.C. DeBoo  , T.N. Carlstrom  , D.P. Schissel  , K. Thomsen  , D.J. Campbell  , J.P. Christiansen  , J.G. Cordey  , E. Righi  , Y. Miura  , N. Suzuki  , M. Mori  , T. Matsuda  , H. Tamai  , T. Fukuda  , Y. Kamada  , T. Matsuda  , M. Sato  , T. Takizuka  , K. Tsuchiya  , S.M. Kaye
Published: November 2002

The ITER Threshold Database, which at present comprises data from nine divertor tokamaks, is described. The main results are presented and discussed. The properties and dependences of the power threshold in individual devices are reviewed. In particular, the analysis shows a rather general linear dependence on magnetic field, but a non-monotonic density dependence that varies from device to device. Investigation of the combined database suggests that the threshold dependence Pthresapproximately=0.3neBT2.5shows reasonable agreement with the data. This expression yields Pthresapproximately=150 MW at a density of 0.5*1020m-3for ITER. Other expressions with weaker size dependence, and therefore lower threshold power for ITER, are also discussed. Their agreement with the present data is poorer than that of the above expression. In addition, the database is investigated by statistical discriminant analysis. The edge data included at present are described and discussed. Finally, there is a discussion of the implications of the results for ITER
Families of rationally connected varieties
Authors: Graber Tom , Harris Joe , Starr Jason
Published: November 2002

We prove that every one-parameter family of complex rationally connected varieties has a section.
Analytic continuation of overconvergent eigenforms
Authors: Buzzard Kevin
Published: November 2002

Let

f
f

be an overconvergent

p
p

-adic eigenform of level

N

p
r

Np^r

,

r
≥
1

r\geq 1

, with non-zero

U
p

U_p

-eigenvalue. We show how

f
f

may be analytically continued to a subset of

X
1

(
N

p
r

)

a
n

X_1(Np^r)^{\mathrm {an}}

containing, for example, all the supersingular locus. Using these results we extend the main theorem of our earlier work with R. Taylor to many ramified cases.
The nature of singularities in mean curvature flow of mean-convex sets
Authors: White Brian
Published: November 2002

This paper analyzes the singular behavior of the mean curvature flow generated by the boundary of the compact mean-convex region of

R

n
+
1

\mathbf {R}^{n+1}

or of an

(
n
+
1
)

(n+1)

-dimensional riemannian manifold. If

n
>
7

n>7

, the moving boundary is shown to be very nearly convex in a spacetime neighborhood of any singularity. In particular, the tangent flows at singular points are all shrinking spheres or shrinking cylinders. If

n
≥
7

n\ge 7

, the same results are shown up to the first time that singularities occur.
The transcription factor Sox9 has essential roles in successive steps of the chondrocyte differentiation pathway and is required for expression of Sox5 and Sox6
Authors: Akiyama Haruhiko , Chaboissier Marie-Christine , Martin James F. , Schedl Andreas , de Crombrugghe Benoit
Published: November 2002

To examine whether the transcription factor Sox9 has an essential role during the sequential steps of chondrocyte differentiation, we have used the Cre/loxP recombination system to generate mouse embryos in which either Sox9 is missing from undifferentiated mesenchymal cells of limb buds or the Sox9 gene is inactivated after chondrogenic mesenchymal condensations. Inactivation ofSox9 in limb buds before mesenchymal condensations resulted in a complete absence of both cartilage and bone, but markers for the different axes of limb development showed a normal pattern of expression. Apoptotic domains within the developing limbs were expanded, suggesting that Sox9 suppresses apoptosis. Expression ofSox5 and Sox6, two other Sox genes involved in chondrogenesis, was no longer detected. Moreover, expression ofRunx2, a transcription factor needed for osteoblast differentiation, was also abolished. Embryos, in which Sox9 was deleted after mesenchymal condensations, exhibited a severe generalized chondrodysplasia, similar to that in Sox5; Sox6double-null mutant mice. Most cells were arrested as condensed mesenchymal cells and did not undergo overt differentiation into chondrocytes. Furthermore, chondrocyte proliferation was severely inhibited and joint formation was defective. Although Indian hedgehog, Patched1, parathyroid hormone-related peptide (Pthrp), and Pth/Pthrp receptor were expressed, their expression was down-regulated. Our experiments further suggested that Sox9 is also needed to prevent conversion of proliferating chondrocytes into hypertrophic chondrocytes. We conclude that Sox9 is required during sequential steps of the chondrocyte differentiation pathway.
Activator recruitment by the general transcription machinery: X-ray structural analysis of the Oct-1 POU domain/human U1 octamer/SNAP190 peptide ternary complex
Authors: Hovde Stacy , Hinkley Craig S. , Strong Katie , Brooks Aimee , Gu Liping , Henry R. William , Geiger James
Published: November 2002

Transcriptional activation of the human U1 snRNA genes is dependent on a noncanonical octamer element contained within an upstream enhancer. The U1 octamer only weakly recruits the Oct-1 POU domain, although recruitment is stimulated by a peptide containing the Oct-1-binding domain of SNAP190. Structural analysis of the Oct-1 POU domain/U1 octamer/SNAP190 peptide complex revealed that SNAP190 makes extensive protein contacts with the Oct-1 POU-specific domain and with the DNA phosphate backbone within the enhancer. Although SNAP190 and OCA-B both interact with the Oct-1 POU domain through the same Oct-1 interface, a single nucleotide within the U1 octamer ablates OCA-B recruitment without compromising activator recruitment by SNAP190.

Supplemental material is available athttp://www.genesdev.org.
Activin type IIA and IIB receptors mediate Gdf11 signaling in axial vertebral patterning
Authors: Oh S. Paul , Yeo Chang-Yeol , Lee Youngjae , Schrewe Heindrich , Whitman Malcolm , Li En
Published: November 2002

Vertebral bodies are segmented along the anteroposterior (AP) body axis, and the segmental identity of the vertebrae is determined by the unique expression pattern of multiple Hox genes. Recent studies have demonstrated that a transforming growth factor β (TGF-β) family protein, Gdf11 (growth and differentiationfactor 11), and the activin type II receptor, ActRIIB, are involved in controlling the spatiotemporal expression of multiple Hox genes along the AP axis, and that the disruption of each of these genes causes anterior transformation of the vertebrae. Skeletal defects are more severe in Gdf11-null mice than in ActRIIB-null mice, however, leaving it uncertain whether Gdf11 signals via ActRIIB. Here we demonstrate using genetic and biochemical studies that ActRIIB and its subfamily receptor, ActRIIA, cooperatively mediate the Gdf11 signal in patterning the axial vertebrae, and that Gdf11 binds to both ActRIIA and ActRIIB, and induces phosphorylation of Smad2. In addition, we also show that these two receptors can functionally compensate for one another to mediate signaling of another TGF-β ligand, nodal, during left–right patterning and the development of anterior head structure.
Inhibition of Hedgehog signaling by direct binding of cyclopamine to Smoothened
Authors: Chen James K. , Taipale Jussi , Cooper Michael K. , Beachy Philip A.
Published: November 2002

The steroidal alkaloid cyclopamine has both teratogenic and antitumor activities arising from its ability to specifically block cellular responses to vertebrate Hedgehog signaling. We show here, using photoaffinity and fluorescent derivatives, that this inhibitory effect is mediated by direct binding of cyclopamine to the heptahelical bundle of Smoothened (Smo). Cyclopamine also can reverse the retention of partially misfolded Smo in the endoplasmic reticulum, presumably through binding-mediated effects on protein conformation. These observations reveal the mechanism of cyclopamine's teratogenic and antitumor activities and further suggest a role for small molecules in the physiological regulation of Smo.
A bulged stem tethers Est1p to telomerase RNA in budding yeast
Authors: Seto Anita G. , Livengood April J. , Tzfati Yehuda , Blackburn Elizabeth H. , Cech Thomas R.
Published: November 2002

It is well established that the template for telomeric DNA synthesis is provided by the RNA subunit of telomerase; however, the additional functions provided by most of the rest of the RNA (>1000 nucleotides in budding yeast) are largely unknown. By alignment of telomerase RNAs of Saccharomyces cerevisiae and six Kluyveromycesspecies followed by mutagenesis of the S. cerevisiae RNA, we found a conserved region that is essential for telomere maintenance. Phylogenetic analysis and computer folding revealed that this region is conserved not only in primary nucleotide sequence but also in secondary structure. A common bulged-stem structure was predicted in all seven yeast species. Mutational analysis showed the structure to be essential for telomerase function. Suppression of bulged-stem mutant phenotypes by overexpression of Est1p and loss of co-immunoprecipitation of the mutant RNAs with Est1p indicated that this bulged stem is necessary for association of Est1p, a telomerase regulatory subunit. Est1p in yeast extract bound specifically to a small RNA containing the bulged stem, suggesting a direct interaction. We propose that this RNA structure links the enzymatic core of telomerase with Est1p, thereby allowing Est1p to recruit or activate telomerase at the telomere.
5′ exon interactions within the human spliceosome establish a framework for exon junction complex structure and assembly
Authors: Reichert Vienna L. , Le Hir Hervé , Jurica Melissa S. , Moore Melissa J.
Published: November 2002

A general consequence of pre-mRNA splicing is the stable deposition of several proteins 20–24 nucleotides (nt) upstream of exon–exon junctions on spliced mRNAs. This exon junction complex (EJC) contains factors involved in mRNA export, cytoplasmic localization, and nonsense-mediated mRNA decay. Here we probed the mechanism and timing of EJC assembly. Over the course of splicing, the 5′ exon is subject to numerous dynamic protein–RNA interactions involving at least nine distinct polypeptides. Within the fully assembled spliceosome, these interactions afford protection to the last 25–27 nt of the 5′ exon intermediate. Coincident with exon ligation, interactions at the 3′ end of the 5′ exon disappear, and new species associate with position −24. Mass spectrometry and Western blotting of purified H, C, and mRNP complexes revealed that at least one EJC component, REF/Aly, can interact with pre-mRNA prior to spliceosome assembly, whereas Y14, Magoh, RNPS1, UAP56, and SRm160 are found in intermediate-containing spliceosomes. Upon exon ligation, association of RNPS1, UAP56, and SRm160 is destabilized. In contrast, REF/Aly, Y14, and Magoh remain stably bound to spliced mRNA, indicating that these three proteins are components of the EJC core.
Strand pairing by Rad54 and Rad51 is enhanced by chromatin
Authors: Alexiadis Vassilios , Kadonaga James T.
Published: November 2002

We investigated the role of chromatin in the catalysis of homologous strand pairing by Rad54 and Rad51. Rad54 is related to the ATPase subunits of chromatin-remodeling factors, whereas Rad51 is related to bacterial RecA. In the absence of superhelical tension, we found that the efficiency of strand pairing with chromatin is >100-fold higher than that with naked DNA. In addition, we observed that Rad54 and Rad51 function cooperatively in the ATP-dependent remodeling of chromatin. These findings indicate that Rad54 and Rad51 have evolved to function with chromatin, the natural substrate, rather than with naked DNA.
Intron status and 3′-end formation control cotranscriptional export of mRNA
Authors: Lei Elissa P. , Silver Pamela A.
Published: November 2002

Messenger RNA export factors are recruited to genes in a transcription-dependent manner. To ascertain the mechanism of this process, we show that RNA polymerase II transcription is sufficient to recruit the Saccharomyces cerevisiae hnRNP protein Npl3 to a gene independent of RNA sequence. In contrast, the cotranscriptional recruitment of the RNA-binding protein Yra1 is dependent on pre-mRNA processing. Yra1 associates with introns of intron-containing genes in a splicing-dependent manner. Conversely, Yra1 recruitment to genes without introns is not dependent on splicing. Finally, 3′-end formation is required for Yra1 recruitment to genes regardless of intron status.
A novel mitochondrial protein, Tar1p, is encoded on the antisense strand of the nuclear 25S rDNA
Authors: Coelho Paulo S.R. , Bryan Anthony C. , Kumar Anuj , Shadel Gerald S. , Snyder Michael
Published: November 2002

In eukaryotes, it is widely assumed that genes coding for proteins and structural RNAs do not overlap. Using a transposon-tagging strategy to globally analyze the Saccharomyces cerevisiae genome for expressed genes, we identified multiple insertions in an open reading frame that is contained fully within and transcribed antisense to the 25S rRNA gene in the nuclear rDNA repeat region on Chromosome XII. Expression of this gene, TAR1(Transcript Antisense to Ribosomal RNA), can be detected at the RNA and protein levels, and the primary sequence of the corresponding 124-amino-acid protein is conserved in several yeast species. Tar1p was found to localize to mitochondria, and overexpression of the protein suppresses the respiration-deficient petite phenotype of a point mutation in mitochondrial RNA polymerase that affects mitochondrial gene expression and mtDNA stability. These findings indicate that coding information for protein and structural RNAs can overlap, raising issues regarding the coevolution of such complex genes, and also suggest that rDNA transcription and mitochondrial function are coordinately regulated in eukaryotic cells.
Promoter proximal splice sites enhance transcription
Authors: Furger Andre , Binnie Justin M. O‘Sullivan, Alexandra , Lee Barbara A. , Proudfoot Nick J.
Published: November 2002

Reconstruction of a gene with its introns removed results in reduced levels of cytoplasmic mRNA. This is partly explained by introns promoting the export of mRNA through coupling splicing to nuclear export processes. However, we show here that splicing signals can have a direct role in enhancing gene transcription. Removal of promoter proximal splice signals from a mammalian gene or the excision of introns from two different yeast genes results in a marked reduction in levels of nascent transcription, based on both nuclear run-on and direct image analysis. This further establishes that mRNA processing and transcription are tightly coupled mechanisms.
An investigation of school meals eaten by primary schoolchildren
Authors: Burgess Abigail L. , Bunker Valda W.
Published: November 2002

The present study compared the calculated nutritional content of midday meals eaten by primary schoolchildren (n=90, 45 boys, 45 girls, mean age 10.5±0.4 years), in the Portsmouth area, with the Caroline Walker Trust (CWT) published guidelines. Comp‐Eat 5 was used to determine the dietary content of children’s midday meals. Children’s lunchtime meals were not deficient in essential micronutrients; however, the macronutrient content of their diet differed significantly from the published guidelines. Data analysis also revealed that significant differences were evident between the macronutrient content of the two meal subgroups (food provided by the school, referred to as “school meals” and food brought from home, referred to as a “packed lunch”). In conclusion, several changes need to be made to midday meals, eaten by primary schoolchildren, before they will meet the CWT guidelines, and the two meal subgroups require separate solutions.
Brand architecture: building brand portfolio value
Authors: Petromilli Michael , Morrison Dan , Million Michael
Published: November 2002

Corporations must routinely ask “how should we allocate existing financial and human resources among our brands to grow shareholder value?” Firms should focus on getting the most from existing brands through better organizing and managing brands and brand inter‐relationships within the existing portfolio. “Brand architecture” is the way a company organizes, manages, and markets their brands. It must align with and support business goals and strategies. Different business strategies require different brand architectures. The two most common types are: “Branded house” architecture – employs a single (master) brand to span a series of offerings that may operate with descriptive sub‐brand names and “House of brands” architecture – each brand is stand‐alone; the sum of performance of the independent brands is greater than they would be if under a master brand. Neither type is better than the other. Some companies use a mix of both. The key is to have a well‐defined brand architecture strategy. Steps to maximize brand architecture: take stock of your brand portfolio from the perspective of customers because their view is the foundation for your strategy; do “brand relationship mapping” to identify the relationships and opportunities between brands across your portfolio. Check for these criteria: the perceived or potential credibility of the brands in that space – the perceptual license; whether or not the company currently has or can develop competencies in that space – the organizational capabilities; and whether the size and current or potential growth of the market is significant enough to merit exploitation and investment – the market opportunity. Mine the opportunities where all three criteria are met (aka, the “sweet spot”). Or use these innovative strategies if all criteria do not intersect: “pooling” and “trading,” branded partnerships’, strategic brand consolidation, brand acquisition, new brand creation. Continuously emphasize the portfolio‐wide thinking and business‐wide implications of brand‐oriented decisions. Create a brand council. When managed strategically and used as a structure to anticipate future business and brand needs, concerns, and issues, brand architecture can be the critical link to business strategy and the means to optimize growth and brand value.
Membrane properties of an unusual intrinsically oscillating, wide‐field teleost retinal amacrine cell
Authors: Solessio Eduardo , Vigh Jozsef , Cuenca Nicolas , Rapp Kevin , Lasater Eric M.
Published: November 2002

In the retina, amacrine cells modulate the transfer of information from bipolar to ganglion cells. The nature of the modulation depends on the synaptic input and the membrane properties of the cells. In the retina of white bass, we identified a class of bistratified, wide‐field amacrine cell characterized by immunopositive labelling for GABA and calmodulin. In isolation, the cells presented resting membrane potentials averaging ‐69 mV although some cells settled at more depolarized values (‐30 mV). Injection of depolarizing current pulses induced oscillatory membrane responses. When elicited from depolarized cells, the oscillations were short‐lived (< 40 ms). For the most part, the oscillatory potentials of hyperpolarized cells remained unattenuated throughout the depolarizing pulse. The frequency of the oscillations increased logarithmically with mean membrane potential, ranging from 74 to 140 Hz. Cells exhibiting depolarized membrane potentials oscillated at twice that rate. When the membrane potential of these cells was hyperpolarized to ‐70 mV, the oscillations became unattenuated and slowed. We found the cells expressed voltage‐gated sodium, potassium and calcium currents and calcium‐dependent potassium currents. We demonstrate that the oscillatory potentials arose as a result of the interplay between calcium and potassium currents. The cells responded to local application of GABA and glycine, both of which modulate the oscillatory potentials. Glutamate and its analogues depolarized the cell and induced oscillatory potentials. Our results indicate that oscillatory responses of a type of wide‐field amacrine cell are an intrinsic feature of the cell and not due to circuit properties.
Ach‐induced endothelial NO synthase translocation, NO release and vasodilatation in the hamster microcirculation in vivo
Authors: Figueroa Xavier F. , González Daniel R. , Martínez Agustín D. , Durán Walter N. , Boric Mauricio P.
Published: November 2002

Studies in cultured cells show that activation of endothelial nitric oxide (NO) synthase (eNOS) requires the dissociation of this enzyme from its inhibitory association with caveolin‐1 (Cav‐1), and perhaps its translocation from plasma membrane caveolae to other cellular compartments. We investigated the hypothesis that in vivo NO‐dependent vasodilatation is associated with the translocation of eNOS from the cell membrane. To this end, we applied ACh topically (10‐100 μm for 10 min) to the hamster cheek pouch microcirculation and measured NO production, blood flow and vessel diameter, and assessed subcellular eNOS distribution by Western blotting. Baseline NO production was 54.4 ± 5.2 pmol min−1 (n= 16). ACh increased NO release, caused arteriolar and venular dilatation and elevated microvascular flow. These responses were inhibited by NG‐nitro‐L‐arginine (30 μm). The maximal increase in NO production induced by 10 μm and 100 μm ACh was 45 ± 20 % and 111 ± 33 %, respectively; the corresponding blood flow increases were 50 ± 10 % and 130 ± 24 %, respectively (n= 4‐6). Both responses followed a similar time course, although increases in NO preceded flow changes. In non‐stimulated tissues, eNOS was distributed mainly in the microsomal fraction. ACh‐induced vasodilatation was associated with eNOS translocation to the cytosolic and Golgi‐enriched fractions. After 1.5, 3.0 or 6.0 min of application, 10 μm ACh decreased the level of membrane‐bound eNOS by ‐13 ± 4 %, ‐60 ± 4 % and ‐19 ± 17 %, respectively; at the same time points, 100 μm ACh reduced microsomal eNOS content by ‐38 ± 9 %, ‐61 ± 16 % and ‐40 ± 18 %, respectively (n= 4‐5). In all cases, microsomal Cav‐1 content did not change. The close ACh concentration dependence and the concomitance between eNOS subcellular redistribution and NO release support the concept that eNOS translocation from the plasma membrane is part of an activation mechanism that induces NO‐dependent vasodilatation in vivo.
Contraction‐induced muscle damage in humans following calcium channel blocker administration
Authors: Beaton Louise J. , Tarnopolsky Mark A. , Phillips Stuart M.
Published: November 2002

Following contraction‐induced damage of skeletal muscle there is a loss of calcium homeostasis. Attenuating the damage‐induced rise in myocellular calcium concentration may reduce proteolytic activation and attenuate other indices of damage; calcium channel blockers have been shown to be effective in this regard. The effect of administration of a calcium channel blocker (CCB), amlodipine, on indices of muscle damage following a unilateral ‘damage protocol’, during which subjects performed 300 maximal isokinetic (0.52 rad s−1) eccentric contractions with the knee extensors was investigated. The design was a randomized, double‐blind crossover. On one occasion, prior to the damage protocol, subjects consumed CCB for 7 days prior to and for 7 days following the damage protocol. Biopsies were taken from the vastus lateralis prior to (baseline) and following the damage protocol at 4 h and 24 h post‐damage. Isometric peak knee extensor torque was reduced (P < 0.05) immediately post‐, 24 h post‐ and 48 h post‐damage protocol compared to pre‐exercise values with no effect of treatment. Desmin disruption was attenuated (P < 0.05) with CCB versus placebo at 4 h post‐damage. Z‐band streaming was significantly (P < 0.05) elevated compared to baseline at both times post‐damage, but was lower with CCB at 4 h (P < 0.05). Damage resulted in increased inflammatory cell (macrophage) infiltration into skeletal muscle at both 4 h and 24 h post‐damage, with no effect of CCB. Neutrophil number was elevated by the damage protocol, but was higher at 24 h post‐damage in the CCB condition (P < 0.05). Creatine kinase (CK) activity was higher (P < 0.05) at 24 h and 48 h following the damage protocol compared to baseline, with no effect of treatment. In conclusion, the reduction in desmin disruption and Z‐band streaming indicates that CCB attenuated, or delayed, the contraction‐induced damage to sarcomeric proteins.
Arm blood flow and metabolism during arm and combined arm and leg exercise in humans
Authors: Volianitis S. , Secher N. H.
Published: November 2002

The cardiovascular response to exercise with several groups of skeletal muscle suggests that work with the arms may decrease leg blood flow. This study evaluated whether intense exercise with the legs would have a similar effect on arm blood flow (Qarm) and O2 consumption (V̇O2,arm). Ten healthy male subjects (age 21 ± 1 year; mean ± S.D.) performed arm cranking at 80 % of maximum arm work capacity (A trial) and combined arm cranking with cycling at 60 % of maximum leg work capacity (A + L trial). The combined trial was a maximum effort for 5‐6 min. Qarm measurement by thermodilution in the axilliary vein and arterial and venous blood samples permitted calculation of V̇O2,arm. During the combined trial, Qarm was reduced by 0.58 ± 0.25 l min−1 (19.1 ± 3.0 %, P < 0.05) from the value during arm cranking (3.00 ± 0.46 l min−1). The arterio‐venous O2 difference increased from 122 ± 15 ml l−1 during the arm trial to 150 ± 21 ml l−1 (P < 0.05) during the combined trial. Thus, V̇O2,arm (0.45 ± 0.06 l min−1) was reduced by 9.6 ± 6.3 % (P < 0.05) and arm vascular conductance from 27 ± 4 to 23 ± 3 ml min−1 (mmHg)−1 (P < 0.05) as noradrenaline spillover from the arm increased from 7.5 ± 3.5 to 13.8 ± 4.2 nmol min−1 (P < 0.05). The data suggest that during maximal whole body exercise in humans, arm vasoconstriction is established to an extent that affects oxygen delivery to and utilisation by working skeletal muscles.
Dopamine mediates circadian clock regulation of rod and cone input to fish retinal horizontal cells
Authors: Ribelayga Christophe , Wang Yu , Mangel Stuart C.
Published: November 2002

A circadian (24‐hour) clock regulates the light responses of fish cone horizontal cells, second order neurones in the retina that receive synaptic contact from cones and not from rods. Due to the action of the clock, cone horizontal cells are driven by cones in the day, but primarily driven by rods at night. We show here that dopamine, a retinal neurotransmitter, acts as a clock signal for the day by increasing cone input and decreasing rod input to cone horizontal cells. The amount of endogenous dopamine released from in vitro retinae was greater during the subjective day than the subjective night. Application of dopamine or quinpirole, a dopamine D2‐like agonist, during the subjective night increased cone input and eliminated rod input to the cells, a state usually observed during the subjective day. In contrast, application of spiperone, a D2‐like antagonist, or forskolin, an activator of adenylyl cyclase, during the subjective day reduced cone input and increased rod input. SCH23390, a D1 antagonist, had no effect. Application of Rp‐cAMPS, an inhibitor of cAMP‐dependent protein kinase, or octanol, an alcohol that uncouples gap junctions, during the night increased cone input and decreased rod input. Because D2‐like receptors are on photoreceptor cells, but not horizontal cells, the results suggest that the clock‐induced increase in dopamine release during the day activates D2‐like receptors on photoreceptor cells. The resultant decrease in intracellular cyclic AMP and protein kinase A activation then mediates the increase in cone input and decrease in rod input.
Effect of stimulation rate, sarcomere length and Ca2+ on force generation by mouse cardiac muscle
Authors: Stuyvers Bruno D. , McCulloch Andrew D. , Guo Jiqing , Duff Henry J. , ter Keurs Henk E. D. J.
Published: November 2002

The relations between stress, stimulation rate and sarcomere length (SL) were investigated in 24 cardiac trabeculae isolated from right ventricles of mice (CF‐1 males, 25‐30 g) and superfused with Hepes solution ([Ca2+]o= 1 mm, pH 7.4, 25 °C). Stress and SL were measured by a strain gauge transducer and laser diffraction technique, respectively. Stress versus stimulation frequency formed a biphasic relation (25 °C, [Ca2+]o= 2 mm) with a minimum at 0.7‐1 Hz (≈15 mN mm−2), a 150 % decrease from 0.1 to 1 Hz (descending limb) and a 75 % increase from 1 to 5 Hz (ascending limb). Ryanodine (0.1 μm) inhibited specifically the descending limb, while nifedipine (0.1 μm) affected specifically the ascending limb. This result suggests two separate sources of Ca2+ for stress development: (1) net Ca2+ influx during action potentials (AP); and (2) Ca2+ entry into the cytosol from the extracellular space during diastolic intervals; Ca2+ from both (1) and (2) is sequestered by the SR between beats. Raising the temperature to 37 °C lowered the stress‐frequency relation (SFR) by ≈0‐15 mN mm−2 at each frequency. Because the amount of Ca2+ carried by ICa,L showed a ≈3‐fold increase under the same conditions, we conclude that reduced Ca2+ loading of the SR was probably responsible for this temperature effect. A simple model of Ca2+ fluxes addressed the mechanisms underlying the SFR. Simulation of the effect of inorganic phosphates (Pi) on force production was incorporated into the model. The results suggested that O2 diffusion limits force production at stimulation rates >3 Hz. The stress‐SL relations from slack length (≈1.75 μm) to 2.25 μm showed that the passive stress‐SL curve of mouse cardiac trabeculae is exponential with a steep increase at SL >2.1 μm. Active stress (at 1 Hz) increased with SL, following a curved relation with convexity toward the abscissa at [Ca2+]= 2 mm. At [Ca2+] from 4 to 12 mm, the stress‐SL curves superimposed and the relation became linear, which revealed a saturation step in the activation of force production. EC coupling in mouse cardiac muscle is similar to that observed previously in the rat, although important differences exist in the Ca2+ dependence of force development. These results may suggest a lower capacity of the SR for buffering Ca2+, which makes the generation of force in mouse cardiac ventricle more dependent on Ca2+ entering during action potentials, particularly at high heart rate.
Endogenous cyclo‐oxygenase activity regulates mouse gastric surface pH
Authors: Baumgartner Heidi K. , Kirbiyik Uzay , Coskun Tamer , Chu Shaoyou , Montrose Marshall H.
Published: November 2002

In the stomach, production of prostaglandins by cyclo‐oxygenase (COX) is believed to be important in mucosal defence. We tested the hypothesis that endogenous COX activity is required for protective gastric surface pH control. Intact stomachs of anaesthetized mice were perfused with a weakly buffered solution (150 mmNaCl+ 4 mm Homopipes) at pH values from 2.5 to 7.0. Gastric effluents were collected to measure pH and estimate amounts of acid or alkali secretion in nanomoles secreted per minute. A switch from net acid to net alkali secretion was seen in response to acidifying luminal pH with an apparent ‘set point’ between pH 4 and 5. At luminal pH 3, the net alkali secretion (12.7 ± 2.8 nmol OH− equivalents min−1) was abolished (2.2 ± 1.7 nmol OH− min−1) by the non‐specific COX inhibitor indomethacin (5 mg kg−1 I.P.). Similar inhibition was observed using a COX‐1 inhibitor (SC‐560; 10 mg kg−1 I.P.), but not a COX‐2 inhibitor (NS‐398; 10 mg kg−1 I.P.). Subsequent treatment with 16,16‐dimethyl prostaglandin E2 (dm‐PGE2; 1 mg kg−1 I.P.) rescued the alkali secretion (21.8 ± 2.7 nmol OH− min−1). In either the absence or presence of the H+,K+‐ATPase inhibitor omeprazole (60 mg kg−1 I.P.), indomethacin blocked similar amounts of net alkali secretion (10.5 ± 2.7 and 16.4 ± 3.4 nmol OH− min−1, respectively). We also used in vivo confocal microscopy to examine pH near the mucosal surface. The gastric mucosal surface of anaesthetized mice was exposed and mucosal surface pH was imaged using the fluorescence intensity ratio of Cl‐NERF as a pH indicator. Results showed a switch from a continuous net acid to net alkali secretion by the stomach in response to changing superfusate pH from 5 to 3. At luminal pH 3, the relatively alkaline surface pH (4.3 ± 0.1) was acidified (3.6 ± 0.2) by indomethacin, and subsequent dm‐PGE2 restored surface pH (4.2 ± 0.2). We conclude that the pre‐epithelial alkaline layer is regulated by endogenous COX activity.
Modulation of arterial baroreflex dynamic response during muscle metaboreflex activation in humans
Authors: Ichinose Masashi , Saito Mitsuru , Wada Hiroyuki , Kitano Asami , Kondo Narihiko , Nishiyasu Takeshi
Published: November 2002

We aimed to investigate the interaction between the arterial baroreflex and muscle metaboreflexes (as reflected by alterations in the dynamic responses shown by muscle sympathetic nerve activity (MSNA), mean arterial blood pressure (MAP) and heart rate (HR)) in humans. In nine healthy subjects (eight male, one female) who performed a sustained 1 min handgrip exercise at 50 % maximal voluntary contraction followed by forearm occlusion, a 5 s period of neck pressure (NP) (30 and 50 mmHg) or neck suction (NS)(‐30 and ‐60 mmHg) was used to evaluate carotid baroreflex function at rest (CON) and during post‐exercise muscle ischaemia (PEMI). In PEMI (as compared with CON): (a) the augmentations in MSNA and MAP elicited by 50 mmHg NP were both greater; (b) MSNA seemed to be suppressed by NS for a shorter period, (c) the decrease in MAP elicited by NS was smaller, and (d) MAP recovered to its initial level more quickly after NS. However, the HR responses to NS and NP were not different between PEMI and CON. These results suggest that during muscle metaboreflex activation, the dynamic arterial baroreflex response is modulated, as exemplified by the augmentation of the MSNA response to arterial baroreflex unloading (i.e. NP) and the reduction in the suppression of MSNA induced by baroreceptor stimulation (i.e. NS).
Reversible changes in Ca2+‐activation properties of rat skeletal muscle exposed to elevated physiological temperatures
Authors: van der Poel Chris , Stephenson D. George
Published: November 2002

Exposure of relaxed rat extensor digitorum longus (EDL; predominantly fast‐twitch) muscle to temperatures in the upper physiological range for mammalian skeletal muscle (43‐46 °C) led to reversible alterations of the contractile activation properties. These properties were studied using the mechanically skinned fibre preparation activated in Ca2+‐buffered solutions. The maximum Ca2+‐activated force (maximum force per cross‐sectional area) and the steepness of force‐pCa (‐log10[Ca2+]) curves as measured by the Hill coefficient (nH) reversibly decreased by factors of 8 and 2.5, respectively, when the EDL muscle was treated at 43 °C for 30 min and 5 and 2.8, respectively, with treatment at 46 °C for 5 min. Treatment at 47 °C for 5 min produced an even more marked depression in maximum specific force, which fully recovered after treatment, and in the Hill coefficient, which did not recover after treatment. After all temperature treatments there was no change in the level of [Ca2+] at which 50 % maximum force was generated. The temperature‐induced depression in force production and steepness of the force‐pCa curves were shown to be associated with superoxide (O2−) production in muscle (apparent rate of O2− production at room temperature, 0.055 ± 0.008 nmol min−1 (g wet weight)−1; and following treatment to 46 °C for 5 min, 1.8 ± 0.2 nmol min−1 (g wet weight)−1) because 20 mm Tiron, a membrane‐permeant O2− scavenger, was able to markedly suppress the net rate of O2− production and prevent any temperature‐induced depression of contractile parameters. The temperature‐induced depression in force production of the contractile apparatus could be reversed either by allowing the intact muscle to recover for 3‐4 h at room temperature or by treatment of the skinned fibre preparation with dithiothreitol (a potent reducing agent) in the relaxing solution. These results demonstrate that mammalian skeletal muscle has the ability to uncouple force production reversibly from the activator Ca2+ as the temperature increases in the upper physiological range through an increase in O2− production.
Halothane, isoflurane and sevoflurane inhibit NADH: ubiquinone oxidoreductase (complex I) of cardiac mitochondria
Authors: Hanley Peter J. , Ray John , Brandt Ulrich , Daut Jürgen
Published: November 2002

We have investigated the effects of volatile anaesthetics on electron transport chain activity in the mammalian heart. Halothane, isoflurane and sevoflurane reversibly increased NADH fluorescence (autofluorescence) in intact ventricular myocytes of guinea‐pig, suggesting that NADH oxidation was impaired. Using pig heart submitochondrial particles we found that the anaesthetics dose‐dependently inhibited NADH oxidation in the order: halothane > isoflurane = sevoflurane. Succinate oxidation was unaffected by either isoflurane or sevoflurane, indicating that these agents selectively inhibit complex I (NADH:ubiquinone oxidoreductase). In addition to inhibiting NADH oxidation, halothane also inhibited succinate oxidation (and succinate dehydrogenase), albeit to a lesser extent. To test the hypothesis that complex I is a target of volatile anaesthetics, we examined the effects of these agents on NADH:ubiquinone oxidoreductase (EC 1.6.99.3) activity using the ubiquinone analogue DBQ (decylubiquinone) as substrate. Halothane, isoflurane and sevoflurane dose‐dependently inhibited NADH:DBQ oxidoreductase activity. Unlike the classical inhibitor rotenone, none of the anaesthetics completely inhibited enzyme activity at high concentration, suggesting that these agents bind weakly to the ‘hydrophobic inhibitory site’ of complex I. In conclusion, halothane, isoflurane and sevoflurane inhibit complex I (NADH:ubiquinone oxidoreductase) of the electron transport chain. At concentrations of ≈2 MAC (minimal alveolar concentration), the activity of NADH:ubiquinone oxidoreductase was reduced by about 20 % in the presence of halothane or isoflurane, and by about 10 % in the presence of sevoflurane. These inhibitory effects are unlikely to compromise cardiac performance at usual clinical concentrations, but may contribute to the mechanism by which volatile anaesthetics induce pharmacological preconditioning.
Exercise induces hepatosplanchnic release of heat shock protein 72 in humans
Authors: Febbraio Mark A. , Ott Peter , Nielsen Henning Bay , Steensberg Adam , Keller Charlotte , Krustrup Peter , Secher Niels H. , Pedersen Bente Klarlund
Published: November 2002

Physical exercise results in the appearance of heat shock protein (HSP) 72 in the circulation that precedes any increase in gene or protein expression in contracting skeletal muscle. In rodents, exercise increases liver HSP72 expression and the hepatosplanchnic viscera are known to release many acute phase proteins. In the present study, we tested the hypothesis that the splanchnic tissue beds release HSP72 during exercise. Seven male subjects performed 120 min of semi‐recumbent cycling at 62 ± 2 % of maximal oxygen uptake. Blood samples were obtained simultaneously from a brachial artery, a femoral vein and the hepatic vein prior to and at 30, 60 and 120 min of exercise. Leg blood flow (LBF) was measured by thermodilution in the femoral vein, and hepatosplanchnic blood flow (HBL) was measured using indocyanine green dye. Net leg and net hepatosplanchnic HSP72 balance were calculated as the product of LBF and femoral venous‐arterial HSP72 difference and the product of HBF and hepatic venous‐arterial HSP72 difference, respectively. Arterial plasma HSP72 was only detected in one subject at rest but progressively appeared in the arterial samples throughout exercise such that at 120 min it was detected in all subjects (0.88 ± 0.35 pg l−1; P < 0.05 compared with rest). The contracting muscle did not, however, contribute to this increase since there was no difference in the femoral venous‐arterial HSP72 concentration at any time. Rather, the increase in arterial HSP72 was accounted for, at least in part, by release from the hepatosplanchnic viscera with values increasing (P < 0.05) from undetectable levels at rest to 5.2 ± 0.2 pg min−1 after 120 min. These data demonstrate that the splanchnic tissues release HSP72 during exercise and this release is responsible, in part, for the elevated systemic concentration of this protein during exercise.