bluuebunny/crossref_metadata_2025 huggingface dataset:
GENERALIZED HECKE ALGEBRAS AND C*-COMPLETIONS
Authors: LANDSTAD MAGNUS B. , LARSEN NADIA S.
Published: January 2009

For a Hecke pair (G, H) and a finite-dimensional representation σ of H on Vσwith finite range, we consider a generalized Hecke algebra [Formula: see text], which we study by embedding the given Hecke pair in a Schlichting completion (Gσ, Hσ) that comes equipped with a continuous extension σ of Hσ. There is a (non-full) projection [Formula: see text] such that [Formula: see text] is isomorphic to [Formula: see text]. We study the structure and properties of C*-completions of the generalized Hecke algebra arising from this corner realisation, and via Morita–Fell–Rieffel equivalence, we identify, in some cases explicitly, the resulting proper ideals of [Formula: see text]. By letting σ vary, we can compare these ideals. The main focus is on the case with dim σ = 1 and applications include ax + b-groups and the Heisenberg group.
COMPLETE ORBIT SPACES OF AFFINE TORUS ACTIONS
Authors: HAUSEN JÜRGEN
Published: January 2009

Given an action of an algebraic torus on a normal affine variety, we describe all open subsets admitting a complete orbit space.
A BARTH–LEFSCHETZ THEOREM FOR SUBMANIFOLDS OF A PRODUCT OF PROJECTIVE SPACES
Authors: BĂDESCU LUCIAN , REPETTO FLAVIA
Published: January 2009

Let X be a complex submanifold of dimension d of ℙm × ℙn (m ≥ n ≥ 2) and denote by α: Pic(ℙm × ℙn) → Pic(X) the restriction map of Picard groups, by NX|ℙm × ℙn the normal bundle of X in ℙm × ℙn. Set t := max{dim π1(X), dim π2(X)}, where π1 and π2 are the two projections of ℙm × ℙn. We prove a Barth–Lefschetz type result as follows:

Theorem. If [Formula: see text] then X is algebraically simply connected, the map α is injective and Coker(α) is torsion-free. Moreover α is an isomorphism if [Formula: see text], or if [Formula: see text] and NX|ℙm×ℙn is decomposable.

These bounds are optimal. The main technical ingredients in the proof are: the Kodaira–Le Potier vanishing theorem in the generalized form of Sommese ([18, 19]), the join construction and an algebraization result of Faltings concerning small codimensional subvarieties in ℙN (see [9]).
SMOOTH n-DIMENSIONAL SUBVARIETIES OF ℙ2n-1 CONTAINING A FAMILY OF VERY DEGENERATE DIVISORS
Authors: SIERRA JOSÉ CARLOS
Published: January 2009

A classification and a detailed geometric description are given for smooth n-dimensional subvarieties X ⊂ ℙ2n-1 containing a family of effective divisors each of them spanning a linear ℙn of ℙ2n-1. Some results on multisecant lines to threefolds X ⊂ ℙ5 follow, as a byproduct.
LOWEST ORDER CONSTRAINED VARIATIONAL CALCULATION FOR POLARIZED LIQUID 3He AT FINITE TEMPERATURE
Authors: BORDBAR G. H. , KARIMI M. J. , VAHEDI J.
Published: January 2009

We have investigated some of the thermodynamic properties of spin-polarized liquid 3 He at finite temperature using the lowest order constrained variational method. For this system, the free energy, entropy and pressure are calculated for different values of the density, temperature and polarization. We have also presented the dependence of specific heat, saturation density and incompressibility on temperature and polarization.
TEXTURED STRUCTURE AND ANISOTROPIC THERMOELECTRIC PROPERTIES OF Ca2.7Bi0.3Co4O9 OXIDE PREPARED BY CONVENTIONAL SOLID-STATE REACTION
Authors: HAO HAOSHAN , HE QINGLIN , CHEN CHANGQING , SUN HONGWEI , HU XING
Published: January 2009

Ca 3-x Bi x Co 4 O 9(x = 0.0, 0.3) samples have been prepared at 1223 K by conventional solid-state reaction method. XRD and SEM investigations reveal that c-axis-oriented structure could be formed in Ca 2.7 Bi 0.3 Co 4 O 9 samples, whereas grains in Ca 3 Co 4 O 9 samples distribute randomly. Moreover, Bi doping increases the grain size and relative density of Ca 2.7 Bi 0.3 Co 4 O 9. The electrical conductivity along the ab plane for Ca 2.7 Bi 0.3 Co 4 O 9 is about four times as large as that along the c-axis, but the Seebeck coefficient is almost isotropic, which leads to a remarkable rise of the power factor in ab plane for Ca 2.7 Bi 0.3 Co 4 O 9 compared with untextured Ca 3 Co 4 O 9. The textured structure in Ca 2.7 Bi 0.3 Co 4 O 9 sample should be attributed to the effect of Bi doping.
OPTIMALLY CONTROLLED TREATMENT STRATEGY USING INTERFERON AND RIBAVIRIN FOR HEPATITIS C
Authors: CHAKRABARTY SIDDHARTHA P. , JOSHI HEM RAJ
Published: January 2009

The main goal of this paper is to determine an optimal treatment strategy using interferon and ribavirin, through mathematical modeling. We formulate a mathematical model using a system of ordinary differential equations, which describes the interaction of target cells (hepatocytes), infected cells, infectious virions, non-infectious virions and the two drugs, namely, interferon and ribavirin. We solve an optimal control problem with an objective functional that minimizes the viral load as well as the side effects of treatment. Finally we derive optimal treatment strategy and then solve it numerically.
A COMPREHENSIVE SIMULATOR OF THE HUMAN PULMONARY SYSTEM: VALIDATION WITH DETERMINATION OF TOTALCO2AND DIAGNOSIS OF ACID-BASE ABNORMALITIES
Authors: BIGDELI MOHAMMAD REZA , HAJIZADEH SOHRAB , BANIEGHBAL BEHZAD , MASJDI MOHAMMAD REZA
Published: January 2009

In previous models, heart-lung-blood interactions and their physicochemical properties have not been considered in comprehensive simulators and an integrated mathematical model has not been presented. The aim of the present study is to combine different phenomena involved in the cardiopulmonary function, which are often considered separately. In this study, the variables that constitute a comprehensive model; which includes physicochemical reactions of O2and CO2in the blood and fluid compartments, V/Q, pH , body temperature and diffusion limitation in the adult human and its ability to provide realistic response under different physiological and pathophysiological conditions; have been evaluated. The new biological system model consists of two subsystems: physicochemical properties of blood and physiological subsystem models. Based on the mentioned parameters, comprehensive simulator model has been suggested as following: [Formula: see text] According to the literature, all patients [COPD (20) and asthma (20)] showed acid-base imbalances. The mathematical model has been validated by diagnosis of acid-base abnormalities via calculating the total CO2and T40HCO3in physiological and pathophysiological conditions, and then the results compared to literature experimental data. Our comprehensive model provides results consistent with dynamic and steady state responses measured in subjects undergoing physiological and pathophysiological conditions. This might enable us to deepen our understanding of the cardiopulmonary system as a whole.
NOISE-INDUCED ALTERNATIVE RESPONSE IN MAP KINASE PATHWAYS WITH MUTUAL INHIBITION
Authors: CHEN AIMIN , ZHANG JIAJUN , YUAN ZHANJIANG , ZHOU TIANSHOU
Published: January 2009

All organisms have the ability to detect and respond to changes in the environment for survival, and as a result, specific cellular signaling pathways have evolved by which organisms sense their environment and respond to signals that they detect. However, an important unsolved problem in cell biology is to understand how specificity from signal to cellular response is maintained between different signal transduction pathways that share similar or identical components. Here, we show, using mathematical and computational modeling, that two typical signaling pathways in a single cell, hyperosmolar and pheromone motigen-avtivated protein kinase in the yeast Saccharomyces cerevisiae with mutual inhibition, can respond alternatively to two costimulated signals in a stochastically fluctuated environment. Within a bistable region over two input signals, noise plays an essential role in achieving specificity of response, while outside it, these pathways achieve specificity by filtering out spurious crosstalk through mutual inhibition.
ON FRAME SYSTEMS IN BANACH SPACES
Authors: JAIN P. K. , KAUSHIK S. K. , GUPTA NISHA
Published: January 2009

Banach frame systems in Banach spaces have been defined and studied. A sufficient condition under which a Banach space, having a Banach frame, has a Banach frame system has been given. Also, it has been proved that a Banach space E is separable if and only if E* has a Banach frame ({φn},T) with each φnweak*-continuous. Finally, a necessary and sufficient condition for a Banach Bessel sequence to be a Banach frame has been given.
LONG RANGE DEPENDENCE, UNBALANCED HAAR WAVELET TRANSFORMATION AND CHANGES IN LOCAL MEAN LEVEL
Authors: BAEK CHANGRYONG , PIPIRAS VLADAS
Published: January 2009

Long range dependent (LRD) stationary time series have historically served to model real time series with apparent changes in local mean level. A natural tool to study changes in local mean level is the unbalanced Haar wavelet transformation (UHT). In this work, UHT is used to study changes in local mean level in LRD models and several real and simulated time series exhibiting LRD. In particular, simulations for LRD models suggest that changes in local mean level occur at times essentially governed by a homogeneous Poisson arrival process, and only the local mean levels themselves inherit the LRD property of the original time series. These properties are compared with the analogous ones in several real and simulated time series. The results are mixed though generally in favor of LRD models. The approach based on UHT is also compared to several alternatives such as defining changes in local mean level through kernel smoothing. The interest throughout is mainly in very long time series such as those collected in the studies of data traffic over Internet.
MICROWAVE-ASSISTED HYDROTHERMAL SYNTHESIS OF NITROGEN-DOPED TITANIA NANOPARTICLES
Authors: YIN SHU , LIU BIN , SATO TSUGIO
Published: January 2009

Nitrogen-doped titania ( TiO 2-x N y) nanoparticles with excellent visible-light-reactive photocatalytic activity were successfully prepared by a microwave-assisted hydrothermal process. The obtained TiO 2-x N y powders showed high specific surface area, fine particle size and excellent photocatalytic ability for the oxidative destruction of nitrogen monoxide under irradiation of both visible-light (λ > 510 nm) and UV light (λ > 290 nm).
HIGH MAGNETIC PROPERTIES OF TbCu7-TYPE MELT SPUN (Sm, Pr)Co7-xHfxCy RIBBONS
Authors: CHANG H. W. , HUANG S. T. , CHEN I. W. , CHANG C. W. , CHANG W. C.
Published: January 2009

The effects of Hf substitution and C content on the magnetic properties, phase evolution and microstructure of melt spun ( Sm , Pr ) Co 7-x Hf x C y (x = 0–0.5; y = 0–0.14) ribbons have been studied. A proper Hf substitution is helpful not only in stabilizing 1:7 phase but also in enhancing its magnetic anisotropy field, as a result, magnetic properties of B r = 6.4 kG , i H c = 7.3 kOe and (BH) max = 8.7 MGOe for SmCo 6.9 Hf 0.1 ribbons are obtained. Besides, a small amount of C addition in the ribbons could slightly modify phase constitution and effectively refine their microstructure to strengthen the exchange coupling effect between magnetic grains. It leads to the improvement of the magnetic properties for SmCo 6.8 Hf 0.2 C 0.12 nanocomposites. Finally, a slight Pr substitution for Sm may further increase the magnetization and the magnetic properties, the optimal magnetic properties of B r = 7.1 kG , i H c = 8.5 kOe and (BH) max = 11.2 MGOe could be achieved for the directly quenched Sm 0.8 Pr 0.2 Co 6.9 Hf 0.1 C 0.12 ribbons.
INFLUENCE OF POROSITY ON SHAPE MEMORY BEHAVIOR OF POROUS TiNi SHAPE MEMORY ALLOY
Authors: XIONG JIANYU , LI YUNCANG , HODGSON PETER D. , WEN CUI'E
Published: January 2009

Porous Ti -50.5at.% Ni shape memory alloy (SMA) samples with a range of porosities were prepared by spacer sintering. The porous structure of the alloy was examined using scanning electron microscopy (SEM). The phase constituents of the porous TiNi alloy were determined by X-ray diffraction (XRD). The shape memory behavior of the porous TiNi alloy was investigated using loading–unloading compression tests. Results indicate that the porous TiNi alloy exhibits superelasticity and the recoverable strain by the superelasticity decreases with the increase of porosity. After a prestrain of 7%, the superelastically recovered strains for the porous TiNi alloy samples with porosities of 46%, 59%, 69% and 77% are 2.0%, 1.8%, 1.5% and 1.3%, respectively. The pores in the TiNi alloy samples cause stress/strain concentration, as well as crack initiation, which adversely affect the shape memory behavior of the porous TiNi alloy.
PIEZOELECTRIC MATERIALS FOR IMPEDANCE DRIVEN MICRO-CHANNEL FLOW
Authors: YEO C. Y. , SHIM W. K. , WOUTERSON E. , LI TAO , MA J.
Published: January 2009

This paper presents study of a novel impedance pumping induced by high frequency actuation. PZT (Lead Zirconate Titanate) cantilever beam was being integrated as a form of high frequency actuator to induce flow. The drive test microchannel has the dimension 15 × 3 × 0.4 mm3, and a significant flow rate of 36 μL/s has being measured. Furthermore, flow behavior as functions of actuation amplitude and frequency are presented. It is found that flows were in positive correlations with compression and frequency. The present novel PZT driven micro impedance pump may offer an alternate solution in microfludic systems.
SYNTHESIS OF MAGNETITE NANOPARTICLES BY THERMAL DECOMPOSITION: TIME, TEMPERATURE, SURFACTANT AND SOLVENT EFFECTS
Authors: MAITY DIPAK , DING JUN , XUE JUN-MIN
Published: January 2009

Monodispersed magnetite ( Fe 3 O 4) nanoparticles can be synthesized by thermal decomposition of iron(III) acetylacetonate, Fe ( acac )3. High saturation magnetization M S of the magnetite particles is extremely important to realize the full potential of magnetite materials in biomedical application. In this work, we have studied the different effects (time, temperature and surfactant) on structure and magnetic properties of Fe 3 O 4 nanoparticles. The M S of the particles are enhanced after the synthesis at a higher reaction temperature and/or a longer reaction time. However, the increase in reaction temperature and/or reaction time resulted in particle size increase and the broadening of the particle size distribution. In this work, high M S value of the magnetite particles has been achieved through adopting surfactant or modification of solvent to overcome the temperature and time effects, while the smaller size particles with an acceptable size distribution has been maintained. Size and morphology of the particles were studied by TEM while magnetic properties of the particles were measured using VSM. The saturation magnetization M S of the particles can be increased at higher reaction temperature and/or longer reaction time, while narrow size distribution of the particles can be maintained either by the selective adsorption of oleic acid to the particle surface or by synthesizing them using solvent free thermal decomposition reaction.
MORPHOLOGY EVOLUTION AT NANO- TO MICRO-SCALE
Authors: ZHAO XU , REN XIUE , SUN CONGTING , ZHANG XU , SI YUNFEI , YAN CHENGLIN , XU JIASHENG , XUE DONGFENG
Published: January 2009

Morphology evolution of inorganic/organic crystals during crystallization is a universal growth phenomenon. In this work, we have developed a capping agent-assisted strategy to clearly identify the whole process of morphology evolution in solution growth system. One kind of morphology evolution trend with three types of morphologies of cuprous oxide ( Cu 2 O ) was kinetically observed at varying the molar ratio of EDTA/ Cu (II) under three different pH values. Two kinds of morphology evolution trends of zinc oxide ( ZnO ) were also kinetically observed in the presence of H 2 O 2 and CH 3 COOH (HAc), respectively. Simulation results show that the morphology evolution of nano- to micro-scale crystals is strongly dependent on the bonding characteristics of a growth system. The present strategy positively explores the interesting principles of morphology evolution of functional materials, and can be widely extended to nano- to micro-scale devices research.
INSIGHT INTO THE STRUCTURE AND FORMATION OF TITANIUM OXIDE NANOTUBES
Authors: ZHU YINGCHUN
Published: January 2009

Titanium oxide nanotube is a promising material for versatile applications. However, its structure and formation mechanism were quite confusedly reported. Therefore, it is essential to fully understand its structure, formation mechanism and stability. In this study, the structure, formation and stability of titanium oxide nanotube were studied in detail. New experimental findings on the morphology of titanium oxide nanotubes were reported, demonstrating close-opened nanotubes, cone-shaped nanotubes, twin and ternary nanotubes etc. A structural model of the titanium oxide nanotubes is proposed on the basis of cylinders of smoothly curved sheets of TiO 6 octahedra, among which H + and H 3 O + are intercalated. The formation mechanism of titanium oxide nanotubes was deduced and discussed on the basis of their structural characteristics and chemical bonding behaviors of constituent atoms. The stability of the nanotubes was also studied under different conditions.
RF SPUTTERED BISMUTH FERRITE THIN FILMS: EFFECT OF ANNEALING DURATION
Authors: ZHENG R. Y. , WANG J. , RAMAKRISHNA S.
Published: January 2009

Polycrystalline BFO thin films of similar thickness but subjected to different annealing durations (2 hr and 4 hr) were deposited on SRO / Pt / TiO 2/ SiO 2/ Si substrates via RF sputtering. Phase identification by using X-ray diffractions confirms the pure BFO phase of the thin films fabricated. Polarization–Electric Field (P–E) loop study measured at different frequencies shows that a longer annealing duration led to the formation of space charges in the BFO thin films and thus caused a poor ferroelectric property observed in the hysteresis loop. The results of leakage current measurement for the two BFO films are consistent with the ferroelectric measurement, where a higher leakage current is demonstrated by the BFO film annealed for 4 hr.
Photorespiratory Metabolism: Genes, Mutants, Energetics, and Redox Signaling
Authors: Foyer Christine H. , Bloom Arnold J. , Queval Guillaume , Noctor Graham
Published: January 2009

Photorespiration is a high-flux pathway that operates alongside carbon assimilation in C3 plants. Because most higher plant species photosynthesize using only the C3 pathway, photorespiration has a major impact on cellular metabolism, particularly under high light, high temperatures, and CO2 or water deficits. Although the functions of photorespiration remain controversial, it is widely accepted that this pathway influences a wide range of processes from bioenergetics, photosystem II function, and carbon metabolism to nitrogen assimilation and respiration. Crucially, the photorespiratory pathway is a major source of H2O2 in photosynthetic cells. Through H2O2 production and pyridine nucleotide interactions, photorespiration makes a key contribution to cellular redox homeostasis. In so doing, it influences multiple signaling pathways, particularly those that govern plant hormonal responses controlling growth, environmental and defense responses, and programmed cell death. The potential influence of photorespiration on cell physiology and fate is thus complex and wide ranging. The genes, pathways, and signaling functions of photorespiration are considered here in the context of whole plant biology, with reference to future challenges and human interventions to diminish photorespiratory flux.
Directional Gravity Sensing in Gravitropism
Authors: Morita Miyo Terao
Published: January 2009

Plants can reorient their growth direction by sensing organ tilt relative to the direction of gravity. With respect to gravity sensing in gravitropism, the classic starch statolith hypothesis, i.e., that starch-accumulating amyloplast movement along the gravity vector within gravity-sensing cells (statocytes) is the probable trigger of subsequent intracellular signaling, is widely accepted. Several lines of experimental evidence have demonstrated that starch is important but not essential for gravity sensing and have suggested that it is reasonable to regard plastids (containers of starch) as statoliths. Although the word statolith means sedimented stone, actual amyloplasts are not static but instead possess dynamic movement. Recent studies combining genetic and cell biological approaches, using Arabidopsis thaliana, have demonstrated that amyloplast movement is an intricate process involving vacuolar membrane structures and the actin cytoskeleton. This review covers current knowledge regarding gravity sensing, particularly gravity susception, and the factors modulating the function of amyloplasts for sensing the directional change of gravity. Specific emphasis is made on the remarkable differences in the cytological properties, developmental origins, tissue locations, and response of statocytes between root and shoot systems. Such an approach reveals a common theme in directional gravity-sensing mechanisms in these two disparate organs.
Roles of Plant Small RNAs in Biotic Stress Responses
Authors: Ruiz-Ferrer Virginia , Voinnet Olivier
Published: January 2009

A multitude of small RNAs (sRNAs, 18–25 nt in length) accumulate in plant tissues. Although heterogeneous in size, sequence, genomic distribution, biogenesis, and action, most of these molecules mediate repressive gene regulation through RNA silencing. Besides their roles in developmental patterning and maintenance of genome integrity, sRNAs are also integral components of plant responses to adverse environmental conditions, including biotic stress. Until recently, antiviral RNA silencing was considered a paradigm of the interactions linking RNA silencing to pathogens: Virus-derived sRNAs silence viral gene expression and, accordingly, viruses produce suppressor proteins that target the silencing mechanism. However, increasing evidence shows that endogenous, rather than pathogen-derived, sRNAs also have broad functions in regulating plant responses to various microbes. In turn, microbes have evolved ways to inhibit, avoid, or usurp cellular silencing pathways, thereby prompting the deployment of counter-counterdefensive measures by plants, a compelling illustration of the neverending molecular arms race between hosts and parasites.
Bias in Plant Gene Content Following Different Sorts of Duplication: Tandem, Whole-Genome, Segmental, or by Transposition
Authors: Freeling Michael
Published: January 2009

Each mode of gene duplication (tandem, tetraploid, segmental, transpositional) retains genes in a biased manner. A reciprocal relationship exists between plant genes retained postpaleotetraploidy versus genes retained after an ancient tandem duplication. Among the models (subfunctionalization, neofunctionalization, balanced gene drive) and ideas that might explain this relationship, only balanced gene drive predicts reciprocity. The gene balance hypothesis explains that more “connected” genes—by protein-protein interactions in a heteromer, for example—are less likely to be retained as a tandem or transposed duplicate and are more likely to be retained postpaleotetraploidy; otherwise, selectively negative dosage effects are created. Biased duplicate retention is an instant and neutral by-product, a spandrel, of purifying selection. Balanced gene drive expanded plant gene families, including those encoding proteasomal proteins, protein kinases, motors, and transcription factors, with each paleotetraploidy, which could explain trends involving complexity. Balanced gene drive is a saltation mechanism in the mutationist tradition.
A Renaissance of Elicitors: Perception of Microbe-Associated Molecular Patterns and Danger Signals by Pattern-Recognition Receptors
Authors: Boller Thomas , Felix Georg
Published: January 2009

Microbe-associated molecular patterns (MAMPs) are molecular signatures typical of whole classes of microbes, and their recognition plays a key role in innate immunity. Endogenous elicitors are similarly recognized as damage-associated molecular patterns (DAMPs). This review focuses on the diversity of MAMPs/DAMPs and on progress to identify the corresponding pattern recognition receptors (PRRs) in plants. The two best-characterized MAMP/PRR pairs, flagellin/FLS2 and EF-Tu/EFR, are discussed in detail and put into a phylogenetic perspective. Both FLS2 and EFR are leucine-rich repeat receptor kinases (LRR-RKs). Upon treatment with flagellin, FLS2 forms a heteromeric complex with BAK1, an LRR-RK that also acts as coreceptor for the brassinolide receptor BRI1. The importance of MAMP/PRR signaling for plant immunity is highlighted by the finding that plant pathogens use effectors to inhibit PRR complexes or downstream signaling events. Current evidence indicates that MAMPs, DAMPs, and effectors are all perceived as danger signals and induce a stereotypic defense response.
Signal Transduction in Responses to UV-B Radiation
Authors: Jenkins Gareth I.
Published: January 2009

UV-B radiation is a key environmental signal that initiates diverse responses in plants that affect metabolism, development, and viability. Many effects of UV-B involve the differential regulation of gene expression. The response to UV-B depends on the nature of the UV-B treatment, the extent of adaptation and acclimation to UV-B, and interaction with other environmental factors. Responses to UV-B are mediated by both nonspecific signaling pathways, involving DNA damage, reactive oxygen species, and wound/defense signaling molecules, and UV-B-specific pathways that mediate photomorphogenic responses to low levels of UV-B. Importantly, photomorphogenic signaling stimulates the expression of genes involved in UV-protection and hence promotes plant survival in UV-B. Photomorphogenic UV-B signaling is mediated by the UV-B-specific component UV RESISTANCE LOCUS8 (UVR8). Both UVR8 and CONSTITUTIVE PHOTOMORPHOGENESIS1 (COP1) are required for UV-B-induced expression of the ELONGATED HYPOCOTYL5 (HY5) transcription factor, which plays a central role in the regulation of genes involved in photomorphogenic UV-B responses.
Sympathetic neural responses to mental stress: responders, nonresponders and sex differences
Authors: Carter Jason R. , Ray Chester A.
Published: January 2009

Mental stress consistently increases heart rate (HR) and blood pressure (BP) in humans, despite inconsistent sympathetic neural responses that include increases, decreases, or no change in muscle sympathetic nerve activity (MSNA). The purpose of the present study was to examine associations between MSNA, BP, and HR responses to mental stress. Leg MSNA, BP, HR, and perceived stress levels were recorded during 3–5 min of mental arithmetic in 82 subjects (53 men and 29 women). Subjects were divided into positive responders (≥Δ3 bursts/min; n = 40), negative responders (≤Δ−3 bursts/min; n = 9), and nonresponders ( n = 33). Mental stress increased MSNA in positive responders (Δ6 ± 1 bursts/min), decreased MSNA in negative responders (Δ−6 ± 1 bursts/min), and did not change MSNA in nonresponders (Δ1 ± 1 bursts/min). Mental stress increased mean BP and HR similarly in positive responders (Δ15 ± 1 mmHg and Δ16 ± 1 beats/min; P < 0.001), nonresponders (Δ15 ± 1 mmHg and Δ19 ± 2 beats/min; P < 0.001), and negative responders (Δ12 ± 2 mmHg and Δ19 ± 3 beats/min; P < 0.001). Perceived stress levels and sex distributions were similar across responders and nonresponders; thus, perceived stress and sex do not appear to influence MSNA during mental stress. However, men demonstrated higher increases of mean BP during mental stress when compared with women (Δ16 ± 1 vs. Δ12 ± 1 mmHg; P < 0.05), despite no differences in MSNA responses. In conclusion, our results demonstrate marked differences in MSNA responses to mental stress and a disassociation between MSNA and BP responses to mental stress, suggesting complex patterns of vascular responsiveness during mental stress.
Differential regulation of sphingosine kinases 1 and 2 in lung injury
Authors: Wadgaonkar Raj , Patel Vipul , Grinkina Natalia , Romano Carol , Liu Jing , Zhao Yutong , Sammani Saad , Garcia Joe G. N. , Natarajan Viswanathan
Published: January 2009

Two mammalian sphingosine kinase (SphK) isoforms, SphK1 and SphK2, possess identical kinase domains but have distinct kinetic properties and subcellular localizations, suggesting each has one or more specific roles in sphingosine-1-phosphate (S1P) generation. Although both kinases use sphingosine as a substrate to generate S1P, the mechanisms controlling SphK activation and subsequent S1P generation during lung injury are not fully understood. In this study, we established a murine lung injury model to investigate LPS-induced lung injury in SphK1 knockout (SphK1−/−) and wild-type (WT) mice. We found that SphK1−/− mice were much more susceptible to LPS-induced lung injury compared with their WT counterparts, quantified by multiple parameters including cytokine induction. Intriguingly, overexpression of WT SphK1 delivered by adenoviral vector to the lungs protected SphK1−/− mice from lung injury and attenuated the severity of the response to LPS. However, adenoviral overexpression of a SphK1 kinase-dead mutant (SphKKD) in SphK1−/− mouse lungs further exacerbated the response to LPS as well as the extent of lung injury. WT SphK2 adenoviral overexpression also failed to provide protection and, in fact, augmented the degree of LPS-induced lung injury. This suggested that, in vascular injury, S1P generated by SphK2 activation plays a distinctly separate role compared with SphK1-dependent S1P generation and survival signaling. Microarray and real-time RT-PCR analysis of SphK1 and SphK2 expression levels during lung injury revealed that, in WT mice, LPS treatment caused significantly enhanced SphK1 expression (∼5×) levels within 6 h, which declined back to baseline levels by 24 h posttreatment. In contrast, expression of SphK2 was gradually induced following LPS treatment and was elevated within 24 h. Collectively, our results for the first time demonstrate distinct functional roles of the two SphK isoforms in the regulation of LPS-induced lung injury.
Complexity of force output during static exercise in individuals with Down syndrome
Authors: Heffernan Kevin S. , Sosnoff Jacob J. , Ofori Edward , Jae Sae Young , Baynard Tracy , Collier Scott R. , Goulopoulou Stella , Figueroa Arturo , Woods Jeffrey A. , Pitetti Kenneth H. , Fernhall Bo
Published: January 2009

Force variability is greater in individuals with Down syndrome (DS) compared with persons without DS and is similar to that seen with normal aging. The purpose of this study was to examine the structure (in both time and frequency domains) of force output variability in persons with DS to determine whether deficits in force control are similar between individuals with DS and older adults. An isometric handgrip task at a constant force (30% of maximal voluntary contraction) was completed by individuals with DS ( n = 29, age 26 yr), and healthy young ( n = 26, age 27 yr) and older ( n = 33, age 70 yr) individuals. Mean, standard deviation (SD), and coefficient of variation (CV) were used to analyze the magnitude of force output variability. Spectral analysis and approximate entropy (ApEn) were used to analyze the structure of force output variability. Mean force output for DS was lower than in young controls ( P < 0.05) but no different from old controls. Individuals with DS had greater SD and CV than young and old controls ( P < 0.05). The DS group had a significantly greater proportion of spectral power within the 0-to 4-Hz bandwidth than the young and older controls ( P < 0.05). The DS group had significantly lower ApEn values than the young controls ( P < 0.05), but there were no differences in ApEn between the DS group and the old controls ( P > 0.05). In conclusion, young persons with DS demonstrate enhanced temporal structure and greater amplitude of low-frequency oscillations in the force output signal than age-matched non-DS peers. Interestingly, young persons with DS and older persons without DS have similar time-dependent structure of force output variability. This would suggest a possible link between premature aging and less complex force output in persons with DS.
A sex-specific relationship between capillary density and anaerobic threshold
Authors: Robbins Jennifer L. , Duscha Brian D. , Bensimhon Daniel R. , Wasserman Karlman , Hansen James E. , Houmard Joseph A. , Annex Brian H. , Kraus William E.
Published: January 2009

Although both capillary density and peak oxygen consumption (V̇o2) improve with exercise training, it is difficult to find a relationship between these two measures. It has been suggested that peak V̇o2 may be more related to central hemodynamics than to the oxidative potential of skeletal muscle, which may account for this observation. We hypothesized that change in a measure of submaximal performance, anaerobic threshold, might be related to change in skeletal muscle capillary density, a marker of oxidative potential in muscle, with training. Due to baseline differences among these variables, we also hypothesized that relationships might be sex specific. A group of 21 subjects completed an inactive control period, whereas 28 subjects (17 men and 11 women) participated in a 6-mo high-intensity exercise program. All subjects were sedentary, overweight, and dyslipidemic. Potential relationships were assessed between change in capillary density with both change in V̇o2 at peak and at anaerobic threshold with exercise training. All variables and relationships were assessed for sex-specific effects. Change in peak V̇o2 was not related to change in capillary density after exercise training in either sex. Men had a positive correlation between change in V̇o2 at anaerobic threshold and change in capillary density with exercise training ( r = 0.635; P < 0.01), whereas women had an inverse relationship ( r = −0.636; P < 0.05) between the change in these variables. These findings suggest that, although enhanced capillary density is associated with training-induced improvements in submaximal performance in men, this relationship is different in women.
Endothelial-Mural Cell Signaling in Vascular Development and Angiogenesis
Authors: Gaengel Konstantin , Genové Guillem , Armulik Annika , Betsholtz Christer
Published: January 2009

Mural cells are essential components of blood vessels and are necessary for normal development, homeostasis, and organ function. Alterations in mural cell density or the stable attachment of mural cells to the endothelium is associated with several human diseases such as diabetic retinopathy, venous malformation, and hereditary stroke. In addition mural cells are implicated in regulating tumor growth and have thus been suggested as potential antiangiogenic targets in tumor therapy. In recent years our knowledge of mural cell function and endothelial-mural cell signaling has increased dramatically, and we now begin to understand the mechanistic basis of the key signaling pathways involved. This is mainly thanks to sophisticated in vivo experiments using a broad repertoire of genetic technologies. In this review, we summarize the five currently best understood signaling pathways implicated in mural cell biology. We discuss PDGFB/PDGFRβ- dependent pericyte recruitment, as well as the role of angiopoietins and Tie receptors in vascular maturation. In addition, we highlight the effects of sphingosine-1-phosphate signaling on adherens junction assembly and vascular stability, as well as the role of TGF-β-signaling in mural cell differentiation. We further reflect recent data suggesting an important function for Notch3 signaling in mural cell maturation.
ApoE-Dependent Modulation of HDL and Atherosclerosis by G2A in LDL Receptor–Deficient Mice Independent of Bone Marrow–Derived Cells
Authors: Parks Brian W. , Srivastava Roshni , Yu Shaohua , Kabarowski Janusz H.S.
Published: January 2009

Objective—

Deletion of the lysophospholipid-sensitive receptor, G2A, in low-density lipoprotein receptor knockout (LDLR
−/−
) mice elevates plasma high-density lipoprotein (HDL) cholesterol and suppresses atherosclerosis. However, chemotactic action of G2A in monocytes/macrophages, in addition to its modulatory effect on HDL, may contribute to the proatherogenic action of G2A.

Methods and Results—

We determined that deletion of G2A in LDLR
−/−
mice increases the ApoA1, ApoE, and cholesterol content of plasma HDL fractions. Hepatocytes were shown to express G2A and hepatocytes from G2A-deficient LDLR
−/−
mice secreted more ApoA1 and ApoE in HDL fractions compared to their G2A-sufficient counterparts. The atheroprotective and HDL modulatory effects of G2A deficiency were dependent on the presence of ApoE, as deletion of G2A in ApoE
−/−
and ApoE
−/−
LDLR
−/−
mice failed to raise HDL and did not suppress atherosclerosis. G2A deficiency in bone marrow–derived cells of LDLR
−/−
mice had no effect on atherosclerosis or HDL, whereas G2A deficiency in resident tissues was sufficient to raise HDL and suppress atherosclerosis.

Conclusion—

These data demonstrate that the chemotactic function of G2A in bone marrow–derived monocytes does not modulate atherosclerosis in LDLR
−/−
mice and suggest an ApoE-dependent function for G2A in the control of hepatic HDL metabolism that might contribute to its proatherogenic action.
Mechanisms Targeting Apolipoprotein B100 to Proteasomal Degradation
Authors: Rutledge Angela C. , Qiu Wei , Zhang Rianna , Kohen-Avramoglu Rita , Nemat-Gorgani Nina , Adeli Khosrow
Published: January 2009

Objectives—

In lipid-poor states, the ubiquitin-proteasomal pathway rapidly degrades misfolded apolipoprotein B100 (apoB) cotranslationally, although the mechanism of delivery from the ER to cytosolic proteasomes is poorly understood. Here we demonstrate key roles of BiP, an ER luminal chaperone, and p97, a cytosolic ATPase anchored to the ER membrane, in the targeting of apoB for proteasomal degradation.

Methods and Results—

Using coimmunoprecipitations, we observed associations of apoB with BiP, p97, Derlin-1, VIMP, and the E3 ubiquitin ligase Hrd1 in HepG2 cells. BiP and p97 were found to bind apoB cotranslationally. Expression of C-terminal truncated apoB molecules in COS-7 cells showed an N-terminal region outside apoB15 and a C-terminal region found in apoB72 were required for BiP and p97 binding, respectively. Interestingly, overexpression of dominant negative p97 demonstrated that the ATPase activity of p97 was essential for proteasomal degradation of apoB but not for apoB binding. However, p97 activity did not appear to affect the N terminus of apoB, which may be cleaved before degradation.

Conclusions—

These data suggest that p97 and BiP play critical roles in the cotranslational delivery of apoB to proteasomes and formation of a degradative complex. Proteasomal degradation appears to selectively target apoB molecules with large C-terminal domains.
The Capacity of Group V sPLA
2
to Increase Atherogenicity of ApoE
−/−
and LDLR
−/−
Mouse LDL In Vitro Predicts its Atherogenic Role In Vivo
Authors: Boyanovsky Boris , Zack Melissa , Forrest Kathy , Webb Nancy R.
Published: January 2009

Objective—

In vitro data indicate that human LDL modified by Group V secretory phospholipase A
2
(GV sPLA
2
) is proatherogenic. Consistent with this, gain and loss of function studies demonstrated that GV sPLA
2
promotes atherosclerosis in LDLR
−/−
mice. The current study investigates whether GV sPLA
2
promotes atherosclerotic processes in apoE
−/−
mice.

Methods and Results—

LDL (
d
=1.019 to 1.063) from apoE
−/−
and LDLR
−/−
mice fed chow or Western diet were hydrolyzed by GV sPLA
2
. Phosphatidylcholine on LDL from LDLR
−/−
mice fed either a chow or Western diet was hydrolyzed to a greater extent (61.1±0.4% and 45.3±4.6%) than the corresponding fractions from apoE
−/−
mice (41.7±3.6% and 39.4±1.2%). ApoE
−/−
LDL induced macrophage foam cell formation in vitro without modification by GV sPLA
2
, whereas hydrolysis of LDLR
−/−
LDL was a prerequisite for foam cell formation. In contrast to findings in LDLR
−/−
mice, GV sPLA
2
deficiency did not significantly reduce atherosclerosis in apoE
−/−
mice, although collagen content was significantly reduced in lesions of apoE
−/−
mice lacking GV sPLA
2
.

Conclusions—

The ability of GV sPLA
2
to promote atherosclerotic lipid deposition in apoE
−/−
and LDLR
−/−
mice may be related to its ability to increase the atherogenic potential of LDL from these mice as assessed in vitro.
Ultrasound and Microbubble-Targeted Delivery of Macromolecules Is Regulated by Induction of Endocytosis and Pore Formation
Authors: Meijering Bernadet D.M. , Juffermans Lynda J.M. , van Wamel Annemieke , Henning Rob H. , Zuhorn Inge S. , Emmer Marcia , Versteilen Amanda M.G. , Paulus Walter J. , van Gilst Wiek H. , Kooiman Klazina , de Jong Nico , Musters René J.P. , Deelman Leo E. , Kamp Otto
Published: January 2009

Contrast microbubbles in combination with ultrasound (US) are promising vehicles for local drug and gene delivery. However, the exact mechanisms behind intracellular delivery of therapeutic compounds remain to be resolved. We hypothesized that endocytosis and pore formation are involved during US and microbubble targeted delivery (UMTD) of therapeutic compounds. Therefore, primary endothelial cells were subjected to UMTD of fluorescent dextrans (4.4 to 500 kDa) using 1 MHz pulsed US with 0.22-MPa peak-negative pressure, during 30 seconds. Fluorescence microscopy showed homogeneous distribution of 4.4- and 70-kDa dextrans through the cytosol, and localization of 155- and 500-kDa dextrans in distinct vesicles after UMTD. After ATP depletion, reduced uptake of 4.4-kDa dextran and no uptake of 500-kDa dextran was observed after UMTD. Independently inhibiting clathrin- and caveolae-mediated endocytosis, as well as macropinocytosis significantly decreased intracellular delivery of 4.4- to 500-kDa dextrans. Furthermore, 3D fluorescence microscopy demonstrated dextran vesicles (500 kDa) to colocalize with caveolin-1 and especially clathrin. Finally, after UMTD of dextran (500 kDa) into rat femoral artery endothelium in vivo, dextran molecules were again localized in vesicles that partially colocalized with caveolin-1 and clathrin. Together, these data indicated uptake of molecules via endocytosis after UMTD. In addition to triggering endocytosis, UMTD also evoked transient pore formation, as demonstrated by the influx of calcium ions and cellular release of preloaded dextrans after US and microbubble exposure. In conclusion, these data demonstrate that endocytosis is a key mechanism in UMTD besides transient pore formation, with the contribution of endocytosis being dependent on molecular size.
Oxidized Phospholipids Induce Type VIII Collagen Expression and Vascular Smooth Muscle Cell Migration
Authors: Cherepanova Olga A. , Pidkovka Nataliya A. , Sarmento Olga F. , Yoshida Tadashi , Gan Qiong , Adiguzel Eser , Bendeck Michelle P. , Berliner Judith , Leitinger Norbert , Owens Gary K.
Published: January 2009

Phenotypic switching of vascular smooth muscle cells (VSMCs) is known to play a critical role in the development of atherosclerosis. However, the factors present within lesions that mediate VSMC phenotypic switching are unclear. Oxidized phospholipids (OxPLs), including 1-palmitoyl-2-(5-oxovaleroyl)-
sn
-glycero-3-phosphorylcholine (POVPC), are active components of minimally modified low density lipoprotein and have been previously shown to induce multiple proatherogenic events in endothelial cells and macrophages, but their effects on VSMCs have been largely unexplored until recently. We previously showed that OxPLs induced phenotypic switching of VSMCs, including suppression of SMC differentiation marker genes. The goal of the present studies was to test the hypothesis that OxPLs alter extracellular matrix production and VSMC migration. Results showed that POVPC activated expression of several extracellular matrix proteins in VSMC. POVPC increased expression of type VIII collagen α1 chain (
Col8a1
) mRNA in cultured VSMCs and in vivo in rat carotid arteries by 9-fold and 4-fold, respectively. POVPC-induced activation of
Col8a1
gene expression was reduced by small interfering RNA–mediated suppression of Krüppel-like factor 4 (Klf4) and Sp1, and was abolished in
Klf4-
knockout VSMCs. POVPC increased Klf4 binding to the
Col8a1
gene promoter both in vivo in rat carotid arteries and in cultured VSMCs based on chromatin immunoprecipitation assays. Moreover, POVPC-induced VSMC migration was markedly reduced in
Klf4
- or type VIII collagen–knockout VSMCs. Given evidence that OxPLs are present within atherosclerotic lesions, it is interesting to suggest that OxPL-induced changes in VSMC phenotype may contribute to the pathogenesis of atherosclerosis at least in part through changes in extracellular matrix composition.
p66Shc Links α
1
-Adrenergic Receptors to a Reactive Oxygen Species-Dependent AKT-FOXO3A Phosphorylation Pathway in Cardiomyocytes
Authors: Guo Jianfen , Gertsberg Zoya , Ozgen Nazira , Steinberg Susan F.
Published: January 2009

p66Shc is an adapter protein that is induced by hypertrophic stimuli and has been implicated as a major regulator of reactive oxygen species (ROS) production and cardiovascular oxidative stress responses. This study implicates p66Shc in an α
1
-adrenergtic receptor (α
1
-AR) pathway that requires the cooperative effects of protein kinase (PK)Cε and PKCδ and leads to AKT-FOXO3a phosphorylation in cardiomyocytes. α
1
-ARs promote p66Shc-YY
239/240
phosphorylation via a ROS-dependent mechanism that is localized to caveolae and requires epidermal growth factor receptor (EGFR) and PKCε activity. α
1
-ARs also increase p66Shc-S
36
phosphorylation via an EGFR transactivation pathway involving PKCδ. p66Shc links α
1
-ARs to an AKT signaling pathway that selectively phosphorylates/inactivates FOXO transcription factors and downregulates the ROS-scavenging protein manganese superoxide dismutase (MnSOD); the α
1
-AR-p66Shc-dependent pathway involving AKT does not regulate GSK3. Additional studies show that RNA interference-mediated downregulation of endogenous p66Shc leads to the derepression of FOXO3a-regulated genes such as MnSOD, p27Kip1, and BIM-1. p66Shc downregulation also increases proliferating cell nuclear antigen expression and induces cardiomyocyte hypertrophy, suggesting that p66Shc exerts an antihypertrophic action in neonatal cardiomyocytes. The novel α
1
-AR- and ROS-dependent pathway involving p66Shc identified in this study is likely to contribute to cardiomyocyte remodeling and the evolution of heart failure.
TRPC1 Associates With BK
Ca
Channel to Form a Signal Complex in Vascular Smooth Muscle Cells
Authors: Kwan Hiu-Yee , Shen Bing , Ma Xin , Kwok Yuk-Chi , Huang Yu , Man Yu-Bun , Yu Shan , Yao Xiaoqiang
Published: January 2009

TRPC1 (transient receptor potential canonical 1) is a Ca
2+
-permeable cation channel involved in diverse physiological function. TRPC1 may associate with other proteins to form a signaling complex, which is crucial for channel function. In the present study, we investigated the interaction between TRPC1 and large conductance Ca
2+
-sensitive K
+
channel (BK
Ca
). With the use of potentiometric fluorescence dye DiBAC
4
(3), we found that store-operated Ca
2+
influx resulted in membrane hyperpolarization of vascular smooth muscle cells (VSMCs). The hyperpolarization was inhibited by an anti-TRPC1 blocking antibody T1E3 and 2 BK
Ca
channel blockers, charybdotoxin and iberiotoxin. These data were confirmed by sharp microelectrode measurement of membrane potential in VSMCs of intact arteries. Furthermore, T1E3 treatment markedly enhanced the membrane depolarization and contraction of VSMCs in response to several contractile agonists including phenylephrine, endothelin-1, and U-46619. In coimmunoprecipitation experiments, an antibody against BK
Ca
α-subunit [BK
Ca
(α)] could pull down TRPC1, and moreover an anti-TRPC1 antibody could reciprocally pull down BK
Ca
(α). Double-labeling immunocytochemistry showed that TRPC1 and BK
Ca
were colocalized in the same subcellular regions, mainly on the plasma membrane, in VSMCs. These data suggest that, TRPC1 physically associates with BK
Ca
in VSMCs and that Ca
2+
influx through TRPC1 activates BK
Ca
to induce membrane hyperpolarization. The hyperpolarizing effect of TRPC1-BK
Ca
coupling could serve to reduce agonist-induced membrane depolarization, thereby preventing excessive contraction of VSMCs to contractile agonists.